Unification of Radio Galaxies and Their Accretion/Jet Properties

We investigate the relation between black hole mass, M_bh, and jet power, Q_jet, for a sample of BL Lacs and radio quasars. We find that BL Lacs are separated from radio quasars by the FR I/II dividing line in M_bh-Q_jet plane, which strongly supports the unification scheme of FR I/BL Lac and FR II/radio quasar. The Eddington ratio distribution of BL Lacs and radio quasars exhibits a bimodal nature with a rough division at L_bol/L_Edd~0.01, which imply that they may have different accretion modes. We calculate the jet power extracted from advection dominated accretion flow (ADAF), and find that it require dimensionless angular momentum of black hole j~0.9-0.99 to reproduce the dividing line between FR I/II or BL Lac/radio quasar if dimensionless accretion rate mdot=0.01 is adopted, which is required by above bimodal distribution of Eddington ratios. Our results suggest that black holes in radio galaxies are rapidly spinning.Comment: To appear JAA in Jun

A Deep Radio Survey of Abell 2125. III. The Cluster Core: Merging and Stripping

We use radio, near-IR, optical, and X-ray observations to examine dynamic processes in the central region of the rich galaxy cluster Abell 2125. In addition to the central triple of E and cD galaxies, including members of both major dynamical subsystems identified from a redshift survey, this region features a galaxy showing strong evidence for ongoing gas stripping during a high-velocity passage through the gas in the cluster core. The disk galaxy C153 exhibits a plume stretching toward the cluster center seen in soft X-rays by Chandra, parts of which are also seen in [O II] emission and near-UV continuum light. Hubble Space Telescope imaging shows a distorted disk with star-forming knots asymmetrically distributed and remnant spiral structure possibly defined by dust lanes. The stars and ionized gas in this disk are kinematically decoupled, demonstrating that pressure stripping (possibly turbulent, as well as ram) must be important, and that tidal disruption is not the only mechanism at work. Comparison of the gas properties seen in the X-ray and optical data on the plume highlight significant and poorly known features of the history of stripped gas in the intracluster medium that could be clarified through further observations of this system. The nucleus of C153 also hosts an active galactic nucleus, shown by the weak and distorted extended radio emission and a radio-compact core. The unusual strength of the stripping signatures in this instance is likely related to the very high relative velocity of the galaxy with respect to the intracluster medium during a cluster-cluster merger and its passage very near the core of the cluster. An additional sign of recent dynamical events is the diffuse starlight asymmetrically placed about the central triple in a cD envelope. Transient and extreme dynamical events as seen in A2125 may be important drivers of galaxy evolution in the cores of rich clusters

A deep radio survey of Abell 2125. I. Radio, optical, and near-infrared observations

We present a description of deep radio, optical, and near-IR observations taken with the VLA, the KPNO 2 m telescope, and the KPNO 4 m telescope of the region containing the rich cluster of galaxies Abell 2125. The reduction of each data set is described. A catalog of radio sources apparently not associated with members of A2125 and the associated R-band magnitudes is presented

A Deep Radio Survey of Abell 2125. II. Accelerated Galaxy Evolution during a Cluster-Cluster Merger

Using our extensive radio, optical, near-IR, and X-ray imaging and spectroscopy, we consider the reason for the unusually large number of radio-detected galaxies, mostly found outside the cluster core, in Abell 2125 (z = 0.2465, richness class 4). With 20 cm VLA data, we detect continuum emission from 90 cluster members. The multiwavelength properties of these galaxies suggest that most of the radio emission is due to an enhanced star formation rate. The recent dynamical study of Miller et al. suggests that A2125 is undergoing a major cluster-cluster merger, with our view within 30° of the merger axis and within 0.2 Gyr of core passage. The combination of projection effects and the physical processes at work during this special time in the cluster\u27s evolution seem likely to be responsible for the unusual level of activity we see in the cluster. We argue that tidal effects on individual cluster members, often far from the cluster core, are responsible for the increased star formation. Our results are consistent with the idea that disk galaxies during this phase of a cluster\u27s evolution undergo rapid evolution through a burst of star formation on their way to becoming S0 galaxies

