SPT 150 GHz luminosity function and SZE contamination¶

Cluster and galaxy sample¶

We build luminosity function from the SPT AGNs (at 150 and 90 GHz) and SUMSS galaxy catalog (at 843 MHz). We use MCXC catalog of galaxy clusters with a total number of 1734 clusters out of which 139 and 333 clusters are there in SPT and SUMSS region respectively.

SPT AGN sample¶

There are 4769 SPT point sources in the present catalog (all_fields_list_brady_astrom_corrected.txt) with information about the S/N as well as Flux (in mJy). Out of these point sources we chose those which have counterparts in the SUMSS catalog within the positional uncertainty of the SPT point sources at 3-sigma level. This allow us to select the AGN sample from the SPT point sources.

The positional uncertainty is sigma_total^2 = sigma_sys^2 + ((FWHM_beam)/S2N)^2, where the FWHM is 1.6' at 90 GHz, 1' at 150 GHz and 0.8' at 220 GHz. Also, sigma_sys is about 10". We chose the smallest sigma_total out of 90, 150 or 220 GHz. The 3-sigma level is chosen by plotting the surface density of the SUMSS galaxies at different sigma levels as in the figure below (at 3-sigma level the SUMSS surface density is equivalent to background density).

There are 3446 SPT point sources (AGNs) which have SUMSS counterparts at 3-sigma level.

SUMSS sample¶

There are 211,050 galaxies in SUMSS catalog (2007). More information about the catalog can be found here: [[http://www.physics.usyd.edu.au/sifa/Main/SUMSS]]

Luminosity function¶

Estimation of the total number of PS or galaxies in a luminosity bin for each cluster¶

• We do not have the redshift information about the SPT PS and SUMSS galaxies, so we assume that they are at the redshift of the cluster in concern. In order to construct the luminosity function we take a logarithmic luminosity bin and loop over all the clusters which are there in the SPT or SUMSS region.

• For each cluster we use its redshift to calculate luminosity distance and the K-correction for the luminosities. Using mass and redshift we calculate the radius and theta_200 for the cluster. In MCXC catalog mass and radius of the cluster are given as the regions where the mean density is 500 times the critical density of the universe and we use NFW profile and Duffy et al. to change them to M_200cr and R_200cr.

• We use a flux cut of 10 mJy, 6 mJy and 30 mJy for the SPT 90 GHz, SPT 150 GHz and SUMSS samples, which are found from the flux histograms (logN-logS plots) for these samples. We find the luminosity cut for each cluster corresponding to these flux cut.

• For each cluster we find all matching radio galaxies within the theta_200, convert the given flux of SPT (both at 90 and 150 GHz) and SUMSS sample to luminosity and count those galaxies whose luminosity lies in the logarithmic luminosity bin we took.

Background estimation for a luminosity bin for each cluster¶

• For the background estimation we use the field logN-logS plots and find the number of PS or galaxies in the logarithmic flux bin that corresponds to the logarithmic luminosity bin we took. In order to find background for each cluster we multiply this field number with the surface area of that cluster (pi*theta_200^2).

We do this for all the clusters and stack the total number and background number of galaxies for each logarithmic luminosity bin. The subtraction of the background number from the total number for each logarithmic luminosity bin gives us the luminosity function.

SPT luminosity function¶