Using deep (11.2hr) VLT/MUSE data from the MEGAFLOW survey, we report the first detection of extended MgII emission from a galaxys halo that is probed by a quasar sightline. The MgII $lambdalambda$ 2796,2803 emission around the $z = 0.702$ galaxy ($l
og(M_*/mathrm{M_odot}) = 10.05^{+0.15}_{-0.11}$) is detected out to $approx$25 kpc from the central galaxy and covers $1.0times10^3$ kpc$^2$ above a surface brightness of $14times10^{-19} mathrm{erg} mathrm{s}^{-1} mathrm{cm}^{-2},mathrm{arcsec}^{-2}$ ($2 sigma$; integrated over 1200 km s$^{-1}$ =19A and averaged over $1.5 ;mathrm{arcsec}^2$). The MgII emission around this highly inclined galaxy ($simeq$75 deg) is strongest along the galaxys projected minor axis, consistent with the MgII gas having been ejected from the galaxy into a bi-conical structure. The quasar sightline, which is aligned with the galaxys minor axis, shows strong MgII $lambda$2796 absorption (EW$_0$ = 1.8A) at an impact parameter of 39kpc from the galaxy. Comparing the kinematics of both the emission and the absorption - probed with VLT/UVES -, to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow ($v_mathrm{out}= 130;mathrm{km},mathrm{s}^{-1}$). We investigate potential origins of the extended MgII emission using simple toy models. With continuum scattering models we encounter serious difficulties in explaining the luminosity of the MgII halo and in reconciling density estimates from emission and absorption. Instead, we find that shocks might be a more viable source to power the extended MgII (and non-resonant [OII]) emission.
Most molecular gas studies of $z > 2.5$ galaxies are of intrinsically bright objects, despite the galaxy population being primarily normal galaxies with less extreme star formation rates. Observations of normal galaxies at high redshift provide a mor
e representative view of galaxy evolution and star formation, but such observations are challenging to obtain. In this work, we present ALMA $rm ^{12}CO(J = 3 rightarrow 2)$ observations of a sub-millimeter selected galaxy group at $z = 2.9$, resulting in spectroscopic confirmation of seven images from four member galaxies. These galaxies are strongly lensed by the MS 0451.6-0305 foreground cluster at $z = 0.55$, allowing us to probe the molecular gas content on levels of $rm 10^9-10^{10} ; M_odot$. Four detected galaxies have molecular gas masses of $rm (0.2-13.1) times 10^{10} ; M_odot$, and the non-detected galaxies have inferred molecular gas masses of $rm < 8.0 times 10^{10} ; M_odot$. We compare these new data to a compilation of 546 galaxies up to $z = 5.3$, and find that depletion times decrease with increasing redshift. We then compare the depletion times of galaxies in overdense environments to the field scaling relation from the literature, and find that the depletion time evolution is steeper for galaxies in overdense environments than for those in the field. More molecular gas measurements of normal galaxies in overdense environments at higher redshifts ($z > 2.5$) are needed to verify the environmental dependence of star formation and gas depletion.
Using the MEGAFLOW survey, which consists of a combination of MUSE and UVES observations of 22 quasar fields selected to contain strong MgII absorbers, we measure covering fractions of CIV and MgII 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 CIV and MgII covering fractions evolve with redshift. In the MUSE data, we found 215 $z=1-1.5$ [OII] emitters with fluxes $>10^{-17}$ 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) CIV (MgII) absorption systems with rest-frame equivalent width (REW) $W_r>$0.05AA associated with at least one [OII] emitter. The covering fractions of $zapprox1.2$ CIV (MgII) absorbers with mean $W_rapprox$0.7AA (1.0AA), exceeds 50% within 23$^{+62}_{-16}$ (46$^{+18}_{-13}$) kpc. Together with published studies, our results suggest that the covering fraction of CIV (MgII) becomes larger (smaller) with time, respectively. For absorption systems that have CIV but not MgII, we find in 73% of the cases no [OII] counterpart. This may indicate that the CIV comes from the intergalactic medium (IGM), i.e. beyond 250 kpc, or that it is associated with lower-mass or quiescent galaxies.
Galactic outflows are thought to eject baryons back out to the circum-galactic medium (CGM). Studies based on metal absorption lines (MgII in particular) in the spectra of background quasars indicate that the gas is ejected anisotropically, with gala
ctic winds likely leaving the host in a bi-conical flow perpendicular to the galaxy disk. In this paper, we present a detailed analysis of an outflow from a z = 0.7 green-valley galaxy (log($M_*$/$mathrm{M}_odot$) = 9.9; SFR = 0.5 $mathrm{M}_odot,mathrm{yr}^{-1}$) probed by two background sources part of the MUSE Gas Flow and Wind (MEGAFLOW) survey. Thanks to a fortuitous configuration with a background quasar (SDSSJ1358+1145) and a bright background galaxy at $z = 1.4$, both at impact parameters of $approx 15,mathrm{kpc}$, we can - for the first time - probe both the receding and approaching components of a putative galactic outflow around a distant galaxy. We measure a significant velocity shift between the MgII absorption from the two sightlines ($84pm17,mathrm{km},mathrm{s}^{-1}$), which is consistent with the expectation from our simple fiducial wind model, possibly combined with an extended disk contribution.
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 goa
ls of this survey are to study the properties of the circum-galactic medium around $zsim1$ star-forming galaxies. The absorption-line selected survey consists of 79 strong MgII absorbers (with rest-frame equivalent width (REW)$gtrsim$0.3AA) and, currently, 86 associated galaxies within 100 projected~kpc of the quasar with stellar masses ($M_star$) from $10^9$ to $10^{11}$ msun. We find that the cool halo gas traced by MgII is not isotropically distributed around these galaxies, as we show 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 $M_{star}lesssim 4times10^9$~msun, implying the cool material is likely to fall back except in the smallest halos. Finally, we find that the mass loading factor $eta$, 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 $zapprox1$ star-forming galaxies. The combination of VLT/MUSE and VLT/UVES observations allows us to connect the kinematic
s of the gas measured through MgII 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 MgII 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.
At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation(1-4). It is believed that they were formed in intense nuclear star
bursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions(5,6), but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies(7). Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which surprisingly turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst(8). The galaxy was probably fed by streams of cold gas, which were able to penetrate the hot halo gas until they were cut off by shock heating from the dark matter halo(9). This result confirms previous indirect indications(10-13) that the first galaxies to cease star formation must have gone through major changes not just in their structure, but also in their kinematics, to evolve into present-day elliptical galaxies.
