Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)

We have surveyed molecular line emission from Sgr B2 over the range from 330 to 355 GHz at the position designated Sgr B2(M). This position is prominent in millimeter continuum maps of the region and is associated with a compact H II region, a hot NH_3 core, and sources of H_2O and OH maser emission. We have also obtained observations contrasting the submillimeter molecular emission from Sgr B2(M) and Sgr B2(N), an additional center of activity thought to be a dense protostellar core. The picture of the interstellar chemistry of these regions which we derive is substantially different from that determined from previous observations at lower frequencies and with lower spatial resolution. In particular, molecules such as SO_2 and CH_3OH dominate the submillimeter spectrum to a much greater extent than they do the low-frequency observations. Much of this difference is due to the higher spatial resolution of the submillimeter observations, which makes them much more sensitive to emission from compact, dense cores. The millimeter data were most effective at sampling material in the surrounding lower density regions. The chemistry of the core sources in Sgr B2 appears similar to that of other dense cores, such as the core of the Orion molecular cloud. The spectral differences between Sgr B2(M) and Sgr B2(N) primarily relate to differences in excitation and column density. For most molecular species the northern source (N) has a column density significantly higher than that found in the middle source (M), often by a factor of about 5. The principal exceptions are the species SO and SO_2 which seem to be substantially more abundant in the middle source. Generally excitation seems to be higher in the northern source, suggesting a somewhat higher density core, although there are some departures indicating that the excitation situation is more complicated. High optical depths in many of the submillimeter transitions systematically bias the interpretation of both column densities and excitation. Many of the millimeter lines may also have high optical depths, particularly those lines arising from the compact core sources

Foxc1 is required by pericytes during fetal brain angiogenesis

Summary Brain pericytes play a critical role in blood vessel stability and blood–brain barrier maturation. Despite this, how brain pericytes function in these different capacities is only beginning to be understood. Here we show that the forkhead transcription factor Foxc1 is expressed by brain pericytes during development and is critical for pericyte regulation of vascular development in the fetal brain. Conditional deletion of Foxc1 from pericytes and vascular smooth muscle cells leads to late-gestation cerebral micro-hemorrhages as well as pericyte and endothelial cell hyperplasia due to increased proliferation of both cell types. Conditional Foxc1 mutants do not have widespread defects in BBB maturation, though focal breakdown of BBB integrity is observed in large, dysplastic vessels. qPCR profiling of brain microvessels isolated from conditional mutants showed alterations in pericyte-expressed proteoglycans while other genes previously implicated in pericyte–endothelial cell interactions were unchanged. Collectively these data point towards an important role for Foxc1 in certain brain pericyte functions (e.g. vessel morphogenesis) but not others (e.g. barriergenesis)

Infrared Photometry and Evolution of Mass-Losing AGB Stars I. Carbon Stars Revisited

As part of a reanalysis of galactic Asymptotic Giant Branch (AGB) stars at infrared (IR) wavelengths, we discuss a sample (357) of carbon stars for which mass loss rates, near-IR photometry and distance estimates exist. For 252 sources we collected mid-IR fluxes from the MSX (6C) and the ISO-SWS catalogues. Most stars have spectral energy distributions up to 21 microns, and some (1/3) up to 45 microns. This wide wavelength coverage allows us to obtain reliable bolometric magnitudes. The properties of our sample are discussed with emphasis on about 70 stars with astrometric distances. We show that mid-IR fluxes are crucial to estimate the magnitude of stars with dusty envelopes. We construct HR diagrams and show that the luminosities agree fairly well with model predictions based on the Schwarzschild's criterion, contrary to what is widely argued in the literature. A problem with the brightness of C stars does not appear to exist. From the relative number of Mira and Semiregular C-variables, we argue that the switch between these classes is unlikely to be connected to thermal pulses. The relevance of the two populations varies with the evolution, with Miras dominating the final stages. We also analyze mass loss rates, which increase for increasing luminosity, but with a spread that probably results from a dependence on a number of parameters (like e.g. different stellar masses and different mechanisms powering stellar winds). Instead, mass loss rates are well monitored by IR colours, especially if extended to 20 microns and beyond, where AGB envelopes behave like black bodies. From these colours the evolutionary status of various classes of C stars is discussed.Comment: 19 pages, 12 figures, 4 tables. Accepted for publication in "Astronomy & Astrophysics