925 research outputs found
Testing 24 micron and Infrared Luminosity as Star Formation Tracers for Galactic Star Forming Regions
We have tested some relations for star formation rates used in extra-galactic
studies for regions within the Galaxy. In nearby molecular clouds, where the
IMF is not fully-sampled, the dust emission at 24 micron greatly underestimates
star formation rates (by a factor of 100 on average) when compared to star
formation rates determined from counting YSOs. The total infrared emission does
no better. In contrast, the total far-infrared method agrees within a factor of
2 on average with star formation rates based on radio continuum emission for
massive, dense clumps that are forming enough massive stars to have the total
infrared luminosity exceed 10^4.5 Lsun. The total infrared and 24 micron also
agree well with each other for both nearby, low-mass star forming regions and
the massive, dense clumps regions
The Gould Belt 'MISFITS' Survey: The Real Solar Neighborhood Protostars
We present an HCO J=3-2 survey of Class 0+I and Flat SED young stellar
objects (YSOs) found in the Gould Belt clouds by surveys with Spitzer. Our goal
is to provide a uniform Stage 0+I source indicator for these embedded protostar
candidates. We made single point HCO J = 3-2 measurements toward the
source positions at the CSO and APEX of 546 YSOs (89% of the Class 0+I + Flat
SED sample). Using the criteria from van Kempen et al. (2009), we classify
sources as Stage 0+I or bona fide protostars and find that 84% of detected
sources meet the criteria. We recommend a timescale for the evolution of Stage
0+I (embedded protostars) of 0.54 Myr. We find significant correlations of
HCO integrated intensity with and but not with
. The detection fraction increases smoothly as a function of
and , while decreasing smoothly with . Using the
Stage 0+I sources tightens the relation between protostars and high extinction
regions of the cloud; 89% of Stage I sources lie in regions with >8
mag. Class 0+I and Flat SED YSOs that are not detected in HCO have, on
average, a factor of ~2 higher and a factor of ~5 lower
than YSOs with HCO detections. We find less YSO contamination, defined as
the number of undetected YSOs divided by the total number surveyed, for sources
with 600 K and 1 . The
contamination percentage is >90% at < 4 mag and decreases as
increases.Comment: 28 pages, 11 figures, 5 tables. Accepted for publication to the
Astrophysical Journa
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