March 25, 2003Lynn Cominsky - Cosmology A3501 Professor Lynn Cominsky Department of Physics and Astronomy Offices: Darwin 329A and NASA EPO (707) Best way to reach me: Astronomy 350 Cosmology

March 25, 2003Lynn Cominsky - Cosmology A3502 Group 8  Robert Angeli  Jacy Maka  Ryan McDaniel  Rena Morabe

March 25, 2003Lynn Cominsky - Cosmology A3503 Composition of the Cosmos

March 25, 2003Lynn Cominsky - Cosmology A3504 Kepler’s Third Law movie  P 2 is proportional to a 3

March 25, 2003Lynn Cominsky - Cosmology A3505 Dark Matter Evidence  In 1930, Fritz Zwicky discovered that the galaxies in the Coma cluster were moving too fast to remain bound in the cluster according to the Virial Theorem KPNO image of the Coma cluster of galaxies - almost every object in this picture is a galaxy! Coma is 300 million light years away.

March 25, 2003Lynn Cominsky - Cosmology A3506 Virial Theorem  Stable galaxies should obey this law: 2K = -U  where K=½mV 2 is the Kinetic Energy  U = -aGMm/r is the Potential Energy (a is usually , and depends on the mass distribution)  Putting these together, we have M=V 2 r/aG.  Measure M, r and V 2 from observations of the galaxies; then use M and r to calculate V virial  Compare V measured to V virial  V measured > V virial which implies M was too small

March 25, 2003Lynn Cominsky - Cosmology A3507 Galaxy Rotation Curves  Measure the velocity of stars and gas clouds from their Doppler shifts at various distances  Velocity curve flattens out!  Halo seems to cut off after r= 50 kpc NGC 3198 v 2 =GM/r where M is mass within a radius r Since v flattens out, M must increase with increasing r!

March 25, 2003Lynn Cominsky - Cosmology A3508 Dark Matter Activity #1  Measure the radial velocity as a function of distance from the center of the galaxy  Calculate the mass of the galaxy at a given distance from the center, for each radial velocity  Measure the light coming from the galaxy inside of a given radius  Calculate the mass of the galaxy again, from the light that it emits at a given distance from the center  Plot the masses (from the radial velocity) vs. the masses (from the light)  Answer the other questions on the worksheet

March 25, 2003Lynn Cominsky - Cosmology A3509 Hot gas in Galaxy Clusters  Measure the mass of light emitting matter in galaxies in the cluster (stars)  Measure mass of hot gas - it is 3-5 times greater than the mass in stars  Calculate the mass the cluster needs to hold in the hot gas - it is times more than the mass of the gas plus the mass of the stars!

March 25, 2003Lynn Cominsky - Cosmology A35010 Dark Matter Halo  The rotating disks of the spiral galaxies that we see are not stable  Dark matter halos provide enough gravitational force to hold the galaxies together  The halos also maintain the rapid velocities of the outermost stars in the galaxies

March 25, 2003Lynn Cominsky - Cosmology A35011 Types of Dark Matter  Baryonic - ordinary matter: MACHOs, white, red or brown dwarfs, planets, black holes, neutron stars, gas, and dust  Non-baryonic - neutrinos, WIMPs or other Supersymmetric particles and axions  Cold (CDM) - a form of non-baryonic dark matter with typical mass around 1 GeV/c 2 (e.g., WIMPs)  Hot (HDM) - a form of non-baryonic dark matter with individual particle masses not more than eV/c 2 (e.g., neutrinos)

March 25, 2003Lynn Cominsky - Cosmology A35012 Big Bang  Written, directed and starring the Physics Chanteuse Lynda Williams  From her CD Cosmic Cabaret  Available from

March 25, 2003Lynn Cominsky - Cosmology A35013 Primordial Matter  Normal matter is 3/4 Hydrogen (and about 1/4 Helium) because as the Universe cooled from the Big Bang, there were 7 times as many protons as neutrons  Almost all of the Deuterium made Helium Hydrogen = 1p + 1e Deuterium = 1p + 1e + 1n Helium = 2p + 2e + 2n

March 25, 2003Lynn Cominsky - Cosmology A35014 Primordial Matter  The relative amounts of H, D and He depend on  = (protons + neutrons) / photons   is very small - We measure about 1 or 2 atoms per 10 cubic meters of space vs. 411 photons in each cubic centimeter  The measured value for  is the same or a little bit smaller than that derived from comparing relative amounts of H, D and He  Conclusion: we may be missing some of baryonic matter, but not enough to account for the observed effects from dark matter!

