2025 天文年會 (ASROC Annual Meeting)

May 16, 2025, 12:00 PM → May 18, 2025, 2:30 PM Asia/Taipei

International Conference Hall 圓形國際會議廳 (College of Management, National Formosa University 國立虎尾科技大學第三校區文理暨管理大樓)

Welcome to ASROC 2025 Annual Meeting

The 2025 Scientific Assembly of the Astronomical Society of the Republic of China (ASROC2025) will be held at the National Formosa University on May 16 (Friday) – May 18 (Sunday), 2025.

This year, the plenary talks will be given by Prof. Makiko Ohtake from the Okayama University, Japan, and Dr. Min-Kai Lin from the Academia Sinica Institute of Astronomy and Astrophysics. The talks’ titles are “Recent and future lunar exploration missions conducted and planned by Japan” and “Bitter-sweet symphonies of planet formation.”

A competition for the best oral and poster award for students will be held during the meeting. The best student oral presentation will be awarded with NTD 10,000 prize and three best student posters will be awarded with NTD 5,000 prize. The three best poster winners need to give a 3-minute oral presentation in the general assembly meeting.

The registration and abstract submission now opened. The deadline for abstract submission is April 6, and for online registration is April 27. Participants of the scientific assembly should submit their abstracts and register on-line. A registration fee of NTD 2,000 (NTD 1500 for students) should be paid on site.

歡迎來到2025天文年會

2025年中華民國天文學會年會將於2025年5月16至5月18日（星期五、六、日）於國立虎尾科技大學舉行。這是國內天文工作者一年一度發表研究的新發現和工作成果的聚會，也是適合交換研究心得或洽商研究合作的場合。歡迎所有與天文和天文物理研究、天文教育（國小、國中、高中及大專院校）、以及天文推廣工作（如社團、社區大學、天文館、科博館等）相關領域的口頭成果報告或壁報論文。

此次年會中除了會員大會、學術論文報告、壁報論文、天文教育和業餘天文活動報告等之外，亦安排兩場大會專題演講，特別邀請大竹真紀子教授（岡山大学​​）與林明楷博士（ASIAA​​）等兩位學者進行大會專題演講 。演講題目分別為“Recent and future lunar exploration missions conducted and planned by Japan” 與 “Bitter-sweet symphonies of planet formation”。

年會設有最佳學生口頭報告獎一名，頒發獎金新台幣10,000元。最佳學生壁報獎三名，每名頒發獎金新台幣5,000元（壁報獎得主必須準備3分鐘演講於5月18日會員大會中報告）。敬請把握摘要投稿截止日期踴躍投稿。

2025年天文年會之網站已經啟動，有意參加年會者請至天文學會網站報名。摘要上傳截止日為 4月 6 日，線上註冊截止日為4月 27 日。一般會員註冊費為新台幣2000元，學生會員註冊費為新台幣1500元，請於會議現場繳交（會員得以該年度學會年費抵免註冊費，永久會員可免繳註冊費）。

 

年會議程委員會 Program Committee
江國興（清華大學 天文所；主席）
王祥宇 (中研院 天文所)
李景輝（中研院 天文所)
秦一男 (淡江大學 物理系)
曾瑋玲 (師範大學 地科系)
潘彥丞（中央大學 天文所)
賴詩萍 (清華大學 天文所)
郭政育（中山大學 物理系)

年會組織委員會 LOC
江國興（清華大學 天文所）
潘國全（清華大學 天文所）
高筱茵（清華大學 天文所）

主辦/協辦/贊助單位/Sponsors
國立虎尾科技大學(NFU)
國立清華大學(NTHU)
國家科學及技術委員會(NSTC)
物理研究推動中心(PRPC)
國家太空中心(TASA)
台灣天文研究聯盟(TARA)

 

asroc2025_poster.pdf

poster_contributions.pdf

Friday, May 16

12:00 PM → 1:30 PM Registration

1:30 PM → 1:45 PM Opening Ceremony

Convener: Albert Kong

1:45 PM → 3:30 PM Plenary session

Convener: Kuo-Chuan Pan (Institute of Astronomy, National Tsing Hua University)

1:45 PM Searching for high-redshift galaxies - Ultra-blue UV continuum slopes from COSMOS-Web

The epoch of cosmic dawn, occurring in the first few hundred million years after the Big Bang, marks a critical period in the formation of the first galaxies and the reionization of the Universe. With the unprecedented capabilities of the James Webb Space Telescope (JWST), deep imaging surveys such as COSMOS-Web have opened a new window into this early era.

In this study, we employ the F150W dropout technique to identify high-redshift galaxy (z=12~22) . Our approach leverages the Lyman-break method in conjunction with NIRCam imaging, ensuring robust detection of galaxies that are undetected in F150W but clearly visible in F277W and F444W. Our photometric analysis, supplemented by visual inspection to remove spurious detections, yields a final sample of 48 candidates. SED modeling with CIGALE provides photometric redshifts reaching up to z≈22. Our analysis of the UV continuum slopes reveals extremely blue values (β ≤ −3.0), consistent with young, metal‑poor, and largely dust‑free stellar populations. These results offer important insights into the formation and evolution of galaxies during the early epochs of the Universe and their role in cosmic reionization. Future spectroscopic follow‑up will be critical for confirming these findings and refining our understanding of the reionization era.

Speaker: Dr Seong Jin Kim (NTHU)

2:00 PM Discovery of a Population of Strong Galaxy-Galaxy Lensed Faint Dusty Star-Forming Galaxies

The measurement of galaxy-galaxy strong lens number density provides statistical constraints on foreground mass distributions. Dusty star-forming galaxies (DSFGs) uncovered in submillimeter surveys are particularly valuable for this purpose, given the large cosmological volumes they probe. Strongly lensed DSFGs have predominantly been identified as one of the brightest sources in previous submillimeter and millimeter surveys. However, theoretical models predict the existence of a population of faint strongly lensed DSFGs, which have been challenging to confirm due to technical limitations. Recently, a faint strongly lensed DSFG was discovered using high-resolution JWST data, providing the first confirmation of the model predictions. To further test the models with a larger sample, we aim to constrain the number density of faint strongly lensed DSFGs. Utilizing the deepest SCUBA-2 submillimeter survey and newly obtained JWST imaging from the COSMOS-Web and PRIMER surveys, we identify a population of 13 strongly lensed faint dusty galaxies in the COSMOS field. Photometric redshift estimation and foreground lens modeling confirmed their lensed nature, with all sources exhibiting higher photometric redshifts than their foreground lenses. Magnification factors were also derived from foreground lens modeling. Our systematic search allows us to place observational constraints on the number density of strongly lensed DSFGs at the faint submillimeter flux end. These findings support theoretical predictions for the existence of a strongly lensed faint DSFG population.

Speaker: Ting-Kai Yang (NTU/ASIAA)

ASROC_2025_TK.pptx

2:15 PM Interstellar hub-filament system and the consequent star formation

Observations of the stellar medium have revealed many structures forming prior to the birth of stars. Filaments being omnipresent and highly correlated with prestellar cores, stellar cluster that contain massive stars are usually found to be embedded in a hub-filament system. Continuum observations could not reveal 3D information, while spectroscopic observations have suggested that hub-filament systems might actually form with a flattened geometry. I will first present our recent effort to describe the formation of interstellar hub-filament systems through the growth of instabilities in a contracting sheet. Secondly, I will show our recent analyses of stellar distribution using data from GAIA DR3, which tentatively show traces of stars originally froming within a flat structure.

Speaker: Yueh-Ning Lee (National Taiwan Normal University)

2:30 PM Linking Multi-Scale Energetics with Fragmentation in Massive Star-Forming Clump SDC40.283

The change in the relative importance of gravity, turbulence, and magnetic field affects the fragmentation of massive star-forming dark clouds. Using dust continuum and polarization data, as well as molecular transition lines from the JCMT, IRAM-30m and the SMA, we investigated the energetics of various star forming regions to understand the correlation between the three factors and fragmentation. In this work, we focused on SDC40.283-0.216, an infrared dark cloud that has one dense clump and shows no signs of fragmentation. SDC40 appears to be dominated by gravity at pc scale (~7 pc) and at sub-pc (~0.2 pc) scale. The change in energy ratio from clump scale (~0.7 pc) to core scale (~0.2 pc) is similar to the trend seen in MM1 in G34.43+00.24, another clump showing no fragmentation while being gravity-dominated. However, results from SDC18.624-0.070 suggest that a strong magnetic field can suppress fragmentation. While the clumps all show no fragmentation, the underlying mechanisms may be different.

Speaker: Ingrid Tseng (NTU / ASIAA)

2:45 PM How might stellar flares energize the atmospheres of rocky exoplanets?

Space weather events sourced from host stars, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence an exoplanet’s habitability and atmospheric evolution history. These time-dependent events may also affect our ability to measure and interpret its properties by modulating reservoirs of key chemical compounds and/or by changing the brightness temperature of the atmosphere. The majority of previous work however, used single-column models and focused on the photochemical effects of stellar flares. Here, using three-dimensional (3D) general circulation models with interactive photochemistry, we simulate the climate and chemical impacts of stellar flare sourced energetic particle precipitation and examine their effects on synchronously rotating TRAPPIST-1e-like planets on a range of spatiotemporal scales. We find that sudden thermospheric cooling is associated with NO and CO2 radiative cooling, and lower atmospheric warming is associated with transient increases in infrared absorbers such as N2O and H2O. In certain regimes, these changes in temperature are strongly affected by O3 variability depending on the flare spectra shape and energy, as found by previous work. The role of O3 in temperature change however, is reduced in the most extreme flaring scenario explored in our simulations. In addition to effects on planetary climate and atmospheric chemistry, we also find that strong flares can energize the middle atmosphere, causing regional enhancements in wind velocities up to 40 m/s in substellar nightsides between 30 and 50 km in altitude. Our results suggest that successive, more energetic eruptive events from younger stars may be an important factor in controlling the atmosphere dynamics of their planets, in addition to the properties of the planet itself.

Speaker: Prof. Howard Chen (Florida Institute of Technology)

3:00 PM A Bayesian View into Merger Jets: Multimessenger Constraints from GW170817, GW190425, and Short GRB Observations

The joint discovery of the binary neutron star (BNS) merger GW170817 and the associated short gamma-ray burst GRB170817A has shed new light on the study of such systems. In this work, assuming all BNS mergers produce GRBs, we aim to investigate the jet geometry of short gamma-ray bursts through a multimessenger approach. Our analysis incorporates observations from two BNS merger events, GW170817 and GW190425, as well as the gamma-ray prompt emission of GRB170817A and its subsequent X-ray afterglow. Additionally, we include the observed rate of short GRBs from a decade of Swift telescope operations to constrain the BNS merger rate.

Speaker: En-Tzu Lin (National Tsing Hua University)

3:15 PM Time-Frequency Correlation of Repeating Fast Radio Bursts

The production mechanism of fast radio bursts (FRBs) remains elusive, and potential correlations between burst occurrence times and various burst properties may offer important clues. Among them, the spectral peak frequency is particularly important because it may encode direct information about the physical conditions and environment at the emission site. Analyzing over 4,000 bursts from the three most active sources -- FRB 20121102A, FRB 20201124A, and FRB 20220912A -- we measure the two-point correlation function ξ(Δt,Δνpeak) in the two-dimensional space of time separation Δt and peak frequency shift Δνpeak between burst pairs. We find a universal trend of asymmetry about Δνpeak at high statistical significance; ξ(Δνpeak) decreases as Δνpeak increases from negative to positive values in the region of short time separation (Δt<0.3 s), where physically correlated aftershock events produce a strong time correlation signal. This indicates that aftershocks tend to exhibit systematically lower peak frequencies than mainshocks, with this tendency becoming stronger at shorter Δt. We argue that the "sad trombone effect" -- the downward frequency drift observed among sub-pulses within a single event -- is not confined within a single event but manifests as a statistical nature that extends continuously to independent yet physically correlated aftershocks with time separations up to Δt∼0.3 s. This discovery provides new insights into underlying physical processes of repeater FRBs.

