1. Point source contamination in Galaxy cluster
Elena Pierpaoli
Ethan Brown

2. Motivation
Understand radio point source contamination in galaxy clusters at GHz
Produce a template of SZ signal from known clusters
Produce simulated point sources maps for statistical analysis of CMB data.

3. Data Used CLUSTERS: POINT SOURCES:
REFLEX and NORAS: X-ray Galaxy Clusters, 80% sky coverage, ~900 clusters (700 used)
POINT SOURCES:
NVSS: 1.4GHz, F>2.5 mJy, 82% sky, ~1.8 M sources.
9C (15 GHz) and followup of ~150 sources with F>25 mJy ( GHz)
WMAP

4. Away from clusters (average)
NVSS number densities
Reference Planck freq,
angle
30GHz,
33'
44GHz,
24'
70GHz,
14'
100GHz,
10.'
100% of clusters
1.02
1.07
1.19
1.34
Brightest 50%
1.23
1.40
Brightest 25%
1.03
1.08
1.25
1.45
Away from clusters (average)
(52.4
deg^-2)
same

5. Away from clusters (average)
NVSS Fluxes at 1.4 GHz
Reference Planck freq,
angle
30GHz,
33'
44GHz,
24'
70GHz,
14'
100GHz,
10.'
100% of clusters
1.16
1.47
2.64
4.26
Brightest 50%
1.30
1.76
3.52
5.90
Brightest 25%
1.98
4.0
6.75
Away from clusters (average)
mJy
220.9
112.7
1.41
649.26

6. Estimating higher frequency emission
Extrapolated 1.4GHz NVSS signal according to:
S ∝ -
Obtained a distribution of  from 9C data

7. Distribution of Spectral Index
mean  = 0.52,  = 0.43

8. Comparison with the data
Point Source Counts for Extrapolated Data
Point Source Counts for
Observational Data

9. Average point source emission at Planck frequencies (mJy)
Reference Planck freq,
angle
30GHz,
33'
44GHz,
24'
70GHz,
14'
100GHz,
10.'
100% of clusters
412.6
261.0
150.5
116
Brightest 50%
505.0
346.6
235.2
191
Brightest 25%
445.5
319.1
267
Away from clusters (average)
332.7
47.53
22.24
619.2
157.8

10. Estimating cluster fluxes
Cluster band luminosity from NORAS/REFLEX
Use scaling relations to convert to bolometric luminosity and then to y.
Assume Beta profile for the cluster, with
beta fixed and theta_c from x-ray observations
ΔI(nu,θ) = ΔI0(nu)(1+ θ2/θc2)(1-3β)/2
Produce a y map to be convolved with the instrument beam at each frequency.

11. Results on (approx) cluster emission (mJy)
Reference Planck freq,
30GHz,
44GHz
70GHz
100GHz
100% of clusters
-8.3
-16.8
-36.4
-56.4
Brightest 50%
-11.9
-24.2
-52.3
-81
Brightest 25%
-30.2
-65.4
-101.2
-14.8

12. Conclusions Byproducts “Real clusters” y maps
Radio point sources are typically more abundant in galaxy clusters (by arcmin) and typically more luminous (by 5-7 times).
Point sources data suggest that index for flux extrapolation is flatter than previously thought.
Cluster signal could be hidden at low frequency by point sources, even for very massive clusters.
Byproducts
“Real clusters” y maps
Set of simulated radio point sources maps