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Sample records for active radio galaxy

  1. Epsiodic Activity in Radio Galaxies

    SciTech Connect

    Saikia, D.J.; Konar, C.; Jamrozy, M.; Machalski, J.; Gupta, Neeraj; Stawarz, L.; Mack, K.-H.; Siemiginowska, A.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-10-15

    One of the interesting issues in our understanding of active galactic nuclei is the duration of their active phase and whether such activity is episodic. In this paper we summarize our recent results on episodic activity in radio galaxies obtained with the GMRT and the VLA.

  2. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  3. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  4. Nuclear activity and the environments of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Dey, Arjun; Vanbreugel, Wil

    1993-01-01

    Much of our present understanding of galaxy evolution over a large redshift range is based on the study of samples selected on the basis of non-thermal radio emission. It is therefore necessary to understand the relationship between radio source activity and the host galaxy. Recent observations suggest that there is a connection between radio galaxy (RG) activity and radio galaxy evolution. For example, high-redshift RGs (z approx. greater than 0.7) show evidence for significant populations of young stars, and have optical continuum morphologies nearly always aligned with the radio axis (McCarthy et al. 1987; Chambers et al. 1987). This phenomenon is generally attributed to radio jet induced star formation (DeYoung 1989), but the lack of high S/N spectra of the galaxy continua, and recent detections of polarized light in a few objects make it hard to rule out other processes such as scattering or synchrotron radiation. A detailed study of the continuum light in the distant RGs is difficult as they are optically very faint. However, nearby RGs (z approx. less than 0.1) have bluer B-V colors than radio-quiet ellipticals, presumably due to the presence of young stellar populations (Smith and Heckman 1989) and several have extended UV continuum emitting regions along their radio axes (van Bruegel et al. 1985a, b, di Serego Alighieri et al. 1989), reminiscent of the alignment effect seen in the high redshift RGs. We have almost completed a continuum imaging survey of nearby (and therefore optically brighter), powerful RGs to study any possible relationships between the optical continuum light and radio source activity. In particular we are interested in (1) whether these lower redshift RGs shown any evidence of the alignment effect (in their rest-frame UV light) that is seen in the distant RGs, and (2) the effects that the radio source has on the environment of the host galaxy.

  5. Radio observations of a hard X-ray selected sample of active galaxies

    NASA Technical Reports Server (NTRS)

    Unger, S. W.; Lawrence, A.; Wilson, A. S.; Elvis, M.; Wright, A. E.

    1987-01-01

    Radio observations of a hard X-ray selected sample of active galaxies obtained with the VLA and Parkes radio telescopes are discussed, and the ratio of the radio to X-ray flux density is used to determine the degree of radio-loudness of the galaxies. A continuous distribution of the degree of radio loudness is found amongst the sample galaxies, and no evidence for distinct radio-quiet and radio-loud populations is noted. The X-ray and radio luminosity is shown to be nonlinearly correlated, with the radio-loud objects all having high X-ray luminosity.

  6. A New Radio Loudness Diagnostic for Active Galaxies: A Radio-to-Mid-Infrared Parameter

    NASA Technical Reports Server (NTRS)

    Melendez, Marcio B.; Kraemer, S. B.; Schmitt, H. R.

    2010-01-01

    We have studied the relationship between the nuclear (high-resolution) radio emission, at 8.4GHz (3.6cm) and 1.4GHz (20cm), the [O IV) (gamma)25.89 micron, [Ne III] (gamma)l5.56 micron and [Ne II] (gamma)l2.81 micron emission lines and the black hole mass accretion rate for a sample of Seyfert galaxies. In order to characterize the radio contribution for the Seyfert nuclei we used the 8.4 GHz/[O IV] ratio, assuming that [0 IV] scales with the luminosity of the active galactic nuclei (AGN). From this we find that Seyfert 1 s (i.e. Seyfert 1.0s, 1.2s and 1.5s) and Seyfert 2s (i.e. Seyfert 1.8s, 1.9s and 2.0s) have similar radio contributions, relative to the AGN. On the other hand, sources in which the [Ne u] emission is dominated either by the AGN or star formation have statistically different radio contributions, with star formation dominated sources more 'radio loud', by a factor of approx.2.8 on average, than AGN dominated sources. We show that star formation dominated sources with relatively larger radio contribution have smaller mass accretion rates. Overall, we suggest that 8.4 GHz/[O IV], or alternatively, 1.4 GHz/[O IV] ratios, can be used to characterize the radio contribution, relative to the AGN, without the limitation of previous methods that rely on optical observables. Key words: Galaxy: stellar content - galaxies: Seyfert - infrared: galaxies

  7. Dust and ionized gas in active radio elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Forbes, D. A.; Sparks, W. B.; Macchetto, F. D.

    1990-01-01

    The authors present broad and narrow bandwidth imaging of three southern elliptical galaxies which have flat-spectrum active radio cores (NGC 1052, IC 1459 and NGC 6958). All three contain dust and extended low excitation optical line emission, particularly extensive in the case of NGC 1052 which has a large H alpha + (NII) luminosity. Both NGC 1052 and IC 1459 have a spiral morphology in emission-line images. All three display independent strong evidence that a merger or infall event has recently occurred, i.e., extensive and infalling HI gas in NGC 1052, a counter-rotating core in IC 1459 and Malin-Carter shells in NGC 6958. This infall event is the most likely origin for the emission-line gas and dust, and the authors are currently investigating possible excitation mechanisms (Sparks et al. 1990).

  8. INFRARED SPECTROSCOPY OF NEARBY RADIO ACTIVE ELLIPTICAL GALAXIES

    SciTech Connect

    Mould, Jeremy; Reynolds, Tristan; Readhead, Tony; Matthews, Keith; Floyd, David; Brown, Michael; Jannuzi, Buell; Atlee, David; Cotter, Garret; Ferrarese, Laura

    2012-11-15

    In preparation for a study of their circumnuclear gas we have surveyed 60% of a complete sample of elliptical galaxies within 75 Mpc that are radio sources. Some 20% of our nuclear spectra have infrared emission lines, mostly Paschen lines, Brackett {gamma}, and [Fe II]. We consider the influence of radio power and black hole mass in relation to the spectra. Access to the spectra is provided here as a community resource.

  9. THE CLUSTERING OF GALAXIES AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Worpel, Hauke; Brown, Michael J. I.; Jones, D. Heath; Floyd, David J. E.; Beutler, Florian

    2013-07-20

    We examine the hypothesis that mergers and close encounters between galaxies can fuel active galactic nuclei (AGNs) by increasing the rate at which gas accretes toward the central black hole. We compare the clustering of galaxies around radio-loud AGNs with the clustering around a population of radio-quiet galaxies with similar masses, colors, and luminosities. Our catalog contains 2178 elliptical radio galaxies with flux densities greater than 2.8 mJy at 1.4 GHz from the Six Degree Field Galaxy Survey. We find tentative evidence that radio AGNs with more than 200 times the median radio power have, on average, more close (r < 160 kpc) companions than their radio-quiet counterparts, suggesting that mergers play a role in forming the most powerful radio galaxies. For ellipticals of fixed stellar mass, the radio power is neither a function of large-scale environment nor halo mass, consistent with the radio powers of ellipticals varying by orders of magnitude over billions of years.

  10. Discovery of Ultra-steep Spectrum Giant Radio Galaxy with Recurrent Radio Jet Activity in Abell 449

    NASA Astrophysics Data System (ADS)

    Hunik, Dominika; Jamrozy, Marek

    2016-01-01

    We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.

  11. Radio galaxies and their environment

    SciTech Connect

    van Breugel, W.

    1993-02-24

    The relationships between radio galaxies and their environment are varied, complex, and evolve with cosmic epoch. Basic questions are what role the environment plays in triggering and fuelling (radio) galaxy activity what the effects of this activity are on its environment, and how radio galaxies and environment evolve. Clearly, this could be the topic of a workshop all in itself and the scope of this review will necessarily be limited. A review of the connections between environment and galaxy activity in general has been given by Heckman. First, I will briefly summarize the relationships between parent galaxy and cluster environments, and radio galaxies. A more detailed discussion of various aspects of this will be given elsewhere by F. Owen, J.0. Burns and R. Perley. I will then discuss the current status of investigations of extended emission-line regions in radio galaxies, again referring elsewhere in this volume for more detailed discussions of some particular aspects (kinematics and ionization mechanisms by K. Meisenheimer; polarization and spectral index lobe asymmetries by G. Pooley). I will conclude with a brief discussion of the current status of observations of high redshift radio galaxies.

  12. FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

    SciTech Connect

    Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L. E-mail: ewilcots@astro.wisc.edu

    2012-08-15

    We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleus (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.

  13. Combined X-Ray and mm-Wave Observations of Radio Quiet Active Galaxies

    NASA Astrophysics Data System (ADS)

    Behar, E.

    2016-06-01

    A connection between the X-ray and radio sources in radio quiet active galaxies (AGNs) will be demonstrated. High radio frequency, i.e., mm-wave observations are promising probes of the X-ray emitting inner regions of the accretion disks in radio quiet AGNs. An argument for simultaneous observations in X-rays and in mm waves will be made, in order to promote these as one of the future science goals of X-ray and AGN astronomy in the next decade. Preliminary results from an exploratory campaign with several space and ground based telescopes will be presented.

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

    NASA Astrophysics Data System (ADS)

    Ramos Almeida, C.; Bessiere, P. S.; Tadhunter, C. N.; Pérez-González, P. G.; Barro, G.; Inskip, K. J.; Morganti, R.; Holt, J.; Dicken, D.

    2012-01-01

    We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2 Jy 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 mag 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 per cent at z < 0.2 and 48 per cent at 0.2 ≤ z < 0.7) than in the PRGs (93 per cent at z < 0.2 and 95 per cent 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 per cent) of disturbed early-type galaxies are capable of hosting powerful radio sources.

  15. Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

    NASA Astrophysics Data System (ADS)

    Banfield, J. K.; Wong, O. I.; Willett, K. W.; Norris, R. P.; Rudnick, L.; Shabala, S. S.; Simmons, B. D.; Snyder, C.; Garon, A.; Seymour, N.; Middelberg, E.; Andernach, H.; Lintott, C. J.; Jacob, K.; Kapińska, A. D.; Mao, M. Y.; Masters, K. L.; Jarvis, M. J.; Schawinski, K.; Paget, E.; Simpson, R.; Klöckner, H.-R.; Bamford, S.; Burchell, T.; Chow, K. E.; Cotter, G.; Fortson, L.; Heywood, I.; Jones, T. W.; Kaviraj, S.; López-Sánchez, Á. R.; Maksym, W. P.; Polsterer, K.; Borden, K.; Hollow, R. P.; Whyte, L.

    2015-11-01

    We present results from the first 12 months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170 000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses 1.4 GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at 3.4 μm from the Wide-field Infrared Survey Explorer (WISE) and at 3.6 μm from the Spitzer Space Telescope. We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is >75 per cent consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects and luminous infrared radio galaxies. We also find a distinct population of Radio Galaxy Zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non-star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (AGN) formation. The completion of the full Radio Galaxy Zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. Currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission and hybrid morphology radio sources.

  16. Dying radio galaxies in clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Parma, P.; Mack, K.-H.; de Ruiter, H. R.; Fanti, R.; Govoni, F.; Tarchi, A.; Giacintucci, S.; Markevitch, M.

    2011-02-01

    Aims: We present a study of five "dying" nearby (z ≤ 0.2) radio galaxies belonging to both the WENSS minisurvey and the B2 bright catalogs WNB1734+6407, WNB1829+6911, WNB1851+5707, B2 0120+33, and B2 1610+29. Methods: These sources have been selected on the basis of their extremely steep broad-band radio spectra, which strongly indicates that either these objects belong to the rare class of dying radio galaxies or we are observing "fossil" radio plasma remaining from a previous instance of nuclear activity. We derive the relative duration of the dying phase from the fit of a synchrotron radiative model to the radio spectra of the sources. Results: The modeling of the integrated spectra and the deep spectral index images obtained with the VLA confirmed that in these sources the central engine has ceased to be active for a significant fraction of their lifetime, although their extended lobes have not yet completely faded away. We found that WNB1851+5707 is in reality composed of two distinct dying galaxies, which appear blended together as a single source in the WENSS. In the cases of WNB1829+6911 and B2 0120+33, the fossil radio lobes are seen in conjunction with a currently active core. A very faint core is also detected in a MERLIN image of WNB1851+5707a, one of the two dying sources composing WNB1851+5707. We found that all sources in our sample are located (at least in projection) at the center of an X-ray emitting cluster. Conclusions: Our results suggest that the duration of the dying phase for a radio source in a cluster can be significantly higher than that of a radio galaxy in the field, although no firm conclusions can be drawn because of the small number statistics involved. The simplest interpretation of the tendency for dying galaxies to be found in clusters is that the low-frequency radio emission from the fading radio lobes lasts longer if their expansion is somewhat reduced or even stopped. Another possibility is that the occurrence of dying

  17. Radio active galactic nuclei in galaxy clusters: Feedback, merger signatures, and cluster tracers

    NASA Astrophysics Data System (ADS)

    Paterno-Mahler, Rachel Beth

    Galaxy clusters, the largest gravitationally-bound structures in the universe, are composed of 50-1000s of galaxies, hot X-ray emitting gas, and dark matter. They grow in size over time through cluster and group mergers. The merger history of a cluster can be imprinted on the hot gas, known as the intracluster medium (ICM). Merger signatures include shocks, cold fronts, and sloshing of the ICM, which can form spiral structures. Some clusters host double-lobed radio sources driven by active galactic nuclei (AGN). First, I will present a study of the galaxy cluster Abell 2029, which is very relaxed on large scales and has one of the largest continuous sloshing spirals yet observed in the X-ray, extending outward approximately 400 kpc. The sloshing gas interacts with the southern lobe of the radio galaxy, causing it to bend. Energy injection from the AGN is insufficient to offset cooling. The sloshing spiral may be an important additional mechanism in preventing large amounts of gas from cooling to very low temperatures. Next, I will present a study of Abell 98, a triple system currently undergoing a merger. I will discuss the merger history, and show that it is causing a shock. The central subcluster hosts a double-lobed AGN, which is evacuating a cavity in the ICM. Understanding the physical processes that affect the ICM is important for determining the mass of clusters, which in turn affects our calculations of cosmological parameters. To further constrain these parameters, as well as models of galaxy evolution, it is important to use a large sample of galaxy clusters over a range of masses and redshifts. Bent, double-lobed radio sources can potentially act as tracers of galaxy clusters over wide ranges of these parameters. I examine how efficient bent radio sources are at tracing high-redshift (z>0.7) clusters. Out of 646 sources in our high-redshift Clusters Occupied by Bent Radio AGN (COBRA) sample, 282 are candidate new, distant clusters of galaxies based on

  18. J1216+0709: A Radio Galaxy with Three Episodes of AGN Jet Activity

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Kharb, Preeti; Srivastava, Shweta; Janardhan, P.

    2016-08-01

    We report the discovery of a “triple-double radio galaxy,” J1216+0709, detected in deep low-frequency Giant Metrewave Radio Telescope (GMRT) observations. J1216+0709 is only the third radio galaxy, after B0925+420 and Speca, with three pairs of lobes resulting from three different episodes of active galactic nucleus (AGN) jet activity. The 610 MHz GMRT image clearly displays an inner pair of lobes, a nearly coaxial middle pair of lobes, and a pair of outer lobes that is bent with respect to the axis of the inner pair of lobes. The total end-to-end projected sizes of the inner, middle, and outer lobes are 40″ (∼95 kpc), 1.‧65 (∼235 kpc), and 5.‧7 (∼814 kpc), respectively. Unlike the outer pair of lobes, both the inner and middle pairs of lobes exhibit asymmetries in arm lengths and flux densities, but in the opposite sense, i.e., the eastern sides are farther and also brighter than the western sides, thus, suggesting the possibility of the jet being intrinsically asymmetric rather than due to a relativistic beaming effect. The host galaxy is a bright elliptical (m r ∼ 16.56) with M SMBH ∼ 3.9 × 109 M ⊙ and a star formation rate of ∼{4.66}-1.61{{+4.65}} M ⊙ yr‑1. The host galaxy resides in a small group of three galaxies (m r ≤ 17.77) and is possibly going through an interaction with faint dwarf galaxies in the neighborhood, which may have triggered the recent episodes of AGN activity.

  19. J1216+0709: A Radio Galaxy with Three Episodes of AGN Jet Activity

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Kharb, Preeti; Srivastava, Shweta; Janardhan, P.

    2016-08-01

    We report the discovery of a “triple-double radio galaxy,” J1216+0709, detected in deep low-frequency Giant Metrewave Radio Telescope (GMRT) observations. J1216+0709 is only the third radio galaxy, after B0925+420 and Speca, with three pairs of lobes resulting from three different episodes of active galactic nucleus (AGN) jet activity. The 610 MHz GMRT image clearly displays an inner pair of lobes, a nearly coaxial middle pair of lobes, and a pair of outer lobes that is bent with respect to the axis of the inner pair of lobes. The total end-to-end projected sizes of the inner, middle, and outer lobes are 40″ (˜95 kpc), 1.‧65 (˜235 kpc), and 5.‧7 (˜814 kpc), respectively. Unlike the outer pair of lobes, both the inner and middle pairs of lobes exhibit asymmetries in arm lengths and flux densities, but in the opposite sense, i.e., the eastern sides are farther and also brighter than the western sides, thus, suggesting the possibility of the jet being intrinsically asymmetric rather than due to a relativistic beaming effect. The host galaxy is a bright elliptical (m r ˜ 16.56) with M SMBH ˜ 3.9 × 109 M ⊙ and a star formation rate of ˜{4.66}-1.61{{+4.65}} M ⊙ yr‑1. The host galaxy resides in a small group of three galaxies (m r ≤ 17.77) and is possibly going through an interaction with faint dwarf galaxies in the neighborhood, which may have triggered the recent episodes of AGN activity.

  20. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    NASA Technical Reports Server (NTRS)

    Romanishin, W.; Hintzen, Paul

    1989-01-01

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud.

  1. An infrared jet in Centaurus A - A link to the extranuclear activity in distant radio galaxies?

    NASA Technical Reports Server (NTRS)

    Joy, Marshall; Harvey, P. M.; Tollestrup, E. V.; Sellgren, K.; Mcgregor, P. J.

    1991-01-01

    High-resolution NIR images of the visually obscured central region of Centaurus A (NGC 5128) were obtained with the University of Texas array camera on the AAT in June 1988, in order to investigate the effect of the active nucleus on the surrounding galaxy. The J (1.25 micron), H (1.65 micron), and K (2.2 micron) images of the central 40 arcsec of the galaxy revealed an emission feature extending about 10 arcsec northeast of the nucleus at the same position angle as the X-ray and radio jets. This jet is most prominent at the 1.25 micron wavelength, where its brightness was comparable to that of the nucleus. The observed properties of the 'infrared jet' were found to be similar to those seen in distant radio sources.

  2. AO Observations of Three Powerful Radio Galaxies

    SciTech Connect

    de Vries, W; van Bruegel, W; Quirrenbach, A

    2002-08-01

    The host galaxies of powerful radio sources are ideal laboratories to study active galactic nuclei (AGN). The galaxies themselves are among the most massive systems in the universe, and are believed to harbor supermassive black holes (SMBH). If large galaxies are formed in a hierarchical way by multiple merger events, radio galaxies at low redshift represent the end-products of this process. However, it is not clear why some of these massive ellipticals have associated radio emission, while others do not. Both are thought to contain SMBHs, with masses proportional to the total luminous mass in the bulge. It either implies every SMBH has recurrent radio-loud phases, and the radio-quiet galaxies happen to be in the ''low'' state, or that the radio galaxy nuclei are physically different from radio-quiet ones, i.e. by having a more massive SMBH for a given bulge mass. Here we present the first results from our adaptive optics imaging and spectroscopy pilot program on three nearby powerful radio galaxies. Initiating a larger, more systematic AO survey of radio galaxies (preferentially with Laser Guide Star equipped AO systems) has the potential of furthering our understanding of the physical properties of radio sources, their triggering, and their subsequent evolution.

  3. A CHANDRA STUDY OF THE RADIO GALAXY NGC 326: WINGS, OUTBURST HISTORY, AND ACTIVE GALACTIC NUCLEUS FEEDBACK

    SciTech Connect

    Hodges-Kluck, Edmund J.; Reynolds, Christopher S.

    2012-02-20

    NGC 326 is one of the most prominent 'X'- or 'Z'-shaped radio galaxies (XRGs/ZRGs) and has been the subject of several studies attempting to explain its morphology through either fluid motions or reorientation of the jet axis. We examine a 100 ks Chandra X-Ray Observatory exposure and find several features associated with the radio galaxy: a high-temperature front that may indicate a shock, high-temperature knots around the rim of the radio emission, and a cavity associated with the eastern wing of the radio galaxy. A reasonable interpretation of these features in light of the radio data allows us to reconstruct the history of the active galactic nucleus (AGN) outbursts. The active outburst was likely once a powerful radio source which has since decayed, and circumstantial evidence favors reorientation as the means to produce the wings. Because of the obvious interaction between the radio galaxy and the intracluster medium and the wide separation between the active lobes and wings, we conclude that XRGs are excellent sources in which to study AGN feedback in galaxy groups by measuring the heating rates associated with both active and passive heating mechanisms.

  4. Radio emission in peculiar galaxies

    NASA Technical Reports Server (NTRS)

    Demellorabaca, Dulia F.; Abraham, Zulema

    1990-01-01

    During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

  5. The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?

    NASA Astrophysics Data System (ADS)

    Shulevski, A.; Morganti, R.; Barthel, P. D.; Murgia, M.; van Weeren, R. J.; White, G. J.; Brüggen, M.; Kunert-Bajraszewska, M.; Jamrozy, M.; Best, P. N.; Röttgering, H. J. A.; Chyzy, K. T.; de Gasperin, F.; Bîrzan, L.; Brunetti, G.; Brienza, M.; Rafferty, D. A.; Anderson, J.; Beck, R.; Deller, A.; Zarka, P.; Schwarz, D.; Mahony, E.; Orrú, E.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Butcher, H. R.; Carbone, D.; Ciardi, B.; de Geus, E.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Heald, G.; Hoeft, M.; Hörandel, J.; Horneffer, A.; van der Horst, A. J.; Intema, H.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McFadden, R.; McKay-Bukowski, D.; McKean, J. P.; Meulman, H.; Mulcahy, D. D.; Munk, H.; Norden, M. J.; Paas, H.; Pandey-Pommier, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rowlinson, A.; Scaife, A. M. M.; Serylak, M.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Wijers, R. A. M. J.; Wise, M. W.; Wucknitz, O.

    2015-07-01

    Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex source 4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial resolution (~ 4″), the source was known to have two inner radio lobes spanning 31 kpc and a diffuse, low-brightness extension running parallel to them, offset by about 11 kpc (in projection). At 62 MHz, we detect the radio emission of this structure extending out to 210 kpc. At 1.4 GHz and intermediate spatial resolution (~ 30″), the structure appears to have a helical morphology. We have derived the characteristics of the radio spectral index across the source. We show that the source morphology is most likely the result of at least two episodes of AGN activity separated by a dormant period of around 35 Myr. The outermost regions of radio emission have a steep spectral index (α< - 1), indicative of old plasma. We connect the spectral index properties of the resolved source structure with the integrated fluxdensity spectral index of 4C 35.06 and suggest an explanation for its unusual integrated flux density spectral shape (a moderately steep power law with no discernible spectral break), possibly providing a proxy for future studies of more distant radio sources through inferring their detailed spectral index properties and activity history from their integrated spectral indices. The AGN is hosted by one of the galaxies located in the cluster core of Abell 407. We propose that it is intermittently active as it moves in the dense environment in the cluster core. In this scenario, the AGN turned on sometime in the past, and has produced the helical pattern of emission, possibly a sign of jet precession/merger during that episode of activity. Using LOFAR, we can trace the relic plasma from that episode of activity out to greater distances from the core than ever

  6. MAGIC detection of renewed activity from the radio galaxy IC 310

    NASA Astrophysics Data System (ADS)

    Cortina, Juan

    2012-11-01

    The MAGIC telescopes have observed a high VHE (E>~100 GeV) gamma-ray flux from the galaxy IC 310. The object (RA: 03h 16m 43.0s, Dec: +41d 19m 29s, J2000) is a TeV radio-loud galaxy located in the Perseus Cluster of galaxies at redshift 0.0189 (Falco et al. 1999). Although formerly considered to be an archetypical head-tail galaxy, recent radio-interferometric observations have shown that IC 310 hosts a blazar-type central engine (Kadler et al....

  7. Intermittent Jet Activity in the Radio Galaxy 4C29.30?

    SciTech Connect

    Jamrozy, M.; Konar, C.; Saikia, D.J.; Stawarz, L.; Mack, K.-H.; Siemiginowska, A.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-04-02

    We present radio observations at frequencies ranging from 240 to 8460 MHz of the radio galaxy 4C29.30 (J0840+2949) using the Giant Metrewave Radio Telescope (GMRT), the Very Large Array (VLA) and the Effelsberg telescope. We report the existence of weak extended emission with an angular size of {approx} 520 arcsec (639 kpc) within which a compact edge-brightened double-lobed source with a size of 29 arcsec (36 kpc) is embedded. We determine the spectrum of the inner double from 240 to 8460 MHz and show that it has a single power-law spectrum with a spectral index is {approx} 0.8. Its spectral age is estimated to be 33 Myr. The extended diffuse emission has a steep spectrum with a spectral index of {approx} 1.3 and a break frequency 240 MHz. The spectral age is {approx}>200 Myr, suggesting that the extended diffuse emission is due to an earlier cycle of activity. We reanalyze archival x-ray data from Chandra and suggest that the x-ray emission from the hotspots consists of a mixture of nonthermal and thermal components, the latter being possibly due to gas which is shock heated by the jets from the host galaxy.

  8. Black Hole Demographics in and Nuclear Properties of Nearby Low Luminosity Radio Galaxies; Connections to Radio Activity?

    NASA Technical Reports Server (NTRS)

    Baum, S. A.; Kleijn, G. A. Verdoes; Xu, C.; ODea, C. P.; deZeeuw, P. T.

    2004-01-01

    We combine the results of an HST STIS and WFPC study of a complete sample of 21 nearby UGC low luminosity radio galaxies with the results of a radio VLA and VLBA study of the same sample. We examine the relationship between the stellar and gaseous properties of the galaxies on tens to hundreds of parsec scale with the properties of the radio jets on the same scale. From the VLA and VLBA data we constrain the physics of the outflowing radio plasma from the tens of parsecs to hundreds of kiloparsec scales. From the WFPC2 H alpha and dust images and the STIS kinematics of the near nuclear gas we obtain constraints on the orientation of near nuclear disks of gas and measures of the nuclear stellar, continuum point source, and line emission fluxes. Under the statistically supported assumption that the radio jet issues perpendicular to the disk, we use the orientation of the optical (large scale accretion?) disks to constrain the three-dimensional orientation of the radio ejection. From HST/STIS spectroscopy of the near-nuclear emission line gas we obtain measures/limits on the black hole masses. We examine correlations between the VLBA and VLA-scale radio emission, the nuclear line emission, and the nuclear optical and radio continuum emission. Though our sample is relatively small, it is uniquely well defined, spans a narrow range in redshift and we have a consistent set of high resolution data with which to carefully examine these relationships. We use the combined radio and optical data to: 1) Constrain the orientation, physics, and bulk outflow speed of the radio plasma; 2) Put limits on the mass accretion rate and study the relationship between black hole mass, radio luminosity, and near nuclear gaseous content; 3) Provide insight into the relationship between BL Lac objects and low luminosity radio galaxies.

  9. SEYFERT GALAXIES: NUCLEAR RADIO STRUCTURE AND UNIFICATION

    SciTech Connect

    Lal, Dharam V.; Shastri, Prajval; Gabuzda, Denise C.

    2011-04-10

    A radio study of a carefully selected sample of 20 Seyfert galaxies that are matched in orientation-independent parameters, which are measures of intrinsic active galactic nucleus power and host galaxy properties, is presented to test the predictions of the unified scheme hypothesis. Our sample sources have core flux densities greater than 8 mJy at 5 GHz on arcsec scales due to the feasibility requirements. These simultaneous parsec-scale and kiloparsec-scale radio observations reveal (1) that Seyfert 1 and Seyfert 2 galaxies have an equal tendency to show compact radio structures on milliarcsecond scales, (2) the distributions of parsec-scale and kiloparsec-scale radio luminosities are similar for both Seyfert 1 and Seyfert 2 galaxies, (3) there is no evidence for relativistic beaming in Seyfert galaxies, (4) similar distributions of source spectral indices in spite of the fact that Seyferts show nuclear radio flux density variations, and (5) the distributions of the projected linear size for Seyfert 1 and Seyfert 2 galaxies are not significantly different as would be expected in the unified scheme. The latter could be mainly due to a relatively large spread in the intrinsic sizes. We also find that a starburst alone cannot power these radio sources. Finally, an analysis of the kiloparsec-scale radio properties of the CfA Seyfert galaxy sample shows results consistent with the predictions of the unified scheme.

  10. The life cycle of radio galaxies

    NASA Astrophysics Data System (ADS)

    Young, Andrew

    2004-06-01

    This thesis will examine some key issues in the life history of radio galaxies. The evolution of radio galaxies can be understood in terms of the history of their relativistic particle distributions and morphologies. Using radio data from the Very Large Array, I examine the relativistic particle acceleration processes in several Fanaroff-Riley I sources. 1116+28, 1243+26, and 1553+24 all show dual spectral components known as jets and sheaths. These and other radio galaxies show that the strength of the acceleration mechanism approaches the strong shock limit for first order Fermi acceleration. Active radio galaxies accelerate electrons that then undergo energy losses by way of synchrotron, adiabatic, and inverse-Compton mechanisms. 3C386 and 3C98 has structure which may indicate that the acceleration process has recently ceased or is coming to an end. An examination of these possibly dying radio sources with large, bright, and diffuse lobes reveals that the shape of the spectra indicates that their acceleration mechanisms approach the strong shock limit. With these derived low frequency spectral indices, an estimate of the true magnetic field strength in the lobes can be made should X-ray observations be available. This will alleviate the need to invoke equipartition assumptions. A radio galaxy will eventually lose almost all of its relativistic electron energy through radiative and adiabatic losses and evolve into a relic state. In this state, there may have no discernible radio core, radio jet, or optical counterpart. However, mechanisms such as cluster merger shocks or re-started radio galaxies could re-energize these relic plasmas. Relic radio sources in the clusters Abell 85 and MKW 3s show that these processes do occur and reveal spectra that are consistent with weak shocks. The sources studied here can be viewed as a snapshot in the timeline of a radio galaxy. The life cycles of radio galaxies have broad implications not just for themselves but also on the

  11. The hydrodynamics of dead radio galaxies

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.; Heinz, Sebastian; Begelman, Mitchell C.

    2002-05-01

    We present a numerical investigation of dead, or relic, radio galaxies and the environmental impact that radio galaxy activity has on the host galaxy or galaxy cluster. We perform axisymmetric hydrodynamical calculations of light, supersonic, back-to-back jets propagating in a β -model galaxy/cluster atmosphere. We then shut down the jet activity and let the resulting structure evolve passively. The dead source undergoes an initial phase of pressure driven expansion until it achieves pressure equilibrium with its surroundings. Thereafter, buoyancy forces drive the evolution and lead to the formation of two oppositely directed plumes that float high into the galaxy/cluster atmosphere. These plumes entrain a significant amount of low entropy material from the galaxy/cluster core and lift it high into the atmosphere. An important result is that a large fraction (at least half) of the energy injected by the jet activity is thermalized in the interstellar medium (ISM)/intracluster medium (ICM) core. The whole ISM/ICM atmosphere inflates in order to regain hydrostatic equilibrium. This inflation is mediated by an approximately spherical disturbance which propagates into the atmosphere at the sound speed. The fact that such a large fraction of the injected energy is thermalized suggests that radio galaxies may have an important role in the overall energy budget of rich ISM/ICM atmospheres. In particular, they may act as a strong and highly time-dependent source of negative feedback for galaxy/cluster cooling flows.

  12. Evolution of luminous IRAS galaxies: Radio imaging

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Hutchings, J. B.

    1993-01-01

    In a recent study of IRAS galaxies' optical morphologies, we found that luminous IR sources lie in the IR color-luminosity plane in groups which separate out by optical spectroscopic type and also by degree of tidal disturbance. We found that the most luminous steep-IR-spectrum sources are generally galaxies in the initial stages of a major tidal interaction. Galaxies with active nuclei were generally found to have flatter IR spectra, to cover a range of IR luminosity, and to be in the later stages of a tidal interaction. We proposed a sequence of events by which luminous IR sources evolve: they start as interacting or merging galaxies, some develop active nuclei, and most undergo extensive star-formation in their central regions. Another way to study these objects and their individual evolution is to study their radio morphologies. Radio emission may arise at a detectable level from supernovae in star-forming regions and/or the appearance of an active nucleus can be accompanied by a nuclear radio source (which may develop extended structure). Therefore, the compact radio structure may trace the evolution of the inner regions of IRAS-luminous sources. If the radio sources are triggered by the interactions, we would expect to find the radio morphology related to the optical 'interactivity' of the systems. Here, we explore using the radio emission of IRAS galaxies as a possible tracer of galaxy evolution. We present and discuss observations of the compact radio morphology of 111 luminous IRAS-selected active galaxies covering a wide range of IR and optical properties.

  13. Very high redshift radio galaxies

    SciTech Connect

    van Breugel, W.J.M., LLNL

    1997-12-01

    High redshift radio galaxies (HzRGs) provide unique targets for the study of the formation and evolution of massive galaxies and galaxy clusters at very high redshifts. We discuss how efficient HzRG samples ae selected, the evidence for strong morphological evolution at near-infracd wavelengths, and for jet-induced star formation in the z = 3 800 HzRG 4C41 17

  14. Radio Galaxies in Galaxy Clusters: Feedback, Merger Signatures, and Signposts

    NASA Astrophysics Data System (ADS)

    Paterno-Mahler, Rachel; Blanton, Elizabeth L.; Randall, Scott W.; Andrade-Santos, Felipe; Ashby, Matthew; Brodwin, Mark; Bulbul, Esra; Clarke, Tracy E.; Golden-Marx, Emmet; Johnson, Ryan; Jones, Christine; Murray, Stephen S.; Wing, Joshua

    2015-01-01

    Extended, double-lobed radio sources are often located in rich galaxy clusters. I will present results of an optical and X-ray analysis of two nearby clusters with such radio sources - one of the clusters is relaxed (A2029) and one of the clusters is undergoing a merger (A98). Because of their association with clusters, extended radio sources can be used to locate clusters at a wide range of distances. The number of spectroscopically confirmed galaxy clusters with is very low compared to the number of well-studied low-redshift clusters. In the Clusters Occupied by Bent Radio AGN (COBRA) survey, we use bent, double-lobed radio sources as signposts to efficiently locate high-redshift clusters. Using a Spitzer Snapshot Survey of our sample of 653 bent, double-lobed radio sources (selected from the FIRST survey and with galaxy hosts too faint to be detected in the SDSS), we have the potential to identify approximately 400 new clusters and groups with redshifts. I will present results from the Spitzer observations regarding the efficiency of the method for finding new clusters. These newly identified clusters will be used to study galaxy formation and evolution, as well as the effect that feedback from active galactic nuclei (AGN) has on galaxies and their environments.

  15. High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

    NASA Astrophysics Data System (ADS)

    Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

    2014-08-01

    A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1radio sources show that about half the sample is significantly obscured with ratios of unobscured: Compton thin (22 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN

  16. Episodic radio galaxies J0116-4722 and J1158+2621: can we constrain the quiescent phase of nuclear activity?

    NASA Astrophysics Data System (ADS)

    Konar, C.; Hardcastle, M. J.; Jamrozy, M.; Croston, J. H.

    2013-04-01

    We present multifrequency radio observations of two well-known episodic Fanaroff-Railey type II (FR II) radio galaxies (J0116-4722 and J1158+2621) and a detailed investigation of the life cycle of episodic radio galaxies from their spectral and radiative properties. Combining our previous work with the present results, we either constrain or place very good limits on the active and quiescent phases of a small sample of episodic FR II radio galaxies. The duration of the quiescent phase can be as small as the hotspot fading time of the previous episode, and as high as a few tens of Myr; however, for none of the sources in our sample is it close to the duration of the active phase of the previous episode. We also find that for many episodic radio galaxies, the nucleus is variable at radio wavelengths. For our small sample of seven episodic radio galaxies, we find four to have strongly variable cores, a much larger proportion than is generally found in samples of normal FR II radio galaxies. Studies with larger samples will be required to establish a statistical association between core variability and episodic radio activity.

  17. Star formation activity in spiral galaxy disks and the properties of radio halos: Observational evidence for a direct dependence

    NASA Technical Reports Server (NTRS)

    Dahlem, Michael; Lisenfeld, Ute; Golla, Gotz

    1995-01-01

    In this article we address observationally the questions: how does star formation (SF) in the disks of galaxies lead to the creation of radio halos, and what minimum energy input into the interstellar medium (ISM) is needed to facilitate this? For the investigation we use a sample of five edge-on galaxies exhibiting radio continuum emmission in their halos and enhanced SF spread over large parts of their disks. In a detailed study of the two galaxies in our sample for which we have the best data, NGC 891 and NGC 4631, we show that the radio halos cut off abruptly at galactocentric radii smaller than those of the underlying thin radio disks. Our most important result is that the halo cutoffs are spatially coincident with the radii where the SF activity in the underlying disks drops sharply. The difference in radius of the emission distributions tracing ongoing SF in the disks (IRAS 50 micrometers, H alpha) versus that of the nonthermal radio continuum thin disks (tracing the distribution of cosmic-ray (CR) electrons) is typically a few kpc. This difference in extent is caused by CR diffusion. We have measured the CR diffusion coefficients in the thin disks of both NGC 891 and NGC 4631. For radial diffusion of CR electrons within the galactic disks the values are D(sub r) = 1.1-2.5 x 10 (exp 29) sq cm/s (NGC 4631) and D(sub r) = 1.2 x 10(exp 29) sq cm/s (NGC 891). For motions in the z-direction in areas within the thin disks where no outflows occur, we derive a firm upper limit of D(sub z) less than or equal to 0.2 x 10(exp 28) sq cm/s for NGC 891. The value for NGC 4631 is D(sub z = 1.4 x 10 (exp 28) sq cm/s. The other three galaxies in our sample, NGC 3044, NGC 4666, and NGC 5775 show (at the sensitivity of our data) less extended, more filamentary radio halos. Isolates spurs or filaments of nonthermal radio continuum emission in their halos are traced only above the most actively star-forming regions in the disks. This, in conjuction with the results obtained for

  18. A two-parameter model for the infrared/submillimeter/radio spectral energy distributions of galaxies and active galactic nuclei

    SciTech Connect

    Dale, Daniel A.; Helou, George; Magdis, Georgios E.; Armus, Lee; Díaz-Santos, Tanio; Shi, Yong

    2014-03-20

    A two-parameter semi-empirical model is presented for the spectral energy distributions of galaxies with contributions to their infrared-submillimeter-radio emission from both star formation and accretion disk-powered activity. This model builds upon a previous one-parameter family of models for star-forming galaxies, and includes an update to the mid-infrared emission using an average template obtained from Spitzer Space Telescope observations of normal galaxies. Star-forming/active galactic nucleus (AGN) diagnostics based on polycyclic aromatic hydrocarbon equivalent widths and broadband infrared colors are presented, and example mid-infrared AGN fractional contributions are estimated from model fits to the Great Observatories All-Sky LIRG Survey sample of nearby U/LIRGS and the Five mJy Unbiased Spitzer Extragalactic Survey sample of 24 μm selected sources at redshifts 0 ≲ z ≲ 4.

  19. Radio continuum polarimetric imaging of high redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Owen, F. N.; Harris, D. E.

    1994-01-01

    Multifrequency images of total and polarized radio continuum emission from the two high redshift radio galaxies 0902+343 (z = 3.40) and 0647+415 (4C 41.17, z = 3.80) are presented. These images represent the most sensitive polarimetric study of high redshift ratio galaxies to date. The emission from both galaxies is substantially polarized, up to 30% in some regions, and both sources sit behind deep 'Faraday screens,' producing large rotation measures, over 10(exp 3) rad/sq. m in magnitude, and large rotation measure gradients across the sources. Such large rotation measures provide further evidence that high redshift radio galaxies are situated in very dense environments. Drawing the analogy to a class of low redshift powerful radio galaxies with similarly large rotation measures, we suggest that 0902+343 and 0647+415 are situated at the centers of dense, x-ray 'colling flow' clusters, and that the cluster gas is substantially magnetized. The remarkable similarity between the optical and radio morphologies of 0647+415 on scales as small as 0.1 sec is presented. We consider, and reject, both synchrotron and inverse Compton radiation as possible sources of the optical emission. We also consider both scattering of light out of a 'cone' of radiation from an obscured nucleus, and jet-induced star formation, and find that both models encounter difficulties in explaining this remarkably close radio-optical alignment. High resolution spectral index images reveal compact, flat spectrum components in both sources. We suggest that these components are the active nuclei of the galaxies. Lastly, high resolution images of 0902+343 show that the southernmost component forms a 'ring' of 0.2 sec radius. We discuss the possibility that this ring is the result of gravitational lensing, along the lines proposed by Kochanek & Lawrence (1990).

  20. Radio Galaxies in Abell Rich Clusters

    NASA Astrophysics Data System (ADS)

    Ledlow, M. J.

    1994-05-01

    We have defined a complete sample of radio galaxies chosen from Abell's northern catalog consisting of all clusters with measured redshifts < 0.09. This sample consists of nearly 300 clusters. A multiwavelength survey including optical CCD R-Band imaging, optical spectroscopy, and VLA 20 cm radio maps has been compiled. I have used this database to study the optical/radio properties of radio galaxies in the cluster environment. In particular, optical properties have been compared to a radio-quiet selected sample to look for optical signatures which may distinguish radio galaxies from normal radio-quiet ellipticals. The correlations between radio morphology and galaxy type, the optical dependence of the FR I/II break, and the univariate and bivariate luminosity functions have been examined for this sample. This study is aimed at understanding radio galaxies as a population and examining their status in the AGN heirarchy. The results of this work will be applied to models of radio source evolution. The results from the optical data analysis suggest that radio galaxies, as a class, cannot be distinguished from non-radio selected elliptical galaxies. The magnitude/size relationship, the surface-brightness profiles, the fundamental plane, and the intrinsic shape of the radio galaxies are consistent between our radio galaxy and control sample. The radio galaxies also trace the elliptical galaxy optical luminosity function in clusters very well; with many more L(*) galaxies than brightest cluster members. Combined with the results of the spectroscopy, the data are consistent with the idea that all elliptical galaxies may at some point in their lifetimes become radio sources. In conclusion, I present a new observational picture for radio galaxies and discuss the important properties which may determine the evolution of individual sources.

  1. From Radio with Love: an overview of the role of radio observations in understanding high-energy emission from active galaxies

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh

    2012-03-01

    The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe is presented here.

  2. From Radio with Love: An Overview of the Role of Radio Observations in Understanding High-Energy Emission from Active Galaxies

    NASA Technical Reports Server (NTRS)

    Ojha, Roopesh

    2012-01-01

    The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe as presented here.

  3. Photoelectric spectrophotometry of radio galaxies

    NASA Technical Reports Server (NTRS)

    Yee, H. K. C.; Oke, J. B.

    1978-01-01

    The absolute energy distributions from 3200 to 10,000 A of 26 3CR radio galaxies are determined on the basis of spectrophotometric observations with the multichannel spectrometer of the Hale 5-m telescope. It is found that there is a continuous range of emission-line characteristics and UV excess in the sample and that a strong correlation exists between the nonthermal component luminosity and hydrogen emission, which favors the hypothesis that direct photoionization by the nuclear radiation is responsible for the emission lines observed. Calculations are performed which show that in almost all cases the power-law component model provides sufficient UV photons to produce the observed H-beta line. Indications are obtained that the optical nuclear component is related to the radio emission in some complex manner and that strong radio galaxies tend to be accompanied by UV excess and emission lines.

  4. The Radio Luminosity Function and Galaxy Evolution of Abell 2256

    NASA Astrophysics Data System (ADS)

    Forootaninia, Zahra

    2015-05-01

    This thesis presents a study of the radio luminosity function and the evolution of galaxies in the Abell 2256 cluster (z=0.058, richness class 2). Using the NED database and VLA deep data with an rms sensitivity of 18 mu Jy.beam--1, we identified 257 optical galaxies as members of A2256, of which 83 are radio galaxies. Since A2256 is undergoing a cluster-cluster merger, it is a good candidate to study the radio activity of galaxies in the cluster. We calculated the Univariate and Bivariate radio luminosity functions for A2256, and compared the results to studies on other clusters. We also used the SDSS parameter fracDev to roughly classify galaxies as spirals and ellipticals, and investigated the distribution and structure of galaxies in the cluster. We found that most of the radio galaxies in A2256 are faint, and are distributed towards the outskirts of the cluster. On the other hand, almost all very bright radio galaxies are ellipticals which are located at the center of the cluster. We also found there is an excess in the number of radio spiral galaxies in A2256 compared to the number of radio ellipticals, counting down to a radio luminosity of log(luminosity)=20.135 W/Hz..

  5. The Cosmic History of Hot Gas Cooling and Radio AGN Activity in Massive Early-Type Galaxies

    NASA Technical Reports Server (NTRS)

    Danielson, A. L. R.; Lehmer, B. D.; Alexander, D. M.; Brandt, W. M.; Luo, B.; Miller, N.; Xue, Y. Q.; Stott, J. P.

    2012-01-01

    We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z approx equals 0.0-1.2 in the Chandra Deep Fields. To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG subset was constructed to span the redshift ranges of z = 0.1-1.2 in the approx equals 4 Ms CDF-S and approx equals 2 Ms CDF-N and z = 0.1-0.6 in the approx equals 250 ks E-CDF-S where the contribution from individually undetected AGNs is expected to be negligible in our stacking. We find that 55 of the ETGs are detected individually in the X-rays, and 12 of these galaxies have properties consistent with being passive hot-gas dominated systems (i.e., systems not dominated by an X-ray bright Active Galactic Nucleus; AGN). On the basis of our analyses, we find little evolution in the mean 0.5-2 keY to B-band luminosity ratio (L(sub x) /L(sub Beta) varies as [1 +z]) since z approx equals 1.2, implying that some heating mechanism prevents the gas from cooling in these systems. We consider that feedback from radio-mode AGN activity could be responsible for heating the gas. We select radio AGNs in the ETG population using their far-infrared/radio flux ratio. Our radio observations allow us to constrain the duty cycle history of radio AGN activity in our ETG sample. We estimate that if scaling relations between radio and mechanical power hold out to z approx equals 1.2 for the ETG population being studied here, the average mechanical power from AGN activity is a factor of approx equals1.4 -- 2.6 times larger than the average radiative cooling power from hot gas over the redshift range z approx equals 0-1.2. The excess of inferred AGN mechanical power from these ETGs is consistent with that found in the local Universe for similar types of galaxies.

  6. Imaging Radio Galaxies with Adaptive Optics

    NASA Astrophysics Data System (ADS)

    de Vries, W. H.; van Breugel, W. J. M.; Quirrenbach, A.; Roberts, J.; Fidkowski, K.

    2000-12-01

    We present 42 milli-arcsecond resolution Adaptive Optics near-infrared images of 3C 452 and 3C 294, two powerful radio galaxies at z=0.081 and z=1.79 respectively, obtained with the NIRSPEC/SCAM+AO instrument on the Keck telescope. The observations provide unprecedented morphological detail of radio galaxy components like nuclear dust-lanes, off-centered or binary nuclei, and merger induced starforming structures; all of which are key features in understanding galaxy formation and the onset of powerful radio emission. Complementary optical HST imaging data are used to construct high resolution color images, which, for the first time, have matching optical and near-IR resolutions. Based on these maps, the extra-nuclear structural morphologies and compositions of both galaxies are discussed. Furthermore, detailed brightness profile analysis of 3C 452 allows a direct comparison to a large literature sample of nearby ellipticals, all of which have been observed in the optical and near-IR by HST. Both the imaging data and the profile information on 3C 452 are consistent with it being a relative diminutive and well-evolved elliptical, in stark contrast to 3C 294 which seems to be in its initial formation throes with an active AGN off-centered from the main body of the galaxy. These results are discussed further within the framework of radio galaxy triggering and the formation of massive ellipticals. The work of WdV and WvB was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. The work at UCSD has been supported by the NSF Science and Technology Center for Adaptive Optics, under agreement No. AST-98-76783.

  7. Evolution of radio galaxies to z = 1

    NASA Technical Reports Server (NTRS)

    Hutchings, J. B.; Neff, S. G.; Weadock, J.; Roberts, L.; Ryneveld, S.; Gower, A. C.

    1994-01-01

    We report Very Large Array (VLA) A-configuration studies of a sample of 49 radio galaxies at redshift less than 1. These were selected with no prior knowledge of their morphology and were chosen to match the redshift and luminosity distribution of a previously studied sample of radio-loud quasars. We compare the radio galaxies with the quasar sample and also with a sample of 29 radio galaxies selected for steep spectrum and double-lobe structure. We find that the radio galaxies have more luminous lobes and mostly weaker cores, and there is no population of one-sided sources associated with the galaxies. The radio galaxies' lobe length ratios and lobe power ratios differ from quasars. The overall sizes of the two types of sources are similar, but the radio galaxies have a 3 times larger upper envelope. The distribution of bend angles is similar but the radio galaxies have fewer very bent and straight sources. We discuss these and other comparisons in detail and suggest that while quasars appear to be viewed within a cone and radio galaxies outside it, the two types of source also have intrinsic differences, and both have individual growth and evolution scenarios. This is supported by previously observed differences in optical properties between the two source types.

  8. Host Galaxies of X-Shaped Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Springmann, Alessondra; Cheung, C. C.

    2007-05-01

    The majority of radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, the active galaxies emitting much of their radiation at radio wavelengths. Classical double-lobed radio galaxies are characterized by a single pair of "active" radio lobes. A small subset show an additional pair of lower surface brightness 'wings' of emission, thus forming an overall winged or X-shaped appearance. Two competing mechanisms have been proposed to explain the "winged" morphology. One model posits that these are the remnants left over from a relatively recent merger of a binary supermassive black hole system. Others have argued that they result naturally from strong backflow in a radio jet cocoon expanding into an asymmetric medium. We used available Sloan Digital Sky Survey r-band images of 11 X-shaped sources to measure the host galaxy ellipticities. By analyzing the host galaxy shapes, we trace the surrounding gas distribution. The radio morphologies are compared to the host galaxy parameters to analogize between differing model expectations. This work was funded by the Department of Energy's Student Undergraduate Laboratory Internship Program and the Stanford Linear Accelerator Center.

  9. MULTI-WAVELENGTH OBSERVATIONS OF A SAMPLE OF INTERMEDIATE-LUMINOSITY RADIO-LOUD ACTIVE GALAXIES

    SciTech Connect

    Lewis, Karen T.; Sambruna, Rita M.; Cheung, Chi C.; Eracleous, Michael; Kadler, Matthias

    2011-07-15

    We present the results from exploratory (12-23 ks) XMM-Newton observations of six optically selected, radio-loud active galactic nuclei (AGNs), together with new radio data and a reanalysis of their archival SDSS spectra. The sources were selected in an effort to expand the current sample of radio-loud AGNs suitable for detailed X-ray spectroscopy studies. The sample includes three broad-line and three narrow-line sources, with X-ray luminosities of the order of L{sub 2-10keV} {approx} 10{sup 43} erg s{sup -1}. The EPIC spectra of the broad-lined sources can be described by single power laws with photon indices {Gamma} {approx} 1.6 and little to negligible absorption (N{sub H} {approx}<10{sup 21} cm{sup -2}); on the contrary, significant absorption is detected in the narrow-lined objects, N{sub H} {approx} 10{sup 23} cm{sup -2}, one of which displays a prominent (equivalent width {approx}2 keV) Fe K{alpha} emission line. Studying their location in several luminosity-luminosity diagrams for radio-loud AGNs, we find that the sources fall at the lower end of the distribution for bright, classical radio-loud AGNs and close to LINER-like sources. As such, and as indicated by the ratios of their optical emission lines, we conclude that the sources of our sample fall on the border between radiatively efficient and inefficient accretion flows. Future deeper studies of these targets at X-rays and longer wavelengths will expand our understanding of the central engines of radio-loud AGNs at a critical transition region.

  10. HOST GALAXIES OF X-SHAPED RADIO SOURCES

    SciTech Connect

    Springmann, A.; Cheung, C.

    2007-01-01

    Most radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, active galaxies that emit much of their radiation at radio wavelengths. Within each radio galaxy, an AGN powers a pair of collimated jets of relativistic particles, forming a pair of giant lobes at the end of the jets and thus giving a characteristic double-lobed appearance. A particular class of radio galaxies has an “X”-or winged-shaped morphology: in these, two pairs of lobes appear to originate from the galactic center, producing a distinctive X-shape. Two main mechanisms have been proposed to explain the X-shape morphology: one being a realignment of the black hole within the AGN and the second positing that the radio jets are expanding into an asymmetric medium, causing backflow and producing secondary wings. By analyzing radio host galaxy shapes, the distribution of the stellar mass is compared to the differing model expectations regarding the distribution of the surrounding gas and stellar material about the AGN. Results show elliptical host galaxies with an orthogonal offset between the semi-major axis of the host galaxy and the secondary radio wings, which lends support to the hydrodynamical model. However, results also show circular host galaxies with radio wings, making the realignment scenario a more likely model to describe the formation of these X-shaped radio sources.

  11. The Radio Properties of Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Hogan, M. T.

    2014-09-01

    Energetic feedback from the Active Galactic Nucleus (AGN) of the Brightest Cluster Galaxy (BCG) is required to prevent catastrophic cooling of the intra-cluster medium (ICM) in galaxy clusters. Evidence for this is seen through the inflation of cavities in the ICM by AGN-launched, radio-emitting jets, and understanding this process is an active area of research. Radio observations play an integral role in this, as they trace the active stages of the feedback cycle. Understanding the radio properties of BCGs is therefore paramount for understanding both galaxy clusters and AGN feedback processes globally. Within this thesis, the BCGs in a large (>700) sample of X-ray selected clusters are studied. We observe these BCGs with a wide variety of facilities, building a census of their radio properties across a range of frequencies, timescales and angular resolutions. Radio spectral energy distributions (SEDs) are built for over 200 BCGs, and then decomposed into two components; a core, attributable to ongoing nuclear activity, and a non-core, attributable to historical accretion. Both components are not only more common, but also significantly more powerful in cool-core (CC) clusters than non-cool core (NCC) clusters. However, it is the presence of an active core that shows BCGs in CC clusters are constantly `on' - explaining how they regulate their environments over gigayear timescales. We observe 35 currently active BCGs at high (15-353 GHz) radio frequencies, and monitor their variability. Self-absorbed, active components are found to be common at high frequency. Little variability is seen on < year timescales, although longer term variation of ~10% annually over few-decade timescales is observed. Evidence is presented for a hitherto unseen component in BCG spectra that may be attributable to a naked Advection Dominated Accretion Flow (ADAF). The milli-arcsecond scale radio properties of 59 sources are studied, with a large range of morphologies recovered although no

  12. Radiative versus Jet Mode in Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2016-07-01

    In the local universe, the vast majority of radio-loud active galaxies show none of the conventional AGN apparatus of accretion disk, torus, corona, or broad/narrow-line regions. Instead such nuclear emission as they have appears to be completely dominated by emission directly from the jet; the accretion, which must be present to drive the jet, appears to be highly radiatively inefficient. However, the most radio-luminous objects in the universe are almost all quasars (type I or type II) which behave in the textbook manner, appearing as a normal radiatively efficient AGN with the addition of a jet. The past decade has seen a substantial evolution in our understanding of the physical origins of these differences, their relation to the host galaxy and environment, and their interpretation in terms of completely unified models of AGN, and I will review our current understanding of these issues in my talk.

  13. MILLIMETER RADIO CONTINUUM EMISSIONS AS THE ACTIVITY OF SUPERMASSIVE BLACK HOLES IN NEARBY EARLY-TYPE GALAXIES AND LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Doi, Akihiro; Nakanishi, Kouichiro; Nagai, Hiroshi; Kohno, Kotaro; Kameno, Seiji

    2011-11-15

    We conducted millimeter continuum observations for samples of nearby early-type galaxies (21 sources) and nearby low-luminosity active galactic nuclei (LLAGNs; 16 sources) at 100 GHz ({lambda}3 mm) using the Nobeyama Millimeter Array (NMA). In addition, we performed quasi-simultaneous observations at 150 GHz ({lambda}2 mm) and 100 GHz for five LLAGNs. Compact nuclear emissions showing flat or inverted spectra at centimeter-to-millimeter wavelengths were found in many LLAGNs and several early-type galaxies. Moreover, significant flux variability was detected in three LLAGNs. These radio properties are similar to Sgr A*. The observed radio luminosities are consistent with the fundamental plane of black hole activity that was suggested on the basis of samples with black hole masses ranging from 10 to 10{sup 10} M{sub Sun }. This implies nuclear jets powered by radiatively inefficient accretion flows onto black holes.

  14. Radio Map of the Andromeda Galaxy.

    PubMed

    Macleod, J M

    1964-07-24

    The University of Illinois radio telescope has resolved the 610.5 Mcy/sec disk component of radio emission from the large galaxy M 31 into several discrete concentrations. In two cases, these correspond to the crossing of the optical major axis by spiral arms. A spur of emission extends southeast from the galaxy near the minor axis. PMID:17816977

  15. MUSE three-dimensional spectroscopy and kinematics of the gigahertz peaked spectrum radio galaxy PKS 1934-63: interaction, recently triggered active galactic nucleus and star formation

    NASA Astrophysics Data System (ADS)

    Roche, Nathan; Humphrey, Andrew; Lagos, Patricio; Papaderos, Polychronis; Silva, Marckelson; Cardoso, Leandro S. M.; Gomes, Jean Michel

    2016-07-01

    We observe the radio galaxy PKS 1934-63 (at z = 0.1825) using the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The radio source is a gigahertz peaked spectrum source and is compact (0.13 kpc), implying an early stage of evolution (≤104 yr). Our data show an interacting pair of galaxies, with projected separation 9.1 kpc and velocity difference Δ(v) = 216 km s-1. The larger galaxy is a M* ≃ 1011 M⊙ spheroidal with the emission-line spectrum of a high-excitation young radio active galactic nucleus (AGN; e.g. strong [O I]6300 and [O III]5007). Emission-line ratios indicate a large contribution to the line luminosity from high-velocity shocks (≃ 550 km s-1). The companion is a non-AGN disc galaxy, with extended Hα emission from which its star formation rate is estimated as 0.61 M⊙ yr-1. Both galaxies show rotational velocity gradients in Hα and other lines, with the interaction being prograde-prograde. The SE-NW velocity gradient of the AGN host is misaligned from the E-W radio axis, but aligned with a previously discovered central ultraviolet source, and a factor of 2 greater in amplitude in Hα than in other (forbidden) lines (e.g. [O III]5007). This could be produced by a fast rotating (100-150 km s-1) disc with circumnuclear star formation. We also identify a broad component of [O III]5007 emission, blueshifted with a velocity gradient aligned with the radio jets, and associated with outflow. However, the broad component of [O I]6300 is redshifted. In spectral fits, both galaxies have old stellar populations plus ˜0.1 per cent of very young stars, consistent with the galaxies undergoing first perigalacticon, triggering infall and star formation from ˜40 Myr ago followed by the radio outburst.

  16. Host Galaxies of X-Shaped Radio Sources

    SciTech Connect

    Springmann, Alessondra; /Wellesley Coll. /SLAC

    2006-09-27

    The majority of radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, the active galaxies emitting much of their radiation at radio wavelengths. Within each radio galaxy, an AGN powers a pair of collimated jets of relativistic particles, forming a pair of giant lobes at the end of the jets and thus giving a characteristic double-lobed appearance. A particular class of radio galaxies have an ''X''-shaped morphology: in these, two pairs of lobes appear to originate from the galactic center, producing a distinctive X-shape. Two main mechanisms have been proposed to explain the X-shape morphology: one being through the merger of a binary supermassive black hole system and the second being that the radio jets are expanding into an asymmetric medium. By analyzing radio host galaxy shapes, we probe the distribution of the stellar mass to compare the differing model expectations regarding the distribution of the surrounding gas and stellar material about the AGN.

  17. Radio luminosity function of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Yuan, Z. S.; Han, J. L.; Wen, Z. L.

    2016-08-01

    By cross-matching the currently largest optical catalogue of galaxy clusters and the NVSS radio survey data base, we obtain a large complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05 < z ≤ 0.45, which have radio emission and redshift information. We confirm that more powerful radio BCGs tend to be these optically very bright galaxies located in more relaxed clusters. We derived the radio luminosity functions of the largest sample of radio BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamic state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift.

  18. Radio structures in QSO-galaxy pairs

    NASA Technical Reports Server (NTRS)

    Akujor, Chidi E.

    1990-01-01

    It is now generally agreed that if quasars and nearby low redshift galaxies are associated, then there should be luminous connections between them. However, most of the observational evidence being presented is in the optical domain, whereas such evidence should also exist at radio frequencies. The author is, therefore, investigating some quasar-galaxy pairs at radio frequencies to search for luminous connections and other structural peculiarities. Radio maps of some of these sources are presented.

  19. GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER

    SciTech Connect

    Wylezalek, Dominika; Stern, Daniel; Eisenhardt, Peter R. M.; Galametz, Audrey; Vernet, Joeel; De Breuck, Carlos; Seymour, Nick; Brodwin, Mark; Gonzalez, Anthony H.; Hatch, Nina; Jarvis, Matt; Rettura, Alessandro; Stanford, Spencer A.; Stevens, Jason A.

    2013-05-20

    We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2 < z < 3.2. These data, obtained for 387 fields, reach 3.6 and 4.5 {mu}m depths of [3.6]{sub AB} = 22.6 and [4.5]{sub AB} = 22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6] - [4.5] > -0.1 (AB), which efficiently selects high-redshift (z > 1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a {>=}2{sigma} level; 10% are overdense at a {>=}5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.

  20. Gas and radio galaxies: a story of love and hate

    NASA Astrophysics Data System (ADS)

    Morganti, Rafaella

    2011-07-01

    Gas in radio galaxies is an important component that plays different roles. Gas can feed the AGN and make it active but dense gas can also be an obstacle for radio jets and (temporarily) destroy their flow. The characteristics of the different phases of gas in the circumnuclear regions of active nuclei hold clear signatures of the influences that the black hole activity has on its surroundings. I will review these effects based on some recent results obtained in the study of neutral hydrogen and CO. In particular, I will concentrate on the effects of radio jets in generating the strong negative feedback of the kind invoked in current scenarios for galaxy evolution.

  1. Gamma-ray detected radio galaxies

    NASA Astrophysics Data System (ADS)

    Beckmann, Volker; Soldi, Simona; De Jong, Sandra; Kretschmer, Karsten; Savchenko, Volodymyr

    2016-07-01

    So far 15 radio galaxies have been detected in the gamma-ray domain by CGRO/EGRET and Fermi/LAT, with a few detections also in the VHE range. We search for distinguishing parameters and estimate the total number of gamma-ray emitting radio galaxies that are potentially detectable by Fermi/LAT. We use Fermi/LAT data in comparison with X-ray and hard X-ray data in order to constrain basic parameters such as the total power of the inverse Compton branch and the position of its peak. We search for possible correlations between the radio, UV, X-ray, and gamma-ray domain and derive the number counts distribution. We then compare their properties with those of the radio galaxies in the 3CRR and SMS4 catalogues. The data show no correlation between the peak of the inverse Compton emission and its luminosity. For the gamma-ray detected radio galaxies the luminosities in the various bands are correlated, except for the UV band, but there is no indication of a correlation of peak frequency or luminosity with the spectral slopes in the X-ray or gamma-ray band. The comparison with other bright radio galaxies shows that the gamma-ray detected objects are among those that have the largest X-ray but rather moderate radio fluxes. Their UV and X-ray luminosities are similar, but gamma-ray detected radio galaxies are predominantly of type FR-I, while the 3CRR sample contains mainly FR-II objects. The number counts of the so far gamma-ray detected radio galaxies shows a very shallow slope, indicating that potentially a fraction of radio galaxies has been missed so far or has not been identified as such, although the predicted number of 22 ± 7 is consistent with the observed 15 objects.

  2. FIR galaxies with compact radio cores

    NASA Astrophysics Data System (ADS)

    Chini, R.; Biermann, P. L.; Kreysa, E.; Kuhr, H.; Mezger, P. G.; Schmidt, J.; Witzel, A.; Zensus, J. A.

