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We present a study of metal-enriched halo gas traced by Mg  ii and C  iv absorption at z < 2 in the MUSE Analysis of Gas around Galaxies survey and the Quasar Sightline and Galaxy Evolution survey. Using these large and complete galaxy surveys in quasar fields, we study the dependence of the metal distribution on galaxy properties and overdensities, out to physical projected separations of 750 kpc. We find that the cool, low-ionization gas is significantly affected by the environment across the full redshift range probed, with ≈2–3 times more prevalent and stronger Mg  ii absorption in higher overdensity group environments and in regions with greater overall stellar mass and star formation rates. Complementary to these results, we have further investigated the more highly ionized gas as traced by C  iv absorption, and found that it is likely to be more extended than the Mg  ii gas, with ≈2 times higher covering fraction at a given distance. We find that the strength and covering fraction of C  iv absorption show less significant dependence on galaxy properties and environment than the Mg  ii absorption, but more massive and star-forming galaxies nevertheless also show ≈2 times higher incidence of C  iv absorption. The incidence of Mg  ii and C  iv absorption within the virial radius shows a tentative increase with redshift, being higher by a factor of ≈1.5 and ≈4, respectively, at z > 1. It is clear from our results that environmental processes have a significant impact on the distribution of metals around galaxies and need to be fully accounted for when analysing correlations between gaseous haloes and galaxy properties. [ABSTRACT FROM AUTHOR]

Quasar outflows are fundamental components of quasar environments that might play an important role in feedback to galaxy evolution. We report on the emergence of a remarkable new outflow absorption-line system in the quasar PG1411+442 (redshift ∼0.089) detected in the UV and visible with the Hubble Space Telescope Cosmic Origins Spectrograph and the Gemini Multi-Object Spectrograph, respectively. This new 'transient' system contains thousands of lines, including Fe  ii and Fe  ii ∗ from excited states up to 3.89 eV, H  i ∗ Balmer lines, Na  i  D λλ5890, 5896, and the first detection of He  i ∗ λ5876 in a quasar. The transient absorber is spatially inhomogeneous and compact, with sizes ≲0.003 pc, based on covering fractions on the quasar continuum source ranging from ∼0.45 in strong UV lines to ∼0.04 in Na  i  D. cloudy photoionization simulations show that large total column densities log  N H(cm−2) ≳ 23.4 and an intense radiation field ≲0.4 pc from the quasar are needed to produce the observed lines in thick zones of both fully ionized and partially ionized gas. The densities are conservatively log  n H(cm−3) ≳ 7 based on Fe  ii ∗, H  i ∗, and He  i ∗ but they might reach log  n H(cm−3) ≳ 10 based on Na  i  D. The transient lines appear at roughly the same velocity shift, v  ∼ −1900 km s−1, as a 'mini-BAL' outflow detected previously, but with narrower Doppler widths, b ∼ 100 km s−1, and larger column densities in more compact outflow structures. We propose that the transient lines identify a clumpy outflow from the broad emission-line region that, at its current speed and location, is still gravitationally bound to the central black hole. [ABSTRACT FROM AUTHOR]

We present new measurements of the flux power-spectrum P (k) of the z < 0.5 H   i Lyman-α Forest spanning scales |$k \sim 0.001\!-\!0.1\, \mathrm{s \, km}^{-1}$|⁠. These results were derived from 65 far-ultraviolet quasar spectra (resolution |$R \sim 18\, 000$|⁠) observed with the Cosmic Origin Spectrograph (COS) on board the Hubble Space Telescope. The analysis required careful masking of all contaminating, coincident absorption from H   i and metal–line transitions of the Galactic interstellar medium and intervening absorbers as well as proper treatment of the complex COS line-spread function. From the P (k) measurements, we estimate the H   i photoionization rate (⁠|$\Gamma _{\rm H\,{\small I}}$|⁠) in the z < 0.5 intergalactic medium. Our results confirm most of the previous |$\Gamma _{\rm H\,{\small I}}$| estimates. We conclude that previous concerns of a photon underproduction crisis are now resolved by demonstrating that the measured |$\Gamma _{\rm H\,{\small I}}$| can be accounted for by ultraviolet emission from quasars alone. In a companion paper, we will present constraints on the thermal state of the z < 0.5 intergalactic medium from the P (k) measurements presented here. [ABSTRACT FROM AUTHOR]

We analyse the intracluster medium (ICM) and circumgalactic medium (CGM) in seven X-ray-detected galaxy clusters using spectra of background quasi-stellar objects (QSOs) (HSTCOS/ STIS), optical spectroscopy of the cluster galaxies (MMT/Hectospec and SDSS), and X-ray imaging/spectroscopy (XMM-Newton and Chandra). First, we report a very low covering fraction of HI absorption in the CGM of these cluster galaxies, fc = 25+25 -15 per cent, to stringent detection limits (N(H I) <1013 cm-2). As field galaxies have an HI covering fraction of ~100 per cent at similar radii, the dearth of CGM HI in our data indicates that the cluster environment has effectively stripped or overionized the gaseous haloes of these cluster galaxies. Secondly, we assess the contribution of warm-hot (105-106 K) gas to the ICM as traced by OVI and broad Ly α (BLA) absorption. Despite the high signal-to-noise ratio of our data, we do not detect OVI in any cluster, and we only detect BLA features in the QSO spectrum probing one cluster. We estimate that the total column density of warm-hot gas along this line of sight totals to ~3 per cent of that contained in the hot T > 107 K X-ray emitting phase. Residing at high relative velocities, these features may trace pre-shocked material outside the cluster. Comparing gaseous galaxy haloes from the low-density 'field' to galaxy groups and high-density clusters, we find that the CGM is progressively depleted of HI with increasing environmental density, and the CGM is most severely transformed in galaxy clusters. This CGM transformation may play a key role in environmental galaxy quenching. [ABSTRACT FROM AUTHOR]