Volume 535, November 2011
|Number of page(s)||10|
|Section||Interstellar and circumstellar matter|
|Published online||11 November 2011|
The formation of active protoclusters in the Aquila rift: a millimeter continuum view⋆
ESO, Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany
2 Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/SAp, CEA Saclay, 91191 Gif-sur-Yvette, France
3 CNRS/INSU, Laboratoire d’Astrophysique de Bordeaux, UMR5804, BP 89, 33271 Floirac Cedex, France
Received: 25 April 2011
Accepted: 30 July 2011
While most stars are believed to form in stellar clusters, the formation and early evolution of young stellar clusters is still largely unknown. Improving our knowledge of the earliest phases of clustered star formation is crucial for understanding the origin of the stellar initial mass function and the efficiency of the star formation process, which both play a key role in the evolution of galaxies. Here, we present an analysis of the Aquila rift complex which addresses the questions of the star formation rate (SFR), star formation efficiency (SFE) and typical lifetime of the Class 0 protostellar phase in two nearby cluster-forming clumps: the Serpens South and W40 protoclusters. We carried out a 1.2 mm dust continuum mapping of the Aquila rift complex with the MAMBO bolometer array on the IRAM 30 m telescope. Using a multi-scale source extraction method, we perform a systematic source extraction in our millimeter continuum map. Based on complementary data from the Herschel Gould Belt survey and Spitzer maps, we characterize the spectral energy distributions (SEDs) of the 77 mm continuum sources detected with MAMBO and estimate their evolutionary stages. Taking advantage of the comprehensive dataset available for the Serpens South region, spanning wavelengths from 2 μm to 1.2 mm, we estimate the numbers of young stellar objects (YSOs) at different evolutionary stages and find a ratio of Class 0 to Class I protostars N(0)/N(I) = 0.19−0.27. This low ratio supports a scenario of relatively fast accretion at the beginning of the protostellar phase, and leads to a Class 0 lifetime of ~4−9 × 104 yr. We also show that both the Serpens South and W40 protoclusters are characterized by large fractions of protostars and high SFRs ~ 20−50M⊙ Myr-1 pc-2, in agreement with the idea that these two nearby clumps are active sites of clustered star formation currently undergoing bursts of star formation, and have the potential ability to form bound star clusters. While the formation of these two protoclusters is likely to have been initiated in a very different manner, the resulting protostellar populations are observed to be very similar. This suggests that after the onset of gravitational collapse, the detailed manner in which the collapse has been initiated does not affect much the ability of a clump to form stars.
Key words: stars: formation / circumstellar matter / ISM: clouds / ISM: structure / dust, extinction / stars: protostars
© ESO, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.