Mapping the Universespectroscopic surveys for BAO measurements

Meeting on fundamental cosmology,

june 2016, Barcelona, Spain

Johan Comparat

1

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