Speaker: Shotaro Yamasaki (National Chung Hsing University)

3:30 PM → 4:15 PM Coffee break and poster session

4:15 PM → 6:15 PM Extragalactic astronomy and cosmology

Convener: Tetsuya Hashimoto (NCHU)

4:15 PM Probing 3D Gas Kinematic of HD 163296 Protoplanetary Disk

Understanding gas dynamics in protoplanetary disks is crucial for searching the planet forming region and comprehending the evolution of planetary systems. Various observational signatures suggest the presence of protoplanets in the disk of HD 163296, such as CO kink structure. To expand our understanding of planetary systems, we aim to focus on the gas kinematic structure of HD 163296. In this work, we successfully obtained the 3D gas kinematic structure using multi-wavelength line observations from ALMA MAPS, providing new insights into localized, non-Keplerian kinematic perturbations associated with potential planets and disk substructures.

Speaker: Jamie Chang (NTHU)

ASROC2025_Oral.pdf

4:30 PM The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in the Massive Star-forming Region Onsala 2

We investigate the magnetic field properties in the massive star-forming region Onsala 2 (ON2) in Cygnus using 850 µm polarization observations from the B-Fields in Star-Forming Region Observations (BISTRO) survey, which is a Large Program of the James Clerk Maxwell Telescope (JCMT). Our data cover the entire ON2 complex at a resolution of 0.12 pc, allowing us to spatially resolve polarized emission from filamentary structures. Within ON2, we estimate the magnetic field strength in identified clumps using the Davis–Chandrasekhar–Fermi method and analyze the energy budgets of the magnetic field, turbulence, and gravity. We further investigate local magnetic field morphologies, gravitational field vectors, and filamentary skeletons to explore the interaction between filaments and magnetic fields across the ON2 complex.

Speaker: Meng-Zhe Yang (National Tsing Hua University)

ASROC2025_Oral_MengZheYang.pptx

4:45 PM Machine learning classification of baseband data of CHIME FRBs

Fast Radio Bursts (FRBs) are enigmatic astrophysical phenomena that manifest as millisecond radio pulses. While the origin of FRBs is still unknown, observations confirm that some FRBs repeat and some do not apparently. In addition to the repetition nature, repeaters are known to show distinct physical properties from non-repeaters: broader pulses with narrower bandwidths for repeaters compared with non-repeaters. This might suggest different origins of these two types, indicating the importance of accurate classification of FRBs. However, the limited capability of the current radio telescopes causes difficulties in long monitoring of FRBs continuously to identify repeating FRBs. In addition, due to the limited telescope sensitivity, some faint repeating FRBs are missed, and hence, they could be misclassified as non-repeaters. The potential misclassified FRBs are known as repeater candidates. Since it is difficult to monitor all FRBs continuously, an alternative approach to the classification has been awaited. To overcome these issues, researchers have identified machine learning as a useful method to address these misclassified non-repeaters. In previous studies, researchers subjected CHIME/FRB catalogue 1 for machine learning using uniform manifold approximation and projection (UMAP). They have reported 188 repeater candidates out of 474 non-repeater in CHIME/FRB catalogue 1. In this work, we use CHIME/FRB baseband 1 catalogue which has significantly improved the positional accuracy (~10 arcsec for the best case) and time resolution of 140 FRBs from CHIME/FRB catalog 1. This improvement leads to more accurate measurements of fluence (only upper limits on fluences for CHIME cat1 while measured fluences for baseband data), duration, and position, etc. compared with the 1st CHIME/FRB catalogue that is used for previous machine learning studies. This enhanced dataset provides a valuable opportunity to refine the classification of FRBs and potentially validate previous findings. Therefore, The main object of our work is as follows: i) To assess the consistency of repeater candidate identification with previous work. ii) To identify new repeater candidates. iii) relationship between the current and previous results. We found 15 repeater candidate signals from 122 non-repeating sources of CHIME baseband catalogue. Among them 14 candidates are reported as candidates in the previous machine learning study, and another 1 new candidate identified in our work. The main objective of our work was achieved successfully. Furthermore, one of our repeater candidates has been confirmed as a repeater by the CHIME/FRB Collaboration.

Speaker: Mohanraj Madheshwaran (National Chung Hsing University)

5:00 PM Unveiling Hidden Lyman-Alpha Emitters in DESI with Deep Learning

Millions of spectra have been collected by the Dark Energy Spectroscopic Instrument (DESI) survey. While the DESI survey is designed to observe specific types of sources, unexpected sources are often included and hidden within the dataset. In this talk, I will show that a fraction of the sources observed by DESI are galaxies producing strong Lyman-alpha emission lines, known as Lyman-alpha emitters (LAEs), at redshifts greater than 2. These LAEs remain hidden in the DESI dataset because the survey and its data pipeline are not designed to detect them. To identify LAEs within the DESI dataset, we have developed and trained a convolutional neural network algorithm capable of automatically detecting LAEs, determining their redshifts, and estimating the emission line profiles simultaneously. Applying this algorithm to a million DESI spectra, we successfully identify approximately 15,000 LAEs. Finally, I will discuss the applications of this newly identified LAE sample, including its role in preparing for the DESI-II survey, which will select LAEs as one of its main target populations, as well as its use in investigating the physical properties of LAEs through high-quality combined spectra.

Speaker: Mr Jui-Kuan Chan (National Taiwan University)

5:15 PM Using Machine Learning to Study Quenching Modes of Galaxies through Spatially Resolved Data from HSC and MaNGA

The Hyper Suprime-Cam (HSC) offers high-resolution, wide-field imaging of the Universe. We explore the application of machine learning methods, specifically DEmP (Hsieh et al., 2014) and Convolutional Neural Networks (CNN), to predict spatially resolved stellar mass and star formation rate maps from HSC-SSP 5-band photometry using approximately 800 overlapping galaxies with MaNGA survey. We then employ a non-parametric method (Lin et al., 2019) to classify galaxy quenching modes as inside-out or outside-in, validating our approach. This work compares the machine learning-based results with those from MaNGA, demonstrating the efficacy of our method. Finally, we discuss potential applications of this technique to other large imaging surveys, such as LSST and Euclid, highlighting its significance in advancing our understanding of galaxy evolution.

Speaker: Wen-Yen Wu (NTNU/ASIAA)

5:30 PM Protocluster Candidates at z~9-10 in the JWST COSMOS-Web field

High-redshift protoclusters are crucial for understanding the formation of galaxy clusters and the evolution of galaxies in dense environments. With its unprecedented near-infrared sensitivity, the James Webb Space Telescope (JWST) enables the first exploration of protoclusters beyond z>10. Among JWST surveys, COSMOS-Web offers the largest area (~0.5 deg^2), making it an optimal field for protocluster searches.
In this study, we identify protoclusters at z ~ 9-10. We select F115W dropout galaxies (8 ≤ z ≤12) but exclude the highest-redshift end (z>11) due to the limited number (<10) of dropouts, yielding a sample of 763 galaxies. Overdensities (δ) are computed by weighting galaxy positions with their photometric redshift probability density functions (PDF), using a 0.9 cMpc aperture and a redshift slice of (±0.5). We implant 1,000 randomly scattered apertures to determine the significance (σ) of each overdensity and identify protocluster cores, as those with (σ≥3.0) and the overdensity greater than three times the standard deviation(δ≥21.8). Member galaxies are then linked using a 2D Friends-of-Friends (FoF) algorithm, with the difference between the 50th percentile of the PDF and the median redshift not exceeding 0.5. At least three member galaxies are required for a protocluster candidate.
We found four protocluster candidates at z ~ 9-10 with halo masses of ~ 10^11 solar mass. The detection of such overdensities at these redshifts provides a critical test for current cosmological simulations. However, confirming these candidates and distinguishing them from low-redshift dusty star-forming galaxies or Balmer break galaxies will require follow-up near-infrared spectroscopic observations. This work is submitted to PASA.

Speaker: Kent-Wei Wu

5:45 PM Luminosity Functions of Galaxy Clusters in eROSITA Final Equatorial-Depth Survey

The galaxy luminosity function, which describes a number density of a galaxy population as a function of their luminosities, provides key insights into galaxy formation and evolution. In this study, we investigate the optical luminosity functions of galaxies in clusters identified in the eROSITA Final Equatorial-Depth Survey (eFEDS), spanning redshifts from 0.1 to 1.3 and halo masses between $10^{13}$ and $10^{15}\ M_\odot/h$. We use the Public Data Releases of the Hyper Suprime-Cam Subaru Strategic Survey. We conduct an empirical model to separate the red-sequence population from the whole galaxy population and conduct a statistical fore/background subtraction. We model the resulting luminosity functions using the Schechter function and constrain the parameters through Markov Chain Monte Carlo (MCMC) fitting. Finally, we examine how the Schechter parameters depend on cluster mass and redshift.

Speaker: HUNG-YU LIN (National Cheng Kung University)

asroc2025 林泓宇.pdf

6:00 PM Cosmology in an extended parameter space: new constraints on dark energy and neutrino masses with DESI BAO

Based on arXiv: 2409.13022 (published in ApJ Letters). We update constraints on cosmological parameters in a 12-parameter model, which extends the standard 6-parameter ΛCDM to include dynamical dark energy and massive neutrinos, along with other new parameters. We use the latest Planck PR4 (2020) likelihoods, DESI DR1 BAO, and the latest uncalibrated type Ia Supernovae (SNe) datasets. In this talk, I will discuss the implications for dynamical dark energy in such an extended model, and at the same time, provide robust bounds on neutrino masses which will be useful for the astro- and particle physics communities. I will also discuss the current status of the weak lensing tension and the Hubble tension in this extended cosmology.

Speaker: Shouvik Roy Choudhury (Academia Sinica Institute of Astronomy and Astrophysics)

Talk_ASROC_Shouvik_Roy_Choudhury.pdf

4:15 PM → 5:15 PM Stars and star clusters

Convener: Ching-Ping Hu (National Changhua University of Education)

4:15 PM Modeling Stellar Spot Signals on T Tauri Stars: Toward Detecting Young Exoplanets

Our ultimate goal is to enhance our understanding of planet formation by identifying the youngest exoplanets orbiting T Tauri Stars (TTSs), systems typically aged around or below 5 Myr. Detecting planets around TTSs poses significant challenges because of the strong stellar activity and interference from protoplanetary disks. Stellar spots, prominent on young stars, generate strong radial velocity (RV) variations, often overshadowing or mimicking planetary signals and complicating exoplanet detection. As star spots rotate with the stellar surface, they induce periodic signals observable in photometry, RV, and average surface effective temperature. By modeling these variations across multiple wavelengths and comparing them with observational data, we can reconstruct stellar spot patterns, isolate spot-induced RV signals, and enhance sensitivity for detecting underlying planetary signals.

In this presentation, we outline our current progress in stellar spot modeling. We introduce our simulation techniques, highlight improvements in the accuracy of stellar model spectra, and present preliminary results. Among these results is a surprising discovery revealing that spot-induced RV signal strength can vary dramatically—by as much as 5 km/s—within a narrow spectral window of only 500 Å, demonstrating the efficacy and importance of our modeling approach.

