El universo: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.

The GalaxiesThe Galaxies

The image shows the The image shows the

Hubble Deep Field: the Hubble Deep Field: the Hubble Space Telescope Hubble Space Telescope was pointed at the same was pointed at the same region of the sky (in the region of the sky (in the constellation Ursa Major) constellation Ursa Major) for 10 days and images for 10 days and images were combined to give the were combined to give the most distant optical view most distant optical view of the Universe. Almost of the Universe. Almost every object is a galaxy, every object is a galaxy, and objects down to visual and objects down to visual magnitude +30 can be magnitude +30 can be seen. seen.

We assume the stars are grouped together into galaxies and that We assume the stars are grouped together into galaxies and that these form the basic building blocks of the visible matter in the these form the basic building blocks of the visible matter in the Universe.Universe.

Classification of GalaxiesClassification of Galaxies Using a system proposed by Edwin Hubble Using a system proposed by Edwin Hubble

(1926 & 1936), astronomers classify galaxies (1926 & 1936), astronomers classify galaxies into three major types:into three major types:• Spiral (~75%) Spiral (~75%) • Elliptical (20%) Elliptical (20%) • Irregular (5%) Irregular (5%)

The The sizessizes of all three types span a wide of all three types span a wide range, fromrange, from• dwarf galaxiesdwarf galaxies

which contain 100 million (10which contain 100 million (1088) stars) stars

toto• giant galaxies giant galaxies

which contain 1 trillion (10which contain 1 trillion (101212) stars) stars

The Hubble ClassificationThe Hubble Classification

Spiral Galaxies Spiral Galaxies

have a have a disk disk componentcomponent and and bulge & halobulge & halo ( (spheroidal spheroidal componentcomponent))

diskdisk contains an ISM of gas & dustcontains an ISM of gas & dust relative sizes of bulge/disk & amount of ISM vary among relative sizes of bulge/disk & amount of ISM vary among

galaxiesgalaxies contain both blue & red starscontain both blue & red stars

Spiral GalaxiesSpiral Galaxies

Structure & DynamicsStructure & Dynamics: : Disk + Spheroid Disk + Spheroid Supported by relatively rapid Supported by relatively rapid

rotation, but in the spheroid - rotation, but in the spheroid - random motions. random motions.

~10-20% gas ~10-20% gas On-going star formation in the On-going star formation in the

disks disks Mix of Pop I and Pop II starsMix of Pop I and Pop II stars

NGC 1232 is located in the constellation Eridanus . The NGC 1232 is located in the constellation Eridanus . The distance is about 100 million light-years.distance is about 100 million light-years. The central areas contain older stars of red color, while the spiral The central areas contain older stars of red color, while the spiral arms are populated by young, blue stars and many star-forming arms are populated by young, blue stars and many star-forming regions. regions.

PropertiesProperties: : Mass: 109 - 1012 M⊙ Mass: 109 - 1012 M⊙ Diameter: 5 - 50 kpc Diameter: 5 - 50 kpc Luminosity: 108 - 1011 L⊙Luminosity: 108 - 1011 L⊙

Barred Spiral Galaxies Barred Spiral Galaxies Some spiral galaxies have a Some spiral galaxies have a

bar of stars cutting through bar of stars cutting through their centers.their centers.• spiral arms are attached spiral arms are attached

to the ends of the barto the ends of the bar• we call them we call them barred barred

spiral galaxies.spiral galaxies.

Some galaxies have disks Some galaxies have disks with with nono spiral arms. spiral arms.• we call then we call then lenticular galaxieslenticular galaxies• they look like a lens seen edge-they look like a lens seen edge-

onon They contain less cool gas They contain less cool gas

than normal spirals.than normal spirals.

Elliptical GalaxiesElliptical Galaxies only have a only have a spheroidalspheroidal component; component; nono disk disk

componentcomponent very little ISM, which is mostly low-density and very little ISM, which is mostly low-density and

ionized.ionized. contain mostly red starscontain mostly red stars

Elliptical Galaxies Elliptical Galaxies

Structure & DynamicsStructure & Dynamics: : Spheroid of old stars with Spheroid of old stars with

little gas or dust little gas or dust Supported by random Supported by random

motions of stars with some motions of stars with some very slow rotation very slow rotation

Very little or no gas or dust Very little or no gas or dust Star formation ended Star formation ended

billions of years ago billions of years ago See only old Pop II stars See only old Pop II stars

PropertiesProperties: : Mass: 105 - 1013 MMass: 105 - 1013 M⊙⊙

Diameter: 1 - 200 kpc Diameter: 1 - 200 kpc Luminosity: 106 - 1012 L⊙Luminosity: 106 - 1012 L⊙

Irregular GalaxiesIrregular Galaxies

““none of the above” category; none of the above” category; neither spiral nor ellipticalneither spiral nor elliptical

appear white & dusty with appear white & dusty with ISMISM• have more in common with have more in common with

the disk component of the disk component of spiralsspirals

distant galaxies are more distant galaxies are more likely to be irregularlikely to be irregular• they were more common they were more common

when the Universe was when the Universe was youngyoung

Irregular Galaxies Irregular Galaxies

IrregularsIrregulars: : Can range up to 90% gas Can range up to 90% gas On-going star formation On-going star formation Dominated by young Pop I stars Dominated by young Pop I stars Dwarf IrregularsDwarf Irregulars: : Very metal poor (<1% solar) Very metal poor (<1% solar) Forming stars for the Forming stars for the firstfirst time time

only now. only now.

