The JCMT Past, Present,

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The JCMT - Past, Present, Future
Doug Johnstone RASC Victoria 2004 With thanks to
D. Pierce-Price, JAC
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The electromagnetic spectrum

• Sub-millimetre waves are between infrared and
  radio waves in the electromagnetic spectrum
• They have a wavelength of just under one
  millimeter

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What are we looking for?

• Exploring the cold universe
• Photons from cold gas and dust lt 100K (-170 C)
• blackbody radiation from dust
• Molecular signatures of rotating molecules
• Not looking at the stars (too warm)
• Exploring regions shielded from starlight
• Cold bodies such as planets, asteroids, and
  comets
• Dense puddles of gas -gt molecular clouds
• The location of star formation
• In distant Galaxies, perhaps the energy of star
  formation

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Location, Location, Location

• Observing in the sub-millimetre is hard
• Moisture in the atmosphere absorbs photons
• Similar principle to microwave oven cooking!
• Energy per photon is terribly low
• UV cooks, infrared warms, radio doesnt worry us
• Put telescope above much of the atmosphere
• Space too expensive (cant launch large dish)
• Top of mountains excellent alternative
• But the astronomer has trouble breathing and
  thinking

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My Last Vacation on Mauna Kea
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The Worlds Largest Sub-mm Telescope

• Primary dish is 15 meters in size
• 276 individual aluminum panels
• Which, by the way, need to be cleaned
• Adjusted to within 25 microns accuracy
• Total weight 70 tons
• And yet even I can crank it to zenith!
• Remarkably flexible secondary (sub-reflector)
• Can wobble and wiggle in two dimensions
• Enclosure is protected from weather
• by the Worlds largest piece of Gore-Tex
• 97 transparent to millimetre photons

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Sub-millimetre Astronomy

• Grains of interstellar dust, at temperatures of a
  few tens of degrees above absolute zero, emit a
  heat glow at sub-millimetre wavelengths
• Molecules in space produce characteristic
  sub-millimetre radiation when they rotate
• But sub-millimetre astronomy is difficult to do,
  needing
• advanced technology
• a good telescope site

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The cold universe

• Sub-millimetre radiation is used to study the
  cold material in the universe
• This includes planets and comets within the solar
  system, as well as the Interstellar Medium (ISM)
• The ISM contains gases (mostly hydrogen) and
  interstellar dust grains (fine particles like
  soot or sand)
• It is a vital part of the life-cycle of stars

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The Interstellar Medium

• Dust in the ISM obscures our view at visible
  wavelengths
• At longer, infrared wavelengths we can see
  through the dust
• To study the cold ISM itself, we use
  submillimeter wavelengths

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Star formation

• There are about 100 billion stars in our Milky
  Way galaxy
• Stars are born when a cloud of gas and dust
  collapses under its own gravity and begins
  nuclear fusion
• Dust absorbs light at optical wavelengths,
  obscuring our view of star formation
• To study these processes, we turn to
  submillimeter waves, which penetrate the dust

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Heterodyne instruments

• Measure the precise spectrum of submillimeter
  radiation
• Study spectral lines from molecules in space
  fingerprints to deduce the physical conditions
  of the gas (temperature, mass, motion)
• Three receivers, RxA3, RxB3, and RxW operate in
  different wavelength ranges

Orion 2.6mm CO, John Bally
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CO - second most common molecule
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CH3OH - not the stuff you drink!
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SCUBA

• The Submillimetre Common-User Bolometer Array
• The best submillimeter camera in the world
• Second only to HST in its impact on research
• Sensitive bolometer arrays, cooled to just 60mK,
  measure continuum radiation
• This radiation is the heat glow of cold
  interstellar dust
• A total of 128 pixels at two wavelengths

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Inside SCUBA
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http//outreach.jach.hawaii.edu/webcams/
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The Galactic Centre

• Go out on a clear night and look at the Milky Way
  - the plane of our own Galaxy
• The Galactic Centre is in the direction of
  Sagittarius
• The dark patches obscuring your view are clouds
  of interstellar dust
• They make it impossible to study the Galactic
  core at visible wavelengths

Galactic plane
Galactic centre
Moon
Bill Keel, U. of Alabama
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SCUBA Galactic Centre map
Pierce-Price et al.

