Galaxies With Active Nuclei

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Galaxies With Active Nuclei
Fig. 14-CO, p.276
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Active Galaxies and Quasars

• Limits of the Observable Universe

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Radio astronomy
1960s Radio astronomy found bright objects ,107 X
bright as normal galaxies at radio wavelengths,
many looked like either normal galaxies or
stars. Turned out to be a number of different
types wjth what is now believed to be similar
power source. Seyfert Galaxies Radio Galaxies
core-halo, radio lobe QSOs or quasars
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Very luminous Different in the distribution of
the energyclearly nonstellar in origin
different intensity, distribution in wavelength
and space. More energy in radio wavelengths
than anything seen before. Location in Space
more found at great distances Quasars are all
very remote.
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Energy Profile
Active galaxies Are intense radio sources. Over
all more Energy. Different profile.not blackbody.
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Seyfert Galaxies
TYPE 1 very luminous at X-ray and uv wavelengths
and have broad emission lines of highly ionized
atoms. Emission lines low density gas Ionized
excited gas Broad lines fast rotation TYPE 2
lack the strong X-ray emissions, emission
broadening not as pronounced.
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Seyferts look like spirals
Seyfert galaxies (1943 Carl Seyfert) Most have
strong redshifts.100s of Mpc. All have active
nuclei.
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Nearby Seyfert Galaxy
Circinus galaxy at 4 Mpc is one of the closest
Seyfert Galaxies.
Cores alone in radio and IR emit up to 10X energy
of our whole galaxy. Energy from small source (lyr.).Fluctuations. Spectral broadening suggests
rotating matter near core. Velocities at cores
are roughly 10,000 km/s. 30X normal. Spectra not
star like.
About 2 of spirals appear to be Seyferts.
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Seyfert galaxy NGC1566
Figure 14.1 (a) Seyfert galaxy NGC1566 looks
like a normal spiral galaxy, but short-exposure
images reveal that its nucleus is very small and
very luminous. (AATB) (b) The small, bright
nucleus of this Seyfert galaxy in the southern
constellation Circinus is ejecting gas at high
speeds in a bright, V-shaped cone located just
above the nucleus (arrow). Higher above the disk,
the ejected gas is visible as the bright pink
regions extending to the top of the image.
Presumably a similar cone of ejected gas is
hidden below the disk of the galaxy. (Andrew S.
Wilson, University of Maryland Patrick L.
Shopbell, Caltech Chris Simpson, Subaru
Telescope Thaisa Storchi-Bergmann and F. K. B.
Barbosa, UFRGS, Brazil Martin J. Ward,
University of Leicester, U.K. and NASA)
Fig. 14-1, p.278
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Seyfert Galaxies are intermediate between normal
spirals and the most violent . Optical images
look like spirals. But the overall energy
emission shows the largest part of the energy is
from the galactic nucleus and is in the form of
invisible radio and infrared radiation,
nonstellar in distribution. Fluctuations in the
energy output shows the energy is produced in a
compact source. luminosities may vary by 50 in
less than a month Seyferts are 3x more likely to
be interacting and 25 have shapes suggesting
tidal forces. Seyferts may have been kicked into
activity by collisions with other galaxies.
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F14.1a
Figure 14.1 (a) Seyfert galaxy NGC1566 looks
like a normal spiral galaxy, but short-exposure
images reveal that its nucleus is very small and
very luminous. (AATB)
Fig. 14-1a, p.278
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F14.1b
Figure 14.1 (b) The small, bright nucleus of
this Seyfert galaxy in the southern constellation
Circinus is ejecting gas at high speeds in a
bright, V-shaped cone located just above the
nucleus (arrow). Higher above the disk, the
ejected gas is visible as the bright pink regions
extending to the top of the image.
Presumably a similar cone of ejected gas is
hidden below the disk of the galaxy. (Andrew S.
Wilson, University of Maryland Patrick L.
