A unique X-ray unabsorbed Seyfert 2 galaxy IRAS F01475-0740

TL;DR

This study investigates IRAS F01475-0740, a peculiar X-ray unabsorbed Seyfert 2 galaxy, revealing a hidden broad line region and unusual dust-to-gas ratio, challenging standard AGN models.

Contribution

The paper presents Suzaku X-ray observations and spectropolarimetry of IRAS F01475-0740, demonstrating its unique properties and proposing an explanation involving high dust-to-gas ratio.

Findings

Detected hidden broad line region via spectropolarimetry.

Observed rapid X-ray variability indicating direct view of the core.

Proposed high dust-to-gas ratio as explanation for unabsorbed X-ray spectrum.

Abstract

X-ray unabsorbed Seyfert 2 galaxies appear to have X-ray absorption column densities that are too low (NH < 10^22 cm-2) to explain the absence of broad emission lines in their optical spectra, challenging the standard AGN unification model. In this paper we report Suzaku exposure on the X-ray unabsorbed Seyfert 2 galaxy IRAS F01475-0740, in which a hidden broad line region was detected through spectropolarimetric observation. The X-ray data show rapid and significant variations on time scales down to 5 ks, indicating that we are viewing its central engine directly. A newly obtained optical spectrum and previous optical/X-ray data suggest that state transition is unlikely in this source. These make IRAS F01475-0740 a very peculiar X-ray unabsorbed Seyfert 2 galaxy which can only be explained by absorption from materials with abnormally high dust-to-gas ratio (by a factor of > 4 larger than Galactic). This is in contrast to most AGNs, which typically show dust-to-gas ratios 3 - 100 times lower than the Galactic.