Cool circumgalactic gas in galaxy clusters: connecting the DESI legacy imaging survey and SDSS DR16 MgII absorbers

Abstract

We investigate the cool gas absorption in galaxy clusters by cross-correlating Mg absorbers detected in quasar spectra from Data Release 16 of the Sloan Digital Sky Survey (SDSS) with galaxy clusters identified in the Dark Energy Spectroscopic Instrument (DESI) survey. We find significant covering fractions (3 − 5 % within 𝑟 500 ), ∼ 4 − 5 times higher than around random sightlines. While the covering fraction of cool gas in clusters decreases with increasing mass of the central galaxy, the total Mg mass within 𝑟 500 is nonetheless ∼ 10 times higher than for SDSS luminous red galaxies (LRGs). The Mg covering fraction versus impact parameter is well described by a power law in the inner regions and a exponential function at larger distances. The characteristic scale of the transition between these two regimes is smaller for large equivalent width absorbers. Cross-correlating Mg absorption with photo-z selected cluster member galaxies from DESI reveals a statistically significant connection. The median projected distance between Mg absorbers and the nearest cluster member is ∼ 200 kpc, compared to ∼ 500 kpc in random mocks with the same galaxy density profiles. We do not find a correlation between Mg strength and the star formation rate of the closest cluster neighbour. This suggests that cool gas in clusters, as traced by Mg absorption, is: (i) associated with satellite galaxies, (ii) dominated by cold gas clouds in the intracluster medium, rather than by the interstellar medium of galaxies, and (iii) may originate in part from gas stripped from these cluster satellites in the past.

Gas distribution from clusters to filaments in IllustrisTNG

“…Recently, Artale et al (2022) found that Mg II, C II, and Si IV are efficient tracers of the halo gas in dense environment, whereas Ne VIII, N V, O VI, and C IV are better tracers of warm hot and low-density gas (WHIM) inside filamentary structure at large scales (and z=0). In particular, the small fraction of halo gas phase inside clusters (with T < 10 5 K and n H > 10 −4 cm −3 ) is supposed to be condensed gas inside halos in high-density and low-temperature star-forming regions, as recently observed via Mg II absorption lines by Lee et al (2021), Anand et al (2022), andMishra &Muzahid (2022). For example, Lee et al (2021) showed that Mg II absorbers are more abundant inside clusters than outside them (> 2R 200 ).…”

Multiphase turbulence in galactic haloes: effect of the driving

“…The gas at these temperatures is traced by ions such as MgII at ∼ 10 4 K (Anand et al 2021(Anand et al , 2022, SiIV at∼ 10 5 K (Zheng et al 2017) and OVI at ∼ 10 5.5 K (Tumlinson et al 2011). We refer the reader to fig.…”

The environments and hosts of metal absorption at z &gt; 5

“…The trends are similar but weaker for C IV. Anand et al (2022) associated Mg II absorbers at 0.4 < 𝑧 < 1 with galaxies in cluster environments, looking for correlations between their strength and the traits of the brightest cluster galaxy (BCG) as well as with the nearest satellite galaxies. The Mg II systems are closer on average to satellite galaxies than a random distribution of Mg II, suggesting a physical association.…”