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Cosmology & Particle Astrophysics, FK7007 Observational Cosmology

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Observational Cosmology

Ariel Goobar

Hubble law:

Hubble parameter

= time derivative of universal scale factor

1917: evidence for expansion existed already in this data, but there was no theoretical prediction suggesting that at the time…

Credits: Saurabh Jha

Best ”standard candles” we know today

Fig. Dan Kasen

Single degenerate

Double degenerate

CSM more likely in SD scenario

- 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.

“dark energy”

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

Cosmology fits

Search

Lightcurve

Hubble diagram

Reference

Perlmutter et al 1994

SN1992bi

z=0.458

z=0.998

Goobar & Leibundgut,

Annual Review of Nuclear and Particle Science 61 (2011) 251-279

Guy et al 2010

1995

AG & Perlmutter 95

AG & Perlmutter 95

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

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

(nm)

(nm)

Mainly from space.

Field of view of Hubble Space Telescope

~100x smaller than available for optical ground based surveys.

(nm)

- 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

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)

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

Amanullah et al

Union 2

w = w0 + (1-a)wa

Fig. adapted by

Joel Johansson

Easy!

Harder!

w = w0 + (1-a)wa

Really, really hard!

37