SIMBAD references

We present results from HST/STIS long-slit spectroscopy of the gas motions in the nuclear region of the Seyfert 2 galaxy NGC 5252. The observed velocity field is consistent with gas in regular rotation with superposed localized patches of disturbed gas. The dynamics of the circumnuclear gas can be accurately reproduced by adding to the stellar mass component a compact dark mass of M_BH=0.95(-0.45;+1.45)x10⁹M_☉, very likely a supermassive black hole (BH). Contrarily to results obtained in similar studies rotational broadening is sufficient to reproduce also the behaviour of line widths. The BH mass estimated for NGC 5252 is in good agreement with the correlation between M_BH and bulge mass. The comparison with the M_BH vs. σ_c relationship is less stringent (mostly due to the relatively large error in σ_c); NGC 5252 is located above the best fit line by between 0.3 and 1.2dex, i.e. 1-4 times the dispersion of the correlation. Both the galaxy's and BH mass of NGC 5252 are substantially larger than those usually estimated for Seyfert galaxies but, on the other hand, they are typical of radio-quiet quasars. Combining the determined BH mass with the hard X-ray luminosity, we estimate that NGC 5252 is emitting at a fraction ∼0.005 of L_Edd. In this sense, this active nucleus appears to be a quasar relic, now probably accreting at a low rate, rather than a low black hole mass counterpart of a QSO.