An integral field spectrograph for supernovae in space A.Ealet Marseille CCPM/CNRS

An integral field spectrograph for

supernovae in space

A.Ealet

Marseille

CCPM/CNRS

HistoryHistory

1998 Discovery of the acceleration of the universe and dark energy using supernovae (SCP and High Z teams) .

2000 Confirmation of dark energy using cosmic microwave background measured from balloons.

2003 Confirmation of dark energy using cosmic microwave background measured from space (WMAP).

2005 First evidence of Baryon acoustic oscillation

And WE DO NOT KNOW AT ALL WHAT IS DARK ENERGY…………

IFU workshop 28 oct. 2010 2Anne EALET

DE history DE history

SN for Cosmology & DESN for Cosmology & DE

SNIa the most powerful and best proven technique. the outcome depending on the ultimate systematic uncertainties.

SNIa is an unique probe of DE because:• Independent of the growth of structure [in contrast to WL and BAO]. This

is important when differentiating between DE and modified gravity models.

• Probes luminosity distances [WL and BAO probe angular diameter distance and to some extent H].

• Allows for dense redshift- and spatial sampling which is important when constraining spatial and temporal variations of DE.


IFU workshop 28 oct. 2010

Anne EALET 4

Building the Hubble diagramF

ain

ter

Brig

hter

1.0

0.5

0.0

-0.5

-1.0

m, r

ela

tiv

e m

agn

itu

des

0.0 0.5 1.0 1.5 2.0

Redshift, z

Freely expanding

Constant deceleration

Concordance

Constant acceleration

Hubble observations

VISIBLE IR

• Today after 10 years…—about 1000 SNe Ia for cosmology—constant ω (state equation) determined to 5%—No strong information of time variation of w—accuracy dominated by systematic effects = calibration, reddening, evolution

Where we are today? Where we are today?


SNe + BAO + CMB...

w 0.969 0.061(stat) 0.065(sys)

MethodologiesMethodologies

6IFU workshop 28 oct. 2010 Anne EALET

Classical method used in most high z SN surveys (SNLS, Essence et..)

Broad bands in photometry with a rolling search Spectroscopy mainly for redshift (host galaxy) and SNIa typing

Caveat = inter calibrations (different filters at different redshifts)modeling with non flux calibrated spectraphotometric corrections

New paradigmReplace photometry by spectro photometrytested in nearby SN (Snfactory) (cf Bailey 09) and cfa (Blondin 10)

-flux calibrated spectra at different epochs

Benefit = synthetize any filters/redshift rangesample of spectra for template modeling and understanding SNSimplify inter calibration with high z

Difficulties = survey implementation and high z spectrscopy on ground

Nearby SN on SnfactoryNearby SN on Snfactory

7

Work on going , 58 published SNIa, calibration 2-3%

Snfactory = a dedicted IFSIn Hawai SN every 2-3 nights

Use a photometric arm to correctNon photometric nightsBuild spectro photometric light curve

More with spectroscopyMore with spectroscopy


- light curves at 2-3 % build with spectrophotometry -explore standardisation with spectroscopy alone

-flux ratio as indicators as R642/543(Bailey 09) Single flux ratio produces better Hubble diagram than stretch + color corrections

- Other indicators can decorrelate color/redenning (under studies)

Preliminary results Snfactory

This method is very promising to improve SN measurement for cosmology

Spectro photometry and flux ratios require accurate relative flux calibration, as well as minimal contamination by host-galaxy light.

Both requirements impose strong conditions on future SN Ia surveys for implementation

This method is very promising to improve SN measurement for cosmology

Spectro photometry and flux ratios require accurate relative flux calibration, as well as minimal contamination by host-galaxy light.

