Cosmic origin exam #3

part 2

Galaxies (major)

• Spiral

• lenticular

• elliptical

Spiral galaxies

• most common - 60% of galaxies

• only major galaxy with active star formation

• disc (spiral) + central bulge

• Barred spiral = 2/3 (SB) a arms closed - c arms spread

• Unbarred = 1/3 (S) a - c

lenticular galaxies

• 20% of galaxies

• disc + central bulge, no spiral

• No active star formation

• S0 no bar

• SB Bar

• flat like spiral

Elliptical galaxies

• 10% of galaxies

• redder, older stars

• spherical

• E0 perfect sphere - E7 oval

elliptical galaxy formation

1. protogalactic cloud collapse with no preferred angular momentum

2. galaxy mergers 2 spiral galaxy merging together

   1. giant elliptical galaxy

   2. largest galaxies in the universe

giant elliptical galaxy

largest galaxies in the universe

Hubble Tuning fork

not an evolution diagram (Hubble though it was)

Other Galaxies

• Irregular

• dwarf galaxies

• dwarf spherical galaxies

Irregular galaxies

• last 10% of major galaxies

• major

Dwarf Galaxies

• not part of the major galaxies

• orbit a (major) host galaxy

Dwarf Spherical Galaxy

• most common galaxy in the universe overall

• not a major galaxy

Ordinary vs Active

Galaxies can be divided into categories ordinary

Ordinary Galaxies

• most light comes from star

• the light is distributed mostly uniformly

• minimal light variability

Active Galaxies

• very bright central bulge

  • 100 times brighter that the rest of the galaxy

• high variability, not distributed uniformly

• light variability on short time scales

• Active galactic nucleus

• 4 types

  • Radio

  • Seyfert

  • Quasar

  • Blazer

Active Galactic Nucleus

• AGN

• supermassive black hole

• billions Ms

• have massive accretion disk

  • actively feeding on matter

• massive relativistic jets

• very common in early universe

Radio Galaxies

• Active galaxy

• almost all giant elliptical galaxies

• characterized by two radio lobes

Seyfert Galaxies

• Active galaxy

• almost all Seyfert galaxies are spirals

• lowest energy/luminosity of active galaxies

• only active galaxy where you can see the host galaxy

Quasar

• most luminous/ energetic

• farthest objects we can see

  • billions of ly away

• oldest object we can see

Blazer

Quasar with relativistic jets pointing at us

Star System

• one or more stars

• you → solar system

Galaxy

• collection of star systems

• you → Milky Way

Group

• About 50 luminous galaxies (not dwarf)

• you → local group

Galaxy Cluster

• About 100 - 1000 luminous galaxies

• you → we aren’t in one

Super Cluster

• 1000 - hundreds of thousands of galaxies

• you → Laniakea Supercluster

  • the virgo supercluster is a lobe of that

Super cluster complex

• galactic filaments

• largest structrue in the universe

• you → Pisces - Cetus supercluster complex

Fritz Zwicky

• 1933

• coma cluster

• first evidence of dark matter

Vera Rubin

• 1965

• Galactic Rotation problem

  • reignites the study of dark matter

• stars on the outer edge of the galaxy move just as fast as stars on the inner part

Dark matter

• Dark matter halo

  • larger than stellar halo

• 90% of galay in dark matter

Dark matter detection

1. Galaxies in cluster - velocities to high

2. Galactic rotation - Vera Rubin

3. Gravitational lensing

Universe’s composition

• Luminous matter - 5%

• Dark matter - 23%

• Dark energy 72%

Einstein

Thought the universe was static but his equation predicted an expanding universe

• added cosmological constant with a minus sign

Redshift

object is moving away

Blueshift

object is moving closer

Edwin Hubble discoveries

• 1929

  1. All (most) all galaxies have redshift → moving away

  2. the further the galaxy the faster its moving

z

• the amount of redshift

• 0 = no redshift

• negative = blueshift

• 13.2 = largest and oldest object we can see