J/AJ/147/14 The mJIVE-20 catalog (Deller+, 2014)
mJIVE-20: a survey for compact mJy radio objects with the Very Long Baseline
Array.
Deller A.T., Middelberg E.
<Astron. J., 147, 14 (2014)>
=2014AJ....147...14D 2014AJ....147...14D
ADC_Keywords: Surveys ; Radio sources ; Interferometry
Keywords: galaxies: active - radio continuum: galaxies - surveys -
techniques: high angular resolution - techniques: interferometric
Abstract:
We present the description and early results of the mJy Imaging VLBA
Exploration at 20cm (mJIVE-20). mJIVE-20 is a large project on the
Very Long Baseline Array which is systematically inspecting a large
sample of mJy radio sources, pre-selected from the Faint Images of the
Radio Sky at Twenty cm (FIRST) survey made with the Very Large Array,
to identify any compact emission that may be present. The survey is
being undertaken using filler time on the VLBA, which utilizes short
segments scheduled in bad weather and/or with a reduced number of
antennas, during which no highly rated science projects can be
scheduled. The newly available multifield capability of the VLBA makes
it possible for us to inspect of the order of 100 sources per hour of
observing time with a 6.75σ detection sensitivity of
approximately 1mJy/beam. The results of the mJIVE-20 survey are made
publicly available as soon as the data are calibrated. After 18 months
of observing, over 20000 FIRST sources have been inspected, with 4336
very long baseline interferometry detections. These initial results
suggest that within the range 1-200mJy, fainter sources are somewhat
more likely to be dominated by a very compact component than brighter
sources. Over half of all arcsecond-scale mJy radio sources contain a
compact component, although the fraction of sources that are dominated
by milliarcsecond scale structure (where the majority of the arcsecond
scale flux is recovered in the mJIVE-20 image) is smaller at around
30%-35%, increasing toward lower flux densities. Significant
differences are seen depending on the optical classification of the
source. Radio sources with a stellar/point-like counterpart in the
Sloan Digital Sky Survey (SDSS) are more likely to be detected
overall, but this detection likelihood appears to be independent of
the arcsecond-scale radio flux density. The trend toward higher radio
compactness for fainter sources is confined to sources that are not
detected in SDSS or that have counterparts classified as galaxies.
These results are consistent with a unification model of active
galactic nuclei in which less luminous sources have on average slower
radio jets, with lower Doppler suppression of compact core emission
over a wider range of viewing angles.
Description:
The mJy Imaging VLBA Exploration at 20cm (mJIVE-20) is a large project
on the Very Long Baseline Array (VLBA) which is systematically
inspecting a large sample of mJy radio sources, pre-selected from the
Faint Images of the Radio Sky at Twenty centimeters (FIRST; Becker et
al. 2012, cat. VIII/90) survey made with the Very Large Array (VLA),
to identify any compact emission that may be present.
The mJIVE-20 survey was approved with an initial allocation of 200hr
of observing time at the filler level priority (VLBA project code
BD161), and has now been extended to a total of 600hr (VLBA project
code BD170).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 198 23629 mJIVE-20 catalog (20-31 Dec 2013)
table4.dat 53 19 Known variable sources observed by mJIVE-20
table5.dat 53 53 Variable sources discovered by mJIVE-20
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
VIII/90 : The FIRST Survey Catalog, Version 12Feb16 (Becker+ 2012)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
J/A+A/551/A97 : Lockman Hole/XMM VLBI observations (Middelberg+, 2013)
J/ApJ/742/49 : Variable and transient radio sources in FIRST
