A la découverte de Laniakea

Transcription

1 SRO12 - MSE velocity survey (MSEv) Dynamics of the dark and luminous cosmic-web during the last three billions years A la découverte de Laniakea Hélène Courtois on behalf of M. Colless (RSAA-ANU, Canberra), J. Comparat (Madrid), M. Fernandez-Lorenzo (IAA, Granada), M. Hudson (Waterloo), A. Johnson (CAS Swinburne), N. Kaiser (IfA Hawaii), 0/15 J. Koda (INAF, Obs. Merate), A. Nusser (Technion, Haifa), C. Schimd (LAM, Marseille)

2 a galaxy redshi< and a peculiar velocity survey covering up to 24,000 square degrees, i.e. 3/4 of the full sky apart from Milky Way. Redshi< for about 2 million galaxies and for a subset radial peculiar velocity early- and late- type galaxies up to redshi< z<0.25 using the Fundamental Plane and oppcal Luminosity- Linewidth techniques. 1 Gpc is significantly deeper than surveys that will be completed in 2025: the oppcal mulp- fiber TAIPAN and the radio SKA Pathfinder WALLABY survey. 1

3 ASKAP-TAIPAN MSEv CF3 CF2 CF1

4 This field of research is currently undergoing a revival, and this survey will achieve the same galaxy number density as in the contemporary pioneering proof- of- concept surveys as Cosmicflows- 2 and 6DF catalogs, while mulpplying the covered universe volume by a factor 150. Only these scales enable strong test of gravitapon models. 3

5 Linear Growth Rate at z=0.05 to z=0.25 for 10,000 deg 2 n = 0.03 h 3 Mpc -3 n = h 3 Mpc -3 Thick and thin (red) error bars account for density-only (RSD) and joint density-velocity MSE constraints, using the same number of galaxies. Dashed (solid) lines correspond to f Ω m γ with γ = 0.5, (0.55), 0.6, 0.65, 0.7 downward. 4

6 Three major science goals define MSEv: (i) linear- growth rate of cosmic structures at low redshi<, obtained thru velocity- velocity comparison and the luminosity fluctuapon method will be free of cosmic variance. This allows one to discriminate between modified theories of gravity at 1% level and provide a significant complement to the high- redshi< constraints provided by the spectroscopic surveys achieved e.g. by PFS- SuMIRe, MD- DESI, Euclid, and WFIRST; 5

7 10,000 deg 2 Relative error on the amplitude of matter fluctuations σ 8 (top) and on the rescaled linear-growth-rate β= f/b (bottom). Density-only (RSD; red dashed) and joint density-velocity power spectra (solid blue) 24,000 deg 2 n = h 3 Mpc -3 6

8 (ii) galaxy formation will be investigated in regard to unprecedented velocity-cosmic-web s 6D phase-space; Cosmic- web components (voids, filaments, sheets, and knots in white, light gray, dark gray, and black, respecpvely) reconstructed from the velocity shear tensor (V- web, le#) and the density field (right), which allows for 10 Pmes lower resolupon scale (adapted from Hoffman et al. 2012, based on N- body simulapon study) 7

9 Three major science goals define MSEv: (conpnued) (iii) dynamical tests probing the scale of homogeneity, and test for the backreacpon conjecture in General RelaPvity, potenpally providing terms dynamically equivalent to both dark maher and dark energy. Averaged dynamics of a domain D (Buchert eqs): 8

10 MSE 1 hour exposure, mid-resolution for effective 11.4 m primary mirror. Keck TF distance, long slits DEIMOS spectrograph 1 hour, resolution=4000.

11 MSEv Number of galaxies from a Schechter function, no K-correction applied. For an SDSS type survey and for MSEv survey. MANGA z=0.03 4,000 deg 2 Source density: - Best option: mean number density of peculiar velocities n=0.03h 3 Mpc -3 allowing an improvement by a factor 3 on cosmological parameters. - Minimal viable option: mean number density of peculiar velocities n=0.003h 3 Mpc -3, with even distribution across sky, covering 10,000 deg 2 Total number of science targets required to be observed to enable science goal: Best option: about 2.5M L*galaxies over 24,000 deg 2 with i < 24.1

12 The best oppon (24,000 deg2 ) will give 96 galaxies/deg2, or 144 galaxies/mse- FoV. This corresponds to 144X19 =2736 (or 144 X37 = 5328 ) fibres per MSE FoV, or 43 millions (or 85 millions) spectra over the full coverage. 16,000 poinpngs are necessary to cover the 24,000deg 2. Peculiar Velocity for spirals : 10 min (S/N=20 in 1hr) while for ellippcals : 1 hour (S/N=2 in NaD). Redshi<s only can be measured in 15 minutes exposure Pme. Total survey Pme: 12,000 X 15 minutes + 4,000 X1 hour = 7000 hours = 875 nights = 4 years of dark and grey Pme. L* galaxy is 8 arcsec large at z=0.25 Hexagonal 19-fibre bundles (minimal requirement) or 37-fibre bundles (optimal requirement) with single fibres of diameter less than 1.2 (0.9 optimal). 11

13 Accurate number of targets and observaponal strategy: The survey is bimodal with short exposure Pmes and low signal to noise required for redshi< measurements,and long exposures of typically 1 hour for peculiar velocity line- width measurements. Short exposures can be accommodated by single fiber spectroscopy. Line- width 3D spectroscopy require mini- IFU setups. The observaponal strategy needs to be think through in more depth and also devised in regard to the other proposed SRO s, with possible "piggy- back" strategy. First light or second light survey: (1) main goal = pec vel survey with fiber bundles + redshi< survey from single fibers, (2) if not possible for the first light, let use first- light facilipes to measure redshi<s, idenpfy sources to be followed- up with fiber bundles during second- light, (3) if first- light capabilipes include too few mini- IFU, use them as benchmark as validapon of method. 12

14 Defining dark and luminous matter distribution velocity and overdensity fields. 13/15

15 slits pencil beam all sky 14

16 To be conpnued.