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The merger remnant NGC 34 is a local luminous infrared galaxy (LIRG) hosting a nuclear starburst and a hard X-ray source associated with a putative, obscured Seyfert 2 nucleus. In this work, we use adaptive optics assisted near-infrared (NIR) integral field unit observations of this galaxy to map the distribution and kinematics of the ionized and molecular gas in its inner |$\mathrm{1.2\, kpc \times 1.2\, kpc}$|⁠ , with a spatial resolution of 70 pc. The molecular and ionized gas kinematics is consistent with a disc with projected major axis along a mean PA = −9 |${_{.}^{\circ}}$| 2 ± 0 |${_{.}^{\circ}}$| 9. Our main findings are that NGC 34 hosts an AGN and that the nuclear starburst is distributed in a circumnuclear star formation ring with inner and outer radii of ≈ 60 and 180 pc, respectively, as revealed by maps of the |$\mathrm{[Fe\, {\small {II}}] / Pa\,\beta }$| and H2/Br  γ emission-line ratios, and corroborated by PCA tomography analysis. The spatially resolved NIR diagnostic diagram of NGC 34 also identifies a circumnuclear structure dominated by processes related to the stellar radiation field and a nuclear region where |$[\rm Fe\, {\small {II}}]$| and H2 emissions are enhanced relative to the hydrogen recombination lines. We estimate that the nuclear X-ray source can account for the central H2 enhancement and conclude that |$[\rm Fe\, {\small {II}}]$| and H2 emissions are due to a combination of photoionization by young stars, excitation by X-rays produced by the AGN and shocks. These emission lines show nuclear, broad, blueshifted components that can be interpreted as nuclear outflows driven by the AGN. [ABSTRACT FROM AUTHOR]

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 < t ≤ 2 Gyr), both shifted from the centre. The third one is an internal intermediate-age spiral arm-like structure, surrounding the blob of young stars. Our results indicate that star formation has occurred through multiple bursts in this source. Furthermore, the youngest stellar populations (t ≲ 2 Gyr) are distributed along a circumnuclear star-forming ring with r ∼ 250 pc. The ring displays star formation rates (SFRs) in the range of 0.002–0.14 M⊙yr−1, favouring the 'pearls-on-a-string' scenario. The old underlying bulge stellar population component (t > 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−1 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. [ABSTRACT FROM AUTHOR]

We present an observational study of the impacts of interactions on the stellar population in a sample of galaxy pairs. Long-slit spectra in the wavelength range 3440-7300 Å obtained with the Gemini Multi-Object Spectrograph (GMOS) at Gemini South for 15 galaxies in nine close pairs were used. The spatial distributions of the stellar population contributions were obtained using the stellar population synthesis code starlight. Taking into account the different contributions to the emitted light, we found that most of the galaxies in our sample are dominated by young/intermediate stellar populations. This result differs from the one derived for isolated galaxies, where the old stellar population dominates the disc surface brightness. We interpreted such different behaviour as being due to the effect of gas inflows along the discs of interacting galaxies on the star formation over a time-scale of the order of about 2 Gyr. We also found that, in general, the secondary galaxy of a pair has a higher contribution from the young stellar population than the primary one. We compared the estimated values of stellar and nebular extinction derived from the synthesis method and the Hα/Hβ emission-line ratio, finding that nebular extinctions are systematically higher than stellar ones by about a factor of 2. We did not find any correlation between nebular and stellar metallicities. Neither did we find a correlation between stellar metallicities and ages, while a positive correlation between nebular metallicities and stellar ages was obtained, with older regions being the most metal-rich. [ABSTRACT FROM AUTHOR]

