Galaxy group at z=0.3 associated with the damped Lyman α system towards quasar Q1127-145

Abstract

We performed a spectroscopic galaxy survey, complete to mF814W≤ 20.3 (LB > 0.15L★B at z= 0.3), within 100 × 100 arcsec2 of the quasar Q1127–145 (zem= 1.18). The Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph (UVES) quasar spectrum contains three zabs < 0.33 Mg ii absorption systems. We obtained eight new galaxy redshifts, adding to the four previously known, and galaxy star formation rates (SFRs) and metallicities were computed where possible. A strong Mg ii system [Wr(2796) = 1.8Å], which is a known damped Lyman α absorber (DLA), had three previously identified galaxies; we found two additional galaxies associated with this system. These five galaxies form a group with diverse properties, such as a luminosity range of 0.04 ≤LB≤ 0.63 L★B, an impact parameter range of 17 ≤D≤ 241 kpc and a velocity dispersion of σ= 115 km s−1. The DLA group galaxy redshifts span beyond the 350 km s−1 velocity spread of the metallic absorption lines of the DLA itself. The two brightest group galaxies have SFRs of ∼few M⊙ yr−1 and should not have strong winds. We have sufficient spectroscopic information to directly compare three of the five group galaxies' (emission‐line) metallicities with the DLA (absorption) metallicity: the DLA metallicity is one‐tenth solar, substantially lower than the three galaxies' metallicity which ranges between less than 1/2 solar to solar. Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC‐2) imaging shows perturbed morphologies for the three brightest group galaxies, with tidal tails extending ∼25 kpc. We favour a scenario where the DLA absorption originates from tidal debris in the group environment. Another absorber exhibits weak Mg ii absorption [Wr(2796) = 0.03Å] and had a previously identified galaxy at a similar redshift. We have identified a second galaxy associated with this system. Both galaxies have solar metallicities and unperturbed morphologies in the HST/WFPC‐2 image. The SFR of one galaxy is much lower than that expected for strong outflows. Finally, we have also identified five galaxies at large impact parameters with no associated Mg ii absorption [Wr(2796) ≲ 5.7 mÅ, 3σ] in the spectrum of Q1127–145.

The MUSE Ultra Deep Field (MUDF). II. Survey design and the gaseous properties of galaxy groups at 0.5 &lt; z &lt; 1.5

“…For instance, Whiting et al (2006) found at least five galaxies at the redshift of a W = 2.5Å Mg ii absorber. Similarly, Kacprzak et al (2010) found five low-mass galaxies associated with a W = 1.8Å absorber. Nestor et al (2011) found ultra-strong Mg ii absorbers with W = 3.6, 5.6Å in two systems associated with massive galaxy pairs, and lastly Gauthier (2013) found another very strong absorber with W = 4.2Å in a group of three galaxies.…”

“…These works found that the closest galaxy is at d = 30 − 70 kpc. In the work by Kacprzak et al (2010) a galaxy is found a smaller impact parameter (17.4 kpc). However, from an analysis of the metallicity of the absorber and of the group galaxies, the authors concluded that the closest galaxy is not hosting the absorber, which is more likely to arise from tidal debris in the group environment.…”

Magellan LDSS3 emission confirmation of galaxies hosting metal-rich Lyman α absorption systems

“…All five galaxies (z ∼ 0.3) are at impact parameters 115 < b < 265 kpc with L < 0.3L * , which is consistent with Mg II absorption occuring in luminous galaxies within 100 kpc impact parameter, but not beyond. On the other hand, the simulations by Kacprzak, Murphy & Churchill (2010) show that DLAs can occur even at 200 kpc impact parameters.…”

“…It is not uncommon for studies to find galaxies with no Mg II absorption in fields of QSOs. Kacprzak, Murphy & Churchill (2010) identify five galaxies along the line of sight to Q1127-145 with no absorption. All five galaxies (z ∼ 0.3) are at impact parameters 115 < b < 265 kpc with L < 0.3L * , which is consistent with Mg II absorption occuring in luminous galaxies within 100 kpc impact parameter, but not beyond.…”

MUSE-ALMA haloes V: physical properties and environment of z ≤ 1.4 H i quasar absorbers

“…Literature references: a Kacprzak et al (2011), b Lane et al (1998), c Muzahid et al (2016), d Rao et al (2006), e Boisse et al (1998), f Rahmani et al (2018b), g Péroux et al (2019). 1 Observed magnitudes in HST F814W fromKacprzak et al (2010)…”