The Infrared Nucleus of the Wolf-Rayet Galaxy Henize 2-10

We have obtained near-infrared images and mid-infrared spectra of the starburst core of the dwarf Wolf-Rayet galaxy He 2-10. We find that the infrared continuum and emission lines are concentrated in a flattened ellipse 3-4'' or 150 pc across which may show where a recent accretion event has triggered intense star formation. The ionizing radiation from this cluster has an effective temperature of 40,000 K, corresponding to $30M_\odot$ stars, and the starburst is $0.5-1.5 \times 10^7$ years old.Comment: 17 pages Latex, 7 postscript figures, 1 postscript table, accepted to A

The eight micron band of silicon monoxide in the expanding cloud around VY Canis Majoris

Observations of vibration-rotation transitions of silicon monoxide in VY CMa show that the lines originate in accelerating, expanding, and cool (600 K) layers of a circumstellar cloud at a distance of roughly 0.15 minutes from the central star. The central stellar velocity, as estimated from observed SiO P Cygni line profiles, is somewhat redshifted from the midpoint of the maser emission features. Most of the silicon is probably in the form of dust grains. The isotopic ratios of silicon are nearly terrestrial

High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion molecular cloud

The pure rotational S(2) line of molecular hydrogen at 12.28 microns was looked for in 44 positions in the Orion moleular cloud with 6 in. beams and 35 km/s spectral resolution; it was detected in 27 positions. Emission was observed over a velocity range of + or - 100 km/s. The lines are approximately symmetric, and have full widths at half maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that seen in the 2 micron hydrogen transitions. However, unexpectedly complex line profiles and point-to-point variations in linear shapes appear, particularly in the region near IRc9

Bα and Ne II line spectroscopy in the vicinity of the Galactic center source IRS 16

Bα(4.05μm) and (Ne II) (12.81 μm) line spectra at spatial resolutions of ~3" and spectral resolutions of 80 km s^(−1) have been obtained on a grid of positions surrounding IRS 16, which may be at the Galactic center. The Bα and (Ne II) line profiles agree within the uncertainties and neither set of spectra shows evidence of ionized gas associated with IRS 16 over a velocity range of −500 to +450 km s^(−1). A spectrum of Bα from an 8" beam centered on IRS 16 and covering −7500 to +6500 km s^(−1) with 500 km s^(−1) resolution shows marginal evidence for a broad‐line component. These data imply that no concentration of moderate velocity gas (|v|<300 km s−^(1)) is directly associated with IRS 16 and that the ionized gas near IRS 16 is for the most part neither very dense nor of very high velocity

The Evolution of Dusty Star Formation and Stellar Mass Assembly in Clusters: Results from the IRAC 3.6, 4.5, 5.8, and 8.0 μm Cluster Luminosity Functions

We present a catalog of 99 candidate clusters and groups of galaxies in the redshift range 0.1 1.5). Using the 3.6 μm LF as a proxy for stellar luminosity, we remove this component from the MIR (5.8 and 8.0 μm ) cluster LFs and measure the LF of dusty star formation/AGNs in clusters. We find that at z 0.4, an additional population of dusty starburst galaxies is required to properly model the 8.0 μm LFs. Comparison to field studies at similar redshifts shows a strong differential evolution in the field and cluster 8.0 μm LFs with redshift. At z ~ 0.65 8.0 μm -detected galaxies are more abundant in clusters compared to the field, but thereafter the number of 8.0 μm sources in clusters declines with decreasing redshift, and by z ~ 0.15, clusters are underdense relative to the field by a factor of ~5. The rapid differential evolution between the cluster and field LFs is qualitatively consistent with recent field galaxy studies that show that the star formation rates of galaxies in high-density environments are larger than those in low-density environments at higher redshift

Looking for Pure Rotational H_2 Emission from Protoplanetary Disks

We report on a limited search for pure-rotational molecular hydrogen emission associated with young, pre-main-sequence stars. We looked for H_2 v=0 J = 3->1 and J = 4->2 emission in the mid-infrared using the Texas Echelon-Cross-Echelle Spectrograph (TEXES) at NASA's 3m Infrared Telescope Facility. The high spectral and spatial resolution of our observations lead to more stringent limits on narrow line emission close to the source than previously achieved. One star, AB Aur, shows a possible (2sigma) H_2 detection, but further observations are required to make a confident statement. Our non-detections suggest that a significant fraction, perhaps all, of previously reported H_2 emission towards these objects could be extended on scales of 5" or more.Comment: 14 pages including 2 figures. Accepted by ApJ Letter

Mid-Infrared Photometry and Spectra of Three High Mass Protostellar Candidates at IRAS 18151-1208 and IRAS 20343+4129

We present arcsecond-scale mid-ir photometry (in the 10.5 micron N band and at 24.8 microns), and low resolution spectra in the N band (R~100) of a candidate high mass protostellar object (HMPO) in IRAS 18151-1208 and of two HMPO candidates in IRAS 20343+4129, IRS 1 and IRS 3. In addition we present high resolution mid-ir spectra (R~80000) of the two HMPO candidates in IRAS 20343+4129. These data are fitted with simple models to estimate the masses of gas and dust associated with the mid-ir emitting clumps, the column densities of overlying absorbing dust and gas, the luminosities of the HMPO candidates, and the likely spectral type of the HMPO candidate for which [Ne II] 12.8 micron emission was detected (IRAS 20343+4129 IRS 3). We suggest that IRAS 18151-1208 is a pre-ultracompact HII region HMPO, IRAS 20343+4129 IRS 1 is an embedded young stellar object with the luminosity of a B3 star, and IRAS 20343+4129 IRS 3 is a B2 ZAMS star that has formed an ultracompact HII region and disrupted its natal envelope.Comment: 40 pages, 8 figures, 3 tables. Accepted for publication in Astrophysical Journal (Part 1