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Sample records for candidate high-redshift blazars

  1. A Catalog of Candidate High-redshift Blazars for GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Arias, Tersi M.; /SLAC /San Francisco State U.

    2006-09-27

    High-redshift blazars are promising candidates for detection by the Gamma-ray Large Area Space Telescope (GLAST). GLAST, expected to be launched in the Fall of 2007, is a high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 200 GeV. It is estimated that GLAST will find several thousand blazars. The motivations for measuring the gamma-ray emission from distant blazars include the study of the high-energy emission processes occurring in these sources and an indirect measurement of the extragalactic background light. In anticipation of the launch of GLAST we have compiled a catalog of candidate high-redshift blazars. The criteria for sources chosen for the catalog were: high radio emission, high redshift, and a flat radio spectrum. A preliminary list of 307 radio sources brighter than 70mJy with a redshift z {ge} 2.5 was acquired using data from the NASA Extragalactic Database. Flux measurements of each source were obtained at two or more radio frequencies from surveys and catalogs to calculate their radio spectral indices {alpha}. The sources with a flat-radio spectrum ({alpha} {le} 0.5) were selected for the catalog, and the final catalog includes about 200 sources.

  2. High redshift blazars

    CERN Document Server

    Ghisellini, G

    2013-01-01

    Blazars are sources whose jet is pointing to us. Since their jets are relativistic, the flux is greatly amplified in the direction of motion, making blazars the most powerful persistent objects in the Universe. This is true at all frequencies, but especially where their spectrum peaks. Although the spectrum of moderate powerful sources peaks in the ~GeV range, extremely powerful sources at high redshifts peak in the ~MeV band. This implies that the hard X-ray band is the optimal one to find powerful blazars beyond a redshift of ~4. First indications strongly suggest that powerful high-z blazars harbor the most massive and active early black holes, exceeding a billion solar masses. Since for each detected blazars there must exist hundreds of similar, but misaligned, sources, the search for high-z blazars is becoming competitive with the search of early massive black holes using radio-quiet quasars. Finding how the two populations of black holes (one in jetted sources, the other in radio-quiet objects) evolve i...

  3. -Rays Radiation of High Redshift Fermi Blazars

    Indian Academy of Sciences (India)

    W. G. Liu; S. H. Fu; X. Zhang; L. Ma; Y. B. Li; D. R. Xiong

    2014-09-01

    Based on the 31 high redshift ( > 2) Flat Spectral Radio Quasars (FSRQs), which is from the second Fermi-LAT AGNs catalogue (2LAC), we studied the correlation between flux densities (R, K, ) in the radio, infrared and -ray wave bands. We found that there is a significant positive correlation between and R, and a weak anticorrelation between and K in the average state. For high redshift blazars, we argue that the seed photon of -ray emission mainly comes from the jet itself and partially from the dusty torus.

  4. Broadband Observations of High Redshift Blazars

    Science.gov (United States)

    Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.

    2016-07-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 (z = 3.37), CGRaBS J0225+1846 (z = 2.69), BZQ J1430+4205 (z = 4.72), and 3FGL J1656.2‑3303 (z = 2.40) using quasi-simultaneous data from the Swift, Nuclear Spectroscopic Telescope Array (NuSTAR) and the Fermi-Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2‑3303, none of the sources were known as γ-ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical‑UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ-ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

  5. Broadband Observations of High Redshift Blazars

    CERN Document Server

    Paliya, Vaidehi S; Fabian, A C; Stalin, C S

    2016-01-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 ($z=3.37$), CGRaBS J0225+1846 ($z=2.69$), BZQ J1430+4205 ($z=4.72$), and 3FGL J1656.2$-$3303 ($z=2.40$), using the quasi-simultaneous data from {\\it Swift}, {\\it NuSTAR}, and {\\it Fermi}-Large Area Telescope (LAT) and also the archival {\\it XMM-Newton} observations. Other than 3FGL J1656.2$-$3303, none of the sources were known as $\\gamma$-ray emitters and our analysis of $\\sim$7.5 years of LAT data reveals the first time detection of the statistically significant $\\gamma$-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of {\\it NuSTAR} observations and reproduce them using a one zone leptonic emission model. The optical$-$UV emission in all the objects can be explained by the radiation from the accretion disk, whereas, X-ray to $\\gamma$-ray window of the SEDs are found to be dominated by the inverse Compton scattering off the broad line reg...

  6. Hidden blazars and emission line variability of high redshift quasars

    Directory of Open Access Journals (Sweden)

    Feng Ma

    2001-01-01

    Full Text Available We have carried out a survey to search for hidden blazars in a sample of z 2 radio{loud quasars. The idea is based on our prediction that we should be able to see large C IV line variability not associated with observed continuum variations or most other emission lines in every radio{loud quasar. Here we report the initial results including the discovery of large C IV line variations in two quasars.

  7. High redshift Fermi blazars observed by GROND and Swift

    CERN Document Server

    Ghisellini, G; Tagliaferri, G; Greiner, J; Schady, P; Rau, A; Foschini, L; Tavecchio, F; Ghirlanda, G; Sbarrato, T

    2012-01-01

    We observed 5 gamma-ray loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) onboard the Swift satellite, and the Gamma-Ray burst Optical Near-Infrared Detector (GROND) instrument. These observations were quasi simultaneous, usually within a few hours. For 4 of these blazars the near-IR to UV data show the presence of an accretion disc, and we could reliably estimate its accretion rate and black hole mass. One of them, PKS 1348+007, was found in an extraordinarily high IR-optical state, almost two orders of magnitude brighter than at the epoch of the Sloan Digital Sky Survey observations. For all the 5 quasars the physical parameters of the jet emitting zone, derived by applying a one-zone emission model, are similar to that found for the bulk of other gamma-ray loud quasars. With our observations we have X-ray data for the full sample of blazars at z>2 present in the Fermi 2-yrs (2LAC) catalog. This allows to have a rather complete view of th...

  8. Photometric Selection of High-Redshift Type Ia Supernova Candidates

    Science.gov (United States)

    Sullivan, M.; Howell, D. A.; Perrett, K.; Nugent, P. E.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R. G.; Conley, A.; Fabbro, S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J. D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C. J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop, R. A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe Ia and core-collapse SNe. Furthermore, for SNe Ia the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100% of the identified SNe II as non-SNe Ia with only a 1%-2% false rejection rate. The predicted parameterization of the SNe Ia has a precision of Δz/(1+zspec)<0.09 in redshift and +/-2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters (e.g., w and ΩM) and find any effect to be negligible.

  9. Awakening of The High Redshift Blazar CGRaBS J0809+5341

    CERN Document Server

    Paliya, Vaidehi S; Stalin, C S; Fabian, A C; Ramya, S; Covino, S; Tagliaferri, G; Sahayanathan, S; Ravikumar, C D

    2015-01-01

    CGRaBS J0809+5341, a high redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by $\\sim$5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute magnitude of -30.5 mag, making it one of the brightest quasars in the Universe. This optical flaring triggered us to carry out observations during the decaying part of the flare covering a wide energy range using the {\\it Nuclear Spectroscopic Telescope Array}, {\\it Swift}, and ground based optical facilities. For the first time, the source is detected in $\\gamma$-rays by the Large Area Telescope onboard the {\\it Fermi Gamma-Ray Space Telescope}. A high optical polarization of $\\sim$10\\% is also observed. Using the Sloan Digital Sky Survey spectrum, accretion disk luminosity and black hole mass are estimated as $1.5 \\times 10^{45}$ erg s$^{-1}$ and $10^{8.4}~M_{\\odot}$ respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source du...

  10. Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710

    CERN Document Server

    Akyuz, A; Donato, D; Perkins, J S; Fuhrmann, L; Angelakis, E; Zensus, J A; Larsson, S; Sokolovsky, K; Kurtanidze, O

    2013-01-01

    Aims. The observation of gamma -ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different wavelengths for a high-redshift (z=2.218) active galactic nucleus. Methods. Optical and radio monitoring, plus Fermi-LAT gamma-ray monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical, ultraviolet, and X-ray information. Other contemporaneous observations were used to construct a broad-band spectral energy distribution. Results. There is evidence of correlation but not a measurable lag between the optical and gamma-ray flaring emission. On the contrary, there is no clear correlation between radio and gamma-ray activity, indicating radio emission regions that are unrelated to the parts of the jet that produce the gamma-rays. The gamma-ray energy spectrum is unusual in showing a change of shape from a power law to a curved spectrum when going from the quiescent state to the active state.

  11. Blazar candidates beyond redshift 4 observed with GROND

    CERN Document Server

    Sbarrato, T; Nardini, M; Tagliaferri, G; Greiner, J; Rau, A; Schady, P

    2013-01-01

    The search for extremely massive high redshift blazars is essential to put strong constraints on the supermassive black holes formation theories. Up to now, the few blazars known to have a redshift larger than 4 have been discovered serendipitously. We try a more systematic approach. Assuming radio-loudness as a proxy for the jet orientation, we select a sample of extremely radio-loud quasars. We measure their black hole masses with a method based on fitting the thermal emission from the accretion disc. We achieve a precision of a factor of two for our measures, thanks to the observations performed with the Gamma-Ray Burst Optical Near-Infrared Detector (GROND). The infrared to optical GROND data allow us to observe directly the peak of the disc emission, thus constraining the overall disc luminosity. We obtain a small range of masses, that peaks at 10^{9.3}Msun. If some of our candidates will be confirmed as blazars, these results would introduce interesting constraints on the mass function of extremely mass...

  12. Candidate High Redshift and Primeval Galaxies in Hubble Deep Field South

    OpenAIRE

    Clements, D.L.; Eales, S. A.; Baker, A. C.

    1999-01-01

    We present the results of colour selection of candidate high redshift galaxies in Hubble Deep Field South (HDF-S) using the Lyman dropout scheme. The HDF-S data we discuss were taken in a number of different filters extending from the near--UV (F300W) to the infrared (F222M) in two different fields. This allows us to select candidates with redshifts from z~3 to z~12. We find 15 candidate z~3 objects (F300W dropouts), 1 candidate z~4 object (F450W dropout) and 16 candidate z$\\sim$5 objects (F6...

  13. Precessing Jet in the High-Redshift Blazar J0017+8135

    CERN Document Server

    Rozgonyi, Kristóf

    2016-01-01

    The prominent flat-spectrum radio quasar J0017+8135 (S5 0014+81) at z = 3.366 is one of the most luminous active galactic nuclei (AGN) known. Its milliarcsecond-scale radio jet structure has been studied with very long baseline interferometry (VLBI) since the 1980s. The quasar was selected as one of the original defining objects of the International Celestial Reference Frame, but left out from its current second realization (ICRF2) because of systematic long-term positional variations. Here we analyse archival 8.6- and 2.3-GHz VLBI imaging data collected at nearly 100 different epochs during more than 20 years, to obtain information about the kinematics of jet components. Because of the cosmological time dilation, extensive VLBI monitoring data are essential to reveal changes in the jet structure of high-redshift AGN. In the case of J0017+8135, the data can be described with a simple kinematic model of jet precession with a 12-year periodicity in the observer's frame.

  14. A search for Population III galaxies in CLASH. I. Singly-imaged candidates at high redshift

    CERN Document Server

    Rydberg, Claes-Erik; Zitrin, Adi; Guaita, Lucia; Melinder, Jens; Asadi, Saghar; Gonzalez, Juan; Östlin, Göran; Ström, Tina

    2014-01-01

    Population III galaxies are predicted to exist at high redshifts and may be rendered sufficiently bright for detection with current telescopes when gravitationally lensed by a foreground galaxy cluster. Population III galaxies that exhibit strong Lya emission should furthermore be identifiable from broadband photometry because of their unusual colors. Here, we report on a search for such objects at z > 6 in the imaging data from the Cluster Lensing And Supernova survey with Hubble (CLASH), covering 25 galaxy clusters in 16 filters. Our selection algorithm returns five singly-imaged candidates with Lya-like color signatures, for which ground-based spectroscopy with current 8-10 m class telescopes should be able to test the predicted strength of the Lya line. None of these five objects have been included in previous CLASH compilations of high-redshift galaxy candidates. However, when large grids of spectral synthesis models are applied to the study of these objects, we find that only two of these candidates are...

  15. Candidate High Redshift and Primeval Galaxies in Hubble Deep Field South

    CERN Document Server

    Clements, D L; Baker, A C

    1999-01-01

    We present the results of colour selection of candidate high redshift galaxies in Hubble Deep Field South (HDF-S) using the Lyman dropout scheme. The HDF-S data we discuss were taken in a number of different filters extending from the near--UV (F300W) to the infrared (F222M) in two different fields. This allows us to select candidates with redshifts from z~3 to z~12. We find 15 candidate z~3 objects (F300W dropouts), 1 candidate z~4 object (F450W dropout) and 16 candidate z$\\sim$5 objects (F606W dropouts) in the ~ 4.7 arcmin^2 WFPC-2 field, 4 candidate z~6 (optical dropouts) and 1 candidate z~8 (F110W dropout) in the 0.84 arcmin^2 NICMOS-3 field. No F160W dropouts are found (z~12). We compare our selection technique with existing data for HDF-North and discuss alternative interpretations of the objects. We conclude that there are a number of lower redshift interlopers in the selections, including one previously identified object (Treu et al. 1998), and reject those objects most likely to be foreground contami...

  16. Photometric Selection of High-Redshift Type Ia SupernovaCandidates

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, M.; Howell, D.A.; Perrett, K.; Nugent, P.E.; Astier,P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R.G.; Conley, A.; Fabbro,S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J.D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C.J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop,R.A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only two to three epochs of multiband real-time photometry, is able to discriminate between SNe Ia and core-collapse SNe. Furthermore, for SNe Ia the method accurately predicts the redshift, phase, and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period 2004 May to 2005 January in the SNLS, 440 SN candidates were discovered, of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test data set, the selection technique correctly identifies 100 percent of the identified SNe II as non-SNe Ia with only a 1 percent-2 percent false rejection rate. The predicted parameterization of the SNe Ia has a precision of bar DELTA z bar/(1+zspec)<0.09 in redshift and +-2-3 rest-frame days in phase, providing invaluable information for planning spectroscopic follow-up observations. We also investigate any bias introduced by this selection method on the ability of surveys such as SNLS to measure cosmological parameters (e.g., w and OMEGA M) and find any effect to be negligible.

  17. Photometric Selection of High-Redshift Type Ia SupernovaCandidates

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, M.; Howell, D.A.; Perrett, K.; Nugent, P.E.; Astier,P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R.G.; Conley, A.; Fabbro,S.; Fouchez, D.; Guy, J.; Hook, I.; Lafoux, H.; Neill, J.D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C.J.; Regnault, N.; Rich, J.; Taillet, R.; Aldering, G.; Baumont, S.; Bronder, J.; Filiol, M.; Knop,R.A.; Perlmutter, S.; Tao, C.

    2006-02-01

    We present a method for selecting high-redshift Type Iasupernovae (SNe Ia) located via rolling SN searches. The technique, usingboth color and magnitude information of events from only two to threeepochs of multiband real-time photometry, is able to discriminate betweenSNe Ia and core-collapse SNe. Furthermore, for SNe Ia the methodaccurately predicts the redshift, phase, and light-curve parameterizationof these events based only on pre-maximum-light data. We demonstrate theeffectiveness of the technique on a simulated survey of SNe Ia andcore-collapse SNe, where the selection method effectively rejects mostcore-collapse SNe while retaining SNe Ia. We also apply the selectioncode to real-time data acquired as part of the Canada-France-HawaiiTelescope Supernova Legacy Survey (SNLS). During the period 2004 May to2005 January in the SNLS, 440 SN candidates were discovered, of which 70were confirmed spectroscopically as SNe Ia and 15 as core-collapseevents. For this test data set, the selection technique correctlyidentifies 100 percent of the identified SNe II as non-SNe Ia with only a1 percent-2 percent false rejection rate. The predicted parameterizationof the SNe Ia has a precision of bar DELTAz bar/(1+zspec)<0.09 inredshift and +-2-3 rest-frame days in phase, providing invaluableinformation for planning spectroscopic follow-up observations. We alsoinvestigate any bias introduced by this selection method on the abilityof surveys such as SNLS to measure cosmological parameters (e.g., w andOMEGA M) and find any effect to be negligible.

  18. Swift multi-wavelength observations of the high-redshift Blazar S5 0836+710 (4C 71.07)

    Science.gov (United States)

    Vercellone, Stefano; Romano, Patrizia; Raiteri, Claudia Maria; Acosta Pulido, Jose; Villata, Massimo; Carnerero Martin, Maria Isabel

    2016-04-01

    We present the preliminary results of a year-long Swift monitoring campaign of the high-redshift (z=2.172) flat-spectrum radio quasar (FSRQ) S5 0836+710 (4C 71.07). The campaign, based on one observation per month, 5 ks each observation, for 12 months, allowed us to investigate the synchrotron and nuclear emission contributions to the optical-UV frequency range of its spectral energy distribution and the X-ray spectral variations along a baseline of a year. We obtained a high-accuracy determination of UVOT magnitudes, an X-ray photon index with an uncertainty of the order of 5%, and well-sampled light curves both in the optical-UV and X-ray energy bands to study their possible modulations and correlations. Our study allowed us to exploit the unique Swift capabilities in terms of both simultaneous energy coverage and schedule flexibility. The Swift monitoring campaign was supported by observations by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) Collaboration, which provided radio, near-infrared, and optical photometric data as well as optical polarimetry. Moreover, a spectroscopic monitoring was obtained at the William Herschel Telescope (WHT) and the Nordic Optical Telescope (NOT). All these observations will allow us to obtain a comprehensive picture of the jet as well as of the nuclear source emission.

  19. H-ATLAS: A Candidate High Redshift Cluster/Protocluster of Star-Forming Galaxies

    CERN Document Server

    Clements, D L; Petitpas, G; Greenslade, J; Cooray, A; Valiante, E; De Zotti, G; O'Halloran, B; Holdship, J; Morris, B; Herranz, I Perez-Fournon D; Riechers, D; Baes, M; Bremer, M; Bourne, N; Dannerbauer, H; Dariush, A; Dunne, L; Eales, S; Fritz, J; Gonzalez-Nuevo, J; Hopwood, R; Ibar, E; Ivison, R J; Leeuw, L L; Maddox, S; Negrello, M J Michaowski M; Omont, A; Oteo, I; Serjeant, S; Valtchanov, I; Vieira, J D; Wardlow, J; van der Werf, P

    2016-01-01

    We investigate the region around the Planck-detected z=3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S_870 >~7 mJy) sources at >4sigma closer than 5 arcmin to the lensed object at 850/870 microns. Ten of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350 micron flux > 250 micron flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ~1 arcsecond, allowing unambiguous cross identification with a 3.6 and 4.5 micron Spitzer source. The optical/near-IR spectral energy distribution (SED) of this source is measured by further observations and found to be co...

  20. H-ATLAS: a candidate high redshift cluster/protocluster of star-forming galaxies

    Science.gov (United States)

    Clements, D. L.; Braglia, F.; Petitpas, G.; Greenslade, J.; Cooray, A.; Valiante, E.; De Zotti, G.; O'Halloran, B.; Holdship, J.; Morris, B.; Pérez-Fournon, I.; Herranz, D.; Riechers, D.; Baes, M.; Bremer, M.; Bourne, N.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Eales, S.; Fritz, J.; Gonzalez-Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Leeuw, L. L.; Maddox, S.; Michałowski, M. J.; Negrello, M.; Omont, A.; Oteo, I.; Serjeant, S.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; van der Werf, P.

    2016-09-01

    We investigate the region around the Planck-detected z = 3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S870 > ˜7 mJy) sources at >4σ closer than 5 arcmin to the lensed object at 850/870 μm. 10 of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350 μm flux >250 μm flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ˜1 arcsec, allowing unambiguous cross identification with a 3.6 and 4.5 μm Spitzer source. The optical/near-IR spectral energy distribution of this source is measured by further observations and found to be consistent with z > 2, but incompatible with lower redshifts. We conclude that this system may be a galaxy cluster/protocluster or larger scale structure that contains a number of galaxies undergoing starbursts at the same time.

