G183: An outer galaxy filament feeding a massive protostar

TL;DR

This study provides a detailed multi-tracer analysis of a 5-pc long outer Galaxy filament G183 and its associated massive protostar, revealing filament structure, kinematics, and accretion processes in a low-density environment.

Contribution

It presents the first detailed multi-tracer observations of an outer Galaxy filament and its massive protostar, demonstrating universal star formation processes across different Galactic environments.

Findings

The filament is a 5 pc long, velocity-coherent structure with a quiescent velocity field.

The protostar S1 has a mass of 156 Msun and shows signs of active accretion.

Detection of hot-core chemistry indicates advanced star formation stages.

Abstract

We present the first detailed multi-tracer observation of a 5-pc long outer Galaxy filament, G183, and the massive young stellar object (YSO) IRAS 05480+2545 associated with it. Using the IRAM 30-m telescope at lambda = 1.4 and 3 mm, we probed the molecular gas distribution at angular resolutions of ~12"-28" (0.1-0.3 pc at d = 2.1 kpc). The velocity-resolved C18O(1-0) observations conclusively show a main filament with a skeleton of ridges. The main filament is a 5 pc long velocity-coherent structure with a continuous and quiescent velocity field along its length up to the star-forming hub that accretes mass from the filament. The internal gas kinematics of most of the G183 filament is dominated by thermal motions (sigma_NT/cs~1) and large-scale velocity gradients arising due to outflows and accretion of matter in the massive YSO. The dispersion-size relation almost up to 1 pc is consistent with Larson's law, suggesting that the origin of the filament is a turbulence cascade. The massive YSO, S1, with no corresponding radio continuum detection is characterized as a high-mass protostellar object with a mass of 156 Msun and an M/L ratio of 0.04. We identify a kinematic signature of the accretion of material from the filament onto the YSO, S1. The rates of molecular gas accretion and entrainment in S1 are estimated to be 8.6 and 2.6 (in units of 10^-4 Msun/yr), respectively. In comparison to the inner Galaxy high-mass star-forming filaments forming massive stars, G183 has a lower column density; however, the accretion and outflow rates in S1 are similar. The detection of hydrocarbons such as CH3CN and HC3N indicates the presence of hot-core chemistry in S1. These results highlight the universality of physical processes involved in massive star formation across a range of Galactic environments.