We report the serendipitous detection of an H-2-bearing damped Lya absorber at z = 0.576 in the spectrum of the QSO J0111-0316 in the Cosmic Ultraviolet Baryon Survey. Spectroscopic observations from Hubble Space Telescope-COS in the far-ultraviolet reveal a damped absorber with log[N(H I)/cm(-2)] = 20.1 +/- 0.2 and log[N(H-2)/cm(-2)] = 18.97(-0.06)(+0.05). The diffuse molecular gas is found in two velocity components separated by Delta nu 60 km s(-1), with >99.9% of the total H-2 column density concentrated in one component. At a metallicity of approximate to 50% of solar, there is evidence for Fe enhancement and dust depletion, with a dust-to-gas ratio kappa(O) approximate to 0.4. A galaxy redshift survey conducted with IMACS and LDSS-3C on Magellan reveals an overdensity of nine galaxies at projected distance d <= 600 proper kpc (pkpc) and line-of-sight velocity offset Delta nu(g) <= 300 km s(-1) from the absorber. The closest is a massive, early-type galaxy at d = 41 pkpc that contains approximate to 70% of the total stellar mass identified at d <= 310 pkpc of the H-2 absorber. The close proximity of the H-2-bearing gas to the quiescent galaxy and the Fe-enhanced chemical abundance pattern of the absorber suggest a physical connection, in contrast to a picture in which DLAs are primarily associated with gas-rich dwarfs. This case study illustrates that deep galaxy redshift surveys are needed to gain insight into the diverse environments that host dense and potentially starforming gas.

This tarball collects the processed data that are included in Y. Chen et al, 2020, "The Keck Baryonic Structure Survey: Using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at z~2".Here is how this file is organised. cats - KBSS catalogs as of Jan 2019, organized as FITS tables. This can be slightly different to the most recent KBSS catalog released at http://ramekin.caltech.edu/KBSS. lya_spec - The stacked spectra near Lya for the KGPS-Full and KGPS- zneb samples. Wavelengths are included as FITS-WCS in the header. The weight spectra are 1/sigma^2, estimated from bootstrap. These files are used to make Figure 5, and subsequently the 2D optical depth maps. wlya - Lya equivalent width as a function of impact parameter, stored as FITS tables. The table entries are, [dtran] - impact parameter; [dtran_lo] - lower edge of the "dtran" bins; [dtran_hi] - higher edge of the "dtran" bins; [ew] - Lya equivalent width; [ew_lo] - the lower 1-sigma limit of "ew"; [ew_hi] - the higher 1-sigma limit of "ew". These data are used to make Figure 6. tau_2d - 2D absorption maps, stored as multi-extension FITS files. [ext 0] - apparent optical depth; [ext 1] - 1-sigma error of ext 1; [ext 2] - dtran and vlos grids of ext 1 and 2. These are used to make Figures 7, 8, 9, 13, 14, 16, 17, 18. model - Best-fit model of the 2D absorption map, in multi-extension FITS. [ext 0] - modeled apparent optical depth; [ext 1] - grid. These are used to make Figure 13. Cite this record as:Chen, Y., Steidel, C., Hummels, C., Rudie, G., Dong, B., Trainor, R., Bogosavljevic, M., Erb, D., Pettini, M., Reddy, N., Shapley, A., Strom, A., Theios, R., Faucher-Giguere, C.-A., & Keres, D. (2020). KBSS Data: structure and kinematics of circumgalactic H I (Version 1.0) [Data set]. CaltechDATA. https://doi.org/10.22002/D1.1458 or choose a different citation style.Download Citation Unique Views: 14Unique Downloads: 1 between July 22, 2020 and July 12, 2021More info on how stats are collected Copyright: cc-zero

We present the discovery of neutral gas detected in both damped Ly alpha absorption (DLA) and H i 21 cm emission outside of the stellar body of a galaxy, the first such detection in the literature. A joint analysis between the Cosmic Ultraviolet Baryon Survey and the MeerKAT Absorption Line Survey reveals an H i bridge connecting two interacting dwarf galaxies (log (M (star)/M (circle dot)) = 8.5 +/- 0.2) that host a z = 0.026 DLA with log[N(H i)/cm(-2)] = 20.60 +/- 0.05 toward the QSO J2339-5523 (z (QSO) = 1.35). At impact parameters of d = 6 and 33 kpc, the dwarf galaxies have no companions more luminous than approximate to 0.05L (*) within at least Delta v = +/- 300 km s(-1) and d approximate to 350 kpc. The H i 21 cm emission is spatially coincident with the DLA at the 2 sigma-3 sigma level per spectral channel over several adjacent beams. However, H i 21 cm absorption is not detected against the radio-bright QSO; if the background UV and radio sources are spatially aligned, the gas is either warm or clumpy (with a spin temperature to covering factor ratio T ( s )/f ( c ) > 1880 K). Observations with VLT-MUSE demonstrate that the alpha-element abundance of the ionized interstellar medium (ISM) is consistent with the DLA (approximate to 10% solar), suggesting that the neutral gas envelope is perturbed ISM gas. This study showcases the impact of dwarf-dwarf interactions on the physical and chemical state of neutral gas outside of star-forming regions. In the SKA era, joint UV and H i 21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments.

