14 research outputs found
University of Maine Williams Hall Dedication Ceremony
Video of the dedication ceremony of Beryl Warner Williams Hall at the University of Maine held on April 28 to honor the legacy of the Bangor native and UMaineâs first Black graduate to earn a degree in mathematics. Williams went on to have a distinguished academic career at Morgan State University and become an active civic leader in Baltimore
The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. VII. Ophiuchus Observed with MIPS
We present maps of 14.4 deg^2 of the Ophiuchus dark clouds observed by the Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS). These high-quality maps depict both numerous point sources and extended dust emission within the star-forming and nonâstar-forming portions of these clouds. Using PSF-fitting photometry, we detect 5779 sources at 24 Îźm and 81 sources at 70 Îźm at the 10 Ď level of significance. Three hundred twenty-three candidate young stellar objects (YSOs) were identified according to their positions on the MIPS/2MASS K versus color-magnitude diagrams, as compared to 24 Îźm detections in the SWIRE extragalactic survey. We find that more than half of the YSO candidates, and almost all those with protostellar Class I spectral energy distributions, are confined to the known cluster and aggregates
Hydrodynamical Simulations of Jet- and Wind-driven Protostellar Outflows
We present two-dimensional hydrodynamical simulations of both jet- and
wind-driven models for protostellar outflows in order to make detailed
comparisons to the kinematics of observed molecular outflows.
Comparing the different simulations with observations, we find that some
outflows, e.g., HH 212, show features consistent with the jet-driven model,
while others, e.g., VLA 05487, are consistent with the wind-driven model.Comment: 38 pages, 14 figures, accepted for publication in Ap
CARMA Large Area Star Formation Survey: Structure and Kinematics of Dense Gas in Serpens Main
We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the
Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey
(CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular
resolution of 7 arcsecs. The gas emission is concentrated in two subclusters
(the NW and SE subclusters). The SE subcluster has more prominent filamentary
structures and more complicated kinematics compared to the NW subcluster. The
majority of gas in the two subclusters has subsonic to sonic velocity
dispersions. We applied a dendrogram technique with N2H+(1-0) to study the gas
structures; the SE subcluster has a higher degree of hierarchy than the NW
subcluster. Combining the dendrogram and line fitting analyses reveals two
distinct relations: a flat relation between nonthermal velocity dispersion and
size, and a positive correlation between variation in velocity centroids and
size. The two relations imply a characteristic depth of 0.15 pc for the cloud.
Furthermore, we have identified six filaments in the SE subcluster. These
filaments have lengths of 0.2 pc and widths of 0.03 pc, which is smaller than a
characteristic width of 0.1 pc suggested by Herschel observations. The
filaments can be classified into two types based on their properties. The first
type, located in the northeast of the SE subcluster, has larger velocity
gradients, smaller masses, and nearly critical mass-per-unit-length ratios. The
other type, located in the southwest of the SE subcluster, has the opposite
properties. Several YSOs are formed along two filaments which have
supercritical mass per unit length ratios, while filaments with nearly critical
mass-per-unit-length ratios are not associated with YSOs, suggesting that stars
are formed on gravitationally unstable filaments.Comment: Accepted to ApJ. 38 pages, 16 figures, 5 table