5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic...

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5 Dark matter and dark energy, the Universe revealed

Transcript of 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic...

Page 1: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

5 Dark matter and dark energy,

the Universe revealed

Page 2: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Our place

Courtesy: NASA

Page 3: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

How much matter?

• Add up all we can see– ~ 1 atom per 10 m-3

• Ω = 1?– ~ 1 atom m-3

• Dark matter– MACHOS– WIMPS

The quintuplet cluster, courtesy NASA http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000908.jpg

Page 4: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

What’s in the dark?

• We can’t see everything

• Dark matter in silhouette

• Dark matter feels the force of gravity

NGC 3314, courtesy NASA: http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000893.jpg

Page 5: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Newton’s law of Gravity

• Every little bit of mass in the Universe attracts every other bit with a force

• The force of attraction between two masses m1 and m2 is proportional to the product of the masses and the inverse square of the distance d between them

– a sphere attracts like a point mass located at its centre

213112

21 skgm1067.6, −−−×== Gd

mmGFm1 m2

attraction

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Mass in a galaxy

• Courtesy ukdmc– UK dark matter

collaboration

http://hepwww.rl.ac.uk/ukdmc/dark_matter/rotation_curves.html

Page 7: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

NGC 3198

• Stars only extend to 10 kpc• Radio doppler shift shows flat

rotation to 30+ kpcNGC 3198

Courtesy: http://bustard.phys.nd.edu/Phys171/lectures/dm.html

Page 8: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

More evidence

• Galaxies have a high mass to luminosity ratio

Sungalaxies LM

LM

⎟⎠⎞

⎜⎝⎛×=⎟

⎠⎞

⎜⎝⎛ 20

Page 9: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

MACHOS

• Massive Compact Halo Objects– candidates:

• red dwarves• brown dwarves• white dwarves• VMOs – very massive objects• SMOs – super massive objects• cold clouds of mainly hydrogen• primordial black holes

– none of these account for all the ‘missing mass’

Page 10: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

23% of energy is dark matter

• Most of it is not baryonic

• WIMPS– Weakly Interactive

Massive Particles NGC 4412 courtesy NASA: http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000933.jpg

Page 11: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Boulby mine

• Dark matter wimp search– source: UKDMC– http://hepwww.rl.ac.uk/ukdmc

/ukdmc.html

Page 12: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Any more ideas?

• Schematic of a spiral galaxy if we include dark matter

• Are WIMPS supersymmetricparticles?

Source: http://bustard.phys.nd.edu/Phys171/lectures/dm.html

Page 13: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Anglo Australian 2dF galaxy survey

http://www.mso.anu.edu.au/2dFGRS/Public/

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Part of the map of the Universe

• The structure of the universe – every dot a galaxy

• Part of the Sloan Survey of distant galaxies from z ≈ 0.05 to z ≈ 0.5

Courtesy: http://www.astro.princeton.edu/~mjuric/universe

/p0.300.gif

Page 15: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

• Clustering of mass is driven by gravity

• Explanation of clustering is a major goal of modern astronomy

Galaxies abound courtesy NASA http://grin.hq.nasa.gov/IMAGES/SMALL/GPN

-2000-000912.jpg

Galactic clustering

Page 16: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Dark Energy• Accelerating expansion of the universe• CosmoΛogical constant

– Λ is negative– 1 = Ω0 = Ωm + ΩΛ

– surely Ω is exactly 1?– zero energy in

the Universe!

• There are no good candidates for dark energy– a fluid – quintessence– vacuum energy

Illustration source: http://www.roundtable.com/Critical_Path/Volume6/ignorance-of-

faculty.jpg

Page 17: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Our Universe• Ω0 = 1.02 ± 0.02• Ωm = 0.27 ± 0.04• Ωb = 0.044 ± 0.004• Ωr = 4.902×10-5

• Ων <0.015, • ΩΛ = 0.73 ± 0.04• q0 = -0.60 ±0.02• t0 = 13.7 ± 0.2 Gyr• baryons/photons is

(6.1 ± 0.7)×10-10

• mneutrinos <0.23 eV • CMB z = 1088 ± 1

NGC 1316 courtesy NASA: http://imgsrc.hubblesite.org/hu/db/2005/11

/images/a/formats/large_web.jpg

Page 18: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Clustering of mass

• How did the universe progress from a few atoms m-3 to matter as we know it at 1026 atoms m-3?

