We systematically search for discrete absorption events in the vast archive of the Rossi X-ray Timing Explorer. This includes dozens of nearby type I and Compton-thin type II AGN and covers timescales from days to over a decade for individual objects. We are sensitive to discrete absorption events due to clouds of full-covering, neutral or mildly-ionized gas with columns 1022−25 cm−2 transiting the line of sight. We detect 13 eclipse events in 8 objects, roughly tripling the number of previously published events from this archive. Despite sensitivity to events with NH up to 1024−25 cm−2, we measured no Compton-thick eclipses in our sample. Peak column densities span 2.5–19 × 1022 cm−2. Event durations span hours to months. We infer the clouds distances from the black hole, assuming Keplerian motion, to span 0.2–80 × 104 Schwarzschild radii. We find no statistically significant difference between the individual cloud properties of type I and II objects. The presence of eclipses in both type Is and IIs argues against sharp-edged cloud distributions. The type II AGN show a level of “base-line” X-ray absorption that is consistent with being constant over timescales from 0.6 to 8.4 yr. This can either be explained by a homogeneous medium, or by X-ray-absorbing clouds that each have NH ≪ 1022 cm−2. Considering the “selection function” of the monitoring, we derive the probability of cloud occultation events. Finally, we derive the first X-ray statistical constraints for clumpy-torus models.

We have undertaken a spectroscopic survey of luminous AGNs and quasars selected in the mid-infrared from Spitzer IRAC surveys. Mid-infrared selection is much less biased with respect to obscuration than optical techniques, and hence enables the discovery of obscured quasars as well as normal, unobscured ones. Our survey is designed to include brighter 24 micron sources over wider areas and also to go to much lower fluxes limits in more limited spatial regions to allow us to disentangle dependences on redshift and luminosity. We have used 4m class telescopes to obtain spectra of the brighter 24 micron targets (targeting high luminosity objects at low z), and 8m class telescopes to identify lower luminosity high-redshift obscured quasars by targeting the fainter 24 micron targets. Fron this survey we have been able to compile a statistically complete sample of ~ 500 AGN, both obscured and unobscured, over a large range of redshift and luminosity. We find that obscured objects outnumber unobscured AGN with an obscured fraction ranging from ~ 90% to ~ 50%. For the most luminous quasars, the number densities of unobscured quasars peaks at z ~ 2.8, and for the obscured objects, the peak may be at slightly higher redshift.

The Atacama Cosmology Telescope (ACT) is a six-meter telescope in the Atacama Desert that observes simultaneously in frequency bands centered at 150, 220 and 270 GHz. ACT has surveyed an area of approximately 450 square degrees in the south (−55 deg) and approximately 500 square degrees along the equator. Most of the sources detected by ACT are blazars. I will present source counts and spectral indices as well as multi-wavelength properties determined by matching with external datasets. In addition to studying sources detected in the survey, we have used the ACT data to statistically study the millimeter properties of radio sources selected from low frequency (1.4 GHz) surveys.

We present the surface brightness profile fitting of a sample of double nucleus disk galaxies, minor merger candidates. We have decomposed these systems into two compact nuclear components and one or two extended galaxy disk components and estimated the luminosity of the primary and secondary nucleus and of the host galaxy and the separation between the two nuclei. Based on the ratio of nuclear luminosities we find that most of the sources qualify as major mergers despite their initial classification as minor merging systems. This is supported by the finding that 65% of the host galaxies are fitted only by one galaxy disk and that the luminosity of both the primary and the secondary nucleus decreases with decreasing nuclear separation, as expected from simulations of disk galaxy mergers. All these results indicate that these sources are most plausibly in the post-merger state of a major merger event. We also identify 19 candidates to binary active nucleus with nuclear separation ≤1 kpc.

