Unveiling the Narrow-Line Seyfert 1 Nature of Mrk 573 using near-Infrared spectroscopy

TL;DR

This study provides evidence that Mrk 573 is an obscured Narrow-Line Seyfert 1 galaxy, distinguished by specific near-infrared spectral features indicative of a broad line region, challenging its previous classification.

Contribution

It is the first to identify Mrk 573 as an NLSy1 using near-infrared spectroscopy, expanding the known members of this rare class from three to four.

Findings

Detection of narrow permitted O I lines and Fe II lines in near-infrared spectrum.

Observation of a broad Paschen Beta component (~1700 km/s).

Evidence of a high-density, optically thick region similar to the BLR.

Abstract

In this letter we present clear evidence that Mrk 573 is an obscured Narrow-Line Seyfert 1 (NLSy1) and not an archetypal Seyfert 2, as it has been classified until now. Only three galaxies have been proposed as members of this class, prior to this work. Here we report near-infrared spectroscopic data taken with LIRIS on the 4.2 m William Herschel Telescope (WHT). Our high quality near-infrared nuclear spectrum in the 0.88-1.35 micron wavelength range shows the permitted O I 1.128,1.317 micron narrow lines, the Fe II 9200-\AA lines and the Fe II 1-micron lines, together with a relatively broad component (~1700 km/s) of Paschen Beta. These features can originate only in an optically thick high density region, similar to those observed in the Broad Line Region (BLR).