A radial velocity survey of the Carina Nebula's O-type stars

Abstract

We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1-2 km s −1 precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6 km s −1 . We calculate a velocity dispersion of ≤ 9.1 km s −1 , consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5 km s −1 radial velocity offset from its neighbor Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive-star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10-15 km s −1 , possibly triggering further massive-star formation. The expansion of the surrounding H ii region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.

The Young Massive Star Cluster Westerlund 2 Observed with MUSE. II. MUSEpack—A Python Package to Analyze the Kinematics of Young Star Clusters

“…Using these data we showed that 1) it is possible to obtain stellar and gas RVs with an accuracy of ∼ 1 km s −1 in nearby YMCs, 2) we can measure spectral types of main and pre-main-sequence stars, and 3) Wd2 shows a bimodal velocity structure with two peaks at (8.10 ± 1.53) km s −1 and (25.41 ± 3.15) km s −1 . The RV dispersion of both peaks is in agreement with the RV dispersion seen in other YMCs such as Trumpler 14 (Kiminki & Smith 2018), the Carina Nebula (e.g., Smith & Brooks 2008), or NGC 3603 (Rochau et al 2010Pang et al 2013). Because of the limited data of only 72 stars, we could not properly address the physical origin of such bimodal RV distribution.…”

Carina’s pillars of destruction: the view from ALMA

“…The pillars sample the 'Southern Pillars', 'Northern Pillars', and the 'Southwestern Pillars' complexes as defined in Hartigan et al (2015), and in the following we use their pillar Table 4 of Hanes et al (2018) and Table 2 of Kiminki & Smith (2018). The colours of the star markers corresponds to their radial velocities of those stars.…”

The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities

“…The stellar velocity dispersion of young star clusters is typically on the order of ∼ 5 km s −1 (e.g., Rochau et al 2010;Pang et al 2013;Cottaar & Hénault-Brunet 2014;Kiminki & Smith 2018). To measure these velocities high-resolution spectrographs are typically used (with resolving power of R ≈ 30000-60000).…”

“…In a recent study, Kiminki & Smith (2018) measured a velocity dispersion of ≤ 9.1 km s −1 or 41 wellconstrained O-type stars in the Trumpler 14 cluster in the Carina Nebula (e.g., Smith & Brooks 2008, and references therein). Rochau et al (2010) used HST/WFPC2 (Gonzaga & Biretta 2010) observations to measure proper motions of NGC 3603 and determined a 1D velocity dispersion of (4.5 ± 0.8) km s −1 .…”