Transcript Science Implications of Various Servicing Options

Science with the New Hubble Instruments
Ken Sembach
STScI Hubble Project Scientist
1
Hubble Has Improved Over Time
• Servicing missions have improved Hubble’s vision.
• Hubble sees farther and
with greater clarity than
any ground-based
optical telescope
WFPC1
WFPC2
• Hubble will be even more powerful
after Servicing Mission 4 next year.
2
New Hubble Science Instruments
• Wide Field Camera 3 (Panchromatic Imaging)
•
Two channels cover near-ultraviolet to near-infrared
wavelengths
• Wide field imaging from 200 to 1000 nm
• Superb sensitivity, wide field of view
•
Replaces WFPC2 during SM4
• Cosmic Origins Spectrograph (Ultraviolet Spectroscopy)
•
Far-ultraviolet channel (110 nm - 180 nm)
• Improves HST sensitivity by at least 10x
•
Near-ultraviolet channel (180 nm - 320 nm)
•
Replaces COSTAR during SM4
3
COS Science Themes
What is the large-scale structure of
matter in the Universe?
How did galaxies form out of the
intergalactic medium?
What types of galactic halos and
outflowing winds do star-forming
galaxies produce?
How were the chemical elements
for life created in massive stars and
supernovae?
How do stars and planetary
systems form from dust grains in
molecular clouds?
What is the composition of
planetary atmospheres and comets in
our Solar System (and beyond)?
4
Spectroscopy
• Spectroscopy is the technique that allows astronomers to disperse
light into its constituent colors and determine the energy levels of
atoms and molecules.
Types of Spectra
Figure reproduced from Universe by Freedman and Kaufmann
5
Cosmic Barcodes
• Each element has its own
unique set of spectral lines.
• The sequence of lines is
determined by the energy
levels populated within the
atom or molecule.
• These series of lines can be
used to identify the chemical
composition of the gas
causing the absorption.
• Pop quiz! What elements are
present in this spectrum?
6
Decoding the Information in a Spectrum
• Astronomers convert two-dimensional spectra (below) into onedimensional plots of intensity versus wavelength.
• This allows precise line wavelengths, shapes, and strengths to be
measured easily.
• The line parameters contain information about the physical properties
of the absorbing material.
Collapse and sum spectrum in
this direction
Plot intensity versus wavelength
Wavelength
7
A Hubble Spectrum is a Beautiful Thing!
8
COS Extracts Information from Light
• Spectral lines contain information
Question
Information
Observable quantity
Chemical composition
Pattern of lines
• What state? Molecular/atomic/ionic
Pattern of lines
• How hot?
Widths of lines
• What is it?
Temperature
• How much? Quantity
Strengths of lines
• How fast?
Wavelengths of lines
Velocity
• Where is it? Location (redshift)
Wavelengths of lines
9
Redshift of Spectral Lines
The light at the wavelength of this line is the color it is when it is
absorbed (in this case, yellow).
This same line is shifted to redder wavelengths when
observed by someone moving away from the absorber.
lobs - labs
The faster the recession, the greater the redshift.
lobs - labs
Wavelength l
10
Redshift and Cosmic Expansion
Hubble’s Law
vr = H0 d
vr = velocity of recession
H0
d
vr
d = distance
H0 = Hubble’s constant
H0 ≈ 20 kilometers per second per million light years
Distance
• The Universe is expanding in all directions.
• Distant objects move away from us faster than nearby objects.
• As a result, distant objects appear redder than they would if they were
nearby - they are redshifted.
11
The Mass/Energy Budget of the Universe
• Even though ordinary matter accounts
for only a small fraction of the mass of
the Universe, it is the only form of
matter that is directly observable.
• About 50% of ordinary matter has yet
to be accounted for in the present-day
Universe. It is “hidden” (or “missing”) in
the form of tenuous intergalactic
material.
Dark Matter and Dark Energy cannot be observed directly, but their
influence on ordinary matter can be seen by Hubble.
12
Where is the Ordinary Matter?
• Most of the ordinary matter in the Universe is in the intergalactic
medium.
• Galaxies contain less than 10% of the ordinary matter.
• Most of the ordinary matter is outside galaxies.
