On the Clustering of Compact Galaxy Pairs in Dark Matter Haloes

TL;DR

This study models the clustering behavior of galaxy pairs using the halo-occupation distribution, revealing that galaxy pairs are more clustered and reside in more massive haloes than single galaxies, with clustering influenced by galaxy type and luminosity.

Contribution

It introduces an HOD model for galaxy pairs, demonstrating their higher clustering amplitudes and central fractions compared to single galaxies, and explores clustering dependence on various galaxy properties.

Findings

Galaxy pairs have larger clustering amplitudes than single galaxies.

Galaxy pairs are predominantly located in more massive dark matter haloes.

Clustering strength varies with galaxy type and luminosity, but not with luminosity contrast.

Abstract

We analyze the clustering of photometrically selected galaxy pairs by using the halo-occupation distribution (HOD) model. We measure the angular two-point auto-correlation function, $\omega(\theta)$, for galaxies and galaxy pairs in three volume-limited samples and develop an HOD to model their clustering. Our results are successfully fit by these HOD models, and we see the separation of "1-halo" and "2-halo" clustering terms for both single galaxies and galaxy pairs. Our clustering measurements and HOD model fits for the single galaxy samples are consistent with previous results. We find that the galaxy pairs generally have larger clustering amplitudes than single galaxies, and the quantities computed during the HOD fitting, e.g., effective halo mass, $M_{eff}$, and linear bias, $b_{g}$, are also larger for galaxy pairs. We find that the central fractions for galaxy pairs are significantly higher than single galaxies, which confirms that galaxy pairs are formed at the center of more massive dark matter haloes. We also model the clustering dependence of the galaxy pair correlation function on redshift, galaxy type, and luminosity. We find early-early pairs (bright galaxy pairs) cluster more strongly than late-late pairs (dim galaxy pairs), and that the clustering does not depend on the luminosity contrast between the two galaxies in the compact group.