GLAST Scientific Objectives

The science questions that GLAST will address are as follows:

Q1: How do active galactic nuclei (AGN) form and evolve? What does the high-energy spectrum of an AGN look like? If the spectrum falls rapidly at high energies, is it due to something intrinsic in the source, or due to absorption by intervening material?

• detect about 5000 AGN at varying distances
• obtain energy spectra that can differentiate between models for high-energy AGN emission
• compare high energy AGN emission to observations at other wavelengths

Q2: What is the nature of jets emanating from AGNs and Galactic black holes? How are the particles in the jets accelerated?

• use LAT as first alert for coordinated ground based activities to study jets
• monitor the variability and flaring behavior in jets
• obtain energy spectra that can differentiate between models for jet emission
  

• resolve thousands of sources at high-galactic latitudes
• determine the contribution of these sources to the isotropic background
• set limits on any truly diffuse component

• map extended sources of high-energy gamma-radiation
• determine energy spectra of resolved components
• identify spectral signatures of acceleration
  

• perform time-resolved spectroscopy of gamma-ray bursts at high energies


• detect hundreds of gamma-ray bursts during five year nominal lifetime


• correlate higher energy burst emission seen by LAT to lower energy bursts seen by GBM


• distinguish between models for the emission by comparing high and low energy burst spectra
  

• obtain accurate positions that can be correlated to known objects at lower energies


• obtain energy spectra and study time variability to aid in identification

• search high energy emission in integrated flux from several years of data for line features that could characterize dark matter annihilation.

Q8: How do rotation-powered pulsars generate high-energy gamma-rays? What is the relation of this radiation to emission observed in lower energy bands?

• perform time-resolved spectroscopy of pulsar beams
• study hundreds of gamma-ray pulsars
• identify new, possibly radio-quiet pulsars by direct detection of pulsed emission
• obtain energy spectra that can differentiate between models for pulsar emission
  

Because of its wide field-of-view, great sensitivity, excellent positional accuracy, timing accuracy free from electronic "dead-time" effects, and wide energy coverage (especially for gamma-ray bursts), GLAST is ideally suited to answer these questions.