Dark Energy Survey Identification of A Low-Mass Active Galactic Nucleus at Redshift 0.823 from Optical Variability

Journal Article · 11 August 2020 · Mon.Not.Roy.Astron.Soc.

DOI: https://doi.org/10.1093/mnras/staa1803 · OSTI ID:1616310

Guo, Hengxiao ^[1]; Burke, Colin J. ^[1]; Liu, Xin  ^[1]; Phadke, Kedar A. ^[2]; Zhang, Kaiwen ^[3]; Chen, Yu-Ching ^[1]; Gruendl, Robert A. ^[1]; Lidman, Christopher ^[4]; Shen, Yue ^[1]; Morganson, Eric ^[5]; Aguena, Michel ^[6]; Allam, Sahar  ^[7]; Avila, Santiago  ^[8]; Bertin, Emmanuel ^[9]; Brooks, David ^[10]; Carnero Rosell, Aurelio ^[11]; Carollo, Daniela ^[12]; Carrasco Kind, Matias ^[1]; Costanzi, Matteo ^[13]; da Costa, Luiz N. ^[14] ; De Vicente, Juan ^[11]; Desai, Shantanu ^[15]; Doel, Peter ^[10]; Eifler, Tim F. ^[16]; Everett, Spencer ^[17]; García-Bellido, Juan  ^[8]; Gaztanaga, Enrique  ^[18]; Gerdes, David W. ^[19]; Gruen, Daniel ^[20]; Gschwend, Julia ^[14]; Gutierrez, Gaston  ^[7]; Hinton, Samuel R. ^[21]; Hollowood, Devon L. ^[17]; Honscheid, Klaus ^[22]; James, David J. ^[23]; Kuehn, Kyler ^[24]; Lima, Marcos ^[6]; Maia, Marcio A.G. ^[14]; Menanteau, Felipe ^[1]; Miquel, Ramon ^[25]; Möller, Anais ^[26]; Ogando, Ricardo L.C. ^[14]; Palmese, Antonella  ^[27]; Paz-Chinchón, Francisco ^[28]; Plazas, Andrés A. ^[29]; Romer, Anita K. ^[30]; Roodman, Aaron ^[31]; Sanchez, Eusebio  ^[11]; Scarpine, Vic ^[7]; Schubnell, Michael ^[19]; Serrano, Santiago ^[18]; Smith, Mathew  ^[32]; Soares-Santos, Marcelle ^[33]; Sommer, Natalia E. ^[3]; Suchyta, Eric ^[34]; Swanson, Molly E.C. ^[5]; Tarle, Gregory ^[19]; Tucker, Brad E. ^[3]; Varga, Tamas N. ^[35]

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1. Illinois U., Urbana, Astron. Dept.; NCSA, Urbana
2. Illinois U., Urbana, Astron. Dept.
3. Illinois U., Urbana
4. Australian Natl. U., Canberra
5. NCSA, Urbana
6. Sao Paulo U.; LIneA, Rio de Janeiro
7. Fermilab
8. Madrid, IFT
9. Paris, Inst. Astrophys.
10. University Coll. London
11. Madrid, CIEMAT
12. OATo, Turin
13. Trieste Observ.; Trieste U.
14. LIneA, Rio de Janeiro; Rio de Janeiro Observ.
15. Indian Inst. Tech., Hyderabad
16. Arizona U., Astron. Dept. - Steward Observ.; Caltech, JPL
17. UC, Santa Cruz, Inst. Part. Phys.
18. Barcelona, IEEC; ICE, Bellaterra
19. Michigan U.
20. Stanford U., Phys. Dept.; KIPAC, Menlo Park; SLAC
21. Queensland U.
22. Ohio State U., CCAPP; Ohio State U.
23. Harvard-Smithsonian Ctr. Astrophys.
24. Macquarie U.; Lowell Observ.
25. ICREA, Barcelona; Barcelona, IFAE
26. Clermont-Ferrand U.
27. Fermilab; Chicago U., KICP
28. Cambridge U., Inst. of Astron.; NCSA, Urbana
29. Princeton U., Astrophys. Sci. Dept.
30. Sussex U.
31. KIPAC, Menlo Park; SLAC
32. Southampton U.
33. Brandeis U.
34. Oak Ridge
35. Garching, Max Planck Inst., MPE; Munich U.

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 |$$L_{{\rm 2-12\, keV}}\approx 7.6\pm 0.4\times 10^{43}$$| 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_• ≈ 10^6.43–10^6.72 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_* ≈ 10^10.5 ± 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.

• Research Organization: Australian Natl. U., Canberra; Indian Inst. Tech., Hyderabad; Rio de Janeiro Observ.; Sao Paulo U.; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Barcelona, IFAE; Chicago U., KICP; Macquarie U.; ICREA, Barcelona; Illinois U., Urbana; Lowell Observ.; UC, Santa Cruz, Inst. Part. Phys.; Trieste U.; Caltech, JPL; Madrid, CIEMAT; Trieste Observ.; NCSA, Urbana; Madrid, IFT; LIneA, Rio de Janeiro; Ohio State U., CCAPP; Ohio State U.; ICE, Bellaterra; Sussex U.; Garching, Max Planck Inst., MPE; Illinois U., Urbana, Astron. Dept.; OATo, Turin; Southampton U.; Paris, Inst. Astrophys.; Munich U.; Arizona U., Astron. Dept. - Steward Observ.; Stanford U., Phys. Dept.; Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); University Coll. London; Barcelona, IEEC; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Michigan U.; Harvard-Smithsonian Ctr. Astrophys.; Cambridge U., Inst. of Astron.; Princeton U., Astrophys. Sci. Dept.; Clermont-Ferrand U.; Brandeis U.; Queensland U.
• Sponsoring Organization: US Department of Energy
• Grant/Contract Number: AC02-07CH11359
• OSTI ID: 1616310
• Report Number(s): FERMILAB-PUB-20-103-AE; oai:inspirehep.net:1787888; arXiv:2003.10457
• Journal Information: Mon.Not.Roy.Astron.Soc., Journal Name: Mon.Not.Roy.Astron.Soc. Journal Issue: 3 Vol. 496
• Country of Publication: United States
• Language: English