The Deep X-Ray Radio Blazar Survey. I. Methods and First Results
Perlman, ES Eric S. ; Padovani, Paolo ; Giommi, Paolo ; et al.
Apr - 1998
ISSN : 00046256 ;
journal : The Astronomical
Issue : 4
type: Article Journal
Abstract
We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed
ROSAT Position Sensitive Proportional Counter data for blazars by correlating the ROSAT WGACAT
database with several publicly available radio catalogs, restricting our candidate list to
serendipitous flat radio spectrum sources (\alpha r ≤ 0.70, where S \nu ∝ \nu \#\#IMG\#\#
[http://ej.iop.org/images/1538-3881/115/4/1253/img1.gif] ). We discuss our survey methods, identification procedure, and first results. Our survey is found to be 95\% efficient at finding
flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85 identifications) and BL Lacertae objects
(22 of our first 85 identifications), a figure that is comparable to or greater than that achieved
by other radio and X-ray survey techniques. The identifications presented here show that all
previous samples of blazars (even when taken together) did not representatively survey the blazar
population, missing critical regions of ( L X , L R ) parameter space within which large fractions
of the blazar population lie. Particularly important is the identification of a large population of
FSRQs ( \#\#IMG\#\# [http://ej.iop.org/icons/Entities/gtrsim.gif] \gtrsim\ 25\% of DXRBS FSRQs) with
ratios of X-ray to radio luminosity \#\#IMG\#\# [http://ej.iop.org/icons/Entities/gtrsim.gif] \gtrsim\
10 -6 (\alpha rx \#\#IMG\#\# [http://ej.iop.org/icons/Entities/lesssim.gif] \lesssim\ 0.78). In addition, as
a result of our greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in
complete samples with 5 GHz (radio) luminosities between 10 31.5 and 10 33.5 ergs s -1 Hz -1 , and
fills in the region of parameter space between X-ray–selected and radio-selected samples of BL Lac
objects. The DXRBS is the very first sample to contain statistically significant numbers of blazars
at low luminosities, approaching what should be the lower end of the FSRQ luminosity function.
keywords :