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.

We report on some preliminary results on the evolution and luminosity functions of submillijansky (sub-mJy) radio sources, based on the VLA Chandra Deep Field South (CDFS) sample.

We combine 610 MHz GMRT data, 1.4 GHz VLA data, and 1.4 GHz WSRT observations, encompassing a ~ 4 square degree field centered on the verification strip of the Spitzer First Look Survey field, to study radio sources down to fluxes of about 0.1 mJy. The spectral index (Figure 1) analysis shows that the majority of multi-component sources are steep-spectrum sources. Nevertheless the spread in the spectral distribution is wide, with a significant number of ultra-steep, flat or inverted sources, possibly indicating a wider range of accretion modes in fainter samples. By cross-correlating 107 multi-component radio sources with the optical catalogues of Marleau et al. (2007) and Papovich et al. (2006), 23 objects were identified.

We present subarcsecond resolution mid-infrared (mid-IR) photometry in the range from 8 to 20 μm of 18 nearby Seyfert galaxies, reporting high spatial resolution nuclear fluxes for the entire sample (see Table 3 of Ramos Almeida et al. 2009). We construct spectral energy distributions (SEDs) that the AGN dominates, relatively uncontaminated by starlight, adding near-IR measurements from the literature at similar angular resolution. We find that the IR SEDs of intermediate-type Seyferts are flatter and present higher 10 to 18 μm ratios than those of Seyfert 2 (Sy2) galaxies.

The Australia Telescope Large Area Survey (ATLAS; Norris et al. 2006) is the widest deep radio survey to date, covering approximately 7 square degrees over two fields, with extensive complementary data. We are investigating all possible discriminants between active galactic nuclei (AGN) and star-forming galaxies (SFG) in ATLAS, to determine a robust formula for distinguishing the two.

NGC 7582 was identified as a starburst galaxy in the optical (Veron et al. 1981) but its X-ray emission is typical of a Seyfert 1 galaxy (Ward et al. 1978). We analyzed a datacube on this object obtained with the GMOS-IFU on the Gemini-South telescope. After a subtraction of the stellar component using the starlight code (Cid Fernandes et al. 2005), we looked for optical signatures of the AGN. We detected a broad Hα component (Figure 1) in the source where Bianchi et al. (2007) identified the AGN in an HST optical image. We also found a broad Hβ feature (Figure 2), but its emission reveals a extended source. We suggest that it is the light of the AGN scattered in the ionization cone. We propose that NGC 7582 is a Seyfert 1 galaxy. A number of other “hot-spots” and Wolf–Rayet features were also identified.

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.

Fe ii comprises up to one third of the line emission in AGNs. For that reason it is an important coolant that needs to be taken into account to fully understand the energetics of the broad line region (BLR). As such, Fe+ is a potential diagnostic of gas density, column density, turbulence, temperature and continuum shape. However, understanding Fe ii is complicated because of the energy level configuration and different mechanisms that may contribute to the line emission.

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 present 2-D mapping and analysis of the gaseous kinematics of the inner 7″ × 5″ of one of nearest (z = 0.0414) and brightest post-starburst quasars (PSQ) by using spectra obtained with the Integral Field Unit (IFU) of the Gemini Multi-Object Spectrograph on the Gemini North Telescope (Allington-Smith et al. 2002). Such quasars are broad-lined AGNs that also show the Balmer jumps and the high-order Balmer absorption lines from A stars typical of massive post-starburst populations of a few hundred Myrs (Brotherton et al. 2007). From measurements of the emission-line profiles, we constructed two-dimensional maps for the flux distributions, line ratios, radial velocities and gas velocity dispersions for the Hβ and [Oiii] emitting gas, similar to those of previous studies by our group (e.g., Barbosa et al. 2009).

Active galactic nuclei can be identified in deep HST surveys using different selection techniques and multiwavelength data. We aim to produce a complete sample of AGN in the GOODS South and North fields by combining X-ray, optical and mid-IR selection criteria, including galaxies displaying nuclear optical variability.

