Optical Astronomy: Towards the HST, VLT and Keck Era

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Optical Astronomy Towards the HST, VLT and Keck
Era

• Introduction Overview
• Chris ODea

Acknowledgements Marc Postman, Jeff Valenti,
Bernard Rauscher
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Aims for this lecture

• Historical overview
• A brief history of optical astronomy
• trends in aperture and detector size
• CCD Detection
• Observing Issues
• Effect of the Atmosphere
• Effect of the Space Environment

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Aims for this lecture II.

• Optical Science
• Pretty Pictures
• HST
• VLT
• The synergy between optical and radio (real
  astrophysics)
• The radio loud/quiet quasar transition
• Time scales for fueling and activity in radio
  galaxies
• Current big issues in optical astronomy

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Atmospheric Transmission (300-1100 nm)
5
History

• Pre-history mismatch between solar and lunar
  cycles required astronomical observations to
  calibrate calendars and predict times for natural
  and agricultural events
• Newgrange, Ireland 3500 BC
• Stonehenge, England 3000 BC
• First millenium BC Greeks search for
• Systematics of planetary motion
• Geometric model for planetary motion
• Ptolemys Almagest (AD 145) presented robust
  geometric model of planetary motion
• 12th century Islam- Need for more accurate
  measurements of positions led to first
  observatories dedicated structures housing
  large, fixed instruments.

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History

• 1575 Tycho Brahes Uraniborg prototype of
  modern observatory
• 1609 Galileo uses telescope for astronomy
• Features on the moon
• Sattelites of Jupiter
• Stars remained unresolved
• Development of reflecting telescopes (enables
  larger collecting areas)
• Gregory 1663, Newton 1668, Cassegrain 1672
• Spectroscopy
• 1817 Fraunhofer combines narrow slit, prism and
  telescope to make first spectrograph and
  discovers spectrum of the sun
• 1859 Kirchoff shows that the solar spectrum
  reveals the chemical composition

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History

• Photography
• 1845 daguerreotype of sun Focault Fizeau
• 1870s - Improvements led to photography of faint
  stars and nebulae
• 1872 Draper obtained photographic spectrum of
  Vega
• 1875-1900 Combination of Photography and
  Spectroscopy led to a shift of astronomy from
  positional measurements to astrophysics

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History

• 1970s 4-m class telescopes become common
• 1980s CCDs are developed
• 1990 HST launched
• 1990s 10-m class telescopes become available

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Newgrange Megalithic Passage Tomb

• Passage is illuminated for 17 min after dawn Dec
  19-23

• Built 3500 BC in County Meath, Ireland
• On winter solstice sun shines down roof box and
  illuminates central 62-ft passage.

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Tycho Brahes Uraniborg

• Built 1576-1580
• Prototype of modern observatory
• First Big Science required 1 of Danish
  national budget!
• Dedicated to precision positional measurements
  (one arcmin) made possible advances by
  Copernicus and Kepler

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Telescopes in Time
1858 Lassell 48 First Large Reflector
1859 Clark 18.5
1609 Galileo 1.75
1672 Newton 1.5
1897 Yerkes 40 Largest Refractor
1948 Hale 200
1917 Hooker 100
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Hubble Humason 1931, ApJ, 74, 43
Edwin Hubble
H560 km/sec/Mpc
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Aperture vs Time
Keck
Galileo
Newton
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The Biggest Telescopes Today
Size Distribution of the 46 largest optical
telescopes
HST
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CCD Camera Development for Ground Applications
Luppino, 1998
DMT38k2 WFHRI36k2
18k x 18k
CFH_MEGA18k2 MMT_MEGA18k2
OMEGA16k2
SDSS10kx12k
UW12kx16k
8k x 8k
CFH8kx12k
UH8K2
Macho 8k2
NOAO8k2 DEIMOS8k2 QUEST8k2 MDM8k2 MAGNUM8k2 CTIO8k
2 ESO8k2
EROS8k2
4k x 4k
NOAO4k2
BTC4k2
UH4k2
MOCAM4k2
8kx8k
4kx4k
2k2
2k x 2k
2kx2k
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CCD Camera Development for Space Applications
SNAP 250x2k2
18k x 18k
GEST 60 3kx6k
GAIA136x2k2
Fame 24 2kx4k
8k x 8k
Kepler 21x2k2
4k x 4k
ACS 4kx4k
WF3 4kx4k
2k x 2k
WFPC2 4x0.8k2
WFPC1 4x0.8k2
STIS 1kx1k
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Astronomy at the end of the 20th Century

