2019ApJS..240....9S

The Milky Way Imaging Scroll Painting project is an unbiased Galactic plane CO survey for mapping regions of l=-10^○ to +250° and | b| ≲5.°2 with the 13.7 m telescope of the Purple Mountain Observatory. The legacy survey aims to observe the ¹²CO, ¹³CO, and C¹⁸O (J = 1-0) lines simultaneously with full-sampling using the nine-beam Superconducting SpectroScopic Array Receiver system with an instantaneous bandwidth of 1 GHz. In this paper, the completed 250 deg² data from l = +25.°8 to +49.°7 are presented with a grid spacing of 30'' and a typical rms noise level of ∼0.5 K for ¹²CO at the channel width of 0.16 km s^–1 and ∼0.3 K for ¹³CO and C¹⁸O at 0.17 km s^–1. The high-quality data, with moderate resolution (∼50''), uniform sensitivity, and high spatial dynamic range, allow us to investigate the details of molecular clouds (MCs) traced by the three CO isotope lines. Three interesting examples are briefly investigated, including distant Galactic spiral arms traced by CO emission with V_LSR < 0 km s^–1, the bubble-like dense gas structure near the H II region W40, and the MCs distribution perpendicular to the Galactic plane.