Radio Galaxies

We critically assess the current state of knowledge of the strengths of the magnetic fields B.Yf threading the horizons of accretion disc-fed black holes in quasars and radio galaxies. We show that those values of B.Yf which correspond to the strengths of the magnetic fields expected to be maintained in accretion discs by the action of hydromagnetic dynamos, according to recent numerical simulations, are significantly lower than those which have been suggested previously, and consequently the strength of the Blandford-Znajek (BZ) process for the extraction of the rotational energy of the black hole is lower than imagined previously. This result appears to be rather robust in the sense that it depends neither on the details of the simulation nor on the actual value of the magnetic field generated by the disc dynamo, but only on the strength of the magnetic transport of angular momentum in the disc, the value of which always emerges as roughly constant from the above simulations. Thus, the BZ process does not appear to be adequate for accounting for the strongest double radio sources accreting at far sub-Eddington rates. However, the BZ luminosity (a) still dominates the luminosity due to accretion and (b) easily accounts for the multitude of low and medium strength radio sources, so that the strongest radio sources can be attributed to BZ luminosities corresponding to exceptionally strong B.Yf' while avoiding the conundrum of too many strong sources which a universally strong BZ process would imply.

The Horizon Expansion Fractal (HEF) model introduces a novel, recursive fractal framework for understanding cosmic expansion, quantum gravity, and black hole physics. At its core, the HEF model proposes that space-time evolves through dynamic, self-similar transformations governed by a fractal scaling function S(H, t) = e-αHt , where H is the Hubble parameter and t is cosmic time. This recursive fractal expansion modifies fundamental physical laws, including the Einstein-Hilbert action and Friedmann equations, by introducing fractal-dependent terms that account for the universe's evolving structure.

We present the discovery of a candidate of giant radio-quiet Lyα blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Lyα halo B3 J2330+3927 at redshift z = 3.087. We obtained narrow-and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Lyα emitters (LAEs) and absorbers (LAAs) at redshift z = 3.09 ± 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 × 24 arcmin 2 (58 × 44 comoving Mpc). We found that B3 J2330+3927 is surrounded by a 130 kpc Lyα halo and a large-scale (∼60 × 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8 arcmin (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Lyα nebulae in the same large-scale structure suggests that giant Lyα nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Lyα nebulae. First, RQLAB may need a prominent (δ ∼ 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Lyα halo around HzRG may not always need a prominent density peak to form if the surrounding Lyα halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Lyα halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey.

We characterize the stellar population of a complete sample of the closest southern radio-galaxies -12 Fanaroff-Riley I (FR I), 8 FR II and 4 with undefined FRx type -and a comparison sample of 18 non-active elliptical and SO galaxies. We measured equivalent widths and continuum colours and their radial variations, and performed spectral synthesis as a function of distance from the nucleus. Only 4 of the radio-galaxies have more than 10% of the total flux at 4020 Å contributed from 100 Myr old or younger stellar population components -including a featureless continuum due to an AGN. All 4 are FRII or FRx. The main difference between the stellar population of the radio-galaxies and that of the non-active ones is that the former have a larger contribution of the intermediate age component, suggesting a relation between the present radio activity and a past episode of star formation which occurred about 1 Gyr ago.

X-ray, optical, and radio observations of a high redshift, Bautz-Morgan type I cluster of galaxies are reported. The cD galaxy contains a powerful, flat spectrum radio source coincident with the possibly stellar nucleus. The cluster is an extremely luminous X-ray source; however, unlike nearby luminous X-ray clusters the X-ray spectrum appears to be rather soft. Two possible interpretations of the soruces are suggested: either the intracluster gas is much cooler in high redshift clusters because they are less relaxed, or the X-ray and radio emissions from WQ 2059-247 are the result of a non thermal QSO/BL Lac type object in the nucleus of the cD.

A key argument in favor of orientation based unification schemes is the finding that among the most powerful 3CRR radio sources the (apparent) median linear size of quasars is smaller than that of radio galaxies, which supports the idea that quasars are a subset of radio galaxies, distinguished by being viewed at smaller angles to the line of sight. Recent measurements of radio sizes for a few other low frequency samples are, however, not in accord with this trend, leading to the claim that orientation may not be the main difference between radio galaxies and quasars. We point out that this "inconsistency" can be removed by making allowance for the temporal evolution of sources in both size and luminosity, as inferred from independent observations. This approach can also readily explain the other claimed "major discrepancy" with the unified scheme, namely, the difference between the radio luminosity-size correlations for quasars and radio galaxies.

