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Prospects – JWST, EUCLID, WFIRST. Jeff Kruk (GSFC) [email protected]. Outline. HST: now to 2015 and beyond… JWST: 2015 - 2025 EUCLID(?): 2018-2023 WFIRST: XX - XX+5…. Sky backgrounds. HST slitless modes. JWST slitless modes. - PowerPoint PPT Presentation
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Prospects – JWST, EUCLID, WFIRST
Jeff Kruk (GSFC)[email protected]
Outline
• HST: now to 2015 and beyond…• JWST: 2015 - 2025• EUCLID(?): 2018-2023• WFIRST: XX - XX+5…
11/15/2010 2J. Kruk STScI Slitless Spectroscopy wkshp
Sky backgrounds
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 3
HST slitless modesInstrument FoV
(arcmin)Platescale R Bandpass
(nm)ACS WFC
grism3.4’x3.4’ 0.05” 100 550-1050
ACS SBC prisms
0.58’x0.51’ 0.025” 7996
115-180125-180
WFC3 NIR grisms
2.05’x2.27’ 0.13” 210130
800-11501075-1700
WFC3 UVIS grism
2.7’x2.7’ 0.04” 70 200-400
NIC3 prisms 0.87’x0.87’ 0.203” 200 0.8-1.21.1-1.91.4-2.5
STIS NUV prism
0.42’x0.42’ 0.024” 2500-10 115-350
11/15/2010 4J. Kruk STScI Slitless Spectroscopy wkshp
JWST slitless modes
Instrument FoV (arcmin)
Platescale R Bandpass (nm)
NIRCAM 2 grisms,
Rotated 90°
2.16’x2.16’ 0.0648” 2000 2400-5000(filters in
series)
NIRSpec* prism, gratings
3.4’x3.6’ 0.1” 1001000, 2700
700-5000
*NIRSpec micro-shutters: 0.2”x0.45” - open area ratio is 0.7 if all left open
11/15/2010 5J. Kruk STScI Slitless Spectroscopy wkshp
EUCLIDNIR slitless spectroscopy
• Launch in 2018 if selected, 5 year mission duration• Survey 20000 deg2
– limiting line flux 4*10-16 ergs/cm2/s• Characteristics (Laureijs et al 2010 SPIE 7731):
– 1.2m primary, 0.35m secondary obscuration– 4 grisms in wheel, identical except for 90° rotations– 1.0-2.0 microns– R=500– Focal plane: (choice still TBD?)
• 12 SCAs: 0.33”/pix 36.4’x48.5’ (0.49 sq deg)• 16 SCAs: 0.31”/pix 46.1’x46.1’ (0.59 sq deg)
11/15/2010 6J. Kruk STScI Slitless Spectroscopy wkshp
WFIRST
• Launch: ?? - depends on JWST schedule• Mission duration: 5 years min, 10 years goal• Objectives:
– 10000 deg2 WL survey (30 gal/sq arcmin)– 20000 deg2 BAO survey (limiting flux 1.6 10-16)– 150 SNIa per z=0.1– (didn’t quite fit into 5 years, but close)
• EOS panel recommendations cuts time in ~half for first 5 years of mission
11/15/2010 7J. Kruk STScI Slitless Spectroscopy wkshp
WFIRST characteristics(details subject to change!)
