Chen, C.T.J., Brandt, W.N., Reines, A.E. et al. (14 more authors) (2017) Hard X-Ray-selected AGNs in Low-mass Galaxies from the NuSTAR Serendipitous Survey. Astrophysical Journal, 837 (1). 48. ISSN 0004-637X
Abstract
We present a sample of 10 low-mass active galactic nuclei (AGNs) selected from the 40-month Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The sample is selected to have robust NuSTAR detections at , to be at , and to have optical r-band magnitudes at least 0.5 mag fainter than an galaxy at its redshift. The median values of absolute magnitude, stellar mass, and 2-10 X-ray luminosity of our sample are , , and erg s-1, respectively. Five objects have detectable broad Hα emission in their optical spectra, indicating black hole masses of . We find that of the galaxies in our sample do not show AGN-like optical narrow emission lines, and one of the 10 galaxies in our sample, J115851+4243.2, shows evidence for heavy X-ray absorption. This result implies that a non-negligible fraction of low-mass galaxies might harbor accreting massive black holes that are missed by optical spectroscopic surveys and X-ray surveys. The mid-IR colors of our sample also indicate that these optically normal low-mass AGNs cannot be efficiently identified with typical AGN selection criteria based on Wide Field Infrared Survey Explorer colors. While the hard ( keV) X-ray-selected low-mass AGN sample size is still limited, our results show that sensitive NuSTAR observations are capable of probing faint hard X-ray emission originating from the nuclei of low-mass galaxies out to moderate redshift (), thus providing a critical step in understanding AGN demographics in low-mass galaxies.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © Year The American Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | galaxies: active; galaxies: dwarf; X-rays: galaxies |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/M001350/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 07 Apr 2017 14:32 |
Last Modified: | 21 Mar 2018 02:24 |
Published Version: | https://doi.org/10.3847/1538-4357/aa5d5b |
Status: | Published |
Publisher: | American Astronomical Society |
Refereed: | Yes |
Identification Number: | 10.3847/1538-4357/aa5d5b |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:114595 |