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Preprocessing among the Infalling Galaxy Population of EDisCS Clusters
Just, Dennis W. Kirby, Matthew Zaritsky, Dennis Rudnick, Gregory Desjardins, Tyler Cool, Richard Moustakas, John Clowe, Douglas De Lucia, Gabriella Aragón-Salamanca, Alfonso
Just, Dennis W.
Kirby, Matthew
Zaritsky, Dennis
Rudnick, Gregory
Desjardins, Tyler
Cool, Richard
Moustakas, John
Clowe, Douglas
De Lucia, Gabriella
Aragón-Salamanca, Alfonso
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Abstract
We present results from a low-resolution spectroscopic survey for 21 galaxy clusters at 0.4 < z < 0.8 selected from the ESO Distant Cluster Survey. We measured spectra using the low-dispersion prism in IMACS on the Magellan Baade telescope and calculate redshifts with an accuracy of σ z = 0.007. We find 1763 galaxies that are brighter than R = 22.9 in the large-scale cluster environs. We identify the galaxies expected to be accreted by the clusters as they evolve to z = 0 using spherical infall models and find that ~30%–70% of the z = 0 cluster population lies outside the virial radius at z ~ 0.6. For analogous clusters at z = 0, we calculate that the ratio of galaxies that have fallen into the clusters since z ~ 0.6 to those that were already in the core at that redshift is typically between ~0.3 and 1.5. This wide range of ratios is due to intrinsic scatter and is not a function of velocity dispersion, so a variety of infall histories is to be expected for clusters with current velocity dispersions of 300 km s−1 lesssim σ lesssim 1200 km s−1. Within the infall regions of z ~ 0.6 clusters, we find a larger red fraction of galaxies than in the field and greater clustering among red galaxies than blue. We interpret these findings as evidence of "preprocessing," where galaxies in denser local environments have their star formation rates affected prior to their aggregation into massive clusters, although the possibility of backsplash galaxies complicates the interpretation.
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Date
2019-10-24
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American Astronomical Society
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Keywords
Galaxies: distances and redshifts, Galaxies: evolution, Galaxies: interactions
Citation
Dennis W. Just et al 2019 ApJ 885 6