Transcript SNAP - Observatoire de Paris

SNAP-L
A wide field imager for dark energy
… and more !
Jean-Paul KNEIB
LAM, Marseille, France
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
1
The SNAP-L Mission
SNAP-L is a ~2m telescope with a wide field optical/near-IR
camera and a 3D optical/near-IR spectrograph.
SNAP-L is a project led by the Department of Energy (US
particle physicist community) started in ~1999
with international partners:
 France: through the spectrograph development and
scientific expertise (SN, WL) [INSU+IN2P3]
 Sweden: SN science
 Canada: WL science
 Other countries interested … and possibilities to have a
stronger contribution in the project.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
2
SNAP-L: the concept
A 2 meter class telescope, 3 mirror anastigmatic design
Provide a wide field flat focal plane, FOV > 0.7 square degrees
Covering ~350 to ~1700 nm
On a L2 orbit for stability and low background
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
3
SNAP-L: focal plane
spectrographe 3D IFU slicer
visible+IR
R=100-200
3’’x3’’ , [0.35-1.7]mm
9 filters
6 visibles
3 IR
Imager visible + IR
pixel scale = 0.10 arcsec/pixel (visible),
0.17 arcsec/pixel (NIR)
36 4kX4k CCDs [0.35-1]mm
36 2kX2k HgCdTe [1-1.7] mm
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
0.5 Gigapixels,
4
R&D on optical/IR Detectors
100
100
90
90
80
80
SNAP req.
70
60
QE (%)
CCD 86135-7-7
HyVis H2RG-32-ALN-03i
50
60
40
40
30
30
20
20
10
10
0
200
400
600
800
1000
1200
SNAP req.
50
0
600
Rockwell #103
Raytheon #141
800
1000
Wavelength (nm)
1200
1400
1600
1800
Wavelength (nm)
100
Important R&D funded by DOE for SNAP
On the detectors have reached the SNAP
requirements.
Latest IR detector should go on the new
WFPC3 camera to be installed on HST
during SM4.
Rockwell detector #103, 300 sec, 140 K
Raytheon detector #09A, 300 sec, 100 K
Read noise (e-)
QE (%)
70
10
SNAP req.
1
1
10
100
Number of Fowler pairs
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
5
SNAP IFU slicer spectrometer
Collimat
or
Pupil &
slit
mirror
IR path
Prism
Slicer
Detector
Entrance
point
Camera
•
IFU concept based on slicer
•
Compact and light (20x30x10 cm)
•
Spectroscopy of SN and host in the
same time
•
Photometric calibration
•
Spectro-z for photo-z calibration
•
Demonstrator being developed at LAM
Visible
IR
Wavelength coverage (mm)
0.35-0.98
0.98-1.70
Field of view
3.0" / 6.0"
3.0" / 6.0"
70-200
70-100
0.15
0.15
detectors
LBL CCD
10 mm
HgCdTe
18 mm
Efficiency with OTA and QE
>50%
>40%
Spectral resolution, l/dl
Spatial resolution element
(arc sec)
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
6
The SNAP-L Mission
SNAP-L is a dedicated mission to measure Dark Energy with
SuperNovae and WL measurements (and possibly Baryon
Acoustic Oscillation).
SNAP-L will have a deep survey and a wide survey
Both dedicated for SN and WL observation strategy but both
useful for « other sciences »
Key advantages of SNAP-L:
PSF, image quality, stable photometry
Wide field, Depth,
Large wavelength coverage (both in visible and
NIR with 9 filters),
on board spectrograph.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
7
Why going in space?
•0.1” angular resolution over wide field (0.7 sq.degree)
•Near-infrared unfettered by atmospheric emission/absorption
•Continuous, year-round observation of selected fields
•Stability!
100000
Paranal sky
Background ( g sec-1)
10000
D=8m
q = 0.3”
1000
100
10
Zodiacal light
1
D=2m
q = l/D
0.1
0
0.5
1
1.5
2
2.5
Wavelength (m m)
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
8
Space-based imaging vs ground
GEMS
COMBO-17
~ 100 galaxies per sq arcmin
(Brown et al. 2003)
~ 35 galaxies per sq arcmin
Space-based imaging has a significantly higher surface density
of resolved sources, which can probe the matter density power
spectrum at higher redshifts than will ever be feasible from the
ground.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
9
SNAP Surveys
Survey
Deep/SNe
Wide /WL
Area(sq.deg) Depth(AB mag) ngal(arcmin-2)
10
1000=>4000
250
107
28.1
100
108.5
26.7
40-50
109
Point Source - 3
Panoramic 7000-10000
30.4
Ngal
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
10
SNAP Deep Survey

Base SNAP survey: 7.5
square degrees near
North ecliptic pole

~3000x as large as ACS
UDF to mAB=30.4 in nine
optical and IR bands.

