Unveiling the Cosmic Cradle: clustering and massive star formation in the enigmatic Galactic bubble N59

Abstract

In this paper, we have conducted an investigation focused on a segment of the Spitzer mid-infrared bubble N59, specifically referred to as R1 within our study. Situated in the inner Galactic plane, this region stands out for its hosting of five 6.7 GHz methanol masers, as well as numerous compact $\mathrm{H}\, \small {\mathrm{II}}$ regions, massive clumps, filaments, and prominent bright rims. As 6.7 GHz masers are closely linked to the initial phases of high-mass star formation, exploring regions that exhibit a high abundance of these maser detections provides an opportunity to investigate relatively young massive star-forming sites. To characterize the R1 region comprehensively, we utilize multi-wavelength (archival) data from optical to radio wavelengths, together with 13CO and C18O data. Utilizing the Gaia DR3 data, we estimate the distance towards the bubble to be 4.66 ± 0.70 kpc. By combining near-infrared (NIR) and mid-infrared (MIR) data, we identify 12 Class I and 8 Class II sources within R1. Furthermore, spectral energy distribution (SED) analysis of selected sources reveals the presence of four embedded high-mass sources with masses ranging from 8.70-14.20 M⊙. We also identified several O and B-type stars from radio continuum analysis. Our molecular study uncovers two distinct molecular clouds in the region, which, although spatially close, occupy different regions in velocity space. We also find indications of a potential hub-filament system fostering star formation within the confines of R1. Finally, we propose that the feedback from the $\mathrm{H}\, \small {\mathrm{II}}$ regions has led to the formation of prominent Bright Rimmed Clouds (BRC) within our region of interest.

Investigating the Star-forming Sites in the Outer Galactic Arm

“…We found a peculiar feature of optically thick 12 CO spectra at N1, associated with AFGL 5157. It displays a red asymmetric profile (or "red profile," where the redshifted peak of a double- peaked profile is more prominent in the case of an optically thick line), revealing outflow motion due to the absorption of colder blueshifted gas in front of the hot core (e.g., Myers 1998;Liu et al 2011;Paulson et al 2024).…”