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Spitzer Observations
Retrieve Data
Requirements
The extragalactic component of the FLS was designed to meet these requirements:
- A 5 square degree imaging survey with IRAC and MIPS to a shallow depth of about one minute per pixel on the sky.
- A total of 4 square degrees within the Spitzer Continuous Viewing Zone (CVZ), in an area where IR cirrus is low: 17h10m+61d, where I(100um) = 1-2 MJy/sr
- A separate 1 square degree region whose location will depend on the sky visibility at the end of In-Orbit Checkout (IOC):
- in near-CVZ area of low cirrus at 16h20m+54d30m, where I(100um) = 0.4 MJy/sr, or
- within the CVZ, if area in (a) is not accessible at the conclusion of IOC.
- MIPS Shallow Survey: 5 passes at fast speed, incorporating three bands
- Total T(int) = 75 sec per point (24 and 70 um), 15 sec (160 um)
- Depth reached is 1.3 mJy at 24 um; confusion-limited at 160 um
- Scan rate = 1 sq.deg. per 3 hours, plus 30% overheads
- Following estimates for a 5 square degree, 20-hour survey
| wavelength (µm) | Flux Limit (mJy, 5-sigma) | Gain over Past | Source Counts |
|---|
| 24 | 1.3 | ~ 100 | ~ 400 |
| 70 | 4.5 | ~ 50 | ~ 1500 |
| 160 | 27.0 | ~ 8+ | ~ 2500 |
+ ISO covered a few square degrees
- IRAC Shallow Survey: 4 bands simultaneously
- Total T(int) = 5x12 sec per point
- Requires ~ 5 hours per sq.deg., including overheads
- Following estimates for a 5 square degree, 20-hour survey
| wavelength (µm) | Flux Limit (mJy, 5-sigma) | Gain over Past | Source Counts | mean z for L* elliptical |
|---|
| 3.6/4.5 | 0.04 | >> 1 | stars + ? | ~ 1 |
| 5.8 | 0.04 | ~ 1+ | stars + ? | ~ 0.4 |
| 8.0 | 0.06 | ~ 1+ | ~ 1500 | ~ 0.3 |
+ ISO covered a few square arcminutes
- Within the above area, a MIPS/IRAC verification survey of 0.25 square degree or less, with ten times the integration time.
- Should fit within ~30% of time dedicated to shallow survey
- Incorporation of ancillary data recommended, primarily for identification purposes.
- Deep R-band or I-band survey, to R(5-sigma) ~ 25.5 mag
- Near-infrared K-band survey to K ~ 18 mag
- Radio survey at 1.4 GHz to 5-sigma sensitivity of ~ 90 micro-Janskys
- Conservative experimental design, emphasizing reliability at the expense of sensitivity.
Main Survey: 4 square degrees with MIPS and IRAC in the Constant Viewing Zone (CVZ)
- 2° x 2° box centered at 17:18:00.0 +59:30:00
- ~ 80 seconds/pixel on the sky (MIPS), ~60 seconds/pixel (IRAC)
- Cirrus: I(100 um) = 1-2 MJy/sr
Verification survey covers ~5% of main survey area with greater depth and redundancy
- 0.2 square degree strip centered at 17:17:00.0, +59:45:00
- ~400 seconds/pixel on the sky (MIPS), ~600 seconds/pixel (IRAC)
Spitzer Observation Summary
| Instrument
| Wavelength (microns)
| Main Survey- Exp. Time (sec)
| Main Survey 5-sigma Sensitivity (mJy)
| Verification Survey- Exp. Time (sec) |
|---|
| IRAC | 3.6 | 5 x 12 | 0.006 | 10 x 12;
16 x 30 |
| IRAC | 4.5 | 5 x 12 | 0.007 | 10 x 12;
16 x 30 |
| IRAC | 5.8 | 5 x 12 | 0.045 | 10 x 12;
16 x 30 |
| IRAC | 8.0 | 5 x 12 | 0.032 | 10 x 12;
16 x 30 |
| MIPS | 24 | 2 x 40 | 0.3 | 8 x 40 |
| MIPS | 70 | 1 x 40 | 30 | 4 x 40 |
| MIPS | 160 | 2 x 4 | 80 | 8 x 4 |
Layout of the Extragalactic Component of the First-Look Survey in the Constant Viewing Zone (CVZ)
The layout of the AORs on the sky is shown in the following figures. The red box marks the field center J1718+5930.
IRAC AORs--Main Survey Layout
Eight AORs cover the field. Click for a larger image. MIPS AORs--Main Survey Layout
Eight AORs cover the field. Each AOR has the following parameters set in Spot:
Each AOR covers roughly 2 degrees by 30 arcminutes with 40 sec per point on the sky (24 micron and 70 micron arrays). The first set is executed and the observations are repeated by the second set with a half-array offset in the starting position. The colors represent 24 micron (green), 70 micron (blue), and 160 micron (peach). Click for a larger image. IRAC AORs--Verification Survey Layout
Six AORs cover the field. Three use 12 second exposure times the other 3 AORs use 30 second exposure times. Click for a larger image. MIPS AORs--Verification Survey Layout
The field is covered 4 times. Each AOR has a slight starting position offset. Click for a larger image. Summary
The total time for the extragalactic FLS using these parameters is 62.4 hours.
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