Science.gov

Sample records for spectrum radio galaxies

  1. 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)

  2. 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

  3. ISO observations of a sample of Compact Steep Spectrum and GHz Peaked Spectrum radio galaxies

    NASA Astrophysics Data System (ADS)

    Fanti, C.; Pozzi, F.; Fanti, R.; Baum, S. A.; O'Dea, C. P.; Bremer, M.; Dallacasa, D.; Falcke, H.; de Graauw, T.; Marecki, A.; Miley, G.; Rottgering, H.; Schilizzi, R. T.; Snellen, I.; Spencer, R. E.; Stanghellini, C.

    2000-06-01

    We present results from observations obtained with ISOPHOT, on board the ISO satellite, of a representative sample of seventeen CSS/GPS radio galaxies and of a control sample of sixteen extended radio galaxies spanning similar ranges in redshift (0.2 <= z <= 0.8) and radio luminosity (P_{2.7 GHz} >= 1026 W/Hz). The observations have been performed at lambda = 60, 90, 174 and 200 mu m. The original purpose of these observations was to check whether CSS/GPS sources are associated with very gas rich galaxies, as required by the scenario in which the growth of the radio source is inhibited by the dense medium of the host galaxy. Unfortunately the resulting performance of ISOPHOT was worse than expected. As a consequence, the detection limit at 60mu m is similar to that obtained previously with IRAS but better than that at 90mu m. Seven of the CSS/GPS sources have detections >= 3sigma at one or more wavelengths, one of which is detected at >= 5sigma . For the comparison sample five objects have detections >= 3sigma one of which is at >= 5sigma . By co-adding the data we have obtained average flux densities at the four wavelengths. We found no evidence that the FIR luminosities of the CSS/GPS sources are significantly different from those of the extended objects and therefore there is not any support for CSS/GPS sources being objects ``frustrated" by an abnormally dense ambient medium. The two samples were then combined, providing FIR information on a new sample of radio galaxies at intermediate redshifts. We compare this information with what previously known from IRAS and discuss the average properties of radio galaxies in the redshift range 0.2 - 0.8. The FIR emission cannot be accounted for by extrapolation of the synchrotron radio spectrum and we attribute it to thermal dust emission. The average FIR luminosity is >= 6 x 1011 Lsun. Over the observed frequency range the infrared spectrum can be described by a power law with spectral index alpha =~ 1.0 +/- 0

  4. The Nearest GHz Peaked-Spectrum Radio Galaxy, PKS 1718-649

    NASA Technical Reports Server (NTRS)

    Tingay, S. J.; Jauncey, D. L.; Reynolds, J. E.; Tzioumis, A. K.; King, E. A.; Preston, R. A.; Lovell, J. E.; McCulloch, P. M.; Costa, M. E.; Nicolson, G.

    1997-01-01

    In this paper we identify PKS 1718-649, at a distance of 56 Mpc (z = 0.014; H(sub o) = 75 km/s/Mpc, q(sub o) = 0), as the nearest GHz peaked-spectrum (GPS) radio galaxy, more than four times closer than any previously known. Extensive observations at radio wavelengths with the Australia Telescope Compact Array, the Southern Hemisphere VLBI Experiment array, and the Swedish-ESO Submillimetre Telescope have allowed us to determine the properties of the radio source: PKS 1718-649 consists of two compact sub-pc-scale components separated by approximately 2 pc, the overall radio polarization is low, and the radio spectrum is peaked near 3 GHz. Order-of-magnitude agreement between the quantitative model for GPS sources of Bicknell et al. and the radio data we present, as well as data at optical wavelengths from the literature, raises the interesting possibility that PKS 1718-649 may be frustrated in its development by the nuclear environment of its host galaxy, NGC 6328. The model of Bicknell et al. suggests free-free absorption as an explanation of the PKS 1718-649 radio spectrum. However, both free-free absorption and synchrotron self-absorption mechanisms are plausible for this source and both may contribute to the overall radio spectrum. PKS 1718-649 provides evidence to strengthen the speculative suggestion that GPS sources arise as a consequence of galaxy merger activity.

  5. The Remarkable X-ray Spectrum of the Broad-Line Radio Galaxy 3C 445

    NASA Technical Reports Server (NTRS)

    Sambruna, R. M.; Reeves, J. N.; Braito, V.

    2007-01-01

    The nearby (z=0.057) radio-loud source 3C 445, optically classified as a Broad-Line Radio Galaxy, exhibits an X-ray spectrum strongly reminiscent of an obscured AGN, suggesting we are seeing this source at a relatively large angle from the radio jet. Here we present an archival 15 ks XMM-Newton observation of 3C 445 which confirms the remarkable complexity of its X-ray emission. The X-ray emission is described by a power law continuum with GAMMA approximately equal to 1.4, absorbed by several layers of cold gas, plus strong cold reflection. A narrow, unresolved Fe Kalpha emission line is detected, confirming previous findings, with EW approximately equal to 400 eV. A soft excess is present below 2 keV over the extrapolation of the hard X-ray power law, which we model with a power law with the same photon index and absorbed by a column density N(sub H)5 approximately equal to 10(sup 20) cm(sup -2) in excess to Galactic. Remarkably, a host of emission lines are present below 2 keV, confirming previous indications from ASCA, due to H- and He-like O, Mg, and Si. The detection of two features at 0.74 and 0.87 keV, identified with OVII and OVIII Radiative Recombination Continuum features, suggest an origin of the lines from a photoionized gas, with properties very similar to radio-quiet obscured AGN. Two different ionized media, or a single stratified medium, are required to fit the soft X-ray data satisfactorily. The similarity of the X-ray spectrum of 3C 445 to Seyferts underscores that the central engines of radio-loud and radio-quiet AGN similarly host both cold and warm gas.

  6. Clustering and Light Profiles of Galaxies in the Environment of 20 Ultra-Steep-Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Bornancini, Carlos G.; Martínez, Héctor J.; Lambas, Diego G.; de Vries, Wim; van Breugel, Wil; De Breuck, Carlos; Minniti, Dante

    2004-02-01

    We have analyzed galaxy properties in the neighborhood of 20 ultra-steep-spectrum (USS) radio sources taken from the Westerbork in the Southern Hemisphere (WISH) catalog of De Breuck and coworkers. Galaxies in these USS fields were identified in deep observations that were carried out in the K' band using the OSIRIS imager at the CTIO 4 m telescope. We find a statistically significant signal of clustering around our sample of USS sources. The angular extension of the detected USS source-galaxy clustering is θc~20'', corresponding to a spatial scale of ~120 h-1 kpc, assuming the sources are at z~1 in an Ωm=0.3, ΩΛ=0.7 model universe. These results are in agreement with those obtained by Best for radio galaxy-galaxy correlation, and Best and coworkers for radio-loud AGN-galaxy correlation. We have also analyzed the light distribution of the galaxies by fitting Sérsic's law profiles. Our results show no significant dependence of the galaxy shape parameters on the projected distance to the USS source. Based on observations obtained at Cerro Tololo Inter-American Observatory (CTIO), a division of the National Optical Astronomy Observatory (NOAO), which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

  7. Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Caccianiga, A.; Foschini, L.; Peterson, B. M.; Mathur, S.; Terreran, G.; Ciroi, S.; Congiu, E.; Cracco, V.; Frezzato, M.; La Mura, G.; Rafanelli, P.

    2016-06-01

    Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of γ-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.

  8. High-frequency excess in the radio continuum spectrum of the type-1 Seyfert galaxy NGC 985

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Inoue, Yoshiyuki

    2016-08-01

    The Seyfert galaxy NGC 985 is known to show a high-frequency excess in its radio continuum spectrum at a milli-Jansky level on the basis of previous observations at 1.4-15 GHz; a steep spectrum at low frequencies (a spectral index, α = -1.10 ± 0.03) changes at ˜10 GHz into an inverted spectrum at higher frequencies (α = +0.86 ± 0.09). We conduct new observations at 15-43 GHz using the Very Large Array and at 100 GHz using the Nobeyama Millimeter Array. As a result, the high-frequency excess has been confirmed as continuing at even higher radio frequencies, up to 43 GHz. The non-detection at 100 GHz was not so strong a constraint, and therefore the spectral behavior above 43 GHz remains unclear. The astrometric position of the high-frequency excess component coincides with the optical position of the Seyfert nucleus and the low-frequency radio position to an accuracy of 0{^''.}1, corresponding to ˜80 pc; the radio source size is constrained to be <0{^''.}02, corresponding to <16 pc. We discuss the physical origin of the observed high-frequency excess component. Dust emission at the Rayleigh-Jeans regime, free-free emission from X-ray radiating high-temperature plasma, free-free emission from the ensemble of broad-line region clouds, or thermal synchrotron from hot accretion flow cannot be responsible for the observed radio flux. Compact jets under synchrotron self-absorption may be unlikely in terms of observed time scales. Alternatively, we cannot rule out the hypotheses of synchrotron jets free-free absorbed by a circumnuclear photo-ionized region, and self-absorbed nonthermal synchrotron from disk corona, as the origin of the high-frequency excess component.

  9. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  10. 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.

  11. Radio properties of Compact Steep Spectrum and GHz-Peaked Spectrum radio sources

    NASA Astrophysics Data System (ADS)

    Orienti, M.

    2016-02-01

    Compact steep spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources represent a large fraction of the extragalactic objects in flux density-limited samples. They are compact, powerful radio sources whose synchrotron peak frequency ranges between a few hundred MHz to several GHz. CSS and GPS radio sources are currently interpreted as objects in which the radio emission is in an early evolutionary stage. In this contribution I review the radio properties and the physical characteristics of this class of radio sources, and the interplay between their radio emission and the ambient medium of the host galaxy.

  12. The local radio-galaxy population at 20 GHz

    NASA Astrophysics Data System (ADS)

    Sadler, Elaine M.; Ekers, Ronald D.; Mahony, Elizabeth K.; Mauch, Tom; Murphy, Tara

    2014-02-01

    We have made the first detailed study of the high-frequency radio-source population in the local Universe, using a sample of 202 radio sources from the Australia Telescope 20 GHz (AT20G) survey identified with galaxies from the 6dF Galaxy Survey (6dFGS). The AT20G-6dFGS galaxies have a median redshift of z = 0.058 and span a wide range in radio luminosity, allowing us to make the first measurement of the local radio luminosity function at 20 GHz. Our sample includes some classical Fanaroff-Riley type I (FR I) and FR II radio galaxies, but most of the AT20G-6dFGS galaxies host compact (FR 0) radio active galactic nuclei which appear to lack extended radio emission even at lower frequencies. Most of these FR 0 sources show no evidence for relativistic beaming, and the FR 0 class appears to be a mixed population which includes young compact steep-spectrum and gigahertz peaked-spectrum radio galaxies. We see a strong dichotomy in the Wide-field Infrared Survey Explorer (WISE) mid-infrared colours of the host galaxies of FR I and FR II radio sources, with the FR I systems found almost exclusively in WISE `early-type' galaxies and the FR II radio sources in WISE `late-type' galaxies. The host galaxies of the flat- and steep-spectrum radio sources have a similar distribution in both K-band luminosity and WISE colours, though galaxies with flat-spectrum sources are more likely to show weak emission lines in their optical spectra. We conclude that these flat-spectrum and steep-spectrum radio sources mainly represent different stages in radio-galaxy evolution, rather than beamed and unbeamed radio-source populations.

  13. Peculiar galaxies and radio sources.

    PubMed

    Arp, H

    1966-03-11

    Pairs of radio sources which are separated by from 2 degrees to 6 degrees on the sky have been investigated. In a number of cases peculiar galaxies have been found approximately midway along a line joining the two radio sources. The central peculiar galaxies belong mainly to a certain class in the recently compiled Atlas of Peculiar Galaxies. Among the radio sources so far associated with the peculiar galaxies are at least five known quasars. These quasars are indicated to be not at cosmological distances (that is, red shifts not caused by expansion of the universe) because the central peculiar galaxies are only at distances of 10 to 100 megaparsecs. The absolute magnitudes of these quasars are indicated to be in the range of brightness of normal galaxies and downward. Some of the radio sources which have been found to be associated with peculiar galaxies are galaxies themselves. It is therefore implied that ejection of material took place within or near the parent peculiar galaxies with speeds between 10(2) and 10(4) kilometers per second. After traveling for times of the order of 10(7) to 10(9) years, the luminous matter (galaxies) and radio sources (plasma) have reached their observed separations from the central peculiar galaxy. The large red shifts measured for the quasars would seem to be either (i) gravitational, (ii) collapse velocities of clouds of material falling toward the center of these compact galaxies, or (iii) some as yet unknown cause.

  14. Polarization Imaging of Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert

    1991-07-01

    Spectropolarimetry of the narrow line radio galaxy 3C234 was used to show in 1982 that there is a hidden broad line region occulted by an opaque torus oriented perpendicular to the radio structure axis. Given the luminosity of the reflected light, it follows that 3C234 would be called a quasar if its orientation with respect to the line of sight were different. Since then similar results were found for five Seyfert 2's. If many NLRG's are occulted quasars in the sky plane, several statistical anomalies in the beam model for superluminal motion are understandable. However, further optical spectropolarimetry has been disappointing in this regard, at least partially because of severe dilution of reflected light by starlight, sometimes polarized, from the host galaxies. We can solve this problem by observing in the UV. Furthermore, recent observations of two NLRGs have revealed OFF- NUCLEAR dust clouds reflecting and strongly "bluening" nuclear light in two NLRG's. Such dust clouds, abundant in the merger debris surrounding many luminous radio galaxies, should show up spectacularly in UV polarization images, providing information on the beam pattern and time history of nuclear emission. We request FOC polarization images of a sample of radio galaxies. We will also get for free and with high efficiency total flux images, suitable for studying the nuclei and the anomalous young stellar populations seen in merging radio galaxies from the ground.

  15. Polarization Imaging of Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert

    1996-07-01

    Spectropolarimetry of the narrow line radio galaxy 3C234 was used to show in 1982 that there is a hidden broad line region occulted by an opaque torus oriented perpendicular to the radio structure axis. Given the luminosity of the reflected light, it follows that 3C234 would be called a quasar if its orientation with respect to the line of sight were different. Since then similar results were found for five Seyfert 2's. If many NLRG's are occulted quasars in the sky plane, several statistical anomalies in the beam model for superluminal motion are understandable. However, further optical spectropolarimetry has been disappointing in this regard, at least partially because of severe dilution of reflected light by starlight, sometimes polarized, from the host galaxies. We can solve this problem by observing in the UV. Furthermore, recent observations of two NLRGs have revealed OFF- NUCLEAR dust clouds reflecting and strongly "bluening" nuclear light in two NLRG's. Such dust clouds, abundant in the merger debris surrounding many luminous radio galaxies, should show up spectacularly in UV polarization images, providing information on the beam pattern and time history of nuclear emission. We request FOC polarization images of a sample of radio galaxies. We will also get for free and with high efficiency total flux images, suitable for studying the nuclei and the anomalous young stellar populations seen in merging radio galaxies from the ground.

  16. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  17. Hybrid spread spectrum radio system

    DOEpatents

    Smith, Stephen F [London, TN; Dress, William B [Camas, WA

    2010-02-09

    Systems and methods are described for hybrid spread spectrum radio systems. A method, includes receiving a hybrid spread spectrum signal including: fast frequency hopping demodulating and direct sequence demodulating a direct sequence spread spectrum signal, wherein multiple frequency hops occur within a single data-bit time and each bit is represented by chip transmissions at multiple frequencies.

  18. 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.

  19. 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.

  20. SETI radio spectrum surveillance system

    NASA Technical Reports Server (NTRS)

    Crow, B.; Lokshin, A.; Marina, M.; Ching, L.

    1985-01-01

    The SETI Radio Spectrum Surveillance System (SRSSS) will provide a data base for assessing the radio frequency interference (RFI) environment for SETI and minimizing RFI disruptions during the search. The system's hardware and software are described and the sensitivity of the system is discussed.

  1. Radio loud far-infrared galaxies

    NASA Technical Reports Server (NTRS)

    Dey, Arjun; Vanbreugel, Wil; Shields, Joseph C.

    1990-01-01

    The first results are presented of a multiwavelength study of Infrared Astronomy Satellite (IRAS) galaxies with excess radio emission. The sample was selected by cross correlating the IRAS Faint Source Survey, and the Point Source Catalogue with the Texas radio survey. Recent optical (imaging and spectroscopic) and radio (VLA) observations are discussed. These observations will be used to investigate possible connections between radio galaxy activity, star formation and galaxy interactions.

  2. 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

  3. 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

  4. 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.

  5. Searches for high redshift radio galaxies

    SciTech Connect

    De Breuck, C.; Van Breugel, W.; Rottgering, H.; Miley, G.

    1997-05-05

    We have started a search for High Redshift Radio Galaxies (HZRGS) in an area covering 7 sr by selecting a sample of Ultra Steep Spectrum (USS) sources with a low flux density cut-off S1400 > 10 mJy and a steep spectral index cut-off of a < -1.3 (S of about nu-alpha) from the WENSS, NVSS and TEXAS surveys. Our first results for 27 sources show that we are almost twice as effective in finding HZRGs than than surveys of relatively bright radio sources with a spectral index cut-off of a < - 1.0. The redshift distribution is consistent with an extension of the z - a relation to a < -1.3, but a large fraction of our sample (40%) consists of objects which are too faint to observe with 3-4 m class telescopes. Our search is aimed at increasing the number of very high redshift radio galaxies for further detailed studies of the formation and evolution of massive galaxies and their environment.

  6. 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.

  7. 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.

  8. Radio properties of fossil galaxy groups

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Khosroshahi, H. G.

    2016-09-01

    We study 1.4 GHz radio properties of a sample of fossil galaxy groups using GMRT radio observations and the FIRST survey catalog. Fossil galaxy groups, having no recent major mergers in their dominant galaxies and also group scale mergers, give us the opportunity to investigate the effect of galaxy merger on AGN activity. In this work, we compare the radio properties of a rich sample of fossil groups with a sample of normal galaxy groups and clusters and show that the brightest group galaxies in fossil groups are under luminous at 1.4 GHz, relative to the general population of the brightest group galaxies, indicating that the dynamically relaxed nature of fossil groups has influenced the AGN activity in their dominant galaxy.

  9. Similarity of jet radiation between flat spectrum radio quasars and GeV narrow-line Seyfert 1 galaxies: a universal δ-L c correlation

    NASA Astrophysics Data System (ADS)

    Zhu, Yong-Kai; Zhang, Jin; Zhang, Hai-Ming; Liang, En-Wei; Yan, Da-Hai; Cui, Wei; Zhang, Shuang-Nan

    2016-11-01

    By modeling the broadband spectral energy distributions (SEDs) of a typical flat spectrum radio quasar (FSRQ, 3C 279) and two GeV narrow-line Seyfert 1 galaxies (NLS1s, PMN J0948+0022 and 1H 0323+342) in different flux stages with one-zone leptonic models, we find a universal correlation between their Doppler factors (δ) and peak luminosities (L c) of external Compton scattering bumps. Compiling a combined sample of FSRQs and GeV NLS1s, it is found that both FSRQs and GeV NLS1s in different stages and in different sources follow the same δ-L c correlation well. This indicates that the variations of observed luminosities may be essentially due to the Doppler boosting effect. The universal δ-L c relation between FSRQs and GeV NLS1s in different stages may be further evidence that the particle acceleration and radiation mechanisms for the two kinds of sources are similar. In addition, by replacing L c with the observed luminosity in the Fermi/LAT band (L LAT), this correlation holds and it may serve as an empirical indicator of δ. We estimate the δ values with L LAT for 484 FSRQs in the Fermi/LAT Catalog and they range from 3 to 41, with a median of 16, which are statistically consistent with the values derived by other methods.

  10. 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.

  11. Remnant radio galaxies in the LOFAR Lockman Hole

    NASA Astrophysics Data System (ADS)

    Brienza, Marisa; Godfrey, Leith; Morganti, Raffaella

    2016-08-01

    I will present recent 150-MHz deep observations performed with the Low-frequency Array (LOFAR) of the well-known extragalactic region of the Lockman Hole. Thanks to its high sensitivity and resolution this data allows us to perform new studies of the radio loud AGN population at low radio frequencies. In particular, we conducted a systematic search of remnant radio galaxies, which represent the final "dying" phase of the radio galaxy evolution, when the jets have switched off. This class of sources is best to investigate the life-cycle of radio loud AGN as well as to quantify the role of radio AGN feedback. Indeed, the modelling of their radio spectrum provides constraints on the time-scales of activity and quiescence of the radio source and on its energy output. For a long time there have been claims that deep low-frequency surveys would have enhanced the detection of this class of sources, which are usually rare in flux limited samples.With our search, we thus intend to provide good statistics on the detection and properties of remnant radio galaxies. To avoid selection biases towards any specific class of objects we used both morphological and spectral selection criteria. To do this we combined the LOFAR data with publicly available surveys at other frequencies as well as dedicated deep observations. We find that the fraction of candidate remnant sources is < 6-8% of the entire radio source population and is dominated by steep spectrum sources. To better understand the observed fraction we developed mock catalogues of the radio sky population based on radio galaxy evolution models. These models are used to constrain the main mechanisms contributing to the source luminosity evolution i.e. adiabatic expansion, radiative losses, as well as to make predictions on their fraction in flux limited samples.

  12. Giant radio galaxies and cosmic web

    NASA Astrophysics Data System (ADS)

    Heinämäki, Pekka

    2016-10-01

    Giant radio galaxies create the welldistinguishable class of sources.These sources are characterized with edge-brightened radio lobes withhighly collimated radio jets and large linear sizes which make themthe largest individual structures in the Universe. They are also knownto be hosted by elliptical/disturbed host galaxies and avoid clustersand high galaxy density regions. Because of GRG, large linear sizeslobes extend well beyond the interstellar media and host galaxyhalo the evolution of the radio lobes may depend on interactionwith this environment. Using our method to extract filamentarystructure of the galaxies in our local universe we study whetherradio lobe properties in some giant radio galaxies are determinedon an interaction of this filament ambient.

  13. Radio loud far-infrared galaxies

    SciTech Connect

    Dey, A; Shields, J.C. . Dept. of Astronomy); Van Breugel, W.J.M. )

    1990-03-01

    We present the first results of a multiwavelength study of IRAS galaxies with excess radio emission. The sample was selected by cross-correlating the IRAS Faint Source Survey (for {vert bar}b{vert bar} {ge} 50{degree}) and the Point Source Catalogue (for 10{degree} < {vert bar}b{vert bar} < 50{degree}) with the Texas radio survey. Recent optical (imaging and spectroscopic) and radio (VLA) observations are discussed. These observations will be used to investigate possible connections between radio galaxy activity, star formation and galaxy interactions. 15 refs., 3 figs.

  14. 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.

  15. 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.

  16. Dumbbell galaxies and precessing radio jets

    NASA Astrophysics Data System (ADS)

    Wirth, A.; Smarr, L.; Gallagher, J. S.

    1982-04-01

    It is suggested that a subclass of inversion-symmetric distorted extended radio sources (Z-shapes) have shapes produced by effects on large scales compared with the central engine. The subclass is defined by those sources whose underlying galaxies have a dumbbell or multiple nuclei optical morphology. New optical observations are presented which indicate that in one well-studied Z-shape source, NGC 326, there are two galaxies passing at a projected distance of about 10 kpc and that the gravitational coupling of the nonradio galaxy on the radio galaxy's atmosphere may be the mechanism which has realigned the jet direction. If the proposed interpretation is correct, some large-scale jet properties of double radio sources reveal more about properties of the gas distribution in galaxies and less about the central engine than heretofore supposed.

  17. Hybrid spread spectrum radio system

    DOEpatents

    Smith, Stephen F.; Dress, William B.

    2010-02-02

    Systems and methods are described for hybrid spread spectrum radio systems. A method includes modulating a signal by utilizing a subset of bits from a pseudo-random code generator to control an amplification circuit that provides a gain to the signal. Another method includes: modulating a signal by utilizing a subset of bits from a pseudo-random code generator to control a fast hopping frequency synthesizer; and fast frequency hopping the signal with the fast hopping frequency synthesizer, wherein multiple frequency hops occur within a single data-bit time.

  18. 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.

  19. 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.

  20. FR II radio galaxies at low frequencies

    NASA Astrophysics Data System (ADS)

    Harwood, Jeremy

    2016-08-01

    Due to their steep spectra, low-frequency observations of FR II radio galaxies potentially provide key insights in to the morphology, energetics and underlying physics 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 talk, we present our latest results using LOFAR and the JVLA at frequencies between 50 and 460 MHz which, along with complementary archival radio and X-ray data, now allows us to undertake well resolved, detailed studies of nearby FR II radio galaxies at low frequencies. We discuss how our improved knowledge of the low-energy electron distribution, magnetic field strength and total energy content of the lobes impacts upon our understanding of the dynamics and energetics of nearby FR II radio galaxies and, for the first time, present the spectral structure of these sources on small spatial scales at low frequencies. We conclude by discussing how these findings change our current understanding of the underlying physics of FR II radio galaxies and, ultimately, their impact on the environment and galaxy evolution as a whole.

  1. 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.

  2. The integrated radio spectrum of Virgo A

    NASA Astrophysics Data System (ADS)

    Vinyaikin, E. N.

    2016-08-01

    The flux density of the radio galaxy Virgo A has been measured at 38 and 151.5 MHz. These measurements and published flux densities at 59 other frequencies from 5.6 MHz to 857 GHz are used to obtain a fit to the frequency dependence of the logarithm of the flux density in the form of a second-order polynomial of the logarithm of the frequency, S_ν ^{Vir A} [Jy] = 1224.4(ν [MHz]/150)^{ - 0.817 + 0.007 log (ν [MHz]/150)} . This spectrum, which has a small positive curvature, agrees slightly better with the observed flux densities than a purely power-lawspectrumwith the spectral index 0.793±0.003 and S 150 [MHz] Vir A = 1187±23 Jy. The relative errors in using the power-law spectrum instead of this spectrum with its small, positive curvature lie in the range (-5.2-1.6)% for frequencies from 70 MHz to 857 GHz. The expected peak frequency of the spectrum of Virgo A is estimated.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. A pseudo-spectrum analysis of galaxy-galaxy lensing

    NASA Astrophysics Data System (ADS)

    Hikage, Chiaki; Oguri, Masamune

    2016-10-01

    We present the application of the pseudo-spectrum method to galaxy-galaxy lensing. We derive explicit expressions for the pseudo-spectrum analysis of the galaxy-shear cross-spectrum, which is the Fourier space counterpart of the stacked galaxy-galaxy lensing profile. The pseudo-spectrum method corrects observational issues such as the survey geometry, masks of bright stars and their spikes, and inhomogeneous noise, which distort the spectrum and also mix the E-mode and the B-mode signals. Using ray-tracing simulations in N-body simulations including realistic masks, we confirm that the pseudo-spectrum method successfully recovers the input galaxy-shear cross-spectrum. We also show that the galaxy-shear cross-spectrum has an excess covariance relative to the Gaussian covariance at small scales (k ≳ 1h Mpc-1) where the shot noise is dominated in the Gaussian approximation. We find that the excess is consistent with the expectation from the halo sample variance (HSV), which originates from the matter fluctuations at scales larger than the survey area. We apply the pseudo-spectrum method to the observational data of Canada-France-Hawaii Telescope Lensing survey shear catalogue and three different spectroscopic samples of Sloan Digital Sky Survey Luminous Red Galaxy, and Baryon Oscillation Spectroscopic Survey CMASS and LOWZ galaxies. The galaxy-shear cross-spectra are significantly detected at the level of 7-10σ using the analytic covariance with the HSV contribution included. We also confirm that the observed spectra are consistent with the halo model predictions with the halo occupation distribution parameters estimated from previous work. This work demonstrates the viability of galaxy-galaxy lensing analysis in the Fourier space.

  8. Broad Line Radio Galaxies with NuSTAR

    NASA Astrophysics Data System (ADS)

    Lohfink, A.; Ogle, P.; Matt, G.; Lanz, L.; Madejski, G.; Reynolds, C.; Walton, D.; Harrison, F.

    2014-07-01

    The formation of relativistic jets is an open question in AGN physics. Despite significant observational efforts it is still unclear why some AGN show strong radio jets while others do not. Of particular interest to answer this question are broad line radio galaxies, which do show a strong jet but otherwise show an X-ray spectrum similar to their radio-quiet kin. While studies of the standard X-ray band (0.5-10 keV) have not yielded any significant insights, the newly launched X-ray mission NuSTAR offers the possibility to also study the hard X-ray spectra of these sources. In combination with coordinated XMM-Newton and Suzaku observations this provides the best broad-band X-ray spectra of broad line radio galaxies to-date. In this talk I will discuss the first results from the NuSTAR Radio Galaxy program and their implications for our understanding of jet formation.

  9. 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.

  10. Birth and Evolution of Radio Galaxies

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions and fit them to the observed data, that cover redshifts up to z 2. This allows us to find the most plausible distributions of FRIIs’ fundamental properties, but also to set more precise limits on the size cut-off and to discuss the possibility of FRII evolution into FRI objects.

  11. 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.

  12. Radio Galaxy NGC 1265 Unveils the Accretion Shock Onto the Perseus Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Pfrommer, C.; Jones, T. W.

    2011-03-01

    We present a consistent three-dimensional model for the head-tail radio galaxy NGC 1265 that explains the complex radio morphology and spectrum by a past passage of the galaxy and radio bubble through a shock wave. Using analytical solutions to the full Riemann problem and hydrodynamical simulations, we study how this passage transformed the plasma bubble into a toroidal vortex ring. Adiabatic compression of the aged electron population causes it to be energized and to emit low surface brightness and steep-spectrum radio emission. The large infall velocity of NGC 1265—which is barely gravitationally bound to the Perseus cluster at its current position—and the low Faraday rotation measure values and variance of the jet strongly argue that this transformation was due to the accretion shock onto Perseus situated roughly at R 200. Estimating the volume change of the radio bubble enables inferring a shock Mach number of M≃ 4.2_{-1.2}^{+0.8}, a density jump of 3.4+0.2 -0.4, a temperature jump of 6.3+2.5 -2.7, and a pressure jump of 21.5 ± 10.5 while allowing for uncertainties in the equation of state of the radio plasma and volume of the torus. Extrapolating X-ray profiles, we obtain upper limits on the gas temperature and density in the infalling warm-hot intergalactic medium of kT <~ 0.4 keV and n <~ 5 × 10-5 cm-3. The orientation of the ellipsoidally shaped radio torus in combination with the direction of the galaxy's head and tail in the plane of the sky is impossible to reconcile with projection effects. Instead, this argues for post-shock shear flows that have been caused by curvature in the shock surface with a characteristic radius of 850 kpc. The energy density of the shear flow corresponds to a turbulent-to-thermal energy density of 14%—consistent with cosmological simulations. The shock-injected vorticity might be important in generating and amplifying magnetic fields in galaxy clusters. We suggest that future polarized radio observations by, e

  13. 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.

  14. 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.

  15. 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.

  16. SUZAKU OBSERVATION OF THE GIANT RADIO GALAXY 3C 326

    SciTech Connect

    Isobe, Naoki; Tashiro, Makoto S.; Seta, Hiromi; Gandhi, Poshak; Hayato, Asami; Nagai, Hiroshi; Hada, Kazuhiro; Matsuta, Keiko

    2009-11-20

    A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical size of about 2 Mpc, was conducted on 2008 January 19-21. In addition to several X-ray sources, diffuse emission was significantly detected and associated with its west lobe, but the east lobe was contaminated by an unidentified X-ray source WARP J1552.4+2007. After careful evaluation of the X-ray and non-X-ray background, the 0.4-7 keV X-ray spectrum of the west lobe is described by a power-law model modified with the Galactic absorption. The photon index and 1 keV flux density were derived as GAMMA = 1.82{sup +0.26}{sub -0.24} +- 0.04 and S {sub X} = 19.4{sup +3.3}{sub -3.2} +- 3.0 nJy, respectively, where the first and second errors represent the statistical and systematic ones. The diffuse X-rays were attributed to be inverse Compton (IC) radiation by the synchrotron radio electrons scattering off the cosmic microwave background photons. This radio galaxy is the largest among those with lobes detected through IC X-ray emission. A comparison of the radio to X-ray fluxes yields the energy densities of electron and magnetic field as u{sub e} = (2.3 +- 0.3 +- 0.3) x 10{sup -13} erg cm{sup -3} and u{sub m} = (1.2{sup +0.2}{sub -0.1} +- 0.2) x 10{sup -14} erg cm{sup -3}, respectively. The galaxy is suggested to host a low-luminosity nucleus with an absorption-corrected 2-10 keV luminosity of <2 x 10{sup 42} erg s{sup -1}, together with a relatively weak radio core. The energetics in the west lobe of 3C 326 were compared with those of moderate radio galaxies with a size of approx100 kpc. The west lobe of 3C 326 is confirmed to agree with the correlations for the moderate radio galaxies, u{sub e} propor to D {sup -2.2+}-{sup 0.4} and u{sub m} propor to D {sup -2.4+}-{sup 0.4}, where D is their total physical size. This implies that the lobes of 3C 326 are still being energized by the jet, despite the current weakness of the nuclear activity.

  17. The Aligned z~1 Radio Galaxy 3C 280

    NASA Astrophysics Data System (ADS)

    Ridgway, Susan E.; Stockton, Alan; Lacy, Mark

    2004-01-01

    The z~1 radio galaxy 3C 280 has a particularly striking rest-frame UV morphology, with multiple line and continuum components precisely aligned with the radio structure, including an obvious semicircular arc. Here we explore the nature of these various components by bringing together Hubble Space Telescope and ground-based imaging, ground-based spectroscopy, and radio mapping. From plausible decompositions of the spectra, we show that the continuum of the nuclear component is likely dominated by a combination of nebular thermal continuum, quasar light, and light from old stars. A component that falls directly on the probable path of the radio jet shows mostly nebular thermal continuum and includes contributions from a relatively young stellar population with age around 100 Myr. The arc appears to be completely dominated by line emission and nebular thermal continuum, with no evidence for a significant stellar contribution. Although much of the aligned light is in UV components, the underlying old elliptical galaxy is also well aligned with the radio axis. The elliptical galaxy is well fitted by a de Vaucouleurs profile, probably has a moderately old stellar population (~3 Gyr), and is a massive system with a velocity dispersion of σ~270 km s-1 that implies that it contains a supermassive black hole. Although the arc and the extended emission surrounding the eastern lobe suggest that interactions between the radio lobe and jet must have been important in creating the UV morphology, the ionization and kinematic properties in these components are more consistent with photoionization than shock excitation. 3C 280 may be a transition object between the compact steep-spectrum radio galaxies, which seem to be shock-dominated, and the extended radio sources, which may have evolved past this phase and rarely show shock signatures. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the

  18. The BL LAC phenomenon: X-ray observations of transition objects and determination of the x-ray spectrum of a complete sample of flat-spectrum radio sources

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    1994-01-01

    This report summarizes the activities related to two ROSAT investigations: (1) x-ray properties of radio galaxies thought to contain BL Lac type nuclei; and (2) x-ray spectra of a complete sample of flat-spectrum radio sources. The following papers describing the research are provided as attachments: Multiple X-ray Emission Components in Low Power Radio Galaxies; New X-ray Results on Radio Galaxies; Analysis Techniques for a Multiwavelength Study of Radio Galaxies; Separation of X-ray Emission Components in Radio Galaxies; X-ray Emission in Powerful Radio Galaxies and Quasars; Extended and Compact X-ray Emission in Powerful Radio Galaxies; and X-ray Spectra of a Complete Sample of Extragalactic Core-dominated Radio Sources.

  19. 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

  20. 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.

