Deep 3 GHz Number Counts from a P(D) Fluctuation Analysis

Дата и время публикации : 2013-11-29T00:34:50Z

Авторы публикации и институты :
T. Vernstrom
Douglas Scott
J. V. Wall
J. J. Condon
W. D. Cotton
E. B. Fomalont
K. I. Kellermann
N. Miller
R. A. Perley

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: Submitted to MNRAS, 18 pages, 17 figures, 7 tables
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO

Краткий обзор статьи: There is considerable disagreement in the published 1.4-GHz radio source counts from deep surveys probing the sub-100 microJy region. Constraints on these counts have implications for studying galaxy populations and evolution, as well as the global star formation history. Here we present a statistical method for estimating the microJy and even sub-microJy source count using new deep wideband 3-GHz data in the Lockman Hole from the Jansky Very Large Array (JVLA). Using the technique known as P(D) analysis, we provide a fresh approach to the investigation of deep radio data in the form of a more robust model, with a comprehensive non-parametric error analysis. We test this method on a large-scale simulation, incorporating realistic clustering and finite source sizes. We discuss in detail our statistical methods for fitting using MCMC, handling correlations, and various systematic effects introduced from the use of wide-band radio interferometric data. Using this new approach we demonstrate that estimates and constraints on the count are possible down to a depth of 50 nJy, almost two orders of magnitude below instrumental and confusion noise. We find the differential source count near 10 microJy to have a slope of -1.7, decreasing to about -1.4 from 0.5 to 3 microJy. This yields estimates of the 3 GHz confusion noise of 1.15 to 1.3 microJy/beam rms, and a radio background temperature from discrete sources of approximately 14 mK. This is in good agreement with, and fits the data somewhat better than, the previous estimate made by fitting a single power-law model. Our counts are consistent with published evolutionary models, although some modifications may be required, e.g. a larger contribution from star-forming galaxies. With these results we are also able to constrain the peak of any possible new radio populations that would contribute to the cosmic radio background down to 50 nJy.

Category: Physics