1. 1 SNIa Calibration from May 2012 Chicago Calibration meeting

2. Current State of SN Systematics Photometric Calibration Uncertainties Dominate! From Sullivan et al. 2011 2

3. 3 Our ability to determine cosmological parameters with D L (z) is completely degenerate with our ability to perform precise photometric calibration. This is currently the main systematic limitation to SN cosmology.

4. Current State of SN Cosmology 4 SNLS

5. 5 SNLS

6. 6 SNLS

7. 7 Discovery data 1998 20 distant SNe10% precision ESSENCE, SNLS … 2009 200 distant SNe3 % precision PanStarrs, DES 2011-2015 2000 SNe1% precision (?) LSST 2018 20,000 SNe< 1% goal Next Steps on Dark Energy: Bigger and Better Imaging Surveys

8. Broadband photometry: “Metrology and Meteorology” Four aspects to the photometry calibration challenge: 1.Relative instrumental throughput calibration 2.Absolute instrumental calibration (Best controlled) 3.Determination of atmospheric transmission 4.Determination of line of sight extinction Historical approach has been to use spectrophotometric sources (known S( )) to deduce the instrumental and atmospheric transmission, but this (on its own) has become problematic if we need % precision: - integral constraints are inadequate, - we don’t know the source spectra to the required precision. Four aspects to the photometry calibration challenge: 1.Relative instrumental throughput calibration 2.Absolute instrumental calibration (Best controlled) 3.Determination of atmospheric transmission 4.Determination of line of sight extinction Historical approach has been to use spectrophotometric sources (known S( )) to deduce the instrumental and atmospheric transmission, but this (on its own) has become problematic if we need % precision: - integral constraints are inadequate, - we don’t know the source spectra to the required precision. Source Atmosphere Instrumental transmission Extinction above the atmosphere

9. 9 Atmospheric Transmission Burke et al, ApJ 720, 811B (2010)

10. 10

11. Potential Color calibration approaches 1.Terrestrial black-body sources, using triple point of metals, and Vega as the transfer standard 2. Theoretical models of stellar spectra DA white dwarf stars, with 20,000K < T <80,000K. Theoretical models depend only on log (g) and T Model of Vega plays a role as well But beware of extinction effects 3. Statistical assemblage of stars, en masse. Color-color diagrams, ubercalibration tie to another photometric system. 4. Shift the calibration approach entirely, and base it on well- characterized detectors. 1.Terrestrial black-body sources, using triple point of metals, and Vega as the transfer standard 2. Theoretical models of stellar spectra DA white dwarf stars, with 20,000K < T <80,000K. Theoretical models depend only on log (g) and T Model of Vega plays a role as well But beware of extinction effects 3. Statistical assemblage of stars, en masse. Color-color diagrams, ubercalibration tie to another photometric system. 4. Shift the calibration approach entirely, and base it on well- characterized detectors. Not mutually exclusive

12. How to address this ? 1.Explicit measurement of atmospheric transmission. 2.Explicit measurement of instrumental response function. use a tunable laser in conjunction with NIST photodiode standard 3.Explicit determination of atmospheric transmission multi-narrowband imager dispersed imager balloon-borne sources (2012) 4.Re-assess Galactic extinction. Schlafly & Finkbeiner (2011) used SDSS to revise SFD dust map, correction factor of 0.78 at 1 micron! 5.Try to shift away from celestial calibrators entirely. 1.Explicit measurement of atmospheric transmission. 2.Explicit measurement of instrumental response function. use a tunable laser in conjunction with NIST photodiode standard 3.Explicit determination of atmospheric transmission multi-narrowband imager dispersed imager balloon-borne sources (2012) 4.Re-assess Galactic extinction. Schlafly & Finkbeiner (2011) used SDSS to revise SFD dust map, correction factor of 0.78 at 1 micron! 5.Try to shift away from celestial calibrators entirely.

13. 13

14. NIST Cal Photodiode Spectral Responsivity NIST photodiode responsivity measurements - InGaAs spectral responsivity - InGaAs spectral responsivity uncertainty of 0.1% (1s) for 1.0<  1.7 mm uncertainty of 0.1% (1s) for 1.0<  1.7 mm Photodiode detectors extremely stable over time - Si stability exceeds 15 years, thus far - Si stability exceeds 15 years, thus far - InGaAs stability exceeds 10 years, thus far - InGaAs stability exceeds 10 years, thus far Standard Detectors − not standard sources − are the calibrator of choice - increased precision in the photodetector calibration, - increased precision in the photodetector calibration, - ease of use, - ease of use, - repeatability of standard detectors relative to standard laboratory sources - repeatability of standard detectors relative to standard laboratory sources Eppeldauer, Metrologia 2009 updated InGaAs figure: courtesy Keith Lykke (NIST) 14

15. 15 Precise Filter Determination

16. 16 Collimated Source Measurements

17. 17 Atmospheric Transmission Burke et al, ApJ 720, 811B (2010)

18. The Variable Aspects of Atmosphere 1.Ozone satellite data 1.Water VaporEW of water lines dual-band GPS differential narrowband 2.Aerosolsstellar monitor balloon-borne lasers 3.Cloudslocal zeropoint adj. 1.Ozone satellite data 1.Water VaporEW of water lines dual-band GPS differential narrowband 2.Aerosolsstellar monitor balloon-borne lasers 3.Cloudslocal zeropoint adj.

