J/MNRAS/516/2736 Optical variability of ∼700 low mass AGNs (Burke+, 2022)
Dwarf AGNs from Optical Variability for the Origins of Seeds (DAVOS):
insights from the dark energy survey deep fields.
Burke C.J., Liu X., Shen Y., Phadke K.A., Yang Q., Hartley W.G.,
Harrison I., Palmese A., Guo H., Zhang K., Kron R., Turner D.J.,
Giles P.A., Lidman C., Chen Y.-C., Gruendl R.A., Choi A., Amon A.,
Sheldon E., Aguena M., Allam S., Andrade-Oliveira F., Bacon D., Bertin E.,
Brooks D., Carnero Rosell A., Carrasco Kind M., 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.,
Garcia-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-Chinchon F., Pieres A., Plazas Malagon A.A., 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.,
(The DES Collaboration)
<Mon. Not. R. Astron. Soc. 516, 2736-2756 (2022)>
=2022MNRAS.516.2736B 2022MNRAS.516.2736B (SIMBAD/NED BibCode)
ADC_Keywords: Black holes ; Galaxies ; Galaxies, dwarf ; Active gal. nuclei ;
Positional data ; Photometry ; Optical ; Stars, masses ;
Redshifts ; Spectroscopy ; Infrared ; X-ray sources
Keywords: black hole physics - galaxies: active - galaxies: dwarf
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
deg2. 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* < 109.5M☉; 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.
Description:
In this work, we perform a systematic search for variable AGN using
Dark Energy Survey. We choose the DES deep fields because of the
exceptional depth (g ∼ 24.6), ∼7 d cadence with a total baseline of ∼6 yr,
and availability of multiwavelength imaging and spectroscopy. Using
these data, we are able to identify optically variable AGN candidates
in dwarf galaxies to z ∼ 1.5 for the first time (i.e see section
Introduction). The DES was a wide-area ∼5000 deg2 survey of the
southern galactic cap in the grizY bands. The DES absolute photometric
calibration has been tied to the spectrophotometric Hubble CALSPEC
standard star C26202 and has been placed on the AB system. In addition
to the wide-area survey, the DES contains a 27 deg2 multiepoch
survey to search for Type Ia supernovae (SNe) called DES-S composed of
10 DES fields each with a uniform cadence of about 7 d in the griz
bands during the observing season.
In this work, we restrict our analysis to three of the 11 (composed of
10 DES-SN fields plus the COSMOS field) DES deep fields (SN-E2, SN-C3,
SN-X3) with weekly cadence from the DES-SN program and with 8-band
(ugrizJHKS) deblended, stacked model-based photometry from Hartley et
al. (2022MNRAS.509.3547H 2022MNRAS.509.3547H) overlapping with ISO survey, Chandra, XMM,
VIDEO and UltraVISTA. After light-curve construction in DES g band
(i.e section 2.4), we proceed to AGN variability selection procedure.
Also, by SED fitting of 63721 light-curves, we found 706 variable
galaxies with our reliable stellar mass estimates (i.e section 2 and
2.7).
Thus, as detailed in section 3.2 Dwarf AGN Candidates, we present a
catalogue in table2.dat of all of our variability-selected AGN
candidates regardless of stellar mass or variability properties. Then,
for dwarf AGN, we present in table3.dat, 15 candidates having
log(τDRW/days) < 1.5 with observed-frame damping time-scales
greater than the 7-d cadence and stellar masses < 1010M☉. This
strict criteria are expected to result in a pure selection of dwarf
AGNs.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 122 706 Variability-selected AGN candidates regardless
of stellar mass or variability properties
table3.dat 119 15 Catalogue of 15 variable AGN candidates with
rapid variability log(τDRW)<1.5
--------------------------------------------------------------------------------
See also:
III/334 : VISTA Deep Extragalactic Observations (VIDEO)
(Jarvis+,2013)
II/363 : The band-merged unWISE Catalog (Schlafly+, 2019)
IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012)
IX/57 : The Chandra Source Catalog (CSC), Release 2.0
(Evans+, 2019)
J/MNRAS/487/4285 : Variable AGN candidates catalog (Pouliasis+, 2019)
J/MNRAS/510/687 : Viewing angle in AGN SED models (Ramos Padilla+, 2022)
J/A+A/474/473 : XMM-LSS survey: AGN classifications (Garcet+, 2007)
J/A+A/544/A156 : UltraVISTA Catalogue Release DR1 (McCracken+, 2012)
J/A+A/622/A103 : Python Code Investigating GALaxy Emission (Boquien+,2019)
J/A+A/634/A50 : Optically variable AGN in the VST/CDF-S (Poulain+, 2020)
J/A+A/627/A33 : Optically variable AGN in COSMOS field (De Cicco+, 2019)
J/A+A/574/A112 : COSMOS field variability-selected AGN nuclei
(De Cicco+, 2015)
J/A+A/488/73 : Variability-selected AGN in Chandra DFS (Trevese+, 2008)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/775/116 : z<0.06 active black hole galaxies from SDSS-DR8
(Reines+, 2013)
J/ApJ/813/82 : z<0.06 broad-line AGN emission-line measures
(Reines+, 2015)
J/ApJ/922/155 : [FeX]λ6374 em. in SDSS dwarf galaxies
(Molina+, 2021)
J/ApJ/888/36 : SDSS/FIRST dwarf galaxies with VLA high res. obs.
