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Durham University

Department of Physics

Staff profile

Publication details for Dr Russell Smith

Smith, Russell J. & Edge, Alastair C. (2017). An extended cold gas absorber in a central cluster galaxy. Monthly Notices of the Royal Astronomical Society: Letters 471(1): L66-L70.

Author(s) from Durham


We present the serendipitous discovery of an extended cold gas structure projected close to the brightest cluster galaxy (BCG) of the z = 0.045 cluster Abell 3716, from archival integral field spectroscopy. The gas is revealed through narrow Na D line absorption, seen against the stellar light of the BCG, which can be traced for ∼25 kpc, with a width of 2–4 kpc. The gas is offset to higher velocity than the BCG (by ∼100 km s−1), showing that it is infalling rather than outflowing; the intrinsic linewidth is ∼80 km s−1 (FWHM). Very weak H α line emission is detected from the structure, and a weak dust absorption feature is suggested from optical imaging, but no stellar counterpart has been identified. We discuss some possible interpretations for the absorber: as a projected low-surface-brightness galaxy, as a stream of gas that was stripped from an infalling cluster galaxy or as a ‘retired’ cool-core nebula filament.