Ionized filaments and ongoing physical processes in massive star-forming sites around l = 345.5 degree

Abstract

Numerous research studies on dust and molecular filaments have been conducted in star-forming sites, but only a limited number of studies have focused on ionized filaments. To observationally study this aspect, we present an analysis of multi-wavelength data of an area of $\sim$74.6 arcmin $\times$ 55 arcmin around l = 345.5 degree. Using the 843 MHz continuum map, two distinct ionized filaments (i.e., IF-A (extent $\sim$8.5 arcmin) and IF-B (extent $\sim$22.65 arcmin)) hosting ionized clumps powered by massive OB stars are identified. Using the $^{13}$CO(2-1) and C$^{18}$O(2-1) line data, the parent molecular clouds of IF-A and IF-B are studied in a velocity range of [$-$21, $-$10] km s$^{-1}$, and have filamentary appearances. At least two cloud components around $-$18 and $-$15 km s$^{-1}$ toward the parent clouds of IF-A and IF-B are investigated, and are connected in velocity space. These filamentary clouds also spatially overlap with each other along the major axis, backing the filamentary twisting/coupling nature. Noticeable Class I protostars and massive stars appear to be observed toward the common zones of the cloud components. These findings support the collision of two filamentary clouds around 1.2 Myr ago. The existence of the ionized filaments seems to be explained by the combined feedback of massive stars. The molecular filaments associated with IF-A and IF-B favour the outcomes of the most recent model concerning the escape and the trap of the ionizing radiation from an O star formed in a filament.