Mid-infrared interferometry of the massive young stellar object NGC 3603 - IRS 9A
Abstract
Context. Very few massive young stellar objects (MYSO) have been studied in the infrared at high angular resolution due to their rarity and large associated extinction. We present observations and models for one of these MYSO candidates, NGC 3603 IRS 9A.
Aims: Our goal is to investigate with infrared interferometry the structure of IRS 9A on scales as small as 200 AU, exploiting the fact that a cluster of O and B stars has blown away much of the obscuring foreground dust and gas.
Methods: Observations in the N-band were carried out with the MIDI beam combiner attached to the VLTI, providing spatial information on scales of about 25-95 milli-arcsec (mas). Additional interferometric observations which probe the structure of IRS 9A on larger scales were performed with an aperture mask installed in the T-ReCS instrument of Gemini South. The spectral energy distribution (SED) is constrained by the MIDI N-band spectrum and by data from the Spitzer Space Telescope. Our efforts to model the structure and SED of IRS 9A range from simple geometrical models of the brightness distribution to one- and two-dimensional radiative transfer computations.
Results: The target is resolved by T-ReCS, with an equivalent (elliptical) Gaussian width of 330 mas by 280 mas (2300 AU by 2000 AU). Despite this fact, a warm compact unresolved component was detected by MIDI which is possibly associated with the inner regions of a flattened dust distribution. Based on our interferometric data, no sign of multiplicity was found on scales between about 200 AU and 700 AU projected separation. A geometric model consisting of a warm (1000 K) ring (400 AU diameter) and a cool (140 K) large envelope provides a good fit to the data. No single model fitting all visibility and photometric data could be found, with disk models performing better than spherical models.
Conclusions: While the data are clearly inconsistent with a spherical dust distribution they are insufficient to prove the existence of a disk but rather hint at a more complex dust distribution.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2010
- DOI:
- 10.1051/0004-6361/200913546
- arXiv:
- arXiv:1009.1598
- Bibcode:
- 2010A&A...520A..78V
- Keywords:
-
- techniques: interferometric;
- circumstellar matter;
- stars:;
- early-type;
- stars: formation;
- stars: pre-main sequence;
- individual: NGC 3603 IRS 9A;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 8 pages, 11 figures. Accepted for publication in A&