OGHReS: Star formation in the Outer Galaxy II (ℓ = 180○-280○)

Urquhart, J. S., König, C., Colombo, D., Karska, A., Giannetti, A., Moore, T. J. T., Yang, A. Y., Wyrowski, F., Sun, Y., Jiang, Z., and others. (2025) OGHReS: Star formation in the Outer Galaxy II (ℓ = 180○-280○). Monthly Notices of the Royal Astronomical Society, 539 (4). pp. 3105-3121. ISSN 0035-8711. E-ISSN 1365-2966. (doi:10.1093/mnras/staf665) (KAR id:109826)

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Official URL: https://doi.org/10.1093/mnras%2Fstaf665

Abstract

The Outer Galaxy High-Resolution Survey (OGHReS) covers 100 square degrees (180○ < ℓ < 280○) in the (2–1) transitions of three CO-isotopologues. We use the spectra to refine the velocities and physical properties to 6 706 Hi-GAL clumps located in the OGHReS region. In a previous paper, we analysed 3 584 clumps between ℓ = 250○ and 280○. Here, we cover a further 3 122 clumps (180○ < ℓ < 250○) and determine reliable velocities for 2 781 of these, finding good agreement with the previously assigned velocities (∼80 per cent within 5 km s−1). We update velocities for 288 clumps and provide new values for an additional 411. Combining these with the previous results, we have velocities and physical properties for 6 193 clumps (92.3 per cent). The 422 non-detections are low surface density clumps or likely contamination by evolved stars and galaxies. Key findings: i) improved correlation between clumps and spiral arm loci, and the discovery of clumps beyond the outer arm supports the existence of a new spiral structure; ii) decreasing trend in the L/M-ratio consistent with less high-mass star formation in the outer Galaxy; iii) increase in the star formation fraction (SFF) in the outer Galaxy, suggesting that more clumps are forming stars despite their lower mass; iv) discrepancies in velocity assignments across different surveys that could affect ∼10 000 clumps, especially in the fourth quadrant.

Item Type:	Article
DOI/Identification number:	10.1093/mnras/staf665
Uncontrolled keywords:	stars: formation; stars: protostars; ISM: molecules; Galaxy: structure; infrared: stars
Subjects:	Q Science > QB Astronomy > QB460 Astrophysics
Institutional Unit:	Schools > School of Engineering, Mathematics and Physics > Physics and Astronomy
Former Institutional Unit:	Divisions > Division of Natural Sciences > Physics and Astronomy
Funders:	University of Kent (https://ror.org/00xkeyj56)
Depositing User:	James Urquhart
Date Deposited:	02 May 2025 15:01 UTC
Last Modified:	22 Jul 2025 09:23 UTC
Resource URI:	https://kar.kent.ac.uk/id/eprint/109826 (The current URI for this page, for reference purposes)

University of Kent Author Information

Urquhart, J. S..

Creator's ORCID:	https://orcid.org/0000-0002-1605-8050
CReDIT Contributor Roles:

Grozdanova, Ivana I..

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