• Submillimeter waves let us see right through to
  the heart of the Milky Way, 27,000 light years
  from Earth
• The clouds of dust and gas, wispy filaments,
  bubbles and shells are shaped by intense winds
  from stars, magnetic fields, and the explosions
  of supernovae
• This is one of the largest, deepest, most
  detailed such map ever made

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Orion optical and infrared
IRAS
Optical

• The familiar constellation Orion contains the
  closest sites of massive star formation, about
  1,500 light years from Earth.

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Orion submillimeter
IRAS
Johnstone Bally

• SCUBA shows us a ridge of interstellar gas and
  dust. Along this ridge are dense knots of
  material where stars are about to be born.

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Dust Emission vs. Starlight
Sub-millimeter
optical light
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Ophiuchus JCMT 2003
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Hubble Deep Field (HDF)
There are as many galaxies in the universe as
there are stars in our own galaxy about 100
billion.
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Dust at the dawn of time

• SCUBA has detected very distant dusty galaxies
• The dust hides the galaxies from optical
  telescopes like Hubble we need the JCMT to see
  them
• Since interstellar dust is created by stars,
  these stellar ashes tell us about star formation
  in the early universe
• The most distant detections are almost nine
  tenths of the way back to the start of time

SCUBA HDF, Hughes et al.
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Smoking supernovae solve a ten billion year-old
mystery
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Other worlds

• Telescopes let us travel a long way from our
  own planet, and our own star, the Sun
• But are there other planets around other stars?
• If we want to look for life elsewhere in the
  Universe, it will probably be on planets
• Extra-solar planets are hard to detect directly
• We need to look for other evidence

JPL/NASA
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Other worlds

• SCUBA has found evidence of extrasolar planets,
  where they have disturbed the dust discs around
  their stars
• The disc around nearby Epsilon Eridani is similar
  to a young Kuiper Belt
• Computer simulations suggest its clumpy ring
  shape is caused by planets
• Similar observations of Fomalhaut, Vega, and Beta
  Pictoris have been made

Greaves et al.
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Other worlds

• SCUBA has found evidence of extrasolar planets,
  where they have disturbed the dust discs around
  their stars
• The disc around nearby Epsilon Eridani is similar
  to a young Kuiper Belt
• Computer simulations suggest its clumpy ring
  shape is caused by planets
• Similar observations of Fomalhaut, Vega, and Beta
  Pictoris have been made

Greaves et al.
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Other worlds
Lynette Cook http//extrasolar.spaceart.org
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PAST PRESENT-FUTURE
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The future-future of JCMT

• New instruments will keep JCMT at the forefront
  of research
• Future strategy will focus on wide-field survey
  projects
• JCMT will complement the Atacama Large Millimetre
  Array (ALMA)
• ALMA has excellent resolution
• JCMT has a much wider field of view
• JCMT will also link with the Submillimeter Array

ALMA fov
JCMT fov
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HARP-B

• Heterodyne Array Receiver Programme at B-band
• An imaging array like SCUBA, but with heterodyne
  detectors to measure spectral information
• A total of 16 detector elements
• The first heterodyne array instrument operating
  at the 850µm wavelength

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SCUBA 2

• The next generation SCUBA
• 1000 times faster mapping speed than SCUBA 1
• total of 12,800 detector elements
• new detector technology
• 16 times larger field of view

SCUBA 1 fov
SCUBA 2 fov
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Summary

• The James Clerk Maxwell Telescope uses
  submillimetre wavelength light to study star
  birth and the cold material in the universe
• From the excellent astronomical site of Mauna
  Kea, the JCMT can take us on a journey through
  our own Galaxy and beyond, all the way back to
  the early universe, and home again
• The future of the JCMT is STILL bright