Near infrared imaging of the cometary globule CG 12 ^*,**

¹ Observatory, PO Box 14, University of Helsinki, Finland e-mail: lauri.haikala@helsinki.fi
² Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720, USA e-mail: reipurth@ifa.hawaii.edu

Received: 7 August 2009
Accepted: 15 October 2009

Abstract

Context. Cometary globule 12 is a relatively little investigated medium- and low mass star forming region 210 pc above the Galactic plane.

Aims. This study sets out to discover the possibly embedded members of the CG 12 stellar cluster, to refine the NIR photometry of the known member stars and to study the star formation activity in CG 12 and its relation to the distribution of molecular gas, dust and mid- to far-infrared emission in the cloud.

Methods. NIR J, H, and Ks imaging and stellar photometry is used to analyse the stellar content and the structure of CG 12.

Results. Several new members and member candidates of the CG 12 stellar cluster were found. The new members include in particular a highly embedded source with a circumstellar disk or shell and a variable star with a circumstellar disk which forms a binary with a previously known A spectral type cluster member. The central source of the known collimated molecular outflow in CG 12 and an associated “hourglass”-shaped object due to reflected light from the source were also detected. The maximum visual extinction in the cloud, based on observations of background stars, is ~20^m, but this is only a lower limit for the extinction through the two dense cloud cores. HIRES-enhanced IRAS images are used together with JHKs imaging to study the two associated IRAS point sources, 13546-3941 and 13547-3944. Two new 12  sources coinciding with NIR excess stars were detected in the direction of IRAS 13546-3941. The IRAS 13547-3944 emission at 12 and 25  originates in the Herbig AeBe star h4636n and the 60 and 100  emission from an adjacent cold source.