Breaking the Copernican Principle

Transcription

1 Breaking the Copernican Principle Wojtek (prn. Voyteck) Hellwing Institute of Cosmology & Gravitation (ICG), University of Portsmouth, UK #16 KIAS Cosmological Workshop Seoul, Collaborators: Adi Nusser, Maciej Bilicki, Martin Feix

2 Copernican Principles

3 The Copernican Principle We are not a PRIVILIDGED observers of the Unverse. I.e. the global properties we infere about Cosmos are close to the cosmc mean (averaged observer).

4 One of the XXI-st century great challenges: Find and understand the physical mechanism behind observed accelerated expansion Using GR as a building block for LCDM requires extrapolation of 15 orders of magnitude.

5 XXI century precison cosmology: one of the goals is test GR on (intermediate) cosmological scales

6 Why testig GR and looking for a theory beyond is important? Urbain Le Verrier and Vulcan (...)

7

8 RSD power spectrum and the conspiracy of the damping tail

9 RSD power spectrum and the conspiracy of the damping tail f(r) DGP Hawken et al de la Torre+ 2013

10 RSD power spectrum and the conspiracy of the damping tail

11 RSD power spectrum and the conspiracy of the damping tail f(r) DGP Hawken et al de la Torre+ 2013

12 Testing GR pairwise velocities The relative velocity difference of a pair of galaxies. This is not an usual ensamble avergare, but a pair-weighted averaged instead: BBKY

13 Testing GR pairwise velocities u1 v1 v2 L.O.S. Ferrieria, Juszkiewicz (ApJL 515) BBKY u2

14 ModGrav Smoking gun? Illustrative error: 1σ in z ~60-80 km/s (like in 2DFGRS and SDSS) f(r) You have been a good friend! Hellwing et al. (2014,PhRL) ArXiv:

15 Testing GR - velocity correlations 3D velocity correlation tensor (for a statistically isotropic and homogenous velocity field) u1 If we ignore non-symetric parts (i.e. the vorticity) or consider only potential flows, then: Górski, 1988 (ApJL 332)

16 Testing GR - velocity correlations Given only the riadial component of galaxy velocities we can build/estimate the two types velocity correlation Functions. The first and second kind, which are connected To each other. These can be expressed as (after Górski et al. 1989): u1 v1 v2 u2 L.O.S. Górski, 1988 (ApJL 332)

17 Modified gravity velocity correlations! Hellwing et al. in prep.

18 Testing GR - velocity correlations Górski, 1988 (ApJL 332) Hellwing et al. in prep.

19 Modified gravity velocity correlations! Cosmic Flows 2 data (>8000 peculiar velocities within ~200 Mpc) Helene Courtois, Brent Tully et al. Hellwing et al. in prep.

20 Modified gravity velocity correlations! Cosmic Flows 2 data (>8000 peculiar velocities within ~200 Mpc) Helene Courtois, Brent Tully et al Hellwing et al. in prep.

21 Modified gravity velocity correlations! Cosmic Flows 2 data (>8000 peculiar velocities within ~200 Mpc) Helene Courtois, Brent Tully et al Hellwing et al. in prep.

22 LG and cosmic velocities: Breaking the Copernican Principle Milky-Way/LG-like observer is a bised observer. The Copernicus Principle is broken for velocity correlations. Or you need much larger volumes to converge to the cosmic mean. Milky Way like observer conditions: 1. Vrms = 622 +/- 150 (within 3.5 Mpc/h top-hat) 2. M200 = (0.5 2)*1e12 Msol/h 3. δlg = within 3.5 Mpc/h top-hat 4. Mvirgo => 1.2e+15 at D=12+/- 2 Mpc/h Spatial selection functions for introducing some degree of observational situation modelling: CF3-like radial Hellwing et al. in prep.

23 LG and cosmic velocities: Breaking the Copernican Principle! Hellwing et al. in prep.

24 LG and cosmic velocities: Breaking the Copernican Principle! Hellwing et al. (arxiv:1609:07120) Hellwing et al (arxiv: ) Hellwing et al. in prep.

25 LG and cosmic velocities: Breaking the Copernican Principle! Hellwing et al. (arxiv:1609:07120) Hellwing et al (arxiv: ) Hellwing et al. in prep.

26 LG and cosmic velocities: Breaking the Copernican Principle! Hellwing et al. (arxiv:1609:07120) Hellwing et al (arxiv: ) Hellwing et al. in prep.

27 LG and cosmic velocities: Breaking the Copernican Principle! Hellwing et al. (arxiv:1609:07120) Hellwing et al (arxiv: ) Hellwing et al. in prep.

28 Conclusions - GR is a fundamental building block of the modern cosmology - But its validity has been thoughtfully tested only on scales of the Solar System, cosmological tests of GR are crucial - A rich source of the cosmological information is galaxy peculiar velocty field - Galaxy velocities properties can be measured in a mostly model independent way - But the systematics and non-linearities are hard to model - The LG environment is crucial and it affects velocities out to 150 Mpc/h. Ignoring this will appears as HUGE cosmic variance errors in your measurements - We might need a constrained realisation simulations to model and correctly account for the impact of the local sructures

29 Thank Thank You You for for your your patience! patience! Grow Grow aa mo mo and and save save aa bro! bro! Or Or alternatively alternatively support support my my sacrfice sacrfice and and donate: donate:

30 Barions finally don't matter? Hellwing et al (arxiv: ) Hellwing et al. In prep. but not universes!