Two New and Remarkable Sightlines through the Galactic Center's Molecular Gas

Until now the known sources in the Galactic center with sufficiently smooth spectra and of sufficient brightness to be suitable for high resolution infrared absorption spectroscopy of interstellar gas occupied a narrow range of longitudes, from the central cluster of hot stars to approximately 30 pc east of the center. In order to more fully characterize the gas within the r ~ 180 pc central molecular zone it is necessary to find additional such sources that cover a much wider longitudinal range. We are in the process of identifying luminous dust-embedded objects suitable for spectroscopy within 1.2 deg in longitude and 0.1 deg in latitude of Sgr A* using the Spitzer GLIMPSE and the 2MASS catalogues. Here we present spectra of H3+ and CO towards two such objects, one located 140 pc west of Sgr A*, and the other located on a line of sight to the Sgr B molecular cloud complex 85 pc to the east of Sgr A*. The sightline to the west passes through two dense clouds of unusually high negative velocities and also appears to sample a portion of the expanding molecular ring. The spectra toward Sgr B reveal at least ten absorption components covering over 200 km/s and by far the largest equivalent width ever observed in an interstellar H3+line; they appear to provide the first near-infrared view into that hotbed of star formation.Comment: 13 pages, incl. 4 figures - accepted by ApJ Letters Dec 14, 2009; minor typos correcte

Do star formation rates of galaxy clusters depend on mass?: blue/late-type fractions, total star formation rates of 115 galaxy clusters as a function of cluster virial mass

There has been plenty of observational evidence of cluster galaxy evolution such as the Butcher-Oemler effect and the decrease in S0 fraction with increasing redshift. As a modern version, the redshift evolution of total star formation rate (SFR) in clusters has been actively debated recently. However, these studies of redshift trend have been always hampered by the possible mass dependence; due to the observational selection effects, clusters found at higher redshift inevitably tend to be more massive and luminous than local counterparts. Consequently, one has to correct for the mass trend before interpreting the redshift trend. As an attempt to break this degeneracy, we investigate the mass dependence of blue/late-type fractions and total SFR of 115 clusters at $z\leq 0.09$ selected from the Sloan Digital Sky Survey. We find that none of blue/late-type fractions, total SFR and total SFR normalized by cluster mass shows significant dependence on cluster virial mass. The scatter is much larger at each cluster mass than a possible trend. Our results indicates that physical mechanisms that depend on cluster mass (such as the ram-pressure stripping) are not likely to be solely responsible for cluster galaxy evolution. Our results also provide an excellent low redshift comparison sample for future high redshift cluster SFR studies.Comment: MNRAS Letters in pres

The Effect of Carbon Dioxide Anaesthesia on Collembola

Excerpt: In a contribution to the Michigan Entomologist by Snider, Shaddy and Butcher (1969), a method of carbon dioxide anaesthesia for some soil arthropods was described as an alternative to etherization which frequently gives rise to unpredictable mortality. They stated (page 359) that CO, has very little long-range effect on most species. Anaesthetization by carbon dioxide has been used on various species of Collembola, particularly of the genus Folsomia Willem, 1902, by myself and my associates for about fifteen years. Until recently no ill effects on the cultures, as a result of this treatment, has been observed or suspected. As part of an investigation into the cause of sudden and fairly frequent sporadic increases in the incidence in our cultures of numerous abnormal specimens, such as those described, for example, in Goto and Ogel (1961), the effect of regular daily anaesthetization with carbon dioxide was examined. Although more extensive experimentation is needed, a brief comment is given here as a warning of possible side effects that might cause serious misinterpretation of quantitative data derived from specimens that have been subjected to carbon dioxide anaesthesia in cultur