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We report the discovery of large, ionized, [O ii]-emitting circumgalactic nebulae around the majority of 30 UV-luminous quasars at z = 0.4–1.4 observed with deep, wide-field integral field spectroscopy with the Multi-Unit Spectroscopy Explorer (MUSE) by the Cosmic Ultraviolet Baryon Survey and MUSE Quasar Blind Emitters Survey. Among the 30 quasars, seven (23%) exhibit [O ii]-emitting nebulae with major axis sizes greater than 100 kpc, 20 greater than 50 kpc (67%), and 27 (90%) greater than 20 kpc. Such large, optically emitting nebulae indicate that cool, dense, and metal-enriched circumgalactic gas is common in the halos of luminous quasars at intermediate redshift. Several of the largest nebulae exhibit morphologies that suggest interaction-related origins. We detect no correlation between the sizes and cosmological-dimming-corrected surface brightnesses of the nebulae and quasar redshift, luminosity, black hole mass, or radio-loudness, but find a tentative correlation between the nebulae and rest-frame [O ii] equivalent width in the quasar spectra. This potential trend suggests a relationship between interstellar medium content and gas reservoirs on CGM scales. The [O ii]-emitting nebulae around the z ≈ 1 quasars are smaller and less common than Lyα nebulae around z ≈ 3 quasars. These smaller sizes can be explained if the outer regions of the Lyα halos arise from scattering in more neutral gas, by evolution in the cool circumgalactic medium content of quasar-host halos, by lower-than-expected metallicities on ≳50 kpc scales around z ≈ 1 quasars, or by changes in quasar episodic lifetimes between z = 3 and 1.

Deep observations are revealing a growing number of young galaxies in the first billion years of cosmic time 1 . Compared to typical galaxies at later times, they show more extreme emission-line properties 2 , higher star formation rates 3 , lower masses 4 , and smaller sizes 5 . However, their faintness precludes studies of their chemical abundances and ionization conditions, strongly limiting our understanding of the physics driving early galaxy build-up and metal enrichment. Here we study a rare population of ultraviolet-selected, low-luminosity galaxies at redshift 2.4 < z < 3.5 that exhibit all the rest-frame properties expected from primeval galaxies. These low-mass, highly compact systems are rapidly forming galaxies able to double their stellar mass in only a few tens of millions of years. They are characterized by very blue ultraviolet spectra with weak absorption features and bright nebular emission lines, which imply hard radiation fields from young hot massive stars 6 , 7 . Their highly ionized gas phase has strongly sub-solar carbon and oxygen abundances, with metallicities more than a factor of two lower than that found in typical galaxies of similar mass and star formation rate at z ≤2.5 8 . These young galaxies reveal an early and short stage in the assembly of their galactic structures and their chemical evolution, a vigorous phase that is likely to be dominated by the effects of gas-rich mergers, accretion of metal-poor gas and strong outflows. A selected group of intermediate-redshift galaxies appear similar to primeval galaxies. Analysing spectra of these nearer analogues for chemical abundances and ionization levels gives an improved understanding of galaxies that are too faint to study well.

Nature Astronomy 1, 0052 (2017); published 2 March 2017; corrected 13 March 2017. In the version of this Letter originally published, in ref. 1 R. J. Bouwens's surname was spelled incorrectly. This has now been corrected in all versions of the Letter.

This paper proposes four new methods to decontaminate spectra of stars and galaxies resulting from slitless spectroscopy used in many space missions such as Euclid. These methods are based on two distinct approaches and simultaneously take into account multiple dispersion directions of light. The first approach, called the local instantaneous approach, is based on an approximate linear instantaneous model. The second approach, called the local convolutive approach, is based on a more realistic convolutive model that allows simultaneous decontamination and deconvolution of spectra. For each approach, a mixing model was developed that links the observed data to the source spectra. This was done either in the spatial domain for the local instantaneous approach or in the Fourier domain for the local convolutive approach. Four methods were then developed to decontaminate these spectra from the mixtures, exploiting the direct images provided by photometers. Test results obtained using realistic, noisy, Euclid-like data confirmed the effectiveness of the proposed methods.

