Left: Hα emission line map of NGC 4098 and 4099, on which is superimposed the continuum emission below and beside the Hα line within a FWHM of 15 Å. The size of the total region shown is ∼1.45 × 1.45 arcmin² (∼44.1 × 44.1 kpc²). Flux is in arbitrary units. Right: Hα line-of-sight velocity field zoomed by a factor of 2 from the brown square drawn on the left panel, on which are overplotted the same continuum isocontours. The size of the total region shown is ∼43.5 × 43.5 arcsec² (∼22.1 × 22.1 kpc²). Each box containing each profile has dimensions of ∼3.4 × 3.4 arcsec² (∼1.7 ×1.7 pc²), which correspond to a binning of 5 × 5 pixels; in other words, each box is the profile average of 25 spaxels. The x scale of each box spans over the free spectral range of the interferometer, ranging from ∼6896 to ∼7376 km s⁻¹, the sampling step being 10.25 km s⁻¹. The y scale is given in arbitrary units. These data have been observed with GHASP on the T193 at OHP.