One of the main goals of the Herschel
Gould Belt survey (André et al. 2010) is to elucidate the physical
mechanisms responsible for the formation and evolution of prestellar cores in molecular clouds. In the
Aquila cloud complex imaged with Herschel
/SPIRE-PACS between 70–500 μm, we have recently identified
a complete sample of 651 starless cores, 446 of them are gravitationally-bound prestellar cores, likely
forming stars in the future. We also detected 58 protostellar cores (Könyves et al. 2010 and 2015, subm.
- see http://gouldbelt-herschel.cea.fr/archives
). This region is dominated by two (proto)clusters which are
currently active sites of clustered star formation (SF): the filamentary Serpens South cloud and the W40
HII region. The latter is powered by massive young stars, and a 2nd
-generation SF can be witnessed in
the surroundings (Maury et al. 2011).
observations also provide an unprecedented census of filaments in Aquila and suggest a
close connection between them and the formation process of prestellar cores, where both structures are
highly concentrated around the protoclusters. About 10–20% of the gas mass is in the form of filaments
~7, while ~50–75% of the dense gas mass above Av
~7–10 is in filamentary structures.
Furthermore, ~90% of our prestellar cores are located above a background column density corresponding
~7, and ~75% of them lie within the densest filamentary structures with supercritical masses per unit
length >16 M⊙
/pc. Indeed, a strong correlation is found between the spatial distribution of prestellar cores
and the densest filaments.
Comparing the statistics of cores and filaments with the number of young stellar objects found by Spitzer
in the same complex, we also infer a typical timescale ~1 Myr for the formation and evolution of both
prestellar cores and filaments.
In summary, our Herschel
findings in Aquila support a filamentary paradigm for the early stages of SF,
where the cores result from the gravitational fragmentation of the densest filaments (cf. André et al. 2014, PPVI).
Eventually, this process may form bound star clusters around Serpens South and W40.