• Questions about the universe have become
  progressively more sophisticated
• From Are there other galaxies? (ca. 1920) to
  What is the origin of structure in the
  universe?
• From How many planets in our solar system?
  (Pluto discovered 1930) to How many extra-solar
  planetary systems lie within 100 light years of
  the sun? and are any inhabited?
• The basics of cosmology (age density of
  universe), detailed maps of the nearby galaxy
  distn, a basic theory of stellar evolution, and
  a census of the stars in the solar neighborhood
  exist (or will exist within 5 years).
• Astronomers today rely heavily on joint
  observations from ground space and data
  spanning large regions of the electromagnetic
  spectrum.

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CCD Detection
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MOS Capacitor

• CCDs are arrays of Metal Oxide Semiconductor
  (MOS) capacitors separated by channel stops
  (implanted potential barriers).
• Application of positive voltage repels majority
  carriers (holes) from region underneath oxide
  layer, forming a potential well for electrons.
• A photon produces an electron-hole pair the hole
  is swept out of depletion region and electron is
  attracted to the positive electrode.
• Photoexcited charge collects in depletion
  region at PN junction.
• Collected charge is shifted to amplifier (CCD) or
  sensed in situ (IR).

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Structure of a 3-Phase CCD

• Consider a 3-phase CCD.
• Columns are separated by non-conducting channel
  stops.
• Rows are defined by electrostatic potential.
• Charge is physically moved within the detector
  during readout.

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CCD Vertical Structure

• In the vertical direction, one sees a PN junction
  and control electrodes.
• Depletion regions form under both the metal gate
  and at the PN junction.
• Charge is collected where these depletion regions
  overlap.

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Charge moves in a CCD

• By changing electrode voltages, charge can be
  moved to the output amplifier.
• This process is called charge transfer.
• In an IR array, this does not happen. Charge is
  sensed in place.

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CCD Readout Amplifier

• Packet of Q electrons is transferred through the
  output
• gate onto a storage capacitor, producing a
  voltage VQ/C.

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The Atmosphere
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Atmospheric absorption versus airmass

• The amount of absorbed radiation depends upon the
  number of absorbers along the line of sight

AM1
AM2
Atmosphere
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Atmospheric absorption versus altitude

• Particle number densities (n) for most absorbers
  fall off rapidly with increasing altitude.
• x0,H20 2 km, x0,CO2 7 km, x0,O3 15-30 km
• So, 95 of atmospheric water vapor is below the
  altitude of Mauna Kea.

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Atmospheric Turbulence

• A diffraction-limited point spread function (PSF)
  has a full-width at half-maximum (FWHM) of
• In reality, atmospheric turbulence smears the
  image
• At Mauna Kea, r00.2 m at 0.5 mm.
• Isoplanatic patch is area on sky over which
  phase is relatively constant.

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Atmospheric Turbulence
1.4O seeing
0.5O seeing
no seeing!
Lick 3-m Figer 1995PhD Thesis
Keck I 10-m Serabyn, Shupe, FigerNature 1998,
394, 448
HST/NICMOS 2.4-m Figer et al. 1999ApJ. 525, 750
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Adaptive Optics Eye Glasses for Ground-based
Telescopes
Laser Guide Star
Atmosphere
Wave Front Sensor
Adjust Mirror Shape
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Adaptive Optics Eye Glasses for Ground-based
Telescopes
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Where does NGST win?

• NGST should perform better than current 10m class
  ground-based telescopes.
• In the mid-IR range (wavelengths ? 3 ?), NGST
  will produce better quality (higher S/N) images
  and spectra than a 50m AO corrected ground-based
  telescope.
• For surveying large fields of view AO only
  works over a small field of view.
• Sky is much darker in space in NGSTs wavelength
  range better faint object detection.

