J/AJ/142/3 1.4GHz observations of Stripe 82 (Hodge+, 2011)
High-resolution very large array imaging of Sloan digital sky survey Stripe 82
at 1.4 GHz
Hodge J.A., Becker R.H., White R.L., Richards G.T., Zeimann G.R.
<Astron. J., 142, 3 (2011)>
=2011AJ....142....3H 2011AJ....142....3H
ADC_Keywords: Radio sources ; Surveys ; Photometry, SDSS
Keywords: catalogs; radio continuum: general; surveys
Abstract:
We present a high-resolution radio survey of the Sloan Digital Sky
Survey (SDSS) Southern Equatorial Stripe, a.k.a. Stripe 82. This
1.4GHz survey was conducted with the Very Large Array primarily in the
A-configuration, with supplemental B-configuration data to increase
sensitivity to extended structure. The survey has an angular
resolution of 1.8" and achieves a median rms noise of 52µJy/beam
over 92deg2. This is the deepest 1.4GHz survey to achieve this large
of an area, filling a gap in the phase space between small, deep and
large, shallow surveys. It also serves as a pilot project for a larger
high-resolution survey with the Expanded Very Large Array. We discuss
the technical design of the survey and details of the observations,
and we outline our method for data reduction. We present a catalog of
17969 isolated radio components, for an overall source density of
∼195sources/deg2. The astrometric accuracy of the data is excellent,
with an internal check utilizing multiply observed sources yielding an
rms scatter of 0.19" in both right ascension and declination. A
comparison to the SDSS-DR7 Quasar Catalog further confirms that the
astrometry is well tied to the optical reference frame, with mean
offsets of 0.02±0.01" in right ascension, and 0.01±0.02" in
declination. A check of our photometry reveals a small, negative
CLEAN-like bias on the level of 35µJy. We report on the catalog
completeness, finding that 97% of FIRST-detected quasars are recovered
in the new Stripe 82 radio catalog, while faint, extended sources are
more likely to be resolved out by the resolution bias. We conclude
with a discussion of the optical counterparts to the catalog sources,
including 76 newly detected radio quasars.
Description:
The data were collected over two VLA cycles (2007-2008 and 2008-2009).
The majority of the observations were taken in the A-configuration,
but we also obtained B-configuration coverage of the area to improve
the sampling of the Fourier (U-V) plane and increase sensitivity to
the extended structure. In the first cycle, we were awarded scheduled
A-configuration time (Program ID AR646), and the B-configuration time
(AR659) was all collected dynamically through the queue. In the second
cycle, we were awarded both the A- and B-configuration time as dynamic
time (AR685).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stripe82.dat 144 17969 The VLA Stripe 82 survey catalog (version 2010may25)
table2.dat 73 76 Newly detected radio quasars
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See also:
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/ApJ/799/72 : Binary AGNs from the VLA Stripe 82 survey (Fu+, 2015)
J/ApJS/188/384 : The VLA-COSMOS survey. IV. (Schinnerer+, 2010)
J/ApJS/188/178 : VLA 1.4GHz obs. of GOODS-North field (Morrison+, 2010)
J/MNRAS/401/1429 : WiggleZ dark energy survey (DR1) (Drinkwater+, 2010)
J/MNRAS/397/281 : Radio imaging in Lockman Hole (Ibar+, 2009)
J/ApJS/180/67 : Photometric selection of QSOs from SDSS. II. (Richards+, 2009)
