Characteristics of Galaxies. Classification: The Hubbl

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NOTES Characteristics of Galaxies Classificati
on The Hubble Tuning Fork Elliptical E0--E7
Spheroids, E0 is spherical, E7 least spherical.
Population II stars, little dust, almost no
star formation. Normal Spirals Sa, Sb, Sc Sa is
most tightly wound, Sc least. Population I
stars in disk, Pop. II in nucleus. Dust and star
formation in disk. Barred Spirals Sba, Sbb,
Sbc Have bars across nucleus, Same winding
rules as normal spirals. Same content as
normal. Irregulars No definite shape. Ex. Large
and small Magellanic clouds. Dominate
universe by number, although generally
smaller. Star formation, but less dust than
disks. Peculiar (Pec) Have a definite form, but
with peculiarities. Radio jets or other
strangeness.
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The Hubble Tuning ForkClassification of Galaxies
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Regular and dwarf ellipticals have no dust
and are made up of old Pop. II stars
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No dustno aliens!
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Supergiant Ellipticals as in Coma rich cluster
(rich in dust), formed from galactic mergers?
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S0 Galaxy in Sextans (the sextant) no spirals.
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M64the black eye galaxy Sa classification
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Irregular galaxies (Irr) about ½ of galaxies are
Irr.
Near the Milky Way
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Peculiar Galaxies (Pec) have a shape, but a
ding. NGC4631 Pec class spiral galaxy with a ding.
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Luminosity classsimilar to stars
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Fritz Zwicky discovered dark matter in galactic
clusters in 1930s.
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Galactic mass for large spirals can be Determined
from galactic rotation curves.
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Which implies the existence of dark matter (not
seen). About half is ordinary (baryonic), but
other half is exotic. WIMPS, etc.?
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We can also find mass from movement in a
binary galaxy system or cluster.
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Distance Standard candles--Cepheids, Supernova
type Ia, standard galaxies like brightest spiral
or Supergiant ellipticals in Cluster cores. If
all else fails, Hubble's Law.
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Hubble's Law v Ho d. Velocity from
redshift is proportional to distance.
Hubbles constant Ho 70 km/s/Mpc (Friedmann
in early 1990s).
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Observations of redshift first done by Milton
Humason, a janitor at Mt. Wilson Observatory
(working for Edwin Hubble.
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Diameter from distance and angular diameter.
Diameter distance times angle (in radians)
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How do we get luminosity?
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Luminosity from distance and flux (or mass and
Mass-Luminosity relation for main sequence stars).
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NOTES Where are you? You are
here--gt Earth, Solar System, Milky Way
Galaxy... The Local Group a galaxy 'poor'
cluster of 27 galaxies three large
spirals, 12 dwarf ellipticals, 4 ellipticals, and
8 Irr. Dust in the plane of the Milky Way
may obscure more. The Local (Virgo)
Supercluster Pancake-shaped. Composed
of the Virgo Cluster (a 'rich' cluster) and
about 100 other clusters including
Local Grp. We are falling toward Virgo
Cluster, which has three supergiant ellipticals
(M87 contains accretion disk indicating
BH or WH in center--a quadrillion solar
masses!) The Pisces-Cetus Complex may include
400 rich (and lots of poor) clusters.
Brent Tully. Is the Universe homogeneous? God's
Bubble Bath Galaxy superclusters seem to from in
bubble structures and filaments
with Voids 100-500 million LY across. Some
call this the Cellular Universe. The Great Wall
and The Stick Man--supercluster structures. The
Great Attractor--hidden by Milky Way Dust in
Centaurus. 1017 Mo! May be dense giant
supercluster with lots of dark matter. Tens
of thousands of galaxies are falling into it,
ignoring the Hubble Flow.
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What is your cosmic address? Earth, Solar System,
Milky Way, then
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The local groupour galaxy cluster--a 'poor'
cluster of 27 galaxies three large spirals, 12
dwarf ellipticals, 4 ellipticals, and 8 Irr.
Dust in the plane of the Milky Way may obscure
more.
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Then the Local (or Virgo) Supercluster
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The Local (Virgo) Supercluster Pancake-shaped.
Composed of the Virgo Cluster (a 'rich'
cluster) and about 100 other clusters including
Local Grp. We are falling toward Virgo Cluster,
which has three supergiant ellipticals.
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M87 in Virgo contains accretion disk indicating
BH or WH in center--a quadrillion solar
masses! BH is 2 billion solar masses. Accretion
disk is shown on the right.
In core
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An X-ray image of the rich galaxy cluster Abell
2142, taken with the Chandra Observatory. This
cluster is clearly elongated, and is believed to
be the result of a recent merger between two
clusters which have fallen together along the
long axis.
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A larger view!
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Galaxy superclusters seem to form in bubble
structures and filaments with Voids 100-500
million LY across. Some call this the Cellular
Universe.
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God's Bubble Bath the quantum foam the universe
may have expanded from minute distortions in
space-time.
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The Great Attractor a big lump in the Universe?
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Great Attractor hidden by Milky Way Dust in
Centaurus. 1017 Msun! May be dense giant
supercluster with lots of dark matter. Tens of
thousands of galaxies are falling into it,
ignoring the Hubble Flow. Alan Dressler, Sandy
Faber, and The Seven Samurai from Harvard
discovered it.
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At largest scale? Homogeneous? Yes. Confirmed
by observations.