J/MNRAS/537/1444   SRG/eROSITA CT AGN cand. in Lockman Hole (Belvedersky+, 2025)

Reflection-dominated Compton-thick AGN candidates in the SRG/eROSITA Lockman Hole survey. Belvedersky M.I., Bykov S.D., Gilfanov M.R., Medvedev P.S., Sunyaev R.A. <Mon. Not. R. Astron. Soc. 537, 1444-1458 (2025)> =2025MNRAS.537.1444B 2025MNRAS.537.1444B (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; X-ray sources Keywords: catalogues - surveys - galaxies: active - galaxies: nuclei - X-rays: galaxies Abstract: We search for reflection-dominated Compton-thick active galactic nuclei (CT AGN) candidates in the Lockman Hole region using the data of SRG/eROSITA Lockman Hole survey. We selected sources with anomalously hard photon indices in the 0.3-8.0keV band, untypical for type I AGN. In particular, we required that the upper end of the 9% error interval did not exceed a fiducial boundary of GAMMA=1.3. We found 291 sources which constitute a rare subpopulation among extragalactic X-ray sources detected by eROSITA in the Lockman Hole field, ∼5%. These sources constitute the eROSITA sample of CT AGN candidates in the Lockman Hole field. We further divide the sources into three categories depending on the availability of reliable redshift and statistically significant detection of intrinsic absorption. We present two catalogues: the bright sample (37 sources) and the faint one (254). We estimate the fraction and sky density of reflection-dominated CT AGN candidates. We show examples of individual spectra and use stacking analysis to search for possible redshift evolution of their properties with redshift. We analyse combined eROSITA spectra of bright sources of different categories with a physically motivated spectral model UXCLUMPY and find them fully consistent with the fits to the ∼1Msec XMM-Newton data for one of our reflection-dominated CT candidate, Type 2 galaxy SRGe J105348.6+573032. The catalogues of CT AGN candidates could be a good starting point for planning future studies and follow-ups at all wavelengths. Description: We present two catalogues of reflection-dominated CT AGN candidates in Lockman Hole: the bright sample (37 sources) and the faint one (254). We estimate the fraction and sky density of reflection-dominated CT AGN candidates. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file tablea1.dat 342 37 SRG/eROSITA CT AGN candidates in Lockman Hole, bright sample tablea2.dat 342 254 SRG/eROSITA CT AGN candidates in Lockman Hole, faint sample -------------------------------------------------------------------------------- Byte-by-byte Description of file: tablea1.dat tablea2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- srcid SRG/eROSITA short unique source ID (srcid) 6- 26 A21 --- Name SRG/eROSITA source name, SRGe JHHMMSS.s+DDMMSS (NAME) 28- 45 F18.14 deg RAdeg SRG/eROSITA right ascension (J2000) (RA) 47- 64 F18.15 deg DEdeg SRG/eROSITA declination (J2000) (DEC) 66- 75 F10.7 arcsec ePos SRG/eROSITA positional uncertainty (98% confidence) (POS_R98) 77- 88 F12.7 ct Cts SRG/eROSITA source count number (CTS) 90- 99 F10.7 ct e_Cts ? SRG/eROSITA source count number error (CTS_ERR) 101-114 E14.7 10-17W/m2 F0.5-2.0 SRG/eROSITA source flux in the 0.5-2.0keV energy range (FLUX_05-20) 116-128 E13.7 10-17W/m2 e_F0.5-2.0 ? SRG/eROSITA source flux error in the 0.5-2.0keV energy range (FLUX05-20ERR) 130 I1 --- Cat [1/3] Category of a reflection-dominated CT AGN candidate (category) (1) 132-147 A16 --- DESI Optical counterpart ID from Bykov et al. (2022, AstL, 48, 653, doi.org/10.1134/S1063773722110044) (desi_id) 149-166 F18.14 deg RADdeg Optical counterpart right ascension (J2000) (desi_ra) 168-185 F18.15 deg DEDdeg Optical counterpart declination (J2000) (desi_dec) 187-192 F6.3 --- mo1-PhIndex ? Photon index derived using the phabs*powerlaw XSPEC model (model 1) (mo1_PhoIndex) 194-198 F5.3 --- E_mo1-PhIndex ? Photon index positive error (90% confidence, model 1) (mo1PhoIndexperr) 200-205 F6.3 --- e_mo1-PhIndex [] Photon index negative error (90% confidence, model 1) (mo1PhoIndexnerr) 207-210 F4.1 --- mo2-PhIndex ? Photon index derived using the phabs*zphabs*zpowerlw XSPEC model (model 2) (mo2_PhoIndex) 212-233 E22.17 --- E_mo2-PhIndex ? Photon index positive error (90% confidence, model 2) (mo2PhoIndexperr) 235-253 F19.17 --- e_mo2-PhIndex ? Photon index negative error (90% confidence, model 2) (mo2PhoIndexnerr) 255-276 F22.18 10-22cm-2 mo2-nH ? Intrinsic absorption derived using the phabs*zphabs*zpowerlw XSPEC model (model 2) (mo2_nH) 278-299 F22.18 10-22cm-2 E_mo2-nH ? Intrinsic absorption positive error (90% confidence, model 2) (mo2nHperr) 301-320 F20.17 10-22cm-2 e_mo2-nH ? Intrinsic absorption negative error (90% confidence, model 2) (mo2nHnerr) 322-340 F19.17 --- z Redshift (z) 342 A1 --- n_z [ps] spectroscopic (s) or photometric (p) redshift (iszspec) -------------------------------------------------------------------------------- Note (1): Categories as follows: 1 = Reflection-dominated CT AGN candidates (intrinsic NH is consistent with zero) 2 = Mildly obscured AGN candidates (intrinsic NH is inconsistent with zero, but less than 1024cm-2) 3 = No redshift available (model without intrinsic NH is applied) -------------------------------------------------------------------------------- Acknowledgements: Mike Belvedersky, mike.belveder(at)gmail.com
(End) Patricia Vannier [CDS] 28-Jan-2025
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