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3 Astro 3303 Galaxies across Cosmic Time A core course in the new Astronomy major with a general astronomy concentration Prereqs: Some background in physics and math. Some astronomy helps; otherwise get hold of any intro astro textbook and read Appendices A & B in the textbook. Textbook: Extragalactic Astronomy and Cosmology by Peter Schneider

5 Fall 2013 Astro Required work: 10 homework assignments 2 in-class tests (30 min each) on M Oct 07 and M Nov 11 (no makeups except in cases of emergency/illness) Final paper/project including an in-class presentation during last week of class (notice the advanced warning!) In class activities and exercises (no makeups for these) A portfolio in which you will keep all of your work done before the end of classes. You should plan on bringing this to class regularly. Pick up today s portfolio handout (1 page)

6 I am *not* Dominik Dominik is a distinguished 2 nd year faculty member at Cornell. He will introduce himself further when he starts lecture in a couple of weeks.

7 A bit about me (Martha Haynes) B.A., Wellesley College M.S. and Ph.D. Indiana University Postdoc, staff scientist, Arecibo Observatory (Puerto Rico), National Astronomy and Ionosphere Center Assistant director, Green Bank Observatory (West Virginia), National Radio Astronomy Observatory Cornell faculty since 1983 (!) Interim president, Associated Universities, Inc (AUI not for profit NGO based in Washington DC, during sabbatic leave) Visiting scientist: Mt. Stromlo Observatory (Australia), European Southern Observatory (Germany), Obs. Astron.&Univ. Milano/Firenze/Bologna (Italy) Vice-President, International Astronomical Union Vice-Chair, National Research Council s 2010 Astronomy & Astrophysics Decade Survey OSTP designee to Astronomy & Astrophysics Advisory Cmte

a galaxy s evolution of its local intergalactic environment.

8 A bit about me My research uses many telescopes but especially Arecibo. I study observational cosmology, the structure of the universe and the impact on a galaxy s evolution of its local intergalactic environment. ALFALFA: The Arecibo Legacy Fast ALFA Survey Me with ALFA: The Arecibo L-band Feed Array a 7 pixel radio camera

9 The Undergraduate ALFALFA Team at Arecibo

10 CCAT: 25 meter submm telescope CCAT Site on C. Chajnantor Me, at 18,400 feet in the high Atacama desert in Chile, at the site of the future CCAT (submillimeter wavelength telescope)

11 HW #1 due Mon Sep 9th HW #1 goes here

12 TOPCAT Try to download and install it; if you have problems check with me!

13 Astro 3303 For next Wed, read Chapter 1 in textbook Bring your portfolio, including PE #1 For Mon Sep 9, do homework #1 Software/database/archive tools we will access and use: TOPCAT: SAOImage:DS9 SDSS: N-S Atlas: NASA Extragalactic Database (NED): VAO:

14 Your Astro3303 portfolio Astronomers observe. The sky (and objects in the sky) change(s). Astronomers keep records of what they observe: their impressions, what happened, what they think. => We ll use the portfolio to develop your thinking and approach to interpreting images and datasets and to keep track of useful information. At the end of the semester, your portfolio should contain all of your assignments, including the homeworks and in-class activities. During many classes, we will hand out assignments which will be done, in large part, during class. If you are not in class, you cannot make up the assignment. Everyone is allowed to miss a reasonable number of classes for good reasons. But if you re not here, you miss out on the discussion and participation, so there is no way to make up the activity

15 Portfolio exercise: the first entry Today s entry includes some important numbers, many of which you may be familiar with. It also includes some useful definitions and concepts which we will review in the coming weeks. Be sure to bring this handout (and your portfolio) with you next Wednesday (yes, we don t meet on Monday, because it is Labor Day). Review any concepts you are not familiar with, especially units of distance, magnitudes, solar units, etc.

16 History - and Fate - of the Universe Hot Big Bang Model 13.8 billion years ago, the universe was much hotter and much denser than it is today. A tremendous release of energy took place: the Big Bang event. Since then, the universe has been expanding. Will the universe keep expanding? Or will the expansion halt? When did the galaxies form? How do galaxies evolve?

