J/A+A/520/A47 Blazars in the Swift-BAT hard X-ray sky (Maselli+, 2010)
The blazar content of the Swift-BAT hard X-ray sky.
Maselli A., Cusumano G., Massaro E., La Parola V., Segreto A., Sbarufatti B.
<Astron. Astrophys. 520, A47 (2010)>
=2010A&A...520A..47M 2010A&A...520A..47M
ADC_Keywords: Active gal. nuclei ; BL Lac objects ; QSOs ; X-ray sources
Keywords: galaxies: active - galaxies: BL Lacertae objects -
radiation mechanisms: non-thermal
Abstract:
We present the results of a study on the blazar content in the
15-150keV map of the entire sky obtained analyzing 39 months of data
collected by the BAT telescope aboard the Swift satellite.
We performed a cross-correlation of the significance map, obtained
with a dedicated highly efficient algorithm (Segreto et al.,
2010A&A...510A..47S 2010A&A...510A..47S) for data processing and image reconstruction of
the BAT survey data, with the blazar population of the Roma-BZCAT
(Massaro et al., 2009, Cat. J/A+A/495/691).
After corrections for source confusion and spurious detections, we
found significance excesses higher than two standard deviations for
304 sources; the corresponding fraction of expected spurious
associations is about 20%. We selected hard X-ray blazars according to
their significance level and carried out a statistical analysis to
characterise their emission properties. A sample of 121 blazars
detected at a significance level sigma>3 is discussed in greater
detail.
The fraction of blazars with uncertain classification in this sample
is considerable, more than twice with respect to the percentage
obtained considering all the blazars classified in the Roma-BZCAT. We
attribute the X-ray flux of the majority of selected BL Lac objects to
the synchrotron emission.
Description:
We reported the list of hard X-ray blazars obtained adopting sigma=3
as detection threshold: with this choice a number of three spurious
sources over a total of 121 blazars is expected.
Each blazar is identified by a three-letter code, where the first two
are BZ for blazar and the third one specifies the type, followed by
the truncated equatorial coordinates (J2000). The codes are defined in
the "Note (1)" below. We obtained 69 FSRQs, 24 BL Lac objects and 28
blazars of uncertain classification, representing 4.4%, 2.4% and 11.0%
of the corresponding populations classified in the BZCAT,
respectively.
This sample has been compared with other lists and catalogues found in
literature (Tueller et al., 2010, Cat. J/ApJS/186/378, Ajello et al.
2009ApJ...699..603A 2009ApJ...699..603A, Cusumano et al., 2010, Cat. J/A+A/510/A48).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 90 121 Blazars detected at sigma>3
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See also:
J/ApJS/186/378 : Hard X-ray survey from Swift-BAT 2004-2006 (Tueller+, 2010)
J/A+A/510/A48 : Palermo Swift-BAT Hard X-ray Catalogue (Cusumano+, 2010)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Source name (1)
15- 35 A21 --- OName Other designation
39- 45 F7.3 deg RAdeg Right ascension (J2000)
47- 53 F7.3 deg DEdeg Declination (J2000)
55- 59 F5.3 --- z ? Redshift
60 A1 --- u_z [?] Comment (uncertainty) on redshift
62- 67 F6.2 fW/m2 FX ? X-ray flux (in 10-12erg/cm2/s) (2)
68 A1 --- n_FX [*] Comment on X-ray flux (2)
70- 77 E8.4 --- X/R ? Ratio between X-ray and radio emission (3)
79- 84 F6.2 --- Sigma Significance in the 39-month 15-150keV map
86 A1 --- T [y] Included in the list of Tueller et al.
(2010, Cat. J/ApJS/186/378)
88 A1 --- A [y] Included in the list of Ajello et al.
(2009ApJ...699..603A 2009ApJ...699..603A)
90 A1 --- C [y] Included in the list of Cusumano et al.
(2010, Cat. J/A+A/510/A48)
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Note (1): The classifications are:
BZB = BL Lac objects, used for AGNs with a featureless optical
spectrum or only with absorption lines of galaxian origin
and weak and narrow emission lines
BZQ = flat-spectrum radio quasars, with an optical spectrum showing
broad emission lines and dominant blazar characteristics
BZU = blazars of uncertain type, adopted for sources with peculiar
characteristics but also showing blazar activity: for
instance, occasional presence/absence of broad spectral lines
or features, transition objects between a radio galaxy and a
BL Lac, galaxies hosting a low luminosity blazar nucleus, etc.
Note (2): X-ray flux in the 0.1-2.4keV energy band, or in the 0.5-2.0keV
band in the case of a recent Swift-XRT observation (marked with * ).
Note (3): The adimensional factor PHI_XR represents the ratio between the
X-ray and the radio emission; the formula is given in the text. This
ratio has proved to be a reliable index to determine the LBL or HBL
classification of BL Lac objects (Giommi et al., 1999MNRAS.310..465G 1999MNRAS.310..465G)
and the value phiXR=1 can be considered a lower limit for HBL sources
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Acknowledgements:
Alessandro Maselli, maselli(at)ifc.inaf.it
(End) Alessandro Maselli [INAF-IASF Palermo], Patricia Vannier [CDS] 25-Jun-2010