Both requirements impose strong conditions on future SN Ia surveys for implementation

Which spectroscopy for a future missionWhich spectroscopy for a future mission


RCa

RSiSiII

Going to high redshift

classical method = SN followed in photometry + typing and systematic control (evolution)

- Identify SNIa by the SiII line (large coverage for a large redshift range)

+ line ratios or any new possible indicators at peak =>good SNR

=> relative flux calibration and galaxy subtraction

New paradigm = replace photometry by spectro-photometry

-requires multi epochs follow up

-relative flux calibration at 1-2%

- galaxy subtraction

Need more observational time but no

photometry

10

Science requirements to specifications Science requirements to specifications Flu

x (

ph

oto

ns)

Si line

Wavelength (µm)

• Identification SN1a up to redshift 1.5 with Si line

•Measure precisely some features =>relative spectro photometry ~ 2%

•Subtraction of the host galaxy

• Redshift of the host galaxy < 0.005(1+z)

Anne EALETmarseille Feb 05 09

bandwidth 0.4 to 1.7-2 µm cover Ca to SiII 0.3 < z < 1.7

FOV > 3’’ Galaxy +SN in one shot

spect resolution()/ pixel ~100 constant to not depend of the redshift

Spatial resolution 0.15’’ Reduce zodiacal light

Line precision 1 nm Redshift precision

spectrophotometry <2 % calibration

Throughput (optic+detector) > 40 % sensitivité

Sensitivity 10-20 erg/s/cm2/A Reach z>1.5 magnitude

UV

Ca

Why in Space?Why in Space?


Anne EALET 11

• Access to z > 1 with low systematic (NIR)

• spectroscopic method for high z

(z>0.3) is not possible from ground even in the visible (sensitivity)

• Continuous, year-round observation of selected fields

…essential for moving to 1-2% measurement

….essential for good spectroscopy

Which Spectroscopy in space for SN Which Spectroscopy in space for SN

• Slitless (as inJDEM /Adept/destiny)—Feasibility proven using HST/ACS

—Multiplex advantage, time series

—Need a wide field, deep survey

— spectro-photometry?

—Limited by the zodiacal background

• IFU/slicer as in JDEM/SNAP (dedicated)

Sensitivity = IFU or slit are more than

10 time more sensitive than slitless

Need pointing (small FOV)


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Why an IFU/Slicer ? Why an IFU/Slicer ?

Pixel level simulation

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Very high sensitivity as a slit + detector noise optimisation

SLICER =

No need for accurate pointing

Correct slit effect thanks to the slices

All flux in the spectrograph

No need of dithering

Measures SN+galaxy in one shot => no ref image

=> easy to operate

SLICER =

No need for accurate pointing

Correct slit effect thanks to the slices

All flux in the spectrograph


Measures SN+galaxy in one shot => no ref image

=> easy to operate

readoutsky

Read noise (e)

Z=1.5 exposure for SNR=18, D=1.5m

New HgCdTe detector can reduce exposure time using very low detector noise + long exposure time with up the ramp + cosmic rejection


An IFU slicer spectrometerAn IFU slicer spectrometer

IR path

Wavelength coverage (m)

0.4-1.70

Field of view 3.0" 6.0"

Spectral resolution, 70-100

Spatial resolution element (arc sec)

0.15

detectors HgCdTe18 m

Efficiency with OTA and QE

55% in NIR

• IFU slicer in glass (French expertise)• Compact (20x30x10 cm)• Light < 12 kg• Galaxy and SN spectrum at the same

time• Readiness TRL5 (CNES)• Full prototyping for performances

References•Aumeunier PASP,2008•Ealet SPIE 2006,2008•Prieto SPIE 2008•Pamplona SPIE 2008•Rossin SPIE 2006

R&D development (2005-2007)R&D development (2005-2007)

15 Anne EALET

A full demonstrator working in the visible and IR at 110 K

Validate the performances slicer concept and test the calibration procedure

Straylight Measurement controlled at 10-3

Wavelength Calibration at the nanometer level relative flux Calibration better than 1 %

a NIR 2kx2k Rockwell device from Berkeley has beenintegrated and read with our own readout system


Conclusion of Ifs/slicer prototypeConclusion of Ifs/slicer prototype

•Wavelength calibration•No need of object position•No need of dithering•Improve naturally the resolution

•Good spectro photometry•All flux are in the slices•Correct slit effect thanks to slices

Real data demonstrator by Marseille team

=> redshift estimation < 0.003 (1+z) even with low resolution and sub sampled => accurate spectro-photometry even with no accurate pointing and low resution

IFU workshop 28 oct. 2010 16Anne EALETWavelength (nm)

Flu

x E

rror

(%)

