NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Exploring the Connection Between Star Formation and AGN Activity in the Local UniverseWe study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from SDSS and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic con- tributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [NeII] 12.8 micron emission-line is well correlated with the star formation rate (SFR) measured from the SDSS spectra, and this holds for the star forming, composite, and AGN-dominated systems. AGN show a clear excess of [NeIII] 15.6 micron emission relative to star forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including: the mid-IR spectral slope, the ratio of the [NeV] 14.3 micron to [NeII] micron 12.8 fluxes, the equivalent widths of the 7.7, 11.3, and 17 micron PAH features, and the optical "D" parameter which measures the distance a source lies from the locus of star forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN-dominance. We find that the PAH 11.3 micron feature is significantly suppressed in the most AGN-dominated systems.
Document ID
20130012783
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
LaMassa, Stephanie M.
(Johns Hopkins Univ. MD, United States)
Heckman. T. M.
(Johns Hopkins Univ. MD, United States)
Ptak, Andrew
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Schiminovich, D.
(Columbia Univ. NY, United States)
O'Dowd, M.
(Lehman (Herbert H.) Coll. Bronx, NY, United States)
Bertincourt, B.
(Columbia Univ. NY, United States)
Date Acquired
August 27, 2013
Publication Date
June 25, 2012
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN7966
Distribution Limits
Public
Copyright
Public Use Permitted.
No Preview Available