Studies of Clusters of Galaxies by Professor Blanton and Collaborators

Professor Elizabeth Blanton and collaborators are conducting a large survey of distant clusters of galaxies. They are using bent, double-lobed radio sources (AGN) as signposts for these high-redshift systems since radio sources with these morphologies usually reside in clusters and the radio emission is easy to see to large distances. The group is following up 653 of these sources that were not detected optically to the limit of the Sloan Digital Sky Survey in infrared light using the Spitzer Space Telescope. Deep, follow-up observations in optical light with the Discovery Channel Telescope have begun and will be crucial for estimating the photometric redshifts (to obtain distances) of the potential clusters and studying the galaxies they contain in more detail.

Top left: Sloan Digital Sky Survey r-band image with 1.4 GHz radio contours superposed. Cluster galaxies are not detected to the limit of the SDSS. Top right: Infrared 3.6 um image of the same field from the Spitzer Snapshot program. The cluster is easily visible. Bottom:  R-band  visible-light image from the LMI at the Discovery Channel Telescope of the same field. The total exposure was 30 minutes, and the seeing was approximately 0.7 arcseconds. Visible-light observations combined with those in the infrared are important for estimating the redshifts, and therefore distances, of the clusters in our survey, as well as for studying the galaxy populations in detail. The cluster shown is at a redshift of 0.96.

Top left: Sloan Digital Sky Survey r-band image with 1.4 GHz radio contours superposed. Cluster galaxies are not detected to the limit of the SDSS. Top right: Infrared 3.6 um image of the same field from the Spitzer Snapshot program. The cluster is easily visible. Bottom: R-band visible-light image from the LMI at the Discovery Channel Telescope of the same field. The total exposure was 30 minutes, and the seeing was approximately 0.7 arcseconds. Visible-light observations combined with those in the infrared are important for estimating the redshifts, and therefore distances, of the clusters in our survey, as well as for studying the galaxy populations in detail. The cluster shown is at a redshift of 0.96.