Mrk 1239: a Type-2 Counterpart of Narrow-line Seyfert-1?

TL;DR

This study suggests that Mrk 1239, traditionally classified as a narrow-line Seyfert-1 galaxy, exhibits characteristics more akin to type-2 active galactic nuclei, indicating potential misclassification issues and a broader diversity within Seyfert galaxy types.

Contribution

The paper provides detailed spectrophotometric and spectropolarimetric evidence that Mrk 1239 is likely a type-2 AGN counterpart of NLS1s, challenging traditional classification boundaries.

Findings

Mrk 1239 shows high polarization and red colors typical of type-2 AGNs.

Spectral analysis reveals two light components with different obscuration levels.

Obscuring clouds are located between the sublimation radius and narrow-line regions.

Abstract

We present new spectrophotometric and spectropolarimetric observations of Mrk 1239, one of the 8 prototypes that defines type-1 narrow-line Seyfert galaxies (NLS1s). Unlike the other typical NLS1s though, a high degree of polarization ($P\sim$5.6%) and red optical-IR ($g-W_4$ = 12.35) colors suggest that Mrk 1239 is more similar to type-2 active galactic nuclei like NGC 1068. Detailed analysis of spectral energy distribution in the UV-optical-IR yields two components from the nucleus: a direct and transmitted component that is heavily obscured ($E_{B-V} \approx 1.6$), and another indirect and scattered one with mild extinction ($E_{B-V} \sim$ 0.5). Such a two-light-paths scenario is also found in previous reports based on the X-ray data. Comparison of emission lines and the detection of He\,{\footnotesize I}*$\lambda$10830 BAL at [-3000,-1000] km s$^{-1}$ indicates that the obscuring clouds are at physical scale between the sublimation radius and that of the narrow emission line regions. The potential existence of powerful outflows is found as both the obscurer and scatterer are outflowing. Similar to many other type-2s, jet-like structure in the radio band is found in Mrk 1239, perpendicular to the polarization angle, suggesting polar scattering. We argue that Mrk 1239 is very probably a type-2 counterpart of NLS1s. The identification of 1 out of 8 prototype NLS1s as a type-2 counterpart implies that there can be a substantial amount of analogs of Mrk 1239 misidentified as type-1s in the optical band. Properties of these misidentified objects are going to be explored in our future works.