Multiphase circumgalactic medium probed with MUSE and ALMA

Abstract

Galaxy halos appear to be missing a large fraction of their baryons, most probably hiding in the circumgalactic medium (CGM), a diffuse component within the dark matter halo that extends far from the inner regions of the galaxies. A powerful tool to study the CGM gas is offered by absorption lines in the spectra of background quasars. Here, we present optical (MUSE) and mm (ALMA) observations of the field of the quasar Q1130−1449 which includes a log [N (HI)/cm −2 ]=21.71±0.07 absorber at z=0.313. Ground-based VLT/MUSE 3D spectroscopy shows 11 galaxies at the redshift of the absorber down to a limiting SFR>0.01 M yr −1 (covering emission lines of [O ii], Hβ, [O iii], [N ii] and Hα), 7 of which are new discoveries. In particular, we report a new emitter with a smaller impact parameter to the quasar line-of-sight (b=10.6 kpc) than the galaxies detected so far. Three of the objects are also detected in CO(1-0) in our ALMA observations indicating long depletion timescales for the molecular gas and kinematics consistent with the ionised gas. We infer from dedicated numerical cosmological RAMSES zoom-in simulations that the physical properties of these objects qualitatively resemble a small group environment, possibly part of a filamentary structure. Based on metallicity and velocity arguments, we conclude that the neutral gas traced in absorption is only partly related to these emitting galaxies while a larger fraction is likely the signature of gas with surface brightness almost four orders of magnitude fainter that current detection limits. Together, these findings challenge a picture where strong-N (H I) quasar absorbers are associated with a single bright galaxy and favour a scenario where the H i gas probed in absorption is related to far more complex galaxy structures.

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

“…We report three such cases in our sample: Q1211z062, Q1232z039 (Fig. 2) and Q1130z031 (Péroux et al 2019).…”

“…Finally, individual exposures were combined including field rotation. The detailed description of the reduction procedure can be found in Péroux et al (2019). We refrained from using the pipeline sky subtraction method, due to unsatisfactory results.…”

“…Both images are in the same scale frame and oriented North up, East to the left. For clarity, we show the Q1130z031 rich group members on a separate figure (for details on this system see Péroux et al 2019).…”

“…Combined with highresolution UV spectroscopy of quasars, these studies have revealed relevant features interpreted as galactic outflows (Schroetter et al 2016;Rahmani et al 2018b;Schroetter et al 2019), warped accretion discs (Rahmani et al 2018a) and galactic fountains (Bouché et al 2016). Alongside the detection of kinematic traces of gas inflows and outflows, new studies detected multiple galaxies associated with one absorber (Bielby et al 2017;Péroux et al 2017;Klitsch et al 2018;Nielsen et al 2018;Péroux et al 2019;Muzahid et al 2019). These findings point towards a more complex view of the gaseous halos of galaxies: from the halo gas of single systems, through tidal streams and halo substructures (Whiting et al 2006; Kacprzak et al 2010) to intra-group gas (Bielby et al 2017;Fossati et al 2019).…”

Cold neutral hydrogen gas in galaxies

“…ALMA, is essential to connect the properties of the galaxies with the absorbing gas (e.g. Péroux et al, 2019). Such observations are also required to link the neutral gas around galaxies with their ionized and molecular gas content, and hence understand the mechanisms through which galaxies acquire the fuel for forming stars.…”