Volume 545, September 2012
|Number of page(s)||17|
|Section||Interstellar and circumstellar matter|
|Published online||10 September 2012|
European Southern Observatory, Alonso de Córdova 3107, Vitacura, 19001 Casilla,
2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
3 I. Physikalisches Institut, Universität zu Köln, Zülpicherstr. 77, 50937 Köln, Germany
Accepted: 12 June 2012
Context. The core mass functions (CMFs) of low-mass star-forming regions are found to resemble the shape of the initial mass function (IMF). A similar result is observed for the dust clumps in high-mass star-forming regions, although on spatial scales of clusters that do not resolve the substructure that is found in these massive clumps. The region IRAS 19410+2336 is one exception, having been observed on spatial scales on the order of ~2500 AU, which are sufficient to resolve the clump substructure into individual cores.
Aims. We investigate the protostellar content of IRAS 19410+2336 at high spatial resolution at 1.4 mm, determining the temperature structure of the region and deriving its CMF.
Methods. The massive star-forming region IRAS 19410+2336 was mapped with the PdBI (BCD configurations) at 1.4 mm and 3 mm in the continuum and several transitions of formaldehyde (H2CO) and methyl cyanide (CH3CN). The H2CO transitions were also observed with the IRAM 30 m Telescope.
Results. We detect 26 continuum sources at 1.4 mm with a spatial resolution as low as ~2200 AU, several of them with counterparts at near- and mid-infrared wavelengths, distributed in two (proto)clusters. With the PdBI CH3CN and PdBI/IRAM 30 m H2CO emission, we derive the temperature structure of the region, ranging from 35 K to 90 K. Using these temperatures, we calculate the core masses of the detected sources, ranging from ~0.7 M⊙ to ~8 M⊙. These masses are strongly affected by the spatial filtering of the interferometer, which removes a common envelope with ~90% of the single-dish flux. Considering only the detected dense cores and accounting for binning effects as well as cumulative distributions, we derive a CMF, with a power-law index β = −2.3 ± 0.2. We resolve the Jeans length of the (proto)clusters by one order of magnitude, and only find a small velocity dispersion between the different subsources.
Conclusions. Since we cannot unambiguously differentiate between protostellar and prestellar cores, the derived CMF is not prestellar. Furthermore, because of the large fraction of missing flux, we cannot establish a firm link between the CMF and the IMF. This implies that future high-mass CMF studies will need to complement the interferometer continuum data with the short spacing information, a task suitable for ALMA. We note that the method of extracting temperatures using H2CO lines becomes less applicable when reaching the dense core scales of the interferometric observations because most of the H2CO appears to originate in the envelope structure.
Key words: stars: formation / instrumentation: high angular resolution / instrumentation: interferometers / ISM: individual objects: IRAS 19410+2336
Based on observations carried out with the IRAM Plateau de Bure Interferometer and the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain):
Data cubes in FITS format are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A51
© ESO, 2012
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