Low-Mass Star Formation in the Gum Nebula: The CG 30/31/38 Complex

Abstract

We present photometric and spectroscopic results for the low-mass pre–main-sequence (PMS) stars with spectral types K–M in the cometary globule (CG) 30/31/38 complex. We obtained multiobject high-resolution spectra for the targets selected as possible PMS stars from multiwavelength photometry. We identified 11 PMS stars brighter than V = 16.5 with ages 5 Myr at a distance of approximately 200 pc. The spatial distribution of the PMS stars, CG clouds, and ionizing sources (O stars and supernova remnants) suggests a possible triggered origin of the star formation in this region. We confirm the youth of the photometrically selected PMS stars using the lithium abundances. The radial velocities of the low-mass PMS stars are consistent with those of the cometary globules. Most of the PMS stars show weak Hα emission with Wλ(Hα) < 10 A. Only one out of the 11 PMS stars shows a moderate near-IR excess, which suggests a short survival time (t < 5 Myr) of circumstellar disks in this star-forming environment. In addition, we find five young late-type stars and one Ae star that have no obvious relation to the CG 30/31/38 complex. We also discuss a possible scenario of the star formation history in the CG 30/31/38 region.