SN

R

in IR

in visible

17

Numerical modelNumerical model

Instrument design

Optical simulation (POP): geometrical distorsions aberrations diffraction

Detector pixelisation

“real’’ PSF

Point like source (x,y,λ)

Sampled PSF

Simulation of detector effects: read noiseDark current inter and intra pixelvariation

Pixeled PSF

PSFs at the output of the optical simulation

Final PSF

Core PSF (86 % du flux)

Rings PSF (4 % du flux)

MODELE NUMERIQUE

slice 1slice 2slice 3slice 4slice 5

spatial

spectral

spatial

spectral

On the detector

Entrance FOV

A spectrum

A monochromatic line

JWST/NIRSPEC IFU slicerJWST/NIRSPEC IFU slicer


-NIRSPEC has a low resolution option (R=100) with slicer (Aluminium slices)

-almost same concept than SNAP but optimised in [1-5]m

SNAP

JWST

JWST SNAP/JDEM

Coverage [0.6-5] m [0.4-1.7]m

resolution 100 100

FOV 3’’x3’’ 3’’x6’’

sampling 0.1’’ 0.15 ’’

throughput 20 % 55 %

Detector noise 6 6

JWST for high z SN spectroscopyJWST for high z SN spectroscopy


• JWST/NIRSPEC can follow z >1 supernovae at peak in a reasonable amount of time• The coverage is not optimized for 0.2<z<0.8 (visible), and dominated by overhead

•For at least 100-300 SN, this need a significant mission time (2 to 4 months) on target of opportunity + a coordination with an imaging wide survey to find them

•A multi epochs approach with spectroscopy only is more difficult to implement on this non dedicated instrument

€

≈

NIRSPEC could do a good complement of follow up for very high z SN as target of opportunity

But could not easily do a fullspectroscopic programfor cosmology

NIRSPEC could do a good complement of follow up for very high z SN as target of opportunity

But could not easily do a fullspectroscopic programfor cosmology


JDEM ISWG studies A new optimised design

SN strategy based on IFU/SLIT spectroscopy only

http://jdem.gsfc.nasa.gov/science/iswg/JDEM_ISWG_Report.pdf

To be implemented in WFIRST?



Conclusion Conclusion

• Spectroscopy for high z supernovae for cosmology is a challenge for a future space mission

• A new approach based on spectroscopy only is under consideration

• Need a specific space instrument to have a high quality data sample

• JWST / NIRSPEC can follow high z SN (z> 1 ) and can be a good complementary approach using target opportunity for a limited sample

Need a coordination with a wide field survey

• A dedicated program with a multi epochs should be better implemented in a future NIR wide field survey as the one planed for WFIRST.



Wfirst is an infrared telescopeLauch 2020-2022

BaselineConcept baseline = JDEM -1.5m telescope-36 IR detectors

Scientific cases-dark energy with 3 probes (BAO,WL,SN)- exoplanets with micro gravitational lensing- guest investigator

Released Aug. 13, the Astro2010 decadal survey — formally titled “New Worlds, New Horizons in Astronomy and Astrophysics”

— designated WFIRST as the top priority for large missions for the decade ahead. The survey envisions WFIRST being developed by NASA in partnership with the U.S. Department of Energy and ESA at an estimated cost of $1.6 billion to study dark energy, hunt for Earth-like planets and advance scientific understanding of the nature and evolution of galaxies.

ASTRO2010

25marseille Feb 05 09 Anne EALET

WHICH SENSITIVITY ?

Sensitivity ~ 10-20 ergs/cm2/s/A

= > ~1e-18 ergs/cm^2/s per spectral element (R=100)

+ SNR/spectral element > 10 at the above flux

= > very challenging , time driver

redshiftredshift

RCa

RSiSiII

Some resultsSome results

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GOOD PSF

at Room Temperature and

at Operating Temperature (110K) ( compared with pixel level simulation)

Insensitivity to slit effect Spectral resolution preserved

even with PSF < slit


marseille Feb 05 09

Wavelength (nm)

Flu

x E

rror

(%)

SN

R

Good photometric measurement

precision

New method

An integral field spectrograph for supernovae in space A.Ealet Marseille CCPM/CNRS

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