My researchMy researchMy research interest have always been aimed towards problems in star formation. My thesis work (in 1984) was titled "Star formation in a region of the Gum Nebula" and dealt with low-mass T Tauri stars and Herbig Haro objects in and close to so called cometary globules in the huge Gum nebula in the southern constellation of Puppis. Ever since I have endeavoured to unveil more about these elusive young objects. A number of long-term studies are going on and some have been been finished. A sample is presented below.
Star formation in the Vela Molecular Ridge
NGC 2266 in Vela Molecular Ridge
Pettersson is continuing the work on star forming regions in Puppis and Vela,partly in collaboration with B. Reipurth at ESO. Objective prism plates from the Schmidt telescope (La Silla, Chile) are used to search for H-alpha-emission-line stars in and near dark clouds seen towards the large molecular complex of the Vela Molecular Ridge (VMR).
About six hundred faint Halpha-emission objects have so far been found, indicating a massive star formation in the clouds. The survey reaches objects with V-magnitudes about 20-21 and is probably complete to a V-magnitude of about 19.
A project to investigate the H-alpha-emission-line objects with multi-object slit spectroscopy using the OPTOPUS at ESO, has been carried out and the result indicates that at least about 80% of the stars found in the objective prism surveys in the VMR definitely appear to be T Tauri stars, the rest are either Herbig Ae/Be stars (more massive young stars) or background Be stars.
Below is a plot, showing the new emission-line stars together with contours showing the extent of VMR cloud D and the northern part of cloud C. The full black dots are the stars, Cr197, RCW32 mark the position of Collinder 197. The new T Tauri associations are also marked as are the associated HII-regions RCW 27 and RCW33. The extent of the molecular clouds, as seen in emission from carbon monoxide, is illustrated with small open squares (lowest contour) and small dots.
The image on the right shows the Collinder 197 region.
The emission nebula is RCW32, note the dark dust lane, typical for regions with star formation.
Recent results with the ROSAT orbiting X-ray observatory have disclosed 35 point-like sources in Collinder 197, occupying the same region as the T Tauri stars. Thus, the population of young pre-main sequence stars in this young open cluster probably amounts to at least 50. The work is continuing, with the ultimate goal of providing an IMF, initial mass function, for this cluster.
H-alpha-emission survey of star forming molecular cloudsA project to make a deep H-alpha-emission survey of most of the major southern star forming molecular clouds have been going on for some time. The purpose of the project is to do a really deep search for faint emission line stars that are likely to be low- to intermediate mass pre-main sequence objects. The observations are made in collaboration with Dr. Reipurth at ESO. It utilises the ESO Schmidt telescope with a hypersensitized fine-grained photographic film, Kodak 4415, together with an RG630 red cut-on filter to isolate the H-alpha region of the spectrum.
So far observations have been almost completed only for the M42-region in Orion . The result is overwhelming in that a stunning number of new objects have been detected and we expect to more than double the number of pre-main sequence objects known here up till now. The survey result will be followed up by a combination of existing infrared and molecular data as well as new slit spectroscopy.
Further results will soon be available for other regions like Rho Ophiuci, Lupus, NGC 2264 and others.
The Zeta Sculptoris cluster
bertil.pettersson@astro.uu.se
Last updated on Jan 9th, 1997
