Transverse Sizes of CIV Absorption Systems Measured from Multiple QSO Sightlines

TL;DR

This study uses quasar sightline tomography to measure the physical sizes and distribution of CIV absorption systems, revealing insights into metal dispersal and enrichment history in the circum-galactic medium from redshift 1.7 to 4.5.

Contribution

First measurement of the real-space size of CIV-enriched regions using quasar pair sightlines, linking absorption clustering to physical metal dispersal scales.

Findings

CIV systems cluster more at small separations, less at large, similar to Lyman-break galaxies.

The typical size of enriched regions is about 0.42 h^-1 Mpc, smaller than line-of-sight correlation scales.

Enrichment by early galaxies (z > 4.3) significantly contributed to metal dispersal.

Abstract

We present tomography of the circum-galactic metal distribution at redshift 1.7 to 4.5 derived from echellete spectroscopy of binary quasars. We find CIV systems at similar redshifts in paired sightlines more often than expected for sightline-independent redshifts. As the separation of the sightlines increases from 36 kpc to 907 kpc, the amplitude of this clustering decreases. At the largest separations, the CIV systems cluster similar to Lyman-break galaxies (Adelberger et al. 2005a). The CIV systems are significantly less correlated than these galaxies, however, at separations less than R_1 ~ 0.42 +/- 0.15 h-1 comoving Mpc. Measured in real space, i.e., transverse to the sightlines, this length scale is significantly smaller than the break scale estimated from the line-of-sight correlation function in redshift space (Scannapieco et al. 2006a). Using a simple model, we interpret the new real-space measurement as an indication of the typical physical size of enriched regions. We adopt this size for enriched regions and fit the redshift-space distortion in the line-of-sight correlation function. The fitted velocity kick is consistent with the peculiar velocity of galaxies as determined by the underlying mass distribution and places an upper limit on the outflow (or inflow) speed of metals. The implied time scale for dispersing metals is larger than the typical stellar ages of Lyman-break galaxies (Shapley et al. 2001), and we argue that enrichment by galaxies at z > 4.3 played a greater role in dispersing metals. To further constrain the growth of enriched regions, we discuss empirical constraints on the evolution of the CIV correlation function with cosmic time. This study demonstrates the potential of tomography for measuring the metal enrichment history of the circum-galactic medium.