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PRODID:-//Heidelberg University//HePhySTO//EN
CALSCALE:GREGORIAN
BEGIN:VEVENT
DTEND:20260416T101500Z
UID:474edc016d5adbb2d12caf25fa8c53cf@physik.uni-heidelberg.de
DTSTAMP:20260411T173102Z
LOCATION:ARI\, Moenchhofstrasse 12-14\, Seminarraum 1.OG
DESCRIPTION:The origin of supermassive black holes in galaxy centers remain
 s one of the key unanswered questions in modern astrophysics. If SMBH seedi
 ng occurs at high redshift\, the outcomes for the black hole (BH) populatio
 n in the local Universe will differ significantly depending on whether the 
 seeds are light (stellar-mass) or heavy (hundreds of thousands solar masses
 ). A recently discovered population of active nuclear intermediate-mass bla
 ck holes (IMBHs\, 1e2<MBH<2e5) in the local Universe seems to favor the lig
 ht-seed scenario. However\, a disproportionately large number of IMBHs accr
 eting close to or above the Eddington limit pose a new question: Are we jus
 t lucky to see short bursts of activity or do they actually grow fast after
  many billions of years of quiescence? An unexpected solution comes from in
 -depth studies of nearby (z<0.3) analogs to Little Red Dots\, an abundant p
 opulation of point-like sources discovered in JWST surveys at high redshift
 s. These sources resemble AGN but lack some important features (X-ray\, hig
 h-ionization emission lines\, mid-IR excess). Our analysis of high-quality 
 spectra of 10 nearby Little Red Dots suggests that they are powered by supe
 rmassive (2e4-3e5 MSun) stars with dust envelopes living in massive young s
 tar clusters hosted by metal-poor Blue Compact Dwarf Galaxies. Dedicated mo
 dels of metal-enriched (i.e. Z=1e-4...1e-2 ZSun\; non-PopIII) SMSs reproduc
 e the observed spectral features of local LRDs\, such as photospheric absor
 ption lines\, stellar winds with high mass loss rates estimated from P-Cygn
 i profiles\, and broad exponential wings of hydrogen and helium lines that 
 mimic AGN\, which originate from Thomson scattering. SMSs are expected to l
 ive for 0.5-2 Myr after which they should collapse into IMBHs (i.e.\, massi
 ve seeds) that will accrete the surrounding (fallback) material at the Eddi
 ngton rate for several million years. This exotic scenario provides a self-
 consistent explanation for the observed properties of low-to-high redshift 
 LRDs and nearby active IMBHs. It also resolves the high-redshift quasar puz
 zle: z=7 MBH=1e9 MSun SMBHs become feasible because the BH seeds can be hea
 vy\, however the seeding can happen as late in the Universe&apos\;s history
  as z=0 even though the chances of achieving the conditions necessary for S
 MSs to form decrease over time because they require a low-metallicity envir
 onment.\n\nImported from https://www.physik.uni-heidelberg.de/hephysto/ (no
  warranty for accuracy).
URL;VALUE=URI:https://www.physik.uni-heidelberg.de/hephysto/index.php?s=tal
 k&id=12564
SUMMARY:ARI Institute Colloquium: Igor Chilingarian - Supermassive black ho
 le seeding: from intermediate-mass black holes to Little Red Dots
DTSTART:20260416T091500Z
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