The relationship between gas and galaxies at z<1 using the Q0107 quasar triplet

Abstract

We study the distribution and dynamics of the circum-and intergalactic medium using a dense galaxy survey covering the field around the Q0107 system, a unique z ≈ 1 projected quasar triplet. With full Ly𝛼 coverage along all three lines-of-sight from z=0.18 to z=0.73, more than 1200 galaxy spectra, and two MUSE fields, we examine the structure of the gas around galaxies on 100-1000 kpc scales. We search for H absorption systems occurring at the same redshift (within 500 km s −1 ) in multiple sightlines, finding with > 99.9% significance that these systems are more frequent in the observed quasar spectra than in a randomly distributed population of absorbers. This is driven primarily by absorption with column densities N(H ) > 10 14 cm −2 , whilst multi-sightline absorbers with lower column densities are consistent with a random distribution. Star-forming galaxies are more likely to be associated with multisightline absorption than quiescent galaxies. HST imaging provides inclinations and position angles for a subset of these galaxies. We observe a bimodality in the position angle of detected galaxy-absorber pairs, again driven mostly by high-column-density absorbers, with absorption preferentially along the major and minor axes of galaxies out to impact parameters of several hundred kpc. We find some evidence supporting a disk/outflow dichotomy, as H absorbers near the projected major-axis of a galaxy show line-of-sight velocities that tend to align with the rotation of that galaxy, whilst minor-axis absorbers are twice as likely to exhibit O at the same redshift.

How identifying circumgalactic gas by line-of-sight velocity instead of the location in 3D space affects O VI measurements

“…This simulation run has 8 (2) times better mass (spatial) resolution compared to the default EAGLE intermediate-resolution runs (e.g., Ref-L0100N1504). We analyze the z = 0.271 snapshot output; 3 this redshift is comparable to the redshifts of targeted galaxies in circumgalactic O VI observations (e.g., Tumlinson et al 2011;Johnson et al 2015Johnson et al , 2017Kacprzak et al 2019;Beckett et al 2021). Because EAGLE applied periodic boundary conditions, the maximum LOS separation is half of the box size and corresponds to a velocity difference of 767 km s −1 (physical) at z = 0.271.…”