Constraining Dark Energy with BOSS. Nicolas Busca - APC Rencontres de Moriond 19/10/2010

Transcription

1 Constraining Dark Energy with BOSS Nicolas Busca - APC Rencontres de Moriond 19/10/2010

2 Outline BOSS: What? How? Current Status of BOSS Constraints on Cosmology Conclusions

3 What: Baryon Acoustic Oscilations distribution of photons (WMAP) distribution of matter (SDSS) BAO physics SDSS data Einsenstein et al (2005) BAO peak C(r) (a.u.) BAO peak z~ z~ Distance (Mpc/h)

4 What: Distances in Cosmology radial comoving coordinate: r(z) =c luminosity distance (SNe): angular diameter distance: da θ Lruler z 0 dz H(z ) d L = (1 + z)r(z) =c(1 + z) d A = L ruler θ longitudinal width: z Lruler z 0 dz H(z ) = r(z) 1+z = c z 1+z 0 dz = (1 + z)h(z)l ruler dz H(z )

5 What: Distances in Cosmology radial comoving coordinate: r(z) =c luminosity distance (SNe): angular diameter distance: da θ Lruler z 0 dz H(z ) d L = (1 + z)r(z) =c(1 + z) d A = L ruler θ longitudinal width: z Lruler z 0 BAOs = r(z) 1+z = c 1+z dz H(z ) z dz = (1 + z)h(z)l ruler 0 dz H(z )

6 How: BOSS Main dark time SDSS III project between Goal: to determine the position of the BAO peak with a precision of 1% at z~0.6 and 1.5% at z~2.3 Implication: best constraints on the e.o.s. of dark energy until the next generation of experiments SDSS - 2.4m telescope Spectroscopic survey with target selection based on SDSS-II photometry 1/4 of the sky (10,000 deg 2 ) two complementary methods: LRG (guaranteed) : z~0.6 Lyα (novel technique) : z~2.3

7 How: BOSS Main dark time SDSS III project between Goal: to determine the position of the BAO peak with a precision of 1% at z~0.6 and 1.5% at z~2.3 Implication: best constraints on the e.o.s. of dark energy until the next generation of experiments Spectroscopic survey with target selection based on SDSS-II photometry 1/4 of the sky (10,000 deg 2 ) two complementary methods: LRG (guaranteed) : z~0.6 Lyα (novel technique) : z~2.3

8 How: BOSS-LRG use galaxies (LRGs) as tracers of matter compute their correlation function C(r) or P(k), measure the position of the acoustic peak guaranteed (peak already observed in SDSS-II data)

9 How: BOSS-LRG C( r) = ρ( r 0 )ρ( r 0 + r) dn pairs d r estimated from the number of pairs of galaxies compare to random data sets (without BAOs) to remove FoV biases use galaxies (LRGs) as tracers of matter compute their correlation function C(r) or P(k), measure the position of the acoustic peak guaranteed (peak already observed in SDSS-II data)

10 How: BOSS-LRG vs SDSS-II 2x volume 5x density 10x statistics 1,600,000 LRGs SDSS main sample SDSS I+II BOSS (SDSS III)

11 How: BOSS-LRG vs SDSS-II SDSS-II data Einsenstein et al (2005) C(r) (a.u.) z~0.3 BAO peak 2x volume 5x densité 10x statistics 1,600,000 LRGs Distance (Mpc/h) SDSS main sample SDSS I+II BOSS (SDSS III)

12 How: BOSS-Lyα z=3 z=2 Distribution of matter sampled by lines of sight of QSO

13 How: BOSS-Lyα { z=3 z=2 15 Distribution of matter sampled by lines of sight of QSO 160,000 QSO expected Flux (a.u.) H H Lyα forest : neutral H absorption ! (nm)

14 How: BOSS-Lyα z=3 C( r) = ρ( r 0 )ρ( r 0 + r) <F(θ, λ)f (θ,λ ) > Estimated from correlations in the transmitted flux In principle little or no bias in the peak position, to be further studied in simulations z=2 15 { Distribution of matter sampled by lines of sight of QSO Flux (a.u.) H H Lyα forest : neutral H absorption ! (nm)

15 How: BOSS-data taking photometry from SDSS-II "./tmp" u g r i z target selection List of targets Flux (a.u.) Wavelength (A o ) SDSS J SDSSp J SDSSp J SDSSp J SDSSp J plate spectrograph optical fibers

16 Flux (a.u.) How: BOSS-data taking photometry from SDSS-II "./tmp" u g r i z Wavelength (A o ) target selection plate List of targets SDSS J SDSSp J SDSSp J SDSSp J SDSSp J spectrograph 1000 fibers/plate optical fibers 150 dedicated to QSO 850 dedicated to LRG

17 How: BOSS-data taking photometry from SDSS-II "./tmp" u g r i z target selection List of targets Flux (a.u.) Wavelength (A o ) SDSS J SDSSp J SDSSp J SDSSp J SDSSp J plate plate goes to focal plane 80min/plate 10min to change the plate spectrograph optical fibers

18 Current Status commissioning phase 3% of the final survey all Lyα commissioning data is being manually scanned Scan the data three times a day. If you don t know why the data will tell you. (P. Billoir)

19 zansatz = 1.90 Lyα SiIV CIV CIII MgII

20 zansatz = 2.10 Lyα SiIV CIV CIII MgII

21 zansatz = 2.00 SiIV CIV CIII MgII

22 zansatz = 2.05 Lyα SiIV CIV CIII MgII

23 Again...

24 And then, again...

25 All Lyα commissioning spectra manually scanned Database of 13,000 spectra of which ~4,000 are QSO Monitoring improve the pipeline calibration target selection automatic spectral characterization automatic determination of z

26 Constraints on Cosmology BOSS in the Hubble diagram d eff L (z) = (1 + z)2 d A (z)

27 Constraints on Cosmology BOSS in the Hubble diagram d eff L (z) = (1 + z)2 d A (z) Lyα LRG SN from Union compilation expected from BOSS who da BOSS?

28 Constraints on Cosmology BOSS + Planck

29 Constraints on Cosmology BOSS + Planck O(5%) uncertainties on w0

30 BOSS Lyα challenges 3 #1: quasar surface density BAO Peak Resolution (%) adapted from MacDonald et al (2005) QSO surface density (deg -2 )

31 BOSS Lyα challenges 3 #1: quasar surface density BAO Peak Resolution (%) estimate from commissioning ideal adapted from MacDonald et al (2005) QSO surface density (deg -2 )

32 BOSS Lyα challenges #2: fit of the continuum simulated QSO spetcrum continuum

33 BOSS Lyα challenges #2: fit of the continuum simulated QSO spetcrum continuum full spectrum impact of the continuum fit on the peak resolution needs to be estimated

34 Conclusions BOSS is taking data since last september in a stable way BOSS will make a precision ( 1%) measurement of the position of the BAO peak at z 0.6 (guaranteed) and z 2.5 (novel technique) This implies measurements of da(z) and H(z) at these z, and O(5%) measurements of w First scientific results in a year