J/MNRAS/539/3105 OGHReS. Star formation in the outer Galaxy II (Urquhart+, 2025)
OGHReS: star formation in the outer Galaxy II (l=180-280°).
Urquhart J.S., Konig C., Colombo D., Karska A., Giannetti A., Moore T.J.T.,
Yang A.Y., Wyrowski F., Sun Y., Jiang Z., Neralwar K.R., Eden D.,
Grozdanova I., Neupane S., Figueira M., Dann E., Veena V.S., Kim W.-J.,
Leurini S., Brand J., Lee M.-Y.
<Mon. Not. R. Astron. Soc. 539, 3105 (2025)>
=2025MNRAS.539.3105U 2025MNRAS.539.3105U (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Space velocities ; Infrared sources ; Carbon monoxide
Keywords: stars: formation - stars: protostars - ISM: molecules -
Galaxy: structure - infrared: stars
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 6706 Hi-GAL clumps located in the OGHReS
region. In a previous paper, we analysed 3584 clumps between
l=250° and 280°. Here, we cover a further 3122 clumps
(180°<l<250°) and determine reliable velocities for 2781 of
these, finding good agreement with the previously assigned velocities
(∼80 per cent within 5km/s). 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 6193
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 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 ∼10000 clumps, especially in the
fourth quadrant.
Description:
Derived clump parameters for HiGAL clumps located in the Galactic
longitudes 180<l<280.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 82 6706 Summary of velocity allocation analysis
table2.dat 97 6193 Updated HiGAL clump parameters
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See also:
J/A+A/591/A149 : Hi-GAL. inner Milky Way: +68≥l≥70 (Molinari+, 2016)
J/MNRAS/471/100 : Hi-GAL compact source catalog. -71.0<l<67.0 (Elia+, 2017)
J/A+A/646/A74 : Distance of HiGAL sources (Mege+, 2021)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 22 A22 --- HiGAL HiGAL clump name (HIGALBMLLL.llll+B.bbbb)
24- 31 F8.4 deg GLON Galactic longitude of clump
33- 39 F7.4 deg GLAT Galactic latitude of clump
41- 44 A4 --- Rel HiGAL reliability flag
46- 49 F4.2 K 12cmrms Spectral noise of 12CO transition
51- 57 F7.1 km/s upVLSR OGHReS assigned velocity
(-9999 = non-detection,
-999 = detection but vlsr ambiguous)
59- 64 F6.1 km/s prevVLSR ? HiGAL assigned velocity
66- 71 F6.1 km/s DVLSR ? Difference between HiGAL and OGHReS
assigned velocities
73- 82 A10 --- Method Method used to allocate the velocity
to each clump
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 22 A22 --- HiGAL HiGAL clump name (HIGALBMLLL.llll+B.bbbb)
24- 27 A4 --- Rel HiGAL reliability flag
29 I1 --- EvolFlag [0/2]? Updated HiGAL evolution flag
(unbound = 0, bound = 1, protostellar = 2)
31- 36 F6.1 deg VLSR OGHReS assigned velocity
38- 42 F5.1 kpc Dist ? Heliocentric distance
44- 48 F5.1 kpc RGC ? Galactocentric distance
50- 56 A7 --- g2dratio Gas to dust ratio
58- 62 F5.2 pc Diam ? Diameter of clump
64- 69 F6.3 [Msun] logMass ? Log of the clump mass in solar units
71- 78 F8.3 g/cm2 SurfDens ? Surface density in units of g/cm^2
80- 85 F6.3 [Lsun] logLum ? Log of the bolometric luminosity of the
clump in solar units
87- 92 F6.3 [-] log(L/M) ? Log of the L/M ratio
94- 97 A4 --- DistRel Distance reliability flag
(high = uncertainty within factor of 2)
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Acknowledgements:
James S. Urquhart, J.S.Urquhart(at)kent.ac.uk
History:
Urquhart et al., Paper I 2024MNRAS.528.4746U 2024MNRAS.528.4746U
(End) James Urquhart [Kent Univ.], Patricia Vannier [CDS] 08-Dec-2025