Star formation in Cometary Globule 1: the second generation^⋆,⋆⋆

¹ Observatory, University of Helsinki, Finland
² Department of Physics, Division of Geophysics and Astronomy, PO Box 64, 00014 University of Helsinki, Finland
e-mail: lauri.haikala@helsinki.fi
³ South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa
⁴ Southern African Large Telescope Foundation, PO Box 9, Observatory, 7935, Cape Town, South Africa

Received: 28 March 2010
Accepted: 9 July 2010

Abstract

Context. Cometary Globule 1 (CG 1) is the archetype Cometary Globule in the Gum nebula.

Aims. We attempt to discover stars possibly embedded in the globule head of the Gum nebula and to map distribution of its ISM.

Methods. We analyse C¹⁸O spectral line observations, NIR spectrosopy, narrow and broad band NIR imaging, and stellar photometry to determine the structure of the CG 1 head and the extinction of stars in its direction.

Results. A young stellar object (YSO) associated with a bright NIR nebulosity and a molecular hydrogen object (MHO 1411, a probable obscured HH-object) were discovered in the globule. Molecular hydrogen and Brγ line emission is seen in the direction of the YSO. The observed maximum optical extinction in the globule head is 9.^m2. The peak N(H₂) column density and the total mass derived from the extinction are 9.0 × 10²¹ cm^-2 and 16.7 M_⊙ (d/300 pc)². The C¹⁸O emission in the globule head is detected in a 1$\mathrm{\prime ̣}$5 by 4′ area with a sharp maximum SW of the YSO. Three regions can be discerned in C¹⁸O line velocity and excitation temperature. Because of variations in the C¹⁸O excitation temperature the integrated C¹⁸O line emission does not follow the optical extinction. It is argued that the changes in the C¹⁸Oexcitation temperatures are caused by radiative heating by NX Pup and interaction of the YSO with the parent cloud. No indication of a strong molecular outflow from the YSO is evident in the molecular line data. The IRAS point source 07178–4429 located in the CG 1 head resolves into two sources in the HIRES enhanced IRAS images. The 12 and 25 μm emission originates mainly in the star NX Puppis and the 60 and 100 μm emission in the YSO.