Planck Intermediate Paper: Physics Of The Hot Gas In The Coma Cluster
Abstract
We present the data analysis of the Coma Cluster observed via Sunyaev-Zeldovich effect with the Planck satellite.
Being a low redshift massive hot clusters, its angular size is so extended that Planck can resolve it spatially. Thanks to its great sensitivity, Planck is capable, for the first time, to detect SZ emission up to r 3-4 t R500. This allow us to study the pressure distribution of the Intracluster Medium to the outermost cluster regions, not yet achieved by any other instrument. We test the validity of some pressure models proposed to described the pressure distribution in clusters. In particular we find that the Arnuad et al. pressure profile for merging systems provides a good fit of the data only at r<R500: at larger radii it seems to underestimate the observed profile up to 20%. This may either indicate that at these larger radii i) the cluster profile is contaminated by unresolved SZ sources along the line of sight ii) the pressure profile of Coma is higher than the mean pressure profile predicted by simulations. Very interestingly the Planck image shows two abrupt variations of the y signal located at approx 33 arcmin to the west and to the south east with respect to the cluster center. Using Planck y profiles extracted from corresponding sectors we verified that both abrupt variations are compatible with the presence of discontinuities of in the underlying density profile and we find pressure jumps of 4.5 and 4.9 in the west and south east, respectively. Finally, we find that the y and radio-synchrotron signals are quasi-linearly correlated on Mpc-scales with very small intrinsic scatter. This implies either that the energy density of cosmic-ray electrons is relatively constant throughout the cluster, or that the magnetic fields fall off much slower with radius than previously thought.- Publication:
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American Astronomical Society Meeting Abstracts #220
- Pub Date:
- May 2012
- Bibcode:
- 2012AAS...22050705M