Search

We detect Ly$\alpha$ emission from a ~5 Mpc-long (comoving) portion of the cosmic web hosting an overdensity ($\delta \approx 25$) of 19 Ly$\alpha$ emitters (LAEs) at $z\approx 4$ within the MUSE Ultra Deep Field (MUDF), reaching an average surface brightness (SB) of $5\times 10^{-20}~\rm{erg~s^{-1}~ cm^{-2}~arcsec^{-2}}$. This large-scale structure has an average SB similar to the filament across the two MUDF quasars at $z\approx 3.22$. However, deep multiwavelength data do not show a clear presence of active galactic nuclei, suggesting that the emission is mainly regulated by the underlying gas density. We find $\approx 0.2$ dex higher star formation compared to control samples and a remarkable predominance (5/7) of blue-peaked emission lines in the spectra of the embedded LAEs, indicative of favorable conditions for gas accretion. Lastly, we quantify the contribution of intragalactic gas to the Ly$\alpha$ SB profile at large distances from LAEs. By studying samples of filaments detected in emission within diverse environments, we are finally gaining new insight into the physics of gas accretion within the cosmic web., Comment: 9 pages, 5 figures, submitted

These are exciting times for studies of galaxy formation and the growth of structures. New observatories and advanced simulations are revolutionising our understanding of the cycling of matter into, through, and out of galaxies. This chapter first describes why baryons are essential for galaxy evolution, providing a key test of Lambda-Cold Dark Matter cosmological model. In particular, we describe a basic framework to convert measurements of the gas properties observed in absorption spectra into global estimates of the condensed (stars and cold gas) matter mass densities. We then review our current understanding of the cycling of baryons from global to galactic scales, in the so-called circumgalactic medium. The final sections are dedicated to future prospects, identifying new techniques and up-coming facilities as well as key open questions. This chapter is complemented with a series of hands-on exercises which provide a practical guide to using publicly available hydrodynamical cosmological simulations. Beyond providing a direct connection between new observations and advanced simulations, these exercises give the reader the necessary tools to make use of these theoretical models to address their own science questions. Ultimately, our increasingly accurate description of the circumgalactic medium reveals its crucial role in transforming the pristine early Universe into the rich and diverse Universe of the present day., Comment: Lecture notes for the 52^nd (March 2023) Saas-Fee Advanced School, Switzerland; 89 pages, 42 figures

We characterize, for the first time, the average extended emission in multiple lines ([OII], [OIII], and Hbeta) around a statistical sample of 560 galaxies at z~0.25-0.85. By stacking the Multi Unit Spectroscopic Explorer (MUSE) 3D data from two large surveys, the MUSE Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF), we detect significant [OII] emission out to ~40 kpc, while [OIII] and Hbeta emission is detected out to ~30 kpc. Via comparisons with the nearby average stellar continuum emission, we find that the line emission at 20-30 kpc likely arises from the disk-halo interface. Combining our results with that of our previous study at z~1, we find that the average [OII] surface brightness increases independently with redshift over z~0.4-1.3 and with stellar mass over M* ~10^{6-12} Msun, which is likely driven by the star formation rate as well as the physical conditions of the gas. By comparing the observed line fluxes with photoionization models, we find that the ionization parameter declines with distance, going from log q (cm/s) ~7.7 at <=5 kpc to ~7.3 at 20-30 kpc, which reflects a weaker radiation field in the outer regions of galaxies. The gas-phase metallicity shows no significant variation over 30 kpc, with a metallicity gradient of ~0.003 dex/kpc, which indicates an efficient mixing of metals on these scales. Alternatively, there could be a significant contribution from shocks and diffuse ionized gas to the line emission in the outer regions., Comment: 9 pages, 6 figures, A&A in press

Filaments connecting halos are a long-standing prediction of cold dark matter theories. We present a detection of the cosmic web emission connecting two quasar-host galaxies at redshift z ~3.22 in the MUSE Ultra Deep Field (MUDF). The very deep observations unlock a high-definition view of the filament morphology, a measure of the transition radius between the intergalactic and circumgalactic medium, and the characterization of the surface brightness profiles along the filament and in the transverse direction. Through systematic comparisons with simulations, we validate the filaments' typical density predicted in the current cold dark-matter model. Our analysis of the MUDF field, an excellent laboratory for quantitatively studying filaments in emission, opens a new avenue to constrain the physical properties of the cosmic web and to trace the distribution of dark matter on large scales., Comment: Published in Nature Astronomy on January 29th, 2025 (online); 4 main figures and 1 table; 7 extended data figures; 1 extended data table. See https://www.nature.com/articles/s41550-024-02463-w

Almost 50% of galaxies in the local Universe are in clusters or groups coexisting with both hot and cold gas components. In the present study, we observationally probed the cold-gas content of X-ray-selected massive galaxy clusters with spectroscopic redshift measured from the SDSS/SPIDERS survey. This paper focuses on the most massive structures: galaxy clusters with a mean mass of M$_{500c}$ = 2.7$\times 10^{14}$ M$_{\odot}$. We used a large number of background quasar optical spectra from SDSS DR16 to probe the diffuse T$=$10$^4$K gas in their intracluster medium. We first analysed a sample of spectra with known MgII absorbers, and then blindly stacked about 16,000 archival spectra at the redshifts of the foreground galaxy clusters. We tentatively ($3.7 \sigma$ significance) detect MgII in the clusters with an equivalent width EW(MgII $\lambda$2796) of 0.056$\pm$0.015 \r{A}, corresponding to a column density of log [N(MgII)/cm$^{-2}$]=12.12$\pm0.1$. We tested our methodology by generating 22,000 mock SDSS spectra with MgII absorbers from TNG50 cosmological magnetohydrodynamical simulations, combining photo-ionisation modelling and ray tracing. We also performed bootstrapping stacking at different cluster redshifts and stacked quasar spectra with no intervening clusters in the line of sight to measure the significance of our detection. These results are in line with the findings of recent, similar observational studies but challenge predictions from TNG simulations. Together, our findings indicate that large amounts of cold gas may be found in the most massive structures of the Universe.

Deep, unbiased surveys are essential to decipher the cosmic evolution of galaxies. The submillimetre (submm) and millimetre (mm) windows complement the UV/optical waveband and are key to revealing the cold and dusty Universe. Traditional ways of conducting deep surveys resort to either lensed fields or target small areas for ultra-long integrations. These surveys have greatly advanced our understanding of dusty star-forming galaxies (DSFGs), but are susceptible to lensing uncertainties and cosmic variance and will be expensive to expand. Here, we summarise our recent multi-wavelength survey of DSFGs in the vicinity of ALMA's calibrators: the ALMACAL survey. These fields have accumulated many hundreds of hours of on-source time, reaching depths and effective areas that are competitive with bespoke cosmological surveys. We summarise the multi-wavelength number counts from ALMACAL and the resolved fraction of the Cosmic Infrared Background (CIB) from submm to mm wavelengths. Meanwhile, combining all available ALMA observations in each field results in impressive frequency coverage, which often yields the redshifts of these DSFGs. The ALMACAL survey has demonstrated the scientific value of calibration scans for all submm/mm and radio telescopes, existing and planned., Comment: 6 pages, 3 figures, published by Proceedings of mm Universe 2023, EPJ Web of conferences, EDP Sciences

High-resolution absorption spectroscopy toward bright background sources has had a paramount role in understanding early galaxy formation, the evolution of the intergalactic medium and the reionisation of the Universe. However, these studies are now approaching the boundaries of what can be achieved at ground-based 8-10m class telescopes. The identification of primeval systems at the highest redshifts, within the reionisation epoch and even into the dark ages, and of the products of the first generation of stars and the chemical enrichment of the early Universe, requires observing very faint targets with a signal-to-noise ratio high enough to detect very faint spectral signatures. In this paper, we describe the giant leap forward that will be enabled by ANDES, the high-resolution spectrograph for the ELT, in these key science fields, together with a brief, non-exhaustive overview of other extragalactic research topics that will be pursued by this instrument, and its synergistic use with other facilities that will become available in the early 2030s., Comment: Accepted for publication in Experimental Astronomy. Version updated to match the published one

