EXPLORING THE CONNECTION BETWEEN STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN THE LOCAL UNIVERSE

Journal Article · Wed Oct 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/758/1/1· OSTI ID:22092128

LaMassa, Stephanie M.; Heckman, T. M. ^[1]; Ptak, A. ^[2]; Schiminovich, D.; Bertincourt, B. ^[3]; O'Dowd, M. ^[4]

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1. Johns Hopkins University, Department of Physics and Astronomy, Baltimore, MD 21218 (United States)
2. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
3. Columbia University, Department of Astronomy, New York, NY 10027 (United States)
4. Lehman College, City University of New York, Bronx, NY 10468 (United States)

We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (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 contributions 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 [Ne II] 12.8 {mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6 {mu}m 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 [Ne V] 14.3 {mu}m to [Ne II] {mu}m 12.8 fluxes, the equivalent widths of the 7.7 {mu}m, 11.3 {mu}m, and 17 {mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical 'D' parameter which measures the distance at which 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 {mu}m feature is significantly suppressed in the most AGN-dominated systems.

• OSTI ID: 22092128
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 758; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
DUSTS
GALAXY NUCLEI
INFRARED SPECTRA
INTERMEDIATE INFRARED RADIATION
LUMINOSITY
NEON IONS
PHOTON EMISSION
POLYCYCLIC AROMATIC HYDROCARBONS
SEYFERT GALAXIES
STAR EVOLUTION
STARS
UNIVERSE
VISIBLE SPECTRA