A clumpy and anisotropic galaxy halo at z=1 from gravitational-arc tomography

Abstract

Every star-forming galaxy has a halo of metal-enriched gas extending out to at least 100 kpc, as revealed by the absorption lines this gas imprints on the spectra of background quasars. However, quasars are sparse and typically probe only one narrow pencil beam through the intervening galaxy. Close quasar pairs and gravitationally lensed quasars have been used to circumvent this inherently one-dimensional technique, but these objects are rare and the structure of the circum-galactic medium remains poorly constrained. As a result, our understanding of the physical processes that drive the re-cycling of baryons across the lifetime of a galaxy is limited. Here we report integral-field (tomographic) spectroscopy of an extended background source -a bright giant gravitational arc. We can thus coherently map the spatial and kinematic distribution of Mg II absorption -a standard tracer of enriched gas- in an intervening galaxy system at redshift 0.98 (i.e., ~8 Gyr ago). Our gravitational-arc tomography unveils a clumpy medium in which the absorption-strength decreases with increasing impact parameter, in good agreement with the statistics towards quasars; furthermore, we find strong evidence that the gas is not distributed isotropically. Interestingly, we detect little kinematic variation over a projected area of ~600 kpc squared, with all line-of-sight velocities confined to within a few tens of km/s of each other. These results suggest that the detected absorption originates from entrained recycled material, rather than in a galactic outflow.

Published online in Nature on 31 January 2018

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• Slicing the cool circumgalactic medium along the major-axis of a star-forming galaxy at $z=0.7$
• Characterizing the abundance, properties, and kinematics of the cool circumgalactic medium of galaxies in absorption with SDSS DR16
• MUSE Analysis of Gas around Galaxies (MAGG) -- IV: The gaseous environment of $z\sim$ 3-4 Lyman-alpha emitting galaxies
• The cold circumgalactic medium in emission: MgII halos in TNG50
• The Relationship Between Galaxy ISM and Circumgalactic Gas Metallicities
• The Angular Momentum of the Circumgalactic Medium in the TNG100 Simulation
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• Metal line emission from galaxy haloes at z~1
• MusE GAs FLOw and Wind (MEGAFLOW) IV: A two sightline tomography of a galactic wind
• Clumpiness of Observed and Simulated Cold Circumgalactic Gas
• Probing Structure in Cold Gas at $z\lesssim 1$ with Gravitationally Lensed Quasar Sight Lines
• Orientation effects on cool gas absorption from gravitational-arc tomography of a z = 0.77 disc galaxy
• Rest-frame UV and optical emission line diagnostics of ionised gas properties: a test case in a star-forming knot of a lensed galaxy at z~1.7
• The relationship between gas and galaxies at z<1 using the Q0107 quasar triplet
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• Resolved galactic superwinds reconstructed around their host galaxies at z>3
• Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet