We present results from our on-going MusE GAs FLOw and Wind (MEGAFLOW) survey, which consists of 22 quasar lines-of-sight, each observed with the integral field unit (IFU) MUSE and the UVES spectrograph at the ESO Very Large Telescopes (VLT). The goals of this survey are to study the properties of the circum-galactic medium around z ∼ 1 star-forming galaxies. The absorption-line selected survey consists of 79 strong Mg ii absorbers (with rest-frame equivalent width (REW) 0.3Å) and, currently, 86 associated galaxies within 100 projected kpc of the quasar with stellar masses (M ) from 10 9 to 10 11 M . We find that the cool halo gas traced by Mg ii is not isotropically distributed around these galaxies from the strong bi-modal distribution in the azimuthal angle of the apparent location of the quasar with respect to the galaxy major-axis. This supports a scenario in which outflows are bi-conical in nature and co-exist with a coplanar gaseous structure extending at least up to 60 to 80 kpc. Assuming that absorbers near the minor axis probe outflows, the current MEGAFLOW sample allowed us to select 26 galaxy-quasar pairs suitable for studying winds. From this sample, using a simple geometrical model, we find that the outflow velocity only exceeds the escape velocity when M 4 × 10 9 M , implying the cool material is likely to fall back except in the smallest halos. Finally, we find that the mass loading factor η, the ratio between the ejected mass rate and the star formation rate (SFR), appears to be roughly constant with respect to the galaxy mass.

We use the MusE GAs FLOw and Wind (MEGAFLOW) survey to study the kinematics of extended disk-like structures of cold gas around z ≈ 1 star-forming galaxies. The combination of VLT/MUSE and VLT/UVES observations allows us to connect the kinematics of the gas measured through Mg ii quasar absorption spectroscopy to the kinematics and orientation of the associated galaxies constrained through integral field spectroscopy. Confirming previous results, we find that the galaxy-absorber pairs of the MEGAFLOW survey follow a strong bimodal distribution, consistent with a picture of Mg ii absorption being predominantly present in outflow cones and extended disk-like structures. This allows us to select a bona-fide sample of galaxy-absorber pairs probing these disks for impact parameters of 10-70 kpc. We test the hypothesis that the disk-like gas is co-rotating with the galaxy disks, and find that for 7 out of 9 pairs the absorption velocity shares the sign of the disk velocity, disfavouring random orbits. We further show that the data are roughly consistent with inflow velocities and angular momenta predicted by simulations, and that the corresponding mass accretion rates are sufficient to balance the star formation rates.

Context. The Milky Way is surrounded by large amounts of diffuse gaseous matter that connects the stellar body of our Galaxy with its large-scale Local Group (LG) environment. Aims. To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21 cm radio observations of neutral hydrogen. Methods. Along 270 sightlines we measure metal absorption in the lines of Si ii, Si iii, C ii, and C iv and associated H i 21 cm emission in HVCs in the velocity range |vLSR| = 100 − 500 km s −1 . With this unprecedented large HVC sample we were able to improve the statistics on HVC covering fractions, ionization conditions, small-scale structure, CGM mass, and inflow rate. For the first time, we determine robustly the angular two point correlation function of the high-velocity absorbers, systematically analyze antipodal sightlines on the celestial sphere, and compare the HVC absorption characteristics with that of Damped Lyman α absorbers (DLAs) and constrained cosmological simulations of the LG (CLUES project). Results. The overall sky-covering fraction of high-velocity absorption is 77 ± 6 percent for the most sensitive ion in our survey, Si iii, and for column densities log N (Si iii) ≥ 12.1. This value is ∼ 4 − 5 times higher than the covering fraction of 21 cm neutral hydrogen emission at log N (H i) ≥ 18.7 along the same lines of sight, demonstrating that the Milky Way's CGM is multi-phase and predominantly ionized. The measured equivalent-width ratios of Si ii, Si iii, C ii, and C iv are inhomogeneously distributed on large and small angular scales, suggesting a complex spatial distribution of multi-phase gas that surrounds the neutral 21 cm HVCs. We estimate that the total mass and accretion rate of the neutral and ionized CGM traced by HVCs is MHVC ≥ 3.0×10 9 M⊙ and dMHVC/dt ≥ 6.1M⊙ yr −1 , where the Magellanic Stream (MS) contributes with more than 90 percent to this mass/mass-flow. If seen from an external vantage point, the Milky Way disk plus CGM would appear as a DLA that would exhibit for most viewing angles an extraordinary large velocity spread of ∆v ≈ 400 − 800 km s −1 , a result of the complex kinematics of the Milky Way CGM that is dominated by the presence of the MS. We detect a velocity dipole of high-velocity absorption at low/high galactic latitudes that we associate with LG gas that streams to the LG barycenter. This scenario is supported by the gas kinematics predicted from the LG simulations. Conclusions. Our study confirms previous results, indicating that the Milky Way CGM contains sufficient gaseous material to feed the Milky Way disk over the next Gyr at a rate of a few solar masses per year, if the CGM gas can actually reach the MW disk. We dem...