It has been known for some time that elliptical galaxies have some form of dust structure at their centers (Kormendy & Djorgovski 1989; van Dokkum & Franx 1995). Nevertheless the exact amount and the origin of the dust is still unknown. In a previous paper, we have shown that all early-type galaxies hosting an AGN have dust at their centers as opposed to only a quarter of the inactive galaxies in a pair-matched sample (Simões Lopes et al. 2007). Here we use Spitzer (IRAC and MIPS) observations of the same sample — 32 active and 32 inactive early-type galaxies — and state-of-the-art spectral modelling from Draine & Li (2007) to estimate the dust mass present in these galaxies. We have also created PAH images by estimating and subtracting the stellar-only contribution to the flux at the 7.9 μm image from the 3.6 μm image.

In the BPT diagram, the distribution of the emission-line galaxies from the Sloan Digital Sky Survey (SDSS) evokes the wings of a seagull. Traditionally, galaxies in the right wing are considered to host AGNs. Our study of the stellar populations of SDSS galaxies showed that ~ 1/4 of galaxies thought to host LINERs are in fact “retired galaxies,” i.e., galaxies that stopped forming stars and are ionized by hot post-AGB stars and white dwarfs (Stasińska et al. 2008). When galaxies that lack some of the lines needed to place them in the BPT diagram are included, the fraction of retired galaxies is even larger (Cid Fernandes et al., these proceedings).

Using a uniformly selected and highly spectroscopically complete sample of Chandra X-ray sources, we show that one cannot use X-ray spectral classifications and optical spectral classifications equivalently. Until a better understanding is reached for how the X-ray and optical classifications relate to the obscuration of the central engine, the use of a mixed classification scheme can only complicate the interpretation of X-ray AGN samples.

We present preliminary results from a study of the SEDs of a complete sample of 65 LIRGs from GOALS. The spectral shapes at λ > 10μm are similar, while the largest variations occur in the NIR (L1μm5μm/L⊙ ~ 1.0–0.01) and UV (L1μm0.12μm/L⊙ ~ 2.0–0.005). Using stellar population synthesis models to fit the UV–NIR continuum data, we derive stellar masses for the host galaxies of log (M*/M⊙) ~ 10.2–11.4 with a mean of ~ 10.8.

Various studies have shown that there is an empirical relation between the nebular metallicity of a galaxy and its stellar mass. Until now, most studies of the mass-metallicity relation (M–Z) have focused on the abundances of the interstellar medium as measured by emission-line features. This technique thus excludes galaxies with AGN from the working samples, due to the difficulty to measure the nebular abundances when emission-lines are powered both by stars and AGN. With our synthesis code starlight, we are able to recover the stellar metallicities of galaxies from the Sloan Digital Sky Survey (SDSS). Therefore, although we still cannot measure the nebular metallicity in AGN hosts, we know their present-day stellar metallicities. Moreover, because we measure the metallicity of stellar populations of different ages in a galaxy, we are also able also recover the history of its chemical enrichment.

We obtained deep images for 49 Seyfert 2 galaxies in 6 infrared bands: J, H, K, L, M, and N with the VLT at Paranal, the NTT at La Silla, and Gemini at Pachón, to compile their nuclear infrared (IR) spectral energy distributions (SEDs). These galaxies were extracted from the Extended 12 μm Galaxy Sample (Rush et al. 1993).

We investigated the use of support vector machines (SVMs) to distinguish quasars from stars using survey databases from different wavebands. We first employed a random forest approach for selection and weighting of features. We find that SVMs are an effective method to preselect quasar candidates from multiwavelength data.

We investigate selection and weighting of features by applying a random forest algorithm to multiwavelength data. Then we employ a k-nearest neighbor method to distinguish quasars from stars. We then compare the performance of this approach based on all features, weighted features, and selected features. We find that the k-nearest neighbor approach combined with random forests effectively separates quasars from stars.

We review briefly direct and indirect methods of measuring the masses of black holes in galactic nuclei, and then focus attention on supermassive black holes in active nuclei, with special attention to results from reverberation mapping and their limitations. We find that the intrinsic scatter in the relationship between the AGN luminosity and the broad-line region size is very small, ~0.11 dex, comparable to the uncertainties in the better reverberation measurements. We also find that the relationship between reverberation-based black hole masses and host-galaxy bulge luminosities also seems to have surprisingly little intrinsic scatter, ~0.17 dex. We note, however, that there are still potential systematics that could affect the overall mass calibration at the level of a factor of a few.