Cosmology & Particle Astrophysics, FK7007 Observational Cosmology

1. Cosmology & Particle Astrophysics, FK7007Observational Cosmology Observational Cosmology Ariel Goobar

2. Part I: THE EXPANSION

3. Birth of observational cosmology (1929) Edwin Hubble’s discovery: Universe expands! Hubble law:

4. Hubble law

5. Hubble parameter = time derivative of universal scale factor

6. Pioneering work: redshift of nebulae VestoSlipher (1875- 1969)

7. Pioneering work: redshift of nebulae VestoSlipher (1875- 1969)

8. Pioneering work: redshift of nebulae VestoSlipher (1875- 1969) 1917: evidence for expansion existed already in this data, but there was no theoretical prediction suggesting that at the time…

9. Estimates of H0 from Type Ia Supernovae: accuratedistances! Credits: Saurabh Jha

10. Type Ia supernovae as standard candles: bright homogeneous objects, excellent for distance estimates

11. Supernova classification Best ”standard candles” we know today

12. Fig. Dan Kasen

13. What systems could lead to SNeIa? Single degenerate Double degenerate CSM more likely in SD scenario

14. Nearly a standard candle

15. Luminosity Distance • where F(x) = sin(x) for a closed universe, sinh(x) for an open universe and x for a flat universe. In the latter case the ΩKterms are set to 1.

16. Cosmological parameters “dark energy”

17. The Nobel Prize in Physics 2011 Saul Perlmutter, The Supernova Cosmology Project Brian P. Schmidt and Adam G. Riess, The High-z Supernova Search Team "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae”

18. 1998: Cosmological constant not zero! 18

19. SCP & HZT – December 2011

20. Cosmology fits Search Lightcurve Hubble diagram Reference SN-cosmology tutorial

21. Perlmutter et al 1994 Two decades of hard work! SN1992bi z=0.458 z=0.998 Goobar & Leibundgut, Annual Review of Nuclear and Particle Science 61 (2011) 251-279 Guy et al 2010

22. 1995

23. Redshift range AG & Perlmutter 95

24. Wide lever arm in redshift is key! AG & Perlmutter 95

25. State of the art 14 9 6 5 4 Gyrs since Big Bang Rodney et al 2012 Rubin et al 2013 (SCP) Suzuki et al 2012 (SCP) Union2.1 data-set + 2 = 582 SNe

26. State of the art 14 9 6 5 4 Gyrs since Big Bang Hubble Space Telescope Rodney et al 2012 Rubin et al 2013 (SCP) Suzuki et al 2012 (SCP) Union2.1 data-set + 2 = 582 SNe

27. (nm)

28. (nm)

29. Mainly from space. Field of view of Hubble Space Telescope ~100x smaller than available for optical ground based surveys. (nm)

30. Is it really Einstein’s Λ?Dark Energy EoS, w=p/ρ • Λ-hypothesis (w=-1) unchallenged by observations • Theoretical understanding still lacking • Expected vacuum energy density, ρvac, has w=-1,but >1056 times off! Amanullah et al 2010

31. Fitting distances from SNIa with SALT β~2.5 (Amanullah et al. 2010): very unusual reddening coefficient Brightness (rest-frame Bmax) and color (c~E(B-V)) at maximum Measured variables Fitted parameters Fitted peak brightness can be color and light-curve shape corrected to form a standard candle that can be used for measuring relative cosmological distances. Shape (x1) Normalised flux Days since maximum (rest-frame)

32. Current & Proposed SNIa Surveys Optical Near-IR LSST (2020?): 8-m/9 sq.deg 250000/yr DES (2012-2016): 4-m/3 sq.deg EUCLID (2020?):1.2 m/0.5 sq.deg Amanullah et al 2010 Fig. from Hook et al

33. Stage IV forecast (SN+WL+BAO) Amanullah et al Union 2 w = w0 + (1-a)wa Fig. adapted by Joel Johansson

35. Easy!

36. Harder!

37. w = w0 + (1-a)wa Really, really hard! 37