Apparent total I magnitude: it
"it" is the apparent total I magnitude reduced to the Mathewson
et al (1992) system.
The reduction of a given magnitude m to it is given by:
it = m + a
where a is constant and given in the table below for each reference
taken into account. The mean it magnitude is calculated as a weighted
mean where the weight ("w", third column) is derived from each source
of magnitude as the inverse square of the mean standard deviation. The
final actual uncertainty sit is derived from the
The DENIS data are extracted from the provisional catalogue of
43,000 galaxies by
Vauglin et al (1999) and Paturel
et al (2003).
The DENIS I-band images were flat-fielded and de-biased at the Paris
Data Analysis Center (PDAC) following the general procedure of
treatment of DENIS data
(Borsenberger 1997). Then, a special program was applied in order
to bin images 2" x 2" and to replace the uniformized sky background by
a constant value. The compressed images were then automatically
transferred to Lyon to be processed. The source extraction was made
with a very conservative threshold (2-sigma above the sky background).
The galaxy extraction was made with a Discriminant Analysis based on
seven parameters (peak intensity over area, Mean surface brightness,
Peak intensity, Axis ratio, Relative surface object/matrix, Elongation
of the matrix and Diffraction cross) and calibrated with a sample of
1146 DENIS objects visually classified as "galaxy", "star" or
"unknown". A visual inspection of every galaxy candidate was made on
the matrix of pixels.