DOC PREVIEW
UW ASTR 101 - Galaxy

This preview shows page 1-2-3-4 out of 12 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

8/9/11 1 1 By the end of today, you should know: • Theories of galaxy formation and evolution • Redshift, “lookback time”, and “light-travel time” • Difference between nearby galaxies and very distant galaxies • What Quasars and ULIRGS are – Quasars as “beacons of light” shining on the universe – Time Variability as a tool for measuring accretion disk sizes (Exercise) 1 Themes • Conservation of: – Angular momentum – Energy • Spectra – Continuous – Broad Emission Lines • Star Formation (and AGN) triggering 2 Galaxy Review - 3 types • Elliptical – No Star Formation (red) – Random Orbits • Spiral – Recent Star Formation (blue) – Ordered Motion in disk • random in Halo • Irregular – Everything else… M87 Pinwheel Galaxy NGC 1427A Galaxy Formation Fgravity Conservation of: Energy8/9/11 2 Angular Momentum Determines Galaxy Type? Conservation of: Angular momentum Better theory for Elliptical Formation: “Hierarchical” scenario 7 Ellipticals are concentrated near the centers of galaxy clusters! Merging Galaxies Another Way to Make Ellipticals Arp 148 Antennae8/9/11 3 9 Merger Simulations (SMBH) http://www.youtube.com/watch?v=IDJNLk274Pk (Milky Way and Andromeda) • http://www.youtube.com/watch?v=dJRc37D2ZZY Review of Galaxy Formation • Galaxies Form from the Gravitational Collapse of Gigantic Clouds of Gas – Collapse stops once Stars Form • Spirals – Collapse a Rotating cloud • Ellipticals – Collapse a NON-Rotating cloud or – Merge 2 spirals together Some Quick Vocabulary • Lookback Time - amount of time from when light from an object was emitted to when that light reaches Earth – telescopes as a time machine – Sun: 8 light-minutes away • Redshift - a unitless number that describes distance. • z=0 Earth, z = vr/c = (λobserved-λrest)/λrest Redshift vs. Lookback Time (different ways to describe the same thing) • 0 • 0.1 • 0.5 • 1.0 • 2.0 • 6.0 • Infinity • 0 billion yr • 1.3 billion yr • 5.0 billion yr • 7.7 billion yr • 10.3 billion yr • 12.7 billion yr • 13.7 billion yr8/9/11 4 13 Why do galaxies at high redshift look irregular and bluish? 1. Still forming 2. Still have star formation Looking at Distant Objects 15 16 Other galaxies we see at high redshift: • ULIRGS – Ultra-Luminous InfraRed GalaxieS • Quasars – QUASi-stellAr Radio sources8/9/11 5 17 ULIRGS Ultra-luminous Infrared Galaxies • Infrared means there is lots of DUST • Spectrum: Both point to Star formation! 18 ULIRGS are often associated with galaxy mergers • Merger triggers star formation 19 25 Quasars: Quasi-Stellar Objects8/9/11 6 Quasars: Quasi-Stellar Objects 1. What is a quasar? 2. What powers a quasar? 3. What evidence convinced astronomers they are active galaxies at great distances? Quasars ALL show high redshifts in their emission lines. Very hot thermal radiation Spectra Continuous Broad Emission Lines Percentage change in the wavelength from the rest wavelength is equal to the fraction the “radial velocity” of the object is relative to the speed of light. This is called the “cosmological redshift” or “z” for short. Redshift 1. What do we mean by a cosmological redshift? How does this redshift differ from a Doppler redshift? How does it differ from a gravitational redshift?8/9/11 7 Gravitational Redshift - Only important when in the vicinity of a large mass Broad Emission Lines Due to Doppler Shift Doppler Effect: Flux 0 km/s Radial Velocity Moving toward us Moving away from us 27 27 Artwork credit: NASA/JPL-Caltech"Active galactic nucleus (AGN) Conservation of: Angular momentum Spectra Continuous Quasars • Every Galaxy Probably has a Supermassive Black Hole at its center (Millions to Billions Times the Mass of the Sun!) and likely goes through a quasar phase. • Gas can fall onto the black hole – Gravitational Potential Energy Radiative Energy • The Galaxy Shines Crazy Bright as a Quasar – Can Shine at all wavelengths, from radio to Gamma-Rays8/9/11 8 Quasars • Quasars are the most distant galaxies we can see – Most distant quasar: z = 6.4 (12.8 billion light-years!) Update: z = 7.1 (~13 billion ly) • A typical quasar is ~2 trillion times more luminous than our Sun! Somewhere stages (3) and (4), galaxy is a quasar. “Quasar Phase” in Galaxy Formation Quasars: Quasi-Stellar Objects Left: optical Below: Radio Waves Radio Galaxies Centaurus A 10 million light years away8/9/11 9 Conservation of: Energy Quasars: extremely luminous AND extremely far away. SMBH feeding at the center of an otherwise “normal” galaxy. PG 0052+251 1.4 billion light years away Quasar at core of “normal” spiral PHL 909 1.5 billion light years away Quasar at core of “normal” elliptical IRAS045005-2958 A collision occurring at 1 million mph Core ripped out of the galaxy. Star (in our galaxy) Quasar (3 billion light years away!!!) Ring PG 1012+008 1.6 billion light years away Merger or mergers?8/9/11 10 Are there any quasars in existence anywhere in the Universe at this time? Yes? No? Reasoning? 1. High luminosities much, much greater than the Milky Way 2. Emission is mostly nonstellar (as opposed to ULIRGS) 3. Often exhibit jets in radio (explosive activity) 4. Optical spectra show rapid internal motion within energy-producing region 5. Energy output highly variable over short time frames (days in gamma-rays) 40 Quasars and the Lyman- α Forest • Quasars “illuminate” the inter-galactic medium (i.e. Hydrogen clouds in between galaxies) 408/9/11 11 41 Quasars and the Lyman- α Forest Very hot thermal radiation 42 Lensed Quasars Einstein Cross Look for discrepant emission lines taken from Hall et al 2000 (CNOC2) 44 Lensed quasars 20 Background, lensed galaxies are BLUER8/9/11 12 45 Double Einstein Ring 46 Review • Hierarchical scenario is the accepted theory for galaxy formation • Galaxy evolution: Star formation seems to “die out” over time as gas is used up • Galaxy mergers can trigger star formation: ULIRGS • Mergers may also trigger AGN • Quasars are useful because they provide a “backlight” for studying the universe – Lyman-alpha forest – Lensed quasars


View Full Document

UW ASTR 101 - Galaxy

Documents in this Course
The Sun

The Sun

5 pages

Load more
Download Galaxy
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Galaxy and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Galaxy 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?