  1. Obscuration, orientation, and the infrared properties of radio-loud active galaxies

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.; O'Dea, Christopher P.; Baum, Stefi A.; Laurikainen, Eija

    1994-01-01

    We report on a study of the mid- and far-infrared (MFIR) properties of several different classes of radio-loud active galactic nuclei (AGNs) using the IRAS database. Our goal is to try to improve the understanding of the possible relationships between the diverse classes of AGNs. The MFIR and radio properties of radio-loud AGNs are especially useful in this regard, since (excluding the blazar class, which we do not study here) the radio emission is thought to be emitted isotropically, and the radio and MFIR radiation should be much less affected by dust obscuration than radiation at shorter wavelengths. We have first compared samples of 3CR broad-line radio galaxies (BLRGs) and narrow-line radio galaxies (NLRGs) matched in radio flux and mean redshift. We find that the BLRGs are stronger than the NLRGs by a factor of 4-5 in their mid-IR emission but are similar to the NLRGs in the far-IR. This is qualitatively consistent with recent 'unification' models for NLRGs and BLRGs which invoke thermal MFIR emission from dusty 'obscuring tori,' but there may be an additional source of far-IR emission present in the more luminous broad-line objects (the radio-loud quasars) studied previously by Heckman, Chambers & Postman (1992). We have also compared samples of Fanaroff-Riley class I (FRI) and Fanaroff-Riley class II (FRII) radio galaxies matched in radio flux and redshift. The FRII galaxies are stronger MFIR emitters than the FRI galaxies by a factor of about 4. This is consistent with suggestions that the central engine in FRI galaxies produces relatively little radiant energy per unit jet power (expecially since we find that the weak MFIR emission from the FRI galaxies may not be powered by the AGN). Comparing samples of gigahertz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources versus non-GPS-CSS sources, we find that the GPS-CSS and non-GPS-CSS sources have similar MFIR strengths. This suggests that the efficiency of the conversion of jet kinetic energy

  2. NASA Radio Frequency Spectrum Management Manual

    NASA Technical Reports Server (NTRS)

    1989-01-01

    The Radio Frequency (RF) Spectrum Management Manual sets forth procedures and guidelines for the management requirements for controlling the use of radio frequencies by the National Aeronautics and Space Administration. It is applicable to NASA Headquarters and field installations. NASA Management Instruction 1102.3 assigns the authority for management of radio frequencies for the National Aeronautics and Space Administration to the Associate Administrator for Space Operations, NASA Headquarters. This manual is issued in loose-leaf form and will be revised by page changes.

  3. 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..

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. Goldstone radio spectrum protection. [deep space network

    NASA Technical Reports Server (NTRS)

    Gaudian, B. A.; Cushman, R. B.

    1980-01-01

    Potential electromagnetic interference to the Goldstone tracking receivers due to neighboring military installations is discussed. Coordination of the military and NASA Goldstone activities in the Mojave Desert area is seen to be an effective method to protect the Goldstone radio spectrum while maintaining compatible operations for the military and Goldstone.

  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. The Compact Steep-Spectrum and Gigahertz Peaked-Spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    O'Dea, Christopher P.

    1998-05-01

    I review the radio to X-ray properties of gigahertz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources, the current hypotheses for their origin, and their use to constrain the evolution of powerful radio galaxies. The GPS and CSS sources are compact, powerful radio sources with well-defined peaks in their radio spectra (near 1 GHz in the GPS and near 100 MHz in the CSS). The GPS sources are entirely contained within the extent of the narrow-line region (<~1 kpc), while the CSS sources are contained entirely within the host galaxy (<~15 kpc). The peaks in the spectra are probably due to synchrotron self-absorption, though free-free absorption through an inhomogeneous screen may also play a role. The turnover frequency varies with linear size l as nu_m~l^-0.65, suggesting a simple physical relationship between these parameters. The radio morphologies are strikingly like those of the large-scale classical doubles, though some sources can have very distorted morphologies suggestive of interactions. Radio polarization tends to be low, and in some cases the Faraday rotation measures can be extremely large. The IR properties are consistent with stellar populations and active galactic nucleus (AGN) bolometric luminosity similar to that of the 3CR classical doubles. The optical host galaxy properties (absolute magnitude, Hubble diagram, evidence for interaction) are consistent with those of the 3CR classical doubles. CSS sources at all redshifts exhibit high surface brightness optical light (most likely emission-line gas) that is aligned with the radio axis. The optical emission-line properties suggest (1) interaction of the radio source with the emission-line gas and (2) the presence of dust toward the emission-line regions. X-ray observations of high-redshift GPS quasars and a couple of GPS galaxies suggest the presence of significant columns of gas toward the nuclei. Searches for cold gas in the host galaxies have revealed large amounts of molecular gas and

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Low-Frequency Radio Observations of Galaxy Cluster Merger Shocks

    NASA Astrophysics Data System (ADS)

    van Weeren, Reinout

    2014-10-01

    In a few dozen merging galaxy clusters diffuse extended radio emission has been found, implying the presence of relativistic particles and magnetic fields in the intracluster medium. A major question is how these particles are accelerated up to such extreme energies. In this talk I will present LOFAR and JVLA radio observations of the Toothbrush galaxy cluster. The Toothbrush cluster hosts diffuse 2 Mpc extended radio emission in the form of a radio relic and halo. Our deep LOFAR and JVLA observations allow a radio spectral study to test the shock origin of the relic and underlying particle acceleration mechanisms.

  17. Searching for Molecular Gas in Southern Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Prandoni, I.; Laing, R. A.; de Ruiter, H. R.; Parma, P.

    2012-07-01

    It has recently been proposed that the jets of low-luminosity radio galaxies are powered by direct accretion of the hot phase of the IGM onto the central black hole. Cold gas remains a plausible alternative fuel supply, however. The most compelling evidence that cold gas plays a role in fueling radio galaxies is that dust is detected more commonly and/or in larger quantities in (elliptical) radio galaxies compared with radio-quiet elliptical galaxies. On the other hand, only small numbers of radio galaxies have yet been detected in CO (and even fewer imaged), and whether or not all radio galaxies have enough cold gas to fuel their jets remains an open question. If so, then the dynamics of the cold gas in the nuclei of radio galaxies may provide important clues to the fuelling mechanism. The only instrument capable of imaging the molecular component on scales relevant to the accretion process is ALMA, but very little is yet known about CO in southern radio galaxies. Our aim is to measure the CO content in a complete volume-limited sample of southern radio galaxies, in order to create a well-defined list of nearby targets to be imaged in the near future with ALMA. APEX has been equipped with a receiver (APEX-1) able to observe the 230 GHz waveband. This allows us to search for CO(2-1) line emission in our target galaxies. Here we present the results of CO(2-1) APEX-1 spectroscopy taken in 2008 and 2010 for our southern sample. The experiment was successful with nearly all targets detected, and several indications for double-horned CO line profiles, consistent with ordered rotation.

  18. 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.

  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. 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.

  1. 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.

  2. Infrared and Radio Features of Galaxies with UV-Excess

    NASA Astrophysics Data System (ADS)

    Martirosyan, Zhaklin R.

    2007-08-01

    Statistical research of galaxies with UV-excess has been carried out. Sample of 702 Kazarian's galaxies (KG) is used. More than 36 % KG have been identified with infra-red sources at wavelengths 12, 25, 60 and 100 microns. The calculation of FIR luminosities has shown that 4 % of KG is luminous IR galaxies with LFIR 10^11Lsun. More than 32 % KG have been identified with radio sources at frequency 1.4 GHz. Definition of radio luminosities has shown, that in the KG sample there is a radio-loud (LR; 10^25 W•Hz-1) BL Lac type object Kaz 273 with known radial velocity. Tight correlation (r = 0.93) between FIR and radio luminosities for galaxies with UV- excess is received. The investigation of connection FIR and radio luminosities for galaxies of different spectral classes has shown that the coefficient of correlation is higher (r = 0.99), and the inclination of dependence is steeper (a = 1.18) for Seyfert type galaxies. From calculations of logarithm of the ratio FIR and radio flux densities it is established, that in the sample there are 4 KG with radio excess, while galaxies with IR-excess are absent.

  3. Discovery of Misaligned Radio Emission in Galaxy Cluster Zw CL 2971

    NASA Astrophysics Data System (ADS)

    Wallack, Nicole; Migliore, C.; Resnick, A.; White, T.; Liu, C.

    2014-01-01

    In a search for green valley galaxies with radio loud active galactic nuclei (AGN), we found one such object that may be associated with the cluster of galaxies Zw CL 2971 (z = 0.098). Serendipitously, we found in this cluster a strong bent-jet radio source associated with the cluster's central dominant (cD) elliptical galaxy. The center of the cD galaxy is coincident (0.35 arcsecond) with the second brightest spot of radio continuum emission (34.3 mJy as measured by FIRST), but the brightest radio hotspot (66.8 mJy) is offset by 4.6 arcseconds 9 kpc at the redshift of the cluster) and has no visible counterpart. Furthermore, the optical spectrum of the cD galaxy has only weak emission lines, suggesting the absence of a currently active nucleus. It is possible that the counterpart is optically faint (possibly due to a recently completed duty cycle) or is not visible due to movement or position. If the radio source is a distant background object, then the brighter jet is most likely magnified by gravitational lensing. If the radio source is located at the redshift of the cluster, then the brighter radio jet trails backward toward and past the cD galaxy to a distance of ~120 kpc, while the fainter jet is bent at a nearly orthogonal angle, ~40 kpc away from the brightest radio hotspot, in the opposite direction. These geometric offsets could be used to constrain the duty cycle history of the AGN creating the radio emission, as well as the dynamical properties of the intracluster medium.

  4. Evolution of low-frequency contribution in emission of steep-spectrum radio sources

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, Alla P.

    2016-10-01

    We consider evolution properties of galaxies and quasars with steep radio spectrum at the decametre band from the UTR-2 catalogue. The ratios of source's monochromatic luminosities at the decametre and high-frequency bands display the dependence on the redshift, linear size, characteristic age of examined objects. At that, the mean values of corresponding ratios for considered galaxies and quasars have enough close quantities,testifying on the unified model of sources. We analyse obtained relations for two types of steep-spectrum sources (with linear steep spectrum (S) and low-frequency steepness after a break (C+)) from the UTR-2 catalogue.

  5. The GOODS-North Radio Galaxies: On the Origin of the Radio Emission

    NASA Astrophysics Data System (ADS)

    Morrison, G.; Dickinson, M.; Owen, F.; Daddi, E.; Chary, R.; Bauer, F.; Mobasher, B.; MacDonald, E.; Koekemoer, A.; Pope, A.

    2008-03-01

    We report on a preliminary study concerning the origin of radio emission within radio galaxies at L(1.4GHz)>1E24 W/Hz in the GOODS-N field. In the local universe, Condon et al. (1989) and Yun et al. (2001) have shown that in galaxies with radio luminosities greater than 1× 10^{23} W/Hz the majority of the radio emission originates from a `monster' i.e., an AGN. Using the Chandra 2Msec X-ray image centered on the GOODS-N field and a reprocessed VLA HDF A-array data plus newly acquired VLA B-array data (σ=5.3μJy), we find that radio galaxies (with spectroscopic redshifts; all have z>1) with L(1.4GHz)>1E24 W/Hz typically have an X-ray detection rate of 72% (60% emit hard X-rays suggesting an AGN origin for the radio emission) in contrast to 25% for radio galaxies with L < 1× 10^{23} W/Hz. The ACS images of these L[1.4 GHz] ≥ 1× 10^{24} W/Hz galaxies typically show compact rather than extended galaxy morphology which is generally found for the less luminous radio emitting galaxies but a few appear to be ongoing galaxy mergers. We also present SED fitting for these luminous radio galaxies including Spitzer IRAC & MIPS 24u photometry and 60% show distinct power-law SED indicative of an AGN. Initial results tell us that the X-ray emitting radio galaxy population are generally not submm sources but the few (˜10%) that are SCUBA sources appear to be the small AGN population found by Pope et al. and others.

  6. The new class of FR0 radio galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.

    2016-08-01

    I present my recent project aimed at studying the bulk of the radio-emitting AGN population. In previous works (Baldi & Capetti 2009, 2010) we provide evidences of an emerging population of compact radio galaxies which lack of extended radio emission. In a pilot JVLA project, we observe a small but representative sub-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 radio-loud AGN live in red massive early-type galaxies, with large black hole masses ( 10^{8} solar mass), 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 (Baldi et al 2015). The emerging FR0 population appears to be the dominant radio class of the local Universe. Considering their properties I peculate their possible origins and the possible cosmological scenarios they imply.

  7. Radio Continuum and H I Study of Blue Compact Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Ramya, S.; Kantharia, N. G.; Prabhu, T. P.

    2011-02-01

    The multifrequency radio continuum and 21 cm H I observations of five blue compact dwarf (BCD) galaxies, Mrk 104, Mrk 108, Mrk 1039, Mrk 1069, and I Zw 97, using the Giant Meterwave Radio Telescope (GMRT) are presented here. Radio continuum emission at 610 MHz and 325 MHz is detected from all the observed galaxies whereas only a few are detected at 240 MHz. In our sample, three galaxies (Mrk 104, Mrk 108, and Mrk 1039) are members of groups and two galaxies (Mrk 1069 and I Zw 97) are isolated galaxies. The radio emission from Mrk 104 and Mrk 108 is seen to encompass the entire optical galaxy whereas the radio emission from Mrk 1039, Mrk 1069, and I Zw 97 is confined to massive H II regions. This, we suggest, indicates that the star formation in the latter group of galaxies has recently been triggered and that the environment in which the galaxy is evolving plays a role. Star formation rates (SFRs) calculated from 610 MHz emission are in the range 0.01-0.1 M sun yr-1 this is similar to the SFR obtained for individual star-forming regions in BCDs. The integrated radio spectra of four galaxies are modeled over the frequency range where data is available. We find that two of the galaxies, Mrk 1069 and Mrk 1039, show a turnover at low frequencies, which is well fitted by free-free absorption whereas the other two galaxies, Mrk 104 and Mrk 108, show a power law at the lowest GMRT frequencies. The flatter spectrum, localized star formation, and radio continuum in isolated galaxies lend support to stochastic self-propagating star formation. The H I observations of four galaxies, Mrk 104, Mrk 108, Mrk 1039, and Mrk 1069, show extended disks as large as ~1.1-6 times the optical size. All the observed BCDs (except Mrk 104) show rotating disk with a half power width of ~50-124 km s-1. Solid body rotation is common in our sample. We note that the tidal dwarf origin is possible for two of the BCDs in our sample.

  8. 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).

  9. 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.

  10. Neutrinos from flat-spectrum radio quasars

    NASA Technical Reports Server (NTRS)

    Mannheim, K.; Stanev, T.; Biermann, P. L.

    1992-01-01

    The GRO observation (Hartman et al., 1992) of a very strong flux of gamma rays with an energy index close to 2 from the distant quasar 3C279 and other extragalactic flat-spectrum radio sources is in very good agreement with models that advocate the important role of very high energy protons and nuclei in the energy transport in AGN. Protons and nuclei cool by interactions on the nonthermal fields in the nuclear jet of the AGN and generate gamma ray and neutrino fluxes. Ultra high energy neutrinos could be observed with sensitive air shower experiments in outbursts as powerful as the one seen by GRO.

  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. 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.

  13. 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.

  14. Molecular disks in radio galaxies. The pathway to ALMA

    NASA Astrophysics Data System (ADS)

    Prandoni, I.; Laing, R. A.; de Ruiter, H. R.; Parma, P.

    2010-11-01

    Context. It has recently been proposed that the jets of low-luminosity radio galaxies are powered by direct accretion of the hot phase of the IGM onto the central black hole. Cold gas remains a plausible alternative fuel supply, however. The most compelling evidence that cold gas plays a role in fueling radio galaxies is that dust is detected more commonly and/or in larger quantities in (elliptical) radio galaxies compared with radio-quiet elliptical galaxies. On the other hand, only small numbers of radio galaxies have yet been detected in CO (and even fewer imaged), and whether or not all radio galaxies have enough cold gas to fuel their jets remains an open question. If so, then the dynamics of the cold gas in the nuclei of radio galaxies may provide important clues to the fuelling mechanism. Aims: The only instrument capable of imaging the molecular component on scales relevant to the accretion process is ALMA, but very little is yet known about CO in southern radio galaxies. Our aim is to measure the CO content in a complete volume-limited sample of southern radio galaxies, in order to create a well-defined list of nearby targets to be imaged in the near future with ALMA. Methods: APEX [This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.] has recently been equipped with a receiver (APEX-1) able to observe the 230 GHz waveband. This allows us to search for CO(2-1) line emission in our target galaxies. Results: Here we present the results for our first three southern targets, proposed for APEX-1 spectroscopy during science verification: NGC 3557, IC 4296 and NGC 1399. The experiment was successful with two targets detected, and possible indications for a double-horned CO line profile, consistent with ordered rotation. These early results are encouraging, demonstrating that APEX can

  15. 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.

  16. Radio identifications of UGC galaxies - starbursts and monsters

    SciTech Connect

    Condon, J.J.; Broderick, J.J.

    1988-07-01

    New and previously published observational data on galaxies with declination less than +82 deg from the Uppsala General Catalog (Nilson, 1973) are compiled in extensive tables and characterized in detail. Optical positions are confirmed by measurement of Palomar Sky Survey O prints, and radio identifications for 176 galaxies are made on the basis of 1.4-GHz Green Bank sky maps or 1.49-GHz observations obtained with the C configuration of the VLA in November-December 1986; contour maps based on the latter observations are provided. Radio-selected and IR-selected galaxy populations are found to be similar (and distinct from optically selected populations), and three radio/IR criteria are developed to distinguish galaxies powered by starbursts from those with supermassive black holes or other monster energy sources. 197 references.

  17. Polarimetry and Unification of Low-Redshift Radio Galaxies

    SciTech Connect

    Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

    1999-11-01

    We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise

  18. X-Ray-emitting Atmospheres of B2 Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Worrall, D. M.; Birkinshaw, M.

    2000-02-01

    We report ROSAT PSPC spatial and spectral analyses of the eight B2 radio galaxies NGC 315, NGC 326, 4C 35.03, B2 0326+39, NGC 2484, B2 1040+31, B2 1855+37, and 3C 449, expected to be representative of the class of low-power radio galaxies. Multiple X-ray components are present in each, and the gas components have a wide range of linear sizes and follow an extrapolation of the cluster X-ray luminosity/temperature correlation, implying that there is no relationship between the presence of a radio galaxy and the gas fraction of the environment. No large-scale cooling flows are found. There is no correlation of radio-galaxy size with the scale or density of the X-ray atmosphere. This suggests that processes on scales smaller than those of the overall gaseous environments are the major influence on radio-source dynamics. The intergalactic medium is usually sufficient to confine the outer parts of the radio structures, in some cases even to within 5 kpc of the core. In the case of NGC 315, an extrapolation suggests that the pressure of the atmosphere may match the minimum pressure in the radio source over a factor of ~40 in linear size (a factor of ~1600 in pressure).

  19. Full Duplex, Spread Spectrum Radio System

    NASA Technical Reports Server (NTRS)

    Harvey, Bruce A.

    2000-01-01

    The goal of this project was to support the development of a full duplex, spread spectrum voice communications system. The assembly and testing of a prototype system consisting of a Harris PRISM spread spectrum radio, a TMS320C54x signal processing development board and a Zilog Z80180 microprocessor was underway at the start of this project. The efforts under this project were the development of multiple access schemes, analysis of full duplex voice feedback delays, and the development and analysis of forward error correction (FEC) algorithms. The multiple access analysis involved the selection between code division multiple access (CDMA), frequency division multiple access (FDMA) and time division multiple access (TDMA). Full duplex voice feedback analysis involved the analysis of packet size and delays associated with full loop voice feedback for confirmation of radio system performance. FEC analysis included studies of the performance under the expected burst error scenario with the relatively short packet lengths, and analysis of implementation in the TMS320C54x digital signal processor. When the capabilities and the limitations of the components used were considered, the multiple access scheme chosen was a combination TDMA/FDMA scheme that will provide up to eight users on each of three separate frequencies. Packets to and from each user will consist of 16 samples at a rate of 8,000 samples per second for a total of 2 ms of voice information. The resulting voice feedback delay will therefore be 4 - 6 ms. The most practical FEC algorithm for implementation was a convolutional code with a Viterbi decoder. Interleaving of the bits of each packet will be required to offset the effects of burst errors.

  20. JET-POWERED MOLECULAR HYDROGEN EMISSION FROM RADIO GALAXIES

    SciTech Connect

    Ogle, Patrick; Guillard, Pierre; Boulanger, Francois; Nesvadba, Nicole; Evans, Daniel A.; Antonucci, Robert; Appleton, P. N.; Leipski, Christian

    2010-12-01

    H{sub 2} pure-rotational emission lines are detected from warm (100-1500 K) molecular gas in 17/55 (31% of) radio galaxies at redshift z < 0.22 observed with the Spitzer IR Spectrograph. The summed H{sub 2} 0-0 S(0)-S(3) line luminosities are L(H{sub 2}) = 7 x 10{sup 38}-2 x 10{sup 42} erg s{sup -1}, yielding warm H{sub 2} masses up to 2 x 10{sup 10} M{sub sun}. These radio galaxies, of both FR radio morphological types, help to firmly establish the new class of radio-selected molecular hydrogen emission galaxies (radio MOHEGs). MOHEGs have extremely large H{sub 2} to 7.7 {mu}m polycyclic aromatic hydrocarbon (PAH) emission ratios: L(H{sub 2})/L(PAH7.7) = 0.04-4, up to a factor 300 greater than the median value for normal star-forming galaxies. In spite of large H{sub 2} masses, MOHEGs appear to be inefficient at forming stars, perhaps because the molecular gas is kinematically unsettled and turbulent. Low-luminosity mid-IR continuum emission together with low-ionization emission line spectra indicates low-luminosity active galactic nuclei (AGNs) in all but three radio MOHEGs. The AGN X-ray emission measured with Chandra is not luminous enough to power the H{sub 2} emission from MOHEGs. Nearly all radio MOHEGs belong to clusters or close pairs, including four cool-core clusters (Perseus, Hydra, A2052, and A2199). We suggest that the H{sub 2} in radio MOHEGs is delivered in galaxy collisions or cooling flows, then heated by radio-jet feedback in the form of kinetic energy dissipation by shocks or cosmic rays.

  1. The host galaxies of radio-loud and radio-quiet AGNs

    NASA Astrophysics Data System (ADS)

    Koziel-Wierzbowska, D.; Vale Asari, N.; Stasinska, G.; Sikora, M.

    2016-08-01

    To infer whether the jet production efficiency depends on the host properties or is determined just by intrinsic properties of the accretion flows we compared optical properties of the host galaxies of radio-quiet (RQ) and radio-loud (RL) Type 2 AGNs. We carefully selected galaxies from SDSS, FIRST, and NVSS catalogues. We confirmed that the fraction of RL AGNs increases with the black hole (BH) masses and decreases with the Eddington ratio. Therefore, the comparison of the nature of the hosts of RL and RQ AGNs requires pairmatching techniques. By pairing RL and RQ samples in BH mass, Eddington ratio and redshift, we showed that the radio-loudness correlates with the host-galaxy concentration index and morphological type, and anti-correlates with the recent specific star-formation rate and dust attenuation. Contrary to some previous studies, we found no significant difference between our radio-loud and radio-quiet samples regarding merger/interaction features.

  2. 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

  3. 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.

  4. 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

  5. Radio Selected Clusters of Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Wing, Joshua; Blanton, Elizabeth

    2010-08-01

    Previous studies have shown that three-component radio sources exhibiting some degree of bending between components are likely to be found in galaxy clusters. Often this radio emission is associated with a cD type galaxy at the center of a cluster. We have cross-correlated the Sloan Digital Sky Survey (SDSS) with samples selected from the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) catalog and measured the richness of the cluster environments surrounding three- component sources exhibiting both bent and straight lobes. This has lead to the discovery and classification of a large number of galaxy clusters out to a redshift of z ~ 0.5. For both bent- and straight- lobed sources without an optical counterpart it is likely that the radio emission is associated with a galaxy fainter than m_r=22 (the limiting magnitude of the SDSS) and at a redshift higher than z~0.8. We propose to observe a small sub-sample of these sources with the FLAMINGOS instrument on the Mayall 4-m telescope in an attempt to discover if these sources are located in high redshift (z≳0.8) galaxy clusters. In our visually-selected bent radio source sample, 78% of sources with counterparts in the SDSS are associated with clusters.

  6. Goldstone radio spectrum signal identification, March 1980 - March 1982

    NASA Technical Reports Server (NTRS)

    Gaudian, B. A.

    1982-01-01

    The signal identification process is described. The Goldstone radio spectrum environment contains signals that are a potential source of electromagnetic interference to the Goldstone tracking receivers. The identification of these signals is accomplished by the use of signal parameters and environment parameters. Statistical data on the Goldstone radio spectrum environment from 2285 to 2305 MHz are provided.

  7. MULTI-FREQUENCY STUDIES OF RADIO RELICS IN THE GALAXY CLUSTERS A4038, A1664, AND A786

    SciTech Connect

    Kale, Ruta; Dwarakanath, K. S.

    2012-01-01

    We present a multi-frequency study of radio relics associated with the galaxy clusters A4038, A1664, and A786. Radio images, integrated spectra, spectral index maps, and fits to the integrated spectra in the framework of the adiabatic compression model are presented. Images of the relic in A4038 at 150, 240, and 606 MHz with the Giant Meterwave Radio Telescope have revealed extended ultra-steep spectrum ({alpha} {approx} -1.8 to -2.7) emission of extent 210 Multiplication-Sign 80 kpc{sup 2}. The model of passively evolving radio lobes compressed by a shock fits the integrated spectrum best. The relic with a circular morphology at the outskirts of the cluster A1664 has an integrated spectral index of {approx} - 1.10 {+-} 0.06 and is best fit by the model of radio lobes lurking for {approx}4 Multiplication-Sign 10{sup 7} yr. The relic near A786 has a curved spectrum and is best fit by a model of radio lobes lurking for {approx}3 Multiplication-Sign 10{sup 7} yr. At 4.7 GHz, a compact radio source, possibly the progenitor of the A786 relic, is detected near the center of the radio relic. The A786 radio relic is thus likely a lurking radio galaxy rather than a site of cosmological shock as has been considered in earlier studies.

  8. 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

  9. Exploring the nature of radio relics and halos in galaxy clusters through GHz radio observations

    NASA Astrophysics Data System (ADS)

    Trasatti, M.

    2014-11-01

    -100m Telescope at 2640 MHz and at 4850 MHz. The same field was observed with a 3-pointing mosaic performed with the WSRT at 2273 MHz. The observations were performed in full polarization mode. The Effelberg observations were carried out during an observational campaign of a small sample of galaxy clusters known to host diffuse non-thermal emission. We include preliminary results from the analysis of Effelsberg C-band data of the galaxy clusters Abell 0115 and Abell 2255. We highlight the importance of high-frequencies observations for the study of both the total intensity and the polarization properties of these sources. The connection of the radio properties observed with the properties of the thermal gas derived from X-ray and S-Z effect observations is also discussed. It is generally assumed that radio relics are observed in stationary conditions. In this case the widely accepted model for radio relics, the diffusive acceleration at merger shocks (DSA), predicts single power-law integrated spectra. However, we observe a departure from a pure power-law integrated spectrum at frequencies > 1.4 GHz for the radio relic in Abell 2256 that puts tension on the commonly assumed conditions for DSA. Moreover, theoretical studies have shown that in the case of strong shocks the DSA model predicts magnetic field compression and alignment with the shock front. At high frequencies, the observed polarized emission is less affected by Faraday effects and it is therefore a better indicator of the intrinsic properties of the sources. Possible alignment of the polarization vectors measured across the extent of radio relics can, therefore, be used to reconstruct the geometry of the shock passage in case of shock acceleration. We show that the polarization properties in the Abell 2256 relic are difficult to be reconciled with a single outgoing shock front, requiring a more complex scenario. We also show how the combination of interferometric and single-dish data in the Fourier domain

  10. 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.

  11. 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

  12. 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.

  13. Constraints on Accretion Disk Physics in Low Luminosity Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Baum, Stefi; Noel-Storr, Jacob; O'Dea, Christopher

    2008-03-01

    It is currently believed that essentially all galaxies harbor a massive black hole in their nuclei. If this is true, then it becomes hard to understand why we do not see the luminosity released by the inevitable accretion of the galaxy ISM onto the black hole in all galaxies. The differences in AGN output between the two classes of narrow-line radio galaxies (FRI and FRII) may hold the vital clue. High radio luminosity FRIIs generally show strong high-excitation narrow lines and are believed to be the obscured counterparts of radio loud quasars. Low radio luminosity FRIs by contrast have weaker, low-ionization lines and low ratios of optical to radio luminosities. A large difference in accretion rate and radiative efficiency between FRI and FRIIs would explain the difference in the optical properties and also provide a new unification between different classes of active galaxies in which the dominant parameter is accretion rate. Spitzer IRAC and MIPS observations already exist for most of a well defined sample of FRIs. However, the previously observed objects are the 'famous' ones, e.g., M87, M84, NGC315, 3C264, 3C31. Thus, the existing datasets are highly selected. Here we propose a very small request to complete the sample. We propose IRAC observations in all 4 bands, and MIPS photometry at 24 and 70 microns of 8, and 7 sources, respectively, for a total request of 1.7 hrs. These observations will complete the sample at very little cost in observing time. The large amount of existing complmentary data at multiple wavebands will greatly enhance the legacy value of the proposed observations. By completing the sample, the proposed IRAC and MIPS observations will produce a well defined and very well studied sample of nearby low luminosity radio galaxies. We will use the completed sample to investigate the properties of the accretion disk radiation, and the circumnuclear obscuring material.

  14. Strong Lyman-alpha emission in three distant radio galaxies

    NASA Technical Reports Server (NTRS)

    Spinrad, H.; Filippenko, A. V.; Wyckoff, S.; Wagner, R. M.; Stocke, J. T.

    1985-01-01

    Very strong, narrow Lyman alpha emission (equivalent width approximately 1000 angstroms) has been discovered in the redshifted ultraviolet spectra of three radio galaxies having z between 1.62 and 1.82. The three are 3C 256, 3C 239, and 3C 241. It is noted that Lyman alpha will probably be a very useful redshift and classification determinant in future spectroscopic surveys of active galaxies at still greater distances.

  15. THE SPITZER HIGH-REDSHIFT RADIO GALAXY SURVEY

    SciTech Connect

    De Breuck, Carlos; Galametz, Audrey; Vernet, Joel; Seymour, Nick; Stern, Daniel; Eisenhardt, P. R. M.; Willner, S. P.; Fazio, G. G.; Lacy, Mark; Rettura, Alessandro; Rocca-Volmerange, Brigitte

    2010-12-10

    We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 1 < z < 5.2 using all three cameras on board the Spitzer Space Telescope. The resulting spectral energy distributions unambiguously show a stellar population in 46 sources and hot dust emission associated with the active nucleus in 59. Using a new rest-frame S{sub 3{sub {mu}m}}/S{sub 1.6{sub {mu}m}} versus S{sub 5{sub {mu}m}}/S{sub 3{sub {mu}m}} criterion, we identify 42 sources where the rest-frame 1.6 {mu}m emission from the stellar population can be measured. For these radio galaxies, the median stellar mass is high, 2 x 10{sup 11} M{sub sun}, and remarkably constant within the range 1 < z < 3. At z>3, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z {approx} 3, but confirmation by more detailed decomposition of stellar and active galactic nucleus (AGN) emission is needed. The rest-frame 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the rest-frame 5 {mu}m hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance-an indicator of jet orientation-is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6'') companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers.

  16. 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.

  17. RADIO AND X-RAY SHOCKS IN CLUSTERS OF GALAXIES

    SciTech Connect

    Hong, Sungwook E.; Kang, Hyesung; Ryu, Dongsu E-mail: hskang@pusan.ac.kr

    2015-10-10

    Radio relics detected in the outskirts of galaxy clusters are thought to trace radio-emitting relativistic electrons accelerated at cosmological shocks. In this study, using the cosmological hydrodynamic simulation data for the large-scale structure formation and adopting a diffusive shock acceleration (DSA) model for the production of cosmic-ray (CR) electrons, we construct mock radio and X-ray maps of simulated galaxy clusters that are projected in the sky plane. Various properties of shocks and radio relics, including the shock Mach number, radio spectral index, and luminosity, are extracted from the synthetic maps and compared with observations. A substantial fraction of radio and X-ray shocks identified in these maps involve multiple shock surfaces along lines of sight (LOSs), and the morphology of shock distributions in the maps depends on the projection direction. Among multiple shocks in a given LOS, radio observations tend to pick up stronger shocks with flatter radio spectra, while X-ray observations preferentially select weaker shocks with larger kinetic energy flux. As a result, in some cases the shock Mach numbers and locations derived from radio and X-ray observations could differ from each other. We also find that the distributions of the spectral index and radio power of the synthetic radio relics are somewhat inconsistent with those of observed real relics; a bit more radio relics have been observed closer to the cluster core and with steeper spectral indices. We suggest that the inconsistency could be explained if very weak shocks with M{sub s} ≲ 2 accelerate CR electrons more efficiently, compared with the DSA model adopted here.

  18. 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.

  19. Extensive gaseous haloes surrounding giant elliptical galaxies - Evidence from depolarization in radio galaxies

    NASA Astrophysics Data System (ADS)

    Strom, R. G.; Jaegers, W. J.

    1988-04-01

    Radio polarization measurements have been used to investigate large scale gaseous components associated with some thirteen double radio sources. At 49 cm a significant proportion of the bridge emission, roughly centered on the parent galaxy, is invariably found to be unpolarized. The authors present evidence that this lack of polarization at long wavelengths is the result of differential Faraday rotation in a large scale halo associated with the central (usually elliptical) galaxy. The haloes, which extend beyond 100 kpc, appear to be the outer envelopes of hot gas such as that observed in the form of extended X-ray emission associated with a number of nearby early-type galaxies.

  20. A search for distant radio galaxies from SUMSS and NVSS - III. Radio spectral energy distributions and the z-α correlation

    NASA Astrophysics Data System (ADS)

    Klamer, Ilana J.; Ekers, Ron D.; Bryant, Julia J.; Hunstead, Richard W.; Sadler, Elaine M.; De Breuck, Carlos

    2006-09-01

    This is the third in a series of papers that present observations and results for a sample of 76 ultrasteep-spectrum radio sources designed to find galaxies at high redshift. Here we present multifrequency radio observations, from the Australia Telescope Compact Array, for a subset of 37 galaxies from the sample. Matched resolution observations at 2.3, 4.8 and 6.2 GHz are presented for all galaxies, with the z < 2 galaxies additionally observed at 8.6 and 18 GHz. New angular size constraints are reported for 19 sources based on high-resolution 4.8- and 6.2-GHz observations. Functional forms for the rest-frame spectral energy distributions are derived: 89 per cent of the sample is well characterized by a single power law, whilst the remaining 11 per cent show some flattening towards higher frequencies: not one source shows any evidence for high-frequency steepening. We discuss the implications of this result in light of the empirical correlation between redshift and spectral index seen in flux-limited samples of radio galaxies. Finally, a new physical mechanism to explain the redshift - spectral index correlation is posited: extremely steep-spectrum radio galaxies in the local universe usually reside at the centres of rich galaxy clusters. We argue that if a higher fractions of radio galaxies, as a function of redshift, are located in environments with densities similar to nearby rich clusters, then this could be a natural interpretation for the correlation. We briefly outline our plans to pursue this line of investigation.

  1. A double radio relic in the merging galaxy cluster ZwCl 0008.8+5215

    NASA Astrophysics Data System (ADS)

    van Weeren, R. J.; Hoeft, M.; Röttgering, H. J. A.; Brüggen, M.; Intema, H. T.; van Velzen, S.

    2011-04-01

    Context. Some merging galaxy clusters host diffuse elongated radio sources, also called radio relics. It is proposed that these radio relics trace shock waves in the intracluster medium (ICM) created during a cluster merger event. Within the shock waves particles are accelerated to relativistic energies, and in the presence of a magnetic field synchrotron radiation will be emitted. Here we present giant metrewave radio telescope (GMRT) and Westerbork synthesis radio telescope (WSRT) observations of a new double relic in the galaxy cluster ZwCl 0008.8+5215. Aims: The aim of the observation is to understand the phenomenon of radio relics. Methods: We carried out radio continuum observations at 241 and 610 MHz with the GMRT, and 1.3-1.8 GHz observations with the WSRT in full polarization mode. Optical V,R, and I band images of the cluster were taken with the 2.5 m Isaac Newton Telescope (INT). An optical spectrum, to determine the redshift of the cluster, was taken with the William Herschel Telescope (WHT). Results: Our observations show the presence of a double radio relic in the galaxy cluster ZwCl 0008.8+5215, for which we find a spectroscopic redshift of z = 0.1032 ± 0.0018 from an optical spectrum of one of the cD galaxies. The spectral index of the two relics steepens inwards to the cluster center. For part of the relics, we measure a polarization fraction in the range ~5-25%. A ROSAT X-ray image displays an elongated ICM and the large-scale distribution of galaxies reveals two cluster cores, all pointing towards a binary cluster merger event. The radio relics are located symmetrically with respect to the X-ray center of the cluster, along the proposed merger axis. The relics have a linear extent of 1.4 Mpc and 290 kpc. This factor of five difference in linear size is unlike that of previously known double relic systems, for which the sizes do not differ by more than a factor of two. Conclusions: We conclude that the double relics in ZwCl 0008.8+5215 are best

  2. 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

  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.

