| Apresentação/Painel: | |
| Autor: | Felipe Donizeti Teston Navarete1 |
| Augusto Damineli1 | |
| Alessandro P. Moises1 | |
| Elysandra Figueredo1,2 | |
| Robert D. Blum3 | |
| Peter S. Conti4 | |
| Instituição: | 1IAG/USP - São Paulo |
| 2Open University | |
| 3NOAO Gemini Science Center - Tucson | |
| 4Univeristy of Colorado | |
| Formato: | Painel |
| Título: | K-band spectrophotometric distance to W3 |
| Resumo: |
The spiral structure of the Milky Way is difficult to trace from our position.
Giant HII regions are the best targets for this job. However, different
methods give discrepant results. The Galactic HII region W3, located in the
Perseus arm, offers a great opportunity to compare these methods. The values
for the distance of W3 and the respective methodology are: a) radio
trigonometric parallax to W3 (Xu et al., 2006); b) spectrophotometry in
the optical range (Humphreys 1978) and c) kinematic model based on radio
recombination lines (Russeil 2003), which leads to a estimated distance of
1.95 ± 0.04 kpc, 2.18 ± 0.01 kpc and 4.2 ± 0.7 kpc,
respectively. The
kinematic model disagrees from the other methods by a factor of 2, and the
same occurs when comparing our K-band spectrophotometric measurements.
In order to check those results, we used NIFS/Gemini North to observe 7 O-type star candidates with a S/N ~130 and spectral resolution R~5200 in the K-band. We classified five W3 stars with spectral types in O6.5 to B1 range. Assuming luminosity class between ZAMS and V, the estimated distance is 1.9 ± 0.9 kpc. This value is in great agreement with the methods a) and b). The kinematic method disagrees with our and all other methods, giving distances 2X larger. |
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