Hubble Deep Field

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Hubble Deep Field
We leave the confort of our Galaxy and journey
out through space and back in time. First an
optical snapshot of an obscure region in the
universe.
HST WFPC 2

• The field-of-view is so narrow, just a few
  foreground stars in our Milky Way galaxy are
  visible and are vastly outnumbered by the far
  more distant galaxies to visual magnitude V29.
  (The relatively bright object with diffraction
  spikes just left of center may be a 20th
  magnitude star.) This "true-color" view was
  assembled from separate images were taken in
  blue, red, and infrared light.. Statistical
  samples of high redshift (zgt3.5) galaxies were
  obtained by looking for blue-band dropout due to
  H Ly-a absorption in intervening protogalactic
  and diffuse neutral H Ly-a clouds.

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Hubble Deep Field South
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HDFS (detail)
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HDFS (detail)
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The Andromeda Galaxy M31 Polomar at optical
wavelengths.
Note the two satellite galaxies, the nearby m 9
elliptical M32, and the flattened
dwarf elliptical M110

• M31, type Sb or Sbc at 700 kpc, is the nearest
  large spiral to the Milky Way, though more
  massive. They both have large central bulges
  surrounded by a disk and spiral arms showing
  vigorous star formation

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Optical Nucleus of M31 with HST
The two intensity peaks are 1.5-2 pc apart and
may represent a merger of two rather massive
(million Solar mass) compact objects, or a
reflection and reprocessing of the central source
off a surrounding gas and dust
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M 100, Grand Design Spiral, HST

• M100, type Sc, at 15 Mpc. This image shows active
  star formation occurring even near the central
  bulge. Blue UV from hot young stars. Pink
  fluorescence H Balmer emission

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Centaurus A, a k a NGC 5128
An elliptical with crossed dust lanes suggests
strong galactic interactions, and perhaps merger
in this case.

• Cen A, at 3-4 Mpc, is the brightest galaxy at
  X-ray and soft gamma-ray wavelengths. It has
  large scale radio jets, collimated optical OIII
  fluorescence, extincted UV, X-ray jets, and rapid
  hard X-ray and gamma-ray emission. It is possibly
  a misaligned blazar emanating from an AGN fed by
  the collision debris, all buried in a cloud of
  cold H and dust. See Great Discovery Poster on
  Quasars and Jet Sources (GDqsr) by Catanese and
  Weekes.

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Cen A at radio, optical, and IR.
ISO emission at 100 m

• Cen As radio image overlaid on optical image,
  with ISO observations shown above. The appearance
  of an elliptical shape with cross-laced dust
  lanes may imply a collision of a large elliptical
  with a smaller spiral galaxy. The collision
  event has fueled mammoth AGN and/or starburst
  activity. The upper radio jet appears more
  directed toward us, and strong time variable X-
  and g-ray emissions point to a black-hole
  maelstrom fed by dissipative gas collapse.

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M 81 at radio

• Enhanced radio emission near spiral arm structure
  is due to active star formation, massive
  short-lived stars, and supernova explosions.
  Planetary nebular HII regions are seen in this
  image as compact sources in the brightest
  regions.

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M 81, 21 cm observations, NRAO

• 21 cm emission traces neutral hydrogen, which is
  found in greatest concentrations in spiral arms.
  The radial profiles of 21 cm emission has been
  used to argue for existence of dark matter (see
  GDdm by Dwek).

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Markarian 315, an optical Seyfert galaxy

• Markarian 315 is a Seyfert galaxy, that is, it
  has enhanced blue emission from the Galaxys
  nucleus and strong optical emission lines. Two
  nuclei in the core of the Seyfert galaxy Mrk 315
  might indicate that nuclear activity is a
  consequence of a strong merger event ultimately
  leading to coalescence of the separate nuclei.
  The frictional transport of massive black holes
  depends strongly variations of the local stellar
  density. See GD_agn by Weaver.

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Cygnus A, NRAO

• The radio lobes of Cygnus A extend out over 100
  kpc on either side, carry some 1061 ergs of
  directed kinetic energy, are highly collimated at
  the base. The ejection of relativistic plasma by
  a central supermassive black hole central engine
  remains the favorite explanation. See GD_qsr by
  Catanese and Weekes.

