J/ApJ/658/203 VLBA imaging and polarimetry survey at 5GHz (Helmboldt+, 2007)
The VLBA imaging and polarimetry survey at 5 GHz.
Helmboldt J.F., Taylor G.B., Tremblay S., Fassnacht C.D., Walker R.C.,
Myers S.T., Sjouwerman L.O., Pearson T.J., Readhead A.C.S., Weintraub L.,
Gehrels N., Romani R.W., Healey S., Michelson P.F., Blandford R.D.,
Cotter G.
<Astrophys. J., 658, 203-216 (2007)>
=2007ApJ...658..203H 2007ApJ...658..203H
ADC_Keywords: Surveys ; Radio sources ; Polarization
Keywords: catalogs - galaxies: active - galaxies: jets - galaxies: nuclei -
radio continuum: galaxies - surveys - techniques: image processing
Abstract:
We present the first results of the VLBA Imaging and Polarimetry
Survey (VIPS), a 5GHz VLBI survey of 1119 sources with flat radio
spectra. Through automated data reduction and imaging routines, we
have produced publicly available I, Q, and U images and have detected
polarized flux density from 37% of the sources. We have also developed
an algorithm to use each source's I image to automatically classify it
as a pointlike source, a core jet, a compact symmetric object (CSO)
candidate, or a complex source. Using data from the Sloan Digital Sky
Survey (SDSS), we have found no significant trend between optical flux
and 5 GHz flux density for any of the source categories.
Description:
We have chosen the Cosmic Lens All-Sky Survey (CLASS; Myers et al.
2003, Cat. VIII/72) as our parent sample. We have also restricted
our sample to lie on the survey area, of the Sloan Digital Sky Survey.
Among our target list, 141 have already been observed at 5 GHz with
the VLBA as part of the Caltech-Jordell Bank Flat-Spectrum survey
(CJF; Taylor et al., 1996ApJS..107...37T 1996ApJS..107...37T; Pollack et al., 2003, Cat.
J/ApJ/589/733), eight have been or will be observed at 15GHz as part
of the Monitoring of Jets in AGNs with VLBA Experiments (MOJAVE)
project (Lister & Homan, 2005, Cat. J/AJ/130/1389), and 20 were
observed for the VIPS pilot program at 5 and 15GHz (Taylor et al.,
2005ApJS..159...27T 2005ApJS..159...27T). Each of these surveys contains VLBA observations
at 5 or 15GHz that have adequate sensitivity for our purposes.
The remaining 958 sources were observed with the VLBA within 18
separate observing runs of approximately 11hr each from 2006 January
to August.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 112 1119 Source properties
table3.dat 46 330 Polarization properties
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See also:
VIII/72 : CLASS survey of radio sources (Myers+, 2003)
J/ApJ/589/733 : VLBI polarimetry of CJF sources (Pollack+, 2003)
J/AJ/130/1389 : Linear polarization of AGN jets at 15GHz (Lister+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq The VIPS source number,
VIPS NNNN in Simbad
6- 16 A11 --- VIPS The VIPS source name (JHHMMm+DDMM)
18- 19 I2 h RAh Hour of Right Ascension (J2000)
21- 22 I2 min RAm Minute of Right Ascension (J2000)
24- 30 F7.4 s RAs Second of Right Ascension (J2000)
32 A1 --- DE- Sign of the Declination (J2000)
33- 34 I2 deg DEd Degree of Declination (J2000)
36- 37 I2 arcmin DEm Arcminute of Declination (J2000)
39- 44 F6.3 arcsec DEs Arcsecond of Declination (J2000)
46- 55 A10 "YYYY/MM/DD" Obs.Date UT date of the observation
57- 62 F6.1 mJy S8.5 CLASS survey 8.5GHz flux density
64- 69 F6.1 mJy S5 ? Total cleaned 5GHz flux density
71- 76 F6.1 mJy Sp5 ? Peak 5GHz flux density
78- 81 F4.2 mJy rms5 The rms noise in the 5GHz VLBA map
83- 84 I2 --- NGc ? Number of dominant Gaussian
components fit (1)
86- 89 A4 --- Ta Automatic source type (2)
91- 94 A4 --- Te Visual inspection source type (2)
96- 99 F4.1 mas R ? Mean radius dominant Gaussian
components
101-105 F5.1 mas Dmax ? Dominant Gaussian components
maximum separation
107-112 F6.1 deg PAjet ? Jet position angle (4)
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Note (1): i.e., that contain more than 95% of the total flux. See Section 2.3.
Note (2): Derived from the automated Gaussian component classification
(see Section 2.3). They are as follows:
PS = point-like sources
SJET = short jet (subdivision of core jet)
LJET = long jet (subdivision of core jet)
CSO = compact symmetric object candidates
CPLX = complex sources
ND = not determined
Visual inspection determination of the I image for sources
where the "by-eye" and automatic classifications disagree.
Note (4): Measured from north through east.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq The VIPS source number
6- 16 A11 --- VIPS The VIPS source name
18- 22 F5.3 --- fpTot Average 5GHz fractional polarization
(see Section 2.4)
24- 28 F5.3 --- fpCore ? Average 5GHz fractional polarization within
brightest Gaussian component
30- 34 F5.3 --- fpOut ? Average 5GHz fractional polarization outside
brightest Gaussian component
36- 38 I3 deg PAtot Polarized intensity-weighted mean electric
vector position angle at 5GHz
40- 42 I3 deg PAcore ? Polarized intensity-weighted mean electric
vector position angle at 5GHz within
brightest Gaussian component
44- 46 I3 deg PAout ? Polarized intensity-weighted mean electric
vector position angle at 5GHz outside
brightest Gaussian component
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 09-Jan-2009