1,980 research outputs found
Massive molecular outflows at high spatial resolution
We present high-spatial resolution Plateau de Bure Interferometer CO(2-1) and
SiO(2-1) observations of one intermediate-mass and one high-mass star-forming
region. The intermediate-mass region IRAS20293+3952 exhibits four molecular
outflows, one being as collimated as the highly collimated jet-like outflows
observed in low-mass star formation sources. Furthermore, comparing the data
with additional infrared H2 and cm observations we see indications that the
nearby ultracompact HII region triggers a shock wave interacting with the
outflow. The high-mass region IRAS19217+1651 exhibits a bipolar outflow as well
and the region is dominated by the central driving source. Adding two more
sources from the literature, we compare position-velocity diagrams of the
intermediate- to high-mass sources with previous studies in the low-mass
regime. We find similar kinematic signatures, some sources can be explained by
jet-driven outflows whereas other are better constrained by wind-driven models.
The data also allow to estimate accretion rates varying from a few times
10^{-5}Msun/yr for the intermediate-mass sources to a few times 10^{-4}Msun/yr
for the high-mass source, consistent with models explaining star formation of
all masses via accretion processes.Comment: 14 pages text, 4 tables, 8 figures, accepted for Ap
SB77-12/13: Amending the ASUM Constitution
SB77-12/13: Amending the ASUM Constitution. This resolution passed during the April 10, 2013 meeting of the Associated Students of the University of Montana (ASUM)
SB62-12/13: Amending House Rules
SB62-12/13: Amending House Rules. This resolution passed 21Y-4N on a roll call vote during the March 13, 2013 meeting of the Associated Students of the University of Montana (ASUM)
The chemistry of fluorine-bearing molecules in diffuse and dense interstellar gas clouds
We present a theoretical investigation of the chemistry of fluorine-bearing
molecules in diffuse and dense interstellar gas clouds. The chemistry of
interstellar fluorine is qualitatively different from that of any other
element, because - unlike the neutral atoms of any other element found in
diffuse or dense molecular clouds - atomic fluorine undergoes an exothermic
reaction with molecular hydrogen. Over a wide range of conditions attained
within interstellar gas clouds, the product of that reaction - hydrogen
fluoride - is predicted to be the dominant gas-phase reservoir of interstellar
fluorine nuclei. Our model predicts HF column densities ~ 1.E+13 cm-2 in dark
clouds and column densities as large as 1.E-11 cm-2 in diffuse interstellar gas
clouds with total visual extinctions as small as 0.1 mag. Such diffuse clouds
will be detectable by means of absorption line spectroscopy of the J = 1 - 0
transition at 243.2 micron using the Stratospheric Observatory for Infrared
Astronomy (SOFIA) and the Herschel Space Observatory (HSO). The CF+ ion is
predicted to be the second most abundant fluorine-bearing molecule, with
typical column densities a factor ~ 100 below those of HF; with its lowest two
rotational transitions in the millimeter-wave spectral region, CF+ may be
detectable from ground-based observatories. HF absorption in quasar spectra is
a potential probe of molecular gas at high redshift, providing a possible
bridge between the UV/optical observations capable of probing H2 in low column
density systems and the radio/millimeter-wavelength observations that probe
intervening molecular clouds of high extinction and large molecular fraction;
at redshifts beyond ~ 0.3, HF is potentially detectable from ground-based
submillimeter observatories in several atmospheric transmission windows.Comment: 34 pages, including 11 figures (10 color), accepted for publication
in Ap
SB97-12/13: Amending Bylaws
SB97-12/13: Amending Bylaws. This resolution passed during the May 8, 2013 meeting of the Associated Students of the University of Montana (ASUM)
SB101-12/13: Amending House Rules
SB101-12/13: Amending House Rules. This resolution passed during the May 8, 2013 meeting of the Associated Students of the University of Montana (ASUM)
SB99-12/13: Amending Bylaws
SB99-12/13: Amending Bylaws. This resolution passed during the May 8, 2013 meeting of the Associated Students of the University of Montana (ASUM)
SB55-12/13: Amending Fiscal Policy
SB55-12/13: Amending Fiscal Policy. This resolution passed with unanimous consent during the February 13, 2013 meeting of the Associated Students of the University of Montana (ASUM)
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