2D mapping of young stars in the inner 180 pc of NGC 1068: correlation with molecular gas ring and stellar kinematics

We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structure at ~100 pc from the nucleus, where it is coincident with an expanding ring of H2 emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age > 2Gyr) dominates the mass, while the flux is dominated by black-body components with temperatures in the range 700 < T < 800 K which we attribute to the dusty torus. We also find some contribution from black-body and power-law components beyond the nucleus which we attribute to dust emission and scattered light.Comment: Accepted for publication in Ap

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 $h_3$ 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-$\sigma$ 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

Feeding Versus Feedback in AGNs from Near-Infrared IFU Observations: The Case of Mrk 766

We have mapped the emission-line flux distributions and ratios as well as the gaseous kinematics of the inner 450 pc radius of the Seyfert 1 galaxy Mrk 766 using integral field near-IR J- and Kl-band spectra obtained with the Gemini nifs at a spatial resolution of 60 pc and velocity resolution of 40 km/s. Emission-line flux distributions in ionized and molecular gas extend up to ~ 300 pc from the nucleus. Coronal [S IX]{\lambda}1.2523{\mu}m line emission is resolved, being extended up to 150 pc from the nucleus. At the highest flux levels, the [Fe II]{\lambda}1.257{\mu}m line emission is most extended to the south-east, where a radio jet has been observed.The emission-line ratios [Fe II]{\lambda}1.2570{\mu}m/Pa{\beta} and $H_2${\lambda}2.1218{\mu}m/Br{\gamma} show a mixture of Starburst and Seyfert excitation; the Seyfert excitation dominates at the nucleus, to the north-west and in an arc-shaped region between 0.2" and 0.6" to the south-east at the location of the radio jet. A contribution from shocks at this location is supported by enhanced [Fe II]/[P II] line ratios and increased [Fe II] velocity dispersion. The gas velocity field is dominated by rotation that is more compact for $H_2$ than for Pa{\beta}, indicating that the molecular gas has a colder kinematics and is located in the galaxy plane. There is about $10^3$ solar masses of hot $H_2$, implying ~ $10^9$ solar masses of cold molecular gas. At the location of the radio jet, we observe an increase in the [Fe II] velocity dispersion (150 km/s), as well as both blueshift and redshifts in the channel maps, supporting the presence of an outflow there. The ionized gas mass outflow rate is estimated to be ~ 10 solar masses/yr, and the power of the outflow ~ 0.08 $L_{bol}$

Probing the Circumnuclear Stellar Populations of Starburst Galaxies in the Near-infrared

We employ the NASA Infrared Telescope Facility's near-infrared spectrograph SpeX at 0.8-2.4$\mu$m to investigate the spatial distribution of the stellar populations (SPs) in four well known Starburst galaxies: NGC34, NGC1614, NGC3310 and NGC7714. We use the STARLIGHT code updated with the synthetic simple stellar populations models computed by Maraston (2005, M05). Our main results are that the NIR light in the nuclear surroundings of the galaxies is dominated by young/intermediate age SPs ($t \leq 2\times10^9$yr), summing from $\sim$40\% up to 100\% of the light contribution. In the nuclear aperture of two sources (NGC1614 and NGC3310) we detected a predominant old SP component ($t > 2\times10^9$yr), while for NGC34 and NGC7714 the younger component prevails. Furthermore, we found evidence of a circumnuclear star formation ring-like structure and a secondary nucleus in NGC1614, in agreement with previous studies. We also suggest that the merger/interaction experienced by three of the galaxies studied, NGC1614, NGC3310 and NGC7714 can explain the lower metallicity values derived for the young SP component of these sources. In this scenario the fresh unprocessed metal poorer gas from the destroyed/interacting companion galaxy is driven to the centre of the galaxies and mixed with the central region gas, before star formation takes place. In order to deepen our analysis, we performed the same procedure of SP synthesis using Maraston (2011, M11) EPS models. Our results show that the newer and higher resolution M11 models tend to enhance the old/intermediate age SP contribution over the younger ages

Infrared identification of IGR J09026-4812 as a Seyfert 1 galaxy

IGR J09026-4812 was discovered by INTEGRAL in 2006 as a new hard X-ray source. Thereafter, an observation with Chandra pinpointed a single X-ray source within the ISGRI error circle, showing a hard spectrum, and improving its high-energy localisation to a subarcsecond accuracy. Thus, the X-ray source was associated to the infrared counterpart 2MASS J09023731-4813339 whose JHKs photometry indicated a highly reddened source. The high-energy properties and the counterpart photometry suggested a high-mass X-ray binary with a main sequence companion star located 6.3-8.1 kpc away and with a 0.3-10 keV luminosity of 8e34 erg/s. New optical and infrared observations were needed to confirm the counterpart and to reveal the nature of IGR J09026-4812. We performed optical and near infrared observations on the counterpart 2MASS J09023731-4813339 with the ESO/NTT telescope on March 2007. We achieved photometry and spectroscopy in near infrared wavelengths and photometry in optical wavelengths. The accurate astrometry at both optical and near infrared wavelengths confirmed 2MASS J09023731-4813339 to be the counterpart of IGR J09026-4812. However, the near infrared images show that the source is extended, thus excluding any Galactic compact source possibility. The source spectrum shows three main emission lines identified as the HeI lambda 1.0830 micron line, and the HI Pa_beta and Pa_alpha lines, typical in galaxies with an active galactic nucleus. The broadness of these lines reached values as large as 4000 km/s pointing towards a type 1 Seyfert galaxy. The redshift of the source is z=0.0391(4). Thus, the near infrared photometry and spectroscopy allowed us to classify IGR J09026-4812 as a Seyfert galaxy of type 1.Comment: 4 pages, 3 figures, Astronomy and Astrophysics in pres