March 25, 2003Lynn Cominsky - Cosmology A35015 Baryonic Dark Matter  Baryons are ordinary matter particles  Protons, neutrons and electrons and atoms that we cannot detect through visible radiation  Primordial Helium (and Hydrogen) – recently measured – increased total baryonic content significantly  Brown dwarfs, red dwarfs, planets  Possible primordial black holes?  Baryonic content limited by primordial Deuterium abundance measurements

March 25, 2003Lynn Cominsky - Cosmology A35016 Baryonic - Brown Dwarfs  Mass around 0.08 M o  Do not undergo nuclear burning in cores  First brown dwarf star Gliese 229B

March 25, 2003Lynn Cominsky - Cosmology A35017 Baryonic - Red Dwarf Stars  HST searched for red dwarf stars in the halo of the Galaxy  Surprisingly few red dwarf stars were found, < 6% of mass of galaxy halo Expected 38 red dwarfs: Seen 0!

March 25, 2003Lynn Cominsky - Cosmology A35018 Ghost Galaxies  Also known as low surface brightness galaxies  Studies have shown that fainter, elliptical galaxies have a larger percentage of dark matter (up to 99%)  This leads to the surprising conclusion that there may be many more ghostly galaxies than those we can see!  Each ghost galaxy has a mass around 10 million M o

March 25, 2003Lynn Cominsky - Cosmology A35019 Baryonic –MACHOs  Massive Compact Halo Objects  Many have been discovered through gravitational micro- lensing  Not enough to account for Dark Matter  And few in the halo! Mt. Stromlo Observatory in Australia (in better days)

March 25, 2003Lynn Cominsky - Cosmology A35020 Baryonic – MACHOs  4 events towards the LMC  45 events towards the Galactic Bulge  8 million stars observed in LMC  10 million stars observed in Galactic Bulge  27,000 images since 6/92

March 25, 2003Lynn Cominsky - Cosmology A35021 Gravitational Microlensing  Scale not large enough to form two separate images movie

March 25, 2003Lynn Cominsky - Cosmology A35022 Baryonic – black holes  Primordial black holes would form at s after the Big Bang from regions of high energy density  Sizes and numbers of primordial black holes are unknown  If too large, you would be able to see their effects on stars circulating in the outer Galaxy  Black holes also exist at the centers of most galaxies – but are accounted for by the luminosity of the galaxy’s central region

March 25, 2003Lynn Cominsky - Cosmology A35023 Black Hole MACHO  Isolated black hole seen in Galactic Bulge  Distorts gravitational lensing light curve  Mass of distorting object can be measured  No star is seen that is bright enough…..

March 25, 2003Lynn Cominsky - Cosmology A35024 Strong Gravitational Lensing

March 25, 2003Lynn Cominsky - Cosmology A35025 Strong Gravitational Lensing  HST image of background blue galaxies lensed by orange galaxies in a cluster  “Einstein’s rings” can be formed for the correct alignment

March 25, 2003Lynn Cominsky - Cosmology A35026 Strong Gravitational Lensing  Spherical lens  Perfect alignment  Note formation of Einstein’s rings movie

March 25, 2003Lynn Cominsky - Cosmology A35027 Strong Gravitational Lensing  Elliptical lens  Einstein’s rings break up into arcs if you can only see the brightest parts movie

March 25, 2003Lynn Cominsky - Cosmology A35028 Dark Matter telescope  At least 8 meter telescope  About 3 degree field of view with high angular resolution  Resolve all background galaxies and find redshifts  Goal is 3D maps of universe back to half its current age

March 25, 2003Lynn Cominsky - Cosmology A35029 Gravitational Lens Movie #1  Dark matter is clumped around orange cluster galaxies  Background galaxies are white and blue  Movie shows evolution of distortion as cluster moves past background during 500 million years

March 25, 2003Lynn Cominsky - Cosmology A35030 Gravitational Lens Movie #2  Dark matter is distributed more smoothly around the cluster galaxies  Background galaxies are white and blue  Movie shows evolution of distortion as cluster moves past background during 500 million years

March 25, 2003Lynn Cominsky - Cosmology A35031 Baryonic – cold gas  We can see almost all the cold gas due to absorption of light from background objects  Gas clouds range in size from 100 pc (Giant Molecular Clouds) to Bok globules (0.1 pc)  Mass of gas is about the same as mass of stars, and is part of total baryon inventory Gas clouds in Lagoon nebula

March 25, 2003Lynn Cominsky - Cosmology A35032 Baryonic –dust  Dust is made of elements heavier than Helium, which were previously produced by stars (<2% of total)  Dust absorbs and reradiates background light Dust clouds of the dark Pipe nebula

March 25, 2003Lynn Cominsky - Cosmology A35033 Non-baryonic - neutrinos  Start with a decaying neutron at rest  This reaction does not conserve energy because the proton and electron together do not weigh as much as the neutron  The reaction also does not conserve momentum, as nothing is moving to the left  The anti-neutrino makes it all balance proton electron neutron anti-electron neutrino