(Reines+, 2020)
J/ApJ/748/124 : AGN X-ray variability in the 4Ms catalog (Young+, 2012)
J/ApJ/830/51 : FourStar galaxy evolution survey (ZFOURGE)
(Straatman+,2016)
J/ApJ/896/10 : NSA low-mass galaxies with long-term PTF obs.
(Baldassare+, 2020)
J/ApJ/894/24 : Optical variability of AGN from the HSC SSP survey
(Kimura+, 2020)
J/ApJ/854/160 : SDSS and DES long-term extreme variability QSOs
(Rumbaugh+, 2018)
J/ApJ/805/96 : SDSS-RM project: velocity dispersions of QSOs
(Shen+, 2015)
J/ApJ/757/83 : The Blanco Cosmology Survey (BCS) (Desai+, 2012)
J/ApJ/789/147 : Star formation histories of LG dwarf galaxies
(Weisz+, 2014)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies
(Kirby+, 2013)
J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)
J/ApJS/228/2 : Chandra Deep Field-South survey: 7Ms sources (Luo+, 2017)
J/ApJS/228/9 : Physical parameters of ∼300000 SDSS-DR12 QSOs
(Kozlowski, 2017)
J/ApJS/201/30 : The Chandra COSMOS survey. III. (Civano+, 2012)
J/ApJS/241/34 : The SDSS Reverberation Mapping (SDSS-RM) project
(Shen+, 2019)
J/AJ/153/107 : Australian Dark Energy Survey (OzDES) quasar catalog
(Tie+, 2017)
J/AJ/154/269 : A new photo-z method for quasars in Stripe 82
(Yang+, 2017)
J/other/Sci/373.789 : optical variability of AGNs (Burke+, 2021)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Name Variable AGB name candidates (Name)
22- 28 F7.4 deg RAdeg Right ascension (J2000) (RA)
30- 37 F8.4 deg DEdeg Declination (J2000) (Dec)
39- 42 F4.1 mag gmag Median DES g magnitude in AB system (g)
44- 47 F4.1 --- SNR Signal to noise ratio as described by
the estimator in equation 9 of the
section 2.5.1 (SNR)
49- 52 F4.1 --- sigLB Ljung-Box test significance as
described in section 2.5.3 AGN-like
variability (σLB
54- 57 F4.1 [Msun] log(M*) Stellar mass estimate with CIGALE code
as described in section 2.7 Stellar
mass estimation (logM*/M☉)
59- 61 F3.1 [Msun] e_log(M*) Mean uncertainty of log (M*)
(errlogM*/M☉)
63- 66 F4.1 --- DChi2 Difference between reduced Χ2
values like χ2fAGN=1 - Χ2
in section 2.7 (ΔΧ2ν)
68- 71 F4.1 [d] log(Tau) Characteristic damping variability
time-scale term τDRW as described
in section 2.8 (logτDRW/days)
73- 77 F5.1 [d] e_log(Tau) Mean uncertainty of log (TauDRW)
(errlogτDRW/days)
79- 82 F4.2 --- zph Photometric redshift zph with method
of Yang et al. 2017AJ....154..269Y 2017AJ....154..269Y,
Cat. J/AJ/154/269 as section 2.6 (zph)
84- 87 F4.2 --- E_zph ? Upper uncertainty of zph (Errzph)
89- 92 F4.2 --- e_zph Lower uncertainty of zph (errzph)
94- 99 F6.4 --- zsp ? Spectroscopic redshift zsp (zsp)
101-104 A4 --- r_zsp Literature reference of zsp
(zspsource) (1)
106-109 F4.1 mag W1-W2 ? WISE W1-W2 colour (W1-W2)
111-116 F6.2 [10-3W/m2] log(F2-7) ? Chandra hard X-ray F2-7keV
(logF2-7keV/ergs-1cm-2)