A brief description of the methodology of construction, contents and usage of the Planck Early Release Compact Source Catalogue (ERCSC), including the Early Cold Cores (ECC) and the Early Sunyaev-Zeldovich (ESZ) cluster catalogue is provided. The catalogue is based on data that consist of mapping the entire sky once and 60% of the sky a second time by Planck, thereby comprising the first high sensitivity radio/submillimetre observations of the entire sky. Four source detection algorithms were run as part of the ERCSC pipeline. A Monte-Carlo algorithm based on the injection and extraction of artificial sources into the Planck maps was implemented to select reliable sources among all extracted candidates such that the cumulative reliability of the catalogue is ≥90%. There is no requirement on completeness for the ERCSC. As a result of the Monte-Carlo assessment of reliability of sources from the different techniques, an implementation of the PowellSnakes source extraction technique was used at the five frequencies between 30 and 143 GHz while the SExtractor technique was used between 217 and 857 GHz. The 10σ photometric flux density limit of the catalogue at |b| > 30 • is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30 and 857 GHz. Sources which are up to a factor of ∼2 fainter than this limit, and which are present in "clean" regions of the Galaxy where the sky background due to emission from the interstellar medium is low, are included in the ERCSC if they meet the high reliability criterion. The Planck ERCSC sources have known associations to stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic interstellar medium features. A significant fraction of unclassified sources are also present in the catalogs. In addition, two early release catalogs that contain 915 cold molecular cloud core candidates and 189 SZ cluster candidates that have been generated using multifrequency algorithms are presented. The entire source list, with more than 15 000 unique sources, is ripe for follow-up characterisation with Herschel, ATCA, VLA, SOFIA, ALMA and other ground-based observing facilities.

BL Lacertae fue observado con el telescopio MAGIC de agosto a diciembre de 2005 (22.2 horas) y de julio a septiembre de 2006 (26.0 horas). En 2005 se detectó, con un nivel de significación 5.1 σ, una fuerte emisión de rayos γ de muy alta energía (VHE). BL Lacertae es el primer objeto BL Lac con un pico de emisión a bajas frecuencias, en el cual se detecta este tipo de emisión. En los datos de 2006, no hay detección en la región de los rayos γ, lo que se atribuye a un menor nivel de flujo en este periodo. En este trabajo mostramos que también se observa una caida en el flujo óptico y milimétrico, lo cual sugiere una conexión entre estas tres bandas de emisión.

M 87 is the only known non blazar radio galaxy to emit very high energy (VHE) gamma-rays. During a monitoring program of M 87, a rapid flare in VHE gamma-rays was detected by the MAGIC telescope in early 2008. The flux was found to be variable above 350 GeV on a timescale as short as 1 day at a significance level of 5.6σ. The highest measured flux reached 15% of the Crab Nebula flux. We observed several substantial changes of the flux level during the 13 day observing period. The flux at lower energies (150 -350 GeV), instead, is compatible with being constant. The energy spectrum can be described by a power law with a photon index of 2.30 ± 0.11 stat ± 0.20 syst . The observed day-scale flux variability at VHE prefers the M 87 core as source of the emission and implies that either the emission region is very compact (just a few Schwarzschild radii) or the Doppler factor of the emitting blob is rather large in the case of a non expanding emission region.

The MAGIC telescope observed the region around the distant blazar 3C 66A for 54.2 hr in 2007 August-December. The observations resulted in the discovery of a γ-ray source centered at celestial coordinates R.A. = 2 h 23 m 12 s and decl.= 43 • 0. ′ 7 (MAGIC J0223+430), coinciding with the nearby radio galaxy 3C 66B. A possible association of the excess with the blazar 3C 66A is discussed. The energy spectrum of MAGIC J0223+430 follows a power law with a normalization of (1.7 ± 0.3 stat ± 0.6 syst ) × 10 -11 TeV -1 cm -2 s -1 at 300 GeV and a photon index Γ = -3.10 ± 0.31 stat ± 0.2 syst .

We use the Herschel-Astrophysical Terahertz Large Area Survey (ATLAS) science demonstration data to investigate the star formation properties of radio-selected galaxies in the GAMA-9h field as a function of radio luminosity and redshift. Radio selection at the lowest radio luminosities, as expected, selects mostly starburst galaxies. At higher radio luminosities, where the population is dominated by active galactic nuclei (AGN), we find that some individual objects are associated with high far-infrared luminosities. However, the far-infrared properties of the radio-loud population are statistically indistinguishable from those of a comparison Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

In order to investigate the far-infrared excess detected from the west hot spot of the radio galaxy Pictor A with the Herschel observatory, a submillimeter photometry is performed with the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array at Band 8 with the reference frequency of 405 GHz. A submillimeter source is discovered at the radio peak of the hot spot. Because the 405 GHz flux density of the source, 80.7 ± 3.1 mJy, agrees with the extrapolation of the synchrotron radio spectrum, the far-infrared excess is suggested to exhibit no major contribution at the ACA band. In contrast, by subtracting the power-law spectrum tightly constrained by the radio and ACA data, the significance of the excess in the Herschel band is well confirmed. No diffuse submillimeter emission is detected within the ACA field of view, and thus, the excess is ascribed to the west hot spot itself. In comparison to the previous estimate based on the Herschel data, the relative contribution of the far-infrared excess is reduced by a factor of ∼ 1.5. The spectrum of the excess below the far-infrared band is determined to be harder than that of the diffusive shock acceleration. This strengthens the previous interpretation that the excess originates via the magnetic turbulence in the substructures within the hot spot. The ACA data are utilized to evaluate the magnetic field strength of the excess and of diffuse radio structure associated to the hot spot.

