We used the Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU) to map the gas distribution, excitation and kinematics within the inner kiloparsec of four nearby low-luminosity active galaxies: NGC3982, NGC4501, NGC2787 and NGC4450. The observations cover the spectral range 5600-7000 Å at a velocity resolution of 120 km s −1 and spatial resolution ranging from 50 to 70 pc at the galaxies. Extended emission in Hα, [N ii]λλ6548,6583, [S ii] λλ6716,6730 over most of the field-of-view is observed for all galaxies, while only NGC3982 shows [O i] λ6300 extended emission. The Hα equivalent widths (W Hα ) combined with the [N ii]/Hα line ratios reveal that NGC3982 and NGC4450 harbor Seyfert nuclei surrounded by regions with LINER excitation, while NGC2787 and NGC4501 harbor LINER nuclei. NGC3982 shows a partial ring of recent star-formation at 500 pc from the nucleus, while in NGC4501 a region at 500pc west of the nucleus shows LINER excitation but has been interpreted as an aging Hii region with the gas excitation dominated by shocks from supernovae. The line-of-sight velocity field of the gas shows a rotation pattern for all galaxies, with deviations from pure disk rotation observed in NGC3982, NGC 4501 and NGC 4450. For NGC4501 and NGC4450, many of these deviations are spatially coincident with dust structures seen in optical continuum images, leading to the interpretation that the deviations are due to shocks in the gas traced by the dust. A speculation is that these shocks lead to loss of angular momentum, allowing the gas to be transferred inwards to feed the AGN. In the case of NGC2787, instead of deviations in the rotation field, we see a misalignment of 40 • between the orientation of the line of nodes of the gas rotation and the photometric major axis of the galaxy. Evidence of compact nuclear outflows are seen in NGC4501 and NGC4450.
Intermediate mass black holes (10 3 -10 5 M ⊙ ) in the center of dwarf galaxies are believed to be analogous to growing Active Galactic Nuclei (AGN) in the early Universe. Their characterization can provide insight about the early galaxies. We present optical and near-infrared integral field spectroscopy of the inner ∼50 pc of the dwarf galaxy NGC 4395, known to harbor an AGN. NGC 4395 is an ideal candidate to investigate the nature of dwarf AGN, as it is nearby (d ≈ 4.4 Mpc) enough to allow a close look at its nucleus. The optical data were obtained with the Gemini GMOS-IFU covering the 4500Å to 7300Å spectral range at a spatial resolution of 10 pc. The J and Kband spectra were obtained with the Gemini NIFS at spatial resolutions of ∼5 pc. The gas kinematics show a compact, rotation disk component with a projected velocity amplitude of 25 km s −1 . We estimate a mass of 7.7 × 10 5 M ⊙ inside a radius of 10 pc. From the Hα broad line component, we estimate the AGN bolometric luminosity as L bol = (9.9 ± 1.4) × 10 40 erg s −1 and a mass M BH = (2.5 +1.0 −0.8 ) × 10 5 M ⊙ for the central black hole. The mean surface mass densities for the ionized and molecular gas are in the ranges (1-2) M ⊙ pc −2 and (1-4)×10 −3 M ⊙ pc −2 and the average ratio between ionized and hot molecular gas masses is ∼500. The emission-line flux distributions reveal an elongated structure at 24 pc west of the nucleus, which is blueshifted relative to the systemic velocity of the galaxy by ≈30 km s −1 . We speculate that this structure is originated by the accretion of a gas-rich small satellite or by a low metallicity cosmic cloud.
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), 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 [S III] λ0.953 µm, [Fe II] λ1.257 µm, [Fe II] λ1.644 µm and H 2 λ2.122 µm. While no correlations with σ were found for H 2 and [S III], a good correlation was found for the two [Fe II] 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 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 in cases where it cannot be directly measured and the [Fe II] emission lines are present in the spectra, allowing us to obtain the mass of the supermassive black hole (SMBH) from the M •-σ relation. The scatter from a one-to-one relationship between σ and its value derived from σ [Fe II] using the equation above for our sample is 0.07 dex, which is smaller than that obtained in previous studies which use σ [O III] in the optical as a proxy for σ. 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 M •-σ relation in which σ was directly measured with those derived from σ [Fe II] reveals only a small average difference of log M • = 0.02 with a scatter of 0.32 dex for the complete sample and log M • = 0.00 with a scatter of 0.28 dex for a subsample excluding barred galaxies.
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