19. Objective grating atmospheric monitor 19

20. PanSTARRS-1 throughput 20 Tonry et al arXiv:1203.0297

21. Closing the loop Instri InstrumentalSensitivity Atmospheric Transmission Instri Spectrophotometric Standards Instri Precisephotometry With this initial effort, come within 5% rms of matching ab initio calculations with observations (eg, Tonry et al, arXiv:1203.0297, 2012)

22. Summary (Chris Stubbs- May 2012) 1.SN cosmology is stalled until we improve calibration Determination of luminosity distance vs. z is completely degenerate with our ability to calibrate photons( ). 2.We need to determine 3 things: instrumental sensitivity function atmospheric transmission extinction along the line of sight 3.A relative determination suffices. Don’t need absolute flux scale (zeropoint), since this is degenerate with M SN. 4.I am dubious about any celestial spectrophotometric standard below the 1% level. 5.We are making (slow) progress towards implementing a relative calibration based on laboratory standards. 1.SN cosmology is stalled until we improve calibration Determination of luminosity distance vs. z is completely degenerate with our ability to calibrate photons( ). 2.We need to determine 3 things: instrumental sensitivity function atmospheric transmission extinction along the line of sight 3.A relative determination suffices. Don’t need absolute flux scale (zeropoint), since this is degenerate with M SN. 4.I am dubious about any celestial spectrophotometric standard below the 1% level. 5.We are making (slow) progress towards implementing a relative calibration based on laboratory standards.

23. Go to Space? HST, Gaia, Euclid -Open issues still for absolute colour calibration -K corrections (precise inter and filter calibration) -SN model -Standard stars and detectors HST, Gaia, Euclid -Open issues still for absolute colour calibration -K corrections (precise inter and filter calibration) -SN model -Standard stars and detectors 23

24. The future (>2020): multiprobe DE projects(LSST, KDUST,…)

25. Absolute Color Calibration: The 5 Step Plan 1. Establish a standard candle - transfer NIST calibration standard to the source input to telescope - transfer NIST calibration standard to the source input to telescope 4. Monitor ACCESS sensitivity - NIST calibrated on-board lamp tracks sensitivity throughout the program - NIST calibrated on-board lamp tracks sensitivity throughout the program 3. Transfer NIST calibrated standard to the Stars - Observe Standard Stars with the calibrated ACCESS payload - Observe Standard Stars with the calibrated ACCESS payload 2. Transfer NIST calibrated standard to the ACCESS payload - calibrate ACCESS payload with NIST certified laboratory irradiance standards - calibrate ACCESS payload with NIST certified laboratory irradiance standards 5. Fit Stellar Atmosphere Models to the flux calibrated observations - confirm performance; refine and extend Standard Star models - confirm performance; refine and extend Standard Star models 25

26. Euclid SN survey ? Basic goal: a significant gain over existing SN surveys  In particular SNLS and DES Euclid has the potential to provide the first NIR survey for SNe from space Provides an independent Euclid probe of cosmology With 6 months of observing time, the most interesting option is the “AAA survey”  Reaches high redshift : up to z ~ 1.5  Cannot be done from the ground Basic goal: a significant gain over existing SN surveys  In particular SNLS and DES Euclid has the potential to provide the first NIR survey for SNe from space Provides an independent Euclid probe of cosmology With 6 months of observing time, the most interesting option is the “AAA survey”  Reaches high redshift : up to z ~ 1.5  Cannot be done from the ground

27. “AAA” survey [Simulations by P. Astier, K. Maguire, S.Spiro] A dedicated Euclid SN survey  6 months total Euclid time  split into two 6-month seasons (observing ~half time) to provide reference images  10 sq deg  4 day cadence  Increased imaging exposure times: y,J,H=1200, 2100, 2100s (no spectra)  Simultaneous ground-based i and z- band Provides 1700 well measured SNeIa with 0.75 < z < 1.5 Complemented with low- and mid-z ground based surveys (not simultaneous) A dedicated Euclid SN survey  6 months total Euclid time  split into two 6-month seasons (observing ~half time) to provide reference images  10 sq deg  4 day cadence  Increased imaging exposure times: y,J,H=1200, 2100, 2100s (no spectra)  Simultaneous ground-based i and z- band Provides 1700 well measured SNeIa with 0.75 < z < 1.5 Complemented with low- and mid-z ground based surveys (not simultaneous) Above: example Euclid lightcurve at z=1.5 and predicted DETF FoM

