Hubble Tuning Fork DiagramLACC: §25.2, 3, 5

• Ellipticals

• Spirals (including Barred Spirals)

• Irregular

An attempt to answer the “big questions”: where are we? what is the universe made of?

1Thursday, May 13, 2010

Galaxies like colorful pieces of candy fill the Hubble Deep Field - humanity's most distant yet optical view of the Universe. The dimmest, some as faint as 30th magnitude (about four billion times fainter than stars visible to the

unaided eye), are the most distant galaxies and represent what the Universe looked like in the extreme past, perhaps less than one billion years after the Big Bang. To make the Deep Field image, astronomers selected an

uncluttered area of the sky [about 2.5 arcmin across] in the constellation Ursa Major (the Big Bear) and pointed the Hubble Space Telescope at a single spot for 10 days accumulating and combining many separate exposures. With

each additional exposure, fainter objects were revealed. The final result can be used to explore the mysteries of galaxy evolution and the infant Universe.

http://apod.nasa.gov/apod/ap980607.html

2Thursday, May 13, 2010

http://ifa.hawaii.edu/~barnes/ast110_06/trotn.html

Hubble Tuning-Fork Diagram

3Thursday, May 13, 2010

Types of Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

All bright galaxies fall into one of three broad classes according to their shape:

• Spiral Galaxies (~75%) • Elliptical Galaxies (20%) • Irregular Galaxies (5%)

4Thursday, May 13, 2010

Types of Galaxies

http://zebu.uoregon.edu/~imamura/123/lecture-3/lecture-3.html

Despite the fact that the Hubble Sequence is based only on the appearance of galaxies (morphology of galaxies), several physical

properties of galaxies vary smoothly along the sequence. We have,little gas and dust <----------------------> lots of gas and dust

mainly Pop II stars <----------------------> Pop I & II starsReddish <----------------------------------> Bluish

little ongoing star formation <------------> star formationlarge bulge <------------------------------> small bulge

tight,smooth arms <---------> open, loose armsMass: 108-1013 MSun (Ellipticals) <--> 1012-109 MSun (Spirals)

5Thursday, May 13, 2010

Types of Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

Spiral Galaxies

Properties:• Mass: 109 - 1012 Msun

• Diameter: 5 - 50 kpc• Luminosity: 108 - 1011 Lsun

Structure & Dynamics:• Disk + Spheroid• Supported by relatively rapid rotation, but spheroid is puffed up by random motions.

Elliptical Galaxies

Properties:• Mass: 105 - 1013 Msun

• Diameter: 1 - 200 kpc• Luminosity: 106 - 1012 Lsun

Structure & Dynamics:• Spheroid of old stars with little gas or dust• Supported by random motions of stars with some very slow rotation

Irregular Galaxies

Properties:• Mass: 106 - 1011 Msun

• Diameter: 1 - 10 kpc• Luminosity: 106 - few x 109 Lsun

Structure & Dynamics:• Chaotic structure, lots of young blue stars• Moderate rotation in Irregulars, but very chaotic motions as well.

6Thursday, May 13, 2010

Spiral Galaxies

http://astronomyonline.org/Astrophotography/GalaxyMorphology.asp

Classification Description

Sa Bright core, tightly wound spiral arms

SbCore dimmer than Sa, spiral arms more loose

ScCore dimmer than Sb, open spiral structure, more dust and gas

SdDim core, loosely wrapped spiral structure, lots of dust and gas and new star growth

7Thursday, May 13, 2010

Barred Spiral Galaxies

http://astronomyonline.org/Astrophotography/GalaxyMorphology.asp

Classification Description

SBa Bright core, tightly wound spiral arms

SBbCore dimmer than SBa, spiral arms more loose

SBcCore dimmer than SBb, open spiral structure, more dust and gas

SBdDim core, loosely wrapped spiral structure, lots of dust and gas and new star growth

8Thursday, May 13, 2010

Spiral Galaxies

http://astronomyonline.org/Astrophotography/GalaxyMorphology.asp

Some other important properties of spiral galaxies include (Sparke and Gallagher, page 172 – 214):• Spiral galaxies produce most of the luminous light in the

Universe due to new star birth in the spiral arms• Majority of galaxies in the Universe are spiral galaxies• Half of all spiral galaxies are in the bared spiral class• Spiral galaxies obey the Tully-Fisher relation – brighter

galaxies rotate faster• Spiral galaxy rotation curves are dominated by Dark

Matter• Rotation of stars in the spiral arms are organized while

the rotation of stars in the bulge are not (random rotation orbits about the nucleus)

