J/ApJ/717/1181 Spitzer power-law galaxies in EGS (Park+, 2010)
AEGIS: a multiwavelength study of Spitzer power-law galaxies.
Park S.Q., Barmby P., Willner S.P., Ashby M.L.N., Fazio G.G.,
Georgakakis A., Ivison R.J., Konidaris N.P., Miyazaki S., Nandra K.,
Rosario D.J.
<Astrophys. J., 717, 1181-1201 (2010)>
=2010ApJ...717.1181P 2010ApJ...717.1181P
ADC_Keywords: Active gal. nuclei ; Photometry, infrared ; X-ray sources ;
Cross identifications ; Redshifts
Keywords: galaxies: active - infrared: galaxies - X-rays: galaxies
Abstract:
This paper analyzes a sample of 489 Spitzer/Infrared Array Camera
(IRAC) sources in the Extended Groth Strip (EGS), whose spectral
energy distributions fit a red power law (PL) from 3.6 to 8.0um. The
median redshift for sources with known redshifts is =1.6. Though
all or nearly all of the sample galaxies are likely to be active
galactic nuclei (AGNs), only 33% were detected in the EGS X-ray survey
(AEGIS-X) using 200ks Chandra observations. The detected sources are
X-ray luminous with LX>1043erg/s and moderately to heavily
obscured with NH>1022cm-2. Stacking the X-ray-undetected sample
members yields a statistically significant X-ray signal, suggesting
that they are on average more distant or more obscured than sources
with X-ray detections. The ratio of X-ray to mid-infrared fluxes
suggests that a substantial fraction of the sources undetected in
X-rays are obscured at the Compton-thick level, in contrast to the
X-ray-detected sources, all of which appear to be Compton thin.
Description:
IRAC observations of the EGS were obtained in 2003-2004 as part of
Guaranteed Time Observation (GTO) program 8. Barmby et al. (2008, Cat.
J/ApJS/177/431) give details of the observations and reductions and
list source photometry in a variety of apertures. This paper uses the
photometry in the 3.06" diameter aperture.
The IRAC data are supplemented by observations from the Far-Infrared
Deep Extragalactic Legacy (FIDEL; dated 2008 August 28) project taken
with the Multiband Imaging Photometer (MIPS) aboard Spitzer.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 99 489 Properties of power-law AGNs
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See also:
J/ApJS/193/30 : UV-to-FIR analysis of sources in the EGS. II. (Barro+, 2011)
J/ApJS/193/13 : Spitzer/IRAC sources in the EGS I. SEDs (Barro+, 2011)
J/ApJS/180/102 : AEGIS-X: Chandra deep survey (Laird+, 2009)
J/AJ/137/179 : AGNs in the EGS Survey (Ramos Almeida+, 2009)
J/ApJS/177/431 : Mid-IR sources in EGS (Barmby+, 2008)
J/MNRAS/382/109 : Massive galaxies in Extended Groth Strip (Trujillo+, 2007)
J/AJ/132/2159 : IRAC counterparts of 6cm galaxies in EGS (Willner+, 2006)
J/ApJ/642/126 : Mid-IR observations in the EGS (Barmby+, 2006)
http://irsa.ipac.caltech.edu/data/SPITZER/docs/spitzermission/
observingprograms/legacy/fidel/ : FIDEL data online page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- EGSPL Extended Groth Strip Power Law identification
5- 23 A19 --- EGSIRAC IRAC Extended Groth Strip identification (1)
25- 29 F5.2 --- alphai The 3.6-8 micron power-law spectral index (2)
31- 34 F4.2 --- Pi The 3.6-8 micron probability (3)
36- 40 F5.2 --- alpham ? The 3.6-24 micron power-law spectral index (2)
42- 45 F4.2 --- Pm ? The 3.6-24 micron probability (3)
47- 50 F4.2 --- z ? Redshift
52- 57 F6.2 uJy S3.6 Spitzer/IRAC 3.6 micron flux density (4)
59- 64 F6.2 uJy S4.5 Spitzer/IRAC 4.5 micron flux density (4)
66- 72 F7.2 uJy S5.8 Spitzer/IRAC 5.8 micron flux density (4)
74- 80 F7.2 uJy S8.0 Spitzer/IRAC 8.0 micron flux density (4)
82- 88 F7.2 uJy S24 ? Spitzer/MIPS 24 micron flux density
90- 93 I4 --- L09 ? X-ray catalog identification (159 sources) (5)
95- 99 F5.2 [10-7W] LX ? Log 2-10keV band luminosity; in erg/s
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Note (1): From the catalog published by Barmby et al. (2008,
Cat. J/ApJS/177/431; in Simbad).
Note (2): Sν∝να. α≤-0.5 is required for
selection as a power law (PL) AGN.
Note (3): Goodness of fit expressed as a probability. The numerical value is
the probability that observations of a source with a power-law SED
would give the actual chi-square or larger. Px>0.1 is required for
selection as a power law (PL) AGN.
Note (4): IRAC flux densities in this table were measured in 3 arcsec diameter
apertures and are the ones used in this paper. They are 3% higher
than the final published values (Barmby et al. 2008,
Cat. J/ApJS/177/431), which should be used for future work.
Note (5): X-ray catalog identification from Laird et al. 2009,
Cat. J/ApJS/180/102, <[LNG2009] egs-NNNN> in Simbad.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Jun-2012