    1987-07-01

    Comparing the IRAS point-source catalog (1985) with sources detected in a VLBI extragalactic radio source survey (Zensus et al., 1984), five FIR sources are found which all show compact radio cores. These objects have been observed with the 30-m MRT at Pico Veleta (Spain) at 1.2-mm wavelength to provide spectral coverage between IRAS and radio bands. The two galaxies among the five sources have luminosities of order 10 to the 12th solar luminosities in the FIR and thus may be super star bursters similar to Arp 220. On the other hand, all five objects have active galactic nuclei, and so the FIR luminosities may be powered by the nuclear activity. Since flat-spectrum radio sources have compact nuclear components, the 1-Jy catalog and its extension to lower flux densities (Kuehr et al., 1979 and 1981) are compared with the IRAS catalog, and a small number of additional active nuclei with strong emission in the FIR are identified. These objects can serve to study the competition between starbursts and nuclear activity to explain high FIR luminosities.

  3. An evolutionary sequence of young radio galaxies

    NASA Astrophysics Data System (ADS)

    Collier, J. D.; Norris, R. P.; Filipović, M. D.; Tothill, N. F. H.

    2016-02-01

    We have observed the faintest sample of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources to date, using the Australia Telescope Compact Array. We test the hypothesis that GPS and CSS sources are the youngest radio galaxies, place them into an evolutionary sequence along with a number of other young active galactic nuclei (AGN) candidates, and search for evidence of the evolving accretion mode and its relationship to star formation. GPS/CSS sources have very small radio jets that have been recently launched from the central supermassive black hole and grow in linear size as they evolve, which means that the linear size of the jets is an excellent indicator of the evolutionary stage of the AGN. We use high-resolution radio observations to determine the linear size of GPS/CSS sources, resolve their jets and observe their small-scale morphologies. We combine this with other multi-wavelength age indicators, including the spectral age, colours, optical spectra, and spectral energy distribution of the host galaxy, in an attempt to assemble all age indicators into a self-consistent model. We observe the most compact sources with Very Large Baseline Interferometry, which reveals their parsec-scale structures, giving us a range of source sizes and allowing us to test what fraction of GPS/CSS sources are young and evolving.

  4. Discovery of rare double-lobe radio galaxies hosted in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Sievers, Jonathan; Wadadekar, Yogesh; Hilton, Matt; Beelen, Alexandre

    2015-12-01

    Double-lobe radio galaxies in the local Universe have traditionally been found to be hosted in elliptical or lenticular galaxies. We report the discovery of four spiral-host double-lobe radio galaxies (J0836+0532, J1159+5820, J1352+3126, and J1649+2635) that are discovered by cross-matching a large sample of 187 005 spiral galaxies from SDSS DR7 (Sloan Digital Sky Survey Data Release 7) to the full catalogues of FIRST (Faint Images of the Radio Sky at Twenty-cm) and NVSS (NRAO VLA Sky Survey). J0836+0532 is reported for the first time. The host galaxies are forming stars at an average rate of 1.7-10 M⊙ yr-1 and possess supermassive black holes (SMBHs) with masses of a few times 108 M⊙. Their radio morphologies are similar to Fanaroff-Riley type II radio galaxies with total projected linear sizes ranging from 86 to 420 kpc, but their total 1.4-GHz radio luminosities are only in the range 1024-1025 W Hz-1. We propose that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions, mergers, and the presence of unusually massive SMBHs, such that the spiral structures are not destroyed. Only one of our sources (J1649+2635) is found in a cluster environment, indicating that processes other than accretion through cooling flows e.g. galaxy-galaxy mergers or interactions could be plausible scenarios for triggering radio-loud active galactic nuclei activity in spiral galaxies.

  5. Gamma-Rays from Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Madejski, Greg

    2016-07-01

    In this presentation, I will overview the properties of radio galaxies gleaned from observations of their gamma-ray emission, including that arising from the nuclear, and extended components. The gamma-ray spectra of radio galaxies measured by the Fermi-LAT and ground based Air Cerenkov telescopes will be considered in the context of their broad-band emission. The presentation will cover the most compelling models for emission processes, and will attempt to constrain the location of the nuclear gamma-ray emission. This will be compared to the observational properties of blazars, which are believed to be radio galaxies with jets pointing along our line of sight. Finally, I will discuss our best estimates for the contribution of unresolved radio galaxies to the diffuse gamma-ray emission.

  6. THE JET-DRIVEN OUTFLOW IN THE RADIO GALAXY SDSS J1517+3353: IMPLICATIONS FOR DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Rosario, D. J.; Taylor, G. B. E-mail: shieldsga@mail.utexas.ed E-mail: krista@mail.utexas.ed

    2010-06-10

    We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a complete search for double-peaked [O III] lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s{sup -1} and 500 km s{sup -1} with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet

  7. WHIM Environment of Giant Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Subrahmanyan, R.; Saripalli, L.; Safouris, V.; Hunstead, R. W.

    2008-08-01

    Simulation studies of the warm-hot intergalactic medium (WHIM) suggest that about half of the baryons at low redshifts---the `missing baryons'---reside in a warm-hot phase. This gas is expected to occupy the intergalactic space in unvirialized and moderate overdensities associated with the large scale structure in the universe. Direct detection of these baryons is difficult, and progress in our understanding of the state of the WHIM requires observational probes of the diffuse gas associated with filaments and sheets. Radio continuum images of the radio galaxy MSH J0505-2835 have been made using the Very Large Array (VLA). The double radio structure of this giant radio source has a projected linear size of 1.8 Mpc, extends well beyond the interstellar medium and any coronal halo associated with the host elliptical galaxy and is interacting with the ambient intergalactic medium. We have examined the 3-D structure in the large scale galaxy distribution in the vicinity of the radio source. The host elliptical galaxy is a member of a sheet-like galaxy overdensity that has a fractional density contrast of order 10. The radio source is located at the boundary between this moderate overdensity and an adjacent void and, therefore, the radio lobes of this giant radio source represent an interaction with ambient WHIM gas. We present a novel method for estimating the properties of the WHIM. The radio data have been used to infer the evolution in the radio source. A lower limit of 4 × 10-15 N m-2 is derived for the pressure in the synchrotron-emitting gas in the lobes of the radio source, which leads to an estimate of 3 × 108 K m-3 for the density-temperature product in the ambient WHIM. Assuming that galaxies trace the unseen WHIM gas in these large-scale structures that represent moderate overdensities, the densities and temperatures we may expect for the ambient WHIM environment---based on the local galaxy overdensity and assuming that the WHIM gas is heated by

  8. Multicolor surface photometry of powerful radio galaxies

    SciTech Connect

    Smith, E.P.

    1988-01-01

    CCD images of 72 powerful radio galaxies have been obtained with the KPNO 2.1m, 4m and CTIO 4m telescopes utilizing B, V, and R filters to study the colors and other photometric properties of these large systems. The GASP software package was used for the data reduction and detailed 2-d surface photometry. In addition, image modeling techniques were employed to investigate the contributions to galaxy properties by point-like nuclear sources seen in some of these galaxies. It was found that powerful radio galaxies show a much higher frequency than normal bright ellipticals of having optical morphologies which deviate from elliptical symmetry. Approximately 50% of the sample exhibit non-elliptically symmetric isophotes. These prominent distortions are present at surface brightness levels of {le} 25 V mag/(arc sec){sup 2}. In addition, a large fraction ({approximately}50%) of the remaining radio galaxies without the aforementioned morphological peculiarities have large isophotal twists ({Delta}P.A. {ge} 10{degree}) or ellipticity gradients. Significantly {approximately}50% of the galaxies with strong optical emission lines in their spectra display optically peculiar structures very similar to those found by Toomre and Toomre (1972) in their simulations of interacting disk galaxies. The galaxies with weak emission lines in their spectra are less frequently ({approximately}10%) distorted from elliptical shape. Those that are exhibit features like isophote twists, double nuclei and close companion galaxies embedded in the radio galaxy optical isophotes. The (B-V) colors of many of the powerful radio galaxies with strong emission lines are blue relative to normal giant ellipticals at the same redshift.

  9. The ultraviolet spectra of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Keel, William C.; Windhorst, Rogier A.

    1991-01-01

    New and archival IUE SWP spectra are reported for nine nearby radio galaxies (V is less than 15 mag), together with optical emissionlike data for these galaxies as well as a number of candidates with weaker line emission. Both their UV line and continuum properties, as well as their UV and UV-optical line ratios, are examined. Ly-alpha emission is found to be common among local radio galaxies, at modest luminosities (typically 10 exp 41-42 erg/s). No apparent relation is found between L(Ly-alpha) and radio power for the nearby radio galaxies alone. The Ly-alpha/H-alpha ratio in low power nearby radio galaxies is 2-5 times lower than the prediction for case B recombination. The destruction of Ly-alpha photons by grains during resonant scattering can explain the observed deficiency for reasonable metallicities. The nearby radio galaxies have in general a small C IV/Ly-alpha ratio (less than 0.1). Comparison of the C IV and Ly-alpha strengths with those in luminous AGN suggests that most of the UV continuum comes from the stellar population, and not from the AGN.

  10. RADIO STACKING REVEALS EVIDENCE FOR STAR FORMATION IN THE HOST GALAXIES OF X-RAY-SELECTED ACTIVE GALACTIC NUCLEI AT z < 1

    SciTech Connect

    Pierce, C. M.; Ballantyne, D. R.; Ivison, R. J.

    2011-11-20

    Nuclear starbursts may contribute to the obscuration of active galactic nuclei (AGNs). The predicted star formation rates (SFRs) are modest, and, for the obscured AGNs that form the X-ray background at z < 1, the associated faint radio emission lies just beyond the sensitivity limits of the deepest surveys. Here, we search for this level of star formation by studying a sample of 359 X-ray-selected AGNs at z < 1 from the Cosmic Evolution Survey field that are not detected by current radio surveys. The AGNs are separated into bins based on redshift, X-ray luminosity, obscuration, and mid-infrared characteristics. An estimate of the AGN contribution to the radio flux density is subtracted from each radio image, and the images are then stacked to uncover any residual faint radio flux density. All of the bins containing 24 {mu}m detected AGNs are detected with a signal-to-noise >3{sigma} in the stacked radio images. In contrast, AGNs not detected at 24 {mu}m are not detected in the resulting stacked radio images. This result provides strong evidence that the stacked radio signals are likely associated with star formation. The estimated SFRs derived from the radio stacks range from 3 M{sub Sun} yr{sup -1} to 29 M{sub Sun} yr{sup -1}. Although it is not possible to associate the radio emission with a specific region of the host galaxies, these results are consistent with the predictions of nuclear starburst disks in AGN host galaxies.

  11. SCUBA Observations of High Redshift Radio Galaxies

    SciTech Connect

    Reuland, M; Rottgering, H; van Breugel, W

    2003-03-11

    High redshift radio galaxies (HzRGs) are key targets for studies of the formation and evolution of massive galaxies.The role of dust in these processes is uncertain. We have therefore observed the dust continuum emission from a sample of z > 3 radio galaxies with the SCUBA bolometer array. We confirm and strengthen the result found by Archibald et al. (1), that HzRGs are massive starforming systems and that submillimeter detection rate appears to be primarily a strong function of redshift. We also observed HzRG-candidates that have so far eluded spectroscopic redshift determination. Four of these have been detected, and provide evidence that they may be extremely obscured radio galaxies, possibly in an early stage of their evolution.

  12. Compact radio sources in luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Parra, Rodrigo

    2007-08-01

    Radio interferometry is an observational technique of high sensitivity and incomparably high spatial resolution. Moreover, because radio waves can freely propagate through interstellar dust and gas, it allows the study of regions of the universe completely obscured at other wavelengths. This thesis reports the observational and theoretical results of my research during the past four years which are mostly based on interferometric radio data. The COLA sample is an infrared selected sample of active star forming galaxies. We conducted 6 cm VLA and VLBI snapshot observations of the northern half of this sample. The radio emission seen at VLA scales is consistent with being powered by star formation activity because it follows the far infrared to radio correlation. We detect 22% of the sample sources in our VLBI snapshots. Based on luminosity arguments, we argue that these sub-parsec VLBI sources are powered by AGN activity. Furthermore, we find that VLBI detections are preferentially found in sources whose VLA scale structures have the highest peak brightnesses suggesting a strong correlation between compact starburst and AGN activity. This observational result is consistent with the theoretical picture of an Eddington-limited nuclear starburst acting as the last valve in the pipeline transporting the gas from kiloparsec scales onto the accretion disc of a buried AGN. Arp 220 is the archetypical ultra luminous infrared galaxy. For many years this source has been known to harbour a compact (~100 pc) cluster of unresolved 18 cm bright sources believed to be bright core collapse supernovae. Using multiwavelength VLBI observations, we obtained for the first time radio spectra for 18 of these sources. We find that over a half of them have spectra consistent with young supernovae. The rest can be better explained as older supernova remnants interacting with the high density starburst ISM. This finding allowed us to constrain the number of possible scenarios for the Arp 220

  13. IRAS observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Rowan-Robinson, M.

    1985-01-01

    The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

  14. Jet Feedback on the Hosts of Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Lanz, L.; Ogle, P. M.; Alatalo, K.; Appleton, P. N.

    2016-06-01

    Feedback due to active galactic nuclei is one of the key components of the current paradigm of galaxy evolution; however our understanding of the process remains incomplete. Radio galaxies with strong rotational H_2 emission provide an interesting window into the effect of radio jet feedback on their host galaxies, since the large masses of warm (>100 K) H_2 cannot solely be heated by star formation, instead requiring jet-driven ISM turbulence to power the molecular emission. I will discuss the insights multiwavelength (X-ray to submm) observations of 22 H_2 luminous radio galaxies yield on the process of jet feedback in these galaxies and the impact on star formation activity. Specifically, I find that the diffuse X-ray and warm H_2 emission are consistent with both being powered by dissipation of the jet's mechanical energy into the interstellar medium (ISM) and that the resulting turbulence injected into the ISM by this process results in the suppression of star formation activity by a factor of 3--6. The hosts of these galaxies show a wide range of star formation activity and optical and IR colors, indicating a diversity of evolutionary states in which this process may be active.

  15. Fermi gamma-ray imaging of a radio galaxy.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Davis, D S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Finke, J; Focke, W B; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Georganopoulos, M; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F-W; Sambruna, R; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stawarz, Ł; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wallace, E; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M; Hardcastle, M J; Kazanas, D

    2010-05-01

    The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields. PMID:20360067

  16. Radio Galaxies in Cooling Cores: Insights from a Complete Sample

    NASA Astrophysics Data System (ADS)

    Eilek, J. A.; Owen, F. N.

    We have observed a new, complete, cooling-core sample with the VLA, in order to understand how the massive black hole in the central galaxy interacts with the local cluster plasma. We find that every cooling core is currently being energized by an active radio jet, which has probably been destabilized by its interaction with the cooling core. We argue that current models of cooling-core radio galaxies need to be improved before they can be used to determine the rate at which the jet is heating the cooling core. We also argue that the extended radio haloes we see in many cooling-core clusters need extended, in situ re-energization, which cannot be supplied solely by the central galaxy.

  17. Pair Cascades in Blazars and Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Roustazadeh Sheikhyousefi, Parisa

    2012-05-01

    Recently some intermediate BL Lac objects (IBL), low frequency peak BL Lac objects (LBL) and flat spectrum radio quasars (FSRQs) were detected as very high energy gamma-ray sources (VHE; E > 100 GeV) by the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope (MAGIC), the High Energy Stereoscopic System (H.E.S.S) and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). These discoveries suggest that VHE gamma-rays may be produced in all types of active galactic nuclei (AGN) and that this is not only a common property of high frequency peaked BL Lac objects (HBL). The detection of the radio galaxies M87, Cen A and NGC 1275 supports this idea. In those AGN, VHE photons may interact with low energy photons from the broadline region (BLR), accretion disk around the black hole or thermal infrared photons form a dust torus by photon-photon pair production if the total center-of-momentum frame energy is above threshold to produce an electron-positron pair. These particles can produce new high energy photons by Compton up-scattering, and again these high energy photons can interact with soft photons to produce a pair of particles. This process will continue, leading to a shower (cascade) of particles and radiation. As the shower develops, it will expand laterally. This may explain the detection of the radio galaxies as VHE gamma-ray sources. The central part of my Ph.D. research work deals with the theoretical simulation of very high energy gamma-ray induced pair cascades in blazars and radio galaxies. Gamma-rays from the core of the AGN interact with low energy photons from the AGN environment and produce pairs of electrons and positrons resulting in Compton supported pair cascades. I developed a Monte Carlo code which treats the processes of gamma-gamma absorption and pair production, gamma-ray and electron/positron propagation, and Compton scattering, tracking particle trajectories in full 3-dimensional geometry. I showed that even for a very weak

  18. Star formation and feedback from radio galaxies: Insights from large multiwavelength surveys

    NASA Astrophysics Data System (ADS)

    Pace, Cameron J.

    Active galactic nuclei (AGN) are believed to play an important role in the evolution of their host galaxies by influencing the galaxy's gas reservoirs. This may affect the growth of the galaxy's massive black hole and star formation in the host galaxy. I address two unanswered questions central to our understanding of AGN: what triggers AGN, and how and to what extent do they affect their host and neighboring galaxies? I study radio galaxies, which are a subset of AGN, because their radio jets may provide a natural feedback mechanism between the AGN and the host and neighboring galaxies. Previous studies, which were limited to small samples, produce conflicting results as to whether mergers or environmental effects lead to triggering. It is also uncertain whether radio galaxies have a net positive (via gas cloud collapse) or negative (via gas heating) effect on star formation. I use a large (˜7,200), statistically significant sample of radio galaxies, for which I extract photometric information from several large-scale, multiwavelength surveys. The radio galaxies are compared to a sample of control galaxies whose properties match those of the radio galaxies, except for their lack of radio activity. This approach allows me to determine the frequency of feedback events and whether radio galaxies are responsible. I derive and compare composite spectral energy distributions (SEDs) for the radio galaxies and control sample, and find a deficit of ultraviolet and infrared emission for slow accreting radio galaxies, suggesting that they may suppress star formation in their hosts. Fast accreting radio galaxies are found to have an infrared excess, which is characteristic of their high accretion rate and not a result of AGN feedback on star formation. I compare the populations of neighbor galaxies of the two samples and find that radio galaxies have an excess of neighbors within 100 kpc, which must play a role in triggering. My results also show that radio galaxies rarely

  19. EXAMINING THE RADIO-LOUD/RADIO-QUIET DICHOTOMY WITH NEW CHANDRA AND VLA OBSERVATIONS OF 13 UGC GALAXIES

    SciTech Connect

    Kharb, P.; Axon, D. J.; Robinson, A.; Capetti, A.; Balmaverde, B.; Chiaberge, M.; Macchetto, D.; Grandi, P.; Giovannini, G.; Montez, R.

    2012-04-15

    We present the results from new {approx}15 ks Chandra-ACIS and 4.9 GHz Very Large Array (VLA) observations of 13 galaxies hosting low-luminosity active galactic nuclei (AGNs). This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti and Balmaverde and Balmaverde and Capetti. The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC 6985). The new VLA observations improve the spatial resolution by a factor of 10: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as 'core', 'power-law', or 'intermediate' galaxies. With more than twice the number of 'power-law' and 'intermediate' galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in Fanaroff-Riley type I radio galaxies and the low-luminosity 'core' galaxies. This result highlights the fact that the 'radio-loud/radio-quiet' dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the 'core' and 'power-law galaxies (Gehan's Generalized Wilcoxon test probability p for the two classes being statistically similar is <10{sup -5}), but not in the optical-to-X-ray spectral indices (p = 0.25). Therefore, the primary difference between the 'core' and 'power-law' galaxies is in their ability to launch

  20. A Comparison of Radio-loud and Radio-quiet E+A Galaxies

    NASA Astrophysics Data System (ADS)

    Camacho, Yssavo; Wallack, Nicole; Learis, Anna; Liu, Charles

    2015-01-01

    E+A galaxies are systems undergoing an important evolutionary transition. Their optical spectra show significant numbers of A-type stars in an elliptical galaxy that has little to no star formation (SF). These galaxies have likely experienced a recent starburst (< 1 Gyr) followed by an even more recent quench in their SF. What caused their recent SF quench remains one of the most prominent questions surrounding E+A galaxies. Within the Goto (2007, MNRAS 381,187) catalogue of 564 E+A galaxies, there is a small fraction (~3%) that have detectable radio continuum emission from FIRST or NVSS. One possible cause for the observed radio continuum is active galactic nuclei (AGN). AGN feedback is believed to be important in galaxy evolution, including SF quenching (Dubois et al. 2013, MNRAS 433, 3297). In an effort to understand better the differences between radio-loud and radio-quiet E+As, we obtained and compared their spectral energy distributions (SEDs) using the publicly available data from SDSS, 2MASS, and WISE. We also compared them to the SEDs of other known galaxy types. We find that the radio-loud and radio-quiet samples exhibit statistically insignificant differences in the optical, near-infrared, and mid-infrared bands. We also compare the two samples on a (J-H) vs. (H-K) color-color diagram. This work was supported by the National Science Foundation via grant AST-1004583 to the CUNY College of Staten Island, and grant AST-1004591 to the American Museum of Natural History.

  1. Radio Galaxy Zoo: discovery of a poor cluster through a giant wide-angle tail radio galaxy

    NASA Astrophysics Data System (ADS)

    Banfield, J. K.; Andernach, H.; Kapińska, A. D.; Rudnick, L.; Hardcastle, M. J.; Cotter, G.; Vaughan, S.; Jones, T. W.; Heywood, I.; Wing, J. D.; Wong, O. I.; Matorny, T.; Terentev, I. A.; López-Sánchez, Á. R.; Norris, R. P.; Seymour, N.; Shabala, S. S.; Willett, K. W.

    2016-08-01

    We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of $z=0.0897$ for the E0-type host galaxy, 2MASX J08231289+0333016, leading to M$_r = -22.6$ and a $1.4\\,$GHz radio luminosity density of $L_{\\rm 1.4} = 5.5\\times10^{24}$ W Hz$^{-1}$. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley (FR) classes I and II. The projected largest angular size of $\\approx8\\,$arcmin corresponds to $800\\,$kpc and the full length of the source along the curved jets/trails is $1.1\\,$Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301,at $1.2-2.6\\times10^{43}$ erg s$^{-1}$ for assumed intra-cluster medium temperatures of $1.0-5.0\\,$keV. Our analysis of the environment surrounding RGZ J082312.9+033301 indicates that RGZ J082312.9+033301 lies within a poor cluster. The observed radio morphology suggests that (a) the host galaxy is moving at a significant velocity with respect to an ambient medium like that of at least a poor cluster, and that (b) the source may have had two ignition events of the active galactic nucleus with $10^7\\,$yrs in between. This reinforces the idea that an association between RGZ J082312.9+033301, and the newly discovered poor cluster exists.

  2. Radio Galaxy Zoo: discovery of a poor cluster through a giant wide-angle tail radio galaxy

    NASA Astrophysics Data System (ADS)

    Banfield, J. K.; Andernach, H.; Kapińska, A. D.; Rudnick, L.; Hardcastle, M. J.; Cotter, G.; Vaughan, S.; Jones, T. W.; Heywood, I.; Wing, J. D.; Wong, O. I.; Matorny, T.; Terentev, I. A.; López-Sánchez, Á. R.; Norris, R. P.; Seymour, N.; Shabala, S. S.; Willett, K. W.

    2016-08-01

    We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of z = 0.0897 for the E0-type host galaxy, 2MASX J08231289+0333016, leading to Mr = -22.6 and a 1.4 GHz radio luminosity density of L1.4 = 5.5 × 1024 W Hz-1. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley classes I and II. The projected largest angular size of ≈8 arcmin corresponds to 800 kpc and the full length of the source along the curved jets/trails is 1.1 Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301 at 1.2-2.6 × 1043 erg s-1 for assumed intracluster medium temperatures of 1.0-5.0 keV. Our analysis of the environment surrounding RGZ J082312.9+033301 indicates that RGZ J082312.9+033301 lies within a poor cluster. The observed radio morphology suggests that (a) the host galaxy is moving at a significant velocity with respect to an ambient medium like that of at least a poor cluster, and that (b) the source may have had two ignition events of the active galactic nucleus with 107 yr in between. This reinforces the idea that an association between RGZ J082312.9+033301 and the newly discovered poor cluster exists.

  3. Radio Galaxy Zoo: discovery of a poor cluster through a giant wide-angle tail radio galaxy

    NASA Astrophysics Data System (ADS)

    Banfield, J. K.; Andernach, H.; Kapińska, A. D.; Rudnick, L.; Hardcastle, M. J.; Cotter, G.; Vaughan, S.; Jones, T. W.; Heywood, I.; Wing, J. D.; Wong, O. I.; Matorny, T.; Terentev, I. A.; López-Sánchez, Á. R.; Norris, R. P.; Seymour, N.; Shabala, S. S.; Willett, K. W.

    2016-05-01

    We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of z = 0.0897 for the E0-type host galaxy, 2MASX J08231289+0333016, leading to Mr = -22.6 and a 1.4 GHz radio luminosity density of L1.4 = 5.5 × 1024 W Hz-1. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley (FR) classes I and II. The projected largest angular size of ≈8' corresponds to 800 kpc and the full length of the source along the curved jets/trails is 1.1 Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301 at 1.2 - 2.6 × 1043 erg s-1 for assumed intra-cluster medium temperatures of 1.0 - 5.0 keV. Our analysis of the environment surrounding RGZ J082312.9+033301 indicates that RGZ J082312.9+033301 lies within a poor cluster. The observed radio morphology infers that (a) the host galaxy is moving at a significant velocity with respect to an ambient medium like that of at least a poor cluster, and that (b) the source may have had two ignition events of the active galactic nucleus with 107 yrs in between. This reinforces the idea that an association between RGZ J082312.9+033301 and the newly discovered poor cluster exists.

  4. AN ACTIVE GALACTIC NUCLEUS DRIVEN SHOCK IN THE INTRACLUSTER MEDIUM AROUND THE RADIO GALAXY 3C 310

    SciTech Connect

    Kraft, R. P.; Nulsen, P. E. J.; Forman, W. R.; Jones, C.; Murray, S. S.; Croston, J. H.; Hardcastle, M. J.

    2012-04-10

    We present results from a 57.6 ks Chandra observation of the cluster gas associated with the fat-double radio galaxy 3C 310. We find a surface brightness discontinuity in the gas outside the southern radio lobe that we attribute to a shock driven by the supersonic inflation of this lobe {approx}180 kpc from the nucleus. Modeling the surface brightness/density jump, the shock has Mach number 1.5-1.9, depending on the assumptions one makes about the density profile and the nature of the energy input. There are not sufficient counts in the image to detect conclusively the temperature jump associated with the shock. The total mechanical energy of the outburst is 5 Multiplication-Sign 10{sup 60} erg. Assuming a Mach 1.9 shock, the age of the outburst is {approx}100 million yrs, and the time-averaged power of the outburst is {approx}1.3 Multiplication-Sign 10{sup 45} erg s{sup -1}. The power input is 100 times greater than the radiative losses of the gas within the radius of the shock. Most importantly, the equivalent heat input due to the entropy increase is roughly 10% of the thermal energy of the gas to the radius of the shock. 3C 310 is another example where regular outbursts of the observed strength with a duty cycle of 0.1 could offset the radiative losses of the gas near the Bondi radius and regulate feedback. We also detect a cool filamentary X-ray arm along the eastern periphery of the southern radio lobe. This arm is probably composed of low-entropy gas dredged up in the inflation of the radio plasma, similar to features seen in M87.

  5. Integrated Radio Continuum Spectra of Galaxies

    NASA Astrophysics Data System (ADS)

    Marvil, Joshua; Owen, Frazer; Eilek, Jean

    2015-01-01

    We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, α, of -0.69 between 1.4 and 4.85 GHz, -0.55 between 325 MHz and 1.4 GHz, and -0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately Δα = -0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% ± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later types

  6. Integrated radio continuum spectra of galaxies

    SciTech Connect

    Marvil, Joshua; Owen, Frazer; Eilek, Jean

    2015-01-01

    We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, α, of –0.69 between 1.4 and 4.85 GHz, –0.55 between 325 MHz and 1.4 GHz, and –0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately Δα = –0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% ± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later

  7. Powerful Activity in the Bright Ages. I. A Visible/IR Survey of High Redshift 3C Radio Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Hilbert, B.; Chiaberge, M.; Kotyla, J. P.; Tremblay, G. R.; Stanghellini, C.; Sparks, W. B.; Baum, S.; Capetti, A.; Macchetto, F. D.; Miley, G. K.; O'Dea, C. P.; Perlman, E. S.; Quillen, A.

    2016-07-01

    We present new rest-frame UV and visible observations of 22 high-z (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope's Wide Field Camera 3 instrument. Using a custom data reduction strategy in order to assure the removal of cosmic rays, persistence signal, and other data artifacts, we have produced high-quality science-ready images of the targets and their local environments. We observe targets with regions of UV emission suggestive of active star formation. In addition, several targets exhibit highly distorted host galaxy morphologies in the rest frame visible images. Photometric analyses reveal that brighter QSOs generally tend to be redder than their dimmer counterparts. Using emission line fluxes from the literature, we estimate that emission line contamination is relatively small in the rest frame UV images for the QSOs. Using archival VLA data, we have also created radio map overlays for each of our targets, allowing for analysis of the optical and radio axes alignment.

  8. Discovery of Giant Relic Radio Lobes Straddling the Classical Double Radio Galaxy 3C452

    NASA Astrophysics Data System (ADS)

    Sirothia, S. K.; Gopal-Krishna; Wiita, Paul J.

    2013-03-01

    We report the discovery of a pair of megaparsec size radio lobes of extremely steep spectrum straddling the well-known classical double radio source 3C452. The existence of such fossil lobes was unexpected since for the past several decades this powerful radio galaxy has been regarded as a textbook example of an edge-brightened double radio source of Fanaroff-Riley type II (FR II), which we now show to be a bona fide "double-double" radio galaxy (DDRG). Thus, 3C452 presents a uniquely robust example of recurrent nuclear activity in which the restarted jets are expanding non-relativistically within the relic synchrotron plasma from an earlier active phase and hence the inner double fed by them has evolved into a perfectly normal FR II radio source. This situation contrasts markedly with the strikingly narrow inner doubles observed in a few other DDRGs that have been interpreted in terms of compression of the synchrotron plasma of the relic outer lobes at the relativistic bow-shocks driven by the near ballistic propagation of the two inner jets through the relic plasma. A key ramification of this finding is that it cautions against the currently widespread use of FR II classical double radio sources for testing cosmological models and unification schemes for active galactic nuclei.

  9. DISCOVERY OF GIANT RELIC RADIO LOBES STRADDLING THE CLASSICAL DOUBLE RADIO GALAXY 3C452

    SciTech Connect

    Sirothia, S. K.; Gopal-Krishna; Wiita, Paul J. E-mail: krishna@ncra.tifr.res.in

    2013-03-01

    We report the discovery of a pair of megaparsec size radio lobes of extremely steep spectrum straddling the well-known classical double radio source 3C452. The existence of such fossil lobes was unexpected since for the past several decades this powerful radio galaxy has been regarded as a textbook example of an edge-brightened double radio source of Fanaroff-Riley type II (FR II), which we now show to be a bona fide ''double-double'' radio galaxy (DDRG). Thus, 3C452 presents a uniquely robust example of recurrent nuclear activity in which the restarted jets are expanding non-relativistically within the relic synchrotron plasma from an earlier active phase and hence the inner double fed by them has evolved into a perfectly normal FR II radio source. This situation contrasts markedly with the strikingly narrow inner doubles observed in a few other DDRGs that have been interpreted in terms of compression of the synchrotron plasma of the relic outer lobes at the relativistic bow-shocks driven by the near ballistic propagation of the two inner jets through the relic plasma. A key ramification of this finding is that it cautions against the currently widespread use of FR II classical double radio sources for testing cosmological models and unification schemes for active galactic nuclei.

  10. The peculiar radio galaxy 3C 433

    NASA Technical Reports Server (NTRS)

    Van Breugel, W.; Helfand, D.; Balick, B.; Heckman, T.; Miley, G.

    1983-01-01

    Radio, optical and X-ray observations are presented of the peculiar radio galaxy 3C 433, a Seyfert 2 object with luminosity an order of magnitude greater than that expected from its complex, shell-type morphology. Observations conducted at 6 and 12 cm with the VLA and at 21 cm with the Westerbork telescope show a striking asymmetry between the northern and southern radio emissions, and an overall X-shaped morphology. Optical observations using the Video Camera and High Gain Video Spectrometer on the 4-m telescope and the Intensified Image Dissector Scanner on the 2.1-m telescope at Kitt Peak confirm the identification of the source with a pair of bright galaxies. Observations in the X-ray from the Einstein Observatory IPC reveal an unresolved source at the position of 3C 433, as well as two serendipitous X-ray sources. The observations may be used to explain the overall structure of the source either in terms of tidal torquing or precessing models of double galaxies; however, it is argued that the tidal torquing model requires fewer assumptions to account for the brightness asymmetry.

  11. THE ROLE OF MERGER STAGE ON GALAXY RADIO SPECTRA IN LOCAL INFRARED-BRIGHT STARBURST GALAXIES

    SciTech Connect

    Murphy, Eric J.

    2013-11-01

    An investigation of the steep, high-frequency (i.e., ν ∼ 12 GHz) radio spectra among a sample of 31 local infrared-bright starburst galaxies is carried out in light of their Hubble-Space-Telescope-based merger classifications. Radio data covering as many as 10 individual bands allow for spectral indices to be measured over three frequency bins between 0.15 and 32.5 GHz. Sources having the flattest spectral indices measured at ∼2 and 4 GHz, arising from large free-free optical depths among the densest starbursts, appear to be in ongoing through post-stage mergers. The spectral indices measured at higher frequencies (i.e., ∼12 GHz) are steepest for sources associated with ongoing mergers in which their nuclei are distinct, but share a common stellar envelope and/or exhibit tidal tails. These results hold after excluding potential active galactic nuclei based on their low 6.2 μm polycyclic aromatic hydrocarbon equivalent widths. Consequently, the low-, mid-, and high-frequency spectral indices each appear to be sensitive to the exact merger stage. It is additionally shown that ongoing mergers, whose progenitors are still separated and share a common envelope and/or exhibit tidal tails, also exhibit excess radio emission relative to what is expected given the far-infrared/radio correlation, suggesting that there may be a significant amount of radio emission that is not associated with ongoing star formation. The combination of these observations, along with high-resolution radio morphologies, leads to a picture in which the steep high-frequency radio spectral indices and excess radio emission arise from radio continuum bridges and tidal tails that are not associated with star formation, similar to what is observed for so-called 'taffy' galaxies. This scenario may also explain the seemingly low far-infrared/radio ratios measured for many high-z submillimeter galaxies, a number of which are merger-driven starbursts.

  12. Jets and Outflows in Radio Galaxies: Implications for AGN Feedback

    NASA Astrophysics Data System (ADS)

    Torresi, Eleonora; Grandi, Paola; Costantini, Elisa; Palumbo, Giorgio G. C.

    One of the main debated astrophysical problems is the role of the AGN feedback in galaxy formation. It is known that massive black holes have a profound effect on the formation and evolution of galaxies, but how black holes and galaxies communicate is still an unsolved problem. For Radio Galaxies, feedback studies have mainly focused on jet/cavity systems in the most massive and X-ray luminous galaxy clusters. The recent high-resolution detection of warm absorbers in some Broad Line Radio Galaxies allow us to investigate the interplay between the nuclear engine and the surrounding medium from a different perspective. We report on the detection of warm absorbers in two Broad Line Radio Galaxies, 3C 382 and 3C 390.3, and discuss the physical and energetic properties of the absorbing gas. Finally, we attempt a comparison between radio-loud and radio-quiet outflows.

  13. COMPARISONS OF COSMOLOGICAL MAGNETOHYDRODYNAMIC GALAXY CLUSTER SIMULATIONS TO RADIO OBSERVATIONS

    SciTech Connect

    Xu Hao; Li Hui; Collins, David C.; Govoni, Federica; Murgia, Matteo; Norman, Michael L.; Cen Renyue; Feretti, Luigina; Giovannini, Gabriele E-mail: hli@lanl.gov E-mail: mlnorman@ucsd.edu E-mail: matteo@oa-cagliari.inaf.it E-mail: lferetti@ira.inaf.it

    2012-11-01

    Radio observations of galaxy clusters show that there are {mu}G magnetic fields permeating the intracluster medium (ICM), but it is hard to accurately constrain the strength and structure of the magnetic fields without the help of advanced computer simulations. We present qualitative comparisons of synthetic Very Large Array observations of simulated galaxy clusters to radio observations of Faraday rotation measure (RM) and radio halos. The cluster formation is modeled using adaptive mesh refinement magnetohydrodynamic simulations with the assumption that the initial magnetic fields are injected into the ICM by active galactic nuclei (AGNs) at high redshift. In addition to simulated clusters in Xu et al., we present a new simulation with magnetic field injections from multiple AGNs. We find that the cluster with multiple injection sources is magnetized to a similar level as in previous simulations with a single AGN. The RM profiles from simulated clusters, both |RM| and the dispersion of RM ({sigma}{sub RM}), are consistent at a first order with the radial distribution from observations. The correlations between the {sigma}{sub RM} and X-ray surface brightness from simulations are in a broad agreement with the observations, although there is an indication that the simulated clusters could be slightly overdense and less magnetized with respect to those in the observed sample. In addition, the simulated radio halos agree with the observed correlations between the radio power versus the cluster X-ray luminosity and between the radio power versus the radio halo size. These studies show that the cluster-wide magnetic fields that originate from AGNs and are then amplified by the ICM turbulence match observations of magnetic fields in galaxy clusters.

  14. Millimeter and submillimeter observations of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Knapp, G. R.; Patten, Brian M.

    1991-01-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals.

  15. A Sleeping Giant Awakened: Reignition of AGN Activity, Reborn Star Formation, and a Multiphase Outflow in one of the Largest Radio Galaxies Known

    NASA Astrophysics Data System (ADS)

    Tremblay, Grant; O'Dea, Christopher; Labiano, Alvaro; Baum, Stefi; McDermid, Richard; Combes, Francoise; Garcia-Burillo, Santiago; Davis, Timothy

    2014-08-01

    3C 236 is the second largest known radio galaxy and one of the largest objects in the known Universe. Its central AGN has recently reignited after a 10 Myr dormancy period, giving rise to a very young and compact radio source and a 1000 km/sec outflow of warm ionized and atomic HI gas. We propose GMOS-N IFU observations to resolve this outflow, determine its driver, and estimate the relative coupling efficiencies between the warm ionized, atomic, and cold molecular gas phases. We will assemble a much-needed spatially resolved Balmer decrement (extinction map) across the dramatic double dust lanes of this source, enabling high spatial resolution star formation rate, efficiency, and gas excitation and velocity maps. These will address several mysteries related to the very high star formation efficiency and the unique nature of the multiphase outflow in this source. 3C 236 is such a remarkable galaxy that whatever the results of the proposed observations, they will have wide-ranging implications for the triggering of star formation and AGN activity, their possibly coupled co-evolution, and the feedback effects of the latter on the former.

  16. A study of the x ray environment of radio galaxies

    NASA Technical Reports Server (NTRS)

    Rhee, George F.; Burns, Jack O.; Owen, Frazer

    1993-01-01

    We are currently working on a program to use extensive x-ray and radio databases to investigate the relationship between extended radio emission and environment in clusters of galaxies. The radio galaxy morphology is determined using VLA imaging and the x-ray properties are determined from Einstein IPC images. This study is motivated by the hypothesis that the key to understanding radio galaxies lies in the local environment. To test this hypothesis we have studied the detailed relationship between galaxy radio emission and the x-ray morphology of their parent clusters. In this pilot study we have used 35 radio sources found in 27 clusters. We have determined the position angle of the x-ray and radio emission, and x-ray and radio luminosities. The x-ray position was taken to be the position of peak flux of the subclump containing the radio galaxy. The radio position was taken to be the position of the galaxy. We do not find a correlation between the x-ray and radio source position angle. This remains true when the sample is divided into subsamples according to radio morphology (wide angle tail, twin jet, narrow angle tail galaxies). We find a weak correlation between the radio source luminosity and the x-ray luminosity. We have computed the distance from the radio galaxy position to the center of the x-ray clump. We find a mean distance from the x-ray clump center of 0.16 Mpc for the radio galaxies in this sample. The mean distance to the nearest clump of x-ray emission is typically half the distance to the optical cluster center. We thus find strong evidence that radio galaxies are located very close to clumps of x-ray emission. These subclumps are not always affiliated with the central cluster x-ray emission. This supports our hypothesis that x-ray emission may provide a key to understanding radio galaxy morphology. We find evidence that radio galaxies occur in clusters that contain prominent substructures. Radio galaxies may thus provide an added diagnostic of

  17. Molecular gas in nearby Early-Type Powerful Classical Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Leon, S.; Lim, J.; Combes, F.; Dinh-v-Trung

    We report the detection of CO(1-0) and CO(2-1) emission from the central region of nearby 3CR radio galaxies(z<0.03). Out of 21 galaxies, 8 have been detected in, at least, one of the two CO transitions. The total molecular gas content is below 109 Msun. Their individual CO emission exhibit, for 5 cases, a double-horned line profile that is characteristic of a disk with a central depression at the rising part of its rotation cu or ring distributions of the molecular gas is consistent with the ob dust disks or rings detected optically in the cores of the galaxies. their gas originates from the mergers of two gas-rich disk galaxies, explain the molecular gas in other radio galaxies, then these galaxie long time ago (few Gyr or more) but their remnant elliptical galaxies (last 107 years or less) become active radio galaxies. Instead, we cannibalism of gas-rich galaxies provide a simpler explanation for th molecular gas in the elliptical hosts of radio galaxies (Lim et al. 2 Given the transient nature of their observed disturbances, these gala active in radio soon after the accretion event when sufficient molecu in their nuclei.

  18. RADIO GALAXY FEEDBACK IN X-RAY-SELECTED GROUPS FROM COSMOS: THE EFFECT ON THE INTRACLUSTER MEDIUM

    SciTech Connect

    Giodini, S.; Finoguenov, A.; Boehringer, H.; Pierini, D.; Smolcic, V.; Massey, R.; BIrzan, L.; Zamorani, G.; Oklopcic, A.; Pratt, G. W.; Koekemoer, A. M.; Salvato, M.; Sanders, D. B.; Kartaltepe, J. S.; Thompson, D.

    2010-05-01

    We quantify the importance of the mechanical energy released by radio galaxies inside galaxy groups. We use scaling relations to estimate the mechanical energy released by 16 radio-active galactic nuclei located inside X-ray-detected galaxy groups in the COSMOS field. By comparing this energy output to the host groups' gravitational binding energy, we find that radio galaxies produce sufficient energy to unbind a significant fraction of the intragroup medium. This unbinding effect is negligible in massive galaxy clusters with deeper potential wells. Our results correctly reproduce the breaking of self-similarity observed in the scaling relation between entropy and temperature for galaxy groups.

  19. Radio emission from dusty galaxies observed by AKARI

    NASA Astrophysics Data System (ADS)

    Pepiak, A.; Pollo, A.; Takeuchi, T. T.; Solarz, A.; Jurusik, W.

    2014-10-01

    We probe radio-infrared correlation for two samples of extragalactic sources from the local Universe from the AKARI All-Sky Catalogue. The first, smaller sample (1053 objects) was constructed by the cross-correlation of the AKARI/FIS All-Sky Survey Bright Source Catalogue, the AKARI IRC All-Sky Survey Point Source Catalogue and the NRAO VLA Sky Survey, i.e. it consists of sources detected in the mid- and far-infrared by AKARI, and at the 1.4 GHz radio frequency by NRAO. The second, larger sample (13,324 objects) was constructed by the cross-correlation of only the AKARI/FIS All-Sky Survey Bright Source Catalogue and the NRAO VLA Sky Survey, i.e. it consists of sources detected in the far-infrared and radio, without a condition to be detected in the mid-infrared. Additionally, all objects in both samples were identified as galaxies in the NED and/or SIMBAD databases, and a part of them is known to host active galactic nuclei (AGNs). For the present analysis, we have restricted our samples only to sources with known redshift z. In this paper, we analyse the far-infrared-radio correlation for both of these samples. We compare the ratio of infrared and radio emission from normal star-forming dusty galaxies and AGNs in both samples. For the smaller sample we obtained =2.14 for AGNs and =2.27 for normal galaxies, while for the larger sample =2.15 for AGNs and =2.22 for normal galaxies. An average value of the slope in both samples is ~2.2, which is consistent with the previous measurements from the literature.

  20. A VERY LARGE ARRAY RADIO SURVEY OF EARLY-TYPE GALAXIES IN THE VIRGO CLUSTER

    SciTech Connect

    Capetti, Alessandro; Kharb, Preeti; Axon, David J.; Merritt, David; Baldi, Ranieri D.

    2009-12-15

    We present the results of an 8.4 GHz Very Large Array radio survey of early-type galaxies extracted from the sample selected by Cote and collaborators for the Advanced Camera for Surveys Virgo Cluster Survey. The aim of this survey is to investigate the origin of radio emission in early-type galaxies and its link with the host properties in an unexplored territory toward the lowest levels of both radio and optical luminosities. Radio images, available for all 63 galaxies with B {sub T} < 14.4, show the presence of a compact radio source in 12 objects, with fluxes spanning from 0.13 mJy to 2700 mJy. The remaining 51 galaxies, undetected at a flux limit of {approx}0.1 mJy, have radio luminosities L {approx}< 4 x 10{sup 18} W Hz{sup -1}. The fraction of radio-detected galaxies are a strong function of stellar mass, in agreement with previous results: none of the 30 galaxies with M {sub *} < 1.7 x 10{sup 10} M {sub sun} is detected, while 8 of the 11 most massive galaxies have radio cores. There appears to be no simple relation between the presence of a stellar nucleus and radio emission. In fact, we find radio sources associated with two nucleated galaxies, but the majority of nucleated objects are not a radio emitter above our detection threshold. A multiwavelength analysis of the active galactic nucleus (AGN) emission, combining radio and X-ray data, confirms the link between optical surface brightness profile and radio loudness in the sense that the bright core galaxies are associated with radio-loud AGNs, while non-core galaxies host radio-quiet AGNs. Not all radio-detected galaxies have an X-ray nuclear counterpart (and vice versa). A complete census of AGNs (and supermassive black holes, SMBHs) thus requires observations, at least, in both bands. Nonetheless, there are massive galaxies in the sample, expected to host a large SMBH (M {sub BH} {approx} 10{sup 8} M {sub sun}), whose nuclear emission eludes detection despite their proximity and the depth and the

  1. Compact radio sources in the spiral galaxy M83

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Long, Knox S.; Winkler, P. Frank; Kuntz, Kip; Blair, William

    2011-04-01

    We are doing a multiband study of the stellar life cycle in the grand-design spiral galaxy M83, one of the most actively star-forming systems in the local Universe. We have already obtained exceptional optical coverage with HST and Magellan, and we have been awarded 750 ks of Chandra time this year. Now we propose an ATCA radio study, crucial for integrating the optical and X-ray studies. The radio study will allow us to achieve three main objectives: a) monitor the long-term evolution of three historical supernovae observed in M83 over the last 100 years, and hence constrain the late stages of evolution of their stellar progenitors; b) determine the distribution, radio spectral index and other physical properties of different types of young supernova remnants; c) resolve the morphology and search for variability of the nuclear sources: in particular, we will investigate the radio evidence for a double nucleus. In addition, we will study the aligned triple source just outside the nucleus: the traditional interpretation is that it is a background radio galaxy, but it has recently been suggested that it could be a recoiling nuclear black hole in M83.

  2. Massive Elliptical Galaxies at High Redshift: NICMOS Imaging of z~1 Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Zirm, Andrew W.; Dickinson, Mark; Dey, Arjun

    2003-03-01

    We present deep, ~1.6 μm, continuum images of 11 high-redshift (0.811radio galaxies observed with NICMOS on board the Hubble Space Telescope. Our NICMOS images probe the rest-frame optical light where stars are expected to dominate the galaxy luminosity. The rest-frame ultraviolet light of eight of these galaxies demonstrates the well-known ``alignment effect,'' with extended and often complex morphologies elongated along an axis close to that of the Fanaroff-Riley type II (FRII) radio source. As has been previously noted from ground-based near-infrared imaging, most of the radio galaxies have rounder, more symmetric morphologies at rest-frame optical wavelengths. Here we show the most direct evidence that in most cases the stellar hosts are normal elliptical galaxies with r1/4-law light profiles. For a few galaxies, very faint traces (less than 4% of the total H-band light) of the UV-bright aligned component are also visible in the infrared images. We derive both the effective radius and surface brightness for nine of 11 sample galaxies by fitting one- and two-dimensional surface-brightness models to them. We compare the high-redshift radio galaxies to lower redshift counterparts. We find that their sizes are similar to those of local FRII radio source hosts and are in general larger than other local galaxies. The derived host galaxy luminosities are very high and lie at the bright end of luminosity functions constructed at similar redshifts. This indicates that the high-redshift radio galaxies are likely rare, massive sources. The galaxies in our sample are also brighter than the rest-frame size-surface-brightness locus defined by the low-redshift sources. Passive evolution roughly aligns the z~1 galaxies with the low-redshift samples with a slope equal to 4.7. This value is intermediate between the canonical Kormendy relation (~3.5) and a constant luminosity line (=5). The optical host is sometimes centered on a local minimum in the rest-frame UV

  3. Radio continuum properties of luminous infrared galaxies. Identifying the presence of an AGN in the radio

    NASA Astrophysics Data System (ADS)

    Vardoulaki, E.; Charmandaris, V.; Murphy, E. J.; Diaz-Santos, T.; Armus, L.; Evans, A. S.; Mazzarella, J. M.; Privon, G. C.; Stierwalt, S.; Barcos-Muñoz, L.

    2015-02-01

    Context. Luminous infrared galaxies (LIRGs) are systems enshrouded in dust, which absorbs most of their optical/UV emission and radiates it again in the mid- and far-infrared. Radio observations are largely unaffected by dust obscuration, enabling us to study the central regions of LIRGs in an unbiased manner. Aims: The main goal of this project is to examine how the radio properties of local LIRGs relate to their infrared spectral characteristics. Here we present an analysis of the radio continuum properties of a subset of the Great Observatories All-sky LIRG Survey (GOALS), which consists of 202 nearby systems (z< 0.088). Our radio sample consists of 35 systems, containing 46 individual galaxies, that were observed at both 1.49 and 8.44 GHz with the VLA with a resolution of about 1 arcsec (FWHM). The aim of the project is to use the radio imagery to probe the central kpc of these LIRGs in search of active galactic nuclei (AGN). Methods: We used the archival data at 1.49 and 8.44 GHz to create radio-spectral-index maps using the standard relation between flux density Sν and frequency ν, Sν ~ ν- α, where α is the radio spectral index. By studying the spatial variations in α, we classified the objects as radio-AGN, radio-SB, and AGN/SB (a mixture). We identified the presence of an active nucleus using the radio morphology, deviations from the radio/infrared correlation, and spatially resolved spectral index maps, and then correlated this to the usual mid-infrared ([NeV]/[NeII] and [OIV]/[NeII] line ratios and equivalent width of the 6.2 μm PAH feature) and optical (BPT diagram) AGN diagnostics. Results: We find that 21 out of the 46 objects in our sample (~45%) are radio-AGN, 9 out of the 46 (~20%) are classified as starbursts (SB) based on the radio analysis, and 16 (~35%) are AGN/SB. After comparing to other AGN diagnostics we find 3 objects out of the 46 (~7%) that are identified as AGN based on the radio analysis, but are not classified as such based on

  4. A case for radio galaxies as the sources of IceCube's astrophysical neutrino flux

    NASA Astrophysics Data System (ADS)

    Hooper, Dan

    2016-09-01

    We present an argument that radio galaxies (active galaxies with mis-aligned jets) are likely to be the primary sources of the high-energy astrophysical neutrinos observed by IceCube. In particular, if the gamma-ray emission observed from radio galaxies is generated through the interactions of cosmic-ray protons with gas, these interactions can also produce a population of neutrinos with a flux and spectral shape similar to that measured by IceCube. We present a simple physical model in which high-energy cosmic rays are confined within the volumes of radio galaxies, where they interact with gas to generate the observed diffuse fluxes of neutrinos and gamma rays. In addition to simultaneously accounting for the observations of Fermi and IceCube, radio galaxies in this model also represent an attractive class of sources for the highest energy cosmic rays.

  5. The new class of FR 0 radio galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, R. D.; Capetti, A.; Giovannini, G.

    2016-02-01

    Are the FRI and FRII radio galaxies representative of the radio-loud (RL) AGN population in the local Universe? Recent studies on the local low-luminosity radio sources cast lights on an emerging population of compact radio galaxies which lack extended radio emission. In a pilot JVLA project, we study the high-resolution images of a small but representative sample of this population. The radio maps reveal compact unresolved or slightly resolved radio structures on a scale of 1-3 kpc. We find that these RL AGN live in red massive early-type galaxies, with large black hole masses (≳ 108 M⊙), and spectroscopically classified as Low Excitation Galaxies, all characteristics typical of FRI radio galaxies which they also share the same nuclear luminosity with. However, they are more core dominated (by a factor of ˜ 30) than FRIs and show a clear deficit of extended radio emission. We call these sources ``FR0'' to emphasize their lack of prominent extended radio emission. A posteriori, other compact radio sources found in the literature fulfill the requirements for a FR0 classification. Hence, the emerging FR0 population appears to be the dominant radio class of the local Universe. Considering their properties we speculate on their possible origins and the possible cosmological scenarios they imply.

  6. Deep HST imaging of distant weak radio and field galaxies

    NASA Technical Reports Server (NTRS)

    Windhorst, R. A.; Gordon, J. M.; Pascarelle, S. M.; Schmidtke, P. C.; Keel, W. C.; Burkey, J. M.; Dunlop, J. S.

    1994-01-01

    We present deep Hubble Space Telescope (HST) Wide-Field Camera (WFC) V- and I-band images of three distant weak radio galaxies with z = 0.311-2.390 and seven field galaxies with z = 0.131-0.58. The images were deconvolved with both the Lucy and multiresolution CLEAN methods, which yield a restoring Full Width at Half Maximum (FWHM) of less than or equal to 0.2 sec, (nearly) preserve photons and signal-to-noise ratio at low spatial frequencies, and produce consistent light profiles down to our 2 sigma surface brightness sensitivity limit of V approximately 27.2 and I approximately 25.9 mag/sq arcsec. Multi-component image modeling was used to provide deconvolution-independent estimates of structural parameters for symmetric galaxies. We present 12-band (m(sub 2750) UBVRIgriJHK) photometry for a subset of the galaxies and bootstrap the unknown FOC/48 zero point at 2750 A in three independent ways (yielding m(sub 2750) = 21.34 +/- 0.09 mag for 1.0 e(-)/s). Two radio galaxies with z = 0.311 and 0.528, as well as one field galaxy with z = 0.58, have the colors and spectra of early-type galaxies, and a(exp 1/4)-like light profiles in the HST images. The two at z greater than 0.5 have little or no color gradients in V - I and are likely giant ellipticals, while the z = 0.311 radio galaxy has a dim exponential disk and is likely an S0. Six of the seven field galaxies have light profiles that indicate (small) inner bulges following a(exp 1/4) laws and outer exponential disks, both with little or no color gradients. These are (early-type) spiral galaxies with z = 0.131-0.528. About half have faint companions or bars. One shows lumpy structure, possibly a merger. The compact narrow-line galaxy 53W002 at z = 2.390 has less than or = 30% +/- 10% of its HST V and I flux in the central kiloparsec (due to its weak Active Galactic Nucleus (AGN)). Most of its light (V approximately equal to 23.3) occurs in a symmetric envelope with a regular a(exp 1/4)-like profile of effective

  7. The relation between infrared and radio emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Helou, George

    1991-01-01

    A remarkable correlation between the far infrared and the radio continuum emission of star forming galaxies was one of the early results based on IRAS data, and has remained one of the most intriguing. Recent work has extended the correlation to early type galaxies, revealing a slightly different ratio in lenticulars. When radio and infrared maps of disk galaxies are compared, the radio disks appear systematically more diffuse. This has been interpreted as a manifestation of the diffusion of cosmic-ray electrons, and has allowed a fresh look at the behavior of magnetic fields and cosmic rays in spiral galaxies, and at their relation to the rest of the interstellar medium.

  8. Size dependence of the radio-luminosity-mechanical-power correlation in radio galaxies

    SciTech Connect

    Shabala, S. S.; Godfrey, L. E. H.

    2013-06-01

    We examine the relationship between source radio luminosity and kinetic power in active galactic nucleus jets. We show that neglecting various loss processes can introduce a systematic bias in the jet powers inferred from radio luminosities for a sample of radio galaxies. This bias can be corrected for by considering source size as well as radio luminosity; effectively the source size acts as a proxy for source age. Based on a sample of Fanaroff-Riley Type II radio sources with jet powers derived from the measured hotspot parameters, we empirically determine a new expression for jet power that accounts for the source size, (Q{sub jet}/10{sup 36} W)=1.5{sub −0.8}{sup +1.8}(L{sub 151}/10{sup 27} W Hz{sup −1}){sup 0.8}(1+z){sup 1.0}(D/kpc){sup 0.58±0.17}, where D is source size and L {sub 151} the 151 MHz radio luminosity. By comparing a flux-limited and volume-limited sample, we show that any derived radio-luminosity-jet-power relation depends sensitively on sample properties, in particular the source size distribution and the size-luminosity correlation inherent in the sample. Such bias will affect the accuracy of the kinetic luminosity function derived from lobe radio luminosities and should be treated with caution.

  9. The column density distribution of hard X-ray radio galaxies

    NASA Astrophysics Data System (ADS)

    Panessa, F.; Bassani, L.; Landi, R.; Bazzano, A.; Dallacasa, D.; La Franca, F.; Malizia, A.; Venturi, T.; Ubertini, P.

    2016-09-01

    In order to investigate the role of absorption in active galactic nuclei (AGN) with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/Imager on Board the Integral Satellite (IBIS) and Swift/The Burst Alert Telescope (BAT) AGN catalogues (˜7-10 per cent of the total AGN population). The 64 radio galaxies have a typical FR II radio morphology and are characterized by high 20-100 keV luminosities (from 1042 to 1046 erg s-1) and high Eddington ratios (log LBol/LEdd typically larger than ˜0.01). The observed fraction of absorbed AGN (NH > 1022 cm-2) is around 40 per cent among the total sample, and ˜75 per cent among type 2 AGN. The majority of obscured AGN are narrow-line objects, while unobscured AGN are broad-line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ˜2-3 per cent, in comparison with the 5-7 per cent found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non-radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

  10. Radio galaxies in ZFOURGE/NMBS: no difference in the properties of massive galaxies with and without radio-AGN out to z = 2.25

    NASA Astrophysics Data System (ADS)

    Rees, G. A.; Spitler, L. R.; Norris, R. P.; Cowley, M. J.; Papovich, C.; Glazebrook, K.; Quadri, R. F.; Straatman, C. M. S.; Allen, R.; Kacprzak, G. G.; Labbe, I.; Nanayakkara, T.; Tomczak, A. R.; Tran, K.-V.

    2016-01-01

    In order to reproduce the high-mass end of the galaxy mass distribution, some process must be responsible for the suppression of star formation in the most massive of galaxies. Commonly active galactic nuclei (AGN) are invoked to fulfil this role, but the exact means by which they do so is still the topic of much debate, with studies finding evidence for both the suppression and enhancement of star formation in AGN hosts. Using the ZFOURGE (FourStar Galaxy Evolution) and NMBS (Newfirm Medium Band Survey) galaxy surveys, we investigate the host galaxy properties of a mass-limited (M ≥ 1010.5 M⊙), high-luminosity (L1.4 > 1024 W Hz-1) sample of radio-loud AGN to a redshift of z = 2.25. In contrast to low-redshift studies, which associate radio-AGN activity with quiescent hosts, we find that the majority of z > 1.5 radio-AGN are hosted by star-forming galaxies. Indeed, the stellar populations of radio-AGN are found to evolve with redshift in a manner that is consistent with the non-AGN mass-similar galaxy population. Interestingly, we find that the radio-AGN fraction is constant across a redshift range of 0.25 ≤ z < 2.25, perhaps indicating that the radio-AGN duty cycle has little dependence on redshift or galaxy type. We do however see a strong relation between the radio-AGN fraction and stellar mass, with radio-AGN becoming rare below ˜1010.5 M⊙ or a halo mass of 1012 M⊙. This halo-mass threshold is in good agreement with simulations that initiate radio-AGN feedback at this mass limit. Despite this, we find that radio-AGN host star formation rates are consistent with the non-AGN mass-similar galaxy sample, suggesting that while radio-AGN are in the right place to suppress star formation in massive galaxies they are not necessarily responsible for doing so.

  11. The environments of high-redshift radio galaxies and quasars: probes of protoclusters

    NASA Astrophysics Data System (ADS)

    Orsi, Álvaro A.; Fanidakis, Nikos; Lacey, Cedric G.; Baugh, Carlton M.

    2016-03-01

    We use the GALFORM semi-analytical model to study high-density regions traced by radio galaxies and quasars at high redshifts. We explore the impact that baryonic physics has upon the properties of galaxies in these environments. Star-forming emission-line galaxies (Ly α and H α emitters) are used to probe the environments at high redshifts. Radio galaxies are predicted to be hosted by more massive haloes than quasars, and this is imprinted on the amplitude of galaxy overdensities and cross-correlation functions. We find that Ly α radiative transfer and active galactic nucleus feedback indirectly affect the clustering on small scales and also the stellar masses, star formation rates and gas metallicities of galaxies in dense environments. We also investigate the relation between protoclusters associated with radio galaxies and quasars, and their present-day cluster descendants. The progenitors of massive clusters associated with radio galaxies and quasars allow us to determine an average protocluster size in a simple way. Overdensities within the protoclusters are found to correlate with the halo descendant masses. We present scaling relations that can be applied to observational data. By computing projection effects due to the wavelength resolution of modern spectrographs and narrow-band filters, we show that the former have enough spectral resolution to map the structure of protoclusters, whereas the latter can be used to measure the clustering around radio galaxies and quasars over larger scales to determine the mass of dark matter haloes hosting them.

  12. Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm

    SciTech Connect

    Stawarz, L.; Sikora, M.; Lasota, J.-P.

    2007-10-15

    We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. We find that AGNs form two distinct and well separated sequences on the radio-loudness -- Eddington-ratio plane. We argue that these sequences mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that another parameter in addition to the accretion rate must play a role in determining the jet production efficiency in active galactic nuclei, and that this parameter is related to properties of the host galaxy. The revealed host-related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. We argue that the huge difference between the radio-loudness reachable by AGNs in disc and elliptical galaxies can be explained by the scenario according to which the spin of a black hole determines the outflows power, and central black holes can reach large spins only in early type galaxies (following major mergers), and not (in a statistical sense) in spiral galaxies.

  13. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  14. Chandra observations of dying radio sources in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-12-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims: We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods: We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results: The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions: We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  15. Evolution of clouds in radio galaxy cocoons

    NASA Astrophysics Data System (ADS)

    Mellema, G.; Kurk, J. D.; Röttgering, H. J. A.

    2002-11-01

    This letter presents a numerical study of the evolution of an emission line cloud of initial density 10 cm-3, temperature 104 K, and size 200 pc, being overtaken by a strong shock wave. Whereas previous simple models proposed that such a cloud would either be completely destroyed, or simply shrink in size, our results show a different and more complex behaviour: due to rapid cooling, the cloud breaks up into many small and dense fragments, which can survive for a long time. We show that such rapid cooling behaviour is expected for a wide range of cloud and shock properties. This process applies to the evolution of emission line clouds being overtaken by the cocoon of a radio jet. The resulting small clouds would be Jeans unstable, and form stars. Our results thus give theoretical credibility to the process of jet induced star formation, one of the explanations for the alignment of the optical/UV and radio axis observed in high redshift radio galaxies.

  16. Ultraluminous infrared galaxies and the radio-optical correlation for quasars

    NASA Technical Reports Server (NTRS)

    Lonsdale, Carol J.; Smith, Harding E.; Lonsdale, Colin J.

    1995-01-01

    Through analysis of available optical spectrophotometric data and radio flux density measurements in the literature, it is demonstrated that a good correlation exists between the radio power and bolometric luminosity of the optically-selected OSOs in the Bright Quasar Sample (BOS) of Schmidt and Green (1983). We have recently used VLBI measurements of a sample of ultraluminous infrared galaxies to infer the likely existence of radio-quiet Active Galactic Nuclei (AGNs) deeply enshrouded in dust within their nuclei (Lonsdale, Smith, and Lonsdale 1993). We employ the radio-bolometric luminosity correlation for the BQS quasars to test whether these hypothetical buried AGNs can be energetically responsible for the observed far-infrared luminosities of the ultraluminous infrared galaxies. The ultraluminous infrared galaxies are shown to follow the same relation between radio core power and bolometric luminosity as the radio-quiet QSOs, suggesting that buried AGNs can account for essentially all the observed infrared luminosity, and raising the possibility that any starburst which may be in progress may not be energetically dominant. The broader implications of the radio-optical correlation in quasars for AGNs and luminous infrared galaxy models and the use of radio astronomy as a probe of the central powerhouse in radio quiet AGNs and luminous infrared galaxies are briefly discussed.

