Abstract
Several galaxy clusters host X-ray cavities, often filled with relativistic electrons emitting in the radio band. In the cluster MS 0735.6+7421 the cavities have been detected through the Sunyaev Zel’dovich (SZ) effect, but it has not been possible to determine if this effect is thermal (produced by a very high temperature gas filling the cavity) or non-thermal (produced by the relativistic electrons that produce the diffuse radio emission detected in the cavity). In this paper we discuss the role of the density of the high temperature gas inside the cavities in determining whether the dominant SZ effect is the thermal or the non-thermal one, and how it can be possible to distinguish between the two possibilities, discussing the role of observations at higher energy bands.
Highlights
Several relaxed galaxy clusters show the presence inside their Intra Cluster Medium (ICM) of couples of cavities in the X-ray emission, usually located in opposite directions compared to the central Brightest Cluster Galaxy [1, 2]
The origin of these cavities is probably due to the mechanical power produced by AGN jets that is converted to heat during the expansion of the lobe in the ICM [3]
The galaxy cluster MS 0735.6+7421 hosts a couple of X-ray cavities [13,14,15], where a diffuse radio emission filling the cavities is observed [4, 16]. These cavities have been observed through the Sunyaev-Zel’dovich effect (SZE) at 30 GHz using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) interferometer [17], which detected a clear deficit in the Sunyaev Zel’dovich (SZ) signal in the direction of the cavities
Summary
Several relaxed galaxy clusters show the presence inside their Intra Cluster Medium (ICM) of couples of cavities in the X-ray emission, usually located in opposite directions compared to the central Brightest Cluster Galaxy [1, 2]. These cavities have been observed through the SZE at 30 GHz using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) interferometer [17], which detected a clear deficit in the SZ signal in the direction of the cavities From these observations, it has not been possible to determine if the dominant component inside the cavities is thermal or non-thermal, because the data were compatible with both a non-thermal electrons population having a low value of the minimum moment (p1 ∼ 1 − 10), and with a thermal population with very high temperature of kT ∼ 1000 keV, or even higher (see fig. in [17]). We summarize the results obtained in [18], and expand further the discussion about how it can be possible to discriminate between the thermal and the non-thermal origin of the SZE inside the cavities, considering the expected SZE in spectral bands with higher energies than the microwave one
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