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SUMMARY:Mapping the central regions of AGN through light echoes as a probe
  of the Hubble constant [Astrophysics Seminar]
DTSTART:20260224T060000Z
DTEND:20260224T070000Z
DTSTAMP:20260418T045600Z
UID:indico-event-413@events.iiap.res.in
DESCRIPTION:Speakers: Amit Kumar Mandal (Center for Theoretical Physics of
  the Polish Academy of Sciences\, Warsaw\, Poland)\n\nAbstract: The light
 -echo(reverberation mapping) technique is a powerful tool to probe the cen
 tral regions of active galactic nuclei(AGN)\, inaccessible to current imag
 ing capabilities. The structure of the broad line region(BLR) and the phys
 ical origin of continuum time delays in AGN are not understood. To address
  these\, we have developed a model that combines a standard accretion disk
  with an optional inner hot flow\,a lamp-post irradiation geometry\,and a 
 BLR structure shaped by radiation pressure acting on dust. The model is pa
 rameterized by the black hole mass\,accretion rate\,viewing angle\,lamp-po
 st height\,cloud density\,and cloud covering factor. With this framework\,
  we are able to reproduce the broadband emission\, the Hβ reverberation d
 elay\, and the observed inter-band continuum time delays. By performing si
 multaneous fitting of the lag-spectrum and the spectral energy distributio
 n\, while treating the accretion rate and luminosity distance as free para
 meters\, this approach enables an independent determination of the Hubble 
 constant. Motivated by this\, we have initiated a photometric AGN monitori
 ng program\, Hubble Constant Constraint through AGN Light curve Observatio
 ns(HALO) at the Obserwatorium Cerro Murphy in Chile. In this talk\, first\
 ,I will present the HALO program\, focusing on modeling time delays\, and 
 discuss its synergy with the LSST survey in addressing the Hubble tension.
  Second\,I will present recent results from BLR reverberation mapping from
  the Seoul National University AGN Monitoring Project\,including an update
 d BLR size-luminosity relation for improved single-epoch black hole mass e
 stimates. Finally\,I will discuss dust reverberation mapping results that 
 constrain the size of the dusty torus in AGN. Hence\,by unifying accretion
  disk\,BLR\,and dust reverberation modeling with dedicated AGN monitoring\
 ,our framework provides an independent route to probe AGN inner structures
  and constrain cosmological parameters in the LSST era.\n\nhttps://events.
 iiap.res.in/event/413/
LOCATION:Auditorium
URL:https://events.iiap.res.in/event/413/
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