0520-ACT Extragalactic Point Sources in the Southern Surveys at 150, 220 and 280 GHz

PAPER

The Atacama Cosmology Telescope Extragalactic Point Sources in the Southern Surveys at 150, 220 and 280 GHz observed between 2008-2010

From this catalog, we obtain: a) a classification of sources based on their spectral properties; b) a calculation of the number counts of these populations at different frequencies; c) data on the variability of the AGN population at a yearly time scale; and d) the SEDs of selected sources. This study is complementary to previous MBAC-ACT works, that include source catalogs from southern survey at 150 GHz from season 2008 (Marriage et al. 2011b), at 150 and 220 GHz from season 2008 (Marsden et al. 2014), and the equatorial survey at 150 and 220 GHz (2009 and 2010 seasons) and 280 GHz (2010 season) presented by Gralla et al. (2020). The latter publication presented only data for the equatorial region; here we extend that work to the southern region including three seasons for 150–220 GHz and two for 280 GHz. In addition, Datta et al. (2019) presented a catalog of intensity and polarization properties of sources located in the equatorial region at 150 GHz.

DATA

2008, 2009, 2010

freq	150	220	280
beam	1.4'	1.0'	0.9'

point sources removal

1. approximating $T_{other} $. On a first pass, we identify the strongest point sources (𝑆/𝑁 > 50). We mask them using 3′ radius circular patches, filled with a constant value obtained as the average temperature on a ring around the source with a diameter range of 5′ to 8′. The second pass includes dimmer sources, down to 𝑆/𝑁 = 5. This process typically requires masking around 10 or 150 sources in a given frequency map after the first and second iterations, respectively. This affects a very small area of the map, less than 1%. This threshold is chosen because the purity of the catalog starts to drop below it (see Sect. 3.3.1), masking below this threshold can modify the Gaussian noise and hence bias the results.

Using the kinematic Sunyaev-Zeldovich effect to determine the peculiar velocities of clusters of galaxies

difference between kSZ and tSZ

the two effects are distinguishable by their different spectra. In the case of the thermal SZ effect, the change in the observed brightness temperature is a Compton distortion with a decrease at low frequencies, an increase at high frequencies, and a zero-crossing at '" 220 GHz. The kinematic SZ effect, in contrast, has the same sign for all frequencies.