Speaker: Shih-Yun Tang (Rice University/Lowell Observatory)

4:30 PM Aged but Populous: Deciphering Survival Galactic Open Clusters

The presence of old open clusters but remaining rich in members challenges the conventional view that such systems dissociate within 1 Gyr in the typically inhospitable Galactic disk. We present a study of eight such clusters—Collinder 261, NGC 2158, NGC 2477, NGC 2506, NGC 6791, NGC 6819, NGC 7786, and Trumpler 5—each with an age comparable to those of globular clusters yet harbors thousands of members. Using Gaia DR3, we determined the most reliable member list so far for these clusters, hereafter fitting the post-main sequence members with isochrones model to derive their ages. For example, NGC 6791, with a cluster radius of 20.6 arcmin and more than 5000 members, lies 4.4 kpc away and has an age of 8.5 Gyr, confirming the longevity and rich membership. With a comparison sample of "false positives", i.e., stars way outside the cluster region yet sharing the same proper motion and parallax ranges, the luminosity function and hence the mass function are derived. A comparison of the Gaia catalog (limiting mag of 21.5) against Pan-STARSS (limiting mag of 23.5) suggests the top-heavy mass function, i.e., depletion of low-mass members in each of these clusters is not due to data incompleteness, lending clear evidence of cluster dissociation. We propose a possible explanation for the survival of these elusive clusters to be their relative orbital isolation from the Galactic disk perturbation.

Speaker: Ms Chia-Ching Lin (Department of Physics, National Central University)

4:45 PM Brown dwarf number density in the JWST COSMOS-Web field

Brown dwarfs are failed stars with very low mass (13 to 75 Jupiter mass), and an effective temperature lower than 2500 K. Their mass range is between Jupiter and red dwarfs. Thus, they play a key role in understanding the gap in the mass function between stars and planets. However, due to their faint nature, previous searches are inevitably limited to the solar neighbourhood (20 pc). To improve our knowledge of the low mass part of the initial stellar mass function and the star formation history of the Milky Way, it is crucial to find more distant brown dwarfs. Using James Webb Space Telescope (JWST) COSMOS-Web data, this study seeks to enhance our comprehension of the physical characteristics of brown dwarfs situated at a distance of kpc scale. The exceptional sensitivity of the JWST enables the detection of brown dwarfs that are up to 100 times more distant than those discovered in the earlier all-sky infrared surveys. The large area coverage of the JWST COSMOS-Web survey allows us to find more distant brown dwarfs than earlier JWST studies with smaller area coverages. To capture prominent water absorption features around 2.7 μm, we apply two colour criteria, F115W – F277W + 1 < F277W – F444W and F277W – F444W > 0.9. We then select point sources by CLASS_STAR, FLUX_RADIUS, and SPREAD_MODEL criteria of the source extractor. Faint sources are visually checked to exclude possibly extended sources. We conduct SED fitting and MCMC simulations to determine their physical properties and associated uncertainties. Our search reveals 25 T-dwarf candidates and 2 Y-dwarf candidates, more than any previous JWST brown dwarf searches. They are located from 0.3 kpc to 4 kpc away from the Earth. The spatial number density of 900-1050 K dwarf is (2.0 ± 0.9) × $10^{-6}$ pc$^{-3}$, 1050-1200 K dwarf is (1.2 ± 0.7) × $10^{-6}$ pc$^{-3}$, and 1200-1350 K dwarf is (4.4 ± 1.3) × $10^{-6}$ pc$^{-3}$. The cumulative number count of our brown dwarf candidates is consistent with the prediction from a standard double exponential model. Three of our brown dwarf candidates were detected by HST, with transverse velocities 12 ± 5 km/s, 12 ± 4 km/s, and 17 ± 6 km/s. Along with earlier studies, the JWST has opened a new window of brown dwarf research in the Milky Way thick disk and halo.

Speaker: Yu-An Chen (NTHU)

ASROC2025_BD.pptx

5:00 PM Understanding the progenitor systems of peculiar 2002es-like and 2003fg-like supernovae with their host galaxies

The 2002es-like and 2003fg-like supernovae (SNe) are weirdos of SNe Ia. While their progenitor systems and explosion mechanisms are still mysterious, they were believed to have different origins from past observations. However, recent studies on their UV light curves indicated that they are actually very similar in the UV and could share the same origin. This work aims to investigate these peculiar explosions with their host-galaxy environments. We will examine and compare the host-galaxy properties of the 2002es-like and 2003fg-like SNe Ia and look for their environmental differences. Our sample contains the UV-to-IR imaging data of 15 2002es-like and 37 2003fg-like SNe Ia collected from the GALEX, PS1, SDSS, SkyMapper, 2MASS, and WISE databases. We extracted the global host-galaxy photometry with the Python package Hostphot and measured their host-galaxy properties (such as stellar mass, age, and star-formation rate) with the Python package Prospector. We then investigate the relations between the host-galaxy properties and various SN parameters (such as light-curve width and color) and discuss how they can shed the light on the origin of these peculiar SNe.

Speaker: Chia-Yu Cheng (NCU)

5:15 PM → 6:15 PM High-energy astrophysics

Convener: Ching-Ping Hu (National Changhua University of Education)

5:15 PM Investigating UV Spectral Differences in Early-Time and Near-Peak Type Ia Supernovae

We investigate the ultraviolet (UV) spectral properties of Type Ia supernovae (SNe Ia) at early times and near peak brightness using observations from the Swift UVOT grism. Our goal is to identify potential differences in UV features between these two phases. We examine how UV flux ratios correlate with key parameters such as the supernova decline rate, host-galaxy stellar mass, metallicity, star formation rate, specific star formation rate, and stellar age. To this end, we construct mean spectra for early-time SNe Ia, grouped by these parameters, and compare them with those of the near-peak sample. We also compare the UV properties of SNe Ia with high ejecta velocities to those with lower velocities. Additionally, we derive host-galaxy properties local to the SNe positions to assess whether UV spectral features are influenced by the local environment. Finally, we explore whether early-phase UV properties show any non-zero Hubble residuals. This comprehensive analysis aims to provide new insights into the explosion physics and progenitor systems of SNe Ia.

Speaker: Snehasish Bhattacharjee (National Central University)

5:30 PM Accelerated Parameter Estimation of Kilonova Implementing Conditional Variational Autoencoder

The coalescence of binary neutron star (BNS) in the event GW170817, leading to the generation of gravitational waves (GW) and accompanied by kilonova (KNe), the electromagnetic (EM) counterpart, has been a prime topic of interest for the Astronomy community in recent times as it provided much insight into multi-messenger astronomy. Since its discovery in 2017, several research teams have put forward models to describe the light curves and the parameters of the observed KNe. Here we propose a technique for parameter estimation where we utilize the strength and flexibility of conditional variational autoencoder (CVAE). Publicly available physical parameters corresponding to single light curves are used as training data. Once the training has concluded, we are able to perform parameter inferences with accuracy. Since this approach is likelihood-free, it provides relatively quicker results. We have demonstrated that the total time, from training until the parameter inference, is under 3 hours. In this work, we show that for a given KNe light curve, we can rapidly perform parameter inference based on the required model.

Speaker: Surojit Saha (Institute of Astronomy, National Tsing Hua University, Taiwan)

5:45 PM Neural Networks for Parameter Estimation of Orphan Afterglows in Rubin and Roman Data

The Rubin and Roman telescopes will come online soon and are expected to detect over 1000 “orphan afterglows” per year: broad-band long lasting emission from a gamma-ray burst (GRB), but without the GRB. Having a method to extract the physical parameters of these orphan afterglows will give us a better understanding of the progenitor systems. We start with a model that takes physical parameters of a GRB and computes the spectra and light curves. We will use this physical model to train a neural network to emulate these results in a fraction of the time. The reduced computational costs will allow us to solve the inverse problem: getting parameters from spectra or light curves.

Speakers: Damien Koon (Florida Institute of Technology), Krupa Pothiwala (Florida Institute of Technology)

Neural Networks for Parameter Estimation of Orphan Afterglows in Rubin and Roman Data

Neural Networks for Parameter Estimation of Orphan Afterglows in Rubin and Roman Data

6:15 PM → 8:15 PM Welcome reception

Saturday, May 17

9:00 AM → 10:00 AM Plenary Talk I: Recent and future lunar exploration missions conducted and planned by Japan, Prof. Makiko Ohtake (Okayama University)

Convener: Wei-Ling Tseng

10:00 AM → 10:45 AM Coffee break, group photo, poster session

10:45 AM → 12:15 PM Town hall meeting of Taiwan Astronomical Research Alliance (TARA)

Convener: Wen-ping Chen (IANCU)

10:45 AM Status and prospect of TARA

Speaker: Wen-ping Chen (IANCU)

11:00 AM Reports from TARA scientists

11:30 AM Discussion

Speaker: Chin-Fei Lee (ASIAA)

12:15 PM → 1:45 PM Lunch

12:15 PM → 1:45 PM Lunch with NSTC: Faculty only

Convener: Wei-Hao Wang (ASIAA)

1:45 PM → 3:30 PM Galaxies

Convener: Chien-Chou Chen (ASIAA)

1:45 PM Progenitor diversity in the accreted stellar halos of Milky Way-like galaxies

The tidal disruptions of dwarf galaxies are thought to be the most important process in building diffuse stellar halos around galaxies. Multiple spectroscopic surveys seek to reconstruct major assembly events with chemical and dynamical information of stellar halo stars. In our recently published paper, we compute the number of progenitors that contribute to the accreted stellar halos of simulated Milky Way–like galaxies as a function of radius (the radial diversity) in three suites of models: Bullock & Johnston, Aquarius, and Auriga. We demonstrate that the difference in the radial diversity between these simulation suites is beyond the halo-to-halo difference within each suite but reflects the star formation efficiency of dwarf galaxies. We compare, at face value, to current constraints on the radial diversity of the Milky Way's accreted halo. These constraints imply that the halo of our Galaxy is dominated by $\sim2$ progenitors in the range 8–45 kpc, in contrast to averages of $7$, $3.5$, or $4.2$ progenitors in the simulation suites over the same region. In addition, we compute the diversity in the energy-angular momentum ($E-L_z$) diagram to investigate the detection limits of current assembly history reconstruction methods based on $E-L_z$ diagrams.

Speaker: Ms Sy-Yun Pu (National Tsing Hua University)

2:00 PM Unsupervised Learning of Galaxy Spectra

The volume of astronomical data is growing at an unprecedented rate. Directly interacting with and interpreting vast amounts of high-dimensional data, such as galaxy spectra, has become increasingly challenging. To address this big-data challenge, dimensionality reduction techniques are essential for uncovering underlying patterns hidden within a dataset. In this talk, I will demonstrate how we reduce the dimensionality of galaxy spectra from the Dark Energy Spectroscopic Instrument survey using a technique called a variational autoencoder (VAE). A VAE can capture nonlinear features in the dataset and project high-dimensional data into a low-dimensional latent space. I will show that with a VAE, the information contained in galaxy spectra can be effectively represented by a few latent coefficients. We find that different types of galaxies, including passive galaxies, star-forming galaxies, and AGNs, are naturally separated in the coefficient space. Moreover, rare objects, such as Type II AGNs and double-peaked emission-line galaxies, emerge as outliers in this space. This highlights the power of dimensionality reduction in revealing key information from high-dimensional datasets. Finally, I will summarize our findings on linking the latent coefficients to the physical properties and morphology of galaxies, providing a machine-learning perspective on galaxy evolution and classification.

