Astronomy and Astrophysics, volume 545A, 51-51 (2012/9-1)
Fragmentation in the massive star-forming region IRAS 19410+2336.
RODON J.A., BEUTHER H. and SCHILKE P.
Abstract (from CDS):
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 IRAS19410+2336 is one exception, having been observed on spatial scales on the order of ∼2500AU, which are sufficient to resolve the clump substructure into individual cores. We investigate the protostellar content of IRAS19410+2336 at high spatial resolution at 1.4mm, determining the temperature structure of the region and deriving its CMF. The massive star-forming region IRAS19410+2336 was mapped with the PdBI (BCD configurations) at 1.4mm and 3mm in the continuum and several transitions of formaldehyde (H2CO) and methyl cyanide (CH3CN). The H2CO transitions were also observed with the IRAM 30m Telescope. We detect 26 continuum sources at 1.4mm with a spatial resolution as low as ∼2200AU, several of them with counterparts at near- and mid-infrared wavelengths, distributed in two (proto)clusters. With the PdBI CH3CN and PdBI/IRAM 30m H2CO emission, we derive the temperature structure of the region, ranging from 35K to 90K. Using these temperatures, we calculate the core masses of the detected sources, ranging from ∼0.7M☉to ∼8M☉. 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. 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.
stars: formation - instrumentation: high angular resolution - instrumentation: interferometers - ISM: individual objects: IRAS 19410+2336
VizieR on-line data:
<Available at CDS (J/A+A/545/A51): maps.dat fits/*>
Table 2:[RBS2012b] NN-a (Nos 1-s to 22-s, 1-n to 8-n), [RBS2012b] c3mm-aR (Nos c3mm-sI to c3mm-sIII, c3mm-nI to c3mm-nII).
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