State-of-the-art 19th century spectroscopy led to the discovery of quantum mechanics, and 20th century spectroscopy led to the confirmation of quantum electrodynamics. State-of-the-art 21st century astrophysical spectrographs, especially ANDES at ESO's ELT, have another opportunity to play a key role in the search for, and characterization of, the new physics which is known to be out there, waiting to be discovered. We rely on detailed simulations and forecast techniques to discuss four important examples of this point: big bang nucleosynthesis, the evolution of the cosmic microwave background temperature, tests of the universality of physical laws, and a real-time model-independent mapping of the expansion history of the universe (also known as the redshift drift). The last two are among the flagship science drivers for the ELT. We also highlight what is required for the ESO community to be able to play a meaningful role in 2030s fundamental cosmology and show that, even if ANDES only provides null results, such `minimum guaranteed science' will be in the form of constraints on key cosmological paradigms: these are independent from, and can be competitive with, those obtained from traditional cosmological probes., Comment: 31 pages, 6 figures; submitted to Experimental Astronomy on behalf of the ANDES Science Team; v2: matches accepted version

The upcoming ByCycle project on the VISTA/4MOST multi-object spectrograph will offer new prospects of using a massive sample of $\sim 1$ million high spectral resolution ($R$ = 20,000) background quasars to map the circumgalactic metal content of foreground galaxies (observed at $R$ = 4000 - 7000), as traced by metal absorption. Such large surveys require specialized analysis methodologies. In the absence of early data, we instead produce synthetic 4MOST high-resolution fibre quasar spectra. To do so, we use the TNG50 cosmological magnetohydrodynamical simulation, combining photo-ionization post-processing and ray tracing, to capture MgII ($\lambda2796$, $\lambda2803$) absorbers. We then use this sample to train a Convolutional Neural Network (CNN) which searches for, and estimates the redshift of, MgII absorbers within these spectra. For a test sample of quasar spectra with uniformly distributed properties ($\lambda_{\rm{MgII,2796}}$, $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05 - 5.15$ \AA, $\rm{SNR} = 3 - 50$), the algorithm has a robust classification accuracy of 98.6 per cent and a mean wavelength accuracy of 6.9 \AA. For high signal-to-noise spectra ($\rm{SNR > 20}$), the algorithm robustly detects and localizes MgII absorbers down to equivalent widths of $\rm{EW}_{\rm{MgII,2796}}^{\rm{rest}} = 0.05$ \AA. For the lowest SNR spectra ($\rm{SNR=3}$), the CNN reliably recovers and localizes EW$_{\rm{MgII,2796}}^{\rm{rest}}$ $\geq$ 0.75 \AA\, absorbers. This is more than sufficient for subsequent Voigt profile fitting to characterize the detected MgII absorbers. We make the code publicly available through GitHub. Our work provides a proof-of-concept for future analyses of quasar spectra datasets numbering in the millions, soon to be delivered by the next generation of surveys., Comment: 13 pages, 9 figures, 1 table. Accepted for publication in MNRAS

We present a study of the metal-enriched halo gas, traced using MgII and [OII] emission lines, in two large, blind galaxy surveys - the MUSE (Multi Unit Spectroscopic Explorer) Analysis of Gas around Galaxies (MAGG) and the MUSE Ultra Deep Field (MUDF). By stacking a sample of ~600 galaxies (stellar masses M* ~10^{6-12} Msun), we characterize for the first time the average metal line emission from a general population of galaxy haloes at 0.7 <= z <= 1.5. The MgII and [OII] line emission extends farther out than the stellar continuum emission, on average out to ~25 kpc and ~45 kpc, respectively, at a surface brightness (SB) level of 10^{-20} erg/s/cm2/arcsec2. The radial profile of the MgII SB is shallower than that of the [OII], suggesting that the resonant MgII emission is affected by dust and radiative transfer effects. The [OII] to MgII SB ratio is ~3 over ~20-40 kpc, also indicating a significant in situ origin of the extended metal emission. The average SB profiles are intrinsically brighter by a factor ~2-3 and more radially extended by a factor of ~1.3 at 1.0 < z <= 1.5 than at 0.7 <= z <= 1.0. The average extent of the metal emission also increases independently with increasing stellar mass and in overdense group environments. When considering individual detections, we find extended [OII] emission up to ~50 kpc around ~30-40 percent of the group galaxies, and extended (~30-40 kpc) MgII emission around two z~1 quasars in groups, which could arise from outflows or environmental processes., Comment: 24 pages, 21 figures, 2 tables, accepted for publication in MNRAS

Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm) wavelengths are required to provide a full inventory of the dusty, distant Universe. However, conducting such surveys to the necessary depth, with sub-arcsec angular resolution, is prohibitively time-consuming, even for the most advanced submm/mm telescopes. Here, we report the most recent results from the ALMACAL project, which exploits the 'free' calibration data from the Atacama Large Millimetre/submillimetre Array (ALMA) to map the lines of sight towards and beyond the ALMA calibrators. ALMACAL has now covered 1,001 calibrators, with a total sky coverage around 0.3 deg2, distributed across the sky accessible from the Atacama desert, and has accumulated more than 1,000h of integration. The depth reached by combining multiple visits to each field makes ALMACAL capable of searching for faint, dusty, star-forming galaxies (DSFGs), with detections at multiple frequencies to constrain the emission mechanism. Based on the most up-to-date ALMACAL database, we report the detection of 186 DSFGs with flux densities down to S870um ~ 0.2mJy, comparable with existing ALMA large surveys but less susceptible to cosmic variance. We report the number counts at five wavelengths between 870um and 3mm, in ALMA bands 3, 4, 5, 6 and 7, providing a benchmark for models of galaxy formation and evolution. By integrating the observed number counts and the best-fitting functions, we also present the resolved fraction of the cosmic infrared background (CIB) and the CIB spectral shape. Combining existing surveys, ALMA has currently resolved about half of the CIB in the submm/mm regime., Comment: 22 pages, 16 figures, accepted for publication in MNRAS

We report the first direct measurement of the helium isotope ratio, 3He/4He, outside of the Local Interstellar Cloud, as part of science verification observations with the upgraded CRyogenic InfraRed Echelle Spectrograph (CRIRES). Our determination of 3He/4He is based on metastable HeI* absorption along the line-of-sight towards Tet02 Ori A in the Orion Nebula. We measure a value 3He/4He=(1.77+/-0.13)x10^{-4}, which is just ~40 per cent above the primordial relative abundance of these isotopes, assuming the Standard Model of particle physics and cosmology, (3He/4He)_p = (1.257+/-0.017)x10^-4. We calculate a suite of galactic chemical evolution simulations to study the Galactic build up of these isotopes, using the yields from Limongi & Chieffi (2018) for stars in the mass range M=8-100 M_sun and Lagarde (2011,2012) for M=0.8-8 M_sun. We find that these simulations simultaneously reproduce the Orion and protosolar 3He/4He values if the calculations are initialized with a primordial ratio (3He/4He)_p=(1.043+/-0.089)x10^-4. Even though the quoted error does not include the model uncertainty, this determination agrees with the Standard Model value to within ~2sigma. We also use the present-day Galactic abundance of deuterium (D/H), helium (He/H), and 3He/4He to infer an empirical limit on the primordial 3He abundance, (3He/H)_p < (1.09+/-0.18)x10^-5, which also agrees with the Standard Model value. We point out that it is becoming increasingly difficult to explain the discrepant primordial 7Li/H abundance with non-standard physics, without breaking the remarkable simultaneous agreement of three primordial element ratios (D/H, 4He/H, and 3He/4He) with the Standard Model values., Comment: 23 pages, 9 figures, Resubmitted to the Astrophysical Journal after addressing referee comments