  17. Steep radio spectra in high-redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.; Chen, Wan

    1991-01-01

    The generic spectrum of an optically thin synchrotron source steepens by 0.5 in spectral index from low frequencies to high whenever the source lifetime is greater than the energy-loss timescale for at least some of the radiating electrons. Three effects tend to decrease the frequency nu(b) of this spectral bend as the source redshift increases: (1) for fixed bend frequency nu* in the rest frame, nu(b) = nu*/(1 + z); (2) losses due to inverse Compton scattering the microwave background rise with redshift as (1 + z) exp 4, so that, for fixed residence time in the radiating region, the energy of the lowest energy electron that can cool falls rapidly with increasing redshift; and (3) if the magnetic field is proportional to the equipartition field and the emitting volume is fixed or slowly varying, flux-limited samples induce a selection effect favoring low nu* at high z because higher redshift sources require higher emissivity to be included in the sample, and hence have stronger implied fields and more rapid synchrotron losses. A combination of these effects may explain the trend observed in the 3CR sample for higher redshift radio galaxies to have steeper spectra, and the successful use of ultrasteep spectrum surveys to locate high-redshift galaxies.

  18. Multiwavelength Study of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh

    2010-08-01

    Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Demographically, Seyfert galaxies may account for ~ 10% of the entire population of active galaxies in the nearby universe. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' Seyferts, based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Detection of broad permitted emission lines in some Seyfert type 2s observed in the polarized light laid the foundation of the Seyfert unification scheme, which hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN (Antonucci and Miller 1985; Antonucci 1993). The primary objective of this thesis work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. The key issue in testing the Seyfert unification scheme has been acquiring a well defined rigorously selected Seyfert sample. I have argued that the Seyfert samples based on flux limited surveys at optical, IR, UV and X-ray are likely to be biased against obscured and faint sources. In order to test the predictions of Seyfert unification scheme I use a sample based on properties (i.e., cosmological redshift, [OIII] emission line luminosity, absolute bulge magnitude, absolute stellar magnitude of the host galaxy and the Hubble stage of the host galaxy) that are independent to the orientation of the obscuring torus, host galaxy and the AGN axis. Furthermore, two Seyfert subtypes of our sample have matched distributions in the orientation-independent properties and this ensures the intrinsic similarity between two Seyfert subtypes within the

  19. The Radio Luminosity Function and Galaxy Evolution in the Coma Cluster

    NASA Technical Reports Server (NTRS)

    Miller, Neal A.; Hornschemeier, Ann E.; Mabasher, Bahram; Brudgesm Terrry J.; Hudson, Michael J.; Marzke, Ronald O.; Smith, Russell J.

    2008-01-01

    We investigate the radio luminosity function and radio source population for two fields within the Coma cluster of galaxies, with the fields centered on the cluster core and southwest infall region and each covering about half a square degree. Using VLA data with a typical rms sensitivity of 28 (mu)Jy per 4.4" beam, we identify 249 radio sources with optical counterparts brighter than r = 22 (equivalent to M(sub r) = -13 for cluster member galaxies). Comprehensive optical spectroscopy identifies 38 of these as members of the Coma cluster, evenly split between sources powered by an active nucleus and sources powered by active star formation. The radio-detected star-forming galaxies are restricted to radio luminosities between about 10(exp 21) and 10(exp 22) W/Hz, an interesting result given that star formation dominates field radio luminosity functions below about 10(exp 23) W/Hz. The majority of the radio-detected star-forming galaxies have characteristics of starbursts, including high specific star formation rates and optical spectra with strong emission lines. In conjunction with prior studies on post-starburst galaxies within the Coma cluster, this is consistent with a picture in which late-type galaxies entering Coma undergo a starburst prior to a rapid cessation of star formation. Optically bright elliptical galaxies (Mr less than or equals -20.5) make the largest contribution to the radio luminosity function at both the high (> approx. 3x10(exp 22) W/Hz) and low (< approx. 10(exp 21) W/Hz) ends. Through a stacking analysis of these optically-bright ellipticals we find that they continue to harbor radio sources down to luminosities as faint as 3x10(exp 19) W/Hz. However, contrary to published results for the Virgo cluster we find no evidence for the existence of a population of optically faint (M(sub r) approx. equals -14) dwarf ellipticals hosting strong radio AGN.

  20. Spectrophotometry of Seyfert 2 galaxies and narrow-line radio galaxies

    NASA Technical Reports Server (NTRS)

    Koski, A. T.

    1978-01-01

    Results are reported for a spectrophotometric survey of several Seyfert 2 galaxies, intermediate Seyferts, and narrow-line radio galaxies. The emission-line spectra of the galaxies are analyzed, emphasizing line intensities, reddening, temperatures, densities, line strength correlations, line widths, and redshift differences. The continuous spectra are examined, and possible ionization sources are considered. It is found that: (1) there are no distinguishing differences between the spectra of Seyfert 2 galaxies and narrow-line radio galaxies; (2) the emission spectra are rich in lines from a wide range of ionization levels; (3) the continuum is starlight diluted by an underlying continuous spectrum; (4) the line widths of both classes of galaxies have the same distribution; (5) there appear to be regions of high and low ionization in the Seyfert 2 and narrow-line radio galaxies; (6) photoionization seems quite likely as the energy input to the gas; and (7) all the galaxies show a UV excess in their spectra.

  1. THE UBIQUITOUS RADIO CONTINUUM EMISSION FROM THE MOST MASSIVE EARLY-TYPE GALAXIES

    SciTech Connect

    Brown, Michael J. I.; Jannuzi, Buell T.; Floyd, David J. E.; Mould, Jeremy R.

    2011-04-20

    We have measured the radio continuum emission of 396 early-type galaxies brighter than K = 9, using 1.4 GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300 ft Telescope, and 64 m Parkes Radio Telescope. For M{sub K} < -24 early-type galaxies, the distribution of radio powers at fixed absolute magnitude spans four orders of magnitude and the median radio power is proportional to K-band luminosity to the power 2.78 {+-} 0.16. The measured flux densities of M{sub K} < -25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.

  2. Modelling feedback and magnetic fields in radio galaxy evolution

    NASA Astrophysics Data System (ADS)

    Huarte-Espinosa, Martin

    2012-08-01

    The intra-cluster medium (ICM) in galaxy clusters contains magnetic fields on Mpc scales. The main probe of these cluster magnetic fields (CMFs) is the Faraday rotation of the polarized emission from radio sources that are either embedded in, or behind the ICM. Several questions are open concerning the structure and evolution of the magnetic fields in both the ICM and the radio sources. We present three-dimensional magnetohydrodynamical numerical simulations to study randomly tangled magnetic fields in the core of a cluster under the effects of light and hypersonic AGN jets. We investigate the power of the jets and carry out synthetic observations to explore the observational signatures of our model radio sources. Our polarization maps agree with the observations, and show that the magnetic structure inside the sources is shaped by the backflow of the jets. Filaments in the synthetic synchrotron emissivity maps suggest that turbulence develops in evolved sources. The polarimetry statistics correlate with time, with the viewing angle and with the jet-to-ambient density contrast. As the sources expand, the linear polarization fraction decreases and the magnetic structure inside thin sources seems more uniform than inside fat ones. Moreover, we see that the jets distort and amplify the CMFs especially at the head of the jets and that this effect correlates with the power and evolution of the jets. We find good agreement with the RM fluctuations of Hydra A. One of the most important results is that the jet-produced RM enhancements may lead to an overestimate of the strength of the CMFs by a factor of about 70%. The physics of radio source expansion may explain the flattening of the RM structure functions at large scales. The advection of metals from a central active galaxy to the ICM in a cool-core cluster is also investigated with an additional suite of hydrodynamical simulations. These metals provide information about the ICM dynamical history and of the CMFs as well

  3. Radio galaxies dominate the high-energy diffuse gamma-ray background

    DOE PAGESBeta

    Hooper, Dan; Linden, Tim; Lopez, Alejandro

    2016-08-09

    It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes,more » radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2(+25.4)(-9.4)% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.« less

  4. Radio galaxies dominate the high-energy diffuse gamma-ray background

    NASA Astrophysics Data System (ADS)

    Hooper, Dan; Linden, Tim; Lopez, Alejandro

    2016-08-01

    It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes, radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2+25.4‑9.4% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.

  5. Centaurus A galaxy, type EO peculiar elliptical, also radio source

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Centaurus A galaxy, type EO peculiar elliptical, also radio source. CTIO 4-meter telescope, 1975. NGC 5128, a Type EO peculiar elliptical galaxy in the constellation Centaurus. This galaxy is one of the most luminous and massive galaxies known and is a strong source of both radio and X-ray radiation. Current theories suggest that the nucleus is experiencing giant explosions involving millions of stars and that the dark band across the galactic disk is material being ejected outward. Cerro Toloto 4-meter telescope photo. Photo credit: National Optical Astronomy Observatories

  6. A Mature Galaxy Cluster at z=1.58 around the Radio Galaxy 7C1753+6311

    NASA Astrophysics Data System (ADS)

    Cooke, E. A.; Hatch, N. A.; Stern, D.; Rettura, A.; Brodwin, M.; Galametz, A.; Wylezalek, D.; Bridge, C.; Conselice, C. J.; De Breuck, C.; Gonzalez, A. H.; Jarvis, M.

    2016-01-01

    We report on the discovery of a z = 1.58 mature cluster around the high-redshift radio galaxy 7C 1753+6311, first identified in the Clusters Around Radio-loud active galactic nuclei survey. Two-thirds of the excess galaxies within the central 1 Mpc lie on a red sequence with a color that is consistent with an average formation redshift of zf ∼ 3. We show that 80 ± 6% of the red sequence galaxies in the cluster core are quiescent, while the remaining 20% are red due to dusty star formation. We demonstrate that the cluster has an enhanced quiescent galaxy fraction that is three times that of the control field. We also show that this enhancement is mass dependent: 91 ± 9% of the {M}*\\gt {10}10.5M⊙ cluster galaxies are quiescent, compared to only 36 ± 2% of field galaxies, whereas the fraction of quiescent galaxies with lower masses is the same in the cluster and field environments. The presence of a dense core and a well-formed, quiescent red sequence suggest that this is a mature cluster. This means that distant radio galaxies do not solely reside in young, uncollapsed protoclusters, rather they can be found in clusters in a wide range of evolutionary states.

  7. Characterizing the radio continuum emission from intense starburst galaxies

    NASA Astrophysics Data System (ADS)

    Galvin, T. J.; Seymour, N.; Filipović, M. D.; Tothill, N. F. H.; Marvil, J.; Drouart, G.; Symeonidis, M.; Huynh, M. T.

    2016-09-01

    The intrinsic thermal (free-free) and non-thermal (synchrotron) emission components that comprise the radio continuum of galaxies represent unique, dust-free measures of star formation rates (SFR). Such high SFR galaxies will dominate the deepest current and future radio surveys. We disentangle the thermal and non-thermal emission components of the radio continuum of six ultraluminous infrared galaxies (LFIR > 1012.5 L⊙) at redshifts of 0.2 ≤ z ≤ 0.5 and 22 IR selected galaxies. Radio data over a wide frequency range (0.8 < ν < 10 GHz) are fitted with a star-forming galaxy model comprising of thermal and non-thermal components. The luminosities of both radio continuum components are strongly correlated to the 60 μm luminosity across many orders of magnitude (consistent with the far-IR to radio correlation). We demonstrate that the spectral index of the radio continuum spectral energy distribution is a useful proxy for the thermal fraction. We also find that there is an increase in mean and scatter of the thermal fraction with FIR to radio luminosity ratio which could be influenced by different time-scales of the thermal and non-thermal emission mechanisms.

  8. Radio afterglows and host galaxies of gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Li, Long-Biao; Zhang, Zhi-Bin; Huang, Yong-Feng; Wu, Xue-Feng; Kong, Si-Wei; Li, Di; Chang, Heon-Young; Choi, Chul-Sung

    2015-08-01

    Considering the contribution of emission from the host galaxies of gamma-ray bursts (GRBs) to radio afterglows, we investigate the effect of host galaxies on observations statistically. For the three types of event, i.e. low-luminosity, standard and high-luminosity GRBs, it is found that a tight correlation exists between the ratio of the radio flux (RRF) of the host galaxy to the total radio peak emission and the observational frequency. Towards lower frequencies, in particular, the contribution from the host increases significantly. The correlation can be used to obtain a useful estimate for the radio brightness of those host galaxies that only have very limited radio afterglow data. Using this prediction, we reconsidered the theoretical radio afterglow light curves for four kinds of event: high-luminosity, low-luminosity, standard and failed GRBs, taking into account the contribution from host galaxies and aiming to explore the detectability of these events by the Five-hundred-metre Aperture Spherical radio Telescope (FAST). Lying at a typical redshift of z = 1, most of the events can be detected easily by FAST. For the less fierce low-luminosity GRBs, their radio afterglows are not strong enough to exceed the sensitivity limit of FAST at such distances. However, since a large number of low-luminosity bursts actually happen very near to us, it is expected that FAST will still be able to detect many of them.

  9. Radio Bubbles in Clusters of Galaxies

    SciTech Connect

    Dunn, Robert J.H.; Fabian, A.C.; Taylor, G.B.; /NRAO, Socorro /KIPAC, Menlo Park

    2005-12-14

    We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with GHz radio emission, to our sample, and also investigating ''ghost bubbles'', i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10MHz and 10GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 {approx}< k/f {approx}< 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have higher upper limits on k/f than the active bubbles, especially when compared to those in the same cluster. A study of the Brightest 55 cluster sample shows that 17, possibly 20, clusters required some form of heating as they have a short central cooling time, t{sub cool} {approx}< 3 Gyr, and a large central temperature drop, T{sub centre}/T{sub outer} < 1/2. Of these between 12 (70 per cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle of bubbles is large in such clusters and that they can play a major role in the heating process.

  10. RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

    SciTech Connect

    Liu, F. K.; Wang Dong; Chen Xian

    2012-02-20

    Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

  11. Millimeter and submillimeter observations of nearby radio galaxies

    SciTech Connect

    Knapp, G.R.; Patten, B.M. Hawaii, University, Honolulu )

    1991-05-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals. 55 refs.

  12. Clustering of galaxies in the overdense regions of radio galaxies at z>0.6

    NASA Astrophysics Data System (ADS)

    Popescu, Nedelia A.

    2007-05-01

    Photometric redshifts technique and red sequence technique are used in order to analyze the clustering of galaxies in the environments of 5 radio galaxies with redshifts z>0.6. The optical and near infrared photometric data, completed with HST morphological data, for radio galaxies 3C220.1, 3C34, 3C61, 3C184, 3C210 are considered (Stanford et al. 2002). The presence of clustering features of galaxies with similar redshifts is revealed in the field of 3C220.1 (z=0.62), 3C34 (z=0.689) and 3C210 (z=1.169) radio galaxies. The comparison of the HST morphology of galaxies with the model spectral galaxy type (determined by means of Z-PEG software - Damien Le Borgne and Brigitte Rocca-Volmerange, 2002) is in a good agreement, confirming the importance of the photometric redshifts determinations.

  13. Fermi/LAT Observations of Swift/BAT Seyfert Galaxies: On the Contribution of Radio-Quiet Active Galactic Nuclei to the Extragalactic gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Mushotzky, Richard F.; Sambruna, Rita M.; Davis, David S.; Reynolds, Christopher S.

    2011-01-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R(sub X,BAT) where radio-loud objects have logR(sub X,BAT) > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be approx.2x10(exp -11) photons/sq cm/s, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the gamma-ray (1-100 GeV) luminosity of < approx.3x10(exp 41) erg/s. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  14. FERMI/LAT OBSERVATIONS OF SWIFT/BAT SEYFERT GALAXIES: ON THE CONTRIBUTION OF RADIO-QUIET ACTIVE GALACTIC NUCLEI TO THE EXTRAGALACTIC {gamma}-RAY BACKGROUND

    SciTech Connect

    Teng, Stacy H.; Mushotzky, Richard F.; Reynolds, Christopher S.; Sambruna, Rita M.; Davis, David S.

    2011-12-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R{sub X,BAT} where radio-loud objects have log R{sub X,BAT} > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be {approx}2 Multiplication-Sign 10{sup -11} photons cm{sup -2} s{sup -1}, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the {gamma}-ray (1-100 GeV) luminosity of {approx}< 3 Multiplication-Sign 10{sup 41} erg s{sup -1}. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  15. Sampling Studies Of Quasars, Radio-loud Galaxies, & Radio-quiet Galaxies -- Searching For The Cause Of Radio Emission

    NASA Astrophysics Data System (ADS)

    Coldwell, G.; Salois, Amee; Soechting, I.; Smith, M.

    2011-01-01

    Comparing the environments of Radio-Loud Galaxies, Radio-Quiet Galaxies, and Quasars offers an opportunity to study the evolution of these objects. Our samples have been carefully chosen from Data Release 7 of the Sloan Digital Sky Survey, which also includes samples studied in the FIRST survey, and have been cut to determine the best possible results. Our study includes three samples. The Quasar sample currently contains 69 objects, the Radio-Loud Galaxy (RLG) sample has 1,335 objects, and the Radio-Quiet Galaxy (RQG) sample contains 2,436 objects (any updates will be given at the meeting). A number of trims were made to produce (smaller) samples with characteristics suited for precise results. By comparing the environments of these three samples we will be able to see any similarities or differences between them. If similarities are detected it suggests that the central object has evolved according to 'nature' - in an isolated manner with little environmental feedback, which may or may not have an effect on its evolution, as supposed by Coldwell et al. (2009). If differences are detected it suggests that the central object has evolved according to `nurture’ and that the environment may have played an important role in the development of their properties. We employ similar procedures used by Coldwell et al. (2009) in their study of blue and red AGNs. Upon the completion of an accurate sample, future work will be pursued studying a number of properties of the environments including studies of: the stellar masses, star formation rates, sersic morphologies, as well as densities and ages of the environments.

  16. Radio spectra of intermediate-luminosity broad-line radio galaxies .

    NASA Astrophysics Data System (ADS)

    Angelakis, E.; Kadler, M.; Lewis, K.; Sambruna, R. M.; Eracleous, M.; Zensus, J. A.

    Within the context of investigating possible differences between the mechanisms at play in Radio Loud AGN and those in Radio Quiet ones, we study the spectral characteristics of a selected sample of Intermediate-Luminosity Broad-Line Radio Galaxies in X-rays, optical, IR and radio. Here, we present the radio spectra acquired with the 100-m radio telescope in Effelsberg between 2.6 and 32 GHz. These measurements reveal a large variety of spectral shapes urging for radio imaging that would disclose the source morphology. Such studies could potentially discriminate between different mechanisms.

  17. The host galaxy/AGN connection in nearby early-type galaxies. Is there a miniature radio-galaxy in every "core" galaxy?

    NASA Astrophysics Data System (ADS)

    Balmaverde, B.; Capetti, A.

    2006-02-01

    This is the second of a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. We selected two samples with 5 GHz VLA radio flux measurements down to 1 mJy, reaching levels of radio luminosity as low as 1036 erg s-1. In Paper I we presented a study of the surface brightness profiles for the 65 objects with available archival HST images out of the 116 radio-detected galaxies. We classified early-type galaxies into "core" and "power-law" galaxies, discriminating on the basis of the slope of their nuclear brightness profiles, following the Nukers scheme. Here we focus on the 29 core galaxies (hereafter CoreG). We used HST and Chandra data to isolate their optical and X-ray nuclear emission. The CoreG invariably host radio-loud nuclei, with an average radio-loudness parameter of Log R = L5 {GHz} / LB ˜ 3.6. The optical and X-ray nuclear luminosities correlate with the radio-core power, smoothly extending the analogous correlations already found for low luminosity radio-galaxies (LLRG) toward even lower power, by a factor of ˜ 1000, covering a combined range of 6 orders of magnitude. This supports the interpretation of a common non-thermal origin of the nuclear emission also for CoreG. The luminosities of the nuclear sources, most likely dominated by jet emission, set firm upper limits, as low as L/L_Edd ˜ 10-9 in both the optical and X-ray band, on any emission from the accretion process. The similarity of CoreG and LLRG when considering the distributions host galaxies luminosities and black hole masses, as well as of the surface brightness profiles, indicates that they are drawn from the same population of early-type galaxies. LLRG represent only the tip of the iceberg associated with (relatively) high activity levels, with CoreG forming the bulk of the population. We do not find any relationship between radio-power and black hole mass. A minimum black hole

  18. Diffuse Radio Emission in the Galaxy Cluster Abell 754

    NASA Astrophysics Data System (ADS)

    Kale, R.; Dwarakanath, K. S.

    2009-09-01

    We present a low frequency (<1.4GHz) study of the diffuse radio halo and relic emission in the galaxy cluster Abell 0754. Images at 150 MHz made using the Giant Metrewave Radio Telescope (GMRT) revealed 4 diffuse features; 3 of which are new. Images at 330 and 1363 MHz were created using archival data from the GMRT and the VLA respectively. These yield synchrotron spectral indices, α (S ∝ν-α), steeper than 2 for the new features. Adiabatic compression of fossil radio galaxy cocoon by shocks can lead to the formation of radio relics (Ensslin & Gopal-Krishna, 2001). In the framework of this model we find that the relic in A754 can be explained as a lurking cocoon of a radio galaxy; no shock compression is required to produce this emission. The implications of this result to the merger scenario in A754 are discussed.

  19. Soft γ-ray selected radio galaxies: favouring giant size discovery

    NASA Astrophysics Data System (ADS)

    Bassani, L.; Venturi, T.; Molina, M.; Malizia, A.; Dallacasa, D.; Panessa, F.; Bazzano, A.; Ubertini, P.

    2016-09-01

    Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of 64 confirmed plus three candidate radio galaxies selected in the soft gamma-ray band. The sample covers all optical classes and is dominated by objects showing a Fanaroff-Riley type II radio morphology; a large fraction (70 per cent) of the sample is made of `radiative mode' or high-excitation radio galaxies. We measured the source size on images from the NRAO VLA Sky Survey, the Faint Images of the Radio Sky at twenty-cm and the Sydney University Molonglo Sky Survey images and have compared our findings with data in the literature obtaining a good match. We surprisingly found that the soft gamma-ray selection favours the detection of large size radio galaxies: 60 per cent of objects in the sample have size greater than 0.4 Mpc while around 22 per cent reach dimension above 0.7 Mpc at which point they are classified as giant radio galaxies (GRGs), the largest and most energetic single entities in the Universe. Their fraction among soft gamma-ray selected radio galaxies is significantly larger than typically found in radio surveys, where only a few per cent of objects (1-6 per cent) are GRGs. This may partly be due to observational biases affecting radio surveys more than soft gamma-ray surveys, thus disfavouring the detection of GRGs at lower frequencies. The main reasons and/or conditions leading to the formation of these large radio structures are still unclear with many parameters such as high jet power, long activity time and surrounding environment all playing a role; the first two may be linked to the type of active galactic nucleus discussed in this work and partly explain the high fraction of GRGs found in the present sample. Our result suggests that high energy surveys may be a more efficient way than radio surveys to find these peculiar objects.

  20. The nature of active galaxies

    NASA Astrophysics Data System (ADS)

    Chapman, Scott Christopher

    Many details of the structure of Active Galactic Nuclei (AGN) galaxies continue to elude researchers in the field. To shed light on some of the enigmas related to the fueling and classification of AGN, I have studied the core structure of a sample of 37 nearby Seyfert galaxies at high resolution using adaptive optics on the CFHT. This dataset consists of near-IR imaging from 1 to 3 μm (the J, H, and K bands). I first describe the instruments and observing techniques along with a presentation of the galaxy sample properties. I then outline the detailed data reduction and image processing required with adaptive optics observations, highlighting some of the associated unavoidable perils. A detailed multi-wavelength study is pursued for two nearby Seyfert galaxies, NGC3227 and NGC2992. With these objects, the current ideas of Seyfert fueling and unification of Seyfert types are scrutinized, focusing on the high spatial resolution achieved using adaptive optics in the near-IR. The dynamical processes and differing classifications of these galaxies are substantially clarified through their core morphologies. These studies show that scientific results can be established with AO data, in spite of the above mentioned artifact. For NGC2992, a spiral structure within the central 6' and a 1' extended feature are traced down to the core at the resolution of our images. We speculate, based on these observed structures, that multiple radio components are superposed which contribute to the observed figure-8 morphology in the VLA images: one associated with the spiral structure in the galaxy disk, and another flowing out of the galaxy plane. I then address whether the classification of Seyfert galaxy types can be explained via patchy dust at fairly large distances (~100 pc) from the central engine. Maps of dust extinction are constructed with the deep view afforded by the near-IR. These are compared with optical images observed with the Hubble Space Telescope (HST) to aid in

  1. Multiwavelength observations of giant radio galaxy 3C 35 and 3C 284

    NASA Astrophysics Data System (ADS)

    Pal, Sabyasachi; Chakrabarti, Sandip Kumar; Patra, Dusmanta; Konar, Chiranjib

    2016-07-01

    We report multi wavelength observations of large radio galaxy 3C35 and 3C284. The low frequency observations were done with the Giant Metrewave Radio Telescope (GMRT) starting from 150 MHz. The high frequency observations were done with Jansky Very Large Array (JVLA). Our main motivation for these observations is to estimate the spectral ages of these galaxies and to examine any proof of extended emission at low radio frequencies due to an earlier cycle of activity. The spectral age is measured by fitting the spectra with different spectral ageing models e.g. Kardashev-Pacholczyk (KP), Jaffe-Perola (JP) and Continuous Injection (CI).

  2. Jet and torus orientations in high redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Drouart, G.; De Breuck, C.; Vernet, J.; Laing, R. A.; Seymour, N.; Stern, D.; Haas, M.; Pier, E. A.; Rocca-Volmerange, B.

    2012-12-01

    We examine the relative orientation of radio jets and dusty tori surrounding the active galactic nucleus (AGN) in powerful radio galaxies at z > 1. The radio core dominance R = Pcore^20 GHz/P_extended^500 MHz serves as an orientation indicator, measuring the ratio between the anisotropic Doppler-beamed core emission and the isotropic lobe emission. Assuming a fixed cylindrical geometry for the hot, dusty torus, we derive its inclination i by fitting optically-thick radiative transfer models to spectral energy distributions obtained with the Spitzer Space Telescope. We find a highly significant anti-correlation (p < 0.0001) between R and i in our sample of 35 type 2 AGN combined with a sample of 18 z ~ 1 3CR sources containing both type 1 and 2 AGN. This analysis provides observational evidence both for the Unified scheme of AGN and for the common assumption that radio jets are in general perpendicular to the plane of the torus. The use of inclinations derived from mid-infrared photometry breaks several degeneracies which have been problematic in earlier analyses. We illustrate this by deriving the core Lorentz factor Γ from the R-i anti-correlation, finding Γ ≳ 1.3. Figures 11, 12, and Tables 1, 2, 6 are available in electronic form at http://www.aanda.org

  3. Radio brightening of FRB 150418 host galaxy candidate

    NASA Astrophysics Data System (ADS)

    Williams, P. K. G.; Berger, E.; Chornock, R.

    2016-02-01

    Keane et al. (2016 Nature 530 453) reported a fading radio transient in the z=0.498 galaxy WISE J071634.59-190039.2 (WISE 0716-19; Williams & Berger, arxiv:1602.08434) that they associated with the fast radio burst FRB 150418.

  4. Complete identification of the Parkes half-Jansky sample of GHz peaked spectrum radio galaxies

    NASA Astrophysics Data System (ADS)

    de Vries, N.; Snellen, I. A. G.; Schilizzi, R. T.; Lehnert, M. D.; Bremer, M. N.

    2007-03-01

    Context: Gigahertz Peaked Spectrum (GPS) radio galaxies are generally thought to be the young counterparts of classical extended radio sources. Statistically complete samples of GPS sources are vital for studying the early evolution of radio-loud AGN and the trigger of their nuclear activity. The "Parkes half-Jansky" sample of GPS radio galaxies is such a sample, representing the southern counterpart of the 1998 Stanghellini sample of bright GPS sources. Aims: As a first step of the investigation of the sample, the host galaxies need to be identified and their redshifts determined. Methods: Deep R-band VLT-FORS1 and ESO 3.6 m EFOSC II images and long slit spectra have been taken for the unidentified sources in the sample. Results: We have identified all twelve previously unknown host galaxies of the radio sources in the sample. Eleven have host galaxies in the range 21.0 < RC < 23.0, while one object, PKS J0210+0419, is identified in the near infrared with a galaxy with Ks = 18.3. The redshifts of 21 host galaxies have been determined in the range 0.474 < z < 1.539, bringing the total number of redshifts to 39 (80%). Analysis of the absolute magnitudes of the GPS host galaxies show that at z>1 they are on average a magnitude fainter than classical 3C radio galaxies, as found in earlier studies. However their restframe UV luminosities indicate that there is an extra light contribution from the AGN, or from a population of young stars. Based on observations collected at the European Southern Observatory Very Large Telescope, Paranal, Chile (ESO prog. ID No. 073.B-0289(B)) and the European Southern Observatory 3.6 m Telescope, La Silla, Chile (prog. ID No. 073.B-0289(A)). Appendices are only available in electronic form at http://www.aanda.org

  5. Accretion processes of radio galaxies at high energies

    NASA Astrophysics Data System (ADS)

    de Jong, Sandra

    2013-10-01

    AGN are the luminous (L>10^42 erg/s) cores of active galaxies, powered by accretion onto the central super massive black hole, either via an accretion disk or via a radiatively inefficient accretion flow. There are still several open questions, for example on the launching of jets, which are present in about 10% of the AGN. Another question appeared with the Fermi/LAT gamma-ray survey, which detected many blazars but also a small group of radio galaxies. Radio galaxies are postulated to be blazars where the observer sees the jet at an angle θ>10 degrees allowing a view of both jet and core, rather than only the jet as is the case with blazars. Radio galaxies are divided into two classes, depending on the radio luminosity of the jets. The Fanaroff-Riley I (FR-I) sources have jets that are bright near the core, where the FR-IIs display extended edge-brightened jets. The FR-I sources are connected to the BL Lacs, which are low-luminosity blazars. FR-II types are thought to be the parent population of the luminous FSRQ, which are also blazars. This thesis presents a study of gamma-ray bright radio galaxies. By analysing X-ray and gamma-ray data in addition to creating broad-band spectral energy distributions (SEDs), we studied two examples of this new class of sources. For the FR-II source 3C 111 we analysed Suzaku/XIS and PIN and INTEGRAL IBIS/ISGRI observations to create a X-ray spectrum. We also used a Swift/BAT spectrum from the 58-month survey. The 0.4-200 keV spectrum of the source shows both thermal, Seyfert-like signatures such as an iron K-α line, and non-thermal jet features. We also analysed gamma-ray data from Fermi/LAT. The gamma-ray and X-ray data are combined with historical radio, infrared and optical observations to build the SED, which can be well represented with a non-thermal jet model. The bolometric luminosity of 3C111 is rather low, and the SED model shows rather a BL Lac type than the expected FSRQ. The next source we studied is the nearby FR

  6. Soft Gamma-ray selected radio galaxies: favouring giant size discovery

    NASA Astrophysics Data System (ADS)

    Panessa, Francesca; Bassani, Loredana

    2016-07-01

    Using the recent INTEGRAL/IBIS and Swift/BAT surveys we have extracted a sample of radio galaxies selected in the soft gamma-ray band. The sample consists of known and candidate radio galaxies. The sample extraction criteria will be presented and its general properties outlined. In particular we provide strong evidence that this soft gamma-ray selection favours the discovery of large size radio objects, otherwise known as Giant Radio Galaxies or GRG. The main reasons and/or conditions leading to the formation of these sources are still unclear and this result suggests that they maybe related to exceptional internal properties of the source central engine, like a high jet power or a long activity time. Broad band analysis of new GRG, discovered during this work, will also be presented.

  7. AN EXAMINATION OF THE OPTICAL SUBSTRUCTURE OF GALAXY CLUSTERS HOSTING RADIO SOURCES

    SciTech Connect

    Wing, Joshua D.; Blanton, Elizabeth L.

    2013-04-20

    Using radio sources from the Faint Images of the Radio Sky at Twenty-cm survey, and optical counterparts in the Sloan Digital Sky Survey, we have identified a large number of galaxy clusters. The radio sources within these clusters are driven by active galactic nuclei, and our cluster samples include clusters with bent, and straight, double-lobed radio sources. We also included a single-radio-component comparison sample. We examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. We use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. We found no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.

  8. Jet Directions in Seyfert Galaxies: Radio Continuum Imaging Data

    NASA Astrophysics Data System (ADS)

    Schmitt, H. R.; Ulvestad, J. S.; Antonucci, R. R. J.; Kinney, A. L.

    2001-02-01

    We present the results of VLA A-array 8.46 GHz continuum imaging of 55 Seyfert galaxies (19 Seyfert 1's and 36 Seyfert 2's). These galaxies are part of a larger sample of 88 Seyfert galaxies, selected from mostly isotropic properties, the flux at 60 μm, and warm infrared 25-60 μm colors. These images are used to study the structure of the radio continuum emission of these galaxies and their position angles, in the case of extended sources. These data, combined with information from broadband B and I observations, have been used to study the orientation of radio jets relative to the plane of their host galaxies (Kinney et al.).

  9. Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Foschini, L.; Ciroi, S.; Cracco, V.; La Mura, G.; Lister, M. L.; Mathur, S.; Peterson, B. M.; Richards, J. L.; Rafanelli, P.

    2015-06-01

    Flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (NLS1s) are a recently discovered class of γ-ray emitting active galactic nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Therefore, we tried to understand the origin of this deficit. Current hypotheses about the nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s and disk-hosted radio-galaxies. To test these hypotheses we built three samples of candidate sources plus a control sample, and calculated their black hole mass and Eddington ratio using their optical spectra. We then performed a Kolmogorov-Smirnov statistical test to investigate the compatibility of our different samples with a beamed population. Our results indicate that, when the inclination angle increases, a beamed source appears as a steep-spectrum radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black hole mass and high Eddington ratio. Further investigations, involving larger complete samples and observations at radio frequency, are needed to understand the incidence of disk-hosted radio-galaxies in the parent population, and to assess whether radio-quiet NLS1s can play a role, as well. Appendix A is available in electronic form at http://www.aanda.org

  10. The host galaxy of a fast radio burst.

    PubMed

    Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-02-25

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts. PMID:26911781

  11. SUZAKU VIEW OF THE SWIFT/BAT ACTIVE GALACTIC NUCLEI. IV. NATURE OF TWO NARROW-LINE RADIO GALAXIES (3C 403 AND IC 5063)

    SciTech Connect

    Tazaki, Fumie; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.

    2011-09-01

    We report the results of Suzaku broadband X-ray observations of the two narrow-line radio galaxies, 3C 403 and IC 5063. Combined with the Swift/Burst Alert Telescope (BAT) spectra averaged for 58 months, we are able to accurately constrain their spectral properties over the 0.5-200 keV band. The spectra of both nuclei are well represented with an absorbed cutoff power law, an absorbed reflection component from cold matter with an iron-K emission line, and an unabsorbed soft component, which gives a firm upper limit for the scattered emission. The reflection strength normalized to the averaged BAT flux is R {identical_to} {Omega}/2{pi} {approx} 0.6 in both targets, implying that their tori have a sufficiently large solid angle to produce the reprocessed emission. A numerical torus model with an opening angle of {approx}50{sup 0} well reproduces the observed spectra. We discuss the possibility that the amount of the normal gas responsible for Thomson scattering is systematically smaller in radio galaxies compared with Seyfert galaxies.

  12. Very-long-baseline radio interferometry observations of low power radio galaxies.

    PubMed Central

    Giovannini, G; Cotton, W D; Feretti, L; Lara, L; Venturi, T; Marcaide, J M

    1995-01-01

    The parsec scale properties of low power radio galaxies are reviewed here, using the available data on 12 Fanaroff-Riley type I galaxies. The most frequent radio structure is an asymmetric parsec-scale morphology--i.e., core and one-sided jet. It is shared by 9 (possibly 10) of the 12 mapped radio galaxies. One (possibly 2) of the other galaxies has a two-sided jet emission. Two sources are known from published data to show a proper motion; we present here evidence for proper motion in two more galaxies. Therefore, in the present sample we have 4 radio galaxies with a measured proper motion. One of these has a very symmetric structure and therefore should be in the plane of the sky. The results discussed here are in agreement with the predictions of the unified scheme models. Moreover, the present data indicate that the parsec scale structure in low and high power radio galaxies is essentially the same. PMID:11607596

  13. The Hot Atmospheres of X-Shaped Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Hodges-Kluck, Edmund

    2011-01-01

    We present an observational and numerical study of X-shaped radio galaxies, a subset of the double-lobed radio galaxies with a second set of lobes or "wings". These sources have been proposed as the "smoking gun" of supermassive black hole mergers, in which case the secondary lobes would be fossil remnants following a black hole spin-flip jet reorientation. However, they may instead originate in the interplay between giant radio lobes and their hot plasma environments, since radio lobes can be considered as bubbles of light fluid in the heavier intracluster medium. Circumstantial evidence from studies of the host galaxies at optical wavelengths indicates that this may indeed be the case, leading to two important questions we attempt to answer in this work: (1) Does it appear that X-shaped radio galaxies are aware of their environments? (2) Can radio galaxies respond to their environments in such a way as to form X-shaped morphology? We use radio, optical, and X-ray imaging data to investigate the first question, finding that, in general, X-shaped sources have jets co-aligned with the major axes of their hot (X-ray emitting) atmospheres and wings co-aligned with their minor axes. However, in at least one case (where the jet clearly does not follow this trend), a deep X-ray observation suggests that rapid reorientation of the jet axis is the best explanation. Moreover,despite the trend we discover, the hydrodynamic models of wing formation have significant theoretical problems. Thus, the second major component of this thesis is concerned with using hydrodynamical simulations to determine whether X-shaped radio galaxies can be produced in response to asymmetries in the atmosphere. We inject jets as light fluids into a model cluster or galactic atmosphere previously in hydrostatic equilibrium, thereby forming bubbles similar to those observed in radio galaxies. Since we inject the jet along the major axis of an asymmetric atmosphere, distortions to the canonical double

  14. A computational study of radio relics in galaxy cluster mergers

    NASA Astrophysics Data System (ADS)

    Owen, Dane Patrick

    Radio relics are extended regions of synchrotron radio emission that have been found in the outskirts of a few dozen galaxy clusters. Relics are often associated with clusters undergoing merger activity. They are not associated optically with a particular member of the cluster and are thought to arise from relativistic electron populations in the intra-cluster medium. The radio phoenix model, where shockwaves from merger activity re-energize a fossil radio plasma through adiabatic compression of the plasma, is one possible method of relic formation. This thesis uses gravitational N-body + SPH simulations with added synchrotron physics to present the largest computational study of radio relics in the radio phoenix model to date, totaling over 50,000 CPU-hours of computation and 4.7 TB of data. I have created a simulation data set of cluster mergers, with 25 different combinations of cluster mass, impact parameter, kinetic energies, cluster concentrations, and cluster-subcluster mass ratios. Using these simulations, I will discuss how high mass ratio collisions of 7:1 (cluster:subcluster mass) are most effective at reviving emission and creating a relic. I also show how this model predicts that clusters with total masses on the order of 6.25 x 10. 14 solar masses are most efficient at creating relics. By varyingthe magnetic pressure in the simulations, I demonstrate how relic formation is relatively insensitive to a wide range of magnetic field strengths. I also examine the great steepening of the spectral index of relics at even moderate (z ~ 0.4) redshifts predicted by the simulations, with the implications for future low-frequency telescope arrays. Finally, I present specific merger simulations for the clusters Abell 85 and 2443. The relic emission in Abell 85 is shown to be well predicted by the radio phoenix model, while the possible merger of Abell 2443 with its subcluster ZwCl 2224.2+1651 is shown to be unlikely as the cause of the relic in that system.

  15. Morphological Evolution in High-Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    van Breugel, Wil J. M.; Stanford, S. A.; Spinrad, Hyron; Stern, Daniel; Graham, James R.

    1998-08-01

    We present deep near-infrared images of high-redshift radio galaxies (HzRGs) obtained with the near-infrared camera (NIRC) on the Keck I telescope. In most cases, the near-IR data sample rest wavelengths that are free of contamination from strong emission lines and at λrest > 4000 Å, where older stellar populations, if present, might dominate the observed flux. At z > 3, the rest-frame optical morphologies generally have faint, large-scale (~50 kpc) emission surrounding multiple, ~10 kpc components. The brightest of these components are often aligned with the radio structures. These morphologies change dramatically at 2 < z < 3, where the K-band images show single, compact structures without bright, radio-aligned features. The linear sizes (~10 kpc) and luminosities [M(Brest) ~ -20 to -22] of the individual components in the z > 3 HzRGs are similar to the total sizes and luminosities of normal radio-quiet star forming galaxies at z = 3-4. For objects where such data are available, our observations show that the line-free, near-IR colors of the z > 3 galaxies are very blue, consistent with models in which recent star formation dominates the observed light. Direct spectroscopic evidence for massive star formation in one of the z > 3 HzRGs exists (4C 41.17). Our results suggest that the z > 3 HzRGs evolve into much more massive systems than the radio-quiet galaxies and that they are qualitatively consistent with models in which massive galaxies form in hierarchical fashion through the merging of smaller star-forming systems. The presence of relatively luminous subcomponents along the radio axes of the z > 3 galaxies suggests a causal connection with the AGN. We compare the radio and near-IR sizes as a function of redshift and suggest that this parameter may be a measure of the degree to which the radio sources have induced star formation in the parent objects. We also discuss the Hubble diagram of radio galaxies, the possibility of a radio power dependence in the K

  16. AGN Zoo and Classifications of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.

    2015-07-01

    We review the variety of Active Galactic Nuclei (AGN) classes (so-called "AGN zoo") and classification schemes of galaxies by activity types based on their optical emission-line spectrum, as well as other parameters and other than optical wavelength ranges. A historical overview of discoveries of various types of active galaxies is given, including Seyfert galaxies, radio galaxies, QSOs, BL Lacertae objects, Starbursts, LINERs, etc. Various kinds of AGN diagnostics are discussed. All known AGN types and subtypes are presented and described to have a homogeneous classification scheme based on the optical emission-line spectra and in many cases, also other parameters. Problems connected with accurate classifications and open questions related to AGN and their classes are discussed and summarized.

  17. Global Cosmological Parameters Determined Using Classical Double Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Guerra, Erick J.; Daly, Ruth A.; Wan, Lin

    2000-12-01

    A sample of 20 powerful extended radio galaxies with redshifts between zero and 2 were used to determine constraints on global cosmological parameters. Data for six radio sources were obtained from the VLA archive, analyzed, and combined with the sample of 14 radio galaxies used previously by Guerra & Daly to determine cosmological parameters. The new results are consistent with our previous results, and indicate that the current value of the mean mass density of the universe is significantly less than the critical value. A universe with Ωm of unity in matter is ruled out at 99.0% confidence, and the best-fitting values of Ωm in matter are 0.10+0.25-0.10 and -0.25+0.35-0.25 assuming zero space curvature and zero cosmological constant, respectively. Note that identical results obtain when the low-redshift bin, which includes Cygnus A, is excluded; these results are independent of whether the radio source Cygnus A is included. The method does not rely on a zero-redshift normalization. The radio properties of each source are also used to determine the density of the gas in the vicinity of the source, and the beam power of the source. The six new radio sources have physical characteristics similar to those found for the original 14 sources. The density of the gas around these radio sources is typical of gas in present-day clusters of galaxies. The beam powers are typically about 1045 ergs s-1.

  18. THE CHANDRA VIEW OF NEARBY X-SHAPED RADIO GALAXIES

    SciTech Connect

    Hodges-Kluck, Edmund J.; Reynolds, Christopher S.; Miller, M. Coleman; Cheung, Chi C.

    2010-02-20

    We present new and archival Chandra X-ray Observatory observations of X-shaped radio galaxies (XRGs) within z {approx} 0.1 alongside a comparison sample of normal double-lobed FR I and II radio galaxies. By fitting elliptical distributions to the observed diffuse hot X-ray emitting atmospheres (either the interstellar or intragroup medium), we find that the ellipticity and the position angle of the hot gas follow that of the stellar light distribution for radio galaxy hosts in general. Moreover, compared to the control sample, we find a strong tendency for X-shaped morphology to be associated with wings directed along the minor axis of the hot gas distribution. Taken at face value, this result favors the hydrodynamic backflow models for the formation of XRGs which naturally explain the geometry; the merger-induced rapid reorientation models make no obvious prediction about orientation.

  19. KILOPARSEC-SCALE RADIO STRUCTURES IN NARROW-LINE SEYFERT 1 GALAXIES

    SciTech Connect

    Doi, Akihiro; Kino, Motoki; Nagira, Hiroshi; Kawakatu, Nozomu; Nagai, Hiroshi; Asada, Keiichi

    2012-11-20

    We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array, which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two {gamma}-ray-emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (1) extended radio luminosities suggesting jet kinetic powers of {approx}> 10{sup 44} erg s{sup -1}, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of {approx}> 10{sup 7} M {sub Sun }, which can generate the necessary jet powers from near-Eddington mass accretion; and (3) two-sided radio structures at kpc scales, requiring expansion rates of {approx}0.01c-0.3c and kinematic ages of {approx}> 10{sup 7} years. On the other hand, most typical NLS1s would be driven by black holes of {approx}< 10{sup 7} M {sub Sun} in a limited lifetime of {approx}10{sup 7} years. Hence, the kpc-scale radio structures may originate in a small window of opportunity during the final stage of the NLS1 phase just before growing into broad-line AGNs.

  20. Clumped X-ray emission around radio galaxies in Abell clusters

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.; Rhee, George; Owen, Frazer N.; Pinkney, Jason

    1994-01-01

    We have made a comparison of the X-ray and radio morphologies for a sample of 41 rich cluster fields using Einstein Observatory Imaging Proportional Counter (IPC) and Very Large Array (VLA) 20 cm images. Surprisingly, we find that 75% of the radio galaxies have a statistically significant X-ray peak or subclump within 5 min of the radio galaxy position. The X-ray luminosity and the generally extended nature of the X-ray subclumps suggest that these subclumps are overdense regions emitting free-free radiation, although there is also evidence for Active Galactic Nuclei (AGN) X-ray emission coming from some of the more compact, high surface brightness X-ray peaks. Some interesting correlations with radio morphology were also discovered. For clusters which contain wide-angle-tailed radio sources associated with centrally dominant galaxies, there are significant elongations or clumps in the central X-ray emission which are unusual for this type of cluster. We suggest that cluster radio galaxies are pointers to particular clusters or regions within clusters that have recently undergone mergers between cluster subsystems.

  1. Testing the CMB Quenching for High-Redshift Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Jianfeng; Gallo, Elena

    2016-04-01

    The identification of a dozen of high-redshift (z > 4) blazars implies that a much larger population of powerful, but mis-aligned jetted AGNs already exists in the early Universe. However, this parent population remains elusive, although they are expected to be within the sensitivity threshold of modern wide-field radio surveys. One appealing mechanism is that the CMB photons upscatter the diffuse synchrotron radio emission in the lobes to the X-ray band. In this scenario, the lobes will turn into luminous X-ray sources. We analyzed the extended X-ray emission around several radio galaxies at z~4 and constructed their broad-band spectral energy distributions (SEDs). Modeling their SEDs will test this CMB quenching scenario for high-redshift radio galaxies.

  2. Surface photometry of radio galaxies. II - Cluster sources

    NASA Technical Reports Server (NTRS)

    Owen, Frazer N.; White, Richard A.

    1991-01-01

    R-band CCD photometric observations are reported for 52 radio galaxies in clusters for which good radio maps are available. Data obtained with the No. 1 0.9-m telescope at KPNO (following the procedures described by Owen and Laing, 1989) are presented in tables and graphs and discussed in detail. Optical and radio luminosity are found to be well correlated in twin-jet, fat-double, narrow-angle-tail, and small-twin-jet sources, all of which are clearly distinguished from the classical doubles as in the scheme of Fanaroff and Riley (1974). It is also shown that the elliptical parent galaxies of the extended radio sources form a one-parameter family with the optical luminosity as the key parameter.

  3. Radio continuum detection in blue early-type weak-emission-line galaxies

    NASA Astrophysics Data System (ADS)

    Paswan, A.; Omar, A.

    2016-06-01

    The star formation rates (SFRs) in weak-emission-line (WEL) galaxies in a volume-limited (0.02 < z < 0.05) sample of blue early-type galaxies (ETGs) identified from the Sloan Digital Sky Survey, are constrained here using 1.4-GHz radio continuum emission. The direct detection of 1.4-GHz radio continuum emission is made in eight WEL galaxies and a median stacking is performed on 57 WEL galaxies using Very Large Array (VLA) Faint Images of Radio Sky at Twenty-cm (FIRST) images. The median stacked 1.4-GHz flux density and luminosity are estimated as 79 ± 19 μJy and 0.20 ± 0.05 × 1021 W Hz-1, respectively. The radio far-infrared correlation in four WEL galaxies suggests that the radio continuum emission from WEL galaxies is most likely a result of star formation activities. The median SFR for WEL galaxies is estimated as 0.23 ± 0.06 M⊙ yr-1, which is much less than SFRs (0.5-50 M⊙ yr-1) in purely star-forming blue ETGs. The SFRs in blue ETGs are found to be correlated with their stellar velocity dispersions (σ) and decreasing gradually beyond σ of ˜100 km s-1. This effect is most likely linked to the growth of a black hole and the suppression of star formation via active galactic nucleus (AGN) feedback. The colour differences between star-forming and WEL subtypes of blue ETGs appear to be driven to a large extent by the level of current star formation activities. In a likely scenario of an evolutionary sequence between subtypes, the observed colour distribution in blue ETGs can be explained best in terms of fast evolution through AGN feedback.

  4. A powerful radio galaxy at z=3.6 in a giant rotating Lyman α halo.

    NASA Astrophysics Data System (ADS)

    van Ojik, R.; Roettgering, H. J. A.; Carilli, C. L.; Miley, G. K.; Bremer, M. N.; Macchetto, F.

    1996-09-01

    We present the discovery and detailed observations of the radio galaxy 1243+036 at a redshift of z=3.57. The radio source was selected on the basis of its extremely steep radio spectrum, suggesting that it might be very distant. The radio source was identified with a galaxy of R magnitude 22.5. Subsequent spectroscopy showed strong Lyman α and [O III]λλ5007,4959 emission, indicating that the object is a radio galaxy at z=3.57. High resolution (0.2") radio maps show an FRII type radio source with a sharply bent radio structure. Strong depolarization of the radio emission indicates that the source is embedded in a magneto-ionic medium. The most spectacular feature of 1243+036 is the presence of a Lyα halo of luminosity ~10^44.5^erg/s which extends over ~20" (135kpc). A 0.6" resolution Lyα image shows that the emission line gas is aligned with the main axis of the radio source and has structure down to the scale of the resolution. High resolution spectra show that the Lyα emitting gas has complex kinematic structure. The gas contained within the radio structure has a relatively high velocity width (~1500km/s FWHM). The component of the Lyα emission that coincides with the bend in the radio structure is blueshifted with respect to the peak of the emission by 1100km/s. There is low surface brightness Lyα emission aligned with, but extending 40kpc beyond both sides of the radio source. This halo has a narrow velocity width (~250km/s FWHM) and a velocity gradient of 450km/s over the extent of the emission. The presence of the quiescent Lyα component aligned with the AGN axis, but outside the radio source, is strong evidence that photoionization by anisotropically emitted radiation from the active nucleus is occurring. Various mechanisms for the origin and kinematics of the Lyα halo are discussed. Because the halo extends beyond the radio structure with less violent and more ordered kinematics than inside the radio structure, we conclude that the outer halo and

  5. Giant Radio Jet Coming From Wrong Kind of Galaxy

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Giant jets of subatomic particles moving at nearly the speed of light have been found coming from thousands of galaxies across the Universe, but always from elliptical galaxies or galaxies in the process of merging -- until now. Using the combined power of the Hubble Space Telescope, the Very Large Array (VLA) and the 8-meter Gemini-South Telescope, astronomers have discovered a huge jet coming from a spiral galaxy similar to our own Milky Way. Radio-optical view of galaxy Combined HST and VLA image of the galaxy 0313-192. Optical HST image shows the galaxy edge-on; VLA image, shown in red, reveals giant jet of speeding particles. For more images, see this link below. CREDIT: Keel, Ledlow & Owen; STScI,NRAO/AUI/NSF, NASA "We've always thought spirals were the wrong kind of galaxy to generate these huge jets, but now we're going to have to re-think some of our ideas on what produces these jets," said William Keel, a University of Alabama astronomer who led the research team. Keel worked with Michael Ledlow of Gemini Observatory and Frazer Owen of the National Radio Astronomy Observatory. The scientists reported their findings at the American Astronomical Society's meeting in Seattle, Washington. "Further study of this galaxy may provide unique insights on just what needs to happen in a galaxy to produce these powerful jets of particles," Keel said. In addition, Owen said, "The loose-knit nature of the cluster of galaxies in which this galaxy resides may play a part in allowing this particular spiral to produce jets." Astronomers believe such jets originate at the cores of galaxies, where supermassive black holes provide the tremendous gravitational energy to accelerate particles to nearly the speed of light. Magnetic fields twisted tightly by spinning disks of material being sucked into the black hole are presumed to narrow the speeding particles into thin jets, like a nozzle on a garden hose. Both elliptical and spiral galaxies are believed to harbor supermassive

  6. LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift

    NASA Astrophysics Data System (ADS)

    Brienza, M.; Godfrey, L.; Morganti, R.; Vilchez, N.; Maddox, N.; Murgia, M.; Orru, E.; Shulevski, A.; Best, P. N.; Brüggen, M.; Harwood, J. J.; Jamrozy, M.; Jarvis, M. J.; Mahony, E. K.; McKean, J.; Röttgering, H. J. A.

    2016-01-01

    Context. Remnant radio galaxies represent the final dying phase of radio galaxy evolution in which the jets are no longer active. Remnants are rare in flux-limited samples, comprising at most a few percent. As a result of their rarity and because they are difficult to identify, this dying phase remains poorly understood and the luminosity evolution is largely unconstrained. Aims: Here we present the discovery and detailed analysis of a large (700 kpc) remnant radio galaxy with a low surface brightness that has been identified in LOFAR images at 150 MHz. Methods: By combining LOFAR data with new follow-up Westerbork observations and archival data at higher frequencies, we investigated the source morphology and spectral properties from 116 to 4850 MHz. By modelling the radio spectrum, we probed characteristic timescales of the radio activity. Results: The source has a relatively smooth, diffuse, amorphous appearance together with a very weak central compact core that is associated with the host galaxy located at z = 0.051. From our ageing and morphological analysis it is clear that the nuclear engine is currently switched off or, at most, active at a very low power state. We find that the source has remained visible in the remnant phase for about 60 Myr, significantly longer than its active phase of 15 Myr, despite being located outside a cluster. The host galaxy is currently interacting with another galaxy located at a projected separation of 15 kpc and a radial velocity offset of ~ 300 km s-1. This interaction may have played a role in the triggering and/or shut-down of the radio jets. Conclusions: The spectral shape of this remnant radio galaxy differs from most of the previously identified remnant sources, which show steep or curved spectra at low to intermediate frequencies. Our results demonstrate that remnant radio galaxies can show a wide range of evolutionary paths and spectral properties. In light of this finding and in preparation for new-generation deep

  7. Brightest cluster galaxies in the extended GMRT radio halo cluster sample. Radio properties and cluster dynamics

    NASA Astrophysics Data System (ADS)

    Kale, R.; Venturi, T.; Cassano, R.; Giacintucci, S.; Bardelli, S.; Dallacasa, D.; Zucca, E.

    2015-09-01

    Aims: First-ranked galaxies in clusters, usually referred to as brightest cluster galaxies (BCGs), show exceptional properties over the whole electromagnetic spectrum. They are the most massive elliptical galaxies and show the highest probability to be radio loud. Moreover, their special location at the centres of galaxy clusters raises the question of the role of the environment in shaping their radio properties. In the attempt to separate the effect of the galaxy mass and of the environment on their statistical radio properties, we investigate the possible dependence of the occurrence of radio loudness and of the fractional radio luminosity function on the dynamical state of the hosting cluster. Methods: We studied the radio properties of the BCGs in the Extended GMRT Radio Halo Survey (EGRHS), which consists of 65 clusters in the redshift range 0.2-0.4, with X-ray luminosity LX ≥ 5 × 1044 erg s-1, and quantitative information on their dynamical state from high-quality Chandra imaging. We obtained a statistical sample of 59 BCGs, which we divided into two classes, depending on whether the dynamical state of the host cluster was merging (M) or relaxed (R). Results: Of the 59 BCGs, 28 are radio loud and 31 are radio quiet. The radio-loud sources are favourably located in relaxed clusters (71%), while the reverse is true for the radio-quiet BCGs, which are mostly located in merging systems (81%). The fractional radio luminosity function for the BCGs in merging and relaxed clusters is different, and it is considerably higher for BCGs in relaxed clusters, where the total fraction of radio loudness reaches almost 90%, to be compared to the ~30% in merging clusters. For relaxed clusters, we found a positive correlation between the radio power of the BCGs and the strength of the cool core, consistent with previous studies on local samples. Conclusions: Our study suggests that the radio loudness of the BCGs strongly depends on the cluster dynamics; their fraction is

  8. A tale of two feedbacks: Star formation in the host galaxies of radio AGNs

    SciTech Connect

    Karouzos, Marios; Im, Myungshin; Jeon, Yiseul; Kim, Ji Hoon; Trichas, Markos; Goto, Tomo; Malkan, Matt; Ruiz, Angel; Lee, Hyung Mok; Kim, Seong Jin; Oi, Nagisa; Matsuhara, Hideo; Takagi, Toshinobu; Murata, K.; Wada, Takehiko; Wada, Kensuke; Shim, Hyunjin; Hanami, Hitoshi; Serjeant, Stephen; White, Glenn J.; and others

    2014-04-01

    Several lines of argument support the existence of a link between activity at the nuclei of galaxies, in the form of an accreting supermassive black hole, and star formation activity in these galaxies. Radio jets have long been argued to be an ideal mechanism that allows active galactic nuclei (AGNs) to interact with their host galaxies and affect star formation. We use a sample of radio sources in the North Ecliptic Pole (NEP) field to study the nature of this putative link, by means of spectral energy distribution (SED) fitting. We employ the excellent spectral coverage of the AKARI infrared space telescope and the rich ancillary data available in the NEP to build SEDs extending from UV to far-IR wavelengths. We find a significant AGN component in our sample of relatively faint radio sources (galaxy, independent of the radio luminosity. In contrast, for narrow redshift and AGN luminosity ranges, we find that increasing radio luminosity leads to a decrease in the specific star formation rate. The most radio-loud AGNs are found to lie on the main sequence of star formation for their respective redshifts. For the first time, we potentially see such a two-sided feedback process in the same sample. We discuss the possible suppression of star formation, but not total quenching, in systems with strong radio jets, that supports the maintenance nature of feedback from radio AGN jets.

  9. COSMOLOGICAL MAGNETOHYDRODYNAMIC SIMULATIONS OF GALAXY CLUSTER RADIO RELICS: INSIGHTS AND WARNINGS FOR OBSERVATIONS

    SciTech Connect

    Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Xu, Hao; Li, Hui; Collins, David C.; O'Shea, Brian W.; Norman, Michael L.

    2013-03-01

    Non-thermal radio emission from cosmic-ray electrons in the vicinity of merging galaxy clusters is an important tracer of cluster merger activity, and is the result of complex physical processes that involve magnetic fields, particle acceleration, gas dynamics, and radiation. In particular, objects known as radio relics are thought to be the result of shock-accelerated electrons that, when embedded in a magnetic field, emit synchrotron radiation in the radio wavelengths. In order to properly model this emission, we utilize the adaptive mesh refinement simulation of the magnetohydrodynamic evolution of a galaxy cluster from cosmological initial conditions. We locate shock fronts and apply models of cosmic-ray electron acceleration that are then input into radio emission models. We have determined the thermodynamic properties of this radio-emitting plasma and constructed synthetic radio observations to compare observed galaxy clusters. We find a significant dependence of the observed morphology and radio relic properties on the viewing angle of the cluster, raising concerns regarding the interpretation of observed radio features in clusters. We also find that a given shock should not be characterized by a single Mach number. We find that the bulk of the radio emission comes from gas with T > 5 Multiplication-Sign 10{sup 7} K, {rho} {approx} 10{sup -28}-10{sup -27} g cm{sup -3}, with magnetic field strengths of 0.1-1.0 {mu}G, and shock Mach numbers of M {approx} 3-6. We present an analysis of the radio spectral index which suggests that the spatial variation of the spectral index can mimic synchrotron aging. Finally, we examine the polarization fraction and position angle of the simulated radio features, and compare to observations.

  10. Multiphase ISM in Radio Loud Early Type Galaxies

    NASA Astrophysics Data System (ADS)

    Sahu, Sheetal Kumar; Chaware, Laxmikant; Pandey, S. K.

    We present optical, IR and X-ray photometric study of a sample of radio loud early type galaxies chosen from B2 sample. To get radial profiles of various photometric and geometrical parameters, We per- formed multiband surface photometry on CCD images of our sample gala- xies in ’BVR’ broad band filter and Hα narrow band filter obtained from IUCAA Girawali Observatory(IGO 2m telescope) Pune(INDIA),that descri- be elliptical isophotes fitted to the 2D light distribution of the galaxies. The main focus of our study is to analyze radial profiles of quantities such as the (local) surface brightness, the ellipticity, and the deviations from elliptical isophotes parametrized by the Fourier coefficients. We generated color maps,residual maps,dust extinction maps, Hα emission maps and x-ray diffuse maps (obtained from CHANDRA data archive) of the galaxies to study the morphology of the dust, ionized and hot gas content present in the galaxies. We carried out detailed analysis of the dust properties(mass and temperature of the dust) for sample galaxies. We also made use of the HST(WFPC2) archival optical images to investigate properties of the dust in the central region(˜10 arcsec) of our sample galaxies, including this we also estimated molecular gas mass, mass loss by red giant stars and mass loss rate from evolved stars in the sample galaxies obtained from IRAS fluxes. This multiwavelength study of our sample galaxies enabled us to find physical correlation among different phases of ISM also to address various issues related to dust i.e origin, nature and ate(evolution)of dust in radio-loud early type galaxies, coexistence of multiphase ISM in extra-galactic environment and its possible implications for the scenarios of formation and evolution of galaxies.

  11. The dynamics and energetics of FR-II radio galaxies

    NASA Astrophysics Data System (ADS)

    Harwood, Jeremy; Morganti, Raffaella; Hardcastle, Martin; Croston, J.

    2016-01-01

    Determining the shape of the energy spectrum for an electron population can often give key insights into the underlying physics of a radio source. In principle, a region emitting via synchrotron radiation will preferentially cool higher energy electrons leading to a steeper, more strongly curved spectrum in older regions of plasma. Models of this so-called spectral aging have become a commonly used tool when describing the processes involved in emission from the lobes of FR-II radio galaxies; however, the lack of high resolution, broad-bandwidth observations has historically meant the details of these spectra have remained largely unexplored on small spatial scales. The broad-bandwidth capabilities of telescopes such as the JVLA, LOFAR, e-MERLIN and ultimately the SKA, will mean that the spectrum of any given source can be determined within the bandwidth of any given observation, producing a detailed spectral shape. This type of detailed spectral analysis is therefore set to become standard practice when dealing with any new broadband radio observations.In this talk, we provide details of the Broadband Radio Astronomy ToolS (BRATS) software package that uses innovative techniques to analyze this new generation of radio data. Through the application of BRATS to LOFAR and JVLA observations, we present results from our latest investigations into the dynamics and energetics of nearby FR-II radio galaxies and their spectral structure on small spatial scales. We go on to discuss how these new findings impact upon our current understanding of the underlying physics of FR-II radio galaxies and, ultimately, their impact of galaxy evolution as a whole.

  12. Ultraviolet and optical spectra of broadline radio galaxies

    NASA Technical Reports Server (NTRS)

    Crenshaw, D. Michael; Peterson, Bradley M.; Wagner, R. Mark

    1988-01-01

    Near-simultaneous ultraviolet and optical spectra of three broadline radio galaxies (3C 382, 3C 445, and PKS 2349-014) have been obtained, and the emission lines of Ly-alpha, H-beta, and H-alpha have been deconvolved into narrow and broad components; published fluxes for 3C 390.3 are also included in this study. Although the broad Ly-alpha/H-beta ratios in these objects cover a large range (1.2-22.3), there is no evidence that these ratios are intrinsically different from those of Seyfert 1 galaxies or quasars. Thus, in general, the higher H-alpha/H-beta ratios in these broadline radio galaxies cannot entirely be due to additional reddening of the broadline region. However, in the specific case of 3C 445, there is evidence that the nonstellar continuum and broadline region are highly reddened.

  13. Is the EGRET Source 3EG J1621+8203 the Radio Galaxy NGC 6251?

    NASA Astrophysics Data System (ADS)

    Mukherjee, R.; Halpern, J.; Mirabal, N.; Gotthelf, E. V.

