Courtesy: NASA

5 Dark matter and dark energy, the Universe revealed

Our place

How much matter? What’s in the dark?

• Add up all we can see • We can’t see – ~ 1 atom per 10 m-3 everything • Ω = 1? • Dark matter in – ~ 1 atom m-3 silhouette • Dark matter • Dark matter – MACHOS feels the force – WIMPS of gravity

The quintuplet cluster, courtesy NASA NGC 3314, courtesy NASA: http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000908.jpg http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000893.jpg

Newton’s law of Gravity Mass in a

• Every little bit of mass in the Universe • Courtesy ukdmc attracts every other bit with a force – UK dark matter • The force of attraction between two masses collaboration

m1 and m2 is proportional to the product of the masses and the inverse square of the distance d between them

attraction m m F = G 1 2 , G = 6 .67 × 10 −11 m 3 kg −1s − 2 d 2 m1 m2 – a sphere attracts like a point mass located at its centre

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

1 ⎛ M ⎞ ⎛ M ⎞ ⎜ ⎟ = 20×⎜ ⎟ NGC 3198 More evidence L L ⎝ ⎠ ⎝ ⎠Sun

Courtesy: http://bustard.phys.nd.edu/Phys171/lectures/dm.html • only extend to 10 kpc • Radio doppler shift shows flat • Galaxies have a high mass to luminosity ratio NGC 3198 rotation to 30+ kpc

MACHOS 23% of energy is dark matter

• Massive Compact Halo Objects – candidates: • red dwarves • brown dwarves • white dwarves • VMOs – very massive objects • SMOs – super massive objects • cold clouds of mainly hydrogen • Most of it is • primordial black holes not baryonic – none of these account for all the • WIMPS ‘missing mass’ – Weakly Interactive NGC 4412 courtesy NASA: Massive Particles http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-000933.jpg

Any more ideas? Boulby mine

• Schematic of a if we include dark matter • Are WIMPS supersymmetric • Dark matter wimp particles? search – source: UKDMC Source: http://bustard.phys.nd.edu/Phys171/lectures/dm.html – http://hepwww.rl.ac.uk/ukdmc /ukdmc.html

2 Anglo Australian 2dF galaxy survey 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 http://www.mso.anu.edu.au/2dFGRS/Public/ /p0.300.gif

Galactic clustering Dark Energy

• Clustering of • Accelerating expansion of the universe mass is driven • CosmoΛogical constant by gravity – Λ is negative • Explanation of – 1 = Ω = Ω + Ω clustering is a 0 m Λ major goal of – surely Ω is exactly 1? modern – zero energy in astronomy the Universe! • There are no good candidates for dark energy

Illustration source: http://www.roundtable.com/Critical_Path/Volume6/ignorance-of- – a fluid – quintessence faculty.jpg – vacuum energy

Galaxies abound courtesy NASA http://grin.hq.nasa.gov/IMAGES/SMALL/GPN -2000-000912.jpg

Our Universe Clustering of mass

• Ω = 1.02 ± 0.02 0 • How did the universe progress from a • Ω = 0.27 ± 0.04 m few atoms m-3 to matter as we know it • Ωb = 0.044 ± 0.004 -5 26 -3 • Ωr = 4.902×10 at 10 atoms m ? Galactic spatial density survey covering 2 million galaxies over an • Ων <0.015, extensive part of the southern sky

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

3 Clues to galaxy formation Mapping dark matter

• Develop the galactic rotational velocity idea • Metallicity (Fe observed in a ’s to get more detailed velocity information for a spectrum) is a clue to density and age much larger range of stars and structures of surroundings of stars • 10 km s-1 ≡ 2.75 milli-arc sec y-1 at 25,000 LY • Halo stars have low metallicity

– hot dark matter and cold dark matter Hipparcos survey set the scenarios predict different populations of scene for milli- Transverse low metallicity stars arc second velocity positional Star • Distribution and velocity surveys are surveys. Image source ESA Earth Radial velocity needed to mine the history of our http://sci.esa.int/science- e/www/object/index.cfm?f galaxy objectid=14060

Edwin Hubble Our galactic history Classifying galaxies (1889 – 1953) • A story for the future • Edwin Hubble – Elliptical NGC 3384 • E0 – E7 in Leo – Lenticular S0 – Spiral • ordinary Sa, Sb, Sc in order of decreasing spiral tightness • barred SBa, SBb, SBc – Irregular

M109, type SBc courtesy: Graphic of galaxy courtesy NASA: http://seds.lpl.arizona.edu/messier/m/m109.html http://solarsystem.nasa.gov/multimedia/gallery/MilkyWay.jpg

M88, NGC4501 Type Sc in Coma Berenices Courtesy M60 NGC 4649 type E2 http://www.noao.edu/image_gallery/images/d3/m88a.jpg Ellipticals courtesy: Spirals http://www.noao.edu/ima ge_gallery/images/d6/m6 0a.jpg

M49 NGC 4472 type E4 courtesy: http://www.noao.edu/image_gallery/images/d5/m49a.jpg M99, NGC4254 Type Sc in Coma Berenices courtesy: http://www.noao.edu/image_gallery/images/d2/m99a.jp g

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

M84, NGC4374 in the Virgo cluster, Type E1 courtesy: M65 type Sa Courtesy: AAO http://www.noao.edu/image_gallery/images/d5/m84.jpg

4 NGC 1232 M51

• Sc galaxy in Eridanus • source: ESO

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

Barred spirals NGC 1365

One of the best barred spirals in the southern M91, NGC4548 type SBb in Coma Berenices Courtesy: http://www.noao.edu/image_gallery/images/d6/m91a.jpg hemisphere Source: http://www.eso.org/outreach/press-rel/pr- 1999/phot-08a-99-preview.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

NGC 1672 Irregular

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

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

Courtesy: NASA/ESA Hubble Heritage

5 Hubble’s tuning fork diagram Tuning fork schematic

• Original diagram suggested an evolutionary sequence • Not that simple

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

Fig. 17.7, Courtesy: Kuhn & Koupelis

Why spirals? Density waves

• 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 Fig. 16.21 Courtesy: Kuhn & Koupelis

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