The Forgotten Quadrant Survey: (CO)-C-12 and (CO)-C-13 (1-0) survey of the Galactic plane in the range 220 degrees < l < 240 degrees-2.degrees 5 < b < 0 degrees

Author(s):Show less -

Benedettini, M. ^[1] ; Molinari, S. ^[1] ; Baldeschi, A. ^{[2, 3, 1]} ; Beltran, M. T. ^[4] ; Brand, J. ^{[5, 6]} ; Cesaroni, R. ^[4] ; Elia, D. ^[1] ; Fontani, F. ^[4] ; Merello, M. ^{[7, 1]} ; Olmi, L. ^[4] ; Pezzuto, S. ^[1] ; Rygl, K. L. J. ^{[5, 6]} ; Schisano, E. ^[1] ; Testi, L. ^{[8, 4]} ; Traficante, A. ^[1]

Affiliation

^[1] INAF Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome - Italy

^[2] Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 - USA

^[3] Northwestern Univ, Ctr Interdisciplinary Explorat & Res Astrophys, Evanston, IL 60208 - USA

^[4] INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence - Italy

^[5] Italian ALMA Reg Ctr, Via P Gobetti 101, I-40129 Bologna - Italy

^[6] INAF Ist Radioastron, Via P Gobetti 101, I-40129 Bologna - Italy

^[7] Univ Sao Paulo, IAG Rua Matao 1226, Cidade Univ, BR-05508090 Sao Paulo - Brazil

^[8] European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching - Germany

• Document type: Journal article
• Source: Astronomy & Astrophysics; v. 633, JAN 23 2020.
• Web of Science Citations: 0

Abstract

Aims. We present the Forgotten Quadrant Survey (FQS), an ESO large project that used the 12 m antenna of the Arizona Radio Observatory to map the Galactic plane in the range 220 degrees< l< 240 degrees and -2.degrees 5< b< 0 degrees, both in (CO)-C-12 (1-0) and (CO)-C-13 (1-0), at a spectral resolution of 0.65 km s(-1) and 0.26 km s(-1). Methods. We used the (1-0) transition of carbon monoxide to trace the molecular component of the interstellar medium. Our data set allows us to easily identify how the molecular dense gas is organised at different spatial scales: from the giant clouds with their denser filamentary networks, down to the clumps and cores that host the new-born stars and to obtain reliable estimates of their key physical parameters such as size and mass. Results. We present the first release of the data of the FQS survey and discuss their quality. Spectra with 0.65 km s(-1) velocity channels have noise ranging from 0.8 K to 1.3 K for (CO)-C-12 (1-0) and from 0.3 K to 0.6 K for (CO)-C-13 (1-0). In this first paper, we used the (CO)-C-12 (1-0) spectral cubes to produce a catalogue of 263 molecular clouds. The clouds are grouped in three main structures corresponding to the Local, Perseus, and Outer arms up to a distance of similar to 8.6 kpc from the Sun. This is the first self-consistent statistical catalogue of molecular clouds of the outer Galaxy obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the sub-parsec scale up to a distance of a few kiloparsec. We found two classes of objects: structures with sizes above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H-2 column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3 +/- 1.4) x 10(20) cm(-2) (K km s(-1))(-1) and (1.2 +/- 0.4) x 10(21) cm(-2) (K km s(-1))(-1), for (CO)-C-12 (1-0) and (CO)-C-13 (1-0), respectively. Conclusions. The FQS contributes to the general effort in producing a new generation of high-quality spectroscopic data for the Galactic plane in the less-studied third Galactic quadrant toward the outer Galaxy. The FQS has produced a data set of great legacy value, largely improving the data quality both in terms of sensitivity and spatial resolution over previous data sets. (AU)

• FAPESP's process: 17/23708-0 - 183 GHz H2O Megamaser galaxies and intensity Calibrations
• Grantee: Manuel Antonio Merello Ferrada
• Support type: Scholarships in Brazil - Post-Doctorate