Observations of the cosmic evolution of different gas phases across time indicate a marked increase in the molecular gas mass density towards $z\sim 2-3$. Such a transformation implies an accompanied change in the global distribution of molecular hydrogen column densities ($N_{\rm{H_2}}$). Using observations by PHANGS-ALMA/SDSS and simulations by GRIFFIN/IllustrisTNG we explore the evolution of this H$_2$ column density distribution function [$f(N_{\rm{H}_2})$]. The H$_2$ (and HI) column density maps for TNG50 and TNG100 are derived in post-processing and are made available through the IllustrisTNG online API. The shape and normalization of $f(N_{\rm{H}_2})$ of individual main-sequence star-forming galaxies are correlated with the star formation rate (SFR), stellar mass (${M_*}$), and H$_2$ mass ($M_{\rm{H}_2}$) in both observations and simulations. TNG100, combined with H$_2$ post-processing models, broadly reproduces observations, albeit with differences in slope and normalization. Also, an analytically modelled $f(N)$, based on exponential gas disks, matches well with the simulations. The GRIFFIN simulation gives first indications that the slope of $f(N_{\rm{H}_2})$ might not majorly differ when including non-equilibrium chemistry in simulations. The $f(N_{\rm{H}_2})$ by TNG100 implies that higher molecular gas column densities are reached at $z=3$ than at $z=0$. Further, denser regions contribute more to the molecular mass density at $z=3$. Finally, H$_2$ starts dominating compared to HI only at column densities above log($N_{\rm{H}_2} / \rm{cm}^{-2}) \sim 21.8-22$ at both redshifts. These results imply that neutral atomic gas is an important contributor to the overall cold gas mass found in the ISM of galaxies including at densities typical for molecular clouds at $z=0$ and $z=3$., Comment: 16 pages, 7 figures. Accepted for publication in MNRAS

Cosmic gas makes up about 90% of baryonic matter in the Universe and H$_2$ is the closest molecule to star formation. In this work we study cold neutral gas and its H$_2$ component at different epochs, exploiting state-of-the-art hydrodynamic simulations that include time-dependent atomic and molecular non-equilibrium chemistry coupled to star formation, feedback effects, different UV backgrounds presented in the recent literature and a number of additional processes - such as gas self-shielding, H$_2$ dust grain catalysis, photoelectric and cosmic-ray heating - occurring during structure formation (ColdSIM). We find neutral-gas mass density parameters $ \Omega_{\rm neutral} \simeq $10$^{-3}$ and increasing from lower to higher redshift, in agreement with available HI data. Resulting H$_2$ fractions can be as high as $\sim $50% at $z\sim $4-8, in line with the latest high-$z$ measurements. Albeit dependent on the adopted UV background, derived $ \Omega_{\rm H_2} $ values agree with observations up to $z\sim$7 and both HI and H$_2$ trends are better reproduced by our non-equilibrium H$_2$-based star formation modelling. The predicted gas depletion timescales decrease towards lower $z$, with H$_2$ depletion times remaining below the Hubble time and comparable to the dynamical time at all considered redshifts. This implies that non-equilibrium molecular cooling is efficient at driving cold-gas collapse in a broad variety of environments and since the very early cosmic epochs. In appendix, we show detailed analyses of individual processes, as well as simple numerical parameterizations and fits to account for them. Our findings suggest that, in addition to HI, non-equilibrium H$_2$ observations are pivotal probes for assessing cold-gas abundances and the role of UV background radiation - Abridged, Comment: 15 pages + appendices; accepted for publication on A&A; comments are welcome

We contrast the latest observations of the cosmic metal density in neutral gas ($\rho_{\rm met,neu}$) with three cosmological galaxy evolution simulations: L-GALAXIES 2020, TNG100, and EAGLE. We find that the fraction of total metals that are in neutral gas is $<40$ per cent at $3\lesssim{} z \lesssim{} 5$ in these simulations, whereas observations of damped Lyman-$\alpha$ (DLA) systems suggest $\gtrsim{}85$ per cent. In all three simulations, hot, low-density gas is also a major contributor to the cosmic metal budget, even at high redshift. By considering the evolution in cosmic SFR density ($\rho_{\rm SFR}$), neutral gas density ($\rho_{\rm HI}$), and mean gas-phase metallicity ($[\langle{}{\rm M/H}\rangle{}]_{\rm neu}$), we determine two possible ways in which the $\rho_{\rm met,neu}$ observed in DLAs at high redshift can be matched by simulations: (a) the $\rho_{\rm SFR}$ at $z\gtrsim{}3$ is greater than inferred from current FUV observations, or (b) current high-redshift DLA metallicity samples have a higher mean host mass than the overall galaxy population. If the first is correct, TNG100 would match the ensemble data best, however there would be an outstanding tension between the currently observed $\rho_{\rm SFR}$ and $\rho_{\rm met,neu}$. If the second is correct, L-GALAXIES 2020 would match the ensemble data best, but would require an increase in neutral gas mass inside subhaloes above $z\sim{}2.5$. If neither is correct, EAGLE would match the ensemble data best, although at the expense of over-estimating $[\langle{}{\rm M/H}\rangle{}]_{\rm neu}$. Modulo details related to numerical resolution and HI mass modelling in simulations, these incompatibilities highlight current tensions between key observed cosmic properties at high redshift., Comment: 16 pages, 5 figures. Accepted by MNRAS

Dust is an essential ingredient of galaxies, determining the physical and chemical conditions in the interstellar medium. Several complementary observational evidences indicate that the cosmic dust mass density significantly drops from redshift $z=1$ to $z=0$. Clearly, and for the first time during cosmic evolution, dust must be destroyed more rapidly than it is formed. By considering the dust production/destruction processes acting in this cosmic time lapse, we find that the drop can be explained if dust is mainly destroyed by astration (49\% contribution in the fiducial case) and supernova shocks within galaxies (42\%). Our results further imply that on average each supernova destroys only $M_{d,sn} =0.45\, M_\odot$ of dust, i.e. $5-10$ times less than usually assumed, with a hard upper limit of $M_{d,sn} < {3.0} M_\odot$ set by the available metal budget and maximal grain growth. The lower efficiency might be explained by effective shielding of dust against shock processing in pre-supernova wind shells., Comment: 10 pages, 2 Figures. Comments welcome

Today, the majority of the cosmic baryons in the Universe are not observed directly, leading to an issue of "missing baryons" at low redshift. Cosmological hydrodynamical simulations have indicated that a significant portion of them will be converted into the so-called Warm-Hot Intergalactic Medium (WHIM), with gas temperature ranging between 10$^5$-10$^7$K. While the cooler phase of this gas has been observed using O VI and Ne VIII absorbers at UV wavelengths, the hotter fraction detection relies mostly on observations of O VII and O VIII at X-ray wavelengths. Here, we target the forbidden line of [Fe XXI] $\lambda$ 1354$\unicode{x212B}$ which traces 10$^7$K gas at UV wavelengths, using more than one hundred high-spectral resolution (R$\sim$49,000) and high signal to noise VLT/UVES quasar spectra, corresponding to over 600 hrs of VLT time observations. A stack of these at the position of known DLAs lead to a 5-$\sigma$ limit of $\mathrm{log[N([Fe\,XXI])]<}$17.4 (${EW_{rest}<22}$m$\unicode{x212B}$), three orders of magnitude higher than the expected column density of the WHIM $\mathrm{log[N([Fe\,XXI])]<}$14.5. This work proposes an alternative to X-ray detected 10$^7$K WHIM tracers, by targeting faint lines at UV wavelengths from the ground benefiting from higher instrumental throughput, enhanced spectral resolution, longer exposure times and increased number of targets. The number of quasar spectra required to reach this theoretical column density with future facilities including 4MOST, ELT/HIRES, MSE and the Spectroscopic Telescope appears challenging at present. Probing the missing baryons is essential to constrain the accretion and feedback processes which are fundamental to galaxy formation., Comment: Accepted for publication MNRAS