Radio-selected galaxies in very rich clusters at z <= 0.25. I. Multiwavelength observations and data reduction techniques

Radio observations were used to detect the "active" galaxy population within rich clusters of galaxies in a nonbiased manner that is not plagued by dust extinction or the K-correction. We present wide-field radio, optical (imaging and spectroscopy), and ROSAT All-Sky Survey (RASS) X-ray data for a sample of 30 very rich Abell (Rgreater than or equal to2) clusters with zless than or equal to0.25. The VLA radio data samples the ultrafaint radio (L(1.4)greater than or equal to2x10(22) W Hz(-1)) galaxy population within these extremely rich clusters for galaxies with M(R)less than or equal to-21. This is the largest sample of low-luminosity 20 cm radio galaxies within rich Abell clusters collected to date. The radio-selected galaxy sample represents the starburst (star formation rate greater than or equal to5 M-circle dot yr(-1)) and active galactic nuclei populations contained within each cluster. Archival and newly acquired redshifts were used to verify cluster membership for most (similar to95%) of the optical identifications. Thus, we can identify all the starbursting galaxies within these clusters, regardless of the level of dust obscuration that would affect these galaxies being identified from their optical signature. Cluster sample selection, observations, and data reduction techniques for all wavelengths are discussed

Gemini-South plus FLAMINGOS demonstration science

We report an infrared 1-1.8 mum (J+H-band), low-resolution (R=450) spectrogram of the highest redshift radio-loud quasar currently known, SDSS J083643.85+005453.3, obtained during the spectroscopic commissioning run of the FLAMINGOS multiobject, near-IR spectrograph at the 8 m Gemini-South Observatory. These data show broad emission from both C IV lambda1549 and C III] lambda1909, with strengths comparable to lower redshift quasar composite spectra. The implication is that there is substantial enrichment of the quasar environment, even at times less than a billion years after the big bang. The redshift derived from these features is z=5.774+/-0.0003, more accurate and slightly lower than the z=5.82 reported in the discovery paper based on the partially absorbed Lyalpha emission line. The infrared continuum is significantly redder than lower redshift quasar composites. Fitting the spectrum from 1.0 to 1.7 mum with a power law f(v) proportional to nu(-alpha), the derived power-law index is alpha=1.55 compared to the average continuum spectral index =0.44 derived from the first Sloan Digital Sky Survey composite quasar. Assuming an SMC-like extinction curve, we infer a color excess of E(B-V)=0.09+/-0.01. Only approximate to6% of quasars in the optically selected Sloan Digital Sky Survey show comparable levels of dust reddening

Research Ethics in Sport and Exercise Science.

This chapter covers common research ethics issues within research proposals in sport and exercise science. Identifying the reason or reasons for the study at the outset is the first and most important part of the research ethics process. A thorough and scientific analysis of previous findings helps the researcher identify strategies to extend current knowledge and practice within sport and exercise science settings. Understanding and application of professional body guidelines for good practice will enhance both the submission for research ethics review and the underlying ethical value providing enhanced confidence in the reliability of the research study. Obvious and overlooked researcher competencies are outlined, identifying a range of opportunities for skills training. Spanning a range of disciplines, sport and exercise science research addresses sensitive topics, issues of disclosure, and physical measurement procedures. This chapter highlights considerations that ensure the research process does not harm participants in the quest to further knowledge and practice. Finally, some solutions to actual and perceived barriers are proposed to help refine and develop the research ethics review process in sport and exercise science

From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with Square Kilometre Array

We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.Comment: To appear in Journal of Astrophysics and Astronomy (JOAA) special issue on "Science with the SKA: an Indian perspective