Broad infrared line emission from the nuclei of Seyfert 2 galaxies

We report spectroscopic observations at $$\lambda /\delta \lambda \simeq 300$$ of the Paschen β hydrogen recombination line in the narrow line X-ray galaxies NGC 5506 and A0945 – 30 ( = MCG-5-23-16), and in the Seyfert 2 galaxy NGC 4388. The line profiles of NGC 5506 and A0945 – 30 are both found to possess broad components of $$\,\text{FWHM}\gt 1500\,\text{km s}^{-1};$$ this removes the previous controversy concerning the presence of broad line components in their Hα line profiles. We use optical, X -ray and mid-infrared data to estimate the extinction towards the line and continuum sources in these objects in order to test the hypothesis that they are in fact moderately obscured Seyfert 1 nuclei. The non-detection of a broad Paschen β line profile in NGC 4388 is consistent with a scattered (as opposed to a transmitted) origin for the observed off-nuclear broad Hα emission, in agreement with models of the optical emission-line geometry in this galaxy.