Methanol Proplyds and a Double Protoplanetary System in the Constellation Norma

Abstract

We have carried out detailed studies of a star-forming region containing two maser sources in the constellation Norma. The sources display a complex spectral distribution of the maser lines and spatial distribution of the maser condensations. The maser condensations may have formed around objects that are hidden by dense molecular cocoons; the velocities of the maser features may represent Keplerian orbital motions. The cocoons, which radiate in thermal methanol and CS lines, correspond to the centers of mass in the maser sources + dense molecular core systems. The velocities of the CS lines or thermal methanol lines can be used to identify the locations of the centers of mass of these systems. If the maser radiation is generated in the atmospheres of protoplanets, the Norma radio source may correspond to two protoplanetary disks, each with a protostar and protoplanetary system. In this case, the masses of the protostars are approximately 13 Mand 38 M� . c � 2005Pleiades Publishing, Inc. Radio-spectroscopic observations of star-forming regions containing dense clumps of gas and dust with various molecular compounds are very promising for studies of the physical states of prestellar material. Radio lines emitted by such clumps can be related to various temporal, dynamical, and thermal evolu- tionary phases of the interstellar medium, and the parameters obtained from the observed emission of various molecules can be used to reconstruct the physical conditions in star-forming regions. Some molecules in prestellar condensates are subject to intense irradiation from neighboring, recently formed, young stars or to dynamical compression by flows of matter from neighboring stars, both of which can act to redistribute the level populations. This can result in nonequilibrium (maser) radiation by these molecules, which are virtually always found in associ- ation with protostellar objects. The spatial structures of the maser condensations shows that they are often laid out in chains or arcs, sometimes displaying char- acteristics consistent with Keplerian disks containing protoplanetary systems. Such disks are called proto- planetary disks, or proplyds (1).