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The SEDIGISM Survey: First Data Release and Overview of the Galactic Structure ORE Open Research Exeter TITLE The SEDIGISM survey: First Data Release and overview of the Galactic structure AUTHORS Schuller, F; Urquhart, JS; Csengeri, T; et al. JOURNAL Monthly Notices of the Royal Astronomical Society DEPOSITED IN ORE 01 June 2021 This version available at http://hdl.handle.net/10871/125888 COPYRIGHT AND REUSE Open Research Exeter makes this work available in accordance with publisher policies. A NOTE ON VERSIONS The version presented here may differ from the published version. If citing, you are advised to consult the published version for pagination, volume/issue and date of publication MNRAS 500, 3064–3082 (2021) doi:10.1093/mnras/staa2369 Advance Access publication 2020 September 11 The SEDIGISM survey: First Data Release and overview of the Galactic structure F. Schuller ,1,2,3‹ J. S. Urquhart ,4‹ T. Csengeri,1,5 D. Colombo,1 A. Duarte-Cabral ,6 M. Mattern,1 A. Ginsburg,7 A. R. Pettitt ,8 F. Wyrowski,1 L. Anderson,9 F. Azagra,2 P. Barnes,10 M. Beltran,11 H. Beuther,12 S. Billington ,4 L. Bronfman,13 R. Cesaroni,11 C. Dobbs,14 D. Eden ,15 M.-Y. Lee,16 S.-N.X.Medina,1 K. M. Menten,1 T. Moore,15 F. M. Montenegro-Montes,2 S. Ragan ,6 A. Rigby ,6 M. Riener,12 D. Russeil,17 E. Schisano ,18 A. Sanchez-Monge,19 A. Traficante ,18 A. Zavagno,17 2 5 13 20 2 21 12 C. Agurto, S. Bontemps, R. Finger, A. Giannetti, E. Gonzalez, A. K. Hernandez, T. Henning, Downloaded from https://academic.oup.com/mnras/article/500/3/3064/5904091 by guest on 28 May 2021 J. Kainulainen,22 J. Kauffmann,23 S. Leurini,24 S. Lopez,7 F. Mac-Auliffe,2 P. Mazumdar,1 S. Molinari ,18 F. Motte,25 E. Muller,26 Q. Nguyen-Luong,27 R. Parra,2 J.-P. Perez-Beaupuits ,2 P. Schilke,19 N. Schneider ,19 S. Suri,19 L. Testi,28 K. Torstensson,2 V. S. Veena,19 P. Venegas,2 K. Wang29 and M. Wienen1,14 Affiliations are listed at the end of the paper Accepted 2020 July 24. Received 2020 July 21; in original form 2020 April 17 ABSTRACT 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 =−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. Key words: surveys – ISM: structure – Galaxy: kinematics and dynamics – radio lines: ISM. continuum surveys have been complemented by spectral line surveys, 1 INTRODUCTION which are essential for estimating distances and determining physical Over the last few decades, many systematic continuum surveys of properties. Some examples include the 12CO (1–0) survey from the Galactic plane have been carried out over the full electromagnetic Dame, Hartmann & Thaddeus (2001), the CO Boston University- spectrum, from the infrared (e.g. GLIMPSE, Churchwell et al. 2009; Five College Radio Astronomy Observatory Galactic Ring Survey MIPSGAL, Carey et al. 2009; Hi-GAL, Molinari et al. 2010)tothe (GRS; Jackson et al. 2006), the Census of High- and Medium-mass (sub)millimetre (ATLASGAL, Schuller et al. 2009; BGPS, Aguirre Protostars (CHaMP; Barnes et al. 2011), the CO High-Resolution et al. 2011;JPS,Mooreetal.2015;Edenetal.2017), and radio range Survey (COHRS; Dempsey et al. 2013), the CO Heterodyne Inner (CORNISH, Hoare et al. 2012;Purcelletal.2013; THOR, Beuther Milky Way Plane Survey (CHIMPS; Rigby et al. 2016, 2019), the et al. 2016,Wangetal.2020; GLOSTAR, Medina et al. 2019). These FOREST unbiased Galactic plane imaging survey with Nobeyama (FUGIN; Umemoto et al. 2017), the Mopra Southern Galactic Plane CO Survey (Burton et al. 2013; Braiding et al. 2018), the Three-mm E-mail: [email protected] (FS); [email protected] (JSU) Ultimate Mopra Milky Way Survey (ThrUMMS; Barnes et al. 2015), C The Author(s) 2020. