abell 1835, a lensing cluster

The subject of this post is Abell 1835, a galaxy cluster at a redshift of z=0.25 that is so massive that it acts as a gravitational lens to amplify the emission from objects at higher (i.e. more distant) redshifts along the line of sight. As well as amplifying the emission from faint and distant galaxies, another advantage of gravitational lenses is that they amplify light achromatically, that is, the amplification is equal at all wavelengths. Gravitational lensing allows us to study the properties of distant galaxies in far greater detail than would otherwise be possible; these rare lensing systems have thus allowed astronomers to push the boundaries of our exploration of the galaxy populations of the early Universe. This was used to good effect at the start of the century with SCUBA and led to the discovery a previously hidden population of submm galaxies by surveying for bright submillimetre radiation associated with known gravitational lenses.

The image above shows a SCUBA-2 map towards some of these lensed sources. The cluster acting as the lens is in the centre of the map and only the brightest and most massive member of that cluster is detected in the submillimetre. As a sense of scale, the central, dashed circle represents the area that was originally mapped by SCUBA. A close up of that region is shown in the cut-out below. Note that the cyan contours delineate regions of increasing sensitivity (towards the centre) in the map.

The two brightest sources in the centre are the lensed and amplified image of a background submillimetre galaxies at a redshift of z>2 – almost 10 times further away than the galaxy cluster acting as the lens. What is also interesting is that we detect a large number of other sources in the relatively wide field that was mapped. These are not lensed sources, but just galaxies that make up the background population.


One Response to abell 1835, a lensing cluster

  1. Anonymous says:

    Very nice, Antonio! I notice the apparent lack of structure in the noise – no stripes or clusters…..


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