Measurements of the cosmic far-infrared background (CIB) indicate that emission from many extragalactic phenomena, including star formation and black hole accretion, in the Universe can be obscured by dust. Resolving the CIB to study the population of galaxies in which this activity takes place is a major goal of submillimetre astronomy. Here, we present interferometric 650$\mu$m submillimetre number counts. Using the Band 8 data from the ALMACAL survey, we have analysed 81 ALMA calibrator fields together covering a total area of 5.5~arcmin$^2$. The typical central rms in these fields is $\sim 100 \mu$Jy~beam$^{-1}$ with the deepest maps reaching $\sigma = 47 \mu$Jy~beam$^{-1}$ at sub-arcsec resolution. Multi-wavelength coverage from ALMACAL allows us to exclude contamination from jets associated with the calibrators. However, residual contamination by jets and lensing remain a possibility. Using a signal-to-noise threshold of $4.5\sigma$, we find 21 dusty, star-forming galaxies with 650$\mu$m flux densities of $\geq 0.7 $mJy. At the detection limit we resolve $\simeq 100$ per cent of the CIB at 650$\mu$m, a significant improvement compared to low resolution studies at similar wavelength. We have therefore identified all the sources contributing to the EBL at 650 microns and predict that the contribution from objects with flux 0.7

With this paper we participate to the call for ideas issued by the European Space Agency to define the Science Program and plan for space missions from 2035 to 2050. In particular we present five science cases where major advancements can be achieved thanks to space-based spectroscopic observations at ultraviolet (UV) wavelengths. We discuss the possibility to (1) unveil the large-scale structures and cosmic web in emission at redshift <~1.7; (2) study the exchange of baryons between galaxies and their surroundings to understand the contribution of the circumgalactic gas to the evolution and angular-momentum build-up of galaxies; (3) constrain the efficiency of ram-pressure stripping in removing gas from galaxies and its role in quenching star formation; (4) characterize the progenitor population of core-collapse supernovae to reveal the explosion mechanisms of stars; (5) target accreting white dwarfs in globular clusters to determine their evolution and fate. These science themes can be addressed thanks to UV (wavelength range lambda ~ 90 - 350 nm) observations carried out with a panoramic integral field spectrograph (field of view ~ 1 x 1 arcmin^2 ), and medium spectral (R = 4000) and spatial (~ 1" - 3") resolution. Such a UV-optimized instrument will be unique in the coming years, when most of the new large facilities such as the Extremely Large Telescope and the James Webb Space Telescope are optimized for infrared wavelengths., Comment: White paper submitted in response to the ESA call Voyage 2050. Accepted for publication by Experimental Astronomy

We are just starting to understand the physical processes driving the dramatic change in cosmic star-formation rate between $z\sim 2$ and the present day. A quantity directly linked to star formation is the molecular gas density, which should be measured through independent methods to explore variations due to cosmic variance and systematic uncertainties. We use intervening CO absorption lines in the spectra of mm-bright background sources to provide a census of the molecular gas mass density of the Universe. The data used in this work are taken from ALMACAL, a wide and deep survey utilizing the ALMA calibrator archive. While we report multiple Galactic absorption lines and one intrinsic absorber, no extragalactic intervening molecular absorbers are detected. However, thanks to the large redshift path surveyed ($\Delta z=182$), we provide constraints on the molecular column density distribution function beyond $z\sim 0$. In addition, we probe column densities of N(H$_2$) > 10$^{16}$ atoms~cm$^{-2}$, five orders of magnitude lower than in previous studies. We use the cosmological hydrodynamical simulation IllustrisTNG to show that our upper limits of $\rho ({\rm H}_2)\lesssim 10^{8.3} \text{M}_{\odot} \text{Mpc}^{-3}$ at $0 < z \leq 1.7$ already provide new constraints on current theoretical predictions of the cold molecular phase of the gas. These results are in agreement with recent CO emission-line surveys and are complementary to those studies. The combined constraints indicate that the present decrease of the cosmic star-formation rate history is consistent with an increasing depletion of molecular gas in galaxies compared to $z\sim 2$., Comment: 11 pages, 10 figures, 2 tables, accepted for publication in MNRAS

We present the concept of BlueMUSE, a blue-optimised, medium spectral resolution, panoramic integral field spectrograph based on the MUSE concept and proposed for the Very Large Telescope. With an optimised transmission down to 350 nm, a larger FoV (1.4 x 1.4 arcmin$^2$) and a higher spectral resolution compared to MUSE, BlueMUSE will open up a new range of galactic and extragalactic science cases allowed by its specific capabilities, beyond those possible with MUSE. For example a survey of massive stars in our galaxy and the Local Group will increase the known population of massive stars by a factor $>$100, to answer key questions about their evolution. Deep field observations with BlueMUSE will also significantly increase samples of Lyman-alpha emitters, spanning the era of Cosmic Noon. This will revolutionise the study of the distant Universe: allowing the intergalactic medium to be detected unambiguously in emission, enabling the study of the exchange of baryons between galaxies and their surroundings. By 2030, at a time when the focus of most of the new large facilities (ELT, JWST) will be on the infra-red, BlueMUSE will be a unique facility, outperforming any ELT instrument in the Blue/UV. It will have a strong synergy with ELT, JWST as well as ALMA, SKA, Euclid and Athena., Comment: 60 pages, 22 figures, minor updates

(Abridged) The Maunakea Spectroscopic Explorer (MSE) is an end-to-end science platform for the design, execution and scientific exploitation of spectroscopic surveys. It will unveil the composition and dynamics of the faint Universe and impact nearly every field of astrophysics across all spatial scales, from individual stars to the largest scale structures in the Universe. Major pillars in the science program for MSE include (i) the ultimate Gaia follow-up facility for understanding the chemistry and dynamics of the distant Milky Way, including the outer disk and faint stellar halo at high spectral resolution (ii) galaxy formation and evolution at cosmic noon, via the type of revolutionary surveys that have occurred in the nearby Universe, but now conducted at the peak of the star formation history of the Universe (iii) derivation of the mass of the neutrino and insights into inflationary physics through a cosmological redshift survey that probes a large volume of the Universe with a high galaxy density. MSE is positioned to become a critical hub in the emerging international network of front-line astronomical facilities, with scientific capabilities that naturally complement and extend the scientific power of Gaia, the Large Synoptic Survey Telescope, the Square Kilometer Array, Euclid, WFIRST, the 30m telescopes and many more., Comment: 9 chapters, 301 pages, 100 figures. This version of the DSC is a comprehensive update of the original version, released in 2016, which can be downloaded at arXiv:1606.00043. A detailed summary of the design of MSE is available in the MSE Book 2018, available at arXiv:1810.08695

Gas-rich galaxies are selected efficiently via quasar absorption lines. Recently, a new perspective on such absorption-selected systems has opened up by studying the molecular gas content of absorber host galaxies using ALMA CO emission line observations. Here, we present an analysis of multiple CO transitions ($L'_{\rm CO} \sim 10^9$ K km s$^{-1}$) in two $z \sim 0.5$ galaxies associated with one Ly$\alpha$ absorber towards J0238+1636. The CO spectral line energy distribution (CO SLED) of these galaxies appear distinct from that of typical star-forming galaxies at similar redshifts and is comparable with that of luminous infrared galaxies or AGN. Indeed, these galaxies are associated with optically identified AGN activity. We infer that the CO line ratios and the $\alpha_{\rm CO}$ conversion factor differ from the Galactic values. Our findings suggest that at least a fraction of absorption selected systems shows ISM conditions deviating from those of normal star-forming galaxies. For a robust molecular gas mass calculation, it is therefore important to construct the CO SLED. Absorption-line-selection identifies systems with widely distributed gas, which may preferentially select interacting galaxies, which in turn will have more excited CO SLEDs than isolated galaxies. Furthermore, we raise the question whether quasar absorbers preferentially trace galaxy overdensities., Comment: 5 pages, 3 figures, 3 tables, Accepted for publication in MNRAS