28. Union2(current) DES LSST in 1 year OPTICAL SN samples

29. JWSTE-ELT Euclid* (schedule permitting) CSP(current) OPTICAL and NIR SN samples

30. ACCESS 30

31. ACCESS Absolute Color Calibration Experiment for Standard Stars M.E. Kaiser & the ACCESS Team Calibration and Standardization of Large Surveys and Missions in Astronomy and Astrophysics 16 April 2012 M.E. Kaiser & the ACCESS Team Calibration and Standardization of Large Surveys and Missions in Astronomy and Astrophysics 16 April 2012 Status, Calibration Strategy, and Design Performance This work supported by NASA grant NNX08AI65G

32. 16 April 2012 Current Standard Star Uncertainties Uncertainty floor (circa 2007) in the fundamental stellar standards is 2%. across the 0.35 - 1.7  m bandpass (Bohlin 2007, Cohen 2007) across the 0.35 - 1.7  m bandpass (Bohlin 2007, Cohen 2007) Judicious selection of standard stars - Observe existing (known) standard stars - Observe existing (known) standard stars - Vega (A0V) - absolute VIS NIR std, bright (V=0.026), - Vega (A0V) - absolute VIS NIR std, bright (V=0.026), pole-on-rotator => variety of thermal zones, complex pole-on-rotator => variety of thermal zones, complex - Sirius (A1V) - IR std, bright (V=-1.47) - Sirius (A1V) - IR std, bright (V=-1.47) - BD +17 o 4708 (sdF8) simpler spectra, SDSS std, fainter +,- - BD +17 o 4708 (sdF8) simpler spectra, SDSS std, fainter +,- - HD 37725 (A3V) - absolute calibrator for IR satellites, - HD 37725 (A3V) - absolute calibrator for IR satellites, possible alternate target: HD84937 (F5V) possible alternate target: HD84937 (F5V) - Minimize spectral features & enable robust modeling - Minimize spectral features & enable robust modeling - Flux level chosen to minimize calibration transfers - Flux level chosen to minimize calibration transfers Major uncertainty contributors: - Earth’s atmosphere - Earth’s atmosphere Sol’n:dedicated monitoring or observe above the atmosphere Sol’n:dedicated monitoring or observe above the atmosphere - Stellar models: describe & extend the data - Stellar models: describe & extend the data Sol’n: Improved stellar models - need data constraints Sol’n: Improved stellar models - need data constraints & test wrt NIST at the 1% level & test wrt NIST at the 1% level A single stellar calibrator spanning the full bandpass introduces less error than when two stellar calibrators are required to span the bandpass. (Lampton 2002, Kim et al., 2004 ) 32

33. Observe above the Earth’s Atmosphere Sounding Rocket observes completely above the Earth’s atmosphere - eliminates problem of measuring residual atmospheric abs’pn seen by balloons - eliminates problem of measuring residual atmospheric abs’pn seen by balloons - OH arises at 70 km; typical balloon altitude: 39 km, rocket altitude: 300 km - OH arises at 70 km; typical balloon altitude: 39 km, rocket altitude: 300 km - OH airglow emission lines are 10-100X stronger than 13th mag star - OH airglow emission lines are 10-100X stronger than 13th mag star - continuous spectral calibration across the 0.35 - 1.7  m bandpass - continuous spectral calibration across the 0.35 - 1.7  m bandpass Balloon: OH introduces additional complexity - increased statistical noise & systematics from bkrnd subtraction - increased statistical noise & systematics from bkrnd subtraction - increased instrument costs to avoid scattered OH airglow - increased instrument costs to avoid scattered OH airglow Rocket disadvantage: Flight times are short (~400 sec) Flight times are short (~400 sec)  Limits faintest standard to ~ 9 th  Limits faintest standard to ~ 9 th magnitude (BD+17 o 4708) magnitude (BD+17 o 4708) with <1% uncertainty with <1% uncertainty Establish repeatability: Two flights per target Two flights per target - Vega & Sirius 12h apart - Vega & Sirius 12h apart - four flights of 2 targets each - four flights of 2 targets each 33

34. ACCESS: Optical Design Spectrograph: Slit: 1mm (33 arcsec/mm ) Grating: Concave, Blaze angle:1.65 o Blaze angle:1.65 o Utilize multiple orders Utilize multiple orders 1 st : 0.9 – 1.9  m 1 st : 0.9 – 1.9  m 2 nd : 0.45 – 0.95  m 2 nd : 0.45 – 0.95  m 3 rd : 0.30 – 0.63  m 3 rd : 0.30 – 0.63  m Cross disperser: Prism spherical figure Prism spherical figure Telescope: F/15.72 Dall-Kirkham Primary figure: ellipse Primary figure: ellipse 393 mm (15.47in) diameter 393 mm (15.47in) diameter Secondary figure: sphere Secondary figure: sphere Coatings: MgF 2 over Al Coatings: MgF 2 over Al 34

35. ACCESS Payload - Spectrograph The End 35