We present 13.9 - 18.2 -GHz observations of the Sunyaev-Zel ’ dovich ( SZ ) effect towards Abell 2146 using the Arcminute Microkelvin Imager ( AMI ) .
The cluster is detected with a peak signal-to-noise ratio of 13 \sigma in the radio source subtracted map from 9 hours of data .
Comparison of the SZ image with the X-ray image from ( 52 ) suggests that both have extended regions which lie approximately perpendicular to one another , with their emission peaks significantly displaced .
These features indicate non-uniformities in the distributions of the gas temperature and pressure , and suggest complex dynamics indicative of a cluster merger .
We use a fast , Bayesian cluster analysis to explore the high-dimensional parameter space of the cluster-plus-sources model to obtain robust cluster parameter estimates in the presence of radio point sources , receiver noise and primordial CMB anisotropy ; despite the substantial radio emission from the direction of Abell 2146 , the probability of SZ + CMB primordial structure + radio sources + receiver noise to CMB + radio sources + receiver noise is 3 \times 10 ^ { 6 } : 1 .
We compare the results from three different cluster models .
Our preferred model exploits the observation that the gas fractions do not appear to vary greatly between clusters .
Given the relative masses of the two merging systems in Abell 2146 , the mean gas temperature can be deduced from the virial theorem ( assuming all of the kinetic energy is in the form of internal gas energy ) without being affected significantly by the merger event , provided the primary cluster was virialized before the merger .
In this model we fit a simple spherical isothermal \beta -model to our data , despite the inadequacy of this model for a merging system like Abell 2146 , and assume the cluster follows the mass-temperature relation of a virialized , singular , isothermal sphere .
We note that this model avoids inferring large-scale cluster parameters internal to r _ { 200 } under the widely used assumption of hydrostatic equilibrium .
We find that at r _ { 200 } the average total mass M _ { T } = \left ( 4.1 \pm 0.5 \right ) \times 10 ^ { 14 } h ^ { -1 } M _ { \odot } and the mean gas temperature T = 4.5 \pm 0.5 keV .