Download Cold galaxies at low and high z - Astrophysics Group

FRONTIERS OF ASTROPHYSICS
- giant telescopes, space missions
and invisible wavelengths
Michael Rowan-Robinson
Imperial College London
Nov 22nd 2008
Institute of Physics, Liverpool
some frontier topics in astrophysics
• Black holes
• The dusty universe
- dramatic starbursts in colliding galaxies
• Exoplanets
- the search for extraterrestial earths
• Cosmology
- measuring the size and age of universe with 5%
precision
- a universe of dark matter, dark energy
Nov 22nd 2008
Institute of Physics, Liverpool
first detection of
electromagnetic radiation
outside the optical band:
Herschel (1800) detected
infrared radiation from the sun
Atmospheric transmission
Nov 22nd 2008
Institute of Physics, Liverpool
X-ray astronomy
The first X-ray satellite,
Uhuru (1970) detected
X-rays from compact
sources in binary
systems (white dwarfs,
neutron stars, black
holes), from quasars
(massive black holes)
and from very hot gas in
clusters of galaxies (100
million degrees)
Nov 22nd 2008
Institute of Physics, Liverpool
HOW TO OBSERVE BLACK HOLES?
• Black holes give off no light from within the
event horizon
• Must observe effects on environment near
horizon, in particular:
– VELOCITIES (matter speeds up near hole)
– ACCRETION (matter being sucked into hole and
heated to X-ray temperatures)
– REDSHIFT (time slows down near hole)
* Effect of Einstein’s General relativity *
Nov 22nd 2008
Institute of Physics, Liverpool
Cygnus X-1, a 10 solar mass black hole in our Galaxy
Nov 22nd 2008
Institute of Physics, Liverpool
X-ray spectra of black holes in
Active Galactic nuclei
• Hypothesis: The
nucleus of an Active
Galaxy contains a black
hole being fed by an
accretion disk. X-rays
illuminate the disk
inducing emission from
iron.
• Prediction: shape of line
distorted by huge
velocities and
gravitational shifts
Nov 22nd 2008
Institute of Physics, Liverpool
X-rays
WE SEE THESE EFFECTS!
• X-ray iron spectrum
from the ASCA satellite
• Clear broadening and
ASCA
redshift
• Requires black hole
Line profile depends on:
• Inclination
• Inner radius
• Outer radius
• X-ray illumination pattern
Tanaka et al. (1995)
Nov 22nd 2008
Institute of Physics, Liverpool
Nov 22nd 2008
Institute of Physics, Liverpool
Nov 22nd 2008
Institute of Physics, Liverpool
AND THEY ARE COMMON
Nandra et al. (2007)
New spectra from XMM-Newton
Nov 22nd 2008
Institute of Physics, Liverpool
the dusty universe
IRAS 1983 - SPITZER, 2003
Nov 22nd 2008
Institute of Physics, Liverpool
IRAS - star forming regions
LMC, the Large Magellanic Cloud
Nov 22nd 2008
Institute of Physics, Liverpool
constellation Orion
Uultraluminous
infrared galaxies
IRAS discovered
ultraluminous infrared
galaxies, forming stars
100-1000 times faster
than our Galaxy, probably
caused by mergers between
two galaxies
this is an image of Arp 220
Nov 22nd 2008
Institute of Physics, Liverpool
Sombrero galaxy
- end product of a galaxy merger
Nov 22nd 2008
Institute of Physics, Liverpool
IC1396, the Elephant’s Trunk
- a dark globule inside
an emission nebula
- a pair of newly
formed stars have
created a cavity
- the animation shows
how the appearance
changes from the
optical, where dust
absorbs light to the
infrared where the dust
radiates
Nov 22nd 2008
Institute of Physics, Liverpool
QuickTime™ and a
MPEG-4 Video decompressor
are needed to see this picture.
Nov 22nd 2008
Institute of Physics, Liverpool
IRAS - dust debris disks
IRAS also discovered dust debris disks around stars, confirmed by
imaging with the Hubble Space Telescope, evidence for planetary
systems in formation. Today over 200 exoplanets are known.
