Optical and near-infrared surveys in star forming regions

Abstract

We have observed several different star formation regions, in top quality observatories: two missions at the Kitt Peak National Observatory, in Arizona, using the 4m and the 0.9m telescopes and two other missions at the Mauna Kea observatory in Hawaii, using the 2.2m optical telescope and the 4m infrared telescope (UKIRT). We have obtained very good quality data, high resolution deep images with seeing of the order of 1 or less, combined with large field of view, with the objective to obtain as much information on each region as possible.In order to probe the more evolved optically visible young stars, we have analyzed surveys to detect H_ emission stars in two very well known star forming regions: NGC 2264 and M 42. They where obtained with a wide field Schmidt telescope associated with the best quality photographic films, providing a survey of an area of 5×5 in the sky and enough sensitivity to reach red photographic magnitudes up to 19 mag, yielding a detection of a much larger number of young stars than previously known. We provide tables with coordinates, finding charts, cross identification with other surveys and magnitudes in public catalogs. Optical narrow-band surveys to detect Herbig-Haro objects are presented as well, for the star forming regions S140 and L1551. In the latter, previous images allowed the determination of proper motion using a cross correlation technique. A modern widefield MOSAIC CCD was used, providing a large scale view of the entire region, as well as high enough resolution (0.26/pix) to detect structure details of the knots inside the shock regions. New Herbig-Haro objects were detected. A possible alignment of the main flow axis with the magnetic field in the cloud is discussed. The same correlation technique was used to measure proper motions in the well known HH 47 jet, using even higher resolution Hubble Space Telescope images (0.1/pix) taken in two epochs. Some other known star forming regions were surveyed at optical and near-infrared wavelengths for a study of both the young sources and the Herbig-Haro objects, in an attempt to relate them and to shed more light into the understanding of the star formation processes in those areas. Two of those regions are presented in this work: the IC 1396N globule and a region called by us the Gulf of Mexico, because of its location in the dark cloud southwest of the North America Nebula. The optical images were obtained in perfect conditions in one of the best observing sites in the world (the Mauna Kea observatory in Hawaii). The surveyed regions were only a few arcminutes wide, but the resolution was good and the areas cover the main region where the star formation processes are occurring. Several new Herbig-Haro objects were found, as well as new H_ emission line stars. The near-infrared observations allowed a view of the interior of the molecular clouds, probing embedded young stars and outflows. In some cases the near-infrared observations lacked the quality necessary for building a comprehensive view of the young sources, and we could not infer physical properties for those stars. But we were able to detect some previously unknown young stars, some of them powering outflows of various types. So far we have seven different star forming regions studied using various techniques, for which we discuss differences and similarities. A few other regions were also observed and their study is planned in the near future. We conclude that the star formation process is much more complex than it was thought a few years ago, and only with the simultaneous use of different techniques applied to several star forming regions will we be able to answer the numerous questions about this process (and probably create many more questions. . . ).