Baryonic Ecosystem IN Galaxies (BEINGMgII)
Year: 2026
Type: article
Abstract: We investigate the origin of intervening cool Mg II absorption detected in the spectra of background quasars and the nature of associated galaxies across a broad redshift range of 0.3 ≤ z ≤ 1.6, and a largely unexplored galactrocentric distance of ≲20 kpc. Using nebular [O II ] λλ 3727, 3729 emission lines identified in DESI fibre spectra centred on quasars, we detect 342 galaxies at a typical detection rate of ∼0.45% at z ≲ 1, which increases with the Mg II equivalent width ( W 2796 ). A significant fraction (74%) of these galaxies are associated with strong absorbers with W 2796 ≥ 2 Å. These absorbers trace galaxies spanning stellar masses of 8.4 ≤ log( M ★ / M ⊙ )≤11.6 and star formation rates (SFRs) of −1 ≤ log(SFR [ M ⊙ yr −1 ]) ≤ 2.7, located at projected galactocentric distances of 4−24 kpc. We find that the average Mg II absorber strength increases from 2.1 Å to 2.8 Å between redshifts of z ∼ 0.4 and 1.2, indicating evolution in the cool gas content of galaxy halos. The relatively constant absorber strength with galactocentric distance implies a clumpy structure of cool gas in the circumgalactic medium (CGM). Further, we find a positive correlation between W 2796 versus stellar mass ( M ★ ), and the SFR, suggesting that the distribution of metal-enriched cool gas in the CGM is closely tied to the properties of the host galaxies. The redshift evolution of gas-phase metallicity suggests that strong Mg II absorbers trace the general population of star-forming galaxies. The velocity dispersion of the cool gas increases with halo mass, and the wide range of the line-of-sight velocity offset (−389 to 364 km s −1 ) between the galaxy systemic velocity and absorbers highlights the dynamical nature of CGM. However, the majority of this gas remains gravitationally bound to the dark matter halos, consistent with a picture of gas recycling via galactic fountains.
Source: Astronomy and Astrophysics
Authors: Reena Chaudhary, Ravi Joshi, Sarbeswar Das, Michele Fumagalli, Glenn G. Kacprzak, Matteo Fossati, Celine Péroux, Luis C. Ho
Institutions: Indian Institute of Astrophysics, Pondicherry University, Trieste Astronomical Observatory, University of Milano-Bicocca, National Institute for Astrophysics, Swinburne University of Technology, Brera Astronomical Observatory, Centre National de la Recherche Scientifique, European Southern Observatory, Aix-Marseille Université, Laboratoire d’Astrophysique de Marseille, European Southern Observatory, Peking University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W4417409134