HUBBLE-SPACE-TELESCOPE MAPPING OF THE ORION NEBULA .1. A SURVEY OF STARS AND COMPACT OBJECTS

We report on a survey of the brightest portions of the Orion Nebula ma de with the Wide Field Planetary Camera 2 of the Hubble Space Telescop e. Fifteen pointings were made, each employing interference filters is olating the principal emission lines of H I, [N II], and [O III] and a nother isolating an interval similar to the V bandpass. A careful surv ey of compact objects of stellar and nearly stellar appearance was mad e and astrometric solutions for individual fields were used to determi ne positions accurate to about 0.1 ''. 344 stars were measured, down t o about V = 22. In addition to structures in several of the previously known Herbig-Haro objects, 145 compact sources that can be classified as proplyds were found. Proplyds are young stars surrounded by circum stellar material which is rendered visible by being in or near an Hn r egion. In the central region, where detection of proplyds is easiest, almost all of the low-mass pre-main-sequence stars have obvious circum stellar material. The fraction falls as one views areas away from the dominant photoionizing star (T)heta(1)C Ori. Six new dark disk proplyd s are found, bringing the total to seven. These are objects showing on ly in silhouette against the bright background of the H II region. Mos t of these are elliptical in form, indicating that they are circumstel lar disks. In addition to these compact sources, the new images allow detection of numerous large structures previously unreported from grou nd-based observations. These include shells and shocks apparently rela ted to Kerbig-Haro objects and high velocity outflows from young stell ar objects. (C) 1996 American Astronomical Society.