The far infrared counterpart of hot spot D, the terminal hot spot of the eastern jet hosted by the radio galaxy Cygnus A, is detected with Herschel Aperture photometery of the source performed in 5 photometric bands covering the wavelength range of 70-350 m. After removing the contamination from another nearby hot spot, E, the far-infrared intensity of hot spot D is derived as 83 ± 13 and 269 ± 66 mJy at 160 and 350 m, respectively. Since the far-infrared spectrum of the object smoothly connects to the radio one, the far-infrared emission is attributed to the synchrotron radiation from the radio-emitting electron population. The radio-to-near-infrared spectrum is confirmed to exhibit a far-infrared break feature at the frequency of br = 2.0 +1.2 -0.8 × 10 12 Hz. The change in energy index at the break (Δ = 0.5) is interpreted as the impact of radiative cooling on an electron distribution sustained by continuous injection from diffusive shock acceleration. By ascribing the derived break to this cooling break, the magnetic field, , in the hot spot is determined as a function of its radius, within a uniform one-zone model combined with the strong relativistic shock condition. An independent -constraint is obtained by assuming the X-ray spectrum is wholly due to synchrotron-self-Compton emission. By combining these conditions, the two parameters are tightly determined as = 120-150 G and = 1.3-1.6 kpc. A further investigation into the two conditions indicates the observed X-ray flux is highly dominated by the synchrotron-self-Compton emission.

In order to investigate the far-infrared excess detected from the western hot spot of the radio galaxy Pictor A with the Herschel observatory, submillimeter photometry is performed with the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array at Band 8 with the reference frequency of 405 GHz. A submillimeter source is discovered at the radio peak of the hot spot. Because the 405 GHz flux density of the source, 80.7 ± 3.1 mJy, agrees with the extrapolation of the synchrotron radio spectrum, the far-infrared excess is suggested to exhibit no major contribution at the ACA band. In contrast, by subtracting the power-law spectrum tightly constrained by the radio and ACA data, the significance of the excess in the Herschel band is well confirmed. No diffuse submillimeter emission is detected within the ACA field of view, and thus, the excess is ascribed to the western hot spot itself. In comparison to the previous estimate based on the Herschel data, the relativ...

We have detected CO(4-3) in the z = 3.8 radio galaxy 4C 41.17 with the IRAM Interferometer. The CO is in two massive (M dyn ∼ 6 × 10 10 M ) systems separated by 1. 8 (13 kpc), and by 400 km s -1 in velocity, which coincide with two different dark lanes in a deep Lyα image. One CO component coincides with the cm-radio core of the radio galaxy, and its redshift is close to that of the He  λ 1640 AGN line. The second CO component is near the base of a cone-shaped region southwest of the nucleus, which resembles the emission-line cones seen in nearby AGN and starburst galaxies. The characteristics of the CO sources and their mm/submm dust continuum are similar to those found in ultraluminous IR galaxies and in some high-z radio galaxies and quasars. The fact that 4C 41.17 contains two CO systems is further evidence for the role of mergers in the evolution of galaxies at high redshift.

Context. We present the results of a long M 87 monitoring campaign in very high energy γ-rays with the MAGIC-I Cherenkov telescope. Aims. We aim to model the persistent non-thermal jet emission by monitoring and characterizing the very high energy γ-ray emission of M 87 during a low state. Methods. A total of 150 h of data were taken between 2005 and 2007 with the single MAGIC-I telescope, out of which 128.6 h survived the data quality selection. We also collected data in the X-ray and Fermi-LAT bands from the literature (partially contemporaneous). Results. No flaring activity was found during the campaign. The source was found to be in a persistent low-emission state, which was at a confidence level of 7σ. We present the spectrum between 100 GeV and 2 TeV, which is consistent with a simple power law with a photon index Γ = 2.21 ± 0.21 and a flux normalization at 300 GeV of (7.7 ± 1.3) × 10 -8 TeV -1 s -1 m -2 . The extrapolation of the MAGIC spectrum into the GeV energy range matches the previously published Fermi-LAT spectrum well, covering a combined energy range of four orders of magnitude with the same spectral index. We model the broad band energy spectrum with a spine layer model, which can satisfactorily describe our data.

We report new observations of the intermediate-frequency peaked BL Lacertae object 3C 66A with the MAGIC telescopes. The data sample we use were taken in 2009 December and 2010 January, and comprises 2.3 hr of good quality data in stereoscopic mode. In this period, we find a significant signal from the direction of the blazar 3C 66A. The new MAGIC stereoscopic system is shown to play an essential role for the separation between 3C 66A and the nearby radio galaxy 3C 66B, which is at a distance of only 6 ′ . The derived integral flux above 100 GeV is 8.3 % of Crab Nebula flux and the energy spectrum is reproduced by a power law of photon index 3.64 ± 0.39 stat ± 0.25 sys . Within errors, this is compatible with the one derived by VERITAS in 2009. From the spectra corrected for absorption by the extragalactic background light, we only find small differences between the four models that we applied, and constrain the redshift of the blazar to z < 0.68.

