2013MNRAS.429.2587R

We use near-infrared (near-IR) spectroscopic data from the inner few hundred parsecs of a sample of 47 active galaxies to investigate possible correlations between the stellar velocity dispersion (σ{sstarf}), obtained from the fit of the K-band CO stellar absorption bands, and the gas velocity dispersion (σ), obtained from the fit of the emission-line profiles of [Siii]λ0.953µm, [Feii]λ1.257µm, [Feii]λ1.644µm and H2λ2.122µm. While no correlations with σ{sstarf} were found for H2 and [Siii], a good correlation was found for the two [Feii] emission lines, expressed by the linear fit σ_*= 95.4±16.1 + (0.25±0.08)×σ_[Fe II]. Excluding barred objects from the sample, a better correlation is found between σ{sstarf} and σ_[Fe II], with a correlation coefficient of R = 0.80 and fitted by the following relation: σ_*= 57.9±23.5 + (0.42±0.10)×σ_[Fe II]. This correlation can be used to estimate σ{sstarf} in cases where it cannot be directly measured and the [Feii] emission lines are present in the spectra, allowing us to obtain the mass of the supermassive black hole (SMBH) from the Mø-σ{sstarf} relation. The scatter from a one-to-one relationship between σ{sstarf} and its value derived from σ_[Fe II] using the equation above for our sample is 0.07dex, which is smaller than that obtained in previous studies which use σ_[O  III] in the optical as a proxy for σ{sstarf}. The use of σ_[Fe II] in the near-IR instead of σ_[O  III] in the optical is a valuable option for cases in which optical spectra are not available or are obscured, as in the case of many active galactic nuclei. The comparison between the SMBH masses obtained using the Mø-σ{sstarf} relation in which σ{sstarf} was directly measured with those derived from σ_[Fe II] reveals only a small average difference of ΔlogMø = 0.02 with a scatter of 0.32dex for the complete sample and ΔlogMø = 0.00 with a scatter of 0.28dex for a subsample excluding barred galaxies.