Science with the New Hubble Instruments. Ken Sembach STScI Hubble Project Scientist

Transcription

1 Science with the New Hubble Instruments Ken Sembach STScI Hubble Project Scientist 1

2 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

3 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 nm) Improves HST sensitivity by at least 10x Near-ultraviolet channel (180 nm nm) Replaces COSTAR during SM4 3

4 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

5 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

6 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

7 Intensity 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

8 A Hubble Spectrum is a Beautiful Thing! 8

9 COS Extracts Information from Light Spectral lines contain information Question Information Observable quantity What is it? Chemical composition Pattern of lines What state? Molecular/atomic/ionic Pattern of lines How hot? Temperature Widths of lines How much? Quantity Strengths of lines How fast? Velocity Wavelengths of lines Where is it? Location (redshift) Wavelengths of lines 9

10 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. λ obs λ abs The faster the recession, the greater the redshift. λ obs λ abs Wavelength λ 10

11 Redshift and Cosmic Expansion Recession velocity of galaxies H 0 d v r Hubble s Law v r = H 0 d v r = velocity of recession d = distance H 0 = Hubble s constant H 0 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

12 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

13 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

14 What is the Density of the Intergalactic Medium? Air has a density of ~ 3x10 19 molecules per cubic centimeter. This is about 30 billion billion molecules. 1 cubic centimeter is about the size of a sugar cube. The Sun s photosphere has a density of about 10 9 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! 1 cc 3 million light years 14

15 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

16 Evolution of the Cosmic Web of Matter 16

17 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) K K 10 8 K Figure from Kang et al

18 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

19 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

20 One Way to Study Dark Matter is to Observe Its Effect on Light from Distant Objects 20

21 A Map of the Dark Matter Bullet Cluster Hubble image + Chandra hot gas detection => Dark Matter distribution (blue) 21

22 HST Images of Type Ia Supernovae 22

23 Expansion History of the Universe 1 Constant or faster in past (expected) Redshift, z 0.1 Slower in past (observed!) Farther in the past 0.01 Riess et al. (1998) Perlmutter et al. (1999) 100 1,000 10,000 Luminosity distance, d L (Mpc) 23

24 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

25 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

26 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

27 WFC3 resolution and sensitivity will capture fine details of unique events in our evolving Solar System. WFC3 and the 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