Star-forming sites IC 446 and IC 447: an outcome of end-dominated collapse of monoceros R1 filament

Abstract

We present an analysis of multiwavelength observations of Monoceros R1 (Mon R1) complex (at d ~760 pc). An elongated filament is investigated in the complex, which is the most prominent structure in the Herschel column density map. An analysis of the FUGIN 12CO(1�0) and 13CO(1�0) line data confirms the existence of the filament traced in a velocity range of [?5, +1] km s?1. The filament is found to host two previously known sites IC 446 and IC 447 at its opposite ends. A massive young stellar object (YSO) is embedded in IC 446, while IC 447 contains several massive B-type stars. The Herschel temperature map reveals the extended warm dust emission (at Td ~ 15�21 K) toward both the ends of the filament. The Spitzer ratio map of 4.5 ?m/3.6 ?m emission suggests the presence of photodissociation regions and signature of outflow activity toward IC 446 and IC 447. Based on the photometric analysis of point-like sources, clusters of YSOs are traced mainly toward the filament ends. The filament is found to be thermally supercritical showing its tendency of fragmentation, which is further confirmed by the detection of a periodic oscillatory pattern (having a period of ~3�4 pc) in the velocity profile of 13CO. Our outcomes suggest that the fragments distributed toward the filament ends have rapidly collapsed, and had formed the known star-forming sites. Overall, the elongated filament in Mon R1 is a promising sample of the "end-dominated collapse" scenario, as discussed by Pon et al. (2011, 2012).