    2016-08-01

    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.

  4. THE UNIFICATION OF POWERFUL QUASARS AND RADIO GALAXIES AND THEIR RELATION TO OTHER MASSIVE GALAXIES

    SciTech Connect

    Podigachoski, Pece; Barthel, Peter; Haas, Martin; Leipski, Christian; Wilkes, Belinda

    2015-06-10

    The unification model for powerful radio galaxies (RGs) and radio-loud quasars postulates that these objects are intrinsically the same but viewed along different angles. Herschel Space Observatory data permit the assessment of that model in the far-infrared spectral window. We analyze photometry from Spitzer and Herschel for the distant 3CR hosts, and find that RGs and quasars have different mid-infrared, but indistinguishable far-infrared colors. Both these properties, the former being orientation dependent and the latter orientation invariant, are in line with expectations from the unification model. Adding powerful radio-quiet active galaxies and typical massive star-forming (SF) galaxies to the analysis, we demonstrate that infrared colors not only provide an orientation indicator, but can also distinguish active from SF galaxies.

  5. A new intermediate Seyfert galaxy - X-ray, optical, and radio properties

    NASA Technical Reports Server (NTRS)

    Ghigo, F. D.; Wyckoff, S.; Wardle, J. F. C.; Cohen, N. L.

    1982-01-01

    It is shown that the X-ray source X0459 + 034 is a Seyfert galaxy of intermediate type, and optical spectroscopy and radio observations were performed to study the nature of the object. The object appears almost stellar and slightly diffuse on Palomar Sky Survey prints. The source is identified as a Type 1.5 Seyfert with broad and narrow line components of redshift 0.016 + or - 0.001, according to H-Beta line profile. In addition, the broad line component H-Beta equivalent width is larger than that of the narrow line component by a factor of three. Finally, it is shown that this is a weak radio source with a steep nonthermal spectrum and an angular extent of approximately 3 in., and the composite radio-to-X-ray spectrum suggests that in different spectral regions, different relativistic electron populations or emission mechanisms are contributing factors.

  6. Mutual distance dependence drives the observed jet-power-radio-luminosity scaling relations in radio galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    The kinetic power of radio jets is a quantity of fundamental importance to studies of the AGN feedback process and radio galaxy physics. A widely used proxy for jet power is the extended radio luminosity. A number of empirical methods have been used to calibrate a scaling relationship between jet power (Q) and radio luminosity (L) of the form log (Q) = βL log (L) + C. The regression slope has typically been found to be βL ˜ 0.7-0.8. Here we show that the previously reported scaling relations are strongly affected by the confounding variable, distance. We find that in a sample of FRI X-ray cavity systems, after accounting for the mutual distance dependence, the jet power and radio luminosity are only weakly correlated, with slope βL ≈ 0.3: significantly flatter than previously reported. We also find that in previously used samples of high-power sources, no evidence for an intrinsic correlation is present when the effect of distance is accounted for. Using a simple model we show that βL is expected to be significantly lower in samples of FRI radio galaxies than it is for FRIIs, due to the differing dynamics for these two classes of radio source. For FRI X-ray cavity systems the model predicts βL(FRI) ≳ 0.5 in contrast to FRII radio galaxies, for which βL(FRII) ≳ 0.8. We discuss the implications of our finding for studies of radio mode feedback, and radio galaxy physics.

  7. 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.

  8. 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.

  9. Flat-Spectrum Radio Sources as Likely Counterparts of Unidentified INTEGRAL Sources (Research Note)

    NASA Technical Reports Server (NTRS)

    Molina, M.; Landi, R.; Bassani, L.; Malizia, A.; Stephen, J. B.; Bazzano, A.; Bird, A. J.; Gehrels, N.

    2012-01-01

    Many sources in the fourth INTEGRAL/IBIS catalogue are still unidentified since they lack an optical counterpart. An important tool that can help in identifying and classifying these sources is the cross-correlation with radio catalogues, which are very sensitive and positionally accurate. Moreover, the radio properties of a source, such as the spectrum or morphology, could provide further insight into its nature. In particular, flat-spectrum radio sources at high Galactic latitudes are likely to be AGN, possibly associated to a blazar or to the compact core of a radio galaxy. Here we present a small sample of 6 sources extracted from the fourth INTEGRAL/IBIS catalogue that are still unidentified or unclassified, but which are very likely associated with a bright, flat-spectrum radio object. To confirm the association and to study the source X-ray spectral parameters, we performed X-ray follow-up observations with Swift/XRT of all objects. We report in this note the overall results obtained from this search and discuss the nature of each individual INTEGRAL source. We find that 5 of the 6 radio associations are also detected in X-rays; furthermore, in 3 cases they are the only counterpart found. More specifically, IGR J06073-0024 is a flat-spectrum radio quasar at z = 1.08, IGR J14488-4008 is a newly discovered radio galaxy, while IGR J18129-0649 is an AGN of a still unknown type. The nature of two sources (IGR J07225-3810 and IGR J19386-4653) is less well defined, since in both cases we find another X-ray source in the INTEGRAL error circle; nevertheless, the flat-spectrum radio source, likely to be a radio loud AGN, remains a viable and, in fact, a more convincing association in both cases. Only for the last object (IGR J11544-7618) could we not find any convincing counterpart since the radio association is not an X-ray emitter, while the only X-ray source seen in the field is a G star and therefore unlikely to produce the persistent emission seen by INTEGRAL.

  10. The evolution of the radio SED of high-z powerful radio galaxies

    NASA Astrophysics Data System (ADS)

    Drouart, G.

    2016-08-01

    The SKA_LOW pathfinder MWA (Murchison Wide Array) executed the first all-sky radio survey in the 80-230MHz range, revealing more than 300000 extragalactic sources. Combined with data up to 20GHz, we build exquisite radio SEDs (>~30 data-points) of a sample of a well-known sample of 70 high redshift radio galaxies (the HeRGE sample: L_3GHz restframe > 10^26 W/Hz and z>1). The synchrotron emission is composed of the core, jet and the lobe emission, providing insight on the direct vicinity of the galaxy and the accretion properties of the central supermassive black hole (SMBH). Combined with our previous multi-wavelength campaign from optical to submm (including VLT, Keck, HST, Spitzer, Herschel, SCUBA, LABOCA, and more recently ALMA), providing information on the host galaxy, we now investigate simultaneously the mechanical (from radio) and radiative (from IR) of the SMBH hosted in these progenitors of our local massive galaxies. I will present the results from our radio SED fitting and discuss the connection with our previous results in term of radio loud AGN evolution at the peak of activity in the Universe.

  11. 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.

  12. Distant FR I radio galaxies in the Hubble Deep Field: implications for the cosmological evolution of radio-loud AGN

    NASA Astrophysics Data System (ADS)

    Snellen, I. A. G.; Best, P. N.

    2001-12-01

    Deep and high-resolution radio observations of the Hubble Deep Field and flanking fields have shown the presence of two distant edge-darkened FRI radio galaxies, allowing for the first time an estimate of their high-redshift space density. If it is assumed that the space density of FRI radio galaxies at z>1 is similar to that found in the local Universe, then the chance of finding two FRI radio galaxies at these high radio powers in such a small area of sky is <1 per cent. This suggests that these objects were significantly more abundant at z>1 than at present, effectively ruling out the possibility that FRI radio sources undergo no cosmological evolution. We suggest that FRI and FRII radio galaxies should not be treated as intrinsically distinct classes of objects, but that the cosmological evolution is simply a function of radio power with FRI and FRII radio galaxies of similar radio powers undergoing similar cosmological evolutions. Since low-power radio galaxies have mainly FRI morphologies and high-power radio galaxies have mainly FRII morphologies, this results in a generally stronger cosmological evolution for the FRIIs than the FRIs. We believe that additional support from the V/Vmax test for evolving and non-evolving population of FRIIs and FRIs respectively is irrelevant, since this test is sensitive over very different redshift ranges for the two classes.

  13. Deep Radio Observations of the Toothbrush Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    Van Weeren, Reinout J.; Jones, C.; Forman, W. R.; Röttgering, H.; Brüggen, M.; Brunetti, G.; de Gasperin, F.; Bonafede, A.; Pizzo, R.; Ferrari, C.; Orrù, E.; Ogrean, G. A.; LOFAR Busyweek Team; surveys KSP, LOFAR

    2014-01-01

    We present LOFAR and JVLA radio observations of the Toothbrush galaxy cluster. The Toothbrush cluster hosts diffuse 2 Mpc extended radio emission in the form of a radio relic and halo. XMM-Newton X-ray observations show that the cluster is undergoing a major merger event. Both the radio relic and halo are likely related to this ongoing merger. Radio relics are proposed to be direct tracers of shock waves in the intracluster medium. The XMM observations indeed reveal a shock, but there is a puzzling 200 kpc spatial offset between the shock position and relic. Our deep LOFAR and JVLA observations allow a detailed spectral study to test the shock origin of the relic and underlying particle acceleration mechanisms. Finally, the LOFAR observations highlight the science that could be obtained from a deep low-frequency all-sky survey.

  14. Flat spectrum multicomponent radio sources - Cosmic conspiracy or geometry

    SciTech Connect

    Pacholczyk, A.G.

    1981-01-01

    Compact radio sources which do not exhibit currently large flux density variations, are often characterized by spectra nearly flat over a wide range of wavelengths. Cotton et al. (1980) recently reported the results of the VLBI multifrequency interferometric and total flux density observations of a typical representative of the flat spectrum class of sources, a BL Lacertae object PKS 0735+178. If 0735+178 is indeed representative of flat spectrum sources, then some mechanism causing the component production and energy loss to be balanced must be operative among this type of radio source to maintain a flat spectrum over at least certain periods of time. This effect is referred to as 'cosmic conspiracy'. It is suggested that the flatness of spectra of this class of radio sources may be related to a specific symmetry in the radio structure, namely, to a predominantly linear, one-dimensional evolution of radio radiating material, rather than spherical, three-dimensional evolution.

  15. 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.

  16. Fate of baby radio galaxies: Dead or alive?

    NASA Astrophysics Data System (ADS)

    Kawakatu, N.; Nagai, H.; Kino, M.

    2009-02-01

    In order to reveal the long-term evolution of relativistic jets in active galactic nuclei (AGNs), we examine the dynamical evolution of variously-sized radio galaxies [i.e., compact symmetric objects (CSOs), medium-size symmetric objects (MSOs), Fanaroff-Riley type II radio galaxies (FRIIs)]. By comparing the observed relation between the hot spot size and the linear size of radio source with a coevolution model of hot spot and cocoon, we find that the advance speed of hot spots and lobes inevitably show the deceleration phase (CSO-MSO phase) and the acceleration phase (MSO-FRII phase). The deceleration is caused by the growth of the cross-sectional area of the cocoon head. Moreover, by comparing the hot spot speed with the sound speed of the ambient medium, we predict that only CSOs whose initial advance speed is higher than 0.3-0.5 c can evolve into FRIIs.

  17. Polarization Imaging of Radio Galaxies -CYC3 Medium

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert

    1992-06-01

    Spectropolarimetry of the narrow line radio galaxy 3C234 was used to show in 1982 that there is a hidden broad line region occulted by an opaque torus orien- ted perpendicular to the radio structure axis. Given the luminosity of the re- flected light, we know that 3C234 would be called a quasar if its orientation with respect to the line of sight were different. Since then similar results were found for NGC1068 and 8 other Seyferts 2s, and for several other N.L.R.G.s. If many NLRG's are occulted quasars in the sky plane, several statistical anomo- lies in the beam model for superluminal motion are understandable. However, fur- thur optical spectropolarimetry has been disappointing in this regard, appa- rently because of severe dilution of reflected light by starlight, sometimes po- larized, from the host galaxies. We can solve this problem by observing in the UV. Furthermore recent observations of several NLRGs have revealed OFF-NUCLEAR dust clouds reflecting and strongly "bluening" nuclear light. Such dust clouds, abundant in the merger debris surrounding many luminous radio galaxies, should show up spectacularly in UV polarization images, providing information on the beam pattern and time history of nuclear emission. We request FOC polarization images of a sample of radio galaxies, including two with bright blue off-nuclear patches found by Dey and van Breugel. We will also get for free and with high efficiency total flux images, suitable for studying the nuclei and anomalous young stellar populations seen in merging radio galaxies from the ground.

  18. What are the gigahertz peaked-spectrum radio sources?

    NASA Technical Reports Server (NTRS)

    O'Dea, C. P.; Baum, S. A.; Stanghellini, C.

    1991-01-01

    The astrophysical implications of recent radio and optical observations of the powerful compact gigahertz peaked-spectrum (GPS) radio sources are discussed. Some tentative conclusions are presented and a scenario based on the existing data is suggested. It is argued that the spectrum is due to synchrotron self-absorption, which is assumed as the basis for the present inferences from the radio spectral shape. The finding that some GPS sources have a very narrow spectral shape is consistent with the hypothesis that there is a narrow range of size scales which dominate the radio luminosity. The highly inverted LF radio spectrum is consistent with the hypothesis that the radio source is tightly confined. The conclusion that the radio polarization of these sources is systematically low is consistent either with a very tangled magnetic field or very large Faraday rotation measures. It is suggested that GPS radio sources are formed when the radio plasma is confined on the scale of the narrow-line region by an unusually dense and clumpy ISM. The existing optical spectroscopic results are also consistent with the existence of a dense and dusty nuclear ISM.

  19. Inverse Compton X-rays from strong FRII radio-galaxies.

    NASA Astrophysics Data System (ADS)

    Brunetti, G.; Setti, G.; Comastri, A.

    1997-09-01

    In the framework of the quasars-radio galaxies unification the radio-emitting lobes of FRII radio galaxies are pervaded by an intense quasar radiation field. Inverse Compton (IC) scattering between the relativistic electrons and the IR-optical photons from a hidden quasar may provide an important contribution to the X-ray emission of these radio galaxies. The soft X-ray emission properties of six strong, high redshift FRIIs (3C 277.2, 280, 294, 324, 356, 368) are compared with our model expectations, taking into account also the contribution from the IC scattering of the CMB photons with the radio electrons. Our estimates are based on a typical quasar spectrum, derived from the infrared and optical properties of a 3C quasar sample, and on the assumption of energy equipartition between relativistic particles and magnetic fields with the same energy density in the electron and proton components and with a fixed low energy cut-off in the particle distribution (Appendix A). We find that the soft X-ray luminosities and spectra of five out of six sources can be satisfactorily explained by our model with the exception of 3C 324 whose X-ray emission is probably dwarfed by that of the galaxies' cluster of which this source is a member. In the case of 3C 277.2 our model requires a luminosity of the hidden quasar which is in perfect agreement with that derived from spectropolarimetric studies. In order to carry out the computations of the IC scattering of the hidden quasar photons, which are propagating radially outward, we have solved the anisotropic IC problem. The formal approach and relevant formulae, which do not appear to be available in the literature, are presented in the Appendix B. One important effect is the prediction that the observed X-ray emission associated with the two radio lobes would be asymmetric if the radio axis is inclined with respect to the plane of the sky, the far-away lobe being the more luminous. The ratio between the X-ray luminosities of the

  20. 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.

  1. Kiloparsec-scale radio emission in Seyfert and LINER galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Wadadekar, Yogesh; Beelen, Alexandre; Kharb, Preeti

    2015-01-01

    Seyfert and LINER galaxies are known to exhibit compact radio emission on ˜10-100 pc scales, but larger Kiloparsec-Scale Radio structures (KSRs) often remain undetected in sub-arcsec high-resolution observations. We investigate the prevalence and nature of KSRs in Seyfert and LINER galaxies using the 1.4 GHz VLA FIRST and NVSS observations. Our sample consists of 2651 sources detected in FIRST and of these 1737 sources also have NVSS counterparts. Considering the ratio of total to peak flux density (θ = (Sint/Speak)1/2) as a parameter to infer the presence of extended radio emission we show that ≥30 per cent of FIRST-detected sources possess extended radio structures on scales larger than 1.0 kpc. The use of low-resolution NVSS observations help us to recover faint extended KSRs that are resolved out in FIRST observations and results in ≥42.5 per cent KSR sources in FIRST-NVSS sub-sample. This fraction is only a lower limit owing to the combination of projection, resolution and sensitivity effects. Our study demonstrates that KSRs may be more common than previously thought and are found across all redshifts, luminosities and radio loudness. The extranuclear radio luminosity of KSR sources is found to be positively correlated with the core radio luminosity as well as the [O III] λ5007 Å line luminosity and this can be interpreted as KSRs being powered by AGN rather than star formation. The distributions of the FIR-to-radio ratios and mid-IR colours of KSR sources are also consistent with their AGN origin. However, contribution from star formation cannot be ruled out particularly in sources with low radio luminosities.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Radio Studies of Galactic Objects, Galaxies and AGNs

    NASA Astrophysics Data System (ADS)

    Han, J. L.; Sun, X. H.; Yang, J.; Wielebinski, R.

    2003-02-01

    The Sino-German Radio Astronomy Conference was held in Xi'an between July 18th and 25th 2002. This conference was also a meeting of radio astronomy in China. The partner group of Max-Plack-Institut for Radioastronomie at National Astronomical Observatories of China took the responsibility for detailed organizations. The conference was focused on "Radio studies of Galactic objects, galaxies and AGNs", with 80 partici- pants plus the 6 helpers. Most radio astronomers in China together with about 30 students enjoyed the fruitful discussions with 9 German senior scientists and 6 famous experts from other countries. In addition, the his- torical sites and culture environments specifically in Xi'an also attracted a dozen companions of delegates.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Towards optimal estimation of the galaxy power spectrum

    NASA Astrophysics Data System (ADS)

    Smith, Robert E.; Marian, Laura

    2015-12-01

    The galaxy power spectrum encodes a wealth of information about cosmology and the matter fluctuations. Its unbiased and optimal estimation is therefore of great importance. In this paper, we generalize the framework of Feldman et al. (1994) to take into account the fact that galaxies are not simply a Poisson sampling of the underlying dark matter distribution. Besides finite survey-volume effects and flux limits, our optimal estimation scheme incorporates several of the key tenets of galaxy formation: galaxies form and reside exclusively in dark matter haloes; a given dark matter halo may host several galaxies of various luminosities; galaxies inherit part of their large-scale bias from their host halo. Under these broad assumptions, we prove that the optimal weights do not explicitly depend on galaxy luminosity, other than through defining the maximum survey volume and effective galaxy density at a given position. Instead, they depend on the bias associated with the host halo; the first and second factorial moments of the halo occupation distribution; a selection function, which gives the fraction of galaxies that can be observed in a halo of mass M at position {r} in the survey; and an effective number density of galaxies. If one wishes to reconstruct the matter power spectrum, then, provided the model is correct, this scheme provides the only unbiased estimator. The practical challenges with implementing this approach are also discussed.

  15. 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

  16. 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

  17. 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.

  18. High energy emission from flat-spectrum radio sources with ˜ kpc-scale structure

    NASA Astrophysics Data System (ADS)

    Augusto, Pedro

    Active Galactic Nuclei emit a substantial portion of their bolometric luminosities in X-rays. For example, the knots in radio jets are prominent sources of synchrotron X-rays while the hotspots of the brightest FRIIs emit self-synchrotron or Inverse Compton radiation. Most high-energy studies on flat-spectrum radio sources have been conducted for blazars which are dominant at γ-rays.Augusto et al. (1998) have built a sample of 55 flat-spectrum radio sources dominated by structures (knots, hotspots, etc.) ˜0.1-2 kpc away from the nucleus. Seventeen (31%) of these are detected in X-rays (they tend to be the radio strongest) evenly splitting, morphologically, both at optical (radio) bands: nine QSO/BLLac (core-jets) on one-side; eight Galaxy/Sy2 (CSO/MSO/FRII) on the other. We have identified five confirmed compact/medium symmetric objects (CSO/MSOs) as X-ray emitters. A comparable type of source to CSO/MSOs is the physically similar (1-15 kpc) compact steep spectrum source (CSS), 28/129 (22%) of which are detected in X-rays, from a literature-selected sample (the percentage is smaller than for the 55-source sample due to a lower ). A 95% conf. level relation is found for CSSs: S_X ∝ (S4.85)0.6 and we found undistinguishable radio/X-ray properties for both the 55-source and CSS samples: clearly, their similar morphologies (e.g. knots in jets) stand up stronger than their radical radio spectrum differences.Only two sources among the 55 (4%) have γ-ray detections and they seem quite abnormal (in αxγ values, at least)-one of them is in a Sy2, not in a blazar.

  19. The X-Ray Weakness of GPS Radio Galaxies: A Volume-Limited Complete Sample

    NASA Technical Reports Server (NTRS)

    Mushotsky, Richard (Technical Monitor); Siemiginowska, Aneta

    2005-01-01

    The XMM-Newton observations of the GPS sample was completed last summer. We are in process of finalizing the paper describing the data and the results. The main goal of the project was to determine the X-ray spectra of the GPS galaxies in comparison to regular radio galaxies. Our XMM observations show evidence that the GPS galaxies are heavily obscured with the large absorbing columns exceeding N(H)greater than le22 cm^-2. Taking into account the obscuration we determined that the intrinsic X-ray luminosities of GPS galaxies are of order le43-le44 erg/s, comparable to low luminosity radio loud quasars. The large GPS samples can confirm the result, as at this moment our evidence is based only on 7 GPS galaxies observed with good S/N/ in X-rays. The first paper summarizing the results of the XMM observation of Mkn 668 has been published Astronomy & Astrophysics. We found soft X-ray signatures of a hot plasma (kT approximately 10^7K) and a hard X-ray emission from the nucleus. The X-ray spectrum above 2.5-keV is characterized by a very flat (observed photon index, Gamma-0.5) power-law continuum, alongside with a strong Fe-K-alpha neutral iron fluorescent line (EW600-eV). The best explanation for the origin of this high energy X-ray emission is in terms of the Compton-reflection of the nuclear emission. The primary X-ray emission is obscured by a Compton-thick (N_H to 10^24 cm-2) matter which becomes transparent at higher energies. The observed above 2.5-keV X-rays are mostly due to reflection which is indicated by a strong Fe-K-alpha line. This source represented the second hard X-ray detection of the GPS galaxy ever (the first one being 1345+125; O'Dea et al. 2000). The observations of the other GPS galaxies in our sample confirmed the trend of the large obscuration present in the spectra. However, we do not have a compelling evidence for a hot gas in the nucleus. The two other GPS galaxies observed with Chandra were added to the total of 7 GPS galaxies. This GPS

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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

  5. New insight on double-double radio galaxies

    NASA Astrophysics Data System (ADS)

    Nandi, Sumana

    2016-07-01

    Striking examples of episodic jet activity in active galactic nuclei (AGN) are the double-double radio galaxies (DDRGs) with two pairs of lobes emerging from the same central engine. The number of DDRGs reported so far is very limited, and it is important to identify more of these to provide a significant statistical overview of the conditions to trigger the jets and the role of jets in terms of feedback mechanisms that affect the host galaxies. Although most DDRGs were believed initially to be giant radio sources with sizes more than a Mpc, a significant number of smaller sized candidate DDRGs have also been identified in our recent study. We started GMRT observation of this sample to confirm that the sources are related to distinct epochs of nuclear activity. In addition to this radio observation we have also investigated the properties of the host galaxies and their environments to understand the triggering mechanisms for recurrent jet emission. Here, I will highlight the main results from these observations and discuss on the possible scenarios responsible for the episodic activity in different types of DDRGs .

  6. 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.

  7. DEEP 1.4 GHz FOLLOW-UP OF THE STEEP SPECTRUM RADIO HALO IN A521

    SciTech Connect

    Dallacasa, D.; Macario, G.; Setti, G.; Brunetti, G.; Cassano, R.; Venturi, T.; Giacintucci, S.; Kassim, N. E.; Lane, W.

    2009-07-10

    In a recent paper, we reported on the discovery of a radio halo with very steep spectrum in the merging galaxy cluster A521 through observations with the Giant Metrewave Radio Telescope. We showed that the steep spectrum of the halo is inconsistent with a secondary origin of the relativistic electrons and supports a turbulent acceleration scenario. At that time, due to the steep spectrum, the available observations at 1.4 GHz (archival NRAO-Very Large Array-VLA-CnB-configuration data) were not adequate to accurately determine the flux density associated with the radio halo. In this paper, we report the detection at 1.4 GHz of the radio halo in A521 using deep VLA observations in the D configuration. We use these new data to confirm the steep spectrum of the object. We consider A521 the prototype of a population of very steep spectrum halos. This population is predicted assuming that turbulence plays an important role in the acceleration of relativistic particles in galaxy clusters, and we expect it will be unveiled by future surveys at low frequencies with the LOFAR and LWA radio telescopes.

  8. Early quenching of massive protocluster galaxies around z = 2.2 radio galaxies

    NASA Astrophysics Data System (ADS)

    Husband, K.; Bremer, M. N.; Stott, J. P.; Murphy, D. N. A.

    2016-10-01

    Radio galaxies are among the most massive galaxies in the high-redshift Universe and are known to often lie in protocluster environments. We have studied the fields of seven z = 2.2 radio galaxies with High Acuity Wide field K-band Imager (HAWK-I) narrow-band and broad-band imaging in order to map out their environment using Hα emitters (HAEs). The results are compared to the blank field HAE survey HiZELS. All of the radio galaxy fields are overdense in HAEs relative to a typical HiZELS field of the same area and four of the seven are richer than all except one of 65 essentially random HiZELS subfields of the same size. The star formation rates of the massive HAEs are lower than those necessary to have formed their stellar population in the preceding Gyr - indicating that these galaxies are likely to have formed the bulk of their stars at higher redshifts, and are starting to quench.

  9. The radio emission from the ultraluminous far-infrared galaxy NGC 6240

    NASA Technical Reports Server (NTRS)

    Colbert, Edward J. M.; Wilson, Andrew S.; Bland-Hawthorn, Jonathan

    1994-01-01

    We present new radio observations of the 'prototypical' ultraluminous far-infrared galaxy NGC 6240, obtained using the Very Large Array (VLA) at lambda = 20 cm in B-configuration and at lambda = 3.6 cm in A-configuration. These data, along with those from four previous VLA observations, are used to perform a comprehensive study of the radio emission from NGC 6240. Approximately 70% (approximately 3 x 10(exp 23) W/Hz) of the total radio power at 20 cm originates from the nuclear region (approximately less than 1.5 kpc), of which half is emitted by two unresolved (R approximately less than 36 pc) cores and half by a diffuse component. The radio spectrum of the nuclear emission is relatively flat (alpha approximately equals 0.6; S(sub nu) proportional to nu(exp -alpha). The supernova rate required to power the diffuse component is consistent with that predicted by the stellar evolution models of Rieke et al. (1985). If the radio emission from the two compact cores is powered by supernova remnants, then either the remnants overlap and form hot bubbles in the cores, or they are very young (approximately less than 100 yr.) Nearly all of the remaining 30% of the total radio power comes from an 'armlike' region extending westward from the nuclear region. The western arm emission has a steep spectrum (alpha approximately equals 1.0), suggestive of aging effects from synchrotron or inverse-Compton losses, and is not correlated with starlight; we suggest that it is synchrotron emission from a shell of material driven by a galactic superwind. Inverse Compton scattering of far-infrared photons in the radio sources is expected to produce an X-ray flux of approximately 2 - 6 x 10(exp -14) ergs/s/sq cm in the 2 - 10 keV band. No significant radio emission is detected from or near the possible ultramassive 'dark core'.

  10. Investigating the thermal and nonthermal properties of galaxy clusters with radio observations

    NASA Astrophysics Data System (ADS)

    Farnsworth, Damon Patrick

    This thesis presents my recent investigations of the tenuous intracluster medium (ICM) in galaxy clusters using radio observations. The ICM is composed primarily of thermal and nonthermal plasma populations, permeated by magnetic fields which influence their evolution. Radio observations provide unique probes of the properties of the ICM, allowing for estimation of particle densities, magnetic field strengths, and even yielding clues to the physical mechanisms of particle acceleration. A major theme of this dissertation is that faint diffuse radio emission may contribute a significant amount of the synchrotron luminosity in galaxy clusters, yet goes unobserved due to an underappreciated deficiency of interferometric radio telescopes. Some of the current physical models do not account for this low surface brightness synchrotron emission, which may hold the key to distinguishing between competing models of relativistic particle acceleration and magnetic field amplification in these low density environments. I first discuss the use of polarization observations to probe magnetized plasmas, exploring various methods of Faraday rotation measure determination. I demonstrate that methods such as traditional fitting of models to polarization angle only (without consideration of the fractional polarization) or the novel Rotation Measure Synthesis may yield erroneous results in the presence of complex Faraday structure. The best way to more accurately recover the true Faraday structure is by fitting models directly to the observables Q and U, using radio polarization observations of the southern lobe of the radio galaxy 3C33 as an example. Next I exhibit results from a 1.4~GHz GBT study of twelve merging galaxy clusters. After subtraction of confusion from Galactic foreground and extragalactic background radio sources, eleven of the twelve clusters exhibited a significant excess of diffuse emission over that found by previous interferometric studies. Faint large-scale radio

  11. THE RADIO PROPERTIES OF RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES ON PARSEC SCALES

    SciTech Connect

    Gu, Minfeng; Chen, Yongjun; Shen, Zhiqiang; Komossa, S.; Zensus, J. A.; Yuan, Weimin; Wajima, Kiyoaki; Zhou, Hongyan

    2015-11-15

    We present the detection of the compact radio structures of 14 radio-loud narrow-line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array (VLBA) observations at 5 GHz performed in 2013. While 50% of the sources of our sample show a compact core only, the remaining 50% exhibit a core-jet structure. The measured brightness temperatures of the cores range from 10{sup 8.4} to 10{sup 11.4} K with a median value of 10{sup 10.1} K, indicating that the radio emission is from non-thermal jets, and that, likely, most sources are not strongly beamed, thus implying a low jet speed in these radio-loud NLS1 galaxies. In combination with archival data taken at multiple frequencies, we find that seven sources show flat or even inverted radio spectra, while steep spectra are revealed in the remaining seven objects. Although all of these sources are very radio-loud with R > 100, their jet properties are diverse in terms of their milliarcsecond (mas) scale (parsec scale) morphology and their overall radio spectral shape. The evidence for slow jet speeds (i.e., less relativistic jets), in combination with the low kinetic/radio power, may offer an explanation for the compact VLBA radio structure in most sources. The mildly relativistic jets in these high accretion rate systems are consistent with a scenario where jets are accelerated from the hot corona above the disk by the magnetic field and the radiation force of the accretion disk. Alternatively, a low jet bulk velocity can be explained by low spin in the Blandford–Znajek mechanism.

  12. Radio Continuum Mapping of the Spiral Galaxy NGC 4321

    NASA Astrophysics Data System (ADS)

    Hyman, Scott D.; Weiler, Kurt W.; van Dyk, Schuyler D.; Sramek, Richard A.; Liang, Wenhui

    1994-12-01

    We have combined numerous, short radio continuum observations of the Virgo Cluster spiral galaxy NGC 4321 (M 100) made at 20 and 6 cm with the Very Large Array (VLA) to produce a deep map of the galaxy. These observations were originally taken for monitoring the radio supernova SN 1979C (Weiler et al. 1986, ApJ, 310, 790; 1991, ApJ, 380, 161) and is analogous to our recent work on NGC 6946 (Hyman et al. 1993, BAAS 25, 1322) using observations taken for monitoring SN 1980K. The maps we derive for NGC 4321 are of superior sensitivity (sigma ~ lt 0.05 mJy/beam at 20 cm) and spatial resolution ( ~ 2" at 20 cm) to those previously published by other investigators (e. g., Knapen et al. 1993, ApJ, 416, 563). We present preliminary measurements and analyses of detected thermal and nonthermal sources, including flux densities, spectral indices, and luminosities, particularly for the very strong circumnuclear radio source, known as a site of intense star formation (e. g., Arsenault et al. 1988, A&A, 200, 29). We also make comparisons of our radio maps with existing data at other wavelengths.

  13. Radio Continuum Mapping of the Spiral Galaxy NGC 4258

    NASA Astrophysics Data System (ADS)

    Calle, Daniel; Hyman, Scott D.; Weiler, Kurt W.; van Dyk, Schuyler D.; Sramek, Richard A.

    1996-05-01

    We have combined numerous, short radio continuum observations of the Seyfert 1 galaxy NGC 4258 (M 106) made at 20 and 6 cm with the Very Large Array (VLA) to produce deep radio maps at these frequencies. These observations were originally taken for monitoring the radio supernova SN 1981K (Weiler et al. 1986, ApJ, 310, 790; Van Dyk et al. 1992, ApJ, 396, 195). The present analysis is analogous to our recent work on NGC 6946 (Hyman et al. 1993, BAAS 25, 1322) and on NGC 4321 (Hyman et al. 1994, BAAS 26, 1498) using observations taken for monitoring SN 1980K and SN 1979C, respectively. The maps we produce for NGC 4258 are of superior sensitivity (sigma ~ lt 0.02 mJy/beam at 6 cm) and spatial resolution ( ~ 0.5" at 6 cm) to those previously published by other investigators (e. g., Turner & Ho 1994, ApJ, 421, 122; Cecil et al. 1995, ApJ, 452, 613). We present preliminary measurements and analyses of the nuclear region, the anomalous arms, and of detected thermal and nonthermal sources throughout the galaxy. We also make comparisons of our radio maps with existing data at other wavelengths and with the results of our analyses of NGC 6946 and NGC 4321.

  14. A new approach to the radio-far infrared correlation for non-calorimeter galaxies.

    NASA Astrophysics Data System (ADS)

    Niklas, S.; Beck, R.

    1997-04-01

    New radio continuum data for a sample of 74 spiral galaxies supports the calorimeter model of Voelk (1989A&A...218...67V) only for steep-spectrum, thin-disk, non-interacting objects which comprise =~30% of the sample. As the spectral indices correlate neither with far infrared surface brightness nor with average (equipartition) magnetic field strength, the data disagree with the model for non-calorimeter galaxies of Helou & Bicay (1993ApJ...415...93H). We are able to explain the radio - far infrared correlation for non-calorimeter galaxies, globally and also on kiloparsec scales within galaxies, with the help of two basic relations with the average volume density of the gas as the primary factor. Firstly, there is strong evidence that the strength of the equipartition magnetic field is correlated with the volume density ρ of the (almost) neutral gas, following a power law with an exponent of m=0.48+/-0.05 for the galactic averages of our sample. Secondly, taking the thermal radio emissivity as an indicator of the average star-formation rate (SFR), we obtain a `Schmidt law' (SFR{prop.to}ρ^n^) with n=1.4+/-0.3. The FIR luminosity is linearly related to SFR. Finally, we assume equipartition between the energy densities of the magnetic field and of the cosmic rays which relates the synchrotron emissivity to the field strength. Combination of these relations leads to a radio - far infrared luminosity correlation with a power-law exponent of x=1.3+/-0.3, very close to what is observed (x=1.25+/-0.08). Forthcoming ISO satellite data can be used as a test of our approach.

  15. Gamma Rays from Radio Galaxies: FERMI/LAT Observations

    NASA Astrophysics Data System (ADS)

    Grandi, Paola

    We review the high energy properties of Misaligned AGNs associated with γ-ray sources detected by Fermi in 24 months of survey. Most of them are nearby emission low power radio galaxies (i.e FRIs) which probably have structured jets. On the contrary, high power radio sources (i.e FRIIs) with GeV emission are rare. The small number of FRIIs does not seem to be related to their higher redshifts. Assuming proportionality between the radio core flux and the γ-ray flux, several of them are expected to be bright enough to be detected above 100 MeV in spite of their distance. We suggest that beaming/jet structural differences are responsible for the detection rate discrepancy observed between FRIs and FRIIs.

