Abstract
ABSTRACT We study the distribution and dynamics of the circumgalactic and intergalactic medium using a dense galaxy survey covering the field around the Q0107 system, a unique z ≈ 1 projected quasar triplet. With full Ly α 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 i absorption systems occurring at the same redshift (within 500 km s−1) in multiple sightlines, finding with >99.9 per cent 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 i) > 1014 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 multi-sightline 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 disc/outflow dichotomy, as H i 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 vi at the same redshift.
Highlights
Galaxies follow a large-scale filamentary structure throughout the Universe, known as the cosmic web (Bond, Kofman & Pogosyan 1996), formed by the gravitational accretion of gas towards the potential wells of dark matter around initial overdensities, as has been modelled in dark-matter-only simulations for decades (e.g. Klypin & Shandarin 1983; Springel et al 2005)
We do not find any significant increase in H I column density along the minor axis, so the increased O VI found near the minor axis may be due to more warm-hot material than in the absorbers found near the major axis
We take advantage of multiple observing campaigns, resulting in a deep, dense galaxy survey covering the field around a unique quasar triplet, to examine the geometry and extent of gas flows in the CGM and IGM on larger scales than most CGM studies
Summary
Galaxies follow a large-scale filamentary structure throughout the Universe, known as the cosmic web (Bond, Kofman & Pogosyan 1996), formed by the gravitational accretion of gas towards the potential wells of dark matter around initial overdensities, as has been modelled in dark-matter-only simulations for decades (e.g. Klypin & Shandarin 1983; Springel et al 2005). A later study by Crighton et al (2010) (hereafter C10) used improved QSO spectra, including QSO-C, in addition to galaxy data from CFHT-MOS, to extend these results They observed a highly significant excess of absorption systems covering all three sightlines over an ensemble of randoms, providing clear evidence that gas and galaxies are associated on scales of hundreds of kpc. We present an updated analysis on the Q0107 triplet, using a much larger sample of galaxies extending to fainter magnitudes, in addition to Hubble Space Telescope imaging providing improved morphologies, and MUSE fields providing kinematics on a subsample of galaxies close to the A and B sightlines We use this data to examine the CGM/IGM on large scales, where the improved imaging allows us to constrain the extent of the ‘galactic fountain’ and the larger galaxy samples allow us to study the presence of absorption features covering multiple sightlines around galaxies of different properties.
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