We report a bimodality in the azimuthal angle (Φ) distribution of gas around galaxies traced by O VI absorption. We present the mean Φ probability distribution function of 29 HST-imaged O VI absorbing (EW>0.1 Å) and 24 non-absorbing (EW<0.1 Å) isolated galaxies (0.08

We present a detailed analysis of a large-scale galactic outflow in the CGM of a massive (M h ∼ 10 12.5 M ⊙ ), star forming (∼ 6.9 M ⊙ yr −1 ), sub-L * (∼ 0.5L * B ) galaxy at z = 0.39853 that exhibits a wealth of metal-line absorption in the spectra of the background quasar Q 0122 − 003 at an impact parameter of 163 kpc. The galaxy inclination angle (i = 63 • ) and the azimuthal angle (Φ = 73 • ) imply that the QSO sightline is passing through the projected minor-axis of the galaxy. The absorption system shows a multiphase, multicomponent structure with ultra-strong, wide velocity spread O VI (log N = 15.16 ± 0.04, ∆v 90 = 419 km s −1 ) and N V (log N = 14.69 ± 0.07, ∆v 90 = 285 km s −1 ) lines that are extremely rare in the literature. The highly ionized absorption components are well explained as arising in a low density (∼ 10 −4.2 cm −3 ), diffuse (∼ 10 kpc), cool (∼ 10 4 K) photoionized gas with a super-solar metallicity ([X/H] 0.3). From the observed narrowness of the Lyβ profile, the non-detection of S IV absorption, and the presence of strong C IV absorption in the low-resolution FOS spectrum we rule out equilibrium/non-equilibrium collisional ionization models. The lowionization photoionized gas with a density of ∼ 10 −2.5 cm −3 and a metallicity of [X/H] −1.4 is possibly tracing recycled halo gas. We estimate an outflow mass of ∼ 2 × 10 10 M ⊙ , a mass-flow rate of ∼ 54 M ⊙ yr −1 , a kinetic luminosity of ∼ 9 × 10 41 erg s −1 , and a mass loading factor of ∼ 8 for the outflowing high-ionization gas. These are consistent with the properties of "down-the-barrel" outflows from infrared-luminous starbursts as studied by Rupke et al. Such powerful, large-scale, metal-rich outflows are the primary means of sufficient mechanical and chemical feedback as invoked in theoretical models of galaxy formation and evolution.

We report four new detections of 21-cm absorption from a systematic search of 21-cm absorption in a sample of 17 strong (rest equivalent width, W r (Mg iiλ2796) ≥ 1 Å) intervening Mg ii absorbers at 0.5 < z abs < 1.5. We also present 20-cm milliarcsecond scale maps of 40 quasars having 42 intervening strong Mg ii absorbers for which we have searched for 21-cm absorption. These maps are used to understand the dependence of 21-cm detection rate on the radio morphology of the background quasar and address the issues related to the covering factor of absorbing gas. Combining 21-cm absorption measurements for 50 strong Mg ii systems from our surveys with the measurements from literature, we obtain a sample of 85 strong Mg ii absorbers at 0.5 < z abs < 1 and 1.1 < z abs < 1.5.We present detailed analysis of this 21-cm absorption sample, taking into account the effect of the varying 21-cm optical depth sensitivity and covering factor associated with the different quasar sight lines. We find that the 21-cm detection rate is higher towards the quasars with flat or inverted spectral index at cm wavelengths. About 70% of 21-cm detections are towards the quasars with linear size, LS < 100 pc. The 21-cm absorption lines having velocity widths, ΔV > 100 km s −1 are mainly seen towards the quasars with extended radio morphology at arcsecond scales. However, we do not find any correlation between the integrated 21-cm optical depth, τdv, or the width of 21-cm absorption line, ΔV, with the LS measured from the milliarcsecond scale images. All this can be understood if the absorbing gas is patchy with a typical correlation length of ∼30−100 pc. We confirm our previous finding that the 21-cm detection rate for a given optical depth threshold can be increased by up to a factor 2 by imposing the following additional constraints: Mg ii doublet ratio <1.1, W(Mg ii)/W(Fe ii) < 1.47 and W(Mg i)/W(Mg ii) > 0.27. This suggests that the probability of detecting 21-cm absorption is higher in the systems with high N(H i). We show that within the measurement uncertainty, the 21-cm detection rate in strong Mg ii systems is constant over 0.5 < z abs < 1.5, i.e., over ∼30% of the total age of universe. We show that the detection rate can be underestimated by up to a factor 2 if 21-cm optical depths are not corrected for the partial coverage estimated using milliarcsecond scale maps. Since stellar feedback processes are expected to diminish the filling factor of cold neutral medium over 0.5 < z < 1, this lack of evolution in the 21-cm detection rate in strong Mg ii absorbers is intriguing. Large blind surveys of 21-cm absorption lines with the upcoming Square Kilometre Array pathfinders will provide a complete view of the evolution of cold gas in galaxies and shed light on the nature of Mg ii systems and DLAs, and their relationship with stellar feedback processes.

