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Date and Time of the Query: 2019-05-26 T06:48:01 PDT
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For refcode 1997MNRAS.292..273W:
Retrieve 92 NED objects in this reference.
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NED Abstract

Copyright by Royal Astronomical Society. 1997MNRAS.292..273W The extinction, flux distribution and luminosity of Seyfert 1 nuclei derived from UBV(RI)_C_ aperture photometry K. Winkler Accepted 1997 July 1. Received 1997 July 1; in original form 1996 August 28 ABSTRACT UBV(RI)_c_ aperture photometry was carried out over a 4-yr period for 92 broad-line Seyfert galaxies. Where possible, the observations were repeated at different epochs in order to try to detect brightness variations. Significant variations were found in the majority of the objects observed at more than one epoch. Plots of the flux measurements through different bands against each other closely resemble linear relationships. Error contours of the data points in these plots are shown to be covariant ellipses. A statistical method is developed that enables one to obtain the best linear fit taking into account the error geometry peculiar to these data. The nuclear colours are determined for 50 significantly variable objects by calculating the best straight-line fits according to this statistical method. Chi-squared tests are used to show that, contrary to claims made in some recent studies, there is no significant deviation of the data from the straight-line fit in the vast majority of cases. This confirms the result of a previous paper that the shape of the nuclear flux distribution remains constant despite variations of the flux. The dereddened intrinsic colours for Seyfert nuclei are derived from the bluest nuclei, and these are then used to determine the nuclear reddening and extinction. It is shown that there are strong reasons to believe that the extinction values thus obtained are more accurate than those obtained though other methods, such as Balmer line ratio measurements. The relationship between galaxy inclination and nuclear extinction is found to be very poorly defined, showing that the extinction largely depends on amount of dust in the circumnuclear region rather than interstellar dust in the galaxy itself. Nuclear fluxes are determined after subtracting the background flux. These and the intrinsic colours are combined with infrared and ultraviolet data to construct the typical Seyfert nuclear flux distribution. The significance of the derived flux distribution for theoretical accretion disc models is discussed. Extinction corrected nuclear absolute magnitudes are then calculated and the effect of reddening and improved background subtraction on the Seyfert luminosity function determinations is briefly described. Key words: methods: statistical - dust, extinction - galaxies: photometry - galaxies: Seyfert.
Retrieve 92 NED objects in this reference.
Please click here for ADS abstract

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