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- ItemThe SEDIGISM survey: first data release and overview of the Galactic structure(Oxford : Oxford Univ. Press, 2021) Schuller, F.; Urquhart, J.S.; Csengeri, T.; Colombo, D.; Duarte-Cabral, A.; Mattern, M.; Ginsburg, A.; Pettitt, A.R.; Wyrowski, F.; Anderson, L.; Azagra, F.; Barnes, P.; Beltran, M.; Beuther, H.; Billington, S.; Bronfman, L.; Cesaroni, R.; Dobbs, C.; Eden, D.; Lee, M.-Y.; Medina, S.-N.X.; Menten, K.M.; Moore, T.; Montenegro-Montes, F.M.; Ragan, S.; Rigby, A.; Riener, M.; Russeil, D.; Schisano, E.; Sanchez-Monge, A.; Traficante, A.; Zavagno, A.; Agurto, C.; Bontemps, S.; Finger, R.; Giannetti, A.; Gonzalez, E.; Hernandez, A.K.; Henning, T.; Kainulainen, J.; Kauffmann, J.; Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.; Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits, J.-P.; Schilke, P.; Schneider, N.; Suri, S.; Testi, L.; Torstensson, K.; Veena, V.S.; Venegas, P.; Wang, K.; Wienen, M.The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) survey used the APEX telescope to map 84 deg2 of the Galactic plane between ℓ = −60° and +31° in several molecular transitions, including 13CO (2 – 1) and C18O (2 – 1), thus probing the moderately dense (∼103 cm−3) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1σ sensitivity of 0.8–1.0 K at 0.25 km s−1 velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position–velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms.
- ItemA Kiloparsec-scale Molecular Wave in the Inner Galaxy: Feather of the Milky Way?(London : Institute of Physics Publ., 2021) Veena, V.S.; Schilke, P.; Sánchez-Monge, Á.; Sormani, M.C.; Klessen, R.S.; Schuller, F.; Colombo, D.; Csengeri, T.; Mattern, M.; Urquhart, J. S.We report the discovery of a velocity coherent, kiloparsec-scale molecular structure toward the Galactic center region with an angular extent of 30° and an aspect ratio of 60:1. The kinematic distance of the CO structure ranges between 4.4 and 6.5 kpc. Analysis of the velocity data and comparison with the existing spiral arm models support that a major portion of this structure is either a subbranch of the Norma arm or an interarm giant molecular filament, likely to be a kiloparsec-scale feather (or spur) of the Milky Way, similar to those observed in nearby spiral galaxies. The filamentary cloud is at least 2.0 kpc in extent, considering the uncertainties in the kinematic distances, and it could be as long as 4 kpc. The vertical distribution of this highly elongated structure reveals a pattern similar to that of a sinusoidal wave. The exact mechanisms responsible for the origin of such a kiloparsec-scale filament and its wavy morphology remains unclear. The distinct wave-like shape and its peculiar orientation makes this cloud, named as the Gangotri wave, one of the largest and most intriguing structures identified in the Milky Way.