  1. H-ATLAS: A Candidate High Redshift Cluster/Protocluster of Star-Forming Galaxies

    Science.gov (United States)

    Clements, D. L.; Braglia, F.; Petitpas, G.; Greenslade, J.; Cooray, A.; Valiante, E.; De Zotti, G.; O'Halloran, B.; Holdship, J.; Morris, B.; Pérez-Fournon, I.; Herranz, D.; Riechers, D.; Baes, M.; Bremer, M.; Bourne, N.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Eales, S.; Fritz, J.; Gonzalez-Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Leeuw, L. L.; Maddox, S.; Michałowski, M. J.; Negrello, M.; Omont, A.; Oteo, I.; Serjeant, S.; Valtchanov, I.; Vieira, J. D.; Wardlow, J.; van der Werf, P.

    2016-06-01

    We investigate the region around the Planck-detected z=3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S870 > ˜7 mJy) sources at >4σ closer than 5 arcmin to the lensed object at 850/870μm. Ten of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350μm flux > 250μm flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ˜1 arcsecond, allowing unambiguous cross identification with a 3.6 and 4.5 μm Spitzer source. The optical/near-IR spectral energy distribution (SED) of this source is measured by further observations and found to be consistent with z > 2, but incompatible with lower redshifts. We conclude that this system may be a galaxy cluster/protocluster or larger scale structure that contains a number of galaxies undergoing starbursts at the same time.

  2. Blazar candidates beyond redshift 4 observed by Swift

    CERN Document Server

    Sbarrato, T; Tagliaferri, G; Foschini, L; Nardini, M; Tavecchio, F; Gehrels, N

    2014-01-01

    We have selected SDSS J222032.50+002537.5 and SDSS J142048.01+120545.9 as best blazar candidates out of a complete sample of extremely radio-loud quasars at z>4, with highly massive black holes. We observed them and a third serendipitous candidate with similar features (PMN J2134-0419) in the X-rays with the Swift/XRT telescope, to confirm their blazar nature. We observed strong and hard X-ray fluxes in all three cases. This allowed us to classify our candidates as real blazars, being characterized by large Lorentz factors (~13) and very small viewing angles (~3deg). All three sources have black hole masses exceeding 10^9Msun and their classification provides intriguing constraints on supermassive black hole formation and evolution models. We confirm our earlier suggestion that there are different formation epochs of extremely massive black holes hosted in jetted (z~4) and non-jetted systems (z~2.5).

  3. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    D' Abrusco, R.; Paggi, A.; Smith, H. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Masetti, N. [INAF/IASF di Bologna, via Gobetti 101, I-40129 Bologna (Italy); Landoni, M. [INAF/Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy); Tosti, G. [Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia (Italy)

    2014-11-01

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q {sub 22} parameter, which is analogous to the q {sub 24} parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources.

  4. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    International Nuclear Information System (INIS)

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q 22 parameter, which is analogous to the q 24 parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources

  5. HerMES: Candidate High-Redshift Galaxies Discovered with Herschel/SPIRE

    CERN Document Server

    Dowell, C Darren; Glenn, J; Arumugam, V; Asboth, V; Aussel, H; Bertoldi, F; Bethermin, M; Bock, J; Boselli, A; Bridge, C; Buat, V; Burgarella, D; Cabrera-Lavers, A; Casey, C M; Chapman, S C; Clements, D L; Conversi, L; Cooray, A; Dannerbauer, H; De Bernardis, F; Ellsworth-Bowers, T P; Farrah, D; Franceschini, A; Griffin, M; Gurwell, M A; Halpern, M; Hatziminaoglou, E; Heinis, S; Ibar, E; Ivison, R J; Laporte, N; Marchetti, L; Martinez-Navajas, P; Marsden, G; Morrison, G E; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Page, M J; Papageorgiou, A; Pearson, C P; Petitpas, G; Perez-Fournon, I; Pohlen, M; Riechers, D; Rigopoulou, D; Roseboom, I G; Rowan-Robinson, M; Sayers, J; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Streblyanska, A; Symeonidis, M; Vaccari, M; Valtchanov, I; Vieira, J D; Viero, M; Wang, L; Wardlow, J; Xu, C K; Zemcov, M

    2013-01-01

    We present a method for selecting $z>4$ dusty, star forming galaxies (DSFGs) using Herschel/SPIRE 250/350/500 $\\mu m$ flux densities to search for red sources. We apply this method to 21 deg$^2$ of data from the HerMES survey to produce a catalog of 38 high-$z$ candidates. Follow-up of the first 5 of these sources confirms that this method is efficient at selecting high-$z$ DSFGs, with 4/5 at $z=4.3$ to $6.3$ (and the remaining source at $z=3.4$), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 $\\mu m$) and in single-band surveys, shows that our method is much more efficient at selecting high-$z$ DSFGs, in the sense that a much larger fraction are at $z>3$. Correcting for the selection completeness and purity, we find that the number of bright ($S_{500\\,\\mu m} \\ge 30$ mJy), red Herschel sources is $3.3 \\pm 0.8$ deg$^{-2}$. This is much higher than the number predicted by current models, suggesting that the...

  6. HerMES: Candidate high-redshift galaxies discovered with Herschel/Spire

    Energy Technology Data Exchange (ETDEWEB)

    Dowell, C. Darren; Bock, J.; Bridge, C.; Cooray, A. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Conley, A.; Glenn, J. [Center for Astrophysics and Space Astronomy 389-UCB, University of Colorado, Boulder, CO 80309 (United States); Arumugam, V. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Asboth, V. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Aussel, H.; Béthermin, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Université Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); Bertoldi, F. [Argelander Institute für Astronomy, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany); Boselli, A.; Buat, V.; Burgarella, D. [Aix-Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille), UMR7326, F-13388 Marseille (France); Cabrera-Lavers, A. [Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Casey, C. M. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Chapman, S. C. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS B3H 3J5 (Canada); Clements, D. L. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Conversi, L. [Herschel Science Centre, European Space Astronomy Centre, Villanueva de la Cañada, E-28691 Madrid (Spain); Dannerbauer, H., E-mail: cdd@astro.caltech.edu [Universität Wien, Institut für Astrophysic, Türkenschanzstraße 17, A-1180, Wien (Austria); and others

    2014-01-01

    We present a method for selecting z > 4 dusty, star-forming galaxies (DSFGs) using Herschel/Spectral and Photometric Imaging Receiver 250/350/500 μm flux densities to search for red sources. We apply this method to 21 deg{sup 2} of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first five of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3-6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 μm) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S {sub 500} {sub μm} ≥ 30 mJy), red Herschel sources is 3.3 ± 0.8 deg{sup –2}. This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z ∼ 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4-6, even after correction for extinction.

  7. HerMES: Candidate High-redshift Galaxies Discovered with Herschel/SPIRE

    Science.gov (United States)

    Dowell, C. Darren; Conley, A.; Glenn, J.; Arumugam, V.; Asboth, V.; Aussel, H.; Bertoldi, F.; Béthermin, M.; Bock, J.; Boselli, A.; Bridge, C.; Buat, V.; Burgarella, D.; Cabrera-Lavers, A.; Casey, C. M.; Chapman, S. C.; Clements, D. L.; Conversi, L.; Cooray, A.; Dannerbauer, H.; De Bernardis, F.; Ellsworth-Bowers, T. P.; Farrah, D.; Franceschini, A.; Griffin, M.; Gurwell, M. A.; Halpern, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Ivison, R. J.; Laporte, N.; Marchetti, L.; Martínez-Navajas, P.; Marsden, G.; Morrison, G. E.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Omont, A.; Page, M. J.; Papageorgiou, A.; Pearson, C. P.; Petitpas, G.; Pérez-Fournon, I.; Pohlen, M.; Riechers, D.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Sayers, J.; Schulz, B.; Scott, Douglas; Seymour, N.; Shupe, D. L.; Smith, A. J.; Streblyanska, A.; Symeonidis, M.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Wang, L.; Wardlow, J.; Xu, C. K.; Zemcov, M.

    2014-01-01

    We present a method for selecting z > 4 dusty, star-forming galaxies (DSFGs) using Herschel/Spectral and Photometric Imaging Receiver 250/350/500 μm flux densities to search for red sources. We apply this method to 21 deg2 of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first five of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3-6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 μm) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S 500 μm >= 30 mJy), red Herschel sources is 3.3 ± 0.8 deg-2. This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z ~ 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4-6, even after correction for extinction. . Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  8. RCT photometry and HCT spectroscopy of blazar candidates in the Kepler field of view

    Science.gov (United States)

    Carini, Michael T.; Goyal, A.; Jose, J.

    2014-01-01

    The results of photometric and spectroscopic monitoring of 9 blazar candidates in the Kepler field of view are presented. These sources were identified as blazar candidates based on their position in the so-called WISE blazar strip. Finding charts and comparison sequences were created using the NOMAD database. R band photometric monitoring was begun in spring 2013 with the Robotically Controlled Telescope(RCT), and spectroscopic observations of 7 of the sources were obtained with the Himalayan Chandra Telescope (HCT) in September, 2013. Light curves for all 9 sources and preliminary spectroscopic classifications for the 7 sources with spectra will be presented.

  9. PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz

    CERN Document Server

    Karamanavis, V; Krichbaum, T P; Angelakis, E; Hodgson, J; Nestoras, I; Myserlis, I; Zensus, J A; Sievers, A; Ciprini, S

    2016-01-01

    Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106 showing a rapid and strong gamma-ray outburst followed by high and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign covering also the radio, optical, UV, and X-ray bands indicating that the flare was accompanied by a simultaneous outburst at optical/UV/X-rays and a delayed outburst at radio bands. Aims: In the current work we explore the phenomenology and physical conditions within the ultra-relativistic jet of the gamma-ray blazar PKS 1502+106. Additionally, we address the question of the spatial localization of the MeV/GeV-emitting region of the source. Methods: We utilize ultra-high angular resolution mm-VLBI observations at 43 and 86 GHz complemented by VLBI observations at 15 GHz. We also employ single-dish radio data from the F-GAMMA program at frequencies matching the VLBI monitoring. Results: PKS 1502+106 sh...

  10. NuSTAR and multifrequency study of the two high-redshift blazars S5 0836+710 and PKS 2149-306

    DEFF Research Database (Denmark)

    Tagliaferri, G.; Ghisellini, G.; Perri, M.;

    2015-01-01

    Powerful blazars are flat-spectrum radio quasars whose emission is dominated by a Compton component peakingbetween a few hundred keV and a few hundred MeV. We observed two bright blazars, PKS 2149–306 at redshift z = 2.345 and S5 0836+710 at z = 2.172, in the hard X-ray band with the Nuclear...... Spectroscopic Telescope Array satellite. Simultaneous soft-X-rays and UV–optical observations were performed with the Swift satellite, whilenear-infrared (near-IR) data were obtained with the Rapid Eye Mount telescope. To study their variability, we repeated these observations for both sources on a timescale...... of a few months. While no fast variability was detected during a single observation, both sources were variable in the X-ray band, up to 50%, between the two observations, with larger variability at higher energies. No variability was detected in the optical/NIR band. These data, together with Fermi...

  11. NuSTAR and multifrequency study of the two high-redshift blazars S5 0836+710 and PKS 2149-306

    CERN Document Server

    Tagliaferri, G; Perri, M; Hayashida, M; Balokovic, M; Covino, S; Giommi, P; Madejski, G M; Puccetti, S; Sbarrato, T; Boggs, S E; Chiang, J; Christensen, F E; Craig, W W; Hailey, C J; Harrison, F A; Stern, D; Zhang, W W

    2015-01-01

    The most powerful blazars are the flat spectrum radio quasars whose emission is dominated by a Compton component peaking between a few hundred keV and a few hundred MeV. We selected two bright blazars, PKS 2149-306 at redshift z=2.345 and S5 0836+710 at z=2.172, in order to observe them in the hard X-ray band with the NuSTAR satellite. In this band the Compton component is rapidly rising almost up to the peak of the emission. Simultaneous soft-X-rays and UV-optical observations were performed with the Swift satellite, while near-infrared (NIR) data were obtained with the REM telescope. To study their variability, we repeated these observations for both sources on a timescale of a few months. While no fast variability was detected during a single observation, both sources were found to be variable in the X-ray band, up to 50%, between the two observations, with larger variability at higher energies. No variability was detected in the optical/NIR band. These data together with Fermi-LAT, WISE and other literatu...

  12. High-redshift standard candles

    DEFF Research Database (Denmark)

    King, Anthea L.; Davis, Tamara M.; Denney, K. D.; Vestergaard, M.; Watson, D.

    2014-01-01

    dark energy equation of state, $w(z)$, and assess the optimal redshift distribution a high-redshift standard-candle survey could take to constrain these models. The more general the form of the dark energy equation of state $w(z)$ being tested, the more useful high-redshift standard candles become. For......We investigate whether future measurements of high redshift standard candles (HzSCs) will be a powerful probe of dark energy, when compared to other types of planned dark energy measurements. Active galactic nuclei and gamma ray bursts have both been proposed as potential HzSC candidates. Due to...... a linear parameterization of $w(z)$, HzSCs give only small improvements over planned supernova and baryon acoustic oscillation measurements; a wide redshift range with many low redshift points is optimal to constrain this linear model. However to constrain a general, and thus potentially more...

  13. Planck intermediate results. XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE

    CERN Document Server

    ,

    2015-01-01

    [Abridged] We use the Planck all-sky submm and mm maps to search for rare sources distinguished by extreme brightness, a few hundreds of mJy, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353 and 857 GHz. This colour-selection favours galaxies in the redshift range z=2-4, which we consider as cold peaks in the cosmic infrared background (CIB). We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500um sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350um. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing ...

  14. Nustar detection of the blazar B2 1023+25 at redshift 5.3

    DEFF Research Database (Denmark)

    Sbarrato, T.; Tagliaferri, G.; Ghisellini, G.;

    2013-01-01

    B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component w...

  15. SEARCHING FOR NEW γ-RAY BLAZAR CANDIDATES IN THE THIRD PALERMO BAT HARD X-RAY CATALOG WITH WISE

    International Nuclear Information System (INIS)

    We searched for γ-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the γ-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE γ-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 γ-ray blazar candidates.

  16. Galaxies at High Redshifts

    CERN Document Server

    Yahil, A; Fernández-Soto, A

    1998-01-01

    Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significant and sharp diminution in the number of L* spiral galaxies at redshifts 1high-redshift galaxies in universes with larger volumes per unit redshift, i.e., open or lambda models, which have lower deceleration parameters.

  17. Galaxies at High Redshifts

    OpenAIRE

    Yahil, A.; Lanzetta, K. M.; Fernandez-Soto, A.

    1998-01-01

    Several conclusions have been reached over the last few years concerning high-redshift galaxies: (1) The excess of faint blue galaxies is due to dwarf galaxies. (2) Star formation peaks at redshifts z ~1-2. (3) It appears to occur piecemeal in any given galaxy and there is no evidence for starbursting throughout a large ~10 kpc galaxy. (4) There is significant and sharp diminution in the number of L* spiral galaxies at redshifts 1

  18. Chasing extreme blazars with INTEGRAL

    CERN Document Server

    Bassani, Loredana; Landi, R; Malizia, A; Bird, A J; Bazzano, A; Ubertini, P

    2013-01-01

    Within the blazar population, hard X-ray selected objects are of particular interest as they tend to lie at each end of the blazar sequence. In particular, flat spectrum radio quasars located at high redshifts display the most powerful jets, the largest black hole masses and the most luminous accretion disks: their spectral energy distribution has a Compton peak in the sub-MeV region which favours their detection by instruments like INTEGRAL/IBIS and Swift/BAT. These sources are even more extreme than blazars selected in other wavebands, like, for example, the gamma-ray range explored by Fermi. Here we report on a sample of 12 high redshift blazars detected so far by INTEGRAL, including 3 newly identified objects. Some properties of the combined IBIS/BAT sample of high redshift blazars (z>2) are also compared to those of a similar similar sample obtained by Fermi.

  19. Optical archival spectra of blazar candidates of uncertain type in the 3rd Fermi Large Area Telescope Catalog

    Science.gov (United States)

    Álvarez Crespo, N.; Massaro, F.; D'Abrusco, R.; Landoni, M.; Masetti, N.; Chavushyan, V.; Jiménez-Bailón, E.; La Franca, F.; Milisavljevic, D.; Paggi, A.; Patiño-Álvarez, V.; Ricci, F.; Smith, Howard A.

    2016-09-01

    Despite the fact that blazars constitute the rarest class among active galactic nuclei (AGNs) they are the largest known population of associated γ-ray sources. Many of the γ-ray objects listed in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs), either because they show multifrequency behavior similar to blazars but lacking optical spectra in the literature, or because the quality of such spectra is too low to confirm their nature. Here we select, out of 585 BCUs in the 3FGL, 42 BCUs which we identify as probable blazars by their WISE infrared colors and which also have optical spectra that are available in the Sloan Digital Sky Survey (SDSS) and/or Six-Degree Field Galaxy Survey Database (6dFGS). We confirm the blazar nature of all of the sources. We furthermore conclude that 28 of them are BL Lacs, 8 are radio-loud quasars with flat radio spectrum and 6 are BL Lac whose emission is dominated by their host galaxy.

  20. Blazar Flaring Patterns (B-FlaP): Classifying Blazar Candidates of Uncertain type in the third Fermi-LAT catalog by Artificial Neural Networks

    CERN Document Server

    Chiaro, G; La Mura, G; Giroletti, M; Thompson, D J; Bastieri, D

    2016-01-01

    The Fermi Large Area Telescope (LAT) is currently the most important facility for investigating the GeV $\\gamma$-ray sky. With Fermi LAT more than three thousand $\\gamma$-ray sources have been discovered so far. 1144 ($\\sim40\\%$) of the sources are active galaxies of the blazar class, and 573 ($\\sim20\\%$) are listed as Blazar Candidate of Uncertain type (BCU), or sources without a conclusive classification. We use the Empirical Cumulative Distribution Functions (ECDF) and the Artificial Neural Networks (ANN) for a fast method of screening and classification for BCUs based on data collected at $\\gamma$-ray energies only, when rigorous multiwavelength analysis is not available. Based on our method, we classify 342 BCUs as BL Lacs and 154 as FSRQs, while 77 objects remain uncertain. Moreover, radio analysis and direct observations in ground-based optical observatories are used as counterparts to the statistical classifications to validate the method. This approach is of interest because of the increasing number ...

  1. Star-forming galaxies at very high redshifts

    OpenAIRE

    Lanzetta, Kenneth M.; Yahil, Amos; Fernandez-Soto, Alberto

    1996-01-01

    Analysis of the deepest available images of the sky, obtained by the Hubble Space Telescope, reveals a large number of candidate high-redshift galaxies. A catalogue of 1,683 objects is presented, with estimated redshifts ranging from $z=0$ to $z>6$. The high-redshift objects are interpreted as regions of star formation associated with the progenitors of present-day normal galaxies at epochs reaching to 95\\% of the time to the Big Bang.

  2. Star-forming galaxies at very high redshifts

    CERN Document Server

    Lanzetta, K M; Fernández-Soto, A; Lanzetta, Kenneth M; Yahil, Amos; Fernandez-Soto, Alberto

    1996-01-01

    Analysis of the deepest available images of the sky, obtained by the Hubble Space Telescope, reveals a large number of candidate high-redshift galaxies. A catalogue of 1,683 objects is presented, with estimated redshifts ranging from z=0 to z>6. The high-redshift objects are interpreted as regions of star formation associated with the progenitors of present-day normal galaxies at epochs reaching to 95\\% of the time to the Big Bang.

