Dust-to-gas ratios in the starburst regions of luminous infrared galaxies

We investigate the properties of dust and dust-to-gas ratios in different starburst regions of luminous infrared galaxies (LIGs). We refer to the sample of seven LIGs recently observed in the mid-infrared by Soifer et al. (2001) using the Keck telescopes with spatial resolution approaching the diffraction limit. These seven objects are among the closest LIGs and have been classified as starburst galaxies from optical spectroscopy. Our goal consists in modelling the continuum spectral energy distribution (SED) of each galaxy, particularly in the infrared range. Models are further constrained by observed emission-line ratios in the optical range. The multi-cloud models consistently account for the coupled effect of shock, photoionization by hot stars, and diffuse secondary radiation from the shock-heated gas. Emission from clouds in the neighbourhood of evolved starbursts and with high shock velocities (~ 500 km/s) explains both the bremsstrahlung and reradiation from dust in the mid-infrared. Clouds with lower velocity (~ 100 km/s) and corresponding to younger starbursts also contribute to both line and continuum spectra. Both low- and high-velocity clouds are thus present in nearly all the sample galaxies. For all the galaxies, an old stellar population is revealed by black body emission in the optical-NIR range. Dust-to-gas ratios vary in different regions of individual galaxies.Comment: 17 pages, 16 figures, and 12 tables. Accepted for publication in MNRA

New catalogue of Wolf-Rayet galaxies and high-excitation extra-galactic HII regions

We present a new compilation of Wolf-Rayet (WR) galaxies and extra-galactic HII regions showing BROAD HeII emission drawn from the literature. Relevant information on the presence of other broad emission lines (NIII 4640, CIV 5808 and others) from WR stars of WN and WC subtypes, and other existing broad nebular lines is provided. In total we include 139 known WR galaxies. Among these, 57 objects show both broad HeII and CIV features. In addition to the broad (stellar) HeII emission, a NEBULAR HeII component is well established (suspected) in 44 (54) objects. We find 19 extra-galatic HII regions without WR detections showing nebular HeII emission. The present sample can be used for a variety of studies on massive stars, interactions of massive stars with the ISM, stellar populations, starburst galaxies etc. The data is accessible electronically and will be updated periodicaly.Comment: Accepted for publication in A&AS. LaTeX, 19 pages including 3 tables. Database and paper available at http://www.obs-mip.fr/omp/astro/people/schaerer/ (minor corrections to references

A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - VI. Metallicity and Geometry as Gas Flow Probes

The use of background quasars provides a powerful tool to probe the cool gas in the circum-galactic medium of foreground galaxies. Here, we present new observations with SINFONI and X-Shooter of absorbing-galaxy candidates at z=0.7-1. We report the detection with both instruments of the H-alpha emission line of one sub-DLA at z_abs=0.94187 with log N(HI)=19.38^+0.10_-0.15 towards SDSS J002133.27+004300.9. We estimate the star formation rate: SFR=3.6+/-2.2 solar masses per year in that system. A detailed kinematic study indicates a dynamical mass M_dyn=10^9.9+/-0.4 solar masses and a halo mass M_halo=10^11.9+/-0.5 solar masses. In addition, we report the OII detection with X-Shooter of another DLA at z_abs=0.7402 with log N(HI)=20.4+/-0.1 toward Q0052+0041 and an estimated SFR of 5.3+/-0.7 solar masses per year. Three other objects are detected in the continuum with X-Shooter but the nature and redshift of two of these objects are unconstrained due to the absence of emission lines, while the third object might be at the redshift of the quasar. We use the objects detected in our whole N(HI)-selected SINFONI survey to compute the metallicity difference between the galaxy and the absorbing gas, delta_HI(X), where a positive (negative) value indicates infall (outflow). We compare this quantity with the quasar line of sight alignment with the galaxy's major (minor) axis, another tracer of infall (outflow). We find that these quantities do not correlate as expected from simple assumptions. Additional observations are necessary to relate these two independent probes of gas flows around galaxies.Comment: 16 pages, 8 figures, accepted for publication in MNRA

Multi-wavelength Study of Galaxy Rotation Curves and its Application to Cosmology

Rotation information for spiral galaxies can be obtained through the observation of different spectral lines. While the Halpha(6563 A) line is often used for galaxies with low to moderate redshifts, it is redshifted into the near-infrared at z>0.4. This is why most high redshift surveys rely on the [OII](3727 A) line. Using a sample of 32 spiral galaxies at 0.155 < z < 0.25 observed simultaneously in both Halpha and [OII] with the Hale 200 inch telescope, the relation between velocity widths extracted from these two spectral lines is investigated, and we conclude that Halpha derived velocities can be reliably compared to high z [OII] measurements. The sample of galaxies is then used along with VIMOS-VLT Deep Survey observations to perform the angular diameter - redshift test to find constraints on cosmological parameters. The test makes it possible to discriminate between various cosmological models, given the upper limit of disc size evolution at the maximum redshift of the data set, no matter what the evolutionary scenario is.Comment: 2 pages, to be published in the proceedings of the Vth Marseille International Cosmology Conferenc