We present results of a deep spectroscopic survey quantifying the statistics of the escape of ionizing radiation from star -forming galaxies at z similar to 3. We measure the ratio of ionizing to non-ionizing UV flux density f(900)/f(1500)obs, where f(900) is the mean flux density evaluated over the range [880, 910] angstrom. We quantify the emergent ratio of ionizing to non-ionizing UV flux density by analyzing high signal-to-noise ratio composite spectra formed from subsamples with common observed properties and numbers sufficient to reduce the statistical uncertainty in the modeled IGM+CGM correction to obtain precise values of < f(900)/f(1500)>(out), including a full-sample average < f(900)/f(1500)>(out) 0.057 +/- 0.006. We show that < f(900)/f(1500)>(out) increases., monotonically with W lambda(Ly alpha), inducing an inverse correlation with UV luminosity as a by-product. We fit the composite spectra using stellar spectral synthesis together with models of the ISM in which a fraction f(c) of the stellar continuum is covered by gas with column density NH (I). We show that the composite spectra simultaneously constrain the intrinsic properties of the stars (L90041500)int along with f(c), N-H (I), E (B - V), and f(esc,abs), the absolute escape fraction of ionizing photons. We find a sample-averaged f(esc,abs) 0.09 +/- 0.01, with subsamples falling along a linear relation < f(esc),(abs)> similar or equal to 0.75[W-lambda(Ly alpha)/110 angstrom]. Using the far-UV luminosity function, the distribution function n(W(Lya)), and the relationship between WA(Ly alpha) and < f(900)/f(1500)>(out), we estimate the total ionizing emissivity of z similar to 3 star forming galaxies with M-uv <= -19.5, which exceeds the contribution of quasi-stellar objects by a factor of similar to 3, and accounts for similar to 50% of the total is an element of(Lyc) at z similar to 3 estimated using indirect methods.

We present Keck/OSIRIS laser guide-star assisted adaptive optics (LGSAO) integral-field spectroscopy of [O III].5007 nebular emission from 12 galaxies hosting optically faint (R = 20-25; nu L-nu similar to 10(44) - 10(46) erg s(-1)) active galactic nuclei (AGNs) at redshift z similar to 2-3. In combination with deep Hubble Space Telescope Wide Field Camera 3 (HST/WFC3) rest-frame optical imaging, Keck/MOSFIRE rest-optical spectroscopy, and Keck/KCWI rest-UV integral-field spectroscopy, we demonstrate that both the continuum and emission-line structures of these sources exhibit a wide range of morphologies, from compact, isolated point sources to double-AGN merging systems with extensive similar to 50 kpc tidal tails. One of the 12 galaxies previously known to exhibit a proximate damped Lya system coincident in redshift with the galaxy shows evidence for both an extended [O III] narrow-line emission region and spatially offset Lya emission (with morphologically distinct blueshifted and redshifted components) indicative of large-scale gas flows photoionized by the central AGN. We do not find widespread evidence of star formation in the host galaxies surrounding these AGNs; the [O III] velocity dispersions tend to be high (sigma = 100-500 km s(-1)), the continuum morphologies are much more compact than a mass-matched star-forming comparison sample, and the diagnostic nebular emission-line ratios are dominated by an AGN-like ionizing spectrum. The sample is most consistent with a population of AGNs that radiate at approximately their Eddington limit and photoionize extended [O III] nebulae whose characteristic sizes scale approximately as the square root of the AGN luminosity.

This Letter reports the discovery of spatially extended line-emitting nebula, reaching to approximate to 100 physical kpc (pkpc) from a damped Ly alpha absorber (DLA) at z(DLA) = 0.313 along the sightline toward quasi-stellar object (QSO) PKS 1127-145 (z(Q)(SO) = 1.188). This DLA was known to be associated with a galaxy group of dynamical mass M-group similar to 3 x 10(12) M-circle dot, but its physical origin remained ambiguous. New wide-field integral field observations revealed a giant nebula detected in [O II], H beta, [O III], H alpha, and [N II] emission, with the line-emitting gas following closely the motions of group galaxies. One of the denser streams passes directly in front of the QSO with kinematics that are consistent with the absorption profiles recorded in the QSO echelle spectra. The emission morphology, kinematics, and line ratios of the nebula suggest that shocks and turbulent mixing layers, produced as a result of stripped gaseous streams moving at supersonic speed across the ambient hot medium, contribute significantly to the ionization of the gas. While the DLA may not be associated with any specific detected member of the group, both the kinematic and dust properties are consistent with the DLA originating in streams of gas stripped from sub-L-* group members at less than or similar to 25 pkpc from the QSO sightline. This study demonstrates that gas stripping in low-mass galaxy groups is effective in releasing metal-enriched gas from star-forming regions, producing absorption systems in QSO spectra, and that combining absorption and emission-line observations provides an exciting new opportunity for studying gas and galaxy co-evolution.