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

    Science.gov (United States)

    Wu, Jianfeng; Gallo, Elena

    2016-04-01

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

  4. Very long term observations of blazars candidates for supermassive black hole binaries

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Bašta, Milan

    Trieste: Proceedings of Science, 2008, s. 1-7. ISSN 1824-8039. [Workshop on Blazar Variability across the Electromagnetic Spectrum. Palaiseau (FR), 22.04.2008-25.04.2008] R&D Projects: GA ČR GA205/08/1207; GA ČR GA205/05/2167 Institutional research plan: CEZ:AV0Z10030501 Keywords : cosmic sources * supermassive black holes * high-energy sources Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics http://pos.sissa.it

  5. UNVEILING THE NATURE OF UNIDENTIFIED γ-RAY SOURCES. VI. γ-RAY BLAZAR CANDIDATES IN THE WISH SURVEY AND THEIR RADIO PROPERTIES

    International Nuclear Information System (INIS)

    According to the Fermi Large Area Telescope Second Source Catalog (2FGL), about one-third of the γ-ray sources listed have no assigned counterparts at lower energies. Many statistical methods have been developed to find proper counterparts for these sources. We explore the sky area covered at low radio frequency by the Westerbork in the Southern Hemisphere (WISH) survey to search for blazar-like associations among the unidentified γ-ray sources (UGSs) listed in the 2FGL. Searching the WISH and NRAO Very Large Array Sky Survey radio surveys within the positional uncertainty regions of the 2FGL UGSs, we select as γ-ray blazar candidates the radio sources characterized by flat radio spectra between 352 MHz and 1400 MHz. We propose new γ-ray blazar associations for eight UGSs and we also discuss their spectral properties at low radio frequencies. We compare the radio flux density distribution of the low radio frequency γ-ray blazar candidates with that of γ-ray blazars associated with other methods. We find significant differences between these distributions. Finally, we discuss the results of this association method and its possible applicability to other regions of the sky and future radio surveys

  6. Searching for new gamma-ray blazar candidates in the 3rd Palermo BAT Hard X-ray Catalog with WISE

    OpenAIRE

    Maselli, A.; Massaro, F.; Cusumano, G.; D'Abrusco, R.; La Parola, V.; Paggi, A.; Segreto, A.; Smith, Howard A.; Tosti, G

    2013-01-01

    We searched for gamma-ray blazar candidates among the 382 unidentified hard X-ray sources of the 3rd Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of SWIFT-BAT survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors which characterize the gamma-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope (2LAC). We used this method exploiting the data ...

  7. High-Redshift Radio Galaxies from Deep Fields

    Indian Academy of Sciences (India)

    C. H. Ishwara-Chandra; S. K. Sirothia; Y. Wadadekar; S. Pal

    2011-12-01

    Most of the radio galaxies with > 3 have been found using the red-shift spectral index correlation.We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 100 times deeper than the known high-redshift radio galaxies, with an aim to detect candidate high-redshift radio galaxies. Here we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been imaged at 327, 610 and 1412 MHz with the Westerbork Synthesis Radio Telescope (WSRT) and at 1400 and 4860 MHz with the Very Large Array (VLA). We find about 150 radio sources with spectra steeper than 1. About two-thirds of these are not detected in Sloan Digital Sky Survey (SDSS), hence are strong candidate high-redshift radio galaxies, which need to be further explored with deep infra-red imaging and spectroscopy to estimate the red-shift.

  8. Planck intermediate results XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE⋆

    DEFF Research Database (Denmark)

    Aghanim, N.; Altieri, B.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Beelen, A.; Benabed, K.; Benoit-Levy, A.; Bernard, J. -P.; Bersanelli, M.; Bethermin, M.; Bielewicz, P.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Calabrese, E.; Canameras, R.; Cardoso, J. -F.; Catalano, A.; Chamballu, A.; Chary, R. -R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Crill, B. P.; Curto, A.; Danese, L.; Dassas, K.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Diego, J. M.; Dole, H.; Donzelli, S.; Dore, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Ensslin, T. A.; Falgarone, E.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Frye, B.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Gjerlow, E.; Gonzalez-Nuevo, J.; Gorski, K. M.; Gregorio, A.; Gruppuso, A.; Guery, D.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Hernandez-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihaenen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J. -M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Le Floc'h, E.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; Lopez-Caniego, M.; Lubin, P. M.; Macias-Perez, J. F.; MacKenzie, T.; Maffei, B.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martinache, C.; Martinez-Gonzalez, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Natoli, P.; Negrello, M.; Nesvadba, N. P. H.; Novikov, D.; Novikov, I.; Omont, A.; Pagano, L.; Pajot, Fernand; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J. -L.; Rachen, J. P.; Reach, W. T.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Sygnet, J. -F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Valtchanov, I.; Van Tent, B.; Vieira, J. D.; Vielva, P.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Zacchei, A.; Zonca, A.

    2015-01-01

    We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These "cold" Planck sources, selected using the High Frequency Instrument (HFI) d...

  9. Dark bubbles around high-redshift radio-loud AGN

    CERN Document Server

    Ghisellini, Gabriele

    2016-01-01

    At redshift larger than 3 there is a disagreement between the number of blazars (whose jet is pointing at us) and the number of expected parents (whose jet is pointing elsewhere). Now we strengthen this claim because (i) the number of blazars in the SDSS+FIRST survey increased, demanding a more numerous parent population, and (ii) the detected blazars have a radio flux large enough to be above the FIRST flux limit even if the jet is slightly misaligned. The foreseen number of these slightly misaligned jets, in principle detectable, is much larger than the radio--detected sources in the FIRST+SDSS survey (at redshift larger than 4). This argument is independent of the presence of an isotropic radio component, such as the hot spot or the radio lobe, and does not depend on the bulk Lorentz factor $\\Gamma$. We propose a scenario that ascribes the lack of slightly misaligned sources to an over-obscuration of the nucleus by a bubble" of dust, possibly typical of the first high-redshift quasars.

  10. An eclipsing binary black hole candidate system in the blazar Mrk 421

    CERN Document Server

    Benitez, E; Fraija, N; Hernandez, X; Lopez-Corona, O; Lora-Clavijo, F D; Mendoza, S

    2015-01-01

    Removing strong outbursts from multiwavelength light curves of the blazar Mrk 421, we construct outburstless time series for this system. A model-independent power spectrum light curve analysis in the optical, hard X-ray and gamma-rays of this outburstless state shows clear evidence for a periodicity of \\approx 400 days. A subsequent full maximum likelihood analysis fitting an eclipse model confirms a periodicity of 387.16 days. The power spectrum of the signal in the outburstless state of the source does not follow a flicker noise behaviour and so, the system producing it is not self-organised. This means that the periodicity is not produced by any internal physical processes associated to the central engine. The simplest physical mechanism to which this periodicity could be ascribed is a dynamical effect produced by an orbiting supermassive black hole companion of mass \\sim 10^7 M_\\odot eclipsing the central black hole, which has a mass \\sim 10^8 M_\\odot. The optimal model restricts the physics of the eclip...

  11. Searching for new gamma-ray blazar candidates in the 3rd Palermo BAT Hard X-ray Catalog with WISE

    CERN Document Server

    Maselli, A; Cusumano, G; D'Abrusco, R; La Parola, V; Paggi, A; Segreto, A; Smith, Howard A; Tosti, G

    2013-01-01

    We searched for gamma-ray blazar candidates among the 382 unidentified hard X-ray sources of the 3rd Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of SWIFT-BAT survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors which characterize the gamma-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope (2LAC). We used this method exploiting the data of the all-sky survey performed by the Wide-Field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE gamma-ray blazar candidates located within the BAT positional uncertainty region at 99% confidence level. We obtained a preliminary list of candidates for which we analysed all the available data in the SWIFT archive to complement the information in the literature and in the radio, infrared and optical catalogs with the information on their optical-UV and soft X-ray emis...

  12. Dusty Quasars at High Redshifts

    CERN Document Server

    Weedman, Daniel

    2016-01-01

    A population of quasars at z ~ 2 is determined based on dust luminosities vLv(7.8 um) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio vLv(0.25 um)/vLv(7.8 um) = UV/IR, assumed to measure obscuration of UV luminosity by the dust which produces IR luminosity. Quasar counts at rest frame 7.8 um are determined for quasars in the Bootes field of the NOAO Deep Wide Field Survey using 24 um sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest frame 7.8 um, but the ratio Lv(100 um)/Lv(7.8 um) is about three times high...

  13. The nature of transition blazars

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, J. J.; Anderson, S. F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Plotkin, R. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Brandt, W. N.; Schneider, D. P. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Burnett, T. H. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Myers, A. D., E-mail: jruan@astro.washington.edu [Department of Physics and Astronomy 3905, University of Wyoming, 1000 East University, Laramie, WY 82071 (United States)

    2014-12-10

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

  14. High-redshift obscured quasars

    OpenAIRE

    Martinez-Sansigre, Alejo; Rawlings, Steve

    2007-01-01

    Using mid-infrared and radio criteria, we select a sample of candidate z~2 obscured quasars. Optical spectroscopy confirms about half of these as type-2 quasars, and modelling the population suggests 50-80% of the quasars are obscured. We find some flat radio spectrum type-2 quasars, and tentative evidence for obscuration unrelated to the torus. Using a similar sample, we also find evidence for a significant fraction of Compton-thick quasars.

  15. An Empirical Limit on Extremely High Redshift Galaxies

    CERN Document Server

    Lanzetta, K M; Fernández-Soto, A; Lanzetta, Kenneth M.; Yahil, Amos; Fernandez-Soto, Alberto

    1998-01-01

    We apply the Lyman absorption signature to search for galaxies at redshifts z infrared images are sensitive to a point source 5 sigma detection threshold of AB(22,000) = 23.8, which adopting plausible assumptions to relate rest-frame ultraviolet flux densities to unobscured star formation rates is easily sufficient to detect the star formation rates expected for massive elliptical galaxy formation to quite high redshifts. For q_0 = 0.5, the infrared images are sensitive to an unobscured star formation rate of 100 h^-2 solar masses per year to redshifts as large as z = 17, and for q_0 = 0, the infrared images are sensitive to an unobscured star formation rate of 300 h^-2 solar masses per year to redshifts as large as z = 14. The primary result of the analysis is that only one extremely high redshift galaxy candidate is identified at the 5 sigma level of significance (and four at the 4 sigma level). This implies a strict upper limit to the surface density of extremely high redshift galaxies of < 1.5 arcmin^-...

  16. Swift for blazars

    CERN Document Server

    Ghisellini, G

    2015-01-01

    I will review recent advances in the field of blazars, highlighting the contribution of Swift. Together with other operating satellites (most notably Fermi, but also AGILE, WISE, Planck) and ground based facilities such as Cherenkov telescopes, Swift was (and is) crucial for improving our understanding of blazars. The main advances in the blazar field made possible by Swift includes the opening of the time domain investigation, since there are several sources with hundreds of simultaneous optical, UV and X-ray data taken at different times; the possibility to measure the black hole mass in very powerful blazars, that show clear signs of accretion disk emission; the possibility to classify blazar candidates, through X-ray observations; the finding of the most powerful and distant blazars, emitting strongly in the hard X-ray band accessible to Swift/BAT. All these improvements had and have a great impact on our understanding on how relativistic jets are formed and emit, on their power, and on how the heavy blac...

  17. 1WHSP: an IR-based sample of $\\sim$1,000 VHE $\\gamma$-ray blazar candidates

    CERN Document Server

    Arsioli, B; Giommi, P; Padovani, P; Marrese, P M

    2015-01-01

    Blazars are the dominant type of extragalactic sources at microwave and at $\\gamma$-ray energies. In the most energetic part of the electromagnetic spectrum (E>100GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. HSP blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. We assembled a sample including 992 sou...

  18. Metals and dust in high redshift AGNs

    CERN Document Server

    Maiolino, R; Marconi, A; Schneider, R; Bianchi, S; Pedani, M; Pipino, A; Matteucci, F; Cox, P; Caselli, P

    2006-01-01

    We summarize some recent results on the metallicity and dust properties of Active Galactic Nuclei (AGN) at high redshift (110). The properties of dust in high-z QSOs are discussed within the context of the dust production mechanisms in the early universe. The dust extinction curve is observed to evolve beyond z>4, and by z~6 it is well described by the properties expected for dust produced by SNe, suggesting that the latter is the main mechanism of dust production in the early universe. We also show that the huge dust masses observed in distant QSOs can be accounted for by SN dust within the observational constraints currently available. Finally, we show that QSO winds, which have been proposed as an alternative mechanism of dust production, may also contribute significantly to the total dust budget at high redshift.

  19. Xray observations of high redshift radio galaxies

    CERN Document Server

    Carilli, C L

    2003-01-01

    I summarize Xray properties of high redshift radio galaxies, beginning with a brief review of what has been learned from Xray observations of low redshift powerful radio galaxies (in particular, Cygnus A), and then turning to Chandra observations of four high redshift radio galaxies. Hot Xray emitting atmospheres of the type seen in low redshift clusters are not detected in the high redshift sources, suggesting that these systems are not yet virialized massive clusters, but will likely evolve into such. Xray emission from highly obscured AGN is detected in all cases. Extended Xray emission is also seen, and the extended emission is clearly aligned with the radio source, and on a similar spatial scale. Multiple mechanisms are proposed for this radio-Xray alignment, including inverse Compton scattering of photons from the AGN (the 'Brunetti mechanism'), and thermal emission from ambient gas that is shocked heated by the expanding radio source. The pressure in the high filling factor shocked gas is adequate to c...

  20. BLAZARS IN THE FERMI ERA: THE OVRO 40 m TELESCOPE MONITORING PROGRAM

    International Nuclear Information System (INIS)

    The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > -200) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (6σ), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with almost a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3σ) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z < 1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent.

  1. Identifying high-redshift gamma-ray bursts with RATIR

    Energy Technology Data Exchange (ETDEWEB)

    Littlejohns, O. M.; Butler, N. R. [School of Earth and Space Exploration, Arizona State University, AZ 85287 (United States); Cucchiara, A. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Watson, A. M.; Lee, W. H.; Richer, M. G.; De Diego, J. A.; Georgiev, L.; González, J.; Román-Zúñiga, C. G. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 México, D. F. (Mexico); Kutyrev, A. S.; Troja, E.; Gehrels, N.; Moseley, H. [NASA, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Klein, C. R.; Fox, O. D.; Bloom, J. S. [Astronomy Department, University of California, Berkeley, CA 94720-7450 (United States); Prochaska, J. X.; Ramirez-Ruiz, E. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2014-07-01

    We present a template-fitting algorithm for determining photometric redshifts, z {sub phot}, of candidate high-redshift gamma-ray bursts (GRBs). Using afterglow photometry, obtained by the Reionization and Transients InfraRed (RATIR) camera, this algorithm accounts for the intrinsic GRB afterglow spectral energy distribution, host dust extinction, and the effect of neutral hydrogen (local and cosmological) along the line of sight. We present the results obtained by this algorithm and the RATIR photometry of GRB 130606A, finding a range of best-fit solutions, 5.6 < z {sub phot} < 6.0, for models of several host dust extinction laws (none, the Milky Way, Large Magellanic Clouds, and Small Magellanic Clouds), consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find that our algorithm provides precise measures of z {sub phot} in the ranges of 4 < z {sub phot} ≲ 8 and 9 < z {sub phot} < 10 and can robustly determine when z {sub phot} > 4. Further testing highlights the required caution in cases of highly dust-extincted host galaxies. These tests also show that our algorithm does not erroneously find z {sub phot} < 4 when z {sub sim} > 4, thereby minimizing false negatives and allowing us to rapidly identify all potential high-redshift events.

  2. High-Redshift, Radio-Loud Quasars

    OpenAIRE

    Stern, Daniel

    2000-01-01

    I discuss two programs to study radio-loud quasars at high (z>4) redshift. Quasars are the most luminous, non-transient objects known and are observed to the earliest cosmic epochs. At lower redshifts, radio-loud quasars are associated with host galaxies having deVaucoleurs profiles. By association, identifying and studying a sample of high-redshift, radio-loud quasars provides important clues to the early Universe and potentially probes early-type galaxy formation. The first aspect of this p...

  3. Observations of GRBs at High Redshift

    CERN Document Server

    Tanvir, N R

    2007-01-01

    The extreme luminosity of gamma-ray bursts (GRBs) and their afterglows means they are detectable, in principle, to very high redshifts. Although the redshift distribution of GRBs is difficult to determine, due to incompleteness of present samples, we argue that for Swift-detected bursts the median redshift is between 2.5 and 3, with a few percent likely at z > 6. Thus, GRBs are potentially powerful probes of the era of reionization, and the sources responsible for it. Moreover, it seems likely that they can provide constraints on the star formation history of the universe, and may also help in the determination of the cosmological parameters.

  4. Modelling high redshift Lyman-alpha Emitters

    CERN Document Server

    Garel, Thibault; Guiderdoni, Bruno; Schaerer, Daniel; Verhamme, Anne; Hayes, Matthew

    2012-01-01

    We present a new model for high redshift Lyman-Alpha Emitters (LAEs) in the cosmological context which takes into account the resonant scattering of Ly-a photons through expanding gas. The GALICS semi-analytic model provides us with the physical properties of a large sample of high redshift galaxies. We implement a gas outflow model for each galaxy based on simple scaling arguments. The coupling with a library of numerical experiments of Ly-a transfer through expanding or static dusty shells of gas allows us to derive the Ly-a escape fractions and profiles. The predicted distribution of Ly-a photons escape fraction shows that galaxies with a low star formation rate have a f_esc of the order of unity, suggesting that, for those objects, Ly-a may be used to trace the star formation rate assuming a given conversion law. In galaxies forming stars intensely, the escape fraction spans the whole range from 0 to 1. The model is able to get a good match to the UV and Ly-a luminosity function (LF) data at 3 < z <...

  5. Radio-loud high-redshift protogalaxy canidates in Bootes

    Energy Technology Data Exchange (ETDEWEB)

    Croft, S; van Breugel, W; Brown, M J; de Vries, W; Dey, A; Eisenhardt, P; Jannuzi, B; Rottgering, H; Stanford, S A; Stern, D; Willner, S P

    2007-07-20

    We used the Near Infrared Camera (NIRC) on Keck I to obtain K{sub s}-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z{sub phot} = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in K{sub s}-band, suggesting that they are still in the process of forming.

  6. The AKARI Deep Field South: Pushing to High Redshift

    CERN Document Server

    Clements, David L

    2016-01-01

    The AKARI Deep Field South (ADF-S) is a large extragalactic survey field that is covered by multiple instruments, from optical to far-IR and radio. I summarise recent results in this and related fields prompted by the release of the Herschel far-IR/submm images, including studies of cold dust in nearby galaxies, the identification of strongly lensed distant galaxies, and the use of colour selection to find candidate very high redshift sources. I conclude that the potential for significant new results from the ADF-S is very great. The addition of new wavelength bands in the future, eg. from Euclid, SKA, ALMA and elsewhere, will boost the importance of this field still further.

  7. Blazar Observations with the MAGIC Telescope

    Science.gov (United States)

    Kneiske, T. M.; Mannheim, K.

    The MAGIC Telescope will be able to detect gamma gay sources down to energies of 30GeV. Therefore a large number of sources will be seen, especially blazars. 30 GeV is also the upper energy limit of EGRET. Therefore it is possible to extrapolate a spectrum of an EGRET source without a complicated model. We make first predictions about the detectability of EGRET blazars calculating the minimum observation time for the MAGIC Telescope. Blazars are often located at high redshifts and their spectra should show some cut-offs at high energies due to pair production processes with low energy background photons. We developed a background radiation model using recent results of optical to infrared data and included this absorption effect in our calculation about the observability. We found that the shape of the spectrum and the intergalactic absorption does not make a big difference for a simple detection of the source. The observation time is only dependent on the flux near the energy threshold of the telescope (30 GeV) and the zenith angle of the blazar. The results are showing that MAGIC will be able to detect more than 50% of the EGRET sources even at high redshift and therefore it will be a good tool for multi-wavelength campaigns.