9Thursday, May 13, 2010

Elliptical Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

Type E: Ellipticals

Show little internal structure: • Elliptical in shape • No disks, spiral arms, or dust lanes • Brightest stars are redClassified by the degree of apparent flatness:

• E0 is circular • E7 is flattest (~3:1 aspect ratio)

10Thursday, May 13, 2010

Irregular Galaxies

http://updatecenter.britannica.com/art?assemblyId=17808&type=A

11Thursday, May 13, 2010

Irregular Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

Type I: Irregulars

Show an irregular, often chaotic structure.Little evidence of systematic rotation.

Catch-all class: • Proposed systematic subclasses, but many

irregulars defy classification.

Significant dwarf irregular population, classified as "dI"

12Thursday, May 13, 2010

Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

Relative Stellar & Gas Content [mass to light ratio]Spirals: • Range is ~10-20% gas • On-going star formation in the disks • Mix of Pop I and Pop II starsEllipticals: • Very little or no gas or dust • Star formation ended billions of years ago • See only old Pop II starsIrregulars: • Can range up to 90% gas • Often a great deal of on-going star formation • Dominated by young Pop I starsDwarf Irregulars: • Very metal poor (<1% solar) • Forming stars for the first time only now.

13Thursday, May 13, 2010

Dwarf Galaxies

http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/types.html

Dwarf Galaxies

Low-luminosity Ellipticals & Irregulars. • Significant number of dwarfs • Most common type of galaxy by number

There are no (convincing) Dwarf Spirals.

Possibilities: • Small versions of their larger cousins • Different population of objects despite their

superficial similarities to larger E's and Irr's

14Thursday, May 13, 2010

Hubble Tuning Fork DiagramLACC: §25.2, 3, 5

• Ellipticals: 20% of galaxies, E0 (spherical) to E7 (elongated), smallest and largest, population II stars, no dust and gas, highest mass to light ratio

• Spirals (including Barred Spirals): 75% of galaxies (1/2 barred, 1/2 not barred), medium sized, population I and II stars, dust and gas in disk, no dwarfs

• Irregular: random shape, small, lots of star formation, lots of dust and gas, lowest mass to light ratio

An attempt to answer the “big questions”: where are we? what is the universe made of?

15Thursday, May 13, 2010

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.

• Ch. 25, pp. 577-578: 3.

Due at the beginning of next week’s first class period (unless there is a test that week, in which

case it’s due the same period as the test).

Be working on your Distance Ladders.

16Thursday, May 13, 2010

GalaxiesLACC: §25.2, 3, 5

• Measuring the Distances to Galaxies

• Galaxy Evolution

• Distribution of Galaxies

An attempt to answer the “big questions”: where are we? what is the universe made of?

17Thursday, May 13, 2010

Galaxy Formation

http://outreach.atnf.csiro.au/education/senior/cosmicengine/galaxy_formation.html

18Thursday, May 13, 2010

Spiral Galaxies: Supermassive Black Holes

http://spaceflightnow.com/news/n0006/05hstblackholes/

The results ... show a close relationship between the black hole mass and the stars that comprise an elliptical galaxy or the central bulge stars of a spiral galaxy.

19Thursday, May 13, 2010

Elliptical Galaxies: Supermassive Black Hole

http://spaceflightnow.com/news/n0006/05hstblackholes/

Though much more analysis remains, an initial look at Hubble evidence favors the idea that titanic black holes did not precede a galaxy's birth but instead co-evolved with the galaxy by trapping a surprisingly exact percentage of the mass of the bulbous hub of stars and gas in a galaxy.