17 Hubble s Law The dominant motion in the Universe is the smooth expansion known as the Hubble flow. Hubble s Law: V obs = H o D where H o is Hubble s constant and D is distance in Mpc Spread in velocity for objects in a cluster due to their orbital motion within the cluster. Recessional velocity = = 1+v/c 1-v/c 1 Hubble s constant X Distance Hubble s constant = 70 (?67.4?) km/s per Mpc

18 The Doppler Shift Simple Doppler formula This reduces to the simple Doppler formula (above) for v << c. Relativisitic Doppler formula Light emitted by a source moving towards us appears bluer. Light emitted by a source moving away from us appears redder. The amount of blueshift or redshift depends on source velocity.

19 Relativistic Doppler Formula We observed galaxies/quasars with redshifts of ~7-10 That does not mean that they are traveling faster than the speed of light This reduces to the simple Doppler formula for v << c. For z= 10, this becomes ( ) v = c 1 - = c In fact, the Cosmic Microwave Background photons have a redshift z = 1000! (Stay tuned..)

20 Hierarchical models How did the structures we see today form and evolve? Do hierarchical models predict this behavior? Can they give us any insight into what is going on? time

WMAP+BAO+SN parameter summary Description Symbol Value Age of universe t H 13.73 ± 0.12 Gyr Hubble constant H o 70.1 ± 1.

21 WMAP+BAO+SN parameter summary Description Symbol Value Age of universe t H ± 0.12 Gyr Hubble constant H o 70.1 ± 1.3 km/s/mpc Baryon density Ω b ± Dark matter density Ω dm ± Dark energy density Ω Λ ± Age at decoupling t cmb ,-3115 yr

22 2013 Planck parameter summary Description Symbol Value Age of universe t H ± Gyr Hubble constant H o 67.4 ± 1.4 km/s/mpc Matter density Ω m ± Baryon density Ω b ± Dark matter density Ω dm ± Dark energy density Ω Λ ± 0.020

Astronomy Picture of the Day: Aug 25, 2013 http://www.apod.nasa.gov/apod/ What about this image is interesting?

24 Astronomy Picture of the Day: Aug 25, What about this image is interesting? What questions do you want to know the answers to? The Colliding Spiral Galaxies of Arp 271 Credit & Copyright: Gemini Observatory, GMOS-South, NSF

Astronomy Picture of the Day: Aug 25, 2013 http://www.apod.nasa.

25 Astronomy Picture of the Day: Aug 25, What about this image is interesting? What questions do you want to know the answers to?

26 Astronomical objects: galaxy What is a galaxy? Composed of billions of stars, gas clouds, dust clouds, diffuse gas, black holes, etc. Variable shape. Milky Way has disk, bulge, halo (why?) Individual objects have different temperatures from really cold (< 3K) to really hot (>10 9 K) Gives off thermal radiation (stars, dust) and non-thermal radiation (energetic sources like supernova remnants, black holes, etc) Can be from 10 6 solar masses to ~10 12 solar masses Individual components generate energy by different processes thermonuclear fusion (stars), collisions among particles, magnetic fields, etc. (i.e. many different mechanisms). Individual components visible at different wavelengths.

Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.

27 Astronomy Picture of the Day A Milky Way Shadow at Loch Ard Gorge (Australia) Credit & Copyright: Alex Cherney Terrastro

28 Definition: what is a galaxy? A galaxy is a self-gravitating collection of about 10 6 to stars, plus an amount up to ~same by mass of gas, and about 10X as much by mass of dark matter. The stars and gas are about 70% hydrogen by mass and 25% helium, the rest being heavier elements (called "metals"). Typical scales are: masses between 10 6 to M (1 solar mass is 2 x kg), and sizes ~ kpc (1 pc = 3.1 x m). Galaxies that rotate have P rot ~ Myr at about 100 km/s. The average separation of galaxies is about 1 Mpc. Between galaxies there is very diffuse hot gas, called the intergalactic medium (IGM); in clusters this is called the intracluster medium (ICM). It was much denser in the past before galaxies formed, accreted the gas and converted it into stars.