    2002-08-01

    We discuss the nature of the unidentified EGRET source 3EG J1621+8203. In an effort to identify the gamma-ray source, we have examined X-ray images of the field from ROSAT PSPC, ROSAT HRI, and ASCA GIS. Of the several faint X-ray point sources in the error circle of 3EG J1621+8203, most are stars or faint radio sources, unlikely to be counterparts to the EGRET source. The most notable object in the gamma-ray error box is the bright FR I radio galaxy NGC 6251. If 3EG J1621+8203 corresponds to NGC 6251, then it would be the second radio galaxy to be detected in high-energy gamma rays after Cen A, which provided the first clear evidence of the detection above 100 MeV of an active galactic nucleus (AGN) with a large-inclination jet. If the detection of more radio galaxies by EGRET has been limited by its threshold sensitivity, there exists the exciting possibility that new high-energy gamma-ray instruments, with much higher sensitivity, will detect a larger number of radio galaxies in the future.

  14. RADIO PROPERTIES OF LOW-REDSHIFT BROAD-LINE ACTIVE GALACTIC NUCLEI INCLUDING EXTENDED RADIO SOURCES

    SciTech Connect

    Rafter, Stephen E.; Crenshaw, D. Michael; Wiita, Paul J.

    2011-03-15

    We present a study of the extended radio emission in a sample of 8434 low-redshift (z < 0.35) broad-line active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. To calculate the jet and lobe contributions to the total radio luminosity, we have taken the 846 radio core sources detected in our previous study of this sample and performed a systematic search in the FIRST database for extended radio emission that is likely associated with the optical counterparts. We found that 51 out of 846 radio core sources have extended emission (>4'' from the optical AGN) that is positively associated with the AGN, and we have identified an additional 12 AGNs with extended radio emission but no detectable radio core emission. Among these 63 AGNs, we found 6 giant radio galaxies, with projected emission exceeding 750 kpc in length, and several other AGNs with unusual radio morphologies also seen in higher redshift surveys. The optical spectra of many of the extended sources are similar to those of typical broad-line radio galaxy spectra, having broad H{alpha} emission lines with boxy profiles and large M{sub BH}. With extended emission taken into account, we find strong evidence for a bimodal distribution in the radio-loudness parameter R ({identical_to}{nu}{sub radio} L{sub radio}/{nu}{sub opt} L{sub opt}), where the lower radio luminosity core-only sources appear as a population separate from the extended sources, with a dividing line at log(R) {approx}1.75. This dividing line ensures that these are indeed the most radio-loud AGNs, which may have different or extreme physical conditions in their central engines when compared to the more numerous radio-quiet AGNs.

  15. The Massive Hosts of Radio Galaxies Across Cosmic Time

    NASA Astrophysics Data System (ADS)

    Seymour, Nick; SHzRG Collaboration

    2007-05-01

    We present the results of a comprehensive Spitzer survey of 69 radio galaxies across 1galaxy stellar emission at rest-frame H-band. Stellar masses derived from rest-frame near-IR data, where AGN and young star contributions are minimized, are significantly more reliable than those derived from rest-frame optical and UV data. We find that the fraction of emitted light at rest-frame H-band from stars is >60% for 75% the high redshift radio galaxies. As expected from unified models of AGN, the stellar fraction of the rest-frame H-band luminosity has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5um) luminosity. Additionally, while the stellar H-band luminosity does not vary with stellar fraction, the total H-band luminosity anti-correlates with the stellar fraction as would be expected if the underlying hosts of these radio galaxies comprise a homogeneous population. The resultant stellar luminosities imply stellar masses of 10^{11-11.5}Msun even at the highest redshifts. Powerful radio galaxies tend to lie in a similar region of mid-IR color-color space as unobscured AGN, despite the stellar contribution to their mid-IR SEDs at shorter-wavelengths. The mid-IR luminosities alone classify most HzRGs as LIRGs or ULIRGs with even higher total-IR luminosities. As expected, these exceptionally high mid-IR luminosities are consistent with an obscured, highly-accreting AGN. Sub-mm observed starformation rates imply very high specific starformation rates, higher than other massive galaxies at these redshift ranges, suggesting we are watching the final formation of massive galaxies and black holes. We also present new evidence that the blackhole accretion rate (from mid-IR luminosity) correlates with radio lobe size and anti

  16. Clues to (Radio) Galaxy Formation from Deep HST Images

    NASA Astrophysics Data System (ADS)

    Windhorst, Rogier A.

    We review recent clues from deep HST images on the formation and evolution of galaxies, and of μJy and mJy radio sources in particular. Constraints from the radio source counts over 7 dex in flux and 1 dex in frequency are discussed. We review recent results from deep HST primary and parallel surveys relevant to (radio) galaxy formation. The WFPC2 galaxy counts as a function of morphological type for B < ~ 27 mag show that E/S0's and Sabc's are only marginally above the non-evolving predictions. The faint blue galaxy counts are dominated by Sd/Irr's, and are explained by a combination of a moderately steep local luminosity function undergoing strong luminosity evolution plus low-luminosity lower-redshift dwarf galaxies. Deep WFPC2 images in the medium-band filter F410M yielded 18 faint, compact Lyα emitting candidates at z ≃ 2.4 surrounding the radio galaxy 53W002 at z𢐲.390, as well as 18 more z ≃ 2.4 candidates in three random parallel fields. These objects appear to be star-forming spheroids smaller (rhl ≍ 0''.1 or 0.5-1 kpc) and fainter (MV (z=0)=-17--> -21) than the bulges of typical galaxies seen today. They may the building blocks from which many of the luminous nearby galaxies were formed through repeated hierarchical mergers. HST/PC images in BV I - as well as in redshifted Lyα - of 53W002 show several morphological components: (1) a blue AGN with < ~ 20-25% of the total continuum light; (2) an r1/4-like light distribution with colors indicating a stellar population age ~0.4 Gyr; and (3) two small blue clouds roughly aligned with the radio axis and the main stellar population. We show that both reflected AGN light and jet-induced starformation likely play a role in explaining its "alignment effect". We discuss a possible formation and evolution scenario of 53W002 in context of its surrounding sub-galactic objects, and argue that it will end up like a giant elliptical today.

  17. The radio sources CTA 21 and OF+247: The hot spots of radio galaxies

    NASA Astrophysics Data System (ADS)

    Artyukh, V. S.; Tyul'bashev, S. A.; Chernikov, P. A.

    2013-06-01

    The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ˜ 10-1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ˜ 10-3 G, and the density of relativistic electrons is n e ˜ 10-3 cm-3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, < E H > = < E e > ˜ 10-7-10-6 erg cm-3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.

  18. Determination of the Cosmic Radio Background from the Radio-Infrared Relation in Galaxies

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Barker, Michael K.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We use the radioactive flux correlation for star forming galaxies in the local universe to derive their contribution to the cosmic radio background (CRB). The CRB from these galaxies is therefore determined by the evolution of the comoving infrared luminosity density with redshift, which is constrained by galaxy number counts at various infrared wavelengths and by the cosmic infrared background. The research of ED was supported by NASA NRA 99-OSS-01 Astrophysics Theory Program. MB acknowledges the support of the "Research Opportunities for Undergraduates in the Laboratory for Astronomy and Solar Physics" for the summer student internship program at NASA/GSFC.

  19. Giant radio galaxies via inverse Compton weakened jets

    NASA Astrophysics Data System (ADS)

    Wiita, Paul J.; Rosen, Alexander; Gopal-Krishna; Saripalli, L.

    Both analytical and numerical models for the propagation of relativistic jets through a hot interstellar medium (ISM) and into an even hotter intergalactic medium (IGM) have been considered. The models by Gopal-Krishna and Wiita (1987), and Wiita and Gopal-Krishna (1987, 1988) were extended to allow for intrinsically extremely powerful jets, which may start off advancing relativistically through the interstellar medium. Eventually the energy density in the lobes becomes comparable to that of the microwave background, and inverse Compton losses of the synchrotron emitting electrons against the background photons become important. It is argued that only powerful radio engines are responsible for giant radio galaxies (GRGs, those whose linear size exceeds 1.5 Mpc), most of the observed peculiarities of the GRGs, such as their rarity, moderate radio flux and relatively strong radio cores can be explained.

  20. REVISITING SCALING RELATIONS FOR GIANT RADIO HALOS IN GALAXY CLUSTERS

    SciTech Connect

    Cassano, R.; Brunetti, G.; Venturi, T.; Kale, R.; Pratt, G. W.; Markevitch, M.

    2013-11-10

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R{sub 500} as P{sub 1.4}∼L{sup 2.1±0.2}{sub 500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L{sub 500} > 5 × 10{sup 44} erg s{sup –1}) clusters branch into two populations—radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P{sub 1.4} scales with the cluster integrated SZ signal within R{sub 500}, measured by Planck, as P{sub 1.4}∼Y{sup 2.05±0.28}{sub 500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that 'SZ-luminous' Y{sub 500} > 6 × 10{sup –5} Mpc{sup 2} clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle

  1. Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, Maxim L.

    2013-01-01

    Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R(sub 500) as P(sub 1.4) approx. L(2.1+/-0.2) - 500). Our bigger and more homogenous sample confirms that the X-ray luminous (L(sub 500) > 5 × 10(exp 44) erg/s)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P(sub 1.4) scales with the cluster integrated SZ signal within R(sub 500), measured by Planck, as P(sub 1.4) approx. Y(2.05+/-0.28) - 500), in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y(sub 500) > 6×10(exp -5) Mpc(exp 2) clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.

  2. Inverse-Compton X-rays from giant radio galaxies at z ~ 1

    NASA Astrophysics Data System (ADS)

    Laskar, T.; Fabian, A. C.; Blundell, K. M.; Erlund, M. C.

    2010-01-01

    We report XMM-Newton observations of three FR II radio galaxies at redshifts between 0.85 and 1.34, which show extended diffuse X-ray emission within the radio lobes, likely due to inverse-Compton up-scattering of the cosmic microwave background. Under this assumption, through spectrum fitting together with archival Very Large Array radio observations, we derive an independent estimate of the magnetic field in the radio lobes of 3C 469.1 and compare it with the equipartition value. We find concordance between these two estimates as long as the turnover in the energy distribution of the particles occurs at a Lorentz factor in excess of ~250. We determine the total energy in relativistic particles in the radio-emitting lobes of all three sources to range between 3 × 1059 and 8 × 1059erg. The nuclei of these X-ray sources are heavily-absorbed powerful active galactic nuclei.

  3. The host galaxy of a fast radio burst

    NASA Astrophysics Data System (ADS)

    Keane, E. F.; Johnston, S.; Bhandari, S.; Barr, E.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Flynn, C.; Jameson, A.; Kramer, M.; Petroff, E.; Possenti, A.; van Straten, W.; Bailes, M.; Burke-Spolaor, S.; Eatough, R. P.; Stappers, B. W.; Totani, T.; Honma, M.; Furusawa, H.; Hattori, T.; Morokuma, T.; Niino, Y.; Sugai, H.; Terai, T.; Tominaga, N.; Yamasaki, S.; Yasuda, N.; Allen, R.; Cooke, J.; Jencson, J.; Kasliwal, M. M.; Kaplan, D. L.; Tingay, S. J.; Williams, A.; Wayth, R.; Chandra, P.; Perrodin, D.; Berezina, M.; Mickaliger, M.; Bassa, C.

    2016-02-01

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy’s redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called ‘missing baryons’. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

  4. Multiwavelength Search and Studies of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2016-06-01

    Since 1950s, Byurakan Astrophysical Observatory (BAO) has always been one of the centres for surveys and studies of active galaxies. Here I review our search and studies of active galaxies during last 30 years using various wavelength ranges, as well as some recent related works. These projects since late 1980s were focused on multiwavelength search and studies of AGN and Starbursts (SB). 1103 blue stellar objects (BSOs) on the basis of their UV-excess were selected using Markarian Survey (First Byurakan Survey, FBS) plates and Markarian's criteria used for the galaxies. Among many blue stars, QSOs and Seyfert galaxies were found by follow-up observations. 1577 IRAS point sources were optically identified using FBS low-dispersion spectra and many AGN, SB and high-luminosity IR galaxies (LIRG/ULIRG) were discovered. 32 extremely high IR/opt flux ratio galaxies were studies with Spitzer. 2791 ROSAT FSC sources were optically identified using Hamburg Quasar Survey (HQS) low-dispersion spectra and many AGN were discovered by follow-up observations. Fine analysis of emission line spectra was carried out using spectral line decomposition software to establish true profiles and calculate physical parameters for the emitting regions, as well as to study the spectral variability of these objects. X-ray and radio selection criteria were used to find new AGN and variable objects for further studies. Multiwavelength approach allowed revealing many new AGN and SB and obtaining a number of interesting relations using their observational characteristics and physical properties.

  5. Radio continuum emission and HI gas accretion in the NGC 5903/5898 compact group of galaxies

    NASA Astrophysics Data System (ADS)

    Wiita, Paul; Gopal-Krishna; Mhaskey, Mukul

    2012-03-01

    We investigate the nature of the multi-component radio continuum and HI emission associated with the nearby galaxy group comprised of two dominant ellipticals, NGC 5898 and NGC 5903 and a dwarf lenticular ESO514-G003. Striking new details of radio emission come from the ongoing TIFR.GMRT.SKY.SURVEY (TGSS) which provides images with a resolution of ˜24^'' x18^'' and rms noise of 5 mJy at 150 MHz. Previous observations of this compact triplet include images at higher frequencies of the radio continuum as well as huge HI trails originating from the vicinity of NGC 5903. The TGSS 150 MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf SO galaxy ESO514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (α˜-1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the HI trails. Both its radio loud members are also the only galaxies that are seen to be connected to an HI filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  6. Radio properties of galaxy groups in the Local Universe (<80 Mpc)

    NASA Astrophysics Data System (ADS)

    Kolokythas, K.

    2013-09-01

    The most likely source of energy injection into the intergalactic medium of galaxy groups is AGN (Active Galactic Nuclei) feedback. Since >50% of galaxies in the local Universe reside in groups and many of them host radiative cooling gas halos, which can fuel a central SMBH, they are probably the key environment for the study of AGN/hot gas interactions. Using a complete, optically selected sample of groups -the Complete Local-Volume Groups Sample (CLoGS) project- observed in both radio and Xray bands, I examine the radio properties of AGN in nearby galaxy groups. My work targets to the characterization of the AGN population in groups, and examination of their impact on the intra-group gas and member galaxies. By focusing on low-frequency radio emission (240 MHz and 610 MHz ), past as well as current AGN activity can be identified with the combination of good spatial resolution at 610 MHz and the sensitivity to older electron populations at 235 MHz. The combination then of radio with optical and X-ray bands reveals the complex interactions with their environment and the physical processes that govern galaxy transformations. Results from our new GMRT observations at 235 and 610 MHz will be presented here for the first time for the systems of 4261, 5982, 1060 and 5903. These systems are good examples of the wide variety of radio properties: from groups dominated by a single powerful central source (4261), through weak AGN and star-formation dominated systems (1060, 5982) to diffuse, merger-related sources (5903). These are all important for the investigation of the IGM/AGN connection and the understanding of the physical mechanisms of the energy injection.

  7. Erratum: A Comparison of Radio Axis with Host Galaxy Plane Axis in Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Schmitt, Henrique R.; Kinney, Anne L.; Storchi-Bergmann, Thaisa; Antonucci, Robert

    1997-08-01

    In the paper ``A Comparison of Radio Axis with Host Galaxy Plane Axis in Seyfert Galaxies'' by Henrique R. Schmitt, Anne L. Kinney, Thaisa Storchi-Bergmann, & Robert Antonucci (ApJ, 477, 623 [1997]), there are errors in Table 1 and Figure 6, and there is a reference to a previous work that should be stated. With respect to the latter, the authors compare the position angle of small-scale radio structures in Seyfert galaxies with the position angle of their host galaxy major axis. In their analysis they find a zone of avoidance, where the small-scale radio axis avoids close alignment with the host galaxy minor axis. The authors wish to note that J. S. Ulvestad and A. S. Wilson (ApJ, 285, 439 [1984]) already observed a paucity of radio structures aligned with the host galaxy minor axis in Seyfert 2 galaxies, although on a smaller sample. Ulvestad & Wilson was referenced in their paper as Ulvestad & Wilson (1984b). In Table 1 there were errors in the references listed in the note to the table. A new version of Table 1 with correct references is given here, and the following reference entries should be added to the reference list of the original paper: Mulchaey, J. S., Wilson, A. S., & Tsvetanov, Z. I. 1996, ApJS, 102, 309; Oke, J. B., & Lauer, T. R. 1979, ApJ, 230, 360; Simkin, S. M. 1975, ApJ, 200, 567. Figure 6a was printed twice, once correctly and once incorrectly in place of Figure 6c. The correct version of Figure 6c appears below.

  8. Super-Sharp Radio "Vision" Measures Galaxy's Motion in Space

    NASA Astrophysics Data System (ADS)

    2005-03-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have measured the motion across the sky of a galaxy nearly 2.4 million light-years from Earth. While scientists have been measuring the motion of galaxies directly toward or away from Earth for decades, this is the first time that the transverse motion (called proper motion by astronomers) has been measured for a galaxy that is not a satellite of our own Milky Way Galaxy. M33 Radio/Optical Image of M33 CREDIT: NRAO/AUI/NSF, NOAO/AURA/NSF (Click on image for more files) An international scientific team analyzed VLBA observations made over two and a half years to detect minuscule shifts in the sky position of the spiral galaxy M33. Combined with previous measurements of the galaxy's motion toward Earth, the new data allowed the astronomers to calculate M33's movement in three dimensions for the first time. "A snail crawling on Mars would appear to be moving across the surface more than 100 times faster than the motion we measured for this galaxy," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. M33 is a satellite of the larger galaxy M31, the well-known Andromeda Galaxy that is the most distant object visible to the naked eye. Both are part of the Local Group of galaxies that includes the Milky Way. In addition to measuring the motion of M33 as a whole, the astronomers also were able to make a direct measurement of the spiral galaxy's rotation. Both measurements were made by observing the changes in position of giant clouds of molecules inside the galaxy. The water vapor in these clouds acts as a natural maser, strengthening, or amplifying, radio emission the same way that lasers amplify light emission. The natural masers acted as bright radio beacons whose movement could be tracked by the ultra-sharp radio "vision" of the VLBA. Reid and his colleagues plan to continue measuring M33's motion and also to make similar measurements of M31's motion

  9. Giant ringlike radio structures around galaxy cluster Abell 3376.

    PubMed

    Bagchi, Joydeep; Durret, Florence; Neto, Gastão B Lima; Paul, Surajit

    2006-11-01

    In the current paradigm of cold dark matter cosmology, large-scale structures are assembling through hierarchical clustering of matter. In this process, an important role is played by megaparsec (Mpc)-scale cosmic shock waves, arising in gravity-driven supersonic flows of intergalactic matter onto dark matter-dominated collapsing structures such as pancakes, filaments, and clusters of galaxies. Here, we report Very Large Array telescope observations of giant ( approximately 2 Mpc by 1.6 Mpc), ring-shaped nonthermal radio-emitting structures, found at the outskirts of the rich cluster of galaxies Abell 3376. These structures may trace the elusive shock waves of cosmological large-scale matter flows, which are energetic enough to power them. These radio sources may also be the acceleration sites where magnetic shocks are possibly boosting cosmic-ray particles with energies of up to 10(18) to 10(19) electron volts. PMID:17082451

  10. ACCRETION PROPERTIES OF HIGH- AND LOW-EXCITATION YOUNG RADIO GALAXIES

    SciTech Connect

    Son, Donghoon; Woo, Jong-Hak; Park, Daeseong; Kim, Sang Chul; Fu, Hai; Kawakatu, Nozomu; Bennert, Vardha N.; Nagao, Tohru

    2012-10-01

    Young radio galaxies (YRGs) provide an ideal laboratory to explore the connection between the accretion disk and radio jet thanks to their recent jet formation. We investigate the relationship between the emission-line properties, the black hole accretion rate, and the radio properties using a sample of 34 low-redshift (z < 0.4) YRGs. We classify YRGs as high-excitation galaxies (HEGs) and low-excitation galaxies (LEGs) based on the flux ratio of high-ionization to low-ionization emission lines. Using the H{alpha} luminosities as a proxy of accretion rate, we find that HEGs in YRGs have {approx}1 dex higher Eddington ratios than LEGs in YRGs, suggesting that HEGs have a higher mass accretion rate or higher radiative efficiency than LEGs. In agreement with previous studies, we find that the luminosities of emission lines, in particular H{alpha}, are correlated with radio core luminosity, suggesting that accretion and young radio activities are fundamentally connected.

  11. Ram pressure statistics for bent tail radio galaxies

    NASA Astrophysics Data System (ADS)

    Mguda, Zolile; Faltenbacher, Andreas; Heyden, Kurt van der; Gottlöber, Stefan; Cress, Catherine; Vaisanen, Petri; Yepes, Gustavo

    2015-02-01

    In this paper, we use the MareNostrum Universe Simulation, a large-scale, hydrodynamic, non-radiative simulation in combination with a simple abundance matching approach to determine the ram pressure statistics for bent radio sources (BRSs). The abundance matching approach allows us to determine the locations of all galaxies with stellar masses ≥ 1011 h- 1 M⊙ in the simulation volume. Assuming that ram pressure exceeding a critical value causes bent morphology, we compute the ratio of all galaxies exceeding the ram pressure limit (RPEX galaxies) relative to all galaxies in our sample. According to our model 50 per cent of the RPEX galaxies at z = 0 are found in clusters with masses larger than 1014.5 h- 1 M⊙ the other half resides in lower mass clusters. Therefore, the appearance of bent tail morphology alone does not put tight constraints on the host cluster mass. In low-mass clusters, M ≤ 1014 h- 1 M⊙, RPEX galaxies are confined to the central 500 h-1 kpc whereas in clusters of ≥ 1015 h- 1 M⊙ they can be found at distances up to 1.5 h-1 Mpc. Only clusters with masses ≥ 1015 h- 1 M⊙ are likely to host more than one BRS. Both criteria may prove useful in the search for distant, high-mass clusters.

  12. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  13. Periodicity analysis of the radio light curve of the Seyfert galaxy III Zw 2

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Xie, G. Z.; Dai, H.; Chen, L. E.; Yi, T. F.; Tang, Y. K.; Bao, Y. Y.; Lü, L. Z.; Na, W. W.; Ren, J. Y.

    2010-02-01

    We have analyzed the radio light curves of the Seyfert galaxy III Zw 2 at 22 and 37 GHz taken from the database of Metsähovi Radio Observatory, and found evidence of quasi-periodic activity. The light curves show great activity, with very complicated non-sinusoidal variations. Period of Pobs = 5.14 ± 0.19 yr was consistently identified by three methods: the Jurkevich method, the power spectrum intensity estimation method and the discrete correlation function method. The variability period of about 5.14 yr in III Zw 2 is caused most likely by the helical motion of the jet.

  14. Infrared imaging of MG 0414 + 0534 - The red gravitational lens systems as lensed radio galaxies

    NASA Technical Reports Server (NTRS)

    Annis, James; Luppino, Gerard A.

    1993-01-01

    We present an IR image of the gravitational lens system MG 0414 + 0534, and IR photometry of PG 1115 + 080, H1413 + 117, and Q1429 - 008. The IR of MG 0414 + 0534 shows a morphology that is similar to the radio and optical morphologies. The object is bright (K-prime = 13.7) and extremely red (I-K-prime = 5.7). MG 0414 + 0534 thus becomes the second radio-selected lens system to have very red optical IR colors. When plotted on a color-magnitude diagram of objects from a radio survey, MG 0414 + 0534 and the other very red system, MG 1131 + 0456, lie near the locus of radio galaxies. We therefore suggest that these systems are lensed high-redshift radio galaxies. In general, lensed radio galaxies should be common among lens systems selected from radio surveys, since a high proportion of radio sources are radio galaxies.

  15. Galactic interaction as the trigger for the young radio galaxy MRC B1221-423

    NASA Astrophysics Data System (ADS)

    Anderson, C. S.; Johnston, H. M.; Hunstead, R. W.

    2013-06-01

    Mergers between a massive galaxy and a small gas-rich companion (minor mergers) have been proposed as a viable mechanism for triggering radio emission in an active galaxy. Until now the problem has been catching this sequence of events as they occur. With MRC B1221-423, we have an active radio galaxy that has only recently been triggered, and a companion galaxy that provides the `smoking gun'. Using spectroscopic data taken with the VIsible Multi Object Spectrograph (VIMOS) integral field unit detector on the European Southern Observatory's Very Large Telescope, we have examined the distribution, ionization state and kinematics of ionized gas in this interacting system. We have also modelled the stellar continuum with synthesized spectra of stellar populations of different ages. From our study of the ionized gas, we have derived preliminary models for the geometry of the interaction, analysed the kinematic behaviour of the ionized gas, and examined the ionization mechanisms at work throughout the system. Our modelling of the stellar continuum allowed us to identify and date distinct stellar populations within the galaxy pair. We find evidence of multiple episodes of widespread starburst activity, and by dating these populations, we provide tentative insight into the history of the interaction.

  16. Multiband observations of Cygnus A: A study of pressure balance in the core of a powerful radio galaxy

    NASA Technical Reports Server (NTRS)

    Carilli, Chris; Conner, Sam; Dreher, John; Perley, Rick

    1990-01-01

    Cygnus A is a powerful double radio source associated with a giant elliptical galaxy at the center of a poor cluster of galaxies. The radio source also sits within the core radius of a dense, cooling flow, x ray emitting cluster gas. Optical spectroscopy and narrow band imaging have revealed copious amounts of narrow line emission from the inner 20 kpc of the associated galaxy. Researchers assume H sub o = 75 km sec (-1) Mpc(-1). Discussed here are the pressures in the three components of the Interstellar Medium (ISM) (i.e., the radio, x ray, and line emitting fluids) within a radius of about 15 kpc of the active nucleus of the Cygnus A galaxy.

  17. A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz

    SciTech Connect

    Giacintucci, Simona; O'Sullivan, Ewan; Vrtilek, Jan; David, Laurence P.; Mazzotta, Pasquale; Gitti, Myriam; Jones, Christine; Forman, William R.; Raychaudhury, Somak; Ponman, Trevor; Venturi, Tiziana; Athreya, Ramana M.; Clarke, Tracy E.; Murgia, Matteo; Ishwara-Chandra, C. H.

    2011-05-10

    We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGNs) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology, and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at {approx}>1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems and are typically associated with small, low-, or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties, and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that co-exist with current activity is found in six groups of the sample.

  18. Super-Sharp Radio "Vision" Measures Galaxy's Motion in Space

    NASA Astrophysics Data System (ADS)

    2005-03-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have measured the motion across the sky of a galaxy nearly 2.4 million light-years from Earth. While scientists have been measuring the motion of galaxies directly toward or away from Earth for decades, this is the first time that the transverse motion (called proper motion by astronomers) has been measured for a galaxy that is not a satellite of our own Milky Way Galaxy. M33 Radio/Optical Image of M33 CREDIT: NRAO/AUI/NSF, NOAO/AURA/NSF (Click on image for more files) An international scientific team analyzed VLBA observations made over two and a half years to detect minuscule shifts in the sky position of the spiral galaxy M33. Combined with previous measurements of the galaxy's motion toward Earth, the new data allowed the astronomers to calculate M33's movement in three dimensions for the first time. "A snail crawling on Mars would appear to be moving across the surface more than 100 times faster than the motion we measured for this galaxy," said Mark Reid, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. M33 is a satellite of the larger galaxy M31, the well-known Andromeda Galaxy that is the most distant object visible to the naked eye. Both are part of the Local Group of galaxies that includes the Milky Way. In addition to measuring the motion of M33 as a whole, the astronomers also were able to make a direct measurement of the spiral galaxy's rotation. Both measurements were made by observing the changes in position of giant clouds of molecules inside the galaxy. The water vapor in these clouds acts as a natural maser, strengthening, or amplifying, radio emission the same way that lasers amplify light emission. The natural masers acted as bright radio beacons whose movement could be tracked by the ultra-sharp radio "vision" of the VLBA. Reid and his colleagues plan to continue measuring M33's motion and also to make similar measurements of M31's motion

  19. 3C 220.3: A Radio Galaxy Lensing a Submillimeter Galaxy

    NASA Astrophysics Data System (ADS)

    Haas, Martin; Leipski, Christian; Barthel, Peter; Wilkes, Belinda J.; Vegetti, Simona; Bussmann, R. Shane; Willner, S. P.; Westhues, Christian; Ashby, Matthew L. N.; Chini, Rolf; Clements, David L.; Fassnacht, Christopher D.; Horesh, Assaf; Klaas, Ulrich; Koopmans, Léon V. E.; Kuraszkiewicz, Joanna; Lagattuta, David J.; Meisenheimer, Klaus; Stern, Daniel; Wylezalek, Dominika

    2014-07-01

    Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z = 2.221. At an observed wavelength of 1 mm, the SMG is lensed into three distinct images. In the observed near infrared, these images are connected by an arc of ~1''.8 radius forming an Einstein half-ring centered near the radio galaxy. In visible light, only the arc is apparent. 3C 220.3 is the only known instance of strong galaxy-scale lensing by a PRG not located in a galaxy cluster and therefore it offers the potential to probe the dark matter content of the radio galaxy host. Lens modeling rejects a single lens, but two lenses centered on the radio galaxy host A and a companion B, separated by 1''.5, provide a fit consistent with all data and reveal faint candidates for the predicted fourth and fifth images. The model does not require an extended common dark matter halo, consistent with the absence of extended bright X-ray emission on our Chandra image. The projected dark matter fractions within the Einstein radii of A (1''.02) and B (0''.61) are about 0.4 ± 0.3 and 0.55 ± 0.3. The mass to i-band light ratios of A and B, M/Li ˜ 8 +/- 4 M⊙ L⊙ -1, appear comparable to those of radio-quiet lensing galaxies at the same redshift in the CfA-Arizona Space Telescope LEns Survey, Lenses Structure and Dynamics, and Strong Lenses in the Legacy Survey samples. The lensed SMG is extremely bright with observed f(250 μm) = 440 mJy owing to a magnification factor μ ~ 10. The SMG spectrum shows luminous, narrow C IV λ1549 Å emission, revealing that the SMG houses a hidden quasar in addition to a violent starburst. Multicolor image reconstruction of the SMG indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive of cones through which UV light escapes a dust-enshrouded nucleus.

  20. 3C 220.3: A radio galaxy lensing a submillimeter galaxy

    SciTech Connect

    Haas, Martin; Westhues, Christian; Chini, Rolf; Leipski, Christian; Klaas, Ulrich; Meisenheimer, Klaus; Barthel, Peter; Koopmans, Léon V. E.; Wilkes, Belinda J.; Bussmann, R. Shane; Willner, S. P.; Ashby, Matthew L. N.; Kuraszkiewicz, Joanna; Vegetti, Simona; Clements, David L.; Fassnacht, Christopher D.; Horesh, Assaf; Lagattuta, David J.; Stern, Daniel; Wylezalek, Dominika

    2014-07-20

    Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z = 2.221. At an observed wavelength of 1 mm, the SMG is lensed into three distinct images. In the observed near infrared, these images are connected by an arc of ∼1''.8 radius forming an Einstein half-ring centered near the radio galaxy. In visible light, only the arc is apparent. 3C 220.3 is the only known instance of strong galaxy-scale lensing by a PRG not located in a galaxy cluster and therefore it offers the potential to probe the dark matter content of the radio galaxy host. Lens modeling rejects a single lens, but two lenses centered on the radio galaxy host A and a companion B, separated by 1''.5, provide a fit consistent with all data and reveal faint candidates for the predicted fourth and fifth images. The model does not require an extended common dark matter halo, consistent with the absence of extended bright X-ray emission on our Chandra image. The projected dark matter fractions within the Einstein radii of A (1''.02) and B (0''.61) are about 0.4 ± 0.3 and 0.55 ± 0.3. The mass to i-band light ratios of A and B, M/L{sub i}∼8±4 M{sub ⊙} L{sub ⊙}{sup −1}, appear comparable to those of radio-quiet lensing galaxies at the same redshift in the CfA-Arizona Space Telescope LEns Survey, Lenses Structure and Dynamics, and Strong Lenses in the Legacy Survey samples. The lensed SMG is extremely bright with observed f(250 μm) = 440 mJy owing to a magnification factor μ ∼ 10. The SMG spectrum shows luminous, narrow C IV λ1549 Å emission, revealing that the SMG houses a hidden quasar in addition to a violent starburst. Multicolor image reconstruction of the SMG indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive of cones through which UV light escapes a dust-enshrouded nucleus.

  1. Flashing superluminal components in the jet of the radio galaxy 3C120

    PubMed

    Gomez; Marscher; Alberdi; Jorstad; Garcia-Miro

    2000-09-29

    A 16-month sequence of radio images of the active galaxy 3C120 with the Very Long Baseline Array reveals a region in the relativistic jet where superluminal components flash on and off over time scales of months, while the polarization angle rotates. This can be explained by interaction between the jet and an interstellar cloud located about 8 parsecs from the center of the galaxy. The cloud, which rotates the polarization direction and possibly eclipses a section of the jet, represents a "missing link" between the ultradense broad-emission-line clouds closer to the center and the lower density narrow-emission-line clouds seen on kiloparsec scales. PMID:11009410

  2. The ATLAS3D Project - XXXI. Nuclear radio emission in nearby early-type galaxies

    NASA Astrophysics Data System (ADS)

    Nyland, Kristina; Young, Lisa M.; Wrobel, Joan M.; Sarzi, Marc; Morganti, Raffaella; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Naab, Thorsten; Oosterloo, Tom; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie

    2016-05-01

    We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS3D survey of early-type galaxies (ETGs). We find that 51 ± 4 per cent of the ETGs in our sample contain nuclear radio emission with luminosities as low as 1018 W Hz-1. Most of the nuclear radio sources have compact (≲25-110 pc) morphologies, although ˜10 per cent display multicomponent core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at subarcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and - for the first time - the global kinematic state. We discuss implications for the growth, triggering, and fuelling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs.

  3. Star Formation Suppression Due to Jet Feedback in Radio Galaxies with Shocked Warm Molecular Gas

    NASA Astrophysics Data System (ADS)

    Lanz, Lauranne; Ogle, Patrick M.; Alatalo, Katherine; Appleton, Philip N.

    2016-07-01

    We present Herschel observations of 22 radio galaxies, selected for the presence of shocked, warm molecular hydrogen emission. We measured and modeled spectral energy distributions in 33 bands from the ultraviolet to the far-infrared to investigate the impact of jet feedback on star formation activity. These galaxies are massive, early-type galaxies with normal gas-to-dust ratios, covering a range of optical and infrared colors. We find that the star formation rate (SFR) is suppressed by a factor of ˜3–6, depending on how molecular gas mass is estimated. We suggest that this suppression is due to the shocks driven by the radio jets injecting turbulence into the interstellar medium (ISM), which also powers the luminous warm H2 line emission. Approximately 25% of the sample shows suppression by more than a factor of 10. However, the degree of SFR suppression does not correlate with indicators of jet feedback including jet power, diffuse X-ray emission, or intensity of warm molecular H2 emission, suggesting that while injected turbulence likely impacts star formation, the process is not purely parameterized by the amount of mechanical energy dissipated into the ISM. Radio galaxies with shocked warm molecular gas cover a wide range in SFR–stellar mass space, indicating that these galaxies are in a variety of evolutionary states, from actively star-forming and gas-rich to quiescent and gas-poor. SFR suppression appears to have the largest impact on the evolution of galaxies that are moderately gas-rich.

  4. Neutral hydrogen in elliptical galaxies with nuclear radio sources and optical emission lines

    NASA Technical Reports Server (NTRS)

    Dressel, L. L.; Bania, T. M.; Oconnell, R. W.

    1982-01-01

    An H I detection survey of eleven elliptical galaxies with powerful nuclear radio sources was conducted, using the 305 m antenna of Arecibo Observatory, to test the hypothesis that large H I mass is conductive to the formation of nuclear radio sources in elliptical galaxies. The H I was detected in emission in UGC 09114 and was possibly detected in absorption in UGC 06671. Observations of the remaining galaxies were not sensitive enough to support or refute the hypothesis. Data was combined from other H I surveys and spectroscopic surveys to search for correlations of H I mass with other galactic properties and environmental conditions. Strong correlations of (O II) lambda 3727 emission with H I content and with nuclear radio power were found. The latter two properties may simply indicate, respectively, whether a significant amount of gas is available to be ionized and whether energy is provided by nuclear activity for ionization. No dependence of H I content on optical luminosity or on degree of isolation from other galaxies was found.

  5. Alignments of radio galaxies in deep radio imaging of ELAIS N1

    NASA Astrophysics Data System (ADS)

    Taylor, A. R.; Jagannathan, P.

    2016-06-01

    We present a study of the distribution of radio jet position angles of radio galaxies over an area of 1 square degree in the ELAIS N1 field. ELAIS N1 was observed with the Giant Metrewave Radio Telescope at 612 MHz to an rms noise level of 10 μJy and angular resolution of 6 arcsec × 5 arcsec. The image contains 65 resolved radio galaxy jets. The spatial distribution reveals a prominent alignment of jet position angles along a `filament' of about 1°. We examine the possibility that the apparent alignment arises from an underlying random distribution and find that the probability of chance alignment is less than 0.1 per cent. An angular covariance analysis of the data indicates the presence of spatially coherence in position angles on scales >0 .^{circ}5. This angular scales translates to a comoving scale of >20 Mpc at a redshift of 1. The implied alignment of the spin axes of massive black holes that give rise to the radio jets suggest the presence of large-scale spatial coherence in angular momentum. Our results reinforce prior evidence for large-scale spatial alignments of quasar optical polarization position angles.

  6. UNIFICATION SCHEME OF RADIO GALAXIES AND QUASARS FALSIFIED BY THEIR OBSERVED SIZE DISTRIBUTIONS

    SciTech Connect

    Singal, Ashok K.; Singh, Raj Laxmi

    2013-03-20

    In the currently popular orientation-based unified scheme, a radio galaxy appears as a quasar when its principal radio-axis happens to be oriented within a certain cone opening angle around the observer's line of sight. Due to geometrical projection, the observed sizes of quasars should therefore appear smaller than those of radio galaxies. We show that this simple, unambiguous prediction of the unified scheme is not borne out by the actually observed angular sizes of radio galaxies and quasars. Except in the original 3CR sample, based on which the unified scheme was proposed, in other much larger samples no statistically significant difference is apparent in the size distributions of radio galaxies and quasars. The population of low-excitation radio galaxies with apparently no hidden quasars inside, which might explain the observed excess number of radio galaxies at low redshifts, cannot account for the absence of any foreshortening of the sizes of quasars at large redshifts. On the other hand, from infrared and X-ray studies, there is evidence of a hidden quasar within a dusty torus in many radio galaxies, at z > 0.5. It is difficult to reconcile this with the absence of foreshortening of quasar sizes at even these redshifts, and perhaps one has to allow that the major radio axis may not have anything to do with the optical axis of the torus. Otherwise, to resolve the dichotomy of radio galaxies and quasars, a scheme quite different from the present might be required.

  7. A physical model of the infrared-to-radio correlation in galaxies

    NASA Technical Reports Server (NTRS)

    Helou, G.; Bicay, M. D.

    1993-01-01

    We explore the implications of the IR-radio correlation in star-forming galaxies, using a simple physical model constrained by the constant global ratio q of IR to radio emission and by the radial falloff of this ratio in disks of galaxies. The modeling takes into account the diffusion, radiative decay, and escape of cosmic-ray electrons responsible for the synchrotron emission, and the full range of optical depths to dust-heating photons. We introduce two assumptions: that dust-heating photons and radio-emitting cosmic-ray electrons are created in constant proportion to each other as part of the star formation activity, and that gas and magnetic field are well coupled locally, expressed as B proportional to n exp beta, with beta between 1/3 and 2/3. We conclude that disk galaxies would maintain the observed constant ratio q under these assumptions if the disk scale height h(0) and the escape scale length l(esc) for cosmic-ray electrons followed a relation of the form l(esc) proportional to h(0) exp 1/2; the IR-to-radio ratio will then depend very weakly on interstellar density, and, therefore, on magnetic field strength or mean optical depth.

  8. Radio continuum spectra of gigahertz-peaked spectrum galaxies

    NASA Astrophysics Data System (ADS)

    Torniainen, I.; Tornikoski, M.; Lähteenmäki, A.; Aller, M. F.; Aller, H. D.; Mingaliev, M. G.

    2007-07-01

    Context: Recent studies have shown that a remarkable share of quasars classified in the literature as gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are actually flaring flat-spectrum sources or blazars. Thus, at least among the quasar-type samples, genuine GPS sources and HFPs seem to be rare. Aims: We have studied variability and the shape of the radio continuum spectra of a sample of 96 galaxy-type GPS sources and HFPs in order to find out whether there is a similar contamination in the galaxy-type samples. Methods: We collected radio data for the sample from the literature, our long-term monitoring campaigns, and recent observations, and then plotted the radio continuum spectra. We also calculated the peak frequencies, the spectral indices, and the variability indices, and finally classified the sources according to these parameters. Results: About 30% of the galaxies in our sample are clearly GPS sources, for another ~30% there are not enough data for a solid classification, and the rest are flat- or steep-spectrum sources. Conclusions: The galaxy-type GPS samples seem to be cleaner than the quasar-type, but there is also a remarkable contamination of other source types among the galaxies. However, there may be a strong selection effect, originating from the different selection criteria of the original samples, which must be taken into consideration when comparing the results of this and our previous study. Both simultaneous spectra and long-term monitoring are essential when classifying convex-spectrum sources. However, even monitoring for several years may not reveal the variable nature of a source with a convex radio spectrum. Figures 4 to 9 are only available in electronic form at http://www.aanda.org Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/469/451

  9. X-Shaped Radio Galaxies and the Gravitational Wave Background

    NASA Astrophysics Data System (ADS)

    Hall Roberts, David; Saripalli, Lakshmi; Subrahmanyan, Ravi

    2015-08-01

    Coalescence of super massive black holes (SMBH's) in galactic mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers (2002) that X-shaped radio galaxies are signposts of such coalescences, and that their abundance might be used to predict the magnitude of the gravitational wave background. In Roberts et al. (2015) we presented radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung (2007) for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources that were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations, much smaller than the 7% suggested by Leahy & Parma (1992). Thus the associated gravitational wave background may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB.

  10. Spectral ageing properties of giant radio galaxy Pictor A

    NASA Astrophysics Data System (ADS)

    Patra, Dusmanta; Chakrabarti, Sandip Kumar; Pal, Sabyasachi; Konar, Chiranjib

    2016-07-01

    We present detailed multi-frequency observations of the strong southern FRII radio galaxy Pictor A. We use low frequency data of Giant Metrewave Radio Telescope (GMRT), starting from 150 MHz. We also use the high frequency available archival data from Jansky Very Large Array (JVLA). We have made radio images of this source at 150 MHz, 250 MHz, 325 MHz, 610 MHz, 1.4 GHz, 5 GHz and 8 GHz. The radio lobes are found to be nearly circular and very bright. A jet is also noticed connecting the hotspots with the nucleus in both lobes. The radio lobes have different spectral indices in the different parts of the lobes. We perform spectral ageing analysis of different parts of the lobes to study evolution of the jet/lobe. The spectral age is constrained by fitting the spectra with different spectral ageing models, e.g., Kardashev-Pacholczyk (KP), Jaffe-Perola(JP) and Continuous Injection (CI). We also studied the spectrum of individual lobes and any possible sign of spectral absorption due to Synchrotron self absorption. Synchrotron self absorption seems to have Been noticed towards low frequency region.

  11. X-ray emission associated with radio galaxies in the Perseus cluster

    NASA Technical Reports Server (NTRS)

    Rhee, George; Burns, Jack O.; Kowalski, Michael P.

    1994-01-01

    In this paper, we report on new x-ray observations of the Perseus cluster made using four separate pointings of the Roentgen Satellite (ROSAT) Positron Sensitive Proportional Counter (PSPC). We searched for x-ray emission associated with 16 radio galaxies and detected six above 3 sigma. We made use of the PSPC spectra to determine if the x-ray emission associated with radio galaxies in Perseus is thermal or nonthermal in origin (i.e., hot gas or an active galactic nuclei (AGN)). For the head-tail radio galaxy IC 310, we find that the data are best fit by a power law model with an unusually large spectral index alpha = 2.7. This is consistent with its unresolved spatial structure. On the other hand, a second resolved x-ray source associated with another radio galaxy 2.3 Mpc from the Perseus center (V Zw 331) is best fit by a thermal model. For three sources with insufficient flux for a full spectral analysis, we calculated hardness ratios. On this basis, the x-ray emission associated with the well known head-tail source NGC 1265 is consistent with thermal radiation. The x-ray spectra of UGC 2608 and UGC 2654 probably arise from hot gas, although very steep power-law spectra (alpha greater than 3.2) are also possible. The spectrum of NGC 1275 is quite complex due to the presence of an AGN and the galaxy's location at the center of a cluster cooling flow.

  12. SPITZER MID-IR SPECTROSCOPY OF POWERFUL 2 JY AND 3CRR RADIO GALAXIES. I. EVIDENCE AGAINST A STRONG STARBURST-AGN CONNECTION IN RADIO-LOUD AGN

    SciTech Connect

    Dicken, D.; Axon, D.; Robinson, A.; Kharb, P.; Tadhunter, C.; Ramos Almeida, C.; Morganti, R.; Kouwenhoven, M. B. N.; Spoon, H.; Inskip, K. J.; Holt, J.; Nesvadba, N. P. H.

    2012-02-01

    We present deep Spitzer/Infrared Spectrograph (IRS) spectra for complete samples of 46 2 Jy radio galaxies (0.05 < z < 0.7) and 19 3CRR FRII radio galaxies (z < 0.1), and use the detection of polycyclic aromatic hydrocarbon (PAH) features to examine the incidence of contemporaneous star formation and radio-loud active galactic nucleus (AGN) activity. Our analysis reveals PAH features in only a minority (30%) of the objects with good IRS spectra. Using the wealth of complementary data available for the 2 Jy and 3CRR samples we make detailed comparisons between a range of star formation diagnostics: optical continuum spectroscopy, mid- to far-IR (MFIR) color, far-IR excess and PAH detection. There is good agreement between the various diagnostic techniques: most candidates identified to have star formation activity on the basis of PAH detection are also identified using at least two of the other techniques. We find that only 35% of the combined 2 Jy and 3CRR sample show evidence for recent star formation activity (RSFA) at optical and/or MFIR wavelengths. This result argues strongly against the idea of a close link between starburst and powerful radio-loud AGN activity, reinforcing the view that, although a large fraction of powerful radio galaxies may be triggered in galaxy interactions, only a minority are triggered at the peaks of star formation activity in major, gas-rich mergers. However, we find that compact radio sources (D < 15 kpc) show a significantly higher incidence of RSFA (>75%) than their more extended counterparts ( Almost-Equal-To 15%-25%). We discuss this result in the context of a possible bias toward the selection of compact radio sources triggered in gas-rich environments.

  13. High Resolution Radio Imaging of the Merging Galaxies NGC3256 and NGC4194

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Campion, S. D.; Ulvestad, J. S.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present new 6cm and 4cm radio continuum images of the central regions of the merging galaxy systems NGC3256 and NGC4194. NGC3256 is imaged with a resolution of approx. 1 in. or approx. 190pc; NGC4194 is imaged with a resolution of approx. 0.3 in. or approx. 50pc. In both systems, we detect numerous compact radio sources embedded in more diffuse radio emission. We detect 65 compact sources in NGC3256 at 6cm and we detect 46 compact sources in NGC4194, both to a limiting luminosity of approx. 5 x 10(exp 18) W/ Hz or approx. 5 times the luminosity of Cas A. Most of the compact radio sources are loosely associated with active star forming regions but not with specific optical emission sources. Several compact radio sources in NGC3256 are near positions of compact X-ray sources detected by Lira et al.. In both NGC3256 and NGC4194, we are able to measure reliable spectral indices for the stronger sources. We find in NGC3256 approx. 20% have nominally flat radio spectral indices (indicating they are dominated by thermal radio emission from HII regions) while approx. 80% have nominally steep spectral indices (indicating they are dominated by nonthermal emission from supernova remnants). In NGC4194, half the compact radio sources have flat spectral indices and half have steep indices. For the flat-spectrum sources, we estimate the number of young massive stars and the associated ionized gas masses. For the steep-spectrum sources, we estimate supernova rates. We compare these results with those from other well-studied merging galaxy systems. We gratefully acknowledge use of the NRAO Very Large Array (VLA) and the VLA Archive. NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  14. Correlation between excitation index and Eddington ratio in radio galaxies

    NASA Astrophysics Data System (ADS)

    Hu, Jing-Fu; Cao, Xin-Wu; Chen, Liang; You, Bei

    2016-09-01

    We use a sample of 111 radio galaxies with redshift z < 0.3 to investigate their nuclear properties. The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the galaxies, or the width of the broad-lines. We find that the excitation index, the relative intensity of low and high excitation lines, is correlated with the Eddington ratio for this sample. The size of the narrow-line region (NLR) was found to vary with ionizing luminosity as RNLR ∝ Lion0.25 (Liu et al. 2013). Using this empirical relation, we find that the correlation between the excitation index and the Eddington ratio can be reproduced by photoionization models. We adopt two sets of spectral energy distributions (SEDs), with or without a big blue bump in ultraviolet as the ionizing continuum, and infer that the modeled correlation between the excitation index and the Eddington ratio is insensitive to the applied SED. This means that the difference between high excitation galaxies and low excitation galaxies is not caused by the different accretion modes in these sources. Instead, it may be caused by the size of the NLR.

  15. MULTIPLE SHOCK STRUCTURES IN A RADIO-SELECTED CLUSTER OF GALAXIES

    SciTech Connect

    Brown, S.; Duesterhoeft, J.; Rudnick, L.

    2011-01-20

    We present a new radio-selected cluster of galaxies, 0217+70, using observations from the Very Large Array and archival optical and X-ray data. The new cluster is one of only seven known that has candidate double peripheral radio relics, and the second of those with a giant radio halo (GRH), as well. It also contains unusual diffuse radio filaments interior to the peripheral relics and a clumpy, elongated X-ray structure. All of these indicate a very actively evolving system, with ongoing accretion and merger activity, illuminating a network of shocks, such as those first seen in numerical simulations. The peripheral relics are most easily understood as outgoing spherical merger shocks with large variations in brightness along them, likely reflecting the inhomogeneities in the shocks' magnetic fields. The interior filaments could be projections of substructures from the sheet-like peripheral shocks or they might be separate structures due to multiple accretion events. ROSAT images show large-scale diffuse X-ray emission coincident with the GRH and additional patchy diffuse emission that suggests a recent merger event. This uniquely rich set of radio shocks and halo offer the possibility, with deeper X-ray and optical data and higher resolution radio observations, of testing the models of how shocks and turbulence couple to the relativistic plasma. The cluster 0217+70 is also overluminous in the radio compared with the empirical radio-X-ray correlation for clusters-the third example of such a system. This new population of diffuse radio emission opens up the possibility of probing low-mass cluster mergers with upcoming deep radio continuum surveys.

  16. The radio core of the ultraluminous infrared galaxy F00183-7111: watching the birth of a quasar

    NASA Astrophysics Data System (ADS)

    Norris, Ray P.; Lenc, Emil; Roy, Alan L.; Spoon, Henrik

    2012-05-01

    F00183-7111 is one of the most extreme ultraluminous infrared galaxies known, with a bolometric luminosity of 9 × 1012 L⊙. Here we present a very long baseline interferometry (VLBI)_ image which shows a compact core-jet active galactic nucleus (AGN) in its core, with a radio luminosity (L2.3 GHz= 6 × 1025 W Hz-1) typical of powerful radio galaxies. Although already radio loud, the quasar jets are only 1.7 kpc long, boring through the dense gas and starburst activity that confine them. This source therefore appears to be powered by a combination of a compact radio-loud AGN surrounded by vigorous starburst activity.

  17. VERITAS UPPER LIMIT ON THE VERY HIGH ENERGY EMISSION FROM THE RADIO GALAXY NGC 1275

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Celik, O.; Aune, T.; Bautista, M.; Cogan, P.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C.

    2009-12-01

    The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E>100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hr. No VHE gamma-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope result.

  18. A Targeted, Distant Galaxy Cluster Survey Using Bent, Double-Lobed Radio Sources

    NASA Astrophysics Data System (ADS)

    Blanton, Elizabeth L.; Paterno-Mahler, Rachel; Wing, Joshua; Ashby, Matthew; Brodwin, Mark

    2014-06-01

    We are conducting a large survey of distant clusters of galaxies using bent, double-lobed radio sources as tracers. Bent, double-lobed radio sources are driven by AGN and achieve their morphologies through interaction with the surrounding gas found in clusters. The lobes can become swept back during large-scale cluster mergers that set the intracluster medium in motion, or through more gentle sloshing motions of cluster cores driven by more minor interactions. These types of radio sources may be found in clusters that are highly disturbed as well as those that are relatively relaxed. In addition, they are found in clusters with a large range of masses. By the nature of their selection, all of the clusters will contain radio-loud active galaxies, so they are expected to be sites of AGN feedback. Based on low-redshift studies, these types of sources can be used to identify rich clusters with a success rate of ~60% (or ~80% if poor clusters and groups are included). We present our survey of 653 bent-double radio sources with optical hosts too faint to appear in the SDSS. The sample was observed in the infrared with Spitzer, and we estimate it will reveal ~400 distant clusters or proto-clusters in the redshift range z ~ 0.7 -- 3.0. The sample of bent-doubles contains both quasars and radio galaxies enabling us to study both radiative and kinetic mode feedback in cluster and group environments at a wide range of redshifts.

  19. The nuclear environment of Radio Galaxies: what's new

    SciTech Connect

    Torresi, E.; Tombesi, F.; Grandi, P.; Longinotti, A. L.; Guainazzi, M.; Nucita, A.

    2010-07-15

    While in Radio-Quiet (RQ) AGN warm gas photoionised by the nuclear engine has been well revealed and studied in X-rays, it is still unclear whether a similar gaseous environment can survive in Radio-Loud (RL) objects. The exploration of the environment surrounding the nuclei of RL sources is an important point to be addressed. It can help to understand the physical link among accretion flows, winds and jet, and the influence that each component can have on the host galaxy. We report on the recent discovery of warm gas in RL AGN, indicating that relativistic collimated plasma (jet) and slower outflows of photoionised gas can coexist in the same source. The physical properties of this gas seem to be very similar to RQ ones, suggesting that RL and RQ AGN environment becomes indistinguishable at large distances from the central engine (e.g. the Narrow Line Region).

  20. Low-frequency radio observations of poor clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Hanisch, R. J.; White, R. A.

    1981-06-01

    Observations have been made at the Clark Lake Radio Observatory of 16 poor clusters of galaxies at 34.3 MHz. Four of the poor clusters were detected at flux densities greater than 20 Jy. The spectra of the four detected clusters are all rather steep. Two of the detected clusters, AWM 4 and AWM 5, are also known to be X-ray sources. The possibility that the X-ray-emitting gas is heated by Coulomb interactions with the relativistic electrons responsible for the radio emission is investigated, and it is found that the observed X-ray luminosities can be accounted for if the electron energy spectrum extends to very low energies (gamma approximately 1-10). Collective plasma effects may increase the heating efficiency and eliminate the need to extrapolate the electron energy spectrum to such low values.

  1. Low-frequency radio observations of poor clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Hanisch, R. J.; White, R. A.

    1981-01-01

    Observations have been made at the Clark Lake Radio Observatory of 16 poor clusters of galaxies at 34.3 MHz. Four of the poor clusters were detected at flux densities greater than 20 Jy. The spectra of the four detected clusters are all rather steep. Two of the detected clusters, AWM 4 and AWM 5, are also known to be X-ray sources. The possibility that the X-ray-emitting gas is heated by Coulomb interactions with the relativistic electrons responsible for the radio emission is investigated, and it is found that the observed X-ray luminosities can be accounted for if the electron energy spectrum extends to very low energies (gamma approximately 1-10). Collective plasma effects may increase the heating efficiency and eliminate the need to extrapolate the electron energy spectrum to such low values.

  2. A comparison between the radio and the X-ray spectra of broad-line radio galaxies

    NASA Astrophysics Data System (ADS)

    Angelakis, E.; Kadler, M.; Lewis, K.; Sambruna, R. M.; Eracleous, M.; Zensus, J. A.

    2008-12-01

    We present the spectral characteristics of a sample of Intermediate-Luminosity Broad-Line Radio Galaxies in X-rays, optical and radio. Here, we focus on the radio spectra acquired with the 100 m radio telescope in Effelsberg between 2.6 GHz and 32 GHz. These measurements reveal different spectral shapes urging for radio imaging that would disclose the source morphology. Comparing them with the X-ray spectra acquired with XMM-Newton, we find that sources with steep radio spectrum are heavily obscured whereas flat spectrum ones appear unabsorbed in accordance with unified scheme.

  3. Chandra ACIS-S Observations of Abell 4059: Signs of Dramatic Interaction between a Radio Galaxy and a Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Heinz, Sebastian; Choi, Yun-Young; Reynolds, Christopher S.; Begelman, Mitchell C.

    2002-04-01

    We present Chandra observations of the galaxy cluster A4059. We find strong evidence that the FR I radio galaxy PKS 2354-35 at the center of A4059 is inflating cavities with radii ~20 kpc in the intracluster medium (ICM), similar to the situation seen in Perseus A and Hydra A. We also find evidence for interaction between the ICM and PKS 2354-35 on small scales in the very center of the cluster. Arguments are presented suggesting that this radio galaxy has faded significantly in radio power (possibly from an FR II state) over the past 108 yr.

  4. Multifrequency radio observations of Cygnus A - Spectral aging in powerful radio galaxies

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Perley, R. A.; Dreher, J. W.; Leahy, J. P.

    1991-01-01

    A detailed analysis of the radio spectrum across the lobes of Cygnus A is presented in order to critically test the synchroton spectral aging theory. The results are in good agreement with the jet model for powerful radio galaxies, involving particle acceleration at the hot spots and outflow into the radio lobes, with subsequent energy loss due to synchrotron radiation. The hot spot spectra are well represented by a spectral aging model involving continuous injection of relativistic particles. Both hot spots have spectral break frequencies around 10 GHz. An injection index of 0.5 is found for both hot spots, consistent with diffusive shock acceleration at a strong nonrelativistic shock in a Newtonian fluid. The LF hot spot emission spectrum falls below the injected power law. This effect is isolated to the hot spots, and is best explained by a low-energy cutoff in the particle distribution.

  5. Are Radio Halos Common in Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Eilek, J. A.; Markovic, T.; Owen, F. N.

    2002-05-01

    Diffuse synchrotron radio halos are known to exist in several rich clusters of galaxies. The detection of a cluster-wide halo demonstrates that the ICM in that cluster has a non-thermal component, namely, relativistic particles and magnetic field. Some authors have suggested that radio halos are rare, and that their host clusters are unusual, having recently undergone a strong merger. We propose a different picture. We suspect that halos may be more common than has been thought, and are a simple by-product of cluster 'weather'. The radio and X-ray powers of known halos are roughly correlated. We find that this correlation is to be expected if the ratio of non-thermal pressure to thermal pressure is the same for the ICM in all rich clusters. We expect this to be the case if ongoing minor mergers maintain flows and turbulence in the ICM. We will discuss constraints the radio-Xray correlation imposes on the turbulence, and how the turbulence is driven. Our speculation can be tested by observations. We are using the VLA at 1.4 GHz to search for radio halos in a set of 30 Abell clusters. They have been chosen based on their X-ray power, angular size and redshift, but irregardless of their structure. We have neither excluded cooling cores nor specialized to clusters undergoing major mergers. All of our targets will be detected at or above a few mJy if they obey the current radio-Xray correlation. Those not detected will give us upper limits which also tell us about the turbulence and re-energization in the ICM of those clusters.

  6. Stacking Searches for Greater Than 100 MeV Gamma Ray Emission from Radio Galaxies and Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Cillis, A. N.; Hartman, R. C.; Bertsch, D. L.

    2003-01-01

    The EGRET telescope on CGRO detected more than sixty sources of high-energy gamma radiation associated with active galactic nuclei (AGN). All but one of those belong to the blazar subclass; the only exception is the nearby radio galaxy Centaurus A. Since there is no obvious reason other than proximity to expect Cen A to be the only non-blazar AGN emitting in high-energy gamma rays, we have utilized the "stacking" technique to search for $>100$-MeV emission from two non-blazar AGN subclasses, radio galaxies and Seyfert galaxies. Maps of gamma-ray counts, exposure, and diffuse background have been created, then co-added in varying numbers based on sorts by redshift, 5-GHZ flux density, and optical brightness, and finally tested for gamma-ray emission. No detection significance greater than $2\\sigma$ has been found for any subclass, sorting parameter, or number of objects co-added. Monte Carlo simulations have also been performed, to validate the technique and estimate the significance of the results.

  7. Giant radio galaxies as effective probes of X-ray gas in large-scale structure

    NASA Astrophysics Data System (ADS)

    Saripalli, Lakshmi; Subrahmanyan, Ravi; Malarecki, Jurek; Jones, Heath; Staveley-Smith, Lister

    2015-08-01

    Giant radio galaxies are AGNs with relativistic jets that dynamically evolve into Mpc scale synchrotron lobes around the host elliptical. The thermal gas environment influences the jet advance and lobe formation. Since the host ellipticals are in filamentary low-density galaxy environments, the ambient gas for the Mpc-scale radio structures is likely the warm-hot X-ray gas inhabiting the intergalactic medium. We have, therefore, used large radio galaxies as probes of the distribution of hot and tenuous gas on mega-parsec scales in these relatively low density large-scale structures.For a sample of 19 giant radio galaxies we obtained radio continuum images of the synchrotron structures, and redshifts of a total of nearly 9000 galaxies in their vicinity. The 2-degree field redshift data traces the large-scale galaxy structure around the radio sources. The radio-optical data allows an estimation of the pressure, temperature and distribution of hot thermal gas associated with the large-scale structure in the vicinity of the radio AGN (Malarecki, Staveley-Smith, Saripalli, Subrahmanyan, Jones, Duffy, Rioja 2013, MNRAS 432, 200).Strong correspondence between radio galaxy lobes and galaxy distribution is observed. The data suggests that galaxies trace gas, and that radio jets and lobes of giant radio galaxies are sensitive tracers of gas on mega-parsec scales and may be used as effective probes of the difficult-to-detect IGM (Malarecki, Jones, Saripalli, Stavele-Smith, Subrahmanyan, 2015, MNRAS in press; arXiv150203954).

  8. Radio emission in the directions of cD and related galaxies in poor clusters. III - VLA observations at 20 cm

    NASA Technical Reports Server (NTRS)

    Burns, J. O.; White, R. A.; Hough, D. H.

    1981-01-01

    VLA radio maps and optical identifications of a sample of sources in the directions of 21 Yerkes poor cluster fields are presented. The majority of the cluster radio sources are associated with the dominant D or cD galaxies (approximately 70 percent). Our analysis of dominant galaxies in rich and poor clusters indicates that these giant galaxies are much more often radio emitters (approximately 25 percent of cD's are radio active in the poor clusters), have steeper radio spectra, and have simpler radio morphologies (i.e., double or other linear structure) than other less bright ellipticals. A strong continuum of radio properties in cD galaxies is seen from rich to poor clusters. It is speculated that the location of these dominant galaxies at the cluster centers (i.e., at the bottom of a deep, isolated gravitational potential well) is the crucial factor in explaining their multifrequency activity. Galaxy cannibalism and gas infall models as fueling mechanisms for the observed radio and X-ray emission are discussed

  9. Radio emission in the directions of cD and related galaxies in poor clusters. III. VLA observations at 20 cm

    SciTech Connect

    Burns, J.O.; White, R.A.; Hough, D.H.

    1981-01-01

    VLA radio maps and optical identifications of a sample of sources in the directions of 21 Yerkes poor cluster fields are presented. The majority of the cluster radio sources are associated with the dominant D or cD galaxies (approx.70%). Our analysis of dominant galaxies in rich and poor clusters indicates that these giant galaxies are much more often radio emitters (approx.25% of cD's are radio active in the poor clusters), have steeper radio spectra, and have simpler radio morphologies (i.e., double or other linear structure) than other less bright ellipticals. A strong continuum of radio properties in cD galaxies is seen from rich to poor clusters. We speculate that the location of these dominant galaxies at the cluster centers (i.e., at the bottom of a deep, isolated gravitational potential well) is the crucial factor in explaining their multifrequency activity. We briefly discuss galaxy cannibalism and gas infall models as fueling mechanisms for the observed radio and x-ray emission.

  10. Sliding not sloshing in A3744: The influence of radio galaxies NGC 7018 and 7016 on cluster gas

    SciTech Connect

    Worrall, D. M.; Birkinshaw, M.