Nov 22nd 2008
Institute of Physics, Liverpool
last week: HST image of exoplanet
in Fomalhaut debris disk
Nov 22nd 2008
Institute of Physics, Liverpool
The Exo-Planet Discovery Era
• <1995
• 1995
Solar System planets
first extra-solar planet ( 51 Peg )
- Hot Jupiters!
• 2008 ~300 exo-planets known
• 2005-10 first Hot and Cool exo-Earths
• 2010-15 Habitable Earths -- common or
rare?
• 2020-30 Extra-solar Life? Are we
alone?
Nov 22nd 2008
Institute of Physics, Liverpool
Exoplanet Discovery Methods
• Doppler Star Wobbles: ~230
• Transits: 39
• Microlensing: 7
Nov 22nd 2008
Institute of Physics, Liverpool
1995 First Doppler Wobble Planet:
51 Peg
Discovered by accident:
Mayor & Queloz
(1995)
Quickly confirmed:
Marcy & Butler (1995)
P = 4.2 days (!)
a = 0.05 AU
T ~2000K
m sin(i) = 0.5 mJ
New class of planet:
“Hot Jupiters” (how did these form ?)
Nov 22nd 2008
Institute of Physics, Liverpool
Nov 22nd 2008
Institute of Physics, Liverpool
WASP’s first 2 new Hot Jupiters
UK WASP Consortium:
Belfast, St.Andrews, Keele,
Open, Leicester, Cambridge,
IAC, SAAO
Nov 22nd 2008
Institute of Physics, Liverpool
Planetary, Brown-dwarf and substellar M-R relation
100
Log [ R / R_Jup ]
10
brown dwarfs,
gas giants and
rocky planets
Low-Mass
Stars
RV discoveries
WASP
Gas Giant
Planets
HAT
TrES
XO
OGLE
Baraffe2003, 5 Gyr
1
Baraffe1998, 5 Gyr
Fortney2007 1Gyr core00 a0.02
Fortney2007 4.5Gyr core10 a0.045
0.1
Fortney2007 Pure Ice
Rock/Ice
Planets
Fortney2007 Pure Rock
Solar-system planets
Fortney2007 Pure Iron
0.01
0.00001
0.0001
0.001
Nov 22nd 2008
0.01
0.1
1
Institute
Log [ M/ M_Jup
]
10
100
1000
of Physics, Liverpool
10000
How to find Earths ?
• Hot Earths:
Transits from Space
– 2007-10 … CoRoT -- Launched 27 Dec 2006.
– 2009-15 … Kepler
– 2017
… PLATO
• Habitable Earths:
Hard to Find
– Habitable Zone: T~300K liquid water on rocky planet
surface
• Cool Earths: Gravitational Lensing
Nov 22nd 2008
Institute of Physics, Liverpool
– 2004-14 … OGLE, PLANET/RoboNet, microFUN, MOA
CoRoT (CNES)
First CoRoT planet:
3 May 2007
Launch 27 Dec 2006
CoRoT-Exo-1b:
6
months/field
P = 1.5 d
 ~ 103 t /min 
1/ 2

Nov 22nd 2008
Institute of Physics, Liverpool
m sin(i) = 1.3 mJ
Space Transit Planet Catch
Planet Size (rE)
A few Earth-like Planets may be found.
Nov 22nd 2008
habitable
hot
Jupiters
Too
large?
Earths
Too
small?
Too hot?
of Physics, Liverpool
PlanetInstitute
Temperature
(K)
OB-03-235 / MB-03-053
2003
first microlens planet
m ~ 1.3 mJ
a ~ 3 AU
MOA
OGLE
Bond et al.
Nov 22nd 2008
(2004)
OGLE
alert
Institute of Physics, Liverpool
Aug 2005
OB-05-390
OB-05-390
smallest cool planet
m ~ 6 m
a ~ 2.9 AU
PLANET/R
oboNet
OGLE
MOA
Nov 22nd 2008
Institute of Physics, Liverpool
ESA: Darwin
~ 2020-30?
infrared space interferometer
destructive interference
cancels out the starlight
snapshot ~500 nearby systems
study ~ 50 in detail
Nov 22nd 2008
Institute of Physics, Liverpool
Life’s Signature:
disequilibrium
atmosphere
(e.g. oxygen-rich)
simulated Darwin spectrum
Which planet
is alive?