  16. The MHz-peaked radio spectrum of the unusual γ-ray source PMN J1603-4904

    NASA Astrophysics Data System (ADS)

    Müller, C.; Burd, P. R.; Schulz, R.; Coppejans, R.; Falcke, H.; Intema, H.; Kadler, M.; Krauß, F.; Ojha, R.

    2016-09-01

    Context. The majority of bright extragalactic γ-ray sources are blazars. Only a few radio galaxies have been detected by Fermi/LAT. Recently, the GHz-peaked spectrum source PKS 1718-649 was confirmed to be γ-ray bright, providing further evidence for the existence of a population of γ-ray loud, compact radio galaxies. A spectral turnover in the radio spectrum in the MHz to GHz range is a characteristic feature of these objects, which are thought to be young due to their small linear sizes. The multiwavelength properties of the γ-ray source PMN J1603-4904 suggest that it is a member of this source class. Aims: The known radio spectrum of PMN J1603-4904 can be described by a power law above 1 GHz. Using observations from the Giant Metrewave Radio Telescope (GMRT) at 150, 325, and 610 MHz, we investigate the behavior of the spectrum at lower frequencies to search for a low-frequency turnover. Methods: Data from the TIFR GMRT Sky Survey (TGSS ADR) catalog and archival GMRT observations were used to construct the first MHz to GHz spectrum of PMN J1603-4904. Results: We detect a low-frequency turnover of the spectrum and measure the peak position at about 490 MHz (rest-frame), which, using the known relation of peak frequency and linear size, translates into a maximum linear source size of ~1.4 kpc. Conclusions: The detection of the MHz peak indicates that PMN J1603-4904 is part of this population of radio galaxies with turnover frequencies in the MHz to GHz regime. Therefore it can be considered the second confirmed object of this kind detected in γ-rays. Establishing this γ-ray source class will help to investigate the γ-ray production sites and to test broadband emission models.

  17. 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.

  18. Radio-Mode Feedback in Massive Galaxies at Redshift 0 < z < 1

    NASA Astrophysics Data System (ADS)

    Sadler, Elaine M.; Croom, Scott M.; Ching, John H. Y.; Johnston, Helen M.; Cannon, Russell D.; Mauch, Tom

    2010-05-01

    We have carried out a large observational study of the radio luminosities, stellar populations, and environments of massive galaxies over the redshift range 0 < z < 1. Radio jets powered by an accreting central black hole are common in massive galaxies, and there is a large class of “optically quiet AGN,” with radio emission but no optical/IR signature of black-hole accretion. The central black holes in these galaxies are probably accreting in a radiatively inefficient mode, and our results suggest that “radio-mode feedback” as described by Croton et al. is likely to occur in all masssive early-type galaxies at z < 0.8. While it appears that radio-loud AGN occur episodically in all massive early-type galaxies, we also identify a sub-population of galaxies with powerful radio sources and a prominent younger (~ 108 yr) stellar population that may have undergone recent mergers.

  19. Experimental solar radio spectrum analyzer (50-100 MHz)

    NASA Technical Reports Server (NTRS)

    Maxwell, A.

    1978-01-01

    Summarized is the work carried out under a NASA Grant covering the period 15 October 1977 to 14 January 1978. The grant provided funds for the acquisition of an experimental radio spectrum analyzer covering the band 50-100 MHz, for use in a program of solar radio observations. Components for the experimental analyzer were duly obtained, and the system was assembled, checked, and put into operation in early February 1978. The analyzer is working in an entirely satisfactory manner and, from the time that it has been put into operation, it has played an important part in the on-going research programs in solar radio astronomy being conducted.

  20. Jet-Reorientation in X-shaped Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Rottmann, H.

    2001-08-01

    The thesis set out to investigate the nature and genesis of the peculiar class of X-shaped radio galaxies. X-shaped sources are puzzling because of the extremely low number of objects of that type. Three scenarios were investigated: 1) X-shaped sources are a class by itself and are formed through a mechanisms unlike normal radio galaxies. 2) X-shaped sources are normal radio galaxies but they are currently in an unusual and/or short lived phase. 3) X-shaped sources are numerous, but selection effects keep us from identifying more of them. The backbone of this work is the multi-frequency spectral analysis. Magnetic fields were calculated using the standard minimum energy assumptions. Break frequencies were determined from the synchrotron spectra by fitting spectral models. The break frequencies were then used to calculate spectral ages. In nearly all sources we have found a gradient of decreasing magnetic fields and spectral indices from the primary towards the secondary lobes. Furthermore, the trend of spectral age clearly indicates increasing ages towards the tips of the secondary lobes. Spectral ages of the secondary lobes have been found to be of the order of a few 10^7 years, which is rather typical for the lobes of 'normal' radio galaxies. Some of the primary lobes (3C223.1, 3C403, NGC326) however are quite young (10^6 years). The young spectral ages of these sources and the short lengths of their primary lobes indicates that possibly the reorientation of their jets is ongoing or has finished only recently. The spectral ages have been used to test the proposed formation scenarios. The required flow speeds in the case of the buoyancy and backflow models is inconsistent with the calculated spectral ages. The predictions of the jet reorientation mechanisms are in excellent agreement with the inferred spectral ages. In the following we have compared the theoretical distribution of projected source angles for a randomly oriented sample of X-shaped sources with the

  1. Turbulent cosmic ray reacceleration and the curved radio spectrum of the radio relic in the Sausage Cluster

    NASA Astrophysics Data System (ADS)

    Fujita, Yutaka; Akamatsu, Hiroki; Kimura, Shigeo S.

    2016-06-01

    It has often been thought that the northern radio relic in the galaxy cluster CIZA J2242.8+5301 (the "Sausage" Cluster) is associated with cosmic ray (CR) electrons that are accelerated at a shock through the diffusive shock acceleration (DSA) mechanism. However, recent radio observations have shown that the radio spectrum is curved, which is inconsistent with the prediction of a simple DSA model. Moreover, the CR electron spectrum before being affected by radiative cooling seems to be too hard for DSA. In this study, we show that these facts are natural consequences if the electrons are reaccelerated in turbulence downstream of the shock. In this model, DSA is not the main mechanism for generating high-energy electrons. We find that the mean free path of the electrons should be much shorter than the Coulomb mean free path for efficient reacceleration. The scale of the turbulent eddies must be smaller than the width of the relic. We also predict hard X-ray spectra of inverse Compton scattering of photons.

  2. Compton Observatory observations of clusters of galaxies and extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    1995-01-01

    This task involved the investigation of the emission of clusters of galaxies, particularly those which contain extended radio emission, in the gamma-ray region of the spectrum. Observations were made of several clusters using the Compton Observatory EGRET instrument. For each cluster a measured flux or upper limit on the gamma-ray flux was obtained. In only one case, Abell 2199, was there a significant measured flux. This source is spatially confused with a know blazar in the field of view. The observation is consistent with all emissions being from the blazar.

  3. 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

  4. 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.

  5. DISCOVERY OF A FLAT-SPECTRUM RADIO NUCLEUS IN NGC 3115

    SciTech Connect

    Wrobel, J. M.; Nyland, K. E-mail: knyland@nrao.edu

    2012-12-01

    The early-type galaxy NGC 3115, at a distance of 10.2 Mpc, hosts the nearest billion-solar-mass black hole. Wong et al. recently inferred a substantial Bondi accretion rate near the black hole. Bondi-like accretion is thought to fuel outflows, which can be traced through their radio emission. This paper reports the discovery of a radio nucleus in NGC 3115, with a diameter less than 0.''17 (8.4 pc), a luminosity at 8.5 GHz of 3.1 Multiplication-Sign 10{sup 35} erg s{sup -1}, and a flat spectrum ({alpha} = -0.23 {+-} 0.20, S{proportional_to}{nu}{sup {alpha}}). The radio source coincides with the galaxy's photocenter and candidate X-ray nucleus. The emission is radio loud, suggesting the presence of an outflow on scales less than 10 pc. On such scales, the Bondi accretion could be impeded by heating due to disruption of the outflow.

  6. 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.

  7. 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

  8. A plethora of diffuse steep spectrum radio sources in Abell 2034 revealed by LOFAR

    NASA Astrophysics Data System (ADS)

    Shimwell, T. W.; Luckin, J.; Brüggen, M.; Brunetti, G.; Intema, H. T.; Owers, M. S.; Röttgering, H. J. A.; Stroe, A.; van Weeren, R. J.; Williams, W. L.; Cassano, R.; de Gasperin, F.; Heald, G. H.; Hoang, D. N.; Hardcastle, M. J.; Sridhar, S. S.; Sabater, J.; Best, P. N.; Bonafede, A.; Chyży, K. T.; Enßlin, T. A.; Ferrari, C.; Haverkorn, M.; Hoeft, M.; Horellou, C.; McKean, J. P.; Morabito, L. K.; Orrù, E.; Pizzo, R.; Retana-Montenegro, E.; White, G. J.

    2016-06-01

    With Low-Frequency Array (LOFAR) observations, we have discovered a diverse assembly of steep spectrum emission that is apparently associated with the intracluster medium (ICM) of the merging galaxy cluster Abell 2034. Such a rich variety of complex emission associated with the ICM has been observed in few other clusters. This not only indicates that Abell 2034 is a more interesting and complex system than previously thought but it also demonstrates the importance of sensitive and high-resolution, low-frequency observations. These observations can reveal emission from relativistic particles which have been accelerated to sufficient energy to produce observable emission or have had their high energy maintained by mechanisms in the ICM. The most prominent feature in our maps is a bright bulb of emission connected to two steep spectrum filamentary structures, the longest of which extends perpendicular to the merger axis for 0.5 Mpc across the south of the cluster. The origin of these objects is unclear, with no shock detected in the X-ray images and no obvious connection with cluster galaxies or AGNs. We also find that the X-ray bright region of the cluster coincides with a giant radio halo with an irregular morphology and a very steep spectrum. In addition, the cluster hosts up to three possible radio relics, which are misaligned with the cluster X-ray emission. Finally, we have identified multiple regions of emission with a very steep spectral index that seem to be associated with either tailed radio galaxies or a shock.

  9. 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

  10. Some results on the radio-SZ correlation for galaxy cluster radio halos

    NASA Astrophysics Data System (ADS)

    Basu, K.

    2013-04-01

    We present correlation results for the radio halo power in galaxy clusters with the integrated thermal Sunyaev-Zel'dovich (SZ) effect signal, including new results obtained at sub-GHz frequencies. The radio data is compiled from several published works, and the SZ measurements are taken from the Planck ESZ cluster catalog. The tight correlation between the radio halo power and the SZ effect demonstrates a clear correspondence between the thermal and non-thermal electron populations in the intra-cluster medium, as already have been shown in X-ray based studies. The radio power varies roughly as the square of the global SZ signal, but when the SZ signal is scaled to within the radio halo radius the correlation becomes approximately linear, with reduced intrinsic scatter. We do not find any strong indication of a bi-modal division in the radio halo cluster population, as has been reported in the literature, which suggests that such duality could be an artifact of X-ray selection. We compare the YSZ dependence of radio halos with simplified predictions from theoretical models, and discuss some implications and shortcomings of the present work.

  11. Search for and study of weak radio galaxies with large angular sizes using the NVSS data

    NASA Astrophysics Data System (ADS)

    Solovyov, D. I.; Verkhodanov, O. V.

    2014-08-01

    A new method for distinguishing candidate giant radio galaxies is proposed and applied. The method is based on comparing the axes of the extended components of NVSS radio sources with separations exceeding 4', described in a catalog of presumably independent objects. Objects detected using the proposed algorithm include 16 new weak giant-radio-galaxy candidates, for which optical and radio identifications have been obtained using the CATS, NED, SDSS, and SkyView databases.

  12. 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.

  13. A Search for Giant Radio Galaxy Candidates and Their Radio-Optical Follow-up

    NASA Astrophysics Data System (ADS)

    del C. Santiago-Bautista, I.; Rodríguez-Rico, C. A.; Andernach, H.; Coziol, R.; Torres-Papaqui, J. P.; Jiménez Andrade, E. F.; Plauchu-Frayn, I.; Momjian, E.

    We present results of a search for giant radio galaxies (GRGs) larger than 1 Mpc in projected size. We designed a computer algorithm to identify contiguous emission regions, large and elongated enough to serve as GRG candidates, and applied it to the entire 1.4-GHz NRAO VLA Sky survey (NVSS) image atlas. Subsequent visual inspection of 1,000 such regions revealed 15 new GRGs, as well as many other candidate GRGs, some of them previously reported, for which no redshift was known. Our optical spectroscopy of 25 host galaxies with two 2.1-m telescopes in Mexico, and four others with the 10.4-m Gran Telescopio Canarias (GTC), yielded another 24 GRGs. We also obtained higher-resolution radio images with the Karl G. Jansky Very Large Array for some unconfirmed GRG candidates.

  14. Methods for Bayesian power spectrum inference with galaxy surveys

    SciTech Connect

    Jasche, Jens; Wandelt, Benjamin D.

    2013-12-10

    We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters

  15. 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.

  16. 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.

  17. 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

    the radio jets are seen at an angle to the line of sight of about 30 deg, intermediate between the radio-galaxy and quasar classes. The relatively hard ASCA response has allowed us to place an upper limit of 5.6 x 10(exp 43) ergs/ s on the 2-10 keV luminosity of any central X-ray component absorbed bN, gas which might be obscuring the broad-line emission region. Attached to this report is an almost final draft of a paper which we have prepared for submission to the Astrophysical Journal. Our combined ASCA and ROSAT results for NGC 6251 rule out our previously preferred flat-spectrum model and inverse-Compton interpretation for the source based on ROSAT data alone, but a softer X-ray spectrum and moderate absorption bring all the available data (including our early VLA HI measurements) into consistency, and we are reasonably confident that we understand the processes responsible for the X-ray emission. We have made some more sensitive HI absorption measurements which are currently being analyzed, and our plans are to publish our ASCA analysis in conjunction with the new HI results. The ASCA data for NGC 4261 have been difficult to interpret. A re-analysis of our ROSAT data with a wider range of physical parameters brings the ROSAT and ASCA results into reasonable agreement only if the emission from hot gas dominates more than suggested by our earlier work, which is itself unexpected since the radio core is bright and a large jet-related X-ray component would bring the source into agreement with results for others of its type. However, we have recently received our Chandra A01 data for this source, with the spatial resolution which allows us to separate thermal and non-thermal emission components. Our ASCA results will be re-interpreted once the analysis of our Chandra data is complete. The interpretation of the ASCA data for BL Lac object 3C 371 is ongoing, in conjunction with analysis of archival multifrequency data. Radio galaxies are complex in their X

  18. On the Origin of Fanaroff-Riley Classification of Radio Galaxies: Deceleration of Supersonic Radio Lobes

    NASA Astrophysics Data System (ADS)

    Kawakatu, Nozomu; Kino, Motoki; Nagai, Hiroshi

    2009-06-01

    We argue that the origin of "FRI/FRII dichotomy"—the division between Fanaroff-Riley class I (FRI) with subsonic lobes and class II (FRII) radio sources with supersonic lobes is sharp in the radio-optical luminosity plane (Owen-White diagram)—can be explained by the deceleration of advancing radio lobes. The deceleration is caused by the growth of the effective cross-sectional area of radio lobes. We derive the condition in which an initially supersonic lobe turns into a subsonic lobe, combining the ram pressure equilibrium between the hot spots and the ambient medium with the relation between "the hot spot radius" and "the linear size of radio sources" obtained from the radio observations. We find that the dividing line between the supersonic lobes and subsonic ones is determined by the ratio of the jet power L j to the number density of the ambient matter at the core radius of the host galaxy \\bar{n}_a. It is also found that the maximal ratio of (L_j/\\bar{n}_a) exists and its value resides in (L_j/\\bar{n}_a)_max≈ 10^{44-47} erg s^{-1} cm^{3}, taking into account considerable uncertainties. This suggests that the maximal value (L_j/\\bar{n}_a)_max separates between FRIs and FRIIs.

  19. An Unlikely Radio Halo in the Low X-Ray Luminosity Galaxy Cluster RXCJ1514.9-1523

    NASA Technical Reports Server (NTRS)

    Marketvitch, M.; ZuHone, J. A.; Lee, D.; Giacintucci, S.; Dallacasa, D.; Venturi, T.; Brunetti, G.; Cassano, R.; Markevitch, M.; Athreya, R. M.

    2011-01-01

    Aims: We report the discovery of a giant radio halo in the galaxy cluster RXCJ1514,9-1523 at z=0.22 with a relatively low X-ray luminosity, L(sub X) (0.1-2.4kev) approx. 7 x 10(exp 44) ergs/s. Methods: This faint, diffuse radio source is detected with the Giant Meterwave Radio Telescope at 327 MHz. The source is barely detected at 1.4 GHz in a NVSS pointing that we have reanalyzed. Results: The integrated radio spectrum of the halo is quite steep, with a slope alpha = 1.6 between 327 MHz and 1.4 GHz. While giant radio halos are common in more X-ray luminous cluster mergers, there is a less than 10% probability to detect a halo in systems with L(sub X) < 8 x 10(exp 44) ergs/s. The detection of a new giant halo in this borderline luminosity regime can be particularly useful for discriminating between the competing theories for the origin of ultrarelativistic electrons in clusters. Furthermore, if our steep radio spectral index is confirmed by future deeper radio observations, this cluster would provide another example of the very rare, new class of ultra-steep spectrum radio halos, predicted by the model in which the cluster cosmic ray electrons are produced by turbulent reacceleration.

  20. 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.

  1. 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.

  2. Radio AGN signatures in massive quiescent galaxies out to z=1.5

    NASA Astrophysics Data System (ADS)

    Man, Allison

    2016-08-01

    This work represents the first multi-wavelength analysis of the average IR and radio emission in 14200 quiescent galaxies out to z=3. By stacking 24um, Herschel and VLA imaging data, we reveal the widespread presence of low-luminosity radio AGN among massive galaxies of Mstar>10^11Msun out to at least z=1.5, reciprocating the fact that massive quiescent galaxies are the preferential hosts of low-lumionsity AGN. Combined with the result of low average 24um emission, we infer that only radio-mode feedback, but not (obscured) quasar-mode feedback, is at work in keeping star formation inefficient in these galaxies.

  3. The multifrequency parsec-scale structure of PKS 2254-367 (IC 1459): a luminosity-dependent break in morphology for the precursors of radio galaxies?

    NASA Astrophysics Data System (ADS)

    Tingay, S. J.; Edwards, P. G.

    2015-03-01

    We present the first multifrequency very long baseline interferometry (VLBI) images of PKS 2254-367, a gigahertz-peaked spectrum (GPS) radio source hosted by the nearby galaxy IC 1459 (D = 20.5 Mpc). PKS 2254-367 and the radio source in NGC 1052 (PKS 0238-084; D = 17.2 Mpc) are the two closest GPS radio sources to us, far closer than the next closest example, PKS 1718-649 (D = 59 Mpc). As such, IC 1459 and NGC 1052 offer opportunities to study the details of the parsec-scale radio sources as well as the environments that the radio sources inhabit, across the electromagnetic spectrum. Given that some models for the origin and evolution of GPS radio sources require a strong connection between the radio source morphology and the gaseous nuclear environment, such opportunities for detailed study are important. Our VLBI images of PKS 2254-367 show that the previously identified similarities between IC 1459 and NGC 1052 continue on to the parsec-scale. Both compact radio sources appear to have symmetric jets of approximately the same luminosity, much lower than typically noted in compact double GPS sources. Similarities between PKS 2254-367 and NGC 1052, and differences with respect to other GPS galaxies, lead us to speculate that a sub-class of GPS radio sources, with low luminosity and with jet-dominated morphologies, exists and would be largely absent from radio source surveys with ˜1 Jy flux density cut-offs. We suggest that this possible low-luminosity, jet-dominated population of GPS sources could be an analogue of the Fanaroff-Riley type I (FR I) radio galaxies, with the higher luminosity lobe-dominated GPS sources being the analogue of the FR II radio galaxies.

  4. LOFAR VLBI studies at 55 MHz of 4C 43.15, a z = 2.4 radio galaxy

    NASA Astrophysics Data System (ADS)

    Morabito, Leah K.; Deller, Adam T.; Röttgering, Huub; Miley, George; Varenius, Eskil; Shimwell, Timothy W.; Moldón, Javier; Jackson, Neal; Morganti, Raffaella; van Weeren, Reinout J.; Oonk, J. B. R.

    2016-09-01

    The correlation between radio spectral index and redshift has been exploited to discover high-redshift radio galaxies, but its underlying cause is unclear. It is crucial to characterize the particle acceleration and loss mechanisms in high-redshift radio galaxies to understand why their radio spectral indices are steeper than their local counterparts. Low-frequency information on scales of ˜1 arcsec are necessary to determine the internal spectral index variation. In this paper we present the first spatially resolved studies at frequencies below 100 MHz of the z = 2.4 radio galaxy 4C 43.15 which was selected based on its ultrasteep spectral index (α < -1; Sν ˜ να) between 365 MHz and 1.4 GHz. Using the International Low Frequency Array Low Band Antenna we achieve subarcsecond imaging resolution at 55 MHz with very long baseline interferometry techniques. Our study reveals low-frequency radio emission extended along the jet axis, which connects the two lobes. The integrated spectral index for frequencies <500 MHz is -0.83. The lobes have integrated spectral indices of -1.31 ± 0.03 and -1.75 ± 0.01 for frequencies ≥1.4 GHz, implying a break frequency between 500 MHz and 1.4 GHz. These spectral properties are similar to those of local radio galaxies. We conclude that the initially measured ultrasteep spectral index is due to a combination of the steepening spectrum at high frequencies with a break at intermediate frequencies.

  5. Radio emission and the hot interstellar medium of early-type galaxies

    NASA Technical Reports Server (NTRS)

    Fabbiano, G.; Gioia, I. M.; Trinchieri, G.

    1989-01-01

    The results of an analysis of a sample of 84 elliptical and S0 galaxies, observed in X-rays with the Einstein Observatory and in radio continuum at 5 GHz, are reported. Radio flux densities result in some of the lowest radio powers yet reported for early-type galaxies. Radio structures extending beyond the optical radius are found only in galaxies with 5 GHz radio power greater than about 10 exp 29.5 ergs/s/Hz. Radio and X-ray luminosities are correlated, although with large intrinsic scatter, suggesting that more than one mechanism may be involved. A correlation between core radio power and the X-ray-to-optical ratio suggests a connection between the hot ISM and nuclear radio sources and points to accreting cooling flows as the fuel for the radio sources. For the same radio core power, extended radio lobes tend to be associated with galaxies with relatively smaller X-ray-to-optical ratios, pointing to the importance of the hot ISM in disrupting the radio jets and confining extended radio structures.

  6. 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.

  7. The REFLEX II galaxy cluster survey: power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Balaguera-Antolínez, A.; Sánchez, Ariel G.; Böhringer, H.; Collins, C.; Guzzo, L.; Phleps, S.

    2011-05-01

    We present the power spectrum of galaxy clusters measured from the new ROSAT-ESO Flux-Limited X-Ray (REFLEX II) galaxy cluster catalogue. This new sample extends the flux limit of the original REFLEX catalogue to 1.8 × 10-12 erg s-1 cm-2, yielding a total of 911 clusters with ≥94 per cent completeness in redshift follow-up. The analysis of the data is improved by creating a set of 100 REFLEX II-catalogue-like mock galaxy cluster catalogues built from a suite of large-volume Λ cold dark matter (ΛCDM) N-body simulations (L-BASICC II). The measured power spectrum is in agreement with the predictions from a ΛCDM cosmological model. The measurements show the expected increase in the amplitude of the power spectrum with increasing X-ray luminosity. On large scales, we show that the shape of the measured power spectrum is compatible with a scale-independent bias and provide a model for the amplitude that allows us to connect our measurements with a cosmological model. By implementing a luminosity-dependent power-spectrum estimator, we observe that the power spectrum measured from the REFLEX II sample is weakly affected by flux-selection effects. The shape of the measured power spectrum is compatible with a featureless power spectrum on scales k > 0.01 h Mpc-1 and hence no statistically significant signal of baryonic acoustic oscillations can be detected. We show that the measured REFLEX II power spectrum displays signatures of non-linear evolution.

  8. 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.

  9. Multicolor surface photometry of powerful radio galaxies. I - Observations and data reduction

    NASA Technical Reports Server (NTRS)

    Smith, Eric P.; Heckman, T. M.

    1989-01-01

    The first of a series of papers which explore the optical morphology, photometric properties, and colors of powerful radio galaxies is presented. This paper reports the observations and data reduction process. The surface photometry techniques used in the analysis are described and the calibration of the results is given. The resulting images reveal that a significant fraction of powerful radio galaxies are morphologically distorted and that many of these galaxies have unusual colors. Results for individual objects are discussed.

  10. 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

  11. 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.

  12. A Transient Radio Source near the Center of the Milky Way Galaxy.

    PubMed

    Zhao, J H; Roberts, D A; Goss, W M; Frail, D A; Lo, K Y; Subrahmanyan, R; Kesteven, M J; Ekers, R D; Allen, D A; Burton, M G; Spyromilio, J

    1992-03-20

    In late December 1990, a new radio source appeared near the center of our galaxy rivaling the intensity of Sgr A(*) (the compact radio source at the galactic center). Following its first detection, the flux density of the galactic center transient (GCT) increased rapidly to a maximum 1 month later, and then declined gradually with a time scale of about 3 months. Surprisingly, the GCT maintained a steep radio spectrum during both its rising and decay phases. The neutral hydrogen (HI) absorption shows similar absorption to that in front of Sgr A(*); this indicates that the GCT lies near the galactic center. Furthermore, both HI and OH observations show an additional deep absorption at +20 kilometers per second with respect to the local standard of rest. Thus, the GCT is either embedded in or located behind a molecular cloud moving with that velocity. The cloud can be seen on infrared images. Its opacity is shown to be inadequate to conceal a supernova near the galactic center. It is argued that the GCT was probably transient radio emission from synchrotron-radiating plasma associated with an x-ray binary system.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Spectrum from Faint Galaxy IRAS F00183-7111

    NASA Technical Reports Server (NTRS)

    2003-01-01

    NASA's Spitzer Space Telescope has detected the building blocks of life in the distant universe, albeit in a violent milieu. Training its powerful infrared eye on a faint object located at a distance of 3.2 billion light-years, Spitzer has observed the presence of water and organic molecules in the galaxy IRAS F00183-7111. With an active galactic nucleus, this is one of the most luminous galaxies in the universe, rivaling the energy output of a quasar. Because it is heavily obscured by dust (see visible-light image in the inset), most of its luminosity is radiated at infrared wavelengths.

    The infrared spectrograph instrument onboard Spitzer breaks light into its constituent colors, much as a prism does for visible light. The image shows a low-resolution spectrum of the galaxy obtained by the spectrograph at wavelengths between 4 and 20 microns. Spectra are graphical representations of a celestial object's unique blend of light. Characteristic patterns, or fingerprints, within the spectra allow astronomers to identify the object's chemical composition and to determine such physical properties as temperature and density.

    The broad depression in the center of the spectrum denotes the presence of silicates (chemically similar to beach sand) in the galaxy. An emission peak within the bottom of the trough is the chemical signature for molecular hydrogen. The hydrocarbons (orange) are organic molecules comprised of carbon and hydrogen, two of the most common elements on Earth. Since it has taken more than three billion years for the light from the galaxy to reach Earth, it is intriguing to note the presence of organics in a distant galaxy at a time when life is thought to have started forming on our home planet.

    Additional features in the spectrum reveal the presence of water ice (blue), carbon dioxide ice (green) and carbon monoxide (purple) in both gas and solid forms. The magenta peak corresponds to singly ionized neon gas, a spectral line often used by

  18. 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.

  19. 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

  20. 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.

  1. The spatial clustering of radio sources in NVSS and FIRST; implications for galaxy clustering evolution

    NASA Astrophysics Data System (ADS)

    Overzier, R. A.; Röttgering, H. J. A.; Rengelink, R. B.; Wilman, R. J.

    2003-07-01

    We have measured the angular correlation function, w(theta ), of radio sources in the 1.4 GHz NVSS and FIRST radio surveys. Below ~ 6arcmin the signal is dominated by the size distribution of classical double radio galaxies, an effect underestimated in some previous studies. We model the physical size distribution of FRII radio galaxies to account for this excess signal in w(theta ). The amplitude of the true cosmological clustering of radio sources is roughly constant at A =~ 1*E-3 for flux limits of 3-40 mJy, but has increased to A =~ 7*E-3 at 200 mJy. This can be explained if powerful (FRII) radio galaxies probe significantly more massive structures compared to radio galaxies of average power at z ~ 1. This is consistent with powerful high-redshift radio galaxies generally having massive (forming) elliptical hosts in rich (proto-)cluster environments. For FRIIs we derive a spatial (comoving) correlation length of r0=14+/-3 h-1 Mpc. This is remarkably close to that measured for extremely red objects (EROs) associated with a population of old elliptical galaxies at z ~ 1 by \\citet{daddi01}. Based on their similar clustering properties, we propose that EROs and powerful radio galaxies may be the same systems seen at different evolutionary stages. Their r0 is ~ 2x higher than that of QSOs at a similar redshift, and comparable to that of bright ellipticals locally. This suggests that r0 (comoving) of these galaxies has changed little from z ~ 1 to z=0, in agreement with current Lambda CDM hierarchical merging models for the clustering evolution of massive early-type galaxies. Alternatively, the clustering of radio galaxies can be explained by the galaxy conservation model. This then implies that radio galaxies of average power are the progenitors of the local field population of early-types, while the most powerful radio galaxies will evolve into a present-day population with r0 comparable to that of local rich clusters.

  2. 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.

  3. DISCOVERY OF A GIANT RADIO HALO IN A NEW PLANCK GALAXY CLUSTER PLCKG171.9-40.7

    SciTech Connect

    Giacintucci, Simona; Kale, Ruta; Venturi, Tiziana; Wik, Daniel R.; Markevitch, Maxim

    2013-03-20

    We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from an NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, and has an extent of {approx}1 Mpc and a radio power of {approx}5 Multiplication-Sign 10{sup 24} W Hz{sup -1} at 1.4 GHz. Its integrated radio spectrum has a slope of {alpha} Almost-Equal-To 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMM-Newton X-ray data shows that the cluster is hot ({approx}10 keV) and disturbed, consistent with X-ray-selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

  4. Discovery of a Giant Radio Halo in a New Planck Galaxy Cluster PLCKG171.9-40.7

    NASA Technical Reports Server (NTRS)

    Giacintucci, Simona; Kale, Ruta; Wik, Daniel R.; Venturi, Tiziana; Markevitch, Maxim

    2013-01-01

    We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from a NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, has an extent of approx.1 Mpc and a radio power of approx. 5×10(exp 24)W/Hz at 1.4 GHz. Its integrated radio spectrum has a slope of alpha approx. = 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMMNewton X-ray data shows that the cluster is hot (approx. 10 keV) and disturbed, consistent with X-ray selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

  5. 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.

  6. 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.

  7. Measuring the VIPERS galaxy power spectrum at z∼1

    NASA Astrophysics Data System (ADS)

    Rota, Stefano; Bel, Julien; Granett, Ben; Guzzo, Luigi

    2016-10-01

    The VIMOS Public Extragalactic Redshift Survey [VIPERS, Guzzo et al. 2014] is using the VIMOS spectrograph at the ESO VLT to measure redshifts for ~ 100,000 galaxies with IAB < 22.5 and 0.5 < z < 1.2, over an area of 24 deg2 (split over the W1 and W4 fields of CFHTLS). VIPERS currently provides, at such redshifts, the best compromise between volume, number of galaxies and dense spatial sampling. We present here the first estimate of the power spectrum of the galaxy distribution, P(k), at redshifts z ~ 0.75 and z ~ 1, obtained from the ~ 55,000 redshifts of the PDR-1 data release. We discuss first constraints on cosmological quantities, as the matter density and the baryonic fraction, obtained for the first time at an epoch when the Universe was about half its current age.

  8. 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.

  9. 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.

  10. Resolving the Steep-Spectrum Emission in the Central Radio Source in ZwCl 0735.7+7421

    NASA Astrophysics Data System (ADS)

    Cohen, A. S.; Clarke, T. E.; Feretti, L.; Kassim, N. E.

    2005-02-01

    It has long been know that an extremely steep spectrum radio source lies at the center of ZwCl 0735.7+7421, a galaxy cluster with high X-ray luminosity and a cooling core. In this Letter, we present VLA observations of this radio source at both 1425 and 325 MHz. With a resolution below 21" (75 kpc) for both 1425 and 325 MHz, we show the morphology of the central source and find that it is most likely a large (400 kpc) radio galaxy rather than diffuse cluster emission. We estimate a steep spectral index of α1400325=-1.54 for the core (although it may be contaminated by lobe emission), while the outer lobes are extremely steep objects, both with α1400325<-3.1. We also find evidence for restarted core activity in the form of a set of inner lobes oriented at a somewhat different angle from the outer lobes. A spectral analysis extending the frequency range down to 74 MHz appears to show a turnover at very low frequencies. Comparison of the minimum-energy radio pressures with the average thermal pressure surrounding the radio cavities from McNamara et al. shows that the radio lobes appear to be roughly in pressure balance with the thermal gas.

  11. A CHANDRA SNAPSHOT SURVEY FOR 3C RADIO GALAXIES WITH REDSHIFTS BETWEEN 0.3 AND 0.5

    SciTech Connect

    Massaro, F.; Harris, D. E.; Paggi, A.; Tremblay, G. R.; Liuzzo, E.; Bonafede, A.

    2013-05-01

    This paper contains an analysis of short Chandra observations of 19 3C sources with redshifts between 0.3 and 0.5 not previously observed in the X-rays. This sample is part of a project to obtain Chandra data for all of the extragalactic sources in the 3C catalog. Nuclear X-ray intensities as well as any X-ray emission associated with radio jet knots, hotspots, or lobes have been measured in three energy bands: soft, medium, and hard. Standard X-ray spectral analysis for the four brightest nuclei has also been performed. X-ray emission was detected for all the nuclei of the radio sources in the current sample with the exception of 3C 435A. There is one compact steep spectrum source while all the others are FR II radio galaxies. X-ray emission from two galaxy clusters (3C 19 and 3C 320), from six hotspots in four radio galaxies (3C 16, 3C 19, 3C 268.2, 3C 313), and extended X-ray emission on kiloparsec scales in 3C 187 and 3C 313, has been detected.

  12. A large anisotropy in the sky distribution of 3CRR quasars and other radio galaxies

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2015-06-01

    We report the presence of large anisotropies in the sky distributions of powerful extended quasars as well as some other sub-classes of radio galaxies in the 3CRR survey, the most reliable and most intensively studied complete sample of strong steep-spectrum radio sources. The anisotropies lie about a plane passing through the equinoxes and the north celestial pole. Out of a total of 48 quasars in the sample, 33 of them lie in one half of the observed sky and the remaining 15 in the other half. The probability that in a random distribution of 3CRR quasars in the sky, statistical fluctuations could give rise to an asymmetry in observed numbers up to this level is only ˜1 %. Also only about 1/4th of Fanaroff-Riley 1 (FR1) type of radio galaxies lie in the first half of the observed sky and the remainder in the second half. If we include all the observed asymmetries in the sky distributions of quasars and radio galaxies in the 3CRR sample, the probability of their occurrence by a chance combination reduces to ˜2×10-5. Two pertinent but disturbing questions that could be raised here are—firstly why should there be such large anisotropies present in the sky distribution of some of the strongest and most distant discrete sources, implying inhomogeneities in the universe at very large scales (covering a fraction of the universe)? Secondly why should such anisotropies lie about a great circle decided purely by the orientation of earth's rotation axis and/or the axis of its revolution around the sun? It seems yet more curious when we consider the other anisotropies, e.g., an alignment of the four normals to the quadrupole and octopole planes in the CMBR with the cosmological dipole and the equinoxes. Then there is the other recently reported large dipole anisotropy in the NVSS radio source distribution differing in magnitude from the CMBR dipole by a factor of four, and therefore not explained as due to the peculiar motion of the Solar system, yet aligned with the CMBR

  13. 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

    2016-11-01

    We present a study of the complete ultraviolet to submillimetre spectral energy distributions (SEDs) of 12 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 active galactic nuclei (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.

