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Exploring the Connection Between Star Formation and AGN Activity in the Local Universe
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Author and Affiliation:
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)
Abstract: We 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.
Publication Date: Jun 25, 2012
Document ID:
20130012783
(Acquired Apr 22, 2013)
Subject Category: ASTROPHYSICS
Report/Patent Number: GSFC-E-DAA-TN7966
Document Type: Preprint
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 51p; In English; Original contains color and black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: ACTIVE GALACTIC NUCLEI; INFRARED RADIATION; POLYCYCLIC AROMATIC HYDROCARBONS; STAR FORMATION; STAR FORMATION RATE; ACTIVE GALAXIES; SPECTROGRAPHS; SPECTROSCOPY; SKY SURVEYS (ASTRONOMY)
Miscellaneous Notes: to be published in The Astrophysical Journal, 2013
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