20Thursday, May 13, 2010

Galaxy Mergers

http://www.galaxydynamics.org/spiralmetamorphosis.html (6 min)

The Milky Way and the Andromeda galaxy will likely fall together and merge within a few billion years. In this speculative simulation, the two galaxies flyby one another, exciting tidal tails and bridges and collide on a second pass finally merging after several convulsions. The last remnants of the smashed spirals show up as shells and ripples surrounding a newborn elliptical galaxy.

http://www.youtube.com/watch?v=dJRc37D2ZZY (1 min)

21Thursday, May 13, 2010

Galaxy Collisions

http://www.theage.com.au/news/national/on-a-collision-course-or-uniting-as-an-intergalactic-super-

system/2008/04/24/1208743153745.html

22Thursday, May 13, 2010

Distant Ladder

http://universe-review.ca/R02-07-candle.htm

23Thursday, May 13, 2010

The Tully-Fisher Relation

http://physics.uoregon.edu/~jimbrau/astr123/Notes/Chapter24.html#dist

24Thursday, May 13, 2010

The Tully-Fisher Relation

http://www.daviddarling.info/encyclopedia/T/Tully-Fisher_relation.html

An observed relation between the luminosity of spiral galaxies and their maximum rotation velocity. The Tully-Fisher relation is used as a way of estimating distances to spirals. The form is a linear relation between the absolute magnitude of a galaxy and the logarithm of the velocity at the flat part of the rotation curve, although the slopes and intercepts of these relations are different for Sa, Sb, and Sc type galaxies. Approximations made in deriving the relation are that the mass-to-light ratios are constant for all galaxies and that the average surface brightness of all galaxies is also equal.

25Thursday, May 13, 2010

Hubble’s Law

http://www.astronomynotes.com/galaxy/s7.htm

26Thursday, May 13, 2010

The Local Grouphttp://www.astronomy.com/asy/objects/

images/local_group_0305_diagram_800.jpg

27Thursday, May 13, 2010

Galaxy Clusters

http://www.astro.washington.edu/larson/Astro101/LecturesBennett/DistanceScale/expansion.html

28Thursday, May 13, 2010

CL0024+17 Galaxy Cluster

http://apod.nasa.gov/apod/ap070516.html

How do we know that dark matter isn't just normal matter exhibiting strange gravity? A new observation of gravitationally magnified faint galaxies far in the distance behind a massive cluster of galaxies is shedding new dark on the subject. The above detailed image from the Hubble Space Telescope indicates that a huge ring of dark matter likely exists surrounding the center of CL0024+17 that has no normal matter counterpart. What is visible in the above image, first and foremost, are many spectacular galaxies that are part of CL0024+17 itself, typically appearing tan in color. Next, a close inspection of the cluster center shows several unusual and repeated galaxy shapes, typically more blue. These are multiple images of a few distant galaxies, showing that the cluster is a strong gravitational lens. It is the relatively weak distortions of the many distant faint blue galaxies all over the image, however, that indicates the existence of the dark matter ring. The computationally modeled dark matter ring spans about five million light years and been digitally superimposed to the image in diffuse blue. A hypothesis for the formation of the huge dark matter ring holds that it is a transient feature formed when galaxy cluster CL0024+17 collided with another cluster of galaxies about one billion years ago, leaving a ring similar to when a rock is thrown in a pond.

29Thursday, May 13, 2010

The Local Supercluster

http://www.pas.rochester.edu/~afrank/A105/LectureXV/LectureXV.html

The Local GroupThe Local

Supercluster

30Thursday, May 13, 2010

The Local Supercluster

http://www.fas.org/irp/imint/docs/rst/Sect20/A2a.html

This (somewhat blurred) map identifies galaxies and galaxy clusters across a field of view 400 million light years

across

We jump now to a map that carries out to 1,000,000,000 light years which includes the

supercluster the Milky Way lies within:

31Thursday, May 13, 2010

GalaxiesLACC: §25.2, 3, 5

• Measuring the Distances to Galaxies: Cepheid Variable (our Local Group), Tully-Fisher Relation (distant spirals), Hubble’s Law (most distant galaxies)

• Galaxy Evolution: mass of central supermassive black holes match size of central bulge, mergers and cannibalism (Milky Way will collide with Andromeda)

• Distribution of Galaxies: Galaxy Clusters (e.g. Local Group); Galaxy Superclusters (e.g. Virgo Supercluster)

An attempt to answer the “big questions”: where are we? what is the universe made of?

32Thursday, May 13, 2010

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.

• Ch. 25, pp. 577-578: 5 (choose from the following: Cepheid Variables, Cepheid Variables, Tully-Fisher Relation, Type Ia Supernova,

Brights Cluster Galaxy ).

• Ch 26: Tutorial Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due at the beginning of next week’s first class period (unless there is a test that week, in which

case it’s due the same period as the test).

Be working on your Distance Ladders.

33Thursday, May 13, 2010