  14. 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.

  15. 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.

  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. Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources

    NASA Astrophysics Data System (ADS)

    Titov, O.; Stanford, Laura M.; Johnston, Helen M.; Pursimo, T.; Hunstead, Richard W.; Jauncey, David L.; Maslennikov, K.; Boldycheva, A.

    2013-07-01

    Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy & Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.

  18. OPTICAL SPECTRA OF CANDIDATE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) FLAT-SPECTRUM RADIO SOURCES

    SciTech Connect

    Titov, O.; Stanford, Laura M.; Johnston, Helen M.; Hunstead, Richard W.; Pursimo, T.; Jauncey, David L.; Maslennikov, K.

    2013-07-01

    Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy and Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.

  19. 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.

  20. Turbulent Cosmic-Ray Reacceleration at Radio Relics and Halos in Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Fujita, Yutaka; Takizawa, Motokazu; Yamazaki, Ryo; Akamatsu, Hiroki; Ohno, Hiroshi

    2015-12-01

    Radio relics are synchrotron emission found on the periphery of galaxy clusters. From the position and the morphology, it is often believed that the relics are generated by cosmic-ray (CR) electrons accelerated at shocks through a diffusive shock acceleration (DSA) mechanism. However, some radio relics have harder spectra than the prediction of the standard DSA model. One example is observed in the cluster 1RXS J0603.3+4214, which is often called the “Toothbrush Cluster.” Interestingly, the position of the relic is shifted from that of a possible shock. In this study, we show that these discrepancies in the spectrum and the position can be solved if turbulent (re)acceleration is very effective behind the shock. This means that for some relics turbulent reacceleration may be the main mechanism to produce high-energy electrons, contrary to the common belief that it is the DSA. Moreover, we show that for efficient reacceleration, the effective mean free path of the electrons has to be much smaller than their Coulomb mean free path. We also study the merging cluster 1E 0657-56, or the “Bullet Cluster,” in which a radio relic has not been found at the position of the prominent shock ahead of the bullet. We indicate that a possible relic at the shock is obscured by the observed large radio halo that is generated by strong turbulence behind the shock. We propose a simple explanation of the morphological differences of radio emission among the Toothbrush, the Bullet, and the Sausage (CIZA J2242.8+5301) Clusters.

  1. TURBULENT COSMIC-RAY REACCELERATION AT RADIO RELICS AND HALOS IN CLUSTERS OF GALAXIES

    SciTech Connect

    Fujita, Yutaka; Takizawa, Motokazu; Yamazaki, Ryo; Akamatsu, Hiroki; Ohno, Hiroshi

    2015-12-20

    Radio relics are synchrotron emission found on the periphery of galaxy clusters. From the position and the morphology, it is often believed that the relics are generated by cosmic-ray (CR) electrons accelerated at shocks through a diffusive shock acceleration (DSA) mechanism. However, some radio relics have harder spectra than the prediction of the standard DSA model. One example is observed in the cluster 1RXS J0603.3+4214, which is often called the “Toothbrush Cluster.” Interestingly, the position of the relic is shifted from that of a possible shock. In this study, we show that these discrepancies in the spectrum and the position can be solved if turbulent (re)acceleration is very effective behind the shock. This means that for some relics turbulent reacceleration may be the main mechanism to produce high-energy electrons, contrary to the common belief that it is the DSA. Moreover, we show that for efficient reacceleration, the effective mean free path of the electrons has to be much smaller than their Coulomb mean free path. We also study the merging cluster 1E 0657−56, or the “Bullet Cluster,” in which a radio relic has not been found at the position of the prominent shock ahead of the bullet. We indicate that a possible relic at the shock is obscured by the observed large radio halo that is generated by strong turbulence behind the shock. We propose a simple explanation of the morphological differences of radio emission among the Toothbrush, the Bullet, and the Sausage (CIZA J2242.8+5301) Clusters.

  2. 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.

  3. Sardinia Radio Telescope wide-band spectral-polarimetric observations of the galaxy cluster 3C 129

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Govoni, F.; Carretti, E.; Melis, A.; Concu, R.; Trois, A.; Loi, F.; Vacca, V.; Tarchi, A.; Castangia, P.; Possenti, A.; Bocchinu, A.; Burgay, M.; Casu, S.; Pellizzoni, A.; Pisanu, T.; Poddighe, A.; Poppi, S.; D'Amico, N.; Bachetti, M.; Corongiu, A.; Egron, E.; Iacolina, N.; Ladu, A.; Marongiu, P.; Migoni, C.; Perrodin, D.; Pilia, M.; Valente, G.; Vargiu, G.

    2016-10-01

    We present new observations of the galaxy cluster 3C 129 obtained with the Sardinia Radio Telescope in the frequency range 6000-7200 MHz, with the aim to image the large-angular-scale emission at high-frequency of the radio sources located in this cluster of galaxies. The data were acquired using the recently commissioned ROACH2-based backend to produce full-Stokes image cubes of an area of 1°×1° centred on the radio source 3C 129. We modelled and deconvolved the telescope beam pattern from the data. We also measured the instrumental polarization beam patterns to correct the polarization images for off-axis instrumental polarization. Total intensity images at an angular resolution of 2.9 arcmin were obtained for the tailed radio galaxy 3C 129 and for 13 more sources in the field, including 3C 129.1 at the galaxy cluster centre. These data were used, in combination with literature data at lower frequencies, to derive the variation of the synchrotron spectrum of 3C 129 along the tail of the radio source. If the magnetic field is at the equipartition value, we showed that the lifetimes of radiating electrons result in a radiative age for 3C 129 of tsyn ≃ 267 ± 26 Myr. Assuming a linear projected length of 488 kpc for the tail, we deduced that 3C 129 is moving supersonically with a Mach number of M = vgal/cs = 1.47. Linearly polarized emission was clearly detected for both 3C 129 and 3C 129.1. The linear polarization measured for 3C 129 reaches levels as high as 70 per cent in the faintest region of the source where the magnetic field is aligned with the direction of the tail.

  4. 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.

  5. Flat-spectrum radio sources - Cosmic conspiracy or relativistic neutrons?

    NASA Technical Reports Server (NTRS)

    Giovanoni, Peter M.; Kazanas, Demosthenes

    1990-01-01

    The intensity spectrum of the core of radio-loud AGN varies smoothly from 10 exp 8.5 to 10 to the 16th Hz, and is flat between 10 to the 9th and 10 to the 10th Hz, implying that a single emission mechanism is responsible. It is proposed here that energy is transported from the central source by relativistic neutrons which travel freely over a large volume and decay into relativistic protons. The protons produce secondary electrons which generate the observed radiation. The photon spectra thus produced are largely model-independent and flat.

  6. 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.

  7. 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.

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

    DOE PAGES

    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

  9. THE SCALING RELATIONS AND THE FUNDAMENTAL PLANE FOR RADIO HALOS AND RELICS OF GALAXY CLUSTERS

    SciTech Connect

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

    2015-11-01

    Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics, and mini-halos for a sample of galaxy clusters from the literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio powers of relics, halos, and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, while the correlations concerning giant radio halos are in general the strongest. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitatively characterize the shock waves and turbulence in the intracluster medium responsible for re-accelerating particles to generate the observed diffuse radio emission. The power of radio halos and relics is correlated with cluster mass proxies and dynamical parameters in the form of a fundamental plane.

  10. 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'.

  11. 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.

  12. Constraining the Redshift Evolution of First Radio Sources in RCS1 Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Gralla, Megan B.; Gladders, Michael D.; Yee, H. K. C.; Barrientos, L. Felipe

    2011-06-01

    We conduct a statistical analysis of the radio source population in galaxy clusters as a function of redshift by matching radio sources from the Faint Images of the Radio Sky at Twenty-Centimeters catalog with 618 optically selected galaxy clusters from the first Red-Sequence Cluster Survey (RCS1). The total number of excess radio source components (above the background level) per cluster is 0.14 ± 0.02 for clusters with 0.35 < z < 0.65 and is 0.10 ± 0.02 for clusters with 0.65 < z < 0.95. The richest clusters in the sample have more radio sources than clusters with low or intermediate richness. When we divide our sample into bins according to cluster richness, we do not observe any significant difference (>1.5σ) in the number of radio sources per unit of cluster mass for the galaxy clusters with 0.35 < z < 0.65 as compared to the galaxy clusters with 0.65 < z < 0.95. Thus, the entire sample can be characterized by the number of (L 1.4 GHz > 4.1 × 1024 W Hz-1) radio sources per unit (1014 M sun) mass, which we measure to be 0.031 ± 0.004. We further characterize the population of galaxy cluster-related radio sources through visual inspection of the RCS1 images, finding that although the radio activity of brightest cluster galaxies (BCGs) also does not strongly evolve between our high- and low-redshift samples, the lower-redshift, richest clusters are more likely to host radio-loud BCGs than the higher-redshift, richest clusters or poorer clusters at the 2σ level. We also find evidence that the number of radio-loud cluster members that are not BCGs per cluster per unit mass is higher at high redshift than at low redshift, at the 3σ level.

  13. 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.

  14. Black hole mass estimate for a sample of radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Calderone, G.; Ghisellini, G.; Colpi, M.; Dotti, M.

    2013-05-01

    We discuss the relationship between a standard Shakura & Sunyaev accretion disc model and the big blue bump (BBB) observed in Type 1 active galactic nuclei. Given the similarity between the BBB and the predicted disc spectrum, we propose a new method to estimate black hole masses which relies on the modelling of both optical and UV data with a Shakura & Sunyaev disc spectrum. We apply this method to a sample of 23 radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies, using data from Wide-field Infrared Survey Explorer, SDSS and GALEX. Our black hole mass estimates are at least a factor of ˜6 above previous results based on single epoch virial methods, while the Eddington ratios are correspondingly lower. Hence, the black hole masses of RL-NLS1 galaxies are typically above 108 M⊙, in agreement with the typical black hole mass of blazars.

  15. 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.

  16. 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.

  17. 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.

  18. Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks

    PubMed Central

    Shi, Zhenguo; Wu, Zhilu; Yin, Zhendong; Cheng, Qingqing

    2015-01-01

    Spectrum sensing technology plays an increasingly important role in cognitive radio networks. Consequently, several spectrum sensing algorithms have been proposed in the literature. In this paper, we present a new spectrum sensing algorithm “Differential Characteristics-Based OFDM (DC-OFDM)” for detecting OFDM signal on account of differential characteristics. We put the primary value on channel gain θ around zero to detect the presence of primary user. Furthermore, utilizing the same method of differential operation, we improve two traditional OFDM sensing algorithms (cyclic prefix and pilot tones detecting algorithms), and propose a “Differential Characteristics-Based Cyclic Prefix (DC-CP)” detector and a “Differential Characteristics-Based Pilot Tones (DC-PT)” detector, respectively. DC-CP detector is based on auto-correlation vector to sense the spectrum, while the DC-PT detector takes the frequency-domain cross-correlation of PT as the test statistic to detect the primary user. Moreover, the distributions of the test statistics of the three proposed methods have been derived. Simulation results illustrate that all of the three proposed methods can achieve good performance under low signal to noise ratio (SNR) with the presence of timing delay. Specifically, the DC-OFDM detector gets the best performance among the presented detectors. Moreover, both of the DC-CP and DC-PT detector achieve significant improvements compared with their corresponding original detectors. PMID:26083226

  19. Novel Spectrum Sensing Algorithms for OFDM Cognitive Radio Networks.

    PubMed

    Shi, Zhenguo; Wu, Zhilu; Yin, Zhendong; Cheng, Qingqing

    2015-01-01

    Spectrum sensing technology plays an increasingly important role in cognitive radio networks. Consequently, several spectrum sensing algorithms have been proposed in the literature. In this paper, we present a new spectrum sensing algorithm "Differential Characteristics-Based OFDM (DC-OFDM)" for detecting OFDM signal on account of differential characteristics. We put the primary value on channel gain θ around zero to detect the presence of primary user. Furthermore, utilizing the same method of differential operation, we improve two traditional OFDM sensing algorithms (cyclic prefix and pilot tones detecting algorithms), and propose a "Differential Characteristics-Based Cyclic Prefix (DC-CP)" detector and a "Differential Characteristics-Based Pilot Tones (DC-PT)" detector, respectively. DC-CP detector is based on auto-correlation vector to sense the spectrum, while the DC-PT detector takes the frequency-domain cross-correlation of PT as the test statistic to detect the primary user. Moreover, the distributions of the test statistics of the three proposed methods have been derived. Simulation results illustrate that all of the three proposed methods can achieve good performance under low signal to noise ratio (SNR) with the presence of timing delay. Specifically, the DC-OFDM detector gets the best performance among the presented detectors. Moreover, both of the DC-CP and DC-PT detector achieve significant improvements compared with their corresponding original detectors. PMID:26083226

  20. 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.

  1. 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.

  2. Confirmation of a Radio-Selected Galaxy Overdensity at z=1.11

    NASA Technical Reports Server (NTRS)

    Stern, Daniel; Holden, Brad; Stanford, S. A.; Spinard, Hyron

    2003-01-01

    We report the discovery of a galaxy overdensity at z = 1.11 associated with the z = 1.110 high-redshift radio galaxy MG1 J04426+0202 (hereafter 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 broadband 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 5 times greater than expected for the radio galaxy. These data suggest a rich galaxy cluster and inspired a 45 ks Chandra X-Ray Observatory observation. As expected, the radio galaxy is unresolved by Chandra but is responsible for approximately half 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 2 orders of magnitude higher than average for X-ray sources at these flux levels [S(0.5-2 keV) > 5 x 10(exp -16) ergs cm (exp -2) s(exp -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(1-6 keV) < 1.9 x 10-15 ergs cm (exp -2) s(exp -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 as a massive cluster in the process of formation.

  3. 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.

  4. Probing the gas content of radio galaxies through H I absorption stacking

    NASA Astrophysics Data System (ADS)

    Geréb, K.; Morganti, R.; Oosterloo, T. A.

    2014-09-01

    Using the Westerbork Synthesis Radio Telescope, we carried out shallow H i absorption observations of a flux-selected (S1.4 GHz > 50 mJy) sample of 93 radio active galactic nuclei (AGN), which have available SDSS (Sloan Digital Sky Survey) redshifts between 0.02 < z < 0.23. Our main goal is to study the gas properties of radio sources down to S1.4 GHz flux densities not systematically explored before using, for the first time, stacking of absorption spectra of extragalactic H i. Despite the shallow observations, we obtained a direct detection rate of ~29%, comparable with deeper studies of radio galaxies. Furthermore, detections are found at every S1.4 GHz flux level, showing that H i absorption detections are not biased toward brighter sources. The stacked profiles of detections and non-detections reveal a clear dichotomy in the presence of H i, with the 27 detections showing an average peak τ = 0.02 corresponding to N(H i) ~(7.4 ± 0.2) × 1018 (Tspin/cf) cm-2, while the 66 non-detections remain undetected upon stacking with a peak optical depth upper limit τ < 0.002 corresponding to N(H i) < (2.26 ± 0.06) × 1017 (Tspin/cf) cm-2 (using a FWHM of 62 kms-1, derived from the mean width of the detections). Separating the sample into compact and extended radio sources increases the detection rate, optical depth, and FWHM for the compact sample. The dichotomy for the stacked profiles of detections and non-detections still holds between these two groups of objects. We argue that orientation effects connected to a disk-like distribution of the H i can be partly responsible for the dichotomy that we see in our sample. However, orientation effects alone cannot explain all the observational results, and some of our galaxies must be genuinely depleted of cold gas. A fraction of the compact sources in the sample are confirmed by previous studies as likely young radio sources (compact steep spectrum and gigahertz peaked spectrum sources). These show an even higher

  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. 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.

  7. The X-Ray Environment of the Dumbbell Radio Galaxy NGC 326

    NASA Astrophysics Data System (ADS)

    Worrall, D. M.; Birkinshaw, M.; Cameron, R. A.

    1995-08-01

    We report the first detailed X-ray observations of the dumbbell radio galaxy NGC 326. The region containing the source was imaged for 5.8 hr in soft X-rays with the ROSAT PSPC as part of a program to measure the X-ray emission in low-power radio galaxies not known to be in rich clusters. Unlike other radio galaxies measured as part of this program, NGC 326 is discovered to be embedded in bright asymmetrical X-ray emitting cluster gas of temperature kT ˜ 2 keV and 0.1-2.4 keV luminosity 3.5 × 1036 W (H0 = 50 km s-1 Mpc-1). There is a peak in the X-ray emission consistent with the location of the radio galaxy core. Five of the 10 brightest galaxies in the region are the brightest optical objects in error circles of excess X-ray emission. In the same observation, ROSA T also detected the unrelated, more distant, cluster Abell 115 and provided its first spectral measurement: kT = 7.2+9-1.9 keV. It has been suggested previously that galaxy kinematics are responsible for the apparent change in direction over time of tbe twin jets of the large-scale radio emission of NGC 326. This was thought to be due either to a misalignment between the radio beam and galaxy axes or to interaction between the two galaxies which form the dumbbell nucleus of NGC 326 and which are known to be passing at about 16 kpc projected separation. Our X-ray results support a different explanation: that buoyancy forces have bent the outer radio structure.

  8. 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.

  9. Radio emission from merging galaxy clusters : characterizing shocks, magnetic fields and particle acceleration

    NASA Astrophysics Data System (ADS)

    van Weeren, Reinout Johannes

    2011-12-01

    In this thesis an interferometric study of diffuse radio sources, so-called halos and relics, in and around galaxy clusters is performed. These sources are thought to trace shocks and turbulence generated by galaxy cluster merger events. GMRT, WSRT and VLA observations are analyzed to measure the spectral and polarimetric properties of the diffuse cluster emission. In addition, a search for new relics and halos is carried out based on existing radio surveys. Numerical simulations of cluster mergers are described, which have the aim of constraining the cluster mergers parameters from observations of double radio relics. The first LOFAR observation of cluster-scale diffuse radio emission is presented. LOFAR is a new pan-European radio telescope that operates at the lowest radio frequencies accessible from the surface of the Earth.

  10. Jupiter's radio spectrum from 74 MHz up to 8 GHz

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Butler, B. J.; Green, D. A.; Strom, R.; Millan, R.; Klein, M. J.; Bird, M. K.; Funke, O.; Neidhöfer, J.; Maddalena, R.; Sault, R. J.; Kesteven, M.; Smits, D. P.; Hunstead, R.

    2003-06-01

    We carried out a brief campaign in September 1998 to determine Jupiter's radio spectrum at frequencies spanning a range from 74 MHz up to 8 GHz. Eleven different telescopes were used in this effort, each uniquely suited to observe at a particular frequency. We find that Jupiter's spectrum is basically flat shortwards of 1-2 GHz, and drops off steeply at frequencies greater than 2 GHz. We compared the 1998 spectrum with a spectrum (330 MHz-8 GHz) obtained in June 1994, and report a large difference in spectral shape, being most pronounced at the lowest frequencies. The difference seems to be linear with log(ν), with the largest deviations at the lowest frequencies (ν). We have compared our spectra with calculations of Jupiter's synchrotron radiation using several published models. The spectral shape is determined by the energy-dependent spatial distribution of the electrons in Jupiter's magnetic field, which in turn is determined by the detailed diffusion process across L-shells and in pitch angle, as well as energy-dependent particle losses. The spectral shape observed in September 1998 can be matched well if the electron energy spectrum at L = 6 is modeled by a double power law E- a (1+( E/ E0)) - b, with a = 0.4, b = 3, E0 = 100 MeV, and a lifetime against local losses τ 0 = 6 × 10 7 s. In June 1994 the observations can be matched equally well with two different sets of parameters: (1) a = 0.6, b = 3, E0 = 100 MeV, τ 0 = 6 × 10 7 s, or (2) a = 0.4, b = 3, E0 = 100 MeV, τ 0 = 8.6 × 10 6 s. We attribute the large variation in spectral shape between 1994 and 1998 to pitch angle scattering, coulomb scattering and/or energy degradation by dust in Jupiter's inner radiation belts.

  11. 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.

  12. 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).

  13. Evolution of the Lyα Halos Around High-Redshift Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Zirm, Andrew W.; Dey, Arjun; Dickinson, Mark; Norman, Colin J.

    2009-03-01

    We have obtained the first constraints on extended Lyα emission at z ~ 1 in a sample of five radio galaxies. We detect Lyα emission from four of the five galaxies. The Lyα luminosities range from 0.1-4 × 1043 erg s-1 and are much smaller than those observed for halos around higher redshift radio galaxies. If the z ≈ 1 radio galaxies are the descendents of the z lsim 2 radio galaxies, then their Lyα luminosities evolve strongly with redshift as ~(1 + z)5. There do not appear to be strong correlations between other parameters, such as radio power, suggesting that this observed evolution is real and not an observational artifact or secondary correlation. We speculate that this evolution of luminous halos may be due to gas depletion (as gas cools, settles, and forms stars) accompanied by an overall rise in the mean gas temperature and a decrease in specific star formation rate in and around these massive galaxies.

  14. 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.

  15. 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.

  16. CHANDRA VIEW OF THE ULTRA-STEEP SPECTRUM RADIO SOURCE IN A2443: MERGER SHOCK-INDUCED COMPRESSION OF FOSSIL RADIO PLASMA?

    SciTech Connect

    Clarke, T. E.; Randall, S. W.; Sarazin, C. L.; Blanton, E. L.; Giacintucci, S.

    2013-08-01

    We present a new Chandra X-ray observation of the intracluster medium in the galaxy cluster A2443, hosting an ultra-steep spectrum radio source. The data reveal that the intracluster medium is highly disturbed. The thermal gas in the core is elongated along a northwest to southeast axis and there is a cool tail to the north. We also detect two X-ray surface brightness edges near the cluster core. The edges appear to be consistent with an inner cold front to the northeast of the core and an outer shock front to the southeast of the core. The southeastern edge is coincident with the location of the radio relic as expected for shock (re)acceleration or adiabatic compression of fossil relativistic electrons.

  17. 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.

  18. 4C 39.24: discovery of a `giant' radio galaxy at z=1.88

    NASA Astrophysics Data System (ADS)

    Law-Green, J. D. B.; Eales, S. A.; Leahy, J. P.; Rawlings, S.; Lacy, M.

    1995-12-01

    The radio source 4C 39.24 (6C 0905+399) is shown to be the north-preceding lobe of a 111-arcsec FR II `classical double' with an unusual asymmetric structure. The core of the radio galaxy has been identified with a galaxy at z=1.883+/-0.003, giving a projected linear size of 4C 39.24 of D=(689+/-4) h^-1 kpc (assuming H_0=100 h km s ^-1 Mpc^-1 and Omega=0.04), making it the most distant `giant' radio galaxy known. We suggest that the `quad-like' structure seen in the north-preceding radio lobe is caused by the multiple imaging by gravitational lensing of a single hotspot.

  19. An X-Ray, Optical, and Radio Search for Supernova Remnants in the Nearby Sculptor Group Sd Galaxy NGC 7793

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas G.; Duric, Nebojsa; Lacey, Christina K.; Ferguson, Annette M. N.; Magnor, Marcus A.; Mendelowitz, Caylin

    2002-02-01

    This paper is the second in a series devoted to examining the multiwavelength properties of supernova remnants (SNRs) located in nearby galaxies. We consider here the resident SNRs in the nearby Sculptor group Sd galaxy NGC 7793. Using our own Very Large Array (VLA) radio observations at 6 and 20 cm, as well as archived ROSAT X-ray data, previously published optical results, and our own Hα image, we have searched for X-ray and radio counterparts to previously known optically identified SNRs and for new previously unidentified SNRs at these two wavelength regimes. Consistent with our prior results for NGC 300, only a tiny minority of the optically identified SNRs have been found at another wavelength. The most noteworthy source in our study is N7793-S26, which is the only SNR in this galaxy that is detected at all three wavelengths (X-ray, optical, and radio). It features a long (~450 pc) filamentary morphology that is clearly seen in both the optical and the radio images. N7793-S26's radio luminosity exceeds that of the Galactic SNR Cas A, and based on equipartition calculations we determine that an energy of at least 1052 ergs is required to maintain this source. Such a result argues for the source being created by multiple supernova explosions rather than by a single supernova event. A second optically identified SNR, N7793-S11, has detectable radio emission but no detectable X-ray emission. A radio-selected sample of candidate SNRs has also been prepared by searching for coincidences between nonthermal radio sources and regions of Hα emission in this galaxy. This search has produced five new candidate radio SNRs to be added to the 28 SNRs that have already been detected by optical methods. A complementary search for new candidate X-ray SNRs has also been conducted by searching for soft-spectrum sources (kT<1 keV) that are coincident with regions of Hα emission. That search has yielded a candidate X-ray SNR that is coincident with one (and possibly two) of the

  20. 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.

  1. Unbiased contaminant removal for 3D galaxy power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.

    2016-11-01

    We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum and (iii) debiasing the resulting estimates. For (i), we show that removing the best-fitting contaminant (mode subtraction) and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a quadratic maximum likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants, is less severe than that commonly ignored due to the survey window.

  2. Unbiased contaminant removal for 3D galaxy power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.

    2016-08-01

    We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit contaminant (mode subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.

  3. Rapidly growing black holes and host galaxies in the distant Universe from the Herschel Radio Galaxy Evolution Project

    NASA Astrophysics Data System (ADS)

    Drouart, G.; De Breuck, C.; Vernet, J.; Seymour, N.; Lehnert, M.; Barthel, P.; Bauer, F. E.; Ibar, E.; Galametz, A.; Haas, M.; Hatch, N.; Mullaney, J. R.; Nesvadba, N.; Rocca-Volmerange, B.; Röttgering, H. J. A.; Stern, D.; Wylezalek, D.

    2014-06-01

    We present results from a comprehensive survey of 70 radio galaxies at redshifts 1 galaxies in our sample are continuously covered across 3.6-870 μm. The total 8-1000 μm restframe infrared luminosities of these radio galaxies are such that almost all of them are either ultra-(LtotIR 1012 L⊙) or hyper-luminous (LtotIR 1013 L⊙) infrared galaxies. We fit the infrared SEDs with a set of empirical templates which represent dust heated by a variety of starbursts (SB) and by an active galactic nucleus (AGN). We find that the SEDs of radio galaxies require the dust to be heated by both AGN and SB, but the luminosities of these two components are not strongly correlated. Assuming empirical relations and simple physical assumptions, we calculate the star formation rate (SFR), the black hole mass accretion rate (ṀBH), and the black hole mass (MBH) for each radio galaxy. We find that the host galaxies and their black holes are growing extremely rapidly, having SFR ≈ 100-5000 M⊙ yr-1 and ṀBH ≈ 1-100 M⊙ yr-1. The mean specific SFRs (sSFR) of radio galaxies at z> 2.5 are higher than the sSFR of typical star forming galaxies over the same redshift range, but are similar or perhaps lower than the galaxy population for radio galaxies at z< 2.5. By comparing the sSFR and the specific ṀBH (sṀBH), we conclude that black holes in radio loud AGN are already, or soon will be, overly massive compared to their host galaxies in terms of expectations from the local MBH-MGal relation. In order to catch up with the black hole, the galaxies require about an order of magnitude more time to grow in mass at the observed SFRs compared to the time the black hole is actively accreting

  4. A multi-wavelength study of galaxy clusters hosting radio sources

    NASA Astrophysics Data System (ADS)

    Wing, Joshua David

    Galaxy clusters play an important role in understanding the formation of structure in the Universe and can be used to constrain cosmological parameters. Thousands of clusters are known in the nearby Universe, but few are confirmed at large distances. Remote clusters provide a view of the early Universe, and are important for studying galaxy evolution. Here, I describe a technique for finding distant clusters using bent, double-lobed radio galaxies. These radio sources are active galactic nuclei (AGN) that result from outflows of material surrounding supermassive black holes in the centers of massive galaxies. These outflows are typically bent as a result of the relative motion between the host galaxy and the surrounding hot gas that fills clusters. Using the Sloan Digital Sky Survey (SDSS) and the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey, I determine the frequency with which bent radio sources are associated with rich galaxy clusters in the nearby Universe (z < 0.5), as compared to non-bent radio sources. I find that > 60% of bent radio sources are located in rich cluster environments, compared to 10 -- 20% of non-bent radio sources. Therefore, bent radio sources are efficient tracers for clusters and are useful as beacons of clusters at large distances. Bent radio sources may achieve their morphologies through large-scale cluster mergers that set the intracluster medium (ICM) in motion. Using a suite of substructure tests, I determine the significance of optical substructure in clusters containing radio sources. I find no preference for substructure in clusters with bent double-lobed sources compared to other types of radio sources, indicating that bent sources will not necessarily preferentially select clusters undergoing recent large-scale mergers. Having established that bent radio sources efficiently locate clusters, I have obtained deep, follow-up observations at optical and near-infrared wavelengths to uncover associated distant

  5. Optical spectroscopy of the radio-loud nuclei of spiral galaxies: Starbursts or monsters

    SciTech Connect

    Heckman, T.M.; Van Breugel, W.; Miley, G.K.; Butcher, H.R.

    1983-08-01

    We present optical spectroscopic data pertaining to the physical state, kinematics, and spatial extent of the emission-line gas near the radio-loud nuclei of spiral galaxies. These data are combined with published optical, radio, and infrared data to evaluate the suggestions by Condon et al. (1982) that the nuclear radio emission in this class of galaxy is produced by multiple supernova remnants generated as a consequence of a nuclear starburst. As a whole, the radio-loud nuclei have stronger emission lines than radio-quiet nuclei of galaxies of similar Hubble/de Vaucouleurs type. This emission-line gas is generally at least as spatially extended as the radio continuum emission. However, we find that only about 1/3 of the spiral galaxies examined have optical spectroscopic properties consistent with those of ''extranuclear starbursts'' (i.e., giant H II regions). The majority of the nuclei seem to require a form of energy input to the ionized gas which is ''harder'' than the Lyman continuum radiation of OB stars, as their emission-line spectra are of the Seyfert or Liner variety. The nuclei with H II region spectra are distinct from the nuclei with Seyfert spectra in terms of radio morphology and radio spectral index, and tend to occur in spiral galaxies of much later Hubble type than do the Seyfert or Liner nuclei (Sc vs Sa). Moreover, the most luminous nuclear radio sources in our sample (PMHz> or =10/sup 22/ Watts Hz/sup -1/ Sr/sup -1/) are not associated with H II region nuclei. We summarize evidence that the putative nuclear starbursts must differ significantly from extranuclear starbursts.

  6. Peculiar radio structures in the central regions of galaxy cluster Abell 585

    NASA Astrophysics Data System (ADS)

    Jamrozy, M.; Stawarz, Ł.; Marchenko, V.; Kuźmicz, A.; Ostrowski, M.; Cheung, C. C.; Sikora, M.

    2014-06-01

    In this paper, we analyse the peculiar radio structure observed across the central region of the galaxy cluster Abell 585 (z = 0.12). In the low-resolution radio maps, this structure appears uniform and diffuse on angular scales of ˜3 arcmin, and is seemingly related to the distant (z = 2.5) radio quasar B3 0727+409 rather than to the cluster itself. However, after a careful investigation of the unpublished archival radio data with better angular resolution, we resolve the structure into two distinct arcmin-scale features, which resemble typical lobes of cluster radio galaxies with no obvious connection to the background quasar. We support this conclusion by examining the spectral and polarization properties of the features, demonstrating in addition that the analysed structure can hardly be associated with any sort of a radio mini-halo or relics of the cluster. Yet at the same time we are not able to identify host galaxies of the radio lobes in the available optical and infrared surveys. We consider some speculative explanations for our findings, including gravitational wave recoil kicks of supermassive black holes responsible for the lobes' formation in the process of merging massive ellipticals within the central parts of a rich cluster environment, but we do not reach any robust conclusions regarding the origin of the detected radio features.

  7. Kiloparsec-scale Radio Structures in Narrow-line Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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 γ-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 >~ 1044 erg s-1, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of >~ 107 M ⊙, 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 ~0.01c-0.3c and kinematic ages of >~ 107 years. On the other hand, most typical NLS1s would be driven by black holes of <~ 107 M ⊙ in a limited lifetime of ~107 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.

  8. 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.

  9. BRIGHT lights, BIG city: high redshift radio galaxies, giant Ly-a halos, and proto-clusters

    NASA Astrophysics Data System (ADS)

    van Breugel, Willem J.; Reuland, Michiel A.; de Vries, Willem H.; Stanford, Adam; Dey, Arjun; Kurk, Jaron; Venemans, Bram; Roettgering, Huub J. A.; Miley, George; De Breuck, Carlos; Dopita, Mike; Sutherland, Ralph; Bland-Hawthorn, Jonathan

    2003-02-01

    High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. We report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-α nebulae centered on the galaxies and to search for over-dense regions around them. We discuss the possible implications for our understanding of the formation and evolution of massive galaxies and galaxy clusters.

  10. High energy γ-radiation from the core of radio galaxy Centaurus A

    NASA Astrophysics Data System (ADS)

    Sahakyan, N. V.

    2012-03-01

    The results of analysis of approximately 3 years of gamma-ray observations (August 2008-July 2011) of the radio galaxy Centaurus A with the Fermi Large Area Telescope (Fermi LAT) are presented. By modeling the surrounding (background) sources including the giant lobes of Centaurus A, and using the standard binned likelihood analysis method, the energy spectrum of the core is derived. In the energy range below several GeV it is described by a single power-law with photon index Γ = 2.73 ± 0.06 in agreement with the report of the Fermi LAT collaboration based on the first 10 months observations of the source. However, at higher energies the new data show significant excess above the extrapolation of the energy spectrum from low energies. The total flux between 200 MeV to 50 GeV is estimated to be (1.63 ± 0.14) × 10-7 ph cm-2 s-1. 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.

  11. Disentangling star formation and AGN activity in powerful infrared luminous radio galaxies at 1 < z < 4

    NASA Astrophysics Data System (ADS)

    Drouart, G.; Rocca-Volmerange, B.; De Breuck, C.; Fioc, M.; Lehnert, M.; Seymour, N.; Stern, D.; Vernet, J.

    2016-09-01

    High-redshift radio galaxies present signs of both star formation and AGN activity, making them ideal candidates to investigate the connection and coevolution of AGN and star formation in the progenitors of present-day massive galaxies. We make use of a sample of 11 powerful radio galaxies spanning 1 galaxy evolution code PÉGASE.3 with an AGN torus model. We find that three components are necessary to reproduce the observed SEDs: an evolved and massive stellar component, a submm bright young starburst, and an AGN torus. We find that powerful radio galaxies form at very high-redshift, but experience episodic and important growth at 1 radio galaxies and no correlation with the AGN bolometric luminosity. Moreover, we find that AGN scattered light have a very limited impact on broad-band SED fitting on our sample. Finally, our analysis also suggests a wide range in origins for the observed star formation,which we partially constrain for some sources.

  12. Discovery of new variable radio sources in the nucleus of the nearby galaxy messier 82.

    PubMed

    Kronberg, P P; Sramek, R A

    1985-01-01

    Widespread variability has been discovered in a large population of radio sources close to the nucleus of an active galaxy. The galaxy, Messier 82 (M82), and others similar to it show evidence for enhanced nuclear activity and unusually strong far-infrared emission. The observational data, obtained with the National Radio Astronomy Observatory's Very Large Array in New Mexico over the past 3 years, provide the first direct "look" at a starburst-the phenomenon of sudden, rapid star formation which occurs near the nucleus of a small fraction of galaxies. Nearly all the brightest of about 40 radio sources in M82' s nucleus decreased in intensity over 2.7 years up to October 1983. One source, which in February 1981 was ten times as bright as our Galaxy's most luminous supernova remnant, turned off within only a few months. Most of the other ten strongest sources are declining so rapidly that they will fade into the background within 30 years. Thus, new supernovae are expected to appear in M82' s nucleus every few years. The discovery has revealed the "engine room" of the mysterious activity in M82 and, by implication, similar active galaxies which have disturbed nuclei and which are unusually luminous in the far infrared. An estimate of the rate of energy input by the radio-visible supernovae closely matches the far-infrared luminosities which were recently measured for M82 and other similar galaxies. PMID:17809994

  13. 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.