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

We report the discovery of two doubly-imaged quasars, SDSS J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and 1.789 and with image separations of 2. ′′ 86 and 2. ′′ 90, respectively. The objects were selected as lens candidates from the Sloan Digital Sky Survey (SDSS). Based on the identical nature of the spectra of the two quasars in each pair and the identification of the lens galaxies, we conclude

Using a homogenous sample of 38, 208 quasars with a sky coverage of ∼ 4000 deg 2 drawn from the SDSS Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole mass, quasar color, and radio loudness. At z < 2.5, quasar clustering depends weakly on luminosity and virial black hole mass, with typical uncertainty levels ∼ 10% for the measured correlation lengths. These weak dependences are consistent with models in which substantial scatter between quasar luminosity, virial black hole mass and the host dark matter halo mass has diluted any clustering difference, where halo mass is assumed to be the relevant quantity that best correlates with clustering strength. However, the most luminous and most massive quasars are more strongly clustered (at the ∼ 2σ level) than the remainder of the sample, which we attribute to the rapid increase of the bias factor at the high-mass end of host halos. We do not observe a strong dependence of clustering strength on quasar colors within our sample. On the other hand, radio-loud quasars are more strongly clustered than are radio-quiet quasars matched in redshift and optical luminosity (or virial black hole mass), consistent with local observations of radio galaxies and radio-loud type 2 AGN. Thus radio-loud quasars reside in more massive and denser environments in the biased halo clustering picture. Using the Sheth et al. ( ) formula for the linear halo bias, the estimated host halo mass for radio-loud quasars is ∼ 10 13 h -1 M ⊙ , compared to ∼ 2 × 10 12 h -1 M ⊙ for radio-quiet quasar hosts at z ∼ 1.5. Subject headings: black hole physics -galaxies: active -cosmology: observations -large-scale structure of universe -quasars: general -surveys 1. INTRODUCTION Quasars are luminous, accreting supermassive black holes (SMBHs) that are thought to reside at the center of almost every massive galaxy (e.g.

We present the results of two complementary ground-based programmes to determine the host galaxy properties of radio-quiet and radio-loud quasars and to compare them with those of radio galaxies. Both infrared images and optical off-nuclear spectra were obtained and we discuss the various strategies used to separate the quasarrelated emission from that of the underlying galaxy. However, the key feature of this project is the use of carefully matched samples, which ensure that the data for different types of object are directly comparable.

We present optical (,3200 to ,9000 A Ê ) off-nuclear spectra of 26 powerful active galaxies in the redshift range 0X1 # z # 0X3Y obtained with the Mayall and William Herschel 4-m class telescopes. The sample consists of radio-quiet quasars, radio-loud quasars (all with 223 $ M V $ 226 and radio galaxies of Fanaroff±Riley Type II (with extended radio luminosities and spectral indices comparable to those of the radio-loud quasars). The spectra were all taken approximately 5 arcsec off-nucleus, with offsets carefully selected so as to maximize the amount of galaxy light falling into the slit, whilst simultaneously minimizing the amount of scattered nuclear light. The majority of the resulting spectra appear to be dominated by the integrated stellar continuum of the underlying galaxies rather than by light from the non-stellar processes occurring in the active nuclei, and in many cases a 4000-A Ê break feature can be identified. The individual spectra are described in detail, and the importance of the various spectral components is discussed. Stellar population synthesis modelling of the spectra will follow in a subsequent paper.

We present the results of fitting deep off-nuclear optical spectra of radio-quiet quasars, radio-loud quasars and radio galaxies at z . 0:2 with evolutionary synthesis models of galaxy evolution. Our aim was to determine the age of the dynamically dominant stellar populations in the host galaxies of these three classes of powerful active galactic nuclei (AGN). Some of our spectra display residual nuclear contamination at the shortest wavelengths, but the detailed quality of the fits longward of the 4000-A Ê break provides unequivocal proof, if further proof were needed, that quasars lie in massive galaxies with (at least at z . 0:2 evolved stellar populations. By fitting a two-component model we have separated the very blue (starburst and/or AGN contamination) from the redder underlying spectral energy distribution, and find that the hosts of all three classes of AGN are dominated by old stars of age 8±14 Gyr: If the blue component is attributed to young stars, we find that, at most, 1 per cent of the visible baryonic mass of these galaxies is involved in star formation activity at the epoch of observation, at least over the region sampled by our spectroscopic observations. These results strongly support the conclusion reached by McLure et al. that the host galaxies of luminous quasars are massive ellipticals which have formed by the epoch of peak quasar activity at z .

