Oxford, MA, United States
Oxford, MA, United States

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Kauffmann J.,Initiative in Innovative Computing IIC | Kauffmann J.,Harvard - Smithsonian Center for Astrophysics | Kauffmann J.,Jet Propulsion Laboratory | Pillai T.,Harvard - Smithsonian Center for Astrophysics | And 6 more authors.
Astrophysical Journal | Year: 2010

We measure the mass and size of cloud fragments in several molecular clouds continuously over a wide range of spatial scales (0.05 ≲ r/pc ≲ 3). Based on the recently developed "dendrogram-technique," this characterizes dense cores as well as the enveloping clouds. "Larson's Third Law" of constant column density, m(r) r 2, is not well suited to describe the derived mass-size data. Solar neighborhood clouds not forming massive stars (≲10 M Ȯ; Pipe Nebula, Taurus, Perseus, and Ophiuchus) obey m(r) ≤ 870 M Ȯ(r/pc)1.33. In contrast to this, clouds forming massive stars (Orion A, G10.15 - 0.34, G11.11 - 0.12) do exceed the aforementioned relation. Thus, this limiting mass-size relation may approximate a threshold for the formation of massive stars. Across all clouds, cluster-forming cloud fragments are found to be - at given radius - more massive than fragments devoid of clusters. The cluster-bearing fragments are found to roughly obey a mass-size law m ∞ r 1.27 (where the exponent is highly uncertain in any given cloud, but is certainly smaller than 1.5). © 2010. The American Astronomical Society. All rights reserved.


Kauffmann J.,Initiative in Innovative Computing IIC | Kauffmann J.,Harvard - Smithsonian Center for Astrophysics | Kauffmann J.,Jet Propulsion Laboratory | Pillai T.,Harvard - Smithsonian Center for Astrophysics | And 7 more authors.
Astrophysical Journal | Year: 2010

We use a new contour-based map analysis technique to measure the mass and size of molecular cloud fragments continuously over a wide range of spatial scales (0.05 ≤ r/pc ≤ 10), i.e., from the scale of dense cores to those of entire clouds. The present paper presents the method via a detailed exploration of the Perseus molecular cloud. Dust extinction and emission data are combined to yield reliable scale-dependent measurements of mass. This scale-independent analysis approach is useful for several reasons. First, it provides a more comprehensive characterization of a map (i.e., not biased toward a particular spatial scale). Such a lack of bias is extremely useful for the joint analysis of many data sets taken with different spatial resolution. This includes comparisons between different cloud complexes. Second, the multi-scale mass-size data constitute a unique resource to derive slopes of mass-size laws (via power-law fits). Such slopes provide singular constraints on large-scale density gradients in clouds. © 2010. The American Astronomical Society. All rights reserved..

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