Studies Of The Spectral Energy Distribution On Low-Redshift Infrared Quasars

Photometric and spectroscopic data from the X-ray to the radio were collected for a local infrared qusai-stellar objects (IR QSOs) sample with33objects. To make sure the accuracy of the data, we carefully examined the photometry in the near-infrared-optical band and remeasured the fluxes in the UV band for several targets. After corrections for the galactic extinction, the aperture effects,and the redshift, we obtained the rest-frame spectral energy distribution (SED) for each object and the mean/median SED for our IR QSOs sample.The SEDs from the X-rays to the radio exhibit that IR QSOs are in the middle of Ultra-Luminous InfraRed Galaxies (ULIRGs) and Palomar-Green Quasars (PG QSOs). Specifically, the SEDs of IR QSOs are higher than PG QSOs and lower than ULIRGs in the shorter wavebands (<1μm) and the situation is the opposite in the longer wavelengths (>1μm). It is possible that IR QSOs are in a transition stage from starburst-dominated ULIRGs to classical QSOs.Active Galactic Nuclei (AGN) and star forming activities are mainly responsible for the energy of IR QSOs. In order to obtain ratios for the two possible components, we fitted the average/median SED of our IR QSOs through a linear combination of starburst galaxy templates and quasar templates. The result shows that the energy from AGN is more important than starburst in the high frequency while in the low frequency star forming is the dominated mechanism of energy in IR QSOs.