Evolution of faint radio sources in the VIDEO-XMM3 field

© 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical SocietyIt has been speculated that low-luminosity radio-loud active galactic nuclei (AGN) have the potential to serve as an important source of AGN feedback, and may be responsible for suppressing star formation activity in massive elliptical galaxies at late times. As such the cosmic evolution of these sources is vitally important to understand the significance of such AGN feedback processes and their influence on the global star formation history of the Universe. In this paper, we present a new investigation of the evolution of faint radio sources out to z ~ 2.5. We combine a 1 square degree Very Large Array radio survey, complete to a depth of 100 μJy, with accurate 10 band photometric redshifts from the following surveys: Visible and Infrared Survey Telescope for Astronomy Deep Extragalactic Observations and Canada-France-Hawaii Telescope Legacy Survey. The results indicate that the radio population experiences mild positive evolution out to z ~ 1.2 increasing their space density by a factor of ~3, consistent with results of several previous studies. Beyond z = 1.2, there is evidence of a slowing down of this evolution. Star-forming galaxies drive the more rapid evolution at low redshifts, z 1.2. The evolution is best fitted by pure luminosity evolution with star-forming galaxies evolving as (1 + z)2.47 ± 0.12 and AGN as (1 + z)1.18 ± 0.21M.Peer reviewe

Mergers as triggers for nuclear activity : A near-IR study of the close environment of AGN in the VISTA-VIDEO survey

copyright 2014 The Authors; Published by Oxford University Press on behalf of the Royal Astronomical SocietyThere is an ongoing debate concerning the driver of nuclear activity in galaxies, with active galactic nuclei (AGN) either being triggered by major or minor galactic mergers or, alternatively, through secular processes like cold gas accretion and/or formation of bars. We investigate the close environment of active galaxies selected in the X-ray, the radio and the mid-IR. We utilize the first data release of the new near-IR VISTA Deep Extragalactic Observations (VIDEO) survey of the XMM-Large Scale Structure field. We use two measures of environment density, namely counts within a given aperture and a finite redshift slice (pseudo- 3D density) and closest neighbour density measures ∑2 and ∑5. We select both AGN and control samples, matching them in redshift and apparent Ks-band magnitude. We find that AGN are found in a range of environments, with a subset of the AGN samples residing in overdense environments. Seyfert-like X-ray AGN and flat-spectrum radio-AGN are found to inhabit significantly overdense environments compared to their control sample. The relation between overdensities and AGN luminosity does not however reveal any positive correlation. Given the absence of an environment density-AGN luminosity relation, we find no support for a scheme where high-luminosity AGN are preferentially triggered by mergers. On the contrary, we find that AGN likely trace over dense environments at high redshift due to the fact that they inhabit the most massive galaxies, rather than being an AGN.Peer reviewe

A randomised phase II trial of Stereotactic Ablative Fractionated radiotherapy versus Radiosurgery for Oligometastatic Neoplasia to the lung (TROG 13.01 SAFRON II)

© 2016 Siva et al. Background: Stereotactic ablative body radiotherapy (SABR) is emerging as a non-invasive method for precision irradiation of lung tumours. However, the ideal dose/fractionation schedule is not yet known. The primary purpose of this study is to assess safety and efficacy profile of single and multi-fraction SABR in the context of pulmonary oligometastases. Methods/Design: The TROG 13.01/ALTG 13.001 clinical trial is a multicentre unblinded randomised phase II study. Eligible patients have up to three metastases to the lung from any non-haematological malignancy, each<5cm in size, non-central targets, and have all primary and extrathoracic disease controlled with local therapies. Patients are randomised 1:1 to a single fraction of 28Gy versus 48Gy in four fractions of SABR. The primary objective is to assess the safety of each treatment arm, with secondary objectives including assessment of quality of life, local efficacy, resource use and costs, overall and disease free survival and time to distant failure. Outcomes will be stratified by number of metastases and origin of the primary disease (colorectal versus non-colorectal primary). Planned substudies include an assessment of the impact of online e-Learning platforms for lung SABR and assessment of the effect of SABR fractionation on the immune responses. A total of 84 patients are required to complete the study. Discussion: Fractionation schedules have not yet been investigated in a randomised fashion in the setting of oligometastatic disease. Assuming the likelihood of similar clinical efficacy in both arms, the present study design allows for exploration of the hypothesis that cost implications of managing potentially increased toxicities from single fraction SABR will be outweighed by costs associated with delivering multiple-fraction SABR. Trials registration:ACTRN12613001157763 , registered 17th October 201