In this paper, we derive oxygen abundance gradients from H ii regions located in 11 galaxies in eight systems of close pairs. Long-slit spectra in the range 4400–7300 Å were obtained with the Gemini Multi-Object Spectrograph at Gemini South (GMOS-S). Spatial profiles of oxygen abundance in the gaseous phase along galaxy discs were obtained using calibrations based on strong emission lines (N2 and O3N2). We found oxygen gradients to be significantly flatter for all the studied galaxies than those in typical isolated spiral galaxies. Four objects in our sample, AM 1219A, AM 1256B, AM 2030A and AM 2030B, show a clear break in the oxygen abundance at galactocentric radius R/R25 between 0.2 and 0.5. For AM 1219A and AM 1256B, we found negative slopes for the inner gradients, and for AM 2030B, we found a positive slope. All three cases show a flatter behaviour to the outskirts of the galaxies. For AM 2030A, we found a positive slope for the outer gradient, while the inner gradient is almost compatible with a flat behaviour. We found a decrease of star formation efficiency in the zone that corresponds to the oxygen abundance gradient break for AM 1219A and AM 2030B. For the former, a minimum in the estimated metallicities was found very close to the break zone, which could be associated with a corotation radius. However, AM 1256B and AM 2030A, present a star formation rate maximum but not an extreme oxygen abundance value. All four interacting systems that show oxygen gradient breaks have extreme SFR values located very close to break zones.The H ii regions located in close pairs of galaxies follow the same relation between the ionization parameter and the oxygen abundance as those regions in isolated galaxies. [ABSTRACT FROM AUTHOR]

We employ the NASA Infrared Telescope Facility's near-infrared spectrograph SpeX at 0.8–2.4 μm to investigate the spatial distribution of the stellar populations (SPs) in the four well-known starburst galaxies: NGC 34, NGC 1614, NGC 3310 and NGC 7714. We use the starlight code updated with the synthetic simple SPs models computed by Maraston. Our main results are that the near-infrared light in the nuclear surroundings of the galaxies is dominated by young-/intermediate-age SPs (t ≤ 2 × 109 yr), summing from ∼40 up to 100 per cent of the light contribution. In the nuclear aperture of two sources (NGC 1614 and NGC 3310), we detected a predominant old SP component (t > 2 × 109 yr), while for NGC 34 and NGC 7714 the younger component prevails. Furthermore, we found evidence of a circumnuclear star formation ring-like structure and a secondary nucleus in NGC 1614, in agreement with previous studies. We also suggest that the merger/interaction experienced by three of the galaxies studied, NGC 1614, NGC 3310 and NGC 7714, 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 the Maraston & Strömbäck evolutionary population synthesis 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. [ABSTRACT FROM PUBLISHER]

We study the kinematics and excitation mechanisms of H2 and [Fe ii] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (0.8–2.4 μm) spectroscopy together with new photoionization models. H2 emission lines are systematically narrower than narrow-line region lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star-forming galaxies. The importance of the thermal excitation in star-forming galaxies may be associated with the presence of supernova remnants close to the region emitting H2 lines. This hypothesis is further supported by the similarity between vibrational and rotational temperatures of H2. We confirm that the diagram involving the line ratios H2 2.121 μm/Brγ and [Fe ii] 1.257 μm/Paβ is an efficient tool for separating emission-line objects according to their dominant types of activities. We suggest new limits to the line ratios in order to discriminate between the different types of nuclear activities. [ABSTRACT FROM AUTHOR]

We present mid-infrared spectra of the Seyfert 2 galaxy NGC 1808, obtained with the Gemini's Thermal-Region Camera Spectrograph at a spatial resolution of ∼26 pc. The high spatial resolution allowed us to detect bright polycyclic aromatic hydrocarbons (PAHs) emissions at 8.6 and 11.3 μm in the galaxy centre (∼26 pc) up to a radius of 70 pc from the nucleus. The spectra also present [Ne ii]12.8 μm ionic lines, and H2 S(2) 12.27 μm molecular gas line. We found that the PAHs profiles are similar to Peeters's A class, with the line peak shifted towards the blue. The differences in the PAH line profiles also suggest that the molecules in the region located 26 pc north-east of the nucleus are more in the neutral than in the ionized state, while at 26 pc south-west of the nucleus, the molecules are mainly in ionized state. After removal of the underlying galaxy contribution, the nuclear spectrum can be represented by a Nenkova's clumpy torus model, indicating that the nucleus of NGC 1808 hosts a dusty toroidal structure with an angular cloud distribution of σ = 70°, observer's view angle i = 90° and an outer radius of R0 ∼ 0.55 pc. The derived column density along the line of sight is NH = 1.5 × 1024 cm2, which is sufficient to block the hard radiation from the active nucleus, and would explain the presence of PAH molecules near to the NGC 1808's active nucleus. [ABSTRACT FROM PUBLISHER]