    2014-03-20

    We present new X-ray (Chandra) and radio (JVLA) observations of the nearby cluster A3744. It hosts two prominent radio galaxies with powers in the range critical for radio-mode feedback. The radio emission from these galaxies terminates in buoyant tendrils reaching the cluster's outer edge, and the radio-emitting plasma clearly influences the cluster's X-ray-emitting atmosphere. The cluster's average gas temperature, of kT = 3.5 keV, is high for its bolometric luminosity of 3.2 × 10{sup 43} erg s{sup –1}, but the 100 kpc-scale cavity carved out by radio-emitting plasma shows evidence of less than 2% of the excess enthalpy. We suggest instead that a high-velocity encounter with a galaxy group is responsible for dispersing and increasing the entropy of the gas in this non-cool-core cluster. We see no evidence for shocks, or established isobaric gas motions (sloshing), but there is much sub-structure associated with a dynamically active central region that encompasses the brightest radio emission. Gas heating is evident in directions perpendicular to the inferred line of encounter between the infalling group and cluster. The radio-emitting tendrils run along boundaries between gas of different temperature, apparently lubricating the gas flows and inhibiting heat transfer. The first stages of the encounter may have helped trigger the radio galaxies into their current phase of activity, where we see X-rays from the nuclei, jets, and hotspots.

  11. Two-dimensional maps of the infrared-to-radio ratio in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Marsh, Kenneth A.; Helou, George

    1994-01-01

    We have produced two-dimensional maps of the intensity ratio Q(sub 60) of 60 micron infrared to 20 cm radio continuum emission, for a set of 25 nearby galaxies, mostly spirals. The ratio maps were obtained from infrared images made using Infrared Astronomical Satellite (IRAS) data with the Maximum Correlation Method, and radio images made using VLA data. Before taking the ratio, the radio images were processed so as to have the same resolution properties as the infrared images; the final spatial resolution in all cases is approximately 1 min, corresponding to 1-2 kpc for most galaxies. These images allow us to study the variations for the Q(sub 60) ratio with unprecedented spatial resolution, and thus represents a major improvement over earlier work. Our new high-resolution maps confirm the slow decrease of Q(sub 60) with increasing radial distance from the nucleus, but show additional structure which is probably associated with separate sites of active star formation in the spiral arms. The maps show Q(sub 60) to be more closely related to infrared surface brightness than to the radial distance in the galaxy disk. We expect that the results will provide improved constraints on the evolution (diffusion, decay and escape) of cosmic-ray electrons in the magnetic field of the disks.

  12. POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

    SciTech Connect

    Humphrey, A.; Vernet, J.; Fosbury, R. A. E.; Villar-Martin, M.; Di Serego Alighieri, S.; Cimatti, A.

    2013-05-01

    We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

  13. RadioActive101 Practices

    ERIC Educational Resources Information Center

    Brites, Maria José; Ravenscroft, Andrew; Dellow, James; Rainey, Colin; Jorge, Ana; Santos, Sílvio Correia; Rees, Angela; Auwärter, Andreas; Catalão, Daniel; Balica, Magda; Camilleri, Anthony F.

    2014-01-01

    In keeping with the overarching RadioActive101 (RA101) spirit and ethos, this report is the product of collaborative and joined-up thinking from within the European consortium spread across five countries. As such, it is not simply a single voice reporting on the experiences and knowledge gained during the project. Rather it is a range of…

  14. Compact radio cores in radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Maini, A.; Prandoni, I.; Norris, R. P.; Giovannini, G.; Spitler, L. R.

    2016-04-01

    Context. The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGNs) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. Aims: We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. Methods: We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. Results: We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. Conclusions: We report on a first direct evidence of radio cores in RQ AGNs at cosmological redshifts. Our detections show that some of the sources that are classified as RQ contain an active AGN that can contribute significantly (~50% or more) to the total radio emission.

  15. Discovery of a Fanaroff-Riley type 0 radio galaxy emitting at γ-ray energies

    NASA Astrophysics Data System (ADS)

    Grandi, Paola; Capetti, Alessandro; Baldi, Ranieri D.

    2016-03-01

    We present supporting evidence for the first association of a Fermi source, 3FGLJ1330.0-3818, Acero et al. (2015) with the Fanaroff-Riley type 0 (FR 0) radio galaxy Tol1326-379. FR 0s represent the majority of the local population of radio-loud active galactic nuclei but their nature is still unclear. They share the same nuclear and host properties as FR Is, but they show a large deficit of extended radio emission. Here we show that FR 0s can emit photons at very high energies. Tol1326-379 has a GeV luminosity of L>1 GeV ˜ 2 × 1042 erg s-1, typical of FR Is, but with a steeper γ-ray spectrum (Γ = 2.78 ± 0.14). This could be related to the intrinsic jet properties but also to a different viewing angle.

  16. AGN feedback in groups of galaxies: a joint X-ray/low-frequency radio study

    NASA Astrophysics Data System (ADS)

    Giacintucci, S.; O'Sullivan, E.; Vrtilek, J. M.; Raychaudhury, S.; David, L. P.; Venturi, T.; Athreya, R.; Gitti, M.

    2010-07-01

    We present an ongoing, low-frequency radio/X-ray study of 18 nearby galaxy groups, chosen for the evidence, either in the X-ray or radio images, of AGN/intragroup gas interaction. We have obtained radio observations at 235 MHz and 610 MHz with the Giant Metrewave Radio Telescope (GMRT) for all the groups, and 327 MHz and 150 MHz for a few. We present results of the recent Chandra/GMRT study of the interesting case of AWM 4, a relaxed poor cluster of galaxies with no evidence of a large cool core and no X-ray cavities associated with the central radio galaxy. Our analysis shows how joining low-frequency radio data (to track the history of AGN outbursts) with X-ray data (to determine the state of the hot gas, its disturbances, heating and cooling) can provide a unique insight into the nature of the feedback mechanism in galaxy groups.

  17. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  18. Constraints on Feedback in the Local Universe: The Relation between Star Formation and AGN Activity in Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher P.; Baum, Stefi A.; Whitmore, Samantha; Ahmed, Rabeea; Pierce, Katherine; Leary, Sara

    2016-02-01

    We address the relation between star formation and active galactic nucleus (AGN) activity in a sample of 231 nearby (0.0002 < z < 0.0358) early-type galaxies by carrying out a multi-wavelength study using archival observations in the UV, IR, and radio. Our results indicate that early-type galaxies in the current epoch are rarely powerful AGNs, with P\\lt {10}22 {{WHz}}-1 for a majority of the galaxies. Only massive galaxies are capable of hosting powerful radio sources while less massive galaxies are hosts to lower radio power sources. Evidence of ongoing star formation is seen in approximately 7% of the sample. The star formation rate (SFR) of these galaxies is less than 0.1 M⊙ yr-1. They also tend to be radio faint (P\\lt {10}22 {{WHz}}-1). There is a nearly equal fraction of star-forming galaxies in radio faint (P\\lt {10}22 {{WHz}}-1) and radio bright galaxies (P≥slant {10}22 {{WHz}}-1) suggesting that both star formation and radio mode feedback are constrained to be very low in our sample. We notice that our galaxy sample and the Brightest Cluster Galaxies follow similar trends in radio power versus SFR. This may be produced if both radio power and SFR are related to stellar mass.

  19. The Radio-Gamma Correlation in Starburst Galaxies

    NASA Astrophysics Data System (ADS)

    Eichmann, B.; Becker Tjus, J.

    2016-04-01

    We present a systematic study of non-thermal electron-proton plasma and its emission processes in starburst galaxies in order to explain the correlation between the luminosity in the radio band and the recently observed gamma luminosity. In doing so, a steady state description of the cosmic-ray (CR) electrons and protons within the spatially homogeneous starburst is considered where continuous momentum losses are included as well as catastrophic losses due to diffusion and advection. The primary source of the relativistic CRs, e.g., supernova remnants, provides a quasi-neutral plasma with a power-law spectrum in momentum where we account for rigidity-dependent differences between the electron and proton spectrum. We examine the resulting leptonic and hadronic radiation processes by synchrotron radiation, inverse Compton scattering, Bremsstrahlung, and hadronic pion production. Finally, the observations of NGC 253, M82, NGC 4945, and NGC 1068 in the radio and gamma-ray bands as well as the observed supernova rate are used to constrain a best-fit model. In the case of NGC 253, M82, and NGC 4945 our model is able to accurately describe the data, showing that: (i) supernovae are the dominant particle accelerators for NGC 253, M82, and NGC 4945, but not for NGC 1068; (ii) all considered starburst galaxies are poor proton calorimeters in which for NGC 253 the escape is predominantly driven by the galactic wind, whereas the diffusive escape dominates in NGC 4945 and M82 (at energies >1 TeV); and (iii) secondary electrons from hadronic pion production are important to model the radio flux, but the associated neutrino flux is below the current observation limit.

  20. AGN JET KINETIC POWER AND THE ENERGY BUDGET OF RADIO GALAXY LOBES

    SciTech Connect

    Godfrey, L. E. H.; Shabala, S. S.

    2013-04-10

    Recent results based on the analysis of radio galaxies and their hot X-ray emitting atmospheres suggest that non-radiating particles dominate the energy budget in the lobes of FR I radio galaxies, in some cases by a factor of more than 1000, while radiating particles dominate the energy budget in FR II radio galaxy lobes. This implies a significant difference in the radiative efficiency of the two morphological classes. To test this hypothesis, we have measured the kinetic energy flux for a sample of 3C FR II radio sources using a new method based on the observed parameters of the jet terminal hotspots, and compared the resulting Q{sub jet}-L{sub radio} relation to that obtained for FR I radio galaxies based on X-ray cavity measurements. Contrary to expectations, we find approximate agreement between the Q{sub jet}-L{sub radio} relations determined separately for FR I and FR II radio galaxies. This result is ostensibly difficult to reconcile with the emerging scenario in which the lobes of FR I and FR II radio galaxies have vastly different energy budgets. However, a combination of lower density environment, spectral aging and strong shocks driven by powerful FR II radio galaxies may reduce the radiative efficiency of these objects relative to FR Is and counteract, to some extent, the higher radiative efficiency expected to arise due to the lower fraction of energy in non-radiating particles. An unexpected corollary is that extrapolating the Q{sub jet}-L{sub radio} relation determined for low power FR I radio galaxies provides a reasonable approximation for high power sources, despite their apparently different lobe compositions.

  1. Fermi LAT Observation of Centaurus a Radio Galaxy

    NASA Astrophysics Data System (ADS)

    Sahakyan, N. V.

    2013-01-01

    The results of analysis of approximately 3 year gamma-ray observations (August 2008-July 2011) of the core of radio galaxy Centaurus A with the Fermi Large Area Telescope (Fermi LAT) are presented. Binned likelihood analysis method applying to the data shows that below several GeV the spectrum can be described by a single power-law with photon index Γ = 2.73 ± 0.06. However, at higher energies the new data show significant excess above the extrapolation of the energy spectrum from low energies. The comparison of the corresponding Spectral Energy Distribution (SED) at GeV energies with the SED in the TeV energy band reported by the H.E.S.S. collaboration shows that we deal with two or perhaps even three components of gamma-radiation originating from different regions located within the central 10 kpc of Centaurus A. The analysis of gamma-ray data of Centaurus A lobe accumulated from the beginning of the operation until November 14, 2011 show extension of the HE gamma-ray emission beyond the WMAP radio image in the case of the Northern lobe [9]. The possible origins of gamma-rays from giant radio lobes of Centaurus A are discussed in the context of hadronic and leptonic scenarios.

  2. The Clustering of Radio Galaxies: Biasing and Evolution versus Stellar Mass

    NASA Astrophysics Data System (ADS)

    Nusser, Adi; Tiwari, Prabhakar

    2015-10-01

    We study the angular clustering of ∼6 × 105 NVSS sources on scales ≳ 50{h}-1 {Mpc} in the context of the ΛCDM scenario. The analysis partially relies on the redshift distribution of 131 radio galaxies, inferred from the Hercules and CENSORS survey, and an empirical fit to the stellar-to-halo mass relation. For redshifts z ≲ 0.7, the fraction of radio activity versus stellar mass evolves as {f}{{{RL}}}∼ {M}*{α 0+{α }1z}, where α0 = 2.529 ± 0.184 and {α }1={1.854}-0.761+0.708. The estimate on α0 is largely driven by the results of Best et al., while the constraint on α1 is new. We derive a biasing factor b(z=0.5)={2.093}-0.109+0.164 between radio galaxies and the underlying mass. The function b(z)=0.33{z}2+0.85z+1.6 fits well the redshift dependence. We also provide convenient parametric forms for the redshift-dependent radio luminosity function, which are consistent with the redshift distribution and the NVSS source count versus flux.

  3. An XMM-Newton view of the radio galaxy 3C 411

    SciTech Connect

    Bostrom, Allison; Reynolds, Christopher S.; Tombesi, Francesco

    2014-08-20

    We present the first high signal-to-noise XMM-Newton observations of the broad-line radio galaxy 3C 411. After fitting various spectral models, an absorbed double power-law (PL) continuum and a blurred relativistic disk reflection model (kdblur) are found to be equally plausible descriptions of the data. While the softer PL component (Γ = 2.11) of the double PL model is entirely consistent with that found in Seyfert galaxies (and hence likely originates from a disk corona), the additional PL component is very hard (Γ = 1.05); amongst the active galactic nucleus zoo, only flat-spectrum radio quasars (FSRQ) have such hard spectra. Together with the flat radio-spectrum displayed by this source, we suggest that it should instead be classified as an FSRQ. This leads to potential discrepancies regarding the jet inclination angle, with the radio morphology suggesting a large jet inclination but the FSRQ classification suggesting small inclinations. The kdblur model predicts an inner disk radius of at most 20 r {sub g} and relativistic reflection.

  4. THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. III. ANALYSIS OF 3CRR OBJECTS

    SciTech Connect

    Dicken, D.; Axon, D.; Robinson, A.; Kharb, P.; Tadhunter, C.; Morganti, R. E-mail: djasps@rit.ed E-mail: c.tadhunter@sheffield.ac.u

    2010-10-20

    We present Spitzer photometric data for a complete sample of 19 low-redshift (z< 0.1) 3CRR radio galaxies as part of our efforts to understand the origin of the prodigious mid- to far-infrared (MFIR) emission from radio-loud active galactic nuclei (AGNs). Our results show a correlation between AGN power (indicated by [O III]{lambda}5007 emission line luminosity) and 24 {mu}m luminosity. This result is consistent with the 24 {mu}m thermal emission originating from warm dust heated directly by AGN illumination. Applying the same correlation test for 70 {mu}m luminosity against [O III] luminosity we find this relation to suffer from increased scatter compared to that of 24 {mu}m. In line with our results for the higher-radio-frequency-selected 2 Jy sample, we are able to show that much of this increased scatter is due to heating by starbursts that boost the far-infrared emission at 70 {mu}m in a minority of objects (17%-35%). Overall this study supports previous work indicating AGN illumination as the dominant heating mechanism for MFIR emitting dust in the majority of low-to-intermediate redshift radio galaxies (0.03 < z < 0.7), with the advantage of strong statistical evidence. However, we find evidence that the low-redshift broad-line objects (z < 0.1) are distinct in terms of their positions on the MFIR versus [O III] correlations.

  5. Radio continuum emission and H I gas accretion in the NGC 5903/5898 compact group of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Mhaskey, Mukul

    Striking new details of radio emission are unveiled from the 2nd Data Release of the ongoing TIFR.GMRT.SKY.SURVEY (TGSS) which provides images with a resolution of 24'' × 18'' and a typical rms noise of 5 mJy at 150 MHz. Previous radio observations of this compact triplet of galaxies include images at higher frequencies of the radio continuum as well as H I emission, the latter showing huge H I trails originating from the vicinity of NGC 5903 where H I is in a kinematically disturbed state. The TGSS 150 MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf SO galaxy ESO514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (alpha -1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the H I trails. Another noteworthy aspect of this triplet of early-type galaxies highlighted by the present study is that both its radio loud members, namely NGC 5903 and ESO514-G003, are also the only galaxies that are seen to be connected to an H I filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  6. The relationship between radio power at 22 and 43 GHz and black hole properties of AGN in elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Park, Songyoun; Sohn, Bong Won; Yi, Sukyoung K.

    2013-12-01

    We investigate the relationship between radio power and properties related to active galactic nuclei (AGNs). Radio power at 1.4 or 5 GHz, which has been used in many studies, can be affected by synchrotron self-absorption and free-free absorption in a dense region. On the other hand, these absorption effects get smaller at higher frequencies. Thus, we performed simultaneous observations at 22 and 43 GHz using the Korean VLBI Network (KVN) radio telescope based on a sample of 305 AGN candidates residing in elliptical galaxies from the overlap between the Sloan Digital Sky Survey (SDSS) Data Release 7 and Faint Images of the Radio Sky at Twenty-Centimeters (FIRST). About 37% and 22% of the galaxies are detected at 22 and 43 GHz, respectively. Assuming no flux variability between the FIRST and KVN observations, spectral indices were derived from FIRST and KVN data and we found that over 70% of the detected galaxies have flat or inverted spectra, implying the presence of optically thick compact regions near the centres of the galaxies. Core radio power does not show a clear dependence on black hole mass at either low (1.4 GHz) or high (22 and 43 GHz) frequencies. However, we found that the luminosity of the [OIII] λ5007 emission line and the Eddington ratio correlate with radio power more closely at high frequencies than at low frequencies. This suggests that radio observation at high frequencies can be an appropriate tool for unveiling the innermost region. In addition, the luminosity of the [OIII] λ5007 emission line and the Eddington ratio can be used as a tracer of AGN activity. Our study suggests a causal connection between high frequency radio power and optical properties of AGNs. Table 5 is available in electronic form at http://www.aanda.org

  7. Far-UV to mid-IR properties of nearby radio galaxies

    NASA Astrophysics Data System (ADS)

    de Ruiter, H. R.; Parma, P.; Fanti, R.; Fanti, C.

    2015-09-01

    Aims: We investigate whether the far-UV continuum of nearby radio galaxies is due solely to the parent galaxy that passively evolves, or if it reveals evidence for the presence of other star-forming or non-stellar components. If the UV excess is due to an additional radiation component, we compare this with other properties such as radio power, optical spectral type (e.g. high- and low-excitation galaxies), and the strength of the emission lines. We also discuss the possible correlation between the ultraviolet flux, IR properties, and the central black hole mass. Methods: We used a sample of low-luminosity B2 radio galaxies and a small sample of higher luminosity 3C radio galaxies at comparable redshift (z< 0.2). Spectral energy distributions (SEDs) were constructed using a number of on-line databases that are freely available now: GALEX, SDSS, 2MASS, and WISE. These were compared with model SEDs of early-type galaxies with passively evolving stellar populations at various ages (typically 0.5-1.3 × 109 years). We established whether a second component was needed to obtain a satisfactory fit with the observed overall SED. We introduce the parameter XUV , which measures the excess slope of the UV continuum between 4500 and 2000 Å with respect to the UV radiation produced by the underlying old galaxy component. Results: We find that the UV excess as measured by XUV is usually small or absent in low-luminosity (FR I) sources, but sets in abruptly at the transition radio power, above which we find mostly FRII sources. XUV behaves very similarly to the strength of the optical emission lines (in particular Hα). Below P1.4 GHz< 1024 WHz-1XUV is close to zero. XUV correlates strongly with the Hα line strength, but only in sources with strong Hα emission. We discuss whether the line emission might be due to photoionization by radiation from the parent galaxy, possibly with additional star formation, or if it requires the presence of a non-stellar active galactic nucleus

  8. The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z = 2.553 discovered through the citizen science project SPACE WARPS

    NASA Astrophysics Data System (ADS)

    Geach, J. E.; More, A.; Verma, A.; Marshall, P. J.; Jackson, N.; Belles, P.-E.; Beswick, R.; Baeten, E.; Chavez, M.; Cornen, C.; Cox, B. E.; Erben, T.; Erickson, N. J.; Garrington, S.; Harrison, P. A.; Harrington, K.; Hughes, D. H.; Ivison, R. J.; Jordan, C.; Lin, Y.-T.; Leauthaud, A.; Lintott, C.; Lynn, S.; Kapadia, A.; Kneib, J.-P.; Macmillan, C.; Makler, M.; Miller, G.; Montaña, A.; Mujica, R.; Muxlow, T.; Narayanan, G.; Briain, D. Ó.; O'Brien, T.; Oguri, M.; Paget, E.; Parrish, M.; Ross, N. P.; Rozo, E.; Rusu, C. E.; Rykoff, E. S.; Sanchez-Argüelles, D.; Simpson, R.; Snyder, C.; Schloerb, F. P.; Tecza, M.; Wang, W.-H.; Van Waerbeke, L.; Wilcox, J.; Viero, M.; Wilson, G. W.; Yun, M. S.; Zeballos, M.

    2015-09-01

    We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (intrinsic LIR ≈ 1013 L⊙) with strong radio emission (intrinsic L1.4 GHz ≈ 1025 W Hz-1) at z = 2.553. The source was identified in the citizen science project SPACE WARPS through the visual inspection of tens of thousands of iJKs colour composite images of luminous red galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (re ≈ 3 arcsec) around an LRG at z = 0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3→2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [O III] and Hα line detections in the near-infrared from Subaru/Infrared Camera and Spectrograph. We have resolved the radio emission with high-resolution (300-400 mas) eMERLIN L-band and Very Large Array C-band imaging. These observations are used in combination with the near-infrared imaging to construct a lens model, which indicates a lensing magnification of μ ≈ 10. The source reconstruction appears to support a radio morphology comprised of a compact (<250 pc) core and more extended component, perhaps indicative of an active nucleus and jet or lobe.

  9. Constraints on Feedback in the Local Universe: The Relation Between Star Formation and AGN Activity in Early Type Galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher P.; Baum, Stefi Alison

    2016-01-01

    We address the relation between star formation and AGN activity in a sample of 231 nearby (0.0002 < z < 0.0358) early type galaxies by carrying out a multi-wavelength study using archival observations in the UV, IR and radio. Our results indicate that early type galaxies in the current epoch are rarely powerful AGNs, with P < 1022 WHz-1 for a majority of the galaxies. Only massive galaxies are capable of hosting powerful radio sources while less massive galaxies are hosts to lower radio power sources. Evidence of ongoing star formation is seen in approximately 7% of the sample. The SFR of these galaxies is less than 0.1 M⊙yr-1. They also tend to be radio faint (P < 1022 WHz-1). There is a nearly equal fraction of star forming galaxies in radio faint (P < 1022 WHz-1) and radio bright galaxies (P ≥ 1022 WHz-1) suggesting that both star formation and radio mode feedback are constrained to be very low in our sample. We notice that our galaxy sample and the Brightest Cluster Galaxies (BCGs) follow similar trends in radio power versus SFR. This may be produced if both radio power and SFR are related to stellar mass.

  10. Disk-Jet Connection in the Radio Galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Olmstead, Alice R.; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Lähteenmäki, Anne; Tornikoski, Merja; Hovatta, Talvikki; Marshall, Kevin; Miller, H. Richard; Ryle, Wesley T.; Chicka, Benjamin; Benker, A. J.; Bottorff, Mark C.; Brokofsky, David; Campbell, Jeffrey S.; Chonis, Taylor S.; Gaskell, C. Martin; Gaynullina, Evelina R.; Grankin, Konstantin N.; Hedrick, Cecelia H.; Ibrahimov, Mansur A.; Klimek, Elizabeth S.; Kruse, Amanda K.; Masatoshi, Shoji; Miller, Thomas R.; Pan, Hong-Jian; Petersen, Eric A.; Peterson, Bradley W.; Shen, Zhiqiang; Strel'nikov, Dmitriy V.; Tao, Jun; Watkins, Aaron E.; Wheeler, Kathleen

    2009-10-01

    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray (2-10 keV), optical (R and V bands), and radio (14.5 and 37 GHz) wave bands, as well as imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. Furthermore, the total radiative output of a radio flare is related to the equivalent width of the corresponding X-ray dip. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole (BH) based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). These findings provide support for the paradigm that BHXRBs and both radio-loud and radio-quiet active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central BH. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the

  11. CONSTRAINING JET PRODUCTION SCENARIOS BY STUDIES OF NARROW-LINE RADIO GALAXIES

    SciTech Connect

    Sikora, Marek; Stasinska, Grazyna; Koziel-Wierzbowska, Dorota; Madejski, Greg M.; Asari, Natalia V.

    2013-03-01

    We study a large sample of narrow-line radio galaxies (NLRGs) with extended radio structures. Using 1.4 GHz radio luminosities L {sub 1.4}, narrow optical emission line luminosities L {sub [OIII]} and L{sub H{sub {alpha}}}, as well as black hole masses M {sub BH} derived from stellar velocity dispersions measured from the optical spectra obtained with the Sloan Digital Sky Survey, we find that (1) NLRGs cover about four decades of the Eddington ratio, {lambda} {identical_to} L {sub bol}/L {sub Edd}{proportional_to}L {sub line}/M {sub BH}; (2) L {sub 1.4}/M {sub BH} strongly correlates with {lambda}; and (3) radio loudness, R{identical_to}L{sub 1.4}/L{sub line}, strongly anti-correlates with {lambda}. A very broad range of the Eddington ratio indicates that the parent population of NLRGs includes both radio-loud quasars (RLQs) and broad-line radio galaxies (BLRGs). The correlations they obey and their high jet production efficiencies favor a jet production model which involves the so-called magnetically choked accretion scenario. In this model, production of the jet is dominated by the Blandford-Znajek mechanism, and the magnetic fields in the vicinity of the central black hole are confined by the ram pressure of the accretion flow. Since large net magnetic flux accumulated in central regions of the accretion flow required by the model can take place only via geometrically thick accretion, we speculate that the massive, 'cold' accretion events associated with luminous emission-line active galactic nucleus can be accompanied by an efficient jet production only if preceded by a hot, very sub-Eddington accretion phase.

  12. The innermost region of the water megamaser radio galaxy 3C 403

    NASA Astrophysics Data System (ADS)

    Tarchi, A.; Brunthaler, A.; Henkel, C.; Menten, K. M.; Braatz, J.; Weiß, A.

    2007-11-01

    Context: The standard unified scheme of active galactic nuclei requires the presence of high column densities of gas and dust potentially obscuring the central engine. So far, few direct subarcsecond resolution studies of this material have been performed toward radio galaxies. Aims: The goal of this paper is to elucidate the nuclear environment of the prototypical X-shaped Fanaroff-Riley type II radio galaxy 3C 403, the only powerful radio galaxy known to host an H2O megamaser. Methods: Very Large Array A-array and single-dish Green Bank and Effelsberg 1.3 cm measurements were performed to locate and monitor the water maser emission. Very Long Baseline Interferometry 6 cm continuum observations were taken to analyze the spatial structure of the nuclear environment at even smaller scales, while the CO J = 1-0 and 2-1 transitions were observed with the IRAM 30-m telescope to search for thermal emission from a spatially extended, moderately dense gas component. Results: Positions of the H2O maser features and the continuum emission from the core coincide within 5 mas (5.5 pc). Intensities of the two main maser components with (isotropic) luminosities sometimes surpassing 1000 L{_⊙} appear to be anti-correlated, with typical timescales for strong variations of one year. If the variations are intrinsic to the cloud(s), the implied angular source size would be ⪉0.3 mas and the brightness temperature ⪆5×10{^8} K. The VLBI continuum observations support a scenario where a nuclear core, represented by the dominant central radio continuum component, is accompanied by a jet and counterjet, directed toward the western and eastern large scale lobes of the galaxy. CO remains undetected, providing a maximum scale size of 50 pc × (500 K/T_b)1/2, with Tb denoting the brightness temperature of the CO J = 1-0 line. Possible scenarios that could produce the observed maser emission are outlined. Adopting a mass of several 108 for the nuclear engine, the observed maser features

  13. Pilot study of the radio-emitting AGN population: the emerging new class of FR 0 radio-galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.; Capetti, Alessandro; Giovannini, Gabriele

    2015-04-01

    We present the results of a pilot JVLA project aimed at studying the bulk of the radio-emitting AGN population, that was unveiled by the NVSS/FIRST and SDSS surveys. The key questions are related to the origin of their radio-emission and to its connection with the properties of their hosts. We obtained A-array observations at the JVLA at 1.4, 4.5, and 7.5 GHz for 12 sources, a small but representative subsample. The radio maps reveal compact unresolved or only slightly resolved radio structures on a scale of 1-3 kpc, with the one exception of a hybrid FR I/FR II source extended over ~40 kpc. Thanks to either the new high-resolution maps or to the radio spectra, we isolated the radio core component in most of them. We split the sample into two groups. Four sources have low black hole (BH) masses (mostly ~107 M⊙) and are hosted by blue galaxies, often showing evidence of a contamination from star formation to their radio emission, and are associated with radio-quiet (RQ) AGN. The second group consists in seven radio-loud (RL) AGN, which are located in red massive (~1011 M⊙) early-type galaxies, have high BH masses (≳108 M⊙), and are spectroscopically classified as low excitation galaxies (LEG). These are all characteristics typical of FR I radio galaxies. They also lie on the correlation between radio core power and [O III] line luminosity defined by FR Is. However, they are more core-dominated (by a factor of ~30) than FR Is and show a deficit of extended radio emission. We dub these sources "FR 0" to emphasize their lack of prominent extended radio emission, which is their single distinguishing feature with respect to FR Is. The differences in radio properties between FR 0s and FR Is might be ascribed to an evolutionary effect, with the FR 0 sources undergoing rapid intermittency that prevents the growth of large-scale structures. However, this contrasts with the scenario in which low-luminosity radio-galaxies are fed by continuous accretion of gas from

  14. The rise and fall of galaxy activity in dark matter haloes

    NASA Astrophysics Data System (ADS)

    Pasquali, Anna; van den Bosch, Frank C.; Mo, H. J.; Yang, Xiaohu; Somerville, Rachel

    2009-03-01

    We use the catalogue of galaxy groups constructed from the Sloan Digital Sky Survey (SDSS DR4) by Yang et al. to study the dependence of galaxy activity on stellar mass, M*, halo mass, Mh, and group hierarchy (central versus satellite galaxies). The wealth of data provided by the SDSS allows us to split the sample on the basis of galaxy activity in star-forming galaxies, galaxies with optical active galactic nuclei (AGN), composite galaxies (both star formation and optical AGN activity) and radio sources. We find a smooth transition in halo mass as the activity of central galaxies changes from star formation to optical AGN activity to radio emission. Star-forming centrals preferentially reside in haloes with Mh < 1012h-1Msolar, central galaxies with optical AGN activity typically inhabit haloes with Mh ~ 1013h-1Msolar and centrals emitting in the radio mainly reside in haloes more massive than 1014h-1Msolar. Although this seems to suggest that the environment (halo mass) determines the type of activity of its central galaxy, we find a similar trend with stellar mass: central star formers typically have stellar masses less than 1010h-2Msolar, while optical AGN hosts and central radio sources have characteristic stellar masses of ~1010.8 and ~1011.6h-2Msolar, respectively. Since more massive haloes typically host more massive centrals, it is unclear whether the activity of a central galaxy is causally connected to its stellar mass or to its halo mass. In general, satellite galaxies have their activity suppressed with respect to central galaxies of the same stellar mass. This holds not only for star formation activity, but also for AGN activity in the optical and the radio. At fixed stellar mass, we find that the activity of satellite galaxies depends only weakly on halo mass. In fact, using a set of reduced conditional probability functions, we find that for satellite galaxies the dependence of galaxy activity on halo mass is more than four times weaker than the

  15. Radio continuum and far-infrared observations of low surface brightness galaxies

    NASA Technical Reports Server (NTRS)

    Hoeppe, G.; Brinks, E.; Klein, U.; Giovanardi, C.; Altschuler, D. R.; Price, R. M.; Deeg, H. -J.

    1994-01-01

    We present Very Large Array (VLA) radio continuum and Infrared Astronomy Satellite (IRAS) far-infrared (FIR) observations of 16 low luminosity galaxies of mostly low surface brightness. All galaxies had previously claimed single dish radio continuum detections. However, at the frequencies of our observations (1.49 and 8.48 GHz), we find significant radio emission for two objects only. We show that the other previously claimed detections are due to confusion with physically unrelated background sources. This implies a low radio continuum detection rate for these galaxies. Re-reduced IRAS scans yield significant far-infrared flux densities in at least one IRAS band for 6 of the 16 galaxies. These, together with the FIR and radio continuum upper limits, are consistent with the well established radio/FIR relation, where most of our galaxies populate the low-luminosity end. From the radio continuum and FIR flux densities and their upper limits we estimate the current star formation rates and demonstrate that the galaxies are currently passive in forming stars, in agreement with previous optical investigations. There is an indication that the galaxies were forming stars more intensively averaged over their lifetime than they are presently.

  16. Non-thermal infrared emission - a unique window on radio galaxy lobes

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert; Leipski, Christian; Rudnick, Lawrence

    2008-03-01

    Powerful radio galaxies play an essential role in the dynamics and thermodynamics of the intracluster medium. Fundamental questions exist, however, about their energy budget - how much energy is transferred and how they apparently distribute it uniformly. High sensitivity Spitzer observations offer a unique and critical tool for probing the energetics of lobes of radio galaxies and the physics of the relativistic particle acceleration process. The work on e.g. M87 has already shown that the energy going into particle acceleration may seriously affect the amount available for heating the external medium. In this last cold cycle, it is critical to establish whether this is a common phenomenon in radio galaxy lobes, spanning a range of morphologies as in our targets, or whether this is simply another special feature of M87. In order to achieve this goal we here propose to obtain deep IRAC observations of six radio galaxies with exceptionally bright and highly structured radio lobes.

  17. The fueling of active galaxies

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars

    1991-01-01

    Collisions of galaxies are often invoked to explain violent phenomena in the universe. The dynamics of interacting galaxies is intrinsically three-dimensional and involves both gas and stellar dynamics. In general, a computational approach is needed to model galactic collisions. Galaxy encounters are studied using a hybrid N-body/hydrodynamics code, capable of integrating systems of stars, gas, and dark matter in a fully self-consistent manner. These experiments demonstrate that gravitational coupling between gas and stars in galactic interactions can drive most of the gas throughout a galaxy into the nucleus of a merger remnant. The high densities in these gas concentrations are likely to result in strong bursts of star formation. Hence, this process may explain the nuclear starbursts in some systems of interacting galaxies. Further collapse of these gas concentrations can trigger even more intense activity if some gas is eventually accreted by a supermassive black hole. Such an evolutionary sequence may account for some quasars and active galactic nuclei.

  18. On the interaction of the PKS B1358–113 radio galaxy with the A1836 cluster

    SciTech Connect

    Stawarz, Ł.; Simionescu, A.; Hagino, K.; Szostek, A.; Kozieł-Wierzbowska, D.; Ostrowski, M.; Cheung, C. C.; Siemiginowska, A.; Harris, D. E.; Werner, N.; Madejski, G.; Begelman, M. C.

    2014-10-20

    Here we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. The galaxy harbors one of the most massive black holes known to date, and our analysis of the acquired optical data reveals that this black hole is only weakly active, with a mass accretion rate M-dot {sub acc}∼2×10{sup −4} M-dot {sub Edd}∼0.02 M{sub ⊙} yr{sup –1}. Based on analysis of new Chandra and XMM-Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L {sub j} ∼ (1-6) × 10{sup –3} L {sub Edd} ∼ (0.5-3) × 10{sup 45} erg s{sup –1}. This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. We also constrain the radio source lifetime as τ{sub j} ∼ 40-70 Myr, meaning the total amount of deposited jet energy E {sub tot} ∼ (2-8) × 10{sup 60} erg. We argue that approximately half of this energy goes into shock heating of the surrounding thermal gas, and the remaining 50% is deposited into the internal energy of the jet cavity. The detailed analysis of the X-ray data provides indication for the presence of a bow shock driven by the expanding radio lobes into the A1836 cluster environment. We derive the corresponding shock Mach number in the range M{sub sh}∼2--4, which is one of the highest claimed for clusters or groups of galaxies. This, together with the recently growing evidence that powerful FR II radio galaxies may not be uncommon in the centers of clusters at higher redshifts, supports the idea that jet-induced shock heating may indeed play an important role in shaping the properties of clusters, galaxy groups, and galaxies in formation. In this context, we speculate on

  19. On the Interaction of the PKS B1358-113 Radio Galaxy with the A1836 Cluster

    NASA Astrophysics Data System (ADS)

    Stawarz, Ł.; Szostek, A.; Cheung, C. C.; Siemiginowska, A.; Kozieł-Wierzbowska, D.; Werner, N.; Simionescu, A.; Madejski, G.; Begelman, M. C.; Harris, D. E.; Ostrowski, M.; Hagino, K.

    2014-10-01

    Here we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. The galaxy harbors one of the most massive black holes known to date, and our analysis of the acquired optical data reveals that this black hole is only weakly active, with a mass accretion rate \\dot{M}_acc ˜ 2 × 10-4 \\dot{M}_Edd ˜ 0.02 M⊙ yr-1. Based on analysis of new Chandra and XMM-Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L j ~ (1-6) × 10-3 L Edd ~ (0.5-3) × 1045 erg s-1. This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. We also constrain the radio source lifetime as τj ~ 40-70 Myr, meaning the total amount of deposited jet energy E tot ~ (2-8) × 1060 erg. We argue that approximately half of this energy goes into shock heating of the surrounding thermal gas, and the remaining 50% is deposited into the internal energy of the jet cavity. The detailed analysis of the X-ray data provides indication for the presence of a bow shock driven by the expanding radio lobes into the A1836 cluster environment. We derive the corresponding shock Mach number in the range {M}_sh ˜ 2{--}4, which is one of the highest claimed for clusters or groups of galaxies. This, together with the recently growing evidence that powerful FR II radio galaxies may not be uncommon in the centers of clusters at higher redshifts, supports the idea that jet-induced shock heating may indeed play an important role in shaping the properties of clusters, galaxy groups, and galaxies in formation. In this context, we speculate on a possible bias against detecting stronger jet-driven shocks in poorer environments

  20. J021659-044920: a relic giant radio galaxy at z ˜ 1.3

    NASA Astrophysics Data System (ADS)

    Tamhane, P.; Wadadekar, Y.; Basu, A.; Singh, V.; Ishwara-Chandra, C. H.; Beelen, A.; Sirothia, S.

    2015-11-01

    We report the discovery of a relic Giant Radio Galaxy (GRG) J021659-044920 at redshift z ˜ 1.3 that exhibits large-scale extended, nearly co-spatial, radio and X-ray emission from radio lobes, but no detection of Active Galactic Nuclei core, jets and hotspots. The total angular extent of the GRG at the observed frame 0.325 GHz, using Giant Metrewave Radio Telescope observations is found to be ˜2.4 arcmin, that corresponds to a total projected linear size of ˜1.2 Mpc. The integrated radio spectrum between 0.240 and 1.4 GHz shows high spectral curvature ({α }_{0.610 GHz}^{1.4 GHz} - {α }_{0.240 GHz}^{0.325 GHz} > 1.19) with sharp steepening above 0.325 GHz, consistent with relic radio emission that is ˜8 × 106 yr old. The radio spectral index map between observed frame 0.325 and 1.4 GHz for the two lobes varies from 1.4 to 2.5 with the steepening trend from outer-end to inner-end, indicating backflow of plasma in the lobes. The extended X-ray emission characterized by an absorbed power law with photon index ˜1.86 favours inverse-Compton scattering of the Cosmic Microwave Background (ICCMB) photons as the plausible origin. Using both X-ray and radio fluxes under the assumption of ICCMB we estimate the magnetic field in the lobes to be 3.3 μG. The magnetic field estimate based on energy equipartition is ˜3.5 μG. Our work presents a case study of a rare example of a GRG caught in dying phase in the distant Universe.

  1. Radio Sources toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Bonamente, M.; Carlstrom, J. E.; Dawson, K.; Hasler, N.; Holzapfel, W.; Joy, M.; LaRoque, S.; Marrone, D. P.; Reese, E. D.

    2007-01-01

    Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5' of the cluster center) are a factor of 8.9 (sup +4.3)(sub -2.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5'). Counts in the outer regions of the cluster fields are, in turn, a factor of 3.3 (sup +4.1) (sub -1.8) greater than those in the noncluster fields. Counts in the noncluster fields are consistent with extrapolations from the results of other surveys. We compute the spectral indices of millijansky sources in the cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of alpha = 0.66 with an rms dispersion of 0.36, where flux S proportional to nu(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

  2. Radio Sources Toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Bonamente, M.; Carlstrom, J. E.; Dawson, K.; Hasler, N.; Holzapfel, W.; Joy, M.; LaRoque, S.; Marrone, D. P.; Reese, E. D.

    2007-01-01

    Extra-galactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zeldovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of mJy source fluxes from 89 fields centered on known massive galaxy clusters and 8 non-cluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5 arcmin of the cluster center) are a factor of 8.9 (+4.2 to -3.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5 arcmin). Counts in the outer regions of the cluster fields are in turn a factor of 3.3 (+4.1 -1.8) greater than those in the noncluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of al[ja = 0.66 with an rms dispersion of 0.36, where flux S varies as upsilon(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

  3. TURBULENCE AND RADIO MINI-HALOS IN THE SLOSHING CORES OF GALAXY CLUSTERS

    SciTech Connect

    ZuHone, J. A.; Markevitch, M.; Giacintucci, S.

    2013-01-10

    A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as radio mini-halos. It has been proposed that the relativistic electrons responsible for the emission have been reaccelerated by turbulence generated by the sloshing of the cool core gas. We present a high-resolution MHD simulation of gas sloshing in a galaxy cluster coupled with subgrid simulations of relativistic electron acceleration to test this hypothesis. Our simulation shows that the sloshing motions generate turbulence on the order of {delta}v {approx} 50-200 km s{sup -1} on spatial scales of {approx}50-100 kpc and below in the cool core region within the envelope of the sloshing cold fronts, whereas outside the cold fronts, there is negligible turbulence. This turbulence is potentially strong enough to reaccelerate relativistic electron seeds (with initial {gamma} {approx} 100-500) to {gamma} {approx} 10{sup 4} via damping of magnetosonic waves and non-resonant compression. The seed electrons could remain in the cluster from, e.g., past active galactic nucleus activity. In combination with the magnetic field amplification in the core, these electrons then produce diffuse radio synchrotron emission that is coincident with the region bounded by the sloshing cold fronts, as indeed observed in X-rays and the radio. The result holds for different initial spatial distributions of pre-existing relativistic electrons. The power and the steep spectral index ({alpha} Almost-Equal-To 1-2) of the resulting radio emission are consistent with observations of mini-halos, though the theoretical uncertainties of the acceleration mechanisms are high. We also produce simulated maps of inverse-Compton hard X-ray emission from the same population of relativistic electrons.

  4. Turbulence and Radio Mini-halos in the Sloshing Cores of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    ZuHone, J. A.; Markevitch, M.; Brunetti, G.; Giacintucci, S.

    2013-01-01

    A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as radio mini-halos. It has been proposed that the relativistic electrons responsible for the emission have been reaccelerated by turbulence generated by the sloshing of the cool core gas. We present a high-resolution MHD simulation of gas sloshing in a galaxy cluster coupled with subgrid simulations of relativistic electron acceleration to test this hypothesis. Our simulation shows that the sloshing motions generate turbulence on the order of δv ~ 50-200 km s-1 on spatial scales of ~50-100 kpc and below in the cool core region within the envelope of the sloshing cold fronts, whereas outside the cold fronts, there is negligible turbulence. This turbulence is potentially strong enough to reaccelerate relativistic electron seeds (with initial γ ~ 100-500) to γ ~ 104 via damping of magnetosonic waves and non-resonant compression. The seed electrons could remain in the cluster from, e.g., past active galactic nucleus activity. In combination with the magnetic field amplification in the core, these electrons then produce diffuse radio synchrotron emission that is coincident with the region bounded by the sloshing cold fronts, as indeed observed in X-rays and the radio. The result holds for different initial spatial distributions of pre-existing relativistic electrons. The power and the steep spectral index (α ≈ 1-2) of the resulting radio emission are consistent with observations of mini-halos, though the theoretical uncertainties of the acceleration mechanisms are high. We also produce simulated maps of inverse-Compton hard X-ray emission from the same population of relativistic electrons.

  5. Dominant Nuclear Outflow Driving Mechanisms in Powerful Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Batcheldor, Dan; Tadhunter, Clive; Holt, Joanna; Morganti, Raffaella; O'Dea, Christopher P.; Axon, David J.; Koekemoer, Anton

    2007-05-01

    In order to identify the dominant nuclear outflow mechanisms in active galactic nuclei, we have undertaken deep, high-resolution observations of two compact radio sources (PKS 1549-79 and PKS 1345+12) with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope. Not only are these targets known to have powerful emission-line outflows, but they also contain all the potential drivers for the outflows: relativistic jets, quasar nuclei, and starbursts. ACS allows the compact nature (<0.15") of these radio sources to be optically resolved for the first time. Through comparison with existing radio maps, we have seen consistency in the nuclear position angles of both the optical emission-line and radio data. There is no evidence for biconical emission-line features on the large scale, and there is a divergence in the relative position angles of the optical and radio structure. This enables us to exclude starburst-driven outflows. However, we are unable to clearly distinguish between radiative AGN wind-driven outflows and outflows powered by relativistic radio jets. The small-scale biconical features, indicative of such mechanisms, could be below the resolution limit of ACS, especially if aligned close to the line of sight. In addition, there may be offsets between the radio and optical nuclei induced by heavy dust obscuration, nebular continuum, or scattered light from the AGN. Based on observations made with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with program 10206.

  6. Radio Point Sources Toward Galaxy Clusters at 30 GHz

    NASA Technical Reports Server (NTRS)

    Coble, K.; Carlstrom, J. E.; Bonamente, M.; Dawson, K.; Holzapfel, W.; Joy, M.; LaRoque, S.; Reese, E. D.

    2006-01-01

    Extra-galactic point sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio point sources toward galaxy clusters at 28.5 GHz. We compute counts of mJy point source fluxes from 90 fields centered on known massive galaxy clusters and 8 non-cluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We also compute counts towards clusters as a function of luminosity in three redshift bins out to z = 1.0 and see no clear evidence for evolution with redshift. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz. The distribution is skewed, with a median spectral index of 0.76 and 25th and 75th percentiles of 0.55 and 0.95, respectively. This is steeper than the spectral indices of brighter field point sources measured by other surveys.

  7. Starbursts and dusty tori in distant 3CR radio galaxies

    NASA Astrophysics Data System (ADS)

    Podigachoski, Pece; Rocca-Volmerange, Brigitte; Barthel, Peter; Drouart, Guillaume; Fioc, Michel

    2016-08-01

    We present a study of the complete ultraviolet to submillimetre spectral energy distributions (SEDs) of twelve 3CR radio galaxy hosts in the redshift range 1.0 < z < 2.5, which were all detected in the far-infrared by the Herschel Space Observatory. The study employs the new spectro-chemical evolutionary code PÉGASE.3, in combination with recently published clumpy AGN torus models. We uncover the properties of the massive host galaxy stellar populations, the AGN torus luminosities, and the properties of the recent starbursts, which had earlier been inferred in these objects from their infrared SEDs. The PÉGASE.3 fitting yields very luminous (up to 1013 L⊙) young stellar populations with ages of several hundred million years in hosts with masses exceeding 1011 M⊙. Dust masses are seen to increase with redshift, and a surprising correlation - or better upper envelope behaviour - is found between the AGN torus luminosity and the starburst luminosity, as revealed by their associated dust components. The latter consistently exceeds the former by a constant factor, over a range of one order of magnitude in both quantities.

  8. Inverse Compton X-Ray Halos Around High-z Radio Galaxies: A Feedback Mechanism Powered by Far-Infrared Starbursts or the Cosmic Microwave Background?

    NASA Technical Reports Server (NTRS)

    Small, Ian; Blundell, Katherine M.; Lehmer, B. D.; Alexander, D. M.

    2012-01-01

    We report the detection of extended X-ray emission around two powerful radio galaxies at z approx. 3.6 (4C 03.24 and 4C 19.71) and use these to investigate the origin of extended, inverse Compton (IC) powered X-ray halos at high redshifts. The halos have X-ray luminosities of L(sub X) approx. 3 x 10(exp 44) erg/s and sizes of approx.60 kpc. Their morphologies are broadly similar to the approx.60 kpc long radio lobes around these galaxies suggesting they are formed from IC scattering by relativistic electrons in the radio lobes, of either cosmic microwave background (CMB) photons or far-infrared photons from the dust-obscured starbursts in these galaxies. These observations double the number of z > 3 radio galaxies with X-ray-detected IC halos. We compare the IC X-ray-to-radio luminosity ratios for the two new detections to the two previously detected z approx. 3.8 radio galaxies. Given the similar redshifts, we would expect comparable X-ray IC luminosities if millimeter photons from the CMB are the dominant seed field for the IC emission (assuming all four galaxies have similar ages and jet powers). Instead we see that the two z approx. 3.6 radio galaxies, which are 4 fainter in the far-infrared than those at z 3.8, also have approx.4x fainter X-ray IC emission. Including data for a further six z > or approx. 2 radio sources with detected IC X-ray halos from the literature, we suggest that in the more compact, majority of radio sources, those with lobe sizes < or approx.100-200 kpc, the bulk of the IC emission may be driven by scattering of locally produced far-infrared photons from luminous, dust-obscured starbursts within these galaxies, rather than millimeter photons from the CMB. The resulting X-ray emission appears sufficient to ionize the gas on approx.100-200 kpc scales around these systems and thus helps form the extended, kinematically quiescent Ly(alpha) emission line halos found around some of these systems. The starburst and active galactic nucleus

  9. ON THE INJECTION SPECTRUM OF RELATIVISTIC ELECTRONS IN HIGH-REDSHIFT RADIO GALAXIES

    SciTech Connect

    Gopal-Krishna; Mhaskey, Mukul

    2012-01-01

    We point out that the remarkable linearity of the ultra-steep radio spectra of high-redshift radio galaxies reflects a previously reported general trend for powerful radio galaxies, according to which the spectral curvature is less for sources having steeper spectra (measured near rest-frame 1 GHz). We argue based on existing theoretical and observational evidence that it is premature to conclude that the particle acceleration mechanism in sources having straight, ultra-steep radio spectra gives rise to an ultra-steep injection spectrum of the radiating electrons. In empirical support for this we show that the estimated injection spectral indices available for a representative sample of 35 compact steep spectrum radio sources are not correlated with their rest-frame (intrinsic) rotation measures, which are known to be typically large, indicating a dense environment, as is also the case for high-z radio galaxies.

  10. The Atacama Cosmology Telescope: measuring radio galaxy bias through cross-correlation with lensing

    NASA Astrophysics Data System (ADS)

    Allison, Rupert; Lindsay, Sam N.; Sherwin, Blake D.; de Bernardis, Francesco; Bond, J. Richard; Calabrese, Erminia; Devlin, Mark J.; Dunkley, Joanna; Gallardo, Patricio; Henderson, Shawn; Hincks, Adam D.; Hlozek, Renée; Jarvis, Matt; Kosowsky, Arthur; Louis, Thibaut; Madhavacheril, Mathew; McMahon, Jeff; Moodley, Kavilan; Naess, Sigurd; Newburgh, Laura; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Sehgal, Neelima; Spergel, David N.; Staggs, Suzanne T.; van Engelen, Alexander; Wollack, Edward J.

    2015-07-01

    We correlate the positions of radio galaxies in the FIRST survey with the cosmic microwave background lensing convergence estimated from the Atacama Cosmology Telescope over 470 deg2 to determine the bias of these galaxies. We remove optically cross-matched sources below redshift z = 0.2 to preferentially select active galactic nuclei (AGN). We measure the angular cross-power spectrum C_l^{κ g} at 4.4σ significance in the multipole range 100 < l < 3000, corresponding to physical scales within ≈2-60 Mpc at an effective redshift zeff = 1.5. Modelling the AGN population with a redshift-dependent bias, the cross-spectrum is well fitted by the Planck best-fitting Λ cold dark matter cosmological model. Fixing the cosmology and assumed redshift distribution of sources, we fit for the overall bias model normalization, finding b(zeff) = 3.5 ± 0.8 for the full galaxy sample and b(zeff) = 4.0 ± 1.1(3.0 ± 1.1) for sources brighter (fainter) than 2.5 mJy. This measurement characterizes the typical halo mass of radio-loud AGN: we find log (M_halo / M_{⊙}) = 13.6^{+0.3}_{-0.4}.

  11. Suzaku observations of two narrow-line radio galaxies (3C 403 and IC 5063)

    NASA Astrophysics Data System (ADS)

    Tazaki, Fumie; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.

    2012-03-01

    We report the results of Suzaku broad band X-ray observations of the two narrow-line radio galaxies (NLRGs), 3C 403 and IC 5063. Combined with the Swift/BAT spectra averaged for 58 months, we are able to accurately constrain their spectral properties over the 0.5-200 keV band. The spectra from the nucleus are well represented with an absorbed cut-off power law, a mildly absorbed reflection component from cold matter with an iron-K emission line, and an unabsorbed soft component, which gives a firm upper limit for the scattered emission. The reflection strength normalized to the averaged BAT flux is R(≡Ω/2π)~0:6 in both targets, implying that their tori have a sufficiently large solid angle to produce the reprocessed emission. The numerical torus model with an opening angle of ~50 degrees by Ikeda et al. (2009, ApJ, 692, 608) well reproduces the observed spectra. We discuss the possibility that the amount of the normal gas responsible for Thomson scattering is systematically smaller in radio galaxies compared with Seyfert galaxies. This difference may be due to gas being expelled by jet activity. The details of this work are given in Tazaki et al. (2011, ApJ, 738, 70).

  12. A CLOSER VIEW OF THE RADIO-FIR CORRELATION: DISENTANGLING THE CONTRIBUTIONS OF STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

    SciTech Connect

    Moric, I.; Smolcic, V.; Riechers, D. A.; Scoville, N.; Kimball, A.; Ivezic, Z.

    2010-11-20

    We extend the Unified Radio Catalog, a catalog of sources detected by various (NVSS, FIRST, WENSS, GB6) radio surveys, and SDSS, to IR wavelengths by matching it to the IRAS Point and Faint Source catalogs. By fitting each NVSS-selected galaxy's NUV-NIR spectral energy distribution (SED) with stellar population synthesis models we add to the catalog star formation rates (SFRs), stellar masses, and attenuations. We further add information about optical emission-line properties for NVSS-selected galaxies with available SDSS spectroscopy. Using an NVSS 20 cm (F{sub 1.4{sub GHz}} {approx}> 2.5 mJy) selected sample, matched to the SDSS spectroscopic ('main' galaxy and quasar) catalogs and IRAS data (0.04 < z {approx}< 0.2) we perform an in-depth analysis of the radio-FIR correlation for various types of galaxies, separated into (1) quasars, (2) star-forming, (3) composite, (4) Seyfert, (5) LINER, and (6) absorption line galaxies using the standard optical spectroscopic diagnostic tools. We utilize SED-based SFRs to independently quantify the source of radio and FIR emission in our galaxies. Our results show that Seyfert galaxies have FIR/radio ratios lower than, but still within the scatter of, the canonical value due to an additional (likely active galactic nucleus (AGN)) contribution to their radio continuum emission. Furthermore, IR-detected absorption and LINER galaxies are on average strongly dominated by AGN activity in both their FIR and radio emission; however their average FIR/radio ratio is consistent with that expected for star-forming galaxies. In summary, we find that most AGN-containing galaxies in our NVSS-IRAS-SDSS sample have FIR/radio flux ratios indistinguishable from those of the star-forming galaxies that define the radio-FIR correlation. Thus, attempts to separate AGNs from star-forming galaxies by their FIR/radio flux ratios alone can separate only a small fraction of the AGNs, such as the radio-loud quasars.

  13. THE MID-INFRARED ENVIRONMENTS OF HIGH-REDSHIFT RADIO GALAXIES

    SciTech Connect

    Galametz, Audrey; Stern, Daniel; De Breuck, Carlos; Vernet, Joeel; Hatch, Nina; Mayo, Jack; Miley, George; Rettura, Alessandro; Seymour, Nick; Adam Stanford, S.

    2012-04-20

    Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2 < z < 3. Galaxy cluster member candidates were isolated using a single Spitzer/IRAC mid-infrared color criterion, [3.6]-[4.5] > -0.1 (AB), in the fields of 48 radio galaxies at 1.2 < z < 3. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1' (i.e., 0.5 Mpc at 1.2 < z < 3) of the radio galaxy to the 5{sigma} flux density limits of our IRAC data (f{sub 4.5} = 13.4 {mu}Jy). We find that radio galaxies lie preferentially in medium to dense regions, with 73% of the targeted fields denser than average. Our (shallow) 120 s data permit the rediscovery of previously known clusters and protoclusters associated with radio galaxies as well as the discovery of new promising galaxy cluster candidates at z > 1.2.

  14. FR II radio galaxies at low frequencies – I. Morphology, magnetic field strength and energetics

    PubMed Central

    Harwood, Jeremy J.; Croston, Judith H.; Intema, Huib T.; Stewart, Adam J.; Ineson, Judith; Hardcastle, Martin J.; Godfrey, Leith; Best, Philip; Brienza, Marisa; Heesen, Volker; Mahony, Elizabeth K.; Morganti, Raffaella; Murgia, Matteo; Orrú, Emanuela; Röttgering, Huub; Shulevski, Aleksandar; Wise, Michael W.

    2016-01-01

    Due to their steep spectra, low-frequency observations of Fanaroff–Riley type II (FR II) radio galaxies potentially provide key insights in to the morphology, energetics and spectrum of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored. In this paper, the first in a series examining FR IIs at low frequencies, we use LOFAR (LOw Frequency ARray) observations between 50 and 160 MHz, along with complementary archival radio and X-ray data, to explore the properties of two FR II sources, 3C 452 and 3C 223. We find that the morphology of 3C 452 is that of a standard FR II rather than of a double-double radio galaxy as had previously been suggested, with no remnant emission being observed beyond the active lobes. We find that the low-frequency integrated spectra of both sources are much steeper than expected based on traditional assumptions and, using synchrotron/inverse-Compton model fitting, show that the total energy content of the lobes is greater than previous estimates by a factor of around 5 for 3C 452 and 2 for 3C 223. We go on to discuss possible causes of these steeper-than-expected spectra and provide revised estimates of the internal pressures and magnetic field strengths for the intrinsically steep case. We find that the ratio between the equipartition magnetic field strengths and those derived through synchrotron/inverse-Compton model fitting remains consistent with previous findings and show that the observed departure from equipartition may in some cases provide a solution to the spectral versus dynamical age disparity. PMID:27284270

  15. FR II radio galaxies at low frequencies - I. Morphology, magnetic field strength and energetics

    NASA Astrophysics Data System (ADS)

    Harwood, Jeremy J.; Croston, Judith H.; Intema, Huib T.; Stewart, Adam J.; Ineson, Judith; Hardcastle, Martin J.; Godfrey, Leith; Best, Philip; Brienza, Marisa; Heesen, Volker; Mahony, Elizabeth K.; Morganti, Raffaella; Murgia, Matteo; Orrú, Emanuela; Röttgering, Huub; Shulevski, Aleksandar; Wise, Michael W.

    2016-06-01

    Due to their steep spectra, low-frequency observations of Fanaroff-Riley type II (FR II) radio galaxies potentially provide key insights in to the morphology, energetics and spectrum of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored. In this paper, the first in a series examining FR IIs at low frequencies, we use LOFAR (LOw Frequency ARray) observations between 50 and 160 MHz, along with complementary archival radio and X-ray data, to explore the properties of two FR II sources, 3C 452 and 3C 223. We find that the morphology of 3C 452 is that of a standard FR II rather than of a double-double radio galaxy as had previously been suggested, with no remnant emission being observed beyond the active lobes. We find that the low-frequency integrated spectra of both sources are much steeper than expected based on traditional assumptions and, using synchrotron/inverse-Compton model fitting, show that the total energy content of the lobes is greater than previous estimates by a factor of around 5 for 3C 452 and 2 for 3C 223. We go on to discuss possible causes of these steeper-than-expected spectra and provide revised estimates of the internal pressures and magnetic field strengths for the intrinsically steep case. We find that the ratio between the equipartition magnetic field strengths and those derived through synchrotron/inverse-Compton model fitting remains consistent with previous findings and show that the observed departure from equipartition may in some cases provide a solution to the spectral versus dynamical age disparity.

  16. IGM Heating and AGN activity in Fossil Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Khosroshahi, H. G.; Klöckner, H.-R.; Ponman, T. J.; Jetha, N. N.; Raychaudhury, S.

    2014-07-01

    Fossil galaxy groups are energetically and morphologically ideal environments to study the intergalactic medium (IGM) heating, because their inter-galactic gas is undisturbed due to the lack of recent group scale mergers. We study the role of active galactic nuclei (AGN) in heating the IGM in a sample of five fossil galaxy groups by employing properties at 610 MHz and 1.4 GHz. We find that two of the dominant galaxies in fossil groups, ESO 3060170 and RX J1416.4+2315, are associated with the radio lobes. We evaluate the PdV work of the radio lobes and their corresponding heating power and compare to the X-ray emission loss within cooling radius. Our results show that the power due to mechanical heating is not sufficiently high to suppress the cooling.

  17. The Environment of z < 1 3CR Radio Galaxies and QSOs: From Proto-clusters to Clusters of Galaxies?

    NASA Astrophysics Data System (ADS)

    Kotyla, J. P.; Chiaberge, M.; Baum, S.; Capetti, A.; Hilbert, B.; Macchetto, F. D.; Miley, G. K.; O’Dea, C. P.; Perlman, E. S.; Sparks, W. B.; Tremblay, G. R.

    2016-07-01

    We study the cluster environment for a sample of 21 radio loud active galactic nuclei from the 3CR catalog at z\\gt 1, 12 radio galaxies (RGs) and nine quasars, with Hubble Space Telescope (HST) images in the optical and IR. We use two different approaches to determine cluster candidates. We identify the early-type galaxies (ETGs) in every field by modeling each of the sources within a 40″ radius of the targets with a Sèrsic profile. Using a simple passive evolution model, we derive the expected location of the ETGs on the red sequence (RS) in the color–magnitude diagram for each of the fields of our sources. For seven targets, the model coincides with the position of the ETGs. A second approach involves a search for over densities. We compare the object densities of the sample as a whole and individually against control fields taken from the GOODS-S region of 3D-HST survey. With this method we determine the fields of ten targets to be cluster candidates. Four cluster candidates are found by both methods. The two methods disagree in some cases, depending on the specific properties of each field. For the most distant RG in the 3CR catalog (3C 257 at z = 2.47), we identify a population of bluer ETGs that lie on the expected location of the RS model for that redshift. This appears to be the general behavior of ETGs in our fields and it is possibly a signature of the evolution of such galaxies. Our results are consistent with half of the z > 1 RGs being located in dense, rapidly evolving environments.

  18. Feedback in the local Universe: Relation between star formation and AGN activity in early type galaxies

    NASA Astrophysics Data System (ADS)

    Vaddi, Sravani; O'Dea, Christopher; Baum, Stefi; Jones, Christine; Forman, William; Whitmore, Samantha; Ahmed, Rabeea; Pierce, Katherine; Leary, Sara

    2015-08-01

    Aim: We address the relation between star formation and AGN activity in a large sample of nearby early type (E and S0) galaxies. The redshift range of the galaxies is 0.0002galaxy evolution and formation. Evidence of AGN feedback is found in massive galaxies in galaxy clusters. However, how common AGN feedback is in the local universe and in small scale systems is still not evident.Methods: To answer this question, we carried out a multiple wavelength study of a sample of 231 early type galaxies which were selected to have an apparent K-band magnitude brighter than 13.5 and whose positions correlate with Chandra ACIS-I and ACIS-S sources. The galaxies in the sample are unbiased regarding their star formation and radio source properties. Using the archival observations at radio, IR and UV from VLA, WISE and GALEX respectively, we obtained the radio power, estimate FUV star formation rate (SFR) and other galaxy properties to study AGN activity and ongoing star formation.Results: The relationship between radio power and stellar mass shows that there is an upper envelope of radio power that is a steep function of stellar luminosity. This suggests that less massive galaxies have low radio power while massive galaxies are capable of hosting powerful radio sources. The Radio-MIR relation shows that galaxies with P>=1022 WHz-1 are potential candidates for being AGN. About ~ 7% of the sample show evidence of ongoing star formation with SFR ranging from 10-3 to 1 M⊙yr-1. These are also less massive and radio faint suggesting the absence of active accretion. There is nearly equal fraction of star forming galaxies in radio faint (P<1022 WHz-1) and radio bright galaxies (P>=1022 WHz-1) . Only ~ 5% of the galaxies in our sample have P>=1022 WHz-1 and most of them do not show evidence of bright accretion disks. We see a weak correlation and a dispersion of

  19. A CO-rich merger shaping a powerful and hyperluminous infrared radio galaxy at z = 2: the Dragonfly Galaxy

    NASA Astrophysics Data System (ADS)

    Emonts, B. H. C.; Mao, M. Y.; Stroe, A.; Pentericci, L.; Villar-Martín, M.; Norris, R. P.; Miley, G.; De Breuck, C.; van Moorsel, G. A.; Lehnert, M. D.; Carilli, C. L.; Röttgering, H. J. A.; Seymour, N.; Sadler, E. M.; Ekers, R. D.; Drouart, G.; Feain, I.; Colina, L.; Stevens, J.; Holt, J.

