A New Infrared Diagnostic for AGNs using 2MASS and New 10 micron Data
Abstract
To study dust in Seyfert (Sy) Galaxies, we have combined new high resolution N band photometry for 87 Sy's with 2MASS J and Ks band photometry to obtain color-magnitude and color-color relations for the central 1 arcs of Active Galactic Nuclei (AGN) from the IRAS 12 micron Sample.
The J-Ks vs. absolute N band color-magnitude diagram shows a trend of increasing absolute N band luminosity with redder J-Ks colors. This result is consistent with a simple first order picture in which an AGN with more emission at N, also has more emission at Ks, which dominates the flux from the bulge stars and leads to a redder J-Ks color. The J-Ks vs Ks-N color-color diagram also shows an interesting relation. Most of the Sy's occupy a limited area of the color-color diagram, but there are many outliers which we believe represent two different dust distributions at work. Those galaxies with very red J-Ks seem to be those that have dust in their host galaxy reddening their nuclear light. On the other hand, those with very red Ks-N colors but with bulge-like J-Ks colors may, through a combination of torus geometry and dust content, lead us to observe along a line of sight of very heavy extinction, absorbing even J and Ks light but allowing N band light to penetrate leading to a redder Ks-N color.- Publication:
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Coevolution of Black Holes and Galaxies
- Pub Date:
- 2004
- Bibcode:
- 2004cbhg.sympE..20G