Survey Astronomy

The statistical analysis of radio source counts can be used to investigate the evolution of galaxies. Total intensity radio source counts have been studied in detail at a range of frequencies, including with the Giant Metrewave Radio Telescope (GMRT) at 150 MHz (George & Stevens 2008).

At 1.4 GHz the polarization properties are poorly understood with previous work finding a larger median polarization intensity with decreasing flux density. At lower flux densities the source counts are increasingly dominated by other populations, such as radio-quiet AGN, star- bursts and normal star forming galaxies. I’m working on polarization Stacking and source counts as a means of determining fiant source counts. Determining faint polarized source counts is difficult, approximately 10 percent of Stokes I sources are detectable in polarized intensity. In this talk we discuss the role of stacking as a way of statistically detecting faint polarized source counts, stacking polarized sources counts down to 0.1 mJy is shown. A discussion on the role of false detections and the importance of understanding the noise statistics is given. Finally, we also show preliminary results from stacking the recent POSSUM simulations, and derive the cumulative source counts expected with POSSUM [PDF Version of talk] – given on 25/08/2010

Polarized Radio Sources: A Study of Luminosity, Redshift and Infrared Colors: The Dominion Radio Astrophysical Observatory Deep Field polarization study has been matched with the Spitzer Wide-Area Infrared Extragalactic survey of the European Large Area Infrared Space Observatory Survey North 1 field. We have used VLA observations with a total intensity rms of 87 microJy/beam to match SWIRE counterparts to the radio sources. Infrared color analysis of our radio sample shows that the majority of polarized sources are elliptical galaxies with an embedded active galactic nucleus. Using available redshift catalogs, we found 429 radio sources of which 69 are polarized with redshifts in the range of 0.04 < z < 3.2. We find no correlation between redshift and percentage polarization for our sample. However, for polarized radio sources, we find a weak correlation between increasing percentage polarization and decreasing luminosity.

Detection Thresholds and Bias Correction in Polarized Intensity: this paper was accepted for publication in Publications of the Astronomical Society of Australia.


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