Tomographic halo model of the unWISE-Blue galaxies using cross-correlations with BOSS CMASS galaxies
Year: 2025
Type: article
Abstract: The halo model offers a framework for investigating galaxy clustering, and for understanding the growth of galaxies and the distribution of galaxies of different types. Here, we use the halo model to study the small-scale clustering and halo occupation distribution (HOD) of the unWISE-Blue galaxy sample, an infrared-selected sample of $$100 million galaxies across the entire extragalactic sky at z ∼ 0.5 − similar redshifts to the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS sample. Although the photometric unWISE galaxies cannot be easily split in redshift, we use their cross-correlation with the BOSS CMASS sample to tomographically probe the HOD of the unWISE galaxies at 0.45 < z < 0.75 . To do so, we develop a new method for applying the halo model to cross-correlations between a photometric sample and a spectroscopic sample in narrow redshift bins, incorporating halo exclusion, post-Limber corrections, and redshift-space distortions. We reveal strong evolution in the CMASS HOD, and modest evolution in the unWISE-Blue HOD. For unWISE-Blue, we find that the average bias and mean halo mass drop from b = 1.6 and log 10 ( M h / M ⊙ ) ∼ 13.4 at z ∼ 0.5 to b = 1.4 and log 10 ( M h / M ⊙ ) ∼ 13.1 at z ∼ 0.7 , and that the satellite fraction drops modestly from $$20% to $$10% in the same range. These results are useful for creating mock samples of the unWISE-Blue galaxies. Furthermore, the techniques developed to obtain these results are applicable to other tomographic cross-correlations between photometric samples and narrowly-binned spectroscopic samples, such as clustering redshifts.
Source: The Open Journal of Astrophysics
DOI: 10.33232/001c.137297
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W4409955417