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Cosmology & Particle Astrophysics, FK7007 Observational Cosmology. Observational Cosmology. Ariel Goobar. Part I: THE EXPANSION. Birth of observational cosmology (1929) Edwin Hubble ’ s discovery: Universe expands!. Hubble law :. Hubble law. Hubble parameter.

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cosmology particle astrophysics fk7007 observational cosmology
Cosmology & Particle Astrophysics, FK7007Observational Cosmology

Observational Cosmology

Ariel Goobar

birth of observational cosmology 1929 edwin hubble s discovery universe expands
Birth of observational cosmology (1929) Edwin Hubble’s discovery: Universe expands!

Hubble law:

Hubble parameter

= time derivative of universal scale factor

pioneering work redshift of nebulae vesto slipher 1875 19692
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…

type ia supernovae as standard candles bright homogeneous objects excellent for distance estimates
Type Ia supernovae as standard candles: bright homogeneous objects, excellent for distance estimates
supernova classification
Supernova classification

Best ”standard candles” we know today

what systems could lead to sneia
What systems could lead to SNeIa?

Single degenerate

Double degenerate

CSM more likely in SD scenario

luminosity distance
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.
cosmological parameters
Cosmological parameters

“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”

sn cosmology tutorial
Cosmology fits



Hubble diagram


SN-cosmology tutorial
two decades of hard work
Perlmutter et al 1994Two decades of hard work!




Goobar & Leibundgut,

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

Guy et al 2010

redshift range
Redshift range

AG & Perlmutter 95

state of the art
State of the art






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

state of the art1
State of the art






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

Mainly from space.

Field of view of Hubble Space Telescope

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


is it really einstein s dark energy eos w p
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

fitting distances from snia with salt
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)

current proposed snia surveys
Current & Proposed SNIa Surveys



LSST (2020?): 8-m/9 sq.deg


DES (2012-2016): 4-m/3 sq.deg

EUCLID (2020?):1.2 m/0.5 sq.deg

Amanullah et al


Fig. from Hook et al

stage iv forecast sn wl bao
Stage IV forecast (SN+WL+BAO)

Amanullah et al

Union 2

w = w0 + (1-a)wa

Fig. adapted by

Joel Johansson

w = w0 + (1-a)wa

Really, really hard!