Multiwavelength characterization of faint ultra steep spectrum radio sources: a search for high-redshift radio galaxies

Context. Ultra steep spectrum (USS) radio sources are one of the efficient tracers of powerful high-z radio galaxies (HzRGs). In contrast to searches for powerful HzRGs from radio surveys of moderate depths, fainter USS samples derived from deeper radio surveys can be useful in finding HzRGs at even higher redshifts and in unveiling a population of obscured weaker radio-loud AGN at moderate redshifts. Aims. Using our 325 MHz GMRT observations (5σ ∼ 800 μJy) and 1.4 GHz VLA observations (5σ ∼ 80−100 μJy) available in two subfields (VLA-VIMOS VLT Deep Survey (VLA-VVDS) and Subaru X-ray Deep Field (SXDF)) of the XMM-LSS field, we derive a large sample of 160 faint USS radio sources and characterize their nature. Methods. The optical and IR counterparts of our USS sample sources are searched using existing deep surveys, at respective wavelengths. We attempt to unveil the nature of our faint USS sources using diagnostic techniques based on mid-IR colors, flux ratios of radio to mid-IR, and radio luminosities. Results. Redshift estimates are available for 86/116 (∼74%) USS sources in the VLA-VVDS field and for 39/44 (∼87%) USS sources in the SXDF fields with median values (zmedian) ∼1.18 and ∼1.57, respectively, which are higher than estimates for non-USS radio sources (zmedian non−USS ∼ 0.99 and ∼0.96), in the two subfields. The MIR color–color diagnostic and radio luminosities are consistent with most of our USS sample sources at higher redshifts (z > 0.5) being AGN. The flux ratio of radio to mid-IR (S 1.4 GHz/S 3.6 μm) versus redshift diagnostic plot suggests that more than half of our USS sample sources distributed over z ∼ 0.5 to 3.8 are likely to be hosted in obscured environments. A significant fraction (∼26% in the VLA-VVDS and ∼13% in the SXDF) of our USS sources without redshift estimates mostly remain unidentified in the existing optical, IR surveys, and exhibit high radio to mid-IR flux ratio limits similar to HzRGs, and so, can be considered as potential HzRG candidates. Conclusions. Our study shows that the criterion of ultra steep spectral index remains a reasonably efficient method to select high-z sources even at sub-mJy flux densities. In addition to powerful HzRG candidates, our faint USS sample also contains populations of weaker radio-loud AGNs potentially hosted in obscured environments

Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?

We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2Jy radio galaxies at intermediate redshifts (0.05<z<0.7) and those of two control samples of quiescent early-type galaxies: 55 ellipticals at redshifts z<0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2<z<0.7 in the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 magnitudes brighter than those present in their quiescent counterparts. Indeed, if we consider the same surface brightness limits, the fraction of disturbed morphologies is considerably smaller in the quiescent population (53% at z<0.2 and 48% at 0.2<z<0.7) than in the PRGs (93% at z<0.2 and 95% at 0.2<z<0.7 considering strong-line radio galaxies only). This supports a scenario in which PRGs represent a fleeting active phase of a subset of the elliptical galaxies that have recently undergone mergers/interactions. However, we demonstrate that only a small proportion (<20%) of disturbed early-type galaxies are capable of hosting powerful radio sources.Comment: 20 pages, 7 figures, accepted for publication in MNRA

FRII radio galaxies in the SDSS: Observational facts

Starting from the Cambridge Catalogues of radio sources, we have created a sample of 401 FRII radio sources that have counterparts in the main galaxy sample of the 7th Data release of the SDSS and analyse their radio and optical properties. We find that the luminosity in the Halpha line - which we argue gives a better measure of the total emission-line flux than the widely used O[III] luminosity - is strongly correlated with the radio luminosity P1.4GHz. We show that the absence of emission lines in about one third of our sample is likely due to a detection threshold and not to a lack of optical activity. We find that the properties of FRII galaxies are mainly driven by the Eddington parameter LHa/"MBH" or, equivalently, P1.4GHz/"MBH". Radio galaxies with hot spots are found among the ones with the highest values of P1.4GHz/"MBH". Compared to classical AGN hosts in the main galaxy sample of the SDSS, our FRII galaxies show a larger proportion of objects with very hard ionizing radiation field and large ionization parameter. A few objects are, on the contrary, ionized by a softer radiation field. We find that the black hole masses and stellar masses in FRII galaxies are very closely related. A comparison sample of line-less galaxies in the SDSS follows the same relation, although on average the masses are smaller. This suggests that the FRII radio phenomenon occurs in normal elliptical galaxies, preferentially in the most massive ones. Although most FRII galaxies are old, some contain traces of young stellar populations. Such young populations are not seen in normal line-less galaxies, suggesting that the activity in some FRII galaxies may be triggered by recent star formation. The "MBH"-Mgal relation in a comparison sample of radio-quiet AGNs from the SDSS is very different, suggesting that galaxies which are still forming stars are also still building their central black holes.Comment: Accepted for publication in MNRAS: 26 pages, 29 figures, 1 tabl

