To the Edge of Infinity Anna M. Quider Institute of Astronomy University of Cambridge 14 July 2009 7 Sept 2010
Jun 27, 2015
To the Edge of Infinity
Anna M. Quider
Institute of AstronomyUniversity of Cambridge
14 July 20097 Sept 2010
Today’s Talk
Primer on Gravity
then...
The development of structure in the universe(from the Big Bang to present-day galaxies)
Gravity
Sir Isaac Newton1643-1727
Gravity
F = G x Ma x Mb
r2
Ma Mb
F
r
Gravity
Gravity
Albert Einstein1879-1955
Gravity
Gravity
Gravity
Black HolesAs far as we know, they only come from the death of a
very massive star
They range in size from stellar mass sized black holes to supermassive black holes that are billions of times the mass
of the Sun
We think a supermassive black hole lives in the center of all large galaxies
Can’t see black holes themselves--can only see their effects
Black HolesSmall black hole
accreting matter from companion star
(Cygnuis X)
Large black hole powering very
energetic jets from a galaxy (quasar)
Small Black Holes
• Made by the death of a massive star (>20Msun)
• Resulting black hole will be at least ~3Msun (any smaller and you’d get a neutron star or white dwarf rather than a black hole) and no more than ~a few x 10Msun (because the black hole must be considerably less massive than the star that made it and the largest stars are ~100Msun)
Supermassive Black Holes
• Made when a small black hole consumes other black holes, stars, and gas
• Can grow to billions of solar masses
• Live in center of galaxies
White circles are galaxiesBlack dots are black holes
t
Supermassive Black Holes
Sagittarius A*: Supermassive black hole in center of our galaxy
Supermassive Black Holes
Gravitational Waves• Emitted when compact objects are in binary orbit
or merge together
• Orbiting objects slowly spiral in towards each
Gravitational Waves
LIGO
Ground-based laser interferometer
4 km
4 km
GravityWhat we need to know:
1. Gravity pulls objects together
2. The more matter an object has, the more matter it can pull towards itself
3. The closer two objects are to each other, the more gravitational attraction they feel
“The rich get richer and the poor get poorer”
In the beginning...
The Big Bang!
In the beginning...
...the universe was an expanding hot soup of particles......the universe cooled as it expanded...
Eventually Hydrogen and Helium atoms form and then things get interesting for astronomers
First Light in Universe
Fluctuations: one part per million
About 400,000 years after the Big Bang
First Light in Universe
Fluctuations: one part per million
About 400,000 years after the Big Bang
First Light in Universe
RedshiftMeans light looks more red to you (the observer) than it actually was when it was emitted from the source
Different kinds:1. Doppler: small scale redshifting and blueshifting of light because the emitting object is moving away from you or towards you -- like hearing a siren approach and pass you
2. Cosmological: Light gets stretched as it travels through the expanding universe and this causes the light to appear more red when it reaches its destination
3. Gravitational: It takes energy for light to climb out of a gravitational potential well so the light appears more red (lower energy) when it finally comes out of the gravitational field
Redshift
Doppler Redshift Cosmological Redshift
Early GalaxiesHubble Deep Field (1995)
Early GalaxiesHubble Deep Field (1995)
Early Galaxies
Hubble Deep Field (1995)
about 3,000 objects
10 days of data with HST
Some galaxies from about 1 billion years after Big Bang
Early Galaxies
Early Galaxies
Hubble Ultra Deep Field (2003-04)
about 10,000 objects
11.3 days of data with HST
Some galaxies from about 800 million years after Big Bang (though may have even younger objects, too!)
Keeping Our Orientation
Early Galaxies
2
Figure 1: HST/ACS images of 25 galaxies at z ~ 2 in the GOODS-N field, each box is 3 arcsec on
a side (from Law et al. 2007b). Note the complex morphologies of these systems.
2. Kinematics:
Given the complications of such morphological studies, invaluable additional information can be
gleaned from the nebular emission lines (e.g., H!, H", [O III], [O II], and [N II]) which provide
good kinematic tracers of the ionized gas surrounding active star forming regions. Such nebular
emission-line spectroscopy has been used (e.g.) to trace the evolution in the Tully-Fisher relation
out to z ~ 1.2 (Weiner et al. 2006; Kassin et al. 2007) and suggests the growing importance of
non-circular motions to this relation with increasing redshift. In combination with new adaptive
optics (AO; e.g. Wizinowich et al. 2006) and integral-field unit (IFU) technologies it has
additionally become possible for ground-based telescopes to overcome the limitations imposed
by atmospheric turbulence and “dissect” galaxies with spectroscopy on hitherto-unprobed sub-
kiloparsec scales.
