Mapping the Universespectroscopic surveys for BAO measurements
Meeting on fundamental cosmology,
june 2016, Barcelona, Spain
Johan Comparat
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Baryonic acoustic oscillations• The acoustic length scale is the comoving
distance sound waves travelled from Big Bang until recombination
• 𝑟𝑠 = 𝑧=1100∞
𝑑𝑧𝑐𝑠(𝑧)
𝐻(𝑧)= 144 𝑀𝑝𝑐
= 0.59672 ∓ 0.00038 degrees on the CMB at a precision of 0.1% with Planck !• Imprint measureable on the 2-pt correlation
function / power spectrum of the complete matter field 𝛿𝑚.
• We measure the 2PCF of galaxies 𝛿𝑜𝑏𝑠 = 𝑏(1 + 𝛽𝜇2)𝛿𝑚.
• Eisenstein & Hu (1998), Planck collaboration (2015)
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Baryonic acoustic oscillations• This measurement of the BAO scale
is nearly free of systematics <0.3% (see Padmanabhan et al. 2012, Ross et al. 2012, Angulo et al. 2014, Prada et al. 2014)
• Future cosmology experiments aim measuring the BAO feature in galaxy clustering for redshift z<4 down to the 0.3% level.
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SDSS-III/BOSS observations
Alam et al. 2015 ApJ. 1501.009631 year : photometry, 4 years : spectroscopy4
At higher z
SDSS-III/BOSS results
With galaxies; V=7 Gpc3/h3
Delubac et al. (2014). 1404.1801; Gil-Marin et al. (2015). 1509.06386, Aubourg et al. (2014)
With Ly-alpha quasars; V=50 Gpc3/h3
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SEE TALKS THIS AFTERNOON BY
Hector Gil-Marín
Andreu Font-Ribera
Next stepscharting the unknownWhere to explore now ?
With what spectrograph?
Dawson et al. 2015
Low redshift : TAIPAN (Australia) and LoRCA (Spain) 1mHigher redshift :<2020 : eBOSS 2.5m>2020 : DESI (US) and 4MOST (Chile) 4m
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SDSS-IV eBOSS, a pathfinderMapping accurately the redshift range 0.6 < z < 3.5
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Aims of the eBOSS survey
Dawson et al. 2015 8
RSD4%
BAO2%
BAO measurement process
Selection function
• n(z, RA,DEC) vs. photometry quality, stellar density, galactic dust …
• galaxy population and its evolution
• redshift measurement
• completeness
simulations
• High resolution mock catalog, HOD, SHAM, SAMS
• Approximate method to produce covariance mocks
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LRG : extension of BOSS knowledge.ELG & QSO : new challenges !
Target selection, QSO & Ly alpha QSO
• Using SDSS + WISE with XDQSOzto select (0.9<z<2.2) quasars, 70 per sq. deg.
• Mag limit: g<22 or r<22
• Median redshift 1.5
• Redshift efficiency 70%
• Area 7500 sq. deg
• +PTF variability, eBOSS adds 6.6 new Ly alpha QSO per sq. deg.
Myers et al. 2015 1508.04472, Palanque-Delabrouille et al. 2015 10
First results this
summer with 2yr data
Target selection test for ELGs
• DV at 2% needs :• Area 1000 - 1500 deg2• Density 135 / deg2 in 0.7<z<1.1• Bias = 1.4• strong emission lines to identify
quickly and accurately redshifts
• Test :• Use DECaLS g,r,z optical bands
(legacysurvey.org)• select g<22.8 and
Comparat et al. 2015, 1509.0640011
A tracer to cover the transition between DM and DE around redshift 0.8
Target selection, test results
• Bias around 1.7 (>1.4)
• Median redshift 0.86, 76% have a reliable redshift in 0.7<z<1.1
• Density 180 /deg2 * eff > 150
• DECaLS Photometry available on an area 1000 - 1500 deg2
• Observations start in September 2016 !
Comparat et al. 2015, 1509.0640012
Observations start in
September for 2 yr
ELG redshift completeness
Comparat et al. 2016Comparat et al. 2015, 1509.06400
• Redshift accuracy depends on the strength of the emission lines
• Redshift window : completeness vs. redshift
• End-2-end sims needed !
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E2E: Emission line Luminosity Function
Comparat et al. 2016, 1605.02875
• ELGs are sampling the emission line LF and the mass function in an incomplete manner
• We have measured anew the [OII], Hbeta, [OIII] LFs to contruct completeness models
• Nbody + GALFORM (Gonzalez-Perez + 2014) reproduces the luminosity functions and observed mag & color distributions
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E2E: ELG stellar population
Comparat, Maraston et al. In prep.
• Create a library of truthful ELG templates for the E2E simulation.
• Measure the stellar population (mass, metallicity, sfr) on stacks of ELG spectra following the LF with Firefly (Wilkinson, Maraston et al. 2015)
• Add spectra to the simulation
• Inform the completeness function and high fidelity mocks
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In preparation
BAO measurement process
Selection function
• n(z, RA,DEC) vs. photometry quality, stellar density, galactic dust …
• the galaxy population in terms of galaxy evolution
• Redshift measurement
• a completeness criterion
simulations
• High resolution mock catalog, HOD, SHAM, SAMS
• Approximate method to produce covariance mocks
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LRG : extension of BOSS knowledge.ELG & QSO : new challenges !
Mocks and simulations for ELGs
Favole, Comparat et al. 2015
Use photometry from CFHT-LS and LenS + spectroscopy from SDSS-III, VIPERS and DEEP2 data.
Combine monopole and angular clustering with the g–g lensing
Compare to high resolution N body lightcones from MultiDark, we find a good model.
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Favole, Comparat et al. 2015
Halos & ELGs
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Timeline for the results and data release• First clustering results expected
this summer using LRG, QSO and Ly alpha QSO
• along a data release of 1/3 of eBOSS.
• ELG obs start in September !
Zhao et al. 2015 19
Outlook. Emission line galaxies and quasars, pixels for the most precise far-universe map with DESI, 4MOST, EUCLID
• 2 multi fiber spectrographs are being built :• At Kitt Peak (USA), DESI (desi.lbl.gov)
• At Paranal (chile), 4MOST (4most.eu)
• In total by 2024, we will have an exhaustive map of 40 000 000 galaxies and quasars covering 0.6 < z < 3.5
• EUCLID satellite to cover H alpha ELG in the infrared to redshift 2
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¿ Questions ?
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Zhu, Comparat et al. 2015. 1507.07979
Thank you for your attention