Abstract

Contributed Talk - Splinter LowMet

Thursday, 12 September 2024, 16:45   (S23)

The Outer Galaxy High-Resolution Survey (OGHReS): observing the molecular gas at low-metallicity in the Milky Way

Dario Colombo, Carsten König, James Urquhart, Eleonore Dann, Agata Karska, Friedrich Wyrowski, Andrea Giannetti
AIfA - Universität Bonn, Max-Planck-Institut für Radioastronomie, University of Kent, Universität zu Köln, Max-Planck-Institut für Radioastronomie, Max-Planck-Institut für Radioastronomie, INAF Radio Astronomy Institute

Modern high-resolution, molecular gas surveys of the Galactic Plane are unveiling an astonishing picture of the three-dimensional gas organization of the Milky Way. The recently concluded Outer Galaxy High-Resolution Survey (OGHReS) observed the molecular gas across the 1mm window and in 100 deg^2 of the Galactic 3rd quadrant (180 < l < 280 deg), one of the main low-metallicity environment of the Milky Way. Using data from OGHReS, we identified 37 outer Galaxy large-scale filaments. Those filaments are similar in length to inner Galaxy filaments, but they have masses, on average, one order of magnitude lower. In addition, they appear distributed almost exclusively across inter-arm spurs and elongated by the intense shear in the region. The analysis of the dense clumps in the filaments has shown that these are essentially quiescent structures, with lower star formation efficiency, but similar dense gas fraction compared to large-scale filaments in the inner Galaxy. The only exception is constituted by the longest filament in the sample (aka “Falkor”), which is actively star-forming, hosts a hot core, and appears to be associated with HI cavities rather than spurs. The full analysis of the dense clumps in the outer Galaxy confirms the trends measured in filaments: while the gas surface density appears constant from the inner to the outer Milky Way, the star formation efficiency (traced by the luminosity-over-mass ratio) decreases of an order of magnitude across the two environments.