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  • The (J)VLA calibrator list is from the VLA, and is largely out of date.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.)

Figure: location of Stripe82 tiles, and the three mini-tiles per tile. The chosen phase calibrator sources (indicated in the sections below, in bold) are also shown. Note that because of the different scaling on the two axes, vertical distances are much less than they appear.