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Observing in Space
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HST Facts

• Deployed 25 Apr 1990
• Mass 11600 kg
• Length 13.1 m
• Primary diameter 2.4 m
• Secondary 0.34 m
• f/24 Ritchey-Chrétien
• 28 arcmin field-of-view
• 0.11 mm lt l lt 3 mm
• 0.043 arcsec FWHM at 5000 Å

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HST Orbit

• Height 590 km
• Orbital period 96.6 minutes
• Precessional period 56 days
• Inclination 28.5
• Continuous viewing zones (CVZ) at ? 61.5

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Space Environment
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Magnetic Flux Tubes
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CCD Radiation Damage

• Radiation damage limits the science lifetime of a
  CCD
• Ionization damage - flat band shifts
• Bulk damage
• Displacement of Si atoms in lattice produces
  traps
• Hot pixels created by electrons from silicon
  valence band jump to trapping centers and
  generate high dark current
• Annealing once a month to mitigate hot pixel
  accumulation.
• WFPC2 is warmed to 20o C
• STIS CCD is warmed -15o C
• 80 of new hot pixels (gt0.1 electron sec 1 pix
  1 ) fixed

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Losses Transferring Charge
SITe 1024 ? 1024 CCD thinned backside
NGC 6752, 8 ? 20s, D amp at the top
Courtesy R. Gilliland (STScI)
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Parallel
Degradation of Charge Transfer Efficiency
Serial
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Optical Science

• Pretty Pictures
• Astrophysics

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Wide Field Planetary Camera 2
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Hubble Deep Field
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There is a Synergy between High Resolution
Optical and Radio Observations
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The Radio Loud/Quiet Transition

• Overall SED is similar for RL and RQ quasars.
• Why the difference in radio power?

Sanders Mirabel 1996, ARAA, 34, 749
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Smooth Distribution in Radio Loudness
FIRST quasars. Solid line all quasars, hatched
region newly discovered quasars .
Traditionally, radio loud objects have log R
3-4. Brinkmann etal 2000, AA, 356, 445
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Unimodal Distribution of Quasar Radio Luminosity
5 GHz luminosity of FIRST Bright Quasar Survey
II. White etal. 2000, ApJS, 126, 133
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Radio Luminosity Optical Line Correlation.
There is a strong correlation between radio
luminosity and optical emission line luminosity
for both RL and RQ objects. (see also Baum
Heckman 1989)
Xu etal 1999, AJ, 118, 1169
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Emission Lines are Powered by Accretion Disk
Luminosity.
There is a strong correlation between X-ray
luminosity and optical emission line luminosity
for both RL and RQ objects.
Xu etal 1999, AJ, 118, 1169
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The AGN Paradigm

• Annotated by M. Voit

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What Causes the RL RQ Transition?

• Earlier data indicated a Bi-modal distribution of
  radio loudness suggesting that the transition was
  very abrupt. New data suggests a continuous
  distribution of radio loudness. Thus, there is a
  more gradual transition.
• Previously it was thought that there was a
  correlation with host galaxy type I.e., RQs are
  in Spirals and RLs in Elliptical hosts. New data
  suggests that Ellipticals host both RQ and RL
  quasars but only those with optically luminous
  nuclei.

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Quasar Host Galaxy Observations

• Sample rest frame optical avoiding bright
  emission lines.
• Match samples in optical luminosity at different
  z. Kukula et al. 2001, MNRAS, 326 1533

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Properties of the Host Galaxies

• The surface brightness profiles are well fit by
  a r¼ law I.e. the host galaxies are bulge
  dominated.

Dunlop etal 2001, astroph
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Properties of the Host Galaxies

• The more luminous nuclei live in galaxies which
  are more bulge dominated.
• Disk-dominated hosts become increasingly rare
  with increasing nuclear power.

Relative contribution of the bulge to the total
luminosity of the host galaxy. RLQs are open,
RQQs are filled circles, are X-ray selected AGN
from Schade etal (2000). Dunlop etal 2001, astroph
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BH Mass vs. Galaxy Bulge Mass
There is a relationship between BH mass and bulge
luminosity. And an even tighter relationship with
the bulge velocity dispersion. M(BH) 10-3
M(Bulge). Ferrarese Merritt 2000, ApJ, 539, L9
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Consistency Between Different Methods

• BH Mass vs bulge magnitude relation is similar
  for both active and quiescent galaxies.

