Results:

Goal: To constrain the production of various types of SNe as a function of host stellar properties. Our first exploration is into how effective a local measurement of host stellar population will be in this effort. If the time-scales for production are long, there should be no correlation with local properties since the SN will have moved far from its birth site. We compare local measures with host integrated properties to judge the effectiveness and to isolate subsets of objects with short timescales that could benefit from a local analysis. This kind of comparison is only possible with relatively nearby galaxies where interesting physical scales are equal to or larger in angular size than the resolution of wide-field survey instruments. GALEX and 2MASS offer near all-sky coverage with sufficient resolution in useful wavebands for this exploration.

Procedure: GALEX and 2MASS background-subtracted images are analyzed using physically sized apertures at 500pc, 1kpc, and 2kpc placed on the site of the SN as determined from the coordinates in the input catalogs. An additional aperture at the GALEX limiting spatial resolution (5.6 arcsec in the NUV) is measured. The IDL aper.pro routine is used with the /exact keyword to minimize aperture approximation errors. We require the GALEX image to have at least 1000 seconds of exposure and we limit the host inclination to <70°. We further restrict our sample by requiring that the physical aperture size be equal to or greater than the spatial resolution of GALEX.

Sample: The starting sample for these experiments is the Asiago SN catalog and the SAI SN catalog. The coordinates for both of these catalogs are cross-checked and discrepancies are resolved where possible with the IAU circulars.

We use three major groupings of SN type:

  1. Thermonuclear SNe (Ia, plotted in black)
  2. Core-collapse SNe showing no Hydrogen (Ib, Ib/c, Ic, plotted in red)
  3. Core-collapse SNe showing Hydrogen (all type II, plotted in green)
    • We also isolate Ic SNe (plotted in orange)

Experiments: The first experiment examines the color distribution of integrated host light and at the sites of SNe to see how SN types distinguish each other. We then add information by looking at color as a function of surface brightness (µ). Taking advantage of the GALEX Nearby Galaxy Atlas (NGA) and the 2MASS Large Galaxy Atlas (LGA), we analyze SN site properties relative to the profile of the host galaxy. Then we compare the SN types by plotting their host and site positions in the color-magnitude and color-color plots of the NGA. Finally, for type Ia SNe, we plot the SN host and site properties as a function of the SN Ia light curve parameters.

Extending the Sample: Not all of the nearby galaxies imaged by GALEX and 2MASS have been analyzed to derive profiles and/or integrated magnitudes. The following lists of hosts will be analyzed to increase the sample substantially: