科研之友
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摘要
NGC 7129 is a bright reflection nebula located in the molecular cloud complex near l = 105 degrees.4, b = +9 degrees.9, about 1.15 kpc distant. Embedded within the reflection nebula is a young cluster dominated by a compact grouping of four early-type stars: BD+65 degrees 1638 (B3V), BD+65 degrees 1637 (B3e), SVS 13 (B5e), and LkH alpha 234 (B8e). About 80 Ha emission sources brighter than V similar to 23 are identified in the region, many of which are presumably T Tauri star members of the cluster. We also present deep (V similar to 23), optical (VRCIC) photometry of a field centered on the reflection nebula and spectral types for more than 130 sources determined from low dispersion, optical spectroscopy. The narrow pre-main sequence evident in the color-magnitude diagram suggests that star formation was rapid and coeval. A median age of about 1.8 Myr is inferred for the H alpha and literature-identified X-ray emission sources having established spectral types, using pre-main sequence evolutionary models. Our interpretation of the structure of the molecular cloud and the distribution of young stellar objects is that BD+65 degrees 1638 is primarily responsible for evacuating the blister-like cavity within the molecular cloud. LkH alpha 234 and several embedded sources evident in near-infrared adaptive optics imaging have formed recently within the ridge of compressed molecular gas. The compact cluster of low-mass stars formed concurrently with the early-type members, concentrated within a central radius of similar to 0.7 pc. Star formation is simultaneously occurring in a semi-circular arc some similar to 3 pc in radius that outlines remaining dense regions of molecular gas. High dispersion, optical spectra are presented for BD+65 degrees 1638, BD+65 degrees 1637, SVS 13, LkH alpha 234, and V350 Cep. These spectra are discussed in the context of the circumstellar environments inferred for these stars.
- 出版日期2015-6