• Imager– 0.4-2.0m– 0.18”/pixel– 4x6 array of SCAs (0.25 deg2)– Filter wheel: 5 filters, R=75 prism, blank
• Spectrometers (2, w/ opposing dispersions)– 1.1-2.0m– 0.37”/pixel– 2x3 array of SCAs (0.26 deg2) each– R=270-327 per 2 pixels
• R = 200-240”, or c/R = 1500-1250km/s/arcsec
11/15/2010 8J. Kruk STScI Slitless Spectroscopy wkshp
WFIRST block diagram(details almost certain to change)
11/15/2010 9J. Kruk STScI Slitless Spectroscopy wkshp
WFIRST focal planes as projected onto the sky
11/15/2010 10J. Kruk STScI Slitless Spectroscopy wkshp
Design Tradesgrism vs. prism
Grism pros:– zero-order gives
wavelength reference– Allows higher dispersion
Grism cons:– Zero order increases
spectral contamination– Higher dispersion not
needed for BAO; if lines resolved, S/N is reduced
– Higher orders contaminate spectra
– 1st order throughput lower than prism
11/15/2010 11J. Kruk STScI Slitless Spectroscopy wkshp
Grism simulation courtesy of David Larson
Design Trades
• Dispersion– σz/(1+z) < 0.001, resolve OIII, don’t resolve Hα
• Bandpass– Redshift coverage & spectral diagnostics vs
zodiacal light– Combined w/dispersion -> length of spectral trace
• Number of roll angles, size of roll offset – 4 rolls: 0°,5°; 170°,175° found sufficient
• Don’t set 2 spectrometers exactly 180° apart
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 12
Imager sim – 225 sec
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 13
Imager simulation – 225sec 1SCA (log stretch)
Courtesy David Larson
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 14
Spectrometer simulation – 225 sec 1SCA (log stretch)
Courtesy David Larson
4° roll offset
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 15
Roll = 0 Roll = 4
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 16
133 ksec deep exp (SN field) asinh stretchGalaxies & stars only - no background
Courtesy David Larson
General issues• EUCLID, WFIRST not as clean as HST
– PSF, pixels are large compared to HST– Pointing stability, dithering, less precise than HST
• What dithering is desirable/required in this context?
• Direct images are obtained with a different instrument at different times – Use edges of traces of bright stars in field for
registration
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 17
Issues continued:calibrations
BAO needs accurate wavelengths• Optical distortion calibration is critical – not challenging
SNIa needs accurate fluxes• If from spectra, flat-field cube is critical – challenging• Would like to derive flat-field internally from the data
– Has been done for imaging instruments (Arendt et al. 2010 ApJS 186 10)
– Dimensionality of problem is higher for slitless spectrometer; will need extensive simulations to test
Persistence corrections• Can pipeline maintain continuous exposure history?
• Initial planning limited to DE programs– Need to reevaluate for larger WFIRST program
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 18
Issues cont.• Datasets are large!
– Manual processing not practical for 109 galaxies• Extract ~109 to obtain 108 emission-line galaxies
– “…it is still mandatory to check and validate the products before any science investigation can commence.” (The WFC3 IR Grism Data Reduction Cookbook – Extracting several 100 grism spectra made easy)
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 19
Issues cont.• Datasets are large!
– Manual processing not practical for 109 galaxies• Extract ~109 to obtain 108 emission-line galaxies
– “…it is still mandatory to check and validate the products before any science investigation can commence.” (The WFC3 IR Grism Data Reduction Cookbook – Extracting several 100 grism spectra made easy)
Uh Oh…..Crowd-sourcing? Doesn’t look like as much fun as
the Galaxy zoo
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 20
WFIRST - what’s next?
• Astro-2010 provided fairly strict guidance,– But details left open for further optimization
• The science goals have expanded to fill a 10-year mission.– While plausible, the nominal design life is 5 years
(so everyone starts out unhappy)• The Science Definition Team may have a big
role in defining the details. Stay tuned.
11/15/2010 21J. Kruk STScI Slitless Spectroscopy wkshp
WFIRST telescope trade:
1.5m on-axis vs 1.3m off-axis
11/15/2010 22J. Kruk STScI Slitless Spectroscopy wkshp
PSF - scaled by effective area Encircled Energy
Diffraction from spider arms not included
EOS observing plan
• BAO+WL: <~2 years• Sne: 0.5 years• Micro-lensing (Galactic bulge): 1.4 years• Galactic plane survey: 0.5 year• Guest-observer surveys: 1 year
– This means you!
11/15/2010 J. Kruk STScI Slitless Spectroscopy wkshp 23
WFIRST SDT
Deadline for applications to the WFIRST Science Definition Team: Nov 23rd, 2010
Please Apply!
Further info: http://wfirst.gsfc.nasa.gov
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