Face-on view of H I surface mass distribution in the survey area overlaid with spiral arms from Reid et al. (2016), and H II regions from [0, 0], and the Sun is at the top-left corner at a Galactocentric distance of 8.34 kpc (Reid et al. 2014). The gray lanes mark the Outer, Perseus, Sagittarius, and Scutum arms with widths from Reid et al. (2014). The Local Spur, Aquila Spur, and Norm Arm are marked with white lines. The long bar (Hammersley et al. 2000; Benjamin et al. 2005; Nishiyama et al. 2005; Benjamin 2008; Cabrera-Lavers et al. 2008) is marked with the shaded half-ellipse. The crosses mark the H II regions from Anderson et al. (2014) excluding the ones that fall into the tangent region (marked with two gray curves).
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