Citation for published item:intongeD em¡ elie nd gtinellD frr nd oniD vind tF nd uu'mnnD quinevere nd qenzelD einhrd nd gorteseD vu nd hv¡ eD omeel nd pletherD homs tF nd qri¡ EgrpioD tvier nd urmerD grsten nd rekmnD imothy wF nd tnowiekiD teven nd vutzD uthrin nd osrioD hvid nd himinovihD hvid nd husterD url nd ngD ting nd uytsD tijn nd forthkurD nhyeet nd vmpertiD ssell nd oertsEforsniD quido F @PHIUA 9xgyvh qe X the omplete sew QH m legy survey of moleulr gs for glxy evolution studiesF9D estrophysil journl supplement seriesFD PQQ @PAF pF PPF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe introduce xCOLD GASS, a legacy survey providing a census of molecular gas in the local universe. Building on the original COLD GASS survey, we present here the full sample of 532 galaxies with CO (1-0) measurements from the IRAM 30 m telescope. The sample is mass-selected in the redshift interval z 0.01 0.05 < < from the Sloan Digital Sky Survey (SDSS) and therefore representative of the local galaxy population with M M 10 9 * >  . The CO (1-0) flux measurements are complemented by observations of the CO (2-1) line with both the IRAM 30 m and APEX telescopes, H I observations from Arecibo, and photometry from SDSS, WISE, and GALEX. Combining the IRAM and APEX data, we find that the ratio of CO (2-1) to CO (1-0) luminosity for integrated measurements is r 0.79 0.03 21 =  , with no systematic variations across the sample. The CO (1-0) luminosity function is constructed and best fit with a Schechter function with parameters L 7.77 2.11 10 K km s pc 9 M  , we are able to extend our study of gas scaling relations and confirm that both molecular gas fractions ( f H 2 ) and depletion timescale (t H dep 2 ( )) vary with specific star formation rate (or offset from the star formation main sequence) much more strongly than they depend on stellar mass. Comparing the xCOLD GASS results with outputs from hydrodynamic and semianalytic models, we highlight the constraining power of cold gas scaling relations on models of galaxy formation.

Using ultra-violet absorption-lines, we analyze the systematic properties of the warm ionized phase of starburst-driven winds in a sample of 39 low-redshift objects that spans broad ranges in starburst and galaxy properties. Total column densities for the outflows are ∼10 21 cm −2 . The outflow velocity (v out ) correlates only weakly with the galaxy stellar mass (M * ), or circular velocity (v cir ), but strongly with both SFR and SFR/area. The normalized outflow velocity (v out /v cir ) correlates well with both SFR/area and SFR/M * . The estimated outflow rates of warm ionized gas (Ṁ ) are ∼ 1 to 4 times the SFR, and the ratioṀ /SF R does not correlate with v out .We show that a model of a population of clouds accelerated by the combined forces of gravity and the momentum flux from the starburst matches the data. We find a threshold value for the ratio of the momentum flux supplied by the starburst to the critical momentum flux needed for the wind to overcome gravity acting on the clouds (R crit ). For R crit > 10 (strong-outflows) the outflows momentum flux is similar to the total momentum flux from the starburst and the outflow velocity exceeds the galaxy escape velocity. Neither is the case for the weak-outflows (R crit < 10). For the weak-outflows, the data severely disagree with many prescriptions in numerical simulations or semianalytic models of galaxy evolution. The agreement is better for the strong-outflows, and we advocate the use of R crit to guide future prescriptions.

The source responsible for reionizing the universe at z > 6 remains uncertain. While an energetically adequate population of star-forming galaxies may be in place, it is unknown whether a large enough fraction of their ionizing radiation can escape into the intergalactic medium. Attempts to measure this escape fraction in intensely star-forming galaxies at lower redshifts have largely yielded upper limits. In this paper, we present new Hubble Space Telescope Cosmic Origins Spectrograph and archival Far-Ultraviolet Spectroscopic Explorer (FUSE) far-UV spectroscopy of a sample of 11 Lyman Break Analogs (LBAs), a rare population of local galaxies that strongly resemble the high-z Lyman Break galaxies. We combine these data with Sloan Digital Sky Survey optical spectra and Spitzer photometry. We also analyze archival FUSE observations of 15 typical UV-bright local starbursts. We find evidence of small covering factors for optically thick neutral gas in three cases. This is based on two independent pieces of evidence: a significant residual intensity in the cores of the strongest interstellar absorption-lines tracing neutral gas and a small ratio of extinction-corrected Hα to UV plus far-IR luminosities. These objects represent three of the four LBAs that contain a young, very compact (∼10 2 pc), and highly massive (∼10 9 M ) dominant central object (DCO). These three objects also differ from the other galaxies in showing a significant amount of blueshifted Lyα emission, which may be related to the low covering factor of neutral gas. All four LBAs with DCOs in our sample show extremely high velocity outflows of interstellar gas, with line centroids blueshifted by about 700 km s −1 and maximum outflow velocities reaching at least 1500 km s −1 . We show that these properties are consistent with an outflow driven by a powerful starburst that is exceptionally compact. We speculate that such extreme feedback may be required to enable the escape of ionizing radiation from star-forming galaxies.

Identifying the population of galaxies that was responsible for the reionization of the universe is a long-standing quest in astronomy. We present a possible local analog that has an escape fraction of ionizing flux of 21%. Our detection confirms the existence of gaps in the neutral gas enveloping the starburst region. The candidate contains a massive yet highly compact star-forming region. The gaps are most likely created by the unusually strong winds and intense ionizing radiation produced by this extreme object. Our study also validates the indirect technique of using the residual flux in saturated lowionization interstellar absorption-lines for identifying such leaky galaxies. Since direct detection of ionizing flux is impossible at the epoch of reionization, this is a highly valuable technique for future studies.