G183: An outer galaxy filament feeding a massive protostar

¹ Department of Astronomy & Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
² Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38400 Saint-Martin-d’Héres, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 26 September 2025
Accepted: 1 December 2025

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 λ = 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 (σ_NT/c_s ~ 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 M_⊙ 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 M_⊙ yr⁻¹), 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.