J/A+A/560/A23 Radio properties of faint BL Lacs (Liuzzo+, 2013)
Exploring the bulk of the BL Lac object population.
I. Parsec-scale radio structures.
Liuzzo E., Giroletti M., Giovannini G., Boccardi B., Tamburri S.,
Taylor G.B., Casadio C., Kadler M., Tosti G., Mignano A.
<Astron. Astrophys. 560, A23 (2013)>
=2013A&A...560A..23L 2013A&A...560A..23L
ADC_Keywords: Active gal. nuclei ; Radio continuum ; VLBI
Keywords: radio continuum: galaxies - galaxies: active - galaxies: jets
Abstract:
The advent of Fermi is changing our understanding on the radio and
gamma-ray emission in Active Galactic Nuclei. Contrary to pre-Fermi
ideas, BL Lac objects are found to be the most abundant emitters in
the gamma-ray band. However, since they are relatively weak radio
sources, most of their parsec-scale structure and their
multi-frequency properties are poorly understood and/or have not been
investigated in a systematically fashion.
Our main goal is to analyze the radio and gamma-ray emission
properties of a sample of 42 BL Lacs selected, for the first time in
the literature, with no constraint on their radio and gamma-ray flux
densities/emission.
Thanks to new Very Long Baseline Array observations at 8 and 15GHz
for the whole sample, we present here fundamental parameters such as
radio flux densities, spectral index information, and parsec-scale
structure. Moreover, we search for gamma-ray counterparts using data
reported in the Second Catalog of Fermi Gamma-ray sources.
Parsec-scale radio emission is observed in the majority of the sources
at both frequencies. Gamma-ray counterparts are found for 14/42
sources.
The comparison between our results in radio and gamma-ray bands points
out the presence of a large number of faint BL Lacs showing "non
classical" properties such as low source compactness, core dominance,
no gamma-ray emission and steep radio spectral indexes. A deeper
multiwavelength analysis will be needed.
Description:
8 and 15GHz VLBA maps for the whole sample of nearby BL Lac objects.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 70 128 Description of FITS maps
maps/* . 128 Individual FITS maps
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See also:
J/A+A/495/691 : Multifrequency catalogue of blazars Roma-BZCAT (Massaro+, 2009)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Target BL Lac name, JHHMM+DDMM,
[MGL2009] BZB JHHMM+DDMM in Simbad
12- 13 I2 h RAh Hour of right ascension (J2000)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 23 F6.3 s RAs Second of right ascension (J2000)
25 A1 --- DE- Sign of declination (J2000)
26- 27 I2 deg DEd Degree of declination (J2000)
29- 30 I2 arcmin DEm Arcminute of declination (J2000)
32- 36 F5.2 arcsec DEs Arcsecond of declination (J2000)
38 A1 --- Band [XU] VLBA band (X=8GHz, U=15GHz)
40- 41 A2 ---- Type [IM UV] UV data (UV) or FITS file of the
cleaned image (IM; resolution ∼0.1mas/pix)
43- 70 A28 ----- FileName Name of the file in subdirectory maps
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Acknowledgements:
Elisabetta Liuzzo,
(End) E. Liuzzo [INAF-IRA & IT-ARC, Italy], P. Vannier [CDS] 02-Dec-2013