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Post Info TOPIC: IRAS 01072+4954
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RE: IRAS 01072+4954
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Title: Discovery of an Intermediate Mass Black Hole at the center of the starburst/Seyfert composite galaxy IRAS 01072+4954
Authors: M. Valencia-S. (1,2), A. Eckart (1,2), J. Zuther (1), S. Fischer (1), S. Smajic (1,2), C. Iserlohe (1), M. Garcia-Marin (1), L. Moser (1), M. Bremer (1), M. Vitale (1,2). ((1) I.Physikalisches Institut, University of Cologne. (2) Max-Planck-Institut fuer Radioastronomie)

The starburst/Seyfert composite galaxy IRAS 01072+4954 (z=0.0236) is an enigmatic source that combines a Seyfert~1-like X-ray emission with a starburst optical spectrum that lacks broad line emission. We performed high angular resolution observations of the central kiloparsec of this galaxy in the near-infrared. Combining our data with 2MASS images of the whole galaxy, we obtain and model the surface brightness profile. We find indications for the presence of an elongated bar-like structure in both data sets. We also model the line of sight velocity distribution of the stars in the bulge. The derived photometrical and kinematical parameters of the bulge are used to evaluate the black hole mass through scaling relations. We find that all reliable estimations of the black hole mass are consistent with the presence of an intermediate mass black hole with a mass of ~10^5 solar masses (or less).

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Blobrana


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Title: Is IRAS 01072+4954 a True-Seyfert 2? Hints from Near Infrared Integral Field Spectroscopy
Authors: M. Valencia-S., J. Zuther, A. Eckart, M. Garcia-Marin, C. Iserlohe, G. Wright

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 A_V = 2.5 mag, and a nuclear star-formation rate Sigma_SFR < 11.6 solar masses 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 M_BH ~ 10^5 solar masses and an upper limit of 2.5x10^6 solar masses. Its bolometric luminosity is L_bol ~ 2.5x10^{42} 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 FWHM_{broad} ~(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.

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