    2015-07-01

    In the low-redshift Universe, the most powerful radio sources are often associated with gas-rich galaxy mergers or interactions. We here present evidence for an advanced, gas-rich (`wet') merger associated with a powerful radio galaxy at a redshift of z ˜ 2. This radio galaxy, MRC 0152-209, is the most infrared-luminous high-redshift radio galaxy known in the Southern hemisphere. Using the Australia Telescope Compact Array, we obtained high-resolution CO(1-0) data of cold molecular gas, which we complement with Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 (WFPC2) imaging and William Herschel Telescope long-slit spectroscopy. We find that, while roughly MH2 ˜ 2 × 1010 M⊙ of molecular gas coincides with the central host galaxy, another MH2 ˜ 3 × 1010 M⊙ is spread across a total extent of ˜60 kpc. Most of this widespread CO(1-0) appears to follow prominent tidal features visible in the rest-frame near-UV HST/WFPC2 imaging. Lyα emission shows an excess over He II, but a deficiency over LIR, which is likely the result of photoionization by enhanced but very obscured star formation that was triggered by the merger. In terms of feedback, the radio source is aligned with widespread CO(1-0) emission, which suggests that there is a physical link between the propagating radio jets and the presence of cold molecular gas on scales of the galaxy's halo. Its optical appearance, combined with the transformational stage at which we witness the evolution of MRC 0152-209, leads us to adopt the name `Dragonfly Galaxy'.

  20. RADIO-LOUD ACTIVE GALACTIC NUCLEUS: IS THERE A LINK BETWEEN LUMINOSITY AND CLUSTER ENVIRONMENT?

    SciTech Connect

    Ineson, J.; Croston, J. H.; Hardcastle, M. J.; Jarvis, M.; Kraft, R. P.; Evans, D. A.

    2013-06-20

    We present here the first results from the Chandra ERA (Environments of Radio-loud AGN) Large Project, characterizing the cluster environments of a sample of 26 radio-loud active galactic nuclei (AGNs) at z {approx} 0.5 that covers three decades of radio luminosity. This is the first systematic X-ray environmental study at a single epoch, and has allowed us to examine the relationship between radio luminosity and cluster environment without the problems of Malmquist bias. We have found a weak correlation between radio luminosity and host cluster X-ray luminosity, as well as tentative evidence that this correlation is driven by the subpopulation of low-excitation radio galaxies, with high-excitation radio galaxies showing no significant correlation. The considerable scatter in the environments may be indicative of complex relationships not currently included in feedback models.

  1. A GMRT study of Seyfert galaxies NGC 4235 and NGC 4594: evidence of episodic activity?

    NASA Astrophysics Data System (ADS)

    Kharb, P.; Srivastava, S.; Singh, V.; Gallimore, J. F.; Ishwara-Chandra, C. H.; Ananda, Hota

    2016-06-01

    Low-frequency observations at 325 and 610 MHz have been carried out for two `radio-loud' Seyfert galaxies, NGC 4235 and NGC 4594 (Sombrero galaxy), using the Giant Meterwave Radio Telescope (GMRT). The 610 MHz total intensity and 325-610 MHz spectral index images of NGC 4235 tentatively suggest the presence of a `relic' radio lobe, most likely from a previous episode of active galactic nucleus (AGN) activity. This makes NGC 4235 only the second known Seyfert galaxy after Mrk 6 to show signatures of episodic activity. Spitzer and Herschel infrared spectral energy distribution (SED) modelling using the CLUMPYDREAM code predicts star formation rates (SFRs) that are an order of magnitude lower than those required to power the radio lobes in these Seyferts (˜0.13-0.23 M⊙ yr-1 compared to the required SFR of ˜2.0-2.7 M⊙ yr-1 in NGC 4594 and NGC 4235, respectively). This finding along with the detection of parsec and sub-kpc radio jets in both Seyfert galaxies, that are roughly along the same position angles as the radio lobes, strongly support the suggestion that Seyfert lobes are AGN powered. SED modelling supports the `true' type 2 classification of NGC 4594: this galaxy lacks significant dust obscuration as well as a prominent broad-line region. Between the two Seyfert galaxies, there is an inverse relation between their radio-loudness and Eddington ratio and a direct relation between their Eddington-scaled jet power and bolometric power.

  2. Unifying X-ray winds in radio galaxies with Chandra HETG

    NASA Astrophysics Data System (ADS)

    Tombesi, Francesco

    2013-09-01

    X-ray winds are routinely observed in the spectra of Seyfert galaxies. They can be classified as warm absorbers (WAs), with v~100-1,000km/s, and ultra-fast outflows (UFOs), with v>10,000km/s. In stark contrast, the lack of sensitive enough observations allowed the detection of WAs or UFOs only in very few radio galaxies. Therefore, we propose to observe a small sample of three radio galaxies with the Chandra HETG - 3C111 for 150ks, 3C390.3 for 150ks and 3C120 for 200ks - to detect and study in detail their WAs. We will quantify the importance of mechanical feedback from winds in radio galaxies and compare them to the radio jet power. We will also test whether WAs and UFOs can be unified in a single, multi-phase and multi-scale outflow, as recently reported for Seyferts.

  3. Kinematic signatures of AGN feedback in moderately powerful radio galaxies at z ~ 2 observed with SINFONI

    NASA Astrophysics Data System (ADS)

    Collet, C.; Nesvadba, N. P. H.; De Breuck, C.; Lehnert, M. D.; Best, P.; Bryant, J. J.; Hunstead, R.; Dicken, D.; Johnston, H.

    2016-02-01

    Most successful galaxy formation scenarios now postulate that the intense star formation in massive, high-redshift galaxies during their major growth period was truncated when powerful AGNs launched galaxy-wide outflows of gas that removed large parts of the interstellar medium. SINFONI imaging spectroscopy of the most powerful radio galaxies at z ~ 2 show clear signatures of such winds, but are too rare to be good representatives of a generic phase in the evolution of all massive galaxies at high redshift. Here we present SINFONI imaging spectroscopy of the rest-frame optical emission-line gas in 12 radio galaxies at redshifts ~2. Our sample spans a range in radio power that is intermediate between the most powerful radio galaxies with known wind signatures at these redshifts and vigorous starburst galaxies, and are about two orders of magnitude more common than the most powerful radio galaxies. Thus, if AGN feedback is a generic phase of massive galaxy evolution for reasonable values of the AGN duty cycle, these are just the sources where AGN feedback should be most important. Our sources show a diverse set of gas kinematics ranging from regular velocity gradients with amplitudes of Δv = 200-400 km s-1 consistent with rotating disks to very irregular kinematics with multiple velocity jumps of a few 100 km s-1. Line widths are generally high, typically around FWHM = 800 km s-1, more similar to the more powerful high-z radio galaxies than mass-selected samples of massive high-z galaxies without bright AGNs, and consistent with the velocity range expected from recent hydrodynamic models. A broad Hα line in one target implies a black hole mass of a few 109 M⊙. Velocity offsets of putative satellite galaxies near a few targets suggest dynamical masses of a few 1011 M⊙ for our sources, akin to the most powerful high-z radio galaxies. Ionized gas masses are 1-2 orders of magnitude lower than in the most powerful radio galaxies, and the extinction in the gas is

  4. Kinematics of the nucleus of the radio galaxy M 87

    NASA Astrophysics Data System (ADS)

    Matveyenko, L. I.; Seleznev, S. V.

    2015-12-01

    The superfine structure of the active region of the radio galaxy M 87 has been investigated at millimeter and centimeter wavelengths. A disk, a core, a jet, and a counterjet have been identified. The disk is inclined to the plane of the sky at an angle of 60◦ toward the jet. We show that the surrounding thermal plasma inflows onto the disk, is transferred in a spiral to the center, and is ejected, carrying away an excess angular momentum as it is accumulated. The remainder falls to the forming central massive body. The temperature of the plasma as it is transferred increases to relativistic values; the ejection velocity increases to 0.02 c. The nozzle diameter decreases as the axis is approached. The central high-velocity bipolar outflow is surrounded by low-velocity components, tubes. The interaction of the rotating flow with the ambient medium collimates and accelerates the flows. Ring currents whose tangential directions are observed as parallel chains of components are generated in the flows. The ring currents of the disk and jets produce aligned magnetic fields. The ejection of the jet and counterjet plasma flows is equiprobable; the motion is along the field in one case and opposite to the field in the other case, causing an acceleration or deceleration. The velocity of the high-velocity jet is a factor of 1.7 higher than the counterjet velocity. The acceleration compensates for the losses of relativistic electrons observed at distances exceeding those corresponding to their radiative cooling time. The hydrodynamic instability of the flow ejection causes precession, the formation of a conical helical flow structure with an increasing pitch. The reaction of the flows curves the disk and the helix axes. The spectra of compact fragments in the high-velocity bipolar outflow have lowfrequency cutoffs determined by reabsorption and absorption in the thermal plasma of the screen. The cutoff frequencies in the spectra increase as the center is approached and pass

  5. Fundamental properties of Fanaroff-Riley type II radio galaxies investigated via Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Kapińska, A. D.; Uttley, P.; Kaiser, C. R.

    2012-08-01

    Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large-scale structure. We explore the intrinsic and extrinsic properties of the population of Fanaroff-Riley type II (FR II) objects, i.e. their kinetic luminosities, lifetimes and the central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux-limited radio catalogues of the Third Cambridge Revised Revised Catalogue (3CRR) and Best et al. We construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, we compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The new Monte Carlo method we present here allows us to (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, as has not been done before, we allow the source physical properties (kinetic luminosities, lifetimes and central densities) to co-evolve with redshift, and we find that all the investigated parameters most likely undergo cosmological evolution. Strikingly, we find that the break in the kinetic luminosity function must undergo redshift evolution of at least (1 + z)3. The fundamental parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. We use the estimated kinetic luminosity functions to set constraints on the duty cycles of these powerful radio sources. A comparison of the duty cycles of powerful FR IIs with those determined from radiative luminosities of active galactic nuclei of

  6. Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation

    SciTech Connect

    Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A

    2006-08-01

    We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.

  7. Imaging the host galaxies of high-redshift radio-quiet QSOs

    NASA Technical Reports Server (NTRS)

    Lowenthal, James D.; Heckman, Timothy M.; Lehnert, Matthew, D.; Elias, J. H.

    1995-01-01

    We present new deep K-band and optical images of four radio-quiet QSOs at z approximately = 1 and six radio-quiet QSOs at z approximately = 2.5, as well as optical images only of six more at z approximately = 2.5. We have examined the images carefully for evidence of extended 'fuzz' from any putative QSO host galaxy. None of the z approximately = 2.5 QSOs shows any extended emission, and only two of the z approximately = 1 QSOs show marginal evidence for extended emission. Our 3 sigma detection limits in the K images, m(sub K) approximately = 21 for an isolated source, would correspond approximately to an unevolved L(sup star) elliptical galaxy at z = 2.5 or 2-3 mag fainter than an L(sup star) elliptical at z = 1, although our limits on host galaxy light are weaker than this due to the difficulty of separating galaxy light from QSO light. We simulate simple models of disk and elliptical host galaxies, and find that the marginal emission around the two z approximately = 1 QSOs can be explained by disks or bulges that are approximately 1-2 mag brighter than an unevolved L(sup star) galaxy in one case and approximately 1.5-2.5 mag brighter than L(sub star) in the other. For two other z approximately = 1 QSOs, we have only upper limits (L approximately = L(sup star)). The hosts of the high-redshift sample must be no brighter than about 3 mag above an unevolved L(sup star) galaxy, and are at least 1 magnitude fainter than the hosts of radio-loud QSOs at the same redshift. If the easily detected K-band light surrounding a previous sample of otherwise similar but radio-loud QSOs is starlight, then it must evolve on timescales of greater than or approximately equal to 10(exp 8) yr (e.g., Chambers & Charlot 1990); therefore our non-detection of host galaxy fuzz around radio-quiet QSOs supports the view that high-redshift radio-quiet and radio-loud QSOs inhabit different host objects, rather than being single types of objects that turn their radio emission on and off over

  8. Jet Feedback on the Interstellar Medium of the Radio Galaxy 3C 293

    NASA Astrophysics Data System (ADS)

    Lanz, Lauranne; Ogle, Patrick M.; Appleton, Philip N.; Emonts, Bjorn; Evans, Daniel A.

    2014-06-01

    We present a 70 ks Chandra observation of the radio galaxy 3C 293. This galaxy belongs to the class of molecular hydrogen emission galaxies (MOHEGs) that have very luminous emission from warm molecular hydrogen. In the case of radio galaxies, the molecular gas appears to be heated by jet-driven ISM turbulence. 3C 293 contains 3.7 x 10^9 solar masses of shock-heated, 100 K molecular hydrogen in an extended 10 kpc scale region. With Chandra, we observe emission from the jets both within the host galaxy and outside of the galaxy, along the 100 kpc radio jets. Some of the soft X-rays are coincident with the radio hotspots, but one X-ray emitting feature is anti-coincident with the radio emission. We model the X-ray spectra of the nucleus, the inner jets, and the X-ray features along the extended radio jets. Both the nucleus and the inner jets show evidence of 10^7 K shock-heated gas. The kinetic power of the jets is more than sufficient to heat the X-ray emitting gas, which serves as a reservoir of thermal and turbulent energy to maintain the molecular hydrogen emission over a time scale of 10^7 years.

  9. Using Data Mining to Find Bent-Double Radio Galaxies in the FIRST Survey

    SciTech Connect

    Kamath,C; Cantu-Paz,E; Fodor,I; Tang,N A

    2001-06-22

    In this paper, the authors describe the use of data mining techniques to search for radio-emitting galaxies with a bent-double morphology. In the past, astronomers from the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey identified these galaxies through visual inspection. This was not only subjective but also tedious as the on-going survey now covers 8000 square degrees, with each square degree containing about 90 galaxies. In this paper, they describe how data mining can be used to automate the identification of these galaxies. They discuss the challenges faced in defining meaningful features that represent the shape of a galaxy and their experiences with ensembles of decision trees for the classification of bent-double galaxies.

  10. Radio continuum emission and H I gas accretion in the NGC 5903/5898 compact group of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gopal-Krishna; Mhaskey, Mukul; Wiita, Paul J.; Sirothia, S. K.; Kantharia, N. G.; Ishwara-Chandra, C. H.

    2012-06-01

    We discuss the nature of the multicomponent radio continuum and H I emission associated with the nearby galaxy group comprised of two dominant ellipticals, NGC 5898 and NGC 5903, and a dwarf lenticular ESO 514-G003. Striking new details of radio emission are unveiled from the second Data Release of the ongoing TIFR GMRT Sky Survey (TGSS) which provides images with a resolution of ˜24 × 18 arcsec2 and a typical rms noise of 5 mJy at 150 MHz. Previous radio observations of this compact triplet of galaxies include images at higher frequencies of the radio continuum as well as H I emission, the latter showing huge H I trails originating from the vicinity of NGC 5903 where H I is in a kinematically disturbed state. The TGSS 150-MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf S0 galaxy ESO 514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (α˜-1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the H I trails. Another noteworthy aspect of this triplet of early-type galaxies highlighted by the present study is that both its radio-loud members, namely NGC 5903 and ESO 514-G003, are also the only galaxies that are seen to be connected to an H I filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  11. Radio-Optical Galaxy Shape Correlations in theCOSMOS Field

    NASA Astrophysics Data System (ADS)

    Tunbridge, Ben; Harrison, Ian; Brown, Michael L.

    2016-09-01

    We investigate the correlations in galaxy shapes between optical and radio wavelengths using archival observations of the COSMOS field. Cross-correlation studies between different wavebands will become increasingly important for precision cosmology as future large surveys may be dominated by systematic rather than statistical errors. In the case of weak lensing, galaxy shapes must be measured to extraordinary accuracy (shear systematics of <0.01%) in order to achieve good constraints on dark energy parameters. By using shape information from overlapping surveys in optical and radio bands, robustness to systematics may be significantly improved without loss of constraining power. Here we use HST-ACS optical data, VLA radio data, and extensive simulations to investigate both our ability to make precision measurements of source shapes from realistic radio data, and to constrain the intrinsic astrophysical scatter between the shapes of galaxies as measured in the optical and radio wavebands. By producing a new image from the VLA-COSMOS L-band radio visibility data that is well suited to galaxy shape measurements, we are able to extract precise measurements of galaxy position angles. Comparing to corresponding measurements from the HST optical image, we set a lower limit on the intrinsic astrophysical scatter in position angles, between the optical and radio bands, of σα > 0.212π radians (or 38.2°) at a 95% confidence level.

  12. Spectroscopic Confirmation of A Radio-Selected Galaxy Overdensity at z = 1.11

    SciTech Connect

    Stanford, S; Stern, D; Holden, B; Spinrad, H

    2004-02-26

    We report the discovery of a galaxy overdensity at z = 1.11 associated with the z = 1.110 high-redshift radio galaxy MG 0442+0202. The group, CL 0442+0202, was found in a near-infrared survey of z > 1 radio galaxies undertaken to identify spatially-coincident regions with a high density of objects red in I - K' color, typical of z > 1 elliptical galaxies. Spectroscopic observations from the Keck I telescope reveal five galaxies within 35'' of MG 0442+0202 at 1.10 < z < 1.11. These member galaxies have broad-band colors and optical spectra consistent with passively-evolving elliptical galaxies formed at high redshift. Archival ROSAT observations reveal a 3{sigma} detection of soft X-ray emission coincident with CL 0442+0202 at a level five times greater than expected for the radio galaxy. These data are suggestive of a rich galaxy cluster and inspired a 45 ks Chandra X-Ray Observatory observation. As expected, the radio galaxy is unresolved to Chandra, but is responsible for approximately half of the observed X-ray flux. The remaining ROSAT flux is resolved into four point sources within 15'' of the radio galaxy, corresponding to a surface density two orders of magnitude higher than average for X-ray sources at these flux levels (S{sub 0.5-2keV} > 5x10{sup -16} ergs cm{sup -2} s{sup -1}). One of these point sources is identified with a radio-quiet, type II quasar at z = 1.863, akin to sources recently reported in deep Chandra surveys. The limit on an extended hot intracluster medium in the Chandra data is S{sub 1-6keV} < 1.9 x 10{sup -15} ergs cm{sup -2} s{sup -1} (3{sigma}, 30'' radius aperture). Though the X-ray observations do not confirm the existence of a massive, bound cluster at z > 1, the success of the optical/near-infrared targeting of early-type systems near the radio galaxy validates searches using radio galaxies as beacons for high-redshift large-scale structure. We interpret CL 0442+0202 to be a massive cluster in the process of formation.

  13. Optical positions of active galaxies

    NASA Astrophysics Data System (ADS)

    Meurs, E. J. A.

    1984-04-01

    Optical positions are calculated for 26 active galaxies (mainly Markarian dn Arakelian objects), using the plate-measuring apparatus at Leiden Observatory on the O plates of the Palomar Sky Survey and applying AGK-3 data in the reductions. The results are presented in a table and have accuracy 0.5 arcsec; a comparison with the positions determined by Clements (1981, 1983) for 19 objects reveals a possible offset of -0.28 arcsec in the right-ascension determinations.

  14. The Host Galaxy and the Extended Emission-Line Region of the Radio Galaxy 3C 79

    NASA Astrophysics Data System (ADS)

    Fu, Hai; Stockton, Alan

    2008-04-01

    We present extensive ground-based spectroscopy and HST imaging of 3C 79, an FR II radio galaxy associated with a luminous extended emission-line region (EELR). Surface brightness modeling of an emission-line-free HST R-band image reveals that the host galaxy is a massive elliptical with a compact companion 0.8'' away and 4 mag fainter. The host galaxy spectrum is best described by an intermediate-age (1.3 Gyr) stellar population (4% by mass), superimposed on a 10 Gyr old population and a power law (αλ = - 1.8); the stellar populations are consistent with supersolar metallicities, with the best fit given by the 2.5 Z⊙ models. We derive a dynamical mass of 4 × 1011 M⊙ within the effective radius from the velocity dispersion. The EELR spectra clearly indicate that the EELR is photoionized by the hidden central engine. Photoionization modeling shows evidence that the gas metallicity in both the EELR and the nuclear narrow-line region is mildly subsolar (0.3-0.7 Z⊙), significantly lower than the supersolar metallicities deduced from typical active galactic nuclei in the Sloan Digital Sky Survey. The more luminous filaments in the EELR exhibit a velocity field consistent with a common disk rotation. Fainter clouds, however, show high approaching velocities that are uncoupled from this apparent disk rotation. The striking similarities between this EELR and the EELRs around steep-spectrum radio-loud quasars provide further evidence for the orientation-dependent unification schemes. The metal-poor gas is almost certainly not native to the massive host galaxy. We suggest that the close companion galaxy could be the tidally stripped bulge of a late-type galaxy that is merging with the host galaxy. The interstellar medium of such a galaxy is probably the source for the low-metallicity gas in 3C 79. Based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative

  15. Radio Astronomy in Malaysia: Current Status and Outreach Activities

    NASA Astrophysics Data System (ADS)

    Hashim, N.; Abidin, Z. Z.; Ibrahim, U. F. S. U.; Umar, R.; Hassan, M. S. R.; Rosli, Z.; Hamidi, Z. S.; Ibrahim, Z. A.

    2011-12-01

    In this paper, we will present the current status of radio astronomical research and outreach in Malaysia. We will also present a short history of our research group, which is currently the only radio astronomical facility in Malaysia. Our group is called the Radio Cosmology Research Lab and was established in 2005 by Dr Zamri Zainal Abidin and Prof Dr Zainol Abidin Ibrahim. We will discuss the future plans for this group including our keen interest in being part of a more global network of radio astronomers. We are already an active member of the South-East Asia Astronomy Network (SEAAN) and aims to have a radio astronomical facility in order to join the Global Very Long Baseline Interferometer (VLBI) as well becoming a research hub for the future Square Kilometer Array (SKA) project. We will also present some of the scientific goals of our group including providing a platform for radio astronomers to be able to do observations of weak and high red-shifted radio objects such as galaxy clusters and supernovae.

  16. Multiwavelength data for bright active galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Abrahamyan, Hayk V.; Paronyan, Gurgen M.; Harutyunyan, Gohar S.

    2012-08-01

    The spectral energy distribution (SED) gives a complete picture of the radiation of space objects and may result in correct classifications compared to those based only on optical (or other local) spectra. This is especially crucial for active galaxies, both AGN and Starbursts (SB). For this, multiwavelength (MW) data are needed taken from available surveys and catalogs. We have cross-correlated the Catalogue of quasars and active galaxies with all-sky or large-area MW catalogues, such as X-ray ROSAT (BSC and FSC), UV GALEX (MIS and AIS), optical APM, MAPS, USNO-B1.0, GSC 2.3.2, and SDSS DR8, NIR 2MASS, MIR/FIR WISE, IRAS (PSC and FSC) and AKARI (IRC and FIS), radio GB6, NVSS, FIRST, and WENSS. We have established accurate positions and photometry for a few thousands of objects that appeared in the catalog with poor data, as well as achieved the best astrometric and photometric data for all objects. This allowed correct cross-correlations and establishing correct MW data for these objects. As a result, we obtained 34 photometric points from X-rays to radio and using VO tools built SEDs for some 10,000 bright objects. Some data from other surveys were also used, such as Chandra, XMM, Spitzer, etc. All objects were grouped into several forms of SED and were compared to the known optical classes given in the catalog (QSO, BLL, Sy1, Sy1.2-1.9, Sy2, LINER, SB, and HII). This allowed reveal obscured AGN, as well as find previously misclassified objects. A homogeneous classification for these objects was established. The first part of this project is presented; establishment of accurate positions and photometry and cross-correlations with MW catalogs.

  17. Accretion modes and unified schemes for FR-II radio galaxies

    NASA Astrophysics Data System (ADS)

    Whysong, David Harold.

    2005-11-01

    A robust and general method of testing for the presence of an obscured quasar inside a radio galaxy is to look for high mid-IR luminosity from the nuclear obscuring material. We conducted a survey of 3CR FR-II radio galaxies and quasars using the Keck I telescope Long Wavelength Spectrometer. The sample is flux-limited and selected on an isotropic property (low-frequency radio lobe flux). We also observed Cygnus A and two FR-I radio galaxies, Centaurus A, and M87. For the FR-I sources, we f0ind that the nuclear mid-IR source in M87 is consistent with pure synchrotron emission from the base of the jet. This result establishes the existence of "nonthermal" narrow line radio galaxies wherein the energetics are dominated by jet kinetic luminosity rather than thermal accretion. However, Cen A does contain a modest quasar-like nucleus, so the central engines of FR-I radio galaxies are heterogeneous in nature. ? showed that for 3CR FR-II sources with Z < 0.5, there appears to be an excess number of low-luminosity Narrow Line Radio Galaxies with small projected linear size relative to the simplest orientation models. The simplest explanation is that there is a population of relatively small, low power FR-IIs that lack hidden quasars. An alternative hypothesis is possible if the opening angle of the dusty torus scales with luminosity and the radio power decreases with time (?). Our observations test these hypotheses. For our FR-II sample, the mid-IR flux is positively correlated with projected linear size of the radio lobes at 99.8% confidence. Many of the smaller radio galaxies have small mid-IR flux (upper limit 3s < 1.5 mJy) which indicates they probably lack a powerful thermal accretion flow. It seems likely that many FR- II radio sources are predominantly powered by nonthermal means, while the largest and most powerful FR-II radio galaxies show, strong mid-IR emission indicating that they harbor a hidden quasar. This is consistent with the fragmentary optical

  18. RADIO GALAXY 3C 230 OBSERVED WITH GEMINI LASER ADAPTIVE-OPTICS INTEGRAL-FIELD SPECTROSCOPY

    SciTech Connect

    Steinbring, Eric

    2011-11-15

    The Altair laser-guide-star adaptive optics facility combined with the near-infrared integral-field spectrometer on Gemini North have been employed to study the morphology and kinematics of 3C 230 at z = 1.5, the first such observations of a high-redshift radio galaxy. These suggest a bi-polar outflow spanning 0.''9 ({approx}16 kpc projected distance for a standard {Lambda} CDM cosmology) reaching a mean relative velocity of 235 km s{sup -1} in redshifted H{alpha} +[N II] and [S II] emission. Structure is resolved to 0.''1 (0.8 kpc), which is well correlated with optical images from the Hubble Space Telescope and Very Large Array radio maps obtained at similar spatial resolution. Line diagnostics suggest that over the 10{sup 7} yr to 10{sup 8} yr duration of its active galactic nucleus activity, gas has been ejected into bright turbulent lobes at rates comparable to star formation, although constituting perhaps only 1% of the baryonic mass in the galaxy.

  19. Contemporaneous observations of the radio galaxy NGC 1275 from radio to very high energy γ-rays

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saggion, A.; Saito, T.; Saito, K.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Tavecchio, F.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Balmaverde, B.; Kataoka, J.; Rekola, R.; Takahashi, Y.

    2014-04-01

    Aims: The radio galaxy NGC 1275, recently identified as a very high energy (VHE, >100 GeV) γ-ray emitter by MAGIC, is one of the few non-blazar active galactic nuclei detected in the VHE regime. The purpose of this work is to better understand the origin of the γ-ray emission and locate it within the galaxy. Methods: We studied contemporaneous multifrequency observations of NGC 1275 and modeled the overall spectral energy distribution. We analyzed unpublished MAGIC observations carried out between October 2009 and February 2010, and the previously published observations taken between August 2010 and February 2011. We studied the multiband variability and correlations by analyzing data of Fermi-LAT in the 100 MeV-100 GeV energy band, as well as Chandra (X-ray), KVA (optical), and MOJAVE (radio) data taken during the same period. Results: Using customized Monte Carlo simulations corresponding to early MAGIC stereoscopic data, we detect NGC 1275 also in the earlier MAGIC campaign. The flux level and energy spectra are similar to the results of the second campaign. The monthly light curve above 100 GeV shows a hint of variability at the 3.6σ level. In the Fermi-LAT band, both flux and spectral shape variabilities are reported. The optical light curve is also variable and shows a clear correlation with the γ-ray flux above 100 MeV. In radio, three compact components are resolved in the innermost part of the jet. One of these components shows a similar trend as the Fermi-LAT and KVA light curves. The γ-ray spectra measured simultaneously with MAGIC and Fermi-LAT from 100 MeV to 650 GeV can be well fitted either by a log-parabola or by a power-law with a subexponential cutoff for the two observation campaigns. A single-zone synchrotron-self-Compton model, with an electron spectrum following a power-law with an exponential cutoff, can explain the broadband spectral energy distribution and the multifrequency behavior of the source. However, this model suggests an

  20. Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Foschini, L.; Berton, M.; Caccianiga, A.; Ciroi, S.; Cracco, V.; Peterson, B. M.; Angelakis, E.; Braito, V.; Fuhrmann, L.; Gallo, L.; Grupe, D.; Järvelä, E.; Kaufmann, S.; Komossa, S.; Kovalev, Y. Y.; Lähteenmäki, A.; Lisakov, M. M.; Lister, M. L.; Mathur, S.; Richards, J. L.; Romano, P.; Sievers, A.; Tagliaferri, G.; Tammi, J.; Tibolla, O.; Tornikoski, M.; Vercellone, S.; La Mura, G.; Maraschi, L.; Rafanelli, P.

    2015-03-01

    We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources of this type and omitting those with steep radio spectra. We analyse data from radio frequencies to X-rays, and supplement these with information available from online catalogues and the literature in order to cover the full electromagnetic spectrum. This is the largest known multiwavelength survey for this type of source. We detected 90% of the sources in X-rays and found 17% at γ rays. Extreme variability at high energies was also found, down to timescales as short as hours. In some sources, dramatic spectral and flux changes suggest interplay between a relativistic jet and the accretion disk. The estimated masses of the central black holes are in the range ~106-8 M⊙, lower than those of blazars, while the accretion luminosities span a range from ~0.01 to ~0.49 times the Eddington limit, with an outlier at 0.003, similar to those of quasars. The distribution of the calculated jet power spans a range from ~1042.6 to ~1045.6 erg s-1, generally lower than quasars and BL Lac objects, but partially overlapping with the latter. Once normalised by the mass of the central black holes, the jet power of the three types of active galactic nuclei are consistent with each other, indicating that the jets are similar and the observational differences are due to scaling factors. Despite the observational differences, the central engine of RLNLS1s is apparently quite similar to that of blazars. The historical difficulties in finding radio-loud narrow-line Seyfert 1 galaxies might be due to their low power and to intermittent jetactivity. Tables 4-9 and Figs. 8-13 are available in electronic form at http://www.aanda.org

  1. A Radio Continuum Study of Dwarf Galaxies: 6 cm imaging of LITTLE THINGS

    NASA Astrophysics Data System (ADS)

    Kitchener, Ben; Brinks, Elias; Heesen, Volker; Hunter, Deidre Ann; Zhang, Hongxin; Rau, Urvashi; Rupen, Michael P.; Little Things Collaboration

    2015-01-01

    To bypass uncertainties introduced by extinction caused by dust at optical wavelengths, we examine to what extent the radio continuum can probe star formation (SF) in dwarf galaxies. We provide VLA 6-cm C-array (4 to 8 GHz) radio continuum images with integrated flux densities for 40 dwarf galaxies taken from LITTLE THINGS. We find 27 harbor significant emission coincident with SF tracers; 17 are new detections. We infer the average thermal fraction to be 39 +- 25%. The LITTLE THINGS galaxies follow the Condon radio continuum - star formation rate (SFR) relation down to an SFR of 0.1 Msol/yr. At lower rates they follow a power-law characterized by a slope of 1.2 +- 0.1 with a scatter of 0.2 dex . We interpret this as an underproduction of the non-thermal radio continuum component. When considering the non-thermal radio continuum to star formation rate slope on its own, we find the slope to be 1.2. The magnetic field strength we find is typically 9.4 +- 3.8 muG in and around star forming regions which is similar to that in spiral galaxies. In a few dwarfs, the magnetic field strength can reach as high as 30 muG in localized 100 pc star forming regions. The underproduction of non-thermal radio continuum is likely due to the escape of Cosmic Ray electrons from the galaxy. The LITTLE THINGS galaxies are consistent with the radio continuum - far infrared luminosity relation. We observe a power-law slope of 1.06 +- 0.08 with a scatter of 0.24 dex which suggests that the 'conspiracy' of the radio continuum - far infrared relation continues to hold even for dwarf galaxies.

  2. Star Formation in 3CR Radio Galaxies and Quasars at z < 1

    NASA Astrophysics Data System (ADS)

    Westhues, Christian; Haas, Martin; Barthel, Peter; Wilkes, Belinda J.; Willner, S. P.; Kuraszkiewicz, Joanna; Podigachoski, Pece; Leipski, Christian; Meisenheimer, Klaus; Siebenmorgen, Ralf; Chini, Rolf

    2016-05-01

    Using the Herschel Space Observatory we have observed a representative sample of 87 powerful 3CR sources at redshift z\\lt 1. The far-infrared (FIR, 70-500 μm) photometry is combined with mid-infrared (MIR) photometry from the Wide-Field Infrared Survey Explorer and cataloged data to analyze the complete spectral energy distributions (SEDs) of each object from optical to radio wavelength. To disentangle the contributions of different components, the SEDs are fitted with a set of templates to derive the luminosities of host galaxy starlight, dust torus emission powered by active galactic nuclei (AGNs), and cool dust heated by stars. The level of emission from relativistic jets is also estimated to isolate the thermal host galaxy contribution. The new data are in line with the orientation-based unification of high-excitation radio-loud AGN, in that the dust torus becomes optically thin longwards of 30 μ {{m}}. The low-excitation radio galaxies and the MIR-weak sources represent an MIR- and FIR-faint AGN population that is different from the high-excitation MIR-bright objects; it remains an open question whether they are at a later evolutionary state or an intrinsically different population. The derived luminosities for host starlight and dust heated by star formation are converted to stellar masses and star-formation rates (SFR). The host-normalized SFR of the bulk of the 3CR sources is low when compared to other galaxy populations at the same epoch. Estimates of the dust mass yield a 1–100 times lower dust/stellar mass ratio than for the Milky Way, which indicates that these 3CR hosts have very low levels of interstellar matter and explains the low level of star formation. Less than 10% of the 3CR sources show levels of star formation above those of the main sequence of star-forming galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  3. Radio Sources In Galaxy Clusters Using The Maxbcg Cluster Catalog, First And NVSS Surveys

    NASA Astrophysics Data System (ADS)

    Wu, Wai Ling; McKay, T. A.

    2008-05-01

    Using the maxBCG cluster catalog derived from the Sloan Digital Sky Survey, the FIRST, and the NVSS radio surveys, we studied the fraction of brightest central galaxies (BCG) in clusters that host a radio source, how much more likely is a radio source to live in a cluster environment compare to the field, and we differentiate the luminosity effect from the richness effect on the radio fraction using a sample of luminous red galaxies (LRG). We present a method to cross-correlate the optical survey and the radio surveys. We also apply the matching of radio sources to clusters to help better determine cluster centers in some pathological cases in the maxBCG cluster catalog.

  4. Radio continuum and far-infrared emission of spiral galaxies: Implications of correlations

    NASA Technical Reports Server (NTRS)

    Rengarajan, T. N.; Iyengar, K. V. K.

    1990-01-01

    Researchers present a study extending the correlation seen between radio continuum and far-infrared emissions from spiral galaxies to a lower frequency of 408 MHz and also as a function of radio spectral index. The tight correlation seen between the two luminosities is then used to constrain several parameters governing the emissions such as the changes in star formation rate and mass function, frequency of supernovae that are parents of the interstellar electrons and factors governing synchrotron radio emission.

  5. VizieR Online Data Catalog: Star formation in active and normal galaxies (Tsai+, 2015)

    NASA Astrophysics Data System (ADS)

    Tsai, M.; Hwang, C.-Y.

    2015-11-01

    We selected 104 active galaxies from the lists of Melendez et al. (2010MNRAS.406..493M), Condon et al. 1991 (cat. J/ApJ/378/65), and Ho & Ulvestad 2001 (cat. J/ApJS/133/77). Most of the sources are identified as Active Galactic Nuclei (AGNs), and a few of them are classified as Luminous InfraRed Galaxies (LIRGs). We obtained 3.6 and 8μm infrared images of these galaxies from the Spitzer Archive (http://sha.ipac.caltech.edu/applications/Spitzer/SHA/) and 8GHz images from the VLA archive (http://archive.nrao.edu/archive/archiveimage.html). We also selected a nearby AGN sub-sample containing 21 radio-selected AGNs for further spatial analysis. We selected 25 nearby AGNs exhibiting no detected radio emission in order to compare with the results of the radio-selected sources. For comparison, we also selected normal galaxies with distances less than 15Mpc from the catalog of Tully 1994 (see cat. VII/145). We only selected the galaxies that have Spitzer archive data and are not identified as AGNs in either the Veron-Cetty & Veron 2006 (see cat. VII/258) AGN catalog or in the NED database (http://ned.ipac.caltech.edu/). Our results for the radio-selected and the non-radio-selected active galaxies are listed in Table1, and those for the normal galaxies are listed in Table2. (2 data files).

  6. Active galactic nucleus feedback in clusters of galaxies.

    PubMed

    Blanton, Elizabeth L; Clarke, T E; Sarazin, Craig L; Randall, Scott W; McNamara, Brian R

    2010-04-20

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

  7. Active galactic nucleus feedback in clusters of galaxies

    PubMed Central

    Blanton, Elizabeth L.; Clarke, T. E.; Sarazin, Craig L.; Randall, Scott W.; McNamara, Brian R.

    2010-01-01

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

  8. The Connection between the Radio Jet and the Gamma-ray Emission in the Radio Galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Casadio, Carolina; Gómez, José L.; Grandi, Paola; Jorstad, Svetlana G.; Marscher, Alan P.; Lister, Matthew L.; Kovalev, Yuri Y.; Savolainen, Tuomas; Pushkarev, Alexander B.

    2015-08-01

    We present the analysis of the radio jet evolution of the radio galaxy 3C 120 during a period of prolonged γ-ray activity detected by the Fermi satellite between 2012 December and 2014 October. We find a clear connection between the γ-ray and radio emission, such that every period of γ-ray activity is accompanied by the flaring of the millimeter very long baseline interferometry (VLBI) core and subsequent ejection of a new superluminal component. However, not all ejections of components are associated with γ-ray events detectable by Fermi. Clear γ-ray detections are obtained only when components are moving in a direction closer to our line of sight. This suggests that the observed γ-ray emission depends not only on the interaction of moving components with the millimeter VLBI core, but also on their orientation with respect to the observer. Timing of the γ-ray detections and ejection of superluminal components locate the γ-ray production to within ∼0.13 pc from the millimeter VLBI core, which was previously estimated to lie about 0.24 pc from the central black hole. This corresponds to about twice the estimated extension of the broad line region, limiting the external photon field and therefore suggesting synchrotron self Compton as the most probable mechanism for the production of the γ-ray emission. Alternatively, the interaction of components with the jet sheath can provide the necessary photon field to produced the observed γ-rays by Compton scattering.

  9. Jets and the infra-red cores of low-redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Birkinshaw, Mark; Worrall, Diana

    2016-07-01

    A complete set of 3.6 - 160 micron images of 3CRR radio galaxies at z < 0.1 has been used to investigate the relationship between AGN radio and dust properties. Higher radio core powers are shown to be related to higher core dust temperatures and luminosities. Low-power sources are indistinguishable from passive galaxies based on their near-IR properties, but at longer wavelengths a strong cold dust continuum is present. The implications for AGN fuelling, energetics, and lifetimes will be presented.

  10. The Peculiar Radio-loud Narrow Line Seyfert 1 Galaxy 1H 0323+342

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Sahayanathan, S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.; Anjum, Ayesha; Pandey, S. B.

    2014-07-01

    We present a multiwavelength study of the radio-loud narrow-line Seyfert 1 galaxy (NLSy1) 1H 0323+342, detected by the Fermi Gamma-Ray Space Telescope. Multiband light curves show many orphan X-ray and optical flares having no corresponding γ-ray counterparts. Such anomalous variability behavior can be due to different locations of the emission region from the central source. During a large flare, a γ-ray flux doubling timescale as small as ~3 hr is noticed. We built spectral energy distributions (SEDs) during different activity states and modeled them using a one-zone leptonic model. The shape of the optical/UV component of the SEDs is dominated by accretion disk emission in all the activity states. In the X-ray band, significant thermal emission from the hot corona is inferred during quiescent and first flaring states; however, during subsequent flares, the nonthermal jet component dominates. The γ-ray emission in all the states can be well explained by inverse-Compton scattering of accretion disk photons reprocessed by the broad-line region. The source showed violent intra-night optical variability, coinciding with one of the high γ-ray activity states. An analysis of the overall X-ray spectrum fitted with an absorbed power-law plus relativistic reflection component hints at the presence of an Fe Kα line and returns a high black hole spin value of a = 0.96 ± 0.14. We argue that 1H 0323+342 possesses dual characteristics, akin to both flat-spectrum radio quasars (FSRQs) and radio-quiet NLSy1 galaxies, though at a low jet power regime compared to powerful FSRQs.

  11. The peculiar radio-loud narrow line Seyfert 1 galaxy 1H 0323+342

    SciTech Connect

    Paliya, Vaidehi S.; Stalin, C. S.; Sahayanathan, S.; Parker, M. L.; Fabian, A. C.; Anjum, Ayesha; Pandey, S. B.

    2014-07-10

    We present a multiwavelength study of the radio-loud narrow-line Seyfert 1 galaxy (NLSy1) 1H 0323+342, detected by the Fermi Gamma-Ray Space Telescope. Multiband light curves show many orphan X-ray and optical flares having no corresponding γ-ray counterparts. Such anomalous variability behavior can be due to different locations of the emission region from the central source. During a large flare, a γ-ray flux doubling timescale as small as ∼3 hr is noticed. We built spectral energy distributions (SEDs) during different activity states and modeled them using a one-zone leptonic model. The shape of the optical/UV component of the SEDs is dominated by accretion disk emission in all the activity states. In the X-ray band, significant thermal emission from the hot corona is inferred during quiescent and first flaring states; however, during subsequent flares, the nonthermal jet component dominates. The γ-ray emission in all the states can be well explained by inverse-Compton scattering of accretion disk photons reprocessed by the broad-line region. The source showed violent intra-night optical variability, coinciding with one of the high γ-ray activity states. An analysis of the overall X-ray spectrum fitted with an absorbed power-law plus relativistic reflection component hints at the presence of an Fe Kα line and returns a high black hole spin value of a = 0.96 ± 0.14. We argue that 1H 0323+342 possesses dual characteristics, akin to both flat-spectrum radio quasars (FSRQs) and radio-quiet NLSy1 galaxies, though at a low jet power regime compared to powerful FSRQs.

  12. Finding Bent-double Radio Galaxies: A Case Study in Data Mining

    SciTech Connect

    Fodor, I.K; Cantu-Paz, E.; Kamath, C.; Tang, N.

    2000-04-11

    This paper presents our early results in applying data mining techniques to the problem of finding radio-emitting galaxies with a bent-double morphology. In the past, astronomers on the FIRST (Faint Images of the Radio Sky at Twenty-cm) survey have detected such galaxies by first inspecting the radio images visually to identify probable bent-doubles, and then conducting observations to confirm that the galaxy is indeed a bent-double. Our goal is to replace this visual inspection by a semi-automated approach. In this paper, we present a brief overview of data mining, describe the features we use to discriminate bent-doubles from non-bent-doubles, and discuss the challenges faced in defining meaningful features in a robust manner. Our experiments show that data mining, using decision trees, can indeed be a viable alternative to the visual identification of bent-double galaxies.

  13. The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004-447. II. The radio view

    NASA Astrophysics Data System (ADS)

    Schulz, R.; Kreikenbohm, A.; Kadler, M.; Ojha, R.; Ros, E.; Stevens, J.; Edwards, P. G.; Carpenter, B.; Elsässer, D.; Gehrels, N.; Großberger, C.; Hase, H.; Horiuchi, S.; Lovell, J. E. J.; Mannheim, K.; Markowitz, A.; Müller, C.; Phillips, C.; Plötz, C.; Quick, J.; Trüstedt, J.; Tzioumis, A. K.; Wilms, J.

    2016-04-01

    Context. Γ-ray-detected radio-loud narrow-line Seyfert 1 (γ-NLS1) galaxies constitute a small but interesting sample of the γ-ray-loud AGN. The radio-loudest γ-NLS1 known, PKS 2004-447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring programme TANAMI. Aims: We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS 2004-447, which are essential for understanding the diversity of the radio properties of γ-NLS1s. Methods: The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active galaxies in the southern hemisphere. Lower resolution radio flux density measurements at multiple radio frequencies over four years of observations were obtained with the Australia Telescope Compact Array (ATCA). Results: The TANAMI VLBI image at 8.4 GHz shows an extended one-sided jet with a dominant compact VLBI core. Its brightness temperature is consistent with equipartition, but it is an order of magnitude below other γ-NLS1s with the sample value varying over two orders of magnitude. We find a compact morphology with a projected large-scale size < 11 kpc and a persistent steep radio spectrum with moderate flux-density variability. Conclusions: PKS 2004-447 appears to be a unique member of the γ-NLS1 sample. It exhibits blazar-like features, such as a flat featureless X-ray spectrum and a core-dominated, one-sided parsec-scale jet with indications for relativistic beaming. However, the data also reveal properties atypical for blazars, such as a radio spectrum and large-scale size consistent with compact-steep-spectrum (CSS) objects, which are usually associated with young radio sources. These characteristics are unique among all γ-NLS1s and extremely rare among γ-ray-loud AGN. The VLBI images shown in Figs. 3 and 4 (as FITS files) and the ATCA

  14. Radio haloes in Sunyaev-Zel'dovich-selected clusters of galaxies: the making of a halo?

    NASA Astrophysics Data System (ADS)

    Bonafede, A.; Intema, H.; Brüggen, M.; Vazza, F.; Basu, K.; Sommer, M.; Ebeling, H.; de Gasperin, F.; Röttgering, H. J. A.; van Weeren, R. J.; Cassano, R.

    2015-12-01

    Radio haloes are synchrotron radio sources detected in some massive galaxy clusters. Their size of Mpc indicates that (re)acceleration processes are taking place in the host cluster. X-ray catalogues of galaxy clusters have been used in the past to search for radio haloes and to understand their connection with cluster-cluster mergers and with the thermal component of the intracluster medium. More recently, the Sunyaev-Zel'dovich effect has been proven to be a better route to search for massive clusters in a wider redshift range. With the aim of discovering new radio haloes and understanding their connection with cluster-cluster mergers, we have selected the most massive clusters from the Planck early source catalogue and we have observed with the Giant Metrewave Radio Telescope at 323 MHz those objects for which deep observations were not available. We have discovered new peculiar radio emission in three of the observed clusters, finding (i) a radio halo in the cluster RXCJ0949.8+1708, (ii) extended emission in Abell 1443 that we classify as a radio halo plus a radio relic, with a bright filament embedded in the radio halo, and (iii) low-power radio emission in CIZA J1938.3+5409 that is ten times below the radio-X-ray correlation and represents the first direct detection of the radio emission in the `upper-limit' region of the radio-X-ray diagram. We discuss the properties of these new radio haloes in the framework of theoretical models for the radio emission.

  15. The compact radio structure of radio-loud NLS1 galaxies and the relationship to CSS sources

    NASA Astrophysics Data System (ADS)

    Gu, M.; Chen, Y.; Komossa, S.; Yuan, W.; Shen, Z.

    2016-02-01

    Narrow-line Seyfert 1 galaxies are thought to be young AGNs with relatively small black hole masses and high accretion rates. Radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar-like characteristics, while others resemble compact steep-spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed by the gamma-ray flaring of some of them. These properties may possibly be contrary to typical radio-loud AGNs, in light of the low black-hole masses, and high accretion rates. We present the compact radio structure of fourteen RLNLS1 galaxies from Very Long Baseline Array observations at 5 GHz in 2013. Although all these sources are very radio-loud with {R > 100}, their jet properties are diverse, in terms of their milli-arcsecond (mas) scale (pc scale) morphology and their overall radio spectral shape. The core brightness temperatures of our sources are significantly lower than those of blazars, therefore, the beaming effect is generally not significant in our sources, compared to blazars. This implies that the bulk jet speed may likely be low in our sources. The relationship between RLNLS1s and compact steep-spectrum sources, and the implications on jet formation are discussed based on the pc-scale jet properties.

  16. Possible breaking of the FIR-radio correlation in tidally interacting galaxies

    NASA Astrophysics Data System (ADS)

    Donevski, D.; Prodanović, T.

    2015-10-01

    Far-infrared (FIR)-radio correlation is a well-established empirical connection between continuum radio and dust emission of star-forming galaxies, often used as a tool in determining star formation rates. Here we expand the point made by Murphy that in the case of some interacting star-forming galaxies there is a non-thermal emission from the gas bridge in between them, which might cause a dispersion in this correlation. Galactic interactions and mergers have been known to give rise to tidal shocks and disrupt morphologies especially in the smaller of the interacting components. Here we point out that these shocks can also heat the gas and dust and will inevitably accelerate particles and result in a tidal cosmic ray population in addition to standard galactic cosmic rays in the galaxy itself. This would result in a non-thermal emission not only from the gas bridges of interacting systems, but from interacting galaxies as a whole in general. Thus both tidal heating and additional non-thermal radiation will obviously affect the FIR-radio correlation of these systems, the only question is how much. In this scenario the FIR-radio correlation is not stable in interacting galaxies, but rather evolves as the interaction/merger progresses. To test this hypothesis and probe the possible impact of tidal cosmic ray population, we have analysed a sample of 43 infrared-bright star-forming interacting galaxies at different merger stages. We have found that their FIR-radio correlation parameter and radio emission spectral index vary noticeably over different merger stages and behave as it would be expected from our tidal-shock scenario. Important implications of departure of interacting galaxies from the FIR-radio correlation are discussed.

  17. Interaction of Radio Jets with Magnetic Fields in Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Soker, Noam

    1997-10-01

    High Faraday rotation measures in the centers of cooling-flow clusters indicate the presence of strong magnetic fields. We examine the effects of these strong fields on the propagation of radio jets emerging from the central cD galaxies of these clusters, and the deformation of the magnetic fields by the fast-propagating jets. We argue that active regions will develop around these radio jets as a result of the violent response of the strong ambient magnetic fields. The magnetic tension can act back on the jets by influencing the development of Rayleigh-Taylor and Kelvin-Helmholtz instability modes, and by exerting a nonaxisymmetric force on the jets. If the jet propagation direction is not along the magnetic field lines, then the jet will be sharply bent by the magnetic tension. Future MHD numerical simulations that will study these effects more quantitatively should be compared directly with specific clusters. If, indeed, some properties of jets expanding from cD galaxies in cooling-flow clusters will turn out to result from interaction with strong magnetic fields in the intracluster medium at the centers of these clusters, then this will strengthen the cooling-flow model, since it will support the presence of inflow.

  18. High-Latitude Radio Emission in a Sample of Edge-on Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Irwin, Judith A.; English, Jayanne; Sorathia, Barkat

    1999-05-01

    We have mapped 16 edge-on galaxies at 20 cm using the Very Large Array in its C configuration, and a subset of these galaxies in the D configuration at 6 and/or 20 cm, in a search for extended (>~1 kpc) radio continuum emission above and below the plane. For five galaxies, we could form spectral index, energy, and magnetic field maps (assuming minimum energy). While the galaxies were partly chosen by radio flux density, they span a variety of star formation rates (SFRs), and only six might be considered ``starburst'' galaxies. A range of Hubble type and degree of isolation are also represented. The galaxies largely fall on the FIR-radio continuum correlation. They also display a correlation between IR surface brightness and warmth, extending the previously observed relation of Lehnert & Heckman to galaxies with lower star formation rates. We find that all but one galaxy show evidence for nonthermal high-latitude radio continuum emission, suggesting that cosmic-ray (CR) halos are common in star-forming galaxies. Of these, eight galaxies are new detections. The high-latitude emission is seen over a variety of spatial scales and in discrete and/or smooth features. In some cases, discrete features are seen on large scales, suggesting that smooth radio halos may consist, in part, of discrete features combined with low spatial resolution. In general, the discrete features emanate from the disk, but estimates of CR diffusion lengths suggest that diffusion alone is insufficient to transport the particles to the high latitudes seen (>15 kpc in one case). Thus CRs likely diffuse through low-density regions and/or are assisted by other mechanisms (e.g., winds). We searched for correlations between the prevalence of high-latitude radio emission and a number of other properties, including the global SFR, supernova input rate per unit star-forming area, E_A, and environment, and do not find clear correlations with any of these properties. A subset of the data allows, at best

  19. NuSTAR Observations of the Powerful Radio Galaxy Cygnus A

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.; Lohfink, Anne M.; Ogle, Patrick M.; Harrison, Fiona A.; Madsen, Kristin K.; Fabian, Andrew C.; Wik, Daniel R.; Madejski, Grzegorz; Ballantyne, David R.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fuerst, Felix; Hailey, Charles J.; Lanz, Lauranne; Miller, Jon M.; Saez, Cristian; Stern, Daniel; Walton, Dominic J.; Zhang, William

    2015-08-01

    We present NuSTAR observations of the powerful radio galaxy Cygnus A, focusing on the central absorbed active galactic nucleus (AGN). Cygnus A is embedded in a cool-core galaxy cluster, and hence we also examine archival XMM-Newton data to facilitate the decomposition of the spectrum into the AGN and intracluster medium components. NuSTAR gives a source-dominated spectrum of the AGN out to \\gt 70 keV. In gross terms, the NuSTAR spectrum of the AGN has the form of a power law ({{Γ }}∼ 1.6-1.7) absorbed by a neutral column density of {N}{{H}}∼ 1.6× {10}23 {{cm}}-2. However, we also detect curvature in the hard (\\gt 10 keV) spectrum resulting from reflection by Compton-thick matter out of our line of sight to the X-ray source. Compton reflection, possibly from the outer accretion disk or obscuring torus, is required even permitting a high-energy cut off in the continuum source; the limit on the cut-off energy is {E}{cut}\\gt 111 keV(90% confidence). Interestingly, the absorbed power law plus reflection model leaves residuals suggesting the absorption/emission from a fast (15,000-26,000 {km} {{{s}}}-1 ), high column-density ({N}W\\gt 3× {10}23 {{cm}}-2), highly ionized (ξ ∼ 2500 {erg} {cm} {{{s}}}-1) wind. A second, even faster ionized wind component is also suggested by these data. We show that the ionized wind likely carries a significant mass and momentum flux, and may carry sufficient kinetic energy to exercise feedback on the host galaxy. If confirmed, the simultaneous presence of a strong wind and powerful jets in Cygnus A demonstrates that feedback from radio-jets and sub-relativistic winds are not mutually exclusive phases of AGN activity but can occur simultaneously.

  20. Diffuse radio emission in the complex merging galaxy cluster Abell2069

    NASA Astrophysics Data System (ADS)

    Drabent, A.; Hoeft, M.; Pizzo, R. F.; Bonafede, A.; van Weeren, R. J.; Klein, U.

    2015-03-01

    Context. Galaxy clusters with signs of a recent merger in many cases show extended diffuse radio features. This emission originates from relativistic electrons that suffer synchrotron losses due to the intracluster magnetic field. The mechanisms of particle acceleration and the properties of the magnetic field are still poorly understood. Aims: We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. Methods: We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT) observations at 346 MHz and Giant Metrewave Radio Telescope (GMRT) observations at 322 MHz. Results: We find an extended diffuse radio feature roughly coinciding with the main component of the cluster. We classify this emission as a radio halo and estimate its lower limit flux density at 25 ± 9 mJy. Moreover, we find a second extended diffuse source located at the cluster's companion and estimate its flux density at 15 ± 2 mJy. We speculate that this is a small halo or a mini-halo. If true, this cluster is the first example of a double-halo in a single galaxy cluster.

  1. Proto-Clusters with Evolved Populations around Radio Galaxies at 2

    NASA Astrophysics Data System (ADS)

    Kodama, T.; Tanaka, M.; Tanaka, I.; Kajisawa, M.

    2007-12-01

    We present an on-going near-infrared survey of proto-clusters around high-z radio-loud galaxies at 2 ≲ z ≲ 3 with a new wide-field instrument MOIRCS on Subaru. Most of these field are known to show a large number of Lyα and/or Hα emitters at the same redshifts of the radio galaxies. We see a clear excess of near-infrared selected galaxies (JHK_s-selected galaxies as well as DRG) in these fields, and they are indeed proto-clusters with not only young emitters but also evolved populations. Spatial distribution of such NIR selected galaxies is filamentary and track similar structures traced by the emitters. There is an hint that the bright-end of the red sequence first appeared between z=3 and 2.

  2. Blue galaxies identified with submilliJansky radio sources in the 1300 + 3034 field

    NASA Technical Reports Server (NTRS)

    Thuan, Trinh X.; Patterson, Richard J.; Condon, J. J.; Mitchell, K. J.

    1992-01-01

    We have obtained deep B and R CCD frames in order to optically identify sub-mJy radio sources discovered in a deep 1.49 GHz VLA survey field centered at alpha (1950) = 13h00m37s, delta(1950) = + 30 deg 34 arcmin. B and R photometry is presented for 37 optical identifications. Using spectral evolution models, we conclude that galaxies brighter than B about 25 identified with sub-mJy radio sources are much bluer than giant elliptical galaxies, but are similar to starburst galaxies with absolute magnitude M(v) = about -23-20 and redshifts in the range 2 = about 0.1-0.8. This population of blue galaxies is the same as that found by Thuan and Condon (1987) in the 0852 + 1716 field using different techniques (optical and near-infrared photometry), suggesting that this population of starburst galaxies at intermediate redshifts is universal.

  3. X-RAY DIPS IN THE SEYFERT GALAXY FAIRALL 9: COMPTON-THICK 'COMETS' OR A FAILED RADIO GALAXY?

    SciTech Connect

    Lohfink, Anne M.; Reynolds, Christopher S.; Mushotzky, Richard F.; Wilms, Joern

    2012-04-20

    We investigate the spectral variability of the Seyfert galaxy Fairall 9 using almost 6 years of monitoring with the Rossi X-ray Timing Explorer with an approximate time resolution of 4 days. We discover the existence of pronounced and sharp dips in the X-ray flux, with a rapid decline of the 2-20 keV flux of a factor of two or more followed by a recovery to pre-dip fluxes after {approx}10 days. These dips skew the flux distribution away from the commonly observed lognormal distribution. Dips may result from the eclipse of the central X-ray source by broad-line region clouds, as has recently been found in NGC 1365 and Mrk 766. Unlike these other examples, however, the clouds in Fairall 9 would need to be Compton-thick, and the non-dip state is remarkably free of any absorption features. A particularly intriguing alternative is that the accretion disk is undergoing the same cycle of disruption/ejection as seen in the accretion disks of broad-line radio galaxies such as 3C120 but, for some reason, fails to create a relativistic jet. This suggests that a detailed comparison of Fairall 9 and 3C120 with future high-quality data may hold the key to understanding the formation of relativistic jets in active galactic nucleus.

  4. PARSEC-SCALE IMAGING OF THE RADIO-BUBBLE SEYFERT GALAXY NGC 6764

    SciTech Connect

    Kharb, P.; O'Dea, C. P.; Axon, D. J.; Robinson, A.; Hota, Ananda; Croston, J. H.; Hardcastle, M. J.; Kraft, R. P.

    2010-11-01

    We have observed the composite active galactic nucleus (AGN)-starburst galaxy NGC 6764 with the Very Long Baseline Array at 1.6 and 4.9 GHz. These observations have detected a 'core-jet' structure and a possible weak counterjet component at 1.6 GHz. The upper limits to the core and jet (1.6-4.9 GHz) spectral index are 0.6 and 0.3, respectively. Taken together with the high brightness temperature of {approx}10{sup 7} K for the core region, the radio emission appears to be coming from a synchrotron jet. At a position angle of {approx}25{sup 0}, the parsec-scale jet seems to be pointing closely toward the western edge of the southern kpc-scale bubble in NGC 6764. A real connection between the parsec- and sub-kpc-scale emission would not only suggest the presence of a curved jet, but also a close link between the AGN jet and the radio bubbles in NGC 6764. We demonstrate that a precessing jet model can explain the radio morphology from parsec to sub-kpc scales, and the model best-fit parameters of jet speed and orientation are fully consistent with the observed jet-to-counterjet surface brightness ratio. The jet however appears to be disrupted on scales of hundreds of parsecs, possibly due to interaction with and entrainment of the interstellar medium gas, which subsequently leads to the formation of bubbles. The jet energetics in NGC 6764 suggest that it would take 12-21 Myr to inflate the (southern) bubble. This timescale corresponds roughly to the starburst episode that took place in NGC 6764 about 15-50 Myr ago, and could be indicative of a close connection between jet formation and the starburst activity in this galaxy.

  5. Low Power Compact Radio Galaxies at High Angular Resolution

    SciTech Connect

    Giroletti, Marcello; Giovannini, G.; Taylor, G.B.; /KIPAC, Menlo Park /NRAO, Socorro

    2005-06-30

    We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us to identify the center of activity on the VLA images. Moreover, these data reveal rich structures, including two-sided jets and secondary components. On the basis of the arcsecond scale structures and of the nuclear properties, we rule out the presence of strong relativistic effects in our LPCs, which must be intrinsically small (deprojected linear sizes {approx}< 10 kpc). Fits of continuous injection models reveal break frequencies in the GHz domain, and ages in the range 10{sup 5}-10{sup 7} yrs. In LPCs, the outermost edge may be advancing more slowly than in more powerful sources or could even be stationary; some LPCs might also have ceased their activity. In general, the properties of LPCs can be related to a number of reasons, including, but not limited to: youth, frustration, low kinematic power jets, and short-lived activity in the radio.

  6. Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy.

    PubMed

    Acciari, V A; Aliu, E; Arlen, T; Bautista, M; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K; Cannon, A; Celik, O; Cesarini, A; Chow, Y C; Ciupik, L; Cogan, P; Cui, W; Dickherber, R; Fegan, S J; Finley, J P; Fortin, P; Fortson, L; Furniss, A; Gall, D; Gillanders, G H; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, P; Karlsson, N; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; LeBohec, S; Maier, G; McCann, A; McCutcheon, M; Millis, J; Moriarty, P; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Petry, D; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Roache, E; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Swordy, S P; Theiling, M; Toner, J A; Varlotta, A; Vincent, S; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Williams, D A; Wissel, S; Wood, M; Walker, R C; Davies, F; Hardee, P E; Junor, W; Ly, C; Aharonian, F; Akhperjanian, A G; Anton, G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Borrel, V; Brucker, J; Brun, F; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L-M; Clapson, A C; Coignet, G; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göhring, D; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jung, I; Katarzyński, K; Katz, U; Kaufmann, S; Kendziorra, E; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Lamanna, G; Lenain, J-P; Lohse, T; Marandon, V; Martin, J M; Martineau-Huynh, O; Marcowith, A; Maurin, D; McComb, T J L; Medina, M C; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; de Oña Wilhelmi, E; Orford, K J; Ostrowski, M; Panter, M; Paz Arribas, M; Pedaletti, G; Pelletier, G; Petrucci, P-O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schröder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Spangler, D; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Superina, G; Szostek, A; Tam, P H; Tavernet, J-P; Terrier, R; Tibolla, O; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Venter, L; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Balestra, S; Barrio, J A; Bastieri, D; Becerra González, J; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Borla Tridon, D; Bosch-Ramon, V; Bose, D; Braun, I; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea del Pozo, E; Delgado Mendez, C; De los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Dominguez, A; Dorner, D; Doro, M; Elsaesser, D; Errando, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; García López, R J; Garczarczyk, M; Gaug, M; Goebel, F; Hadasch, D; Hayashida, M; Herrero, A; Hildebrand, D; Höhne-Mönch, D; Hose, J; Hsu, C C; Jogler, T; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Miyamoto, H; Moldón, J; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Oya, I; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Prada, F; Prandini, E; Puchades, N; Reichardt, I; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Satalecka, K; Scalzotto, V; Scapin, V; Schweizer, T; Shayduk, M; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sitarek, J; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Torres, D F; Turini, N; Vankov, H; Wagner, R M; Zabalza, V

    2009-07-24

    The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole. PMID:19574351

  7. The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A: Constraints on Abundances in the Accreting Material

    NASA Technical Reports Server (NTRS)

    Markowitz, A.; Takahashi, T.A; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J. N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-01-01

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  8. The Suzaku Observation of the Nucleus of theRadio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

    SciTech Connect

    Markowitz, A.; Takahashi, T.; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J.N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-06-27

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The net exposure times after screening were: 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X-ray Detector (HXD) PIN, and 17.1 ks for the HXD-GSO. The hard X-rays are fit by two power-laws of the same slope, absorbed by columns of 1.5 and 7 x 10{sup 23} cm{sup -2} respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature vapec model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The Fe K{alpha} line width yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  9. The Trivariate / Radio Optical X-Ray / Luminosity Function CD Galaxies - Part Two - the Fuelling of Radio Sources

    NASA Astrophysics Data System (ADS)

    Valentijn, E. A.; Bijleveld, W.