ABSTRACT We present photometric parameters of the galaxies in the direction of the galaxy cluster LCDCS-S001 and improved kinematic parameters from new spectroscopic observations. From GMOS multi-object spectroscopy, we have been able to confirm a new set of 10 cluster members, resulting in a total 22 objects from previous observations. With these data, a dispersion velocity of σ= 887 ± 249 km s−1, a virial radius R200= 0.98 ± 0.22 Mpc and a mass of M200= (5.4 ± 2.8) × 1014 M⊙ have been derived. From GMOS i′ and r′ images, we have extracted the individual sources and derived their magnitudes, relative positions and the bulge+disc brightness profile decomposition. We show that the cluster has an elongated morphology along the north-south direction, with ellipticity ɛ= 0.49 ± 0.14, well represented by a King model with a core radius RC= 283 ± 66 kpc, above the typical core radii of regular clusters. It shows at least one local overdensity, north-west from the cluster centre, very compact and with a very high central density. The i′ luminosity function of LCDCS-S001 has an almost flat faint-end, α=−1.16 ± 0.18. As for the constituent galaxies, we have found that a large fraction of the cluster galaxies are late-type systems. Extensive simulations were made in order to verify the validity of our conclusions. We discuss the implication of these results for the evolutionary status of LCDCS-S001 and conclude that this cluster is still dynamically young. [ABSTRACT FROM AUTHOR]

We present mid-infrared (mid-IR) spectra of the Compton-thick Seyfert 2 galaxy NGC 3281, obtained with the Thermal-Region Camera Spectrograph at the Gemini-South telescope. The spectra present a very deep silicate absorption at 9.7 µm, and [S IV] 10.5 µm and [Ne II] 12.7 µm ionic lines, but no evidence of polycyclic aromatic hydrocarbon emission. We find that the nuclear optical extinction is in the range 24 mag ⩽ Av ⩽ 83 mag. A temperature T = 300 K was found for the blackbody dust continuum component of the unresolved 65 pc nucleus and the region at 130 pc SE, while the region at 130 pc NW reveals a colder temperature (200 K). We describe the nuclear spectrum of NGC 3281 using a clumpy torus model that suggests that the nucleus of this galaxy hosts a dusty toroidai structure. According to this model, the ratio between the inner and outer radius of the torus in NGC 3281 is R0/Rd = 20, with 14 clouds in the equatorial radius with optical depth of πv = 40 mag. We would be looking in the direction of the torus equatorial radius (i = 60°), which has outer radius of R0 ~ 11 pc. The column density is NH ≈ 1.2 x 1024cm-2 and the iron Kα equivalent width (≈0.5-1.2 keV) is used to check the toms geometry. Our findings indicate that the X-ray absorbing column density, which classifies NGC 3281 as a Compton-thick source, may also be responsible for the absorption at 9.7µm providing strong evidence that the silicate dust responsible for this absorption can be located in the active galactic nucleus toms. [ABSTRACT FROM AUTHOR]