We present a study comparing O VI λλ1031, 1037 doublet absorption found towards group galaxy environments with that of isolated galaxies. The O VI absorption in the circumgalactic medium (CGM) of isolated galaxies has been studied previously by the "Multiphase Galaxy Halos" survey, where the kinematics and absorption properties of the CGM have been investigated. We extend these studies to group environments. We define a galaxy group to have two or more galaxies having a line-of-sight velocity difference of no more than 1000 km s −1 and located within 350 kpc (projected) of a background quasar sightline. We identified a total of six galaxy groups associated with O VI absorption W r > 0.06 Å that have a median redshift of z gal = 0.1669 and a median impact parameter of D = 134.1 kpc. An additional 12 non-absorbing groups were identified with a median redshift of z gal = 0.2690 and a median impact parameter of D = 274.0 kpc. We find the average equivalent width to be smaller for group galaxies than for isolated galaxies (3σ). However, the covering fractions are consistent with both samples. We used the pixel-velocity two-point correlation function method and find that the velocity spread of O VI in the CGM of group galaxies is significantly narrower than that of isolated galaxies (10σ). We suggest that the warm/hot CGM does not exist as a superposition of halos, instead, the virial temperature of the halo is hot enough for O VI to be further ionised. The remaining O VI likely exists at the interface between hot, diffuse gas and cooler regions of the CGM.

Non-resonant Fe ii* (λ2365, λ2396, λ2612, λ2626) emission can potentially trace galactic winds in emission and provide useful constraints to wind models. From the 3.15 × 3.15 mosaic of the Hubble Ultra Deep Field (UDF) obtained with the VLT/MUSE integral field spectrograph, we identify a statistical sample of 40 Fe ii* emitters and 50 Mg ii (λλ2796, 2803) emitters from a sample of 271 [O ii]λλ3726, 3729 emitters with reliable redshifts from z = 0.85 − 1.50 down to 2 × 10 −18 (3 σ) ergs s, covering the M range from 10 8 − 10 11 M . The Fe ii* and Mg ii emitters follow the galaxy main sequence, but with a clear dichotomy. Galaxies with masses below 10 9 M and star formation rates (SFRs) of 1 M yr −1 have Mg ii emission without accompanying Fe ii* emission, whereas galaxies with masses above 10 10 M and SFRs 10 M yr −1 have Fe ii* emission without accompanying Mg ii emission. Between these two regimes, galaxies have both Mg ii and Fe ii* emission, typically with Mg ii P-Cygni profiles. Indeed, the Mg ii profile shows a progression along the main sequence from pure emission to P-Cygni profiles to strong absorption, due to resonant trapping. Combining the deep MUSE data with HST ancillary information, we find that galaxies with pure Mg ii emission profiles have lower star formation rate surface densities than those with either Mg ii P-Cygni profiles or Fe ii* emission. These spectral signatures produced through continuum scattering and fluorescence, Mg ii P-Cygni profiles and Fe ii* emission, are better candidates for tracing galactic outflows than pure Mg ii emission, which may originate from H ii regions. We compare the absorption and emission rest-frame equivalent widths for pairs of Fe ii transitions to predictions from outflow models and find that the observations consistently have less total re-emission than absorption, suggesting either dust extinction or non-isotropic outflow geometries.