J/ApJS/179/114 : VLA 1.4GHz survey of E-CDF-S (Miller+, 2008)
J/ApJS/179/71 : VLA survey of the CDF-S I. (Kellermann+, 2008)
J/AJ/136/1889 : 20cm observations of deep Swire Field (Owen+, 2008)
J/AJ/135/2470 : Radio observations of the HDFS region. IV. (Huynh+, 2008)
J/MNRAS/381/211 : Radio galaxies in the 2SLAQ LRG Survey (Sadler+, 2007)
J/ApJS/172/46 : VLA-COSMOS survey. II. (Schinnerer+, 2007)
J/AJ/132/2409 : Deep ATLAS radio observations of CDFS (Norris+, 2006)
J/MNRAS/372/741 : SXDF 100µJy catalogue (Simpson+, 2006)
J/AJ/131/1216 : Faint radio sources in the CDF-S ACS field (Afonso+, 2006)
J/AJ/130/1373 : Radio observations of the HDFS region. II (Huynh+, 2005)
J/MNRAS/352/131 : 13+38 XMM-Newton/ROSAT 1.4GHz radio catalog (Seymour+, 2004)
J/A+A/403/857 : VLA-VIRMOS Deep Field (Bondi+, 2003)
J/AJ/125/2411 : SIRTF First-Look Survey (Condon+, 2003)
J/AJ/125/465 : Phoenix Deep Survey 1.4-GHz microJy Catalog (Hopkins+, 2003)
J/ApJS/143/1 : FIRST-APM Source Catalog (McMahon+, 2002)
J/ApJ/533/611 : 1.4GHz survey in HDF region (Richards+, 2000)
http://www.physics.drexel.edu/~gtr/vla/stripe82/ : Stripe 82 VLA home page
http://third.ucllnl.org/cgi-bin/stripe82cutout : Stripe 82 image cutouts
http://www.cfht.hawaii.edu/Science/CFHLS/ : CFHTLS home page
http://sundog.stsci.edu/ : The VLA FIRST survey home page
Byte-by-byte Description of file: stripe82.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Str82 Source designation; column added by CDS (1)
18- 19 I2 h RAh Right Ascension J2000 (hours) (2)
21- 22 I2 min RAm Right Ascension J2000 (minutes) (2)
24- 29 F6.3 s RAs Right Ascension J2000 (seconds) (2)
31 A1 --- DE- Declination J2000 (sign) (2)
32- 33 I2 deg DEd Declination J2000 (degrees) (2)
35- 36 I2 arcmin DEm Declination J2000 (minutes) (2)
38- 42 F5.2 arcsec DEs Declination J2000 (seconds) (2)
44- 48 F5.3 --- p(S) [0,1] Probability of being a side lobe (3)
50- 57 F8.2 mJy/beam Fpeak Peak flux density at 1.4GHz in mJy/beam (4)
59- 67 F9.2 mJy Fint [0.1/2349] Integrated flux density at 1.4GHz (4)
70- 75 F6.3 mJy rms [0.03/15.1] Local noise estimate at the
source position σ (5)
77- 82 F6.2 arcsec Maj [0/60] Major axis (FWHM) (6)
84- 89 F6.2 arcsec Min [0/22] Minor axis (FWHM) (6)
91- 95 F5.1 deg PA [0/180] Position angle (6)
98-102 F5.2 arcsec fMaj Fitted major axis before deconvolution (7)
104-108 F5.2 arcsec fMin Fitted minor axis before deconvolution (7)
110-114 F5.1 deg fPA [0/180] Fitted PA before deconvolution (7)
116-127 A12 --- Field Name of the coadded image containing
the source (8)
129-130 I2 --- N1 [0/25] Number of SDSS counterparts (9)
132-136 F5.2 arcsec r1 [0/8]?=99 Closest SDSS match (9)
138-142 F5.2 mag m1 [-1/28.1]?=99 SDSS i magnitude of closest
SDSS match (9)
144 A1 --- c1 [sg-] SDSS class: s=star, g=galaxy
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Note (1): This column (added by CDS) contains the source name built from
the rule registered at IAU ('J' followed by truncated J2000-position).
Note (2): Position (J2000) of the source. The positional errors are a
function of source brightness, size, and noise in the map. They are
best found using a simple rule-of-thumb approach, as the HAPPY-derived
errors tend to be underestimated. An empirical equation for the
accuracy at 90% confidence is fSizex(1/SNR+1/20) where fSize is the
fitted major or minor axis size, and SNR is the signal-to-noise ratio
(White et al. 1997, see VIII/92). Systematic errors are smaller than
0.05".