ABSTRACT We present an observational study of the impacts of the interactions on the kinematics, stellar populations and oxygen abundances of the components of the galaxy pair AM 2322−821. A fairly symmetric rotation curve for the companion (AM 2322B) galaxy with a deprojected velocity amplitude of 110 km s−1 was obtained, and a dynamical mass of 1.1-1.3 × 1010 M⊙ within a radius of 4 kpc was estimated using this deprojected velocity. Asymmetries in the radial velocity field were detected for the companion, very likely due to the interaction between the galaxies. The interaction between the main and companion galaxies was modelled using numerical N-body/hydrodynamical simulations, with the result indicating that the current stage of the system would be about 90 Myr after perigalacticon. The spatial variation in the distribution of the stellar population components in both galaxies was analysed using the stellar population synthesis code starlight. The companion galaxy is dominated by a very young ( t≤ 1 × 108 yr) population, with the fraction that this population is of the total flux at λ 5870 Å increasing outwards in the galaxy disc. On the other hand, the stellar population of AM 2322A is heterogeneous along the slit positions observed. Spatial profiles of oxygen abundance in the gaseous phase were obtained using the diagnostic diagram R23= ([O ii]λ 3727 +[O iii]λ 4959 +[O iii]λ 5007)/Hβ versus [O iii]λ 5007/[O ii]λ 3727 where we compared the observed values with the ones obtained from photoionization models. Such gradients of oxygen abundance are significantly flatter for this pair of galaxies than in typical isolated spiral galaxies. This metallicity distribution is interpreted as the gradients having been destroyed by interaction-induced gas flows from the outer parts to the centre of the galaxy. [ABSTRACT FROM AUTHOR]

We study how the spectral fitting of galaxies, in terms of light fractions, derived in one spectral region translates into another region, by using results from evolutionary synthesis models. In particular, we examine propagation dependencies on evolutionary population synthesis (EPS) models (, , Maraston and ), age, metallicity and stellar evolution tracks over the near-ultraviolet-near-infrared (NUV-NIR, 3500 Å to 2.5 μm) spectral region. Our main results are as follows: as expected, young ( Myr) stellar population fractions derived in the optical cannot be directly compared to those derived in the NIR, and vice versa. In contrast, intermediate to old age ( Myr) fractions are similar over the whole spectral region studied. The metallicity has a negligible effect on the propagation of the stellar population fractions derived from NUV to NIR. The same applies to the different EPS models, but restricted to the range between 3800 and 9000 Å. However, a discrepancy between /Maraston and / models occurs in the NIR. Furthermore, the initial mass function is not important for the synthesis propagation. Compared to synthesis results, our propagation predictions agree at ∼95 per cent confidence level in the optical, and ∼85 per cent in the NIR. In summary, spectral fitting performed in a restricted spectral range should not be directly propagated from the NIR to the UV/optical, or vice versa. We provide equations and an on-line form [panchromatic averaged stellar population (PaASP)] to be used for this purpose. [ABSTRACT FROM AUTHOR]

We present SOAR/OSIRIS cross-dispersed near-infrared (NIR) integrated spectra of 12 Galactic globular clusters that are employed to test Maraston NIR evolutionary population synthesis models, and to provide spectral observational constraints to calibrate future models. We measured equivalent widths () of the most prominent NIR absorption features: λ 1.49 μm, Mg λ 1.58 μm, Fe /Mg , λ 1.59 μm, Si , λ 1.71 μm, Mg , λ 2.21 μm, Na and λ 2.26 μm, Ca as well as the λ 1.62 μm, λ 2.29 μm, CO and λ 2.05 μm, CN molecular bands. Optical of G band (4300 Å), Hβ, Mg, Fe (4531, 527 and 5335 Å) and Na (5897 Å) were also measured. The globular clusters were compared with model predictions with ages within 4-15 Gyr, and metallicities between 0.005 and 2 . Observed integrated colours ( and ) were also compared with models. The NIR integrated spectra among our sample appear qualitatively similar in most of the absorption features. The Maraston models can properly predict the optical observed in globular clusters. Regarding the NIR, they do underestimate the strength of Mg 1.49 μm, but they can reproduce the observed of Fe 1.58 μm, Si 1.59 μm and CO 2.29 μm, in about half of our sample. The remaining objects require the inclusion of intermediate-age populations. Thus, we suggest that the presence of C- and O-rich stars in models is important to reproduce the observed strengths of metallic lines. Another possibility is the lack of α-enhancement in the models. In the case of the optical and NIR Fe lines, standard models and those that include blue horizontal branch stars produce similar results. A similar trend is observed for Na 5895 Å, while in the case of the G band, the models with blue horizontal branch do describe better the observations. For most of the sample, the optical to NIR colours are well described by the Maraston models. In general, Maraston models can provide reliable information on the NIR stellar population of galaxies, but only when and colours are taken together; in other words, and continuum fluxes should be simultaneously fitted. However, the results should be taken with caution, since the models tend to predict results biased towards young ages. [ABSTRACT FROM AUTHOR]

