Color selection is an efficient technique for extracting candidate AGNs. Many AGNs have been selected on the basis of colors at various wavelengths. In this work, we extracted AGN candidates using near-infrared colors and investigated their properties.

massclean is a new, sophisticated and robust stellar cluster image and photometry simulation package. This package can create color–magnitude diagrams and standard FITS images in any of the traditional optical and near-infrared bands based on cluster characteristics input by the user, including but not limited to distance, age, mass, radius and extinction. At the limit of very distant, unresolved clusters, we have checked the integrated colors created in massclean against those from other simple stellar population models, with consistent results. Because the algorithm populates the cluster with a discrete number of tenable stars, it can be used as part of a Monte Carlo method to derive the probabilistic range of characteristics (integrated colors, for example) consistent with a given cluster mass and age. We present the first ever mass-dependent integrated colors as a function of age, derived from over 100 000 Monte Carlo runs, which can be used to improve the current age-determination methods for stellar clusters.

The Japanese infrared satellite AKARI has unique capabilities for near-infrared spectroscopy and an all-sky survey in the mid- and far-infrared. We present the recent results on active galactic nuclei that use the unique capabilities of AKARI.

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.

To study the evolution of binary star clusters, we have imaged seven systems in the Small Magellanic Cloud with the SOAR 4m telescope using B and V filters. The sample contains pairs with well-separated components (d < 30 pc) as well as systems that apparently have merged, as evidenced by their unusual structures. By employing isochrone fitting to their color–magnitude diagrams, we have determined reddening values, ages and metallicities, and by fitting King models to their radial stellar-density profiles we estimated core radii. Disturbances of the density profiles are interpreted as evidence of interactions. Properties such as the distances between their components and their age differences are addressed in terms of the timescales involved, to assess the physical connection of the system. In two cases, the age difference is more than 50 Myr, which suggests a chance alignment, capture or sequential star formation.

In this review I first summarize why binaries are key objects in the study of stellar populations, to understand the evolution of star clusters and galaxies, and thus to understand the universe. I then focus on four specific topics:

1. (i) the formation (through binaries) and evolution of very massive stars in dense clusters and the importance of stellar-wind mass loss. I discuss preliminary computations of wind mass-loss rates of very massive stars performed with the Munich hydrodynamical code and the influence of these new rates on the possible formation of an intermediate-mass black hole in the cluster MGG 11 in M82;

2. (ii) the evolution of intermediate-mass binaries in a starburst with special emphasis on the variation of the supernova (SN) Ia rate (i.e., on the delayed time distribution of SNe Ia). A comparison with SN Ia rates in elliptical galaxies may provide important clues to SN Ia models as well as to the evolution of SN Ia progenitors;

3. (iii) the evolution of double-neutron-star mergers in a starburst (i.e., the delayed time distribution of these mergers) and what this tells us about the suggestion that these mergers may be important production sites of r-process elements;

4. (iv) the possible effect of massive binaries on the self-enrichment of globular clusters.

We present two ongoing studies of gas phase abundances around high redshift quasars. First, we examine broad emission line (BEL) metallicities for 29 quasars with 2.3 < z < 4.6 and far-infrared (far-IR) luminosities (LFIR) from 1013.4 to ≤ 1012.2 L⊙, corresponding to star formation rates (SFRs) of 6740 to ≤ 1360 M⊙ yr−1. Quasar samples sorted by LFIR might represent an evolutionary sequence if SFRs in quasar hosts generally diminish across quasar lifetimes. We create three composite spectra from rest-frame ultra-violet Sloan Digital Sky Survey spectra with increasing far-IR luminosity. We measure the N V(λ1240)/C IV(λ1550) and Si IV(λ1397)+O IV](λ1402)/C IV(λ1550) emission line flux ratios for each composite and find uniformly high (~5-10 times solar) metallicities for the three composites, and no evidence for changes in metal enrichment with changes in ongoing SFR. Second, we present preliminary results from the largest ever survey of high resolution associated absorption line (AAL) region metallicities and physical properties in a sample of high redshift (z > 3) quasars. This includes five quasars with previously known AALs at z > 4 and two well measured z ~3 quasars with unusually rich absorption spectra. We determine well-constrained metallicities of about twice solar for five AAL systems. We find a range of lower limits for AAL metallicities in the z > 4 quasars from 1/100ths solar to 3 times solar. Overall, these results for typically super-solar gas-phase metallicities near quasars are consistent with evolutionary schemes where the major episodes of star formation in the host galaxies occur before the visibly luminous quasar phase. High SFRs (comparable to ULIRGs) in the host galaxies are not clearly linked to younger or chemically less mature quasar environments.

