Other Galaxy Types. Active Galaxies. A diagram of an active galaxy, showing the primary components. Active Galaxies

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1 Other Galaxy Types Active Galaxies Active Galaxies Seyfert galaxies Radio galaxies Quasars Origin??? Different in appearance Produce huge amount of energy Similar mechanism a Galactic mass black hole at the galaxy's center The infalling material onto the black hole produces an accretion disk (many hundreds of light-years across) It is from this accretion disk that the magnetic fields are produced Collisions between atoms produce x-rays and gamma-rays Acceleration of particles produces radio waves unified model "different" kinds of active galaxies only because our angle of view changes??? Seyfert, radio galaxies and quasars may simply be normal galaxies in an active phase??? all galaxies may have dormant black holes??? A diagram of an active galaxy, showing the primary components

2 Accretion Disk - material is being pulled into the black hole from outside the nuclear region Active Galaxies wide range of activities: X-rays and gamma-rays are emitted from the area Radio-jets extend on each side of the galaxy perpendicular to the central accretion disk Rapidly moving gas clouds Active Galaxies faint radio sources rapid rotation of the matter near the center scattered all over the sky do not register on optical plates, too far away to be seen visually they are emitting enormous amount of radio energy violent activity, usually in their cores.

3 M104: The Sombrero Galaxy strong X-Ray emitter unusually high velocities are observed for stars near its center; it may have a black hole of approximately 1 billion solar masses at its core Quasars very far from us detected at high energies (gamma-rays), usually 100 MeV or more (up to several TeV! ) Highly variable most powerful particle accelerators in the Universe Double Lobed Radio Galaxies The total energy in a single radio lobe is about Joules an enormous amount

4 Seyfert Galaxies emission spectral lines in their nuclei, which is evidence of highly excited gas Gravitational lensing Type I - very broad lines -- gas velocities of over 1000 km/sec 2% of all spiral galaxies galaxies without radio lobes but with extremely bright, tiny cores variable After billion years starting out with a very smooth distribution of matter directly after the Big Bang gravity of the more massive clumps of stars starts to attract more matter

5 After billion years larger clumps grow from merging of smaller once After 1-2 billion years after growing to a fraction of the size of our own galaxy, the clumps are large enough for the Hubble Space Telescope to see them After 2-4 billion years larger irregular looking objects form through collisions and mergers between these sub-galactic sized clumps After 4-13 billion years galaxies as we see them today form and take their final shape. The elliptical and the spiral galaxies with old red stellar populations in their centers form first and the spiral galaxies disks form later from infalling surrounding gas.

6 Evolution of Galaxies Different for different types After 2-4 billion years larger irregular looking objects form through collisions and mergers between these sub-galactic sized clumps Resent Observations Colliding Galaxies Evolution of Galaxies Current Theory distance 200 million light years Arp 273 The larger galaxy: is strongly tidally distorted The companion: relatively undisturbed spiral disk, but a luminous, star burst nucleus (one in which there is a burst of new star formation). 1. All galaxies have formed at the same time; they are equally old ~ x 10 9 yrs 2. Different galactic types are at different evolutionary stages Elliptical Galaxies all stars born long ago during giant single star-forming process, exhausting all interstellar star-forming material Spiral Galaxies ongoing star-forming processes 3. Reason for this difference different physical parameters of E & Sp Compactness Rotation Environment Hidden matter

7 Evolution of Galaxies Different for different types Galaxy rotation problem Ellipticals formed remarkably early in the universe while spiral galaxies took much longer to form Galaxy rotation problem Measuring Galactic Rotation Curves Near the galactic center velocities do not increase linearly Actual Galactic Rotation Speeds At large radii the rotation speeds remain pretty much the same flat rotation

8 two mass components that must be added to the bright central bulge and the outer disk very dense core at the center of the galaxy large halo of dark matter that would surround the galaxy -- as much as 90% of the total mass in a galaxy The Solution Model the galactic rotation curve the mass of the galaxy is distributed differently than optical observations would indicate Fritz Zwicky 1933 two classes of dark matter baryonic (all "normal matter composed of baryons: protons, neutrons, and electrons) dark matter MACHOs (Massive Compact Halo Objects) "shadow matter" unknown non-baryonic subatomic particles WIMPs (Weakly Interacting Massive Particles), neutrinos, and axions Dark Matter Estimation from galactic rotation Evolution of Galaxies Current Theory Compactness - Mass/Radius Proportional to the gravitational potential of the system proportional to the amount of energy one has to bring into the system to extend the system to infinity Environment Different galaxies live in different environments Reach clusters contain only E and S0 types Sp & Irr prefer poor clusters Evolution in different environments takes place differently Hidden matter 10 times larger (in average) in E than in Sp Rotation Sp & E rotate in a different way apparently affects their evolution