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تسجيل مستخدم جديدThe Nearby QSO Host I Zw 1: NIR Probing of Structural Properties and Stellar Populations
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J. Scharwaechter
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The likely merger process and the properties of the stellar populations in the I Zw 1 host galaxy are analyzed on the basis of multi-wavelength observations (with the ISAAC camera at the Very Large Telescope (VLT/UT1) of the European Southern Observatory (ESO), Chile (Paranal), with the interferometer of the Berkeley-Illinois-Maryland Association (BIMA), USA (Hat Creek/California), and with the IRAM Plateau de Bure Interferometer (PdBI), France) and N-body simulations. The data give a consistent picture of I Zw 1, with properties between those of ultra-luminous infrared galaxies (ULIRGs) and QSOs as displayed by transition objects in the evolutionary sequence of active galaxies.
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The relation between tidal interactions, starbursts, and the onset and/or fueling of active galactic nuclei (AGN) is a matter of debate. I Zw 1 is considered as the prototypical narrow-line Seyfert 1 galaxy (NLS1) and as one of the closest quasi-stel
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are complemented by new observations of the 12CO(2-1) and 13CO(1-0) line with IRAM Plateau de Bure mm-interferometer (PdBI) at 0.9 and 1.9 resolution, respectively. These measurements, which are part of a multi-wavelength study of the host galaxy of I Zw 1, are aimed at comparing the ISM properties of a QSO host with those of nearby galaxies as well as to obtain constraints on galaxy formation/evolution models. Our images of the 12CO(1-0) line emission show a ring-like structure in the circumnuclear molecular gas distribution with an inner radius of about 1.2 kpc. The presence of such a molecular gas ring was predicted from earlier lower angular resolution PdBI 12CO(1-0) observations. A comparison of the BIMA data with IRAM PdBI 12CO(2-1) observations shows variations in the excitation conditions of the molecular gas in the innermost 1.5 comprising the nuclear region of I Zw 1. The observed properties of the molecular cloud complexes in the disk of the host galaxy suggest that they can be the sites of massive circumnuclear star formation, and show no indications of excitation by the nuclear AGN. This all indicates that the molecular gas in a QSO host galaxy has similar properties to the gas observed in nearby low luminosity AGNs.
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