  14. The dynamics and excitation of circumnuclear disks in radio-active galaxies

    NASA Astrophysics Data System (ADS)

    Mould, Jeremy; Brown, Michael; Jannuzi, Buell; McGregor, Peter; Floyd, David; Jones, Heath; Ferrarese, Laura

    2011-08-01

    Powerful radio-active galaxies may harbor a heavily obscured Active Galactic Nucleus (AGN), where the black hole is hidden by an optically and geometrically thick dust "torus". Near-IR spectroscopy with Adaptive Optics (AO) has shown that the ratio of atomic to molecular hydrogen varies greatly across the nuclear regions, thus allowing one to set limits of the size of the torus. AO IFU observations with Gemini and Keck will enable a study of a complete sample of early-type galaxies harboring radio AGNs, resulting in a complete picture of the kinematics and distribution of the gas around the nucleus, and trace the 2-D structure of the torus in these galaxies. The time is right to survey a complete sample of nearby radio-active galaxies to (1) characterize the dynamics of these circumnuclear disks as a function of galaxy mass and (2) outline the ecology of the gas flows that support them. %First we must see which of Brown et al's %complete sample of nearby radiogalaxies have emission As a first step, we need to determine which of our selected sample of 23 nearby radio-active galaxies have emission lines in J & H and are thus amenable to NIR IFU observations. This we propose to do with FLAMINGOS. To survey our sample for suitable objects for the Keck/Gemini follow-up will require approximately 22 nights distributed evenly over the next four observing semesters.%It will take 11 nights in 11B & 12B and

  15. Giant radio relics in galaxy clusters: reacceleration of fossil relativistic electrons?

    NASA Astrophysics Data System (ADS)

    Pinzke, Anders; Oh, S. Peng; Pfrommer, Christoph

    2013-10-01

    Many bright radio relics in the outskirts of galaxy clusters have low inferred Mach numbers, defying expectations from shock acceleration theory and heliospheric observations that the injection efficiency of relativistic particles plummets at low Mach numbers. With a suite of cosmological simulations, we follow the diffusive shock acceleration as well as radiative and Coulomb cooling of cosmic ray electrons during the assembly of a cluster. We find a substantial population of fossil electrons. When reaccelerated at a shock (through diffusive shock acceleration), they are competitive with direct injection at strong shocks and overwhelmingly dominate by many orders of magnitude at weak shocks, M≲ 3, which are the vast majority at the cluster periphery. Their relative importance depends on cooling physics and is robust to the shock acceleration model used. While the abundance of fossils can vary by a factor of ˜10, the typical reaccelerated fossil population has radio brightness in excellent agreement with observations. Fossil electrons with 1 ≲ γ ≲ 100 (10 ≲ γ ≲ 104) provide the main seeds for reacceleration at strong (weak) shocks; we show that these are well resolved by our simulation. We construct a simple self-similar analytic model which assumes steady recent injection and cooling. It agrees well with our simulations, allowing rapid estimates and physical insight into the shape of the distribution function. We predict that the Low-Frequency Array (LOFAR) should find many more bright steep-spectrum radio relics, which are inconsistent with direct injection. A failure to take fossil cosmic ray electrons into account will lead to erroneous conclusions about the nature of particle acceleration at weak shocks; they arise from well-understood physical processes and cannot be ignored.

  16. High radio-frequency properties and variability of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Hogan, M. T.; Edge, A. C.; Geach, J. E.; Grainge, K. J. B.; Hlavacek-Larrondo, J.; Hovatta, T.; Karim, A.; McNamara, B. R.; Rumsey, C.; Russell, H. R.; Salomé, P.; Aller, H. D.; Aller, M. F.; Benford, D. J.; Fabian, A. C.; Readhead, A. C. S.; Sadler, E. M.; Saunders, R. D. E.

    2015-10-01

    We consider the high radio-frequency (15-353 GHz) properties and variability of 35 brightest cluster galaxies (BCGs). These are the most core-dominated sources drawn from a parent sample of more than 700 X-ray selected clusters, thus allowing us to relate our results to the general population. We find that ≥6.0 per cent of our parent sample (≥15.1 per cent if only cool-core clusters are considered) contain a radio source at 150 GHz of at least 3 mJy (≈1×1023 W Hz-1 at our median redshift of z ≈ 0.13). Furthermore, ≥3.4 per cent of the BCGs in our parent sample contain a peaked component (Gigahertz Peaked Spectrum, GPS) in their spectra that peaks above 2 GHz, increasing to ≥8.5 per cent if only cool-core clusters are considered. We see little evidence for strong variability at 15 GHz on short (week-month) time-scales although we see variations greater than 20 per cent at 150 GHz over six-month time frames for 4 of the 23 sources with multi-epoch observations. Much more prevalent is long-term (year-decade time-scale) variability, with average annual amplitude variations greater than 1 per cent at 15 GHz being commonplace. There is a weak trend towards higher variability as the peak of the GPS-like component occurs at higher frequency. We demonstrate the complexity that is seen in the radio spectra of BCGs and discuss the potentially significant implications of these high-peaking components for Sunyaev-Zel`dovich cluster searches.

  17. Probing the Disk-Jet Connection of the Radio Galaxy 3C120 Observed With Suzaku

    SciTech Connect

    Kataoka, Jun; Reeves, James N.; Iwasawa, Kazushi; Markowitz, Alex G.; Mushotzky, Richard F.; Arimoto, Makoto; Takahashi, Tadayuki; Tsubuku, Yoshihiro; Ushio, Masayoshi; Watanabe, Shin; Gallo, Luigi C.; Madejski, Greg M.; Terashima, Yuichi; Isobe, Naoki; Tashiro, Makoto S.; Kohmura, Takayoshi; /Tokyo Inst. Tech. /NASA, Goddard /Garching, Max Planck Inst., MPE /JAXA, Sagamihara /SLAC /Ehime U. /Wako, RIKEN /Saitama U. /Kogakuin U.

    2007-01-03

    Broad line radio galaxies (BLRGs) are a rare type of radio-loud AGN, in which the broad optical permitted emission lines have been detected in addition to the extended jet emission. Here we report on deep (40ksec x 4) observations of the bright BLRG 3C 120 using Suzaku. The observations were spaced a week apart, and sample a range of continuum fluxes. An excellent broadband spectrum was obtained over two decades of frequency (0.6 to 50 keV) within each 40 ksec exposure. We clearly resolved the iron K emission line complex, finding that it consists of a narrow K{sub {alpha}} core ({sigma} {approx_equal} 110 eV or an EW of 60 eV), a 6.9 keV line, and an underlying broad iron line. Our confirmation of the broad line contrasts with the XMM-Newton observation in 2003, where the broad line was not required. The most natural interpretation of the broad line is iron K line emission from a face-on accretion disk which is truncated at {approx} 10 r{sub g}. Above 10 keV, a relatively weak Compton hump was detected (reflection fraction of R {approx_equal} 0.6), superposed on the primary X-ray continuum of {Lambda} {approx_equal} 1.75. Thanks to the good photon statistics and low background of the Suzaku data, we clearly confirm the spectral evolution of 3C 120, whereby the variability amplitude decreases with increasing energy. More strikingly, we discovered that the variability is caused by a steep power-law component of {Lambda} {approx_equal} 2.7, possibly related to the non-thermal jet emission. We discuss our findings in the context of similarities and differences between radio-loud/quiet objects.

  18. 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.

  19. 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.

  20. A radio detection survey of narrow-line Seyfert 1 galaxies using very long baseline interferometry at 22 GHz

    NASA Astrophysics Data System (ADS)

    Doi, Akihiro; Oyama, Tomoaki; Kono, Yusuke; Yamauchi, Aya; Suzuki, Syunsaku; Matsumoto, Naoko; Tazaki, Fumie

    2016-10-01

    We conducted a high-sensitivity radio detection survey for 40 narrow-line Seyfert 1 (NLS1) galaxies using a very long baseline interferometry (VLBI) technique at 22 GHz through phase-referencing long-time integration and using a newly developing recorder with a data rate of 8 Gbps, which is a candidate of the next generation VLBI data recording systems of the Japanese VLBI Network. The baseline sensitivity was typically a few mJy. The observations resulted in a detection rate of 12/40 for our radio-selected NLS1 sample: 11 out of the 12 detected NLS1s showed inverted radio spectra between 1.4 and 22 GHz on the basis of the Very Large Array flux densities and the VLBI detections. These high fractions suggest that a compact radio core with a high brightness temperature is frequently associated with NLS1 nuclei. On the other hand, at least half of the sample indicated apparently steep spectra even with the limited VLBI sensitivity. Both the inverted and the steep spectrum radio sources are included in the NLS1 population.

  1. 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.

  2. FERMI LARGE AREA TELESCOPE VIEW OF THE CORE OF THE RADIO GALAXY CENTAURUS A

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Atwood, W. B.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Bastieri, D.; Baughman, B. M.; Brandt, T. J.; Bonamente, E. E-mail: fukazawa@hep01.hepl.hiroshima-u.ac.j

    2010-08-20

    We present {gamma}-ray observations with the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope of the nearby radio galaxy Centaurus A (Cen A). The previous EGRET detection is confirmed, and the localization is improved using data from the first 10 months of Fermi science operation. In previous work, we presented the detection of the lobes by the LAT; in this work, we concentrate on the {gamma}-ray core of Cen A. Flux levels as seen by the LAT are not significantly different from that found by EGRET, nor is the extremely soft LAT spectrum ({Gamma} = 2.67 {+-} 0.10{sub stat} {+-} 0.08{sub sys} where the photon flux is {Phi} {proportional_to} E {sup -{Gamma}}). The LAT core spectrum, extrapolated to higher energies, is marginally consistent with the non-simultaneous HESS spectrum of the source. The LAT observations are complemented by simultaneous observations from Suzaku, the Swift Burst Alert Telescope and X-ray Telescope, and radio observations with the Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry program, along with a variety of non-simultaneous archival data from a variety of instruments and wavelengths to produce a spectral energy distribution (SED). We fit this broadband data set with a single-zone synchrotron/synchrotron self-Compton model, which describes the radio through GeV emission well, but fails to account for the non-simultaneous higher energy TeV emission observed by HESS from 2004 to 2008. The fit requires a low Doppler factor, in contrast to BL Lac objects which generally require larger values to fit their broadband SEDs. This indicates that the {gamma}-ray emission originates from a slower region than that from BL Lac objects, consistent with previous modeling results from Cen A. This slower region could be a slower moving layer around a fast spine, or a slower region farther out from the black hole in a decelerating flow. The fit parameters are also consistent with Cen A being able to accelerate

  3. The interplay between galaxy transition and molecular gas in the next generation of radio facilities

    NASA Astrophysics Data System (ADS)

    Alatalo, Katherine A.; SPOGS Team

    2016-01-01

    The well-known galaxy color bimodality suggests that the paths which galaxies transition from blue, gas-rich spirals to red, gas-poor early-type (elliptical and lenticular) galaxies must be traveled rapidly to explain the dearth of intermediate stage objects. Studying the relationship between the interstellar fuel out of which stars form, and the global changes that galaxies undergo provides a window not only into the paths of transitions that galaxies take, but also how the transition mechanisms can feed back upon the relationship between molecular gas and star formation. I will discuss our results from z=0 transitioning galaxy surveys from CARMA and IRAM, and the ways in which next generation radio telescopes will not only provide detailed insights into the relationship between gas and transition at z=0, but also how this relationship evolves with redshift.

  4. 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.

  5. Radio AGN in 13,240 galaxy clusters from the Sloan Digital Sky Survey

    SciTech Connect

    Croft, S; de Vries, W; Becker, R

    2007-05-30

    We correlate the positions of 13,240 Brightest Cluster Galaxies (BCGs) with 0.1 {le} z {le} 0.3 from the maxBCG catalog with radio sources from the FIRST survey to study the sizes and distributions of radio AGN in galaxy clusters. We find that 19.7% of our BCGs are radio-loud, and this fraction depends on the stellar mass of the BCG, and to a lesser extent on the richness of the parent cluster (in the sense of increasing radio loudness with increasing mass). The intrinsic size of the radio emission associated with the BCGs peaks at 55 kpc, with a tail extending to 200 kpc. The radio power of the extended sources places them on the divide between FR I and FR II type sources, while sources compact in the radio tend to be somewhat less radio-luminous. We also detect an excess of radio sources associated with the cluster, instead of with the BCG itself, extending out to {approx} 1.4 kpc.

  6. A robust power spectrum split cancellation-based spectrum sensing method for cognitive radio systems

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Gao, Rui

    2014-12-01

    Spectrum sensing is an essential component to realize the cognitive radio, and the requirement for real-time spectrum sensing in the case of lacking prior information, fading channel, and noise uncertainty, indeed poses a major challenge to the classical spectrum sensing algorithms. Based on the stochastic properties of scalar transformation of power spectral density (PSD), a novel spectrum sensing algorithm, referred to as the power spectral density split cancellation method (PSC), is proposed in this paper. The PSC makes use of a scalar value as a test statistic, which is the ratio of each subband power to the full band power. Besides, by exploiting the asymptotic normality and independence of Fourier transform, the distribution of the ratio and the mathematical expressions for the probabilities of false alarm and detection in different channel models are derived. Further, the exact closed-form expression of decision threshold is calculated in accordance with Neyman—Pearson criterion. Analytical and simulation results show that the PSC is invulnerable to noise uncertainty, and can achive excellent detection performance without prior knowledge in additive white Gaussian noise and flat slow fading channels. In addition, the PSC benefits from a low computational cost, which can be completed in microseconds.

  7. COLA. III. RADIO DETECTION OF ACTIVE GALACTIC NUCLEUS IN COMPACT MODERATE LUMINOSITY INFRARED GALAXIES

    SciTech Connect

    Parra, R.; Conway, J. E.; Aalto, S.; Appleton, P. N.; Norris, R. P.; Pihlstroem, Y. M.; Kewley, L. J.

    2010-09-01

    We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median L{sub IR} = 10{sup 11.01} L{sub sun}) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores ({approx}10{sup 21} W Hz{sup -1}) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whose VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity.

  8. 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.

  9. New X-ray and radio observations of the galaxy cluster A2319

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.; Parsignault, D. R.; Gursky, H.; Brinkman, A. C.; Heise, J.; Harris, D. E.

    1977-01-01

    A significantly improved position for the X-ray source 3U 1921 + 43 has been obtained by ANS and Uhuru. The combined ANS-Uhuru error box is only about 7 by 7 arcmin and is centered on the cD galaxy in the Abell 2319 cluster of galaxies. Radio observations of this cluster indicate that the emission at 610 MHz includes several discrete sources and a weak extended component. This strengthens the general association between extended radio halos and X-ray emission from clusters of galaxies. The radio halo fills the X-ray error box and is consistent with the limits reported for the angular size of the X-ray source

  10. 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)

  11. Origin of X-rays and nature of accretion in the radio galaxy 3C 88

    NASA Astrophysics Data System (ADS)

    Gliozzi, Mario

    2005-10-01

    Studies of stellar dynamics have established that the presence of supermassive black holes is almost ubiquitous not only in AGN, but also in normal galaxies. Therefore, of crucial importance is the role played by low-power AGN, which represent the link between powerful AGN and normal galaxies. We propose to observe (35 ks) the radio galaxy 3C88, which complements and extends towards lower X-ray luminosities our sample of low-power radio galaxies hosting a LINER. 3C88 is an FRII/LINER which hosts a black hole of estimated mass. Specific goals are: investigate the origin of X-rays (jet vs. accretion related emission); assess the nature of the accretion in low-power objects; investigate possible intrinsic differences in the X-ray properties of FRIs and FRIIs.

  12. 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.

  13. ROSAT Discovery of Asymmetrical Cluster Gas around the Radio Galaxy NGC 326

    NASA Astrophysics Data System (ADS)

    Worrall, D. M.; Birkinshaw, M.; Cameron, R. A.

    1994-05-01

    The Position Sensitive Proportional Counter on board ROSAT is the first X-ray detector to have made a long pointed observation of the nearby radio galaxy NGC 326. The region containing the source was imaged for 5.8 hours in soft (0.1 - 2.4 keV) X-rays as part of a program to measure the X-ray emission in low-power radio galaxies not known to be in rich clusters. Unlike other radio galaxies measured as part of this program, NGC 326 is discovered to be embedded in bright asymmetrical X-ray emitting cluster gas. There is a peak in the X-ray emission consistent with the location of the radio-galaxy core, and the gas extends a few hundred kpc from this peak (H_o = 50 km s(-1) Mpc(-1) ) even averaged over directions of least extent. The presence of large-scale X-ray emitting gas is consistent with NGC 326's membership of the Zwicky cluster 0056.9+2636. NGC 326 is known to have a `dumbbell nucleus' where two galaxies are passing at about 16 kpc projected separation (Wirth, Smarr & Gallagher 1982, AJ, 87, 602); the kinematics of the dumbbell system provides a possible explanation for the apparent change in direction over time of the twin jets of the kpc-scale radio emission. We compare radio and X-ray images to assess the influence of the gas distribution on the radio structures. Support from NASA grant NAG5-1882 & contract NAS8-39073 is gratefully acknowledged.

  14. 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.

  15. 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.

  16. Flat spectrum radio quasars: MAGIC results and unexpected features

    NASA Astrophysics Data System (ADS)

    De Caneva, G.; Barres de Almeida, U.; Gonzalez, J. Becerra; Berger, K.; Lindfors, E.; Mazin, D.; Paneque, D.; Saito, K.; Schultz, C.; Sitarek, J.; Stamerra, A.; Tavecchio, F.; Hayashida, M.; MAGIC Collaboration; Fermi-LAT Collaboration

    2012-12-01

    The detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra. Often neither the emission nor the variability features of recently discovered VHE-FSRQs can be explained with the models developed so far for BL Lacs. Here we present the latest MAGIC results for all the three FSRQs known to be VHE emitters. We start with the 2010 discovery of PKS 1222+21 (z = 0.432), whose fast variability challenges simple one-zone emission models, requiring a more complicated scenario. Second, we present the latest results on 3C 279, the most distant AGN (z = 0.536) and first FSRQ detected in very high energies. It was observed in 2011, first during a monitoring campaign and later observations were triggered by a flare detected with Fermi-LAT. Finally, we report the 2012 detection of PKS 1510-089 (z = 0.36). This summary of VHE observations is the first step for a forthcoming study of multiwavelength spectral properties of these sources aimed at identifying the physical processes responsible for their emission and at explaining their observed variability.

  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. 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

    is 10-50 times higher than the SFE estimated with the 7.7 μm PAH emission of evolved radio galaxies. Our results suggest that the apparently low SFE of evolved radio galaxies may be caused by an underestimation of the SFR and/or an overestimation of the molecular gas densities in these sources. Conclusions: The molecular gas of 3C 293, while not incompatible with a mild AGN-triggered flow, does not reach the high velocities (≳500 km s-1) observed in the H i spectrum. We find no signatures of AGN feedback in the molecular gas of 3C 293. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Calibrated data as FITS files are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/564/A128

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. THE LOW-FREQUENCY RADIO CATALOG OF FLAT-SPECTRUM SOURCES

    SciTech Connect

    Massaro, F.; Giroletti, M.; D'Abrusco, R.; Paggi, A.; Cowperthwaite, Philip S.; Masetti, N.; Tosti, G.; Funk, S.

    2014-07-01

    A well known property of the γ-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-γ-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with γ-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified γ-ray sources allowed us to extend the radio-γ-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of γ-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

  6. 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

  7. VLA Radio Continuum Imaging of Radio-Infrared Supernebulae in Starburst Galaxies at 1.3 cm

    NASA Astrophysics Data System (ADS)

    Tsai, C.-W.; Turner, J. L.; Beck, S. C.

    2005-12-01

    We present 1''-resolution VLA K-band images of 14 nearby starburst galaxies in which we have detected compact (sub-arcsecond) and luminous mid-IR sources with LWS imaging spectrograph on Keck Observatory. Of the galaxies observed, 11 are detected with strong continuum emission at 1.3 cm. In the VLA K-band where synchrotron emission is weak and dust emission has not yet kicked in, therefore the radio continuum emission should be dominated by thermal free-free emission. The strong extended free-free emission indicates the existence of ˜ 104 - 105 O stars living in active regions of these starburst galaxies. Our K-band maps also reveal many compact sources which are presumbly ''radio-infrared supernebulae", or RISN. These nebulae are dense, young (< 1 Myr), and require the immediate presence of thousands of young O stars within regions only a few parsecs in extent. RISN in these galaxies are excited by massive (105 - 106 MSun) super star clusters (SSCs) which may be the precursors to globular clusters.

  8. JET PROPERTIES OF GeV-SELECTED RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES AND POSSIBLE CONNECTION TO THEIR DISK AND CORONA

    SciTech Connect

    Sun, Xiao-Na; Lin, Da-Bin; Liang, En-Wei; Zhang, Jin; Xue, Zi-Wei; Zhang, Shuang-Nan

    2015-01-01

    The observed spectral energy distributions of five GeV-selected narrow-line Seyfert 1 (NLS1) galaxies are fitted with a model including the radiation ingredients from the relativistic jet, the accretion disk, and the corona. We compare the properties of these GeV NLS1 galaxies with flat spectrum radio quasars (FSRQs), BL Lacertae objects (BL Lacs), and radio-quiet (RQ) Seyfert galaxies, and explore possible hints for jet-disk/corona connection. Our results show that the radiation physics and the jet properties of the GeV NLS1 galaxies resemble that of FSRQs. The luminosity variations of PMN J0948+0022 and 1H 0323+342 at the GeV band is tightly correlated with the beaming factor (δ), similar to that observed in FSRQ 3C 279. The accretion disk luminosities and the jet powers of the GeV NLS1 galaxies cover both the ranges of FSRQs and BL Lacs. With the detection of bright corona emission in 1H 0323+342, we show that the ratio of the corona luminosity (L {sub corona}) to the accretion disk luminosity (L {sub d}) is marginally within the high end of this ratio distribution for an RQ Seyfert galaxy sample, and the variation of jet luminosity may connect with L {sub corona}. However, it is still unclear whether a system with a high L {sub corona}/L {sub d} ratio prefers to power a jet.

  9. The search for faint radio supernova remnants in the outer Galaxy: five new discoveries

    NASA Astrophysics Data System (ADS)

    Gerbrandt, Stephanie; Foster, Tyler J.; Kothes, Roland; Geisbüsch, Jörn; Tung, Albert

    2014-06-01

    Context. High resolution and sensitivity large-scale radio surveys of the Milky Way are critical in the discovery of very low surface brightness supernova remnants (SNRs), which may constitute a significant portion of the Galactic SNRs still unaccounted for (ostensibly the "missing SNR problem"). Aims: The overall purpose here is to present the results of a systematic, deep data-mining of the Canadian Galactic plane Survey (CGPS) for faint, extended non-thermal and polarized emission structures that are likely the shells of uncatalogued SNRs. Methods: We examine 5 × 5 degree mosaics from the entire 1420 MHz continuum and polarization dataset of the CGPS after removing unresolved "point" sources and subsequently smoothing them. Newly revealed extended emission objects are compared to similarly prepared CGPS 408 MHz continuum mosaics, as well as to source-removed mosaics from various existing radio surveys at 4.8 GHz, 2.7 GHz, and 327 MHz, to identify candidates with non-thermal emission characteristics. We integrate flux densities at each frequency to characterise the radio spectra behaviour of these candidates. We further look for mid- and high-frequency (1420 MHz, 4.8 GHz) ordered polarized emission from the limb brightened "shell"-like continuum features that the candidates sport. Finally, we use IR and optical maps to provide additional backing evidence. Results: Here we present evidence that five new objects, identified as filling all or some of the criteria above, are strong candidates for new SNRs. These five are designated by their Galactic coordinate names G108.5+11.0, G128.5+2.6, G149.5+3.2, G150.8+3.8, and G160.1-1.1. The radio spectrum of each is presented, highlighting their steepness, which is characteristic of synchrotron radiation. CGPS 1420 MHz polarization data and 4.8 GHz polarization data also provide evidence that these objects are newly discovered SNRs. These discoveries represent a significant increase in the number of SNRs known in the outer

  10. 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

  11. OT1_mhaas_2: The Herschel Legacy of powerful 3C radio galaxies and quasars at z<1

    NASA Astrophysics Data System (ADS)

    Haas, M.

    2010-07-01

    We propose Herschel observations of a complete sample of 3C radio-galaxies and quasars at redshift z<1. For all sources Spitzer mid-IR spectra are available. The aim is to quantify the orientation-dependence of AGN radiation (AGN unification), to investigate the interplay between accretion onto the central black-hole and star-formation in the hosts, and to understand the evolution of the black-hole/stellar-bulge relation. The low-frequency radio-selection provides us with powerful and massive active galaxies free from any orientation/obscuration bias, a requirement for testing AGN unification. The properties of the 3C sources are well known throughout the electromagnetic spectrum, except in the far-IR/sub-mm, where most of them were hitherto outside the capability of space missions to reach reliable measurements. We propose PACS 70-160 micron photometry of 72 sources supplemented by SPIRE 250-500 micron photometry of 11 sufficiently bright sources, in order to measure their detailed spectral energy distributions between available Spitzer and SCUBA/MAMBO data. Depending on redshift of the sources and predicted flux, the filter choice is optimised to provide best rest-frame FIR coverage. The rest-frame FIR emission serves as an isotropic calorimeter and the MIR/FIR luminosity ratio is determined by the relative strength of the AGN and star-forming contributions combined with dust obscuration. These observations will return crucial new information on the energy processes in powerful AGN and their hosts at z<1, providing an essential anchor for studies of galaxy and AGN evolution, in particular for a consistent comparison with Herschel observations of several (radio-loud) AGN samples at cosmic epochs z>1.

  12. 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).

  13. 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

  14. The connection between radio loudness and central surface brightness profiles in optically selected low-luminosity active galaxies

    NASA Astrophysics Data System (ADS)

    Richings, A. J.; Uttley, P.; Körding, E.

    2011-08-01

    Recent results indicate a correlation between nuclear radio loudness of active galaxies and their central stellar surface-brightness profiles, in that 'core' galaxies (with inner logarithmic slope γ≤ 0.3) are significantly more radio loud than 'power-law' galaxies (γ≥ 0.5). This connection, which indicates possible links between radio loudness and galaxy formation history (e.g. through black hole spin), has so far only been confirmed for a radio-selected sample of galaxies. Furthermore, it has since been shown that the Nuker law, which was used to parametrize the brightness profiles in these studies, gives a poor description of the brightness profile, with its parameters varying systematically with the radial fitted extent of the profile. Here, we present an analysis of the central surface brightness profiles of the active galaxies of Hubble type T≤ 3, that were identified by the optically selected Palomar spectroscopic survey of nearby galaxies. We fit the brightness profiles using Sérsic, Core-Sérsic and, where necessary, Double-Sérsic models, which we fit to the semimajor axis brightness profiles extracted from high-resolution images of the galaxies from the Hubble Space Telescope. We use these fits to classify the galaxies as 'Core', 'Sérsic' or 'Double-Sérsic'. We compare the properties of the active galactic nuclei (AGN) and their host galaxies with this classification, and we recover the already established trend for Core galaxies to be more luminous and contain a higher mass supermassive black hole. Defining the radio loudness of an AGN as the ratio of the nuclear radio luminosity to [O III] line luminosity, which allows us to include most of the AGN in our sample and prevents a bias against dim nuclei that are harder to extract from the brightness profiles, we find that AGN hosted in Core galaxies are generally more radio loud than those hosted in Sérsic galaxies, although there is a large overlap between the two subsamples. The correlation

  15. Magnetic field amplification and flat spectrum radio quasars

    NASA Astrophysics Data System (ADS)

    Chen, Xuhui; Chatterjee, Ritaban; Zhang, Haocheng; Pohl, Martin; Fossati, Giovanni; Böttcher, Markus; Bailyn, Charles D.; Bonning, Erin W.; Buxton, Michelle; Coppi, Paolo; Isler, Jedidah; Maraschi, Laura; Urry, Meg

    2014-07-01

    We perform time-dependent, spatially resolved simulations of blazar emission to evaluate several flaring scenarios related to magnetic-field amplification and enhanced particle acceleration. The code explicitly accounts for light-travel-time effects and is applied to flares observed in the flat spectrum radio quasar (FSRQ) PKS 0208-512, which show optical/γ-ray correlation at some times, but orphan optical flares at other times. Changes in both the magnetic field and the particle acceleration efficiency are explored as causes of flares. Generally, external Compton (EC) emission appears to describe the available data better than a synchrotron self-Compton (SSC) scenario, and in particular orphan optical flares are difficult to produce in the SSC framework. X-ray soft-excesses, γ-ray spectral hardening, and the detections at very high energies of certain FSRQs during flares find natural explanations in the EC scenario with particle acceleration change. Likewise, optical flares with/without γ-ray counterparts can be explained by different allocations of energy between the magnetization and particle acceleration, which may be related to the orientation of the magnetic field relative to the jet flow. We also calculate the degree of linear polarization and polarization angle as a function of time for a jet with helical magnetic field. Tightening of the magnetic helix immediately downstream of the jet perturbations, where flares occur, can be sufficient to explain the increases in the degree of polarization and a rotation by ≥180° of the observed polarization angle, if light-travel-time effects are properly considered.

  16. World Administrative Radio Conference. Issues for US International Spectrum Policy

    NASA Astrophysics Data System (ADS)

    1991-11-01

    U.S. preparations for the 1992 World Administrative Radio Conference to be held in Spain, February 1992 are examined. WARC-92 will attempt to reassign radio frequencies internationally in order to take advantage of new radio-based technologies and applications, such as digital audio broadcasting, high definition television, and personal communications services, while still accommodating the needs of existing users and services. The impacts of the realignment will be felt throughout the U.S. economy and around the world, and the agreements reached at WARC-92 will influence the development of radio-based systems and services well into the next century.

  17. A multi-frequency study of the radio galaxy NGC 326

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Ekers, R. D.; Fomalont, E. B.

    We present preliminary results of a multi-frequency study of the inversion symmetric radio galaxy NGC326 based on VLA observations at 1.4, 1.6, 4.8, 8.5, and 14.9 GHz. These data allow us to investigate in detail the morphological, spectral and polarization properties of this peculiar object at different levels of spatial resolution.

  18. Radio emission at the centre of the galaxy cluster Abell 3560: evidence for core sloshing?

    NASA Astrophysics Data System (ADS)

    Venturi, T.; Rossetti, M.; Bardelli, S.; Giacintucci, S.; Dallacasa, D.; Cornacchia, M.; Kantharia, N. G.

    2013-10-01

    Context. We study the interplay between the radio emission associated with the dominant galaxy in clusters and the properties of the surrounding intracluster medium on the basis of its X-ray emission. Aims: Previous radio observations of the galaxy cluster A 3560, located in the Shapley Concentration core, revealed complex radio emission associated with the brightest cluster member. To understand the origin of this radio emission we performed a detailed multiwavelength study with high-quality proprietary data in the radio and X-ray bands and by means of optical data available in the literature. Methods: We observed the cluster with the Giant Metrewave Radio Telescope, the Very Large Array, and the Australia Telescope Compact array at 240 and 610 MHz, 1.28, 1.4, 2.3, 4.8, and 8.4 GHz, and performed a detailed morphological and spectral study of the radio emission associated with the brightest cluster galaxy (BCG). Furthermore, we observed the cluster with the XMM-Newton and Chandra observatories to derive the properties of the intracluster gas. Finally, we made use of literature data to obtain the bidimensional distribution of the galaxies in the cluster. Results: The radio emission, associated with the north-eastern nucleus of the dumb-bell BCG, is the result of two components: an active radio galaxy, with jets and lobes, plus aged diffuse emission, which is not refurbished with new electrons at present. Our Chandra data show that the radio active nucleus of the BCG has extended X-ray emission, which we classify as a low-luminosity corona. A residual image of the XMM-Newton brightness distribution shows a spiral-like feature, which we interpret as the signature of gas sloshing. A sub-group is clearly visible in the surface brightness residual map, and this is also supported by the XMM-Newton temperature analysis. The optical bidimensional analysis shows substructure in A 3560. A galaxy clump was detected at the location of the X-ray sub-group, and another group is

  19. 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.

  20. Analysis of a discrete spectrum analyzer for the detection of radio frequency interference

    NASA Technical Reports Server (NTRS)

    Levitt, B. K.

    1977-01-01

    As the radio frequency spectrum becomes increasingly overcrowded, interference with mission-critical DSN operations is rising at an alarming rate. To alleviate this problem the DSN is developing a wideband surveillance system for on-site detection and identification of potential sources of radio frequency interference (RFI), which will complement the existing frequency coordination activities. The RFI monitoring system is based on a wideband, multi-look discrete spectrum analyzer operating on fast Fourier transform principles. An extensive general statistical analysis is presented of such spectrum analyzers and derives threshold detection performance formulas for signals of interest. These results are then applied to the design of the RFI spectrum analyzer under development.

  1. Extracting Physical Parameters for the First Galaxies from the Cosmic Dawn Global 21-cm Spectrum

    NASA Astrophysics Data System (ADS)

    Burns, Jack O.; Mirocha, Jordan; harker, geraint; Tauscher, Keith; Datta, Abhirup

    2016-01-01

    The all-sky or global redshifted 21-cm HI signal is a potentially powerful probe of the first luminous objects and their environs during the transition from the Dark Ages to Cosmic Dawn (35 > z > 6). The first stars, black holes, and galaxies heat and ionize the surrounding intergalactic medium, composed mainly of neutral hydrogen, so the hyperfine 21-cm transition can be used to indirectly study these early radiation sources. The properties of these objects can be examined via the broad absorption and emission features that are expected in the spectrum. The Dark Ages Radio Explorer (DARE) is proposed to conduct these observations at low radio astronomy frequencies, 40-120 MHz, in a 125 km orbit about the Moon. The Moon occults both the Earth and the Sun as DARE makes observations above the lunar farside, thus eliminating the corrupting effects from Earth's ionosphere, radio frequency interference, and solar nanoflares. The signal is extracted from the galactic/extragalactic foreground employing Bayesian methods, including Markov Chain Monte Carlo (MCMC) techniques. Theory indicates that the 21-cm signal is well described by a model in which the evolution of various physical quantities follows a hyperbolic tangent (tanh) function of redshift. We show that this approach accurately captures degeneracies and covariances between parameters, including those related to the signal, foreground, and the instrument. Furthermore, we also demonstrate that MCMC fits will set meaningful constraints on the Ly-α, ionizing, and X-ray backgrounds along with the minimum virial temperature of the first star-forming halos.

  2. GALAXY CLUSTER RADIO RELICS IN ADAPTIVE MESH REFINEMENT COSMOLOGICAL SIMULATIONS: RELIC PROPERTIES AND SCALING RELATIONSHIPS

    SciTech Connect

    Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Smith, Britton D.; O'Shea, Brian W.; Turk, Matthew J.

    2011-07-10

    Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at shock fronts, which is thought to be responsible for radio relics-extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron shock acceleration.

  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. The log N-log S curve for 3CR radio galaxies and the problem of identifying faint radio galaxies

    NASA Technical Reports Server (NTRS)

    Burbidge, G. R.; Narlikar, J. V.

    1976-01-01

    The log N-log S slope of optically identified galaxies in the 3CR catalog is analyzed for galaxies with flux levels greater than 10 Jy and located at galactic latitudes greater than 7 deg. For the 86 galaxies with known redshifts, the slope is found to be about 1.16; for all 119 galaxies, the slope is found to be about 1.50. If the 113 unidentified sources are included, the slope steepens to about 1.81. It is shown that this steepness is caused by the unidentified sources. Assuming that the slope is due to evolution at redshifts of 1 to 3 and that the unidentified sources are bright ellipticals, the mean redshifts and apparent brightnesses of these galaxies are calculated. The results indicate that it is impossible to observe the unidentified sources with existing ground-based telescopes, implying that it is presently impossible to establish directly that evolution is responsible for the steep log N-log S curve of the 3CR galaxies.

  6. 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.

  7. Radio and X-Ray Properties of Submillimeter Galaxies in the A2125 Field

    NASA Astrophysics Data System (ADS)

    Wagg, J.; Owen, F.; Bertoldi, F.; Sawitzki, M.; Carilli, C. L.; Menten, K. M.; Voss, H.