There exist strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies; however it is still under debate how such a relation comes about and whether it is relevant for all or only a subset of galaxies. A rich multi-wavelength dataset is available for the North Ecliptic Pole field, most notably surveyed by the AKARI infrared space telescope. We investigate the star-formation properties of the host galaxies of radio-AGN together with the radio feedback mechanism, potentially responsible for the eventual quenching of star formation. Using broadband SED modelling, the nuclear and host galaxy components of these sources are studied as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while offering evidence supporting a “maintenance” type of feedback from powerful radio-jets.

Using the Delingha 13.7 m telescope with a 9-beam SIS superconducting receiver installed, we carried out mapping of C18O and C17O J = (1 − 0) toward molecular clouds in the central molecular zone (CMZ) and in the halo of our galaxy. From the integrated intensity ratio of C18O to C17O, the isotope ratio 18O/17O ratio can be estimated, which is considered to be one of the most useful tracers of nuclear processing and metal enrichment. Here preliminary results are presented toward Sgr A, Sgr B2, Sgr C, Sgr D, and the 1.°3 complex in the CMZ and M+5.3–0.3 in the halo.

Based on optical identifications of ROSAT sources, we have created a large homogeneous catalog of X-ray selected AGN. The Hamburg-RASS Catalog (HRC) and Byurakan-Hamburg-RASS Catalog (BHRC) made up on the basis of optical identification of X-ray sources from ROSAT Bright Source (BSC) and Faint Source (FSC) catalogues, respectively, have been used. These identiifcations were based on low-dispersion spectra of Hamburg Quasar Survey (HQS). As a result, a new large sample of X-ray selected AGN has been compiled containing 4253 sources with photon count rate CR > 0.04 ct/s in the area with galactic latitudes |b|>20 and declinations δ>0. All these sources are classified as AGN or candidate AGN. We have carried out multiwavelength studies in several wavelength ranges (X-ray, optical, radio). Catalogues that more or less guarantee the completeness condition (all-sky or large area surveys) were used. A number of erroneous classifications were found (some AGN had been classified as stars or galaxies); 1024 and 59 from HRC and BHRC, respectively. Out of 4253 sources, 3352 are spectroscopically confirmed AGN (given in Veron-Cetty & Veron and Roma Blazar catalogs), and the rest 901 are candidate AGN. For 210 of them spectra are available in SDSS DR9, and the results of their classification are given in another paper. We calculated absolute magnitudes, fluxes, improved coordinates and redshifts. An attempt is made to find a connection between the radiation fluxes in different bands for different types of sources, and identify their typical characteristics, thus confirming candidate AGN and in some cases finding new ones.

Within a few parsecs around the central black hole A*, chemistry in the dense molecular cloud material of the circumnuclear disk (CND) can be affected by many energetic phenomena such as high UV-flux from the massive central star cluster, X-rays from A*, shock waves, and an enhanced cosmic-ray flux. Recently, spectroscopic surveys with the IRAM 30 meter and the APEX 12 meter telescopes of substantial parts of the 80–500 GHz frequency range were made toward selected positions in and near the CND. These data sets contain lines from the molecules HCN, HCO+, HNC, CS, SO, SiO, CN, H2CO, HC3N, N2H+, H3O+ and others. We conduct Large Velocity Gradient analyses to obtain column densities and total hydrogen densities, n, for each species in molecular clouds located in the southwest lobe of the CND. The data for the above mentioned molecules indicate 105 cm−3 ≲ n < 106 cm−3, which shows that the CND is tidally unstable. The derived chemical composition is compared with a chemical model calculated using the UCL_CHEM code that includes gas and grain reactions, and the effects of shock waves. Models are run for varying shock velocities, cosmic-ray ionization rates, and number densities. The resulting chemical composition is fitted best to an extremely high value of cosmic-ray ionization rate ζ ∼ 10−14 s−1, 3 orders of magnitude higher than the value in regular Galactic molecular clouds, if the pre-shock density is n=105 cm−3.

