J/ApJ/896/10 NSA low-mass galaxies with long-term PTF obs. (Baldassare+, 2020)
A search for optical AGN variability in 35000 low-mass galaxies with the
Palomar Transient Factory.
Baldassare V.F., Geha M., Greene J.
<Astrophys. J., 896, 10-10 (2020)>
=2020ApJ...896...10B 2020ApJ...896...10B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby; Active gal. nuclei; Photometry; Optical;
Redshifts
Keywords: Active galactic nuclei; Dwarf galaxies; Variable radiation sources
Sky surveys; AGN host galaxies
Abstract:
We present an analysis of the long-term optical variability for ∼50000
nearby (z<0.055) galaxies from the NASA-Sloan Atlas (NSA), 35000 of
which are low-mass (M*<1010M☉). We use difference imaging of
Palomar Transient Factory (PTF) R-band observations to construct light
curves with typical baselines of several years. We then search for
subtle variations in the nuclear light output. We determine whether
detected variability is AGN-like by assessing the fit quality to a
damped random walk model. We identify 417 variability-selected AGNs,
including 237 with stellar masses between 107 and 1010M☉.
75% of low-mass galaxies with AGN-like variability have narrow
emission lines dominated by star formation. After controlling for
nucleus magnitude, the fraction of variable AGNs is constant down to
M*=109M☉, suggesting no drastic decline in the BH occupation
fraction down to this stellar mass regime. Combining our NASA-Sloan
Atlas sample with samples of nearby galaxies with broad Hα
emission, we find no dependence of variability properties with black
hole mass. Our PTF work demonstrates the promise of long-term optical
variability searches in low-mass galaxies for finding AGNs missed by
other selection techniques.
Description:
The Palomar Transient Factory (PTF) began operations in 2009, using
the 48 inch Samuel Oschin Telescope at Palomar Observatory. PTF
observed primarily in the R band with an exposure time of 60s and
typical 5σ limiting magnitude of mR=20.5mag. The pixel size of
the CCD is 1"/pix.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 86 237 Low-mass galaxies with AGN-like variability
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
J/AcA/50/421 : OGLE-II DIA BUL_SC1 field (Wozniak, 2000)
J/MNRAS/375/989 : Quasar variability (Wold+, 2007)
J/ApJ/670/92 : New sample of low-mass black holes in AGN (Greene+, 2007)
J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)
J/ApJ/728/26 : QSO selection based on photometric variability (Macleod+, 2011)
J/AJ/142/153 : Precision spectrophotometry at the level of 0.1% (Yan, 2011)
J/ApJ/753/22 : Swift/UVOT observations of SN 2011fe (Brown+, 2012)
J/ApJ/775/116 : z<0.06 active black hole galaxies from SDSS-DR8 (Reines+, 2013)
J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)
J/ApJ/813/82 : z<0.06 broad-line AGN emission-line measures (Reines+, 2015)
J/ApJ/830/13 : Host-galaxy NUV-NIR data of superluminous SNe (Perley+, 2016)
J/ApJ/858/118 : Kinematic data of 3 nearby low-mass galaxies (Nguyen+, 2018)
J/ApJ/872/198 : LCs of tidal disruption flare AT2018zr (van Velzen+, 2019)
J/ApJS/243/21 : A complete sample of broad-line AGN from SDSS-DR7 (Liu+, 2019)
http://www.nsatlas.org/ : NASA-Sloan Atlas home page
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- ObjID Identifier, NASA-Sloan Atlas (NSA) version 0
11- 19 F9.5 deg RAdeg Right Ascension, decimal degree (J2000)
21- 29 F9.5 deg DEdeg Declination, decimal degree (J2000)
31- 37 F7.4 --- zspec [-0.0018/0.055] SDSS spectroscopic redshift
39- 43 F5.2 [Msun] logMs [6.4/10] Log of stellar mass
45- 48 I4 --- Np [20/1589] Number of points
50- 56 F7.2 d Baseline [59.93/2144.17] Baseline
58- 62 F5.2 mag RmagMed [15.3/21] Median R band magnitude
64- 68 F5.3 mag Std [0.01/0.3] Standard deviation in light curve
70- 75 F6.2 --- SigVar [2/167] Significance, light curve is variable
77- 81 F5.2 --- SigQSO [2/12] Significance, light curve is an AGN
83- 86 F4.2 --- SigNoQSO [0/9] Significance, light curve is
a false alarm
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 21-Sep-2021