The Herschel Virgo Cluster Survey. XI. Environmental effects on molecular gas and dust in spiral disks

We investigate the dust-to-gas mass ratio and the environmental effects on the various components of the interstellar medium for a spatially resolved sample of Virgo spirals. We have used the IRAM-30m telescope to map over their full extent NGC 4189, NGC 4298, NGC 4388, and NGC 4299 in the 12CO(1-0) and the 12CO(2-1) lines. We observed the same lines in selected regions of NGC 4351, NGC 4294, and NGC 4424. The CO observations are combined with Herschel maps in 5 bands between 100-500 {\mu}m from the HeViCS survey, and with HI data from the VIVA survey, to obtain spatially resolved dust and gas distributions. We studied the environmental dependencies by adding to our sample eight galaxies with 12CO(1-0) maps from the literature. We estimate the integrated mass of molecular hydrogen for the galaxies observed in the CO lines. We find molecular-to-total gas mass fractions between 0.04 \leq fmol \leq 0.65, with the lowest values for the dimmest galaxy in the B-band. The integrated dust-to-gas ratio ranges between 0.011 and 0.004. For the 12 mapped galaxies we derive the radial distributions of the atomic gas, molecular gas, and dust. We also study the effect of different CO-to-H2 conversion factors. Both the molecular gas and the dust distributions show steeper radial profiles for HI-deficient galaxies and the average dust-to-gas ratio for these galaxies increases or stays radially constant. On scales of \sim 3 kpc, we find a strong correlation between the molecular gas and the 250 micron surface brightness that is tighter than average for non-deficient galaxies. The correlation becomes linear if we consider the total gas surface mass density. However, the inclusion of atomic hydrogen does not improve the statistical significance of the correlation. The environment can modify the distributions of molecules and dust within a galaxy, although these components are more tightly bound than the atomic gas.Comment: 17pp, 14 fig., accepted for publications in Astronomy and Astrophysic

African Linguistics in Central and Eastern Europe, and in the Nordic Countries

Non peer reviewe

Language endangerment and language documentation in Africa

Non peer reviewe

CO in late-type galaxies within the central region of Abell 1367

We present 12CO (J = 1→ 0) and 12CO (J = 2 →1) spectra for 19 bright, late–type galaxies (spirals) in the central region of the galaxy cluster Abell 1367 (z = 0.02) from observations make with the IRAM 30–m telescope. All 19 spirals were observed at the position of their optical center and for a subset, at multiple positions. For each spiral the integrated CO (J = 1 ! 0) intensity from the central pointing, in few cases supplemented with intensities from offset pointings, was used to estimate its molecular hydrogen mass and H2 deficiency. Accepting the considerable uncertainties involved in determining H2 deficiencies, spirals previously identified by us to have redder colours and higher Hi deficiencies as a result of environmental influence, were found to be more H2 deficient compared to members of the sample in less advanced evolutionary states. For eight of the observed spirals multiple pointing observations were made to investigate the distribution of their molecular gas. For these spirals we fitted Gaussiansto the CO intensities projected in a line across the galaxy. In two cases, CGCG097–079 and CGCG097–102(N), the offset between the CO and optical intensity maxima was significantly larger than the pointing uncertainty and the FWHMs of the fits were significantly greater than those of the other spirals, irrespective of optical size. Both signatures are indicators of an abnormal molecular gas distribution. In the case of CGCG097–079, which is considered an archetype for ram pressure stripping, our observations indicate the CO intensity maximum lies 15.6 ± 8.5 arcsec (6 kpc) NW of the optical centre at the same projected position as the Hi intensity maximum.Peer reviewe