Obscured quasars hidden in deep X-ray surveys can be recovered by looking at mid-infrared wavelengths, where dust re-radiates the absorbed radiation. Here we present a sample of obscured quasars in the redshift range 1 < z < 4 based on data from the UKIDSS Ultra-Deep Survey (UDS), the deepest near-IR survey over ~ 1 sq. deg. to date. Candidates that are primarily selected by their 24 μm emission are probed by decomposing their spectral energy distribution (SED) to disentangle the emission from the AGN and its host galaxy. We show preliminary results on their host galaxy properties as well as their clustering, showing that obscured quasars are found in galaxies located in the green valley, residing in dark matter haloes not different from normal galaxies at those redshifts.

Influence of the dark energy at small scales is considered. Interaction and energy exchange between ordinary matter and dark energy is proposed as a working hypothesis. Some observational facts are put into the base of this consideration: the large rate of lunar retreat and the acceleration of cosmic expansion which proves the energy exchange between ordinary matter and dark energy. If the possibility of the space and matter expansion at the scales under consideration is accepted one can show that the dark energy transformed into the object's potential energy is enough to generate cluster of galaxies over the Hubble time due to matter ejection mechanism.

We discuss an analysis of the redshift evolutions and distributions of the gamma-ray luminosity and photon spectral index of flat spectrum radio quasar (FSRQ) type blazars. We utilize data from the Fermi Gamma-ray Space Telescope, with redshfits as determined from optical spectroscopy by Shaw et al. We find that FSRQs have evolved significantly in luminosity but negligibly in photon index, and contribute in toto roughly 20% of the total gamma-ray output of the Universe.

The Galactic center (GC) region hosts three of the most massive resolved young clusters in the Local Group and constitutes a test bed for studying the star formation history of the region and inferring the possibility of a top-heavy scenario. Further, recent detection of a large number of apparently isolated massive stars within the inner 80 pc of the Galactic center has raised fundamental questions regarding massive star formation in a such a dense and harsh environment. Noting that most of the isolated massive stars have spectral analogs in the Quintuplet cluster, we have undertaken a combined analysis of the infrared spectra of both selected Quintuplet stars and the isolated objects using Gemini spectroscopy. We present preliminary results, aiming at α-elements versus iron abundances, stellar properties, ages and radial velocities which will differentiate the top-heavy and star-formation scenarios.

The Wide-field Infrared Survey Explorer (WISE) has scanned the entire sky with unprecedented sensitivity in four infrared bands, at 3.4, 4.6, 12, and 22 μm. The WISE Point Source Catalog contains more than 560 million objects, among them hundreds of thousands of galaxies with Active Nuclei (AGN). While type 1 AGN, owing to their bright and unobscured nature, are easy to detect and constitute a rather complete and unbiased sample, their type 2 counterparts, postulated by AGN unification, are not as straightforward to identify. Matching the WISE catalog with known QSOs in the Sloan Digital Sky Survey we confirm previous identification of the type 1 locus in the WISE color space. Using a very large database of the popular Clumpy torus models, we find the colors of the putative type 2 counterparts, and also, for the first time, predict their number vs. flux relation that can be expected to be observed in any given WISE color range. This will allow us to put statistically very significant constraints on the torus parameters. Our results are a successful test of the AGN unification scheme.

The discovery of the two giant γ-ray lobes (Fermi bubbles) in the Galactic center (see Dobler et al. 2010 and Su et al. 2010) was one of the most impressive events of the last few years in astrophysics. However, some indications on giant structures in the Galactic center (GC) were observed several years before by WMAP in the radio frequency range between 23 and 33 MHz (Finkbeiner 2004), and by ROSAT in hard X-rays (Bland-Hawthorn & Cohen 2003). Recent observations performed by the Planck Collaboration (Ade et al. 2012) found also lobes in the microwave range which spatially coincided the Fermi bubbles that indicated on the common origin of these phenomena.

We describe preliminary results for two ALMA projects – 1) imaging the HCN(4-3) line and H26α lines in Arp 220 and 2) measurements of the dust continuum in a sample of 107 high redshift galaxies to probe the evolution of the ISM masses. The HCN observations in Arp 220 at 1/2″ resolution provide the first high resolution imaging of the dense star forming gas in this prototypical ULIRG. The HCN is seen in two clearly delineated, counter-rotating disks. The H26α line is a definitive probe of the star formation rate in Arp 220, avoiding obscuration by dust and contamination by AGN luminosity contributions. In the second project, the remarkable continuum sensitivity of ALMA in Band 7 is used to measure the long wavelength Rayleigh-Jeans tail of the dust emission from a sample of 120 galaxies in COSMOS at z = 0.3 to 2.2, providing estimates for the dust masses and hence their ISM masses. This technique will enable measurements for hundreds of galaxies at high-z with observations of typically ~10 min per galaxy. This is in contrast to CO line imaging which typically requires a few hours per galaxy even with the sensitivity of ALMA. The dust-based mass estimates also avoid the uncertainties associated with the CO-to-H2 conversion factor.