We employ Infrared Telescope Facility SpeX near-infrared (NIR; 0.8–2.4 μm) spectra to investigate the stellar population (SP), active galactic nuclei (AGN) featureless continuum (FC) and hot dust properties in nine Sy 1 and 15 Sy 2 galaxies. Both thestarlight code and the hot dust as an additional base element were used for the first time in this spectral range. We found evidence of correlation among the equivalent widths Si i 1.59 μm × Mg i 1.58 μm, equally for both kinds of activity. Part of the and strengths may be related to galaxy inclination. 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 ∼90 per cent of the Sy 1 galaxies, and only of ∼25 per cent of the Sy 2; about 50 per cent of the Sy 2 galaxies require an FC component contribution ≳20 per cent, while this fraction increases to about 60 per cent in the Sy 1; also, in about 50 per cent of the Sy2, the combined FC and young components contribute with more than 20 per cent, while this occurs in 90 per cent of the Sy1, suggesting recent star formation in the central region. The central few hundred parsec of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1 μm CN band can be used as a tracer of intermediate-age SPs. The simultaneous fitting of SP, FC and hot dust components increased in ∼150 per cent the number of AGNs with hot dust detected and the mass estimated. The NIR emerges as an excellent window to study the SP of Sy 1 galaxies, as opposed to the usually heavily attenuated optical range. Our approach opens a new way to investigate and quantify the individual contribution of the three most important NIR continuum components observed in AGNs. [ABSTRACT FROM AUTHOR]

We present an observational study about the effects of the interactions in the kinematics, stellar population and abundances of the components of the galaxy pair AM 2306-721. Rotation curves for the main and companion galaxies were obtained, showing a deprojected velocity amplitude of 175 and 185 km s−1, respectively. The interaction between the main and companion galaxies was modelled using numerical N-body/hydrodynamical simulations, with the result indicating that the current stage of the merger would be about 250 Myr after perigalacticum. The spatial variation in the distribution of the stellar-population components in both galaxies was analysed by fitting combinations of stellar-population models of different age groups. The central region of main galaxy is dominated by an old (5–10 Gyr) population, while significant contributions from a young (200 Myr) and intermediate (1 Gyr) components are found in the disc, and being enhanced in the direction of the tidal features. The stellar population of the companion galaxy is overall much younger, being dominated by components with 1 Gyr or less, quite widely spread over the whole disc. Spatial profiles of the oxygen abundance were obtained from a grid of photoionization models using the R23 line ratio. The disc of the main galaxy shows a clear radial gradient, while the companion galaxy presents oxygen abundance relatively homogeneous across the disc. The absence of an abundance gradient in the secondary galaxy is interpreted in terms of mixing by gas flows from the outer parts to the centre of the galaxy due to the gravitational interaction with the more massive primary. [ABSTRACT FROM AUTHOR]

We study the central (inner few hundred parsecs) stellar populations of four starburst galaxies (NGC 34, 1614, 3310 and 7714) in the near-infrared (NIR), from 0.8 to 2.4 μm, by fitting combinations of stellar population models of various ages and metallicities. The NIR spectra of these galaxies feature many absorption lines. For the first time, we fit simultaneously as much as 15 absorption features in the NIR. The observed spectra are best explained by stellar populations containing a sizable amount (20–56 per cent by mass) of ∼1-Gyr-old stellar population with thermally pulsing asymptotic giant branch stars. We found that the metallicity of the stars which dominates the light is solar. Metallicities substantially different from solar give a worse fit. Though the ages and metallicities we estimate using the NIR spectroscopy are in agreement with values from the literature based on the ultraviolet/optical, we find older ages and a larger age spread. This may be due to the fact that the optical is mostly sensitive to the last episode of star formation, while the NIR better maintains the record of previous stellar generations. Another interesting result is that the reddening estimated from the whole NIR spectrum is considerably lower than that based on emission lines. Finally, we find a good agreement of the free emission-line spectrum with photoionization models, using as input spectral energy distribution the synthetic composite template we derived as best fit. [ABSTRACT FROM AUTHOR]