Projected quasar galaxy pairs provide powerful means to study the circumgalactic medium (CGM) that maintains the relics of galactic feedback and the accreted gas from the intergalactic medium. Here, we study the nature of a Lyman Limit system (LLS) with N(HI)=10$^{19.1\pm0.3}$ cm$^{-2}$ and a dust-uncorrected metallicity of [Fe/H]$=-1.1\pm0.3$ at $z=0.78$ towards Q0152$-020$. The MgII absorption profiles are composed of a main saturated and a few weaker optically thin components. Using MUSE observations we detect one galaxy close to the absorption redshift at an impact parameter of 54 kpc. This galaxy exhibits nebular emission lines from which we measure a dust-corrected star formation rate of $10^{+8}_{-5}$ M$_\odot$ yr$^{-1}$ and an emission metallicity of [O/H]$=-0.1\pm0.2$. By combining the absorption line kinematics with the host galaxy morphokinematics we find that while the main absorption component can originate from a galactic wind at $V_{\rm w}=110\pm4$ km s$^{-1}$ the weaker components cannot. We estimate a mass ejection rate of $\dot M\gtrsim0.8$ M$_\odot$ yr$^{-1}$ that translates to a loading factor of $\eta\gtrsim0.1$. Since the local escape velocity of the halo, $V_{\rm esc}\simeq430$ km s$^{-1}$, is a few times larger than $V_{\rm w}$, we expect this gas will remain bound to the host galaxy. These observations provide additional constraints on the physical properties of winds predicted by galaxy formation models. We also present the VLT/X-Shooter data analysis of 4 other absorbing systems at $1.1

Studying the flow of baryons into and out of galaxies is an important part of understanding the evolution of galaxies over time. We present a detailed case study of the environment around an intervening Ly $\alpha$ absorption line system at $z_{\rm abs} = 0.633$, seen towards the quasar J0423$-$0130 ($z_{\rm QSO} = 0.915$). We detect with ALMA the $^{12}$CO(2--1), $^{12}$CO(3--2) and $1.2$~mm continuum emission from a galaxy at the redshift of the Ly $\alpha$ absorber at a projected distance of $135$ kpc. From the ALMA detections, we infer ISM conditions similar to those in low redshift Luminous Infrared Galaxies. DDT MUSE integral field unit observations reveal the optical counterpart of the $^{12}$CO emission line source and three additional emission line galaxies at the absorber redshift, which together form a galaxy group. The $^{12}$CO emission line detections originate from the most massive galaxy in this group. While we cannot exclude that we miss a fainter host, we reach a dust-uncorrected star-formation rate (SFR) limit of > $0.3 \text{M}_{\odot} \text{ yr}^{-1}$ within $100$ kpc from the sightline to the background quasar. We measure the dust-corrected SFR (ranging from $3$ to $50$ M$_{\odot}$ yr$^{-1}$), the morpho-kinematics and the metallicities of the four group galaxies to understand the relation between the group and the neutral gas probed in absorption. We find that the Ly $\alpha$ absorber traces either an outflow from the most massive galaxy or intra-group gas. This case study illustrates the power of combining ALMA and MUSE to obtain a census of the cool baryons in a bounded structure at intermediate redshift., Comment: 17 pages, 9 figures, 9 tables, accepted for publication in MNRAS

We present MUSE observations of the field of the quasar Q0152$-$020 whose spectrum shows a Lyman limit system (LLS) at redshift $z_{\rm abs} = 0.38$, with a metallicity Z $\gtrsim 0.06$ Z$_\odot$. The low ionization metal lines associated with the LLS present two narrow distinct absorption components with a velocity separation of 26 km ${\rm s}^{-1}$. We detect six galaxies within 600 km ${\rm s}^{-1}$ from the absorption redshift; their projected distances from the quasar sightline range from 60 to 200 kpc. The optical spectra of five of these galaxies exhibit prominent nebular emission lines, from which we deduce extinction-corrected star formation rates in the range SFR = 0.06-1.3 M$_\odot$~yr$^{-1}$, and metallicities between 0.2 Z$_\odot$ and Z$_\odot$. The sixth galaxy is only detected in the stellar continuum. By combining our data with archival Keck/HIRES spectroscopy of the quasar and HST/WFPC2 imaging of the field, we can relate absorption line and galaxy kinematics; we conclude that the LLS is most likely associated with the galaxy closest to the quasar sight-line (galaxy "a"). Our morphokinematic analysis of galaxy "a" combined with the absorption line kinematics supports the interpretation that one of the absorption components originates from an extension of the stellar disk of galaxy "a", while the other component may arise in accreting gas in a warped disk with specific angular momentum $\sim 3$ times larger than the specific angular momentum of the galaxy halo. Such warped disks are common features in hydrodynamical simulations of cold-flow accretion onto galaxies; the data presented here provide observational evidence in favour of this scenario., Comment: accepted for publication in MNRAS

In these proceedings we describe the WEAVE-QSO survey, which will observe around 400,000 high redshift quasars starting in 2018. This survey is part of a broader WEAVE survey to be conducted at the 4.2m William Herschel Telescope. We will focus on chiefly on the science goals, but will also briefly summarise the target selection methods anticipated and the expected survey plan. Understanding the apparent acceleration in the expansion of the Universe is one of the key scientific challenges of our time. Many experiments have been proposed to study this expansion, using a variety of techniques. Here we describe a survey that can measure this acceleration and therefore help elucidate the nature of dark energy: a survey of the Lyman-alpha forest (and quasar absorption in general) in spectra towards z>2 quasars (QSOs). Further constraints on neutrino masses and warm dark matter are also anticipated. The same data will also shed light on galaxy formation via study of the properties of inflowing/outflowing gas associated with nearby galaxies and in a cosmic web context. Gas properties are sensitive to density, temperature, UV radiation, metallicity and abundance pattern, and so constraint galaxy formation in a variety of ways. WEAVE-QSO will study absorbers with a dynamic range spanning more than 8 orders of magnitude in column density, their thermal broadening, and a host of elements and ionization species. A core principal of the WEAVE-QSO survey is the targeting of QSOs with near 100% efficiency principally through use of the J-PAS (r < 23.2) and Gaia (r < 20) data., Comment: 8 pages, 2 figures, proceedings of the SF2A conference, Lyon, 2016

We present the study of a sample of nine QSO fields, with damped-Ly-alpha (DLA) or sub-DLA systems at z~0.6, observed with the X-Shooter spectrograph at the Very Large Telescope. By suitably positioning the X-Shooter slit based on high spatial resolution images of HST/ACS we are able to detect absorbing galaxies in 7 out of 9 fields (~ 78\% success rate) at impact parameters from 10 to 30 kpc. In 5 out of 7 fields the absorbing galaxies are confirmed via detection of multiple emission lines at the redshift of DLAs where only 1 out of 5 also emits a faint continuum. In 2 out of these 5 fields we detect a second galaxy at the DLA redshift. Extinction corrected star formation rates (SFR) of these DLA-galaxies, estimated using their H-alpha fluxes, are in the range 0.3-6.7 M_sun yr^-1. The emission metallicities of these five DLA-galaxies are estimated to be from 0.2 to 0.9 Z_sun. Based on the Voigt profile fits to absorption lines we find the metallicity of the absorbing neutral gas to be in a range of 0.05--0.6 Z_sun. The two remaining DLA-galaxies are quiescent galaxies with SFR < 0.4 M_sun yr^-1 (3-sigma) presenting continuum emission but weak or no emission lines. Using X-Shooter spectrum we estimate i-band absolute magnitude of -19.5+/-0.2 for both these DLA-galaxies that indicates they are sub-L* galaxies. Comparing our results with that of other surveys in the literature we find a possible redshift evolution of the SFR of DLA-galaxies., Comment: MNRAS accepted

We use a background quasar to detect the presence of circum-galactic gas around a $z=0.91$ low-mass star forming galaxy. Data from the new Multi Unit Spectroscopic Explorer (MUSE) on the VLT show that the host galaxy has a dust-corrected star-formation rate (SFR) of 4.7$\pm$0.2 Msun/yr, with no companion down to 0.22 Msun/yr (5 $\sigma$) within 240 kpc (30"). Using a high-resolution spectrum (UVES) of the background quasar, which is fortuitously aligned with the galaxy major axis (with an azimuth angle $\alpha$ of only $15^\circ$), we find, in the gas kinematics traced by low-ionization lines, distinct signatures consistent with those expected for a "cold flow disk" extending at least 12 kpc ($3\times R_{1/2}$). We estimate the mass accretion rate $\dot M_{\rm in}$ to be at least two to three times larger than the SFR, using the geometric constraints from the IFU data and the HI column density of $\log N_{\rm HI} \simeq 20.4$ obtained from a {\it HST}/COS NUV spectrum. From a detailed analysis of the low-ionization lines (e.g. ZnII, CrII, TiII, MnII, SiII), the accreting material appears to be enriched to about 0.4 $Z_\odot$ (albeit with large uncertainties: $\log Z/Z_\odot=-0.4~\pm~0.4$), which is comparable to the galaxy metallicity ($12+\log \rm O/H=8.7\pm0.2$), implying a large recycling fraction from past outflows. Blue-shifted MgII and FeII absorptions in the galaxy spectrum from the MUSE data reveal the presence of an outflow. The MgII and FeII doublet ratios indicate emission infilling due to scattering processes, but the MUSE data do not show any signs of fluorescent FeII* emission., Comment: 17 pages, 11 figures, in press (ApJ), minor edits after the proofs. Data available at http://muse-vlt.eu/science/j1422/