IFU studies at z ~ 1.5 (Wright et al. 2007, 2009) confirm a slight increase in non-circular
motions relative to the local universe, but also find evidence of organized rotation within their
galaxy sample. At higher redshifts, numerous studies at z ~ 2 - 3 (e.g., Förster-Schreiber et al.
2006; Genzel et al. 2008; Law et al. 2007a, 2009; Nesvadba et al. 2008) have found that galaxies
have extremely large velocity dispersions (# ~ 80 km s-1
) as compared to their rotational velocity
(V) about a preferred kinematic axis. While exact values of the ratio V/# vary from less than
unity up to about 4 – 5, there is clearly a dynamical difference from disk galaxies in the nearby
universe, which typically have V/# ~ 15 – 20 (e.g., Dib et al. 2006).
Galaxies from about 3.3 billion years after Big Bang
Gravitational Lensing
Gravity distorts and magnifies light from distant galaxies
Gravitational Lensingdistorts: stretched arcs and/or multiple images
magnifies: more light reaches the Earth
Early Galaxies
The Cosmic HorseshoeThe Clone
The Cosmic EyeThe 8 o’clock Arc
Keck TelescopesHawaii, USA
10 meter mirror diameter
Keck Telescopes
The Rest of the GalaxiesSloan Digital Sky Survey
Surveying 1/4 of night sky
About 1 million galaxies analyzed
The Rest of the Galaxies
The Rest of the GalaxiesGalaxy Clusters
-Contain 1000s of galaxies-Are the largest structures
held together by gravity
Perseus Cluster
Dark Matter
Only interacts through gravity
Does not interact with light
Normal matter follows the dark matter’s clumping
The Rest of the Galaxies
Dark Matter and a Cluster
Abell 2218
Dark Matter and a Cluster
Bullet ClusterBlue = dark matterRed = gas in cluster
Dark Matter and a Galaxy
Dark Matter EvidenceSpiral Galaxy Rotation Curves
Only luminous matter(theoretically predicted)
Observed
Dark Matter EvidenceSpiral Galaxy Rotation Curves
Only luminous matter(theoretically predicted)
Observed
Curve for NGC3198
Different Galaxy TypesSpiral Galaxy
Spiral Galaxy Formation
Spiral Galaxy Formation
Spiral Galaxy Formation
Different Galaxy TypesElliptical Galaxy
Different Galaxy Types
A Little Reminder...
Early galaxies don’t look like the galaxies
we see in the present-day universe!
Galaxy Mergers
z Age of Universe
7 0.75 Billion Years2 3.3 Billion Years1 6 Billion Years
0.5 8.6 Billion Years0 Today
Galaxy MergersAntennae Galaxies
Galaxy MergersOur Local Group
Milkey Way’s Mergers
Andromeda, here we come!!!(meet you in a few billion years!)
What is the fate of the universe?
density of universe > critical density: Positive Curvature: Closed. Volume is finite but unbounded. density = crititcal density: Zero Curvature: Flat. Volume is infinite. density < critical density: Negative Curvature: Open. Volume is infinite.
Depends on density of universe (which controls geometry of universe)
What is the fate of the universe?Depends on density of universe
(which controls geometry of universe)
Dark energy could be complicating the picture...
Latest evidence is that the universe’s expansion is
accelerating due to some unknown repulsive energy!
We call this repulsive energy “Dark Energy” because we
have no idea what it is
Supernovae Type Ia
white dwarf
large companion starType 1a Supernova
All Type 1a Supernovae have the same luminosity so their apparent brightness is directly due to their
distance from us.
Supernovae Type Ia
Mass-Energy budget of Universe
Bringing it full circle
Gravity shapes the structure of the universe
Bringing it full circle
Tiny variations in the very early universe + gravity create the large-scale structure of the universe
Gravity shapes the structure of the universe
Bringing it full circle
Tiny variations in the very early universe + gravity create the large-scale structure of the universe
Gravitational lensing let’s us study galaxies and dark matter in the universe
Gravity shapes the structure of the universe
Bringing it full circle
Tiny variations in the very early universe + gravity create the large-scale structure of the universe
Gravitational lensing let’s us study galaxies and dark matter in the universe
Galaxies have different types and ages and they merge together
Gravity shapes the structure of the universe