Nov 22nd 2008
Institute of Physics, Liverpool
The distances of
the galaxies
In 1924 Edwin Hubble used Cepheid
variable stars to estimate the distance
of the Andromeda Nebula. It clearly lay
far outside the Milky Way System.
This opened up the idea of a universe of
galaxies.
Nov 22nd 2008
Institute of Physics, Liverpool
The expansion of the universe
Five years later he announced, based on distances to 18
galaxies, that the more distant a galaxy, the faster it is moving
away from us
velocity/distance = constant, Ho
(the Hubble law)
This is just what would be expected in an expanding universe.
The Russian mathematician Alexander Friedmann had
shown that expanding universe models are what would be
expected according to Einstein’s General Theory of Relativity, if
the universe is homogeneous (everyone sees the same picture)
and isotropic (the same in every direction).
Nov 22nd 2008
Institute of Physics, Liverpool
The Hubble
Space Telescope
Key Program
Following the first HST
servicing mission, which
fixed the telescope
aberration, a large
amount of HST
observing time was
dedicated to measuring
Cepheids in distant
galaxies, to try to
measure the Hubble
constant accurately.
Nov 22nd 2008
Institute of Physics, Liverpool
The HST Key program final
result
Ho = 72 km/s/Mpc
uncertainty 10%
(Freedman et al 2001)
log V
Nov 22nd 2008
Institute of Physics, Liverpool
Implications of the Hubble
constant
Ho is (velocity/distance) so has the dimensions of (1/time).
1/Ho is the expansion age of the universe (how old the
Universe would be if no forces acting) = 13.6 billion yrs
For simplest model universe with only gravity acting, age of
universe would be 9.1 billion years (gravity slows expansion)
Nov 22nd 2008
Institute of Physics, Liverpool
The age of the universe
We can use the colours and
brightnesses of the stars in
globular clusters to estimate
the age of our Galaxy
~ 12 billion years
Long-lived radioactive isotopes
give a similar answer
Allowing time for our Galaxy to
form, the age of the universe is
~ 13 billion years
Nov 22nd 2008
Institute of Physics, Liverpool
The age of the universe problem
• This is a problem for the simplest models, where
gravity slows down the expansion
• To get consistency between the HST Key Program
value of Ho and the observed age of the universe,
we need to reverse the deceleration of the universe
• Something is pushing the galaxies apart
Nov 22nd 2008
Institute of Physics, Liverpool
The discovery of the Cosmic
Microwave Background, 1965
The discovery of the Cosmic Microwave Background (CMB) by
Penzias and Wilson in 1965, and the confirmation of its blackbody
spectrum by COBE in 1991, showed that we live in a hot Big
Bang universe, dominated by radiation in its early stages.
Nov 22nd 2008
Institute of Physics, Liverpool
How much matter is there in the
universe ?
The light elements D, He, Li
are generated from nuclear
reactions about 1 minute
after the Big Bang. The
abundances turn out to
depend sensitively on the
density of ordinary matter
in the universe.
density ~ 4.10-28 kg/cu m
Wb ~ 0.04
Nov 22nd 2008
Institute of Physics, Liverpool
Evidence for Dark Matter
the speed at which stars
orbit round a galaxy points
to the existence of a halo
of dark matter.
sensitive surveys show
that this can not be due to
stars, or gas.
Nov 22nd 2008
Institute of Physics, Liverpool
Evidence for Dark Matter 2
images of clusters
of galaxies with
HST show arcs
due to gravitational
lensing. These can
be used to weigh
the cluster. Again,
the cluster is
dominated by dark
matter.
Nov 22nd 2008
Abell 2218
Institute of Physics, Liverpool
Large scale structure
The 3-dimensional
distribution of
galaxies shows
structure on
different scales.
This can be used
to estimate the
average density
of the universe.
