Halo-model Analysis of the Clustering of Photometrically Selected Galaxies from SDSS

TL;DR

This study uses halo-model analysis to understand how different types of galaxies cluster in the SDSS, revealing that early- and late-type galaxies occupy halos separately, which improves modeling accuracy.

Contribution

Introduces a new halo segregation model for early- and late-type galaxies that better fits clustering data than previous mixed models.

Findings

Early- and late-type galaxies occupy halos separately.

The segregation model fits the clustering data well.

Results are consistent with previous SDSS spectroscopic studies.

Abstract

We measure the angular 2-point correlation functions of galaxies in a volume limited, photometrically selected galaxy sample from the fifth data release of the Sloan Digital Sky Survey. We split the sample both by luminosity and galaxy type and use a halo-model analysis to find halo-occupation distributions that can simultaneously model the clustering of all, early-, and late-type galaxies in a given sample. Our results for the full galaxy sample are generally consistent with previous results using the SDSS spectroscopic sample, taking the differences between the median redshifts of the photometric and spectroscopic samples into account. We find that our early- and late- type measurements cannot be fit by a model that allows early- and late-type galaxies to be well-mixed within halos. Instead, we introduce a new model that segregates early- and late-type galaxies into separate halos to the maximum allowed extent. We determine that, in all cases, it provides a good fit to our data and thus provides a new statistical description of the manner in which early- and late-type galaxies occupy halos.