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We mapped the stellar population and emission gas properties in the nuclear region of NGC 6868 using datacubes extracted with Gemini Multi-Object Spectrograph (GMOS) in the Integral Field Unit (IFU) mode. To obtain the star-formation history of this galaxy we used the starlight code together with the new generation of MILES simple stellar population models. The stellar population dominating (95% in light fraction) the central region of NGC 6868 is old and metal rich (~10 Gyr, 2.2 Z⊙). We also derived the kinematics and emission line fluxes of ionized gas with the IFSCube package. A rotation disk is clearly detected in the nuclear region of the galaxy and no broad components were detected. Also, there is a region where the emission lines disappear almost completely, probably due to diffuse ionized gas component. Channel maps, diagnostic diagrams and stellar kinematics are still under analysis.

Understanding the interplay between the phenomena of active galactic nuclei (AGN) and starbursts remains an open issue in studies of galaxy evolution. The galaxy NGC 34 is the remnant of the merger of two former gas-rich disc galaxies and it also hosts a strong nuclear starburst. In this work, we map the ionized and molecular gas present in the nuclear regions of the galaxy NGC 34 using adaptive optics (AO) assisted near infrared (NIR) integral field unity (IFU) observations. Our main goals are to better constrain the energy source of this object and to use NGC 34 as a laboratory to probe the AGN-starburst connection in the context of galaxy evolution and AGN feeding and feedback processes.

We employ IRTF SpeX NIR (0.8--2.4mu m) spectra to investigate the stellar population (SP), active galactic nuclei (AGN), featureless continuum (FC) and hot dust properties in 9 Sy1 and 15 Sy2 galaxies. Both the {\sc starlight} code and the hot dust as an additional base element were used for the first time in this spectral range. Our synthesis shows significant differences between Sy1 and Sy2 galaxies: the hot dust component is required to fit the K-band spectra of ~90% of the Sy1 galaxies, and only of ~25% of the Sy2; about 50% of the Sy2 galaxies require an FC component contribution >20%; this fraction increases to about 60% in the Sy1. In about 50% of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1microns CN band can be used as a tracer of intermediate-age stellar populations., To appear in IAU S262 proceedings, 4 pages, 4 figures

The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are older and alpha-enhanced in the not rotating bulge of NGC 1052 and counter rotating core of NGC 7796, while they show a strong spread of alpha/Fe and age along the rotating disk of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796., Comment: 2 pages, to appear in the Proceedings of IAU Symposium 241 "Stellar populations as building blocks of galaxies", A. Vazdekis & R. Peletier, eds

We analyze long slit spectroscopy of NGC 1052, the third brightest member of a group of eleven galaxies. This elliptical is a typical LINER with a stellar rotating disk. We have found a strong negative radial gradient of the abundance ratio Mg/Fe, which suggests an enhancement of α-elements particulary towards the nuclear region, and higher metallicity and age at the galactic nucleus too. We have measured the Lick line-strength indices along the major axis of the galaxy. This information, together with single-aged stellar population models of Thomas et al. (2003), was used to determine the star formation history of NGC 1052. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The spectroscopic properties of a sample of nine Seyfert 1, six NLS1, 26 Seyfert 2, and three starburst galaxies have been studied at mid-infrared wavelengths in order to determine if the frequency of detection of the brightest emission lines and the continuum shape are correlated with the degree of activity. The raw data were obtained from the Spitzer Infrared Spectrograph (IRS) archive and reduced with the pipeline (version 17.2). The spectra of the galaxies were grouped by type of activity. We conclude through this study that in general the continuum shape of the active galactic nuclei (AGN) is flat between 5 μm and 12 μm, and strong variations are found at longer wavelengths in this sample.

We investigate the NIR spectra of 24 Seyfert galaxies observed with the instrument SpeX at the NASA Infrared Telescope Facility (ITRF) in the short cross-dispersed mode. The results of the spectral synthesis fitting procedure are presented and discussed in details by Riffel et al. (2009). The approach followed here is based on the starlight code (see Cid Fernandes et al. 2005). The spectral synthesis shows that the NIR continuum of active galaxies can be explained in terms of at least three components: a non-thermal continuum, dust emission, and the stellar population of the circumnuclear region. The study of the stellar population is a critical step in the analysis of the continuum emission of Seyfert galaxies. Moreover, our results are consistent with the predictions of the unified model for AGNs, as the non-thermal continuum and the hot dust emission are present in all Sy 1 sources and only in a small fraction of the Sy 2s. Regarding the stellar population component, our results point to a mean metallicity solar to above solar, if we consider the light-weighted values, while for the mass-weighted mean metallicity our results indicate a sub-solar value. We associate this discrepancy with the well known age–metallicity degeneracy: i.e., for a fixed mass, a high-metallicity stellar population looks cooler — and older — than a low-metallicity population, thus resulting in a higher M/L ratio. Moreover, this is consistent with a galaxy chemical enrichment scenario in which the young population is enriched by the evolution of the early massive stars. In this context, the light-weighted metallicity is more sensitive to the young component, while the mass-weighted metallicity to the old stellar population. The main results can be summarized as follows: (i) The NIR stellar population synthesis does not reproduce the optical results well. (ii) Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies. The hot dust component is required to fit the K-band spectra of ∼80% of the Sy 1 galaxies, and only of ∼40% of the Sy 2s. Besides, about 50% of the Sy 2 galaxies require a featureless continuum contribution in excess of 20%, while this fraction increases to about 60% in the Sy 1s. Also, in about 50% of the Sy 2s, the combined featureless continuum and young stellar population components contribute with more than 20%, while this occurs in 90% of the Sy 1. This suggests recent star formation in the central region of our galaxy sample. (iii) The light at 1.223 μm in the central regions of the galaxies contains a substantial fraction from intermediate-age stellar populations with a mean metallicity near solar. Our analysis confirms that the 1.1 μm CN band can be used as an unambiguous tracer of intermediate-age stellar populations.

We have carried out an extensive program of observations of the ionized gas in 74 luminous elliptical and lenticular galaxies, selected to include a variety of properties in radio and X-ray emission, and in kinematical behavior. For each galaxy we have obtained broad-band R and V images and narrow-band images, centered at the Hα and [NII] emission lines, to derive the luminosity and distribution of the ionized gas. We found that a large fraction (≃ 70%) of E and S0 galaxies in our sample contain ionized gas. The gas morphology and size varies from small disks (mean diameter 1 – 4 kpc) to large filamentary structures (extending up to 10 kpc from the galaxy center). Comparison with previous measurements shows reasonable agreement for a few galaxies, but considerable scatter for a large fraction, possibly due to differences in the limiting flux thresholds.