  8. Near real-time selection of high redshift GRBs with Swift

    OpenAIRE

    Campana, S.; Tagliaferri, G.; Malesani, D.; Stella, L.; D'Avanzo, P.; Chincarini, G.; S. Covino(INAF - Oss. Astronomico di Brera)

    2006-01-01

    A good fraction of GRBs detected by Swift are at a large redshift (up to z=6.3, so far). Their study allows us to investigate, among other things, the cosmic star formation in the early Universe (possibly up to the re-ionization era) and the chemical enrichment of the high-redshift gas. Here we present and discuss a method of selection which identifies high-redshift candidates based only upon promptly-available information provided by Swift. This method relies upon, Galactic extinction, GRB d...

  9. NuSTAR Detection of the Blazar B2 1023+25 at Redshift 5.3

    Science.gov (United States)

    Sbarrato, T.; Tagliaferri, G.; Ghisellini, G.; Perri, M.; Puccetti, S.; Balokovic, M.; Nardini, M.; Stern, D.; Boggs, S. E.; Brandt, W. N.; Christensen, F. E.; Giommi, P.; Greiner, J.; Hailey, C. J.; Harrison, F. A.; Hovatta, T.; Madejski, G. M.; Rau, A.; Schady, P.; Sudilovsky, V.; Urry, C. M.; Zhang, William W.

    2013-01-01

    B2 1023+25 is an extremely radio-loud quasar at zeta = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is approximately 5.5 × 10 (exp -14) erg cm(exp -2) s(exp -1) (5-10 keV) and the photon spectral index is Gamma(x) approx. =1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of approximately 3deg, and has significant Doppler boosting, with a large bulk Lorentz factor approximately 13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

  10. NuSTAR detection of the blazar B2 1023+25 at redshift 5.3

    CERN Document Server

    Sbarrato, T; Ghisellini, G; Perri, M; Puccetti, S; Balokovic, M; Nardini, M; Stern, D; Boggs, S E; Brandt, W N; Chirstensen, F E; Giommi, P; Greiner, J; Hailey, C J; Harrison, F; Hovatta, T; Madejski, G M; Rau, A; Schady, P; Sudilovsky, V; Urry, C M; Zhang, W W

    2013-01-01

    B2 1023+25 is an extremely radio-loud quasar at z=5.3 which was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ~5.5x10^(-14) erg cm^(-2)s^(-1) (5-10keV) and the photon spectral index is Gamma_X=1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ~3deg, and has significant Doppler boosting, with a large bulk Lorentz factor ~13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray Universe and to study extremely active supermassive black holes located at very high redshift.

  11. NuSTAR DETECTION OF THE BLAZAR B2 1023+25 AT REDSHIFT 5.3

    International Nuclear Information System (INIS)

    B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ∼ 5.5 x 10-14 erg cm-2 s-1 (5-10 keV) and the photon spectral index is ΓX ≅ 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ∼3°, and has significant Doppler boosting, with a large bulk Lorentz factor ∼13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift

  12. NuSTAR DETECTION OF THE BLAZAR B2 1023+25 AT REDSHIFT 5.3

    Energy Technology Data Exchange (ETDEWEB)

    Sbarrato, T. [Dipartimento di Scienza e Alta Tecnologia, Università dell' Insubria, Via Valleggio 11, I-22100 Como (Italy); Tagliaferri, G.; Ghisellini, G. [INAF-Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy); Perri, M.; Puccetti, S.; Giommi, P. [ASI-Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy); Baloković, M.; Harrison, F. A.; Hovatta, T. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Nardini, M. [Dipartimento di Fisica G. Occhialini, Università di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Greiner, J.; Rau, A.; Schady, P.; Sudilovsky, V. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Madejski, G. M., E-mail: tullia.sbarrato@brera.inaf.it [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); and others

    2013-11-10

    B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is ∼ 5.5 x 10{sup -14} erg cm{sup -2} s{sup -1} (5-10 keV) and the photon spectral index is Γ{sub X} ≅ 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of ∼3°, and has significant Doppler boosting, with a large bulk Lorentz factor ∼13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

  13. The visibility of high-redshift galaxies

    International Nuclear Information System (INIS)

    The most visible galaxies - that is, those which have the largest apparent sizes and isophotal luminosities when seen at a given distance - are those with a particular observed surface brightness. Extending this argument to high-redshift galaxies, it is clear that this optimum surface brightness moves progressively to brighter intrinsic surface brightnesses, so as to counteract the effect of K-corrections and cosmological dimming. Thus the galaxies appearing in faint surveys will be from a population distinctly different from those 'normal' galaxies observed nearby. Galaxies in deep surveys are more likely to be spirals and to be of high surface brightness. This has very important implications for observational studies of galaxy evolution. (author)

  14. Morphologies at High Redshift from Galaxy Zoo

    Science.gov (United States)

    Masters, Karen; Melvin, Tom; Simmons, Brooke; Willett, Kyle; Lintott, Chris

    2015-08-01

    I will present results from Galaxy Zoo classification of galaxies observed in public observed frame optical HST surveys (e.g. COSMOS, GOODS) as well as in observed frame NIR with (ie. CANDELS). Early science results from these classifications have investigated the changing bar fraction in disc galaxies as a function of redshift (to z~1 in Melvin et al. 2014; and at z>1 in Simmons et al. 2015), as well as how the morphologies of galaxies on the red sequence have been changing since z~1 (Melvin et al. in prep.). These unique dataset of quantitative visual classifications for high redshift galaxies will be made public in forthcoming publications (planned as Willett et al. for Galaxy Zoo Hubble, and Simmons et al. for Galaxy Zoo CANDELS).

  15. A flat spectrum candidate for a track-type high energy neutrino emission event, the case of blazar PKS 0723-008

    CERN Document Server

    Kun, E; Gergely, L Á

    2016-01-01

    In this Letter we present a model for consecutive emission of low frequency gravitational waves, high energy neutrinos, ultra-high energy cosmic rays, and luminous radio afterglow, all generated by the merger of two supermassive black holes acting as engine. The main contributing events are the spin-flip of the dominant black hole, gravitational wave burst, final coalescence, followed by formation of a new jet, particle acceleration and interaction with the surrounding material (leading to a radio flux density peak and the hardening at radio frequencies). Cross-correlating the Parkes Catalogue and the 2nd Planck Catalogue of Compact Sources with the arrival direction of the track-type neutrino detections by the IceCube, two flat spectrum radio sources emerge as possible origin in the framework of the proposed model. We discuss the blazar PKS 0723-008 as an excellent candidate exhibiting key elements of this complex process, with traces of a spin-flip, high-energy neutrino emission, and five-fold increased rad...

  16. SDSS J013127.34-032100.1: a candidate blazar with a 11 billion solar mass black hole at $z$=5.18

    CERN Document Server

    Ghisellini, G; Sbarrato, T; Gehrels, N

    2015-01-01

    The radio-loud quasar SDSS J013127.34-032100.1 at a redshift z=5.18 is one of the most distant radio-loud objects. The radio to optical flux ratio (i.e. the radio-loudness) of the source is large, making it a promising blazar candidate. Its overall spectral energy distribution, completed by the X-ray flux and slope derived through Target of Opportunity Swift/XRT observations, is interpreted by a jet non-thermal plus an accretion disc and molecular torus model. We estimate that its black hole mass is (1.1+-0.2)e10 Msun, the largest found at these redshifts. We derive a viewing angle between 3 and 5 degrees. This implies that there must be other (hundreds) sources with the same black hole mass of SDSS J013127.34-032100.1, but whose jets are pointing away from Earth. We discuss the problems posed by the existence of such large black hole masses at such redshifts, especially in jetted quasars. In fact, if they are associated to rapidly spinning black holes, the accretion efficiency is high, implying a slower pace...

  17. Application of the MST clustering to the high energy gamma-ray sky. II - Possible detection of gamma-ray emission from blazar candidates in the 1WHSP sample

    CERN Document Server

    Campana, R; Bernieri, E

    2016-01-01

    We present the results of a photon cluster search in the 7-years Fermi-Large Area Telescope extragalactic Pass 8 gamma-ray sky by means of the Minimum Spanning Tree (MST) algorithm, at energies higher than 10 GeV. We found 16 clusters of photons, corresponding to candidate gamma-ray sources, located very close to infrared-selected sources in the 1WHSP (WISE High Synchrotron Peaked) sample, and therein classified as either "new" or "candidate" blazars. In this paper some properties of the MST clusters and of the associated sources are presented.

  18. Application of the MST clustering to the high energy γ-ray sky. II—Possible detection of γ-ray emission from blazar candidates in the 1WHSP sample

    Science.gov (United States)

    Campana, R.; Massaro, E.; Bernieri, E.

    2016-06-01

    We present the results of a photon cluster search in the 7-years Fermi-Large Area Telescope extragalactic Pass 8 γ-ray sky by means of the Minimum Spanning Tree (MST) algorithm, at energies higher than 10 GeV. We found 16 clusters of photons, corresponding to candidate γ-ray sources, located very close to infrared-selected sources in the 1WHSP (WISE High Synchrotron Peaked) sample, and therein classified as either "new" or "candidate" blazars. In this paper some properties of the MST clusters and of the associated sources are presented.

  19. Jets, black holes and disks in blazars

    Directory of Open Access Journals (Sweden)

    Ghisellini Gabriele

    2013-12-01

    Full Text Available The Fermi and Swift satellites, together with ground based Cherenkov telescopes, has greatly improved our knowledge of blazars, namely Flat Spectrum Radio Quasars and BL Lac objects, since all but the most powerful emit most of their electro–magnetic output at γ–ray energies, while the very powerful blazars emit mostly in the hard X–ray region of the spectrum. Often they show coordinated variability at different frequencies, suggesting that in these cases the same population of electrons is at work, in a single zone of the jet. The location of this region along the jet is a matter of debate. The jet power correlates with the mass accretion rate, with jets existing at all values of disk luminosities, measured in Eddington units, sampled so far. The most powerful blazars show clear evidence of the emission from their disks, and this has revived methods of finding the black hole mass and accretion rate by modelling a disk spectrum to the data. Being so luminous, blazars can be detected also at very high redshift, and therefore are a useful tool to explore the far universe. One interesting line of research concerns how heavy are their black holes at high redshifts. If we associate the presence of a relativistic jets with a fastly spinning black hole, then we naively expect that the accretion efficiency is larger than for non–spinning holes. As a consequence, the black hole mass in jetted systems should grow at a slower rate. In turn, this would imply that, at high redshifts, the heaviest black holes should be in radio–quiet quasars. We instead have evidences of the opposite, challenging our simple ideas of how a black hole grows.

  20. FRONTIER FIELDS: HIGH-REDSHIFT PREDICTIONS AND EARLY RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Coe, Dan; Bradley, Larry [Space Telescope Science Institute, Baltimore, MD (United States); Zitrin, Adi, E-mail: DCoe@STScI.edu [California Institute of Technology, Pasadena, CA (United States)

    2015-02-20

    The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new ''blank'' fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Previous programs have yielded a dozen or so z > 9 candidates, including perhaps fewer than expected in the Ultra Deep Field and more than expected in shallower Hubble images. In this paper, we present high-redshift (z > 6) number count predictions for the Frontier Fields and candidates in three of the first Hubble images. We show the full Frontier Fields program may yield up to ∼70 z > 9 candidates (∼6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 < z < 8 and gravitational lensing models submitted by the community. However, in the first two deep infrared Hubble images obtained to date, we find z ∼ 8 candidates but no strong candidates at z > 9. We defer quantitative analysis of the z > 9 deficit (including detection completeness estimates) to future work including additional data. At these redshifts, cosmic variance (field-to-field variation) is expected to be significant (greater than ±50%) and include clustering of early galaxies formed in overdensities. The full Frontier Fields program will significantly mitigate this uncertainty by observing six independent sightlines each with a lensing cluster and nearby blank field.

  1. High Redshift Galaxy Populations and their Descendants

    CERN Document Server

    Guo, Qi

    2008-01-01

    We study model predictions for three high-redshift galaxy populations: Lyman break galaxies at z~3 (LBGs), optically selected star-forming galaxies at z~2 (BXs), and distant red galaxies at z~2 (DRGs).Our galaxy formation model simultaneously reproduces the abundances, redshift distributions and clustering of all three observed populations. The star formation rates (SFRs) of model LBGs and BXs are lower than those quoted for real samples, reflecting different initial mass functions and scatter in model dust properties. About 85% of model galaxies selected as DRGs are star-forming, with SFRs ranging up to 100 M_sun/yr. Model LBGs, BXs and DRGs together account for less than half of all star formation over the range 1.510^{11}M_sun are classified as LBGs or BXs at the relevant redshifts, while 65% are classified as DRGs. Almost all model LBGs and BXs are central galaxies, but about a quarter of DRGs are satellites. Half of all LBG descendants at z=2 would be identified as BX's, but very few as DRGs. Clustering ...

  2. High Energy Continuum of High Redshift Quasars

    Science.gov (United States)

    Elvis, Martin

    2000-01-01

    Discussion with the RXTE team at GSFC showed that a sufficiently accurate background subtraction procedure had now, been derived for sources at the flux level of PKS 2126-158. However this solution does not apply to observations carried out before April 1997, including our observation. The prospect of an improved solution becoming available soon is slim. As a result the RXTE team agreed to re-observe PKS2126-158. The new observation was carried out in April 1999. Quasi-simultaneous optical observations were obtained, as Service observing., at the 4-meter Anglo-Australian Telescope, and ftp-ed from the AAT on 22April. The RXTE data was processed in late June, arriving at SAO in early July. Coincidentally, our collaborative Beppo-SAX observation of PKS2126-158 was made later in 1999, and a GTO Chandra observation (with which we are involved) was made on November 16. Since this gives us a unique monitoring data for a high redshift quasar over a broad pass-band we are now combining all three observations into a single comprehensive study Final publication of the RXTE data will thus take place under another grant.

  3. Absorption features of high redshift galactic winds

    CERN Document Server

    Fangano, A P M; Richter, P

    2007-01-01

    The environment of high-redshift galaxies is characterized by both wind-driven outflowing gas and gravitationally infalling streams. To investigate such galaxy-IGM interplay we have generated synthetic optical absorption line spectra piercing the volume surrounding a starbursting analog of a Lyman Break Galaxy selected in a $z \\approx 3$ output from a SPH simulation, including a detailed treatment of mechanical feedback from winds. Distributions for several observable species (HI, CIII, CIV, SiII, SiIII, SiIV, OVI, OVII, and OVIII) have been derived by post-processing the simulation outputs. The hot wind material is characterized by the presence of high-ionization species such as OVI, OVII, and OVIII (the latter two observable only in X-ray bands); the colder ($T<10^{5.5}$ K) infalling streams can be instead identified by the combined presence of SiII, SiIII, and CIII optical absorption together with OVI that surrounds the cooler gas clumps. However, both line profile and Pixel Optical Depth analysis of th...

  4. Early metal enrichment in high-redshift quasars

    OpenAIRE

    Maiolino, R.

    2009-01-01

    Quasars are powerful systems whose spectrum is rich of metal features that allow us to investigate the chemical evolution of galaxies at very high redshift, even close to the reionization epoch. I review the main observational constraints on the metallicity of quasars host galaxies at high redshift and discuss the implications and issues for models of galaxy evolution in the early universe.

  5. Extremes of the jet-accretion power relation of blazars, as explored by NuSTAR

    CERN Document Server

    Sbarrato, T; Tagliaferri, G; Perri, M; Madejski, G M; Stern, D; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Harrison, F A; Zhang, W W

    2015-01-01

    Hard X-ray observations are crucial to study the non-thermal jet emission from high-redshift, powerful blazars. We observed two bright z>2 flat spectrum radio quasars (FSRQs) in hard X-rays to explore the details of their relativistic jets and their possible variability. S5 0014+81 (at z=3.366) and B0222+185 (at z=2.690) have been observed twice by the Nuclear Spectroscopic Telescope Array (NuSTAR) simultaneously with Swift/XRT, showing different variability behaviours. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when no gamma-ray emission is detected. The two sources have proven to have respectively the most luminous accretion disk and the most powerful jet among known blazars. They are located at the extreme end of the jet-accretion disk relation previously found for gamma-ray detected blazars.

  6. Bayesian High-Redshift Quasar Classification from Optical and Mid-IR Photometry

    CERN Document Server

    Richards, Gordon T; Peters, Christina M; Krawczyk, Coleman M; Chase, Greg; Ross, Nicholas P; Fan, Xiaohui; Jiang, Linhua; Lacy, Mark; McGreer, Ian D; Trump, Jonathan R; Riegel, Ryan N

    2015-01-01

    We identify 885,503 type 1 quasar candidates to i3.5 than the traditional mid-IR selection "wedges" and to 2.23. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.

  7. The infrared-dark dust content of high redshift galaxies

    CERN Document Server

    Ferrara, A; Ouchi, M; Fujimoto, S

    2016-01-01

    We present a theoretical model aimed at explaining the IRX-$\\beta$ relation for high redshift (z >5) galaxies. Recent observations (Capak+2015; Bouwens+2016) have shown that early Lyman Break Galaxies, although characterized by a large UV attenuation (e.g. flat UV beta slopes), show a striking FIR deficit, i.e. they are "infrared-dark". This marked deviation from the local IRX-beta relation can be explained by the larger molecular gas content of these systems. While dust in the diffuse ISM attains relatively high temperatures (Td = 45 K for typical size a=0.1 um; smaller grains can reach Td = 60 K), a sizable fraction of the dust mass is embedded in dense gas, and therefore remains cold. If confirmed, the FIR deficit might represent a novel, powerful indicator of the molecular content of high-z galaxies which can be used to pre-select candidates for follow-up deep CO observations. Thus, high-z CO line searches with ALMA might be much more promising than currently thought.

  8. Photometric selection of high-redshift type Ia supernovae

    CERN Document Server

    Sullivan, M; Perrett, K; Nugent, P; Astier, Pierre; Aubourg, E; Balam, D; Basa, S; Carlberg, R; Conley, A; Fabbro, S; Fouchez, D; Guy, J; Hook, I; Lafoux, H; Neill, J D; Pain, R; Palanque-Delabrouille, Nathalie; Pritchet, C; Regnault, N; Rich, J; Taillet, R; Aldering, G; Baumont, S; Bronder, J; Filiol, M; Knop, R; Perlmutter, S; Tao, C

    2005-01-01

    We present a method for selecting high-redshift type Ia supernovae (SNe Ia) located via rolling SN searches. The technique, using both color and magnitude information of events from only 2-3 epochs of multi-band real-time photometry, is able to discriminate between SNe Ia and core collapse SNe. Furthermore, for the SNe Ia, the method accurately predicts the redshift, phase and light-curve parameterization of these events based only on pre-maximum-light data. We demonstrate the effectiveness of the technique on a simulated survey of SNe Ia and core-collapse SNe, where the selection method effectively rejects most core-collapse SNe while retaining SNe Ia. We also apply the selection code to real-time data acquired as part of the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). During the period May 2004 to January 2005 in the SNLS, 440 SN candidates were discovered of which 70 were confirmed spectroscopically as SNe Ia and 15 as core-collapse events. For this test dataset, the selection technique ...

  9. Gemini Spectroscopy of Supernovae from SNLS: Improving High Redshift SN Selection and Classification

    CERN Document Server

    Howell, D A; Perrett, K; Bronder, T J; Hook, I M; Astier, Pierre; Aubourg, E; Balam, D; Basa, S; Carlberg, R G; Fabbro, S; Fouchez, D; Guy, J; Lafoux, H; Neill, J D; Pain, R; Palanque-Delabrouille, Nathalie; Pritchet, C J; Regnault, N; Rich, J; Taillet, R; Knop, R; McMahon, R G; Perlmutter, S; Walton, N A

    2005-01-01

    We present new techiques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing five year project with the goal of measuring the equation of state of Dark Energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, where the median SN Ia redshift is z=0.81 (0.155 <= z <= 1.01). These improvements were realized because we use the unprecedented color coverage and lightcurve sampling of the SNLS to predict whether a candidate is an SN Ia and estimate its redshift, before obtaining a spectrum, using a new technique called the "SN pho...

