Science Highlight




Science Highlights - An ALMA+ACA measurement of the shock in the Bullet Cluster







The thermal Sunyaev-Zeldovich (SZ) effect presents a relatively new tool for characterising galaxy cluster merger shocks, traditionally studied through X-ray observations. Widely regarded as the “textbook example” of a cluster merger bow shock, the western, most-prominent shock front in the Bullet Cluster (1E0657-56) represents the ideal test case for such an SZ study. A combination of ALMA+ACA observations provides sensitivity to the electron pressure difference across the shock front, as shown in the images of the raw (left), model (middle), and residual (right) ALMA+ACA interferometric data. The model subtraction is performed directly in Fourier space, whereas the dashed line in the center and right panels indicate the (already known) inferred position of the shock front. Previously observed X-ray contours are overlaid on the left panel. The positive signal at the shock front is not due to an increment of the SZ signal; rather it is an artifact of the high-pass filtering effects of ALMA+ACA.

For full details, please refer to the Di Mascolo et al. (2019) publication here.

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