The final 800 sq. deg of sky covered by FIRST was observed with the new, improved JVLA. The data were split between two bandpasses at 1335 and 1730 MHz and included all four Stokes parameters, thus allowing both spectral and polarimetric results. The lower frequency bandpass data were considered part of FIRST and are available through the FIRST website (http://sundog.stsci.edu/). Here we present the higher frequency bandpass data as pertain to AGN. Foremost, we present spectral index results for the 5000 quasars with spectroscopic redshifts and the 50,000 quasars with photometric redshifts that fall in the survey area. The spectral indices are analyzed as a function of redshift and optical properties both for quasars detected above the 1 mJy limit and, via image stacking, for quasars at flux densities down to 10 mJy.

Radio continuum (cont) and radio recombination line (RRL) observations with the Yamaguchi 32-m radio telescope toward the lower part of the Galactic center lobe (GCL) in the Galactic center region are presented. While two ridges of the GCL were seen in both continuum and RRL images, the spatial coverage of the ridges of the continuum and RRL is not coincident. We distinguish the continuum emission of the GCL into thermal and non-thermal emission by assuming an electron temperature of the ionized gas of 4370 K, estimated based on the line width (14.1 km s−1). The thermal emission was found to be located inside and surrounded by the non-thermal emission.

We are performing a multi-frequency radio analysis of a well-known deep field: the Lockman Hole, which is one of the best studied sky regions in different wavebands. This will provide us with important complementary data (for example redshifts) to the radio data, allowing us to characterize the physical and evolutionary properties of the various classes of sources composing the faint radio population. LOFAR imaging of the Lockman Hole can play an important role in this project, allowing, for the very first time, to observe the sub-mJy source population at very low frequencies (30-200 MHz), where self-absorption phenomena are expected to be very important. Here we present some preliminary results.

Blazars (BL Lacertae objects and flat spectrum radio quasars) are strong γ-ray emitters, the γ-ray emissions are strongly beamed. In this work, we compiled a sample of Fermi blazars with available beaming factors, δR, to investigate the correlation between the γ-ray flux density, logfγ, and redshift, logz for the whole sample and the subclasses of the present sample. The analysis shows that there is no correlation between logfγ and logz for the observed γ-ray flux density, but there are strong correlations between the de-beamed flux densities, logfγdb and logz for the whole sample and the subclasses. Our results confirm that the γ-ray emissions are strongly beamed and imply that it is possible for one to use the radio beaming factor, δR for the beaming effect discussions in the γ-ray bands for Fermi blazars.

Based on our deep image of Sgr A using broadband data observed with the VLA† at 6 cm, we present a new perspective of the radio bright zone at the Galactic center. We further show the radio detection of the X-ray Cannonball, a candidate neutron star associated with the Galactic center SNR Sgr A East. The radio image is compared with the Chandra X-ray image to show the detailed structure of the radio counterparts of the bipolar X-ray lobes. The bipolar lobes are likely produced by the winds from the activities within Sgr A West, which could be collimated by the inertia of gas in the CND, or by the momentum driving of Sgr A*; and the poloidal magnetic fields likely play an important role in the collimation. The less-collimated SE lobe, in comparison to the NW one, is perhaps due to the fact that the Sgr A East SN might have locally reconfigured the magnetic field toward negative galactic latitudes. In agreement with the X-ray observations, the time-scale of ∼1 × 104 yr estimated for the outermost radio ring appears to be comparable to the inferred age of the Sgr A East SNR.

The radio flux from the synchrotron emission of electrons accelerated in the forward bow shock of G2 is expected to have peaked when the forward shock passes close to the pericenter from the Galactic center, around autumn of 2013. This radio flux is model dependent. We find that if G2 were to be a momentum-supported bow shock of a faint star with a strong wind, the radio synchrotron flux from the forward-shock heated ISM is well below the quiescent radio flux of Sgr A*. By contrast, if G2 is a diffuse cloud, the radio flux is predicted to be much larger than the quiescent radio flux and therefore should have already been detected or will be detected shortly. No such radiation has been observed to date. Radio measurements can reveal the nature of G2 well before G2 completes its periapsis passage.

