Speaker
Paula Stella Teixeira
(University of Vienna, Department of Astrophysics)
Description
It is well established for several decades that filamentary structures are very common in star forming molecular clouds. Observational studies of how these structures evolve and fragment to form cores (and subsequently stars) may ultimately lead us to better understand how the core mass function (CMF) and stellar initial mass function (IMF) are assembled. The fragmentation of these filamentary structures may be probed by analyzing the spatial distribution and physical properties of dense cores. Due to their youth, protostars forming within these cores have not yet had enough time to move away from their birthsites and as such their spatial distribution is a fossil signature of the fragmentation scale of their parental filament. We report Submillimeter Array (SMA) 1.3mm observations of the OMC1 northern filaments that were previously identified from SCUBA JCMT 850 micron continuum and VLA ammonia observations. We discovered 24 new compact sources along an extent of ~3' within the filaments. The sources range in mass from 0.5 to 2.8 MSun and 5 of them are driving CO molecular outflows. The millimeter emission is arising from the inner part of the envelope and circumstellar disk; these compact sources are therefore in the Class 0/I evolutionary phase. The spatial analysis of the protostars shows that these are divided into small groups, that coincide with previously identified clumps, and that these are separated by a quasi-equidistant length of ~30' (0.06pc). This separation is dominated by the Jeans length of the filament, and therefore indicates that the main physical process in the filament's evolution was thermal fragmentation. Within the protostellar groups, the typical separation is ~7"" (2800au), which is again consistent with the Jeans length of the parental clumps within which the protostars are embedded. These results point to hierarchical (2-level) thermal fragmentation process of the OMC1-n filament. We will also discuss how these findings compare with those of OMC3 (Takahashi et al., 2013), and how it connects with the hierarchical fragmentation of the larger scale Orion molecular cloud.
Author
Paula Stella Teixeira
(University of Vienna, Department of Astrophysics)