ESSENCE: Determining the Nature of Dark Energy with High-z Supernovae

Transcription

1 ESSENCE: Determining the Nature of Dark Energy with High-z Supernovae Ryan Foley UC Berkeley ESSENCE Team

2 Equation of State: SupErNovae trace Cosmic Expansion C. Aguilera (NOAO/CTIO) B. Barris (IfA/UH) A. C. Becker (UW) S. Blondin (ESO) P. Challis (CfA) R. Chornock (UCB) A. Clocchiatti (PUC) R. Covarrubias (UW) T. M. Davis (ANU) A. V. Filippenko (UCB) A. Garg (CfA/Harvard) P. Garnavich (NDU) M. Hicken (CfA/Harvard) S. Jha (UCB) R. P. Kirshner (CfA/Harvard) K. Krisciunas (NDU) B. Leibundgut (ESO) W. Li (UCB) T. Matheson (NOAO) A. Miceli (UW) G. Miknaitis (UW) G. Pignata (PUC) J. L. Prieto (OSU) A. Rest (NOAO/CTIO) A. G. Riess (STScI) M. E. Salvo (ANU) B. P. Schmidt (ANU) R. C. Smith (NOAO/CTIO) J. Sollerman (DARK, NBI, KU) J. Spyromilio (ESO) C. Stubbs (CfA/Harvard) N. B. Suntzeff (NOAO/CTIO) J. L. Tonry (IfA/UH) W. M. Wood-Vasey (CfA/Harvard) A. Zenteno (NOAO/CTIO)

3 Type Ia SNe: One Parameter Family σ ~ 0.13 mag Color Rate of decline Peak brightness δd/d ~ 0.06 (Supernova Cosmology Project, Kim et al)

4 Type Ia SNe are precise standard(izable) candles s~0.11mag Prieto et. al. (2005) Krisciunas et. al. (2003)

5 The Accelerating Universe! Riess et. al. 1998

6 Higher-z SN team: 8 new z>1.0 Riess et al, ApJ, 2004

7 Where we are now ~200 SNe Ia published Most people believe the Universe is accelerating Many current surveys (CFHT-LS, SDSS, etc) Gearing up for the next phase (DES, JDEM, etc) Schmidt Time to measure w!

8 Equation of State Dependence For a flat Universe, luminosity distance depends only upon z, Ω Λ, w. 71 difference in distance modulus w=-1.1 w=-0.9 empty! m =0.3! m =1 Text ~0.04 mag! Difference in apparent SN brightness vs. consensus model redshift

9 ESSENCE Survey 5 year project on 4m telescope at CTIO in Chile Started in 2002/3. 30 half-nights Wide field images in RI bands, 32 fields, every 4 nights, 11 -deg Same-night detection of SNe Spectroscopy Magellan, Keck, Gemini telescopes Goal is ~200 SNe, 0.2<z<0.7 Distances to 2% in Δz=0.1 bins CTIO 4m

10 Image Subtraction (High-z Supernova Team) 10

11 Hardware for real-time reductions Dual networks 1 Gb/sec compute link 100 Mb/s admin link 10 compute nodes 2 x 1.2 GHz CPUs 1 GB RAM each 300 GB local IDE disk 1 TB SCSI RAID disk array 2 TB IDE RAID disk array

12 Astrometry, magnitudes, and finding charts are published to the web.

13 Discoveries are announced immediately on our web site.

14 Monte-Carlo Simulation: 200-SN Hubble Diagram ESSENCE team, Monte Carlo, Garnavich et.al., in prep.

15 Current Metrology Chain for Ground-based Astronomical Flux Measurements. Black Body Calibrator Celestial Calibrator, Vega Celestial Sources Supernova measurements require knowing relative instrumental sensitivity vs. λ

16 Vega is primary celestial calibrator 5000 A 1 µm 2% 4%

17 An alternative calibration approach Calibrate relative system response primary corrector optics filter detector relative to Si photodiode. Measure transfer function of atmosphere with dedicated spectrograph

18 Jan 2005 test run Used tunable laser/fiber optic source Blanco 4m telescope MOSAIC II imager November calibrations delayed to December

19 Tunable laser (400 nm - 2 microns) Second harmonic (532 nm) generator Mixer (to 355 nm) micron NdYAG pulsed pump laser Tunable downconverter

20 Goal is relative l response for each pixel

21 950 nm

22 960 nm

23 970 nm

24 980 nm

25 990 nm

26 1000 nm

27 1010 nm

28 1020 nm

29 10 nm Scan through wavelength as seen by one pixel

30 I zeropoint offset (mags) R zeropoint offset (mags) Miknaitus 2005 Pignata et al igure 4.2: Effect of systematic error in photometric calibration on measurement of. Contours represent change in measured w. A small zeropoint offset creates a large difference in w. ESSENCE has calibrated its fields to have ~2% instrumental photometry (and there is still further improvement) Sources of systematic error can be roughly divided into two types: those which mpact the photometric measurements of survey data (addressed in the following sec-

31 K-Corrections Systematic flux µ w Bandpass 0.3% 0.3%?? Spectal DB 1.5% 0.01%?? K-correction variation tends to come from phase coverage of spectra and so is less of an effect for overall LC

32 Jha, Riess, & Kirshner 2005 Fig. 17. Effect of a local void on constraints of the dark energy equation of state, using a simulated sample of 200 SN Ia with 0.3 z 0.8 as expected from the ESSENCE survey (Miknaitis et al. 2005). We perform a cosmological fit using the same simulated high-redshift sample plus three nearby samples: (1) the full MLCS2k2 Hubble flow sample with 95 SN Ia, (2) the nearby Hubble flow objects with H We need to understand the local Universe too! 0 d SN < 7000 km s 1 (48 SN Ia) and (3) the distant Hubble flow objects with H 0 d SN > 8000 km s 1 (40 SN Ia). The figure shows 68.3% (1-σ) confidence regions (shaded), and the mean values of Ω M and w (crosses). The input cosmology for the simulated objects is Ω M = 0.3, Ω Λ = 0.7 (w = 1), with the distance scale set by the full If Hubble the flow Hubble sample. In the bubble cosmological is fit, real, we assumewe a flat Universe will and need a priorto on Ω M properly = 0.30±0.04. The different low-redshift samples have a strong effect on the estimation of w, with w = 0.99 ± 0.12 for characterize it before we attack w. the full Hubble flow sample, w = 1.19 ± 0.17 for the nearby Hubble flow sample and w = 0.80 ± 0.11 for the distant Hubble flow sample.

33 Contamination Matheson et al. 2005

34 Evolution Matheson et al. 2005

35 Recent Status

36 ESSENCE Attention to Systematics photometric calibrations on 0.9m flux propagation error propagation filter functions new calibration technique Sirius re-calibration Landolt spectrophotometry atlas artificial SNe

37 Anticipated Cosmology Limits Real +2dF Results early 2006 Tonry & Miknaitis

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