We present a detailed study of two partial Lyman limit systems (pLLSs) of neutral hydrogen column density N-HI approximate to ( 1 - 3) x 10(16) cm(-2 )discovered at z = 0.5 in the Cosmic Ultraviolet Baryon Survey (CUBS). Available far-ultraviolet spectra from the Hubble Space Telescope Cosmic Origins Spectrograph and optical echelle spectra from MIKE on the Magellan Telescopes enable a comprehensive ionization analysis of diffuse circumgalactic gas based on resolved kinematics and abundance ratios of atomic species spanning five different ionization stages. These data provide unambiguous evidence of kinematically aligned multiphase gas that masquerades as a single-phase structure and can only be resolved by simultaneous accounting of the full range of observed ionic species. Both systems are resolved into multiple components with inferred alpha-element abundance varying from [alpha/H] approximate to-0.8 to near solar and densities spanning over two decades from log n(H)/cm(-3) approximate to -2.2 to < -4.3. Available deep galaxy survey data from the CUBS program taken with VLT/MUSE, Magellan/LDSS3-C and Magellan/IMACS reveal that the z = 0.47 system is located 55 kpc from a star-forming galaxy with prominent Balmer absorption of stellar mass M-star approximate to 2 x 10(10 )M(circle dot), while the z = 0.54 system resides in an overdense environment of 11 galaxies within 750 kpc in projected distance, with the most massive being a luminous red galaxy of M-star approximate to 2 x 10(11) M-circle dot at 375 kpc. The study of these two pLLSs adds to an emerging picture of the complex, multiphase circumgalactic gas that varies in chemical abundances and density on small spatial scales in diverse galaxy environments. The inhomogeneous nature of metal enrichment and density revealed in observations must be taken into account in theoretical models of diffuse halo gas.

We present the first statistical analysis of kinematically resolved, spatially extended emission around z = 2-3 galaxies in the Keck Baryonic Structure Survey (KBSS) using the Keck Cosmic Web Imager (KCWI). Our sample of 59 star-forming galaxies (z(med) = 2.29) comprises the subset with typical KCWI integration times of similar to 5 h and with existing imaging data from the Hubble Space Telescope and/or adaptive optics-assisted integral field spectroscopy. The high-resolution images were used to evaluate the azimuthal dependence of the diffuse emission with respect to the stellar continuum within projected galactocentric distances of less than or similar to 30 proper kpc. We introduce cylindrically projected 2D spectra (CP2D) that map the averaged spectral profile over a specified range of azimuthal angle, as a function of impact parameter around galaxies. The averaged CP2D spectrum of all galaxies shows clear signatures of resonant scattering by outflowing gas. We stacked the CP2D spectra of individual galaxies over ranges of azimuthal angle with respect to their major axes. The extended emission along the galaxy principal axes is statistically indistinguishable, with residual asymmetry of <= 2 percent (similar to 2 sigma) of the integrated emission. The symmetry implies that the scattering medium is dominated by outflows in all directions within 30 kpc. Meanwhile, we find that the blueshifted component of emission is marginally stronger along galaxy minor axes for galaxies with relatively weak emission. We speculate that this weak directional dependence of emission becomes discernible only when the escape fraction is low. These discoveries highlight the need for similar analyses in simulations with radiative transfer modelling.