The use of background quasars provides a powerful tool to probe the cool gas in the circum-galactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z=0.7-1. We report the detection with both instruments of the H-alpha emission line of one sub-DLA at z_abs=0.94187 with log N(HI)=19.38^+0.10_-0.15 towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR=3.6+/-2.2 solar masses per year in that system. A detailed kinematic study indicates a dynamical mass M_dyn=10^9.9+/-0.4 solar masses and a halo mass M_halo=10^11.9+/-0.5 solar masses. In addition, we report the OII detection with X-Shooter of another DLA at z_abs=0.7402 with log N(HI)=20.4+/-0.1 toward Q0052+0041 and an estimated SFR of 5.3+/-0.7 solar masses per year. Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might be at the redshift of the quasar. We use the objects detected in our whole N(HI)-selected SINFONI survey to compute the metallicity difference between the galaxy and the absorbing gas, delta_HI(X), where a positive (negative) value indicates infall (outflow). We compare this quantity with the quasar line of sight alignment with the galaxy's major (minor) axis, another tracer of infall (outflow). We find that these quantities do not correlate as expected from simple assumptions. Additional observations are necessary to relate these two independent probes of gas flows around galaxies., Comment: 16 pages, 8 figures, accepted for publication in MNRAS

Aims. We have searched for temporal variations of narrow absorption lines in high resolution quasar spectra. A sample of 5 distant sources have been assembled, for which 2 spectra - VLT/UVES or Keck/HIRES - taken several years apart are available. Methods. We first investigate under which conditions variations in absorption line profiles can be detected reliably from high resolution spectra, and discuss the implications of changes in terms of small-scale structure within the intervening gas or intrinsic origin. The targets selected allow us to investigate the time behavior of a broad variety of absorption line systems, sampling diverse environments: the vicinity of active nuclei, galaxy halos, molecular-rich galaxy disks associated with damped Lya systems, as well as neutral gas within our own Galaxy. Results. Absorption lines from MgII, FeII or proxy species with lines of lower opacity tracing the same kind of gas appear to be remarkably stable (1 sigma upper limits as low as 10 % for some components on scales in the range 10 - 100 au), even for systems at z_abs ~ z_e. Marginal variations are observed for MgII lines toward PKS 1229-021 at z_abs = 0.83032; however, we detect no systems displaying changes as large as those reported in low resolution SDSS spectra. In neutral or diffuse molecular media, clear changes are seen for Galactic NaI lines toward PKS 1229-02 (decrease of N by a factor of four for one of the five components over 9.7 yr), corresponding to structure at a scale of about 35 au, in good agreement with known properties of the Galactic interstellar medium. Tentative variations are detected for H2 J=3 lines toward FBQS J2340-0053 at z_abs =2.05454 (~35% change in column density), suggesting the existence of structure at the 10 au-scale for this warm gas. A marginal change is also seen in CI from another velocity component (~70% variation in N(CI))., Comment: 12 pages, 6 figures, to appear in Astronomy & Astrophysics

We report observations of four sub-damped Lyman-alpha (sub-DLA) quasar absorbers at z<0.5 obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at z<0.5 and improved constraints on sub-DLA chemical evolution. All four of our sub-DLAs are consistent with near-solar or super-solar metallicities and relatively modest ionization corrections; observations of more lines and detailed modeling will help to verify this. Combining our data with measurements from the literature, we confirm previous suggestions that the N(HI)-weighted mean metallicity of sub-DLAs exceeds that of DLAs at all redshifts studied, even after making ionization corrections for sub-DLAs. The absorber toward PHL 1598 shows significant dust depletion. The absorbers toward PHL 1226 and PKS 0439-433 show the S/P ratio consistent with solar, i.e., they lack a profound odd-even effect. The absorber toward Q0439-433 shows super-solar Mn/Fe. For several sub-DLAs at z<0.5, [N/S] is below the level expected for secondary N production, suggesting a delay in the release of the secondary N or a tertiary N production mechanism. We constrain the electron density using Si II* and C II* absorption. We also report different metallicity vs. Delta V_90 relations for sub-DLAs and DLAs. For two sub-DLAs with detections of emission lines from the underlying galaxies, our measurements of the absorption-line metallicities are consistent with the emission-line metallicities, suggesting that metallicity gradients are not significant in these galaxies., Comment: 77 pages, 13 figures; accepted for publication in the Astrophysical Journal. Submitted (in the original form) May 26, 2014; accepted Apr. 15, 2015

In this work, we study argon abundances in the interstellar medium of high-redshift galaxies (23.5 are required to probe the final stages of this process of cosmic reionisation., Comment: 14 pages, 9 figures, 7 tables, MNRAS accepted

We report here a study of nitrogen and $\alpha$-capture element (O, S, and Si) abundances in 18 Damped Ly$\alpha$ Absorbers (DLAs) and sub-DLAs drawn from the ESO-UVES Advanced Data Products (EUADP) database. We report 9 new measurements, 5 upper and 4 lower limits of nitrogen that when compiled with available nitrogen measurements from the literature makes a sample of 108 systems. The extended sample presented here confirms the [N/$\alpha$] bimodal behaviour suggested in previous studies. Three-quarter of the systems show $\langle$[N/$\alpha$]$\rangle=-0.85$ ($\pm$0.20 dex) and one-quarter ratios are clustered at $\langle$[N/$\alpha$]$\rangle= -1.41$ ($\pm$0.14 dex). The high [N/$\alpha$] plateau is consistent with the HII regions of dwarf irregular and blue compact dwarf galaxies although extended to lower metallicities and could be interpreted as the result of a primary nitrogen production by intermediate mass stars. The low [N/$\alpha$] values are the lowest ever observed in any astrophysical site. In spite of this fact, even lower values could be measured with the present instrumentation, but we do not find them below [N/$\alpha$] $\approx$ $-1.7$. This suggests the presence of a floor in [N/$\alpha$] abundances, which along with the lockstep increase of N and Si may indicate a primary nitrogen production from fast rotating, massive stars in relatively young or unevolved systems., Comment: 16 pages, 14 figures, 12 tables, MNRAS accepted

Nitrogen is thought to have both primary and secondary origins depending on whether the seed carbon and oxygen are produced by the star itself (primary) or already present in the interstellar medium (secondary) from which star forms. DLA and sub-DLA systems with typical metallicities of -3.0

The gas-phase and stellar metallicities have proven to be important parameters to constrain the star formation history of galaxies. However, HII regions associated with recent star-formation may not have abundances typical for the galaxy as a whole and it is believed that the bulk of the metals may be contained in the neutral gas. It is therefore important to directly probe the metal abundances in the neutral gas, which can be done by using absorption lines imprinted on a background quasar. Recently, we have presented studies of the stellar content of a small sample of such quasar absorbers with HI column densities measured to be in the sub-Damped Lyman-alpha to Damped Lyman-alpha range. Here, we present observations covering 300 nm to 2.5 microns of emission line spectra of three of these absorbing-galaxies using the long-slit spectrograph X-Shooter on the VLT. This allows us to compare the neutral and ionised phase metallicities in the same objects and relates these measures to possible signature of low-metallicity gas accretion or outflows of gas enriched by star formation. Our results suggest that the abundances derived in absorption along the line-of-sight to background quasars are reliable measures of the overall galaxy metallicities. In addition to a comparison of abundances in different phases of the gas, a potential observational consequence of differences in fueling mechanisms for disc galaxies is the internal distribution of their chemical abundances. We present some evidence for small negative metallicity gradients in the three systems. The flat slopes are in line with the differences observed between the two phases of the gas. These results suggest that a comparison of the HI and HII metallicities is a robust indicator of abundance gradients in high-redshift galaxies and do not favour the presence of infall of fresh gas in these objects., Comment: 17 pages, 10 figures, accepted for publication in MNRAS

