A<i>Far Ultraviolet Spectroscopic Explorer</i>Survey of Interstellar Molecular Hydrogen in the Small and Large Magellanic Clouds

Tumlinson, Jason; Shull, J. M.; Rachford, B. L.; Browning, Matthew K.; Snow, Theodore P.; Fullerton, A. W.; Jenkins, Edward B.; Savage, Blair D.; Crowther, P. A.; Moos, H. W.; Sembach, Kenneth R.; Sonneborn, G.; York, Donald G.

doi:10.1086/338112

Cited by 215 publications

(370 citation statements)

References 56 publications

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“…In the disc of the Milky Way, the molecular fraction increases sharply beyond log N(H) > 20.7 (Savage et al 1977). High-latitude Galactic lines of sight show a similar transition (Gillmon et al 2006), as do those towards the Magellanic Clouds, albeit at higher column densities (log N(H) = 21.3 and 22 for the LMC and SMC, respectively; Tumlinson et al 2002). However, while there is a possible dependence on the H 2 fraction with N(H i) in high-z DLAs, a sharp transition has not yet been observed (Ledoux et al 2003;Noterdaeme et al 2008).…”

Section: Note On Moleculesmentioning

confidence: 88%

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Noterdaeme

Petitjean

Pâris

et al. 2014

A&A

107

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We present a study of ∼100 high redshift (z ∼ 2−4) extremely strong damped Lyman-α systems (ESDLA, with N(H i) ≥ 0.5 × 10 22 cm −2 ) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) Data Release 11. We study the neutral hydrogen, metal, and dust content of this elusive population of absorbers and confirm our previous finding that the high column density end of the N(H i) frequency distribution has a relatively shallow slope with power-law index −3.6, similar to what is seen from 21-cm maps in nearby galaxies. The stacked absorption spectrum indicates a typical metallicity ∼1/20th solar, similar to the mean metallicity of the overall DLA population. The relatively small velocity extent of the low-ionisation lines suggests that ESDLAs do not arise from large-scale flows of neutral gas. The high column densities involved are in turn more similar to what is seen in DLAs associated with gamma-ray burst afterglows (GRB-DLAs), which are known to occur close to star-forming regions. This indicates that ESDLAs arise from a line of sight passing at very small impact parameters from the host galaxy, as observed in nearby galaxies. This is also supported by simple theoretical considerations and recent high-z hydrodynamical simulations. We strongly substantiate this picture by the first statistical detection of Ly α emission with L ESDLA (Ly α) (0.6 ± 0.2) × 10 42 erg s −1 in the core of ESDLAs (corresponding to about 0.1 L at z ∼ 2−3), obtained through stacking the fibre spectra (of radius 1 corresponding to ∼8 kpc at z ∼ 2.5). Statistical errors on the Ly α luminosity are of the order of 0.1 × 10 42 erg s −1 but we caution that the measured Ly α luminosity may be overestimated by ∼35% due to sky light residuals and/or FUV emission from the quasar host and that we have neglected flux-calibration uncertainties. We estimate a more conservative uncertainty of 0.2 × 10 42 erg s −1 . The properties of the Ly α line (luminosity distribution, velocity width and velocity offset compared to systemic redshift) are very similar to that of the population of Lyman-α emitting galaxies (LAEs) with L LAE (Ly α) ≥ 10 41 erg s −1 detected in long-slit spectroscopy or narrow-band imaging surveys. By matching the incidence of ESDLAs with that of the LAEs population, we estimate the high column density gas radius to be about r gas = 2.5 kpc, i.e., significantly smaller than the radius corresponding to the BOSS fibre aperture, making fibre losses likely negligible. Finally, the average measured Ly α luminosity indicates a star-formation rate consistent with the Schmidt-Kennicutt law, SFR (M yr −1 ) ≈ 0.6/ f esc , where f esc < 1 is the Ly α escape fraction. Assuming the typical escape fraction of LAEs, f esc ∼ 0.3, the Schmidt-Kennicutt law implies a galaxy radius of about r gal ≈ 2.5 kpc. Finally, we note that possible overestimation of the Ly α emission would result in both smaller r gas and r gal . Our results support a close association between LAEs and stro...

