J/ApJ/766/60 GALEX Time Domain Survey I. UV variable sources (Gezari+, 2013)
The GALEX Time Domain Survey.
I. Selection and classification of over a thousand ultraviolet variable sources.
Gezari S., Martin D.C., Forster K., Neill J.D., Huber M., Heckman T.,
Bianchi L., Morrissey P., Neff S.G., Seibert M., Schiminovich D.,
Wyder T.K., Burgett W.S., Chambers K.C., Kaiser N., Magnier E.A.,
Price P.A., Tonry J.L.
<Astrophys. J., 766, 60 (2013)>
=2013ApJ...766...60G 2013ApJ...766...60G
ADC_Keywords: Ultraviolet ; Active gal. nuclei ; Stars, variable ; Surveys ;
Redshifts ; Photometry, ugriz ; X-ray sources
Keywords: surveys; ultraviolet: general
Abstract:
We present the selection and classification of over a thousand
ultraviolet (UV) variable sources discovered in ∼40deg2 of GALEX
Time Domain Survey (TDS) NUV images observed with a cadence of 2 days
and a baseline of observations of ∼3 years. The GALEX TDS fields were
designed to be in spatial and temporal coordination with the
Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging
and simultaneous optical transient detections via image differencing.
We characterize the GALEX photometric errors empirically as a function
of mean magnitude, and select sources that vary at the 5σ level
in at least one epoch. We measure the statistical properties of the UV
variability, including the structure function on timescales of days
and years. We report classifications for the GALEX TDS sample using a
combination of optical host colors and morphology, UV light curve
characteristics, and matches to archival X-ray, and spectroscopy
catalogs. We classify 62% of the sources as active galaxies (358
quasars and 305 active galactic nuclei), and 10% as variable stars
(including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic
variables). We detect a large-amplitude tail in the UV variability
distribution for M-dwarf flare stars and RR Lyrae, reaching up to
|Δm|=4.6mag and 2.9mag, respectively. The mean amplitude of the
structure function for quasars on year timescales is five times larger
than observed at optical wavelengths. The remaining unclassified
sources include UV-bright extragalactic transients, two of which have
been spectroscopically confirmed to be a young core-collapse supernova
and a flare from the tidal disruption of a star by dormant
supermassive black hole. We calculate a surface density for variable
sources in the UV with NUV<23mag and |Δm|>0.2mag of ∼8.0, 7.7,
and 1.8deg-2 for quasars, active galactic nuclei, and RR Lyrae
stars, respectively. We also calculate a surface density rate in the
UV for transient sources, using the effective survey time at the
cadence appropriate to each class, of ∼15 and 52deg-2/yr for M
dwarfs and extragalactic transients, respectively.
Description:
Here we present the analysis of 42 GALEX Time Domain Survey (TDS)
fields which intersect with the Pan-STARRS1 Medium Deep Survey (PS1
MDS; Kaiser et al. 2010SPIE.7733E..0EK) footprint, for a total area on
the sky of 39.91deg2, which were monitored over a baseline of 3.32yr
(2008 February-2011 June).
The Pan-STARRS1 observations are obtained through a set of five
broadband filters, (gP1, rP1, iP1, zP1, and yP1). Further
information on the passband shapes is described in Stubbs et al.