• The hot ionized intergalactic gas has will be studied by COS.
• The intergalactic medium provides the raw materials needed to
build galaxies, stars, planets, and life.
• The intergalactic gas is hard to detect because it is so tenuous.
• It has such a low density that it is not yet possible to image it.
13
What is the Density of the Intergalactic Medium?
• Air has a density of ~ 3x1019 molecules per cubic centimeter.
• This is about 30 billion billion molecules.
• 1 cubic centimeter is about the size of a sugar cube.
1 cc
• The Sun’s photosphere has a density of about 109 atoms per cc.
• This is a much better vacuum than can be produced in any laboratory.
• The interstellar medium has a density of about 1 atom per cc.
• Take the air particles in a box the size of a sugar cube and stretch the cube
in one dimension 33 light years to get the same density!
• The intergalactic medium has a density of about 1/100,000 atom per cc.
• Take the box and stretch it 3 million light years, or about 4 times further than
the Andromeda galaxy!
Milky Way
Andromeda
Keep going!
3 million light years
14
Evolution of the Cosmic Web of Matter
Simulation by Volker Springel (MPIA)
QuickTime™ and a
decompressor
are needed to see this picture.
• The intergalactic gas evolves with time under the influence of gravity.
• Large-scale gaseous structures collapse into sheets and filaments.
• Shocks in the collapsing structures heat the intergalactic gas to high temperatures.
15
Evolution of the Cosmic Web of Matter
16
A Representation of What the Cosmic Web
Might Look Like Now
Redshift = 0
(1024 h-1 Mpc)3
Temperature
Much of the gas is at temperatures
of 100,000 to 1,000,000 degrees
(greenish colors in figure).
Clusters of galaxies form at the
intersections of the filaments
where the gas is hottest (bluish
colors in figure).
104 K
105 - 106 K
108 K
Figure from Kang et al. 2004
17
COS is Designed to Study the Cosmic Web
COS will greatly increase the number of
quasar sight lines explored by Hubble.
In just a few days, COS can sample as
much of the Universe as all existing STIS
observations of quasars have probed!
Cosmic web absorption features
WFC3 Science Themes
What are dark matter and dark
energy?
How and when did galaxies first
assemble?
How universal are the processes of
star formation in galaxies?
How do stars evolve, and what is
their distribution of masses?
How does star-formation and
planetary disk formation depend on
environmental conditions?
What is the composition of planets,
comets, and minor planets in our
Solar System (and beyond)?
19
One Way to Study Dark Matter is to Observe Its
Effect on Light from Distant Objects
20
A Map of the Dark Matter
Bullet Cluster
Hubble image + Chandra hot gas detection => Dark Matter distribution (blue)
21
HST Images of Type Ia Supernovae
22
Expansion History of the Universe
Redshift, z
1
Constant or
faster in past
(expected)
Slower in past
(observed!)
0.1
Farther in the past
Riess et al. (1998)
Perlmutter et al. (1999)
0.01
100
1,000
Luminosity distance, dL (Mpc)
10,000
23
The High Redshift Universe
• Redshifts above ~6-7 are largely unexplored
because they require a large field of view
and high sensitivity at infrared wavelengths.
• WFC3 has a filter complement that
enables identification of galaxies in
the very early universe (z ~ 7-10).
• WFC3 has the sensitivity needed
to overcome cosmic variance.
24
WFC3 Will Peer into the Hearts of Galaxies
• High angular resolution, great
sensitivity and multi-wavelength
coverage will give WFC3
unprecedented views into the
cores of galaxies.
• WFC3 will observe ultraluminous
infrared galaxies created by
firestorms of star formation after
galaxy-galaxy collisions.
25
WFC3 Panchromatic Imaging
of Star-Forming Regions
•
Ultraviolet observations reveal young stars
that are flooding their surroundings with
intense ultraviolet light.
•
Infrared observations penetrate
deeper into regions heavily
obscured by dust.
26
WFC3 and the Solar System
• WFC3 resolution
and sensitivity will
capture fine details
of unique events in
our evolving Solar
System.
• WFC3 studies of the Solar System will help us
understand how planetary systems evolve and
what conditions are needed to support life.
27