MusE GAs FLOw and Wind (MEGAFLOW) VI. A study of C iv and Mg ii absorbing gas surrounding [O ii] emitting galaxies. Issue 1 (21st May 2021)

• Record Type: Journal Article
• Authors: Schroetter, Ilane; Bouché, Nicolas F; Zabl, Johannes; Rahmani, Hadi; Wendt, Martin; Muzahid, Sowgat; Contini, Thierry; Schaye, Joop; Schmidt, Kasper B; Wisotzki, Lutz
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 506:Issue 1(2021)
• Page Start: 1355
• Page End: 1363
• Publication Date: 2021-05-21
• Subjects: galaxies: evolution -- galaxies: formation -- intergalactic medium -- quasars: absorption lines; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1447
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Using the MEGAFLOW survey, which consists of a combination of MUSE and UVES observations of 22 quasar fields selected to contain strong Mg ii absorbers, we measure the covering fractions of C iv and Mg ii as a function of impact parameter b using a novel Bayesian logistic regression method on unbinned data, appropriate for small samples. We also analyse how the C iv and Mg ii covering fractions evolve with redshift. In the MUSE data, we found 215 $z = 1{-}1.5$ [O ii ] emitters with fluxes ${\gt}10^{-17}$ erg s −1 cm −2 and within 250 kpc of quasar sight-lines. Over this redshift path $z = 1{-}1.5$, we have 19 (32) C iv (Mg ii ) absorption systems with rest-frame equivalent width (REW) $W_r\gt $ 0.05 Å associated with at least one [O ii ] emitter. The covering fractions of $z\approx 1.2$ C iv (Mg ii ) absorbers with mean $W_r\approx$ 0.7 Å (1.0 Å), exceeds 50 per cent within 23$^{+62}_{-16}$ (46$^{+{18}}_{-13}$ ) kpc. Together with published studies, our results suggest that the covering fraction of C iv (Mg ii ) becomes larger (smaller) with time, respectively. For absorption systems that have C iv but not Mg ii, we find in 73 per cent of the cases no [O ii ] counterpart. This may indicate that C iv comes from the intergalactic medium (IGM), i.e. beyond 250 kpc, or that it is associated with lower mass or quiescent galaxies.