8 research outputs found
Gemini NIFS survey of feeding and feedback processes in nearby Active Galaxies: I - Stellar kinematics
We use the Gemini Near-Infrared Integral Field Spectrograph (NIFS) to map the
stellar kinematics of the inner few hundred parsecs of a sample of 16 nearby
Seyfert galaxies, at a spatial resolution of tens of parsecs and spectral
resolution of 40 km/s. We find that the line-of-sight (LOS) velocity fields for
most galaxies are well reproduced by rotating disk models. The kinematic
position angle (PA) derived for the LOS velocity field is consistent with the
large scale photometric PA. The residual velocities are correlated with the
hard X-ray luminosity, suggesting that more luminous AGN have a larger impact
in the surrounding stellar dynamics. The central velocity dispersion values are
usually higher than the rotation velocity amplitude, what we attribute to the
strong contribution of bulge kinematics in these inner regions. For 50% of the
galaxies, we find an inverse correlation between the velocities and the
Gauss-Hermitte moment, implying red wings in the blueshifted side and blue
wings in the redshifted side of the velocity field, attributed to the movement
of the bulge stars lagging the rotation. Two of the 16 galaxies (NGC 5899 and
Mrk 1066) show an S-shape zero velocity line, attributed to the gravitational
potential of a nuclear bar. Velocity dispersion maps show rings of low-
values (50-80 km/s) for 4 objects and "patches" of low-sigma for 6 galaxies at
150-250 pc from the nucleus, attributed to young/ intermediate age stellar
populations.Comment: To be published in MNRA
A Decade of Near-Infrared Variability in NGC4388: Insights into the AGN Structure
Variability studies have proven to be a powerful diagnostic tool for
understanding the physics and properties of of Active Galactic Nuclei (AGNs).
They provide insights into the spatial and temporal distribution of the
emitting regions, the structure and dynamics of the accretion disk, and the
properties of the central black hole. Here, we have analysed the K-band
spectral variability of the Seyfert 1.9/2 galaxy NGC4388 spanning five epochs
over a period of ten years. We have performed spectral synthesis of the nuclear
region and found that the contribution of warm dust (T~800K) declined by 88%
during these 10 years. In the same period, the [CaVIII] coronal line decreased
61%, whereas BrG emission declined 35%. For the HeI and H2, we did not detect
any significant variation beyond their uncertainties. Based on the time span of
these changes, we estimate that the region where the warm dust is produced is
smaller than 0.6pc, which suggests that this spectral feature comes from the
innermost part of the region sampled, directly from the AGN torus. On the other
hand, the bulk of [CaVIII] is produced in the inner ~2pc and the nuclear BrG
region is more extended, spanning a region larger than 3pc. Lastly, HeI and H2
are even more external, with most of the emission probably being produced in
the host galaxy rather than in the AGN. This is the first spectroscopic
variability study in the NIR for an AGN where the central source is not
directly visible.Comment: Accepted in MNRAS. 8 pages, 3 figure
Gemini NIFS survey of feeding and feedback in nearbyActive Galaxies - III. Ionized versus warm molecular gasmasses and distributions
We have used the Gemini Near-Infrared Integral Field Spectrograph (NIFS) in
the J and K bands to map the distribution, excitation and kinematics of the
ionized HII and warm molecular gas H, in the inner few 100 pc of 6 nearby
active galaxies: NGC 788, Mrk 607, NGC 3227, NGC 3516, NGC 5506, NGC 5899. {For
most galaxies, this is the first time that such maps have been obtained}. The
ionized and H gas show distinct kinematics: while the H gas is mostly
rotating in the galaxy plane with low velocity dispersion (), the
ionized gas usually shows signatures of outflows associated with higher
values, most clearly seen in the [FeII] emission line. These two gas
species also present distinct flux distributions: the H is more uniformly
spread over the whole galaxy plane, while the ionized gas is more concentrated
around the nucleus and/or collimated along the ionization axis of its Active
Galactic Nucleus (AGN), presenting a steeper gradient in the average surface
mass density profile than the H gas. The total HII masses cover the range
M, with surface mass densities in the range
3-150 M pc, while for the warm H the values are 10
times lower. We estimate that the available gas reservoir is at least
100 times more massive than needed to power the AGN. If this gas form new stars
the star-formation rates, obtained from the Kennicutt-schmidt scalling
relation, are in the range 1-260 10 M yr. But
the gas will also - at least in part - be ejected in the form of the observed