29 Morphological Classification

31 Galaxy Zoo

32 Galaxy Zoo

33 Galaxy Zoo

34 Galaxy Zoo What physical processes drive morphological differences? Do galaxies change their morphology as they evolve? Morphological segregation Ellipticals dominate in high density regions (clusters) Spirals dominate low density regions Mergers/.interactions/disturbed morphology more common at earlier epochs in the history of the universe.

35 The Sombrero Galaxy

36 IZw 18

37 Hoag s Object Ring galaxy

38 NGC 520: the Flying Fish

39 Arp 295

40 The Perseus Cluster

41 NGC 1275 (galaxy in a cluster of galaxies)

42 Abell 370

43 The Milky Way as a Galaxy Diameter ~25 kpc R ~ 8 kpc Thickness ~ 4 kpc

44 The Milky Way See the table of basic MW properties in PE #1. The Milky Way is known in a fair amount of detail, and both the gas and stars split cleanly into different populations or phases.

45 Constituents of the Milky Way The Milky Way is known in a fair amount of detail, and both the gas and stars split cleanly into different populations or phases. Stars: Disk: ~5 x M Bulge: ~ M Halo: ~10 9 M Globulars: ~10 8 M Gas: H 2 clouds: ~ 3 x 10 9 M HI gas: 5 x 10 9 M HII regions: ~10 8 M Dark matter: Halo: 5.5 x to 2 x M

46 The size of a galaxy Optical image Starlight

47 The size of a galaxy Radio image Atomic gas (HI) Optical image Starlight

48 Rotation curves: V(R) : variation of rotation speed with distance from center of galaxy V rad (R) : observed variation of radial velocity with distance from center

49 Portfolio Ex #1 Messier 31 The Andromeda nebula (galaxy) NGC 205 Consider the two small galaxies: M32 and NGC 205. M32

50 PE #1: Group discussion How would you determine whether or not M32 and NGC 205 were small satellites of M31 or rather more distant galaxies (in the background)? Be very specific about what you would measure and how that would lead you to the answer. M31 has an observed heliocentric radial velocity of -300 km/s. Is that interesting/surprising? What does it tell you?

51 The Local Group of Galaxies Two main galaxies: Milky Way Andromeda (M31) Lots of dwarf galaxies Distance from MW to Andromeda: 2.5 Mlyr = 778 kpc Cartoon from E. Grebel

52 Elliptical galaxies display a variety of sizes and masses Giant elliptical galaxies can be 20 times larger than the Milky Way Dwarf elliptical galaxies are extremely common and can contain as few as a million stars M32 M31 - Andromeda

larger than the Milky Way Dwarf elliptical galaxies

53 Elliptical galaxies display a variety of sizes and masses Giant elliptical galaxies can be 20 times larger than the Milky Way Dwarf elliptical galaxies are extremely common and can contain as few as a million stars

54 An elliptical galaxy This is a very bright elliptical galaxy, called a cd galaxy. Its outer envelope extends to more than 1,000,000 light years, many times bigger than the Milky Way.

55 Lots of elliptical galaxies It is located in the Coma cluster of galaxies. Clusters contain thousands of galaxies.

56 The Perseus Cluster

57 Luminosity function The L.F. gives the number of galaxies per unit volume per luminosity (or magnitude) interval. Schechter (1980) expressed the LF as an analytic function with both a power law and an exponential: = faint end slope L * = luminosity at knee of L.F. Bright galaxies are rare. Low L galaxies only seen nearby. (L) cd s too bright! log L

58 For next time (Wed Sep 4) Read Chapter 1 and Appendix A & B in Schneider s textbook Start looking at HW #1 (due Mon Sep 9 th ) Try to download and install TOPCAT and learn to use it! Please bring your portfolio for next time.

Galaxies. The majority of known galaxies fall into one of three major classes: spirals (78 %), ellipticals (18 %) and irregulars (4 %).

Galaxies. The majority of known galaxies fall into one of three major classes: spirals (78 %), ellipticals (18 %) and irregulars (4 %). Galaxies Collection of stars, gas and dust bound together by their common gravitational pull. Galaxies range from 10,000 to 200,000 light-years in size. 1781 Charles Messier 1923 Edwin Hubble The distribution