The circumgalactic medium (CGM) of late-type galaxies is characterized using UV spectroscopy of 11 targeted QSO/galaxy pairs at z 0.02 with the Hubble Space Telescope Cosmic Origins Spectrograph (COS) and ∼60 serendipitous absorber/galaxy pairs at z 0.2 with the Space Telescope Imaging Spectrograph. CGM warm cloud properties are derived, including volume filling factors of 3%-5%, cloud sizes of 0.1-30 kpc, masses of 10-10 8 M , and metallicities of ∼0.1-1 Z . Almost all warm CGM clouds within 0.5 R vir are metal-bearing and many have velocities consistent with being bound, "galactic fountain" clouds. For galaxies with L 0.1 L * , the total mass in these warm CGM clouds approaches 10 10 M , ∼10%-15% of the total baryons in massive spirals and comparable to the baryons in their parent galaxy disks. This leaves 50% of massive spiral-galaxy baryons "missing." Dwarfs (<0.1 L * ) have smaller area covering factors and warm CGM masses ( 5% baryon fraction), suggesting that many of their warm clouds escape. Constant warm cloud internal pressures as a function of impact parameter (P /k ∼ 10 cm −3 K) support the inference that previous COS detections of broad, shallow O vi and Lyα absorptions are of an extensive (∼400-600 kpc), hot (T ≈ 10 6 K), intra-cloud gas which is very massive ( 10 11 M ). While the warm CGM clouds cannot account for all the "missing baryons" in spirals, the hot intra-group gas can, and could account for ∼20% of the cosmic baryon census at z ∼ 0 if this hot gas is ubiquitous among spiral groups.

We use high-quality, medium-resolution Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) observations of 82 UV-bright AGN at redshifts z AGN < 0.85 to construct the largest survey of the low-redshift intergalactic medium (IGM) to date: 5138 individual extragalactic absorption lines in H I and 25 different metal-ion species grouped into 2611 distinct redshift systems at z abs < 0.75 covering total redshift pathlengths ∆z HI = 21.7 and ∆z OVI = 14.5. Our semi-automated line-finding and measurement technique renders the catalog as objectively-defined as possible. The cumulative column-density distribution of H I systems can be parametrized dN (> N )/dz = C 14 (N/10 14 cm −2 ) −(β−1) , with C 14 = 25 ± 1 and β = 1.65 ± 0.02. This distribution is seen to evolve both in amplitude, C 14 ∝ (1 + z) 2.3±0.1 , and slope β(z) = 1.75 − 0.31 z for z ≤ 0.47. We observe metal lines in 418 systems, and find that the fraction of IGM absorbers detected in metals is strongly dependent on N HI . The distribution of O VI absorbers appear to evolve in the same sense as the Lyα forest. We calculate contributions to Ω b from different components of the low-z IGM and determine the Lyα decrement as a function of redshift. IGM absorbers are analyzed via a two-point correlation function in velocity space. We find substantial clustering of H I absorbers on scales of ∆v = 50 − 300 km s −1 with no significant clustering at ∆v 1000 km s −1 . Splitting the sample into strong and weak absorbers, we see that most of the clustering occurs in strong, N HI 10 13.5 cm −2 , metal-bearing IGM systems. The full catalog of absorption lines and fully-reduced spectra is available via the Mikulski Archive for Space Telescopes (MAST) as a high-level science product at

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Using the new Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we obtained moderate-resolution, high signal/noise ultraviolet spectra of HD 209458 and its exoplanet HD 209458b during transit, both orbital quadratures, and secondary eclipse. We compare transit spectra with spectra obtained at non-transit phases to identify spectral features due to the exoplanet's expanding atmosphere. We find that the mean flux decreased by 7.8 ± 1.3% for the C II 1334.5323Å and 1335.6854Å lines and by 8.2 ± 1.4% for the Si III 1206.500Å line during transit compared to non-transit times in the velocity interval -50 to +50 km s −1 . Comparison of the C II and Si III line depths and transit/nontransit line ratios shows deeper absorption features near -10 and +15 km s −1 and less certain features near -40 and +30-70 km s −1 , but future observations are needed to verify this first detection of velocity structure in the expanding atmosphere of an exoplanet. Our results for the C II lines and the non-detection of Si IV 1394.76Å absorption are in agreement with Vidal-Madjar et al. (2004), but we find absorption during transit in the Si III line contrary to the earlier result. The 8 ± 1% obscuration of the star during transit is far larger than the 1.5% obscuration by the exoplanet's disk. Absorption during transit at velocities between -50 and +50 km s −1 in the C II and Si III lines requires high-velocity ion absorbers. Assuming hydrodynamic model values for the gas temperature and outflow velocity at the limb of the outflow as seen in the C II lines, we find mass-loss rates in the range (8-40)×10 10 g s −1 . These rates assume that the carbon abundance is solar, which is not the case for the giant planets in the solar system. Our mass-loss rate estimate is consistent with theoretical hydrodynamic models that include metals in the outflowing gas.Subject headings: planets and satellites: atmospheres -planets and satellites: individual (HD 209458b) -planets and satellites: physical evolution -stars: individual (HD 209458) -ultraviolet: stars

We present basic data and modeling for a survey of the cool, photo-ionized Circum-Galactic Medium (CGM) of low-redshift galaxies using far-UV QSO absorption line probes. This survey consists of "targeted" and "serendipitous" CGM subsamples, originally described in Stocke et al. (2013, Paper 1). The targeted subsample probes low-luminosity, late-type galaxies at z < 0.02 with small impact parameters ( ρ = 71 kpc), and the serendipitous subsample probes higher luminosity galaxies at z 0.2 with larger impact parameters ( ρ = 222 kpc). HST and FUSE UV spectroscopy of the absorbers and basic data for the associated galaxies, derived from ground-based imaging and spectroscopy, are presented. We find broad agreement with the COS-Halos results, but our sample shows no evidence for changing ionization parameter or hydrogen density with distance from the CGM host galaxy, probably because the COS-Halos survey probes the CGM at smaller impact parameters. We find at least two passive galaxies with H I and metal-line absorption, confirming the intriguing COS-Halos result that galaxies sometimes have cool gas halos despite no on-going star formation. Using a new methodology for fitting H I absorption complexes, we confirm the CGM cool gas mass of Paper 1, but this value is significantly smaller than found by the COS-Halos survey. We trace much of this difference to the specific values of the low-z meta-galactic ionization rate assumed. After accounting for this difference, a best-value for the CGM cool gas mass is found by combining the results of both surveys to obtain log (M/M ) = 10.5 ± 0.3, or ∼ 30% of the total baryon reservoir of an L ≥ L * , star-forming galaxy.