THE PLANCK SUNYAEV-ZEL'DOVICH VERSUS THE X-RAY VIEW OF THE COMA CLUSTER

Journal Article · Sun Jan 20 04:00:00 EST 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/763/1/L3· OSTI ID:22078334

Fusco-Femiano, R ^[1]; Lapi, A; Cavaliere, A ^[2]

---

1. IAPS-INAF, Via Fosso del Cavaliere, I-00133 Roma (Italy)
2. Dip. Fisica, Univ. 'Tor Vergata', Via Ricerca Scientifica 1, I-00133 Roma (Italy)

The Planck collaboration has recently published precise and resolved measurements of the Sunyaev-Zel'dovich (SZ) effect in Abell 1656 (the Coma cluster of galaxies), thus directly gauging the electron pressure profile in the intracluster plasma. On the other hand, such a quantity may be also derived from combining the density and temperature provided by X-ray observations of the thermal bremsstrahlung radiation emitted by the plasma. We find a model-independent tension between the SZ and the X-ray pressure, with the SZ one being definitely lower by 15%-20%. We propose that such a challenging tension can be resolved in terms of an additional, non-thermal support to the gravitational equilibrium of the intracluster plasma. This can be straightforwardly included in our Supermodel, so as to fit in detail the Planck SZ profile while being consistent with the X-ray observables. Possible origins of the non-thermal component include cosmic-ray protons, ongoing turbulence, and relativistic electrons; given the existing observational constraints on the first two options, here we focus on the third. For this to be effective, we find that the electron population must include not only an energetic tail accelerated to {gamma} {approx}> 10{sup 3} responsible for the Coma radiohalo, but also many more, lower energy electrons. The electron acceleration is to be started by merging events similar to those that provided the very high central entropy of the thermal intracluster plasma in Coma.

• OSTI ID: 22078334
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 763; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
BACKGROUND RADIATION
BREMSSTRAHLUNG
COSMIC PROTONS
COSMIC RADIATION
DENSITY
ELECTRONS
ENTROPY
GALAXY CLUSTERS
PLASMA
RELATIVISTIC RANGE
TURBULENCE
X RADIATION
X-RAY GALAXIES