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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]

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Arecibo Synergy with GLAST (and other gamma-ray telescopes)

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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


GLAST LAT AGILE

TeV

Known Gamma-ray Sources Are Multiwavelength

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.

INTEGRAL GLAST GBM Swift


Gamma-ray Facilities: More Numerous, More Capable

Swift

GLAST

INTEGRAL

ARGO-YBJ

H.E.S.S.

CANGAROO

Milagro

MAGIC

VERITAS


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


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


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


  • 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

    • Pulsars (already discussed by Alice Harding)

  • Special thanks to Chris Salter for advice!

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.


Diffuse Emission

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?

  • 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.

  • The Arecibo GALFACTS program is strongly complementary to the gamma-ray diffuse study.


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?


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?


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.

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.

What sort of compact object?

How are the particles accelerated?

Are there different types of such high-mass binary systems?


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)?


Summary

The nonthermal nature of high-energy gamma-ray 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 gamma-ray astrophysics.


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