CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources Page: 2 of 23
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
2
1. Introduction
As extrema of the AGN population, blazars are of particular interest for a number
of topics in accretion and jet physics. These sources are characterized by flat radio spec-
tra; high variability, especially in the optical; significant polarization; and bimodal syn-
chrotron/Compton SEDs. They are believed to be high-power radio AGN with a strong jet
component viewed "pole-on." For this model, Doppler boosting ensures that non-thermal jet
emission will be strong. In cases where the non-thermal emission dominates the thermal flux
from the accretion and surrounding broad-line region, the objects are known as HBL or BL
Lacs. We are particularly interested in blazars since, at a-ray energies, high-power blazars
appear to dominate the observed EGRET sources (Hartman et al. 1999). The GeV Comp-
ton peak flux, in fact, likely dominates the cosmic background radiation at these energies.
Similarly, the synchrotron IR-mm peak can dominate the point source contribution to the
microwave sky (Giommi et al. 2006). Thus, large blazar surveys, probing the blazar popu-
lation and its evolution, can be helpful for both a-ray and microwave source identifications
and for understanding cosmic backgrounds in these energy bands.
Flat-spectrum radio surveys are the prime source of blazar discoveries. Moreover, stud-
ies show that bright, flat-spectrum sources strongly correlate with sources in the >100 MeV
sky (Mattox et al. 2001; Hartman et al. 1999; Sowards-Emmerd et al. 2005). In particular,
our work has shown that high-energy associations are especially powerful when interfero-
metric measurements of core flux density and spectral index are available. Further, since
the "trough" between the blazar radio and a-ray components lies in the optical to X-ray
range, counterparts at these wavelengths are often faint. Indeed, many are known to have
R > 23, well below the sensitivity of the Second Digitized Sky Survey (DSS2). Positive iden-
tification is greatly helped by precise sub-arcsecond positions and structures, which require
interferometric measurements at cm wavelengths.
Our survey is designed as an extension of the largest high-frequency interferometric
survey currently available, the Cosmic Lens All-Sky Survey (CLASS) (Myers et al. 2003).
We have replicated as closely as possible its selection criteria and extended the survey to
the full sky at high Galactic latitudes through a combination of published data, reanalysis
of archival data, and new observations. The product represents the largest sample of bright,
compact, flat-spectrum sources available to date.
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Healey, Stephen E.; Romani, Roger W.; Taylor, Gregory B.; Sadler, Elaine M.; Ricci, Roberto; Murphy, Tara et al. CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources, article, February 20, 2007; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc882645/m1/2/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.