Russell Johnston Dept of Physics and Astronomy University of Glasgow

Edwin Hubble

Hubble measured the shift in colour, or wavelength, of the light from distant galaxies. Galaxy

Hubble measured the shift in colour, or wavelength, of the light from distant galaxies. Galaxy Laboratory

Hubble’s Law: 1929 Distant galaxies are receding from us with a speed proportional to their distance

Spacetime is expanding like the surface of a balloon. As the balloon expands, galaxies are carried farther apart

Although Hubble got the expansion law correct, his measurement of the current rate of expansion was quite wrong, and took many decades to correct.

Measuring the Hubble constant was a key project of the Hubble Space Telescope

More recently we have extended the Hubble diagram to great distances, using e.g. Supernovae…. Region probed by Hubble’s data

redshift ‘Speeding up’ model ‘Slowing down’ model Models with different shapes Hubble’s law for nearby supernovae measure of distance ….This has led to a remarkable discovery: The expansion of the Universe is speeding up!

What is driving the cosmic acceleration?…

Around Galaxies Distance from the Galaxy Centre (kpc) Orbital velocity (km/s) Typical size of galaxy disk

What we see What is really there.

We can also measure the redshifts of many galaxies. We call this a redshift survey. Redshift surveys can tell us many useful things: How galaxies cluster in space How galaxies evolve in time Different types of galaxy and where (and when) they are found How galaxies formed in the first place How much dark matter and dark energy… And

The First Redshift Surveys CfA Survey #1 : CfA # 1 Surveyed a total of 1100 galaxies Marc Davis, John Tonry Dave Latham, John Huchra, Redshift range: out to z 0.0 5

Our own Galaxy de Lapparent, Geller, and Huchra (1986), ApJ, 302, L1

Filament Rich cluster Void?

CfA # 2 The First Redshift Surveys CfA Survey #2 : John Huchra & Surveyed a total of 18,000 galaxies Margaret Geller Redshift range: out to z Mpc

Redshift surveys (mid- 1980s) 1 Mpc = 3.26 milion light years

The largest structures in LCRS are much smaller than the survey size The size of the structures is similar in both samples LCRS 1995 (LAS CAMPANAS)

The First Redshift Surveys IRAS PSCz : 1992 – 1996, 15,000 galaxies Team originally consisted of around 24 members including: Catalogued over 83% of the sky - Will Sutherland, Steve Maddox, Largest full sky survey. Will Saunders, Carlos Frenk & Seb Oliver, Luis Teodoro.

Survey s…. The Next Generation Ran from 1998 to Used the multifibre spectrograph on the Anglo Australian Telescope. The survey covered two strips : NGP - SGP - Photometry was taken from the APM galaxy catalogue. Galaxies brighter than Recovered a total of 245,591 redshifts, 220,000 of which were galaxies out to The Two Degree Field Galaxy Redshift Survey (2dFGR S)

The Two Degree Field Galaxy Redshift Survey (2dFGR S) 35 collaborators fro UK, Australia and the US. including: Carlos Frenk, Matthew Colles, Richard Ellis, Ofer Lahav, John Peacock, Will Sutherland…. and these guys: Keith Taylor Simon Driver Karl Glazebrook Nick Cross Shaun Cole Peder Norberg Warrick Couch

The Two Degree Field Galaxy Redshift Survey (2dFGR S)

The Two Degree Field Galaxy Redshift Survey (2dFGR S)

= 100 Mpc diameter

The Sloan Digital Sky Survey (SDSS) Most ambitious ongoing survey to date. Began in early nineties and was due to complete in 2008 …. ish Uses a dedicated 2.5m telescope on Apache Point, new Mexico and a pair of spectrographs that measure more than 600 galaxy spectra in a single observation. Currently on data release 5 which contains galaxies. On completion will have surveyed over 1 million galaxies. The Survey has over 150 collaborators at 26 institutions

The Sloan Digital Sky Survey (SDSS)

SDSS CfA

Sloan Digital Sky Survey: The Footprint of the Survey

Area and Size of Redshift Surveys

CMBR fluctuations, years after the Big Bang, are the seeds of today’s galaxies The pattern of CMBR temperature fluctuations can be used to constrain the background cosmological model and its parameters Galaxies and Cosmology: the Basic Paradigm