Shopbell, Caltech Chris Simpson, Subaru
Telescope Thaisa Storchi-Bergmann and F. K. B.
Barbosa, UFRGS, Brazil Martin J. Ward,
University of Leicester, U.K. and NASA)
Fig. 14-1b, p.278
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Figure 14.2 (a) Seyfert galaxy
Figure 14.2 (a) Seyfert galaxy NGC7674 is
distorted, with tails to upper right and upper
left (arrows) in this false-color image. Note the
companion galaxies. (John W. Mackenty, Institute
for Astronomy, University of Hawaii)
Fig. 14-2a, p.279
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Seyfert galaxy NGC4151 has a brilliant nucleus
in visible-light images.
Fig. 14-2b, p.279
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Doppler shifts
The Space Telescope Imaging Spectrograph reveals
Doppler shifts showing that part of the expelled
gas has a blue shift (to the right) and is
approaching us and part has a red shift (to the
left) and is receding. (John Hutchings, Dominion
Astrophysical Observatory Bruce Woodgate,
GSFC/NASA Mary Beth Kaiser, Johns Hopkins
University and the STIS Team)
Fig. 14-2c, p.279
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Energy fluctuations
Energy fluctuations suggest relatively Small
object as Origin of energy.
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Radio Galaxies
Most Energy in radio region Most are giant
ellipticals, M87 Different wavelengths, longer,
than Seyferts Differ in size, HUGE, Some sources
are larger than the visible region of the
galaxy Show evidence of jets of matter from the
core. TWO TYPES turn out to be due just to view
point. CORE-HALO 50 kpc visible galaxy, 1 pc
central nucleus as bright as a galaxy, similar in
energy to Seyfert LOBE huge, 10X size of Milky
Way, size of local group.
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Double-lobed Radio Sources
p.280
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Core halo and radio lobe
Radio Galaxies active galaxies emit most of
their radiation in the radio region. ( Longer
wavelengths than Seyferts and much broader in
extension of the source, 100s of kpc across.
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Centarus A
RADIO LOBE,NGC5128 Centarus A, _at_ 4Mpc, close
up a) X ray image of lobes b) Optical image c)d)
increasing optical resolution
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If they were visible the radio lobes of Centarus
A would be 10X the size of the full Moon.
p.280
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p.280
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p.280
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Cygnus A

• Cygnus A
• Galaxies in collision
• Million light years lobe to lobe.
• Optical image of central objects
• Lobes are aligned with the core, hot spots on
  leading edges.

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p.280
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NGC 1265
Head to tail Radio galaxy, moving rapidly through
space
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Core Halo
M87 Jet. Giant elliptical galaxy
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View point
Double-exhaust model geometry suggests the radio
lobes are inflated by jets of excited gas
emerging from the central galaxy
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BL Lac Objects
Blazars are 10,000 times more luminous than the
Milky Way and fluctuate in only a matter of
hours. Now believed to be cores of active
galaxies .. We happen to be looking directly into
the brilliant jets.
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Energy Source ?
Large energy production and small physical
size. Accretion of matter into a black
hole Masses between a few million and a billion
solar masses Source of matter this time is not a
binary star but entire stars and clouds of gas
forming accretion disks.
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Accretion is efficient at converting infalling
mass into energy. As much as 10 to 20 percent of
the total mass-energy of the infalling matter can
be radiated away before it passes the event
horizon.  The small size of the source is a
direct consequence of the compact nature of black
holes. Even a billion solar mass black hole has
a radius of only 20 AU and An accretion disk
would have a radius of less than a parsec.
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Model of energy source
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p.281
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Images by HST of Virgo cluster and core NGC4261
elliptical galaxy.
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Figure 14.3
F14.3The jet at the center of giant elliptical
galaxy M87 is only a few percent the diameter of
the entire galaxy. The jet is emerging at nearly
half the speed of light. Hubble Space Telescope
images reveal a small, rapidly spinning disk at
the center of the galaxy with the jet emerging
parallel to the axis of the disk.
