GALEX Observing Program Description:

The GOALS GALEX sample consists of 135 systems observed as part of GALEX Cycle 1 program #13 (PI Mazzarella), GALEX Cycle 5 program #38 (PI Howell), the Nearby Galaxy Survey (NGS), and the All Sky Survey (AIS). All systems have been observed in both the FUV and NUV. Integration times range from ~100s for the AIS data to > 1500s for the Cycle 1, Cycle 5, and NGS data. Aside from a handful of galaxies not yet observed from the Cycle 5 program, the 135 systems described in Howell et al. (2010) represent all GOALS targets accessible to GALEX.

Although they are rare in the local Universe, recent IR and sub-mm surveys indicate that LIRGs dominate the radiant energy density of the Universe at high redshifts. In order to interpret rest-frame UV observations of high-redshift IR/sub-mm galaxies, it is essential to measure UV properties that can be observed with high spatial resolution and high S/N only in their nearby analogs. These GALEX observations are therefore of critical importance for understanding the origin and evolution of luminous starburst galaxies and AGNs in the local Universe and through cosmic time.

Primary questions to be answered include:
  • How do the star formation rates derived from UV emission vary with the stage of the interaction/merger, the mass ratio of the galaxies, the geometry of the encounter, and the properties of each galaxy as known from multi-wavelength observations?
  • How do the proportions of UV emission contained in the nuclei, spiral arms, tidal tails, and disk overlap regions change as a function of the interaction/merger stage? When do star-forming regions in tidal tails first ''light up,'' peak, and fade?
  • We are also analyzing the GALEX data in conjunction with other observations in GOALS to address these additional questions:
    • What are the proportions of star formation in UV-bright regions with low extinction vs. dust-enshrouded regions?
    • How do UV extinction maps (from UV/IR images) depend on the properties of each system?
    • How do the emergent UV fluxes compare to predictions from models of the UV interstellar radiation field strengths derived from far-IR line ratio diagnostics?
    • What fraction of UV radiation is escaping from LIRGs and ULIRGs into the intergalactic medium?
A tabulated target list of the GALEX imaging program is provided here.