We present results from the Keck Baryonic Structure Survey (KBSS) including the first detailed measurements of the column densities, kinematics, and internal energy of metal-bearing gas within the virial radius (35?100 physical kpc) of eight ?L* galaxies at z?2. From our full sample of 130 metal-bearing absorbers, we infer that halo gas is kinematically complex when viewed in singly, doubly, and triply ionized species. Broad O vi and C iv absorbers are detected at velocities similar to the lower-ionization gas but with a very different kinematic structure, indicating that the circumgalactic medium (CGM) is multiphase. There is a high covering fraction of metal-bearing gas within 100 kpc, including highly ionized gas such as O vi; however, observations of a single galaxy probed by a lensed background QSO suggest the size of metal-bearing clouds is small (vi-bearing gas). The mass in metals found within the halo is substantial, equivalent to ?25% of the metal mass within the interstellar medium. The gas kinematics unambiguously show that 70% of galaxies with detected metal absorption have some unbound metal-enriched gas, suggesting galactic winds may commonly eject gas from halos at z?2. When modeled assuming that ions with different ionization potentials can originate within a single gaseous structure, significant thermal broadening is detected in CGM absorbers that dominates the internal energy of the gas. Some 40% of the detected gas has temperatures in the range 10(4.5?5.5) K where cooling times are short, suggesting the CGM is dynamic, with constant heating or cooling to produce this short-lived thermal phase.

We present initial results from the Cosmic Ultraviolet Baryon Survey (CUBS). CUBS is designed to map diffuse baryonic structures at redshift z less than or similar to 1 using absorption-line spectroscopy of 15 UV-bright QSOs with matching deep galaxy survey data. CUBS QSOs are selected based on their NUV brightness to avoid biases against the presence of intervening Lyman limit systems (LLSs) at z(abs) < 1. We report five new LLSs of log N(H I)/cm(-2) greater than or similar to 17.2 over a total redshift survey path-length of Delta z(LL) = 9.3, and a number density of n(z) = 0.43(-0.18)(+0.26) . Considering all absorbers with log N(H I)/cm(-2) > 16.5 leads to n(z) = 1.08(-0.25)(+0.31) at z(abs) < 1. All LLSs exhibit a multicomponent structure and associated metal transitions from multiple ionization states such as C II, CIII, MgII, Si II, Si III, and OVI absorption. Differential chemical enrichment levels as well as ionization states are directly observed across individual components in three LLSs. We present deep galaxy survey data obtained using the VLT-MUSE integral field spectrograph and the Magellan Telescopes, reaching sensitivities necessary for detecting galaxies fainter than 0.1L(*) at d less than or similar to 300 physical kpc (pkpc) in all five fields. A diverse range of galaxy properties is seen around these LLSs, from a low-mass dwarf galaxy pair, a co-rotating gaseous halo/disc, a star-forming galaxy, a massive quiescent galaxy, to a galaxy group. The closest galaxies have projected distances ranging from d = 15 to 72 pkpc and intrinsic luminosities from approximate to 0.01L(*) to approximate to 3L(*). Our study shows that LLSs originate in a variety of galaxy environments and trace gaseous structures with a broad range of metallicities.

We present new measurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z similar to 2. Using the spectra of similar or equal to 3000 galaxies with redshifts < z > = 2.3 +/- 0.4 from the Keck Baryonic Structure Survey, we assemble a sample of more than 200 000 distinct foreground-background pairs with projected angular separations of 3-500 arcsec and spectroscopic redshifts, with < z(fg)> = 2.23 and < z(bg)> = 2.57 (foreground, background redshifts, respectively.) The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess HI Ly alpha optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 less than or similar to D-tran/pkpc less than or similar to 4000) and line-of-sight velocity. We obtain accurate galaxy systemic redshifts, providing significant information on the line-of-sight kinematics of HI gas as a function of projected distance D-tran. We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of HI. The best-fitting model suggests that galaxy-scale outflows with initial velocity v(out) similar or equal to 600 km s(-1) dominate the kinematics of circumgalactic HI out to D-tran similar or equal to 50 kpc, while HI at D-tran greater than or similar to 100 kpc is dominated by infall with characteristic v(in) less than or similar to circular velocity. Over the impact parameter range 80 less than or similar to D-tran/pkpc less than or similar to 200, the HI line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Ly alpha equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond D-tran similar or equal to 300 pkpc (similar to 1 cMpc), the line-of-sight kinematics are dominated by Hubble expansion.

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.