Very-high-resolution radio observations show that
the jet originates in a tiny active region at the
very center of the disk. (M87 AURA/NOAO/NSF
jet NASA/STScI radio image NRAO and J. Biretta)
Fig. 14-3, p.283
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Figure 14.4
Figure 14.4 (a) Galaxy NGC4261 looks like a
distorted fuzzy blob in an Earth-based photograph
at visible wavelengths (white), but radio
telescopes reveal jets leading into radio lobes
(orange). (b) A Hubble Space Telescope image of
the core of the galaxy reveals a bright central
spot surrounded by a disk with its axis pointing
at the radio lobes. (L. Ferrarese, Johns Hopkins
University, and NASA)
Fig. 14-5, p.285
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Figure 14.5 An accretion disk
Figure 14.4 An accretion disk around a massive
black hole. Matter flowing inward passes first
through a large, opaque torus then into a
thinner, hotter disk and finally into a hot,
narrow cavity around the black hole. Gas clouds
above and below the disk are excited by radiation
from the hot disk. This diagram is not to scale.
The central cavity may be only 0.01 pc in radius,
while the outer torus may be 1000 pc in radius.
Fig. 14-4, p.284
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See animation.
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Core Doppler shifts
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Fig. 25.19 Radio studies. Giant molecular clouds
Doppler shift. Spinning about a 40 M solar mass
black hole less than 0.2 pc across.
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CORE SPECTRA DIFFERENCES For the observed spectra
to match theoretical predictions it must be
assumed to be reprocessed. I.e. absorbed and
reemitted at longer wave lengths.   JET AND LOBE
SPECTRA DIFFERENCES Jets have charged particle
outflows and strong magnetic fields, Synchrotron
radiation.
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Synchrotron radiation
Charged particles spiral around the magnetic
field lines. Electrons move the fastest , are
the Lightest thus are responsible for most of
this nonthermal radiation.
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Left. Radiation models
Right. Typical active galaxy spectrum
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Quasar History
1960s Objects whose images looked like distant
stars were found with strange radio
emissions. Difficult to identify at first. The
problem solution began with the recognition of
the spectra as being redshifted farther than
anything previously seen. Large redshift far
away. Correct energy output for the implied
distance leads to a huge energy output. Factors
of 107 larger than the entire Milky Way in the
radio region.
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To get around the need to explain such a huge
unknown energy requirement. It was suggested
these redshifts might be due to gravitational
effects. Eg gravitational redshifts. Eventually
QUASARS were identified as galaxies far away in
space and time with active nuclei when the host
galaxies were resolved in images.
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Quasars
QUASAR, QSO
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Large red shifts
Unusual spectra explained first by Maarten
Schmidt,1963. Z ??/? From Doppler formula
??/? v/c
So. V Zc and from Hubble V HD Most common Z
of 2, less above Z of 2.7, Quasars about 1000 X
more common then
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The spectrum of 3C273
Figure 14.8 The spectrum of 3C273 (top) contains
three hydrogen Balmer lines red-shifted by 15.8
percent. The drawing shows the unshifted
positions of the lines. (Courtesy Maarten Schmidt)
Fig. 14-7b, p.287
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Figure 14.8
Figure 14.9 Spectra of four quasars are compared
here with an idealized spectrum for an imaginary
quasar that has no velocity of recession. The
first three Balmer lines of hydrogen are visible,
plus lines of other atoms, but the red shifts of
the quasars move these lines to longer
wavelengths. Nevertheless, the relative spacing
of the spectral lines is unchanged, and
astronomers can recognize the lines even with a
large red shift. (C. Pilachowski, M. Corbin,
AURA/NOAO/NSF)
Fig. 14-8, p.287
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Figure 14.9 At high velocities, the relativistic
Doppler formula must be used in place of the
classical approximation. Note that no matter how
large z gets, the velocity can never equal that
of light. See p 288 and Lab Ex.
