A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey^{⋆,⋆⋆,⋆⋆⋆}

¹ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
e-mail: vera.konyves@cea.fr; pandre@cea.fr
² Institut d’Astrophysique Spatiale, UMR8617, CNRS/Université Paris-Sud 11, 91405 Orsay, France
³ Univ. Bordeaux, LAB, UMR5804, 33270 Floirac, France
⁴ CNRS, LAB, UMR5804, 33270 Floirac, France
⁵ Department of Physics and Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria, BC, V8W 3P6, Canada
⁶ National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
⁷ School of Physics & Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA, UK
⁸ Istituto di Astrofisica e Planetologia Spaziali-INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁹ CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹⁰ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse Cedex 4, France
¹¹ Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
¹² Jeremiah Horrocks Institute, University of Central Lancashire, Preston, Lancashire, PR1 2HE, UK
¹³ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
¹⁴ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁵ Institut d’Astrophysique de Paris, Sorbonne Universités, UPMC Univ. Paris 06, CNRS UMR 7095, 75014 Paris, France
¹⁶ Scientific Support Office, Directorate of Science and Robotic Exploration, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁷ INAF-IRA, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁸ Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
¹⁹ RALSpace, The Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, England
²⁰ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, England

Received: 10 February 2015
Accepted: 13 July 2015

Abstract

We present and discuss the results of the Herschel Gould Belt survey (HGBS) observations in an ~11 deg² area of the Aquila molecular cloud complex at d ~ 260 pc, imaged with the SPIRE and PACS photometric cameras in parallel mode from 70 μm to 500 μm. Using the multi-scale, multi-wavelength source extraction algorithm getsources, we identify a complete sample of starless dense cores and embedded (Class 0-I) protostars in this region, and analyze their global properties and spatial distributions. We find a total of 651 starless cores, ~60% ± 10% of which are gravitationally bound prestellar cores, and they will likely form stars inthe future. We also detect 58 protostellar cores. The core mass function (CMF) derived for the large population of prestellar cores is very similar in shape to the stellar initial mass function (IMF), confirming earlier findings on a much stronger statistical basis and supporting the view that there is a close physical link between the stellar IMF and the prestellar CMF. The global shift in mass scale observed between the CMF and the IMF is consistent with a typical star formation efficiency of ~40% at the level of an individual core. By comparing the numbers of starless cores in various density bins to the number of young stellar objects (YSOs), we estimate that the lifetime of prestellar cores is ~1 Myr, which is typically ~4 times longer than the core free-fall time, and that it decreases with average core density. We find a strong correlation between the spatial distribution of prestellar cores and the densest filaments observed in the Aquila complex. About 90% of the Herschel-identified prestellar cores are located above a background column density corresponding to A_V ~ 7, and ~75% of them lie within filamentary structures with supercritical masses per unit length ≳16 M_⊙/pc. These findings support a picture wherein the cores making up the peak of the CMF (and probably responsible for the base of the IMF) result primarily from the gravitational fragmentation of marginally supercritical filaments. Given that filaments appear to dominate the mass budget of dense gas at A_V> 7, our findings also suggest that the physics of prestellar core formation within filaments is responsible for a characteristic “efficiency” for the star formation process in dense gas.