Speaker: YICHIEH CHANG (National Taiwan University)

2:15 PM Exploring Galactic Quenching: A Comparative Analysis of Criteria and Insights into Quenching Mechanisms

Galaxy quenching—the cessation of star formation—is a pivotal phase in galaxy evolution, which can occur due to various internal or external processes. Differentiating between spatial quenching patterns, such as inside-out versus outside-in modes, sheds light on the quenching mechanisms. However, the characterization of quenching modes involves how “quenched” regions are defined. In this study, we utilize a sample of ~ 10,000 galaxies from the SDSS/MaNGA survey and systematically investigate the spatial distribution of quenched areas using four commonly adopted tracers: the 4000 Å break (Dn4000), specific star formation rate (sSFR), post-starburst (PSB) criteria, and LI(N)ER regions from BPT diagrams. Our goal is to evaluate how each definition affects identifying quenching patterns. By quantifying the fraction and concentration of quenched areas within galaxies, we reveal that different tracers yield significantly different spatial quenching features: sSFR, Dn4000, and LI(N)ER-based definitions tend to indicate inside-out quenching, while the PSB tracer identifies both inside-out and outside-in patterns. These discrepancies reflect the sensitivity of each tracer to different timescales and stellar populations. Our findings emphasize that relying on a single quenching definition can lead to incomplete interpretations of quenching processes. A multi-tracer approach is thus crucial for a comprehensive understanding of how galaxies shut down star formation.

Speaker: Zi-Hua Ho (NTHUIoA)

Oral_ZiHuaHo.pptx

2:30 PM How Do Post-starburst Galaxies Quench? Analysis of Galaxy Merger

It is generally believed that galaxies evolved from star-forming to quiescent over time, but the mechanism of how galaxies quench remains a question. Post-starburst galaxies (PSBs) are transitional galaxies that have rapid quenching recently, making them crucial for understanding galaxy quenching. In a theoretical model, it increased SFR during the early stage of galaxy merger. Then, massive inflowing gas produced starbursts at the center. Subsequently, black hole grew rapidly, and remaining gas blew out. Finally, the star formation of galaxy quickly faded and then terminated.
This research used MaNGA IFU spectra which provide spatially resolved information. We use spectra characteristics to identify PSBs in three types, obscured post-starburst (OPSBs), fading post-starburst (FPSBs), and quenched post-starburst (QPSBs), that represent three phases from the end of starburst to quiescent. We found the percentage of PSBs with tidal features and the percentage of Seyferts are higher than those of control samples. Moreover, the percentage of tidal features also decreased overtime, from OPSBs to QPSBs. The absorption line indices EW(H$\delta_A$) show that the stellar population at the outskirt is older than the center in QPSBs. In addition, the attenuation is the highest near the centers of OPSBs and then decreases over time, which means there is a large amount of gas gathered in galaxy centers near the time of starburst. These features are consistent with the merger scenario. Therefore, our analysis suggests that rapid quenching is driven by merger in the local universe.

Speaker: Min-Hsuan Chung (National Taiwan Normal University)

ASROC_report_Chung_MinHsuan.pptx

2:45 PM The origin of dust and molecular gas in galactic winds

The origin of dust and molecular gas observed outside of galaxies remains puzzling and poorly understood. Dust is expected to be rapidly destroyed via sputtering, suppressing the formation of molecular hydrogen. In addition, cool clouds should be dispersed via fluid instabilities within a few cloud-crushing times. To study this problem, we use a suite of cloud-crushing simulations featuring a novel non-equilibrium chemistry network coupled with a dust evolution model that includes both sputtering and dust growth (accretion). We find that when cooling dominates over cloud destruction, the cloud develops into a two-phase structure: a warm, diffuse phase and a cold, dense phase. Dust in the cloud survives and can even reform due to dust growth in the cold phase. This leads to the formation of molecular hydrogen in the cold phase when a significant amount of dust survives. Our results support the scenario that the observed dust and molecular gas outside of galaxies originate from the interstellar medium entrained by galactic winds.

Speaker: Chia-Yu Hu (Institute of Astrophysics, National Taiwan University)

3:00 PM Probing the Circumgalactic Medium of Green Valley Galaxies

How galaxies transition from star-forming to passive remains an open question. To shed light on this process, one can study the properties of the circumgalactic medium (CGM)—the site of gas inflow and outflow—around galaxies in transition, known as green valley galaxies. By doing so, we can better understand how gas flow processes drive galaxy transformation. In this talk, I will present our investigation of the CGM properties of green valley galaxies by combining Hubble COS UV spectroscopic data with the galaxy catalog from the Dark Energy Spectroscopic Instrument (DESI). This large dataset allows us to measure the kinematic properties, spatial distribution, and column density of multiphase gas surrounding green valley galaxies. Finally, I will compare these CGM properties with those of star-forming and passive galaxies and discuss the implications of our findings for the physical mechanisms that quench star formation.

Speaker: Jin-Tong Feng (the graduate institute of astrophysics at NTU)

3:15 PM Generalized Gauss's Law of Gravity with a Conserved and Re-distributed Field Flux of a Transition to Non-spherical Equipotential Surface

A gravitational field flux conservation and redistribution picture is proposed with generalizing the Integral Gauss's law of gravity at non-relativistic limit. 1/r dependence along with a disk thickness dependence of gravitational field and the flat rotation curves are obtained by a Gaussian surface with cylindrical symmetry,
where most of the gravitational flux lines are assumed to be distributed eventually along the disk plane instead of the spherical distribution of Newtonian gravity.
For disk galaxies, a spherical to cylindrical transition across a critical field strength of the Gaussian surface symmetry is shown to give directly the M ∝ v4 baryonic Tully-Fisher relation. The Faber-Jackson relation of the elliptical galaxies can be explained by an off-spherical symmetry transition for the gravitational flux redistribution.
This transition is assumed to occur spatially between the core and the outskirts of disk galaxies. Such a spatial re-distribution of gravitational flux may give a geometric mapping between the generalized Gaussian surface of the field flux distribution and the real structures in various astronomical scales.
The structural-dynamical relations of disk galaxies revealed by the radial acceleration relation of SPARC data (Spitzer Photometry and Accurate Rotation Curves) have been compared by this mechanism.
The gravitational flux re-distribution transition suggests that the 10^-10 m/s^2 acceleration scale in MOND related studies can equivalently be interpreted as a critical field strength where the transition occurs. This gravitational flux redistribution picture may create a need for a non-Newtonian non-relativistic limit for the General Relativity. The implications of the temporal evolution of the "cylindrical to spherical
transition" of the gravitational field flux re-distribution mechanism, including an intrinsic instability of the gravitational field transition, spatial and temporal, is also discussed.

Speaker: Dr Te Chun Wang (Retired teacher)

asroc 2025 gravitational flux.pdf

asroc 2025 gravitational flux.pptx

1:45 PM → 3:30 PM High-energy astrophysics

Convener: Hung-Yi Pu (National Taiwan Normal University)

1:45 PM Statistical Inference of Fast Radio Burst Environments Using Galaxy Number Density: Similarities Between CHIME Repeaters and Non-Repeaters

Fast radio bursts (FRBs) are short-duration, bright radio emission pulses with energies. The exact origin of FRBs remains a mystery. However, FRBs are classified into two types depending on their repetition: repeaters and non-repeaters. Different progenitor types, such as magnetars for repeaters and cataclysmic events for non-repeaters, might explain their distinct behaviors. Therefore, understanding the difference between these two populations is a key to constraining their origins. However, due to the difficulty in precisely localizing FRBs, it is challenging to confirm if their progenitors differ. In this study, we attempt to estimate the galaxy number density associated with FRBs in the CHIME catalog using the galaxy catalog WISE × PS1. Since our method focuses on large-scale galaxy environments around FRBs, it is independent of the localization problem, allowing us to use samples of 26 repeaters and 238 non-repeaters, about two times larger than localized FRBs at present. If repeaters and non-repeaters originate in distinct galactic environments, it could imply different host and progenitor types. Conversely, similar environments might suggest a common progenitor. Here, we present our findings by comparing the density increments of both repeaters and non-repeater sources. The Kolmogorov-Smirnov (KS) test for the distributions of galaxy number densities around the FRB sources indicates no significant difference between repeaters and non-repeaters with a p-value of 0.405. Our finding suggests that repeaters and non-repeaters could share similar galactic environments and, hence, similar host and progenitor types. In addition to this, we find the majority of FRBs occur in underdense galactic environments compared to randomly selected regions, exhibiting a mild preference for young stellar populations.

Speaker: Vignesh Vavillakula Venkataramana Rao (National Chung Hsing University)

Vignesh ASROC-2025 slides.pdf

2:00 PM Anti-correlation between Flux and Photon Index of Hard X-ray Emission from The Crab

Using Swift Burst Alert Telescope event-mode data during Gamma Ray Burst occurrences, we conducted spectral analysis for the Crab system. From 38 good observations, which spans over a period of 18 years from 2006 to 2023, we found that the Crab's X-ray flux does not only flicker, but also significantly anti-correlates to its spectral power-law photon index. Since emission contribution of the Crab pulsar in this energy range is small, this anti-correlation is mainly about the emission of the Crab nebula. We suggest that this anti-correlation is an observational supporting evidence for the long-standing notion that the nebula emission is due to synchrotron radiation of shocked pulsar winds in the nebula.

Speaker: Koothodil Abhijith Augustine (Institute of Astronomy, National Tsing Hua University, Hsinchu)

Abhi_ASROC_2025.pptx

2:15 PM Properties of Double-Outbursts of MAXI J1834-021 In 2023

The Galactic transient black hole candidate exhibited 'faint' outbursting activity for approximately 10 months following its discovery on February 05, 2023. We study the evolution of both the temporal and spectral properties of the source using archival data from the NICER and NuSTAR satellites. The outburst profiles and the nature of QPOs suggest that the source underwent a mini-outburst following the primary outburst. A monotonic evolution of low-frequency QPOs from higher to lower frequencies is observed, which is further analyzed using the propagating oscillatory shock (POS) model. This analysis suggests the presence of a receding shock. Spectral analysis using both phenomenological (a combined disk blackbody plus power-law) and physical (TCAF) models allowed us to understand the accretion flow dynamics of the source during its active phases in 2023. The combined NICER and NuSTAR spectral fit of the source on March 10, 2023, using the TCAF and kerbb models, is studied to understand the broadband nature of the source. These physical models also estimate intrinsic source parameters such as mass, spin, distance, and inclination angle. Throughout the entire outbursting phase, the source remained in a harder spectral state, with a clear dominance of nonthermal emissions from 'hot' Compton cloud. The 2023 outbursting activity of MAXI J1834-021 can be classified as a combination of double 'failed' outbursts, as no softer spectral states were observed.

Speaker: Dipak Debnath (National Tsing Hua University)

2:30 PM Two Possible Optical--X-Ray Anti-Correlations of PSR J1023+0038

Using 18 X-ray/B-band simultaneous XMM-Newton observations (717 ks in total) of PSR J1023+0038 taken during the low-mass X-ray binary (LMXB) state, we find a general trend that the amplitude of the B-band orbital modulation was lower when the observed X-ray flux was higher. Depending on the analysis method adopted, the statistical significance of the anti-correlation can be from 1.3$\sigma$ to 3.1$\sigma$. This result challenges the general belief that the X-ray emission is one of the major heating sources for the optical modulation in redback pulsar binaries. We also extended the analysis to the GeV $\gamma$-ray band using the Fermi-LAT data, but the result is insignificant to claim any relations. Moreover, another X-ray/optical correlation regarding the low modes of the system was found in some of the XMM-Newton observations, and the astrophysical reason behind is currently unclear yet. These possible anti-correlations likely support that the irradiation is generally stronger when the X-ray flux is in a fainter state, indicating that there is a more dominant irradiation source than the X-ray emission.

