The mean temperature and pressure profiles, along with their associated intrinsic scatters, are also shown in Fig. 7. Overall, at larger radii, the mean temperatures are relatively flat, and we do not detect the clear decrease found in other studies (see Fig. 8; e.g. Vikhlinin et al. 2006; Leccardi & Molendi 2008; Arnaud et al. 2010; Eckert et al. 2013b; McDonald et al. 2014). Specifically, we do not see a temperature increase at small radii ∼0.2r500 before a subsequent decrease at large radii. However, our temperature profile is compatible with the results of Leccardi & Molendi (2008) in that region, and only 1–2σ lower than the profiles obtained by Vikhlinin et al. (2006) and McDonald et al. (2014). While this difference is not statistically significant, it may be due to the selection effects given that the Leccardi & Molendi (2008) sample is most similar to ours in mass and redshift. Given the modest statistical significance of this difference, it may simply be due to noise fluctuations. However, inaccurate subtraction of the X-ray background may also play a role. For example, oversubtraction of the hard background would tend to bias spectroscopic X-ray temperatures low while biasing our derived temperatures high (via the reduction in X-ray-derived density). The difference could also be related to cluster physics. For instance, clumping within the ICM, which is expected to increase with radius, will tend to bias spectroscopically derived temperatures low compared to the X-ray/SZ values derived in our analysis (e.g. Mazzotta et al. 2004; Rasia et al. 2005; Vazza et al. 2013). Elongation of the cluster along the line of sight, which will increase the SZ brightness compared to the X-ray brightness, could also artificially boost the temperatures recovered in our analysis (e.g. Cooray 2000). Another possibility for the slightly higher than expected temperatures at large radii may be biases in the SZ data. Indirect evidence for such an effect can be found by comparing the pressure profiles obtained by Sayers et al. (2013b), based solely on Bolocam data, to those obtained by Sayers et al. (2016) based on a joint analysis of Bolocam and Planck for a nearly identical set of clusters. Beyond ≃0.5r500, the latter work found a lower value for the pressure profile, with the difference increasing to a factor of ≃1.5 at r500. This implies that the Bolocam data alone may be overestimating the pressure at large radii, which would bias our temperature profiles high in that region. This can be seen in the mean pressure profile plot. However there is good agreement in the radial range of interest in this study when compared with Arnaud et al. (2010) and Planck Collaboration V (2013). In addition, the mean temperature profiles recovered for the CC and NCC subsets in the innermost shell are not different at a statistically significant level (i.e. the CC subset does not show a significant drop towards the cluster centre). This is likely a result of the coarse binning required by the SZ data. Specifically, the innermost shell extends to 0.15r500, which is generally not small enough to resolve the cool core. All of the potential biases and physical effects noted in this paragraph apply to the individual cluster temperature profiles as well, and therefore may explain differences compared to other studies (e.g. ACCEPT) that appear for some clusters.
Citation: Mazzotta et al. 2004
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