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GALAXIAS Optico Infrarojo The Galactic Disk The disk of our Galaxy is made up of three main components: Stars Gas Dust The gas in between stars is the “Interstellar Medium” (or “ISM”) Like everywhere, most gas in the disk is hydrogen . Molecular (H 2 ): Cold, dense, tightly clumped.

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Slide2 l.jpg

Optico

Infrarojo


The galactic disk l.jpg
The Galactic Disk

The disk of our Galaxy is made up of three main components:

  • Stars

  • Gas

  • Dust


The gas in between stars is the interstellar medium or ism l.jpg
The gas in between stars is the “Interstellar Medium” (or “ISM”)

Like everywhere, most gas in the disk is hydrogen.

  • Molecular (H2):

    • Cold, dense, tightly clumped.

    • Stars form within molecular clouds.

  • “Neutral” or Atomic (HI):

    • Cool, less dense, less tightly clumped.

    • Most common phase; the reservoir for forming the next generation of stars.

  • “Ionized” (HII):

    • Hot, more diffuse.

    • By-product of forming young stars.


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Young massive stars die out, and electrons and nuclei recombine

Gas is compressed, and cools

Atomic HI

Molecular H2

Ionized HII

Young massive O-stars form, and ionize the gas


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Fountains and Blowouts recombine

SNe from newly formed massive stars can make holes in the disk, driving material out of the Galaxy or redistributing it


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Blowout in M82 “starburst” galaxy… recombine

Red is “false color”, showing location of extremely hot gas detected in

X-rays.

Hot because the gas is mostly the “ejecta” from supernovae!


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Los brazos de la galaxia son regiones de alta densidad donde ocurre la mayor parte del proceso de formación de nuevas estrellas.

Por otro lado, las ondas de choque generadas por explosiones de estrellas evitan que los brazos se dispersen.


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Los brazos no son rígidos; más bien son ciertas zonas que las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

Se calcula que el Sol ya dio varias vueltas completas. En este momento, está en una zona "tranquila", al borde de un brazo secundario.


The bulge a very crowded neighborhood l.jpg
The Bulge: las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.A Very Crowded Neighborhood

The density of stars in the bulge is about

50,000 per cubic parsec

By comparison, the nearest star to the Sun is 1.3 pc away!


Milky way is believed to have a bar at its center l.jpg
Milky Way is believed to have a bar at its center… las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.


The galactic halo ancient stars l.jpg
The Galactic Halo: Ancient Stars las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

No gas, so no star formation…

…just a bunch of old stars, either by themselves or in globular clusters.


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  • Ordered Rotation las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

    • Nearly circular orbits (like planets around the Sun)

  • Randomly

    • Highly elliptical orbits, plunging in and out of the center of the galaxy, atrandom orientations.

Stuff in Galaxies moves in two basic ways…


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Side View of the Milky Way las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

The “halo” is really the “stellar halo” – turns out there’s actually a larger halo we can’t even see!

Globular clusters live in the halo


Turns out there s a lot of this invisible matter l.jpg
Turns out there’s a lot of this invisible matter. las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.


Overall properties of the galactic disk halo and bulge l.jpg
Overall Properties of the las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.Galactic Disk, Halo, and Bulge


Observational tracers of magnetic fields l.jpg
Observational tracers of magnetic fields las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

  • Polarization of starlight:perpendicular field in 2 or 3 kpc

    orientation // B⊥ ------------- 9000 stars

  • Zeeman splitting: parallel field, in situ (masers, clouds)

    △ ∝ B// ------ 30 masers

  • Polarization at infrared, mm:perpendicular field orientation // B⊥------ clouds & star formation regions

  • Synchrotron radiation:vertical field structures (added)

    total intensity S ∝ B⊥2/7, p%∝ B⊥u2 / B⊥t2

  • Faraday rotation:parallel field, integrated (the halo & disk)

    RM∝∫ne B//ds ------ 500 pulsars + >1000 EGSes


Large scale magnetic field in the galactic disk l.jpg
Large-scale magnetic field in the Galactic disk las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

The largest coherent field structrue detected in the Universe!


Poloidal toroidal fields near gc l.jpg

Poloidal & Toroidal fields near GC las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

(from Novak et al. 2003)

Predicted B-direction

GC

Toroidal fields

(Novak et al. 2003, 2000)

permeated in the

central molecular zone

(400pc*50pc)

sub-mm obs of p%

toroidal field directions

determined by averaged

RMs of plumes or SNR!

Poloidal field

filaments Unique to GC

--- dipolar geometry!

(Morris 1994; Lang et al.1999)

150pc


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The Milky Way: las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

A Barred Spiral Galaxy

The Milky Way is a “spiral” galaxy, sometimes also called a “late type” galaxy.


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Side View las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

“edge-on”

Top View

“face-on”


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“Sombrero Galaxy” las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.


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  • Elliptical Galaxies las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico. (or just “ellipticals”)

    • No disk! old!

“spheroidals”


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“S0” galaxies las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.: Like ellipticals, but usually a bit flatter.


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Early Types las estrellas atraviesan en su movimiento de rotación alrededor del centro galáctico.

Late Types

Unbarred and Barred Spirals

Ellipticals

Lenticulars


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Varying amounts of bulge & disk components suggests different formation & evolution history

On average…

  • Older Stars

  • Gas Poor

  • More Massive

  • On-going Star Formation

  • Gas Rich

  • Less Massive


Early type galaxies from the sloan digital sky survey sdss l.jpg
Early-Type Galaxies different formation & evolution historyfrom the Sloan Digital Sky Survey (SDSS)


Late type galaxies from sdss l.jpg
Late-Type different formation & evolution historyGalaxies From SDSS

(red because of dust)


There are galaxies beyond the hubble sequence that continue this trend l.jpg
There are galaxies beyond the Hubble Sequence that continue this trend.

???

“Dwarf” or “Irregular” Galaxies


Dwarf or irregular galaxies tend to have more chaotic appearances l.jpg
this trend.Dwarf” or “Irregular” galaxies tend to have more chaotic appearances…

  • Low mass (107-109 stars, vs 1010 for spirals)

  • High star formation rates (usually)

  • No obvious bulge or spiral patterns.

  • Most numerous type of galaxy in the Universe!



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“Gas Infall” this trend.

  • Galaxies continue to form stars.

    • Just enough gas in galaxy disks today to form stars for <109 years.

    • Fresh gas must keep it going.

  • Fraction of metals (non-H, He) in stars is lower than expected.

    • Fresh Hydrogen must be flowing in.


Merging or galaxy interactions l.jpg
“Merging” or “Galaxy Interactions” this trend.

  • Gravity pulls galaxies together!

  • They can orbit each other & eventually merge!


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“The Antennae” this trend.(Hubble Image @ Right)



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“Minor Mergers” this trend.

We know this is currently happening…


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Zoom-in this trend.

M16 (Eagle)

M17 (Horseshoe)

Milky Way

M8 (Lagoon)

Hale-Bopp

Jupiter

Picture credit: W. Keel


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Eagle Nebula this trend.

(M16)


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Eagle Nebula this trend.

(M16)


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Eagle Nebula this trend.

(M16)


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size of our solar system this trend.

Eagle Nebula

(M16)


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