The Two-Point Correlation of 2QZ Quasars and 2SLAQ LRGs: From a Quasar Fueling Perspective

TL;DR

This study measures the spatial correlation between quasars and luminous red galaxies using large surveys, revealing that quasars are more strongly associated with star-forming galaxies, supporting models where galaxy interactions trigger quasar activity.

Contribution

It provides the first detailed measurement of quasar-LRG cross-correlation on large scales, distinguishing between galaxy populations and linking quasar activity to recent star formation.

Findings

Quasars have a clustering radius of 5.3 ± 0.6 h^{-1} Mpc.

Stronger correlation with blue, star-forming galaxies.

Correlation flattens on scales less than 5 h^{-1} Mpc.

Abstract

Public data from the 2dF quasar survey (2QZ) and 2dF/SDSS LRG & QSO (2SLAQ), with their vast reservoirs of spectroscopically located and identified sources, afford us the chance to more accurately study their real space correlations in the hopes of identifying the physical processes that trigger quasar activity. We have used these two public databases to measure the projected cross correlation, $\omega_p$, between quasars and luminous red galaxies. We find the projected two-point correlation to have a fitted clustering radius of $r_0, = 5.3 \pm 0.6 $ and a slope, $\gamma =1.83 \pm 0.42 $ on scales from 0.7-27$h^{-1}$Mpc. We attempt to understand this strong correlation by separating the LRG sample into 2 populations of blue and red galaxies. We measure at the cross correlation with each population. We find that these quasars have a stronger correlation amplitude with the bluer, more recently starforming population in our sample than the redder passively evolving population, which has a correlation that is much more noisy and seems to flatten on scales $< 5h^{-1}$Mpc. We compare this result to published work on hierarchical models. The stronger correlation of bright quasars with LRGs that have undergone a recent burst of starformation suggests that the physical mechanisms that produce both activities are related and that minor mergers or tidal effects may be important triggers of bright quasar activity and/or that bright quasars are less highly biased than faint quasars.