J. Tackenberg, H. Beuther, Th. Henning, F. Schuller, M. Wienen, F. Motte, F. Wyrowski, S. Bontemps, L. Bronfman, K. Menten, L. Testi, B. Lefloch
In this study, we present an unbiased sample of the earliest stages of
massive star formation across 20 square-degree of the sky. Within the region
10deg < l < 20deg and |b| < 1deg, we search the ATLASGAL survey at 870 micron
for dense gas condensations. These clumps are carefully examined for
indications of ongoing star formation using YSOs from the GLIMPSE source
catalog as well as sources in the 24 micron MIPSGAL images, to search for
starless clumps. We calculate the column densities as well as the kinematic
distances and masses for sources where the v_lsr is known from spectroscopic
observations. Within the given region, we identify 210 starless clumps with
peak column densities > 1 x 10e23 cm^(-2). For the first time, we identify
potential starless clumps on the other side of the Galaxy. The sizes of the
clumps range between 0.1 pc and 3 pc with masses between a few tens of solar
masses up to several ten thousands of solar masses. Most of them may form
massive stars, but in the 20 square-degree we only find 14 regions massive
enough to form stars more massive than 20 solar masses and 3 regions with the
potential to form stars more massive than 40 40 solar masses. The slope of the
high-mass tail of the clump mass function for clumps on the near side of the
Galaxy is 2.2 and, therefore, Salpeter-like. We estimate the lifetime of the
most massive starless clumps to be 60000 yr. The sample offers a uniform
selection of starless clumps. In the large area surveyed, we only find a few
potential precursors of stars in the excess of 40 solar masses. It appears that
the lifetime of these clumps is somewhat shorter than their free-fall times,
although both values agree within the errors. In addition, these are ideal
objects for detailed studies and follow-up observations.
View original:
http://arxiv.org/abs/1201.4732
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