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. SEDIGISM DR1 3065 Table 1. Main characteristics of recent, large-scale CO surveys of the inner Galactic plane. Survey Transitions Coverage Angular Velocity rms Reference resolution resolution −1 name (arcsec) (km s )(Tmb)(K) GRS 13CO (J = 1–0) 18◦≤ ≤ 55◦.7, 46 0.21 ∼0.2 Jackson et al. (2006) |b|≤1◦.0 CHaMP CO/13CO/C18O/ 280◦≤ ≤ 300◦, 37–40 0.08–0.10 0.4–0.7 Barnes et al. (2011) + ◦ ◦ CN/N2H /HNC/ −4 ≤ b ≤+2 HCO+/HCN (J = 1–0) COHRS 12CO (J = 3–2) 10◦≤ ≤ 65◦,161 ∼1 Dempsey, Thomas & Currie (2013) |b|≤0◦.5 CHIMPS 13CO/C18O28◦≤ ≤ 46◦,150.5 ∼0.6 Rigby et al. (2016) (J = 3–2) |b|≤0◦.5 FUGIN CO/13CO/C18O10◦≤ ≤ 50◦, |b|≤1◦.0 20 1.3 0.3–0.5 Umemoto et al. (2017) Downloaded from https://academic.oup.com/mnras/article/500/3/3064/5904091 by guest on 28 May 2021 (J = 1–0) 198◦≤ ≤ 236◦, |b|≤1◦.0 Mopra-CO CO/13CO/C18O/ 305◦≤ ≤ 345◦, 35 0.1 0.7–1.5 Burton et al. (2013) C17O(J = 1–0) |b|≤0◦.5 ThrUMMS CO/13CO/C18O/ 300◦≤ ≤ 360◦, 72 0.3 0.7–1.3 Barnes et al. (2015) CN (J = 1–0) |b|≤1◦.0 MWISPa CO/13CO/C18O −10◦≤ ≤ 250◦, 50 0.16 0.3–0.5 Su et al. (2019) (J = 1–0) |b|≤5◦.2 FQS 12CO/13CO 220 ◦≤ ≤ 240◦, 55 0.26/0.65 0.3–1.3 Benedettini et al. (2020) (J = 1–0) −2◦.5 ≤ b ≤ 0◦ SEDIGISM 13CO/C18O −60◦≤ ≤+18◦, 30 0.25 0.8–1.1 Schuller et al. (2017) (J = 2–1) |b|≤0◦.5 + W43 aObservations for the MWISP survey are still ongoing; the Su et al. (2019) paper focuses on a region covering 25◦.8≤ ≤+49◦.7. the Milky Way Imaging Scroll Painting (MWISP; Su et al. 2019), and molecular gas forms within the spiral arms themselves. Furthermore, the Forgotten Quandrant Survey (Benedettini et al. 2020). In Table 1 it is unclear if the enhanced star-forming activity observed (Urquhart and Fig. 1, we present a summary of these recently completed CO et al. 2014a) is directly attributable to the presence of spiral arms or surveys and show their coverage on a schematic top-down view of is simply the result of source crowding within the arms (Moore et al. the Milky Way. 2012). This wealth of data has greatly enhanced our view of the Galactic The SFE is the result of a number of stages: the conversion of neu- structure and its major components. However, there is still no tral gas to molecular clouds, then to dense, potentially star-forming consensus on the exact structure of the Galaxy. For instance, it is clumps, and finally to proto-stars and young stellar objects. Each of not firmly established how many spiral arms are present and what these stages has its own conversion efficiency. Identifying the stage is their exact location (e.g. Taylor & Cordes 1993; Drimmel 2000; that is primarily affected by the environment could bring constraints Siebert et al. 2011;Garc´ıa et al. 2014;Reidetal.2014, 2016;Vallee´ on the dominant SF-regulating mechanism. Some progress has been 2017; Gaia Collaboration et al. 2018), nor what is the exact size made recently to investigate the effects of environment on the SFE and orientation angle of the central bar (e.g. Bissantz, Englmaier & in our Galaxy, based on limited samples of objects (Eden et al. 2012; Gerhard 2003; Pettitt et al. 2014;Lietal.2016b) – thus making Moore et al. 2012; Longmore et al. 2013; Ragan et al. 2018). In order it difficult to pin-point and study the large-scale distribution of to extend these studies to much larger samples, we have performed molecular gas in the Galaxy. a large-scale (∼84 deg2) spectroscopic survey of the inner Galactic Progress is also being made in the characterisation of the earliest disc: the SEDIGISM (Structure, Excitation and Dynamics of the phases of (high-mass) star formation (e.g.
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