We present a multi-wavelength analysis of the properties of Extremely Red Galaxy (ERG) populations, selected in the GOODS-South/Chandra Deep Field South field. By using all the photometric and spectroscopic information available on large deep samples of Extremely Red Objects (EROs, 645 sources), IRAC EROs (IEROs, 294 sources), and Distant Red Galaxies (DRGs, 350 sources), we derive redshift distributions, identify AGN powered and Star-formation powered galaxies, and, using the radio observations of this field, estimate robust (AGN-and dust-unbiased) Star Formation Rate Densities ( ρ * ) for these populations. We also investigate the properties of "pure" (galaxies that conform to only one of the three ERG criteria considered) and "combined" (galaxies that verify all three criteria) sub-populations. Overall, a large number of AGN are identified (up to ∼ 30%, based on X-rays, and mid-infrared criteria), the majority of which are type-2 (obscured) objects. Among ERGs with no evidence for AGN activity, we identify sub-populations covering a wide range of average star-formation rates, from below 10 M ⊙ yr -1 to as high as 200 M ⊙ yr -1 . Applying a redshift separation (1 ≤ z < 2 and 2 ≤ z ≤ 3) we find significant evolution (an increase of a factor of 2 or higher) of ρ * for EROs and DRGs, while none is observed for IEROs. The former populations can contribute more than 20% to the global ρ * at 2 ≤ z ≤ 3. The emission from AGN activity is typically not strong in the ERG population, with AGN increasing the average radio luminosity of ERG sub-populations by, nominally, less than 20%. AGN are common, however, and, if no discrimination is attempted, this could significantly increase the ρ * estimate (by over 100% in some cases). Thus, and while the contribution of star forming processes to the radio luminosity in galaxies with AGN remains uncertain, a comprehensive identification of AGN in these populations is necessary to obtain meaningful results.

Powerful extended radio galaxies like Cygnus A can be used for cosmological tests. The characteristic, time-independent length D for several radio sources is calculated and compared to the average physical length for a sample of radio galaxies. The ratio of these two lengths as a function of redshift is used to constrain cosmological parameters. Cygnus A is the only low-redshift (z < 0:5) radio galaxy for which we have an estimate for D. We comment on the sensitivity to this one low-redshift point, and results including and excluding Cygnus A are shown. A low density universe is favored, and the one free model parameter is relatively well constrained.

We study the mutual alignment of radio sources within two surveys, FIRST and TGSS. This is done by producing two position angle catalogues containing the preferential directions of respectively 30 059 and 11 674 extended sources distributed over more than 7 000 and 17 000 square degrees. The identification of the sources in the FIRST sample was performed in advance by volunteers of the Radio Galaxy Zoo project, while for the TGSS sample it is the result of an automated process presented here. After taking into account systematic effects, marginal evidence of a local alignment on scales smaller than 2.5 • is found in the FIRST sample. The probability of this happening by chance is found to be less than 2 per cent. Further study suggests that on scales up to 1.5 • the alignment is maximal. For one third of the sources, the Radio Galaxy Zoo volunteers identified an optical counterpart. Assuming a flat ΛCDM cosmology with Ω m = 0.31, Ω Λ = 0.69, we convert the maximum angular scale on which alignment is seen into a physical scale in the range [19, 38] Mpc h −1 70. This result supports recent evidence reported by Taylor and Jagannathan of radio jet alignment in the 1.4 deg 2 ELAIS N1 field observed with the Giant Metrewave Radio Telescope. The TGSS sample is found to be too sparsely populated to manifest a similar signal.

We present the X-ray data and the optical identifications for a deep ROSAT PSPC observation in the &quot;Marano field&quot;. In the inner region of the ROSAT field (15&#39; radius) we detected 50 X-ray sources with Sx � 3.7×10−15 erg cm−2 s−1 . When corrected for the differ- ent sensitivity over the field, the estimated observed sur- face density at Sx

We have observed 250 of the 258 southern sources in the complete 5 GHz 1 Jy sample by Kühr et al. (1981) using the Australia Telescope Compact Array (ATCA) at 18.5 GHz. This paper focuses on the polarization properties of this sample, while other properties will be addressed in a future paper. The analysis subdivides the sample into flat and steep spectrum sources using the classification of Stickel et al. (1994), where spectral indices were measured between 2.7 and 5 GHz. The polarized flux has been measured with a S /N > 5 for 170 sources (114 flat-spectrum and 56 steep-spectrum). Upper limits have been set for additional 27 sources (12 flat-spectrum and 15 steep-spectrum). The median fractional polarization at 18.5 GHz for the flat-spectrum sub-sample is Π 18.5 2.7%, which is about a factor of 2 higher than at 1.4 GHz (Π 1.4 1.4%, based on NVSS data). No evidence was found of significant correlations of the fractional polarization with other source properties. The median value of Π 18.5 for the steep spectrum sources is 4.8%, but our sample might be biased against extended sources. We find some correlation between Π 18.5 and both the low-frequency (1.4-5 GHz) and the high-frequency (5-18.5 GHz) spectral indices. An important application of this work is in estimating the contamination of CMB polarization maps by extragalactic radio sources. Our results indicate that such contamination is within that estimated by Mesa et al. (2002).