otflows
A panchromatic spatially resolved study of the inner 500pc of NGC1052 -- II: Gas excitation and kinematics
We map the optical and near-infrared (NIR) emission-line flux distributions
and kinematics of the inner 320535pc of the elliptical galaxy
NGC1052. The integral field spectra were obtained with the Gemini Telescope
using the GMOS-IFU and NIFS instruments, with angular resolutions of 0''88 and
0''1 in the optical and NIR, respectively. We detect five kinematic components:
(1 and 2) Two spatially unresolved components, being a broad line region
visible in H, with a FWHM of 3200km s and an
intermediate-broad component seen in the [OIII]4959,5007
doublet; (3) an extended intermediate-width component with 280<FWHM<450km
s and centroid velocities up to 400km s, which dominates the flux
in our data, attributed either to a bipolar outflow related to the jets,
rotation in an eccentric disc or a combination of a disc and large-scale gas
bubbles; (4 and 5) two narrow (FWHM<150km s) components, one visible in
[OIII], and one visible in the other emission lines, extending beyond the
field-of-view of our data, which is attributed to large-scale shocks. Our
results suggest that the ionization within the observed field of view cannot be
explained by a single mechanism, with photoionization being the dominant
mechanism in the nucleus with a combination of shocks and photoionization
responsible for the extended ionization.Comment: Accepted at MNRAS. 17 pages, 17 figure
Observational constraints on the stellar recycled gas in active galactic nuclei feeding
Near-infrared long-slit spectroscopy has been used to study the stellar population (SP) of the low luminosity active galactic nuclei (AGNs) and matched analogues (LLAMA) sample. To perform the SP fits we have employed the X-shooter simple stellar population models together with the STARLIGHT code. Our main conclusions are: The star formation history of the AGNs is very complex, presenting many episodes of star formation during their lifetimes. In general, AGN hosts have higher fractions of intermediate-age SP (light-weighted mean ages, L ≲ 4.5 Gyr) when compared with their analogues ( L ≲ 8.0 Gyr). AGNs are more affected by reddening and require significant fractions of featureless continuum and hot dust components. The ratio between the AGN radiated energy and the gravitational potential energy of the molecular gas (ERad/EPG) for the AGN is compared with the L and a possible anticorrelation is observed. This suggests that the AGN is affecting the star formation in these galaxies, in the sense that more energetic AGN [log(ERad/EPG) ≳ 3] tend to host nuclear younger SP ( L ≲4 Gyr). We found that the recent (t <2 Gyr) returned (recycled) stellar mass is higher in AGN than in the controls. We also provide evidence that the mass-loss of stars would be enough to feed the AGN, thus providing observational constraints for models that predict that AGN feeding is partially due to the recycled gas from dying stars
A sinfoni view of the nuclear activity and circumnuclear star formation in NGC 4303 – II. Spatially resolved stellar populations
We present a spatially resolved stellar population study of the inner ∼200 pc radius of NGC 4303 based on near-infrared integral field spectroscopy with SINFONI/VLT at a spatial resolution of 40–80 pc and using the STARLIGHT code. We found that the distribution of the stellar populations presents a spatial variation, suggesting an age stratification. Three main structures stand out. Two nuclear blobs, one composed by young stars (t ≤ 50 Myr) and one with intermediate-age stars (50 Myr 2 Gyr) is distributed outside the two blob structures. For the nuclear region (inner ∼60 pc radius) we derived an SFR of 0.43 M yr and found no signatures of non-thermal featureless continuum and hot dust emission, supporting the scenario in which an LLAGN/LINER-like source is hidden in the centre of NGC 4303. Thus, our results reveal a rather complex star formation history in NGC 4303, with different stellar population components coexisting with a low efficiency accreting black hole in its centre.The Brazilian authors acknowledge support from FAPERGS (Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul) and CNPq (Conselho Nacional de Desenvolvimento
Cientıfico e Tecnologico). L.C. acknowledges support from CNPq ´special visitor fellowship PVE 313945/2013-6 under the Brazilian program Science without Borders. L.C. and S.A. are supported
by grants AYA2012-32295, AYA2012- 39408, ESP2015-68964-P, and ESP2017-83197-P, and J.P. is supported by grant AYA2017-85170-R, all from the Ministerio de Econom´ıa y Competitividad of Spain. The STARLIGHT project is supported by the Brazilian agencies CNPq, CAPES and FAPESP (Fundação de Amparo a pesquisa do Estado de Sao Paulo) and by the France-Brazil CAPES/Cofecub progra