We present a systematic investigation of physical conditions and elemental abundances in four optically thick Lyman-limit systems (LLSs) at z = 0.36-0.6 discovered within the cosmic ultraviolet baryon survey (CUBS). Because intervening LLSs at z < 1 suppress far-UV (ultraviolet) light from background QSOs, an unbiased search of these absorbers requires a near-UV-selected QSO sample, as achieved by CUBS. CUBS LLSs exhibit multicomponent kinematic structure and a complex mix of multiphase gas, with associated metal transitions from multiple ionization states such as CII, CIII, NIII, MgII, SIII, SIIII, OII, OIII, OvI, and FeII absorption that span several hundred km s(-1) in line-of-sight velocity. Specifically, higher column density components (logN(HI)/cm(-2) greater than or similar to 16) in all four absorbers comprise dynamically cool gas with K and modest non-thermal broadening of km s(-1). The high quality of the QSO absorption spectra allows us to infer the physical conditions of the gas, using a detailed ionization modelling that takes into account the resolved component structures of Hi and metal transitions. The range of inferred gas densities indicates that these absorbers consist of spatially compact clouds with a median line-of-sight thickness of pc. While obtaining robust metallicity constraints for the low density, highly ionized phase remains challenging due to the uncertain , we demonstrate that the cool-phase gas in LLSs has a median metallicity of , with a 16-84 percentile range of [alpha/H] = (-1.3, -0.1). Furthermore, the wide range of inferred elemental abundance ratios ([C/alpha], [N/alpha], and [Fe/alpha]) indicate a diversity of chemical enrichment histories. Combining the absorption data with deep galaxy survey data characterizing the galaxy environment of these absorbers, we discuss the physical connection between star-forming regions in galaxies and diffuse gas associated with optically thick absorption systems in the z < 1 circumgalactic medium.

The intergalactic medium (IGM) acts like a calorimeter recording energy injection by cosmic structure formation, shocks and photoheating from stars and active galactic nuclei. It was recently proposed that spatially inhomogeneous TeV-blazars could significantly heat up the underdense IGM, resulting in patches of both cold and warm IGM around z similar or equal to 2-3. The goal of this study is to compare predictions of different blazar heating models with recent observations of the IGM. We perform a set of cosmological simulations and carefully compute mock observables of the Lyman-alpha (Ly alpha) forest. We perform a detailed assessment of different systematic uncertainties which typically impact this type of observables and find that they are smaller than the differences between our models. We find that our inhomogeneous blazar heating model is in good agreement with the Ly alpha line properties and the rescaled flux probability distribution function at high redshift (2.5 < z < 3) but that our blazar heating models are challenged by lower redshift data (2 < z < 2.5). Our results could be explained by hell reionization although state-of-the-art models fall short on providing enough heating to the low-density IGM, thus motivating further radiative transfer studies of inhomogeneous hell reionization. If blazars are indeed hosted by group-mass haloes of 2 x 10(13)M(circle dot), a later onset of blazar heating in comparison with previous models would be favoured, which could bring our findings here in agreement with the evidence of blazar heating from local gamma-ray observations.

Metal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low-metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six local (z < 0.02) galaxies that power strong nebular C iv emission approaching that encountered at z > 6. We find that the strength and spectral profile of the nebular C iv in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C iv escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe 2-4 times above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high redshift, but also suggests a unique path toward validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra.

The combination of the MOSDEF and KBSS-MOSFIRE surveys represents the largest joint investment of Keck/MOSFIRE time to date, with similar to 3000 galaxies at 1.4 less than or similar to z less than or similar to 3.8, roughly half of which are at z similar to 2. MOSDEF is photometric- and spectroscopic-redshift selected with a rest-optical magnitude limit, while KBSS-MOSFIRE is primarily selected based on rest-UV colours and a rest-UV magnitude limit. Analysing both surveys in a uniform manner with consistent spectral-energy-distribution (SED) models, we find that the MOSDEF z similar to 2 targeted sample has higher median M-* and redder rest U-V colour than the KBSS-MOSFIRE z similar to 2 targeted sample, and smaller median SED-based SFR and sSFR (SFR(SED) and sSFR(SED)). Specifically, MOSDEF targeted a larger population of red galaxies with U-V and V-J >= 1.25, while KBSS-MOSFIRE contains more young galaxies with intense star formation. Despite these differences in the z similar to 2 targeted samples, the subsets of the surveys with multiple emission lines detected and analysed in previous work are much more similar. All median host-galaxy properties with the exception of stellar population age - i.e. M-*, SFR(SED), sSFR(SED), A(V), and UVJ colours - agree within the uncertainties. Additionally, when uniform emission-line fitting and stellar Balmer absorption correction techniques are applied, there is no significant offset between both samples in the [O iii]lambda 5008/H beta versus [N ii]lambda 6585/H alpha diagnostic diagram, in contrast to previously reported discrepancies. We can now combine the MOSDEF and KBSS-MOSFIRE surveys to form the largest z similar to 2 sample with moderate-resolution rest-optical spectra and construct the fundamental scaling relations of star-forming galaxies during this important epoch.