To The Edge of Infinity

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