The circumgalactic medium (CGM) of typical galaxies is crucial to our understanding of the cycling of gas into, through and out of galaxies. One way to probe the CGM is to study gas around galaxies detected via the absorption lines they produce in the spectra of background quasars. Here, we present medium resolution and new ~0.4-arcsec resolution (~3 kpc at z~1) 3D observations with VLT/SINFONI of galaxies responsible for high-N(HI) quasar absorbers. These data allow to determine in details the kinematics of the objects: the four z~1 objects are found to be rotation-supported as expected from inclined discs, while the fifth z~2 system is dispersion-dominated. Two of the systems show sign of interactions and merging. In addition, we use several indicators (star formation per unit area, a comparison of emission and absorption kinematics, arguments based on the inclination and the orientation of the absorber to the quasar line-of-sight and the distribution of metals) to determine the direction of the gas flows in and out of these galaxies. In some cases, our observations are consistent with the gas seen in absorption being due to material co-rotating with their halos. In the case of absorbing-galaxies towards Q1009-0026 and Q2222-0946, these indicators point toward the presence of an outflow traced in absorption., Comment: 18 pages, 11 figures, accepted for publication in MNRAS

The results of a large area, ~600 deg^2, K-band flux-limited spectroscopic survey for luminous quasars are presented. The survey utilises the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) in regions of sky within the Sloan Digital Sky Survey (SDSS) footprint. The K-band excess (KX) of all quasars with respect to Galactic stars is exploited in combination with a photometric redshift/classification scheme to identify quasar candidates for spectroscopic follow-up observations. The data contained within this investigation will be able to provide new constraints on the fraction of luminous quasars reddened by dust with E(B-V)<=0.5 mag. The spectroscopic sample is defined using the K-band, 14.0<=K<=16.6, and SDSS i-band limits of i=19.5, 19.7 and 22.0 over sky areas of 287, 150 and 196 deg^2, respectively. The survey includes >3200 known quasars from the SDSS and more than 250 additional confirmed quasars from the KX-selection. A well-defined sub-sample of quasars in the redshift interval 1.0<=z<=3.5 includes 1152 objects from the SDSS and 172 additional KX-selected quasars. The quasar selection is >95 per cent complete with respect to known SDSS quasars and >95 per cent efficient, largely independent of redshift and i-band magnitude. The properties of the new KX-selected quasars confirm the known redshift-dependent effectiveness of the SDSS quasar selection and provide a sample of luminous quasars experiencing intermediate levels of extinction by dust. The catalogue represents an important step towards the assembly of a well-defined sample of luminous quasars that may be used to investigate the properties of quasars experiencing intermediate levels of dust extinction within their host galaxies or due intervening absorption line systems., Comment: 22 pages, 17 figures, accepted for publication in MNRAS. Resolution of Figures 2 and 5 have been reduced for submission. Tables 4 and 6 are available with the online version

We present for the first time predictions for UV line emission of intergalactic and circumgalactic gas from Adaptive Mesh Resolution (AMR) Large Scale Structure (LSS) simulations at redshifts 0.3

We report three additional SINFONI detections of H-alpha emission line from quasar absorbers, two of which are new identifications. These were targeted among a sample of systems with log N(HI)>19.0 and metallicities measured from high-resolution spectroscopy. The detected galaxies are at impact parameters ranging from 6 to 12 kpc from the quasar's line-of-sight. We derive star formation rates (SFR) of a few solar masses per year for the two absorbers at z_abs~1 and SFR=17 solar masses per year for the DLA at z_abs~2. These three detections are found among a sample of 16 DLAs and sub-DLAs (5 at z_abs~1 and 7 at z_abs~2). For the remaining undetected galaxies, we derive flux limits corresponding to SFR<0.1--11.0 solar masses per year depending on redshift of the absorber and depth of the data. When combined with previous results from our survey for galaxy counterparts to HI-selected absorbers, we find a higher probability of detecting systems with higher metallicity as traced by dust-free [Zn/H] metallicity. We also report a higher detection rate with SINFONI for host galaxies at z_abs~1 than for systems at z_abs~2. Using the NII/H-alpha ratio, we can thus compare absorption and emission metallicities in the same high-redshift objects, more than doubling the number of systems for which such measures are possible., Comment: 16 pages, 8 figures, accepted for publication in MNRAS

[Abridged] In order to understand which process (e.g. galactic winds, cold accretion) is responsible for the cool (T~10^4 K) halo gas around galaxies, we embarked on a program to study the star-formation properties of galaxies selected by their MgII absorption signature in quasar spectra. Specifically, we searched for the H-alpha line emission from galaxies near very strong z=2 MgII absorbers (with rest-frame equivalent width EW>2 \AA) because these could be the sign-posts of outflows or inflows. Surprisingly, we detect H-alpha from only 4 hosts out of 20 sight-lines (and 2 out of the 19 HI-selected sight-lines), despite reaching a star-formation rate (SFR) sensitivity limit of 2.9 M/yr (5-sigma) for a Chabrier initial mass function. This low success rate is in contrast with our z=1 survey where we detected 66%\ (14/21) of the MgII hosts. Taking into account the difference in sensitivity between the two surveys, we should have been able to detect >11.4 of the 20 z=2 hosts whereas we found only 4 galaxies. Interestingly, all the z=2 detected hosts have observed SFR greater than 9 M/yr, well above our sensitivity limit, while at z=1 they all have SFR less than 9 M/yr, an evolution that is in good agreement with the evolution of the SFR main sequence. Moreover, we show that the z=2 undetected hosts are not hidden under the quasar continuum after stacking our data and that they also cannot be outside our surveyed area. Hence, strong MgII absorbers could trace star-formation driven winds in low-mass halos (Mhalo < 10^{10.6} Msun). Alternatively, our results imply that z=2 galaxies traced by strong MgII absorbers do not form stars at a rate expected (3--10 M/yr) for their (halo or stellar) masses, supporting the existence of a transition in accretion efficiency at Mhalo ~ 10^{11} Msun. This scenario can explain both the detections and the non-detections., Comment: 14 pages, 4 fig.; MNRAS in press, minor corrections to match proofs

We present deep ground based imaging of the environments of five QSOs that contain sub-Damped Lyman-alpha systems at z<1 with the SOAR telescope and SOI camera. We detect a clear surplus of galaxies in these small fields, supporting the assumption that we are detecting the galaxies responsible for the absorption systems. Assuming these galaxies are at the redshift of the absorption line systems, we detect luminous L>L* galaxies for four of the five fields within 10" of the QSO. In contrast to previous imaging surveys of DLA systems at these redshifts, which indicate a range of morphological types and luminosities for the host galaxies of the systems, the galaxies we detect in these sub-DLA fields appear to be luminous (L>L*). In the case of the absorber towards Q1009-0026 at z=0.8866 we have spectroscopic confirmation that the candidate galaxy is at the redshift of the absorber, at an impact parameter of ~35 kpc with a luminosity of 3 < L/L* < 8 depending on the magnitude of the K-correction. These observations are in concordance with the view that sub-DLAs may be more representative of massive galaxies than DLA systems. The environments of the absorbers span a range of types, from the inner disk of a galaxy, the periphery of a luminous galaxy, and the outskirts of interacting galaxies. The large impact parameters to some of the candidate galaxies suggest that galactic outflows or tidal tails are likely responsible for the material seen in absorption. We find a weak correlation between N(HI) and the impact parameter at the 2 sigma level, which may be expected from the heterogeneous population of galaxies hosting the absorption line systems and random orientation angles. In addition, we detect a possible gravitationally lensed image of the BL-Lac object Q0826-2230., Comment: 11 pages, 4 Figures, Accepted for Publication in MNRAS