118-122 A5 --- Field [SN-C3/SN-E2/SN-X3] DES deep fields as
SN-C3 for 300 cases, SN-E2 for 234 cases
and SN-X3 for 172 cases (Field)
--------------------------------------------------------------------------------
Note (1): Literature reference as follows:
2dF = Two Degree Field system spectrograph, 62 sources in our sample
2dFG = 2dF Galaxy catalog survey, 1 source in our sample
ACES = Airborne Cavity Enhanced Spectrometer, 9 sources in our sample
GAMA = Galaxy and mass assembly spectroscopic survey, 8 sources
in our sample
PanS = Pan-optic spectroscopic survey, 27 sources in our sample
SDSS = SDSS spectroscopic survey, 34 sources in our sample
SNLS = Supernova Legacy Survey, 2 sources in our sample
VIPE = VIPERS spectroscopic survey, 1 source in our sample
VVDS = VIRMOS VLT Deep Survey, 2 source in our sample
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Name Variable AGB name candidates (Name)
22- 28 F7.4 deg RAdeg Right ascension (J2000) (RA)
30- 37 F8.4 deg DEdeg Declination (J2000) (Dec)
39- 42 F4.1 mag gmag Median DES g magnitude in AB system (g)
44- 47 F4.1 --- SNR Signal to noise ratio as described by
the estimator in equation 9 of the
section 2.5.1 (SNR)
49- 52 F4.1 --- sigLB Ljung-Box test significance as
described in section 2.5.3 AGN-like
variability (σLB
54- 57 F4.1 [Msun] log(M*) Stellar mass estimate with CIGALE code
as described in section 2.7 Stellar
mass estimation (logM*/M☉)
59- 61 F3.1 [Msun] e_log(M*) Mean uncertainty of log (M*)
(errlogM*/M☉)
63- 66 F4.1 --- DChi2 Difference between reduced Χ2
values like χ2fAGN=1 - Χ2
in section 2.7 (ΔΧ2ν)
68- 70 F3.1 [d] log(Tau) Characteristic damping variability
time-scale term τDRW as described
in section 2.8 (logτDRW/days)
72- 74 F3.1 [d] e_log(Tau) Mean uncertainty of log (TauDRW)
(errlogτDRW/days)
76- 79 F4.2 --- zph Photometric redshift zph with method
of Yang et al. 2017AJ....154..269Y 2017AJ....154..269Y,
Cat. J/AJ/154/269 as section 2.6 (zph)
81- 84 F4.2 --- E_zph Upper uncertainty of zph (Errzph)
86- 89 F4.2 --- e_zph Lower uncertainty of zph (errzph)
91- 96 F6.4 --- zsp ? Spectroscopic redshift zsp (zsp)
98-101 A4 --- r_zsp Literature reference of zsp
(zspsource) (1)
103-106 F4.1 mag W1-W2 ? WISE W1-W2 colour (W1-W2)
108-113 F6.2 [10-3W/m2] log(F2-7) ? Chandra hard X-ray F2-7keV
(logF2-7keV/ergs-1cm-2)
115-119 A5 --- Field [SN-C3/SN-E2/SN-X3] DES deep fields as
SN-C3 for 10 cases, SN-E2 for 3 cases
and SN-X3 for 2 cases (Field)
--------------------------------------------------------------------------------
Note (1): Literature reference as follows:
2dF = Two Degree Field system spectrograph, 4 sources in our sample
SDSS = SDSS spectroscopic survey, 1 source in our sample
PanS = Pan-optic spectroscopic survey, 1 source in our sample
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 06-Aug-2025