  10. Which blazars are neutrino loud?

    International Nuclear Information System (INIS)

    Protons accelerated in the cores of active galactic nuclei can effectively produce neutrinos only if the soft radiation background in the core is sufficiently high. We find restrictions on the spectral properties and luminosity of blazars under which they can be strong neutrino sources. We analyze the possibility that the neutrino flux is highly beamed along the rotation axis of the central black hole. The enhancement of the neutrino flux compared to the GeV γ-ray flux from a given source makes the detection of neutrino point sources more probable. At the same time the smaller open angle reduces the number of possible neutrino-loud blazars compared to the number of γ-ray loud ones. We present a table of 15 blazars which are the most likely candidates for the detection by future neutrino telescopes

  11. The Environments of High Redshift QSOs

    CERN Document Server

    Kim, Soyoung; Trenti, M; Pavlovsky, C M; Djorgovski, S G; Scarlata, C; Stern, D; Mahabal, A; Thompson, D; Dickinson, M; Panagia, N; Meylan, G

    2008-01-01

    We present a sample of i-dropout candidates identified in five Hubble Advanced Camera for Surveys fields centered on Sloan Digital Sky Surveys QSOs at redshift $z\\sim 6$. Our fields are as deep as the Great Observatory Origins Deep Survey (GOODS) ACS images which are used as a reference field sample. The galaxies are color-selected. We find them to be overdense in two fields, underdense in two fields, and as dense as the average density of GOODS in one field. The two excess fields show significantly different color distribution from that of GOODS at the 99.5% confidence level, strengthening the idea that the excess objects are indeed associated with the QSO. The distribution of {\\it i}-dropout counts in the five fields is broader than that derived from GOODS at the 80% to 98.5% confidence level, depending on which selection criteria were adopted to identify i-drops; its width cannot be explained by cosmic variance alone. However, the observed excess counts are compatible with what one would expect if QSOs at ...

  12. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

    CERN Document Server

    Fan, X

    1999-01-01

    We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg^2 of five-color (u'g'r'i'z') imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z=4.63, 4.75, 4.90 and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z > 4 objects were recovered from the data. The quasars all have i* < 20 and have luminosities comparable to that of 3C273. The spectra of the quasars have similar features (strong, broad emission lines and substantial absorption blueward of the Ly alpha emission line) seen in previously known high-redshift quasars. Although the photometric accuracy and image quality fail to meet the final survey requirements, our success rate for identifying high-redshift quasars (17 quasars from 27 candidates) is much higher than that of previ...

  13. Gamma-ray astronomy from the ground and the space: first analyses of the HESS-II hybrid array and search for blazar candidates among the unidentified Fermi-LAT sources

    International Nuclear Information System (INIS)

    This manuscript is about high energy gamma-ray astronomy (between 30 GeV and 300 GeV) with the Fermi-LAT satellite and very high energy gamma-ray astronomy (above ∼100 GeV) via the H.E.S.S. experiment. The second phase of the H.E.S.S. experiment began in July 2012 with the inauguration of a fifth 28 m-diameter telescope added to the initial array composed of four 12 m-diameter imaging atmospheric Cherenkov telescopes. In the first part of this thesis, we present the development of an analysis in hybrid mode based on a multivariate method dedicated to detect and study sources with different spectral shapes and the first analysis results on real data. The second part is dedicated to the research of blazar candidates among the Fermi-LAT unidentified sources of the 2FGL catalog. A first development is based on a multivariate approach using discriminant parameters built with the 2FGL catalog parameters. A second development is done with the use of the WISE satellite catalog and a non-parametric technic in order to find the blazar-like infrared counterparts of the unidentified sources of the 2FGL catalog. (author)

  14. The high redshift Integrated Sachs-Wolfe effect

    International Nuclear Information System (INIS)

    In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky Survey Data Release Six (SDSS DR6) of about one million photometrically selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high redshift, aiming at constraining the behavior of the expansion rate and thus the behaviour of dark energy at those epochs. This unique sample significantly extends previous catalogs to higher redshifts while retaining high efficiency in the selection algorithm. We compute the auto-correlation function (ACF) of QSO number density from which we extract the bias and the stellar contamination. We then calculate the cross-correlation function (CCF) between QSO number density and Cosmic Microwave Background (CMB) temperature fluctuations in different subsamples: at high z > 1.5 and low z 1.5. We focus on the capabilities of the ISW to constrain the behaviour of the dark energy component at high redshift both in the Λ CDM and Early Dark Energy cosmologies, when the dark energy is substantially unconstrained by observations. At present, the inclusion of the ISW data results in a poor improvement compared to the obtained constraints from other cosmological datasets. We study the capabilities of future high-redshift QSO survey and find that the ISW signal can improve the constraints on the most important cosmological parameters derived from Planck CMB data, including the high redshift dark energy abundance, by a factor ∼ 1.5

  15. High Redshift Intergalactic Medium: Probes and Physical Models

    CERN Document Server

    Sethi, S K

    2004-01-01

    Recent years have seen major advances in understanding the state of the intergalactic medium (IGM) at high redshift. Some aspects of this understanding are reviewed here. In particular, we discuss: (1) Different probes of IGM like Gunn-Peterson test, CMBR anisotropies, and neutral hydrogen emission from reionization, and (2) some models of reionization of the universe.

  16. High-Redshift Galaxies: The HDF and More

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Yahil, A.

    1998-01-01

    We review our present knowledge of high-redshift galaxies, emphasizing particularly their physical properties and the ways in which they relate to present-day galaxies. We also present a catalogue of photometric redshifts of galaxies in the Hubble Deep Field and discuss the possibilities that this kind of study offers to complete the standard spectroscopically based surveys.

  17. High-Redshift Galaxies The HDF and More

    CERN Document Server

    Fernández-Soto, A; Yahil, A

    1998-01-01

    We review our present knowledge of high-redshift galaxies, emphasizing particularly their physical properties and the ways in which they relate to present-day galaxies. We also present a catalogue of photometric redshifts of galaxies in the Hubble Deep Field and discuss the possibilities that this kind of study offers to complete the standard spectroscopically based surveys.

  18. Chandra Survey of Radio-quiet, High-redshift Quasars

    CERN Document Server

    Bechtold, J; Shields, J; Czerny, B; Janiuk, A; Hamann, F; Aldcroft, T L; Elvis, M; Dobrzycki, A; Bechtold, Jill; Siemiginowska, Aneta; Shields, Joseph; Czerny, Bozena; Janiuk, Agnieszka; Hamann, Fred; Aldcroft, Thomas L.; Elvis, Martin; Dobrzycki, Adam

    2003-01-01

    We observed 17 optically-selected, radio-quiet high-redshift quasars with the Chandra Observatory ACIS, and detected 16 of them. The quasars have redshift between 3.70 and 6.28 and include the highest redshift quasars known. When compared to low-redshift quasars observed with ROSAT, these high redshift quasars are significantly more X-ray quiet. We also find that the X-ray spectral index of the high redshift objects is flatter than the average at lower redshift. These trends confirm the predictions of models where the accretion flow is described by a cold, optically-thick accretion disk surrounded by a hot, optically thin corona, provided the viscosity parameter alpha >= 0.02. The high redshift quasars have supermassive black holes with masses ~10^{10} M_{sun}, and are accreting material at ~0.1 the Eddington limit. We detect 10 X-ray photons from the z=6.28 quasar SDS 1030+0524, which may have a Gunn-Peterson trough and be near the redshift of reionization of the intergalactic medium. The X-ray data place an...

  19. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

    Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Brandt, W. N.;

    2009-01-01

    We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z > 4. These weak emission-line quasars (WLQs) constitute a promine...

  20. Leveraging Spitzer's Legacy: Quasars and Feedback at High Redshift

    Science.gov (United States)

    Richards, Gordon; Anderson, Scott; Bauer, Franz; Deo, Rajesh; Fan, Xiaohui; Gallagher, Sarah; Myers, Adam; Strauss, Michael; Zakamska, Nadia

    2009-04-01

    Recent research efforts to understand the evolution of galaxies and quasars are beginning to form a consistent picture. Galaxies and their supermassive black holes grow through mergers, but with decreasing characteristic mass scales over time. Much less, however, is known about the evolution of galaxies at high redshifts and the role played by energy injection from the onset of active black hole growth. Understanding these events requires investigating a statistically significant number of high-redshift quasars and crossing the L* boundary in luminosity. To construct an appropriate data set requires both relatively wide-areas (to find these rare objects) and moderate-depth imaging (to probe below L* in luminosity). Unfortunately, existing optical and MIR surveys fail to meet both of these requirements. Furthermore, both optical and MIR quasar selection are blindest at the most crucial redshifts. Here we propose to address these gaps with targeted IRAC observations of a few hundred high-redshift quasars from the Sloan Digital Sky Survey. Such a sample will enable the construction of a proper training set for the discovery of 2.5learn how to identify high-redshift quasars in other fields over a large range in luminosity. With this knowledge, we will crack open the high-z quasar discovery space within existing IRAC legacy surveys (SWIRE, XFLS, Bootes, COSMOS). With a large sample of high-redshift quasars spanning a large range in luminosity, we can turn the quasar luminosity function and quasar clustering analysis into tools for distinguishing between different evolutionary models and feedback prescriptions. In all, we will observe 330 SDSS quasars using 307 pointings/AORs, totaling 48.5 hours of IRAC time.

  1. Cosmic ray loading and PeV neutrino production in blazars

    CERN Document Server

    Zhang, B Theodore

    2016-01-01

    IceCube has reported the detection of PeV neutrinos, for which blazars are strong candidate sources. The stacking search of neutrinos for known individual blazars by IceCube, however, puts stringent upper limit to their neutrino flux. Here using the upper limit we constrain the cosmic ray loading factor in blazars, i.e., the ratio of the cosmic ray to bolometric radiation luminosity of blazar jets is $\\xi_{\\rm cr}\\la2$ for flat cosmic ray spectrum. Combined with the blazar density measured by Fermi-LAT, we compute the limit to the diffuse PeV neutrino flux produced by all-sky blazars, and find that blazars, dominated by flat spectrum radio quasars, can only contribute a fraction $\\la10\\%$ of the IceCube detected diffuse PeV neutrino flux. Thus blazars can hardly be the sources of the bulk PeV neutrinos.

  2. An optical and infrared study of blazars

    Science.gov (United States)

    Mead, Andrew Robert Graham

    Some of the optical and infrared properties of blazars are discussed. The evidence of bulk relativistic flows in quasars and blazars is also discussed. The observational study has two parts. First a series of infrared and optical polarization measurements are presented. Second a study of the cluster environments of blazars is reported. The polarization study consisted of 156 observations of 37 blazars and candidate blazars at infrared and optical frequencies. The observations of the quasar 1253-055 (3C 279) showed a U polarization of 45.5 + or - 0.9 percent. This is the highest ever seen in a blazar. The effect of the proposed blue bump on the observations of 1641+399 (3C 345) is discussed, as are other sources of unpolarized contaminating flux. The interpretation of the observed spectrum is discussed in terms of shock acceleration models and the synchrotron-self-Compton jet pictures. It is shown that frequency dependence is a common feature of the polarization behavior with the polarization generally increasing towards higher frequencies. No evidence is found to support the claim that frequency dependence is related to high levels of polarization. The possible explanations of the observed frequency dependence are discussed. The study of the cluster environments of blazars was formulated as a test of a unified scheme. Deep CCD observations were obtained for a sample of blazars and quasars with extended radio structure. The strength of the cluster environment was parameterized by the amplitude of the quasar-galaxy spatial correlation function Bgq. The evaluation of this quantity is subject to large systematic errors as a result of the uncertainty in the galaxy luminosity function.

  3. The high redshift galaxy population in hierarchical galaxy formation models

    CERN Document Server

    Kitzbichler, M G; Kitzbichler, Manfred G.; White, Simon D. M.

    2006-01-01

    We compare observations of the high redshift galaxy population to the predictions of the galaxy formation model of Croton et al. (2006). This model, implemented on the Millennium Simulation of the concordance LCDM cosmogony, introduces "radio mode" feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the low redshift galaxy population. Here we compare the predictions of this same model to the observed counts and redshift distributions of faint galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment gives moderately good agreement with most of the data, although the predicted abundance of relatively massive (~M*) galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this mo...

  4. Detectability of Gravitational Waves from High-Redshift Binaries.

    Science.gov (United States)

    Rosado, Pablo A; Lasky, Paul D; Thrane, Eric; Zhu, Xingjiang; Mandel, Ilya; Sesana, Alberto

    2016-03-11

    Recent nondetection of gravitational-wave backgrounds from pulsar timing arrays casts further uncertainty on the evolution of supermassive black hole binaries. We study the capabilities of current gravitational-wave observatories to detect individual binaries and demonstrate that, contrary to conventional wisdom, some are, in principle, detectable throughout the Universe. In particular, a binary with rest-frame mass ≳10^{10}M_{⊙} can be detected by current timing arrays at arbitrarily high redshifts. The same claim will apply for less massive binaries with more sensitive future arrays. As a consequence, future searches for nanohertz gravitational waves could be expanded to target evolving high-redshift binaries. We calculate the maximum distance at which binaries can be observed with pulsar timing arrays and other detectors, properly accounting for redshift and using realistic binary waveforms. PMID:27015470

  5. Infrared/optical energy distributions of high redshifted quasars

    Science.gov (United States)

    Soifer, B. T.; Neugebauer, G.; Oke, J. B.; Matthews, K.; Lacy, J. H.

    1982-01-01

    Measurements at 1.2, 1.6 and 2.2 microns were combined with visual spectrophotometry of 21 quasars having redshifts z or = 2.66. The primary result is that the rest frame visual/ultraviolet continua of the high redshift quasars are well described by a sum of a power law continuum with slope of approximately -0.4 and a 3000 A bump. The rest frame visual/ultraviolet continua of these quasars are quite similar to that of 3C273, the archetype of low redshift quasars. There does not appear to be any visual/ultraviolet properties distinguishing high redshift quasars selected via visual or radio techniques.

  6. High redshift supermassive blackholes: accretion through cold flows

    CERN Document Server

    Feng, Yu; Croft, Rupert; Khandai, Nishikanta

    2013-01-01

    We use zoom-in techniques to re-simulate three high-redshift (z > 5.5) halos which host 10^9 solar mass blackholes from the ~ Gpc volume, MassiveBlack cosmological hydrodynamic simulation. We examine a number of factors potentially affecting supermassive blackhole growth at high redshift in cosmological simulations. These include numerical resolution, feedback prescriptions and formulation of smoothed particle hydrodynamics. We find that varying the size of the region over which feedback energy is deposited directly, either for fixed number of neighbours or fixed volume makes very little difference to the accretion history of blackholes. Changing mass resolution by factors of up to 64 also does not change the blackhole growth history significantly. We find that switching from the density-entropy formulation to the pressure-entropy formulation of smoothed particle hydrodynamics slightly increases the accretion rate onto blackholes. In general numerical details appear to have small effects on the main fueling m...

  7. High-Redshift galaxies light from the early universe

    CERN Document Server

    Appenzeller, Immo

    2008-01-01

    This book provides a comprehensive account of the scientific results on high-redshift galaxies accumulated during the past ten years. Apart from summarizing and critically discussing the wealth of observational data, the observational methods which made it possible to study these very distant and extremely faint objects are described in detail. Moreover, the technical feasibilities and physical limitations for existing and for future ground-based and space-based telescopes are discussed. Thus, apart from summarizing the knowledge accumulated so far, the book is designed as a tool for planning future observational and instrumental programs and projects. In view of the potential importance of the observational results of the high-redshift universe for basic physics the book is written for astronomers as well as for physicists without prior astronomical knowledge. For this purpose it contains introductory chapters describing the basic concepts and notations used in modern astronomy and a brief overview of the pr...

  8. Tunable filter imaging of high-redshift quasar fields

    NARCIS (Netherlands)

    J. Swinbank; J. Baker; J. Barr; I. Hook; J. Bland-Hawthorn

    2012-01-01

    We have used the Taurus Tunable Filter to search for Lyα emitters in the fields of three high-redshift quasars: two at z∼ 2.2 (MRC B1256−243 and MRC B2158−206) and one at z∼ 4.5 (BR B0019−1522). Our observations had a field of view of around 35 arcmin2, and reached AB magnitudes of ∼21 (MRC B1256−24

  9. Metals in Star-Forming Galaxies at High Redshift

    OpenAIRE

    Leitherer, Claus

    2005-01-01

    The chemical composition of high-redshift galaxies is an important property that gives clues to their past history and future evolution. Measuring abundances in distant galaxies with current techniques is often a challenge, and the canonical metallicity indicators can often not be applied. I discuss currently available metallicity indicators based on stellar and interstellar absorption and emission lines, and assess their limitations and systematic uncertainties. Recent studies suggest that s...

  10. The X-ray variability of high redshift QSOs

    CERN Document Server

    Manners, J C; Lawrence, A

    2002-01-01

    We present an analysis of X-ray variability in a sample of 156 radio quiet quasars taken from the ROSAT archive, covering a redshift range 0.1 2) in the sense that QSOs of the same X-ray luminosity are more variable at z > 2. We discuss possible explanations for this effect. The simplest explanation may be that high redshift QSOs are accreting at a larger fraction of the Eddington limit than local AGN.

  11. An Empirical Limit on Extremely High Redshift Galaxies

    OpenAIRE

    Lanzetta, Kenneth M.; Yahil, Amos; Fernandez-Soto, Alberto

    1998-01-01

    We apply the Lyman absorption signature to search for galaxies at redshifts z \\~ 6 - 17 using optical and infrared images of the Hubble Deep Field. The infrared images are sensitive to a point source 5 sigma detection threshold of AB(22,000) = 23.8, which adopting plausible assumptions to relate rest-frame ultraviolet flux densities to unobscured star formation rates is easily sufficient to detect the star formation rates expected for massive elliptical galaxy formation to quite high redshift...

  12. Finding high-redshift voids using Lyman α forest tomography

    Science.gov (United States)

    Stark, Casey W.; Font-Ribera, Andreu; White, Martin; Lee, Khee-Gan

    2015-11-01

    We present a new method of finding cosmic voids using tomographic maps of Lyα forest flux. We identify cosmological voids with radii of 2-12 h-1 Mpc in a large N-body simulation at z = 2.5, and characterize the signal of the high-redshift voids in density and Lyα forest flux. The void properties are similar to what has been found at lower redshifts, but they are smaller and have steeper radial density profiles. Similarly to what has been found for low-redshift voids, the radial velocity profiles have little scatter and agree very well with the linear theory prediction. We run the same void finder on an ideal Lyα flux field and tomographic reconstructions at various spatial samplings. We compare the tomographic map void catalogues to the density void catalogue and find good agreement even with modest-sized voids (r > 6 h-1 Mpc). Using our simple void-finding method, the configuration of the ongoing COSMOS Lyman Alpha Mapping And Tomography Observations (CLAMATO) survey covering 1 deg2 would provide a sample of about 100 high-redshift voids. We also provide void-finding forecasts for larger area surveys, and discuss how these void samples can be used to test modified gravity models, study high-redshift void galaxies, and to make an Alcock-Paczynski measurement. To aid future work in this area, we provide public access to our simulation products, catalogues, and sample tomographic flux maps.