    2009-07-01

    We present the radio and X-ray properties of 1.2 mm MAMBO source candidates in a 1600 arcmin2 field centered on the Abell 2125 galaxy cluster at z = 0.247. The brightest, nonsynchrotron millimeter source candidate in the field has a photometric redshift z = 3.93+1.11 -0.80 and is not detected in a 31 ks Chandra X-ray exposure. These findings are consistent with this object being an extremely dusty and luminous starburst galaxy at high redshift, possibly the most luminous yet identified in any blank-field millimeter survey. The deep 1.4 GHz Very Large Array imaging identifies counterparts for 83% of the 29 mm source candidates identified at >=4σ (S 1.2 mm = 2.7-52.1 mJy), implying that the majority of these objects are likely to lie at z lsim 3.5. The median millimeter-to-radio wavelength photometric redshift of this radio-detected sample is z ~ 2.2 (first and third quartiles of 1.7 and 3.0), consistent with the median redshift derived from optical spectroscopic surveys of the radio-detected subsample of bright submillimeter galaxies (S 850 μm > 5 mJy). Three millimeter-selected quasars are confirmed to be X-ray luminous in the high-resolution Chandra imaging, while another millimeter source candidate with potential multiple radio counterparts is also detected in the X-ray regime. Both of these radio counterparts are positionally consistent with the millimeter source candidate. One counterpart is associated with an elliptical galaxy at z = 0.2425, but we believe that a second counterpart associated with a fainter optical source likely gives rise to the millimeter emission at z ~ 1.

  8. 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

  9. Defying jet-gas alignment in two radio galaxies at z ~ 2 with extended light profiles: Similarities to brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We report the detection of extended warm ionized gas in two powerful high-redshift radio galaxies, NVSS J210626-314003 at z = 2.10 and TXS 2353-003 at z = 1.49, that does not appear to be associated with the radio jets. This is contrary to what would be expected from the alignment effect, a characteristic feature of distant, powerful radio galaxies at z ≥ 0.6. The gas also has smaller velocity gradients and line widths than most other high-z radio galaxies with similar data. Both galaxies are part of a systematic study of 50 high-redshift radio galaxies with SINFONI, and are the only two that are characterized by the presence of high surface-brightness gas not associated with the jet axis and by the absence of such gas aligned with the jet. Both galaxies are spatially resolved with ISAAC broadband imaging covering the rest-frame R band, and have extended wings that cannot be attributed to line contamination. We argue that the gas and stellar properties of these galaxies are more akin to gas-rich brightest cluster galaxies in cool-core clusters than the general population of high-redshift radio galaxies at z ≳ 2. In support of this interpretation, one of our sources, TXS 2353-003, for which we have Hα narrowband imaging, is associated with an overdensity of candidate Hα emitters by a factor of ~8 relative to the field at z = 1.5. We discuss possible scenarios of the evolutionary state of these galaxies and the nature of their emission line gas within the context of cyclical AGN feedback. Based on observations carried out with the Very Large Telescope of ESO under Program IDs 079.A-0617, 084.A-0324, 085.A-0897, and 090.A-0614.Appendix A is available in electronic form at http://www.aanda.org

  10. A comprehensive study of the radio properties of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Hogan, M. T.; Edge, A. C.; Hlavacek-Larrondo, J.; Grainge, K. J. B.; Hamer, S. L.; Mahony, E. K.; Russell, H. R.; Fabian, A. C.; McNamara, B. R.; Wilman, R. J.

    2015-10-01

    We examine the radio properties of the brightest cluster galaxies (BCGs) in a large sample of X-ray selected galaxy clusters comprising the Brightest Cluster Sample (BCS), the extended BCS and ROSAT-ESO Flux Limited X-ray cluster catalogues. We have multifrequency radio observations of the BCG using a variety of data from the Australia Telescope Compact Array, Jansky Very Large Array and Very Long Baseline Array telescopes. The radio spectral energy distributions of these objects are decomposed into a component attributed to on-going accretion by the active galactic nuclei (AGN) that we refer to as `the core', and a more diffuse, ageing component we refer to as the `non-core'. These BCGs are matched to previous studies to determine whether they exhibit emission lines (principally Hα), indicative of the presence of a strong cooling cluster core. We consider how the radio properties of the BCGs vary with cluster environmental factors. Line emitting BCGs are shown to generally host more powerful radio sources, exhibiting the presence of a strong, distinguishable core component in about 60 per cent of cases. This core component more strongly correlates with the BCG's [O III] 5007 Å line emission. For BCGs in line emitting clusters, the X-ray cavity power correlates with both the extended and core radio emission, suggestive of steady fuelling of the AGN over bubble-rise time-scales in these clusters.

  11. BVR Photometry Of An Inverted-spectrum, Flat-spectrum Radio Source With The Rowan 0.4-meter Telescope

    NASA Astrophysics Data System (ADS)

    Guerra, Erick; Diekewicz, A.

    2012-01-01

    Several galaxies have been selected for an exploratory campaign with 0.4-meter telescope atop Science Hall at Rowan University. These galaxies exhibit inverted radio spectra on the basis of fluxes in the GB6 and VLA FIRST catalogs and have SDSS magnitudes in g-band less than 15.5. The results of BVR photometry of one of these galaxies, CGCG 215-024, are presented. These are the first results from an ongoing campaign to expand the function of the observatory atop Science Hall. Efforts to mitigate bulding vibration and light pollution in future work will be presented. The authors would like to acknowledge Ric and Jean Edelman for their gift that funded the 0.4-meter telescope.

  12. 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.

  13. Spectral ageing in the lobes of FR-II radio galaxies: new methods of analysis for broad-band radio data

    NASA Astrophysics Data System (ADS)

    Harwood, Jeremy J.; Hardcastle, Martin J.; Croston, Judith H.; Goodger, Joanna L.

    2013-11-01

    The broad-bandwidth capabilities of next generation telescopes such as the Jansky Very Large Array (JVLA) mean that the spectrum of any given source varies significantly within the bandwidth of any given observation. Detailed spectral analysis taking this variation into account is set to become standard practice when dealing with any new broad-band radio observations; it is therefore vital that methods are developed to handle this new type of data. In this paper, we present the Broadband Radio Astronomy ToolS (BRATS) software package and, use it to carry out detailed analysis of JVLA observations of three powerful radio galaxies. We compare two of the most widely used models of spectral ageing, the Kardashev-Pacholczyk and Jaffe-Perola models and also results of the more complex, but potentially more realistic, Tribble model. We find that the Tribble model provides both a good fit to observations as well as providing a physically realistic description of the source. We present the first high-resolution spectral maps of our sources and find that the best-fitting injection indices across all models take higher values than have previously been assumed. We present characteristic hotspot advance speeds and make comparison to those derived from dynamical ages, confirming the previously known discrepancy in speed remains present when determined at high spectral resolutions. We show that some previously common assumptions made in determining spectral ages with narrow-band radio telescopes may not always hold and strongly suggest that these are accounted for in future investigations.

  14. Implications of the ISO LWS spectrum of the prototypical ultraluminous galaxy: ARP 220

    NASA Technical Reports Server (NTRS)

    Fischer, J.; Satyapal, S.; Luhman, M. L.; Melnick, G.; Cox, P.; Cernicharo, J.; Stacey, G. J.; Smith, H. A.; Lord, S. D.; Greenhouse, M. A.

    1997-01-01

    The low resolution far infrared spectrum of the galaxy Arp 220, obtained with the low wavelength spectrometer (LWS) onboard the Infrared Space Observatory (ISO), is presented. The spectrum is dominated by the OH, H2O, CH, NH3 and O I absorption lines. The upper limits on the far infrared fine structure lines indicate a softer radiation in Arp 220 than in starburst galaxies.

  15. Radio AGN signatures in massive quiescent galaxies out to z=1.5

    NASA Astrophysics Data System (ADS)

    Järvelä, Emilia

    2016-08-01

    Detection of gamma-rays from narrow-line Seyfert 1 galaxies (NLS1) by Fermi confirmed the presence of powerful relativistic jets in them, and thus challenged our understanding of active galactic nuclei (AGN). In the current AGN paradigm powerful relativistic jets are produced in massive elliptical galaxies with supermassive black holes. NLS1s differ from them significantly; they harbour lower mass black holes accreting at higher Eddington ratios, have preferably compact radio morphology, reside mostly in spiral galaxies, and were thought to be radio-quiet.Fermi's discovery invokes questions about the AGN evolution; what triggers and maintains the AGN activity, and what are the evolutionary lines of the different populations? It is also necessary to revise the AGN unification schemes to fit in NLS1s. They convolute the whole AGN scenario, but offer us a new look on the jet phenomena and will help us construct a more comprehensive big picture of AGN.Despite their importance, NLS1s are rather poorly studied as a class. For example, some NLS1s seem to be totally radio-silent, but a considerable fraction are radio-loud and thus probably host jets. This, along with other observational evidence, implies that they do not form a homogeneous class. However, it remains unclear what is triggering the radio loudness in some of them, but, for example, the properties of the host galaxy and the large-scale environment might play a role. Also the parent population of NLS1s remains an open question.We used various statistical methods, for example, multiwavelength correlations and principal component analysis to study a large sample of NLS1 sources. We will present the results and discuss the interplay between their properties, such as emission properties, black hole masses, large-scale environments, and their effect on radio loudness. We will also introduce the Metsähovi Radio Observatory NLS1 galaxy observing programme, which is the first one dedicated to systematical observations

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

    SciTech Connect

    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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. The very flat radio spectrum of 0735 plus 178 - A cosmic conspiracy

    NASA Technical Reports Server (NTRS)

    Cotton, W. D.; Wittels, J. J.; Shapiro, I. I.; Marcaide, J.; Owen, F. N.; Spangler, S. R.; Rius, A.; Angulo, C.; Clark, T. A.; Knight, C. A.

    1980-01-01

    Multifrequency interferometric and total flux density measurements of the radiation from 0735 plus 178 are discussed. It is shown that it is far more likely that the very flat radio spectrum of this source results from a superposition of incoherent synchrotron radiation from four distinct, homogeneous components, each with a peaked spectrum, than from radiation from a single inhomogeneous component.

  2. Curved Radio Jet in Center of Nearby Galaxy Complicates Picture of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    New observations with the National Science Foundation's Very Long Baseline Array (VLBA) indicate that the inner workings of active galaxies may be considerably more complex than astronomers have previously thought. Drs. Alan Roy and James Ulvestad of the National Radio Astronomy Observatory, together with Drs. Edward Colbert and Andrew Wilson of the Space Telescope Science Institute and the University of Maryland, used the VLBA to image a light-year-sized radio jet in NGC 4151, a relatively nearby spiral galaxy. The jet seen by the radio telescopes is not aligned as the scientists expected, and this misalignment may require changes to theoretical models of active galactic nuclei. The astronomers presented their findings today to the American Astronomical Society meeting in Winston- Salem, North Carolina. The radio structure at the center of the Seyfert galaxy NGC 4151, located approximately 43 million light-years from Earth, was imaged with a resolution of better than 1 light-year. The radio images were made using the 25-meter (82-foot) telescopes of the VLBA, an array of 10 telescopes spread out over the full length and width of the United States, from the Virgin Islands to Hawaii. Seyfert galaxies are spiral galaxies that are nearby examples of galaxies containing active galactic nuclei (AGN), which are thought to be powered by black holes having masses millions of times greater than the Sun. They represent nearby cousins of the more distant and energetic quasars; their relative proximity to Earth permits images to be made with much finer spatial resolution than is possible for quasars. The radio images of NGC 4151 reveal a chain of knots several light years in length, separated by a few light months, which then appear to make a fairly sharp turn -- about 55 degrees -- to merge with a previously known straight radio jet about 800 light-years in length. This large-scale radio jet is nearly coincident with a complex of gas clouds imaged at optical wavelengths with

  3. Radio jets clearing the way through a galaxy: watching feedback in action.

    PubMed

    Morganti, Raffaella; Fogasy, Judit; Paragi, Zsolt; Oosterloo, Tom; Orienti, Monica

    2013-09-01

    The energy released by an active galactic nucleus (AGN) has a strong impact on the surrounding interstellar medium (ISM). This feedback is considered to be the regulating factor for the growth of the central massive black hole and for the rate of star formation in a galaxy. We have located, using very-long-baseline interferometry, the fast outflow of neutral hydrogen in the young, restarted radio-loud AGN 4C12.50. The outflow is located 100 parsec from the nucleus where the radio jet interacts with the ISM, as well as around the associated radio lobe. These observations show that the radio plasma drives the outflow and removes gas from the central regions and that jet-driven outflows can play a relevant role in feedback mechanisms.

  4. 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).

  5. 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.

  6. 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

  7. Can giant radio halos probe the merging rate of galaxy clusters?

    NASA Astrophysics Data System (ADS)

    Cassano, R.; Brunetti, G.; Giocoli, C.; Ettori, S.

    2016-09-01

    Observations of galaxy clusters both in the radio and X-ray bands probe a direct link between cluster mergers and giant radio halos, suggesting that these sources can be used as probes of the cluster merging rate with cosmic time. While all giant radio halos are found in merging clusters, not every merging cluster hosts a giant radio halo. In this paper we carry out an explorative study that combines the observed fractions of merging clusters and radio halos with the merging rate predicted by cosmological simulations, and we attempt to infer constraints on merger properties of clusters that appear disturbed in X-rays and clusters that host radio halos. We used classical morphological parameters to identify merging systems and analysed the largest current (mass-selected M500 ≳ 6 × 1014M⊙ and 0.2 ≤ z ≤ 0.33) sample of galaxy clusters with radio and X-ray data; we extracted this sample from the Planck Sunyaev-Zeldovich cluster catalogue. We found that the fraction of merging clusters in this sample is fm ~ 62-67%, while that of clusters with radio halos is fRH ~ 44-51%. We assume that the morphological disturbance measured in the X-rays is driven by the merger with the largest mass ratio, ξ (ξ = Mi/M1< 1, where Mi and M1 are the progenitor masses), which is still ongoing in the cluster at the epoch of observation. Results from theoretical studies allow us to derive the fraction of mergers with mass ratio above a minimum threshold (those with ξ≳ξ_min) in our sample, under the assumption of a timescale τm for the duration of merger-induced disturbance. The comparison of the theoretical merger fraction with the observed merger fraction allows us to constrain a region in the (ξmin, τm) plane. We find that under the assumption of τm ~ 2-3 Gy, as constrained by simulations, the observed merger fraction matches the theoretical value for ξmin ~ 0.1-0.18. This is consistent with optical and near-infrared (IR) observations of galaxy clusters in the sample

  8. RADIO ACTIVE GALAXY NUCLEI IN GALAXY CLUSTERS: HEATING HOT ATMOSPHERES AND DRIVING SUPERMASSIVE BLACK HOLE GROWTH OVER COSMIC TIME

    SciTech Connect

    Ma, C.-J.; McNamara, B. R.; Nulsen, P. E. J.

    2013-01-20

    We estimate the average radio active galactic nucleus (AGN, mechanical) power deposited into the hot atmospheres of galaxy clusters over more than three quarters of the age of the Universe. Our sample was drawn from eight major X-ray cluster surveys and includes 685 clusters in the redshift range 0.1 < z < 0.6 that overlap the area covered by the NRAO VLA Sky Survey (NVSS). The radio-AGN mechanical power was estimated from the radio luminosity of central NVSS sources, using the relation of Cavagnolo et al. that is based on mechanical powers determined from the enthalpies of X-ray cavities. We find only a weak correlation between radio luminosity and cluster X-ray luminosity, although the most powerful radio sources reside in luminous clusters. The average AGN mechanical power of 3 Multiplication-Sign 10{sup 44} erg s{sup -1} exceeds the X-ray luminosity of 44% of the clusters, indicating that the accumulation of radio-AGN energy is significant in these clusters. Integrating the AGN mechanical power to redshift z = 2.0, using simple models for its evolution and disregarding the hierarchical growth of clusters, we find that the AGN energy accumulated per particle in low luminosity X-ray clusters exceeds 1 keV per particle. This result represents a conservative lower limit to the accumulated thermal energy. The estimate is comparable to the level of energy needed to 'preheat' clusters, indicating that continual outbursts from radio-AGN are a significant source of gas energy in hot atmospheres. Assuming an average mass conversion efficiency of {eta} = 0.1, our result implies that the supermassive black holes that released this energy did so by accreting an average of {approx}10{sup 9} M {sub Sun} over time, which is comparable to the level of growth expected during the quasar era.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. VIMOS-VLT and Spitzer observations of a radio galaxy at z= 2.5*

    NASA Astrophysics Data System (ADS)

    Villar-Martín, M.; Sánchez, S. F.; De Breuck, C.; Peletier, R.; Vernet, J.; Rettura, A.; Seymour, N.; Humphrey, A.; Stern, D.; di Serego Alighieri, S.; Fosbury, R.

    2006-02-01

    We present: (i) a kinematic and morphological study of the giant Lyα nebula associated with the radio galaxy MRC 2104-242 (z= 2.49) based on integral field spectroscopic Visible Multiobject Spectrograph (VIMOS) data from the Very Large Telescope (VLT), and (ii) a photometric study of the host (proto?) galaxy based on Spitzer Space Telescope data. The galaxy appears to be embedded in a giant (>~120 kpc) gas reservoir that surrounds it completely. The kinematic properties of the nebula suggest that it is a rotating structure, which would imply a lower limit to the dynamical mass of ~3 × 1011Msolar. An alternate scenario is that the gas is infalling. Such a process would be able to initiate and sustain significant central starburst activity, although it is likely to contribute with less than 10 per cent of the total stellar mass. The near- to mid-infrared spectral energy distribution of the radio galaxy suggests the existence of a reddened, E(B-V) = 0.4 +/- 0.1, evolved stellar population of age >~1.8 Gyr and mass (5 +/- 2) × 1011Msolar. The implied formation redshift is zf>~ 6. This stellar mass is similar to the stellar masses found for massive early-type galaxies at z~ 2 in deep, near-infrared surveys.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Orientation and size of the `Z' in X-shaped radio galaxies

    NASA Astrophysics Data System (ADS)

    Zier, C.

    2005-12-01

    Some X-shaped radio galaxies show a Z-symmetric morphology in the less luminous secondary lobes. Within the scenario of a merger between two galaxies, each hosting a supermassive black hole in its centre, this structure has been explained before. As the smaller galaxy spirals towards the common centre, it releases gas to the interstellar medium of the larger active galaxy. The ram pressure of this streaming gas will bend the lobes of the pre-merger jet into a Z-shape. After the black holes have merged, the jet propagates in a new direction that is aligned with the angular momentum of the binary black hole. In this paper we deproject the pre- and post-merger jets. Taking into account the expected angles between the jet pairs and with the assumption that their directions are uncorrelated, we show that one of three possible orientations of the jets with respect to the line of sight is more likely than the others. This actually depends on the distance where the bending occurs. Another result of our deprojection is that the streaming gas bends the jet into a Z-shape in a range between about 30 and 100 kpc distance to the centre of the primary galaxy. We confirm this finding by comparing our predictions for the properties of the rotational velocity field and its radius with observations and numerical simulations of merging galaxies. Thus, our results support the merger scenario as explanation for X- and Z-shaped radio galaxies with the jet pointing along the former axis of orbital angular momentum of the binary.

  3. Properties of Lya Emitters Around the Radio Galaxy MRC 0316-257

    SciTech Connect

    Venemans, B; Rottgering, H; Miley, G; Kurk, J; De Breuck, C; van Breugel, W; Carilli, C; Ford, H; Heckman, T; Pentericci, L; McCarthy, P

    2004-08-12

    Observations of the radio galaxy MRC 0316-257 at z = 3.13 and the surrounding field are presented. Using narrow- and broad-band imaging obtained with the VLT*, 92 candidate Ly{alpha} emitters with a rest-frame equivalent width of > 15 AngstromS were selected in a {approx} 7{prime} x 7{prime} field around the radio galaxy. Spectroscopy of 40 candidate emitters resulted in the discovery of 33 emission line galaxies of which 31 are Ly{alpha} emitters with redshifts similar to that of the radio galaxy, while the remaining two galaxies turned out to be [{omicron} II] emitters. The Ly{alpha} profiles had widths (FWHM) corresponding to 120-800 kms{sup -1},with a median of 260 kms{sup -1}. Where the signal-to-noise spectra was large enough, the Ly{alpha} profiles are found to be asymmetric, with apparent absorption troughs blueward of the profile peaks, indicative of absorption along the line of sight of an {Eta}{Iota} mass of 1-5000 {mu}{circle_dot}. Besides that of the radio galaxy and one of the emitters that is an QSO, the continuum of the emitters is faint, with luminosities ranging from 1.3 L{sub *} to < 0.03 L{sub *}.The colors of the confirmed emitters are, on average, very blue. The median UV continuum slope is {beta}=-1.65, bluer than the average slope of LBGs with Ly{alpha} emitters is 2.6 {Mu}{circle_dot}{sup -1} as measured by the Ly{alpha} emission line or < 3.9 {Mu}{circle_dot}{sup -1} as measured by the UV continuum. The properties of the Ly{alpha} galaxies (faint, blue and small) are consistent with young star forming galaxies which are nearly dust free. The density of Ly{alpha} emitting galaxies in the field around MRC 0316-257 is a factor of 3.3{sup +0.5}{sub -0.4} larger compared with the density of Ly{alpha} emitters at that redshift. The velocity distribution of the spectroscopically confirmed emitters has a dispersion of 640 km s{sup -1}, corresponding to a FWHM of 1510 km s{sup -1}, which is substantially smaller than the width of the narrow

  4. 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.

  5. 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.

  6. The influence of X-ray gas on the dynamics of the Z-shaped radio galaxy NGC 326

    NASA Astrophysics Data System (ADS)

    Worrall, Diana

    2005-09-01

    We propose a sensitive Chandra observation of NGC 326, the archetypal Z-shaped radio galaxy. We will establish how much of a component of X-ray emission detected with ROSAT arises from a galaxy atmosphere, and measure its temperature and density. The results will test our model for Z-shaped radio sources, in which the external atmosphere is key to shaping the morphology of this important class of radio galaxy. By combining the Chandra results with our detailed radio spectral imaging we will measure the mass density of the radio plasma, and hence determine its composition. As compared with other sources for which this has been attempted, these measurements will benefit from the controlling physics being more secure.

  7. 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.

  8. 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.

  9. The X-Ray Weakness of GPS Radio Galaxies: A Volume-Limited Complete Sample

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard F. (Technical Monitor); Siemiginowska, Aneta (Principal Investigator)

    2004-01-01

    The XMM observations of Mkn 668 have been analyzed. We found soft X-ray signatures of a hot plasma (kT approximately 10^7 approximately K) and a hard X-ray emission from the nucleus. The X-ray spectrum above 2.5 approximately keV is characterized by a very flat (observed photon index, Gamma approximately 0.5) power-law continuum, alongside with a strong Fe-K-alpha neutral iron fluorescent line (EW approximately 600 approximately eV). The best explanation for the origin of this high energy X-ray emission is in terms of the Compton-reflection of the nuclear emission. The primary X-ray emission is obscured by a Compton-thick (N_H approximately 10^24 approximately cm-2) matter which becomes transparent at higher energies. The observed above 2.5-keV X-rays are mostly due to reflection which is indicated by a strong Fe-K-alpha line. This represents the second hard X-ray detection of the GPS galaxy ever (the first one being 1345+125; O Dea et al. 2000). Interestingly, the both such trend is confirmed by our on going XMM-Newton observations of a larger GPS sample, it would lead us to looking into the question on how the dense nuclear environment impacts the nature and evolution of a GPS source, and more generally, on the history of radio power in the universe. The paper summarizing the results has been submitted to Astronomy and Astrophysics in December 2003.

  10. The impact of the SZ effect on cm-wavelength (1-30 GHz) observations of galaxy cluster radio relics

    NASA Astrophysics Data System (ADS)

    Basu, Kaustuv; Vazza, Franco; Erler, Jens; Sommer, Martin

    2016-07-01

    Radio relics in galaxy clusters are believed to be associated with powerful shock fronts that originate during cluster mergers, and are a testbed for the acceleration of relativistic particles in the intracluster medium. Recently, radio relic observations have pushed into the cm-wavelength domain (1-30 GHz) where a break from the standard synchrotron power law spectrum has been found, most noticeably in the famous "Sausage" relic. Such spectral steepening is seen as an evidence for non-standard relic models, such as ones requiring seed electron population with a break in their energy spectrum. In this paper, however, we point to an important effect that has been ignored or considered insignificant while interpreting these new high-frequency radio data, namely the contamination due to the Sunyaev-Zel'dovich (SZ) effect that changes the observed synchrotron flux. Even though the radio relics reside in the cluster outskirts, the shock-driven pressure boost increases the SZ signal locally by roughly an order of magnitude. The resulting flux contamination for some well-known relics are non-negligible already at 10 GHz, and at 30 GHz the observed synchrotron fluxes can be diminished by a factor of several from their true values. At higher redshift the contamination gets stronger due to the redshift independence of the SZ effect. Interferometric observations are not immune to this contamination, since the change in the SZ signal occurs roughly at the same length scale as the synchrotron emission, although there the flux loss is less severe than single-dish observations. Besides presenting this warning to observers, we suggest that the negative contribution from the SZ effect can be regarded as one of the best evidence for the physical association between radio relics and shock waves. We present a simple analytical approximation for the synchrotron-to-SZ flux ratio, based on a theoretical radio relic model that connects the nonthermal emission to the thermal gas properties

  11. 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.

  12. 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.

  13. 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.

  14. A multi-frequency study of the radio galaxy NGC 326. I. The data

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Parma, P.; de Ruiter, H. R.; Bondi, M.; Ekers, R. D.; Fanti, R.; Fomalont, E. B.

    2001-12-01

    We present the results of a multi-frequency study of the inversion symmetric radio galaxy NGC 326 based on Very Large Array observations at 1.4, 1.6, 4.8, 8.5 and 14.9 GHz. The morphological, spectral and polarization properties of this peculiar object are studied at different levels of spatial resolutions. The interpretation of the data will be discussed in forthcoming papers.

  15. A Chandra Study of the Radio Galaxy NGC 326: Wings, Outburst History, and Active Galactic Nucleus Feedback

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Constraints on radio source clustering towards galaxy clusters: application for cm-wavelength simulations of blind sky surveys

    NASA Astrophysics Data System (ADS)

    Lew, Bartosz

    2016-10-01

    We derive constraints on radio source clustering towards Planck-selected galaxy clusters using the NVSS point source catalog. The constraint can be used for making a more realistic Sunyaev-Zeldovich effect (SZE) mocks, calculating predictions of detectable clusters count and for quantifying source confusion in radio surveys.

  4. 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.

  5. DISK-JET CONNECTION IN THE RADIO GALAXY 3C 120

    SciTech Connect

    Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Olmstead, Alice R.; Chicka, Benjamin; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Laehteenmaeki, Anne; Tornikoski, Merja; Hovatta, Talvikki; Marshall, Kevin; Miller, H. Richard; Ryle, Wesley T.; Benker, A. J.; Brokofsky, David; Campbell, Jeffrey S.; Chonis, Taylor S.; Gaskell, C. Martin; Bottorff, Mark C.

    2009-10-20

    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

  6. A new giant luminous arc gravitational lens associated with a z = 0.62 galaxy cluster, and the environments of distant radio galaxies

    NASA Technical Reports Server (NTRS)

    Dickinson, Mark

    1993-01-01

    In the course of a survey investigating the cluster environments of distant 3CR radio galaxies, I have identified a previously unknown 'giant luminous arc' gravitational lens. The lensing cluster is associated with the radio galaxy 3C 220.1 at z = 0.62 and is the most distant cluster now known to produce such arcs. I present imaging and spectroscopic observations of the cluster and the arc, and discuss the implications for the cluster mass. At z greater than 0.6 the cluster velocity dispersions implied by such giant arcs may provide an interesting constraint on theories of large scale structure formation. The parent investigation in which this arc was identified concerns galaxy clusters and radio galaxy environments at 0.35 less than z less than 0.8. At the present epoch, powerful FR 2 radio galaxies tend to be found in environments of poor or average galaxy density. In contrast, at the higher redshifts investigated here, richer group and cluster environments are common. I present additional data on other clusters from this survey, and discuss its extension to z greater than 1 through a program of near-infrared and optical imaging.

  7. ON THE POPULATIONS OF RADIO GALAXIES WITH EXTENDED MORPHOLOGY AT z < 0.3

    SciTech Connect

    Lin, Yen-Ting; Shen Yue; Strauss, Michael A.; Lunnan, Ragnhild; Richards, Gordon T.

    2010-11-10

    Extended extragalactic radio sources have traditionally been classified into Fanaroff and Riley (FR) I and II types, based on the ratio r{sub s} of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source (r{sub s} {identical_to} S/T). In this paper, we examine the distribution of various physical properties as a function of r{sub s} of 1040 luminous (L {approx}> L{sub *}) extended radio galaxies (RGs) at z < 0.3 selected with well-defined criteria from the SDSS, NVSS, and FIRST surveys. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on r{sub s} , FR I and FR II RGs overlap in their host galaxy properties. However, the rare LD sources with r{sub s} {approx}> 0.8 and [O III] {lambda}5007 line luminosity >10{sup 6} L{sub sun} are markedly different on average from the rest of the RGs, in the sense that they are hosted in lower mass galaxies, live in relatively sparse environments, and likely have higher accretion rates onto the central supermassive black hole (SMBH). Thus, these high emission line luminosity, high-r{sub s} LD RGs, and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the 'classical double' morphology (roughly corresponding to the LD sources with r{sub s} {approx}> 0.8 and emission lines); at lower accretion rates, the jets from a radiatively inefficient accretion flow generate radio lobes without apparent 'hot spots' at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates and in galaxies with dense galactic structure, sources with prominent

  8. 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.

  9. 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.

  10. 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.

  11. Internal dynamics of Abell 1240: a galaxy cluster with symmetric double radio relics

    NASA Astrophysics Data System (ADS)

    Barrena, R.; Girardi, M.; Boschin, W.; Dasí, M.

    2009-08-01

    Context: The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. Aims: We aim to obtain new insights into the internal dynamics of the cluster Abell 1240, which appears to contain two roughly symmetric radio relics, separated by ~2 h_70-1 Mpc. Methods: Our analysis is based mainly on redshift data for 145 galaxies mostly acquired at the Telescopio Nazionale Galileo and on new photometric data acquired at the Isaac Newton Telescope. We also use X-ray data from the Chandra archive and photometric data from the Sloan Digital Sky Survey (Data Release 7). We combine galaxy velocities and positions to select 89 cluster galaxies and analyze the internal dynamics of the Abell 1237 + Abell 1240 cluster complex, Abell 1237 being a close companion of Abell 1240 in its southern direction. Results: We estimate similar redshifts for Abell 1237 and Abell 1240, < z > = 0.1935 and < z > = 0.1948, respectively. For Abell 1237, we estimate a line-of-sight (LOS) velocity dispersion of σV ~ 740 km s-1and a mass of M ~ 6 × 1014 h_70-1 M⊙. For Abell 1240, we estimate a LOS σV ~ 870 km s-1and a mass in the range M ~ 0.9-1.9 × 1015 h_70-1 M⊙, which takes account of its complex dynamics. Abell 1240 is shown to have a bimodal structure with two galaxy clumps roughly aligned along its N-S direction, the same as defined by the elongation of its X-ray surface brightness and the axis of symmetry of the relics. The two brightest galaxies of Abell 1240, associated with the northern and southern clumps, are separated by a LOS rest-frame velocity difference Vrf ~ 400 km s-1and a projected distance D ~ 1.2 h_70-1 Mpc. The two-body model agrees with the hypothesis that we are looking at a cluster merger that occurred largely in the plane of the sky, the two galaxy clumps being separated by a rest-frame velocity difference Vrf ~ 2000 km s-1at a time of 0.3 Gyr after the crossing core, while Abell 1237

  12. BROADBAND JET EMISSION IN YOUNG AND POWERFUL RADIO SOURCES: THE CASE OF THE COMPACT STEEP SPECTRUM QUASAR 3C 186

    SciTech Connect

    Migliori, Giulia; Siemiginowska, Aneta; Celotti, Annalisa

    2012-04-20

    We present the X-ray analysis of a deep ({approx}200 ks) Chandra observation of the compact steep spectrum radio-loud quasar 3C 186 (z = 1.06) and investigate the contribution of the unresolved radio jet to the total X-ray emission. The spectral analysis is not conclusive on the origin of the bulk of the X-ray emission. In order to examine the jet contribution to the X-ray flux, we model the quasar spectral energy distribution, adopting several scenarios for the jet emission. For the values of the main physical parameters favored by the observables, a dominant role of the jet emission in the X-ray band is ruled out when a single-zone (leptonic) scenario is adopted, even including the contribution of the external photon fields as seed photons for inverse Compton emission. We then consider a structured jet, with the blazar component that-although not directly visible in the X-ray band-provides an intense field of seed synchrotron photons Compton-scattered by electrons in a mildly relativistic knot. In this case, the whole X-ray emission can be accounted for if we assume a blazar luminosity within the range observed from flat spectrum radio quasars. The X-ray radiative efficiency of such a (structured) jet is intimately related to the presence of a complex velocity structure. The jet emission can provide a significant contribution in X-rays if it decelerates within the host galaxy on kiloparsec scales. We discuss the implications of this model in terms of jet dynamics and interaction with the ambient medium.

  13. Radio Spectrum Management in the Asia-Pacific Region

    NASA Astrophysics Data System (ADS)

    Tzioumis, T.

    2004-06-01

    The Asia-Pacific region comprises countries in ITU-R Region 3 from South and East Asia, Oceania and the Pacific islands, while excluding the Americas. Organizations in the Asia- Pacific region face special challenges in coping with the very diverse cultures and languages of the different nations. Telecommunications in each country are usually administered by a single National Communications Administration. These administrations participate in a number of regional umbrella organizations which promote cooperation in the development of communications in the Asia-Pacific. Those with relevance to radio astronomy are briefly oulined in this paper.

  14. Extragalactic jets as probes of distant clusters of galaxies and the clusters occupied by bent radio AGN (COBRA) survey

    NASA Astrophysics Data System (ADS)

    Blanton, Elizabeth L.; Paterno-Mahler, Rachel; Wing, Joshua D.; Ashby, M. L. N.; Golden-Marx, Emmet; Brodwin, Mark; Douglass, E. M.; Randall, Scott W.; Clarke, T. E.

    2015-03-01

    We are conducting a large survey of distant clusters of galaxies using radio sources with bent jets and lobes as tracers. These radio sources are driven by AGN and achieve their bent morphologies through interaction with the surrounding gas found in clusters of galaxies. Based on low-redshift studies, these types of sources can be used to identify clusters very efficiently. We present initial results from 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 it has revealed ~200 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.

  15. What is the optimal way to measure the galaxy power spectrum?

    NASA Astrophysics Data System (ADS)

    Smith, Robert E.; Marian, Laura

    2016-04-01

    Measurements of the galaxy power spectrum contain a wealth of cosmological information. In Smith & Marian, we generalized the power spectrum methodology of Feldman et al. to take into account the key tenets of galaxy formation: galaxies form and reside exclusively in dark matter haloes; a given dark matter halo may host galaxies of various luminosities; galaxies inherit the large-scale bias of their host halo. In this paradigm, we derived the optimal weighting scheme for maximizing the signal-to-noise ({S}/{N}) on a given band power estimate. For a future all-sky flux-limited galaxy redshift survey of depth bJ > 22, we demonstrate that the optimal weighting scheme does indeed provide improved {S}/{N} at the level of ˜20 per cent when compared to Feldman et al. and ˜60 per cent relative to Percival et al., for scales of the order of k ˜ 0.5 h Mpc-1. Using a Fisher matrix approach, we show the cosmological information yield is also increased relative to these alternate methods - especially the primordial power spectrum amplitude and dark energy equation of state. Caveats: uncertainties in cluster masses, non-linear halo bias and redshift distortions may reduce information gains.

  16. Radio, millimeter-submillimeter, and infrared spectra of flat-spectrum extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Bloom, Steven D.; Marscher, Alan P.; Gear, Walter K.; Terasranta, Harri; Valtaoja, Esko; Aller, Hugh D.; Aller, Margo F.

