Site Map
Contacts
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

Probing the close environment of massive young stars with spectro-astrometry

J. M. C. Grave, M. S. N. Kumar

Abstract

Aims. We test the technique of spectro-astrometry to investigate the close environment of massive young stellar objects (MYSOs).
Methods. Archival VLT near infrared K band spectra (R = 8900) of three massive young stellar objects and one Wolf-Rayet star are examined for spectro-astrometric signatures. The young stellar objects display emission lines such as Brγ, CO 2–0 and CO 3–1 that are characteristic of ionised regions and molecular disks respectively. Two of the sample sources also display emission lines such as NIII and MgII that are characteristic of high temperatures.
Results. Most of the emission lines show spectro-astrometric signal at various levels resulting in different positional displacements. The shapes and magnitudes of the positional displacements imply the presence of large disks/envelopes in emission and expanding shells of ionised gas. The results obtained for the source 18006-2422nr766 in particular provide larger estimates (>300 AU) for CO emitting regions, indicating that in MYSOs, CO may also arise from inner regions of extended dense envelopes.
Conclusions. The overall results from this study demonstrate the utility of spectro-astrometry to constrain the sizes of physical entities such as disks/envelopes, UCHII regions and/or ionised shells in the close environment of a massive young star.

Keywords
techniques: spectroscopic – stars: formation – ISM: HII regions – line: profiles – methods: observational

Astronomy and Astrophysics
Volume 462, Page L37
February 2007

>> PDF>> DOI

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

Proceed on CAUP's website|Go to IA website