안녕하십니까.

오는 수요일(7월 8일) 오후 4:00에 아래와 같이 2026년 상반기 정규 콜로키움이 진행될 예정입니다.

발표 후에는 연사와의 대화시간(5:00-5:40) 및 저녁 식사가 예정되어 있으니 많은 참여 부탁드립니다.

발표자: 송현미 교수 (Chungnam National University)

호스트: 선광일

장소: 장영실홀 331-2

일시: 7월 8일 (수) 오후 4:00

교육학점: 천문연 소속 현장참석자의 경우 필수 0.5 학점 부여

이번 콜로키움은 오프라인으로만 진행하므로 유의 하시기를 바랍니다

제목: Lighting Up the Early Universe: Probing Lyman-Alpha Emitters through Radiative Transfer Simulations and Narrowband Surveys

초록: 

Lyman-alpha emitters (LAEs) provide a crucial window into the high-redshift universe, allowing us to trace star formation, probe the epoch of reionization, and map the circumgalactic medium (CGM). However, because Lyα is a resonant line, its photons are endlessly scattered by neutral hydrogen, making it inherently difficult to extract intrinsic physical properties from observed spectra and surface brightness profiles (SBPs). In this talk, I will present a multi-scale approach to decoding these complex radiative transfer effects. First, we explore the detailed physics of the CGM using an outflowing-halo Monte Carlo Radiative Transfer (MCRT) model. By applying this model to deep integral-field observations of 163 LAEs from MUSE at z=3-6, we demonstrate that simultaneously fitting both the Lyα spectrum and the SBP is absolutely essential to break severe parameter degeneracies. This modeling reveals that the spatial extent of Lyman-Alpha Halos (LAHs) is largely driven by the physical extents of the medium and the source, coupled with low expanding velocities at large radii, rather than solely by optical depth. Building on these physical insights, we then transition to the massive statistical power of the One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey, which provides uniformly selected LAEs across multiple cosmic epochs. I will present our recent targeted search for Lyman-continuum (LyC) leaking galaxies among a pristine sample of 851 LAEs at z=4.5. Using deep CFHT u/u∗ band imaging, we identified 12 "gold" and 39 "silver" individual LyC leaker candidates. While stacking the full sample yields a non-detection--reflecting highly stochastic intergalactic medium transmission and intrinsic faintness--the robust individual candidates provide critical clues into the sources responsible for cosmic reionization, revealing tentative correlations between LyC leakage, UV continuum flux, and Lyα equivalent width. Finally, I will discuss our ongoing work on measuring LAHs around LAEs at z=2.4 and 3.1 using the ODIN narrowband survey. By combining large statistical samples with insights gained from radiative transfer modeling, this effort will help connect the observed properties of Lyα halos to the underlying distribution and kinematics of gas around galaxies.

진행언어: 한국어

슬라이드언어: 영어

천문연 콜로키움 위원회 (김종수, 선광일, 이창원, 문홍규, 한정열, 홍성욱)

운영위원회 (김진호, 홍준석, 석지연, 이재현, 유영삼, 송상헌)

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Dear all,

The KASI's regular colloquium is scheduled at Jul. 8, as shown below.

A conversation session with speakers and dinner are scheduled after the colloquium.

Speaker: Prof. Hyunmi Song (Chungnam National University)

Host: Kwang-Il Seon

Place: Jang Yeong-sil Hall 331-2

Time: July 8 (Wed) 4:00 pm 

KASI Educational credits: 0.5 educational credits are awarded to off-line attendees.

Note that this colloquium is offline only.

Title: Lighting Up the Early Universe: Probing Lyman-Alpha Emitters through Radiative Transfer Simulations and Narrowband Surveys

Abstract: 

Lyman-alpha emitters (LAEs) provide a crucial window into the high-redshift universe, allowing us to trace star formation, probe the epoch of reionization, and map the circumgalactic medium (CGM). However, because Lyα is a resonant line, its photons are endlessly scattered by neutral hydrogen, making it inherently difficult to extract intrinsic physical properties from observed spectra and surface brightness profiles (SBPs). In this talk, I will present a multi-scale approach to decoding these complex radiative transfer effects. First, we explore the detailed physics of the CGM using an outflowing-halo Monte Carlo Radiative Transfer (MCRT) model. By applying this model to deep integral-field observations of 163 LAEs from MUSE at z=3-6, we demonstrate that simultaneously fitting both the Lyα spectrum and the SBP is absolutely essential to break severe parameter degeneracies. This modeling reveals that the spatial extent of Lyman-Alpha Halos (LAHs) is largely driven by the physical extents of the medium and the source, coupled with low expanding velocities at large radii, rather than solely by optical depth. Building on these physical insights, we then transition to the massive statistical power of the One-hundred-deg2 DECam Imaging in Narrowbands (ODIN) survey, which provides uniformly selected LAEs across multiple cosmic epochs. I will present our recent targeted search for Lyman-continuum (LyC) leaking galaxies among a pristine sample of 851 LAEs at z=4.5. Using deep CFHT u/u∗ band imaging, we identified 12 "gold" and 39 "silver" individual LyC leaker candidates. While stacking the full sample yields a non-detection--reflecting highly stochastic intergalactic medium transmission and intrinsic faintness--the robust individual candidates provide critical clues into the sources responsible for cosmic reionization, revealing tentative correlations between LyC leakage, UV continuum flux, and Lyα equivalent width. Finally, I will discuss our ongoing work on measuring LAHs around LAEs at z=2.4 and 3.1 using the ODIN narrowband survey. By combining large statistical samples with insights gained from radiative transfer modeling, this effort will help connect the observed properties of Lyα halos to the underlying distribution and kinematics of gas around galaxies.

Language: Korean

Slide Language: English

KASI Colloquium committee (Jongsoo Kim, Kwang-Il Seon, Chang Won Lee, Hong-Kyu Moon, Jeong-Yeol Han, Sungwook Hong)

Working committee (Jinho Kim, Junseok Hong,  Ji Yeon Seok, Jaehyun Lee, Young Sam Yu, Sanghun Song)