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VERSION:2.0
PRODID:-//Heidelberg University//HePhySTO//EN
CALSCALE:GREGORIAN
BEGIN:VEVENT
DTEND:20261105T111500Z
UID:c0ff7fcc6b74ea3d5160d0ca5d1e30b5@physik.uni-heidelberg.de
DTSTAMP:20261007T220303Z
LOCATION:ARI\, Moenchhofstrasse 12-14\, Seminarraum 1.OG
DESCRIPTION:Little Red Dots (LRDs) are compact sources at z > 5 discovered 
 with JWST\, characterized by\nbroad Balmer emission lines\, narrow absorpti
 on features\, and strong Balmer breaks. These signatures point to dense\, o
 ptically thick hydrogen gas surrounding rapidly growing black holes\, but t
 heir interpretation depends critically on how Balmer photons propagate thro
 ugh this gas. In this talk\, I will present the formation of Balmer lines i
 n LRDs via scattering processes using 3D Monte Carlo radiative transfer sim
 ulations. I will first discuss how various scattering processes reshape hyd
 rogen-line profiles and ratios\, demonstrating that broad\nand asymmetric B
 almer lines do not necessarily trace gas kinematics alone. I will then focu
 s on modeling\nthe Halpha and Hbeta profiles of LRDs observed with JWST/NIR
 Spec and constraining the n=2 hydrogen column\ndensity from the Balmer brea
 k. The observations reveal a fundamental puzzle: Hbeta absorption is system
 atically deeper than Halpha\, despite the substantially larger scattering c
 ross-section of Halpha. A homogeneous medium cannot\nreproduce this orderin
 g or simultaneously satisfy the column-density constraints from Halpha\, Hb
 eta\, and the Balmer\nbreak. We show that these tensions are resolved by a 
 multiphase medium consisting of dense\, optically thick\nclumps embedded in
  diffuse hot gas. Our results demonstrate that Balmer spectra encode the un
 resolved\nphase structure of gas in LRDs.\n\nImported from https://www.phys
 ik.uni-heidelberg.de/hephysto/ (no warranty for accuracy).
URL;VALUE=URI:https://www.physik.uni-heidelberg.de/hephysto/index.php?s=tal
 k&id=13008
SUMMARY:ARI Institute Colloquium: Seok-Jun Chang - Formation of Balmer Line
 s in Little Red Dots with Radiative Transfer in Multiphase Gas
DTSTART:20261105T101500Z
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