Many grand-design spiral galaxies display strings of knots along their arms on K-band images. Near-infrared (NIR) spectra and broad-band colours of such knots have identified them as very young, massive stellar complexes. The low absorption in the NIR makes it possible to derive complete statistics of such complexes and thereby estimate the associated star-formation rate. We have obtained deep NIR maps of eight grand-design spirals using VLT/HAWK-I and identified massive complexes with ages of < 10 Myr using NIR colour–colour diagrams. The youngest, most massive complexes are well-aligned and concentrated in the arm regions of the grand-design galaxies with strong spiral perturbations. Their absolute magnitudes have a bright tail reaching almost MK = −16 mag. Both the fraction of young to old sources and the ratio of diffuse to more compact objects suggest a dependence on the strength of the spiral pattern in the host galaxy.

In this work, we analyze observations of the solar radius at 22 and 43 GHz obtained with the 13.7 m antenna of the Itapetinga Radio Observatory (Atibaia, Brazil) and at submillimeter-wave frequencies, 212 and 405 GHz, obtained by the Solar Submillimeter-wave Telescope (SST) (El Leoncito, San Juan, Argentina). The radius is defined as the limb position where the intensity is equal to half of the quiet Sun value. These measured radii are then compared with those predicted by a model of the solar atmosphere proposed by Selhorst, Silva, and Costa (2005). The results show that at 22 and 43 GHz, the emission comes from regions high in the chromosphere. Furthermore, the Itapetinga observations yield radii of 985” ± 5” and 981” ± 6”, at 22 and 43 GHz respectively, consistent with the theoretical positions in the atmosphere. On other hand, the submillimeter observations resulted in a mean radius of 972” ± 3” and 975” ± 5” at 212 and 405 GHz, respectively, considered equal within the uncertainties. The latter results can be explained by the origin of the emission being very close to the region of minimum temperature, between the photosphere and chromosphere. This is a dynamic region largely affected by many solar features, like spicules and plages.

Comet-like orbits with low perihelion distances tend to be affected by relativistic effects. In this work we discuss the origin of the relativistic corrections, how they affect the orbital evolution and how to implement these corrections in a numerical integrator. We also propose a model that mimics the principal relativistic effects and, contrary to the original “exact” formula, has low computational cost. Our model is appropriated for numerical simulations but not for precise ephemeris computations.

We present preliminary results from the largest-ever survey of high-resolution associated absorption line (AAL) region metallicities and physical properties in a sample of high redshift (z > 3) quasars.

We present results from a survey of nearby AGN using the adaptive optics assisted integral-field spectrometer SINFONI on the VLT. These data enable us to study at high angular resolution (~ 0.″08) the distribution and kinematics of the low-ionization gas traced by the BrΓλ2.17 μm recombination line and [Si vi] λ 1.96 μm, [Al ix] λ 2.04 μm, and [Ca viii] λ 2.32 μm, the most prominent coronal lines in the near-IR. Overall, our results show that the coronal lines extend to a radius similar to that of narrow Brγ emission, mimicking in most cases the narrow-line region (NLR). In addition, the kinematics of the highly ionized species, and most of the Brγ kinematics, is dominated by non-circular motions with higher dispersion along the ionization cones, indicating that material is being accelerated and outflowing from a region very close to the AGN.