Details of processes through which galaxies convert their gas into stars need to be studied in order to obtain a complete picture of galaxy formation. One way to tackle these phenomena is to relate the HI gas and the stars in galaxies. Here, we present dynamical properties of Damped and sub-Damped Lyman-alpha Systems identified in H-alpha emission with VLT/SINFONI at near infra-red wavelengths. While the DLA towards Q0302-223 is found to be dispersion-dominated, the sub-DLA towards Q1009-0026 shows clear signatures of rotation. We use a proxy to circular velocity to estimate the mass of the halo in which the sub-DLA resides and find M_halo=10^12.6 M_sun. We also derive dynamical masses of these objects, and find M_dyn=10^10.3 M_sun and 10^10.9 M_sun. For one of the two systems (towards Q0302-223), we are able to derive a stellar mass of M_*=10^9.5 M_sun from Spectral Energy Distribution fit. The gas fraction in this object is 1/3rd, comparable to similar objects at these redshifts. Our work illustrates that detailed studies of quasar absorbers can offer entirely new insights into our knowledge of the interaction between stars and the interstellar gas in galaxies., Comment: 6 pages, 2 figures. Accepted for publication in MNRAS

Detailed studies of Damped and sub-Damped Lyman-alpha systems (DLA), the galaxies probed by the absorption they produce in the spectra of background quasars, rely on identifying the galaxy responsible for the absorber with more traditional methods. Integral field spectroscopy provides an efficient way of detecting faint galaxies near bright quasars, further providing immediate redshift confirmation. Here, we report the detection of H-alpha emission from a DLA and a sub-DLA galaxy among a sample of 6 intervening quasar absorbers targeted. We derive F(H-alpha)=7.7+/-2.7*10^-17 erg/s/cm^2 (SFR=1.8+/-0.6 M_sun/yr) at impact parameter b=25 kpc towards quasar Q0302-223 for the DLA at z_abs=1.009 and F(H-alpha)=17.1+/-6.0*10^-17 erg/s/cm^2 (SFR=2.9+/-1.0 M_sun/yr) at b=39 kpc towards Q1009-0026 for the sub-DLA at z_abs=0.887. These results are in line with low star formation rates previously reported in the literature for quasar absorbers. We use the NII 6585/H-alpha ratio to derive the HII emission metallicities and compare them with the neutral gas H I absorption metallicities derived from high-resolution spectra. In one case, the absorption metallicity is actually found to be higher than the emission line metallicity. For the remaining objects, we achieve 3-sigma limiting fluxes of the order F(H-alpha)~10^-17 erg/s/cm^2 (corresponding to SFR~ 0.1 M_sun/yr at z~1 and ~1 M_sun/yr at z~2), i.e. among the lowest that have been possible with ground-based observations. We also present two other galaxies associated with C IV systems and serendipitously discovered in our data., Comment: 16 pages, 8 figures. Accepted for publication in MNRAS

We have measured redshifts for 243 z ~3 quasars in nine VLT VIMOS LBG redshift survey areas, each of which is centred on a known bright quasar. Using spectra of these quasars, we measure the cross-correlation between neutral hydrogen gas causing the Lya forest and 1020 Lyman-break galaxies at z ~3. We find an increase in neutral hydrogen absorption within 5 h^-1 Mpc of a galaxy in agreement with the results of Adelberger et al. (2003, 2005). The Lya-LBG cross-correlation can be described by a power-law on scales larger than 3 h^-1 Mpc. When galaxy velocity dispersions are taken into account our results at smaller scales (<2 h^-1 Mpc) are also in good agreement with the results of Adelberger et al. (2005). There is little immediate indication of a region with a transmission spike above the mean IGM value which might indicate the presence of star-formation feedback. To measure the galaxy velocity dispersions, which include both intrinsic LBG velocity dispersion and redshift errors, we have used the LBG-LBG redshift space distortion measurements of Bielby et al. (2010). We find that the redshift-space transmission spike implied in the results of Adelberger et al. (2003) is too narrow to be physical in the presence of the likely LBG velocity dispersion and is likely to be a statistical fluke. Nevertheless, neither our nor previous data can rule out the presence of a narrow, real-space transmission spike, given the evidence of the increased Lya absorption surrounding LBGs which can mask the spike's presence when convolved with a realistic LBG velocity dispersion. Finally, we identify 176 CIV systems in the quasar spectra and find an LBG-CIV correlation strength on scales of 10 h^-1 Mpc consistent with the relation measured at ~Mpc scales., Comment: 33 pages, 16 figures, accepted by MNRAS

We searched for evidence of reddening of background SDSS QSO spectra due to dust in intervening DLA systems. We utilise the Data Releases 5 and 7 to arrive at sample sizes of 475 (DR5) and 676 (DR7) absorbers, based on two different published lists of SDSS DLAs. Both samples span roughly the redshift range of 2.2 < z_abs < 5.2, with a mean of z~3.0, and the majority of the DLAs (75%) below z=3.3. We construct geometric mean spectra in the absorber restframes ranging from 1240 to ~2800 A, and composite spectra of samples matching the 'DLA' QSOs in i band magnitude and emission redshift z_em, but without absorption lines. By comparing the slopes of these composite spectra with their matched counterparts, we find no sign of reddening in the ensemble of the absorbers from these samples. Owing to both the unprecedently large sizes of the DLA samples themselves and the non-DLA SDSS QSO sample, from which we can draw our matching spectra, we can place very tight limits for this non-detection ( =-0.0013+-0.0025 (DR5) and =-0.0017+-0.0022 (DR7). Interestingly, when applying our technique to the samples of York et. al. (2006), vandenBerk et al. (2008) (intervening and intrinsic MgII absorbers) and the smaller DLA-subsample and pool of comparison QSOs of Vladilo et al. (2008), we do recover their results, i.e. detect the same amount of reddening as these authors do. Furthermore, we have tested whether subsamples of our large sample in categories involving the absorbers (HI column densities, presence or absence of accompanying metal absorption, absorber redshift) or the background quasars (emission redshift, brightness) do reveal dust extinction, but found no trends. These results are at odds with both detections of dust reddening from previous studies, and also with expectations from observations of high-redshift galaxies. (abridged), Comment: 16 pages, 12 figures, accepted for publication in MNRAS

We have combined the results from our recent observations of Damped and sub-Damped Lyman-alpha systems with the MIKE and UVES spectrographs on the Magellan Clay and VLT Kueyen telescopes with ones from the literature to determine the N(HI)-weighted mean metallicity of these systems based both on Fe, a depleted element in QSO absorbers and the local ISM, and Zn a relatively undepleted element. In each case, the N(HI)-weighted mean metallicity is higher and shows faster evolution in sub-DLAs than the classical DLA systems. Large grids of photoionisation models over the sub-DLA \nhI range with CLOUDY show that the ionisation corrections to the abundances are in general small, however the fraction of ionized H can be up to ~90 per cent. The individual spectra have been shifted to the rest frame of the absorber and averaged together to determine the average properties of these systems at z<1.5. We find that the average abundance pattern of the Sub-DLA systems is similar to the gas in the halo of the Milky Way, with an offset of ~0.3 dex in the overall metallicity. Both DLAs and Sub-DLAs show similar characteristics in their relative abundances patterns, although the DLAs have smaller <[Mn/Zn]> as well as higher <[Ti/Zn]> and <[Cr/Zn]>. We calculate the contribution of sub-DLAs to the metal budget of the Universe, and find that the sub-DLA systems at z<1.5 contain a comoving density of metals Omega_met (3.5-15.8)x10^{5} M_sun Mpc^{-3}, at least twice the comoving density of metals in the DLA systems. The sub-DLAs do however track global chemical evolution models much more closely than do the DLAs, perhaps indicating that they are a less dust biased metallicity indicator of galaxies at high redshifts than the DLA systems., Comment: 13 Pages, 14 Pages: Accepted for Publication in MNRAS 5/2009 Added/Fixed references