  13. Spectroscopic confirmation of high-redshift supernovae with the ESO VLT

    CERN Document Server

    Lidman, C E; Folatelli, G; Garavini, G; Nobili, S; Aldering, G; Amanullah, R; Antilogus, P; Astier, Pierre; Blanc, G; Burns, M S; Conley, A; Deustua, S E; Doi, M; Ellis, R; Fabbro, S; Fadeev, V; Gibbons, R; Goldhaber, G; Goobar, A; Groom, D E; Hook, I; Kashikawa, N; Kim, A G; Knop, R A; Lee Byung Cheol; Méndez, J; Morokuma, T; Motohara, K; Nugent, P; Pain, R; Perlmutter, S; Prasad, V; Quimby, R; Raux, J; Regnault, N; Ruiz-Lapuente, P; Sainton, G; Schaefer, B E; Schahmaneche, K; Smith, E; Spadafora, A L; Stanishev, V; Walton, N A; Wang, L; Wood-Vasey, W M; Yasuda, N

    2004-01-01

    We present VLT FORS1 and FORS2 spectra of 39 candidate high-redshift supernovae that were discovered as part of a cosmological study using Type Ia supernovae (SNe Ia) over a wide range of redshifts. From the spectra alone, 20 candidates are spectrally classified as SNe Ia with redshifts ranging from z=0.212 to z=1.181. Of the remaining 19 candidates, 1 might be a Type II supernova and 11 exhibit broad supernova-like spectral features and/or have supernova-like light curves. The candidates were discovered in 8 separate ground-based searches. In those searches in which SNe Ia at z ~ 0.5 were targeted, over 80% of the observed candidates were spectrally classified as SNe Ia. In those searches in which SNe Ia with z > 1 were targeted, 4 candidates with z > 1 were spectrally classified as SNe Ia and later followed with ground and space based observatories. We present the spectra of all candidates, including those that could not be spectrally classified as supernova.

  14. Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies

    CERN Document Server

    Bian, Fuyan; Dopita, Michael; Juneau, Stephanie

    2016-01-01

    We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [OIII]/H$\\beta$ versus [NII]/H$\\alpha$ nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums and compact galaxy sizes. In particular, the ionization parameters and electron densities in these analogs are comparable to those in $z\\simeq2-3$ galaxies, but higher than those in normal SDSS galaxies by $\\simeq$0.6~dex and $\\simeq$0.9~dex, respectively. The mass-metallicity relation (MZR) in these local analogs shows $-0.2$~dex offset from that in SDSS star-forming galaxies at the low mass end, which is consistent with the MZR of the $z\\sim2-3$ galaxies. We compare the lo...

  15. CLASH: Extreme Emission Line Galaxies and Their Implication on Selection of High-Redshift Galaxies

    CERN Document Server

    Huang, Xingxing; Wang, Junxian; Ford, Holland; Lemze, Doron; Moustakas, John; Shu, Xinwen; Van der Wel, Arjen; Zitrin, Adi; Frye, Brenda L; Postman, Marc; Bartelmann, Matthias; Benitez, Narciso; Bradley, Larry; Broadhurst, Tom; Coe, Dan; Donahue, Megan; Infante, Leopoldo; Kelson, Daniel; Koekemoer, Anton; Lahav, Ofer; Medezinski, Elinor; Moustakas, Leonidas; Rosati, Piero; Seitz, Stella; Umetsu, Keiichi

    2014-01-01

    We utilize the CLASH (Cluster Lensing And Supernova survey with Hubble) observations of 25 clusters to search for extreme emission-line galaxies (EELGs). The selections are carried out in two central bands: F105W (Y105) and F125W (J125), as the flux of the central bands could be enhanced by the presence of [O III] 4959, 5007 at redshift of about 0.93-1.14 and 1.57-1.79, respectively. The multi-band observations help to constrain the equivalent widths of emission lines. Thanks to cluster lensing, we are able to identify 52 candidates down to an intrinsic limiting magnitude of 28.5 and to a rest-frame [O III] 4959,5007 equivalent width of about 3737 angstrom. Our samples include a number of EELGs at lower luminosities that are missed in other surveys, and the extremely high equivalent width can be only found in such faint galaxies. These EELGs can mimic the dropout feature similar to that of high redshift galaxies and contaminate the color-color selection of high redshift galaxies when the S/N ratio is limited ...

  16. Dark matter accretion wakes of high-redshift black holes

    OpenAIRE

    Mohayaee, Roya; Colin, Jacques

    2008-01-01

    Anisotropic emission of gravitational waves during the merger or formation of black holes can lead to the ejection of these black holes from their host galaxies. A recoiled black hole which moves on an almost radial bound orbit outside the virial radius of its central galaxy, in the cold dark matter background, reaches its apapsis in a finite time. The low value of dark matter velocity dispersion at high redshifts and also the black hole velocity near the apapsis passage yield a high-density ...

  17. A new method to search for high-redshift clusters using photometric redshifts

    Energy Technology Data Exchange (ETDEWEB)

    Castignani, G.; Celotti, A. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Chiaberge, M.; Norman, C., E-mail: castigna@sissa.it [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-09-10

    We describe a new method (Poisson probability method, PPM) to search for high-redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for megaparsec-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. sample, which are selected within the COSMOS survey, and to the specific data set used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. (1) We use two z ∼ 1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z = 2. We find that the PPM detects the cluster candidates up to z = 1.5, and it correctly estimates both the redshift and size of the two clusters. (2) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e., z = 1.0, 1.5, and 2.0) in the COSMOS field. We find that the PPM detects the simulated clusters within the considered redshift range with a statistical 1σ redshift accuracy of ∼0.05. The PPM is an efficient alternative method for high-redshift cluster searches that may also be applied to both present and future wide field surveys such as SDSS Stripe 82, LSST, and Euclid. Accurate photometric redshifts and a survey depth similar or better than that of COSMOS (e.g., I < 25) are required.

  18. Hard X-Ray Detection of the High Redshift Quasar 4C 71.07

    Science.gov (United States)

    Malizia, A.; Bassani, L.; Dean, A. J.; McCollough, M. L.; Stephen, J. B.; Zhang, S. N.

    1999-01-01

    BATSE/OSSE observations of the high redshift quasar 4C 71.07 indicate that this is the brightest and furthest AGN so far detected 20 keV. BATSE Earth occultation data have been used to search for emission from 4C 71.07 from nearly 3 years of observation. The mean source flux over the- whole period in the BATSE energy range 20-100 keV is (13.2 +/- 1.06) x 10(exp -11) erg/square cm/s corresponding to a luminosity of 2 x 10(exp 48 erg/s. The BATSE light curve over the 3 years of observations shows several flare-like events, one of which (in January 1996) is associated with an optical flare (R=16.1) but with a delay of 55 days. The OSSE/BATSE spectral analysis indicates that the source is characterized by a flat power spectrum (Gamma is approximately 1.1- 1.3) when in a low state: this spectral form is consistent within errors with the ASCA and ROSAT spectra. This means that the power law observed from 0.1 to 10 keV extends up to at least 1 MeV but steepens soon after to meet EGRET high energy data. BATSE data taken around the January 1996 flare suggests that the spectrum could be steeper when the source is in a bright state. The upsilon-F-upsilon representation of the source is typical of a low frequency peaked/ gamma- ray dominated blazar, with the synchrotron peak in the mm-FIR band and the Compton peak in the MeV band. The BATSE and OSSE spectral data seem to favour a model in which the high energy - flux is due to the sum of the synchrotron self-Compton and the external Compton contributions: this is also supported by the- variability behaviour of the source.

  19. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data V. Hobby-Eberly Telescope Observations

    OpenAIRE

    Schneider, Donald P.; Fan, Xiaohui; Strauss, Michael A.; Gunn, James E.; Richards, Gordon T.; Hill, Gary J.; MacQueen, Phillip J.; Ramsey, Lawrence W.

    2000-01-01

    We report the discovery of 27 quasars with redshifts between 3.58 and 4.49. The objects were identified as high-redshift candidates based on their colors in Sloan Digital Sky Survey commissioning data. The redshifts were confirmed with low resolution spectra obtained at the Hobby-Eberly Telescope. The quasars' $i^*$ magnitudes range from 18.55 to 20.97. Nearly 60% of the quasar candidates observed are confirmed spectroscopically as quasars. Two of the objects are Broad Absorption Line quasars...

  20. Bulge growth through disk instabilities in high-redshift galaxies

    CERN Document Server

    Bournaud, Frederic

    2015-01-01

    The role of disk instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disk galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges. This secular growth of bulges in modern disk galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudo-bulges at slow rates and with long star-formation timescales. Disk instabilities at high redshift (z>1) in moderate-mass to massive galaxies (10^10 to a few 10^11 Msun of stars) are very different from those found in modern spiral galaxies. High-redshift disks are globally unstable and fragment into giant clumps containing 10^8-10^9 Msun of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disk evolution and bulge growth through various mechanisms, on short timescales. The giant clumps can...

  1. Bimodal star formation - Constraints from galaxy colors at high redshift

    Science.gov (United States)

    Wyse, Rosemary F. G.; Silk, Joseph

    1987-01-01

    The possibility that at early epochs the light from elliptical galaxies is dominated by stars with an initial mass function (IMF) which is deficient in low-mass stars, relative to the solar neighborhood is investigated. V-R colors for the optical counterparts of 3CR radio sources offer the most severe constraints on the models. Reasonable fits are obtained to both the blue, high-redshift colors and the redder, low-redshift colors with a model galaxy which forms with initially equal star formation rates in each of two IMF modes: one lacking low-mass stars, and one with stars of all masses. The net effect is that the time-integrated IMF has twice as many high-mass stars as the solar neighborhood IMF, relative to low mass stars. A conventional solar neighborhood IMF does not simultaneously account for both the range in colors at high redshift and the redness of nearby ellipticals, with any single star formation epoch. Models with a standard IMF require half the stellar population to be formed in a burst at low redshift z of about 1.

  2. XMM-Newton observations of three high redshift radio galaxies

    CERN Document Server

    Belsole, E; Hardcastle, M J

    2004-01-01

    We present results on the physical states of three high-redshift powerful radio galaxies (3C 292 at z=0.7, 3C 184 at z=1, and 3C322 at z=1.7). They were obtained by combining radio measurements with X-ray measurements from XMM-Newton that separate spectrally and/or spatially radio-related and hot-gas X-ray emission. Originally observed as part of a programme to trace clusters of galaxies at high redshift, none of the sources is found to lie in a rich X-ray-emitting environment similar to those of some powerful radio galaxies at low redshift, although the estimated gas pressures are sufficient to confine the radio lobes. The weak gas emission is a particularly interesting result for 3C 184, where a gravitational arc is seen, suggesting the presence of a very massive cluster. Here Chandra data complement the XMM-Newton measurements in spatially separating X-ray extended emission from that associated with the nucleus and rather small radio source. 3C 292 is the source for which the X-ray-emitting gas is measured...

  3. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    International Nuclear Information System (INIS)

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an iP1 dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB zP1 magnitude of 19.4, a luminosity of 3.8 × 1047 erg s–1, and a black hole mass of 6.9 × 109 M☉. It is a broad absorption line quasar with a prominent Lyβ peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 iP1 dropout quasars and could potentially find more than 10 zP1 dropout (z > 6.8) quasars.

  4. X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS

    International Nuclear Information System (INIS)

    The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth τ at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 2.2±0.6, tending to τ ≈ 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z x ∝(1 + z)7.1±0.5 correlation in the present sample, the host column density scales as NH∝Lx0.7±0.1

  5. The High Redshift Integrated Sachs-Wolfe Effect

    CERN Document Server

    Xia, Jun-Qing; Baccigalupi, Carlo; Matarrese, Sabino

    2009-01-01

    In this paper we rely on the quasar (QSO) catalog of the Sloan Digital Sky Survey Data Release Six (SDSS DR6) of about one million photometrically selected QSOs to compute the Integrated Sachs-Wolfe (ISW) effect at high redshift, aiming at constraining the behavior of the expansion rate and thus the behaviour of dark energy at those epochs. This unique sample significantly extends previous catalogs to higher redshifts while retaining high efficiency in the selection algorithm. We compute the auto-correlation function (ACF) of QSO number density from which we extract the bias and the stellar contamination. We then calculate the cross-correlation function (CCF) between QSO number density and Cosmic Microwave Background (CMB) temperature fluctuations in different subsamples: at high z>1.5 and low z1.5. We focus on the capabilities of the ISW to constrain the behaviour of the dark energy component at high redshift both in the \\LambdaCDM and Early Dark Energy cosmologies, when the dark energy is substantially unco...

  6. Far-Infrared Line Emission from High Redshift Quasars

    Science.gov (United States)

    Benford, D. J.; Cox, P.; Hunter, T. R.; Malhotra, S.; Phillips, T. G.; Yun, M. S.

    2002-01-01

    Recent millimeter and submillimeter detections of line emission in high redshift objects have yielded new information and constraints on star formation at early epochs. Only CO transitions and atomic carbon transitions have been detected from these objects, yet bright far-infrared lines such as C+ at 158 microns and N+ at 205 microns should be fairly readily detectable when redshifted into a submillimeter atmospheric window. We have obtained upper limits for C+ emission &om two high redshift quasars, BR1202-0725 at z=4.69 and BRI1335-0415 at z=4.41. These limits show that the ratio of the C+ line luminosity to the total far-infrared luminosity is less than 0.0l%, ten times smaller than has been observed locally. Additionally, we have searched for emission in the N+ 205 micron line from the Cloverleaf quasar, H1413+117, and detected emission in CO J=7-6. The N+ emission is found to be below the amount predicted based on comparison to the only previous detection of this line, in the starburst galaxy M82.

  7. Accessing the population of high redshift Gamma Ray Bursts

    CERN Document Server

    Ghirlanda, G; Ghisellini, G; Mereghetti, S; Tagliaferri, G; Campana, S; Osborne, J P; O'Brien, P; Tanvir, N; Willingale, R; Amati, L; Basa, S; Bernardini, M G; Burlon, D; Covino, S; D'Avanzo, P; Frontera, F; Gotz, D; Melandri, A; Nava, L; Piro, L; Vergani, S D

    2015-01-01

    Gamma Ray Bursts (GRBs) are a powerful probe of the high redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and gamma-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Ep-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence o...

  8. On the diversity of O vi absorbers at high redshift

    CERN Document Server

    Draganova, Nadya

    2015-01-01

    In this thesis, we systematically analyze the properties of intergalactic \\Ovi absorbing gas structures at high redshift using optical spectra with intermediate ($\\sim 6.6$ \\kms FWHM) and high ($\\sim 4.0$ \\kms FWHM) resolution, obtained with UVES/VLT. We complement our analysis with synthetic spectra obtained from extensive cosmological simulations that are part of the OWLS project (Schaye et al. 2010). Our main conclusions are: 1) Both the observations and simulations imply that \\Ovi absorbers at high redshift arise in structures spanning a broad range of scales and different physical conditions. When the \\Ovi components are characterized by small Doppler parameters, the ionizing mechanism is most likely photoionization; otherwise, collisional ionization is the dominant mechanism. 2) The baryon- and metal-content of the \\Ovi absorbers at $z\\approx2$ is less than one per cent of the total mass-density of baryons and metals at that redshift. Therefore, \\Ovi absorbers do not trace the bulk of baryons and metals...

  9. Infrared-Faint Radio Sources are at high redshifts

    CERN Document Server

    Herzog, Andreas; Norris, Ray P; Sharp, Rob; Spitler, Lee R

    2013-01-01

    Context. Infrared-Faint Radio Sources (IFRS) are characterised by relatively high radio flux densities and associated faint or even absent infrared and optical counterparts. The resulting extremely high radio-to-infrared flux density ratios up to several thousands were previously known only for High-redshift Radio Galaxies (HzRGs), suggesting a link between these classes of object. However, the optical and infrared faintness of IFRS makes their study diffcult. So far, no redshift is known for an original IFRS which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims. This work tests the hypothesis that IFRS follow the relation between 3.6 um flux density and redshift found for HzRGs. Furthermore, redshifts will enable us to reveal the intrinsic radio and infrared properties of IFRS and we will test the current suggestions that IFRS are high-redshift radio-loud active galactic nuclei. Methods. A sample of IFRS was spectroscopically observed using the Focal Reducer and lo...

  10. The First High Redshift Quasar from Pan-STARRS

    CERN Document Server

    Morganson, Eric; Decarli, Roberto; Walter, Fabian; Chambers, Ken; McGreer, Ian; Fan, Xiaohui; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Price, Paul; Rix, Hans-Walter; Sweeney, Bill; Waters, Christopher

    2011-01-01

    We present the discovery of the first high redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i dropoutout in PS1, confirmed photometrically with the SAO Widefield InfraRed Camera (SWIRC) at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph (TWIN) at the Calar Alto 3.5 m telescope. It has a redshift of 5.73, an AB z magnitude of 19.4, a luminosity of 3.8 x 10^47 erg/s and a black hole mass of 6.9 x 10^9 solar masses. It is a Broad Absorption Line quasar with a prominent Ly-beta peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high redshift quasar search that is projected to discover more than a hundred i dropout quasars, and could potentially find more than 10...

  11. On the Evolution of High-Redshift Active Galactic Nuclei

    CERN Document Server

    Mao, Jirong

    2016-01-01

    We build a simple physical model to study the high-redshift active galactic Nucleus (AGN) evolution within the co-evolution framework of central black holes (BHs) and their host galaxies. The correlation between the circular velocity of a dark halo $V_c$ and the velocity dispersion of a galaxy $\\sigma$ is used to link the dark matter halo mass and BH mass. The dark matter halo mass function is converted to the BH mass function for any given redshift. The high-redshift optical AGN luminosity functions (LFs) are constructed. At $z\\sim 4$, the flattening feature is not shown at the faint end of the optical AGN LF. This is consistent with observational results. If the optical AGN LF at $z\\sim 6$ can be reproduced in the case in which central BHs have the Eddington-limited accretion, it is possible for the AGN lifetime to have a small value of $2\\times 10^5$ yrs. The X-ray AGN LFs and X-ray AGN number counts are also calculated at $2.03$, respectively, using the same parameters adopted in the calculation for the o...

  12. Using Morphology to Identify Galaxy Mergers at High Redshift

    Science.gov (United States)

    Blancato, Kirsten; Kartaltepe, J. S.; CANDELS Collaboration

    2014-01-01

    We analyzed a set of 22,003 galaxies in three of the five CANDELS fields: COSMOS, UDS, and GOODS-S, in order to determine how well automated image statistics did with classifying galaxy morphology and mergers at high redshifts (z > 1). For each galaxy in our set, we have multi-wavelength data, photometric redshifts from SED fitting, visual classifications from the CANDELS structure and morphology group, and automated image statistics. The redshifts of our sample range from z = .01 to 4 with = 1.33. We constructed a conservative set of 1,914 galaxies that we believe to be mergers and interactions. Of this set of merging galaxies, 1,343 were at a redshift greater than z = 1. We also identified a conservative set of 535 spheroids and a set of 2,902 disks. Several different quantitative methods were then used to attempt an automated classification of these visually classified samples. Of the different image statistics, we found M20 and Gini to be the most successful at picking out high redshift mergers and morphological characteristics. Blancato was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  13. The Parkes selected regions: powerful radio galaxies and quasars at high redshifts

    International Nuclear Information System (INIS)

    A complete sample of extragalactic radio sources with flux density S>=0.1 Jy at 2.7 GHz has been compiled to probe the radio luminosity function to redshifts z approx.3-4. VLA maps are presented for the 188 sources in this flux density range; 178 sources remain in the complete sample after examination for confusion. The new radio data define the structures and positions sufficiently well for a re-examination of existing plate material to have yielded an identification content of 56 per cent of the sample down to V approx.21. The results from this programme will strongly constrain the behaviour of the radio population at high redshifts. Unless the comoving density of sources falls for z>2, the identification candidates should include many objects with zapprox.3-4. (author)

  14. Relativistic jet feedback in high-redshift galaxies I: Dynamics

    CERN Document Server

    Mukherjee, Dipanjan; Sutherland, Ralph S; Wagner, A Y

    2016-01-01

    We present the results of three dimensional relativistic hydrodynamic simulations of interaction of AGN jets with a dense turbulent two-phase interstellar medium, which would be typical of high redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent ISM. The jet driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multi-phase ISM and radial outflows. One of the striking result of this work is that low power jets (P_jet < 10^{43} erg/s) although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  15. Theoretical considerations for star formation at low and high redshift

    CERN Document Server

    Elmegreen, Bruce G

    2015-01-01

    Star formation in strongly self-gravitating cloud cores should be similar at all redshifts, forming single or multiple stars with a range of masses determined by local magneto-hydrodynamics and gravity. The formation processes for these cores, however, as well as their structures, temperatures, Mach numbers, etc., and the boundedness and mass distribution functions of the resulting stars, should depend on environment, as should the characteristic mass, density, and column density at which cloud self-gravity dominates other forces. Because the environments for high and low redshift star formation differ significantly, we expect the resulting gas to stellar conversion details to differ also. At high redshift, the universe is denser and more gas-rich, so the active parts of galaxies are denser and more gas rich too, leading to slightly shorter gas consumption timescales, higher cloud pressures, and denser, more massive, bound stellar clusters at the high mass end. With shorter consumption times corresponding to ...