Absorption line spectroscopy using background quasars can provide strong constraints on galactic outflows. In this paper, we investigate possible scaling relations between outflow properties, namely outflow velocity the mass ejection rate \\( M_ out\\), and the mass loading factor \\(\\) and the host galaxy properties, such as star formation rate (SFR), SFR surface density, redshift, and stellar mass using galactic outflows probed by background quasars from MEGAFLOW and other surveys. We find that \\(V_ out\\) (\\(\\)) is (anti-)correlated with SFR and SFR surface density. We extend the formalism of momentum-driven outflows of Heckman et al. to show that it applies not only to down the barrel studies but also to winds probed by background quasars, suggesting a possible universal wind formalism. Under this formalism, we find a clear distinction between ``strong'' and ``weak'' outflows where ``strong'' outflows seem to have tighter correlations with galaxy properties (SFR or galaxy stellar mass) than ``weak'' outflows.

The presence of large ionised gaseous nebulae found around some ultraluminous X-ray sources (ULXs) provides the means to assess the mechanical and radiative feedback of the central source, and hence constrain the efficiency and impact on the surroundings of the super-Eddington regime powering most of these sources. NGC 1313 X--1 is an archetypal ULX which has been reported to be surrounded by abnormally high [O I]\\(\\)6300/H\\( >\\) 0.1 ratios and for which high-resolution spectroscopy in X-rays has hinted the presence of powerful outflows. We report observations taken with the Multi-Unit Spectroscopic Explorer of NGC 1313 X--1 in order to confirm the presence of a nebula inflated by the winds, investigate its main sources of ionisation and estimate the mechanical output of the source. We detect a bubble of 452 \\(\\) 266\\,pc in size, roughly centred around the ULX, which shows clear evidence for shock ionisation in the outer edges. We estimate shock velocities to be in the \\(160-180\\)\\,km/s range based on the line ratios. This suggests that an average and continuous outflow power of \\((2-4.5) 10^40\\) erg/s over a timescale of \\((4.5-7.8) 10^5\\)\\,yr is required to inflate the bubble. In the interior of the bubble and closer to the ULX we detect an extended (\\(\\)140\\,pc) X-ray ionised region. Additionally, we detect two supernova remnants coincidentally close to the bubble of which we also report age and explosion energy estimates. The elongated morphology and the kinematics of the bubble strongly suggest that the bubble is being inflated by winds and/or jets emanating from the central source, supporting the presence of winds found through X-ray spectroscopy. The estimated mechanical power is comparable or higher than the X-ray luminosity of the source, providing additional evidence in support of NGC 1313 X--1 harbouring a super-Eddington accretor.

We present, for the first time, spatially resolved spectroscopy for the entire Hickson Compact Group 31 obtained with the MUSE instrument at the VLT,and an in-depth analysis of this compact group. To obtain a complete understanding of the system, we derived radial velocity and dispersion velocity maps, maps of the ionization mechanism of the system, chemical abundances and their distribution over the whole system, star formation rates and ages of the different star-forming regions, and the spatial distribution of the Wolf-Rayet stellar population. We also reconstructed the star formation history of the galaxies HCG 31 A, C, B and F, measured the emission-line fluxes, and performed a stellar population synthesis. Our main findings are: (i) that there is clearly disturbed kinematics due to the merger event that the system is experiencing; (ii) that the ionization is produced exclusively via star formation except for the nucleus of the galaxy HCG 31 A, where there is a small contribution of shocks; (iii) that there is low oxygen abundance distributed homogeneously through the system; (iv) that there is a prominent population of carbon Wolf-Rayet stars in the central zone of the group; and (v) that there are clear evidences of the tidal origin of the galaxies HCG 31 E, HCG 31 H, and HCG 31 F because they show quite high oxygen abundances for their stellar mass. All these findings are clear evidence that HCG 31 is currently in an early merging phase and manifesting a starburst in its central region.

