Why the selected area for the Dark Energy Survey was chosen to have such a shape? Are there any reasons?
In the paper I found this
The target footprint of the DES wide-area and supernova surveys are shown in Figure 2. All RA, DEC coordinates in this paper refer to the J2000 epoch. The wide-area footprint shape was selected to obtain a large overlap with the South Pole Telescope survey (Carlstrom et al. 2011) and Stripe 82 from SDSS (Abazajian et al. 2009), and includes a connection region to enhance overall calibration. Given the cosmo- logical goals of the survey, DES avoids the Galactic plane to minimize stellar foregrounds and extinction from interstellar dust.