Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.207j&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Astronomy and Astrophysics
Astronomy
Scientific paper
Hot cores are hot, compact and dense condensations that represent one of the earliest stages in massive star formation. These objects are chemically very rich and are expected to show a chemical segregation naturally produced by the progressive decrease of the temperature of gas and dust with increasing distance to the central star. The detection of this segregation, however, has remained elusive since it occurs at spatial scales ≤1300 AU (i.e. angular scales ≤1" at the typical distances of high-mass star forming regions). Here, we present very high angular resolution observations (beam of 0.3", 300AU) recently carried out with the SMA toward the massive hot core in the AFGL2591 star forming region. Thanks to the total 8GHz bandwidth of the SMA, we have simultaneously imaged the emission of key molecular species such as CH_3OH, H_2CO, H_2S, SO, SO_2, OCS or HC_3N with unprecedented high-angular resolution. The SMA images show a clear chemical segregation of the molecular gas within the AFGL2591 hot core, with species such as i) H_2S and SO peaking at an inner core coincident with the radiocontinuum peak; ii) SO_2, HC_3N, and OCS located in a double-peaked structure circumventing the radiocontinuum peak; and iii) CH_3OH, which surrounds the two previous structures in a coherent, outer shell (see Figure 1). We have compared our SMA images with gas phase+dust grain chemical modelling of the hot core, and we conclude that the observed chemical segregation is a consequence of the combination of two different chemical effects, a strong UV photodissociation and a high-temperature gas-phase chemistry, within an almost dust-free cavity in the innermost regions of the AFGL2591 hot core. This pilot study shows the need to carry out comprehensive studies of the chemical complexity in massive hot cores at very high angular resolutions, in order to clearly establish the physical structure of these cores, and the physical and chemical processes taking place within them. These studies will greatly benefit from the large simultaneous bandwidth and very high-angular resolution (down to 5 mas) achieved by the Atacama Large Millimeter Array (ALMA).
de Wit Willem-Jan
Jiménez-Serra Izaskun
Martín-Pintado Jesús
Viti Serena
Zhang Qian
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