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NGC 3351

• This fine galaxy is seen almost face-on and is
  one of a small group in Leo whose members are at
  distance of about 25 million light years. Despite
  the distance, several of these galaxies appear in
  Messier's catalogue, about one third of which
  consists of galaxies. Though the exact form of
  our own galaxy, the Milky Way, is not known,
  there is increasing evidence that it is a barred
  spiral, perhaps like M95. While the 'bar' is the
  dominant feature in a picture taken from afar, it
  is easy to imagine that this structure could be
  very difficult to detect from inside the galaxy,
  especially if seen from a position at right
  angles to it.

_at_Anglo-Australian Observatory credit David Malin
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NGC 2997
_at_Anglo-Australian Observatory credit David Malin

• The disc of NGC 2997 is inclined at about 45
  degrees to our line of sight, revealing its
  internal structure and giving the galaxy an oval
  appearance. Seen face-on, NGC 2997 would look
  rather like M83. Like most spirals, the galaxy
  has two prominent spiral arms, which appear to
  originate in the yellow nucleus, are peppered
  with bright red blobs of ionised hydrogen which
  are similar to regions of star formation in our
  own Milky Way. Within these gas clouds are
  produced the hot blue stars which generate most
  of the light in the arms of the galaxy. A much
  older population of yellowish stars are
  concentrated around the nucleus.

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NGC 253
_at_Anglo-Australian Observatory credit David Malin

• A mere 10 million light years away, NGC 253 is
  one of the nearest spiral galaxies, a member of a
  small group straggling across the southern
  constellation of Sculptor. It appears elongated
  because we see it almost edge-on. This galaxy is
  also one of the dustiest galaxies known and much
  of its internal detail is hidden by obscuring
  matter which can be seen as dark patches against
  the background stars. Despite the obscuration,
  two spiral arms and many bluish clusters of stars
  can be seen around the edge of the galaxy. NGC
  253 is so close to us that some of the brightest
  stars are apparent as individuals within the
  spiral arms.

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M87
_at_Anglo-Australian Observatory credit David Malin

• Messier 87 (NGC 4486) is at the heart of the
  Virgo cluster and has a mass many times that of
  the Milky Way, itself no lightweight. Unlike our
  galaxy however, M87 is approximately spherical
  and contains relatively little gas and dust. It
  is composed mainly of cool stars, which gives it
  a yellowish colour, in contrast to the blue of
  spiral galaxies. Despite the lack of star-forming
  materials, M87 is not a quiescent backwater. It
  is a powerful source of radio waves and the
  orbits of stars near its nucleus suggest they are
  held by a very massive, extremely compact core.
  Also, from the nucleus (but not seen here)
  extends a curious jet, all of which suggests that
  a massive black hole is hidden in the bright core
  of the galaxy.

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NGC 1365
_at_Anglo-Australian Observatory credit David Malin
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Sombrero Galaxy
_at_Anglo-Australian Observatory credit David Malin
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Galaxy, id lost in the files
_at_Anglo-Australian Observatory credit David Malin
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NGC 1232

• Keck image

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NGC 1566
_at_Anglo-Australian Observatory credit David Malin
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NGC 2442
_at_Anglo-Australian Observatory credit David Malin
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Coma cluster with ROSAT. The structure of hot gas
in clusters of galaxies is traced by its diffuse
X-ray emission.
ROSAT PSPC 0.5-2.0 keV

• Coma cluster, lying near the north galactic pole
  at 100 Mpc, contains more than 1000 bright
  galaxies. The image shows the merging of the
  larger, brighter central cluster and a fainter
  group of galaxies to the right. The field is
  2.7 degrees wide by 2.5 degrees.

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Hubble-Tuning Fork
Credit Zombeck, _at_Cambridge Univ. Press
Hubble Tuning Fork classifies regular galaxies
but not irregular, peculiar/interacting galaxies,
or AGNs. The symbol E characterizes the
ellipticity and the letters a, b, c following S
and SB characterize the increasing degree of
open-ness of the spiral arms. (see GDmisc by
Dermer).