(Thyagarajan+, 2011)
J/A+A/520/A113 : VLBI detection of 398 extragalactic radio sources
(Bourda+, 2010)
J/AJ/136/580 : Sixth VLBA calibrator survey: VCS6 (Petrov+, 2008)
J/ApJ/658/203 : VLBA imaging and polarimetry survey at 5GHz (Helmboldt+, 2007)
J/AJ/127/2565 : Faint FIRST variable radio sources (De Vries+, 2004)
J/AJ/125/465 : Phoenix Deep Survey 1.4-GHz microJy Catalog (Hopkins+, 2003)
J/ApJS/141/13 : VLBA calibrator survey: VCS1 catalog (Beasley+, 2002)
http://safe.nrao.edu/vlba/mjivs : mJIVE-20
http://astrogeo.org/rfc : Radio fundamental catalog
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [MJV]
4- 8 I05 --- MJV [0/24478] The mJIVE-20 number
10- 11 I2 h RAh FIRST Hour of Right Ascension (J2000)
13- 14 I2 min RAm FIRST Minute of Right Ascension (J2000)
16- 21 F6.3 s RAs FIRST Second of Right Ascension (J2000)
23 A1 --- DE- FIRST Sign of the Declination (J2000)
24- 25 I2 deg DEd FIRST Degree of Declination (J2000)
27- 28 I2 arcmin DEm FIRST Arcminute of Declination (J2000)
30- 34 F5.2 arcsec DEs [0/60] FIRST Arcsecond of Declination (J2000)
36- 42 F7.2 mJy Fpk FIRST peak flux density (in mJy/beam)
44- 50 F7.2 mJy Fint FIRST integrated flux density
52- 56 F5.2 mas BMaj VLBI synthesized beam major axis
58- 62 F5.2 mas BMin VLBI synthesized beam minor axis
64- 68 F5.1 deg BPA VLBI synthesized beam position angle
70 A1 --- l_Vpk Limit flag on Vpk
71- 77 F7.2 mJy Vpk VLBI peak flux density (in mJy/beam)
79- 83 F5.2 mJy e_Vpk ? Error in Vpk
85- 86 I2 h RAVh ? VLBI Hour of Right Ascension (J2000)
88- 89 I2 min RAVm ? VLBI Minute of Right Ascension (J2000)
91- 99 F9.6 s RAVs ? VLBI Second of Right Ascension (J2000)
101-108 F8.6 s e_RAVs ? Error in RAVs
110 A1 --- DEV- ? VLBI Sign of the Declination (J2000)
111-112 I2 deg DEVd ? VLBI Degree of Declination (J2000)
114-115 I2 arcmin DEVm ? VLBI Arcminute of Declination (J2000)
117-124 F8.5 arcsec DEVs ? VLBI Arcsecond of Declination (J2000)
126-132 F7.5 arcsec e_DEVs ? Error in DEVs
134-138 F5.3 --- V/Fpk ? Ratio of VLBI to FIRST peak flux densities
140-146 F7.2 mJy Vint ? VLBI integrated flux density
148-154 F7.2 mJy e_Vint ? Error in Vint
156-160 F5.3 --- V/Fint ? Ratio of VLBI integrated flux density to
FIRST peak flux density
162-166 F5.1 mas DMaj ? VLBI single-gaussian deconvolved major axis
168-172 F5.1 mas e_DMaj ? Error in DMaj
174-178 F5.1 mas DMin ? VLBI single-gaussian deconvolved minor axis
180-184 F5.1 mas e_DMin ? Error in DMin
186-190 F5.1 deg DPA ? VLBI single-gaussian deconvolved position
angle
192-196 F5.1 deg e_DPA ? Error in DPA
198 A1 --- C [C] C = Complex flag (1)
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Note (1): Denotes a source for which the signal-to-noise ratio of the
single Gaussian fit was less than the cutoff value of 6.75, but for
which the peak image pixel exceeded a threshold set based on expected
image noise, triggering a manual inspection of the data which verified
this source to be real.
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Byte-by-byte Description of file: table[45].dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- --- [MJV]
4- 8 I05 --- MJV [1591/22015] The mJIVE-20 number
10- 14 A5 --- --- [FIRST]
16- 36 A21 --- FIRST The FIRST identifier (JHHMMSS.sss+DDMMSS.ss)
38- 41 F4.1 mJy Fpk FIRST peak flux density (in mJy/beam)
43 A1 --- l_Vpk [<] Upper limit flag on Vpk
44- 47 F4.1 mJy Vpk VLBI peak flux density (in mJy/beam)
49 A1 --- l_V/Fpk [<] Upper limit flag on Vpk/Fpk
50- 53 F4.2 --- V/Fpk Ratio of VLBI to FIRST peak flux densities
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History:
* 26-Jan-2015:
# Tables 4 and 5 from electronic version of the journal
# mJIVE-20 catalog copied at http://safe.nrao.edu/vlba/mjivs/catalog.html
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 26-Jan-2015