Guo, H;
Burke, CJ;
Liu, X;
Phadke, KA;
Zhang, K;
Chen, Y-C;
Gruendl, RA;
... Varga, TN; + view all
(2020)
Dark Energy Survey identification of a low-mass active galactic nucleus at redshift 0.823 from optical variability.
Monthly Notices of the Royal Astronomical Society
, 496
(3)
pp. 3636-3647.
10.1093/mnras/staa1803.
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Abstract
We report the identification of a low-mass active galactic nucleus (AGN), DES J0218−0430, in a redshift z = 0.823 galaxy in the Dark Energy Survey (DES) Supernova field. We select DES J0218−0430 as an AGN candidate by characterizing its long-term optical variability alone based on DES optical broad-band light curves spanning over 6 yr. An archival optical spectrum from the fourth phase of the Sloan Digital Sky Survey shows both broad Mg II and broad H β lines, confirming its nature as a broad-line AGN. Archival XMM–Newton X-ray observations suggest an intrinsic hard X-ray luminosity of L2−12keV≈7.6±0.4×1043 erg s−1, which exceeds those of the most X-ray luminous starburst galaxies, in support of an AGN driving the optical variability. Based on the broad H β from SDSS spectrum, we estimate a virial black hole (BH) mass of M• ≈ 106.43–106.72 M⊙ (with the error denoting the systematic uncertainty from different calibrations), consistent with the estimation from OzDES, making it the lowest mass AGN with redshift > 0.4 detected in optical. We estimate the host galaxy stellar mass to be M* ≈ 1010.5 ± 0.3 M⊙ based on modelling the multiwavelength spectral energy distribution. DES J0218−0430 extends the M•–M* relation observed in luminous AGNs at z ∼ 1 to masses lower than being probed by previous work. Our work demonstrates the feasibility of using optical variability to identify low-mass AGNs at higher redshift in deeper synoptic surveys with direct implications for the upcoming Legacy Survey of Space and Time at Vera C. Rubin Observatory.
| Type: | Article |
|---|---|
| Title: | Dark Energy Survey identification of a low-mass active galactic nucleus at redshift 0.823 from optical variability |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/staa1803 |
| Publisher version: | https://doi.org/10.1093/mnras/staa1803 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, black hole physics, surveys, galaxies: active, galaxies: high-redshift, galaxies: nuclei, quasars: general, DIGITAL SKY SURVEY, STELLAR POPULATION SYNTHESIS, SUPERMASSIVE BLACK-HOLES, DWARF GALAXIES, SEYFERT-1 GALAXY, QUASAR, EVOLUTION, DISTRIBUTIONS, SPECTROSCOPY, SAMPLE |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10113203 |
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