We present the X-ray data and the optical identifications for a deep ROSAT PSPC observation in the "Marano field". In the inner region of the ROSAT field (15 ′ radius) we detected 50 X-ray sources with S x ≥ 3.7 × 10 −15 erg cm −2 s −1. When corrected for the different sensitivity over the field, the estimated observed surface density at S x ≥ 4 × 10 −15 erg cm −2 s −1 is 272 ± 40 sources/sq.deg. Four X-ray sources, corresponding to 8% of the total sample, have been detected in radio images with a flux limit of about 0.2 mJy. Careful statistical analysis of multi-colour CCD data in the error boxes of the 50 X-ray sources has led to the identification of 42 sources, corresponding to 84% of the Xray sample. These 42 reliable identifications are 33 AGNs (including two radio galaxies and one BL Lac candidate; 79% of the identified sources), 2 galaxies, 3 groups or clusters of galaxies and 4 stars. If we divide our sample into two equally populated sub-samples as a function of flux, at S x = 6.5 × 10 −15 erg cm −2 s −1 , we find that the percentage of identifications remains approximately constant (88% and 80% in the high and low flux sub-samples, respectively). AGNs are the dominant class of objects in both sub-samples (90% of the optical identifications in the high flux sub-sample and 65% in the low flux subsample), while the few identifications with clusters and galaxies are all in the low flux sub-sample. We also show that it is likely that a few of the 8 unidentified sources are such because the derived X-ray positions may be offset with respect to the real ones due to confu

We present new results on the nature of the faint radio galaxy population obtained from a deep identification study in the Marano Field. This work represents the highest identification fractions attained to date in literature for sub-mJy radio samples. Star-forming galaxies constitute a significant fraction of the optical counterparts of sub-mJy radio sources, although they are not the dominant identification class (as formerly believed). We also present a new determination of the co-moving star formation density from z = 0 to z 0.35 using the radio luminosity function of star-forming galaxies. For the local determination, we used a sample of 231 spiral galaxies taken from the B ≤ 12 Revised Shapley-Ames Catalogue, while for the non-local determination, we used a sample of 87 star-forming galaxies taken from the Benn et al. (1993) sample. The inferred local star formation rate is about twice as great as the H α estimate, while the intermediate 0.05 < z < 0.35 star formation rate is consistent with coeval ultraviolet and H α estimates. This is due to large-scale structure, rarely accounted for in estimates of the cosmic star formation history; the situation could improve significantly with deep moderate-area radio surveys. > ∼ 0.2 mJy) have been performed in the 'Marano

We present new results on the nature of the faint radio galaxy population obtained from a deep identification study in the Marano Field. This work represents the highest identification fractions attained to date in literature for sub-mJy radio samples. Star-forming galaxies constitute a significant fraction of the optical counterparts of sub-mJy radio sources, although they are not the dominant identification class (as formerly believed). We also present a new determination of the co-moving star formation density from z = 0 to z 0.35 using the radio luminosity function of star-forming galaxies. For the local determination, we used a sample of 231 spiral galaxies taken from the B ≤ 12 Revised Shapley-Ames Catalogue, while for the non-local determination, we used a sample of 87 star-forming galaxies taken from the Benn et al. (1993) sample. The inferred local star formation rate is about twice as great as the H α estimate, while the intermediate 0.05 < z < 0.35 star formation rate is consistent with coeval ultraviolet and H α estimates. This is due to large-scale structure, rarely accounted for in estimates of the cosmic star formation history; the situation could improve significantly with deep moderate-area radio surveys. > ∼ 0.2 mJy) have been performed in the 'Marano

We present the first results of our Hubble Space Telescope HST WFPC2 F814W snapshot imaging survey, targeting virtually all sub-mJy decimetric radio-selected star-forming galaxies. The radio selection at ,1 GHz is free from extinction effects and the radio luminosities are largely unaffected by AGN contamination, making these galaxies ideal tracers of the cosmic star formation history. A subsample of four targets is presented here, selected at 1.4 GHz from the spectroscopically homogenous and complete samples of Benn et al. and Hopkins et al. The redshifts are confined to a narrow range around z , 0X2Y to avoid differential evolution, with a radio luminosity close to L p where the galaxies dominate the comoving volume-averaged star formation rate. We find clearly disturbed morphologies resembling those of ultraluminous infrared galaxies, indicating that galaxy interactions may be the dominant mechanism for triggering star formation at these epochs. The morphologies are also clearly different from those of coeval quasars and radio galaxies, as found in starforming galaxies selected at other wavelengths. This may prove challenging for models that propose direct causal links between AGN evolution and the cosmic star formation history at these epochs. The asymmetries are typically much larger than seen in the Canada±France Redshift Survey at similar redshifts, optical luminosities and Ha-derived star formation rates, indicating the possible existence of an obscuration-related morphological bias in such samples.

