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Unveiling a population of galaxies harboring low-mass black holes with X-rays

Schram, M. and Silverman, J. D. and Greene, J. E. and Brandt, W. N. and Luo, B. and Xue, Y. Q. and Capak, P. and Kakazu, Y. and Kartaltepe, J. and Mainieri, V. (2013) Unveiling a population of galaxies harboring low-mass black holes with X-rays. Astrophysical Journal, 773 (2). Art. No. 150. ISSN 0004-637X. doi:10.1088/0004-637X/773/2/150.

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We report the discovery of three low-mass black hole (BH) candidates residing in the centers of low-mass galaxies at z < 0.3 in the Chandra Deep Field-South Survey. These BHs are initially identified as candidate active galactic nuclei based on their X-ray emission in deep Chandra observations. Multi-wavelength observations are used to strengthen our claim that such emission is powered by an accreting supermassive BH. While the X-ray luminosities are low at L_X ~ 10^(40) erg s^(–1) (and variable in one case), we argue that they are unlikely to be attributed to star formation based on Hα or UV fluxes. Optical spectroscopy from Keck and the VLT allows us to (1) measure accurate redshifts, (2) confirm their low stellar host mass, (3) investigate the source(s) of photo-ionization, and (4) estimate extinction. With stellar masses of M_* < 3 × 10^9 M_☉ determined from Hubble Space Telescope/Advanced Camera for Surveys imaging, the host galaxies are among the lowest mass systems known to host actively accreting BHs. We estimate BH masses M_(BH) ~ 2 × 10^5 M_☉ based on scaling relations between BH mass and host properties for more luminous systems. In one case, a broad component of the Hα emission-line profile is detected, thus providing a virial mass estimate. BHs in such low-mass galaxies are of considerable interest as the low-redshift analogs to the seeds of the most massive BHs at high redshift which have remained largely elusive to date. Our study highlights the power of deep X-ray surveys to uncover such low-mass systems.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Silverman, J. D.0000-0002-0000-6977
Brandt, W. N.0000-0002-0167-2453
Luo, B.0000-0002-9036-0063
Capak, P.0000-0003-3578-6843
Kartaltepe, J.0000-0001-9187-3605
Additional Information:© 2013 American Astronomical Society. Received 2013 February 22; accepted 2013 May 10; published 2013 August 5. The authors fully appreciate the useful discussions with Aaron Barth and Masayuki Tanaka that improved the paper. This work was supported by the World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. Y.Q.X. acknowledges the financial support of the Thousand Young Talents (QingNianQianRen) program (KJ2030220004), the USTC startup funding (ZC9850290195), and the National Natural Science Foundation of China through NSFC-11243008. W. N. Brandt and B. Luo acknowledge the NASA ADP grant NNX10AC99G and the CXC grant AR3-14015X.
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Thousand Young TalentsKJ2030220004
USTC startup fundingZC9850290195
National Natural Science Foundation of ChinaNSFC-11243008
Subject Keywords:galaxies: active; X-rays: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20130924-084223399
Persistent URL:
Official Citation:Unveiling a Population of Galaxies Harboring Low-mass Black Holes with X-Rays M. Schramm et al. 2013 ApJ 773 150
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41489
Deposited On:24 Sep 2013 16:33
Last Modified:10 Nov 2021 04:30

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