CMBR fluctuations, years after the Big Bang, are the seeds of today’s galaxies The pattern of CMBR temperature fluctuations can be used to constrain the background cosmological model and its parameters Both the CMBR and present-day galaxy clustering favour : Galaxies and Cosmology: the Basic Paradigm Cold dark matter + non-zero cosmological constant

CMBR fluctuations, years after the Big Bang, are the seeds of today’s galaxies The pattern of CMBR temperature fluctuations can be used to constrain the background cosmological model and its parameters Both the CMBR and present-day galaxy clustering favour : Galaxies and Cosmology: the Basic Paradigm Cold dark matter + non-zero cosmological constant The Concordance Model

From Lineweaver (1998)

The cosmological constant now dominates over CDM and baryonic dark matter (i.e. atoms). It is not yet clear if is constant, or perhaps evolves with time. More generally, is referred to as ‘Dark Energy’.

Dark Energy Cold Dark Matter Atoms The cosmological constant now dominates over CDM and baryonic dark matter (i.e. atoms). It is not yet clear if is constant, or perhaps evolves with time. More generally, is referred to as ‘Dark Energy’.

Dark Energy Cold Dark Matter Atoms The cosmological constant now dominates over CDM and baryonic dark matter (i.e. atoms). It is not yet clear if is constant, or perhaps evolves with time. More generally, is referred to as ‘Dark Energy’. Unlike ‘normal’ matter, dark energy is gravitationally repulsive : it is causing the expansion of the Universe to accelerate.

Dark Energy Cold Dark Matter Atoms The cosmological constant now dominates over CDM and baryonic dark matter (i.e. atoms). It is not yet clear if is constant, or perhaps evolves with time. More generally, is referred to as ‘Dark Energy’. Unlike ‘normal’ matter, dark energy is gravitationally repulsive : it is causing the expansion of the Universe to accelerate. This affects the rate of growth of cosmic structure, which we can model via computer simulations

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 140 Mpc 11 Gyr ago

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 140 Mpc 8 Gyr ago

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 140 Mpc Present day

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 20 Mpc 11 Gyr ago

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 8 Gyr ago 20 Mpc

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect Present day 20 Mpc

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 11 Gyr ago 20 Mpc

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect 8 Gyr ago 20 Mpc

Hierarchical clustering: Galaxies form out of the mergers of fragments: CDM halos at high redshift. Clusters form where filaments and sheets of matter intersect Present day 20 Mpc

Which simulation model matches the observations?...

Hubble’s tuning fork classification We see spiral and elliptical galaxies…

Morphological Segregation Nowadays we find few spiral galaxies in rich clusters. This is thought to be because the spiral disks are disrupted by tidal forces…

Morphological Segregation Nowadays we find few spiral galaxies in rich clusters. This is thought to be because the spiral disks are disrupted by tidal forces… …Conversely, many ellipticals (and some spirals) may have formed from galaxy mergers. See talk by Bonnie Steves

A long time ago, in a galaxy far, far away…

z = 2.0 Light travel time = 10.3 billion years

z = 2.1 Light travel time = 10.5 billion years

z = 2.2 Light travel time = 10.6 billion years

z = 2.3 Light travel time = 10.8 billion years

z = 2.4 Light travel time = 10.9 billion years

z = 2.5 Light travel time = 11.0 billion years

z = 2.6 Light travel time = 11.1 billion years

z = 2.7 Light travel time = 11.2 billion years

z = 2.8 Light travel time = 11.3 billion years

z = 2.9 Light travel time = 11.4 billion years

z = 3.0 Light travel time = 11.5 billion years

z = 3.1 Light travel time = 11.6 billion years

z = 3.2 Light travel time = 11.6 billion years

z = 3.3 Light travel time = 11.7 billion years

z = 3.4 Light travel time = 11.8 billion years

z = 3.6 Light travel time = 11.9 billion years

z = 3.7 Light travel time = 11.9 billion years

z = 3.8 Light travel time = 12.0 billion years

z = 4.0 Light travel time = 12.1 billion years

z = 4.1 Light travel time = 12.1 billion years

z = 4.3 Light travel time = 12.2 billion years

z = 4.4 Light travel time = 12.2 billion years

z = 4.5 Light travel time = 12.3 billion years

z = 4.6 Light travel time = 12.3 billion years

z = 5.0 Light travel time = 12.5 billion years