Search

We use optical Integral Field Spectroscopy (IFU) to study the gas emission structure and kinematics in the inner 3.4$\times$4.9 kpc$^2$ region of the galaxy UGC 8782 (3C 293), host of a radio loud Active Galactic Nucleus (AGN). The observations were performed with the GMOS-IFU on the Gemini North telescope, resulting in a spatial resolution of $\sim725$ pc at the distance of the galaxy. While the stars present ordered rotation following the orientation of the large scale disc, the gas shows a disturbed kinematics. The emission-line profiles present two kinematic components: a narrow ($\sigma\lesssim200$ km s$^{-1}$) component associated with the gas in the disc of the galaxy and a broad ($\sigma\gtrsim200$ km s$^{-1}$) component produced by gas outflows. Emission-line ratio diagrams indicate that the gas in the disc is excited by the AGN radiation field, while the emission of the outflow includes additional contribution of shock excitation due to the interaction of the radio jet with the environment gas. Deviations from pure rotation, of up to 30 km s$^{-1}$, are observed in the disc component and likely produced by a previous merger event. The broad component is blueshifted by $\sim150-500$ km s$^{-1}$ relative to the systemic velocity of the galaxy in all locations. We construct radial profiles of the mass outflow rate and kinetic power of the ionized gas outflows, which have the maximum values at $\sim1$ kpc from the nucleus with peak values of $\dot{M}_{\rm out,\Delta R}=0.5\pm0.1$ M$_\odot$ yr$^{-1}$ and $\dot{K}_{\rm out,\Delta R} =$(6.8$\pm$1.1)$\times$10$^{41}$ erg s$^{-1}$. The kinetic coupling efficiency of these outflows is in the range of 1$-$3 per cent, indicating that they could be powerful enough to affect the star formation in the host galaxy as predicted by theoretical simulations., Comment: Accepted for publication by MNRAS

We use the Gemini NIFS instrument to map the H$_2 2.1218\mu$m and Br$\gamma$ flux distributions in the inner 0.04-2 kpc of a sample of 36 nearby active galaxies ($0.001\lesssim z\lesssim0.056$) at spatial resolutions from 4 to 250 pc. We find extended emission in 34 galaxies. In $\sim$55% of them, the emission in both lines is most extended along the galaxy major axis, while in the other 45% the extent follows a distinct orientation. The emission of H$_2$ is less concentrated than that of Br$\gamma$, presenting a radius that contains half of the flux 60% greater, on average. The H$_2$ emission is driven by thermal processes - X-ray heating and shocks - at most locations for all galaxies, where $0.46$ (seen in 40% of the galaxies), shocks are the main H$_2$ excitation mechanism, while in regions with H$_2$/Br$\gamma, Comment: 21 pages, accepted for publication in MNRAS

The near-infrared spectra of Active Galactic Nuclei (AGN) present emission lines of different atomic and molecular species. The mechanisms involved in the origin of these emission lines in AGN are still not fully understood. We use J and K band integral field spectra of six luminous ($43.1, Comment: 18 pages, accepted for publication in MNRAS

We use Gemini Near-Infrared Integral Field Spectrograph (NIFS) adaptive optics assisted data-cubes to map the stellar population of the inner few hundred parsecs of a sample of 18 nearby Seyfert galaxies. The near-infrared light is dominated by the contribution of young to intermediate old stellar populations, with light-weighted mean ages $_L\ \lesssim $ 1.5\,Gyr. Hot dust ($HD$) emission is centrally peaked (in the unresolved nucleus), but it is also needed to reproduce the continuum beyond the nucleus in nearly half of the sample. We have analysed the stellar population properties of the nuclear region and their relation with more global properties of the galaxies. We find a correlation between the X-ray luminosity and the contributions from the $HD$, featureless continuum $FC$ and reddening $A_V$. We attribute these correlations to the fact that all these properties are linked to the mass accretion rate to the active galactic nuclei (AGN). We also find a correlation of the bolometric luminosity $log(LBol_{obs})$ with the mass-weighted mean age of the stellar population, interpreted as due a delay between the formation of new stars and the triggering/feeding of the AGN. The gas reaching the supermassive black hole is probably originated from mass loss from the already somewhat evolved intermediate-age stellar population ($_L \lesssim $ 1.5\,Gyr). In summary, our results show that there is a significant fraction of young to intermediate age stellar populations in the inner few 100\,pc of active galaxies, suggesting that this region is facing a rejuvenation process in which the AGN, once triggered, precludes further star formation, in the sense that it can be associated with the lack of new star formation in the nuclear region., Comment: Accepted for publication in MNRAS

We used Gemini NIFS integral field spectroscopy to analyse the molecular and ionised gas kinematics of six nearby (z ⩽ 0.015) Seyfert galaxies with a spatial coverage of 0.1 – 0.6 kpc2. By fitting the emission-line profiles using multiple Gaussian components we determined that the ionised and hot molecular gas kinematics are dominated by gas outflows and rotation, respectively, even though three objects also present molecular outflows.

