J/ApJ/841/113 Roma-BZCAT synchrotron peak & Compton dominance (Mao+, 2017)
An investigation of blazars without redshifts:
not a missing population at high redshift.
Mao P., Urry C.M.
<Astrophys. J., 841, 113 (2017)>
=2017ApJ...841..113M 2017ApJ...841..113M
ADC_Keywords: BL Lac objects ; QSOs
Keywords: accretion, accretion disks; astronomical databases: miscellaneous;
BL Lacertae objects: general; quasars: general
Abstract:
We investigate a sample of 622 blazars with measured fluxes at 12
wavebands across the radio-to-gamma-ray spectrum but without
spectroscopic or photometric redshifts. This sample includes hundreds
of sources with newly analyzed X-ray spectra reported here. From the
synchrotron peak frequencies, estimated by fitting the broadband
spectral energy distributions (SEDs), we find that the fraction of
high-synchrotron-peaked blazars in these 622 sources is roughly the
same as in larger samples of blazars that do have redshifts. We
characterize the no-redshift blazars using their infrared colors,
which lie in the distinct locus called the WISE blazar strip, then
estimate their redshifts using a KNN regression based on the redshifts
of the closest blazars in the WISE color-color plot. Finally, using
randomly drawn values from plausible redshift distributions, we
simulate the SEDs of these blazars and compare them to known blazar
SEDs. Based on all these considerations, we conclude that blazars
without redshift estimates are unlikely to be high-luminosity, high-
synchrotron-peaked objects, which had been suggested in order to
explain the "blazar sequence"-an observed trend of SED shape with
luminosity-as a selection effect. Instead, the observed properties of
no-redshift blazars are compatible with a causal connection between
jet power and electron cooling, i.e., a true blazar sequence.
Description:
We base our blazar sample on data from the Multi-wavelength Catalog of
blazars, Roma-BZCAT1 v5.0 (see Massaro+ 2009, J/A+A/495/691). The
details of the sample selection from Roma-BZCAT, as well as the
association of sources across multiple wavelengths, can be found in
Paper I (Mao+, 2016, J/ApJS/224/26). We define as Sample I the 2220
blazars in that paper, all of which have redshifts and radio fluxes.
In this paper, we focus on the 622 spectroscopically confirmed BL Lacs
that do not have redshift estimates, which we call Sample II.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 138 2943 *Synchrotron peak and Compton dominance for
samples I and II
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Note on table3.dat: See the "Description" section above for the
sample definitions.
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/59 : the FIRST Survey, version 1999Jul (White+ 1999)
V/139 : The SDSS Photometric Catalog, DR9 (Adelman-McCarthy+, 2012)
V/147 : The SDSS Photometric Catalog, DR12 (Alam+, 2015)
J/MNRAS/323/757 : Deep X-Ray Radio Blazar Survey (DXRBS). II. (Landt+, 2001)
J/A+A/445/441 : SED of BL Lacertae objects (Nieppola+, 2006)
J/A+A/488/867 : Synchrotron peak frequency of 135 AGN (Nieppola+, 2008)
J/A+A/495/691 : Multifrequency catalog of blazars Roma-BZCAT (Massaro+, 2009)
J/ApJ/748/68 : WISE IR colors of gamma-ray blazars (D'Abrusco+, 2012)
J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)
J/ApJS/206/12 : Blazars with γ-ray counterparts. I. (D'Abrusco+, 2013)
J/ApJS/215/14 : WISE γ-ray blazar radio candidates (D'Abrusco+, 2014)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/ApJ/810/14 : Third catalog of LAT-detected AGNs (3LAC) (Ackermann+, 2015)
J/ApJS/224/26 : SEDs of Roma BZCAT blazars (Mao+, 2016)
http://www.sdss3.org/ : SDSS-III home page
http://www.asdc.asi.it/bzcat/ : Roma BZCAT - 5th edition home page
http://fermi.gsfc.nasa.gov/ssc/data/access/lat/4yr_catalog/ : 3FGL home page
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- BZCAT BZCAT identifier (1)
15- 19 F5.2 [Hz] logPk [12/18]? Log observed frame synchrotron peak
frequency (2)
21- 40 A20 --- n_logPk Note on logPk (3)
42- 46 F5.2 [Hz] logPkr [12/18]? Log rest frame synchrotron peak
frequency (2)
48- 78 A31 --- n_logPkr Note on logPkr (3)
80- 84 F5.2 [Hz] logPkC [19/25]? Log observed frame Compton peak
frequency (2)
86-102 A17 --- n_logPkC Note on logPkC (4)
104-108 F5.2 [Hz] logPkCr [18/25]? Log rest frame Compton peak
frequency (2)
110-126 A17 --- n_logPkCr Note on logPkCr (4)
128-132 F5.2 --- AC [-1.5/2.1]? Compton Dominance in observed
frame (fpeak,C/fpeak,s)
134-138 F5.2 --- ACr [-1.1/2.6]? Compton Dominance corrected
to rest frame (Lpeak,C/Lpeak,s;
only for Sample I)
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Note (1): A total of 652 objects (362 Sample I FSRQ, 62 Sample I BL Lac, 228
Sample II BL Lac) had enough data fitted with a physical peak in
fluxes, and 339 objects from Sample I (294 FSRQ, 45 BL Lac) had good
fits in luminosities.
Please note that BZBJ1701+3954 identifier is ambiguous and can be
two different sources; note added by CDS.
Note (2): νLν, only for Sample I.
Note (3): Peaks are considered unphysical if the fitted peak frequency falls
outside the 12 - 18 range.
Note (4): Peaks are considered unphysical if the fitted peak frequency falls
outside the 19 - 26 range.
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Nomenclature note:
Objects are <[MGL2015] 5BZB JHHMM+DDMMa> in Simbad.
History:
From electronic version of the journal
References:
Mao et al. Paper I. 2016ApJS..224...26M 2016ApJS..224...26M Cat. J/ApJS/224/26
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Jan-2018