CHemical Abundances Of Spirals


1000 HII region spectra from 13 spiral galaxies drawn from the Spitzer Infrared Nearby Galaxies Survey (SINGS) using MODS on the Large Binocular Telescope (LBT). The survey aims to increase by more than an order of magnitude the number of HII regions in spiral galaxies with sufficient quality spectra to provide accurate measurements of the physical conditions (temperatures, densities, ionization parameters) necessary to accurately determine their absolute and relative chemical abundances. These will be used to solve the above problems and will be of use to multiple future studies of the SINGS galaxies.

The history of a galaxy is one of increasing abundances of heavy elements as successive generations of stars return their newly synthesized elements to the interstellar medium. The status of the abundances of the interstellar medium can be determined through analyzing the emission line spectra of ionized gas (HII) regions. However, after decades of observations, the present day measurements of the chemical abundances in the interstellar media (ISM) in spiral galaxies carry unacceptably high uncertainties. In order to definitively establish the abundances in spiral galaxies, our goal is to observe, reduce, and analyze a sample of approximately

NGC 628

Slit Positions for 3 CHAOS fields observed in NGC 628

NGC 628 CHAOS Field 1, Region 20. Top: extracted 1D flux-calibrated spectra

Bottom Left: Ha image with the region marked (magenta square),

Bottom Right: Derived  O/H (blue at far right) plotted over the strong-line O/H data from Moustakas 2010.

NOTE: This 1D spectrum is from an early reduction.  Current sky subtraction is better.