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  • Special tiles for the VLASS pilot

    Tile definitions

    • Stripe 82 (-50 to 59d, -1.25 to 1.25d) will be observed in four “squashed” tiles, 30d x 2.42d; each will be made up of three 10d X 2.42d “sub-tiles”:

      • A: 300 to 330d (20-22h), -1.21 to 1.21d

      • B: 330 to 360/0d (22-24/0h), -1.21 to 1.21d

      • C: 0d to 30d (0-2h), -1.21 to 1.21d

      • D: 30 to 60d (2-4h), -1.21 to 1.21d

    • Cygnus: centered on RA=20h40m, dec=+41. (303 to 317d, 37 to 45d)

    • COSMOS: 145d to 155d in RA, 0d to 8d in dec

    • SDSS SGC: about 15 degrees (in dec) north of the SDSS Stripe 82; same RA coverage. For this one, we are going to try “split mini-tiles”: e.g. do 4x10, which takes  2 hours, then move over 30 degrees (2 hours) in RA and do another 4x10 mini-tile. The two mini-tiles will have roughly the same az-el coverage.

    (Note: original Stripe82 tile definition was for a dec range of [-1.33,1.33], but that led to SBs longer than 4 hours, so we removed a row from the top and bottom for a new range of [1.21,1.21].)

    Resources for choosing phase calibrator

    - the NRAO calibrator list (“P” calibrator in both L and C band if possible, close to tile, bright in L and C band)

    - Lorant’s “TCAL” runs to observe potential calibrators: (and run2, etc.)

    - Steve reports on the calibrators previously used in their observations of Stripe82 (VLA/15A-421): J2101+0341, J2136+0041, J2212+0152, J2247+0000, J0016-0015, J0022+0014, J0059+0006, J0149+0555, J0217+0144, J0239+0416, J0339-0146

    Phase calibrators

    Guidelines for choosing calibrators:

    • Avoid calibrators with declination < -3d... becomes difficult to use for calibration (esp. of amplitude) due to satellite belt

    • Closer is better than brighter: any reasonably bright source (>100 mJy) will give plenty of S/N, so the important thing is to be near all parts of the tile. As close as possible!

    • The (J)VLA calibrator list is from the VLA, and is largely out of date. We can’t always trust the P/S codes.

    (Note: the “corner distances” below were calculated using original tile dec range of [-1.33,1.33], so the max distances will be a bit less than the values below.)