Note (3): p(S) indicates the probability that the source is spurious, most
likely because it is a sidelobe of a nearby bright source. Low values
mean the source is unlikely to be spurious. The probabilities are
computed using an algorithm based on multiple voting oblique decision
tree classifiers, which were trained on deep VLA fields. The algorithm
was developed for the FIRST survey (see Becker et al. 2012, VIII/90).
Note that the algorithm is optimized for the FIRST survey, whereas the
rms computation for this catalog has changed significantly. The values
of P(S) are therefore not very reliable for this catalog.
Note (4): Fpeak and Fint are the peak and integrated flux densities; Fpeak
is in mJy/beam derived by fitting an elliptical Gaussian model to the
source. The uncertainty is given by the rms noise at the source
position. Fint is the integrated flux density in mJy derived from the
elliptical Gaussian model fit. The uncertainty in Fint can be
considerably greater than that of Fpeak depending on source size and
morphology. An expression to estimate the uncertainty can be found in
Schinnerer et al. (2004AJ....128.1974S 2004AJ....128.1974S). For point sources, the
relative uncertainty (σ(I)/I) reduces to:
σ(I)/I = [2.5(σ/Fint)2 + 0.0012]0.5
Note (5): The rms is calculated by combining the measured noise from all
grid images contributing to the co-added map at the source position.
Note (6): Maj, Min, and PA give the major and minor axes (FWHM in arcsec)
and position angle (degrees east of north) derived from the elliptical
Gaussian model for the source. Maj and Min have had the elliptical
Gaussian PSF deconvolved. Noise can cause the fitted values of the
major and minor axes prior to deconvolution to be smaller than the
beam, and the deconvolved size is given as zero in that case. The
uncertainties in the deconvolved sizes depend on both brightness and
size.
Note (7): fMaj, fMin, and fPA give the major and minor axes (FWHM in
arcsec) and position angle (degrees east of north) derived from the
elliptical Gaussian model for the source. These are the fitted sizes
before deconvolution of the 1.8arcsec circular clean beam.
Note (8): The Field Name is the name of the coadded image containing the
source. Note that the field name encodes the center of the field;
field hhmmm+ddmmm is centered at hh:mm.m+dd:mm.m. The letter appended
to the field name indicates the last catalog release in which the
image was modified.
Note (9): These columns give information on optical counterparts from the
SDSS-DR6 catalog (Cat. II/282). The matches were performed using the
CasJobs web interface. Column "N1" gives the number of matches within
a radius of 8". For the closest match, Columns "r1" gives the
separation in arcsec, and "m1" the magnitude in the SDSS i band.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Radio hour of Right Ascension (J2000)
4- 5 I2 min RAm Radio minute of Right Ascension (J2000)
7- 12 F6.3 s RAs Radio second of Right Ascension (J2000)
14 A1 --- DE- Radio sign of declination (J2000)
15- 16 I2 deg DEd Radio degree of declination (J2000)
18- 19 I2 arcmin DEm Radio arcminute of Declination (J2000)
21- 25 F5.2 arcsec DEs Radio arcsecond of Declination (J2000)
28- 32 F5.2 mJy/beam Fpeak [0.3/14] 1.4GHz peak flux density
36- 40 F5.2 mJy Fint [0.2/33] 1.4GHz integrated flux density
44- 48 F5.2 arcsec Maj [0/8] Deconvolved major axis
52- 56 F5.2 arcsec Min [0/5] Deconvolved minor axis
61- 65 F5.3 --- z [0.1/4.5] Redshift from SDSS-DR7 quasar catalog
(Schneider et al. 2010, VII/260)
69- 73 F5.2 mag rmag [17/21]? SDSS apparent r-band magnitude
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History: Copied from
http://www.physics.drexel.edu/~gtr/outgoing/stripe82/stripe82_2010may25.cat
or from electronic version for table 2
(End) Francois Ochsenbein [CDS] 09-Jul-2015