Dusty spirals versus gas kinematics in the inner kiloparsec of four low-luminosity active galactic nuclei

Abstract

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.

Optical spectroscopy of local type-1 AGN LINERs

“…NGC 4450. Brum et al (2017) found a clear rotating disc pattern with the line of nodes oriented along the North-South direction with some deviations. The flat and low amplitude rotation curve presented in Fig.…”

“…For ground-based data, this criterion clearly identifies 6 and 3 cases out of 15 with outflows (40 %) and rotation (20 %), respectively ( There are not systematic studies of outflows in type-1 LINERs via ground-based spectroscopy, but only works of individual cases (e.g. Dopita et al 2015;Brum et al 2017). The detection rate of outflows in ground-based data is lower than what found in studies of sample of nearby (z < 0.2) type-2 luminous AGNs and quasars (e.g.…”

Gemini NIFS survey of feeding and feedback in nearby active galaxies – V. Molecular and ionized gas kinematics

“…The equation is based on Bertola et al ( 1991 ) and has already been used in previous works by our group using similar data (e.g. Schnorr-M üller et al 2014 ;Diniz et al 2015 ;Brum et al 2017Brum et al , 2019.…”

The OH Megamaser galaxy IRAS11506−3851: an AGN and star formation revealed by multiwavelength observations

“…We use the penalized Pixel-Fitting (pPXF) routine (Cappellari & Emsellem 2004;Cappellar 2017) for fitting the absorption spectra of IRAS11506 and measure the stellar kinematics. To perform the measurements we use as spectral templates, the single stellar populations (SSP) models of Bruzual & Charlot (2003), which have similar spectral resolution of the GMOS data and have been previously used to measure the stellar kinematics of nearby galaxies from GMOS-IFU data (Brum et al 2017). The line-of-sight velocity distribution of the stars is assumed to be Gaussian, as we fit only the two first moments (V and σ ).…”