Sequential star formation in a cometary globule (BRC37) of IC1396

TL;DR

This study investigates sequential star formation in a cometary globule of IC1396, revealing that UV radiation from exciting stars likely triggered the formation of low-mass stars and a brown dwarf in a specific spatial sequence.

Contribution

It provides observational evidence for sequential star formation driven by UV radiation in a cometary globule, including the possible formation of a brown dwarf by UV impact.

Findings

Six H_alpha emission stars aligned towards exciting stars

Four low-mass YSOs formed ~1 Myr ago at the globule tip

Potential UV-induced formation of a young brown dwarf

Abstract

We have carried out near-IR/optical observations to examine star formation toward a bright-rimmed cometary globule (BRC37) facing the exciting star(s) of an HII region (IC1396) containing an IRAS source, which is considered to be an intermediate-mass protostar. With slit-less spectroscopy we detected ten H_alpha emission stars around the globule, six of which are near the tip of the globule and are aligned along the direction to the exciting stars. There is evidence that this alignment was originally towards an O9.5 star, but has evolved to align towards a younger O6 star when that formed. Near-IR and optical photometry suggests that four of these six stars are low-mass young stellar objects (YSOs) with masses of ~0.4 M_sun. Their estimated ages of ~1 Myr indicate that they were formed at the tip in advance of the formation of the IRAS source. Therefore, it is likely that sequential star formation has been taking place along the direction from the exciting stars towards the IRAS source, due to the UV impact of the exciting star(s). Interestingly, one faint, H_alpha emission star, which is the closest to the exciting star(s), seems to be a young brown dwarf that was formed by the UV impact in advance of the formation of other YSOs at the tip.