Query : 2015A&A...577L...6S

2015A&A...577L...6S - Astronomy and Astrophysics, volume 577, L6-6 (2015/5-1)

Evolution of column density distributions within Orion A.


Abstract (from CDS):

We compare the structure of star-forming molecular clouds in different regions of Orion A to determine how the column density probability distribution function (N-PDF) varies with environmental conditions such as the fraction of young protostars. A correlation between the N-PDF slope and Class 0 protostar fraction has been previously observed in a low-mass star-formation region (Perseus); here we test whether a similar correlation is observed in a high-mass star-forming region. We used Herschel PACS and SPIRE cold dust emission observations to derive a column density map of Orion A. We used the Herschel Orion Protostar Survey catalog to accurately identify and classify the Orion A young stellar object content, including the cold and relatively short-lived Class 0 protostars (with a lifetime of ∼0.14Myr). We divided Orion A into eight independent regions of 0.25 square degrees (13.5pc2); in each region we fit the N-PDF distribution with a power law, and we measured the fraction of Class 0 protostars. We used a maximum-likelihood method to measure the N-PDF power-law index without binning the column density data. We find that the Class 0 fraction is higher in regions with flatter column density distributions. We tested the effects of incompleteness, extinction-driven misclassification of Class 0 sources, resolution, and adopted pixel-scales. We show that these effects cannot account for the observed trend. Our observations demonstrate an association between the slope of the power-law N-PDF and the Class 0 fractions within Orion A. Various interpretations are discussed, including timescales based on the Class 0 protostar fraction assuming a constant star-formation rate. The observed relation suggests that the N-PDF can be related to an evolutionary state of the gas. If universal, such a relation permits evaluating the evolutionary state from the N-PDF power-law index at much greater distances than those accessible with protostar counts.

Abstract Copyright:

Journal keyword(s): ISM: clouds - ISM: structure - stars: formation - ISM: individual objects: Orion A

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2226 1
2 NAME Ori A MoC 05 38 -07.1           ~ 2913 0
3 LDN 1641 MoC 05 39.0 -07 00           ~ 468 0
4 NAME Gould Belt PoG ~ ~           ~ 843 1

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