Molecular clouds under the influence of massive stars in the Galactic HII region G353.2+0.9

The Galactic HII region G353.2+0.9 is excited by the massive open cluster Pismis-24. By analyzing (sub-)mm molecular-line and -continuum we study the detailed morphology of the gas and dust, as well as their physical parameters and their variation across the PDR. We observed various molecules and transitions to derive the physical properties of the molecular gas through line ratios, and both LTE and non-LTE analyses. The physical properties of the gas were derived with a Bayesian approach for the non-LTE analysis. Based on the continuum data at 870 micron, we derived the dust mass and the column density of H2, and thus the molecular abundances. The total mass of the gas in the region is ca. 2000 Mo, while that of the dust is ca. 21 Mo. A velocity gradient in the region suggests that the expansion of the ionized gas is pushing the molecular gas away from the observer. We unambiguously identify the ionization front, at the location of which we detect an increase in gas density and temperature. We find at least 14 clumps at different positions and LSR velocities. We derive kinetic temperatures in the ranges 11-45 K (CS) and 20-45 K (CN). The H2 number density is typically around 1e5 cm^-3 from CS and few 1e5 cm^-3 from CN, with maxima above 1e6 cm^-3. The abundances of the molecules observed vary across the region, and appear to be higher in regions further away from the ionization front.Comment: 14 pages, 11 figures. Accepted for publication in Astronomy and Astrophysic

Nova-like Cataclysmic Variables in the Infrared

Novalike cataclysmic variables have persistently high mass transfer rates and prominent steady state accretion disks. We present an analysis of infrared observations of twelve novalikes obtained from the Two Micron All Sky Survey, the Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer All Sky Survey. The presence of an infrared excess at >3-5 microns over the expectation of a theoretical steady state accretion disk is ubiquitous in our sample. The strength of the infrared excess is not correlated with orbital period, but shows a statistically significant correlation (but shallow trend) with system inclination that might be partially (but not completely) linked to the increasing view of the cooler outer accretion disk and disk rim at higher inclinations. We discuss the possible origin of the infrared excess in terms of emission from bremsstrahlung or circumbinary dust, with either mechanism facilitated by the mass outflows (e.g., disk wind/corona, accretion stream overflow, and so on) present in novalikes. Our comparison of the relative advantages and disadvantages of either mechanism for explaining the observations suggests that the situation is rather ambiguous, largely circumstantial, and in need of stricter observational constraints.Peer reviewe