The stellar population, metallicity distribution and ionized gas in the elliptical galaxies NGC 6868 and 5903 are investigated in this paper by means of long-slit spectroscopy and stellar population synthesis. Lick indices in both galaxies present a negative gradient indicating an overabundance of Fe, Mg, Na and TiO in the central parts with respect to the external regions. We found that Mg2 correlates both with Fe i λ5270 and Fe i λ5335, suggesting that these elements probably underwent the same enrichment process in NGC 6868. However, only a marginal correlation of Mg2 and Fe i λ5270 occurs in NGC 5903. The lack of correlation between computed galaxy mass and the Mg2 gradient suggests that these elliptical galaxies were formed by merger events. The stellar population synthesis shows the presence of at least two populations with ages of 13 and 5 Gyr old in both galaxies. We have estimated the metallicity of the galaxies using single-aged stellar population (SSP) models. The central region of NGC 6868 presents a deficiency of alpha elements with respect to iron and solar metallicity. The external parts present a roughly uniform distribution of ratios and metallicities ranging from and solar. A similar conclusion applies to NGC 5903. Concerning the emitting gas conspicuously detected in NGC 6868, we test three hypotheses as ionizing source: an H ii region, post-AGB (asymptotic giant branch) stars and an active galactic nucleus (AGN). Diagnostic diagrams involving the ratios and indicate that values measured in the central region of NGC 6868 are typical of LINERs (Low-Ionization Nuclear Emission-Line Regions). Together with the stellar population synthesis, this result suggests that the main source of gas ionization in NGC 6868 is non-thermal, produced by a low-luminosity AGN, probably with some contribution of shocks to explain ionization at distances of from the nucleus. [ABSTRACT FROM AUTHOR]

We present a spectroscopic and photometric analysis for eight field galaxies in the direction of the galaxy cluster LCDCS-S001. The spectra were obtained with the GMOS instrument at the Gemini South Observatory. The objects were selected in an i′-band image and the multiobject spectroscopic observations were centred at 7500 Å. For the galaxies ID 440 and ID 461, we have determined redshifts of and 0.7465, respectively. For the other six galaxies we have confirmed the previous measurements of redshift. The redshifts of the field galaxies are in the range of . We determined the blue and visual luminosities and they are brighter than . The galaxies ID 180, ID 266 and ID 461 follow the Faber–Jackson relation of the Coma and Virgo early-type galaxies, and therefore do not present a brightening of the B luminosity as observed in galaxies at higher redshifts. The stellar velocity dispersion was measured for five galaxies (ID 146, ID 180, ID 266, ID 428 and ID 440) and estimated to be in the range of . Lick indices were measured and used to determine the stellar population properties of the galaxies ID 120 and ID 146, by means of spectral synthesis. The first galaxy, ID 120, presents in its spectrum absorption and emission lines, and we have found that the main contribution in the flux at λ5870 Å is of a 0.1-Gyr stellar population of solar metallicity. For ID 146, the dominant flux contribution at λ4200 Å is provided by a stellar population of 10 Gyr of subsolar metallicity. From stellar population synthesis, we estimated reddening values of and 0.82 for ID 120 and ID 146, respectively. According to classical diagnostic diagrams the emission lines present in the spectrum of ID 120 indicate that it is a starburst galaxy. [ABSTRACT FROM AUTHOR]

