marek kowalski 11.5.2009 ptf, szczecin exploding stars, cosmic acceleration and dark energy...

Marek Kowalski11.5.2009 PTF, Szczecin

Exploding Stars, Cosmic Acceleration and Dark Energy

Supernova 1994D

Marek KowalskiHumboldt-Universität zu BerlinSzczecin, 11.5.2009


Outline

A brief history of Cosmology

Supernova observations today

A mysteries: Dark Energy

3


HistoryEinstein, 1916:General Relativity


History

−8πGTμν = Rμν − 12 gμνR

Energy Curvature

Einstein, 1916:General Relativity


General Relativity:Gravitational bending of light


General Relativity:Gravitational bending of light

Abell 2218: A Galaxy Cluster Lens, Andrew Fruchter et al. (HST)


General Relativity:The Universe can have curvature



−8πGTμν = Rμν − 12 gμνR + gμνΛ

Curvature

I want a static Universe - I’ll add a cosmological constant

Energy



History continues...



Edwin Hubble, 1929: Redshift of Galaxies


Redshift of spectral lines:

“Doppler effect”

z =λobs −λemit

λemit

v ≈z⋅(speed of light)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

The larger the distance to a Galaxy, the faster it is flying away from us:

velocity = H0 x distance


Hubble:The Universe is expanding!

Einstein:The cosmological constant was the biggest Blunder of my life!



Edwin Hubble, 1929: Redshift of Galaxies


10 years ago: Detection of the accelerated

Universe by two teams of astronomers




The cosmological constant might be back!

B. Schmidt S. Perlmutter


Outline

A brief history of Cosmology


A mysteries: Dark Energy

3




1

Supernova Type Ia

•Type Ia supernovae (SNe Ia) provide bright “standard candle” that can be used to construct a Hubble diagram.

• Accretion sends mass of white dwarf star to Chandrasekhar limit leading to gravitational collapse and a thermo-nuclear explosion of its outer layers.

• Each one is a strikingly similar explosion event with nearly the same peak intensity.


“Standard” Candles

• Nearby supernovae used to study SNe light curve (z<0.1)• Brightness not quite standard

Stretching the timescale:

€

t'= s× t

M '= M+α (s−1)

Correcting the Brightness:

Intrinsically brighter SNe have wider

lightcurves.


Spectra used for Identification & Redshift determination


Searching for Supernovae



Reference new picture difference

SN-Candidate





For example with the: • Canadian-French-Hawaii Telescope: 3.6 m

• MegaCam Camera: 3.6 108 pixels

Marek Kowalski11.5.2009 PTF, SzczecinSloan Digital Sky Survey


SNe at large Redshifts (z>1)



Observations from Space with the Hubble Space Telescopes:

15


SNe Type Ia & Acceleration of the Universe

Normalization

fainter then expected

M

1 00.73 0.270 1

slightly brighter M

fain

ter

Supernova Cosmology Project Kowalski et al., Ap.J. (2008)

Marek Kowalski11.5.2009 PTF, Szczecin18

Perlmutter et al., 1999

Cosmological Parameter

M

SNe + BAO + CMB

Curvature:

CMB: Komatsu et al. 2008BAO: Eisenstein et al., 2005

m = 0.274 ± 0.016(stat) ± 0.013(sys)

Ωk= 1-Ωm -ΩΛ

Ωk = −0.009 ± 0.010(stat) ± 0.003(sys)

M

Kowalski et al., 2008

Marek Kowalski7. Juli 2008

DarkEnergy:65%

DarkMatter:30%

70%

70%

25%

25%


Outline

Introduction to Supernova Cosmology


A mystery: Dark Energy

3


Is Dark Energy a property of the Vacuum?

Ground-state of a scalar

Quantum-field:

E0 =

12

hω ii∑

ρvac =

1

2

h

(2π )3kd 3k =

hkmax4

16π 20

kmax

∫

Vacuum-Energy density:

(with ultraviolet Cut-off kmax)

Casimir-Effekt Energiedifferenz


Vakuum energy:Before: E = 0After: Axρ>0

Pressure (p) of Vacuum energy follows with assumption of energy conservation:Axρ+Axp = 0 p = - ρ

ρ

x

A

Is Dark Energy a property of the Vacuum?

Vacuum energy has all the properties of the Cosmological constant , it has negative pressure and hence can lead to acceleration of Universe.


Fundamental Problems of Vakuum Energy/Cosmological Constante:

Why so small?

Expectation: ρ planck)4

120 orders of magntides to larger then the observed value!

Why now?

Matter: ρ R-3

Vakuum Energy: ρ konstant

New Physics:

• Quintessence fields• Extra dimensions• Modification of Gravity• …More data will hopefully tell us!


Future projectsin SN Cosmology

Projekt z-Range # SNe

Pan-STARRS 0.1-0.5 ~104

LSST (2015) 0.1-0.9 ~106

SNAP (2017) 0.2-3.0 >3000

(JDEM/Euclid)SNAP


Conclusion

• 3/4 of the energy budget of the Universe consists of Dark Energy

• It looks like a cosmological constant / vacuum energy - but this interpretation has problems

• Next generation telescopes will produce unprecedented cosmological observations, and perhaps provide an answer


Back Up


Beobachtete Energiedichten

ρ ~ kmax4

ρPl ~ (M Planck )4 ~ (1018 GeV)4 ~ 10113GeV/cm3

ρobs ~ (10−12 GeV)4 ~ 10−7 GeV/cm3

Erwartete Energiedichten:

Gravitation:

ρSUSY ~ (MSUSY )4 ~ (103GeV)4 ~ 1053GeV/cm3

SUSY:

ρEW ~ (MEW )4 ~ (246 GeV)4 ~ 1051GeV/cm3

Electroweak:

Fundamentale Probleme mit derVakuum-Energie/Kosmologischen Konstante:


Zustandsgleichung: w =p/ρ

19


Zustandsgleichung: w =p/ρ

w =−0.97 ±0.06(stat) ±0.06(sys) SNe + BAO + CMB

19

cosmological constant


heterogener Datensatz


Study of - mean deviation- residual slope

A heterogenous data sample


Test for Tension

high-zlow

-z

mean deviation: OK


Test for Tension

high-zlow

-z

residual slope: (OK)

marek kowalski 11.5.2009 ptf, szczecin exploding stars, cosmic acceleration and dark energy...

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