J/ApJS/213/3 Low-frequency flat spectrum sources (LORCAT) (Massaro+, 2014)
The low-frequency radio catalog of flat-spectrum sources.
Massaro F., Giroletti M., D'Abrusco R., Masetti N., Paggi A.,
Cowperthwaite P.S., Tosti G., Funk S.
<Astrophys. J. Suppl. Ser., 213, 3 (2014)>
=2014ApJS..213....3M 2014ApJS..213....3M
ADC_Keywords: Cross identifications ; Radio continuum ; Surveys ;
Active gal. nuclei ; QSOs
Keywords: galaxies: active; quasars: general; radiation mechanisms: non-thermal;
surveys
Abstract:
A well known property of the γ-ray sources detected by Cos-B in
the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and
recently by the Fermi observations is the presence of radio
counterparts, particularly for those associated with extragalactic
objects. This observational evidence is the basis of the
radio-γ-ray connection established for the class of active
galactic nuclei known as blazars. In particular, the main spectral
property of the radio counterparts associated with γ-ray blazars
is that they show a flat spectrum in the GHz frequency range. Our
recent analysis dedicated to search blazar-like candidates as
potential counterparts for the unidentified γ-ray sources
allowed us to extend the radio-γ-ray connection in the MHz
regime. We also showed that blazars below 1GHz maintain flat radio
spectra. Thus, on the basis of these new results, we assembled a
low-frequency radio catalog of flat-spectrum sources built by
combining the radio observations of the Westerbork Northern Sky Survey
and of the Westerbork in the southern hemisphere catalog with those of
the NRAO Very Large Array Sky survey (NVSS). This could be used in the
future to search for new, unknown blazar-like counterparts of
γ-ray sources. First, we found NVSS counterparts of Westerbork
Synthesis Radio Telescope radio sources, and then we selected
flat-spectrum radio sources according to a new spectral criterion,
specifically defined for radio observations performed below 1GHz. We
also described the main properties of the catalog listing 28358 radio
sources and their logN-logS distributions. Finally, a comparison with
the Green Bank 6cm radio source catalog was performed to investigate
the spectral shape of the low-frequency flat-spectrum radio sources at
higher frequencies.
Description:
We have assembled a low-frequency radio catalog of flat-spectrum
sources (LORCAT) built by combining the radio observations of the two
main Westerbork Synthesis Radio Telescope (WSRT) surveys (i.e., WENSS
and WISH) at 325MHz and 352MHz, respectively, with those of the NVSS
at 1.4GHz.
The WENSS is a low-frequency radio survey that covers the northern sky
above +30° in declination performed at 325MHz to a limiting flux
density of ∼18mJy at the 5σ level (Rengelink et al. 1997,
Cat. J/A+AS/124/259, superseded by VIII/62). The version of the WENSS
catalog used in our analysis was implemented as a combination of two
separate catalogs obtained from the WENSS Web site: the WENSS Polar
Catalog that comprises 18186 sources above +72° in declination and
the WENSS Main Catalog including 211234 objects in the declination
range between +28° and +76°.
We also used the WISH catalog (Cat. VIII/69), which is the southern
extension of the WENSS. WISH is a low-frequency (352MHz) radio survey
covering most of the sky between -26° and -9° to the same
limiting flux density of the WENSS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 28358 Low-frequency radio catalog of flat-spectrum
sources (LORCAT) catalog
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See also:
VIII/90 : The FIRST Survey Catalog, Version 12Feb16 (Becker+ 2012)
VIII/81 : Sydney University Molonglo Sky Survey (SUMSS V2.1) (Mauch+ 2008)
VIII/79 : The VLA Low-frequency Sky Survey at 74MHz (Cohen+ 2007)
VIII/69 : The WISH catalogue at 352 MHz (de Breuck+ 2002)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/62 : The Westerbork Northern Sky Survey (WENSS) (Leiden, 1998)
VIII/40 : GB6 catalog of radio sources (Gregory+ 1996)
J/MNRAS/432/1294 : Fermi unassociated sources ATCA observations (Petrov+, 2013)
J/ApJS/209/10 : UGSs. V. kernel approach (Massaro+, 2013)
J/ApJS/207/4 : Unidentified γ-ray sources. III. Radio (Massaro+, 2013)
J/ApJS/206/13 : Blazars with γ-ray counterparts. II. (Massaro+, 2013)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
J/A+A/541/A160 : Planck + X/γ observations of blazars (Giommi+, 2012)
J/ApJ/752/61 : Blazars in unidentified γ-ray sources (Massaro+, 2012)
J/AZh/89/388 : Flat-spectrum radio sources variability (Gorshkov+, 2012)
J/ApJ/741/30 : Radio/γ-ray correlation in AGN (Ackermann+, 2011)
J/ApJS/188/405 : Fermi-LAT first source catalog (1FGL) (Abdo+, 2010)
J/ApJ/718/587 : The Fermi-AT20G catalog (Mahony+, 2010)
J/ApJ/709/1407 : SED of the Fermi blazars (Li+, 2010)
J/A+A/495/691 : Multifrequency cat. of blazars, Roma-BZCAT (Massaro+, 2009)
J/ApJ/707/L56 : VLBI and bright Fermi/LAT sources (Kovalev, 2009)
J/ApJS/171/61 : All-Sky Survey of Flat-Spectrum Radio Sources (Healey+, 2007)
J/A+A/386/97 : The Parkes quarter-Jansky flat-spectrum cat. (Jackson+, 2002)
J/ApJ/481/95 : Radio identification of EGRET sources (Mattox+ 1997)
http://www.astron.nl/wow/testcode.php?survey=2 : WISH catalog home page
http://www.astron.nl/wow/testcode.php?survey=1 : WENSS catalog home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- WSRT WSRT identifier (HHMM.m+DDMM; B1950)
13- 16 A4 --- --- [NVSS]
17- 30 A14 --- NVSS NVSS identifier (JHHMMSS+DDMMSS)
32- 33 I2 h RAh NVSS Hour of Right Ascension (J2000)
35- 36 I2 min RAm NVSS Minute of Right Ascension (J2000)
38- 42 F5.2 s RAs NVSS Second of Right Ascension (J2000)
44 A1 --- DE- NVSS Sign of the Declination (J2000)
45- 46 I2 deg DEd NVSS Degree of Declination (J2000)
48- 49 I2 arcmin DEm NVSS Arcminute of Declination (J2000)
51- 54 F4.1 arcsec DEs NVSS Arcsecond of Declination (J2000)
56- 60 F5.2 arcsec Sep [0/92.3] Angular separation between WSRT & NVSS
position
62- 66 F5.2 --- alpha [-1/0.4] Low frequency radio spectral index
(αlow)
68- 71 F4.2 --- e_alpha Uncertainty in alpha
73- 77 A5 --- Cat WSRT original survey identifier (1)
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Note (1): Westerbork Synthesis Radio Telescope (WSRT) survey identifier:
wenss = the Westerbork Northern Sky Survey (WENSS; Rengelink et al. 1997,
Cat. J/A+AS/124/259, superseded by VIII/62) at 325MHz;
in Simbad.
wish = the Westerbork in the southern hemisphere (WISH) survey (De Breuck
et al. 2002, Cat. VIII/69) at 352MHz (Nori et al. 2014ApJS..212....3N 2014ApJS..212....3N)
in Simbad.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Aug-2014