The nature of the unknown sources of ultra-high energy cosmic rays can be revealed through the detection of the GZK feature in the cosmic ray spectrum. The only two experiments that have probed this energy range, AGASA and HiRes, have apparently conflicting results. HiRes measured a flux consistent with the GZK feature while AGASA reported a larger than expected flux

We present a lepto-hadronic model for the VHE emission from the relativistic jets of FR I radiogalaxies. We assume that protons and electrons are accelerated in a compact region near the base of the jet, and they cool emitting multiwavelength radiation as they propagate along the jet. The particle distributions are obtained using an inhomogeneous steady-state transport equation that accounts for the cooling processes as well as the convection of particles in the jet. The dominant processes that contribute to the photon SED are electron and proton synchrotron radiation, inverse Compton interactions, and the inelastic collisions pp and pγ. The accompanying neutrino output is obtained and the possibility of detection with Km3Net and IceCube is discussed for the cases of Cen A and M87.

We report intensity variations of different spectral components in the BL Lac object S5 0716+714 detected during coordinated BeppoSAX and optical observations in 1996 and 1998. The transition between synchrotron and inverse Compton emission has been clearly detected as sharp X-ray spectral breaks at around 2-3 keV on both occasions. Correlated optical and soft X-ray variability was found during the second Bep-poSAX pointing when intensive optical monitoring could be arranged. The hard (Compton) component changed by a factor of 2 between the two observations, but remained stable within each exposure. During events of rapid variability S5 0716+714 showed spectral steepening with intensity, a behaviour rarely observed in BL Lacs. We interpret these findings as the probable consequence of a shift of the synchrotron peak emission from the IR/optical band to higher energies, causing the synchrotron tail to push into the soft X-ray band more and more as the source brightens.

Deep imaging data on radio-selected BL Lacertae objects are presented. The complete 1 Jy sample consists of 37 objects. Altogether 25 objects were observed which span a large range of redshifts (up to z = 1.34) with 12 objects having z > 0.5. In addition, three objects are located at an unknown distance. Altogether in eleven objects the host galaxy could be resolved. All nine objects with z < ∼ 0.4 were resolved and all eleven objects with z > ∼ 0.7 or unknown redshift were unresolved. In all (six) low-z (z < ∼ 0.2) objects, an elliptical host galaxy was preferred. Of the remaining objects, only in one case (2007+777) did a disc-type galaxy give better fit than elliptical, but in this case neither can be preferred. The absolute brightness of the host galaxies (median MR = −23.82) is similar to the findings of X-ray selected BL Lacs and low redshift radio galaxies. Also the sizes (median re = 14.8 kpc) of the galaxies are similar. This supports the idea that (at least low redshift) BL Lacs belong to one family of objects. These results agree well with other recent studies on BL Lacs. There is a strong correlation between the brightness of the active nucleus and redshift. At low redshift radio and X-ray selected BL Lacs have similar brightnesses. No (or only weak) correlation was found between the brightness of the nucleus and the host galaxy.

We present ALMA Atacama Compact Array (ACA) 870 µm continuum maps of 28 infrared-bright SDSS quasars with Herschel/SPIRE detections at redshifts 2-4, the largest such sample ever observed with ALMA. The ACA detections are centred on the SDSS coordinates to within 1 for about 80 per cent of the sample. Larger offsets indicate that the far-infrared (FIR) emission detected by Herschel might come from a companion source. The majority of the objects (∼70 per cent) have unique ACA counterparts within the SPIRE beam down to 3-4 resolution. Only a 30 per cent of the sample show clear evidence for multiple sources with secondary counterparts contributing to the total 870 µm flux within the SPIRE beam by at least 25 per cent. We discuss the limitations of the data based on simulated pairs of point-like sources at the resolution of the ACA and present an extensive comparison of our findings with recent works on the multiplicities of sub-millimetre galaxies. We conclude that, despite the coarse resolution of the ACA, our data support the idea that, for a large fraction of FIR-bright quasars, the sub-mm emission comes from single sources. Our results suggest that, on average, optically bright quasars with strong FIR emission are not triggered by early-stage mergers but are instead, together with their associated star formation rates, the outcome of either late-stage mergers or secular processes.

