Download and other gamma-ray telescopes

Gamma-ray Large
Area Space
Telescope
Arecibo Synergy with GLAST
(and other gamma-ray telescopes)
Frontiers of Astronomy with the
World’s Largest Radio Telescope
12 September 2007
Dave Thompson
GLAST Large Area Telescope
Multiwavelength Coordinator
[email protected]
for the GLAST Mission Team
see http://glast.gsfc.nasa.gov and links therein
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Known Gamma-ray Sources Are Multiwavelength
GLAST LAT
AGILE
TeV
INTEGRAL
GLAST GBM
Swift
Gamma-ray
sources are
nonthermal,
typically produced
by interactions of
high-energy
particles.
Known classes of
gamma-ray sources
are
multiwavelength
objects, seen
across much of the
spectrum.
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Gamma-ray Facilities: More Numerous, More Capable
Swift
GLAST
INTEGRAL
CANGAROO
MAGIC
ARGO-YBJ
Milagro
H.E.S.S.
VERITAS
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GLAST: Gamma-ray Large Area Space Telescope
Two GLAST instruments:
Large Area Telescope
LAT: 20 MeV – >300 GeV (LAT
was originally called GLAST
by itself)
LAT field of view ~2.5 sr
GLAST Burst Monitor
GBM: 10 keV – 25 MeV
GBM field of view ~9 sr
Launch: This Winter
Lifetime: 5 years minimum, 10
years goal
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What Do Gamma-ray Measurements Offer?
• Huge energy range – 9+ orders of magnitude
• All-sky coverage, from both ground and space (GLAST
will see the entire sky every three hours)
• Excellent sensitivity compared to previous instruments
(GLAST LAT is about 30 times more sensitive than
EGRET on the Compton Gamma Ray Observatory)
• Good source locations – 1 arcmin in many cases
• High time resolution for individual photons
• Imaging for some extended sources
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Some Other Needs for Astrophysics
• Distance – redshift, Dispersion Measure, proper motion,
column density
• Composition – spectroscopy
• Precise source locations and imaging
• Velocities
• Polarization
• Magnetic fields
• Theories to connect the observations to physical
models
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What gamma-ray science topics offer the best
opportunities for cooperation with the Arecibo telescope?
Some possibilities:
• Gamma-ray bursts (talk tomorrow)
• Diffuse Galactic emission
• Blazars
• Radio galaxies
• Microquasars
So far, gamma-ray telescopes have
only seen the brightest objects – the
“tip of the iceberg.” The fainter
sources are where Arecibo will be
critical.
• Pulsars (already discussed by Alice Harding)
Special thanks to Chris Salter for advice!
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Diffuse Emission
• Diffuse gamma-ray emission comes from
particle interactions with matter and photon
fields. Due to the limited angular resolution of
gamma-ray detectors, it also represents a
significant background.
• The model we use (shown above) uses
GALPROP, a cosmic-ray propagation code that
incorporates information about gas, radiation,
and magnetic fields.
How do the GALFACTS and
GALPROP/gamma-ray studies
compare in interpreting the
Galactic magnetic
field/particle distributions?
What do these results imply
about particle confinement
and propagation?
Can we use this information to
search for local sources of
cosmic rays?
• The Arecibo GALFACTS program is strongly
complementary to the gamma-ray diffuse study.
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Blazars
• Blazars are a major gamma-ray source class.
• There is some evidence of correlation between
gamma-ray flares and emergence of new radio
components of the jet, seen in VLBI.
• Several VLBI programs are monitoring blazars for
GLAST (MOJAVE, VIPS, Boston, Australian).
• GLAST is expected to see more than 1000 blazars.
Most will not be bright radio sources.
• Higher sensitivity VLBI measurements will be
needed.
What do the combined radio/gamma-ray
observations tell us about particle acceleration and
interaction – processes, location?
What can this information reveal about jet
formation and collimation?
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Radio Galaxies
Left: TeV and radio
images of M87, one of a
handful of radio
galaxies seen in
gamma rays.
Right: TeV variability of M87.
Is the gamma-ray variability related to
changes in the jet? In the core?
What about fainter radio galaxies?
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Microquasars – Binary Systems
LSI 5039 – compact object in orbit
around an O star.
Gamma-ray emission varies during
the 4 day orbit.
VLBI suggests that the emission
comes from a jet.
What sort of
compact object?
How are the
particles
accelerated?
Are there different
types of such highmass binary
systems?
LSI +61 303 – compact
object in orbit around a Be
star.
Gamma-ray emission varies
during the 26 day orbit.
VLBI suggests that the
emission comes from a
pulsar wind.
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The Unknown
Over half the sources in the
third EGRET catalog remain
unidentified.
GLAST will detect many
more sources.
Identifying and
understanding such sources
will be a multiwavelength
challenge.
What other types of objects
produce high-energy gamma rays
and radio?
Are there radio-quiet gamma-ray
sources (e.g. beamed)?
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Summary
The nonthermal nature of high-energy gammaray emission almost assures that gamma-ray
sources will be radio sources.
The new generation of gamma-ray telescopes is
already expanding the number and types of
sources, and this process will accelerate with
GLAST.
Radio, especially the great sensitivity of
Arecibo, will be a critical partner with gammaray astrophysics.
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