The solar type protostar IRAS16293-2422: new constraints on the physical structure

Abstract

Context. The low mass protostar IRAS16293-2422 is a prototype Class 0 source in studies of the chemical structure during the initial phases of life of solar type stars. Aims. To derive the chemical structure accurately, a precise determination of the source physical structure is required. The goal of this study is to derive the structure of IRAS16293-2422. Methods. We reanalyzed all available continuum data (single dish and interferometric, from millimeter to MIR) to derive accurate density and dust temperature profiles. Using ISO observations of water, we also reconstructed the gas temperature profile. Results. Our analysis shows that the envelope surrounding IRAS16293-2422 is described well by the Shu "inside-out" collapsing envelope model or a single power-law density profile with index equal to 1.8. In contrast to some previous studies, our analysis does not show evidence of a large (≥800 AU in diameter) cavity. Conclusions. Although IRAS16293-2422 is a multiple system composed of two or three objects, our reconstruction will be useful in deriving the chemical structure of the large cold envelope surrounding these objects and the warm component, treated here as a single source, from single-dish observations of molecular emission.

A study of deuterated water in the low-mass protostar IRAS 16293-2422

“…However, since the gas is practically thermally coupled with the dust, the impact in the gas temperature is certainly negligible. The largest difference between the gas and dust temperature is less than 10% (Crimier et al 2010). The discrepancy on the water abundance therefore results in a different deuteration ratio in the outer envelope.…”

“…The source structure used in the modeling was determined by Crimier et al (2010) with a radius extending from 22 AU to 6100 AU (see Fig. 2); however, the structure in the hot corino region (T ≥ 100 K) may be uncertain since disks probably exist in the inner part of the protostellar envelopes.…”

“…For a radius greater than 1280 AU, the envelope is considered as static (the velocity is fixed at 0). This radius corresponds to a change in the slope of the density profile, marking the transition of the collapsing/static envelope (Shu 1977), and its value has been determined by Crimier et al (2010). To reproduce the widths of the absorption lines, the turbulence Doppler b-parameter (equal to 0.6 × FWHM) is fixed at 0.3 km s −1 .…”

“…As source A is more massive than source B, we considered that the structure is centered on core A. According to interferometric data of the HDO 3 1,2 −2 2,1 line at 226 GHz, deuterated water is mainly emitted by core A (Jørgensen et al 2011 Crimier et al (2010). The expected abundance profile of water is added (dashed-dotted line) on an arbitrary Y-scale.…”

“…The N(H 2 ) column density of the ρ Oph cloud has been estimated at ∼1.5 × 10 22 cm −2 by van Dishoeck et al (1995) and at 5 × 10 22 cm −2 by Caux et al (1999). Adding a molecular cloud with these characteristics to the structure determined by Crimier et al (2010) does not allow deep absorption lines to be modeled. This hypothesis is therefore insufficient to explain the deep HDO absorption lines.…”