Fig. 14-9, p.288
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Typical quasar
Looked like stars.. Hence the name Quasi-stellar
radio Source. QUASAR.
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Figure 14.6 Quasars
Figure 14.6 Quasars have starlike images clearly
different from the images of distant galaxies.
The spectra of quasars are unlike the spectra of
stars or galaxies. (C. Steidel, Caltech, NASA)
Fig. 14-6, p.286
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3C 273 Better telescopes show ancient/distant
active galaxy
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Image of 3C273
Figure 14.7 (a) This image of 3C273 shows the
bright quasar at the center surrounded by faint
fuzz. Note the jet protruding to lower right.
Fig. 14-7a, p.287
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Quasar jets
3C 175 at 1500 Mpc, million light years across
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QUASAR LIFFETIMES A quasar would only require a
100 solar masses/ year. Quasars are early events
in the universe. Long ago Far away More mass
was available earlier. Brightest galaxies would
require about 1000 solar masses / year. Quasars
must be this active for only a few tens of
millions of years or the universe would have a
large number of large black holes. not seen
with large frequency- lensing Black holes eat
out cavities in their host galaxies, then become
dormant until some event kicks them back into
activity. E.G. galaxy collisions.
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QUASARS as Probes Light from the Quasars pass
through the gas. Each cloud leaves its mark.
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Twin quasar just a double image gravitationally
lensed.
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Figure 14.10 Gravitational lensing
Fig. 14-10, p.289
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Lensing amplifies the light. Multiple images may
have time delays of several days to several
years.. a chance to restudy an event.
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Fig. 14-10, p.289
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MAPPING DARK MATTER Calculate required
distribution of matter to cause the observed
distortions
Fig 25.24 Multiple images. Einstein cross.
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Fig. 14-10, p.289
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Fig. 14-10, p.289
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Figure 14.11 Quasar 0351026 (top) is located
near a faint galaxy (bottom) that has the same
red shift and thus, presumably, the same distance
from Earth as the quasar. The extended red region
around the quasar (fuzz) is typical of
lower-red-shift quasars and typically reveals the
spectrum of a normal galaxy. Thus, this image
shows two interacting galaxies, one of which
contains a quasar. (AURA/NOAO/NSF)
Fig. 14-11, p.290
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Figure 14.12
Figure 14.12 Two negative images, much enlarged,
of the quasar 1059730. The lower image shows an
extra point of lightapparently a supernova that
exploded in the galaxy associated with the
quasar. (Courtesy Bruce Campbell)
Fig. 14-12, p.291
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Galaxy cluster lensing
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(a) Optical image of galaxy cluster (b)
Required distribution of dark matter
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Active galaxy evolution
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Galaxies formed as small irregular clumps of gas,
dust and dark matter, Grew by mergers into
larger systems. Observed redshift of 6 implies
13 billion years to earliest mergers. Intense
starburst formation source of first
blackholes. Blackholes merged. Sank to centers of
galaxies. Very bright, fuelled by lots of
available matter Some supermassive blackholes may
have formed directly from protogalaxies Others
took time. Peak quasar redshift of 2-3
corresponds to an epoch 1-2 billion years latter
than time of fartherist quasars.( i.e. 11
billion yrs. ago).
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Early quasars in host galaxies. HST long exposures
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Figure 14.13
Figure 14.13 The bright object at the center of
each of these images is a quasar. Fainter objects
near the quasar are galaxies distorted by
collisions. Compare the upper left ring-shaped
galaxy with Figure 13-14, and compare the tail in
the lower left image with the Antennae galaxies
in Figure 13-12. (J. Bahcall, Institute for
Advanced Study, Mike Disney, University of Wales,
NASA)
Fig. 14-13, p.291
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