We investigate the properties of local HI-selected galaxies detected in blind radio surveys by using semi-analytic galaxy formation models in the hierarchical structure formation scenario. By drawing a detailed comparison between the properties of the HI-selected galaxies and the quasar absorption systems, we investigate a link between the local galaxy population and the quasar absorption systems, particularly for Damped Lymanα absorption (DLA) systems (NHI ≥ 1020.3 cm−2) and sub-DLA systems (1019 < NHI < 1020.3 cm−2).

We find that DLA galaxies, in which the HI column densities are as high as those of DLA systems, contribute primarily to the population of local HI-selected galaxies at MHI ≥ 108M⊙. By contrast, in the low-mass range MHI ≤ 107M⊙, sub-DLA galaxies replace DLA galaxies as the dominant population. The HI-selected galaxies would be a strong probe of DLA/sub-DLA systems.

Using a hydrodynamic adaptive mesh refinement code, we simulate the growth and evolution of a typical disk galaxy hosting a supermassive black hole (SMBH) within a cosmological volume. The simulation covers a dynamical range of 10 million, which allows us to study the transport of matter and angular momentum from super-galactic scales down to the outer edge of the accretion disk around the SMBH. A dynamically interesting circumnuclear disk develops in the central few hundred parsecs of the simulated galaxy, through which gas is stochastically transported to the central black hole.

Most, if not all, galaxies with a significant bulge component harbor a central supermassive black hole. In our own Milky Way Galaxy, a disk of stars at a distance r ~ 0.05–1 pc orbits the radio source Sgr A* at the center. Stellar orbits show that the gravitational potential on a scale of ~ 0.5 pc is dominated by a concentrated mass of MBH ≈ 3.6 × 106M⊙, which is associated with a supermassive black hole. In addition to the black hole, the models require the presence of an extended mass of (0.5–1.5) × 106M⊙ in the central parsec, which can be explained well by the mass of the stars that make up the cluster. Thus, the Galactic center star cluster is composed of a central supermassive black hole and a self-gravitating disk that is several Gyrs old and comprised of late-type CO absorption stars. Significant disk rotation in the sense of the general Galactic rotation has been detected. This system is probably a strongly warped, thin single disk; the mean eccentricity of the observed stellar orbits in the disk is e ≈ 0.36 ± 0.06.

We present a detailed study of the stellar populations (SPs) and kinematics of the bulge and inner disk regions of nearby spiral galaxies (Sa-Sd) based on deep long-slit Gemini/GMOS data. We find that the SPs of spiral galaxies are not well matched by single episodes of star formation; representative SPs must involve average SP values integrated over the star formation history (SFH) of the galaxy, such as those derived from the “full population synthesis” method used here. Our spiral bulges follow the same correlations of increasing light-weighted age and metallicity with central velocity dispersion as those of elliptical galaxies and early-type bulges found in other studies, but when SFHs more complex and realistic than a single burst are invoked, the trend with age is shallower and its scatter much reduced. In a mass-weighted context, all bulges are predominantly composed of old and metal-rich SPs. Bulge formation appears to be dominated by early processes that are common to all spheroids, whether they currently reside in disks or not. While monolithic collapse cannot be ruled out in some cases, merging must be invoked to explain the SP gradients in most bulges. Further bulge growth via secular processes, or “rejuvenated” star formation, generally contributes minimally to the stellar mass budget. We also demonstrate how the combination of our full population synthesis modeling of high-quality optical spectra of integrated SPs along with optical-NIR broad-band imaging can single out potential model weaknesses and help determine the reliability of the inferred SFHs.

The primordial lithium abundance inferred from WMAP and standard Big Bang nucleosysnthesis is approximately three times higher than the plateau value measured in old metal-poor Population II stars, suggesting that these stars have undergone atmospheric Li depletion. To constrain the physics responsible for such depletion, we conducted a homogeneous analysis of a large sample of stars in the metal-poor globular cluster NGC 6397, covering all evolutionary phases from below the main-sequence turnoff to high up the red-giant branch (RGB). The dwarf, turnoff, and early subgiant stars form a thin abundance plateau, with a sharpe edge in the middle of the subgiant branch, where Li dilution caused by the inward extension of the convective envelope starts (the beginning of the so-called first dredge up). A second steep abundance drop is seen at the RGB bump, again highlighting the need for the onset of nonstandard mixing in this evolutionary phase. Moreover, by also measuring the sodium abundances of the targets, we have gained insight into the degree of pollution by early cluster self-enrichement, and may separate highly polluted, Li-poor and Na-rich stars from stars formed from pristine material. Our observational findings strictly limit both the extent of lithium surface depletion, which in turn constrains the efficiency of mixing below the outer convection zone, and the resulting spread in lithium abundance in metal-poor turn-off stars.

