ESSENCE Search Fields

ESSENCE/the w Project:
SN Search Fields

General Description

In order to optimize the discovery of supernovae, we have carefully selected ~25 Mosaic pointings distributed over the sky. The selection was complicated by the fact that we must observe the same fields for three months (Oct, Nov, & Dec) during only the first HALF of the scheduled nights (usually every other night of dark and grey time). The selection, and distribution, of fields was driven by this constraint to be within the RA range of ~23h to ~3h, and even this range pushes the limits at either end of the observing season.

Additional selection criteria included...

fields must be between Dec = +01:00 and Dec = -25:00 to allow follow-up from Northern hemisphere telescopes
must be able to observe each field set during allocated time each half night (i.e., field set must be DISTRIBUTED to allow observations of all fields)
throughout search season (approximately Sep 15 - Dec 30), field must be at airmass X<1.7 at some time during night
should minimize bright stars, with no stars m<8 and preferably few stars with m<10
low galactic extinction
low I-band cirrus
out of the galactic plane
maximize overlap with other surveys (SDSS, NDWFS, DLS, etc.)
moon preferably not passing through the fields
preferably out of the ecliptic plane

The selection analysis focused on the galactic extinction, survey overlap, and airmass as a function of time and month. For survey overlap, we concentrated on two large optical surveys, the Sloan Digital Sky Survey (SDSS) and the NOAO Deep Wide Field Survey (NDWFS). In particular, we tried to pick as many fields as possible in the SDSS equatorial strip, since in this area photometric redshifts (photo-z) for objects detected by SDSS are already publically available the SDSS SkyServer pages (click on Navigate).

Two Field Sets

The ESSENCE telescope schedule provides for observations every other night on the CTIO 4m telescope. In order to maximize the sky coverage, and therefore the number of SNe discovered and followed, we have selected TWO sets of fields which will be observed on alternate ESSENCE nights. This provides a field revisit cadence of every 4 nights, sufficient to produce high quality light curves under normal Oct-Nov conditions at CTIO (especially for intermediate and higher-z SNe where time dilation helps!).

Set A Fields

Field Name	RA (J2000)	Dec (J2000)	Depth	RAW	Comments
waa6	23:25:01.12	-09:14:59.7	shallow		in SDSS -10 strip
wx01	23:36:01.44	-10:10:01.6	intermediate		in SDSS -10 strip
wx04	00:07:01.28	-10:19:56.1	shallow		in SDSS -10 strip
wx06	00:13:31.11	-10:19:56.5	intermediate		in SDSS -10 strip
wx09	00:17:01.86	-00:29:31.0	shallow		photo-z available, in SDSS equat. strip
wx11	00:28:00.55	+00:25:46.9	intermediate		photo-z available, in SDSS equat. strip
wbb6	01:09:00.16	+00:10:43.3	shallow		photo-z available, in SDSS equat. strip
wx14	01:15:00.31	-00:31:22.6	intermediate		photo-z available, in SDSS equat. strip
wcc3	2:05:20.30	-03:45:00.0	intermediate		in NDWFS, also High-z 2000
wcc1	2:10:00.90	-03:45:00.0	intermediate		in NDWFS, also High-z 2000
wx17	02:20:00.42	-07:49:15.0	intermediate		in SDSS -10 strip
wdd5	02:31:00.25	-08:24:17.3	intermediate		EXTRA, in SDSS -10 strip

Set B Fields

Field Name	RA (J2000)	Dec (J2000)	Depth	Comments
waa7	23:30:01.20	-09:44:55.9	shallow		in SDSS -10 strip
wx02	23:42:01.29	-09:39:58.2	intermediate		in SDSS -10 strip
wx05	00:07:31.07	-09:29:55.8	shallow		in SDSS -10 strip
wx07	00:19:31.10	-10:34:57.0	intermediate		in SDSS -10 strip
wx10	00:27:00.25	-00:23:21.6	shallow		photo-z available, in SDSS equat. strip
wx12	00:31:00.35	-00:47:21.9	intermediate		photo-z available, in SDSS equat. strip
wbb5	01:12:00.46	+00:15:42.9	shallow		photo-z available, in SDSS equat. strip
wx15	01:18:00.41	-00:04:16.8	intermediate		photo-z available, in SDSS equat. strip
wcc2	02:07:40.60	-03:45:00.0	intermediate		in NDWFS, also High-z 2000
wcc9	02:05:20.52	-04:55:00.0	intermediate		in NDWFS
wx18	02:20:00.03	-09:19:19.4	intermediate		in SDSS -10 strip
wdd4	02:34:30.35	-08:19:18.2	intermediate		EXTRA, in SDSS -10 strip

We also have templates for a few more EXTRA fields in our complete list of field names and previews.

MOSOCS Files

To support more efficient observing and reduce the number of errors due to typos in coordinates or guide star selection, we use the mosocs task available for the MosaicII imager which controls not only the Mosaic imager but also the telescope (sending slew requests) and the guider (setting up on previously selected guide stars).

Old Fields Page

(2002 fields)

Last updated: November 16, 2004 by C. Aguilera