Provides ~150 epochs
over 22 months (each to
mAB=27.8) for time
domain studies in all nine
bands [SNe, AGNs]
20 Nov. 2006
Hubble Deep Field
GOODS Survey area
Jean-Paul KNEIB - prospective spatial PNG
11
SNe Systematic Control
SNe observation strategy:
Goal: Observe 2000 hig-redshift SN in
photometry and spectroscopy up to z~1.7
How: 22-month survey covering 7.5
sq.degree, with 2400s exposure per field
every 4 days.
The 9 band photometry will allow to select SN
candidates for spectroscopy, and ensure
quality rest-frame photometry.
40% of the time is reserved for on-board
spectroscopy, with a large fraction for z>1
SNe. SN redshift determine through the SiII
broad line.
NICMOS on HST has shown that spectrophotometry calibration can achieve better
than 1% error
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
12
SNAP Wide Area Survey




~1000 sq.deg. ‘wide’
survey the deep field,
but discussion for
extension to 4000
sq.deg.
Roughly 1 year for
1000°2
of observing time
Four dithered 500
second exposures at
each location; sensitive
to mAB=28.1 (point
source)
Every field observed in
all nine optical NIR
filters
20 Nov. 2006GOODS
Survey area Jean-Paul KNEIB - prospective spatial PNG
Hubble Deep
Field
13
WL 2-points stat: What is measured?
<g2>~0.01 82 1.6 zs1.4 q-(n+2)/2
Mass power spectrum normalisation
Slope of the power spectrum
Mean density parameter
Redshift of the sources
Ultimately Dark Energy constraints
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
14
Lensing Mass Map
3D Mapping of the
mass distribution.
COSMOS field as
an example.
-green countours:
X-ray
-Color blobs:
optical/phot-z
detection
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
15
Ground/Space comparison

Shear Calibration
error estimate for a
constant PSF :


Ground 0.7’’
Space 0.1’’
m: is calibrated with
‘realistic’ image
simulation m~5e-3.
m depends on PSF
stability and
ellipticity
20 Nov. 2006
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Jean-Paul KNEIB
Waerbeke
et al- prospective spatial PNG
16
Ground/Space Comparison


A space 4k
sq.deg survey,
is equivalent to
a ground 20k
sq. deg survey
for similar
photo-z bias.
Space photo-z
bias should ~5
times better, a
factor of 3
improvement
in the FOM
20 Nov. 2006
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Jean-Paul KNEIB - prospective spatial PNG
17
Photometric Redshift
NIR Filters are crucial
for photo-z accuracy
and to reduce
catastrophic failures
(see Ilbert et al 2006)
Filter optimisation for
photo-z in progress,
possibility to include
“U-band” filter.
20 Nov. 2006
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Jean-Paul KNEIB - prospective spatial PNG
18
The standard method -Results
Ilbert et al 2006
20 Nov. 2006
CFHT-LS deep field
photo-z show that
SED templates
needs to be
optimized !!!
Jean-Paul KNEIB - prospective spatial PNG
19
Calibration - template optimization
CFHT-LS optimize 4 templates with 2800 spectroscopic z
Need of
spectro-z
Calibration.
Optimized
templates
On-board
spectrograph
can measure
redshift in
parallel of the
SN and WL
survey
(~50 000
spectro-z per
year of WL
observation
AB<24.5)
20 Nov. 2006
Initial
templates
Jean-Paul KNEIB - prospective spatial PNG
20
Calibration - improvement
Calibration
method is
successful
to remove
systematics.
More spectro-z
the better,
feasibility is on
progress but is
looking good.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
21
Dark Energy Constraints
Produce
Good photo z
Use 3 WL
Methods
Very powerful
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
22
what SNAP can also

Dark energy:






SNII
Galaxy clustering /
baryon oscillations
Galaxy clusters and their
clustering
Strong lensing
Correlation with other
surveys

ISW, SZ, dark baryons
20 Nov. 2006
Non-dark energy
science






Galaxy evolution
Quasars and AGN
Solar system objects
Nearby galaxies,
structure, stellar pops,
globular clusters
High-z objects
MW structure + stars
Jean-Paul KNEIB - prospective spatial PNG
23
Strong Lensing with SNAP-L
Cabanac et al 2006
 Current example:
SL2S:
automatic search
through the CFHT-LS for
arcs and partial rings
around elliptical galaxies
(~40 candidates out of
the first 28 sq.degree) +
Follow-up with an ACS
snapshot program.
COSMOS: 1.5 strong
lenses in 1.7 sq deg.
=> ~10-40 thousands
strong lensing system in
SNAP-L WL survey.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
24
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Marshall et al 2006
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
25
UDF Can see
Galaxies at z~6
And has candidates
up to z~8 - similarly
SNAP-L will image
these distant
galaxies …
20 Nov. 2006
ACS/grism, Keck/LRIS & VLT/FORS2
observations confirm z=5.83
Jean-Paul KNEIB - prospective spatial PNG
26
High-z galaxies
Stiavelli et al 2004
Expect ~100 000 z>7
galaxies in the SNAP-L SN
surveys down to AB~29.
Unique way to map large
scale structure at z>7
(faster than JWST) and
find rare objects (QSOs,
strong lenses, …)
SNAP-L can be seen as a
survey telescope for JWST.
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
27
Probing the end of dark ages
Xiaohui Fan

z~3 quasars: 200 –
400 per sq. deg

Hundreds of z~6
quasars

Maybe 10 luminous
quasars at z = 9 – 10?
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
28
Conclusion



SNAP is a well advanced concept (R&D well advanced
and ready for integration) currently proposed in the
NASA JDEM context, but JDEM contract is being rediscussed for an early launch (goal 2014).
SNAP is dedicated to dark energy and will provide at
least 2 surveys (AB=30,28 point sources) for SN and WL
but these can address many other sciences.
France (CNES) through the spectrograph contribution
is well involved, and other participation might be
possible to become a stronger partner (telescope, WL
data center and analysis …)
20 Nov. 2006
Jean-Paul KNEIB - prospective spatial PNG
29