We carried out large–scale (4 × 2 degree) CO multi–line observations toward the central molecular zone (CMZ) in the Galactic center (GC) with the NANTEN2 4m telescope and mapped several diffuse molecular features located at relatively high Galactic latitudes above 0°.6. These high–latitude features are composed of diffuse molecular halo gas and molecular filaments according to their morphological aspects. Their high velocities and high intensity ratios between 12CO J = (2−1) and J = (1−0) clearly indicate their location in the GC, and their total mass amount to ∼10% of that of the CMZ. We discuss that magnetic field is a possible mechanism of these high–latitude molecular features lifting up toward high galactic latitude.

We find a convex-like feature at a distance of 0.68 pc (17″) from the position of the supermassive black hole, Sgr A*, at the center of the nuclear stellar cluster. This feature resembles a stellar bow shock with a symmetry axis pointing to the center. We discuss the possible nature of the feature and the implications of its alignment with other dusty comet-like objects inside the central parsec.

Radiatively inefficient, hot accretion flows are widely considered as a relevant accretion mode in low-luminosity AGNs. We study spectral formation in such flows using a refined model with a fully general relativistic description of both the radiative (leptonic and hadronic) and hydrodynamic processes, as well as with an exact treatment of global Comptonization. We find that the X-ray spectral index–Eddington ratio anticorrelation as well as the cut-off energy measured in the best-studied objects favor accretion flows with rather strong magnetic field and with a weak direct heating of electrons. Furthermore, they require a much stronger source of seed photons than considered in previous studies. The nonthermal synchrotron radiation of relativistic electrons seems to be the most likely process capable of providing a sufficient flux of seed photons. Hadronic processes, which should occur due to basic properties of hot flows, provide an attractive explanation for the origin of such electrons.

In 2011, we discovered a compact gas cloud (“G2”) with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus.

I have combined data from sky surveys in the UV to the mid-IR, along with radio and X-ray data, to identify the most luminous QSOs in the Universe. The primary sky surveys were the Sloan Digital Sky Survey (SDSS) 7th Data Release QSO Catalog, which provides unambiguous broad-line QSO classification and robust redshifts, and the Wide-field Infrared Survey Explorer (WISE) mid-IR catalog, because a large percentage of QSO bolometric luminous emerges in the IR. Out of the 100,000 SDSS/WISE QSOs, we find 140 (< 0.2%) with bolometric luminosity greater than 2×1014Lo, with redshifts ranging from about 1.7 to 5. The most luminous QSO found has Lbol ≈7×1014Lo. Merger-based galaxy evolution models predict that the host galaxies of such sources at peak QSO luminosity are undergoing a short-lived phase of extreme AGN feedback and massive star-formation activity after a major merger. Upcoming sub-mm observations with the new Atacama Large Millimeter/Sub-millimeter Array (ALMA), for a subset of the sample, will soon reveal crucial host galaxy properties of this unique sample.

An upgrade of the low frequency observing system of the VLA developed by NRL and NRAO, called low band (LB), will open a new era of Galactic center (GC) transient monitoring. Our previous searches using the VLA and GMRT have revealed a modest number of radio-selected transients, but have been severely sensitivity and observing time limited. The new LB system, currently accessing the 236--492 MHz frequency range, promises ≥5 × improved sensitivity over the legacy VLA system. The new system is emerging from commissioning in time to catch any enhanced sub-GHz emission from the G2 cloud event, and we review existing limits based on recent observations. We also describe a proposed 24/7 commensal system, called the LOw Band Observatory (LOBO). LOBO offers over 100 VLA GC monitoring hours per year, possibly revealing new transients and helping validate ASTRO2010's anticipation of a new era of transient radio astronomy. A funded LOBO pathfinder called the VLA Low Frequency Ionosphere and Transient Experiment (VLITE) is under development. Finally, we consider the impact of LB and LOBO on our GC monitoring program.

Markarian survey (or the First Byurakan Survey, FBS) was the first systematic survey for active galaxies and was a new method for search for such objects. Until now, it is the largest objective prism survey of the sky (17,000 deg2). It was carried out in 1965–1980 by B. E. Markarian and his colleagues and resulted in discovery of 1517 UV-excess (Markarian) galaxies. They contain many active galaxies, as well as powerful gamma-, X-ray, IR and radio sources (Mrk 180, 231, 421, 501, etc.), BCDGs (Mrk 116) and interacting/merging systems (Mrk 266, 273, etc.). They led to the classification of Seyfert galaxies into Sy1 and Sy2 and the definition of Starbursts (SB). Several catalogs of Markarian galaxies have been published (Mazzarella & Balzano 1986; Markarian et al. 1989; Bicay et al. 1995; Petrosian et al. 2007) and they are accessible in all corresponding databases. Markarian survey also served as a basis for search for UVX stellar objects (including QSOs and Seyferts), late-type stars and optical identification of IR sources. At present the survey is digitized and DFBS database is available. I will review the main characteristics of the Markarian survey, its comparison with other similar surveys and the importance of Markarian galaxies in modern astrophysics.