March 25, 2003Lynn Cominsky - Cosmology A35034 Neutrino mysteries  Neutrinos are believed to have zero mass and therefore can travel at the speed of light  Neutrinos interact very weakly with other particles  There are about 100 million neutrinos per cubic meter  There are three types of neutrinos (and anti- neutrinos): electron, muon and tau  More (or less) types of neutrinos would lead to more (or less) primordial Helium than we see

March 25, 2003Lynn Cominsky - Cosmology A35035 Neutrino mysteries  Not enough neutrinos are detected from the nuclear reactions in the Sun (“Solar neutrino problem”)  Oscillations between different types of neutrinos would solve the Solar neutrino problem  Oscillations also imply that neutrinos have a small amount of mass electron neutrino muon neutrino

March 25, 2003Lynn Cominsky - Cosmology A35036 Non-baryonic - axions  Extremely light particles, with typical mass of eV/c 2  Interactions are weaker than ordinary weak interaction  Density would be 10 8 per cubic centimeter  Velocities are low  Axions may be detected when they convert to low energy photons after passing through a strong magnetic field

March 25, 2003Lynn Cominsky - Cosmology A35037 Searching for axions  Superconducting magnet to convert axions into microwave photons  Cryogenically cooled microwave resonance chamber  Cavity can be tuned to different frequencies  Microwave signal amplified if seen

March 25, 2003Lynn Cominsky - Cosmology A35038 Non-baryonic - WIMPs  Weakly Interacting Massive Particles  Predicted by Supersymmetry (SUSY) theories of particle physics  Supersymmetry tries to unify the four forces of physics by adding extra dimensions  WIMPs would have been easily detected in acclerators if M < 15 GeV/c 2  The lightest WIMPs would be stable, and could still exist in the Universe, contributing most if not all of the Dark Matter

March 25, 2003Lynn Cominsky - Cosmology A35039 CDMS for WIMPs  Cryogenic Dark Matter Search  6.4 million events studied - 13 possible candidates for WIMPs  All are consistent with expected neutron flux Cryostat holds T= 0.01 K CDMS Lab 35 feet under Stanford

March 25, 2003Lynn Cominsky - Cosmology A35040 Detecting WIMPs?  Laboratory experiments - DAMA experiment 1400 m underground at Gran Sasso Laboratory in Italy announced the discovery of seasonal modulation evidence for 52 GeV WIMPs  100 kg of Sodium Iodide, operated for 4 years  CDMS has 0.5 kg of Germanium, operated for 1 year, but claims better background rejection techniques 

March 25, 2003Lynn Cominsky - Cosmology A35041 HDM vs. CDM models  Supercomputer models of the evolution of the Universe show distinct differences  Rapid motion of HDM particles washes out small scale structure – the Universe would form from the “top down”  CDM particles don’t move very fast and clump to form small structures first – “bottom up” CDM HDM

March 25, 2003Lynn Cominsky - Cosmology A35042 CDM models vs. density  CDM models as a function of z (look-back time) NowZ=0.5Z=1.0 Critical density Low density Largest structures are now just forming

March 25, 2003Lynn Cominsky - Cosmology A35043 Dark Matter and Dark Energy  Assume that  total = 1, then for  H o = 65 km s -1 Mpc -1, we measure:  b = 0.04 (+/ ) (baryons)  m = 0.4 (+/- 0.2) (all matter) <  < 0.1 (hot dark matter)   = 0.6 – 0.7 (dark energy)  This makes the age of the Universe around 15 billion years  (Joel Primack’s talk at DM2000)

March 25, 2003Lynn Cominsky - Cosmology A35044 Dark Matter Activity #2  You will search a paper plate “galaxy” for some hidden mass by observing its effect on how the “galaxy” “rotates” In order to balance, the torques on both sides must be equal: T 1 = F 1 X 1 = F 2 X 2 = T 2 where F 1 = m 1 g and F 2 = m 2 g

March 25, 2003Lynn Cominsky - Cosmology A35045 Web Resources  Astronomy picture of the Day  Imagine the Universe  Dark Matter 2000 (conference at UCLA)  Center for Particle Astrophysics  Dark Matter telescope

March 25, 2003Lynn Cominsky - Cosmology A35046 Web Resources  Jonathan Dursi’s Dark Matter Tutorials & Java applets  MACHO project  National Center for Supercomputing Applications  Pete Newbury’s Gravitational Lens movies

March 25, 2003Lynn Cominsky - Cosmology A35047 Web Resources  Alex Gary Markowitz’ Dark Matter Tutorial  Martin White’s Dark Matter Models  Livermore Laboratory axion search