PropertiesProperties: : Mass: 106 - 1011 MMass: 106 - 1011 M⊙⊙

Diameter: 1 - 10 kpc Diameter: 1 - 10 kpc Luminosity: 106 - few x 109 LLuminosity: 106 - few x 109 L⊙⊙ Structure & DynamicsStructure & Dynamics: : Chaotic structure, lots of young Chaotic structure, lots of young blue stars blue stars Moderate rotation in Irregulars, Moderate rotation in Irregulars, but very chaotic motions as well.but very chaotic motions as well.

Groups and Clusters of GalaxiesGroups and Clusters of Galaxies Among large galaxies…Among large galaxies…

• most (75–85%) are spiralsmost (75–85%) are spirals• they tend to associate in loose they tend to associate in loose

groups groups of several galaxiesof several galaxies

Some galaxies are associate in Some galaxies are associate in clustersclusters..• contain hundreds of galaxiescontain hundreds of galaxies

Our Our Local GroupLocal Group (at least 40) is an (at least 40) is an example. example.

dominated by two large dominated by two large spiralsspirals

•the Milky Waythe Milky Way•AndromedaAndromeda

LMCLMC• The Large Magellanic The Large Magellanic

Cloud is one of the Cloud is one of the closest galaxies – 50 kpc. closest galaxies – 50 kpc. The Sagitarrius dwarf is The Sagitarrius dwarf is at 24 kpc.at 24 kpc.

• It is of fundamental It is of fundamental importance for:importance for: - studies of stellar - studies of stellar populationspopulations

- interstellar medium- interstellar medium - dark objects in the - dark objects in the

Galactic Halo through Galactic Halo through microlensing microlensing

- determinations of the - determinations of the extragalactic distance extragalactic distance scale scale

LMCLMC

Morphologically:Morphologically: In the optical wavelength is In the optical wavelength is

dominated by the bar, regions dominated by the bar, regions of strong star formation, and of strong star formation, and dust absorption. dust absorption.

- in the near IR is more - in the near IR is more uniform, hint of some spiral uniform, hint of some spiral structure structure (de Vaucouleurs & (de Vaucouleurs & Freeman 1973),Freeman 1973), but with very but with very low contrast.low contrast.

The LMC is generally The LMC is generally considered an irregular considered an irregular galaxy as a result of these galaxy as a result of these characteristics. It is in fact the characteristics. It is in fact the prototype of the class of prototype of the class of galaxies called “Magellanic galaxies called “Magellanic Irregulars'' Irregulars'' (de Vaucouleurs & (de Vaucouleurs & Freeman 1973).Freeman 1973).

LMCLMC

The The kinematical kinematical properties:properties: Gas – HI maps Gas – HI maps (Kim et al 1998).(Kim et al 1998). From discrete LMC tracers:From discrete LMC tracers: (Gyuk, Dalal & Griest 2000).(Gyuk, Dalal & Griest 2000). A common result from all A common result from all

these studies is that the line-these studies is that the line-of-sight velocity dispersion of of-sight velocity dispersion of the tracers is at least a factor the tracers is at least a factor of 2 smaller than their rotation of 2 smaller than their rotation velocity. This implies that the velocity. This implies that the LMC is kinematically cold, and LMC is kinematically cold, and must therefore be a disk must therefore be a disk system.system.

TypeType Age Age Velocity Velocity dispersion dispersion (km/s) (km/s)

RSGRSG Young Young 1515

HIIHII YoungYoung 66

Carbon Carbon starsstars

YoungYoung 1515

PNsPNs Intermediate Intermediate 2020

LPVLPV OldOld 3333

GCGC OldOld 3030

SMCSMC The Small Magellanic Cloud (SMC) dwarf The Small Magellanic Cloud (SMC) dwarf

galaxy is a satellite galaxy of our Milky Way.galaxy is a satellite galaxy of our Milky Way. It contains numerous emission nebulae, It contains numerous emission nebulae,

which are clouds of gas that glow red as the which are clouds of gas that glow red as the hydrogen gas they contain is ionised by hydrogen gas they contain is ionised by radiation from nearby hot young stars.radiation from nearby hot young stars.

The SMC lies about 185,000 light year from The SMC lies about 185,000 light year from Earth, in the constellation Tucana.Earth, in the constellation Tucana.

Regions of the Milky Way GalaxyRegions 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

Regions of the Milky Way GalaxyRegions of the Milky Way Galaxy

DiskDisk• younger generation of starsyounger generation of stars• contains gas and dustcontains gas and dust• location of the open clusterslocation of the open clusters

BulgeBulge• mixture of both young and old starsmixture of both young and old stars

HaloHalo• older generation of starsolder generation of stars• contains no gas or dustcontains no gas or dust• location of the globular clusterslocation of the globular clusters