Extrasolar planetary host stars are enriched in key planet-building elements. These enrichments have the potential to drastically alter the building blocks available for terrestrial planet formation. Here we report on the combination of dynamical models of late-stage terrestrial planet formation within known extrasolar planetary systems with chemical equilibrium models of the composition of solid material within the disk. This allows us to constrain the bulk elemental composition of extrasolar terrestrial planets. A wide variety of resulting planetary compositions exist, ranging from those that are essentially “Earth-like”, containing metallic Fe and Mg-silicates, to those that are dominated by graphite and SiC. This implies that a diverse range of terrestrial planets are likely to exist within extrasolar planetary systems.

We present the results of a cross-correlation analysis of the projected positions of AGNs and galaxies at redshifts from 0.3 to 3.0. It is widely accepted that the origin of AGN activity is accretion of matter onto a massive black hole at the center of a galaxy (e.g., Lynden-Bell 1969). To explain the activity of AGNs, a large fraction of matter in the galaxy must be delivered to the inner region on a short timescale (Hopkins et al. 2008). One possible mechanism for causing rapid gas inflows into the central region is a major galaxy merger between gas-rich galaxies (e.g., Kauffmann & Haehnelt 2000). If this is the case, AGNs are expected to be found in an environment with higher galaxy density than that of typical galaxies. We investigated environments of ~ 750 AGNs, which is about a ten times larger sample than used in previous studies, and we find a significant excess of galaxies around the AGNs in the redshift range of 0.3 to 1.8. We used the Japanese Virtual Observatory (JVO) to obtain the Subaru Suprime-Cam images and UKIDSS data around known AGNs. The datasets accessed through the JVO are: Catalog of Quasars and Active Galactic Nuclei by Veron-Cetty et al. (2006), SDSS DR-5 Quasar Catalog by Schneider et al. (2007), Subaru Suprime-Cam Reduced Image Archive of JVO, and UKIDSS DR2 catalog by Warren et al. (2007). We divided all the AGN samples into four redshift groups, 0.3≲z ≲ 0.8, 0.8≲ z ≲ 1.5, 1.5≲ z ≲ 1.8, and 1.8≲ z ≲ 3.0. For each redshift group, the dataset was further divided into a fainter group (MV ≥ −25 mag) and a brighter group (MV < −25 mag). We found that the correlation length of the high-redshift bright sample (1.5≲ z ≲ 1.8) was larger than that of the low-redshift faint sample (0.3≲ z ≲ 0.8). We also found that the correlation length was larger for the faint group at redshift range 0.8≲ z ≲1.5. These results can be explained by downsizing of mass assembly. More details can be found in the paper by Shirasaki et al. (2009). Our result implies that the Japanese Virtual Observatory can be a powerful tool to investigate the co-evolution of central black holes and galaxies at the intermediate redshift universe.

We present flux-calibrated integrated spectra in the optical spectral range of Galactic open clusters (GOCs) and Magellanic Cloud (MC) stellar clusters (SCs) obtained at CASLEO (Argentina). The SC parameters were derived using the equivalent-width (EW) method and the template-matching procedure by comparing the line strengths and continuum distribution of the cluster spectra with those of template spectra with known parameters. MC cluster reddening values were also estimated by interpolation between the available extinction maps. The derived ages for the GOCs range from 3 Myr to 4 Gyr, while those of the MC SCs vary from 3 Myr to 7 Gyr. E(B−V) colour-excess values in the MCs appear to be all lower than 0.17 mag, while those of the GOCs range from 0.00 to 2.40 mag. The present data led us to upgrade the spectral libraries of reference spectra or templates of solar and MC metallicities.