We present the results of radio monitoring observations of Sgr A* at 7 mm (i.e. 43 GHz) with the VLBI Exploration of Radio Astrometry (VERA), which is a VLBI array in Japan. VERA provides angular resolution on millisecond scales, resolving structures within 100 Schwarzschild radii of Sgr A* , similar to the Very Large Baseline Array (VLBA). We performed multi-epoch observations of Sgr A* in 2005 - 2008, and started monitoring it again with VERA from 2013 January to trace the current G2 encounter event. Our preliminary results in 2013 show that Sgr A* on mas scales has been in an ordinary state as of August 2013, although some fraction of the G2 cloud already passed the pericenter of Sgr A* in April 2013. We will continue monitoring Sgr A* with VERA and the newly developed KaVA (KVN and VERA Array).

We searched the time lag between the intra-day variables (IDVs) of Sagittarius A* at 22, 43, and 86 GHz bands using the Korean VLBI Network (KVN). The time lags between the IDV flare peaks at 22 and 43 GHz are reported, and they suggest that the flare emissions come from adiabatically expanding plasma blobs, ejected close to the Galactic center black hole. We searched the time lags between light curves at 90 and 102 GHz using the Nobeyama Millimeter Array, but could not find significant time lags. In order to detect the diversity of the time lags of Sgr A* flares, we performed observations of Sgr A* in the 22, 43, and 86 GHz bands using the KVN in the winter of 2013. Because the receiver system of KVN can observe Sgr A* in these three bands simultaneously, the KVN is very useful to detect the time lags of Sgr A* flares.

The history of the International Astronomical Union (IAU) meetings goes back to 1922 when the IAU I General Assembly (GA) was held in Rome, Italy, following the IAU creation in 1919. However, until 1953, no individual symposia were organized and GA was the only official gathering for astronomers. Altogether, 8 IAU GA were held during 1922–1952.

Despite their discovery almost 30 years ago, the origin of the Galactic center nonthermal filaments (NTFs) remains poorly understood. The improved capabilities of the VLA offer a fantastic opportunity to make a multi-frequency, full spectropolarimetric study of the radio arc at high angular resolution. Observations presented here are from DnC and CnB array configuration data taken at S, C and X band (coverage between 2-12 GHz; continuum only). In addition there are also Ka and Q band (continuum and spectral line coverage) observations that are part of the study but not shown in this short proceedings. These data will allow us to make the first high angular resolution Faraday study of the Galactic center radio arc.

The Seyfert galaxy MCG–6-30-15 has recently been observed in the infrared using SINFONI on the VLT, reaching a very high spatial resolution of 0.1 arcsec. This allowed us for the first time to detect a stellar kinematically decoupled core in the inner r < 125 pc of the galaxy. Here we summarise the main theories for the formation of the decoupled core and the implications on the study of this galaxy.

We discuss the morphology of star forming clouds and filaments in the central (≲ 50 kpc) regions of 16 low redshift (z<0.3) cool core brightest cluster galaxies (BCGs). The sample spans decades-wide ranges of X-ray mass deposition and star formation rates as well as active galactic nucleus (AGN) mechanical power, encompassing both high and low extremes of the supposed intracluster medium (ICM) cooling and AGN heating feedback cycle. Amid evidence that the gas fueling both star formation and AGN activity has condensed from the hot atmosphere, we present new and archival Hubble Space Telescope (HST) images of far ultraviolet (FUV) continuum emission directly associated with young stars, acting as a calorimeter for the degree to which the suppression of star formation by AGN mechanical feedback may be spatially or temporally inefficient. We discuss evidence for temporal and possibly cyclical variation in star formation rate, wherein elevated cooling episodes are permitted when AGN feedback is in a low-power state, and vice-versa. Several sources exhibit strong morphological evidence that low levels of star formation can survive and may indeed be triggered by the passage of a propagating radio source. We conclude by discussing the apparent coexistence of feedback and star formation. If AGN mechanical power does establish an “entropy floor”, this floor must be porous, or raise and lower as the AGN varies in power.