We present kinematic parameters and stellar population properties of selected galaxies in the high-redshift galaxy cluster LCDCS-S001, determined by spectroscopic data obtained with the Gemini multi-object spectrograph instrument in the Gemini South Observatory. The objects were selected in an i′-band cluster field image, and multi-object spectroscopic observations centred at 7500 Å were performed for 40 objects. Spectral features were successfully identified for 20 objects, and used to determine the redshift of the cluster. We found that 12 objects are cluster members and estimate a median redshift of 0.709 for this cluster. The relative velocities of the cluster members were used to estimate the projected cluster mass, which was found to be 3.54 × 10 14+2.33−1.41 M⊙. Lick and Dn(4000) indices were measured and used to determine the stellar population properties of the galaxies, by means of a spectral synthesis through Bruzual & Charlot evolutive models. We found that the bulk of stellar population for the cluster members has a spectrum compatible with solar metallicity and an age between 3.0 and 7.0 Gyr; with only one exception, the flux contribution of younger stars in the spectra does not exceed 25 per cent at 4200 Å. Emission [O ii] lines were detected for four galaxies, all of which showing a stronger contribution of young stars compared with other cluster galaxies. The equivalent width of the [O ii]λ3727 emission line was compared with Magris, Binette & Bruzual models for H ii regions. We found good correspondence between our values and the theoretical predictions for solar metallicity and with star formation time-scales . [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopy is used to study the kinematics and excitation mechanisms of H2 and [Fe ii] lines in a sample dominated by Seyfert 2 galaxies. The spectra simultaneously cover the JHK bands, allowing us to compare line fluxes emitted in the interval 0.8–2.4 μm and avoiding aperture and seeing effects. The H2 lines are systematically narrower than the narrow-line region lines, suggesting that, very likely, the H2 does not originate from the same parcel of gas that forms the narrow-line region. Emission-line ratios between H2 lines favour thermal excitation mechanisms for the molecular gas in active galactic nuclei. It was found that non-thermal excitation contributes, at most, 30 per cent of the observed H2. Thermal excitation is also confirmed by the rather similar vibrational and rotational temperatures in the objects (∼2000 K). The mass of hot H2 ranges from 102 to 103 , with nearly half of objects showing values of . It shows that the fraction of molecular mass present in the nuclear region and emitting in the near-infrared is a very small fraction of the warm molecular mass present in the centre. A diagnostic diagram composed of the line ratios H2/Brγ and [Fe ii]/Paβ proves to be a useful tool in the near-infrared for separating emission-line objects by their degree of nuclear activity. We found that active galactic nuclei are characterized by H2 2.121 μm/Brγ and [Fe ii] 1.257 μm/Paβ flux ratios between 0.6 and 2. Starburst/H ii galaxies display line ratios <0.6 while low-ionization nuclear emission-line regions are characterized by values larger than 2 in either ratio. [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopic observations in the range 0.8-2.4¼m are used to study the kinematics and excitation mechanisms of Molecular Hydrogen and [FeII] lines in a sample of AGNs. The width of H2 lines is narrower than [FeII] lines, therefore they do not originate from the same parcel of gas. The molecular emission is found to be purely thermal but with heating processes which vary among the objects. A clear correlation between H2/Br³ and [FeII] 1.257¼m/Pa² is found for our sample objects supplemented with data from the literature. The correlation of these line ratios is a useful diagnostic tool in the NIR to separate emitting line objects by their level of nuclear activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html [ABSTRACT FROM PUBLISHER]

In this work we investigate the stellar population, metallicity distribution and ionized gas in the elliptical galaxy NGC 5044, using long-slit spectroscopy and a stellar population synthesis method. We found differences in the slope of FeI and Mg2 lines gradients, which suggests an enhancement of ± elements, particularly towards the central region. The stellar population synthesis shows that the contribution, at »5870, of the most metallic and old stellar population ($Z/Z_\odot \sim 0.0$ and 1010year) is dominant in NGC 5044. The presence of a non-thermal ionization source, such as a low-luminosity AGN and/or shock ionization, is implied by the large values of the ratio [NII]/H± observed in all sampled regions. However, the emission lines observed in the external regions indicate the presence of an additional ionization source, probably hot, post-AGB stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]