Courtesy: Oxford APM survey http://www-astro.physics.ox.ac.uk/~wjs/apm_grey.gif

Galactic spatial density survey covering 2 million galaxies over an extensive part of the southern sky

Page 19: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Clues to galaxy formation

• Metallicity (Fe observed in a star’s spectrum) is a clue to density and age of surroundings of stars

• Halo stars have low metallicity– hot dark matter and cold dark matter

scenarios predict different populations of low metallicity stars

• Distribution and velocity surveys are needed to mine the history of our galaxy

Page 20: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Mapping dark matter• Develop the galactic rotational velocity idea

to get more detailed velocity information for a much larger range of stars and structures

• 10 km s-1 ≡ 2.75 milli-arc sec y-1 at 25,000 LY

Radial velocity

Transverse velocity

Earth

Star

Hipparcossurvey set the scene for milli-

arc second positional

surveys. Image source ESA

http://sci.esa.int/science-e/www/object/index.cfm?f

objectid=14060

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Our galactic history

• A story for the future

Graphic of Milky Way galaxy courtesy NASA: http://solarsystem.nasa.gov/multimedia/gallery/MilkyWay.jpg

Page 22: 5 Dark matter and dark energy, the Universe revealedMapping dark matter • Develop the galactic rotational velocity idea to get more detailed velocity information for a much larger

Classifying galaxies• Edwin Hubble

– Elliptical• E0 – E7

– Lenticular S0– Spiral

• ordinary Sa, Sb, Sc in order of decreasing spiral tightness

• barred SBa, SBb, SBc

– Irregular

Edwin Hubble (1889 – 1953)

NGC 3384 in Leo

M109, type SBc courtesy: http://seds.lpl.arizona.edu/messier/m/m109.html

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Ellipticals

M49 NGC 4472 type E4 courtesy: http://www.noao.edu/image_gallery/images/d5/m49a.jpg

M60 NGC 4649 type E2 courtesy:

http://www.noao.edu/image_gallery/images/d6/m6

0a.jpg

M84, NGC4374 in the Virgo cluster, Type E1 courtesy: http://www.noao.edu/image_gallery/images/d5/m84.jpg

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Spirals

M98, NGC4192 Type Sb in Coma Berenices Courtesy: http://www.noao.edu/image_gallery/images/d4/m98a.jpg

M99, NGC4254 Type Sc in Coma Berenices courtesy: http://www.noao.edu/image_gallery/images/d2/m99a.jp

g

M88, NGC4501 Type Sc in Coma Berenices Courtesy http://www.noao.edu/image_gallery/images/d3/m88a.jpg

M65 type Sa Courtesy: AAO

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NGC 1232

• Sc galaxy in Eridanus

• source: ESO

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M51

Courtesy: http://heritage.stsci.edu/2001/10/big.html

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Barred spirals

M91, NGC4548 type SBb in Coma Berenices Courtesy: http://www.noao.edu/image_gallery/images/d6/m91a.jpg

NGC 3185 type Sba Courtesy: http://astronote.org/note/files/objects/img/ngc3185.jpg

NGC 3185 type SBc Courtesy: http://astronote.org/note/files/objects/img/ngc3185.jp

g

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NGC 1365

One of the best barred spirals in the southern hemisphere Source:

http://www.eso.org/outreach/press-rel/pr-1999/phot-08a-99-preview.jpg

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NGC 1672

Courtesy: NASA/ESA Hubble Heritage; http://www.spacetelescope.org/images/html/heic0706a.html

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Irregular

Large Magellanic Cloud source:http://www.ast.cam.ac.uk/AAO/images/captions/uks014.html

Small Magellanic Cloud Source:http://www.ast.cam.ac.uk/AAO/images/captions/uks017.html

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Hubble’s tuning fork diagram

• Original diagram suggested an evolutionary sequence

• Not that simple

Source: http://www.astr.ua.edu/preprints/white/gal_tuningfrk.html

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Tuning fork schematic

Fig. 17.7, Courtesy: Kuhn & Koupelis

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Why spirals?

• Effect is not a consequence of differential rotation

• ~ 20 rotations around our galaxy for our Sun

• Spiral pattern would be lost

Fig. 16.19 Courtesy Kuhn & Koupelis

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Density waves

Fig. 16.21 Courtesy: Kuhn & Koupelis