  16. Relativistic jet feedback in high-redshift galaxies I: Dynamics

    Science.gov (United States)

    Mukherjee, Dipanjan; Bicknell, Geoffrey V.; Sutherland, Ralph; Wagner, Alex

    2016-06-01

    We present the results of three dimensional relativistic hydrodynamic simulations of interaction of AGN jets with a dense turbulent two-phase interstellar medium, which would be typical of high redshift galaxies. We describe the effect of the jet on the evolution of the density of the turbulent ISM. The jet driven energy bubble affects the gas to distances up to several kiloparsecs from the injection region. The shocks resulting from such interactions create a multi-phase ISM and radial outflows. One of the striking result of this work is that low power jets (Pjet ≲ 1043ergs-1) although less efficient in accelerating clouds, are trapped in the ISM for a longer time and hence affect the ISM over a larger volume. Jets of higher power drill through with relative ease. Although the relativistic jets launch strong outflows, there is little net mass ejection to very large distances, supporting a galactic fountain scenario for local feedback.

  17. Probing the bias of radio sources at high redshift

    CERN Document Server

    Passmoor, Sean; Faltenbacher, Andreas; Johnston, Russell; Smith, Mathew; Ratsimbazafy, Ando; Hoyle, Ben

    2012-01-01

    The relationship between the clustering of dark matter and that of luminous matter is often described using the bias parameter. Here, we provide a new method to probe the bias of intermediate to high-redshift radio continuum sources for which no redshift information is available. We matched radio sources from the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey data to their optical counterparts in the Sloan Digital Sky Survey (SDSS) to obtain photometric redshifts for the matched radio sources. We then use the publicly available semi-empirical simulation of extragalactic radio continuum sources (S3) to infer the redshift distribution for all FIRST sources and estimate the redshift distribution of unmatched sources by subtracting the matched distribution from the distribution of all sources. We infer that the majority of unmatched sources are at higher redshifts than the optically matched sources and demonstrate how the angular scales of the angular two-point correlation function can be used...

  18. Close companions to two high-redshift quasars

    International Nuclear Information System (INIS)

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i AB = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW0 ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y AB = 25) at a separation of 0.''9. The red i 775 – Y 105 color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  19. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui; Bian, Fuyan [Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Haiman, Zoltàn [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Jiang, Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Schneider, Donald P., E-mail: imcgreer@as.arizona.edu [Department of Astronomy and Astrophysics and the Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i {sub AB} = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW{sub 0} ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ∼ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ∼4.5 mag fainter than the quasar (Y {sub AB} = 25) at a separation of 0.''9. The red i {sub 775} – Y {sub 105} color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.

  20. A Global Probe of Cosmic Magnetic Fields to High Redshifts

    Science.gov (United States)

    Kronberg, P. P.; Bernet, M. L.; Miniati, F.; Lilly, S. J.; Short, M. B.; Higdon, D. M.

    2008-03-01

    Faraday rotation (rotation measure [RM]) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as z increases beyond ~1 because of the scalings of electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, dN/dz. In this new global analysis of an unprecedented large sample of RMs of high-latitude quasars extending out to z ~ 3.7, we find that the distribution of RM broadens with redshift in the 20-80 rad m-2 range, despite the (1 + z)-2 wavelength dilution expected in the observed Faraday rotation. Our results indicate that the universe becomes increasingly "Faraday-opaque" to sources beyond z ~ 2; that is, as z increases, progressively fewer sources are found with a "small" RM in the observer's frame. This is in contrast to sources at zlesssim 1. They suggest that the environments of galaxies were significantly magnetized at high redshifts, with magnetic field strengths that were at least as strong within a few Gyr of the big bang as at the current epoch. We separately investigate a simple unevolving toy model in which the RM is produced by Mg II absorber systems, and find that it can approximately reproduce the observed trend with redshift. An additional possibility is that the intrinsic RM associated with the radio sources was much higher in the past, and we show that this is not a trivial consequence of the higher radio luminosities of the high-redshift sources.

  1. Blazar Sequence in Fermi Era

    Indian Academy of Sciences (India)

    Liang Chen

    2014-09-01

    In this paper, we review the latest research results on the topic of blazar sequence. It seems that the blazar sequence is phenomenally ruled out, while the theoretical blazar sequence still holds. We point out that black hole mass is a dominated parameter accounting for high-power-high-synchrotron-peaked and low-power-low-sychrotron-peaked blazars. Because most blazars have similar size of emission region, theoretical blazar sequence implies that the break of Spectral Energy Distribution (SED) is a cooling break in nature.

  2. A new method to search for high redshift clusters using photometric redshifts

    CERN Document Server

    Castignani, Gianluca; Celotti, Annalisa; Norman, Colin

    2014-01-01

    We describe a new method (Poisson Probability Method, PPM) to search for high redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for Mpc-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. (2009) sample, that are selected within the COSMOS survey, and on the specific dataset used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. i) We use two z~1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z=2. We find that the PPM detects the cluster candidates up to z=1.5, and it correctly estimates both the redshift and size of the two clusters. ii) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e...

  3. Blazar Compton Efficiencies

    International Nuclear Information System (INIS)

    The Fermi gamma-ray space telescope has dramatically increased the number of gamma-ray blazars known and means that for the first time, a large sample of blazars selected by the strength of their inverse Compton emission exists. We have cross-identified the blazars listed in the first Fermi-LAT catalog (1FGL) with the CRATES radio catalogue. Using the 8.4 GHz flux density as a proxy for the jet power, we have computed their Compton efficiencies, a measure of the ability of the jet to convert the power in the ultrarelativistic jet electrons into gamma-rays through the inverse Compton process. We have compared the Compton efficiencies of the two blazar subsets, BL Lacs and FSRQs, and find no evidence that they are different. We also do not find an anti-correlation between Compton efficiency and synchrotron peak frequency.

  4. X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Eitan, Assaf; Behar, Ehud, E-mail: sassafe@tx.technion.ac.il, E-mail: behar@physics.technion.ac.il [Physics Department, Technion, Haifa 32000 (Israel)

    2013-09-01

    The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth {tau} at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. Only 10/37 quasars at z < 2 are absorbed, and only 5/30 radio-quiet quasars are absorbed. We find a weak correlation between {tau} and z, and an even weaker correlation between {tau} and radio luminosity. These findings lead to the conclusion that although a diffuse IGM origin for the quasar absorption is unlikely, the optical depth does seem to increase with redshift, roughly as (1 + z){sup 2.2{+-}0.6}, tending to {tau} Almost-Equal-To 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z < 2, and a cold, diffuse IGM at higher redshift. If, conversely, the absorption occurs at the quasar, and owing to the steep L{sub x} {proportional_to}(1 + z){sup 7.1{+-}0.5} correlation in the present sample, the host column density scales as N{sub H}{proportional_to}L{sub x}{sup 0.7{+-}0.1}.

  5. UNIDENTIFIED γ-RAY SOURCES: HUNTING γ-RAY BLAZARS

    International Nuclear Information System (INIS)

    One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified γ-ray sources (UGSs). Despite the major improvements of Fermi in the localization of γ-ray sources with respect to the past γ-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of γ-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the γ-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic γ-ray source. With this new IR diagnostic tool, we searched for γ-ray blazar candidates associated with the UGS sample of the second Fermi γ-ray LAT catalog (2FGL). We found that our method associates at least one γ-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with γ-ray sources in the 2FGL catalog.

  6. Tev Blazars: Status of Observations

    OpenAIRE

    Krennrich, F.; Biller, S. D.; Bond, I. H.; Boyle, P. J.; Bradbury, S. M.; Breslin, A. C.; J. H. Buckley(Department of Physics, Washington University, St. Louis, USA); Burdett, A. M.; Bussons-Gordo, J.; Carter-Lewis, D. A.; Catanese, M.; Cawley, M. F.; Fegan, D. J.; Finley, J. P.; Gaidos, J. A.

    1998-01-01

    The close relation between ground-based TeV observations and satellite borne $\\gamma$-ray measurements has been important for the understanding of blazars. The observations which involve the TeV component in blazar studies are reviewed.

  7. The progenitors of the compact early-type galaxies at high redshift

    International Nuclear Information System (INIS)

    We use GOODS and CANDELS images to identify progenitors of massive (M > 1010 M ☉) compact early-type galaxies (ETGs) at z ∼ 1.6. Because merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z ∼ 3 on the basis of their mass, star-formation rate (SFR), and central stellar density, and we find that these account for a large fraction of, and possibly all, compact ETGs at z ∼ 1.6. We find that the average far-UV spectral energy distribution (SED) of the candidates is redder than that of the non-candidates, but the optical and mid-IR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration and consistent with more evolved (aging) star formation. This is in line with other evidence suggesting that compactness is a sensitive predictor of passivity among high-redshift massive galaxies. We also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended 'halos' surrounding the compact 'core,' both in individual images and in stacks. We argue that this is generally inconsistent with the morphology of merger remnants, even if gas rich, as predicted by N-body simulations. This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the Hubble Space Telescope images, with their stellar mass assembling in situ, and that they have not experienced any major merging until the epoch of observations at z ∼ 1.6.

  8. Bayesian High-redshift Quasar Classification from Optical and Mid-IR Photometry

    Science.gov (United States)

    Richards, Gordon T.; Myers, Adam D.; Peters, Christina M.; Krawczyk, Coleman M.; Chase, Greg; Ross, Nicholas P.; Fan, Xiaohui; Jiang, Linhua; Lacy, Mark; McGreer, Ian D.; Trump, Jonathan R.; Riegel, Ryan N.

    2015-08-01

    We identify 885,503 type 1 quasar candidates to i≲ 22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) “AllWISE” data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with 3.5\\lt z\\lt 5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z\\gt 3.5 than the traditional mid-IR selection “wedges” and to 2.2\\lt z\\lt 3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z\\gt 3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.

  9. Probing Gravity in the High-Redshift Universe with HETDEX

    Science.gov (United States)

    Malz, A. I.; Shandera, S.

    2014-01-01

    The addition of dark matter and dark energy to general relativity is degenerate with a modification of the dependence of curvature on the stress-energy tensor in the absence of exotic sources of matter and energy; it is thus valuable to explore the latter as a potential improvement over the former. Though it is inherently difficult to distinguish existing evidence for the general relativity paradigm from that of its more promising alternatives, such theories are associated with different histories for the largely unexplored growth of structure. Zhang, et al. (2007) have enabled discrimination of these possibilities via a new observable parameter EG and have predicted the efficacy of several future astronomical surveys to determine its value. In this work, we examine the ability of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) to contribute to calculations of this indicator of gravity at the highest redshifts (1.9 < z < 3.5). We show that a prerequisite of such a measurement is a deeper understanding of the nature of Lyman-α emitting galaxies (LAEs). If HETDEX can constrain the statistical properties of the typical LAE velocity dispersion, then it will not be necessary to wait for the (as yet unplanned) next generation of high-resolution spectrographs to obtain a test of general relativity in the high-redshift universe.

  10. "Observing and Analyzing" Images From a Simulated High Redshift Universe

    CERN Document Server

    Morgan, Robert J; Scannapieco, Evan; Thacker, Robert J

    2015-01-01

    We investigate the high-redshift evolution of the restframe UV-luminosity function (LF) of galaxies via hydrodynamical cosmological simulations, coupled with an emulated observational astronomy pipeline that provides a direct comparison with observations. We do this by creating mock images and synthetic galaxy catalogs of approximately 100 square arcminute fields from the numerical model at redshifts ~ 4.5 to 10.4. We include the effects of dust extinction and the point spread function (PSF) for the Hubble WFC3 camera for comparison with space observations. We also include the expected zodiacal background to predict its effect on space observations, including future missions such as the James Webb Space Telescope (JWST). When our model catalogs are fitted to Schechter function parameters, we predict that the faint-end slope alpha of the LF evolves as alpha = -1.16 - 0.12 z over the redshift range z ~ 4.5 to 7.7, in excellent agreement with observations from e.g., Hathi et al. (2010). However, for redshifts z ...

  11. Are GRBs the same at high redshift and low redshift?

    CERN Document Server

    Littlejohns, O M; Willingale, R; Evans, P A; O'Brien, P T; Levan, A J

    2013-01-01

    The majority of Swift gamma-ray bursts (GRBs) observed at z > 6 have prompt durations of T90 < 30s, which, at first sight, is surprising given that cosmological time-dilation means this corresponds to < 5s in their rest frames. We have tested whether these high-redshift GRBs are consistent with being drawn from the same population as those observed at low-redshift by comparing them to an artificially red-shifted sample of 114 z < 4 bursts. This is accomplished using two methods to produce realistic high-z simulations of light curves based on the observed characteristics of the low-z sample. In Method 1 we use the Swift/BAT data directly, taking the photons detected in the harder bands to predict what would be seen in the softest energy band if the burst were seen at higher-z. In Method 2 we fit the light curves with a model, and use that to extrapolate the expected behaviour over the whole BAT energy range at any redshift. Based on the results of Method 2, a K-S test of their durations finds a ~1% pr...

  12. POPULATION III STARS AND REMNANTS IN HIGH-REDSHIFT GALAXIES

    International Nuclear Information System (INIS)

    Recent simulations of Population III star formation have suggested that some fraction form in binary systems, in addition to having a characteristic mass of tens of solar masses. The deaths of metal-free stars result in the initial chemical enrichment of the universe and the production of the first stellar-mass black holes. Here we present a cosmological adaptive mesh refinement simulation of an overdense region that forms a few 109 M☉ dark matter halos and over 13,000 Population III stars by redshift 15. We find that most halos do not form Population III stars until they reach Mvir ∼ 107 M☉ because this biased region is quickly enriched from both Population III and galaxies, which also produce high levels of ultraviolet radiation that suppress H2 formation. Nevertheless, Population III stars continue to form, albeit in more massive halos, at a rate of ∼10–4 M☉ yr–1 Mpc–3 at redshift 15. The most massive starless halo has a mass of 7 × 107 M☉, which could host massive black hole formation through the direct gaseous collapse scenario. We show that the multiplicity of the Population III remnants grows with halo mass above 108 M☉, culminating in 50 remnants located in 109 M☉ halos on average. This has implications that high-mass X-ray binaries and intermediate-mass black holes that originate from metal-free stars may be abundant in high-redshift galaxies

  13. Distribution of streaming rates into high-redshift galaxies

    CERN Document Server

    Goerdt, Tobias; Dekel, Avishai; Teyssier, Romain

    2015-01-01

    We study the accretion along streams from the cosmic web into high-redshift massive galaxies using three sets of AMR hydro-cosmological simulations. We find that the streams keep a roughly constant accretion rate as they penetrate into the halo centre. The mean accretion rate follows the mass and redshift dependence predicted for haloes by the EPS approximation, dM / dt is proportional to Mvir^{1.25} (1 + z)^{2.5}. The distribution of the accretion rates can well be described by a sum of two Gaussians, the primary corresponding to "smooth inflow" and the secondary to "mergers". The same functional form was already found for the distributions of specific star formation rates in observations. The mass fraction in the smooth component is 60 - 90 %, insensitive to redshift or halo mass. The simulations with strong feedback show clear signs of re-accretion due to recycling of galactic winds. The mean accretion rate for the mergers is a factor 2 - 3 larger than that of the smooth component. The standard deviation o...

  14. The fate of high-redshift massive compact galaxies

    CERN Document Server

    de la Rosa, Ignacio G; Ferreras, Ignacio; Almeida, Jorge Sánchez; Vecchia, Claudio Dalla; Martínez-Valpuesta, Inma; Stringer, Martin

    2016-01-01

    Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disk decomposition catalogues based on the Sloan Digital Sky Survey (SDSS) to check the hypothesis that red nuggets have survived as compact cores embedded inside the haloes or disks of present-day massive galaxies. In this study, we designate a "compact core" as the bulge component that satisfies a prescribed compactness criterion. Photometric and dynamic mass-size and mass-density relations are used to show that, in the inner regions of galaxies at z ~ 0.1, there are "abundant" compact cores matching the peculiar properties of the red nuggets, an abundance comparable to that of red nuggets at z ~ 1.5. Furthermore, the morphology distribution of the present-day galaxies hosting compact cores is used to demonstrate that, in addition to the standard channel connecting red ...

  15. A Global Probe of Cosmic Magnetic Fields to High Redshifts

    CERN Document Server

    Kronberg, P P; Miniati, F; Lilly, S J; Short, M B; Higdon, D M

    2007-01-01

    Faraday rotation (RM) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as $z$ increases beyond $\\sim $1 because of the scalings of electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, $d$N/$dz$. In this new global analysis of an unprecedented large sample of RM's of high latitude quasars extending out to $z\\sim $3.7 we find that the distribution of RM broadens with redshift in the 20 $-$ 80 rad m$^{-2}$ range range, despite the (1 +$z$)$^{-2}$ wavelength dilution expected in the observed Faraday rotation. Our results indicate that the Universe becomes increasingly ``Faraday-opaque'' to sources beyond $z \\sim$ 2, that is, as $z$ increases progressively fewer sources are found with a ``small'' RM in the observer's frame. This is in contrast to sources at $z \\la$1. They suggest that the environments of galaxies were significantly magnetized at high redshifts, with magnetic field strengths that w...

  16. Is deuterium in high-redshift Lyman limit systems primordial?

    International Nuclear Information System (INIS)

    Detections of deuterium in high-redshift Lyman limit absorption systems along the line of sight to QSOs promise to reveal the primordial deuterium abundance. At present, the deuterium abundances (D/H) derived from the very few systems observed are significantly discordant. Assuming the validity of all the data, if this discordance does not reflect intrinsic primordial inhomogeneity, then it must arise from processes operating after the primordial nucleosynthesis epoch. We consider processes that might lead to significant deuterium production or destruction and yet allow the cloud to mimic a chemically unevolved system. These processes include, for example, anomalous/stochastic chemical evolution and D/4He photodestruction. In general, we find it unlikely that these processes could have significantly altered D/H in Lyman limit clouds. We argue that chemical evolution scenarios, unless very finely tuned, cannot account for significant local deuterium depletion since they tend to overproduce 12C, even when allowance is made for possible outflow. Similarly, D/4He photodestruction schemes engineered to locally produce or destroy deuterium founder on the necessity of requiring an improbably large γ-ray source density. Future observations of D/H in Lyman limit systems may provide important insight into the initial conditions for the primordial nucleosynthesis process, early chemical evolution, and the galaxy formation process. copyright 1997 The American Astronomical Society

  17. Sources and Evolution of Dust in the High Redshift Universe

    Science.gov (United States)

    Dwek, Eli

    2015-08-01

    Understanding the sources and evolution of dust in the very high redshift universe (z > 8-9) poses unique challenges to observers and theorists alike.The peak of the infrared emission from the dust falls in the ~ 80-120 micron region in the rest frame of the galaxy, or about 850 micron to 2 mm in the observers' frame. Sensitivity and background confusion are the main obstacles for the detection of these high-z galaxies and their association with optical and near-IR counterparts. Observations with instruments such as the SCUBA-2, AzTEC, Mambo, Laboca, and GISMO2 offer the best hope for detecting such sources.On the theoretical side, the sources of dust in these galaxies are confined to massive stars with main sequence lifetimes that are shorter than the age of the universe. This leaves core collapse supernovae (CCSNe) as the main source of thermally-condensed dust in these objects. Dust is not only produced by CCSNe, but also destroyed by them in the remnant phase of their evolution. Accounting for the mass of dust inferred from the far-IR/millimeter observations requires therefore an understanding of the various physical processes affecting the evolution of dust in the very high-z universe, and a carefull evaluation of the balance between their different dust formation and destruction mechanisms.