(2010ApJS..191..376S 2010ApJS..191..376S).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 104 1078 GALEX Time Domain Survey (TDS) catalog
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See also:
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
III/250 : The VIMOS VLT deep survey (VVDS-DEEP) (Le Fevre+ 2005)
II/255 : SWIRE ELAIS N1 Source Catalogs (Surace+, 2004)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
J/ApJS/201/30 : The Chandra COSMOS survey. III. (Civano+, 2012)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/ApJ/734/13 : GALEX ultraviolet halos around bright stars (Murthy+, 2011)
J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
J/MNRAS/411/2770 : Hot white dwarfs in GALEX-DR5 (Bianchi+, 2011)
J/AJ/140/1987 : SDSS-GALEX QSO catalog (Hutchings+, 2010)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJ/696/1195 : COSMOS AGN spectroscopic survey. I. (Trump+, 2009)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/ApJS/180/102 : AEGIS-X: Chandra deep survey (Laird+, 2009)
J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009)
J/AJ/136/259 : Second GALEX UV variability cat. (GUVV-2) (Wheatley+, 2008)
J/ApJ/676/944 : GALEX & CFHTLS cand. tidal disruption events (Gezari+, 2008)
J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007)
J/ApJS/173/673 : M dwarf UV flares in GALEX (Welsh+, 2007)
J/ApJS/172/383 : AGN candidates in the COSMOS field (Trump+, 2007)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
J/ApJS/172/29 : XMM-Newton survey in COSMOS field. I. (Hasinger+, 2007)
J/AJ/133/1780 : GALEX/SDSS quasar catalog (Trammell+, 2007)
J/AJ/131/2373 : Extended Chandra Deep Field-South survey (Virani+, 2006)
J/AJ/130/825 : GALEX ultraviolet variability catalog (Welsh+, 2005)
J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)
J/MNRAS/356/568 : Deep Chandra survey of the Groth Strip (Nandra+, 2005)
J/ApJ/633/638 : 315 SDSS variable quasar sample (Wilhite+, 2005)
J/A+A/439/413 : XMDS/VVDS 4σ catalogue (Chiappetti+, 2005)
J/A+A/428/1043 : Redshifts from VIMOS VLT Deep Survey (Le Fevre+, 2004)
J/MNRAS/343/293 : ELAIS deep X-ray survey. I. (Manners+, 2003)
J/ApJS/139/369 : Chandra Deep Field South. 1 Ms catalog (Giacconi+, 2002)
J/MNRAS/268/305 : Variability of optically selected quasars (Hook+ 1994)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- ID GALEX TDS name (fieldname_MOSpointing-NN)
18- 25 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
27- 34 F8.4 deg DEdeg Declination in decimal degrees (J2000)
37 A1 --- l_mlow Limit flag on mlow
38- 42 F5.2 mag mlow [17.9/23.1] Low-state GALEX/NUV AB magnitude
corrected for Galactic extinction
45 A1 --- l_Dmmax Limit flag on Dmax
46- 49 F4.2 mag Dmmax [0.2/4.6] Maximum amplitude of NUV variability
|Δmmax|
51 A1 --- l_sigint Limit flag on sigint
52- 55 F4.2 mag sigint [0/3.6] Intrinsic rms scatter σint
57 A1 --- l_Sd Limit flag on Sd
58- 61 F4.2 mag Sd [0/1.5]? Structure function on days (3)
63 A1 --- l_Sy Limit flag on Sy
64- 67 F4.2 mag Sy [0/4.1]? Structure function on years (3)
69 A1 --- LC [VF] Light curve type: V=stocharstic, F=flaring
71- 73 A3 --- Mph Optical host morphology: pt=point, ext=extended
75- 79 F5.2 mag rmag [8.8/45.3]? Optical host r-band AB magnitude
corrected for Galactic extinction
81- 83 A3 --- OT Optical color class (1)
85- 89 F5.3 --- z [0/4.1]? Redshift
91 A1 --- X [X ] X-ray source match
93-104 A12 --- Class Classification (2)
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Note (1): Optical class as follows:
Mdw = color of an M dwarf star;
RRL = color of an RR Lyrae star;
QSO = color of a quasar.
Note (2): Classification as follows:
Mdw = Mdwarf star
STAR = star;
CV = cataclysmic variable star;
RRL = RR Lyrae star;
BHB = blue horizontal branch star
LPV = luminous pulsating variable star;
AGN = active galactic nucleus;
QSO = quasar;
Orphan Var = orphan optical host with stochastic UV variability;
Orphan Trans = orphan optical host with a transient UV source;
Galaxy Trans = galaxy optical host with a transient UV source;
Galaxy Flare = galaxy optical host with a flaring UV light curve.
Note (3): the structure function characterizes the variability (section 3.2;
see di Clemente et al. 1996ApJ...463..466D 1996ApJ...463..466D).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Nov-2014