S22A0037
S22A0037
This proposal aims for taking optical and near-infrared spectra and imaging with Keck/LRIS and Keck/MOSFIRE, respectively, of a drastically fading quasar at the epoch of the cosmic noon, z=1.767 (by a factor of ∼30 in rest-UV broad-band brightness, probably indicating the large decline in accretion rate) between the SDSS and HSC-SSP data (over ∼15 years). This quasar is the best candidate of so-called changing-look quasars in which AGN activity shuts down for some reason in a short time scale. In this proposal, we mainly measure the flux of the remaining broad component of CIV, CIII], MgII, and Hβ emission lines in the spectroscopic observations and construct the spectral energy distribution of the host galaxy covering the shortward and longward of the 4000Å break with high signal-to-noise ratios in the imaging observations. The follow-up observations in this proposal for this object after the fading, combined with the previous data (before the fading), enable us to study in great detail (i) what happens in this kind of rapid change in accretion state, including examination of whether or not obscuration of the accretion disk happens, (ii) the host galaxy properties without being affected by strong radiation from AGN.
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