The intensities of the emission lines present in the spectra (obtained
with 125 Å mm-1 dispersion) of the nuclear region and
of a region located at 87 towards the NE on the major
axis, were derived fitting
Gaussian curves to their profiles. In the nuclear spectrum the H
emission line is affected by the underlying H
absorption line, so
Gaussian curves were interactively fitted to determine the absorption
component and to isolate the H
emission. This procedure was verified
by adding both, emission and absorption components,
to reproduce the original profile. The internal reddening correction was
carried out using the interstellar extinction curves given by Seaton
(1979), assuming that the optical properties of the dust in
NGC 2442 are
similar to those in the Galaxy. The logarithmic extinction c, at
H
, was obtained using for the intrinsic ratio H
/H
the
values 3.1 and 2.85 for the nucleus and for the region at the NE,
respectively (Veilleux & Osterbrock 1987). The
measured and corrected line intensities
and
,
relative to H
= 1.00, are listed in Table 2 as well as the
errors. These errors were estimated from the noise level around each line.
The values of c and of the corrected H
flux are given at the
bottom of the table.
![]() ![]() ![]() b c is the logarithmic extinction at H ![]() c ![]() |
The mean radial velocities of all the spectra were derived measuring the
centroids of Gaussian
profiles centered on the emission lines [O I] 6300,
[N II]
6548, 6584, H
, and [S II]
6717, 6731
in the spectra obtained with a dispersion of 32 Å mm-1. The errors
are estimated to be 3 to 26
, depending on the
signal-to-noise ratio. The optical heliocentric radial velocities are shown
in Fig. 5 superposed on the CO velocity field as obtained by
Bajaja et al. (1995).
The spectrum at the nuclear region of the galaxy (Fig. 2)
shows two velocity components, on each of the prominent lines, with
approximately the same intensity and a separation of about
145 .
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