The Sunyaev–Zel'dovich effect at 5″: RX J1347.5−1145 imaged by ALMA

Abstract

We present the first image of the thermal Sunyaev–Zel'dovich effect (SZE) obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combining 7-m and 12-m arrays in Band 3, we create an SZE map toward a galaxy cluster RX J1347.5−1145 with 5″ resolution (corresponding to a physical size of 20 h−1 kpc), the highest angular and physical spatial resolutions achieved to-date for imaging the SZE, while retaining extended signals out to 40″. The 1 σ statistical sensitivity of the image is 0.017 mJy beam−1 or 0.12 mKCMB at the 5″ full width at half maximum. The SZE image shows a good agreement with an electron pressure map reconstructed independently from the X-ray data and offers a new probe of the small-scale structure of the intracluster medium. Our results demonstrate that ALMA is a powerful instrument for imaging the SZE in compact galaxy clusters with unprecedented angular resolution and sensitivity. As the first report on the detection of the SZE by ALMA, we present detailed analysis procedures including corrections for the missing flux, to provide guiding methods for analyzing and interpreting future SZE images obtained by ALMA.

Deeply cooled core of the Phoenix galaxy cluster imaged by ALMA with the Sunyaev–Zel’dovich effect

“…As in Kitayama et al (2016), we find that the simulation results on average follow the linear relation…”

“…We plot in figure 4 azimuthally averaged intensity profiles in four quadrants with position angles of 315 • − 45 • (north), 45 • − 135 • (east), 135 • − 225 • (south), and 225 • − 315 • (west). The statistical error in each bin is computed using equation (1) of Kitayama et al (2016). The SZE intensities in four quadrants are consistent with one another within the error, while the signal in the north quadrant tends to be weaker than the other directions at θ < 15 ′′ .…”

“…Imaging was done with the Common Astronomy Software Applications package (CASA: McMullin et al 2007) version 5.6.1. The procedure was similar to Kitayama et al (2016). We adopted the multi-frequency synthesis mode in joint mosaic imaging.…”

“…As in Kitayama et al (2016), we performed X-ray thermodynamic mapping using the contour binning algorithm (Sanders 2006). In addition to the central region at θX < 1.5 ′′ mentioned above, we defined subregions with nearly equal photon counts by adopting the signal-to-noise ratio (S/N) threshold of 100 (i.e., ∼ 10000 counts) in the 0.7 − 7.0 keV band.…”

Galaxy Cluster Pressure Profiles as Determined by Sunyaev Zel’dovich Effect Observations with MUSTANG and Bolocam. II. Joint Analysis of 14 Clusters

“…Despite this, we find T SZ uncertainties of∼2 times larger than the statistical spectroscopic X-ray temperature uncertainties. In light of new SZ instruments (e.g., MUSTANG-2, NIKA2, and ALMA Dicker et al 2014;Calvo et al 2016;Kitayama et al 2016) coming online with vastly improved mapping speeds, our results are encouraging for the prospects of physically characterizing the ICM of newly discovered systems with rapid follow-up programs.…”