Dwarf AGNs from Optical Variability for the Origins of Seeds (DAVOS): insights from the dark energy survey deep fields. Issue 2 (13th August 2022)

• Record Type: Journal Article
• Authors: Burke, Colin J; Liu, Xin; Shen, Yue; Phadke, Kedar A; Yang, Qian; Hartley, Will G; Harrison, Ian; Palmese, Antonella; Guo, Hengxiao; Zhang, Kaiwen; Kron, Richard; Turner, David J; Giles, Paul A; Lidman, Christopher; Chen, Yu-Ching; Gruendl, Robert A; Choi, Ami; Amon, Alexandra; Sheldon, Erin; Aguena, M; Allam, S; Andrade-Oliveira, F; Bacon, D; Bertin, E; Brooks, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Conselice, C; Costanzi, M; da Costa, L N; Pereira, M E S; Davis, T M; De Vicente, J; Desai, S; Diehl, H T; Everett, S; Ferrero, I; Flaugher, B; García-Bellido, J; Gaztanaga, E; Gruen, D; Gschwend, J; Gutierrez, G; Hinton, S R; Hollowood, D L; Honscheid, K; Hoyle, B; James, D J; Kuehn, K; Maia, M A G; Marshall, J L; Menanteau, F; Miquel, R; Morgan, R; Paz-Chinchón, F; Pieres, A; Malagón, A A Plazas; Reil, K; Romer, A K; Sanchez, E; Schubnell, M; Serrano, S; Sevilla-Noarbe, I; Smith, M; Suchyta, E; Tarle, G; Thomas, D; To, C; Varga, T N; Wilkinson, R D;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 516:Issue 2(2022)
• Page Start: 2736
• Page End: 2756
• Publication Date: 2022-08-13
• Subjects: black hole physics -- galaxies: active -- galaxies: dwarf; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac2262
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present a sample of 706, z < 1.5 active galactic nuclei (AGNs) selected from optical photometric variability in three of the Dark Energy Survey (DES) deep fields (E2, C3, and X3) over an area of 4.64 deg 2 . We construct light curves using difference imaging aperture photometry for resolved sources and non-difference imaging PSF photometry for unresolved sources, respectively, and characterize the variability significance. Our DES light curves have a mean cadence of 7 d, a 6-yr baseline, and a single-epoch imaging depth of up to g ∼ 24.5. Using spectral energy distribution (SED) fitting, we find 26 out of total 706 variable galaxies are consistent with dwarf galaxies with a reliable stellar mass estimate ($M_{\ast }\lt 10^{9.5}\, {\rm M}_\odot$ ; median photometric redshift of 0.9). We were able to constrain rapid characteristic variability time-scales (∼ weeks) using the DES light curves in 15 dwarf AGN candidates (a subset of our variable AGN candidates) at a median photometric redshift of 0.4. This rapid variability is consistent with their low black hole (BH) masses. We confirm the low-mass AGN nature of one source with a high S/N optical spectrum. We publish our catalogue, optical light curves, and supplementary data, such as X-ray properties and optical spectra, when available. We measure a variable AGN fraction versus stellar mass and compare to results from a forward model. This work demonstrates the feasibility of optical variability to identify AGNs with lower BH masses in deep fields, which may be more 'pristine' analogues of supermassive BH seeds.