Speaker: Ka Yui Au (National Cheng Kung University)

j1023_asroc.pptx

2:45 PM Simultaneous observations of an active repeater FRB 20240114A with Lulin One-meter Telescope and FAST

The radiation mechanism of fast radio bursts (FRBs) remains unknown. Because currently-survived theoretical models can basically explain the common features of FRBs in radio, including their short timescales and extremely high brightness temperatures, solely using radio data is not effective in distinguishing FRB models. Simultaneously detected optical counterparts of FRBs are the final piece of the puzzle to uncover their mysterious radiation mechanism because major theoretical FRB models, i.e., magnetosphere and external shocks, predict significantly different optical-to-radio fluence ratios. However, the hypothetical optical counterpart is yet to be detected because FRBs disappear in ~1 ms, making the simultaneous counterpart search challenging. To overcome this problem, we take advantage of monitoring observations by the Five-hundred-meter Aperture Spherical Telescope (FAST). FAST is the most sensitive single-dish radio telescope, regularly monitoring known repeating FRB sources. Once its monitoring is scheduled, we trigger simultaneous Target-of-Opportunity (ToO) observations with the Lulin One-meter Telescope (LOT; optical) in Taiwan, using a CMOS camera with a time resolution of ~17 ms. This is one of the shortest timescales conducted by CMOS cameras for FRBs so far, enhancing the sensitivity to the optical counterpart. In 2024, we triggered two ToO observations of LOT to conduct simultaneous observations of FRB 20240114A during part of the FAST's monitoring campaign. FRB 20240114A was first discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and is known as an active repeater. More than 17 (61) FRBs were detected with FAST on 7 (14) July during the LOT ToO observations. Based on the non-detection of optical counterparts to these bursts, the brightest case of the magnetospheric scenario of the optical counterpart is excluded.

Speaker: Tetsuya Hashimoto (National Chung Hsing University)

ASROC_2025.pdf

ASROC_2025.pdf

3:00 PM The Stability of Superorbital Period of Low-mass X-ray Binary 4U1820-30

4U 1820-30 is a ultra-compact low mass X-ray binary located near the center of globular cluster NGC 6624. In addition to its 685s orbital variation, it also exhibits a superorbital orbital modulation with a period of ~171 days. From the stability of this period, the superorbital modulation was considered being induced by a hierarchical third star orbiting around the binary system. To further confirm the stability of the period, we analyzed the light curves collected by Ginga, RXTE/ASM, RXTE/PCA, Swift, MAXI and Fermi. Combined with the result from Vela 5B observation, the superorbital period measured from the power spectra was found in fact decreasing form 176 days to 166 days. Phase analysis allows us to trace the superorbital period variation in more detail. The phase evolution revealed that the period may have experienced an abrupt change (glitch) from 170.78±0.79 days to 167.46±0.18 days around MJD 52502. On the other hand, the phase evolution was also well-fitted with a quadratic curve, indicating a period derivative of $\dot{𝑃}/𝑃=(−8.41 ± 1.58)×10^{−4} 𝑦𝑟^{−1}$. Either of these results challenges the stability of superorbital period predicted by the triple model.

Speaker: Jun-Lei Wu (Institute of Astronomy, National Central University)

3:15 PM The stellar size and morphology of X-ray-selected Active Galactic Nuclei Observed with JWST.

Theories of the formation of massive galaxies suggest that active galactic nuclei (AGN) play an important role in their evolution by shutting down star formation, which slows down stellar mass growth. However, the size and shape of galaxies during the AGN phase are not well established. Such information may shed light on the formation pathways in which galaxies evolve. Thanks to the high-angular resolution and sensitivity in the near-infrared of JWST NIRCAM, it is now possible to resolve the shape and sizes of galaxies during the bulk of stellar mass growth. Here, we present our results on the size and mass of X-ray-selected AGN detected from the C-COSMOS survey within the footprint of the COSMOS-Web program. Using our custom JWST pipeline, we show that most X-ray-selected AGN reside in massive galaxies with a significant bulge component but the imaging also shows signs of substructure such as disk, bars, and arms. Compared to the typical galaxy population, their size and mass relationship is sharper than that of star-forming galaxies.

Speaker: Bovornpratch Vijarnwannaluk (ASIAA)

1:45 PM → 3:30 PM Solar system and exoplanets

Convener: Wei-Ling Tseng

1:45 PM Modeling Streamer Structures in Collapsing Prestellar Cores

Streamers have been observed with high-resolution ALMA observations around many protoplanetary disks undergoing formation. They have been suggested to dominate the mass accretion budget from the collapsing prestellar core. Understanding the formation of streamers is there for important for explaining how protoplanetary disks receive mass from the envelope. We propose a model to explain the formation of streamer structures by considering density enhancements due to gravitational instability. We test our model against sources where streamers have been detected (ex. Per-emb-2 and Per-emb-50 observed with NOEMA) and fit for model parameters. This allows us to gain deeper insights into the physical origin of streamers and their role in mass transport from the core to the disk. In the future, the model can be applied to analyze many archival data that show signs of streamers.

Speaker: Tsung-Han Chuang (NTNU)

2:00 PM What If Planet Nine Is Currently Near Its Perihelion?

The outer solar system is theoretically predicted to harbor an undiscovered planet, often referred to as Planet Nine (P9). Simulations suggest that its gravitational influence could explain the unusual clustering of Kuiper Belt Objects (KBOs). However, there has been no observational evidence for the existence of P9 so far, since its predicted orbit is distantly beyond Neptune’s, where it reflects only a faint amount of Sunlight. As a result, P9 is expected to be very faint in optical wavelengths. In addition, P9 was suggested to have a semi-major axis of 700 AU and an eccentricity of 0.6, which means the heliocentric distance of P9 could vary between 280 AU and 1120 AU. Such a large distance led to the need for far-infrared all-sky surveys to detect the thermal radiation from P9. Our previous work searched for P9 using IRAS and AKARI and found one P9 candidate in the distance range of 500 – 700 AU with $M_{P9}$ ≤ $M_{Neptune}$. In this work, we continue our search with a closer distance range of 280 – 500 AU due to the uncertainty of P9’s current heliocentric distance. If P9 is currently approaching or passing its perihelion, we will have a chance to detect it in this work. We aim to search for P9 candidates moving slowly from an IRAS position to another AKARI position over 23 years with an angular separation of 69.6’ – 166’. The expected flux and orbital motion of P9 were estimated based on assumptions for its mass, distance, and effective temperature to ensure that it can be detected in two surveys. After a rigorous selection process, we found 3 good candidates from 643 possible IRAS – AKARI pairs. The AKARI detection probability map indicated that these 3 good candidates are likely slow-moving objects, which is consistent with our expectation of P9’s motion.

Speaker: Mr Terry Long Phan (Institute of Astronomy, National Tsing Hua University, Hsinchu, Taiwan)

2:15 PM Detecting a Possible Planetary companion of HAT-P-12b through Transit Timing Variations.

We present Transit Timing Variations (TTVs) of HAT-P-12b, a low-density sub-Saturn mass planet orbiting a metal-poor K4 dwarf star. Using 14 years of observational data, we analyzed 46 lightcurves with various models, including linear, orbital decay, apsidal precession, and sinusoidal models, to investigate the presence of additional planets. Frequency analysis using the Generalized Lomb-Scargle (GLS) periodogram identified a significant periodic signal at 0.00415 cycles/day (FAP = 5.1 $\times 10^{-6}$ %), suggesting the influence of an additional planetary companion. The sinusoidal model provides the best fit among the tested models, resulting in the lowest reduced $\chi_r^2$ of 3.2. Sinusoidal fitting of the timing residuals suggests that the companion has an estimated mass of approximately 0.02 $M_J$, assuming it is in a 2:1 Mean-Motion Resonance (MMR) with HAT-P-12b.

Speaker: Kaviya Parthasarathy (National Tsing Hua University)

2:30 PM Observations and Comparative Analyses of Sodium in Mercury’s and the Moon’s Exospheres

Both Mercury and the Moon possess tenuous, collisionless "atmospheres", known as "exospheres". Mercury’s proximity to the Sun, coupled with the absence of a dense atmosphere, exposes its surface to intense solar wind, solar radiation, energetic particles, and interplanetary meteoroid impacts. These interactions contribute to the formation and variability of its surface-bound exosphere. The Moon experiences similar exospheric production mechanisms.

In 1985, sodium was first detected in Mercury’s exosphere (Potter & Morgan, 1985). Through ground-based observations with the spectrometer, Potter and Morgan resolved the spectra and found the sodium D lines performed in their measurements, with the surface density estimated to be 1.5 × 10^5 cm^−3. Afterwards, a similar detection in the Moon’s exosphere followed (Potter & Morgan, 1988). Subsequent studies predicted (Ip, 1986; Smyth, 1986) and later confirmed (Potter, Killen & Morgan, 2002) the elongated structure of Mercury’s sodium exosphere due to solar radiation pressure acceleration, revealing an extended tail and bimodal high-latitude distributions.

While the Moon’s sodium exosphere, when viewed in an Earth-centered coordinate frame, exhibits a projected sodium spot with an angular size of approximately 3◦ ×3◦ (Smith et al., 1999) in the anti-sunward direction. This feature has been observed using all-sky cameras (Matta et al., 2019; Baumgardner et al., 2021), highlighting the role of radiation pressure and surface interactions in shaping its distribution.

We have conducted a series of observations on both Mercury’s sodium tail and the Moon’s sodium spot by different approaches, utilizing different system of instruments. Our goal is to explore Mercury’s sodium exosphere based on our own observations and refine the lunar sodium exospheric model with our data. Combining the observations of Mercury’s and Moon’s sodium, we can first understand the spatial distributions and characteristics of sodium exospheres, so as to probe into the surface processes of solar system objects.

Speaker: Chen-Yen Hsu (IANCU)

2:45 PM Transit Timing Variations of an Ultra-Short-Period Hot Jupiter WASP-18Ab

Long-term transit follow-up observations sometimes show Transit Timing
Variations (TTVs), which can provide clues to understanding the
evolution of the planetary system. We study an exoplanet WASP-18Ab which
has a mass about 10.43 Jupiter Mass and an orbital period 0.94 day only.
It is expected to experience the tidal interaction with its central
star, and shrink down its orbit. We fit the mid-transit times from light
curves obtained by TESS, CHEOPS, and also published literature data. Our
results indicate that (i) the orbit of WASP-18Ab is not decaying, (ii)
the TTVs of WASP-18Ab cannot be explained by the apsidal precession
model, and (iii) the models with sinusoidal variations provides a better
fit to the mid-transit times.

Speaker: Hsin-Min Liu (NTHU)

3:00 PM The Dynamical Evolution of Centaur with Considering the Non-Gravitational Force

Since the discovery of the first Centaur object in 1977, objects populated in the planet-crossing orbits between Jupiter and Neptune are believed to be the crucial segments of material transportation and evolution sequence in our solar system. The dynamical study reveals a clear, evidential evolution pathway from the orbital space beyond Neptune to the orbit within Jupiter, which is commonly accepted nowadays. The dichotomy of the Centaur and Trans-Neptunian Objects provides a clue to their origin and dynamical evolution history. However, there are still some unanswered questions. I will present my recent dynamical study in characterizing the dynamic properties of Centaur objects and Short-Period Comets from both qualitative and statistical points of view.

Speaker: Yu-Chi Cheng (IANCU)

3:15 PM Simultaneous Multi-site, Multi-wavelength, and Multi-messenger Monitoring of the Nearby Red Dwarf GJ 3147

We present a multi-site, multi-wavelength, and multi-messenger observing campaign of GJ 3147, a nearby (10 pc) red dwarf known for its frequent flaring activity. From November 11 to 17, 2021, the star was observed with photometry (Weihai, Xinglong, Lijiang, Nanshan, and Maidanak) and photopolarimetry (Lulin and ARIES). In about 100 data hours, three major flares and numerous minor ones were detected, including a major event on November 16 observed (1) by multiple telescopes all at R band, thereby with different sample functions, leading to the derivation of the underlined flare profile, e.g., the peak amplitude, impulse (energizing) and decay (cooling) timescales, which would have been otherwise unavailable with a single telescope alone, (2) with the same sampling function at g’, r’, and i’ bands, allowing us to estimate the flare temperature of approximately 8000 K. Additionally, the star was found to have a quiescent polarization level of 5.8% in g’, 2% in r’, and 0.5% in i’, suggesting scattering by an inhomogeneous atmosphere, likely due to dust condensation.

