The Spitzer Extragalactic Representative Volume Survey (SERVS): The Environments of High-z SDSS Quasi-Stellar-Objects

TL;DR

This study investigates the environments of high-redshift SDSS QSOs using deep Spitzer data, revealing significant galaxy over-densities at z~2 and z~3, and finds good agreement with galaxy formation models.

Contribution

First large-scale analysis of high-z QSO environments using deep infrared data, combining observational data with semi-analytic galaxy formation models.

Findings

Significant galaxy over-density detected around QSOs at z~2 and z~3.

Model predictions align well with observed source densities.

Deep infrared data enables effective foreground contamination filtering.

Abstract

This paper presents a study of the environments of SDSS Quasi-Stellar-Objects (QSOs) in the Spitzer Extragalactic Representative Volume Survey (SERVS). We concentrate on the high-redshift QSOs as these have not been studied in large numbers with data of this depth before. We use the IRAC 3.6-4.5{\mu}m colour of objects and ancillary r-band data to filter out as much foreground contamination as possible. This technique allows us to find a significant (> 4-{\sigma}) over-density of galaxies around QSOs in a redshift bin centred on z ~ 2.0 and a (> 2-{\sigma}) over-density of galaxies around QSOs in a redshift bin centred on z ~ 3.3. We compare our findings to the predictions of a semi-analytic galaxy formation model, based on the {\Lambda}CDM millennium simulation, and find for both redshift bins that the model predictions match well the source-density we have measured from the SERVS data.