Star formation in the Cometary Globule Ori I-2

TL;DR

This study investigates star formation in the cometary globule Ori I-2 using multi-wavelength observations, revealing triggered star formation and identifying various classes of young stellar objects, including embedded protostars and outflows.

Contribution

It provides a detailed multi-wavelength analysis of the young stellar population in Ori I-2, identifying new protostars and outflows, and demonstrating triggered star formation in the globule.

Findings

Identification of 125 sources within the region.

Discovery of multiple classes of young stellar objects, including Class 0/I and Class II.

Detection of a new Herbig-Haro object, HH 992.

Abstract

We investigate the young stellar population in and near the cometary globule Ori,I-2. The analysis is based on deep Nordic Optical Telescope R-band and H-alpha images, JCMT SCUBA 450 and 850 micron images combined with near-infrared 2MASS photometry and mid-infrared archival Spitzer images obtained with the IRAC (3.6, 4.5, 5.8 and 8 micron), and MIPS (24 and 70 micron) instruments. We identify a total of 125 sources within the 5'x5' region imaged by IRAC. Of these sources 87 are detected in the R-band image and 51 are detected in the 2MASS survey. The detailed physical properties of the sources are explored using a combination of near/mid-infrared color-color diagrams, greybody fitting of SEDs and an online SED fitting tool that uses a library of 2D radiation transfer based accretion models of young stellar objects with disks. Ori I-2 shows clear evidence of triggered star formation with four young low luminosity pre-main sequence stars embedded in the globule. At least two, possibly as many as four, additional low-mass PMS objects, were discovered in the field which are probably part of the young sigma-Orionis cluster. Among the PMS stars which have formed in the globule, MIR-54 is a young, deeply embedded Class 0/I object, MIR-51 and 52 are young Class II sources, while MIR-89 is a more evolved, heavily extincted Class II object with its apparent colors mimicking a Class 0/I object. The Class II source, MIR-52, which is strong a H-alpha emission line star appears to drive an outflow approximately aligned with the outflow from MIR-54, and because of the proximity of the two outflows, either star could contribute. MIR-89 appears to excite a low excitation HH object, HH 992, discovered for the first time in this study.