    1994-01-01

    We present radio to submillimeter-wave continuum spectra of 44 bright, compact extragalactic radio sources with flat spectra at centimeter wavelengths ('blazars'). Infrared J, H, and K flux densities are added to the spectra of six of these objects. These spectra are useful in comparisons of x-ray and gamma-ray measurements with the multiwaveband properties of blazars. A number of the objects have been detected as strong, hard gamma-ray sources by the Compton Gamma Ray Observatory (CGRO). The millimeter-wave spectra of the gamma-ray bright blazars we observe are flatter on average than for the sample as a whole.

  17. PREDICTIONS FOR ULTRA-DEEP RADIO COUNTS OF STAR-FORMING GALAXIES

    SciTech Connect

    Mancuso, Claudia; Lapi, Andrea; De Zotti, Gianfranco; Bressan, Alessandro; Perrotta, Francesca; Danese, Luigi; Cai, Zhen-Yi; Negrello, Mattia; Bonato, Matteo

    2015-09-01

    We have worked outty predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. Such predictions were obtained by coupling epoch-dependent star formation rate (SFR) functions with relations between SFR and radio (synchrotron and free–free) emission. The SFR functions were derived taking into account both the dust-obscured and the unobscured star formation, by combining far-infrared, ultraviolet, and Hα luminosity functions up to high redshifts. We have also revisited the South Pole Telescope counts of dusty galaxies at 95 GHz, performing a detailed analysis of the Spectral Energy Distributions. Our results show that the deepest SKA1-MID surveys will detect high-z galaxies with SFRs two orders of magnitude lower compared to Herschel surveys. The highest redshift tails of the distributions at the detection limits of planned SKA1-MID surveys comprise a substantial fraction of strongly lensed galaxies. We predict that a survey down to 0.25 μJy at 1.4 GHz will detect about 1200 strongly lensed galaxies per square degree, at redshifts of up to 10. For about 30% of them the SKA1-MID will detect at least 2 images. The SKA1-MID will thus provide a comprehensive view of the star formation history throughout the re-ionization epoch, unaffected by dust extinction. We have also provided specific predictions for the EMU/ASKAP and MIGHTEE/MeerKAT surveys.

  18. X-Ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

    SciTech Connect

    Ostorero, L.; Moderski, R.; Stawarz, L.; Diaferio, A.; Kowalska, I.; Cheung, C.C.; Kataoka, J.; Begelman, M.C.; Wagner, S.J.; /Heidelberg Observ.

    2010-06-07

    In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the GPS spectral energy distribution (SED) with the source expansion, predicting significant and complex high-energy emission, from the X-ray to the {gamma}-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N{sub H}) and radio (N{sub HI}) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes.

  19. X-RAY-EMITTING GHz-PEAKED-SPECTRUM GALAXIES: TESTING A DYNAMICAL-RADIATIVE MODEL WITH BROADBAND SPECTRA

    SciTech Connect

    Ostorero, L.; Diaferio, A.; Moderski, R.; Stawarz, L.; Kowalska, I.; Cheung, C. C.; Kataoka, J.; Begelman, M. C.; Wagner, S. J.

    2010-06-01

    In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-peaked-spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the spectral energy distribution (SED) of GPS sources with their expansion, predicting significant and complex high-energy emission, from the X-ray to the {gamma}-ray frequency domain. Here, we test this model with the broadband SEDs of a sample of 11 X-ray-emitting GPS galaxies with compact-symmetric-object morphology, and show that (1) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism and (2) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk-dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N {sub H}) and radio (N {sub HI}) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes.

  20. The complex structure of Abell 2345: a galaxy cluster with non-symmetric radio relics

    NASA Astrophysics Data System (ADS)

    Boschin, W.; Barrena, R.; Girardi, M.

    2010-10-01

    Context. The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated. Aims: We aim to obtain new insights into the internal dynamics of the cluster Abell 2345. This cluster exhibits two non-symmetric radio relics well studied through recent, deep radio data. Methods: Our analysis is based on redshift data for 125 galaxies acquired at the Telescopio Nazionale Galileo and on new photometric data acquired at the Isaac Newton Telescope. We also use ROSAT/HRI archival X-ray data. We combine galaxy velocities and positions to select 98 cluster galaxies and analyze the internal dynamics of the cluster. Results: We estimate a mean redshift < z > = 0.1789 and a line-of-sight (LOS) velocity dispersion σV ~ 1070 km s-1. The two-dimensional galaxy distribution reveals the presence of three significant peaks within a region of ~1 h70-1 Mpc (the E, NW, and SW peaks). The spectroscopic catalog confirms the presence of these three clumps. The SW and NW clumps have similar mean velocities, while the E clump has a larger mean velocity (Δ Vrf ~ 800 km s-1); this structure causes the presence of the two peaks we find in the cluster velocity distribution. The difficulty in separating the galaxy clumps leads to a very uncertain mass estimate M ~ 2 × 1015 h70-1 M⊙. Moreover, the E clump well coincides with the main mass peak as recovered from the weak gravitational lensing analysis and is off-set to the east from the BCG by ~1.3´. The ROSAT X-ray data also show a very complex structure, mainly elongated in the E-W direction, with two (likely three) peaks in the surface brightness distribution, which, however, are off-set from the position of the peaks in the galaxy density. The observed phenomenology agrees with the hypothesis that we are looking at a complex cluster merger occurring along two directions: a major merger along the ~E-W direction (having a component along the LOS) and a minor merger in the western cluster

  1. A Secure Distributed Spectrum Sensing Scheme in Cognitive Radio

    NASA Astrophysics Data System (ADS)

    Nhan, Nguyen-Thanh; Koo, Insoo

    Distributed spectrum sensing provides an improvement for primary user detection but leads a new security threat into CR system. The spectrum sensing data falsification malicious users can decrease the cooperative sensing performance. In this paper, we propose a distributed scheme in which the presence and absence hypotheses distribution of primary signal is estimated based on past sensing received power data by robust statistics, and the data fusion are performed according to estimated parameters by Dempster-Shafer theory of evidence. Our scheme can achive a powerful capability of malicious user elimination due to the abnormality of the distribution of malicious users compared with that of other legitimate users. In addition, the performance of our data fusion scheme is enhanced by supplemented nodes’ reliability weight.

  2. 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).

  3. On the stability and energy dissipation in magnetized radio galaxy jets.

    NASA Astrophysics Data System (ADS)

    Bromberg, Omer; Tchekhovskoy, Alexander

    2016-07-01

    It is commonly accepted that the relativistic jets observed in radio galaxies are launched magnetically and are powered by the rotational energy of the central supermassive black hole. Such jets carry most of their energy in the form of electromagnetic Poynting flux. However by the time the ejecta reach the emission zone most of that energy is transferred to relativistic motions of the jet material with a large fraction given to non-thermal particles, which calls for an efficient dissipation mechanism to work within the jet without compromising its integrity. Understanding the energy dissipation mechanisms and stability of Poynting flux dominated jets is therefore crucial for modeling these astrophysical objects. In this talk I will present the first self consistent 3D simulations of the formation and propagation of highly magnetized (σ ˜25), relativistic jets in a medium. We find that the jets develop two types of instability: i) a local, "internal" kink mode which efficiently dissipates half of the magnetic energy into heat, and ii) a global "external" mode that grows on longer time scales and causes the jets to bend sideways and wobble. Low power jets propagating in media with flat density profiles, such as galaxy cluster cores, are susceptible to the global mode, and develop FRI like morphology. High power jets remain stable as they cross the cores, break out and accelerate to large distances, appearing as FRII jets. Thus magnetic kink instability can account for both the magnetic energy dissipation and the population dichotomy in radio galaxy jets.

  4. The Complex Circumnuclear Environment of the Broad-line Radio Galaxy 3C 390.3 Revealed by Chandra HETG

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Reeves, J. N.; Kallman, T.; Reynolds, C. S.; Mushotzky, R. F.; Braito, V.; Behar, E.; Leutenegger, M. A.; Cappi, M.

    2016-10-01

    We present the first high spectral resolution X-ray observation of the broad-line radio galaxy 3C 390.3 obtained with the high-energy transmission grating spectrometer on board the Chandra X-ray Observatory. The spectrum shows complex emission and absorption features in both the soft X-rays and Fe K band. We detect emission and absorption lines in the energy range E = 700–1000 eV associated with ionized Fe L transitions (Fe XVII–XX). An emission line at the energy of E ≃ 6.4 keV consistent with the Fe Kα is also observed. Our best-fit model requires at least three different components: (i) a hot emission component likely associated with the hot interstellar medium in this elliptical galaxy with temperature kT = 0.5 ± 0.1 keV; (ii) a warm absorber with ionization parameter logξ = 2.3 ± 0.5 erg s‑1 cm, column density logN H = 20.7 ± 0.1 cm‑2, and outflow velocity v out < 150 km s‑1 and (iii) a lowly ionized reflection component in the Fe K band likely associated with the optical broad-line region or the outer accretion disk. These evidences suggest the possibility that we are looking directly down the ionization cone of this active galaxy and that the central X-ray source only photoionizes along the unobscured cone. This is overall consistent with the angle-dependent unified picture of active galactic nuclei.

  5. A FAST RADIO BURST IN THE DIRECTION OF THE CARINA DWARF SPHEROIDAL GALAXY

    SciTech Connect

    Ravi, V.; Shannon, R. M.; Jameson, A.

    2015-01-20

    We report the real-time discovery of a fast radio burst (FRB 131104) with the Parkes radio telescope in a targeted observation of the Carina dwarf spheroidal galaxy. The dispersion measure of the burst is 779 cm{sup –3} pc, exceeding predictions for the maximum line-of-sight Galactic contribution by a factor of 11. The temporal structure of the burst is characterized by an exponential scattering tail with a timescale of 2.0{sub −0.5}{sup +0.8} ms at 1582 MHz that scales as frequency to the power –4.4{sub −1.8}{sup +1.6} (all uncertainties represent 95% confidence intervals). We bound the intrinsic pulse width to be <0.64 ms due to dispersion smearing across a single spectrometer channel. Searches in 78 hr of follow-up observations with the Parkes telescope reveal no additional sporadic emission and no evidence for associated periodic radio emission. We hypothesize that the burst is associated with the Carina dwarf galaxy. Follow-up observations at other wavelengths are necessary to test this hypothesis.

  6. 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

  7. ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES

    SciTech Connect

    Afonso, J.; Bizzocchi, L.; Grossi, M.; Messias, H.; Fernandes, C. A. C.; Ibar, E.; Ivison, R. J.; Simpson, C.; Chapman, S.; Gonzalez-Solares, E.; Jarvis, M. J.; Rottgering, H.; Norris, R. P.; Dunlop, J.; Best, P.; Pforr, J.; Vaccari, M.; Seymour, N.; Farrah, D.; Huang, J.-S.; and others

    2011-12-20

    Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610 MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.

  8. Multicolor surface photometry of a sample of low luminosity radio galaxies

    NASA Astrophysics Data System (ADS)

    Sahu, Sheetal Kumar; Pandey, S. K.; Chakradhari, N. K.; Baburao Pandge, Mahadev

    2015-08-01

    We present a detailed multiband photometric study of five galaxies, selected from a sample of low luminosity early-type galaxies from B2 sample, which have mpg = 15.7, mV = 16.5, redshifts up to 0.2, radio powers P408 = 1023 - 1026.5 W Hz-1 and between 1022 - 1025 W Hz-1 at 1.4 GHz. We have used observed BVR and Hα images from IGO 2m telescope (Pune, India) and 2m HCT, Indian Astronomical Observatory (IAO Hanle, India), and archival multiband data from SDSS (ugriz), 2MASS (JHKs ), WISE, Spitzer (mid-IR), XMM, CHANDRA (X-ray), UV (GALEX) and radio from VLA, IRAM for this study.We used standard technique of surface photometry by fitting ellipses to the isophotes for studying the distribution of light in the galaxies by studying their surface brightness profiles, ellipticity profiles, position angle profiles, variation of center of isophotes along semi-major axis, shapes of isophotes, radial color gradients, twists in isophotes and fine structure variations from smooth light profile. The obtained surface brightness profiles are fitted to the core-Sersic model for decomposing the galaxy light profiles and quantify the radial stellar distributions of the sample galaxies.The multiband color index profiles, e.g. u-g, g-r, r-i, i-z, B-R, B-V, J-Hs , J-Ks , H-Ks , R-Ks , 3.4-4.6 μm, 4.6-12 μm (mid-IR) and FUV-NUV(UV), are obtained and combined with various maps e.g . unsharp-masked images, residual maps, quotient maps, dust extinction maps, Hα emission maps, CO intensity maps, diffuse X-ray emission maps and extinction curves of the galaxies to study the morphology, properties and physical correlations of different phases (e.g cool gas, dust, ionized gas and hot gases) of Inter Stellar Medium and to examine various star formation related processes in the galaxies.

  9. The diffuse neutrino flux from FR-II radio galaxies and blazars: A source property based estimate

    NASA Astrophysics Data System (ADS)

    Becker, Julia K.; Biermann, Peter L.; Rhode, Wolfgang

    2005-05-01

    Water and ice Cherenkov telescopes of the present and future aim for the detection of a neutrino signal from extraterrestrial sources at energies Eν > PeV [Woschnagg and AMANDA Collaboration, Astro-ph/0409423, talk at Neutrino 2004; Montaruli, in: Peter W. Gorham, Particle Astrophysics Instrumentation, Proceedings of the SPIE, vol. 4858, 2003, p. 92; IceCube Collaboration, Astropart. Phys. 20 (2004) 507]. Some of the most promising extragalactic sources are active galactic nuclei (AGN). In this paper, the neutrino flux from two kinds of AGN sources will be estimated assuming pγ interactions in the jets of the AGN. The first analyzed sample contains FR-II radio galaxies while the second AGN type examined are blazars. The result is highly dependent on the proton's index of the energy spectrum. To normalize the spectrum, the connection between neutrino and disk luminosity will be used by applying the jet-disk symbiosis model from Falcke and Biermann [Astron. Astrophys. 293 (1995) 665]. The maximum proton energy and thus, also the maximum neutrino energy of the source is connected to its disk luminosity, which was shown by Lovelace [Nature 262 (1976) 649] and was confirmed by Falcke et al. [Astron. Astrophys. 298 (1995) 375].

  10. MOLECULAR CO(1-0) GAS IN THE z {approx} 2 RADIO GALAXY MRC 0152-209

    SciTech Connect

    Emonts, B. H. C.; Feain, I.; Mao, M. Y.; Norris, R. P.; Ekers, R. D.; Rees, G.; Stevens, J. B.; Miley, G.; Roettgering, H. J. A.; Villar-Martin, M.; Sadler, E. M.; Morganti, R.; Oosterloo, T. A.; Saikia, D. J.; Tadhunter, C. N.

    2011-06-10

    We report the detection of molecular CO(1-0) gas in the high-z radio galaxy MRC 0152-209 (z = 1.92) with the Australia Telescope Compact Array Broadband Backend (ATCA/CABB). This is the third known detection of CO(1-0) in a high-z radio galaxy to date. CO(1-0) is the most robust tracer of the overall molecular gas content (including the widespread, low-density, and sub-thermally excited component), hence observations of CO(1-0) are crucial for studying galaxy evolution in the early universe. We derive L'{sub CO} = 6.6 {+-} 2.0 x 10{sup 10} K km s{sup -1} pc{sup 2} for MRC 0152-209, which is comparable to that derived from CO(1-0) observations of several high-z submillimeter and star-forming BzK galaxies. The CO(1-0) traces a total molecular hydrogen mass of M{sub H{sub 2}} = 5 x 10{sup 10} ({alpha}{sub x}/0.8) M{sub sun}. MRC 0152-209 is an infrared bright radio galaxy, in which a large reservoir of cold molecular gas has not (yet) been depleted by star formation or radio source feedback. Its compact radio source is reliably detected at 40 GHz and has a steep spectral index of {alpha} = -1.3 between 1.4 and 40 GHz (4-115 GHz in the galaxy's rest frame). MRC 0152-209 is part of an ongoing systematic ATCA/CABB survey of CO(1-0) in high-z radio galaxies between 1.7 < z < 3.

  11. Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies

    NASA Astrophysics Data System (ADS)

    Gürkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Smith, D. J. B.; Bourne, N.; Dunne, L.; Maddox, S.; Ivison, R. J.; Fritz, J.

    2015-10-01

    We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-μm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O III] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-μm luminosity and stellar mass measurements from the Sloan Digital Sky Survey-Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass.

  12. THE CONNECTION BETWEEN THE RADIO JET AND THE GAMMA-RAY EMISSION IN THE RADIO GALAXY 3C 120

    SciTech Connect

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

  13. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2016-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

  14. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks

    PubMed Central

    Salim, Shelly; Moh, Sangman

    2016-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead. PMID:27376290

  15. An Energy-Efficient Game-Theory-Based Spectrum Decision Scheme for Cognitive Radio Sensor Networks.

    PubMed

    Salim, Shelly; Moh, Sangman

    2016-06-30

    A cognitive radio sensor network (CRSN) is a wireless sensor network in which sensor nodes are equipped with cognitive radio. In this paper, we propose an energy-efficient game-theory-based spectrum decision (EGSD) scheme for CRSNs to prolong the network lifetime. Note that energy efficiency is the most important design consideration in CRSNs because it determines the network lifetime. The central part of the EGSD scheme consists of two spectrum selection algorithms: random selection and game-theory-based selection. The EGSD scheme also includes a clustering algorithm, spectrum characterization with a Markov chain, and cluster member coordination. Our performance study shows that EGSD outperforms the existing popular framework in terms of network lifetime and coordination overhead.

  16. Suzaku Observations of the Broad-Line Radio Galaxy 3C390.3

    NASA Technical Reports Server (NTRS)

    Sambruna, rita

    2007-01-01

    We present the results of a 100ks Suzaku observation of the BLRG 3C390.3. The observations were performed to attempt to disentangle the contributions to the X-ray emission of this galaxy from an AGN and a jet component, via variability and/or the spectrum. The source was detected at high energies up to 80 keV, with a complex 0.3--80keV spectrum. Preliminary analysis of the data shows significant flux variability, with the largest amplitudes at higher energies. Deconvolution of the spectrum shows that, besides a standard Seyfert-like spectrum dominating the 0.3--8keV emission, an additional, hard power law component is required, dominating the emission above 10 keV. We attribute this component to a variable jet.

  17. Spectrum sensing and resource allocation for multicarrier cognitive radio systems under interference and power constraints

    NASA Astrophysics Data System (ADS)

    Dikmese, Sener; Srinivasan, Sudharsan; Shaat, Musbah; Bader, Faouzi; Renfors, Markku

    2014-12-01

    Multicarrier waveforms have been commonly recognized as strong candidates for cognitive radio. In this paper, we study the dynamics of spectrum sensing and spectrum allocation functions in cognitive radio context using very practical signal models for the primary users (PUs), including the effects of power amplifier nonlinearities. We start by sensing the spectrum with energy detection-based wideband multichannel spectrum sensing algorithm and continue by investigating optimal resource allocation methods. Along the way, we examine the effects of spectral regrowth due to the inevitable power amplifier nonlinearities of the PU transmitters. The signal model includes frequency selective block-fading channel models for both secondary and primary transmissions. Filter bank-based wideband spectrum sensing techniques are applied for detecting spectral holes and filter bank-based multicarrier (FBMC) modulation is selected for transmission as an alternative multicarrier waveform to avoid the disadvantage of limited spectral containment of orthogonal frequency-division multiplexing (OFDM)-based multicarrier systems. The optimization technique used for the resource allocation approach considered in this study utilizes the information obtained through spectrum sensing and knowledge of spectrum leakage effects of the underlying waveforms, including a practical power amplifier model for the PU transmitter. This study utilizes a computationally efficient algorithm to maximize the SU link capacity with power and interference constraints. It is seen that the SU transmission capacity depends critically on the spectral containment of the PU waveform, and these effects are quantified in a case study using an 802.11-g WLAN scenario.

  18. The X-ray view of the nuclei of FRII radio galaxies

    NASA Astrophysics Data System (ADS)

    Gliozzi, M.; Rinn, A.; Sambruna, R.

    2005-12-01

    Fanaroff Riley II radio galaxies (FRIIs) can be divided into three subclasses based on their optical spectral properties: 1) objects with broad emission lines (BLO); 2) objects with high ionization narrow lines, which are considered obscured versions of BLO; 3) objects with low ionization narrow lines, whose optical properties are very similar to FRIs. We use the available data from the Chandra and XMM-Newton archives to investigate the nuclear properties of FRIIs. We show that the X-ray spectroscopy is able to discriminate between the three subclasses, and provides important clues on the physical conditions at the core of FRIIs.

  19. Simulations on Head-Tail Radio Galaxies Using Magnetic Tower Model

    SciTech Connect

    Gan, Zhaoming; Li, Hui; Li, Shengtai; Yuan, Feng

    2015-08-19

    The presentation is a series of slides showing diagrams, equations, and various photographs. In summary, a detailed comparison was carried out between hydrodynamic jet and MHD jet models (the magnetic tower jet, more precisely), in an effort to understand the underlying physics of observed radio galaxies, and also its possible indications for jet feedback. It was found that the results of magnetic tower model usually lie in a reasonable regime, and in several aspects, the magnetic tower jet seems more preferred than pure hydrodynamic jet models.

  20. Constraints on jets and accretion disks in low luminosity radio galaxies

    NASA Astrophysics Data System (ADS)

    Tilak, Avanti

    Multiwavelength data has greatly advanced our understanding of AGN and their environments. I study a sample of 21 nearby low luminosity radio galaxies, selected on the basis of distance, radio luminosity, size and Hubble type from the Uppsala Galactic Catalog. I present 1 new and 12 archival Chandra datasets. X-ray imaging of all sources shows nuclear X-ray emission from the AGN. 11 out of these 13 sources also show diffuse emission associated with the host galaxy. I discovered three new X-ray jets. In conjunction with the six known X-ray jets, nine out of the thirteen galaxies exhibit X-ray jet emission. Thus X-ray jets are fairly ubiquitous in low luminosity radio galaxies. The nuclear X-ray spectra are best described by a combination of hot gas and powerlaw models. The nuclear flux and luminosity densities seem well-correlated with their optical and radio counterparts. The correlation is stronger if the contribution from the powerlaw component to the X-ray emission is isolated. Thus the powerlaw component may be the true description of emission from the central region (either from the accretion disk or parsec-scale jet). I investigate the nature of core emission by fitting synchrotron models as well as by comparing disk models with broad-band spectral energy distributions of the AGN. In general, the core emission seems consistent with a synchrotron-jet model. I present VLBA imaging and polarization data for 10 sources in our sample. All 10 sources show corejet morphology, consistent with relativistic jet velocities on parsec scales. The jets are expected to decelerate on scales similar to the extent of the X-ray jets. Assuming synchrotron emission, it is possible that some fraction of the bulk kinetic energy of the jets is being channeled for reacceleration of electrons within the jet, necessary to produce the observed X-ray emission. In the VLBA data, 5 out of 10 sources show polarization. The polarization observations are broadly consistent with unification

  1. 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.

  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. 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.; O'Briain, D.; O'Brien, T.; Oguri, M.; Paget, E.; Parrish, M.; Ross, N. P.; Rozo, E.; Rusu, Cristian 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.

  4. The cluster-galaxy cross spectrum. An additional probe of cosmological and halo parameters

    NASA Astrophysics Data System (ADS)

    Hütsi, G.; Lahav, O.

    2008-12-01

    Context: There are several wide field galaxy and cluster surveys planned for the near future, e.g. BOSS, WFMOS, ADEPT, Hetdex, SPT, eROSITA. In the simplest approach, one would analyze these independently, thus neglecting the extra information provided by the cluster-galaxy cross pairs. Aims: In this paper we have focused on the possible synergy between these surveys by investigating the amount of information encoded in the cross pairs. Methods: We present a model for the cluster-galaxy cross spectrum within the halo model framework. To assess the gain in performance due to inclusion of the cluster-galaxy cross pairs, we carry out a Fisher matrix analysis for a BOSS-like galaxy redshift survey targeting luminous red galaxies and a hypothetical mass-limited cluster redshift survey with a lower mass threshold of 1.7 × 1014 h-1 M⊙ over the same volume. Results: On small scales, a cluster-galaxy cross spectrum directly probes the density profile of the halos, instead of the density profile convolved with itself, as is the case for the galaxy power spectrum. Due to this different behavior, adding information from the cross pairs helps to tighten constraints on the halo occupation distribution (e.g. a factor of ~2 compression of the error ellipses on the m_glow-α plane) and offers an alternative mechanism compared with techniques that directly fit halo density profiles. By inclusion of the cross pairs, a factor of ~2 stronger constraints are obtained for σ_8, while the improvement for the dark energy figure-of-merit is somewhat weaker: an increase by a factor of 1.4. We have also written down the formalism for the case when only photometric redshifts are available for both the clusters and the galaxies. For the analysis of the photometric surveys the inclusion of the cluster-galaxy cross pairs might be very beneficial since the photo-z errors for the clusters are usually significantly smaller than for the typical galaxies.

  5. HOST GALAXIES, CLUSTERING, EDDINGTON RATIOS, AND EVOLUTION OF RADIO, X-RAY, AND INFRARED-SELECTED AGNs

    SciTech Connect

    Hickox, Ryan C.; Jones, Christine; Forman, William R.; Murray, Stephen S.; Brodwin, Mark; Narayan, Ramesh; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E.; Kochanek, Christopher S.; Eisenstein, Daniel; Jannuzi, Buell T.; Dey, Arjun; Brown, Michael J. I.; Stern, Daniel; Eisenhardt, Peter R.; Gorjian, Varoujan; Cool, Richard J.

    2009-05-01

    We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, X-ray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 < z < 0.8 using redshifts from the AGN and Galaxy Evolution Survey (AGES). We select AGNs with observations in the radio at 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays from the Chandra XBooetes Survey, and mid-IR from the Spitzer IRAC Shallow Survey. The radio, X-ray, and IR AGN samples show only modest overlap, indicating that to the flux limits of the survey, they represent largely distinct classes of AGNs. We derive host galaxy colors and luminosities, as well as Eddington ratios, for obscured or optically faint AGNs. We also measure the two-point cross-correlation between AGNs and galaxies on scales of 0.3-10 h {sup -1} Mpc, and derive typical dark matter halo masses. We find that: (1) radio AGNs are mainly found in luminous red sequence galaxies, are strongly clustered (with M {sub halo} {approx} 3 x 10{sup 13} h {sup -1} M {sub sun}), and have very low Eddington ratios {lambda} {approx}< 10{sup -3}; (2) X-ray-selected AGNs are preferentially found in galaxies that lie in the 'green valley' of color-magnitude space and are clustered similar to the typical AGES galaxies (M {sub halo} {approx} 10{sup 13} h {sup -1} M {sub sun}), with 10{sup -3} {approx}< {lambda} {approx}< 1; (3) IR AGNs reside in slightly bluer, slightly less luminous galaxies than X-ray AGNs, are weakly clustered (M {sub halo} {approx}< 10{sup 12} h {sup -1} M {sub sun}), and have {lambda}>10{sup -2}. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a 'quasar' phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between {approx}10{sup 12} and 10{sup 13} M {sub sun}. After this event

  6. A Deep New View of Thermal and Magnetic Structure in the Radio Galaxy Fornax A

    NASA Astrophysics Data System (ADS)

    Anderson, Craig; Gaensler, Bryan; Feain, Ilana

    2012-10-01

    Feedback processes in radio lobes are a critical ingredient in out understanding of galactic formation and evolution, and cosmology more broadly. The detailed way in which these processes operate is critically dependent on the magnetic structure and thermal particle content of the lobes, but our understanding in this regard is still poor. Using the powerful new combination of the broad observing bandwidth provided by CABB and modern spectropolarimetric techniques, we intend to substantially improve our knowledge of thermal and magnetic structure in radio lobes by performing and analysing mosaiced observations of the radio galaxy Fornax A from 1.1-3.1GHz. We will measure the thermal material content of the lobes to a limit three orders of magnitude lower than previous observations, discern between existing models for the magnetic structure of radio lobes and, as a secondary objective, of foreground objects backlit by the lobe emission. This will be among the very first comprehensive, broadband spectropolarimetric studies of this class of object. Our total time request for this project is 108 hours split over three array configurations.

  7. Connection Between X-Ray Dips and Superluminal Ejections in the Radio Galaxy 3C 120

    NASA Technical Reports Server (NTRS)

    Aller, Margo F.

    2005-01-01

    This work represents a part of a long-term study of the X-ray flux variability of 3C 120 and its relation to flux and structural changes in the radio jet of this galaxy. The grant included fiinding for the rediiction and analysis of data obt,ained during the time pwiod of Rossi XTE cycle 8 (March 1, 2003-February 29, 2004). Prior RXTE observations, combined with single dish monitoring at centimeter wavelengths and 43 GHz mapping (monthly until February 1999 and bimonthly thereafter) of the inner jet with the VLBA, had identified the presence of X-ray dips in the light curves and X-ray spectral hardening 4 weeks prior to the ejection of new VLBI components in the radio jet. This suggested a picture in which the radio jet was fed by accretion events near the black hole. The specific goals of the cycle 8 observations were to better define the relation between the X-ray dips and the radio events using higher sampling, to include more events in the correlation and hence improve the statistics, to look for a possible optical X-ray connection, and to search for quasi periodicities on timescales of 1-3 days. In cycle 8 this project was awarded time for 4 pointings weekly with RXTE.

  8. 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.

  9. Radio Emission from Weak Spherical Shocks in the Outskirts of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Kang, Hyesung

    2015-04-01

    In Kang (2015) we calculated the acceleration of cosmic-ray electrons at weak spherical shocks that are expected to form in the cluster outskirts, and estimated the diffuse synchrotron radiation emitted by those electrons. There we demonstrated that, at decelerating spherical shocks, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws predicted for constant planar shocks, because the shock compression ratio and the flux of inject electrons decrease in time. In this study, we consider spherical blast waves propagating through a constant density core surrounded by an isothermal halo with ρ∝ r^{-n} in order to explore how the deceleration of the shock affects the radio emission from accelerated electrons. The surface brightness profile and the volume-integrated radio spectrum of the model shocks are calculated by assuming a ribbon-like shock surface on a spherical shell and the associated downstream region of relativistic electrons. If the postshock magnetic field strength is about 0.7 or 7μG, at the shock age of ˜ 50 Myr, the volume-integrated radio spectrum steepens gradually with the spectral index from α_{inj} to α_{inj}+0.5 over 0.1-10 GHz, where α_{inj} is the injection index at the shock position expected from the diffusive shock acceleration theory. Such gradual steepening could explain the curved radio spectrum of the radio relic in cluster A2266, which was interpreted as a broken power-law by Trasatti et al. (2015), if the relic shock is young enough so that the break frequency is around 1$ GHz.

  10. Radio jet emission from GeV-emitting narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Angelakis, E.; Fuhrmann, L.; Marchili, N.; Foschini, L.; Myserlis, I.; Karamanavis, V.; Komossa, S.; Blinov, D.; Krichbaum, T. P.; Sievers, A.; Ungerechts, H.; Zensus, J. A.

    2015-03-01

    Context. With the current study we aim at understanding the properties of radio emission and the assumed jet from four radio-loud and γ-ray-loud narrow-line Seyfert 1 galaxies that have been detected by Fermi. These are Seyfert 1 galaxies with emission lines at the low end of the FWHM distribution. Aims: The ultimate goal is twofold: first we investigate whether a relativistic jet is operating at the source producing the radio output, and second, we quantify the jet characteristics to understand possible similarities with and differences from the jets found in typical blazars. Methods: We relied on the most systematic monitoring of radio-loud and γ-ray-detected narrow-line Seyfert 1 galaxies in the cm and mm radio bands conducted with the Effelsberg 100 m and IRAM 30 m telescopes. It covers the longest time-baselines and the most radio frequencies to date. This dataset of multi-wavelength, long-term radio light-curves was analysed from several perspectives. We developed a novel algorithm to extract sensible variability parameters (mainly amplitudes and time scales) that were then used to compute variability brightness temperatures and the corresponding Doppler factors. The jet powers were computed from the light curves to estimate the energy output and compare it with that of typical blazars. The dynamics of radio spectral energy distributions were examined to understand the mechanism causing the variability. Results: The length of the available light curves for three of the four sources in the sample allowed a firm understanding of the general behaviour of the sources. They all display intensive variability that appears to be occurring at a pace rather faster than what is commonly seen in blazars. The flaring events become progressively more prominent as the frequency increases and show intensive spectral evolution that is indicative of shock evolution. The variability brightness temperatures and the associated Doppler factors are moderate, implying a mildly

  11. Are quiescent galaxies truly devoid of star formation? The mid-, far-infrared and radio properties of quiescent galaxies at z = 0.1 - 3

    NASA Astrophysics Data System (ADS)

    Man, Allison W. S.

    Quiescent galaxy candidates are typically identified by their low unobscured star formation rates from deep field photometric surveys. However, their selection technique relies on the assumption of a universal dust attenuation curve. It is important to verify the selection through independent SFR indicators at longer wavelengths. Current mid-, far-infrared and radio surveys are limited to detecting only galaxies with very strong star formation or AGN activity. Here, I present the first comprehensive stacking results across mid-, far-infrared and radio wavelengths using Spitzer, Herschel and VLA data in the COSMOS field (Man et al. 2014). We find that the rest-frame NUV-r and r-J color criteria, combined with low 24 μm emission, provides a robust selection of truly quiescent galaxies out to z = 3. Additionally, we find evidence of radio emission in excess of the expected total star formation in quiescent galaxies at z ~ 0-1.5, indicative of a ubiquitous presence of low-luminosity radio AGN among them.

  12. Spectrum Handoffs Based on Preemptive Repeat Priority Queue in Cognitive Radio Networks.

    PubMed

    Yang, Xiaolong; Tan, Xuezhi; Ye, Liang; Ma, Lin

    2016-01-01

    Cognitive radio can significantly improve the spectrum efficiency, and spectrum handoff is considered as an important functionality to guarantee the quality of service (QoS) of primary users (PUs) and the continuity of data transmission of secondary users (SUs). In this paper, we propose an analytical framework based on a preemptive repeat identical (PRI) M/G/1 queuing network model to characterize spectrum handoff behaviors with general service time distribution of both primary and secondary connections, multiple interruptions and transmission delay resulting from the appearance of primary connections. Then, we derive the close-expression of the extended data delivery and the system sojourn time in both staying and changing scenarios. In addition, based on analysis of spectrum handoff behaviors resulting from multiple interruptions caused by the appearance of the primary connections, we investigate the traffic-adaptive policy, by which the considered SU will optimally adjust its handoff spectrum policy. Moreover, we investigate the admissible region and provide the reference for designing the admission control rule for the arriving secondary connection requests. Finally, simulation results verify that our proposed analytical framework is reasonable and can provide the reference for executing the optimal spectrum handoff strategy and designing the admission control rule for the SU in cognitive radio networks. PMID:27447644

  13. Spectrum Handoffs Based on Preemptive Repeat Priority Queue in Cognitive Radio Networks

    PubMed Central

    Yang, Xiaolong; Tan, Xuezhi; Ye, Liang; Ma, Lin

    2016-01-01

    Cognitive radio can significantly improve the spectrum efficiency, and spectrum handoff is considered as an important functionality to guarantee the quality of service (QoS) of primary users (PUs) and the continuity of data transmission of secondary users (SUs). In this paper, we propose an analytical framework based on a preemptive repeat identical (PRI) M/G/1 queuing network model to characterize spectrum handoff behaviors with general service time distribution of both primary and secondary connections, multiple interruptions and transmission delay resulting from the appearance of primary connections. Then, we derive the close-expression of the extended data delivery and the system sojourn time in both staying and changing scenarios. In addition, based on analysis of spectrum handoff behaviors resulting from multiple interruptions caused by the appearance of the primary connections, we investigate the traffic-adaptive policy, by which the considered SU will optimally adjust its handoff spectrum policy. Moreover, we investigate the admissible region and provide the reference for designing the admission control rule for the arriving secondary connection requests. Finally, simulation results verify that our proposed analytical framework is reasonable and can provide the reference for executing the o