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Section: Note On Moleculesmentioning

confidence: 88%

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Noterdaeme

Petitjean

Pâris

et al. 2014

A&A

107

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“…They found a GDR value that is about 8 times the Galactic value, which is consistent with the difference in metallicity. More recently, Tumlinson et al (2002) measured N(H I )+N(H 2 )…”

Section: Discussionmentioning

confidence: 99%

Multi-wavelength analysis of the dust emission in the Small Magellanic Cloud

Bot

Boulanger

Lagache

et al. 2004

A&A

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Abstract.We present an analysis of dust grain emission in the diffuse interstellar medium of the Small Magellanic Cloud (SMC). This study is motivated by the availability of 170 µm ISOPHOT data covering a large part of the SMC, with a resolution making it possible to disentangle the diffuse medium from the star forming regions. After data reduction and subtraction of Galactic foreground emission, we used the ISOPHOT data together with HiRes IRAS data and ATCA/Parkes combined H  column density maps to determine dust properties for the diffuse medium. We found a far infrared emissivity per hydrogen atom 30 times lower than the Solar neighborhood value. The modeling of the spectral energy distribution of the dust, taking into account the enhanced interstellar radiation field, gives a similar conclusion for the smallest grains (PAHs and very small grains) emitting at shorter wavelength. Assuming Galactic dust composition in the SMC, this result implies a difference in the gas-to-dust ratio (GDR) 3 times larger than the difference in metallicity. This low depletion of heavy elements in dust could be specific of the diffuse ISM and not apply to all the SMC dust if it results from efficient destruction of dust by supernovae explosions.

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“…2.2). The minimum column density that can be detected at 4σ significance for an unresolved, optically thin absorption line at wavelength, λ 0 , with oscillator strength, f , in a spectrum with a given S /N per resolution element and a spectral resolution R = λ/Δλ can be calculated (e.g., Tumlinson et al 2002;Richter et al 2001) via N ≥ 1.13 × 10 20 cm −2 4…”

Section: Spectra Selection and Reductionmentioning

confidence: 99%

The neutral gas extent of galaxies as derived from weak intervening Ca ii absorbers

Richter

Krause

Fechner

et al. 2011

A&A

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We present a systematic study of weak intervening Ca ii absorbers at low redshift (z < 0.5), based on the analysis of archival highresolution (R ≥ 45 000) optical spectra of 304 quasars and active galactic nuclei observed with VLT/UVES. Along a total redshift path of Δz ≈ 100 we detected 23 intervening Ca ii absorbers in both the Ca ii H & K lines, with rest frame equivalent widths W r,3934 = 15−799 mÅ and column densities log N(Ca ii) = 11.25−13.04 (obtained by fitting Voigt-profile components). We obtain a bias-corrected number density of weak intervening Ca ii absorbers of dN/dz = 0.117 ± 0.044 at z abs = 0.35 for absorbers with log N(Ca ii) ≥ 11.65 (W r,3934 ≥ 32 mÅ). This is ∼2.6 times the value obtained for damped Lyman α absorbers (DLAs) at low redshift. All Ca ii absorbers in our sample show associated absorption by other low ions such as Mg ii and Fe ii; 45 percent of them have associated Na i absorption. From ionization modelling we conclude that intervening Ca ii absorption with log N(Ca ii) ≥ 11.5 arises in DLAs, sub-DLAs and Lyman-limit systems (LLS) at H i column densities of log N(H i) ≥ 17.4. Using supplementary H i information for nine of the absorbers we find that the Ca ii/H i ratio decreases strongly with increasing H i column density, indicating a column-density-dependent dust depletion of Ca. The observed column density distribution function of Ca ii absorption components follows a relatively steep power law, f (N) ∝ N −β , with a slope of −β = −1.68, which again points towards an enhanced dust depletion in high column density systems. The relatively large cross section of these absorbers together with the frequent detection of Ca ii absorption in high-velocity clouds (HVCs) in the halo of the Milky Way suggests that a considerable fraction of the intervening Ca ii systems trace (partly) neutral gas structures in the halos and circumgalactic environment of galaxies (i.e., they are HVC analogs). Based on the recently measured detection rate of Ca ii absorption in the Milky Way HVCs we estimate that the mean (projected) Ca ii covering fraction of galaxies and their gaseous halos is f c,CaII = 0.33. Using this value and considering all galaxies with luminosities L ≥ 0.05 L we calculate that the characteristic radial extent of (partly) neutral gas clouds with log N(H i) ≥ 17.4 around low-redshift galaxies is R HVC ≈ 55 kpc.

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AFar Ultraviolet Spectroscopic ExplorerSurvey of Interstellar Molecular Hydrogen in the Small and Large Magellanic Clouds

Cited by 215 publications

References 56 publications

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

A connection between extremely strong damped Lyman-αsystems and Lyman-αemitting galaxies at small impact parameters

Multi-wavelength analysis of the dust emission in the Small Magellanic Cloud

The neutral gas extent of galaxies as derived from weak intervening Ca ii absorbers

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