Speaker: Chen Yu Tai (IANCU)

ASROC_Stellar_Flare_GJ3147.pdf

ASROC_Stellar_Flare_GJ3147.pptx

3:30 PM → 4:15 PM Coffee break and poster session

4:00 PM → 6:00 PM Gravitational waves

Convener: Surojit Saha (Institute of Astronomy, National Tsing Hua University, Taiwan)

4:00 PM High Frequency Gravitational Wave (HFGW)

I will briefly review HFGW physics and the current situation of HFGW detection.

Speaker: Yi Yang (National Yang Ming Chiao Tung University)

20250517 HFGW.pptx

4:15 PM Using Likelihood Ratio for Searching Gravitational Waves from Single Detector with SPIIR Pipeline

We propose using likelihood ratio as a new ranking statistic for SPIIR to detect gravitational waves (GWs) from single detector data. We derived the forms of likelihood ratio for a candidate using its signal-to-noise ratio (SNR), chi-square, and auto-correlation length. For significance estimation, the background was constructed using one-week of data, and we used an exponential fit to extrapolate false alarm rate (FAR) estimates beyond the limit of one per observation time. Furthermore, we used a machine learning (ML) network SIGMa-Net to veto short-duration noise transients (glitches) to improve sensitivity. Here we show that, our method can recover all 6 single-detector events from O3 GWTC catalog, and no detector artefact has been assigned high significance.

Speaker: Weichangfeng Guo (University of Western Australia)

4:30 PM Improving Compact Binary Coalescence Searches by Vetoing Local Noise Transients

Compact binary coalescence (CBC) searches, which look for signals from binary black holes, binary neutron stars, and neutron star–black hole mergers, are a major part of contemporary gravitational wave (GW) astronomy. However, the sensitivity of these searches is often limited by local noise transients, or glitches, which can closely resemble real astrophysical signals in terms of time–frequency morphology. In this talk, I will present both analytical and machine learning (ML) methods we have developed to identify and veto such glitches, thereby improving the performance of CBC searches. On the analytical side, we introduce two chi-square tests: one using simulated sine–Gaussian waveforms and another using real glitches as basis vectors. Both tests help distinguish noise transients from astrophysical signals and lead to a significant improvement in search sensitivity. We also present an ML-based veto using sine–Gaussian projection (SGP) maps, which highlight clear differences between glitches and astrophysical signals. These maps serve as effective input features for classification, making them well-suited for real-time vetoing. This ML veto is currently being implemented in the SPIIR single-detector searches.

Speaker: Sunil Choudhary (University of Western Australia)

4:45 PM Noise Subtraction using Machine Learning on the Gravitational Wave Data

Now we are in the O4 run of the LIGO-Virgo-KAGRA (LVK) collaboration. Many machine learning techniques are being applied on the detection and data analysis on Gravitational Wave (GW) data. In this talk, I will introduce the current status of the noise subtraction method DeepClean in O4 run and how DeepClean and other machine learning techniques on the detection and parameter estimation of the GW signals of the Compact Binary Coalescence (CBC) events will work together as a whole machine learning pipeline.

Speaker: Chia-Jui Chou (National Yang Ming Chiao Tung University, Department of Electrophysics, Taiwan)

Noise Subtraction using Machine Learning on the Gravitational Data.pdf

5:00 PM Investigating Relations Between Denoised GW Structures and the Performance of ML-based GW Analysis

We investigated the relationship between the GW denoiser’s signal recovery and the prediction of the ML-based CBC analysis by training BBH, NSBH, and BNS binary classifiers on denoised strain data. We found that the GW detector can make confident detections when the signal recovery, measured by overlap, is larger than 0.2 for BBH, NSBH, and 0.1 for BNS. The results are consistent with our statements in the previous work. We also trained several regressors to investigate the relationship between the signal recovery and the parameter estimation results. Our work provides new insight into evaluating and developing future GW denoisers.

Speaker: Yu-Chiung Lin (National Tsing Hua University)

oral_fin.pdf

5:15 PM Glitch Vetoing for Core-Collapse Supernova Gravitational Wave detection via Machine Learning

The search for gravitational waves (GWs) from astrophysical sources has become a central pursuit in modern astrophysics. Among the most compelling but elusive targets are GWs from core-collapse supernovae (CCSNe), which are expected to produce highly complex and stochastic waveforms. However, the presence of non-Gaussian, transient noise artifacts—commonly referred to as glitches—poses a significant challenge to their detection, especially since glitches often mimic the unpredictable time-frequency structure of CCSN signals. To improve the reliability of CCSN detection in the presence of such artifacts, we developed a supervised machine learning (ML) framework specifically designed to distinguish between glitches and CCSN waveforms. Our approach utilizes 31 distinct CCSN models derived from recent self-consistent simulations to train and evaluate the classifier. We trained various models under different CCSN waveform constraints, and tested their robustness using CCSN signal injections into both glitch-contaminated and stationary noise environments across multiple detectors. Our best-performing model, evaluated at a fixed False Positive Rate of 5%, achieves a True Positive Rate of 50% for signals with a signal-to-noise ratio (SNR) greater than 12.57. This corresponds to a detection horizon of approximately 3.89 kpc for standard CCSN events and up to 80.15 kpc for more energetic explosions. These results highlight the potential of ML-based glitch vetoing to enhance the sensitivity and confidence of CCSN GW searches in real detector data.

Speaker: Andy Chen (Natinal Yang Ming Chiao Tung University)

ASROC CCSNet Slide

5:30 PM Machine Learning on Gravitational Wave Sky Localization: GW-SkyLocator_ARQS

Rapid localization plays an important role in multi-messenger astronomy. GW-SkyLocator_ARQS is a machine-learning method that realizes the low-latency search on compact binary coalescence. We provide the performance of GW-SkyLocator_ARQS on binary neutron star events with three detectors and four detectors.

Speaker: Chin Yi Chang (NTHU)

0517_ASROC.pptx

5:45 PM Investigation of the scattered light noise in KAGRA interferometer

The scattered light is the diffused light recoupling to the main optical beam inside the interferometers. In the KAGRA interferometer, the scattered light noise sometimes contaminated the sensitivity in the band of 30 ~ 100 Hz. It appeared in the time-frequency map with the characteristic arch-shape with a period of 2.5 seconds. With more understanding of scattering light, we may mitigate the loss of sensitivity at this frequency band. The previous research reported that the periodic motion frequency is close to the resonant frequency of Type-Bp suspension - 0.42 Hz and found the power recycling mirrors moved a lot at the same time.
In our research, we developed a new method to efficiently quantify the periodic behavior of scattered light in the strain or other channels by targeting and identifying the arch shapes in a time-frequency map, especially the Q-spectrogram. The benefit of using constant Q-transform is its variation of frequency resolution for different frequency bands. i.e. Q = f/δf. By adjusting the Q value, the pattern in the time-frequency map could be clearer.
Applying our method to the data would give us the time information of when scattered light noise can be seen in the time-frequency map and the period of the arch-shape pattern of the scattered light noise. By analyzing the data over several days, we found a positive correlation between the scattered light noise occurrence and the low-frequency seismic motion near the power recycling mirrors.

Speaker: Shih-Hong Hsu (National Yang-Ming Chiao-Tung university)

ASROC_v3.pdf

4:15 PM → 6:00 PM Galaxies

Convener: Ting-Wen Lan

4:15 PM Simulation studies of global resistive MHD accretion flows around spinning AGNs: the impact of resistivity on the MAD state

We investigate the effect of resistivity on the dynamics of accretion flow using a global simulation model. Our approach involves employing a resistive magnetohydrodynamic model (Res-MHD) around spinning active galactic nuclei (AGNs). We conduct a comparative study of 2D and 3D resistive models surrounding black holes. In our analysis, we examine the dynamics of accretion flow while considering globally uniform resistivity values that range from approximately 0 to 0.1. We observe that the mass accretion rate is quite similar during the initial phases of the simulation for both the 2D and 3D models. However, as the flow becomes more turbulent, multi-dimensional effects start to dominate, leading to differences in the mass accretion rates between the 3D and 2D models. All the resistive models in a highly magnetized flow fall into the Magnetically Arrested Disk (MAD) state. We find that high-resistivity flow reduces magnetorotational instability (MRI) turbulence in the accretion flow, while the turbulent structures remain qualitatively similar in low-resistivity flows. Additionally, we observe signs of plasmoid formation in low-resistivity flows compared to those with high resistivity. Furthermore, we do not find a clear correlation between the variability of accretion flow and resistivity. Lastly, our findings indicate that low-resistivity models produce jets with higher power than those with higher resistivity.

Speaker: Mohammed Ramiz Aktar (Institute of Astronomy, National Tsing Hua University)

ASROC2025-Ramiz.pptx

4:30 PM Jet-Driven Inflow and Physical conditions of Molecular gas in NGC 1068 from CO(1-0) and CO(2-1) observations

We present a detailed analysis of molecular gas in jet-interacting regions of NGC 1068 using ALMA archival data of CO(1-0) and CO(2-1) transitions. We identified a distinct feature where CO(1–0) shows redshifted absorption while CO(2–1) exhibits emission at the same location and velocity, observed consistently across several regions along the jet. Spectral profiles of CO(2–1) reveal redshifted secondary emission components, while CO(1–0) shows blended inverse P-Cygni–like absorption, particularly on the northeast (approaching) side of the jet. These redshifted features are interpreted as inflowing molecular gas, with the CO(2–1)–only component at $\sim1230~\mathrm{km~s^{-1}}$ likely tracing denser or shock-heated gas and CO(1-0) is likely tracing low density clouds or diffuse gas. Our results provide strong evidence for jet-driven inflow, highlighting the dual role of AGN jets in both removing and funnelling gas toward the nucleus. Excitation temperatures and optical depths were derived from a combination of emission and absorption line, revealing the physical condition of the gas.
Excitation temperatures were derived assuming local thermodynamic equilibrium (LTE), yielding values ranging from 69 K to 83 K across the studied regions. Using optical depth measurements we computed CO column densities of (2.61-4.38) $\times~10^{14}~\mathrm{cm^{-2}}$, corresponding to $\mathrm{H_2}$ column density of (3.26-5.47) $\times~10^{14}~\mathrm{cm^{-2}}$. Molecular gas masses were estimated from the integrated CO(1-0) fluxes, yielding values between $1.85\times10^{27}$ and $2.11\times10^{7}~\mathrm{M_{\odot}}$.

Speaker: Mahitosh Ray (National Central University)

4:45 PM Why are the radio sources missing in the Fornax cluster?

Recently, the ASKAP POSSUM and MeerKAT surveys revealed an apparent lack of radio source counts in the Fornax galaxy cluster field. The sources in this patch of sky also appeared to be less polarised. These observations are peculiar and could be important signatures of depolarisation on galaxy cluster scales. In this work, we quantified the effects on polarisation of radio point sources behind a large-scale intracluster shock. Our ray-tracing calculations revealed that, generally, bright sources do not experience any significant changes in polarisation, whereas faint sources either get severely depolarised or enhanced as their radiation propagates through the intracluster medium. Notably, most of the dim sources behind the shock gain linear polarisation. This is because the gas and magnetic fields are highly compressed within the shock, causing it to be more linearly polarised than the surrounding medium. We also carried out a magnetohydrodynamic FLASH simulation of an in-falling subcluster into a main cluster and found a substantial increase in the local Faraday rotation measures behind the shock front. These effects would impact the interpretations of radio observations, particularly with BURSTT and SKA-Low, where the polarisation bias in faint sources must be corrected for in the statistical analyses of dense rotation measure grids.

