Massive Stars in Molecular Clouds Rich in High-energy Sources: The Bridge of G332.809-0.132 and CS 78 in NGC 6334
Abstract
Detections of massive stars in the direction of the H II region CS 78 in NGC 6334 and of G332.809-0.132 are here presented. The region covered by the G332.809-0.132 complex coincides with the RCW 103 stellar association. In its core (40' in radius), approximately 110 OB candidate stars (Ks < 10 mag and 0.4 < ${A}_{{K}_{s}}$ < 1.6 mag) were identified using 2MASS, DENIS, and GLIMPSE data. This number of OB stars accounts for more than 50% of the observed number of Lyman continuum photons from this region. Medium-resolution K-band spectra were obtained for seven early types, including one WN 8 star and one Ofpe/WN 9 star; the latter is located near the RCW 103 remnant and its luminosity is consistent with a distance of ≈3 kpc. The area analyzed encloses 9 of the 34 OB stars previously known in RCW 103, as well as IRAS 16115-5044, which we reclassify as a candidate luminous blue variable. The line of sight is particularly interesting, crossing three spiral arms; a molecular cloud at -50 (with RCW 103 in the Scutum-Crux arm) and another at -90 km s-1 (in the Norma arm) are detected, both rich in massive stars and supernova remnants. We also report the detection of a B supergiant as the main ionizing source of CS 78, 2MASS J17213513-3532415. Medium-resolution H- and K-band spectra display H I and He I lines, as well as Fe II lines. By assuming a distance of 1.35 kpc, we estimate a bolometric magnitude of -6.16, which is typical of supergiants. ∗ Based on observations collected at the European Southern Observatory (ESO Programmes 087.D-09609). † M.M. is currently employed by USTC. This works was designed during her ESA fellowship (2010) and partially carried out at the MPIfR.
- Publication:
-
The Astronomical Journal
- Pub Date:
- August 2020
- DOI:
- 10.3847/1538-3881/ab9950
- arXiv:
- arXiv:2007.11074
- Bibcode:
- 2020AJ....160...65M
- Keywords:
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- Stellar evolution;
- Infrared sources;
- Supergiant stars;
- Early-type emission stars;
- 1599;
- 793;
- 1661;
- 428;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 44 pages, 15 figures