Is IRAS 01072+4954 a True-Seyfert 2? Hints from Near Infrared Integral Field Spectroscopy

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In contrast to the predictions of the unified model, some X-ray unobscured Seyfert 2 galaxies have been discovered in the last decade. One of them, the starburst/Seyfert composite galaxy IRAS 01072+4954 (z=0.0236), has a typical Type 1 X-ray emission, while its optical spectrum resembles an HII galaxy and lacks the expected broad lines. We performed near-infrared integral-field observations of this object with the aim to determine the nature of its nuclear emission and to find indications for the existence or absence of a broad-line region. Several reasons have been proposed to explain such peculiar emission. We studied the validity of such hypotheses, including the possibility for it to be True-Seyfert 2. We found little obscuration towards the nucleus Aᵥ = 2.5 mag, and a nuclear star-formation rate SigmaₛFR < 11.6 Msun yr⁻¹ kpc⁻², which is below the average in Seyferts. Unresolved hot-dust emission with T 1150 K seems to indicate the presence of a torus with its axis close to the line of sight. We found that IRAS 01072+4954 hosts a low mass black hole with an estimated mass of MBH 10⁵ Msun and an upper limit of 2.5x10⁶ Msun. Its bolometric luminosity is Lbol 2.5x10⁴² erg/s, which yields a high accretion rate with an Eddington ratio 0.2. If the relations found in more massive systems also apply to this case, then IRAS 01072+4954 should show broad emission lines with FWHMbroad (400-600) km/s. Indeed, some indications for such narrow broad-line components are seen in our data, but the evidence is not yet conclusive. This source thus seems not to be a True-Seyfert 2, but an extreme case of a narrow line Seyfert 1, which, due to the faintness of the active nucleus, does not have strong FeII emission in the optical.