Speaker: Alvina On (National Center for Theoretical Sciences)

On-ASROC2025.pdf

5:00 PM A Deep Search for a Strong Diffuse Interstellar Band in the Circumgalactic Medium

Diffuse interstellar bands (DIBs) are weak, mysterious absorption features that have been detected ubiquitously in the Milky Way and other galaxies. However, their existence outside of galaxies remains unknown.
In this talk, I will present our study of searching for a DIB (DIB$\lambda4430$) outside of galaxies in the circumgalactic medium (CGM) environments. To this end, we make use of approximately 60,000 spectra of MgII absorbers, tracers of the cool CGM, from the Sloan Digital Sky Surveys, to create composite spectra with uncertainties for absorption line measurements being a few m$\overset{\circ}{A}$. I will show that even with very high quality data, there is no detectable DIB signals across the entire $E_{(B-V)}$ range traced by MgII absorption. The measurements are inconsistent with the signals detected within the Milky Way by $\sim5\sigma$, indicating that environmental factors affect the abundance of the DIB$\lambda4430$ carrier. This research is the first probing for DIBs outside of galaxies, and sheds light on the underlying mechanisms that regulate the production and destruction of DIB carriers.

Speaker: Chih-Yuan Chang (Institute of Astronomy and Astrophysics, Academia Sinica)

5:15 PM How Can Astrophysical Events Resolve the Fermi Paradox?

This study explores a possible solution to the Fermi paradox, which questions why we have not observed alien civilizations despite the vastness of the universe. Previous simulations by Zackrisson et al. (2015) suggested that a Kardashev-III type civilization, capable of harnessing the energy of an entire galaxy, could expand across 50% of the Milky Way (MW) in just 25 Myr. Similarly, Wright et al. (2021) proposed that galactic rotation could accelerate the transition from Kardashev-II to Kardashev-III civilizations. However, these models have not been confirmed by observations, and the paradox remains unresolved. This study investigates whether extreme astrophysical phenomena, such as supernova explosions and dense Giant Molecular Clouds (GMCs), could prevent alien civilizations from reaching a Kardashev-III level, thus explaining their apparent absence. Using simulations based on Wright et al. (2021), the researchers analyze the impact of supernova explosions in MW-like galaxies. The research findings show that with a supernova rate of 0.3 events per year, the effect on alien expansion is minimal, aligning with Burns & Parsons (2022). However, in galaxies with a much higher supernova rate (300 events per year), the time required to colonize 50% of the galaxy is delayed from 35 Myr to 70 Myr. Additionally, previous research by Burns & Parsons (2022) suggests that dense GMCs could have an even greater impact on hindering extraterrestrial expansion. This study aims to test and confirm that hypothesis as well. By considering these astrophysical barriers, this research suggests that extreme cosmic events may significantly slow down or even prevent the emergence of Kardashev-III civilizations, offering a potential resolution to the Fermi paradox.

Speaker: Mr Deriyan Senjaya (Department of Physics NTHU Taiwan)

5:30 PM Determining the mass of cosmic dust: the systematic errors induced by temperature-dependent opacity

One of the most powerful tools in the study of galaxies is the thermal emission of interstellar dust, which dominates their spectral energy distribution (SED) at far-infrared wavelengths. Using a dust emission model such as a modified blackbody, fits to the SED reveal the dust (and interstellar medium) column density and its temperature, making the dust SED a key tracer in Galactic and extragalactic studies.
However, SED fit results depend strongly on the adopted value for dust opacity. Recent experimental findings suggest that our previously adopted values for far-infrared dust opacity, which were extrapolated from shorter wavelengths, may be systematically biased. Dust opacity appears to be higher than previously thought and, crucially, dependent on temperature: as materials get warmer, their opacity increases and its wavelength dependence becomes shallower. It is essential to understand how these findings change our interpretation of dust emission SEDs.
I will present my team’s work to quantify the effect of temperature-dependent dust opacity on SED fits. This effect has been identified as a possible source of bias for some time, but has not yet been studied quantitatively. We use optical data on several candidate dust materials to model dust opacity as a function of wavelength and temperature, and we produce a grid of synthetic galaxy SEDs. By fitting these synthetic observations with a fixed-opacity model we can then recover the bias in the fit results. We find that the dust masses recovered by the fit can be underestimated or overestimated depending on the target’s temperature, redshift, and choice of photometric bands.
Finally, we explore the relevance of our findings for the determination of dust abundances in the early Universe, where dust mass estimates pose a challenge to dust formation models (the so-called “dust budget crisis”).

Speaker: Lapo Fanciullo (National Chung Hsing University)

Fanciullo_ASROC_Presentation.pdf

5:45 PM AstroSat UV Deep Field - probing interstellar dust of star-forming galaxies at redshift ~ 0.4 - 0.8

Multi-band observation of deep fields provides a unique scope to study different aspects of galaxy evolution by effectively detecting fainter sources in the distant universe. We utilize the angular resolution (~1.2 arcsec), sensitivity, and field of view of the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat to image several HST deep fields in the FUV and NUV bands. Combining UVIT imaging with other multi-band data from HST, KPNO, Spitzer, and Herschel, we study the UV continuum slope ($\beta$) and IRX-$\beta$ relation in a sample of UV-selected galaxies between redshift 0.4 and 0.75 in the AUDF-north field to show: (1) the interstellar extinction at z~0.6 follows the global $\beta$-z relation, reinforcing the gradual reddening of galaxy UV continuum with cosmic time (2) the selected galaxies support diverse attenuation laws with a specific preference to the SMC-like attenuation. Utilizing the JWST MIRI imaging of a sample of galaxies in the AUDF-south field, we further probe the 7.7 and 11.3 $\mu$m emission strength of the Polycyclic Aromatic Hydrocarbon (PAH) dust molecules at varying stellar UV radiation field at $z\sim0.6$. Our study shows a good correlation of PAH strength with galaxy stellar mass and rest-frame UV luminosity. Overall, I will present important insights on galaxy dust evolution at a less explored redshift regime that links the cosmic noon to the present day.

Speaker: Chayan Mondal (Academia Sinica Institute of Astronomy and Astrophysics (ASIAA))

4:15 PM → 6:00 PM High-energy astrophysics

Convener: Hsiang-Yi Karen Yang (National Tsing Hua University)

4:15 PM Exploring Core-Collapse Supernovae with GPU Acceleration Code GAMER: Dynamics, Magnetism, Gravitational Waves

Core-collapse supernovae (CCSNe) are among the most energetic astrophysical events and key sites for nucleosynthesis of heavy elements, and also thought be the multimessenger signal site, especially gravitational waves (GW). They are driven mainly by the neutrino explosion, but also complicate interplay of equation of state, gravity, and magnetohydrodynamics. We present results from numerical simulations of CCSNe conducted using the GPU-accelerated Adaptive-MEsh-Refinement code (GAMER). In particular, we investigate the role of rotation and magnetic fields in shaping the explosion outcome. Our study also explores the possible generation of GW signals, analyzing their characteristics and detectability. Additionally, we incorporate a numerical hybrid equation of state (EoS), combining a nuclear EoS with the Helmholtz EoS, which is crucial for modeling the long-term evolution of the supernova remnant. Tracer particles are used to track ejecta properties and nucleosynthesis pathways.

Speaker: Inhyeok Song (Institute of Astronomy, National Tsing Hua University)

ASROC_2025_Slides.pptx

4:30 PM Impact of r-Process Heating on Disk Outflows from Neutron Star Mergers

The detection of the neutron star merger event GW170817 through gravitational wave detectors and electromagnetic observations has provided critical insights into the properties of merger ejecta. In these mergers, the observed light curve, powered by radioactive decay, indicates that rapid neutron capture (r-process) nucleosynthesis generates heavy elements. The final abundances of these elements are shaped by ejecta properties such as velocity, electron fraction, and thermal evolution. These properties, in turn, are influenced by feedback from r-process heating. In this study, we perform viscous hydrodynamic simulations to investigate how nuclear heating affects disk outflows. By implementing a parameterized heating model based on local temperature and electron fraction histories, we find that r-process heating significantly modifies ejecta characteristics. Specifically, our simulations reveal a 10% increase in ejecta mass resulting from nuclear heating, accompanied by enhanced radial velocity and suppressed convective motion. These findings underscore the importance of incorporating r-process heating feedback into neutron star merger models to accurately predict outflow properties.

Speaker: Li-Ting Ma (Institute of Astronomy, National Tsing-Hua University)

2025ASROC_liting.pdf

4:45 PM The Dzhanibekov Effect and Acceleration of Highest-Energy Cosmic Rays in Magnetars

Magnetars, highly magnetized neutron stars, exhibit transient bursting activities and might accelerate ultrahigh-energy cosmic rays (CRs). Due to their strong magnetic fields, a magnetar can be deformed into a triaxial shape, leading to unstable free precession where one of the principal axes flips, a phenomenon known as the Dzhanibekov effect.
This phenomenon induces a sudden increase in the Euler force, disturbing the surface layer and potentially causing plastic flow and fractures. Such deformations may trigger a magnetar burst. If degenerate electrons are released from fractured regions, they could ignite pair plasma formation, producing photons similar to observed magnetar bursts.

The initial electron stream may also generate a strong electric field, briefly accelerating ions to ∼1 ZeV. Nuclear spallation reactions limit this process, predicting high-energy CR neutrons correlated with magnetar bursts. Furthermore, the spallation of ∼ZeV nuclei may explain ~10 PeV neutrino events observed by IceCube and KM3Net. These findings highlight the Dzhanibekov effect’s possible role in magnetar transients and its potential link to cosmic-ray and neutrino observations.

Speaker: Tomoki Wada (Tohoku Univ/ NCHU)

ppt file

Wada_2505ASROC.pdf

5:00 PM Simulating AGN feedback in galaxy clusters with pre-existing turbulence

Active galactic nuclei (AGN) feedback’s role in suppressing cooling flows in cool-core clusters is acknowledged, but the primary heating mechanism of AGN jets is debated. One potential heating mechanism is heating caused by turbulence within the intracluster medium (ICM). However, there has been disagreement between simulation and observational studies. Therefore, the goal of our study is to elucidate this discrepancy using 3D hydrodynamic simulations including both AGN feedback and pre-existing turbulence. Our results indicate that turbulence has a limited impact on entropy. From examining the second-order velocity structure (VSF$_2$) and power spectrum, we found that the turbulence dissipation rates per unit mass obtained from this two methods are consistent. Therefore, we will calculate the turbulent heating rate and assess its ability to offset radiative cooling. Leveraging new XRISM data, our research provides key insights into the long-standing problem of AGN heating in clusters.

Speaker: Jia-Lun Li (National Tsing Hua University)

Simulating feedback from active galactic nuclei in galaxy clusters with pre-existing turbulence.pdf

5:15 PM Time-dependent polarisation of radio emission from AGN jets during the neutrino flare episodes

Jet-star interactions in hadronic jets would facilitate proton-proton (pp) interactions in addition to electromagnetic flaring activities. The charged pions resulted from the pp interactions will give rise to neutrino emission, while the secondary electrons may modify the synchrotron spectrum.
In this work, we determine the spectropolarimetric signatures of AGN jets during neutrino flaring events triggered by pp interaction when a star traverses into the jets. We consider stars of different stellar types,
such as WR stars, red supergiant stars, and solar like stars. We focus on how stellar wind properties -
particularly the mass loss rate - affect the size of the emitting region by establishing pressure balance with the jet ram pressure, leading to a transition from optically thin to thick emission produced by the secondary electrons.

Speaker: Yee Xuan Yap (NTHU)

5:30 PM Effects on polarization properties of radio galaxies by magnetized AGN jets

Radio galaxies are a subtype of active galactic nuclei (AGN) generated by supermassive black hole jets. Polarization measurements of the radio lobes could potentially probe the magnetic field geometry and initial magnetization of the jets. Previous polarization observations have found magnetic field aligned with the jet axis; however, the connection between the magnetization of the jets and the observed polarized emission remains poorly understood. In this research, we use 3D magnetohydrodynamic code GAMER-2 to simulate magnetized AGN jets with a toroidal field geometry within an isolated cluster. We perform simulations with different jet magnetization, and study their difference in the evolution of field geometry within the lobes, and polarization and rotation measure maps.

