Young Stars near Cometary Globule CG 30 in the Tumultuous Gum Nebula

Abstract

We have conducted a high-dispersion ($R\sim$ 34,000) optical spectroscopic study of 10 young stars near the cometary gloule CG 30 in the Gum Nebula, a diffuse H \textsc{ii} region home to at least 32 cometary globules. All 10 spectroscopically observed stars at the nebula's northern edge are of low mass (spectral types M4.5 - K5), have broad H$\alpha$ emission, and show spectral veiling. Eight of the 10 are classical T Tauri stars. We spectroscopically measure the photospheric properties of CG 30 IRS 4 inside CG 30. Though embedded, CG 30 IRS 4 is T Tauri-like, with relatively slow projected rotation and moderate veiling. Undepleted Li absorptions, strong H$\alpha$ emissions, and positions well above the main sequence on an HR diagram suggest the 10 stars are $\lesssim$1 Myr old. Using our measurements, previous spectroscopy, and previous photometry of 11 other young stars in the area, we determine stellar, kinematic, and accretion properties of a total of 21 young stars. Shared radial velocities, proper motions, distances, and ages suggest 14 of the young stars (including CG 30 IRS 4) are kinematically related to CG 30. From \textit{Gaia} DR2 distances to 6 of these stars, we derive a distance of $358.1\pm 2.2$ pc to the cometary globule complex CG 30/31/38. The CG 30 association has an accretor fraction of $29\pm 14$\%, low for quiescent clusters of similar age but consistent with other irradiated clusters. The Gum Nebula's moderate radiation environment ($G_0=6.6_{-2.7}^{+3.2}$ at CG 30) may be strong enough to shorten disk lifetimes.

20 pages, 7 figures, 9 tables

References in corpus (13)

• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• The Dartmouth Stellar Evolution Database
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• Proplyds and Massive Disks in the Orion Nebula Cluster Imaged with CARMA and SMA
• ALMA survey of Class II protoplanetary disks in Corona Australis: a young region with low disk masses
• A Young Planet Search in Visible and IR Light: DN Tau, V836 Tau, and V827 Tau
• Proplyds around a B1 star - 42 Orionis in NGC 1977
• SMA CO(2-1) Observations of CG30: A Protostellar Binary System with a High-Velocity Quadrupolar Molecular Outflow
• On the accretion properties of young stellar objects in the L1615/L1616 cometary cloud
• Kinematics of the Young Stellar Objects associated with the Cometary Globules in the Gum Nebula
• HII region G46.5-0.2: the interplay between ionizing radiation, molecular gas and star formation

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• Collision of Two Stellar Associations in the Nearby Gum Nebula