BH Mass vs bulge magnitude for quiescent
galaxies, Seyferts and nearby quasars. Size of
symbol for AGN is proportional to the Hß FWHM.
Merritt Ferrarese 2001, astro-ph/0107134
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BH Masses

• BH Masses tend to be high in these luminous
  quasars.
• Estimates of BH mass from Hß line widths and host
  spheroid luminosity are in rough agreement.
• RLQs tend to have higher BH mass than RQQs.
• Assumes Mbh 0.0025 Msph

Comparison between BH masses estimated from the
host galaxy spheriod luminosity and the Hß
line-width by McLure Dunlop (2001). The shaded
area marks BH masses greater then 109 solar
masses. RLQs are open, RQQs are filled circles.
Dunlop etal 2001, astroph
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What Fraction of Eddington Luminosity?

• RQQ and RLQs are radiating at 1-10 of their
  Eddington luminosity.

Observed nuclear absolute magnitude vs that
expected if the BH is emitting at the Eddington
luminosity. RLQs are open, RQQs are filled
circles. Solid, dashed, and dot-dashed are 100,
10 and 1 of Eddington luminosity. Dunlop etal
2001, astroph
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The Paradigm Shift

• Earlier data indicated a Bi-modal distribution of
  radio loudness suggesting that the transition was
  very abrupt. New data suggests a continuous
  distribution of radio loudness. Thus, there is a
  more gradual transition.
• Previously it was thought that there was a
  correlation with host galaxy type I.e., RQs are
  in Spirals and RLs in Elliptical hosts. New data
  suggests that Ellipticals host both RQ and RL
  quasars but only those with optically luminous
  nuclei.
• This is consistent with a correlation between
  optically luminous nuclei and massive BHs and
  between BH mass and host galaxy bulge mass.

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Is it BH Spin ?

• Possibilities include
• BH Mass (but both RQs and RLs live in big bulges
  and thus have high BH Mass)
• Mass accretion rate (but RQs and RLs have similar
  optical luminosities)
• BH Spin

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Time Scales for Gas Transport, Fueling, and AGN
Activity
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Double-Doubles -- Born-again Radio Sources

• 5-10 of gt 1 Mpc radio sources show
  double-double structure.
• Working hypothesis the radio galaxy turned off
  and then turned back on --creating a new double
  propagating outwards amidst the relic of the
  previous activity.
• Schoenmakers etal (2000)

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Schematic of Supersonic Jet Model

• Concept from Scheuer 1974, Blandford Rees 1974.
  Illustration from Carvalho ODea 2001.

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Probing Time Scales of Activity

• The double-doubles allow us to probe the
  timescale of recurrent activity and the nature of
  the fuelling/triggering of the activity.
• Selection effects will limit the time scales
  which can be detected in the double-doubles
• If the source tuns off for lt 106 yr the effects
  on the larger source may not be noticable, and
  the younger source may not be resolved from the
  core.
• If the source turns off for gt 108 yr, the larger
  source will fade.

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3C236 - 4 Mpc Radio Source

• The largest radio galaxy known.
• WSRT 92 cm image (55x96) Mack etal. 1997)
  overlayed on DSS image.

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The Inner 2 Kpc Double
Inner 2 kpc double is well aligned with outer 4
Mpc double

Global VLBI 1.66 GHz image (Schilizzi etal 2001)
superposed on HST WFPC2 V band image At z0.1,
and Ho75, 1 arcsec 1.7 kpc ODea etal. 2001,
AJ, 121, 1915
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The Host Galaxy (in color)

• Note
• dust lane along major axis
• tilted inner disk
• blue knots along inner
• edge of dust lane
• 3-color image.
• STIS Near-UV MAMA (F25SRF2 2300Å) 1440s
• WFPC2 F555W (V) 600s
• WFPC2 F702W (R) 560s
• ODea etal. 2001, AJ, 121, 1915

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STIS Near-UV Image

• Note the 4 very blue regions in an arc along the
  inner edge of the dust lane 0.5 (800 pc) from
  the nucleus, and perpendicular to the radio
  source axis.
• Regions are resolved with sizes 0.3 (500 pc)
• No strong emission lines in the F25SRF2 filter
• Most likely to be due to relatively young star
  formation
• Bruzual-Charlot population synthesis models are
  consistent with ages ? 5-10 Myr for knots 1,3 and
  100 Myr for knots 2,4
• STIS NUV image with global VLBI image (Schilizzi
  etal 2001) superposed.
• ODea etal. 2001, AJ, 121, 1915

