A WEAK LENSING VIEW OF THE DOWNSIZING OF STAR-FORMING GALAXIES*

Abstract

We describe a weak lensing view of the downsizing of star-forming galaxies based on cross-correlating a weak lensing ( κ ) map with a predicted map constructed from a redshift survey. Moderately deep and high-resolution images with Subaru/Hyper Suprime-Cam covering the DLS F2 field provide a κ map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with is the basis for construction of the predicted map. The zero-lag cross-correlation between the κ and predicted maps is significant at the 30 σ level. The width of the cross-correlation peak is comparable to the angular scale of rich clusters at , the median depth of the redshift survey. Slices of the predicted map in redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalized cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in slices where there are no known massive clusters, there is a significant signal in the cross-correlation originating from lower mass groups that trace the large-scale of the universe. Spectroscopic measurements enable division of the sample into star-forming and quiescent populations. In regions surrounding massive clusters of galaxies, the significance of the cross-correlation with maps based on star-forming galaxies increases with redshift from 5 σ at z  = 0.3 to 7 σ at the fractional contribution of the star-forming population to the total cross-correlation signal also increases with redshift. This weak lensing view is consistent with the downsizing picture of galaxy evolution established from other independent studies.