In a series of papers on lensed kinematics, we seek to combine the sensitivity of 3D forward modelling to low signal-to-noise ratio outskirts with the enhanced spatial resolution of cluster lensing. In this first paper, we (i) present and validate our methodology, which directly constrains the source parameters by incorporating lensing deflections into the \\(GalPaK^3D\\) forward-modelling algorithm, and (ii) investigate the evolution of the stellar-mass and baryonic-mass Tully-Fisher relations (sTFR and bTFR) since \\(z 1\\). We define a robust sample of strongly lensed star-forming galaxies (SFGs) from the MUSE Lensing Cluster survey, spanning magnifications \\( = 1.4 - 12.4\\) and stellar masses \\(M_ = 10^8.1 - 10^10.3 M_\\). Using a series of mock galaxies, we find that our method is significantly more reliable at recovering morpho-kinematic properties than approaches that ignore differential magnification, even for relatively modest magnifications (\\( < 6\\)). Restricting the analysis to 95 rotationally supported SFGs with well-constrained velocities, we find a significant evolution of the sTFR zero-point (\\( b^sTFR = -0.42^+0.05_-0.05~dex\\) in stellar mass) but no detectable evolution of the bTFR zero-point (\\( b^bTFR = 0.00^+0.06_-0.06~dex\\) in baryonic mass) relative to \\(z 0\\). Our results are consistent with a mild evolution of the stellar-to-halo mass ratio and support the view that the sTFR has evolved only weakly over the past \\( 8\\) Gyr, aside from shifts driven by the redshift dependence of halo-defining quantities such as the critical density and overdensity. The absence of detectable evolution in the bTFR zero-point suggests that the increasing contribution of cold gas mass at higher redshift fully compensates the evolution observed in the stellar component alone. [abridged]

The circumgalactic medium (CGM) serves as a baryon reservoir that connects galaxies to the intergalactic medium and fuels star formation. The spatial distribution of the metal-enriched cool CGM has not yet been directly revealed at cosmic noon (z~2-4), as bright emission lines at these redshifts are not covered by optical integral field units. To remedy this situation, we aim for the first-ever detections and exploration of extended SiII* emission (low-ionization state, LIS), referred to as ``SiII* halos'', at redshifts ranging from z=2 to 4 as a means to trace the metal-enriched cool CGM. We use a sample of 39 galaxies with systemic redshifts of z=2.1-3.9 measured with the [CIII] doublet in the MUSE Hubble Ultra Deep Field catalog, which contains integration times spanning from ~30 to 140 hours. We search for extended SiII*1265, 1309, 1533 emission (fluorescent lines) around individual galaxies. We also stack a subsample of 14 UV-bright galaxies. We report five individual detections of SiII*1533 halos. We also confirm the presence of SiII*1533 halos in stacks for the subsample containing UV-bright sources. The other lines do not show secure detections of extended emission in either individual or stacking analyses. These detections may imply that the presence of metal-enriched CGM is a common characteristic for UV-bright galaxies. To investigate whether the origin of SiII* is continuum pumping as suggested in previous studies, we check the consistency of the equivalent width (EW) of SiII* emission and the EW of SiII absorption for the individual halo object with the most reliable detection. We confirm the equivalence, suggesting that photon conservation works for this object and pointing toward continuum pumping as the source of SiII*. We also investigate SiII* lines in a RAMSES-RT zoom-in simulation including continuum pumping and find ubiquitous presence of extended halos.

We investigate the burstiness of star formation and the ionizing efficiency of a large sample of galaxies at \\(0.7 < z < 1.5\\) using HST grism spectroscopy and deep ultraviolet (UV) imaging in the GOODS-N and GOODS-S fields. The star formation history (SFH) in these strong emission line low-mass galaxies indicates an elevated star formation rate (SFR) based on the H\\(\\) emission line at a given stellar mass when compared to the standard main sequence. Moreover, when comparing the H\\(\\) and UV SFR indicators, we find that an excess in SFR(H\\(\\)) compared to SFR(UV) is preferentially observed in lower-mass galaxies below \\(10^9\\) M\\(\\), which are also the highest-EW galaxies. These findings suggest that the burstiness parameters of these strong emission line galaxies may differ from those inferred from hydrodynamical simulations and previous observations. For instance, a larger burstiness duty cycle would explain the observed SFR(H\\(\\)) excess. We also estimate the ionizing photon production efficiency \\(_ion\\), finding a median value of Log(\\(_ion\\)/erg\\(^-1\\) Hz)\\(=24.80 0.26\\) when adopting a Galactic dust correction for H\\(\\) and an SMC one for the stellar component. We observe an increase of \\(_ion\\) with redshift, further confirming similar results at higher redshifts. We also find that \\(_ion\\) is strongly correlated with EW(H\\(\\)), which provides an approach for deriving \\(_ion\\) in early galaxies. Lower-mass, lower-luminosity galaxies have a higher \\(_ion\\). Overall, these results provide further support for faint galaxies playing a major role in the reionization of the Universe.