Tuesday, February 5, 2013

1302.0113 (Ming-Yi Lin et al.)

Role of AGNs in the Ultra-Luminous Infrared Galaxy phase since z ~ 3    [PDF]

Ming-Yi Lin, Sebastien Foucaud, Yasuhiro Hashimoto
In order to understand the mutual influence between active galactic nuclei (AGN) and star formation during the evolution of galaxies, we investigate 142 galaxies detected in both X-ray and 70{\mu}m observations in the COSMOS (Cosmic Evolution Survey) field. All of our data are obtained from archive, X-ray point source catalogs from Chandra and XMM-Newton observation; far-infrared 70{\mu}m point source catalog from Spitzer-MIPS observation. Although the IRAC colors of our samples indicate the existence of star formation, the ratio of rest frame 2-10 keV luminosity to total infrared luminosity (8-1000{\mu}m) shows that AGN predominates the spectral energy distribution (SED). We identify obscured AGN in these 70{\mu}m luminous galaxies as characterized by a larger hardness ratio. The higher X-ray obscuration fraction indicates an extra contribution from the star formation in the host galaxy in addition to the usual AGN dusty torus. If AGN feedback occurs in their host galaxies, the star formation must be quenched and dust in host galaxy will be dispersed. However, our temperature fitting shows there is no significant dust temperature enhancement in far-infrared wavelength, suggesting the thermal radiative feedback is absent from the AGN to the galaxy.
View original: http://arxiv.org/abs/1302.0113

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