In dimenionless
units:
Wo ~ 0.27
Nov 22nd 2008
Institute of Physics, Liverpool
Need for Dark Matter
So there is far more matter (Wo ~ 0.27 ) out
there than can be accounted for by the stuff we
are made of (Wb ~ 0.04).
85% of the matter in the universe is ‘dark’
matter (the neutralino ?)
Particle Physicists hope to detect this at the
Large Hadron Collider
Nov 22nd 2008
Institute of Physics, Liverpool
Supernovae as
Standard candles
Type Ia supernovae (explosion
of a white dwarf star in a binary
system) seem to be remarkably
uniform in their light curves.
They behave like
‘standard candles’ and can be
used to estimate distances.
Nov 22nd 2008
Institute of Physics, Liverpool
Distant Type Ia supernovae
Recently a breakthrough in search techniques,
using 4-m telescopes to locate new supernovae, and
8-m telescopes plus the Hubble Space Telescope to
follow them up, has resulted in the detection
of Type Ia supernovae at huge distances.
Nov 22nd 2008
Institute of Physics, Liverpool
Evidence for dark energy
Over 100 Type Ia
supernova have been
found at redshifts 0.5-1.5
Comparing these to nearby
supernova, we find that in
cosmological models with
matter only, the distant
supernovae are fainter than
expected for their redshift.
‘Dark energy’ is pushing the
galaxies apart.
Nov 22nd 2008
Institute of Physics, Liverpool
redshift, or distance
What is Dark Energy ?
According to Einstein’s General Theory of Relativity,
there can be an extra term in the equation for
gravity, which on large scales turns gravity into a
repulsive force (the ‘cosmological repulsion’)
This extra term, denoted L, behaves like the energy
density of the vacuum, hence ‘dark energy’
So far there is no particle physics explanation for this
dark energy
Nov 22nd 2008
Institute of Physics, Liverpool
Mapping the Cosmic
Microwave Background
The CMB is incredibly smooth, to one part in 100,000, but the
very small fluctuations, or ‘ripples’, first mapped by the COBE
mission, are the precursors of the structure we see today.
They also tell us about the matter and energy present in the
early universe
Nov 22nd 2008
Institute of Physics, Liverpool
History of the universe
Nov 22nd 2008
Institute of Physics, Liverpool
Origin of the universe
there are speculations about the origin of the universe
theoretical physicists are trying to unify gravitation (ie General Relativity) and
quantum theory into a single unified ‘theory of everything’
current favourite is ‘string theory’, but so far this makes no predictions about
the observed universe, instead we have the ‘string landscape’
one popular idea is ‘chaotic inflation’ - our universe arose out of a vacuum
fluctuation in an infinite fluctuating void
in this picture there might be many parallel universes, each with different
properties - the ‘multiverse’
currently no evidence to support this idea, or the ‘anthropic principle’, which is
supposed to select which type of universe we find ourselves in
Nov 22nd 2008
Institute of Physics, Liverpool
Fate of the universe
if the current consensus model, with a dominant role for dark energy, is
correct, the fate of the universe is a bleak one
the distances between galaxies will increase at an ever-accelerating rate, but
the horizon will remain fixed at more or less its current size, 13 billion light yrs
eventually, after 100 billion years, our Galaxy will have merged with
Andromeda and our other neighbours in the Local Group into a single large
and dying galaxy
there will be no other galaxies within our observable horizon
eventually all star formation will cease, all stars will die, black holes will
evaporate, and finally protons and neutrons will decay
as the Greek poet Sappho put it:
Nov 22nd 2008
‘nothing will remain of us’
Institute of Physics, Liverpool
The unanswerable questions
• Is the universe spatially finite or infinite ?
- there is a horizon defined by how far
light has travelled since the Big Bang
• What was there before the Big Bang ?
-our theories break down before we can
extrapolate to the Big Bang itself
Nov 22nd 2008
Institute of Physics, Liverpool
how to detect z = 10 galaxies ?
James Webb Space Telescope
Nov 22nd 2008
Institute of Physics, Liverpool
ALMA, 2010
Nov 22nd 2008
Institute of Physics, Liverpool