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Ages Estimated via Comparison with Stellar
Population Models

• (Top) UV-V color as a function of time for
  Bruzual-Charlot models with both constant star
  formation and an instantaneous burst.
• (Bottom) Evolution in color-color space of 3
  models. Plotted are the colors of the 4 knots,
  the nucleus, and the older population in the host
  galaxy.
• Knots 1, 3 are consistent with 5-10 Myr, and
  knots 2, 4 with 100 Myr.
• ODea etal. 2001, AJ, 121, 1915

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Star Formation Properties
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Time Scales
Dynamical Ages Large radio source t7.8x108
(v/0.01c) yr (comparable to the age of the oldest
blue knots) Small radio source t3.2x105
(v/0.01c) yr (much younger than the youngest blue
knots) Dynamical time scale of the disk on the
few hundred pc scale t107 yr
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Alignments and the Bardeen-Petterson effect

• The small and large scale radio source are
  aligned to within about 10 deg.
• The radio sources are aligned to within a few
  degrees of perpendicular to the inner" (1 kpc)
  dust disk but are poorly aligned with the
  perpendicular to the larger dust lane.
• The Bardeen-Petterson effect will cause the
  black hole to swing its rotation axis into
  alignment with the rotation axis of the disk of
  gas (on scales of hundreds to thousands of
  Schwarzschild radii) which is feeding it and
  conversely will keep the spin axis of the inner
  disk aligned with the BH spin (e.g., Bardeen
  Petterson 1975 Rees 1978)
• The combination of the long term stability of the
  jet ejection axis and the alignment of the jets
  with the inferred rotation axis of the inner
  kpc-scale dust disk suggests that the orientation
  of the inner dust disk has also been stable over
  the lifetime of the radio source.
• This also implies that the outer misaligned dust
  lane (which presumably feeds the disk) settles
  into the same preferred plane as the disk.

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The Scenario

• The small and large radio sources are due to two
  different events of mass infall.
• Spectral aging estimates in the hot spotes of the
  large source imply the radio source may have
  turned off for 107 yr in between the two
  events.
• The difference in the ages of the young and old
  star formation regions also implies two different
  triggers.

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Implications

• The two episodes of radio activity and the two
  episodes of star formation are due to non-steady
  transport of gas in the disk.
• If the young radio source and the young starburst
  (knots 1,3) are related by the same mass
  transport event, the gas must be transported from
  the hundreds of pc scale to the sub-pc scale on
  the dynamical time scale.

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The Current Big Issues
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Current Big Issues for Optical Astronomy

• Planet Formation Evolution
• When, where, how frequently do planets form?
• How important is dynamical evolution in planet
  formation and consequent habitability?
• Answers will require powerful (high S/N, high
  res.) spectroscopic observations as 1 AU ? 0.002
  at Orion

?
?
?
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Current Big Issues for Optical Astronomy

• Star Formation Evolution
• Must have a more predictive and comprehensive
  theory for star formation evolution
• Will require studies of stellar systems in
  hundreds of other galaxies at (angular
  spectral) resolutions comparable with the work
  done in our own Galaxy

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Current Big Issues in Optical Astronomy

• Galaxy Formation Evolution
• When do the first stars and galaxies form?
• What processes trigger this formation and how do
  they affect a galaxys evolution?
• Develop a predictive theory of galaxy formation
  and evolution

Theory
HST Deep Field
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Current Big Issues for Optical Astronomy

• Large-scale Structure
• How are (proto) galaxies clusters distributed
  at when universe was only 25 of its current age
  (z gt 2)?
• How do the distributions depend on the galaxys
  mass, morphology, or star formation rate in these
  early epochs?
• How does structure evolve from the very smooth
  pattern when universe was only a few 100,000
  years old (z 1000) to the highly clumped and
  coherent pattern seen since last 6 billion years
  or so (z lt 1)?
• Answers will require large area telescope(s) with
  large FOV and (moderate resolution) spectrograph

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The End