The center of our Galaxy is home to a massive black hole, Sgr A*, and a nuclear star cluster containing stellar populations of various ages. While the late type stars may be too old to have retained memory of their initial orbital configuration, and hence formation mechanism, the kinematics of the early type stars should reflect their original distribution. In this contribution we present a new statistic which uses directly-observable kinematic stellar data to infer orbital parameters for stellar populations, and is capable of distinguishing between different origin scenarios. We use it on a population of B-stars in the Galactic center that extends out to large radii (∼0.5 pc) from the massive black hole. We find that the high K-magnitude population (≲15 M⊙) form an eccentric distribution, suggestive of a Hills binary-disruption origin.

Employing Fermi/LAT γ-ray observations, several independent groups have found excess extended γ-ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of ~ 103 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse Galactic background at the GC. We have performed a revaluation of these two models for the extended γ-ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsar population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of several thousand MSPs with parameters consistent with the average spectral shape of Fermi/LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ+τ− annihilation channel is not a good fit to the data. But a mixture of τ+τ− and bb with a 〈σ v〉 of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.

We report on the detection of 36 and 44 GHz Class I methanol (CH3OH) maser emission in the Sagittarius A (Sgr A) complex with the Karl G. Jansky Very Large Array (VLA). These VLA observations show that the Sgr A complex harbors at least three different maser tracers of shocked regions in the radio regime. The 44 GHz masers correlate with the positions and velocities of previously detected 36 GHz CH3OH masers, but less with 1720 MHz OH masers. Our detections agree with theoretical predictions that the densities and temperatures conducive for 1720 MHz OH masers may also produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise in regions too hot and too dense for 36 GHz masers to form. This agrees with the non-detection of 1720 MHz OH masers in the same area, which are thought to be excited under even cooler and less dense conditions. We speculate that the geometry of the 36 GHz masers outlines the current location of a shock front.

We present a new way of describing the flares occurring from Sgr A* within a single zone with a self-consistent calculation of the particle distribution. The results allow us to give an interpretation to the flaring events generated very close to the supermassive black hole (SMBH) without assuming a specific particle distribution. We conclude that the flare data are more likely generated by a weakly magnetized plasma in which the particles flow in and out as expected from an accretion flow. Such a plasma, with prescription for non-thermal acceleration, injection, escape, and cooling losses, gives a spectrum with a break between the infra-red and the X-ray, allowing a better simultaneous match in the different wavelengths. The parameters favor the non-thermal synchrotron spectrum, and a decrease/increase of the magnetic field and plasma density are not favored for producing the flare event, but particle acceleration must be happening by other means. We show that under certain conditions, the real particle distribution can differ significantly from the standard distributions used in such studies.

Over the last decade, X-ray observations of Sgr A* have revealed a black hole in a deep sleep, punctuated roughly once per day by brief flares. The extreme X-ray faintness of this supermassive black hole has been a long-standing puzzle in black hole accretion. To study the accretion processes in the Galactic center, Chandra (in concert with numerous ground- and space-based observatories) undertook a 3 Ms campaign on Sgr A* in 2012. With its excellent observing cadence, sensitivity, and spectral resolution, this Chandra X-ray Visionary Project (XVP) provides an unprecedented opportunity to study the behavior of the closest supermassive black hole. We present a progress report from our ongoing study of X-ray flares, including the brightest flare ever seen from Sgr A*. Focusing on the statistics of the flares and the quiescent emission, we discuss the physical implications of X-ray variability in the Galactic center.

We present a data cube of the [NeII] (12.8 μm) emission from the inner 2 pc of Sgr A West with 1″ and 4 km s−1 resolution, and with substantially better SNR and velocity resolution than previous observations of the ionized gas. We compare the observations to two proposed models of the gas motions and distribution: flows along tidally stretched streamers, and more nearly circular motions with density wave compression. The density wave model provides a considerably better fit to the kinematics of the northern arm and western arc. Neither model fits the eastern arm and bar kinematics well.

To help understand the origin of the spiral pattern we calculated orbits in the potential of a black hole in a star cluster and find that the orbits naturally evolve to set up a one-armed spiral wave very similar to that observed, both spatially and kinematically. Magnetic or other perturbing forces may influence the formation of the spiral wave, but self gravity is not required. Because a density wave evolves on the orbit precession timescale, rather than the orbital timescale, a wave pattern should persist for several 105 yr. No net inward motion of the gas is required by the model. If there is inflow, it is much smaller than is suggested by the infalling streamer model.