A synchrotron self-Compton scenario for the very high energy gamma-ray emission of the radiogalaxy M87

M87 is the first extragalactic source detected in the TeV range that is not a blazar. With the increasing performances of ground-based Cherenkov telescopes, we can now probe the variability in the gamma-ray flux at small timescales, thus putting strong constraints on the size of the emitting zone. A modification of standard emission models of TeV blazars appears necessary to account for the gamma-ray observations despite this misalignment. We explain TeV gamma-ray spectra and fast variability of M87 by invoking an emission zone close to the central supermassive black hole, which is filled with several plasma blobs moving in the large opening angle of the jet formation zone. We develop a new multi-blob synchrotron self-Compton (SSC) model with emitting blobs beyond the Alfven surface in the jet, at a distance of about 100 r_g from the central engine. This model is explicitly adapted to deal with large viewing angles and moderate values of the Lorentz factor inferred from (general relativistic) magnetohydrodynamic models of jet formation. This scenario can account for the recent gamma-ray observations of M87 made by the High Energy Stereoscopic System (H.E.S.S.) telescope array. We find individual blob radii of about 10^{14} cm, which is compatible with the variability on timescales of days recently reported by the H.E.S.S. collaboration and is of the order of the black hole gravitational radius. Predictions of the very high energy emission for three other sources with extended optical or X-ray jet which could be misaligned blazars still with moderate beaming are presented for one Seyfert 2 radiogalaxy, namely Cen A, one peculiar BL Lac, PKS 0521-36, and one quasar, 3C 273.Comment: 10 pages, 8 figures; accepted in A&

A Pilot Study of Lay Health Worker Outreach and Colorectal Cancer Screening Among Chinese Americans

The research team recruited eight Chinese American (seven females, one male) lay health workers (LHWs). They received 12 h of training about colorectal cancer (CRC), its screening, and basic health education techniques. Each LHW were asked to recruit ten participants and conduct two educational sessions. Of the 81 participants recruited, 73 had not received colorectal cancer screening. Their mean age was 63.0 years, and 72.6% were women. Knowledge of colorectal cancer, its causes, and its screening increased significantly. Receipt of first colorectal cancer screening test increased from 0.0% at baseline to 55.7% for fecal occult blood tests, 7.1% for sigmoidoscopy, and 7.1% for colonoscopy. LHW outreach is feasible and may be effective in promoting CRC screening among Chinese Americans

Identification of serum biomarkers for colon cancer by proteomic analysis

Colorectal cancer (CRC) is often diagnosed at a late stage with concomitant poor prognosis. Early detection greatly improves prognosis; however, the invasive, unpleasant and inconvenient nature of current diagnostic procedures limits their applicability. No serum-based test is currently of sufficient sensitivity or specificity for widespread use. In the best currently available blood test, carcinoembryonic antigen exhibits low sensitivity and specificity particularly in the setting of early disease. Hence, there is great need for new biomarkers for early detection of CRC. We have used surface-enhanced laser desorbtion/ionisation (SELDI) to investigate the serum proteome of 62 CRC patients and 31 noncancer subjects. We have identified proteins (complement C3a des-arg, α1-antitrypsin and transferrin) with diagnostic potential. Artificial neural networks trained using only the intensities of the SELDI peaks corresponding to identified proteins were able to classify the patients used in this study with 95% sensitivity and 91% specificity

The radio core of the Ultraluminous Infrared Galaxy F00183-7111: watching the birth of a quasar

F00183-7111 is one of the most extreme Ultra-Luminous Infrared Galaxies known. Here we present a VLBI image which shows that F00183-7111 is powered by a combination of a radio-loud Active Galactic Nucleus surrounded by vigorous starburst activity. Although already radio-loud, the quasar jets are only 1.7 kpc long, boring through the dense gas and starburst activity that confine them. We appear to be witnessing this remarkable source in the brief transition period between merging starburst and radio-loud "quasar-mode" accretion.Comment: Submitted to MNRA