    1983-09-01

    In order to the test the hypothesis that radio sources in elliptical galaxies are fuelled by a fraction of accreted X-ray gas, a sample of 81 cD galaxies in clusters and 23 cD galaxies in poor groups is studied. Various subsamples have been defined (reviewed in Table t) according to the origin of the cD galaxy classification (optically, radio or X-ray selected). A catalogue is presented, listing the measured optical, radio and X-ray luminosities from various origins, but all transformed to a uniform and homogeneous system: optical Mv (38 kpc metric diameter), radio P1.4 (1.4 GHz monochromatic total radio power) and Lx (1 Mpc metric diameter 0.5-3.0 keV X-ray band). The three luminosity parameters are investigated for cross- correlations by studying power-power plots and by analysing how the integral radio luminosity function, expressed in fractions of radio detections (F(> P1.4)), depend on Mv and Lx. All three parameters are found to correlate with each other. F(> P1.4) increases with both increasing Lx and brighter Mv and Lx also increases with brighter Mv. The determinations of the different regression relations are internally consistent. The empirical conclusions from the analysis are: (i) The mean Mv of poor group cDs is 0.m4 fainter than the mean Mv of cluster cDs. (ii) The bivariate radio luminosity functions of both samples confirm, both in shape and in their dependence on Mv, those of normal and giant ellipticals. (iii) cD galaxies have an increasing probability to contain a central (≲ 28 kpc) radio source when the X-ray luminosity of their halo (˜1 Mpc diameter) increases. 50 ± 9% of Lx ≧ 1044 erg s-1 cDs have a central radio source with P1.4 ≧ 1024WHz-1, while 12+l2-5% of Lx < 1043 ergs-1 cDs have a radio source of that power. This important conclusion is summarised in Fig. 5. (iv) Comparing rich cluster cDs and poor group cDs a relation between Mv and Lx is found. This relation holds among the rich cluster cDs as well. The physical origins of

  10. Quasars and Active Galaxies: A Reading List.

    ERIC Educational Resources Information Center

    Fraknoi, Andrew

    1988-01-01

    Contains the annotated bibliographies of introductory books and sections of books, recent introductory articles, more advanced articles, and more advanced books dealing with quasars and active galaxies. (CW)

  11. The search for giant radio galaxies in the PS 102 survey

    NASA Astrophysics Data System (ADS)

    Butenko, A. V.; Dagkesamanskii, R. D.; Samodurov, V. A.; Tyulbashev, S. A.

    2014-06-01

    The possibility of selecting extended radio sources that are potential candidates for giant radio galaxies among objects in the Pushchino catalog at 102 MHz is considered. The method used is based on the analysis of objects in a α 1- α 2 diagram, where α 1 and α 2 are two-frequency spectral indices ( S ν ˜ ν - α ), formally calculated using 102-365 and 365-1400 MHz data, based on the identifications of Pushchino radio sources with objects of the Texas (365 MHz) and Green Bank (1400 MHz) catalogs. The calculated spectra are abnormally steep at 102-365 MHz and flat or even inverted at 365-1400 MHz, due to the fact that the 365-MHz flux densities of extended radio sources measured with the Texas radio interferometer are appreciably underestimated. Ten objects among the fifteen Pushchino radio sources selected using this criterion proved to be already known large radio galaxies. The possibility of improving the efficiency of the method by using larger samples and applying some additional criteria selecting candidate giant radio galaxies is considered.

  12. Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission

    SciTech Connect

    Kataoka, J.; Stawarz, L.; Takahashi, Y.; Cheung, C.C.; Hayashida, M.; Grandi, P.; Burnett, T.H.; Celotti, A.; Fegan, S.J.; Fortin, P.; Maeda, K.; Nakamori, T.; Taylor, G.B.; Tosti, G.; Digel, S.W.; McConville, W.; Finke, J.; D'Ammando, F.; /IASF, Palermo /INAF, Rome

    2012-06-07

    We report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {ge} 1% on average for BLRGs, while {le} 0.1% for Seyfert 1 galaxies.

  13. Radio Constraints on Heavily Obscured Star Formation within Dark Gamma-Ray Burst Host Galaxies

    NASA Astrophysics Data System (ADS)

    Perley, D. A.; Perley, R. A.

    2013-12-01

    Highly dust-obscured starbursting galaxies (submillimeter galaxies and their ilk) represent the most extreme sites of star formation in the distant universe and contribute significantly to overall cosmic star formation beyond z > 1.5. Some stars formed in these environments may also explode as gamma-ray bursts (GRBs) and contribute to the population of "dark" bursts. Here we present Very Large Array wideband radio-continuum observations of 15 heavily dust-obscured Swift GRBs to search for radio synchrotron emission associated with intense star formation in their host galaxies. Most of these targets (11) are not detected. Of the remaining four objects, one detection is marginal, and for two others we cannot yet rule out the contribution of a long-lived radio afterglow. The final detection is secure, but indicates a star formation rate (SFR) roughly consistent with the dust-corrected UV-inferred value. Most galaxies hosting obscured GRBs are therefore not forming stars at extreme rates, and the amount of optical extinction seen along a GRB afterglow sightline does not clearly correlate with the likelihood that the host has a sufficiently high SFR to be radio-detectable. While some submillimeter galaxies do readily produce GRBs, these GRBs are often not heavily obscured—suggesting that the outer (modestly obscured) parts of these galaxies overproduce GRBs and the inner (heavily obscured) parts underproduce GRBs relative to their respective contributions to star formation, hinting at strong chemical or initial mass function gradients within these systems.

  14. Radio constraints on heavily obscured star formation within dark gamma-ray burst host galaxies

    SciTech Connect

    Perley, D. A.; Perley, R. A.

    2013-12-01

    Highly dust-obscured starbursting galaxies (submillimeter galaxies and their ilk) represent the most extreme sites of star formation in the distant universe and contribute significantly to overall cosmic star formation beyond z > 1.5. Some stars formed in these environments may also explode as gamma-ray bursts (GRBs) and contribute to the population of 'dark' bursts. Here we present Very Large Array wideband radio-continuum observations of 15 heavily dust-obscured Swift GRBs to search for radio synchrotron emission associated with intense star formation in their host galaxies. Most of these targets (11) are not detected. Of the remaining four objects, one detection is marginal, and for two others we cannot yet rule out the contribution of a long-lived radio afterglow. The final detection is secure, but indicates a star formation rate (SFR) roughly consistent with the dust-corrected UV-inferred value. Most galaxies hosting obscured GRBs are therefore not forming stars at extreme rates, and the amount of optical extinction seen along a GRB afterglow sightline does not clearly correlate with the likelihood that the host has a sufficiently high SFR to be radio-detectable. While some submillimeter galaxies do readily produce GRBs, these GRBs are often not heavily obscured—suggesting that the outer (modestly obscured) parts of these galaxies overproduce GRBs and the inner (heavily obscured) parts underproduce GRBs relative to their respective contributions to star formation, hinting at strong chemical or initial mass function gradients within these systems.

  15. Evidence for particle re-acceleration in the radio relic in the galaxy cluster PLCKG287.0+32.9

    SciTech Connect

    Bonafede, A.; Brüggen, M.; Intema, H. T.; Girardi, M.; Nonino, M.; Kantharia, N.; Van Weeren, R. J.; Röttgering, H. J. A.

    2014-04-10

    Radio relics are diffuse radio sources observed in galaxy clusters, probably produced by shock acceleration during cluster-cluster mergers. Their large size, of the order of 1 Mpc, indicates that the emitting electrons need to be (re)accelerated locally. The usually invoked diffusive shock acceleration models have been challenged by recent observations and theory. We report the discovery of complex radio emission in the Galaxy cluster PLCKG287.0+32.9, which hosts two relics, a radio halo, and several radio filamentary emission. Optical observations suggest that the cluster is elongated, likely along an intergalactic filament, and displays a significant amount of substructure. The peculiar features of this radio relic are that (1) it appears to be connected to the lobes of a radio galaxy and (2) the radio spectrum steepens on either side of the radio relic. We discuss the origins of these features in the context of particle re-acceleration.

  16. Discovery of a suspected giant radio galaxy with the KAT-7 array

    NASA Astrophysics Data System (ADS)

    Colafrancesco, S.; Mhlahlo, N.; Jarrett, T.; Oozeer, N.; Marchegiani, P.

    2016-02-01

    We detect a new suspected giant radio galaxy (GRG) discovered by KAT-7. The GRG core is identified with the Wide-field Infrared Survey Explorer source J013313.50-130330.5, an extragalactic source based on its infrared colours and consistent with a misaligned active galactic nuclei-type spectrum at z ≈ 0.3. The multi-ν spectral energy distribution (SED) of the object associated with the GRG core shows a synchrotron peak at ν ≈ 1014 Hz consistent with the SED of a radio galaxy blazar-like core. The angular size of the lobes are ˜4 arcmin for the NW lobe and ˜1.2 arcmin for the SE lobe, corresponding to projected linear distances of ˜1078 kpc and ˜324 kpc, respectively. The best-fitting parameters for the SED of the GRG core and the value of jet boosting parameter δ = 2, indicate that the GRG jet has maximum inclination θ ≈ 30 deg with respect to the line of sight, a value obtained for δ = Γ, while the minimum value of θ is not constrained due to the degeneracy existing with the value of Lorentz factor Γ. Given the photometric redshift z ≈ 0.3, this GRG shows a core luminosity of P1.4 GHz ≈ 5.52 × 1024 W Hz-1, and a luminosity P1.4 GHz ≈ 1.29 × 1025 W Hz-1 for the NW lobe and P1.4 GHz ≈ 0.46 × 1025 W Hz-1 for the SE lobe, consistent with the typical GRG luminosities. The radio lobes show a fractional linear polarization ≈9 per cent consistent with typical values found in other GRG lobes.

  17. A non-thermal study of the brightest cluster galaxy NGC 1275 - the Gamma-Radio connection over four decades

    NASA Astrophysics Data System (ADS)

    Dutson, K. L.; Edge, A. C.; Hinton, J. A.; Hogan, M. T.; Gurwell, M. A.; Alston, W. N.

    2014-08-01

    Emission from the active nucleus in the core of the brightest cluster galaxy of the Perseus cluster, NGC 1275, has varied dramatically over the past four decades. Prompted by the Fermi detection of flaring in the γ-ray band, we present the recent increased activity of this source in the context of its past radio and γ-ray output. The broad correspondence between the high-frequency radio data and the high-energy (HE) emission is striking. However, on short time-scales this correlation breaks down and the 1.3 mm Submillimeter Array flux is apparently unaffected during Fermi -detected flaring activity. The fact that NGC 1275 is also detected at TeV energies during the periods of HE γ-ray flaring suggests that the short-time-scale variation might be primarily related to changes in the inverse Compton scattering of photons by the electron population in the jet. The longer-time-scale changes suggest a 30-40 year variation in the fuelling of the black hole that affects the power of the inner jet. NCG 1275 is a laboratory for the class of brightest cluster galaxies, and its variability on these time-scales has implications for our understanding of massive galaxies in cooling-core clusters. The case of NGC 1275 highlights the need for wide coverage across the radio band to correctly account for the contribution to emission from a synchrotron self-absorbed core (for example when considering contamination of Sunyaev-Zel'dovich effect observations), and the danger of variability biases in radio surveys of galaxies.

  18. SLOSHING COLD FRONTS IN GALAXY GROUPS AND THEIR PERTURBING DISK GALAXIES: AN X-RAY, OPTICAL, AND RADIO CASE STUDY

    SciTech Connect

    Gastaldello, Fabio; Di Gesu, Laura; Ghizzardi, Simona; Rossetti, Mariachiara; Giacintucci, Simona; Girardi, Marisa; Roediger, Elke; Brighenti, Fabrizio; Buote, David A.; Humphrey, Philip J.; Eckert, Dominique; Ettori, Stefano; Mathews, William G.

    2013-06-10

    We present a combined X-ray, optical, and radio analysis of the galaxy group IC 1860 using the currently available Chandra and XMM data, multi-object spectroscopy data from the literature, and Giant Metrewave Radio Telescope (GMRT) data. The Chandra and XMM imaging and spectroscopy reveal two surface brightness discontinuities at 45 and 76 kpc shown to be consistent with a pair of cold fronts. These features are interpreted as due to sloshing of the central gas induced by an off-axis minor merger with a perturber. This scenario is further supported by the presence of a peculiar velocity of the central galaxy IC 1860 and the identification of a possible perturber in the optically disturbed spiral galaxy IC 1859. The identification of the perturber is consistent with the comparison with numerical simulations of sloshing. The GMRT observation at 325 MHz shows faint, extended radio emission contained within the inner cold front, as seen in some galaxy clusters hosting diffuse radio mini-halos. However, unlike mini-halos, no particle reacceleration is needed to explain the extended radio emission, which is consistent with aged radio plasma redistributed by the sloshing. There is a strong analogy between the X-ray and optical phenomenology of the IC 1860 group and that of two other groups, NGC 5044 and NGC 5846, showing cold fronts. The evidence presented in this paper is among the strongest supporting the currently favored model of cold-front formation in relaxed objects and establishes the group scale as a chief environment for studying this phenomenon.

  19. Obscured Star-Formation in Merging Galaxies: High Resolution Radio Imaging of a Time-Ordered Sequence

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Campion, S. D.; Ulvestad, J. S.

    2003-01-01

    We present new, deep, high resolution 6cm and 4cm radio continuum images of the central regions of a time-ordered sequence of seven large galaxy mergers. The radio observations are able to detect star-forming re- gions that are completely obscured at optical wavelengths. In all systems, we detect numerous compact radio sources embedded in more diffuse ra- dio emission, with limiting luminosities of approx. 1-5 x 10(exp l8) W Hz or approx. 1-5 times the luminosity of Cas A. Many of the compact radio sources are loosely associated with active starforming regions but not with specific optical or W emission sources. Several of the compact radio sources are coincident with Ultra-luminous X-ray objects (ULX's). In most systems, we are able to measure reliable spectral indices for the stronger sources. We find that the fraction of compact radio cources with nominally flat radio spectral indices (indicating they ae dominated by thermal radio emission from HII regions) decreases with merger age, while the fraction of sources with nonimally steep spectral indices (indicating they are dominated by nonthermal emission from supernova remnants) increases. For the flat-spectrum sources, we estimate the numbers of young massive stars, associated ionized gas masses, we estimate supernova rates and required star-formation rates, We compare these results with those from other well-studied merging galaxy systems and from other determinations of star-formation rates. We gratefully acknowledge use of the NRAO Very Large Array (VLA) and the VLA Archive. NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  20. Jet-driven outflows of ionized gas in the nearby radio galaxy 3C 293

    NASA Astrophysics Data System (ADS)

    Mahony, E. K.; Oonk, J. B. R.; Morganti, R.; Tadhunter, C.; Bessiere, P.; Short, P.; Emonts, B. H. C.; Oosterloo, T. A.

    2016-01-01

    Fast outflows of gas, driven by the interaction between the radio jets and interstellar medium (ISM) of the host galaxy, are being observed in an increasing number of galaxies. One such example is the nearby radio galaxy 3C 293. In this paper we present integral field unit observations taken with OASIS on the William Herschel Telescope, enabling us to map the spatial extent of the ionized gas outflows across the central regions of the galaxy. The jet-driven outflow in 3C 293 is detected along the inner radio lobes with a mass outflow rate ranging from ˜0.05 to 0.17 M⊙ yr-1 (in ionized gas) and corresponding kinetic power of ˜0.5-3.5 × 1040 erg s-1. Investigating the kinematics of the gas surrounding the radio jets (i.e. not directly associated with the outflow), we find linewidths broader than 300 km s-1 up to 5 kpc in the radial direction from the nucleus (corresponding to 3.5 kpc in the direction perpendicular to the radio axis at maximum extent). Along the axis of the radio jet linewidths >400 km s-1 are detected out to 7 kpc from the nucleus and linewidths of >500 km s-1 at a distance of 12 kpc from the nucleus, indicating that the disturbed kinematics clearly extend well beyond the high surface brightness radio structures of the jets. This is suggestive of the cocoon structure seen in simulations of jet-ISM interaction and implies that the radio jets are capable of disturbing the gas throughout the central regions of the host galaxy in all directions.

  1. Spitzer mid-IR spectroscopy of powerful 2Jy and 3CRR radio galaxies. II. AGN power indicators and unification

    SciTech Connect

    Dicken, D.; Tadhunter, C.; Morganti, R.; Axon, D.; Robinson, A.; Magagnoli, M.; Kharb, P.; Ramos Almeida, C.; Hardcastle, M.; Nesvadba, N. P. H.; Singh, V.; Kouwenhoven, M. B. N.; Rose, M.; Spoon, H.; Inskip, K. J.; Holt, J.

    2014-06-20

    It remains uncertain which continuum and emission line diagnostics best indicate the bolometric powers of active galactic nuclei (AGNs), especially given the attenuation caused by the circumnuclear material and the possible contamination by components related to star formation. Here we use mid-IR spectra along with multiwavelength data to investigate the merit of various diagnostics of AGN radiative power, including the mid-IR [Ne III] λ25.89 μm and [O IV] λ25.89 μm fine-structure lines, the optical [O III] λ5007 forbidden line, and mid-IR 24 μm, 5 GHz radio, and X-ray continuum emission, for complete samples of 46 2Jy radio galaxies (0.05 < z < 0.7) and 17 3CRR FRII radio galaxies (z < 0.1). We find that the mid-IR [O IV] line is the most reliable indicator of AGN power for powerful radio-loud AGNs. By assuming that the [O IV] is emitted isotropically, and comparing the [O III] and 24 μm luminosities of the broad- and narrow-line AGNs in our samples at fixed [O IV] luminosity, we show that the [O III] and 24 μm emission are both mildly attenuated in the narrow-line compared to the broad-line objects by a factor of ≈2. However, despite this attenuation, the [O III] and 24 μm luminosities are better AGN power indicators for our sample than either the 5 GHz radio or the X-ray continuum luminosities. We also detect the mid-IR 9.7 μm silicate feature in the spectra of many objects but not ubiquitously: at least 40% of the sample shows no clear evidence for these features. We conclude that, for the majority of powerful radio galaxies, the mid-IR lines are powered by AGN photoionization.

  2. VizieR Online Data Catalog: Compact radio cores in radio galaxies. (Jones+, 1994)

    NASA Astrophysics Data System (ADS)

    Jones, P. A.; McAdam, W. B.; Reynolds, J. E.

    1999-04-01

    This catalog contains compact core fluxes for a list of 175 southern radio galaxies, measured with the Parkes-Tidbinbilla Interferometer (PTI, Norris et al. 1988ApJS...67...85N) on a single 275 km baseline at 2.3 GHz and 8.4 GHz. The sample consists of large angular size ( > 0.5 arcmin) steep spectrum sources from Jones & McAdam (1992ApJS...80..137J) observed to determine the fraction of flux contained in compact (VLBI-scale) cores. Of the 172 sources observed at 2.3 GHz (100 milliarcsec fringe spacing), 63 had cores detected and upper limits were determined for the remaining 109. Of the 88 sources observed at 8.4 GHz (30 milliarcsec fringe spacing), 38 had cores detected and 50 have upper limits. A comparison of the detections and upper limits at the two frequencies shows that the cores have flat or inverted spectra. The core fluxes quoted here may vary by around 20 % if there is structure on the scale of the fringe spacing and the cores are probably intrinsically variable. (1 data file).

  3. Axial Ratio of Edge-On Spiral Galaxies as a Test for Bright Radio Halos

    NASA Astrophysics Data System (ADS)

    Singal, J.; Kogut, A.; Jones, E.; Dunlap, H.

    2015-01-01

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan & Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo.

  4. AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

    SciTech Connect

    Singal, J.; Jones, E.; Dunlap, H.; Kogut, A.

    2015-01-20

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

  5. Highlights of the Merging Cluster Collaboration's Analysis of 26 Radio Relic Galaxy Cluster Mergers

    NASA Astrophysics Data System (ADS)

    Dawson, William; Golovich, Nathan; Wittman, David M.; Bradac, Marusa; Brüggen, Marcus; Bullock, James; Elbert, Oliver; Jee, James; Kaplinghat, Manoj; Kim, Stacy; Mahdavi, Andisheh; Merten, Julian; Ng, Karen; Annika, Peter; Rocha, Miguel E.; Sobral, David; Stroe, Andra; Van Weeren, Reinout J.; Merging Cluster Collaboration

    2016-01-01

    Merging galaxy clusters are now recognized as multifaceted probes providing unique insight into the properties of dark matter, the environmental impact of plasma shocks on galaxy evolution, and the physics of high energy particle acceleration. The Merging Cluster Collaboration has used the diffuse radio emission associated with the synchrotron radiation of relativistic particles accelerated by shocks generated during major cluster mergers (i.e. radio relics) to identify a homogenous sample of 26 galaxy cluster mergers. We have confirmed theoretical expectations that radio relics are predominantly associated with mergers occurring near the plane of the sky and at a relatively common merger phase; making them ideal probes of self-interacting dark matter, and eliminating much of the dominant uncertainty when relating the observed star formation rates to the event of the major cluster merger. We will highlight a number of the discovered common traits of this sample as well as detailed measurements of individual mergers.

  6. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    2002-09-01

    Scientists at the Carnegie Observatories in Pasadena, California, have uncovered six times the expected number of active, supermassive black holes in a single viewing of a cluster of galaxies, a finding that has profound implications for theories as to how old galaxies fuel the growth of their central black holes. The finding suggests that voracious, central black holes might be as common in old, red galaxies as they are in younger, blue galaxies, a surprise to many astronomers. The team made this discovery with NASA'S Chandra X-ray Observatory. They also used Carnegie's 6.5-meter Walter Baade Telescope at the Las Campanas Observatory in Chile for follow-up optical observations. "This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," said Dr. Paul Martini, lead author on a paper describing the results that appears in the September 10 issue of The Astrophysical Journal Letters. "The question now is, how do these black holes produce bright X-ray sources, similar to what we see from much younger galaxies?" Typical of the black hole phenomenon, the cores of these active galaxies are luminous in X-ray radiation. Yet, they are obscured, and thus essentially undetectable in the radio, infrared and optical wavebands. "X rays can penetrate obscuring gas and dust as easily as they penetrate the soft tissue of the human body to look for broken bones," said co-author Dr. Dan Kelson. "So, with Chandra, we can peer through the dust and we have found that even ancient galaxies with 10-billion-year-old stars can have central black holes still actively pulling in copious amounts of interstellar gas. This activity has simply been hidden from us all this time. This means these galaxies aren't over the hill after all and our theories need to be revised." Scientists say that supermassive black holes -- having the mass of millions to billions of suns squeezed into a region about the size of our Solar System -- are the engines in the cores of

  7. Radio structures of Seyfert galaxies. VII - Extension of a distance-limited sample

    NASA Technical Reports Server (NTRS)

    Ulvestad, James S.; Wilson, Andrew S.

    1989-01-01

    The VLA has been used at 6 and 20 cm to observe 27 Seyfert galaxies with recessional velocities less than 4600 km/s that had not been mapped previously. The sample shows weak trends for Seyfert 2 galaxies to have more luminous and larger radio sources than Seyfert 1 galaxies. A 20 cm radio luminosity function is constructed for each Seyfert type and shown to be fairly flat for powers betwen 10 to the 20th and 10 to the 23rd W/Hz. About 10 percent of the galaxies in the present sample may have flat-spectrum components contributing a substantial amount of their total flux density at centimeter wavelengths.

  8. A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

    NASA Astrophysics Data System (ADS)

    Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.

    2016-03-01

    We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population, σ _V=949_{-60}^{+80} km s-1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M200 ˜ 7-9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the Pradio-LX relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.

  9. INTEGRAL and RXTE Observations of Broad-Line Radio Galaxy 3C 111

    NASA Astrophysics Data System (ADS)

    Chernyakova, M.; Favre, P.; Courvoisier, T. J.-L.; Lutovinov, A.; Molkov, S.; Beckmann, V.; Gros, A.; Gehrels, N.; Prodiut, N.; Walter, R.; Zdziarski, A.

    2004-10-01

    3C 111 is an X-ray bright broad-line radio galaxy which is classified as a Fanaroff-Riley type II source with a double-lobe/single jet morphology, and re- ported superluminal motion. It is a well-known X- ray source, and was observed by every major X-ray observatory since HEAO-1. In this paper we present the results of the RXTE and INTEGRAL data anal- ysis and compare them with the results of the previ- ous observations. Key words: X rays: radio galaxies; X rays: individ- uals: 3C 111.

  10. Dust in BL Lac objects and Fanaroff-Riley radio galaxies: infrared region

    NASA Astrophysics Data System (ADS)

    Seal Braun, P.

    2015-12-01

    Here 28 BL Lac objects, 18 FR I type radio galaxies, 4 FR I/II type radio galaxies and 10 FR II type radio galaxies are studied from FIR (far infrared) to optical region (180 μm to 0.44 μm) to understand the nature of infrared emission from these objects and the physical properties of dust in the emitting region. Using the flux densities from 2MASS, IRAS, ISO, SCUBA (40 % samples), WISE All-sky Data, AKARI (10 % samples) data and optical (B) observations, the spectral energy distributions are constructed. FIR and NIR spectral indices (α_{FIR} and α_{NIR}) are estimated. The dust temperatures and dust masses of all the samples are estimated from FIR flux densities. The SEDs of most of the samples (90 %) show steep slopes from FIR to optical region and about 10 % of the samples show flat continuous spectra from FIR to NIR region. The SEDs of 80 % FR I type radio galaxies and 1 out of 4 FR I/II type radio galaxies and two RBLs show a bump in the NIR to optical region. The SEDs of these sources are compared with Radiative transfer models. From FIR to MIR region, the SEDs of 90 % of the objects studied here can be fitted to the models with luminosities L˜ 10^{9.5} L0, considering uncertainty from 10 % to 20 %. But the observable fluxes in the NIR region are higher and can be fitted to other models with higher L˜ 10^{12.5} L0. Since there is a difference in emission in NIR region, mainly for FR I radio galaxies, so the variation of apparent K magnitudes with logarithm of redshift z is also studied. The WISE colours, (W1 - W2) and (W2 - W3) are compared with isodensity contours. Comparing with radiative transfer models it can be suggested that, in the FIR and MIR region the infrared emission is from the dust containing large grains, small graphites and PAHs at temperature ˜50 K-100 K. In the NIR region hot dust is mainly due to small grains at temperature ˜1200 K and the emission is mainly from synchrotron radiation produced in the inner part of the relativistic

  11. Search for clustering of background objects near distant radio galaxies using the MST method

    NASA Astrophysics Data System (ADS)

    Keshelava, T. V.; Verkhodanov, O. V.

    2015-07-01

    The minimal spanning tree (MST) method was used to explore the statistical properties of field objects near distant radio galaxies (0.3 ≤ z ≤ 1.2) on SDSS images. The average diagrams of MST branch lengths were found to differ statistically for field objects near radio galaxies with z < 0.7 and z > 0.7, although zones of the subsample considered show no signs of clustering down to the SDSS limiting magnitude at a significance level greater than 5σ.

  12. Quark nugget dark matter: Comparison with radio observations of nearby galaxies

    NASA Astrophysics Data System (ADS)

    Lawson, K.; Zhitnitsky, A. R.

    2016-06-01

    It has been recently claimed that radio observations of nearby spiral galaxies essentially rule out a dark matter source for the galactic haze [1]. Here we consider the low energy thermal emission from a quark nugget dark matter model in the context of microwave emission from the galactic centre and radio observations of nearby Milky Way like galaxies. We demonstrate that observed emission levels do not strongly constrain this specific dark matter candidate across a broad range of the allowed parameter space in drastic contrast with conventional dark matter models based on the WIMP paradigm.

  13. The correlation between far-IR and radio continuum emission from spiral galaxies

    NASA Technical Reports Server (NTRS)

    Dickey, John M.; Garwood, Robert W.; Helou, George

    1987-01-01

    A sample of 30 galaxies selected for their intense IRAS flux at 60 and 100 micron using the Arecibo telescope at 21 cm to measure the continuum and HI line luminosities were observed. The centimeter wave continuum correlates very well with the far-infrared flux, with a correlation coefficient as high as that found for other samples, and the same ratio between FIR and radio luminosities. Weaker correlations are seen between the FIR and optical luminosity and between the FIR and radio continuum. There is very little correlation between the FIR and the HI mass deduced from the integral of the 21 cm line. The strength of the radio continuum correlation suggests that there is little contribution to either the radio and FIR from physical processes not affecting both. If they each reflect time integrals of the star formation rate then the time constants must be similar, or the star formation rate must change slowly in these galaxies.

  14. A comparison of properties of different population radio galaxies based on the Planck mission microwave data

    NASA Astrophysics Data System (ADS)

    Verkhodanov, O. V.; Solovyov, D. I.; Ulakhovich, O. S.; Khabibullina, M. L.

    2016-04-01

    Applying the stacking method, we examine the areas of the cosmic microwave background radiation (CMB) maps, constructed according to the Planck SpaceObservatory data in the neighbourhood of different populations of radio sources and giant elliptical galaxies. The samples of objects include giant radio galaxies (GRG), radio sources, selected by the radio-spectral index and redshift, as well as the gamma-ray bursts, used as a secondary comparative sample. We have studied the topological properties of the CMB signal in the neighbourhood of the average object of the population, namely, we searched for the presence of the maxima and minima in the average area. The difference of the signal in the neighbourhood of GRGs from the other types of objects was discovered.

  15. Radio Sources Associated with Intermediate X-ray Luminosity Objects in Merging Galaxy Systems

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Ulvestad, J. S.; Oegerle, William R. (Technical Monitor)

    2002-01-01

    We present new, high-resolution 6, 3.6, and 2 cm radio images of a time-ordered sequence of merging galaxy systems. The new data have a resolution of less than 100pc and a sensitivity comparable to a few x Cas A. We detect compact radio sources in all systems, generally embedded in more diffuse radio emission at the longer wavelengths. Several of the compact radio sources are coincident with compact Intermediate-luminosity X-ray Objects (IXOs) in these systems, and many more are within the 3$/sigma$ Chandra position errors for other IXOs. The fraction of radio identifications and the nature of the radio sources changes as a function of merger stage. These data suggest that the IXOs are associated with complexes of supernova remnants, and therefore with star formation that has occurred within the last $/sim$10$circumflex7$ yr, but are not located in HII regions where copious star formation is occurring currently.

  16. New southern galaxies with active nuclei

    SciTech Connect

    Maia, M.A.G.; Da costa, L.N.; Willmer, C.; Pellegrini, P.S.; Rite, C.

    1987-03-01

    A list of AGN candidates, identified from optical spectra taken as part of an ongoing redshift survey of southern galaxies, is presented. The identification, coordinates, morphological type, measured heliocentric radial velocity, and proposed emission type are given for the galaxies showing evidence of nonstellar nuclear activity. Using standard diagnostics, several new Seyferts and low-ionization nuclear-emission regions (LINERs) are identified among the emission-line galaxies observed. 14 references.

  17. The impact of compact radio sources on their host galaxies: observations

    NASA Astrophysics Data System (ADS)

    Tadhunter, C.

    2016-02-01

    I review the observational evidence that CSS/GPS radio sources have a significant impact on the evolution of their host galaxies, particularly on the kpc-scales of the galaxy bulges. Starting with an overview of the observational evidence for jet-cloud interactions and warm ionised outflows in CSS/GPS sources, I then consider the challenges involved in quantifying the feedback effect of the warm outflows in terms of their mass outflow rates and kinetic powers. For the best-observed cases it is shown that the warm outflows may have a major negative feedback effect in the very central regions, but probably lack the power to heat and eject the full cool ISM contents of the host galaxies. In contrast, the recently-discovered neutral and molecular outflows are more massive and powerful and therefore carry more destructive potential. However, the feedback effect of such outflows is not necessarily negative: there is now clear observational evidence that the molecular outflows are formed as the hot, compressed gas cools behind fast shocks driven into the ISM by the relativistic jets. The natural endpoint of this process is the formation of stars. Therefore, jet-induced star formation may be a significant process in CSS/GPS radio galaxies. Finally, I discuss whether CSS/GPS sources are ``imposters'' in flux-limited radio samples, due the flux boosting of the radio sources by strong jet-cloud interactions in the early stages of radio source evolution.

  18. COSMIC EVOLUTION OF RADIO SELECTED ACTIVE GALACTIC NUCLEI IN THE COSMOS FIELD

    SciTech Connect

    Smolcic, V.; Salvato, M.; Scoville, N.; Zamorani, G.; Bardelli, S.; Ciliegi, P.; Schinnerer, E.; Bondi, M.; BIrzan, L.; Carilli, C. L.; Elvis, M.; Impey, C. D.; Trump, J. R.; Koekemoer, A. M.; Merloni, A.; Scodeggio, M.; Paglione, T

    2009-05-01

    We explore the cosmic evolution of radio luminous active galactic nuclei (AGNs) with low radio powers (L {sub 1.4GHz} {approx}< 5 x 10{sup 25} W Hz{sup -1}) out to z = 1.3 using to date the largest sample of {approx}600 low-luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio-luminosity function for these AGNs, and its evolution with cosmic time assuming two extreme cases: (1) pure luminosity and (2) pure density evolution. The former and latter yield L {sub *} {proportional_to} (1 + z){sup 0.8} {sup {+-}} {sup 0.1}, and {phi}{sub *} {proportional_to} (1 + z){sup 1.1} {sup {+-}} {sup 0.1}, respectively, both implying a fairly modest change in properties of low-radio-power AGNs since z = 1.3. We show that this is in stark contrast with the evolution of powerful (L {sub 1.4GHz} > 5 x 10{sup 25} W Hz{sup -1}) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willot et al. We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGNs. Our findings suggest that high- and low-radio-power AGN activities are triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z {approx} 1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the 'radio mode' in cosmological models.

  19. On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C+67.13

    NASA Astrophysics Data System (ADS)

    Hagino, K.; Stawarz, Ł.; Siemiginowska, A.; Cheung, C. C.; Kozieł-Wierzbowska, D.; Szostek, A.; Madejski, G.; Harris, D. E.; Simionescu, A.; Takahashi, T.

    2015-06-01

    Here we analyze radio, optical, and X-ray data for the peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy (BCG), CGPG 0719.8+6704, is a pair of interacting ellipticals with projected separation ˜10 kpc, the brighter of which hosts the radio source 4C+67.13. The Fanaroff-Riley type-II radio morphology of 4C+67.13 is unusual for central radio galaxies in local Abell clusters. Our new optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are active, albeit at low accretion rates corresponding to the Eddington ratio ˜ {{10}-4} (for the estimated black hole masses of ˜ 3× {{10}8} {{M}⊙ } and ˜ {{10}9} {{M}⊙ }). The gathered X-ray (Chandra) data allowed us to confirm and to quantify robustly the previously noted elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a large spatial offset (˜60 kpc projected) between the position of the BCG and the cluster center inferred from the modeling of the X-ray surface brightness distribution. Detailed analysis of the brightness profiles and temperature revealed also that the cluster gas in the vicinity of 4C+67.13 is compressed (by a factor of about ˜1.4) and heated (from ≃ 2.0 keV up to 2.7 keV), consistent with the presence of a weak shock (Mach number ˜1.3) driven by the expanding jet cocoon. This would then require the jet kinetic power of the order of ˜ {{10}45} erg s-1, implying either a very high efficiency of the jet production for the current accretion rate, or a highly modulated jet/accretion activity in the system. Based on service observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  20. Radio galaxy populations and the multitracer technique: pushing the limits on primordial non-Gaussianity

    NASA Astrophysics Data System (ADS)

    Ferramacho, L. D.; Santos, M. G.; Jarvis, M. J.; Camera, S.

    2014-08-01

    We explore the use of different radio galaxy populations as tracers of different mass haloes and therefore, with different bias properties, to constrain primordial non-Gaussianity of the local type. We perform a Fisher matrix analysis based on the predicted auto- and cross-angular power spectra of these populations, using simulated redshift distributions as a function of detection flux and the evolution of the bias for the different galaxy types (star-forming galaxies, starburst galaxies, radio-quiet quasars, FR I and FR II AGN galaxies). We show that such a multitracer analysis greatly improves the information on non-Gaussianity by drastically reducing the cosmic variance contribution to the overall error budget. By applying this method to future surveys, we predict a constraint of σ fnl = 3.6 on the local non-Gaussian parameter for a galaxy detection flux limit of 10 μJy and σ fnl = 2.2 for 1 μJy. We show that this significantly improves on the constraints obtained when using the whole undifferentiated populations (σ fnl = 48 10 μJy and σ fnl = 12 for 1 μJy). We conclude that continuum radio surveys alone have the potential to constrain primordial non-Gaussianity to an accuracy at least a factor of 2 better than the present constraints obtained with Planck data on the cosmic microwave background bispectrum, opening a window to obtain σ fnl ˜ 1 with the Square Kilometre Array.

  1. The relationship between the carbon monoxide intensity and the radio continuum emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Adler, David S.; Lo, K. Y.; Allen, Ronald J.

    1991-01-01

    The relationship between the velocity-integrated CO emission and the nonthermal radio continuum brightness in the disks of normal spiral galaxies is examined on a variety of length scales. On a global scale, the total CO intensity correlates strongly with the total radio continuum flux density for a sample of 31 galaxies. On scales of about 2 kpc or more in the disk of individual galaxies, it is found that the ratio I(CO)/T(20) remains fairly constant over the entire disk as well as from galaxy to galaxy. For the eight spirals in the sample, the disk-averaged values of I(CO)/T(20) range from 0.6-2.4, with the average over all eight galaxies being 1.3 +/- 0.6. It is concluded that what these various length scales actually trace are differences in the primary heating mechanism of the gas in the beam. The observed relationship between CO and nonthermal radio continuum emission can be explained by assuming that molecular gas in galactic disks is heated primarily by cosmic rays. The observed relationship is used to show that the brightness of synchrotron emission is proportional to n(cr) exp 0.4 - 0.9 in galactic disks.

  2. RADIO DETECTION OF GREEN PEAS: IMPLICATIONS FOR MAGNETIC FIELDS IN YOUNG GALAXIES

    SciTech Connect

    Chakraborti, Sayan; Yadav, Naveen; Ray, Alak; Cardamone, Carolin

    2012-02-10

    Green Peas are a new class of young, emission line galaxies that were discovered by citizen volunteers in the Galaxy Zoo project. Their low stellar mass, low metallicity, and very high star formation rates make Green Peas the nearby (z {approx} 0.2) analogs of the Lyman break galaxies which account for the bulk of the star formation in the early universe (z {approx} 2-5). They thus provide accessible laboratories in the nearby universe for understanding star formation, supernova feedback, particle acceleration, and magnetic field amplification in early galaxies. We report the first direct radio detection of Green Peas with low frequency Giant Metrewave Radio Telescope observations and our stacking detection with archival Very Large Array FIRST data. We show that the radio emission implies that these extremely young galaxies already have magnetic fields ({approx}> 30 {mu}G) even larger than that of the Milky Way. This is at odds with the present understanding of magnetic field growth based on amplification of seed fields by dynamo action over a galaxy's lifetime. Our observations strongly favor models with pregalactic magnetic fields at {mu}G levels.

  3. Einstein observations of active galaxies and quasars

    NASA Technical Reports Server (NTRS)

    Schreier, E. J.

    1979-01-01

    The radio galaxies Centaurus A and Signus B are discussed. In both these sources, a comparison of the radio and imaged X-ray flux is allowed for the measurement of the magnetic fields. Einstein observations of quasars are discussed. The number of known X-ray emitting QSO's was increased from 3 to 22 and the distances where these QSO's were seen to correspond to an age of 15 billion years. It was shown that these quasars contributed significantly to the X-ray background.

  4. Deep Hubble Space Telescope imaging of 53W044 - An S0 radio galaxy at z = 0.311

    NASA Technical Reports Server (NTRS)

    Keel, William C.; Windhorst, Rogier A.

    1993-01-01

    Images of the Wide Field Camera (WFC) and Faint-Object Camera (FOC) of the radio galaxy 53W044 are presented. The WFC images are used to examine the structure of the galaxy, and show evidence for a significant disk, on the basis of which 53W044 is classified as an S0. This radio galaxy is near the maximum radio power associated with sources in S0 host galaxies. The FOC image is combined with ground-based spectroscopy to study 53W044's stellar population, which appears normal for an E/S0 galaxy of modest luminosity. No evidence is found for a significant contribution from a nuclear blue-continuum source, and the stellar population is old with a continuum level at 2100 A, consistent with what is seen in nearby radio galaxies.

  5. Multi-frequency properties of an narrow angle tail radio galaxy J 0037+18

    NASA Astrophysics Data System (ADS)

    Patra, Dusmanta; Chakrabarti, Sandip Kumar; Pal, Sabyasachi; Konar, Chiranjib

    2016-07-01

    We will present multi-frequency properties of narrow angle tailed radio galaxy J 0037+18 using data from Giant Metrewave Radio Telescope (GMRT) and Jansky Very Large Array (JVLA). The angle between two lobes is only 38 degree. We will discuss magnetic field and particle life time of the jet. Spectral properties of the source will be discussed. We also used optical and X-ray data to investigate host environment.

  6. CONNECTION BETWEEN THE ACCRETION DISK AND JET IN THE RADIO GALAXY 3C 111

    SciTech Connect

    Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Harrison, Brandon; Agudo, Ivan; Taylor, Brian W.; Markowitz, Alex; Rivers, Elizabeth; Rothschild, Richard E.; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Laehteenmaeki, Anne; Tornikoski, Merja; Gomez, Jose L.; Gurwell, Mark

    2011-06-10

    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 lt-day of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with a steeper slope at shorter timescales. The break timescale of 13{sup +12}{sub -6} days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons-the corona-situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the Fanaroff-Riley class I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole.

  7. Radio jet propagation and wide-angle tailed radio sources in merging galaxy cluster environments

    NASA Astrophysics Data System (ADS)

    Loken, Chris; Roettiger, Kurt; Burns, Jack O.; Norman, Michael

    1995-05-01

    The intracluster medium (ICM) within merging clusters of galaxies is likely to be in a violent or turbulent dynamical state which may have a significant effect on the evolution of cluster radio sources. We present results from a recent gas + N-body simulation of a cluster merger, suggesting that mergers can result in long-lived, supersonic bulk flows, as well as shocks, within a few hundred kiloparsecs of the core of the dominant cluster. These results have motivated our new two-dimensional and three-dimensional simulations of jet propagation in such environments. The first set of simulations models the ISM/ICM transition as a contact discontinuity with a strong velocity shear. A supersonic (Mj = 6) jet crossing this discontinuity into an ICM with a transverse, supersonic wind bends continuously, becomes 'naked' on the upwind side, and forms a distended cocoon on the downwind side. In the case of a mildly supersonic jet (Mj = 3), however, a shock is driven into the ISM and ISM material is pulled along with the jet into the ICM. Instabilities excited at the ISM/ICM interface result in the jet repeatedly pinching off and reestablishing itself in a series of 'disconnection events.' The second set of simulations deals with a jet encountering a shock in the merging cluster environment. A series of relatively high-resolution two-dimensional calculations is used to confirm earlier analysis predicting that the jet will not disrupt when the jet Mach number is greater than the shock Mach number. A jet which survives the encounter with the shock will decrease in radius and disrupt shortly thereafter as a result of the growth of Kelvin-Helmholtz instabilities. We also find, in disagreement with predictions, that the jet flaring angle decreases with increasing jet density. Finally, a three-dimensional simulation of a jet crossing an oblique shock gives rise to a morphology which resembles a wide-angle tailed radio source with the jet flaring at the shock and disrupting to form

  8. Radio jet propagation and wide-angle tailed radio sources in merging galaxy cluster environments

    NASA Technical Reports Server (NTRS)

    Loken, Chris; Roettiger, Kurt; Burns, Jack O.; Norman, Michael

    1995-01-01

    The intracluster medium (ICM) within merging clusters of galaxies is likely to be in a violent or turbulent dynamical state which may have a significant effect on the evolution of cluster radio sources. We present results from a recent gas + N-body simulation of a cluster merger, suggesting that mergers can result in long-lived, supersonic bulk flows, as well as shocks, within a few hundred kiloparsecs of the core of the dominant cluster. These results have motivated our new two-dimensional and three-dimensional simulations of jet propagation in such environments. The first set of simulations models the ISM/ICM transition as a contact discontinuity with a strong velocity shear. A supersonic (M(sub j) = 6) jet crossing this discontinuity into an ICM with a transverse, supersonic wind bends continuously, becomes 'naked' on the upwind side, and forms a distended cocoon on the downwind side. In the case of a mildly supersonic jet (M(sub j) = 3), however, a shock is driven into the ISM and ISM material is pulled along with the jet into the ICM. Instabilities excited at the ISM/ICM interface result in the jet repeatedly pinching off and reestablishing itself in a series of 'disconnection events.' The second set of simulations deals with a jet encountering a shock in the merging cluster environment. A series of relatively high-resolution two-dimensional calculations is used to confirm earlier analysis predicting that the jet will not disrupt when the jet Mach number is greater than the shock Mach number. A jet which survives the encounter with the shock will decrease in radius and disrupt shortly thereafter as a result of the growth of Kelvin-Helmholtz instabilities. We also find, in disagreement with predictions, that the jet flaring angle decreases with increasing jet density. Finally, a three-dimensional simulation of a jet crossing an oblique shock gives rise to a morphology which resembles a wide-angle tailed radio source with the jet flaring at the shock and

  9. VERY LONG BASELINE ARRAY IMAGING OF PARSEC-SCALE RADIO EMISSIONS IN NEARBY RADIO-QUIET NARROW-LINE SEYFERT 1 GALAXIES

    SciTech Connect

    Doi, Akihiro; Asada, Keiichi; Inoue, Makoto; Fujisawa, Kenta; Nagai, Hiroshi; Hagiwara, Yoshiaki; Wajima, Kiyoaki

    2013-03-01

    We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz ({lambda}18 cm) with milliarcsecond resolution. This is the first systematic very long baseline interferometry study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of {approx}> 5 Multiplication-Sign 10{sup 6} K and contain radio cores with high brightness temperatures of >6 Multiplication-Sign 10{sup 7} K, indicating a nonthermal process driven by jet-producing central engines as in radio-loud NLS1s and other active galactic nucleus classes. VLBA images of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear structures. A large portion of the radio power comes from diffuse emission components that are distributed within the nuclear regions ({approx}< 300 pc), which is a common characteristic throughout the observed NLS1s. Jet kinetic powers limited by the Eddington limit may be insufficient to allow the jets to escape to kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of {approx}< 10{sup 7} M {sub Sun }.

  10. Ultrafast outflows in radio-loud active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Tazaki, F.; Mushotzky, R. F.; Ueda, Y.; Cappi, M.; Gofford, J.; Reeves, J. N.; Guainazzi, M.

    2014-09-01

    Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order of ˜0.1c in a limited sample of six broad-line radio galaxies. They are observed as blueshifted Fe XXV-XXVI K-shell absorption lines, similarly to the ultrafast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the search for such Fe K absorption lines to a larger sample of 26 radio-loud active galactic nuclei (AGN) observed with XMM-Newton and Suzaku. The sample is drawn from the Swift Burst Alert Telescope 58-month catalogue and blazars are excluded. X-ray bright Fanaroff-Riley Class II radio galaxies constitute the majority of the sources. Combining the results of this analysis with those in the literature we find that UFOs are detected in >27 per cent of the sources. However, correcting for the number of spectra with insufficient signal-to-noise ratio, we can estimate that the incidence of UFOs is this sample of radio-loud AGN is likely in the range f ≃ (50 ± 20) per cent. A photoionization modelling of the absorption lines with XSTAR allows us to estimate the distribution of their main parameters. The observed outflow velocities are broadly distributed between vout ≲ 1000 km s-1 and vout ≃ 0.4c, with mean and median values of vout ≃ 0.133c and vout ≃ 0.117c, respectively. The material is highly ionized, with an average ionization parameter of logξ ≃ 4.5 erg s-1 cm, and the column densities are larger than NH > 1022 cm-2. Overall, these characteristics are consistent with the presence of complex accretion disc winds in a significant fraction of radio-loud AGN and demonstrate that the presence of relativistic jets does not preclude the existence of winds, in accordance with several theoretical models.

  11. Rotation of the polarization vector from distant radio galaxies in the perturbed FRW metric

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Sankha Subhra

    2016-06-01

    Analysis of the correlation between the angular positions of distant radio galaxies on the sky and the orientations of their polarization vectors with respect to their major axes indicates a dipolar anisotropy in the large scale. We consider a single mode of large-scale scalar perturbation to the FRW metric. Using Newman-Penrose formalism, we calculate the rotation of the galaxy major axis with respect to the polarization vector as the elliptic image and the polarization vector are carried through the perturbed spacetime. The dependence of the rotation on the polar angular coordinate of the galaxy is qualitatively similar to the claimed dipole pattern.

  12. [O III] line properties in two samples of radio-emitting narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Foschini, L.; Ciroi, S.; Cracco, V.; La Mura, G.; Di Mille, F.; Rafanelli, P.

    2016-06-01

    The [O III] λλ 4959, 5007 lines are a useful proxy to test the kinematic of the narrow-line region (NLR) in active galactic nuclei (AGN). In AGN, and particularly in narrow-line Seyfert 1 galaxies (NLS1s) these lines often show few peculiar features, such as blue wings, often interpreted as outflowing component, and a shift - typically toward lower wavelengths - of the whole spectroscopic feature in some exceptional sources, the so-called blue outliers, which are often associated to strong winds. We investigated the incidence of these peculiarities in two samples of radio-emitting NLS1s, one radio-loud and one radio-quiet. We also studied a few correlations between the observational properties of the [O III] lines and those of the AGN. Our aim was to understand the difference between radio-quiet and radio-loud NLS1s, which may in turn provide useful information on the jet formation mechanism. We find that the NLR gas is much more perturbed in radio-loud than in radio-quiet NLS1s. In particular the NLR dynamics in γ-ray emitting NLS1s appears to be highly disturbed, and this might be a consequence of interaction with the relativistic jet. The less frequently perturbed NLR in radio-quiet NLS1s suggests instead that these sources likely do not harbor a fully developed relativistic jet. Nonetheless blue-outliers in radio-quiet NLS1s are observed, and we interpret them as a product of strong winds.

  13. Combining physical galaxy models with radio observations to constrain the SFRs of high-z dusty star-forming galaxies

    NASA Astrophysics Data System (ADS)

    Lo Faro, B.; Silva, L.; Franceschini, A.; Miller, N.; Efstathiou, A.

    2015-03-01

    We complement our previous analysis of a sample of z ˜ 1-2 luminous and ultraluminous infrared galaxies [(U)LIRGs], by adding deep Very Large Array radio observations at 1.4 GHz to a large data set from the far-UV to the submillimetre, including Spitzer and Herschel data. Given the relatively small number of (U)LIRGs in our sample with high signal-to-noise (S/N) radio data, and to extend our study to a different family of galaxies, we also include six well-sampled near-infrared (near-IR)-selected BzK galaxies at z ˜ 1.5. From our analysis based on the radtran spectral synthesis code GRASIL, we find that, while the IR luminosity may be a biased tracer of the star formation rate (SFR) depending on the age of stars dominating the dust heating, the inclusion of the radio flux offers significantly tighter constraints on SFR. Our predicted SFRs are in good agreement with the estimates based on rest-frame radio luminosity and the Bell calibration. The extensive spectrophotometric coverage of our sample allows us to set important constraints on the star formation (SF) history of individual objects. For essentially all galaxies, we find evidence for a rather continuous SFR and a peak epoch of SF preceding that of the observation by a few Gyr. This seems to correspond to a formation redshift of z ˜ 5-6. We finally show that our physical analysis may affect the interpretation of the SFR-M⋆ diagram, by possibly shifting, with respect to previous works, the position of the most dust obscured objects to higher M⋆ and lower SFRs.

  14. Fermi monitoring of radio-loud narrow-line Seyfert 1 galaxies

    SciTech Connect

    Paliya, Vaidehi S.; Stalin, C. S.; Ravikumar, C. D.

    2015-02-01

    We present detailed analysis of the γ-ray flux variability and spectral properties of the five radio-loud narrow line Seyfert 1 (RL-NLSy1) galaxies, detected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope, namely 1H 0323+342, SBS 0846+513, PMN J0948+0022, PKS 1502+036, and PKS 2004−447. The first three sources show significant flux variations, including the rapid variability of a few hours by 1H 0323+342. The average γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 shows deviation from a simple power-law (PL) behavior, whereas the PL model gives a better fit for the other three sources. The spectra of 1H 0323+342, SBS 0846+513, and PMN J0948+0022, which are in low, flaring, and moderately active states, respectively, show significant curvature. Such curvature in the γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 could be due to the emission region located inside the broad line region (BLR) where the primary mechanism of the γ-ray emission is inverse-Compton (IC) scattering of BLR photons occurring in the Klein–Nishina regime. The γ-ray emission of SBS 0846+513 is explained by IC scattering of dusty torus photons, which puts the emission region outside the BLR and thus under the Thomson regime. Therefore, the observed curvature of SBS 0846+513 could be intrinsic to the particle energy distribution. The presence of curvature in the γ-ray spectrum and flux variability amplitudes of some of the RL-NLSy1 galaxies suggests that these sources could be akin to low/moderate jet power flat spectrum radio quasars.

  15. Jet drifts and flips in radio galaxies as probes of the historical evolution of spin axis in supermassive black holes

    NASA Astrophysics Data System (ADS)

    Saripalli, Lakshmi; Subrahmanyan, Ravi; Hall Roberts, David

    2015-08-01

    Jets in radio galaxies create twin lobes of synchrotron plasma on opposite sides of the host elliptical. The jets are believed to emerge along the spin axis of the central supermassive black hole. The history of evolution in spin axis is traced in the off axis distortions in the radio structure. We have analyzed the radio structures in a large sample of distorted radio galaxies to examine black hole spin axis behavior. These sources are selected specifically to have low axial-ratio structures and hence off-axis distortions that are, however, unbiased with respect to the nature of the distortions.We have imaged 52 radio galaxies having length to width ratio less than 1 to obtain detailed radio structures that enable a tracing of the origin of the off-axis radio emission. The unique sample consists of radio sources where the off axis radio emission originates from strategic locations - regions closer to the host galaxy and from the outer ends of the jets. A third category consists of sources where there is only a swathe of radio emission nearly orthogonal to the radio axis and passing through the central radio core.Our study has highlighted the potential of radio galaxies in tracing black hole spin axis changes over time; we use the occurrence rates of the different categories of sources to derive occurrence rates of drifts and flips in black hole axis. Since the host galaxies are an unbiased sampling of luminous elliptical galaxies, the rates derived are relevant to this parent population (Roberts, Cohen, Lu, Saripalli and Subrahmanyan, 2015, arXiv150203954; Roberts, Saripalli, Subrahmanyan, 2015, arXiv150302021).

  16. Integral field spectroscopy of the circum-nuclear region of the radio Galaxy Pictor A

    NASA Astrophysics Data System (ADS)

    Couto, Guilherme S.; Storchi-Bergmann, Thaisa; Robinson, Andrew; Riffel, Rogemar A.; Kharb, Preeti; Lena, Davide; Schnorr-Müller, Allan

    2016-05-01

    We present optical integral field spectroscopy of the inner 2.5 × 3.4 kpc2 of the broad-line radio galaxy Pictor A, at a spatial resolution of ≈400 pc. Line emission is observed over the whole field of view, being strongest at the nucleus and in an elongated linear feature (ELF) crossing the nucleus from the south-west to the north-east along PA ≈70°. Although the broad double-peaked Hα line and the [O I]6300/Hα and [S II]6717+31/Hα ratios are typical of active galactic nuclei (AGNs), the [N II]6584/Hα ratio (0.15-0.25) is unusually low. We suggest that this is due to the unusually low metallicity of the gas. Centroid velocity maps show mostly blueshifts to the south and redshifts to the north of the nucleus, but the velocity field is not well fitted by a rotation model. Velocity dispersions are low (<100 km s- 1 ) along the ELF, ruling out a jet-cloud interaction as the origin of this structure. The ELF shows both blueshifts and redshifts in channel maps, suggesting that it is close to the plane of the sky. The ELF is evidently photoionized by the AGN, but its kinematics and inferred low metallicity suggest that this structure may have originated in a past merger event with another galaxy. We suggest that the gas acquired in this interaction may be feeding the ELF.

  17. Hubble Space Telescope imaging of a radio-quiet galaxy at redshift z = 3.4

    NASA Technical Reports Server (NTRS)

    Giavalisco, Mauro; Macchetto, F. Duccio; Madau, Piero; Sparks, William B.

    1995-01-01

    We have observed with the Wide Field/Planetary Camera (WF/PC) on the Hubble Space Telescope (HST) a radio-quiet Ly alpha-emitting galaxy at redshift z = 3.428 (G2 below). The images probe the rest-frame UV light around 1250 A with an angular resolution of approx. = 0.1 sec, corresponding to 1.4 h(exp -1, sub 50) kpc at redshift z = 3.4 (in this Letter we use q(sub 0) = 0 and H(sub 0) = 50 h(exp -1, sub 50) km/s/Mpc). The light profile of the central approx. 10h(exp -1, sub 50) kpc region is well fitted by an r(exp 1/4) law with r(sub e) approx. = 1.3 h(exp -1, sub 50) kpc, suggesting a dynamically relaxed state. The outer regions are characterized by the presence of substructures, such as an elongated formation and low surface brightness nebulosities. The isophotal analysis shows no evidence of an active galactic nuclei (AGN)-like unresolved source in the center. The structural properties of G2 are consistent with a dynamically hot stellar system observed during an early phase of star formation, very likely the progenitor of an elliptical or the bulge of a spiral galaxy.

  18. Jet-Intracluster Medium Interactions of the Head Tail Radio Galaxy 3C 129

    NASA Technical Reports Server (NTRS)

    Krawczynski, Henric S. W.

    2005-01-01

    The 50 ksec XMM observations of the galaxy cluster 3C 129 were taken as scheduled, and the data are of good quality. We analyzed the data in the following way. After standard cleaning, we flat-fielded the XMM surface brightness maps. Combining the data from the EPIC MOS and PN Camera CCDs, we performed a cross-correlation analysis of the X-ray surface brightness distribution with the 1.4 GHz VLA radio map. We found evidence for cavities in the X-ray emitting Intra-Cluster Medium (ICM) associated with the radio tail of the head-tail radio galaxy 3C 129. This discovery is very interesting as it excludes the presence of a large fraction of thermal plasma in the radio tail. Together with the observation of an apparent pressure mismatch between the radio plasma and the ICM, and an upper limit on the magnetic field inside the radio tail (from the radio spectral indices map) the observation implies that the tail pressure is dominated either by low-energy electrons/positrons, or, by relativistic protons. Furthermore, we studied the energy spectrum of an X-ray "hot-spot" associated with the head of the radio galaxy 3C 129. It seems likely that the X-ray hot-spot originates from shocked gas in front of the radio galaxy. , The analysis turned out to be much more difficult than anticipated. The main reason is the lack of a comprehensive, publicly available background model that is key for the analysis of extended sources. Small groups like our do not have the man-power to come up with a background model themselves. We used the model from Read & Ponman (A&A 409, 395, 2003). However, the background subtracted X-ray surface brightness maps show a bright ring in the outer 20% of the camera. We tried to get rid of this ring and contacted the XMM helpdesk and Read & Ponman, the authors of the background paper. However, up to this day, we did not entirely succeed to remove the brightness enhancement at the outer parts of the camera. Unfortunately, our results are somewhat sensitive

  19. Induced star formation and morphological evolution in very high redshift radio galaxies

    SciTech Connect

    van Breugel, W.J.M., LLNL

    1997-10-01

    Near-infrared, sub-arcsecond seeing images obtained with the W M Keck I Telescope of show strong evolution at rest-frame optical wavelengths in the morphologies of high redshift radio galaxies (HzRGs) with 1 9 < z < 4 4 The structures change from large-scale low surface brightness regions surrounding bright, multiple component and often radio-aligned features at z > 3, to much more compact and symmetrical shapes at z < 3 The linear sizes ({approximately} 10 kpc) and luminosities (M{sub B} {approximately} -20 to -22) of the individual components in the z > 3 HzRGs are similar to the total sizes and luminosities of normal, radio-quiet, star forming galaxies seen at z = 3 - 4 `R`-band, 0 1`` resolution images with the Hubble Space Telescope of one of these HzRGs, 4C41 17 at z = 3 800, show that at rest-frame UV wavelengths the galaxy morphology breaks up in even smaller, {approximately} 1 kpc-sized components embedded in a large halo of low suface brightness emission The brightest UV emission is from a radio-aligned, edge-brightened feature (4C41 17.North) downstream from a bright radio knot A narrow-band Ly-{alpha} image, also obtained with HST, shows an arc-shaped Ly-{alpha} feature at this same location, suggestive of a strong jet/cloud collision Deep spectropolarimetric observations with the W M Keck II Telescope of 4C41 17 show that the radio-aligned UV continuum is unpolarized Instead the total light spectrum shows ahsorption lines and P-Cygni type features that are similar to the radio-quiet z = 3 - 4 star forming galaxies This shows that the rest-frame UV light in 4C41 17 is dominated by starlight, not scattered light from a hidden AGN The combined HST and Keck data suggest that the radio--aligned rest-frame UV continuum is probably caused by jet-induced star formation The strong morphological evolution suggests that we see the first evidence for the assemblage of massive ellipticals, the parent population of very powerful radio sources at much lower redshifts

  20. Correlations between the far-infrared, radio, and blue luminosities of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Condon, J. J.; Anderson, M. L.; Helou, G.

    1991-01-01

    FIR-radio luminosity correlations are presently derived for two statistically complete samples spanning a wide luminosity range. While observed correlations are tight, they are not linear; the observed scattering is mostly intrinsic. An empirical correction to the radio luminosities, based on observed blue luminosities, makes the corrected FIR-radio correlation linear and eliminates most of the residual variance. A two-component model that is consistent with the improved correlation is proposed for the heating luminosity within galaxies. The first, radio-loud component contains young massive stars that heat the dust, while contributing to the cool cirrus dust-heating interstellar radiation field. The second, radio-quiet component is made up of less massive older stars.

  1. A kiloparsec-scale internal shock collision in the jet of a nearby radio galaxy.

    PubMed

    Meyer, Eileen T; Georganopoulos, Markos; Sparks, William B; Perlman, Eric; van der Marel, Roeland P; Anderson, Jay; Sohn, Sangmo Tony; Biretta, John; Norman, Colin; Chiaberge, Marco

    2015-05-28

    Jets of highly energized plasma with relativistic velocities are associated with black holes ranging in mass from a few times that of the Sun to the billion-solar-mass black holes at the centres of galaxies. A popular but unconfirmed hypothesis to explain how the plasma is energized is the 'internal shock model', in which the relativistic flow is unsteady. Faster components in the jet catch up to and collide with slower ones, leading to internal shocks that accelerate particles and generate magnetic fields. This mechanism can explain the variable, high-energy emission from a diverse set of objects, with the best indirect evidence being the unseen fast relativistic flow inferred to energize slower components in X-ray binary jets. Mapping of the kinematic profiles in resolved jets has revealed precessing and helical patterns in X-ray binaries, apparent superluminal motions, and the ejection of knots (bright components) from standing shocks in the jets of active galaxies. Observations revealing the structure and evolution of an internal shock in action have, however, remained elusive, hindering measurement of the physical parameters and ultimate efficiency of the mechanism. Here we report observations of a collision between two knots in the jet of nearby radio galaxy 3C 264. A bright knot with an apparent speed of (7.0 ± 0.8)c, where c is the speed of light in a vacuum, is in the incipient stages of a collision with a slower-moving knot of speed (1.8 ± 0.5)c just downstream, resulting in brightening of both knots--as seen in the most recent epoch of imaging. PMID:26017450

  2. Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action in the Seyfert Galaxy IC 5063

    NASA Astrophysics Data System (ADS)

    Morganti, R.; Oosterloo, T. A.; Oonk, J. B. R.; Frieswijk, W.; Tadhunter, C. N.

    2015-12-01

    High-resolution (0.5 arcsec) CO(2-1) observations performed with the Atacama Large Millimetre/submillimetre Array have been used to trace the kinematics of the molecular gas in the Seyfert 2 galaxy{IC 5063}. Although one of the most radio-loud Seyfert galaxy, IC 5063 is a relatively weak radio source (P1.4GHz=3 ×1023 W Hz-1). The data reveal that the kinematics of the gas is very complex. A fast outflow of molecular gas extends along the entire radio jet (˜ 1 kpc), with the highest outflow velocities about 0.5 kpc from the nucleus, at the location of the brighter hot-spot in the W lobe. All the observed characteristics can be described by a scenario of a radio plasma jet expanding into a clumpy medium, interacting directly with the clouds and inflating a cocoon that drives a lateral outflow into the interstellar medium. This suggests that most of the observed cold molecular outflow is due to fast cooling of the gas after the passage of a shock and that it is the end product of the cooling process.

