Poster Presentation
MIR Search of Heavily Obscured z > 3 AGN Missed in X-ray Surveys
Presenter: Naoki Matsumoto (Tohoku University)
X-ray emission is a unique and ubiquitous feature of AGN, and X-ray surveys of AGN have demonstrated their high completeness and low contamination rate even for low-luminous and/or obscured populations. However, it is possible that such X-ray surveys miss a significant population of heavily obscured AGN, e.g. Compton-thick AGN, due to the effect of extinction even in the hard X-ray band. Such heavily obscured AGN in the early universe could represent an early violent formation and growth phase of SMBHs and their host spheroidal components.
In order to search for the heavily obscured AGN at z > 3 missed in the X-ray surveys, we focus on the hot dust emission at 2-6 um redshifted into the Spitzer MIPS 24 um band. It corresponds to the ~1500 K thermal emission which makes an excess in the SED, known as one of the observational features of AGN. Identification of the hot dust emission relies on the redshift determination mostly obtained with photometric method, because the band covers longer rest-frame wavelength range for objects at z < 3. We constructed a large sample of galaxies with photometric redshift using HSC-SSP and CLAUDS wide(~5 deg^2) and deep(~27 mag) imaging dataset(Vijarnwannaluk et al. 2022). In order to estimate the intrinsic AGN luminosity, we conducted a SED fitting analysis to the MIPS selected sample with CIGALE code(Boquien et al. 2019, Yang et al. 2020, 2022) utilizing the multi-wavelength data from radio 1.4 GHz to optical CLAUDS u* band in the XMM-LSS field.
As a result of SED fitting analysis, we obtained 35 X-ray non-detected objects as the candidates. The estimated AGN bolometric luminosities reach 10^46-47 erg/s, suggesting that they are strongly obscured in the X-ray band.
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