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$_2$, 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$_2$ gas show distinct kinematics: while the H$_2$ gas is mostly rotating in the galaxy plane with low velocity dispersion ($\sigma$), the ionized gas usually shows signatures of outflows associated with higher $\sigma$ values, most clearly seen in the [FeII] emission line. These two gas species also present distinct flux distributions: the H$_2$ 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$_2$ gas. The total HII masses cover the range $2\times10^5-2\times10^7$ M$_{\odot}$, with surface mass densities in the range 3-150 M$_{\odot}$ pc$^{-2}$, while for the warm H$_2$ the values are 10$^{3-4}$ times lower. We estimate that the available gas reservoir is at least $\approx$ 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$\times$ 10$^{-3}$ M$_{\odot}$ yr$^{-1}$. But the gas will also - at least in part - be ejected in the form of the observed otflows.

We present and characterize a sample of 20 nearby Seyfert galaxies selected for having BAT 14--195keV luminosities $L_X \ge 10^{41.5}$ erg s$^{-1}$, redshift $z\le$0.015, being accessible for observations with the Gemini Near-Infrared Field Spectrograph (NIFS) and showing extended [OIII]$\lambda$5007 emission. Our goal is to study Active Galactic Nuclei (AGN) feeding and feedback processes from near-infrared integral-field spectra, that include both ionized (HII) and hot molecular (H$_2$) emission. This sample is complemented by other 9 Seyfert galaxies previously observed with NIFS. We show that the host galaxy properties (absolute magnitudes $M_B$, $M_H$, central stellar velocity dispersion and axial ratio) show a similar distribution to those of the 69 BAT AGN. For the 20 galaxies already observed, we present surface mass density ($\Sigma$) profiles for HII and H$_2$ in their inner $\sim$500 pc, showing that HII emission presents a steeper radial gradient than H$_2$. This can be attributed to the different excitation mechanisms: ionization by AGN radiation for HII and heating by X-rays for H$_2$. The mean surface mass densities are in the range ($0.2\le \Sigma_{HII} \le 35.9$)M$_\odot$pc$^{-2}$, and ($0.2\le \Sigma_{H2} \le 13.9$)$\times10^{-3}$M$_\odot$pc$^{-2}$, while the ratios between the HII and H$_2$ masses range between $\sim$200 to 8000. The sample presented here will be used in future papers to map AGN gas excitation and kinematics, providing a census of the mass inflow and outflow rates and power as well as their relation with the AGN luminosity., Comment: Accepted for publication in MNRAS

The giant HII region W31 hosts the populous star cluster W31-CL and others projected on or in the surroundings. The most intriguing object is the stellar cluster SGR1806-20, which appears to be related to a Luminous Blue Variable (LBV) - a luminous supergiant star. We used the deep VVV J-,H-and K$_s$-bands photometry combined with 2MASS data in order to address the distance andother physical and structural properties of the clusters W31-CL, BDS 113 and SGR1806-20. Field-decontaminated photometry was used to analyse colour-magnitude diagrams and stellar radial density profiles, using procedures that our group has developed and employed in previous studies. We concludethat the clusters W31-CL and BDS113 are located at 4.5kpc and 4.8kpc and have ages of 0.5Myr and 1Myr, respectively. This result, together with the pre-main sequence (PMS) distribution in the colour-magnitude diagram, characterises them as members of the W31 complex. The present photometry detects the stellar content, addressed in previous spectroscopic classifications, in the direction of thecluster SGR1806-20, including the LBV, WRs, and foreground stars. We derive an age of 10$\pm$4Myr and a distance of d=8.0$\pm$1.95kpc. The cluster is extremely absorbed, with AV= 25mag. Thepresent results indicate that SGR1806-20 is more distant by a factor 1.8 with respect to the W31 complex, and thus not physically related to it., Comment: 11 pages, 9 figures, accepted to publication

The understating of the origin of the H2 line emission from the central regions of galaxies represent an important key to improve our knowledge about the excitation and ionization conditions of the gas in these locations. Usually these lines can be produced by Starburts, shocks and/or radiation from an active galactic nucleus (AGN). Luminous Infrared Galaxies (LIRG) represent ideal and challenging objects to investigate the origin of the H2 emission, as all processes above can be observed in a single object. In this work, we use K-band integral field spectroscopy to map the emission line flux distributions and kinematics and investigate the origin of the molecular and ionized gas line emission from inner 1.4x2.4 kpc2 of the LIRG NGC6240, known to be the galaxy with strongest H2 line emission. The emission lines show complex profiles at locations between both nuclei and surrounding the northern nucleus, while at locations near the southern nucleus and at 1" west of the northern nucleus, they can be reproduced by a single gaussian component. We found that the H2 emission is originated mainly by thermal processes, possible being dominated by heating of the gas by X-rays from the AGN at locations near both nuclei. For the region between the northern and southern nuclei shocks due to the interacting process may be the main excitation mechanism, as indicated by the high values of the H2l2.12um/Brg line ratio. A contribution of fluorescent excitation may also be important at locations near 1" west of the northern nucleus, which show the lowest line ratios. The [FeII]l2.072um/Brg ratio show a similar trend as observed for H2l2.12um/Brg, suggesting that [FeII] and H2 line emission have similar origins. Finally, the [CaVIII]l2.32um coronal line emission is observed mainly in regions next to the nuclei, suggesting it is originated gas ionized by the radiation from the AGN., Accepted for publication in ApSS