The Core of M87 (at the center of Virgo)

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The Core of M87 (at the center of Virgo)
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Radio Jets
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Giant Radio Lobes
If the jets last long enough, they can blast out
of the galaxy for millions of light years the
largest single coherent structures in the
universe.
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Seyfert Galaxies
Some galaxies have unusually bright nuclei
Increasing exposure times.
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Quasars(Quasi-stellar Objects)
Strange stars were found with spectral lines
that turned out to be normal lines but at
extremely high red Doppler shifts. The expansion
of the Universe means that they must be VERY far
away, yet they were not too faint.
Star
QSO
Even Seyfert nuclei would not be bright enough.
The energy output would have to be up to 100s of
times that from a whole normal galaxy, but the
source was point-like.
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Host Galaxies of Quasars
Finally, we were able to obtain deep images of
quasars, and show that indeed they are extremely
bright galactic nuclei. The only power source
that is adequate is a supermassive black hole,
eating up to several solar masses per year.
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Supermassive Black Holes
Centaurus A
You know the Milky Way has a 3 million solar mass
BH at its center. Are they common? Bigger?
Luminosities seem to require them. How could we
prove the theory? A billion solar mass black
hole is still only the size of the solar system.
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Evidence of a very small size
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Measuring the Monsters Mass
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The Best Case of a mass and disk measurement
Using very long baseline radio interferometry,
very bright spots very near an active galactic
nucleus have been seen actually in orbit around
it. We have both their Doppler shift and their
motion on the sky. This gives the size and
configuration of the disk, and a direct
measurement of the black hole mass.
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Black Hole blowing bubbles
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Images of AGN disks
Recently, the theory of AGN has received
spectacular visual confirmation from the Hubble
Space Telescope.
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Jet Mechanism
The magnetic field pulled in near the black hole
can wind around it, and gas is forced out at very
high speeds along the rotation axis, making the
superjets.
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Zooming in on the central engine
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Unification of Active Galactic Nuclei
Depending on what the viewing angle is, what we
see can be rather different. This is now sorted
out.
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Distances to Nearby Galaxies
The distance to Is measured by Which gives you
Venus Radar echoes Astronomical Unit
Nearby Stars Parallax Main sequence luminosities
Star Clusters Main sequence fitting Luminosities of Cepheids
Nearby Galaxies Apparent brightness of Cepheids Relation of distance to redshift
There is a chain of links which get us out to the
distances of galaxies. Errors in any one affect
all the further ones.
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Distances deep into the Universe
You must use nearby galaxies to calibrate
distance indicators that can be seen across the
Universe. 1) brightest star (hypergiants), then
HII region (star form.) 2) largest spiral in
cluster 3) brightest galaxy in
cluster Tully-Fisher relation Luminosity in
red or infrared correlated with 21-cm broadening
(number of stars) (rotation
rate) Hubble expansion distance correlated
with redshift
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Hubble Expansion what it is not
In an explosion, the stuff that is moving faster
will have gotten further, so you would see what
Hubble saw. Despite the term Big Bang to
describe the expanding Universe, that is NOT what
is going on!
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Hubble Expansion what it is
Space itself is expanding into the future
The apparent increase of velocity with distance
is due to the increase in the amount of space
that has expanded in a given amount of time.
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There is no spatial center of expansion
The center is the beginning There is no edge
(except the present)
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The motion is only apparent
Galaxies stay fixed on the co-moving grid.
Their separation only increases because the
amount of space between them increases. The scale
of the Universe increases, but not the scale of
particles, galaxies, or even clusters (anything
bound). The expansion is only apparent on scales
of millions of light years.
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Local structure interferes with Hubble flow
We have to be careful in determining the
expansion rate.
Local flow field
Supercluster density field
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Galactic Redshifts
The relation is given by Dv/H D is distance, v
is redshift velocity, and H is the Hubble
constant. H is about 25 (km/s)/(million ly). The
redshift is called z, where z Dl/l v/c.
Remember these are only apparent velocities,
caused by the expansion of space.
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The Hubble Constant and the Age of the Universe
If you plot the scale of the Universe vs time,
the Hubble constant is the slope of the line now.
If its really constant, then the age of the
Universe is just 1/H since Hv/D(d/t)/d.
Thats because if you know how fast we are
expanding, you can run the movie backwards and
see when everything crunches together. If the
Universe is slowing its expansion, you get a
younger age.
You can compare the age gotten this way with the
oldest globular cluster, or other independent
methods. Recently they have all come into
agreement.
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Cepheids are the key link
One primary justification for the Hubble Space
Telescope was to
resolve Cepheids in galaxies far enough away to
measure the Hubble flow properly, and thus obtain
the age of the Universe. Along with other
methods, this gives about 14 billion years.
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Redshift takes us from 2-D to 3-D
Huge surveys are ongoing to get redshifts for
hundreds of thousands of galaxies. These give us
the large-scale structure of the Universe.
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Quasar Spectra and the Lyman-alpha Forest
Redshifts tell us where everything is
QSO
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Galaxy Filaments
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Cosmic Foam
Gravity acting on dark matter gives the basic
layout of matter in space. Clusters will continue
to collect, but the space between them will
continue to expand.