Speaker: Hsu Zheng-Xian (NTHU)

Magnetized jets.pptx

5:45 PM Iliad: A GPU-Based General Relativisitc Monte Carlo Radiative Transfer Code in Kerr Spacetime

Modeling the multiwavelength spectra of hot accretion flows around black holes requires incorporating key radiative processes, including synchrotron emission, bremsstrahlung, and inverse Compton scattering, along with general relativistic effects. We present Iliad, a GPU-accelerated Monte Carlo ray tracing code for radiative transfer in Kerr spacetime. Covering frequencies from radio to X-ray, Iliad efficiently computes spectra and images by simulating photon trajectories and interactions with energetic electrons. The code is particularly suited for interpreting ongoing and upcoming mm/sub-mm VLBI observations of supermassive black holes, such as those at the centers of the Milky Way and M87. This tool enables high-fidelity modeling crucial for testing theoretical predictions against horizon scale observations.

Speaker: Hung-Yi Pu (National Taiwan Normal University)

6:00 PM → 6:15 PM Asteroid ASIAA naming ceremony

Convener: Yi Chou (Institute of Astronomy, National Central University)

6:15 PM → 8:15 PM Banquet

Sunday, May 18

9:00 AM → 10:00 AM Plenary Talk II: Bitter-sweet symphonies of planet formation, Dr. Min-Kai Lin (ASIAA)

Convener: Albert Kong

10:00 AM → 11:00 AM General assembly, Heaven Quest Award (天問獎), best poster award presentations

Convener: Albert Kong

11:00 AM → 11:30 AM Coffee break

11:30 AM → 1:00 PM Outreach and education

Convener: Hao-Yuan Duan

11:30 AM 3D數位星象儀在天文教育推廣上的應用

南瀛天文館具有全國唯一球幕3D星象劇場，每場次除了播映球幕影片之外，還包含了簡短的星象解說節目，從星座介紹、在太陽系內遨遊、特殊天象、各種主題式節目等，透過身歷其境的模擬效果，讓觀影民眾獲取天文新知。本主題將分享近年來在星象節目製作的經驗以及探討星象軟體發展的潛力。

Speaker: CHUNG-EN LEE (臺南市南瀛科學教育館)

11:45 AM 人人都是星艦工程師：與AI打造專屬你的天文探索App

隨著AI輔助的程式撰寫工具興起，軟體開發的技術門檻大幅降低，即便沒有程式設計經驗的人，也能透過與AI的協作，快速實踐自己的創意構想。天文教育領域也受益於此趨勢，現在人人都能成為星艦工程師，建造出專屬的「天文探索方舟」。我將以Replit、Windsurf、Cursor等工具為例，示範大眾如何與AI協作，結合開放資料，打造出專屬個人學習需求與興趣的天文探索App。

Speaker: Mr Yi-Hao Su (Astrohackers in Taiwan社群)

人人都是星艦工程師：與AI打造專屬你的天文探索App

12:00 PM Learning astronomy from unphysical scenes in movies

At the conclusion of our three-hour classes, it is not uncommon for students to exhibit signs of fatigue, causing a noticeable decline in their attentiveness to the lecture. This is particularly evident during physics classes when numerous theoretical equations are introduced. Following these equations for an extended period can be challenging for students, especially on warm days or after lunch. As fatigue sets in, students may start to nod off or yawn, further diminishing their ability to absorb and retain information effectively.

How can we get tired students back into the lecture? How can we keep them interested in the class content? I propose to answer this ambitious question by incorporating sci-fi movies into the class. Young generations of students are interested in sci-fi movies such as “Star Wars”, “Interstellar”, “Gravity”. “Star Trek”…etc. In fact, not a small number of students started learning physics inspired by these movies. Although some movies do a very good job of following the physis laws, however, these are still fiction. Unfortunately, they are full of unphysical phenomena/scenes, impossible to happen in the real world. In this project, we select an unphysical scene in a sci-fi movie as the topic of the week. We try to identify the problem of the scene and explain why it is unphysical, what happens if the scene follows real physics laws. In this talk, I will summarize the progress of our experiments this semester.

Speaker: Tomo Goto (IoA)

12:15 PM Estuary Planetarium: Developing Astronomical Game and Tools for Public

‘Estuary Planetarium’ has been funded since June 2024. We have a strong passion for teaching and outreach in astronomy. The image of "estuary" represents the connection between the stream of human history to the vast, and boundless ocean of the universe. Our team hopes to play such a role, guiding everyone into the world of astronomy. We used interactive astronomical teaching tools and escape room games to engage the public in exploring the fascinating phenomena in our solar system. In this presentation, we demonstrate our methodology and teaching tools, and share how we inspire the public and children. We will also discuss our future plans and upcoming activities. Let's set sail and explore the beautiful ocean of astronomy.

Speaker: Hsiang-Yu Chen (National Central University)

11:30 AM → 1:00 PM Star formation: (including high-energy astrophysics)

Convener: Shih-Ping Lai

11:30 AM Inferring Dense Confined Circumstellar Medium around Supernova Progenitors via Long-term Hydrodynamical Evolution

Circumstellar interaction of supernova (SN) ejecta is an essential process in the evolution and observations of SNe have found the signature of circumstellar interaction both in the early and late evolutionary phase of SNe. Here we show that if the SN forward shock plunges into tenuous stellar wind from dense circumstellar medium (CSM) residing in the vicinity of the progenitor, the subsequent time evolutions of the SN-CSM interaction system deviates from the prediction of self-similar solution. In this case, the propagation of the forward shock will be driven by the ram pressure of the dense confined CSM component until it will be mostly compressed by the SN ejecta component, and the forward shock decelerates faster than the prediction of thin-shell approximation once the confined CSM component reaches homologous expansion. When the ram pressure of the SN ejecta can again act on the shocked shell consisting of tenuous wind component, the forward shock velocity recovers and the overall evolution converges to that without the CSM breakout. We also show that this peculiar evolution will be reflected in observational signatures originating from SN-CSM interaction, taking rapid decline and rebrightening of radio emission as examples. Our results shed light on the importance of taking into account the effect of initial SN-CSM interaction even when we focus on observational properties of SNe a few years after the explosion.

Speaker: Tomoki Matsuoka (ASIAA)

ASROC2025_matsuoka.pdf

11:45 AM NICER Magnetar Burst Catalog

In this paper, we present a comprehensive catalog of magnetar bursts detected with NICER, aimed at characterizing their temporal and spectral properties. This study includes all available NICER observations of known magnetars and two magnetar-like rotation-powered pulsars, covering 7.5 years of data. Using the Bayesian blocks method, we systematically search for rapid flux variations in the light curves to identify bursts. With NICER’s large effective area and high timing resolution, we perform detailed timing and spectral analyses, measuring key burst parameters such as T90 duration, fluence, and peak flux. By examining parameter distributions and correlation coefficients, we explore potential relationships between burst properties. Additionally, we compare burst characteristics across different magnetars and magnetar-like pulsars, identifying similarities and differences that may provide insight into their emission mechanisms. This catalog serves as a valuable resource for understanding magnetar bursts, with implications for burst trigger mechanisms and magnetospheric dynamics.

Speaker: Che-Yen Chu (National Changhua University of Education)

ASROC2025_MGTburst.pdf

12:00 PM Probing Magnetic Structures of Supernova Remnants and Pulsar Wind Nebulae with the Imaging X-ray Polarimetry Explorer

X-ray polarization is a powerful tool for studying particle acceleration in high-energy astrophysical phenomena such as supernova remnants (SNRs) and pulsar wind nebulae (PWNe). Measurements of X-ray polarization provide valuable insights into the geometry and physical processes within these objects, revealing details about their magnetic field structures, particle acceleration mechanisms, and the nature of the emitting particles.
The launch of NASA’s Imaging X-ray Polarimetry Explorer (IXPE) in 2021 has enabled high-resolution mapping of magnetic field structures in these remnants and nebulae at X-ray energies, significantly advancing our understanding of their complex dynamics and underlying physics.
In this presentation, I will give a brief overview of IXPE and highlight some of our recent findings on X-ray polarization and the magnetic morphology of SNRs and PWNe.

Speaker: Yi-Jung Yang (National Central University)

12:15 PM Exploring Complex Organic Molecules in the Orion Protostellar Cores

Complex organic molecules (COMs) in solar-like young stellar objects (YSOs) are of great interest due to their potential link to the origin of life. Under the ALMA Survey of Orion PGCCs (ALMASOP) project, we have identified 11 out of 56 protostellar cores that are rich in warm COMs. Our modeling suggests that the observed COMs are primarily located in the warm, innermost regions of the envelope. Interestingly, in some cases, the COMs also appear to trace the base of bipolar jets and the rotating ring structure near or within the disk boundary. These findings demonstrate that COMs are not only valuable for their potential role in prebiotic chemistry within the eventual protoplanetary disk, but also serve as insightful tracers of the physical processes occurring in the innermost regions of protostellar systems.

Speaker: Shih-Ying Hsu (ASIAA)

12:30 PM Where the Ices Melt: Snow Lines of CH₃OH and NH₃ in Orion KL - Insights from ALMA Band 1 Mapping

Orion KL is a chemically rich high-mass star-forming region, characterized by strong molecular line emission and complex thermal structures. Using ALMA Band 1 data, we present rotational temperature (T_rot) and column density (N_tot) maps of CH₃OH and NH₃, two key tracers of dense gas and warm chemistry. CH₃OH, often considered a cornerstone molecule in the formation pathways of complex organic molecules (COMs), traces regions of active desorption and grain-surface chemistry, while NH₃ serves as a robust gas thermometer. In the central Orion KL region encompassing the Hot Core, Source I, and surrounding gas, we find consistent T_rot patterns between the two species, suggesting co-evolution or shared thermal excitation. The N_tot distributions further reveal abundance variations across the inferred snow lines (~100 K for CH₃OH and ~90 K for NH₃), offering new insights into the thermal-chemical structure and desorption processes shaping this prototypical high-mass star-forming environment.

Speaker: Yo-Ling Chuang (ASIAA)

12:45 PM Unveiling Central ortho-H2D+ Depletion at Sub-kau Scales in Prestellar Core G205.46M3

Prestellar cores represent the initial conditions of star formation. The Orion B prestellar core G205.46 M3 has been reported to exhibit two substructures, B1 and B2, which have been proposed as the stellar embryos of a future protobinary system. At this stage, heavy molecules such as CO are significantly depleted in these cold, dense environments, limiting our ability to probe core centers. In contrast, deuterated molecular ions, particularly oH2D+, emerge as key tracers due to enhanced deuterium fractionation at low temperatures. We present the ALMA oH2D+ and 820um continuum maps at ~300au resolution, showing oH2D+ depletion in the prestellar core G205.46M3. We identify a significant oH2D+ depletion zone of ~600au in diameter toward B1. Chemo-dynamical modeling reproduces the observed deuteration profiles with a core age of approximately 0.42 Myr, comparable to the free-fall time. This suggests that the substructures formed via turbulent fragmentation through rapid contraction rather than through slow, quasi-static contraction. Our observations also reveal that the gas between B1 and B2 exhibits nearly thermal velocity dispersion, which is consistent with a turbulent scenario in which turbulence dissipates in no more than a few free-fall times. Our results highlight the critical role of deuterated ions in probing both the chemical evolution and dynamical state of dense cores.

Speaker: Sheng-Jun Lin (ASIAA, Taiwan)

1:00 PM → 2:00 PM Lunch and departure