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El universo:

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The image shows the Hubble Deep Field: the Hubble Space Telescope was pointed at ... determinations of the extragalactic distance scale. LMC. Morphologically: ... – PowerPoint PPT presentation

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Title: El universo:


1
El universo
Edad 13.7 millardos de años (1 de
error) Expansión 71 km/sec/Mpc actualmente (5
de error) 73 Energía oscura 23 materia
oscura fría 4 átomos de materia
ordinaria Ocurrió una etapa de expansión rápida
(inflación) Se expandirá para siempre.
2
The Galaxies
We assume the stars are grouped together into
galaxies and that these form the basic building
blocks of the visible matter in the Universe.
  • The image shows the Hubble Deep Field the Hubble
    Space Telescope was pointed at the same region of
    the sky (in the constellation Ursa Major) for 10
    days and images were combined to give the most
    distant optical view of the Universe. Almost
    every object is a galaxy, and objects down to
    visual magnitude 30 can be seen.

3
Classification of Galaxies
  • Using a system proposed by Edwin Hubble (1926
    1936), astronomers classify galaxies into three
    major types
  • Spiral (75)
  • Elliptical (20)
  • Irregular (5)
  • The sizes of all three types span a wide range,
    from
  • dwarf galaxies
  • which contain 100 million (108) stars
  • to
  • giant galaxies
  • which contain 1 trillion (1012) stars

4
The Hubble Classification
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9
Spiral Galaxies
  • have a disk component and bulge halo
    (spheroidal component)
  • disk contains an ISM of gas dust
  • relative sizes of bulge/disk amount of ISM vary
    among galaxies
  • contain both blue red stars

10
Spiral Galaxies
Properties Mass 109 - 1012 M? Diameter 5 -
50 kpc Luminosity 108 - 1011 L?
  • Structure Dynamics
  • Disk Spheroid
  • Supported by relatively rapid rotation, but in
    the spheroid - random motions.
  • 10-20 gas
  • On-going star formation in the disks
  • Mix of Pop I and Pop II stars

NGC 1232 is located in the constellation Eridanus
. The distance is about 100 million light-years.
The central areas contain older stars of red
color, while the spiral arms are populated by
young, blue stars and many star-forming regions.
11
Barred Spiral Galaxies
  • Some spiral galaxies have a bar of stars cutting
    through their centers.
  • spiral arms are attached to the ends of the bar
  • we call them barred spiral galaxies.
  • Some galaxies have disks with no spiral arms.
  • we call then lenticular galaxies
  • they look like a lens seen edge-on
  • They contain less cool gas than normal spirals.

12
Elliptical Galaxies
  • only have a spheroidal component no disk
    component
  • very little ISM, which is mostly low-density and
    ionized.
  • contain mostly red stars

13
Elliptical Galaxies
Properties Mass 105 - 1013 M? Diameter 1 -
200 kpc Luminosity 106 - 1012 L?
  • Structure Dynamics
  • Spheroid of old stars with little gas or dust
  • Supported by random motions of stars with some
    very slow rotation
  • Very little or no gas or dust
  • Star formation ended billions of years ago
  • See only old Pop II stars

14
Irregular Galaxies
  • none of the above category neither spiral nor
    elliptical
  • appear white dusty with ISM
  • have more in common with the disk component of
    spirals
  • distant galaxies are more likely to be irregular
  • they were more common when the Universe was young

15
Irregular Galaxies
Properties Mass 106 - 1011 M? Diameter 1 -
10 kpc Luminosity 106 - few x 109 L?
Structure Dynamics Chaotic structure, lots of
young blue stars Moderate rotation in
Irregulars, but very chaotic motions as well.
  • Irregulars
  • Can range up to 90 gas
  • On-going star formation
  • Dominated by young Pop I stars
  • Dwarf Irregulars
  • Very metal poor (lt1 solar)
  • Forming stars for the first time only now.

16
Groups and Clusters of Galaxies
  • Among large galaxies
  • most (7585) are spirals
  • they tend to associate in loose groups of several
    galaxies
  • Some galaxies are associate in clusters.
  • contain hundreds of galaxies
  • Our Local Group (at least 40) is an example.
  • dominated by two large spirals
  • the Milky Way
  • Andromeda

17
LMC
  • The Large Magellanic Cloud is one of the closest
    galaxies 50 kpc. The Sagitarrius dwarf is at 24
    kpc.
  • It is of fundamental importance for
  • - studies of stellar populations
  • - interstellar medium
  • - dark objects in the Galactic Halo
    through microlensing
  • - determinations of the extragalactic
    distance scale

18
LMC
  • Morphologically
  • In the optical wavelength is dominated by the
    bar, regions of strong star formation, and dust
    absorption.
  • - in the near IR is more uniform, hint of
    some spiral structure (de Vaucouleurs Freeman
    1973), but with very low contrast.
  • The LMC is generally considered an irregular
    galaxy as a result of these characteristics. It
    is in fact the prototype of the class of galaxies
    called Magellanic Irregulars'' (de Vaucouleurs
    Freeman 1973).

19
LMC
  • The kinematical properties
  • Gas HI maps (Kim et al 1998).
  • From discrete LMC tracers
  • (Gyuk, Dalal Griest 2000).
  • A common result from all these studies is
    that the line-of-sight velocity dispersion of the
    tracers is at least a factor of 2 smaller than
    their rotation velocity. This implies that the
    LMC is kinematically cold, and must therefore be
    a disk system.

20
SMC
  • The Small Magellanic Cloud (SMC) dwarf galaxy is
    a satellite galaxy of our Milky Way.
  • It contains numerous emission nebulae, which are
    clouds of gas that glow red as the hydrogen gas
    they contain is ionised by radiation from nearby
    hot young stars.
  • The SMC lies about 185,000 light year from Earth,
    in the constellation Tucana.

21
Regions of the Milky Way Galaxy
  • The Milky Way Galaxy consists of a thin disk
    about 100,000 light-years in diameter with a
    central bulge.
  • The spherical region surrounding the entire disk
    is called the halo.

Sun is in disk, 28,000 l.y. out from center
22
Regions of the Milky Way Galaxy
  • Disk
  • younger generation of stars
  • contains gas and dust
  • location of the open clusters
  • Bulge
  • mixture of both young and old stars
  • Halo
  • older generation of stars
  • contains no gas or dust
  • location of the globular clusters
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