  3. A Giant Metrewave Radio Telescope Multifrequency Radio Study of the Isothermal Core of the Poor Galaxy Cluster AWM 4

    NASA Astrophysics Data System (ADS)

    Giacintucci, Simona; Vrtilek, Jan M.; Murgia, Matteo; Raychaudhury, Somak; O'Sullivan, Ewan J.; Venturi, Tiziana; David, Laurence P.; Mazzotta, Pasquale; Clarke, Tracy E.; Athreya, Ramana M.

    2008-07-01

    We present a detailed radio morphological study and spectral analysis of the wide-angle tail radio source 4C +24.36 associated with the dominant galaxy in the relaxed galaxy cluster AWM 4. Our study is based on new high-sensitivity GMRT observations at 235, 327, and 610 MHz and on literature and archival data at other frequencies. We find that the source major axis is likely oriented at a small angle with respect to the plane of the sky. The wide-angle tail morphology can be reasonably explained by adopting a simple hydrodynamical model in which both ram pressure (driven by the motion of the host galaxy) and buoyancy forces contribute to bend the radio structure. The spectral index progressively steepens along the source major axis from α ~ 0.3 in the region close to the radio nucleus to beyond 1.5 in the lobes. The results of the analysis of the spectral index image allow us to derive an estimate of the radiative age of the source of ~160 Myr. The cluster X-ray-emitting gas has a relaxed morphology and short cooling time, but its temperature profile is isothermal out to at least 160 kpc from the center. Therefore, we seek evidence of energy ejection from the central AGN to prevent catastrophic cooling. We find that the energy injected by 4C +24.36 in the form of synchrotron luminosity during its lifetime is far less than the energy required to maintain the high gas temperature in the core. We also find that it is not possible for the central source to eject the requisite energy in the intracluster gas in terms of the enthalpy of buoyant bubbles of relativistic fluid, without creating discernible large cavities in the existing X-ray XMM-Newton observations.

  4. A DISTANT RADIO MINI-HALO IN THE PHOENIX GALAXY CLUSTER

    SciTech Connect

    Van Weeren, R. J.; Andrade-Santos, F.; Forman, W. R.; Jones, C.; Intema, H. T.; Lal, D. V.; Brüggen, M.; De Gasperin, F.; Hoeft, M.; Nuza, S. E.; Röttgering, H. J. A.; Stroe, A.

    2014-05-10

    We report the discovery of extended radio emission in the Phoenix cluster (SPT-CL J2344-4243, z = 0.596) with the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. The diffuse emission extends over a region of at least 400-500 kpc and surrounds the central radio source of the Brightest Cluster Galaxy, but does not appear to be directly associated with it. We classify the diffuse emission as a radio mini-halo, making it the currently most distant mini-halo known. Radio mini-halos have been explained by synchrotron emitting particles re-accelerated via turbulence, possibly induced by gas sloshing generated from a minor merger event. Chandra observations show a non-concentric X-ray surface brightness distribution, which is consistent with this sloshing interpretation. The mini-halo has a flux density of 17 ± 5 mJy, resulting in a 1.4 GHz radio power of (10.4 ± 3.5) × 10{sup 24} W Hz{sup –1}. The combined cluster emission, which includes the central compact radio source, is also detected in a shallow GMRT 156 MHz observation and together with the 610 MHz data we compute a spectral index of –0.84 ± 0.12 for the overall cluster radio emission. Given that mini-halos typically have steeper radio spectra than cluster radio galaxies, this spectral index should be taken as an upper limit for the mini-halo.

  5. Determining the radio active galactic nuclei contribution to the radio-far-infrared correlation using the black hole Fundamental Plane relation

    NASA Astrophysics Data System (ADS)

    Wong, O. Ivy; Koss, M. J.; Schawinski, K.; Kapińska, A. D.; Lamperti, I.; Oh, K.; Ricci, C.; Berney, S.; Trakhtenbrot, B.

    2016-08-01

    We investigate the 1.4-GHz radio properties of 92 nearby (z < 0.05) ultra-hard X-ray selected active galactic nuclei (AGNs) from the Swift Burst Alert Telescope (BAT) sample. Through the ultra-hard X-ray selection, we minimize the biases against obscured or Compton-thick AGNs as well as confusion with emission derived from star formation that typically affect AGN samples selected from the ultraviolet, optical and infrared wavelengths. We find that all the objects in our sample of nearby, ultra-hard X-ray selected AGNs are radio quiet; 83 per cent of the objects are classed as high-excitation galaxies and 17 per cent as low-excitation galaxies. While these low-z BAT sources follow the radio-far-infrared correlation in a similar fashion to star-forming galaxies, our analysis finds that there is still significant AGN contribution in the observed radio emission from these radio-quiet AGNs. In fact, the majority of our BAT sample occupy the same X-ray-radio Fundamental Plane as has been observed in other samples, which include radio-loud AGNs - evidence that the observed radio emission (albeit weak) is connected to the AGN accretion mechanism, rather than star formation.

  6. The Evolution of the Acceleration Mechanisms of Cosmic Rays and Relativistic Electrons in Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Tsvyk, N.

    There are estimated an efficacy for different acceleration mechanisms of e- and p-cosmic rays (CRs) in radio galaxies, using an evolution model for jet gaps and shock fronts with a turbulence. It is shown that diffusion shock acceleration of the CRs is the most efficient mechanism in the FR II radio galaxies (RGs). At the same time, there are a break-pinch mechanism (for a short-term at a jet gap moment), and a stochastic turbulent mechanism (for an all time when RG exist), that to play a grate part in acceleration of the CRs (give to 10-50 % of the all acceleration efficiency). It is predicted what properties of radio emission spectra give us to recognize a type of acceleration mechanisms of e-CR in the RG.

  7. Cluster candidates around low-power radio galaxies at z ∼ 1-2 in cosmos

    SciTech Connect

    Castignani, G.; Celotti, A.; De Zotti, G.; Chiaberge, M.; Norman, C.

    2014-09-10

    We search for high-redshift (z ∼1-2) galaxy clusters using low power radio galaxies (FR I) as beacons and our newly developed Poisson probability method based on photometric redshift information and galaxy number counts. We use a sample of 32 FR Is within the Cosmic Evolution Survey (COSMOS) field from the Chiaberge et al. catalog. We derive a reliable subsample of 21 bona fide low luminosity radio galaxies (LLRGs) and a subsample of 11 high luminosity radio galaxies (HLRGs), on the basis of photometric redshift information and NRAO VLA Sky Survey radio fluxes. The LLRGs are selected to have 1.4 GHz rest frame luminosities lower than the fiducial FR I/FR II divide. This also allows us to estimate the comoving space density of sources with L {sub 1.4} ≅ 10{sup 32.3} erg s{sup –1} Hz{sup –1} at z ≅ 1.1, which strengthens the case for a strong cosmological evolution of these sources. In the fields of the LLRGs and HLRGs we find evidence that 14 and 8 of them reside in rich groups or galaxy clusters, respectively. Thus, overdensities are found around ∼70% of the FR Is, independently of the considered subsample. This rate is in agreement with the fraction found for low redshift FR Is and it is significantly higher than that for FR IIs at all redshifts. Although our method is primarily introduced for the COSMOS survey, it may be applied to both present and future wide field surveys such as Sloan Digital Sky Survey Stripe 82, LSST, and Euclid. Furthermore, cluster candidates found with our method are excellent targets for next generation space telescopes such as James Webb Space Telescope.

  8. THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Padovani, P.; Mainieri, V.; Rosati, P.; Miller, N.; Kellermann, K. I.; Tozzi, P.

    2011-10-10

    We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 {mu}Jy at the field center and redshift {approx}5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P {approx}> 3 x 10{sup 24} W Hz{sup -1}) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for {approx}30% of the sample and {approx}60% of all AGNs, and outnumbering radio-loud AGNs at {approx}< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

  9. The VLA Survey of Chandra Deep Field South. V. Evolution and Luminosity Functions of Sub-millijansky Radio Sources and the Issue of Radio Emission in Radio-quiet Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Padovani, P.; Miller, N.; Kellermann, K. I.; Mainieri, V.; Rosati, P.; Tozzi, P.

    2011-10-01

    We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 μJy at the field center and redshift ~5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P >~ 3 × 1024 W Hz-1) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for ~30% of the sample and ~60% of all AGNs, and outnumbering radio-loud AGNs at <~ 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

  10. Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    2000-01-01

    The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with correlations between the X-ray and radio emission used on one hand to argue for a nuclear origin for the X-rays, and on the other hand for a thermal origin. Our observations (normally between 10 and 25 ks in length) routinely detected the target sources, and demonstrated that both resolved (thermal) and unresolved X-ray emission are typically present. Highlights of our work included two of the first detections of high-power radio galaxies at high redshift, 3C 280 and 3C 220.1. When combined with the work of two other groups, we find that of the 38 radio galaxies at z > 0.6 in the 3CRR sample, 12 were observed in ROSAT pointed observations and 9 were detected with the four most significant detections exhibiting source extent, including 3C 280 and 3C 220.1. Moreover, we discovered extended emission around five 3CRR quasars at redshift greater than about 0.4, one of which is at z > 0.6. Unification predicts that the X-ray environments of powerful radio galaxies and quasars should be similar, and our results show that powerful radio sources are finding some of the highest-redshift X-ray clusters known to date, pointing to deep gravitational potential wells early in the Universe.

  11. VLBI, MERLIN and HST observations of the giant radio galaxy 3C 236

    NASA Astrophysics Data System (ADS)

    Schilizzi, R. T.; Tian, W. W.; Conway, J. E.; Nan, R.; Miley, G. K.; Barthel, P. D.; Normandeau, M.; Dallacasa, D.; Gurvits, L. I.

    2001-03-01

    We present VLBI and MERLIN data at 1.66 and 4.99 GHz on the central component coincident with the nucleus of the giant radio galaxy, 3C 236. The nuclear radio structure is composed of two complexes of emission which are resolved on scales from 1 milli-arcsec (mas) to 1 arcsec. Oscillations with an amplitude of ~ 5degr can be seen in the compact radio structure. Spectral index distributions are plotted at angular resolutions of 10 and 25 mas and allow us to identify the core component in the south-east emission complex. Re-examination of the HST WFPC-2 image of 3C 236 by de Koff et al. (\\cite{dekoff}), shows that the normal to the dust disk in the nucleus is ~ 30degr from the plane of the sky and within 12degr of parallel to the overall orientation of the radio source. We suggest that the radio axis is also at an angle of ~ 30degr to the plane of the sky and that the north-west jet is on the approaching side. This orientation implies an overall size of 4.5 Mpc (H_0 = 75 km s-1 Mpc-1, q_0 = 0.5) for 3C 236. The coincidence of a dust feature and the south-east compact jet, within the astrometric errors, leads us to suggest that the dust may be in the form of a cloud encountered by the jet in the first ~ 400 pc of its journey out from the nucleus. One-sided emission at 5 GHz on 1 mas scales would suggest that the jets are ejected initially at <= 35degr to the line of sight, but this is difficult to reconcile with the obvious orientation stability of the jet system as a whole. Free-free absorption of the counter-jet may be an alternative explanation for the one-sideness. At the resolution of WSRT data at 327 MHz, the jet to the south-east is apparently continuous over a distance of 2.5 Mpc, making this the largest jet known in the universe. It is likely, however, that activity in the nucleus of 3C 236 is episodic but with a shorter duty cycle than in the double-double sources studied by Schoenmakers et al. (\\cite{schoenmakers}) and Kaiser et al. (\\cite{kaiser}).

  12. VLT spectropolarimetry of two powerful radio galaxies at z ~ 1.4: ultraviolet continuum, emission-line properties and the nature of high-redshift dust

    NASA Astrophysics Data System (ADS)

    Solórzano-Iñarrea, C.; Best, P. N.; Röttgering, H. J. A.; Cimatti, A.

    2004-07-01

    Deep spectropolarimetric observations, obtained with the Very Large Telescope, are presented for two powerful radio galaxies, 0850-206 (z = 1.3373) and 1303+091 (z = 1.4093). These observations cover the rest-frame wavelength range ~1450-3750 Å. New radio observations and continuum images of the same sources are also presented. These galaxies are the first two observed from a complete sample of nine radio sources with redshifts in the range 1.3 <= z <= 1.5 (selected from the equatorial sample of powerful radio sources of Best, Röttgering & Lehnert), as part of a project aimed to investigate the multicomponent nature of the ultraviolet (UV) continuum in radio galaxies and, in particular, any variations of the continuum properties with the radio source age. The larger radio source of the two, 0850-206, presents a high continuum fractional polarization, averaging 17 per cent across the observed wavelength range and reaching 24 per cent at rest-frame wavelengths of <~2000 Å. The smaller radio source, 1303+091, shows a lower continuum polarization, averaging 8 per cent and rising to 11 per cent for rest-frame wavelengths >~3000 Å. For both galaxies, the position angle of the electric vector is generally constant with wavelength and within ~15° of perpendicular to the radio axis. Both their total flux spectra and polarized flux spectra reveal the 2200-Ådust feature, and comparison with dust scattering models suggests that the composition of the dust in these galaxies is similar to that of Galactic dust. In 0850-206, scattered quasar radiation dominates the UV continuum emission, with the nebular continuum accounting for no more than ~22 per cent and no requirement for any additional emission component such as emission from young stars. In contrast, in 1303+091, unpolarized radiation could be a major constituent of the UV continuum emission, with starlight accounting for up to ~50 per cent and the nebular continuum accounting for ~11 per cent. The emission

  13. Fueling the central engine of radio galaxies. III. Molecular gas and star formation efficiency of 3C 293

    NASA Astrophysics Data System (ADS)

    Labiano, A.; García-Burillo, S.; Combes, F.; Usero, A.; Soria-Ruiz, R.; Piqueras López, J.; Fuente, A.; Hunt, L.; Neri, R.

    2014-04-01

    Context. Powerful radio galaxies show evidence of ongoing active galactic nuclei (AGN) feedback, mainly in the form of fast, massive outflows. But it is not clear how these outflows affect the star formation of their hosts. Aims: We investigate the different manifestations of AGN feedback in the evolved, powerful radio source 3C 293 and their impact on the molecular gas of its host galaxy, which harbors young star-forming regions and fast outflows of H i and ionized gas. Methods: We study the distribution and kinematics of the molecular gas of 3C 293 using high spatial resolution observations of the 12CO(1-0) and 12CO(2-1) lines, and the 3 mm and 1 continuum taken with the IRAM Plateau de Bure interferometer. We mapped the molecular gas of 3C 293 and compared it with the dust and star-formation images of the host. We searched for signatures of outflow motions in the CO kinematics, and re-examined the evidence of outflowing gas in the H i spectra. We also derived the star formation rate (SFR) and star formation efficiency (SFE) of the host with all available SFR tracers from the literature, and compared them with the SFE of young and evolved radio galaxies and normal star-forming galaxies. Results: The 12CO(1-0) emission line shows that the molecular gas in 3C 293 is distributed along a massive (M(H2) ~ 2.2 × 1010M⊙) ~24″(21 kpc-) diameter warped disk, that rotates around the AGN. Our data show that the dust and the star formation are clearly associated with the CO disk. The 12CO(2-1) emission is located in the inner 7 kpc (diameter) region around the AGN, coincident with the inner part of the 12CO(1-0) disk. Both the 12CO(1-0) and 12CO(2-1) spectra reveal the presence of an absorber against the central regions of 3C 293 that is associated with the disk. We do not detect any fast (≳500 km s-1) outflow motions in the cold molecular gas. The host of 3C 293 shows an SFE consistent with the Kennicutt-Schmidt law of normal galaxies and young radio galaxies, and it

  14. The hot and cold interstellar matter of early type galaxies and their radio emission

    NASA Technical Reports Server (NTRS)

    Kim, Dong-Woo; Fabbiano, Giuseppina

    1990-01-01

    Over the last few years, the knowledge of the interstellar matter (ISM) of early type galaxies has increased dramatically. Many early type galaxies are now known to have ISM in three different phases: cold (neutral hydrogen (HI), dust and molecular material), warm (ionized) and hot (S-ray emitting) gas. Early type galaxies have smaller masses of cold ISM (10 to the 7th power - 10 to the 8th power solar mass; Jura et al. 1987) than later type spiral galaxies, while they have far more hot gas (10 to the 9th power - 10 to the tenth power solar mass; Forman et al. 1985, Canizares et al. 1987). In order to understand the relationship between the different phases of the ISM and the role of the ISM in fueling radio continuum sources and star formation, researchers compared observational data from a wide range of wavelengths.

  15. GAMA/WiggleZ: the 1.4 GHz radio luminosity functions of high- and low-excitation radio galaxies and their redshift evolution to z = 0.75

    NASA Astrophysics Data System (ADS)

    Pracy, Michael B.; Ching, John H. Y.; Sadler, Elaine M.; Croom, Scott M.; Baldry, I. K.; Bland-Hawthorn, Joss; Brough, S.; Brown, M. J. I.; Couch, Warrick J.; Davis, Tamara M.; Drinkwater, Michael J.; Hopkins, A. M.; Jarvis, M. J.; Jelliffe, Ben; Jurek, Russell J.; Loveday, J.; Pimbblet, K. A.; Prescott, M.; Wisnioski, Emily; Woods, David

    2016-07-01

    We present radio active galactic nuclei (AGN) luminosity functions over the redshift range 0.005 < z < 0.75. The sample from which the luminosity functions are constructed is an optical spectroscopic survey of radio galaxies, identified from matched Faint Images of the Radio Sky at Twenty-cm survey (FIRST) sources and Sloan Digital Sky Survey images. The radio AGN are separated into low-excitation radio galaxies (LERGs) and high-excitation radio galaxies (HERGs) using the optical spectra. We derive radio luminosity functions for LERGs and HERGs separately in the three redshift bins (0.005 < z < 0.3, 0.3 < z < 0.5 and 0.5 < z < 0.75). The radio luminosity functions can be well described by a double power law. Assuming this double power-law shape the LERG population displays little or no evolution over this redshift range evolving as {˜ } (1+z)^{0.06^{+0.17}_{-0.18}} assuming pure density evolution or {˜ } (1+z)^{0.46^{+0.22}_{-0.24}} assuming pure luminosity evolution. In contrast, the HERG population evolves more rapidly, best fitted by {˜ } (1+z)^{2.93^{+0.46}_{-0.47}} assuming a double power-law shape and pure density evolution. If a pure luminosity model is assumed, the best-fitting HERG evolution is parametrized by {˜ } (1+z)^{7.41^{+0.79}_{-1.33}}. The characteristic break in the radio luminosity function occurs at a significantly higher power (≳1 dex) for the HERG population in comparison to the LERGs. This is consistent with the two populations representing fundamentally different accretion modes.

  16. NuSTAR reveals the Comptonizing corona of the broad-line radio galaxy 3C 382

    SciTech Connect

    Ballantyne, D. R.; Bollenbacher, J. M.; Brenneman, L. W.; Madsen, K. K.; Baloković, M.; Harrison, F. A.; Walton, D. J.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Lohfink, A. M.; Marinucci, A.; Markwardt, C. B.; Zhang, W. W.; Stern, D.

    2014-10-10

    Broad-line radio galaxies (BLRGs) are active galactic nuclei that produce powerful, large-scale radio jets, but appear as Seyfert 1 galaxies in their optical spectra. In the X-ray band, BLRGs also appear like Seyfert galaxies, but with flatter spectra and weaker reflection features. One explanation for these properties is that the X-ray continuum is diluted by emission from the jet. Here, we present two NuSTAR observations of the BLRG 3C 382 that show clear evidence that the continuum of this source is dominated by thermal Comptonization, as in Seyfert 1 galaxies. The two observations were separated by over a year and found 3C 382 in different states separated by a factor of 1.7 in flux. The lower flux spectrum has a photon-index of Γ=1.68{sub −0.02}{sup +0.03}, while the photon-index of the higher flux spectrum is Γ=1.78{sub −0.03}{sup +0.02}. Thermal and anisotropic Comptonization models provide an excellent fit to both spectra and show that the coronal plasma cooled from kT{sub e} = 330 ± 30 keV in the low flux data to 231{sub −88}{sup +50} keV in the high flux observation. This cooling behavior is typical of Comptonizing corona in Seyfert galaxies and is distinct from the variations observed in jet-dominated sources. In the high flux observation, simultaneous Swift data are leveraged to obtain a broadband spectral energy distribution and indicates that the corona intercepts ∼10% of the optical and ultraviolet emitting accretion disk. 3C 382 exhibits very weak reflection features, with no detectable relativistic Fe Kα line, that may be best explained by an outflowing corona combined with an ionized inner accretion disk.

  17. Galaxy interactions and strength of nuclear activity

    NASA Technical Reports Server (NTRS)

    Simkin, S. M.

    1990-01-01

    Analysis of data in the literature for differential velocities and projected separations of nearby Seyfert galaxies with possible companions shows a clear difference in projected separations between type 1's and type 2's. This kinematic difference between the two activity classes reinforces other independent evidence that their different nuclear characteristics are related to a non-nuclear physical distinction between the two classes. The differential velocities and projected separations of the galaxy pairs in this sample yield mean galaxy masses, sizes, and mass to light ratios which are consistent with those found by the statistical methods of Karachentsev. Although the galaxy sample discussed here is too small and too poorly defined to provide robust support for these conclusions, the results strongly suggest that nuclear activity in Seyfert galaxies is associated with gravitational perturbations from companion galaxies, and that there are physical distinctions between the host companions of Seyfert 1 and Seyfert 2 nuclei which may depend both on the environment and the structure of the host galaxy itself.

  18. X-raying the Winds of Luminous Active Galaxies

    NASA Astrophysics Data System (ADS)

    Brandt, W. N.; Chartas, G.; Gallagher, S. C.; Gibson, R. R.; Miller, B. P.

    2009-12-01

    We briefly describe some recent observational results, mainly at X-ray wavelengths, on the winds of luminous active galactic nuclei (AGNs). These winds likely play a significant role in galaxy feedback. Topics covered include (1) Relations between X-ray and UV absorption in Broad Absorption Line (BAL) and mini-BAL quasars; (2) X-ray absorption in radio-loud BAL quasars; and (3) Evidence for relativistic iron K BALs in the X-ray spectra of a few bright quasars. We also mention some key outstanding problems and prospects for future advances; e.g., with the International X-ray Observatory (IXO).

  19. Multiwavelength Study of Radio Loud Early-Type Galaxies from the B2 Sample

    NASA Astrophysics Data System (ADS)

    Sahu, Sheetal Kumar; Chaware, Laxmikant; Pandey, S. K.; Kulkarni, Samridhi; Pandge, M. B.; Chakradhari, N. K.

    2014-07-01

    We present multiwavelength study of a sample of radio loud early-type galaxies chosen from the B2 sample. We performed surface photometry in BVR broad band filters and Hα narrow band filter on CCD images of sample galaxies using IGO 2m telescope, Pune (INDIA), to get radial profiles of various photometric and geometrical parameters that describe elliptical isophotes fitted to the 2D light distribution of the galaxies. The analysis of radial profiles of quantities such as the (local) surface brightness, the ellipticity, and the deviations from elliptical isophotes parametrized by the Fourier coefficients are main focus of our study. We generated color maps, residual maps, and dust extinction maps, Hα emission maps of the galaxies to study the morphology of the dust and ionized gas content present in the galaxies. We carried out detailed analysis of the properties of the dust present in our sample galaxies. Additionaly, we investigated properties of the dust in the central ~10 arcsec region of our sample galaxies using optical images available from the HST (WFPC2) data archive. We estimated mass and temperature of the dust, molecular gas mass, in the sample galaxies using FIR fluxes of the galaxies obtained from IRAS. We used spectroscopic data available from the SDSS (DR7) to get an estimate of the mass of the central super massive black-hole for B2 1257+28 (NGC 4874). We plotted rotation curve for coma cluster (Abell 1656), which indicates the presence of dark matter halo around the galaxy B2 1257+28.

  20. HYDRODYNAMIC MODELS OF RADIO GALAXY MORPHOLOGY: WINGED AND X-SHAPED SOURCES

    SciTech Connect

    Hodges-Kluck, Edmund J.; Reynolds, Christopher S.

    2011-05-20

    We present three-dimensional hydrodynamic models of radio galaxies interacting with initially relaxed hot atmospheres and explore the significant off-axis radio lobe structures that result under certain conditions. With a focus on the 'winged' and 'X-shaped' radio galaxy population, we confirm the importance of observed trends such as the connection of wing formation with jets co-aligned with the major axis of the surrounding atmosphere. These wings are formed substantially by the deflection of lobe plasma flowing back from the hot spots (backflow) and develop in two stages: supersonic expansion of an overpressured cocoon at early times followed by buoyant expansion at later times. We explore a limited parameter space of jet and atmosphere properties and find that the most prominent wings are produced when a decaying jet is injected into a small, dense, highly elliptical atmosphere. On the basis of this search, we argue that the deflection of backflow by gradients in the hot atmosphere is a strong candidate for forming observed wings but must work in tandem with some other mechanism for forming the initial wing channels. Our models indicate that lobe interaction with the hot atmosphere may play a dominant role in shaping the morphology of radio galaxies.

  1. FUELING LOBES OF RADIO GALAXIES: STATISTICAL PARTICLE ACCELERATION AND THE EXTRAGALACTIC {gamma}-RAY BACKGROUND

    SciTech Connect

    Massaro, F.; Ajello, M.

    2011-03-01

    The recent discovery of the {gamma}-ray emission from the lobes of the closest radio galaxy Centaurus A by Fermi implies the presence of high-energy electrons at least up to {gamma} {approx} 10{sup 5}-10{sup 6}. These high-energy electrons are required to interpret the observed {gamma}-ray radiation in terms of inverse Compton emission off the cosmic microwave background (IC/CMB), the widely accepted scenario to describe the X-ray emission of radio galaxy lobes. In this Letter, we consider the giant radio lobes of FR II radio galaxies showing that it is possible to maintain electrons at energies {gamma} {approx} 10{sup 5}-10{sup 6}, assuming an acceleration scenario (driven by turbulent magnetic fields) that compensates radiative losses. In addition, we consider the contribution to the diffuse extragalactic {gamma}-ray background due to the IC/CMB emission of FR IIs' lobes, showing its relevance in the keV to MeV energy range.

  2. Time-Dependence of VHE Gamma-Ray induced Pair Cascades in Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Roustazadeh, Parisa; Boettcher, Markus; Thrush, Samantha

    2016-04-01

    Recently, several intermediate frequency peaked BL Lac objects (IBL), low frequency peaked BL Lac objects (LBL) and flat spectrum radio quasars (FSRQ) were detected as very high energy ( VHE, E > 100 ˜ GeV) γ-ray sources. These discoveries suggest that γγ absorption and pair cascades might occur in those objects, leading to excess γ-ray emission which may be observable also in off-axis viewing directions (i.e., like in radio galaxies) when deflected by moderately strong magnetic fields. Here, we investigate the time dependence of the Compton γ-ray emission from such VHE γ-ray induced pair cascades. We show that the cascade emission is variable on time scales much shorter than the light-crossing time across the characteristic extent of the external radiation field, depending on the viewing angle and γ-ray energy. Thus, we find that the cascade Compton interpretation for the Fermi γ-ray emission from radio galaxies is still consistent with the day-scale variability detected in the Fermi γ-ray emission of radio galaxies, such as NGC 1275, which we use as a specific example.

  3. Relativistic and Slowing Down: The Flow in the Hotspots of Powerful Radio Galaxies and Quasars

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    2003-01-01

    The 'hotspots' of powerful radio galaxies (the compact, high brightness regions, where the jet flow collides with the intergalactic medium (IGM)) have been imaged in radio, optical and recently in X-ray frequencies. We propose a scheme that unifies their, at first sight, disparate broad band (radio to X-ray) spectral properties. This scheme involves a relativistic flow upstream of the hotspot that decelerates to the sub-relativistic speed of its inferred advance through the IGM and it is viewed at different angles to its direction of motion, as suggested by two independent orientation estimators (the presence or not of broad emission lines in their optical spectra and the core-to-extended radio luminosity). This scheme, besides providing an account of the hotspot spectral properties with jet orientation, it also suggests that the large-scale jets remain relativistic all the way to the hotspots.

  4. The radio source and bipolar nebulosity in the Seyfert galaxy NGC 3516

    NASA Technical Reports Server (NTRS)

    Miyaji, Takamitsu; Wilson, Andrew S.; Perez-Fournon, Ismael

    1992-01-01

    Results of radio continuum and optical emission-line observations of the type 1 Seyfert galaxy NGC 3516 are presented. The radio maps reveal an elongated one-sided curved structure, which comprises a series of small-scale 'blobs' and extends up to 4 kpc from the nucleus. This radio structure is aligned and cospatial with one side of the double-sided and highly symmetric Z-shaped emission-line structure. It is argued that these morphological features are associated with a bipolar gaseous outflow from the nucleus of NGC 3516. The radio 'blobs' are elongated roughly perpendicular to the apparent local direction of the outflow, a result which is interpreted in terms of synchrotron emission from outflow-driven shock waves.

  5. Particle accelerators in the hot spots of radio galaxy 3C 445, imaged with the VLT.

    PubMed

    Prieto, M Almudena; Brunetti, Gianfranco; Mack, Karl-Heinz

    2002-10-01

    Hot spots (HSs) are regions of enhanced radio emission produced by supersonic jets at the tip of the radio lobes of powerful radio sources. Obtained with the Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C 445 show bright knots embedded in diffuse optical emission distributed along the post-shock region created by the impact of the jet into the intergalactic medium. The observations reported here confirm that relativistic electrons are accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the diffuse emission tracing the rims of the front shock and the multiple knots demonstrate the presence of additional continuous re-acceleration processes of electrons (Fermi-II). PMID:12364799

  6. The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

    SciTech Connect

    Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard; Marshall, Kevin; Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver

    2014-10-10

    Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

  7. Extremely red objects in the fields of high redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Persson, S. E.; Mccarthy, P. J.; Dressler, Alan; Matthews, Keith

    1993-01-01

    We are engaged in a program of infrared imaging photometry of high redshift radio galaxies. The observations are being done using NICMOS2 and NICMOS3 arrays on the DuPont 100-inch telescope at Las Campanas Observatory. In addition, Persson and Matthews are measuring the spectral energy distributions of normal cluster galaxies in the redshift range 0 to 1. These measurements are being done with a 58 x 62 InSb array on the Palomar 5-m telescope. During the course of these observations we have imaged roughly 20 square arcminutes of sky to limiting magnitudes greater than 20 in the J, H, and K passbands (3 sigma in 3 square arcseconds). We have detected several relatively bright, extremely red, extended objects during the course of this work. Because the radio galaxy program requires Thuan-Gunn gri photometry, we are able to construct rough photometric energy distributions for many of the objects. A sample of the galaxy magnitudes within 4 arcseconds diameter is given. All the detections are real; either the objects show up at several wavelengths, or in subsets of the data. The reddest object in the table, 9ab'B' was found in a field of galaxies in a rich cluster at z = 0.4; 9ab'A' lies 8 arcseconds from it.

  8. Deep Hubble Space Telescope imaging of a compact radio galaxy at z = 2.390

    NASA Technical Reports Server (NTRS)

    Windhorst, Rogier; Mathis, Douglas F.; Keel, William C.

    1992-01-01

    The radio galaxy with the highest redshift in the Leiden-Berkeley Deep Survey, 53W002, is described and examined in terms of UV profile in relation to an early-type galaxy. The HST WFC images have a resolution of 0.2 arcsec FWHM, and the I- and V-band structures are assessed. The source is elongated in a manner similar to the Ly alpha cloud in V, and the structure is highly compact in I. The present object with a young starburst has very high central UV surface brightnesses relative to nearby luminous early-type galaxies, while the light profiles are similar. The data are concluded to suggest that 53W002 is a young galaxy that has a regular light profile at z = 2.390 even though it has been forming stars since not more than about 0.5 Gyr before z = 2.390. Such a scenario is consistent with concurrent dynamical collapse and star formation in the compact radio galaxy.

  9. Observational model of the ionized gas in Seyfert and radio-galaxy nuclei*

    PubMed Central

    Osterbrock, Donald E.

    1978-01-01

    Equivalent widths of the total emission-line Hβ in Seyfert 1, Seyfert 2, and intermediate-type Seyfert galaxies, expressed in terms of the featureless continuum, all have approximately the same frequency distribution. This suggests that the energy-input mechanism to both the narrow-line, low-density gas and the broad-line, high-density gas is photoionization by the featureless continuum. The reason for the weakness of the narrow emission lines in extreme Seyfert 1 galaxies is then the absorption of most of the ionizing photons in the dense gas near the central source. The statistics of line widths can be fitted by a model in which the dense gas has typical rotational velocity 5000 km/sec and typical turbulent velocity 2000 km/sec. A model is proposed in which the dense gas forms a rotating, turbulent disk with dimension ≈0.1 pc and height/diameter ≈2/5. Seyfert 2 galaxies are objects with little dense gas, and intermediate-type Seyfert galaxies are objects in which the dense gas is optically thin to ionizing radiation at least along the poles. Most radio galaxies have strong narrow emission lines, suggesting that escape of radio plasma can only occur where some ionizing photons can also escape from the dense gas. Other predictions, implications, and tests of this model are discussed. Images PMID:16592488

  10. Suppression of Star Formation in the Hosts of Low-excitation Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Pace, Cameron; Salim, Samir

    2016-02-01

    The feedback from radio-loud active galactic nuclei (R-AGNs) may help maintain low star-formation (SF) rates in their early-type hosts, but the observational evidence for this mechanism has been inconclusive. We study systematic differences of aggregate spectral energy distributions (SEDs) of various subsets of ∼4000 low-redshift R-AGNs from Best & Heckman with respect to (currently) inactive control samples selected to have matching redshift, stellar mass, population age, axis ratio, and environment. Aggregate SEDs, ranging from the ultraviolet (UV) through mid-infrared (mid-IR, 22 μm), were constructed using a Bayesian method that eliminates biases from non-detections in Galaxy Evolution Explorer and Wide-field Infrared Survey Explorer. We study rare high-excitation sources separately from low-excitation ones, which we split by environment and host properties. We find that both the UV and mid-IR emission of non-cluster R-AGNs (80% of sample) are suppressed by ∼0.2 dex relative to that of the control group, especially for moderately massive galaxies (log M* ≲ 11). The difference disappears for high-mass R-AGNs and for R-AGNs in clusters, where other, non-AGN quenching/maintenance mechanisms may dominate, or where the suppression of SF due to AGNs may persist between active phases of the central engine, perhaps because of the presence of a hot gaseous halo storing AGN energy. High-excitation (high accretion rate) sources, which make up 2% of the R-AGN sample, do not show any evidence of SF suppression (their UV is the same as in controls), but they exhibit a strong mid-IR excess due to AGN dust heating.

  11. Deep galaxy count predictions in the radio, infrared, and X-ray spectral bands

    NASA Technical Reports Server (NTRS)

    Treyer, Marie-Agnes; Silk, Joseph

    1993-01-01

    The existence of a dominant population of strongly evolving starburst sources at moderate redshift is a plausible explanation for the excess number of faint blue galaxies detected in deep sky surveys. Multiwavelength observations at faint magnitudes would allow the existence of such a population to be confirmed. We use observed luminosity correlations and physical properties of known starburst galaxies to predict their contribution to the deep radio, infrared, and X-ray counts, as well as to the diffuse extragalactic background radiation in these various spectral bands.

  12. A Search for Excess Galaxies around Distant Flat Spectrum Radio Quasars

    NASA Astrophysics Data System (ADS)

    Fried, J. W.

    1992-02-01

    We present deep direct imaging data of 14 radio-loud flat- spectrum quasars with redshifts between z = 1.7 and 3.4. Fugmann (1988) found a strong increase in foreground galaxy density towards a similar sample of quasars. He interpreted this as being due to gravitational lensing, which raises the background objects into flux limited samples. Our data do not show an excess of galaxies in the vicinities of the quasars. However, we do find two candidates for gravitationally lensed quasars.

  13. New View of X-Ray Jet Blasting Through Nearest Radio Galaxy

    NASA Astrophysics Data System (ADS)

    2003-04-01

    By combining radio and X-ray observations, astronomers have obtained their most detailed view yet of the effects a powerful galactic jet has as it blasts its way through stars and gas on its way out from the centre of a galaxy. New observations of our nearest neighbouring radio galaxy, Centaurus A, (10 million light years away in the southern sky) show intense X-rays in places where the fast-moving jet is apparently running into the gas and stars that make up the galaxy. Because Centaurus A is the nearest radio galaxy, it is a key object for understanding how all other radio galaxies work. Results from the research will be presented at the UK/Ireland National Astronomy Meeting in Dublin by Dr Martin Hardcastle of the University of Bristol. Only a small minority of galaxies have powerful jets of electrically charged particles but, where they are present, they can have profound effects on the galaxies they inhabit. They are believed to come from close to a central massive black hole and in many cases they extend for hundreds of thousands of light years. Astronomers have been aware of radio emission and visible light from such jets for many years, but more recently, scientists using the orbiting observatory Chandra have discovered that X-ray emission from jets is also common. The X-rays come from electrons carrying large amounts of energy - comparable with the energies reached in the accelerators used in particle physics experiments on Earth. The team working on Centaurus A, led by Dr Hardcastle, a Royal Society Research Fellow at the University of Bristol, and Dr Ralph Kraft, of the Harvard-Smithsonian Center for Astrophysics in the USA, observed its jet with both Chandra and the Very Large Array radio telescope in New Mexico. The radio observations, taken between 1991 and 2002, showed that parts of the jet are moving away from the centre of the galaxy at speeds of about half the speed of light. However, the regions of the jet that are emitting the most X-rays were

  14. A consequence of the asymmetry of jets in quasars and active nuclei of galaxies

    NASA Astrophysics Data System (ADS)

    Shklovsky, I. S.

    The possibility that radio emission of quasars and radio galaxies is a result of ejections of plasmoids issuing from the supercritical accretion on massive black holes at the center of galaxies is discussed. Evidence from observations of Cygnus A, Centaurus A, and Fornax A are cited to suggest that one-sided and two-sided jets occur near the center of galaxies. The ejection of a jet is shown to be a nonsymetrical event, thus allowing the possibility that all jets are one-sided, with two-sided jets actually being evidence for one remnant jet in the company of another remnant or an active event. The recoil velocity acquired by a black hole because of the ejection of plasmoids is modeled numerically. The black hole is determined to necessarily escape from the parent galaxy, which then ceases being a compact source. Short-lived quasars are therefore extinguished when super-critically accreting regimes end.

  15. KILOPARSEC-SCALE JETS IN THREE RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES

    SciTech Connect

    Richards, Joseph L.; Lister, Matthew L.

    2015-02-10

    We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array. We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20–70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a 45° bend is apparent in the third. Very Long Baseline Array images at 7.6 GHz reveal parsec-scale jet structures, in two cases with extended structure aligned with the inner regions of the kiloparsec-scale jets. Based on this alignment, the ratio of the radio core–luminosity to the optical luminosity, the jet/counter-jet intensity and extension length ratios, and moderate core brightness temperatures (≲10{sup 10} K), we conclude these jets are mildly relativistic (β≲0.3, δ∼1−1.5) and aligned at moderately small angles to the line of sight (10–15°). The derived kinematic ages of ∼10{sup 6}–10{sup 7} yr are much younger than radio galaxies but comparable to other NLS1s. Our results increase the number of radio-loud NLS1s with known kiloparsec-scale extensions from 7 to 10 and suggest that such extended emission may be common, at least among the brightest of these sources.

  16. The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

    NASA Technical Reports Server (NTRS)

    Terebey, S.; Fich, M.; Taylor, R.

    1999-01-01

    A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

  17. A multifrequency radio continuum and IRAS faint source survey of markarian galaxies

    NASA Technical Reports Server (NTRS)

    Bicay, M. D.; Kojoian, G.; Seal, J.; Dickinson, D. F.; Malkan, M. A.

    1995-01-01

    Results are presented from a multifrequency radio continumm survey of Markarian galaxies (MRKs) and are supplemented by IRAS infrared data from the Faint Source Survey. Radio data are presented for 899 MRKs observed at nu = 4.755 GHz with the National Radio Astronomy Observatory (NRAO)-Green Bank 300 foot (91 m) telescope, including nearly 88% of those objects in Markarian lists VI-XIV. In addition, 1.415 GHz measurements of 258 MRKs, over 30% of the MRKs accessible from the National Aeronomy and Ionosphere Center (NAIC)-Arecibo, are reported. Radio continuum observations of smaller numbers of MRKs were made at 10.63 GHz and at 23.1 GHz and are also presented. Infrared data from the IRAS Faint Source Survey (Ver. 2) are presented for 944 MRKs, with reasonably secure identifications extracted from the NASA/IPAC Extragalactic Database. MRKs exhibit the same canonical infrared characteristics as those reported for various other galaxy samples, that is well-known enhancement of the 25 micrometer/60 micrometer color ratio among Seyfert MRKs, and a clear tendency for MRKs with warmer 60 micrometer/100 micrometer colors to also possess cooler 12 micrometer/25 micrometer colors. In addition, non-Seyfert are found to obey the well-documented infrared/radio luminosity correlation, with the tightest correlation seen for starburst MRKs.

  18. The star formation rates of active galactic nuclei host galaxies

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Teimoorinia, Hossen; Rosario, David J.; Mendel, J. Trevor

    2016-05-01

    Using artificial neural network predictions of total infrared luminosities (LIR), we compare the host galaxy star formation rates (SFRs) of ˜21 000 optically selected active galactic nuclei (AGN), 466 low-excitation radio galaxies (LERGs) and 721 mid-IR-selected AGN. SFR offsets (ΔSFR) relative to a sample of star-forming `main-sequence' galaxies (matched in M⋆, z and local environment) are computed for the AGN hosts. Optically selected AGN exhibit a wide range of ΔSFR, with a distribution skewed to low SFRs and a median ΔSFR = -0.06 dex. The LERGs have SFRs that are shifted to even lower values with a median ΔSFR = -0.5 dex. In contrast, mid-IR-selected AGN have, on average, SFRs enhanced by a factor of ˜1.5. We interpret the different distributions of ΔSFR amongst the different AGN classes in the context of the relative contribution of triggering by galaxy mergers. Whereas the LERGs are predominantly fuelled through low accretion rate secular processes which are not accompanied by enhancements in SFR, mergers, which can simultaneously boost SFRs, most frequently lead to powerful, obscured AGN.

  19. The parsec-scale structure and evolution of the nearby Fanaroff-Riley type II radio galaxy Pictor A

    NASA Technical Reports Server (NTRS)

    Tingay, S. J.; Jauncey, D. L.; Reynolds, J. E.; Tzioumis, A. K.; McCulloch, P. M.; Ellingsen, S. P.; Costa, M. E.; Lovell, J. E. J.; Preston, R. A.; Simkin, S. M.

    2000-01-01

    We present very long baseline interferometry (VLBI) images of the core emission from a nearby bright FR II radio galaxy, Pictor A, revealing its parsec-scale jet structure and evolution for the first time.

  20. The X-Ray Core of the Low-Luminosity Radio Galaxy 3C346 and ASCA Spectroscopy to Test BL LAC/Radio Galaxy Unification

    NASA Technical Reports Server (NTRS)

    Worrall, Diana

    2000-01-01

    Radio galaxies are relatively faint sources for Advanced Spacecraft for Cosmology Astrophysics (ASCA), and so in order to get the best possible results from the observations two things have been necessary, both of which delayed the fast preparation of papers. Firstly, the best possible data screening and background subtraction were necessary to improve the signal-to-noise, and all our several initial analysis trials were discarded in favor of using FTOOLS versions 4.1 and above. Secondly, we found that the ASCA spectra were statistically too poor to discriminate well between non-thermal and thermal models, never mind the mixture of the two which we expected on the basis of our ROSAT spatial separation of components in radio galaxies. This means that in each case we have needed to combine the ASCA spectroscopy with analysis of data from other X-ray or radio observations in order to exploit the ASCA data to the full. Our analysis for 3C 346 has yielded the cleanest final result. This powerful radio galaxy at a redshift of 0.161, lies in a poor cluster, which we have separated well from the dominant X-ray component of unresolved emission using a spatial analysis of archival ROSAT data. We were then able to fix the thermal component in our ASCA spectral analysis, and have found evidence that the unresolved emission varied by 32 +/- 13% over the 18 months between the ROSAT and ASCA observations. The unresolved X-ray emission does not suffer from intrinsic absorption, and we have related it to radio structures on both milliarcsecond scales and the arcsecond scales which Chandra can resolve. The source is a target of a Chandra AO2 proposal which we have recently submitted to follow up on our ASCA (and ROSAT) work. 3C 346's orientation to the line of sight is uncertain. However, the absence of X-ray absorption, and the radio/optical/X-ray colors, when combined with with previous radio evidence that the source is a foreshortened radio galaxy of the FRII class, suggest that

  1. Testing the dark matter origin of the WMAP-Planck haze with radio observations of spiral galaxies

    SciTech Connect

    Carlson, Eric; Linden, Tim; Profumo, Stefano; Hooper, Dan E-mail: dhooper@fnal.gov E-mail: profumo@ucsc.edu

    2013-07-01

    If the Galactic WMAP radio haze, as recently confirmed by Planck, is produced by dark matter annihilation or decay, similar diffuse radio halos should exist around other galaxies with physical properties comparable to the Milky Way. If instead the haze is due to an astrophysical mechanism peculiar to the Milky Way or to a transient event, a similar halo need not exist around all Milky Way ''twins''. We use radio observations of 66 spiral galaxies to test the dark matter origin of the haze. We select galaxies based on morphological type and maximal rotational velocity, and obtain their luminosities from a 1.49 GHz catalog and additional radio observations at other frequencies. We find many instances of galaxies with radio emission that is less than 5% as bright as naively expected from dark matter models that could produce the Milky Way haze, and at least 3 galaxies that are less than 1% as bright as expected, assuming dark matter distributions, magnetic fields, and cosmic ray propagation parameters equal to those of the Milky Way. For reasonable ranges for the variation of these parameters, we estimate the fraction of galaxies that should be expected to be significantly less bright in radio, and argue that this is marginally compatible with the observed distribution. While our findings therefore cannot rule out a dark matter origin for the radio haze at this time, we find numerous examples (including the Andromeda Galaxy) where, if dark matter is indeed the origin of the Milky Way haze, some mechanism must be in place to suppress the corresponding haze of the external galaxy. We point out that Planck data will offer opportunities to improve this type of constraint in a highly relevant frequency range and for a potentially larger set of candidate galaxies.

  2. Tracing the evolution of active galactic nuclei host galaxies over the last 9 Gyr of cosmic time

    SciTech Connect

    Goulding, A. D.; Forman, W. R.; Jones, C.; Murray, S. S.; Paggi, A.; Ashby, M. L. N.; Huang, J.-S.; Kraft, R.; Willner, S. P.; Hickox, R. C.; Coil, A. L.; Cooper, M. C.; Newman, J. A.; Weiner, B. J.

    2014-03-01

    We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.

  3. Dwarf Galaxies with Active Massive Black Holes

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Greene, J. E.; Geha, M. C.

    2014-01-01

    Supermassive black holes (BHs) live at the heart of essentially all massive galaxies with bulges, power AGN, and are thought to be important agents in the evolution of their hosts. However, the birth and growth of the first supermassive BH "seeds" is far from understood. While direct observations of these distant BHs in the infant Universe are unobtainable with current capabilities, massive BHs in present-day dwarf galaxies can place valuable constraints on the masses, formation path, and hosts of supermassive BH seeds. Using optical spectroscopy from the SDSS, we have systematically assembled the largest sample of dwarf galaxies hosting active massive BHs to date. These dwarf galaxies have stellar masses comparable to the Magellanic Clouds and contain some of the least-massive supermassive BHs known.

  4. Radio-loud narrow-line Seyfert 1 galaxies with high-velocity outflows

    NASA Astrophysics Data System (ADS)

    Komossa, S.; Xu, D.; Zensus, J. A.

    2016-02-01

    We have studied four radio-loud Narrow-line Seyfert 1 (NLS1) galaxies with extreme optical emission-line shifts, indicating radial outflow velocities of up 2450 km s-1. The shifts are accompanied by strong line broadening, up to 2270 km s-1 in [NeV]. A significant ionization stratification (higher line shift at higher ionization potential) of most ions implies that we see a large-scale wind rather than single, localized jet-cloud interactions. The observations are consistent with a scenario, where the signatures of outflows are maximized because of a pole-on view into the central engine of these radio-loud NLS1 galaxies.

  5. Broad-line region structure and kinematics in the radio galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Kollatschny, W.; Ulbrich, K.; Zetzl, M.; Kaspi, S.; Haas, M.

    2014-06-01

    Context. Broad emission lines originate in the surroundings of supermassive black holes in the centers of active galactic nuclei (AGN). These broad-line emitting regions are spatially unresolved even for the nearest AGN. The origin and geometry of broad-line region (BLR) gas and their connection with geometrically thin or thick accretion disks is of fundamental importance for the understanding of AGN activity. Aims: One method to investigate the extent, structure, and kinematics of the BLR is to study the continuum and line profile variability in AGN. We selected the radio-loud Seyfert 1 galaxy 3C 120 as a target for this study. Methods: We took spectra with a high signal-to-noise ratio of 3C 120 with the 9.2 m Hobby-Eberly Telescope between Sept. 2008 and March 2009. In parallel, we photometrically monitored the continuum flux at the Wise observatory. We analyzed the continuum and line profile variations in detail (1D and 2D reverberation mapping) and modeled the geometry of the line-emitting regions based on the line profiles. Results: We show that the BLR in 3C 120 is stratified with respect to the distance of the line-emitting regions from the center with respect to the line widths (FWHM) of the rms profiles and with respect to the variability amplitude of the emission lines. The emission line wings of Hα and Hβ respond much faster than their central region. This is explained by accretion disk models. In addition, these lines show a stronger response in the red wings. However, the velocity-delay maps of the helium lines show a stronger response in the blue wing. Furthermore, the He ii λ4686 line responds faster in the blue wing in contradiction to observations made one and a half years later when the galaxy was in a lower state. The faster response in the blue wing is an indication for central outflow motions when this galaxy was in a bright state during our observations. The vertical BLR structure in 3C 120 coincides with that of other AGN. We confirm the

  6. A SURVEY OF RADIO RECOMBINATION LINES USING THE OOTY RADIO TELESCOPE AT 328 MHz IN THE INNER GALAXY

    SciTech Connect

    Baddi, Raju

    2012-02-15

    A survey of radio recombination lines in the Galactic plane with longitude -32 Degree-Sign < l < +80 Degree-Sign and latitude b < {+-}3 Degree-Sign using Ooty Radio Telescope (ORT) at 328 MHz is reported. ORT observations were made using a New Digital Backend (NDB) recently added to the telescope. With the NDB ORT had a beam of 2.{sup 0}3 Multiplication-Sign 2.{sup 0}2 sec({delta}) and a passband of {approx}1 MHz in the spectral line mode. The above-mentioned Galactic region was divided into {approx}2 Degree-Sign Multiplication-Sign 2 Degree-Sign patches with the ORT beam pointed to the center. The ORT observations form a study of the distribution of extended low-density warm-ionized medium (ELDWIM) in the inner Galaxy using H271{alpha} RLs. By obtaining kinematical distances using V{sub LSR} of the H271{alpha} RLs, the distribution of ELDWIM clouds within the inner Galaxy has been deduced for the region given above.

  7. Radio continuum observations of the quasar-galaxy pair 3C 232-NGC 3067

    NASA Technical Reports Server (NTRS)

    Haxthausen, Eric; Carilli, Chris; Vangorkom, Jacqueline H.

    1990-01-01

    The quasar-galaxy pair 3C 232-NGC 3067 is well known to show absorption by gas associated with the foreground galaxy against the background quasar (see Stocke et al. this volume). Observations by Carilli, van Gorkom, and Stocke (Nature 338, 134, 1989) found that the absorbing gas is located in a long tail of gas which extends from the galaxy toward the quasar and beyond (in projection). Though the HI observations of NGC 3067 indicate that the galaxy has been severely disturbed, there is no obvious candidate in the field which could cause such a disturbance, leading to the conclusion that the system has undergone a recent merger. The radio continuum observations of this system were designed to study the nature of this highly disturbed galaxy. New continuum observations confirm the notion that NGC 3067 is a highly disturbed system, and, in particular, the notion that the western half of the galaxy extends only 1/2 as far in radius as the eastern half. This disturbance must have occurred recently, since the galactic rotation would smooth out the observed asymmetry in about 10(exp 8) years. Researchers are left with the problem that there are no obvious candidates which could have caused such a disturbance.

  8. Chandra Observations of the Nuclei of Radio Galaxies: 3C 295 and Hydra A

    NASA Technical Reports Server (NTRS)

    Harris, D. E.; McNamara, B. R.; David, L. P.; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    The angular resolution available with Chandra allows us to isolate the X-ray emission from the nucleus of many radio galaxies and obtain their spectra. As expected from unification schemes, spectra so far obtained can best be interpreted as heavily absorbed power laws. We present the spectral parameters so derived for 3C 295 and Hydra A and compare them to data obtained at other wavelengths.

  9. Correlation Analysis of Optical and Radio Light Curves for a Large Sample of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Smith, A. G.; Aller, H. D.; Aller, M. F.

    1995-08-01

    The Rosemary Hill Observatory has accumulated internally consistent light curves extending over as much as 26 years for a large sample of active galactic nuclei. Forty-six of these optical records have been compared with similar radio records from the University of Michigan Radio Astronomy Observatory and the Algonquin Radio Observatory. For 18 objects, pairs of records were sufficiently long and unconfused to allow reliable application of the Discrete Correlation Function analysis; this group included 8 BL Lacertids, 8 quasars, and 2 Seyfert galaxies. Nine of the 18 sources showed positive radio-optical correlations, with the radio events lagging the optical by intervals ranging from 0 to 14 months. Consistent with the relativistic beaming model of the BL Lacertids, the group displaying correlations was dominated by this type of object.

  10. Radio Continuum Variability and Molecular Gas Reservoirs in the Type-Transitioning Seyfert Galaxy Mrk 590

    NASA Astrophysics Data System (ADS)

    Koay, Jun Yi; Vestergaard, Marianne; Casasola, Viviana; Peterson, Bradley M.

    2015-08-01

    Sometime between 2006 and 2012, the broad Hβ emission line of Mrk 590, once classified as a bona-fide Seyfert 1 galaxy, has completely disappeared! The optical-UV continuum emission has decreased to the point where it can be fully accounted for by stellar population models of the host galaxy. As such, Mrk 590 would now be classified as a Seyfert 1.9 or 2 galaxy, which goes against the prevailing scheme of AGN classification and unification where the presence of broad emission lines depends only on source orientation. Similar decreases in X-ray and radio continuum fluxes show that the central engine of Mrk 590 may be turning off or transitioning into a radiatively inefficient mode of accretion. We discuss the origin of the compact, unresolved radio emission in Mrk 590 and the physics of its variability in relation to the variability observed at other wavelengths, based on archival radio data and new VLBI observations. We also present recent ALMA observations of the CO(3-2) spectral line and sub-mm continuum emission; these provide the strongest limits to date on the molecular gas mass in the central ~100 pc, plus reveal the gas distribution and kinematics in the central kpc, to determine if this intriguing AGN is indeed running out of fuel.

  11. A surface brightness correlation between carbon monoxide and nonthermal radio continuum emission in the galaxy

    NASA Technical Reports Server (NTRS)

    Allen, R. J.

    1992-01-01

    The relation between the projected face-on velocity-integrated CO (1-0) brightness ICO and the 20 cm nonthermal radio continuum brightness T20 is examined as a function of radius in the Galactic disk. Averaged in 1 kpc annuli, the ratio ICO/T20 is nearly constant with a mean value of 1.51 +/- 0.34 km/s from 2 to 10 kpc. The manner in which ICO and T20 are derived for the Galaxy is different in several significant respects from the more direct observational determinations possible in nearby galaxies. The fact that the Galaxy also follows this correlation further strengthens the generality of the result.

  12. Bent-Double Radio Sources as Tracers of Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Blanton, E. L.

    1999-12-01

    An imaging and spectroscopic study of 384 bent-double radio sources selected from the VLA FIRST survey is presented. In most models, the bending of the sources' lobes is a result of interaction with a dense intra-cluster medium in which the host galaxies are embedded. Therefore, these types of radio objects should act as tracers of clusters of galaxies. We find that approximately 60% of the bent doubles are located in cluster environments with Abell richness class 0 or greater. The remaining 40% are found in groups (some of them poor). We discuss possible scenarios that could produce bent doubles in these surroundings. Several radio and optical properties of the bent doubles and their environments are examined for possible correlations. The results are consistent with similar studies done for radio sources found in Abell clusters. Several moderate-to-high-z bent double sources are studied in detail, and spectroscopy confirms them to be associated with rich clusters. These clusters represent the most distant clusters known (up to z = 0.95) that are associated with wide-angle-tail (WAT) radio sources. The WAT morphology is the most common one in our sample; these sources are high-power FR Is with large linear extents and opening angles and are usually found to be associated with cD galaxies in the cores of clusters. The FIRST project is supported by grants from the National Geographic Society, the National Science Foundation (AST-94-19906), NASA (NAG5-6035), NATO, IGPP, Columbia University, and Sun Microsystems.

  13. ISOCAM survey and dust models of 3CR radio galaxies and quasars

    NASA Astrophysics Data System (ADS)

    Siebenmorgen, R.; Freudling, W.; Krügel, E.; Haas, M.

    2005-01-01

    A survey of all 3CR sources imaged with ISOCAM and ISOPHOT was recently published by Siebenmorgen et al. (2004) and Haas et al. (2004). The sample consists mostly of radio-loud active galactic nuclei (AGN). For each source, we present spatially integrated mid-infrared (MIR) fluxes. In total, we detected 68 objects of the 3CR catalogue, at redshifts z=2.5, and obtained upper limits for 17 objects. The one with the highest redshift is 4C+72.26 at z=3.53. ISOCAM data are combined with other photometric measurements to construct the spectral energy distribution from optical to radio wavelengths. The MIR emission may include synchrotron radiation of the AGN, stars of the host galaxy or dust. Extrapolation of radio core fluxes to the MIR show that the synchrotron contribution is in most cases negligible. In 53 cases (~75% of our detected 3CR sources), the MIR emission can be attributed to dust. The hot dust component is mainly due to small grains and PAHs. In order to describe dust emission we apply new radiative transfer models. In the models the dust is heated by a central source which emits photons up to energies of 1keV. By varying three parameters, luminosity, effective size and extinction, we obtain a fit to the SED for our objects. In the models, a type 1 AGN is represented by a compact dust distribution, the dust is therefore very warm and emission of PAHs is weak because of photo-destruction. In AGNs of type 2, the dust is relatively colder but PAH bands are strong. Our models contain also dust at large (several kpc) distance from the AGN. Such a cold dust component was neglected in previous computations which therefore underestimated the AGN contribution to the far infrared (FIR). However to constrain the cold component we await future Herschel/ALMA photometry. The modelling demonstrates that an AGN heating suffices to explain the ISO broad band data. Starburst activity is not necessary but will be searched for by our IRS Spitzer Space Telescope program and

  14. New Detections of Radio Minihalos in Cool Cores of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Giacintucci, Simona; Markevitch, Maxim; Venturi, Tiziana; Clarke, Tracy E.; Cassano, Rossella; Mazzotta, Pasquale

    2013-01-01

    Cool cores of some galaxy clusters exhibit faint radio minihalos. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146,RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations.The radio luminosities of our minihalos and candidates are in the range of 102325 W Hz1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck.We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

  15. WFPC2 LRF Imaging of Emission-Line Nebulae in 3CR Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Privon, G. C.; O'Dea, C. P.; Baum, S. A.; Axon, D. J.; Kharb, P.; Buchanan, C. L.; Sparks, W.; Chiaberge, M.

    2008-04-01

    We present Hubble Space Telescope WFPC2 Linear Ramp Filter images of high surface brightness emission lines (either [O II], [O III], or H α + [N II]) in 80 3CR radio sources. We overlay the emission-line images on high-resolution VLA radio images (eight of which are new reductions of archival data) in order to examine the spatial relationship between the optical and radio emission. We confirm that the radio and optical emission-line structures are consistent with weak alignment at low redshift (z < 0.6) except in the compact steep-spectrum (CSS) radio galaxies where both the radio source and the emission-line nebulae are on galactic scales and strong alignment is seen at all redshifts. There are weak trends for the aligned emission-line nebulae to be more luminous and for the emission-line nebula size to increase with redshift and/or radio power. The combination of these results suggests that there is a limited but real capacity for the radio source to influence the properties of the emission-line nebulae at these low redshifts (z < 0.6). Our results are consistent with previous suggestions that both mechanical and radiant energy are responsible for generating alignment between the radio source and emission-line gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 05-26555. These observations are associated with program 5957.

  16. New detections of radio minihalos in cool cores of galaxy clusters

    SciTech Connect

    Giacintucci, Simona; Markevitch, Maxim; Clarke, Tracy E.; Mazzotta, Pasquale

    2014-01-20

    Cool cores of some galaxy clusters exhibit faint radio 'minihalos'. Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146, RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations. The radio luminosities of our minihalos and candidates are in the range of 10{sup 23-25} W Hz{sup –1} at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40-160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck. We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

  17. An ISOPHOT Study of the Disk of Galaxy NGC6946: 60(micro)m Infrared and Radio Continuum Correlation

    NASA Technical Reports Server (NTRS)

    Lu, N. Y.; Helou, G.; Tuffs, R.; Xu, C.; Malhotra, S.; Werner, M. W.; Thronson, H.

    1996-01-01

    We combine the ISOPHOT 60(micro)m image of Tuffs, et al. (1996) and VLA radio continuum images at 6 and 20cm from the literature to study the 60(micro)m light distribution and its correlation with radio continuum within the disk of nearby spiral galaxy NGC6946, at an effective resolution of + - 52.

  18. STRONG MOLECULAR HYDROGEN EMISSION AND KINEMATICS OF THE MULTIPHASE GAS IN RADIO GALAXIES WITH FAST JET-DRIVEN OUTFLOWS

    SciTech Connect

    Guillard, P.; Ogle, P. M.; Emonts, B. H. C.; Appleton, P. N.; Morganti, R.; Oosterloo, T.; Tadhunter, C.; Evans, D. A.; Evans, A. S.

    2012-03-10

    Observations of ionized and neutral gas outflows in radio galaxies (RGs) suggest that active galactic nucleus (AGN) radio jet feedback has a galaxy-scale impact on the host interstellar medium, but it is still unclear how the molecular gas is affected. Thus, it is crucial to determine the physical conditions of the molecular gas in powerful RGs to understand how radio sources may regulate the star formation in their host galaxies. We present deep Spitzer Infrared Spectrograph (IRS) high-resolution spectroscopy of eight nearby RGs that show fast H I outflows. Strikingly, all of these H I-outflow RGs have bright H{sub 2} mid-IR lines that cannot be accounted for by UV or X-ray heating. This strongly suggests that the radio jet, which drives the H I outflow, is also responsible for the shock excitation of the warm H{sub 2} gas. In addition, the warm H{sub 2} gas does not share the kinematics of the ionized/neutral gas. The mid-IR-ionized gas lines (with FWHM up to 1250 km s{sup -1} for [Ne II] 12.8 {mu}m) are systematically broader than the H{sub 2} lines, which are resolved by the IRS in Almost-Equal-To 60% of the detected lines (with FWHM up to 900 km s{sup -1}). In five sources, 3C 236, 3C 293, 3C 459, 4C 12.50, and PKS 1549-79, the [Ne II] 12.8 {mu}m line, and to a lesser extent the [Ne III] 15.5 {mu}m and [Ne V] 14.3 {mu}m lines, clearly exhibits blueshifted wings (up to -900 km s{sup -1} with respect to the systemic velocity) that match well the kinematics of the outflowing H I or ionized gas. The H{sub 2} lines do not show these broad wings, except tentative detections in 4C 12.50, 3C 459, and PKS 1549-79. This shows that, contrary to the H I gas, the H{sub 2} gas is inefficiently coupled to the AGN jet-driven outflow of ionized gas. While the dissipation of a small fraction (<10%) of the jet kinetic power can explain the turbulent heating of the molecular gas, our data show that the bulk of the warm molecular gas is not expelled from these galaxies.

  19. Ultrahigh-energy Cosmic Rays from Fanaroff Riley class II radio galaxies

    NASA Astrophysics Data System (ADS)

    Rachen, Joerg; Biermann, Peter L.

    1992-08-01

    The hot spots of very powerful radio galaxies (Fanaroff Riley class II) are argued to be the sources of the ultrahigh energy component in Cosmic Rays. We present calculations of Cosmic Ray transport in an evolving universe, taking the losses against the microwave background properly into account. As input we use the models for the cosmological radio source evolution derived by radioastronomers (mainly Peacock 1985). The model we adopt for the acceleration in the radio hot spots has been introduced by Biermann and Strittmatter (1987), and Meisenheimer et al. (1989) and is based on first order Fermi theory of particle acceleration at shocks (see, e.g., Drury 1983). As an unknown the actual proportion of energy density in protons enters, which together with structural uncertainties in the hot spots should introduce no more than one order of magnitude in uncertainty: We easily reproduce the observed spectra of high energy cosmic rays. It follows that scattering of charged energetic particles in intergalactic space must be sufficiently small in order to obtain contributions from sources as far away as even the nearest Fanaroff Riley class II