The young stellar cluster [DBS2003] 157 associated with the H ii region GAL 331.31-00.34

M. C. Pinheiro*, Z. Abraham, M. V. F. Copetti, R. Ortiz, D. A. Falceta-Goncalves, A. Roman-Lopes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

We report a study of the stellar content of the near-infrared (NIR) cluster [DBS2003] 157 embedded in the extended H ii region GAL 331.31-00.34, which is associated with the IRAS source 16085-5138. JHK photometry was carried out in order to identify potential ionizing candidates, and the follow-up NIR spectroscopy allowed the spectral classification of some sources, including two O-type stars. A combination of NIR photometry and spectroscopy data was used to obtain the distance of these two stars, with the method of spectroscopic parallax: IRS 298 (O6 V, 3.35 +/- 0.61 kpc) and IRS 339 (O9 V, 3.24 +/- 0.56 kpc). Adopting the average distance of 3.29 +/- 0.58 kpc and comparing the Lyman continuum luminosity of these stars with that required to account for the radio continuum flux of the H ii region, we conclude that these two stars are the ionizing sources of GAL 331.31-00.34. Young stellar objects (YSOs) were searched by using our NIR photometry and mid-infrared (MIR) data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The analysis of NIR and MIR colourcolour diagrams resulted in 47 YSO candidates. The GLIMPSE counterpart of IRAS 16085-5138, which presents IRAS colour indices compatible with an ultracompact H ii region, has been identified. The analysis of its spectral energy distribution between 2 and m revealed that this source shows a spectral index a= 3.6 between 2 and m, which is typical of a YSO immersed in a protostellar envelope. Lower limits to the bolometric luminosity and the mass of the embedded protostar have been estimated as L= 7.7 x 10(3) L? and M= 10 M?, respectively, which correspond to a B0B1 V zero-age main sequence star.

Original languageEnglish
Pages (from-to)2425-2435
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume423
Issue number3
DOIs
Publication statusPublished - Jul 2012

Keywords

  • stars: early-type
  • stars: pre-main-sequence
  • H II regions
  • Herbig-Haro objects
  • METHANOL MASER SURVEY
  • SPECTRAL ATLAS
  • SOUTHERN MILKY
  • INNER GALAXY
  • OB STARS
  • EMISSION
  • OBJECTS
  • COLORS
  • CLASSIFICATION
  • POPULATION

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