Rigby, AJ, Moore, TJT, Plume, R, Eden, DJ, Urquhart, JS, Thompson, MA, Mottram, JC, Brunt, CM, Butner, HM, Dempsey, JT, Gibson, SJ, Hatchell, J, Jenness, T, Kuno, N, Longmore, SN, Morgan, LK, Polychroni, D, Thomas, H, White, GJ and Zhu, M (2015) CHIMPS: the $^{13}$CO/C$^{18}$O (J=3-2) Heterodyne Inner Milky Way Plane Survey. Monthly Notices of the Royal Astronomical Society, 456 (3). pp. 2885-2899. ISSN 0035-8711

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Abstract

We present the $^{13}$CO/C$^{18}$O (J=3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) which has been carried out using the Heterodyne Array Receiver Program on the 15 m James Clerk Maxwell Telescope (JCMT) in Hawaii. The high-resolution spectral survey currently covers |b| < 0.5 deg and 28 < l < 46 deg, with an angular resolution of 15 arcsec in 0.5 km/s velocity channels. The spectra have a median rms of $\sim$ 0.6 K at this resolution, and for optically thin gas at an excitation temperature of 10 K, this sensitivity corresponds to column densities of $N_{\mathrm{H}_{2}} \sim 3 \times 10^{20}\,$cm$^{-2}$ and $N_{\mathrm{H}_{2}} \sim 4 \times 10^{21}\,$cm$^{-2}$ for $^{13}$CO and C$^{18}$O, respectively. The molecular gas that CHIMPS traces is at higher column densities and is also more optically thin than in other publicly available CO surveys due to its rarer isotopologues, and thus more representative of the three-dimensional structure of the clouds. The critical density of the J=3-2 transition of CO is $\gtrsim 10^{4}$ cm$^{-3}$ at temperatures of $\leq 20$ K, and so the higher density gas associated with star formation is well traced. These data complement other existing Galactic plane surveys, especially the JCMT Galactic Plane Survey which has similar spatial resolution and column density sensitivity, and the Herschel infrared Galactic Plane Survey. In this paper, we discuss the observations, data reduction and characteristics of the survey, presenting integrated emission maps for the region covered. Position-velocity diagrams allow comparison with Galactic structure models of the Milky Way, and while we find good agreement with a particular four arm model, there are some significant deviations.

Item Type:	Article
Additional Information:	This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record CHIMPS: the 13CO/C18O (J=3-2) Heterodyne Inner Milky Way Plane Survey is available online at: http://dx.doi.org/10.1093/mnras/stv2808
Uncontrolled Keywords:	astro-ph.GA; astro-ph.GA
Subjects:	Q Science > QB Astronomy
Divisions:	Astrophysics Research Institute
Publisher:	Oxford University Press
Related URLs:	http://arxiv.org/abs/1512.08235v1
Date Deposited:	04 Jan 2016 11:22
Last Modified:	02 Mar 2022 10:34
DOI or ID number:	10.1093/mnras/stv2808
URI:	https://researchonline.ljmu.ac.uk/id/eprint/2511

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