AN INFRARED COMPARISON OF TYPE-1 AND TYPE-2 QUASARS
- Department of Physics and Astronomy and Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 (United States)
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Department of Physics and Astronomy, Haverford College, Haverford, PA 19041 (United States)
- NOAO/CTIO, 950 N. Cherry Ave, Tuscon, AZ 85719 (United States)
We model the optical to far-infrared spectral energy distributions (SEDs) of a sample of six type-1 and six type-2 quasars selected in the mid-infrared. The objects in our sample are matched in mid-IR luminosity and selected based on their Spitzer IRAC colors. We obtained new targeted Spitzer Infrared Spectrograph and Multiband Imaging Photometer for Spitzer observations and used archival photometry to examine the optical to far-IR SEDs. We investigate whether the observed differences between samples are consistent with orientation-based unification schemes. The type-1 objects show significant emission at 3 mum. They do not show strong polycyclic aromatic hydrocarbon (PAH) emission and have less far-IR emission on average when compared to the type-2 objects. The SEDs of the type-2 objects show a wide assortment of silicate features, ranging from weak emission to deep silicate absorption. Some also show strong PAH features. In comparison, silicate is only seen in emission in the type-1 objects. This is consistent with some of the type-2's being reddened by a foreground screen of cooler dust, perhaps in the host galaxy itself. We investigate the active galactic nucleus contribution to the far-IR emission and find it to be significant. We also estimate the star formation rate (SFR) for each of the objects by integrating the modeled far-IR flux and compare this with the SFR found from PAH emission. We find that the type-2 quasars have a higher average SFR than the type-1 quasars based on both methods, though this could be due to differences in bolometric luminosities of the objects. While we find pronounced differences between the two types of objects, none of them are inconsistent with orientation-based unification schemes.
- OSTI ID:
- 21378177
- Journal Information:
- Astrophysical Journal, Vol. 706, Issue 1; Other Information: DOI: 10.1088/0004-637X/706/1/508; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ABSORPTION
BOLOMETERS
DUSTS
EMISSION
ENERGY SPECTRA
GALAXIES
LUMINOSITY
PHOTOMETERS
PHOTOMETRY
POLYCYCLIC AROMATIC HYDROCARBONS
QUASARS
SILICATES
STARS
AROMATICS
COSMIC RADIO SOURCES
HYDROCARBONS
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICON COMPOUNDS
SORPTION
SPECTRA