We present optical spectroscopy of 62 objects selected from several samples of ultra steep spectrum (USS) radio sources. 46 of these are from our primary catalog, consisting of 669 sources with radio spectral indices α < −1.30 (S ν ∝ ν α); this first spectroscopic sub-sample was selected on the basis of their faint optical and near-IR identifications. Most are identified as narrow-lined radio galaxies with redshifts ranging from z = 0.25 to z = 5.19. Ten objects are at z > 3, nearly doubling the number of such sources known to date. Four of the USS radio sources are identified with quasars, of which at least three have very red spectral energy distributions. The source TN J0936−2242 is identified with an extremely red object (ERO, R − K > 5); both it and a close companion are at z = 1.479. The spectrum of the ERO closely resembles that of previously discovered radio galaxies at z ∼ 1.5. Five sources show continuum emission, but fail to show any clear emission or absorption features, despite integrations of ∼ 1h with the Keck telescope. We suggest that these objects could be (i) radio galaxies with faint emission lines in the "redshift desert" at 1.5 ∼ < z ∼ < 2.3, (ii) radio galaxies with an obscured AGN, which are dominated by a stellar continuum observed with insufficient S/N, or (iii) pulsars. Three radio sources identified with faint objects in the K−band images remain undetected in 50−90 min spectroscopic integrations with the Keck telescope, and are possible z > 7 candidates.

We report deep Keck narrow-band Lyα images of the luminous z > 3 radio galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100−200 kpc scale emission line nebulae, centered on these galaxies, which exhibit a wealth of morphological structure, including extended low surface brightness emission in the outer regions, radially directed filaments, coneshaped structures and (indirect) evidence for extended Lyα absorption. We discuss these features within a general scenario where the nebular gas cools gravitationally in large Cold Dark Matter (CDM) halos, forming stars and multiple stellar systems. Merging of these "building" blocks triggers large scale starbursts, forming the stellar bulges of massive radio galaxy hosts, and feeds super-massive black holes which produce the powerful radio jets and lobes. The radio sources, starburst superwinds and AGN radiation then disrupt the accretion process limiting galaxy and black hole growth, and imprint the observed filamentary and cone-shaped structures of the Lyα nebulae. 1 Based on observations made at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

We present neutral hydrogen, ultraviolet, optical and near-infrared imaging, and optical spectroscopy, of Minkowski's Object (MO), a star forming peculiar galaxy near NGC 541. The observations strengthen evidence that star formation in MO was triggered by the radio jet from NGC 541. Key new results are the discovery of a 4.9 × 10 8 M ⊙ double H I cloud straddling the radio jet downstream from MO, where the jet changes direction and decollimates; strong detections of MO, also showing double structure, in UV and Hα; and numerous H II regions and associated clusters in MO. In UV, MO resembles the radio-aligned, rest-frame UV morphologies in many high redshift radio galaxies (HzRGs), also thought to be caused by jet-induced star formation. MO's stellar population is dominated by a 7.5 Myr-old, 1.9 × 10 7 M ⊙ instantaneous burst, with current star formation rate 0.52 M ⊙ yr −1 (concentrated upstream from where the H I column density is high). This is unlike the jet-induced star formation in Centaurus A, where the

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 Lyα 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 −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 −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 ≈60 kpc along the radio-axis. The dynamical structures traced in the Lyα line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Lyα 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.

PKS 1138-262 is a massive radio galaxy at z = 2.16 surrounded by overdensities of Lyα emitters, Hα emitters, EROs and X-ray emitters. Numerous lines of evidence exist that it is located in a forming cluster. We report on Keck spectroscopy of candidate members of this protocluster, including nine of the 18 X-ray sources detected by Pentericci et al. (2002) in this field. Two of these X-ray sources (not counting PKS 1138-262 itself) were previously confirmed to be members of the protocluster; we have discovered that an additional two (both AGN) are members of a filamentary structure, at least 3.5 Mpc in projection, aligned with the radio jet axis, the 150 kpc-sized emission-line halo, and the extended X-ray emission around the radio galaxy. Three of the nine X-ray sources observed are lower redshift AGN, and three are M-dwarf stars.

We have observed the giant radio galaxy Centaurus A and the globular cluster ω Centauri in the TeV energy region using the CANGAROO-III stereoscopic system. The system has been in operation since 2004 with an array of four Imaging Atmospheric Cherenkov Telescopes (IACT) with ∼100-m spacings. The observations were carried out in March and April 2004. In total, approximately 10 hours data were obtained for each target. No statistically significant gamma-ray signal has been found above 420 GeV over a wide angular region (a one-degree radius from the pointing center) and we derive flux upper limits using all of the field of view. Implications for the total energy of cosmic rays and the density of the cold dark matter are considered.

Heating and acceleration of magnetospheric plasma have been studied using in-situ plasma and field observations. There are a large number of observation reports that cold and hot plasma coexist in the Earth’s magnetosphere. However, the dominant heating/acceleration mechanisms and regions are not well understood. Moreover, it remains unclear whether the heating/acceleration mechanisms depend on mass. It can help the more understanding of the heating/acceleration mechanism to investigate the hot and cold plasma in the Earth’s magnetosphere. However, only a few satellite missions have been able to observe the thermal component of magnetospheric plasma with mass determination. Therefore, a small number of studies focused on mass-dependent processes in the typical energy range (&lt;1-10 keV) of magnetospheric ions. In this study, we first separated the plasma into hot and cold populations, and then perform statistical analysis for each population. We also perform similar analysis for di...