Details

Autor(en) / Beteiligte

• Moisés, A. P.
• Damineli, A.
• Figuerêdo, E.
• Blum, R. D.
• Conti, P. S.
• Barbosa, C. L.

Titel

Spectrophotometric distances to Galactic H ii regions

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2011-02, Vol.411 (2), p.705-760

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

2011

Link zum Volltext

Quelle

Wiley Online Library

Beschreibungen/Notizen

• We present a near-infrared study of the stellar content of 35 H ii regions in the Galactic plane, 24 of which have been classified as giant H ii regions. We have selected these optically obscured star-forming regions from the catalogues of Russeil, Conti & Crowther and Bica et al. In this paper, we have used the near-infrared domain J-, H- and K s-band colour images to visually inspect the sample. Also, we have used colour-colour and colour-magnitude diagrams to indicate ionizing star candidates, as well as the presence of young stellar objects such as classical T Tauri stars and massive young stellar objects (MYSOs). We have obtained Spitzer Infrared Array Camera images for each region to help further characterize them. Spitzer and near-infrared morphology were used to place each cluster in an evolutionary phase of development. Spitzer photometry was also used to classify the MYSOs. A comparison of the main sequence in the colour-magnitude diagrams for each observed cluster was used to infer whether or not the cluster kinematic distance is consistent with brightnesses of the stellar sources. We find qualitative agreement for a dozen of the regions, but about half the regions have near-infrared photometry that suggests they may be closer than the kinematic distance. A significant fraction of these already have spectrophotometric parallaxes that support smaller distances. These discrepancies between kinematic and spectrophotometric distances are not a result of the spectrophotometric methodologies, as independent non-kinematic measurements are in agreement with the spectrophotometric results. For instance, the trigonometric parallaxes of star-forming regions were collected from the literature and show the same effect of smaller distances when compared to the kinematic results. In our sample of H ii regions, most of the clusters are evident in the near-infrared images. Finally, it is possible to distinguish among qualitative evolutionary stages for these objects.