The Milky Way Imaging Scroll Painting Survey: Data Release 1

TL;DR

DR1 of MWISP presents a wide-area, multi-line CO survey of the northern Galactic plane, mapping $^{12}$CO$(J=1\rightarrow0)$, $^{13}$CO$(J=1\rightarrow0)$, and $C^{18}$O$(J=1\rightarrow0)$ to census molecular gas across a wide density range. Observations with the PMO 13.7 m telescope achieve a spatial resolution of ~50$''$ and velocity resolution $0.16$ km s$^{-1}$, covering $9.75^\circ \le l \le 229.75^\circ$ and $|b|\le 5.25^\circ$, with data regridded into regular 3D datacubes of 30$''$ pixels in $l$-$b$ and $0.16$ km s$^{-1}$ channels. The DR1 data cubes contain about $3.33\times 10^{7}$ spectra per isotopologue, with median rms sensitivities of 0.47 K for $^{12}$CO and 0.25 K for $^{13}$CO and C$^{18}$O, and a total $^{12}$CO flux of $7.69\times 10^{7}$ K km s$^{-1}$ arcmin$^{2}$, of which $82\%$ is recovered by the DBSCAN cloud catalog. Together, these data and the cloud sample provide a unique resource for studying molecular gas distribution, cloud structure, dynamics, and Galactic ecology.

Abstract

We present the first data release (DR1) of the Milky Way Imaging Scroll Painting (MWISP) survey, a mapping in the J=(1-0) transition lines of 12CO, 13CO, and C18O toward the northern Galactic plane during 2011-2022. The MWISP survey was conducted using the PMO 13.7 m telescope at a spatial resolution of approximately 50" and a velocity resolution of 0.16 km/s at 115 GHz. DR1 fully covered 2310 square degrees within the Galactic longitude (l) and latitude (b) range of 9.75 deg =< l =< 229.75 deg and |b| =< 5.25 deg. The surveyed area was divided into cell units of 30'x30' for practical purposes and On-The-Fly (OTF) mapping was performed toward each target cell unit. The data were regridded into a regular 3D datacube in l-b-V_LSR with a pixel size of 30" in l-b axes and 0.16 km/s in theV_LSR axis. The median rms noise is 0.47 K, 0.25 K, and 0.25 K for 12CO, 13CO, and C18O, respectively. The equivalent 3 sigma sensitivity in 12CO luminosity is approximately 0.23 K km/s, making MWISP the most sensitive survey of its kind. In this paper, we describe the survey data, including the calibration, data cleaning, data mosaic processes, and the data products. The final mosaicked data cubes contain about 3.33x10^7 spectra (pixels) for each CO isotopologue line. Color composite images, made from the intensities of the isotopologue lines, and some concise descriptions are provided. We constructed a molecular cloud catalog based on the mosaicked 12CO data cube using the clustering algorithm DBSCAN, detecting 103,517 molecular clouds, 10,790 of which exhibit 13CO emission and 304 of which show C18O emission. Based on the histogram of voxel brightness temperature, we estimated a total 12CO flux of 7.69+/-0.38x10^7 K km/s arcmin^2, 82% of which is captured by the DBSCAN algorithm. The data, together with the cloud sample, provide unique information on molecular gas in the northern Milky Way.