  18. Updated F(T) gravity constraints from high redshift cosmography

    CERN Document Server

    Piedipalumbo, Ester; Cianci, Roberto

    2015-01-01

    In the last dozen years a wide and variegated mass of observational data revealed that the universe is now expanding at an accelerated rate. In the absence of a well-based theory to interpret the observations, cosmography provides information about the evolution of the Universe from measured distances, only assuming that the geometry of the can be described by the Friedmann-Lemaitre-Robertson -Walker metric. We perform a high-redshift analysis allows us to put constraints on the cosmographic parameters up to the 5fth order, thus inducing indirect constraints on any gravity theory. Here we are interested in the so called teleparallel gravity theory, f(T). Actually we use the analytical expressions of the present day values of f(T) and its derivatives as functions of the cosmographic parameters to map the cosmography region of confidences into confidence ranges for f(T) and its derivative. Moreover, we show how these can be used to test some teleparallel gravity models without solving the dynamical equations. O...

  19. Neutral chlorine and molecular hydrogen at high redshift

    CERN Document Server

    Balashev, S A; Klimenko, V V; Petitjean, P; Srianand, R; Ledoux, C; Ivanchik, A V; Varshalovich, D A

    2015-01-01

    Chlorine and molecular hydrogen are known to be tightly linked together in the cold phase of the local interstellar medium through rapid chemical reactions. We present here the first systematic study of this relation at high redshifts using H$_2$-bearing damped Ly$\\alpha$ systems (DLAs) detected along quasar lines of sight. Using high-resolution spectroscopic data from VLT/UVES and Keck/HIRES, we report the detection of Cl$\\,$I in 9 DLAs (including 5 new detections) out of 18 high-$z$ DLAs with $N($H$_2) \\ge 10^{17.3}\\,$cm$^{-2}$ (including a new H$_2$ detection at $z=3.09145$ towards J$\\,$2100$-$0641) and present upper limits for the remaining 9 systems. We find a $\\sim$5$\\,\\sigma$ correlation between $N$(Cl$\\,$I) and $N$(H$_2$) with only $\\sim$0.2$\\,$dex dispersion over the range 18.1$\\,<\\,$log$\\,N$(H$_2$)$\\,<\\,$20.1, thus probing column densities 10 times lower those seen towards nearby stars, roughly following the relation $N$(Cl$\\,$I$) \\approx 1.5\\times10^{-6} \\times N($H$_2)$. This relation betwee...

  20. MAGNETICALLY REGULATED GAS ACCRETION IN HIGH-REDSHIFT GALACTIC DISKS

    International Nuclear Information System (INIS)

    Disk galaxies are in hydrostatic equilibrium along their vertical axis. The pressure allowing for this configuration consists of thermal, turbulent, magnetic, and cosmic-ray components. For the Milky Way the thermal pressure contributes ∼10% of the total pressure near the plane, with this fraction dropping toward higher altitudes. Out of the rest, magnetic fields contribute ∼1/3 of the pressure to distances of ∼3 kpc above the disk plane. In this Letter, we attempt to extrapolate these local values to high-redshift, rapidly accreting, rapidly star-forming disk galaxies and study the effect of the extra pressure sources on the accretion of gas onto the galaxies. In particular, magnetic field tension may convert a smooth cold-flow accretion to clumpy, irregular star formation regions and rates. The infalling gas accumulates on the edge of the magnetic fields, supported by magnetic tension. When the mass of the infalling gas exceeds some threshold mass, its gravitational force cannot be balanced by magnetic tension anymore, and it falls toward the disk's plane, rapidly making stars. Simplified estimations of this threshold mass are consistent with clumpy star formation observed in SINS, UDF, GOODS, and GEMS surveys. We discuss the shortcomings of pure hydrodynamic codes in simulating the accretion of cold flows into galaxies, and emphasize the need for magnetohydrodynamic simulations.

  1. The numerical frontier of the high-redshift Universe

    CERN Document Server

    Greif, Thomas H

    2014-01-01

    The first stars are believed to have formed a few hundred million years after the big bang in so-called dark matter minihalos with masses ~10^6 M_sun. Their radiation lit up the Universe for the first time, and the supernova explosions that ended their brief lives enriched the intergalactic medium with the first heavy elements. In the wake of their feedback, the first galaxies assembled in halos with masses ~10^8 M_sun, and hosted the first normal stellar populations. In this review, I summarize the theoretical progress made in the field of high-redshift star and galaxy formation since the turn of the millennium, with an emphasis on numerical simulations. These have become the method of choice to understand the multi-physics problem posed by the simultaneous collapse of the dark matter and gas over many orders of magnitude in scale. In particular, I focus on the evolution of minihalos beyond the initial collapse of the gas, including disk fragmentation, protostellar evolution, and radiative feedback. I also d...

  2. Evolution of high-redshift Lyman-limit absorption systems

    Energy Technology Data Exchange (ETDEWEB)

    Lanzetta, K.M. (Cambridge University Institute of Astronomy (England))

    1991-07-01

    Results are presented of a new spectroscopic survey of high-redshift Lyman-limit absorption systems. Based on this data set, the rate of incidence of the Lyman-limit systems with z greater than about 2.5 is found to evolve strongly with redshift in the sense that the product of the number density per unit comoving volume and the absorption cross section increases with increasing redshift. If the observed evolution indicates intrinsic evolution of the absorbers, this result suggests that the evolution detected previously for the C IV-selected absorbers over a similar redshift range is not naturally interpreted as evolution of the ionization level of the absorbers rather than as a chemical enrichment effect. The data are also used to investigate the H I column density distribution and to examine the multiple-component structure of the absorbing complexes. The H I column density distribution is found to be well fitted by a power-law form. 35 refs.

  3. X-ray Absorption of High Redshift Quasars

    CERN Document Server

    Eitan, Assaf

    2013-01-01

    Soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astro-physical context. We construct the largest sample to date of 58 high redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (> 1800). We measure the optical depth tau at 0.5 keV, and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars drive their observed absorption, e.g., redshift, radio luminosity, radio loudness, or the X-ray luminosity. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption, and with a comparison sample of gamma ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. On...

  4. Close companions to two high-redshift quasars

    CERN Document Server

    McGreer, Ian D; Strauss, Michael A; Haiman, Zoltan; Richards, Gordon T; Jiang, Linhua; Bian, Fuyan; Schneider, Donald P

    2014-01-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z=4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyman alpha emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i_AB = 23.6) located 2arcsec (11 kpc projected) from the quasar with strong Lyman alpha emission (EW_0 ~ 100Ang) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z=6.25), is included in our recent HST SNAP survey of z~6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y_AB=25) at a separation of 0.9 arcsec. The red i_775-Y_105 color of the galaxy and its proximity to the quasar (7 kpc projected if at the quasar redshift) strongly favor an associati...

  5. The Growth Efficiency of High-Redshift Black Holes

    CERN Document Server

    Pacucci, Fabio; Ferrara, Andrea

    2015-01-01

    The observational evidence that Super-Massive Black Holes ($M_{\\bullet} \\sim 10^{9-10} \\, \\mathrm{M_{\\odot}}$) are already in place less than $1 \\, \\mathrm{Gyr}$ after the Big Bang poses stringent time constraints on the growth efficiency of their seeds. Among proposed possibilities, the formation of massive ($\\sim 10^{3-6} \\, \\mathrm{M_{\\odot}}$) seeds and/or the occurrence of super-Eddington ($\\dot{M}>\\dot{M}_{Edd}$) accretion episodes may contribute to the solution of this problem. In this work, using realistic initial conditions, we analytically and numerically investigate the accretion flow onto high-redshift ($z \\sim 10$) black holes to understand the physical requirements favoring rapid and efficient growth. Our model identifies a "feeding-dominated" accretion regime and a "feedback-limited" one, the latter being characterized by intermittent (duty cycles ${\\cal D} \\lesssim 0.5$) and inefficient growth, with recurring outflow episodes. We find that low-mass seeds ($\\lesssim 10^{3-4} \\, \\mathrm{M_{\\odot...

  6. The dust budget crisis in high-redshift submillimetre galaxies

    CERN Document Server

    Rowlands, K; Dunne, L; Aragón-Salamanca, A; Dye, S; Maddox, S; da Cunha, E; van der Werf, P

    2014-01-01

    We apply a chemical evolution model to investigate the sources and evolution of dust in a sample of 26 high-redshift ($z>1$) submillimetre galaxies (SMGs) from the literature, with complete photometry from ultraviolet to the submillimetre. We show that dust produced only by low-intermediate mass stars falls a factor 240 short of the observed dust masses of SMGs, the well-known `dust-budget crisis'. Adding an extra source of dust from supernovae can account for the dust mass in 19 per cent of the SMG sample. Even after accounting for dust produced by supernovae the remaining deficit in the dust mass budget provides support for higher supernova yields, substantial grain growth in the interstellar medium or a top-heavy IMF. Including efficient destruction of dust by supernova shocks increases the tension between our model and observed SMG dust masses. The models which best reproduce the physical properties of SMGs have a rapid build-up of dust from both stellar and interstellar sources and minimal dust destructi...

  7. A survey of luminous high-redshift quasars with SDSS and WISE. I. target selection and optical spectroscopy

    CERN Document Server

    Wang, Feige; Fan, Xiaohui; Yang, Jinyi; Yi, Weimin; Bian, Fuyan; McGreer, Ian D; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Jiang, Linhua; Green, Richard; Wang, Shu; Cai, Zheng; Wang, Ran; Yue, Minghao

    2016-01-01

    High-redshift quasars are important tracers of structure and evolution in the early universe. However, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. High-redshift quasar surveys based on only optical colors suffer from incompleteness and low identification efficiency, especially at $z\\gtrsim4.5$. We have developed a new method to select $4.7\\lesssim z \\lesssim 5.4$ quasars with both high efficiency and completeness by combining optical and mid-IR Wide-field Infrared Survey Explorer (WISE) photometric data, and are conducting a luminous $z\\sim5$ quasar survey in the whole Sloan Digital Sky Survey (SDSS) footprint. We have spectroscopically observed 99 out of 110 candidates with $z$-band magnitudes brighter than 19.5 and 64 (64.6\\%) of them are quasars with redshifts of $4.4\\lesssim z \\lesssim 5.5$ and absolute magnitudes of $-29\\lesssim M_{1450} \\lesssim -26.4$. In addition, we also observed 14 fainter candidates selected with the same crite...

  8. Gemini Spectroscopy of Supernovae from the Supernova Legacy Survey: Improving High-Redshift Supernova Selection and Classification

    Science.gov (United States)

    Howell, D. A.; Sullivan, M.; Perrett, K.; Bronder, T. J.; Hook, I. M.; Astier, P.; Aubourg, E.; Balam, D.; Basa, S.; Carlberg, R. G.; Fabbro, S.; Fouchez, D.; Guy, J.; Lafoux, H.; Neill, J. D.; Pain, R.; Palanque-Delabrouille, N.; Pritchet, C. J.; Regnault, N.; Rich, J.; Taillet, R.; Knop, R.; McMahon, R. G.; Perlmutter, S.; Walton, N. A.

    2005-12-01

    We present new techniques for improving the efficiency of supernova (SN) classification at high redshift using 64 candidates observed at Gemini North and South during the first year of the Supernova Legacy Survey (SNLS). The SNLS is an ongoing 5 year project with the goal of measuring the equation of state of dark energy by discovering and following over 700 high-redshift SNe Ia using data from the Canada-France-Hawaii Telescope Legacy Survey. We achieve an improvement in the SN Ia spectroscopic confirmation rate: at Gemini 71% of candidates are now confirmed as SNe Ia, compared to 54% using the methods of previous surveys. This is despite the comparatively high redshift of this sample, in which the median SN Ia redshift is z=0.81 (0.155<=z<=1.01). These improvements were realized because we use the unprecedented color coverage and light curve sampling of the SNLS to predict whether a candidate is a SN Ia and to estimate its redshift, before obtaining a spectrum, using a new technique called the ``SN photo-z.'' In addition, we have improved techniques for galaxy subtraction and SN template χ2 fitting, allowing us to identify candidates even when they are only 15% as bright as the host galaxy. The largest impediment to SN identification is found to be host galaxy contamination of the spectrum-when the SN was at least as bright as the underlying host galaxy the target was identified more than 90% of the time. However, even SNe in bright host galaxies can be easily identified in good seeing conditions. When the image quality was better than 0.55", the candidate was identified 88% of the time. Over the 5 year course of the survey, using the selection techniques presented here, we will be able to add ~170 more confirmed SNe Ia than would be possible using previous methods. APC, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France. DSM/DAPNIA, CEA/Saclay, 91191 Gif-sur-Yvette Cedex, France.

  9. Rapid, Machine-Learned Resource Allocation: Application to High-redshift GRB Follow-up

    CERN Document Server

    Morgan, Adam N; Richards, Joseph W; Broderick, Tamara; Butler, Nathaniel R; Bloom, Joshua S

    2011-01-01

    As the number of observed Gamma-Ray Bursts (GRBs) continues to grow, follow-up resources need to be used more efficiently in order to maximize science output from limited telescope time. As such, it is becoming increasingly important to rapidly identify bursts of interest as soon as possible after the event, before the afterglows fade beyond detectability. Studying the most distant (highest redshift) events, for instance, remains a primary goal for many in the field. Here we present our Random forest Automated Triage Estimator for GRB redshifts (RATE GRB-z) for rapid identification of high-redshift candidates using early-time metrics from the three telescopes onboard Swift. While the basic RATE methodology is generalizable to a number of resource allocation problems, here we demonstrate its utility for telescope-constrained follow-up efforts with the primary goal to identify and study high-z GRBs. For each new GRB, RATE GRB-z provides a recommendation - based on the available telescope time - of whether the e...

  10. On the faint end of the high redshift AGN luminosity function

    CERN Document Server

    Shankar, F; Shankar, Francesco; Mathur, Smita; Shankar, Francesco; Mathur, Smita

    2007-01-01

    Using the results of recent optical surveys we conclude that the {\\it non}-detection of quasars down to faint magnitudes implies a significant flattening of the high redshift (z~6) optical active galactic nuclei (AGN) luminosity function for M_{1450}>-26.7. We find that all the data are consistent with a faint-end slope for the optical AGN luminosity function of \\beta=-2.2 and \\beta=-2.8, at the 90% and 99% confidence level respectively, flatter than the bright-end slope of \\beta'~ -3.2. We also show that X-ray deep surveys have probed even fainter magnitudes than the optical ones yielding more significant constraints on the shallow faint-end slope of the optical luminosity function. The inclusion of Type II AGN candidates, detected in the Chandra deep fields, hints towards an higher normalization for the total AGN luminosity function, if these sources lie at 5

  11. Core Dominance Parameter for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    S. H. Li; J. H. Fan; D. X. Wu

    2014-09-01

    In this paper, we compiled 572 blazars that have known core dominance parameter (log ), out of which 121 blazars are -ray loud blazars. We compared log between 121 blazars and the rest with non -ray detections, and found that -ray loud blazars showed a different distribution, and their average value of log is greater than that for non -ray blazars. Our analysis suggests that the -ray emissions are strongly beamed.

  12. Strong Clustering of High-Redshift Lyman-alpha Forest Absorption Systems

    OpenAIRE

    Fernandez-Soto, A.; Lanzetta, K. M.; Barcons, X.; Carswell, R. F.; Webb, J. K.; Yahil, A.

    1996-01-01

    We use new observations of very weak CIV absorption lines associated with high-redshift Lyman-alpha absorption systems to measure the high-redshift Lyman-alpha line two-point correlation function (TPCF). These very weak CIV absorption lines trace small-scale velocity structure that cannot be resolved by Lyman-alpha absorption lines. We find that (1) high-redshift Lyman-alpha absorption systems with N(HI) > 3.10^14 cm^{-2} are strongly clustered in redshift, (2) previous measurements of the Ly...

  13. The potential of INTEGRAL for the detection of high redshift GRBs

    DEFF Research Database (Denmark)

    Gorosabel, J.; Lund, Niels; Brandt, Søren Kristian; Westergaard, Niels Jørgen Stenfeldt; Ceron, J.M.C.

    2004-01-01

    We discuss INTEGRAL's ability to detect a high redshift population of Gamma-Ray Bursts (GRBs) in comparison to other high-energy missions. Emphasis is placed on the study of the relative capabilities of IBIS on board INTEGRAL with respect to SWIFT and HETE 2 in detecting a high redshift populatio......, IBIS might be able to detect high redshift (z greater than or similar to 7) GRBs, unreachable by SWIFT and HETE 2. We discuss the relevance of performing near-infrared (NIR) observations of the INTEGRAL GRBs and the strategy that large-class telescopes might follow....

  14. FORMATION OF THE FIRST NUCLEAR CLUSTERS AND MASSIVE BLACK HOLES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    We present a model for the formation of massive black holes (∼1000 M sun) due to stellar-dynamical processes in the first stellar clusters formed at early cosmic times (z ∼ 10-20). These black holes are likely candidates as seeds for the supermassive black holes detected in quasars and nearby quiescent galaxies. The high redshift black hole seeds form as a result of multiple successive instabilities that occur in low metallicity (Z ∼ 10-5 Z sun) protogalaxies. We focus on relatively massive halos at high redshift (T vir > 104 K, z ∼> 10) after the very first stars in the universe have completed their evolution. This set of assumptions ensures that (1) atomic hydrogen cooling can contribute to the gas cooling process, (2) a UV field has been created by the first stars, and (3) the gas inside the halo has been mildly polluted by the first metals. The second condition implies that at low density H 2 is dissociated and does not contribute to cooling. The third condition sets a minimum threshold density for fragmentation, so that stars form efficiently only in the very inner core of the protogalaxy. Within this core, very compact stellar clusters form. The typical star cluster masses are of order 105 M sun and the typical half mass radii ∼1 pc. A large fraction of these very dense clusters undergoes core collapse before stars are able to complete stellar evolution. Runaway star-star collisions eventually lead to the formation of a very massive star, leaving behind a massive black hole remnant. Clusters unstable to runaway collisions are always the first, less massive ones that form. As the metallicity of the universe increases, the critical density for fragmentation decreases and stars start to form in the entire protogalactic disk so that (1) accretion of gas in the center is no longer efficient and (2) the core collapse timescale increases. Typically, a fraction ∼0.05 of protogalaxies at z ∼ 10-20 form black hole seeds, with masses ∼1000-2000 M sun

  15. Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study

    CERN Document Server

    Garavini, G; Nobili, S; Aldering, G; Amanullah, R; Antilogus, P; Astier, Pierre; Blanc, G; Bronder, J; Burns, M S; Conley, A; Deustua, S E; Doi, M; Fabbro, S; Fadeev, V; Gibbons, R; Goldhaber, G; Goobar, A; Groom, D E; Hook, I; Howell, D A; Kashikawa, N; Kim, A G; Kowalski, M; Kuznetsova, N; Lee, B C; Lidman, C; Méndez, J; Morokuma, T; Motohara, K; Nugent, P; Pain, R; Perlmutter, S; Quimby, R; Raux, J; Regnault, N; Ruiz-Lapuente, P; Sainton, G; Schahmaneche, K; Smith, E; Spadafora, A L; Stanishev, V; Thomas, R C; Walton, N A; Wang, L; Wood-Vasey, W M; Project, N Y T S C

    2007-01-01

    We develop a method to measure the strength of the absorption features in Type Ia supernova (SN Ia) spectra and use it to make a quantitative comparison between the spectra of Type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 < z < 0.912) SNe Ia observed by the Supernova Cosmology Project . Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca II H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z=0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.

  16. Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study

    Energy Technology Data Exchange (ETDEWEB)

    Supernova Cosmology Project; Nugent, Peter E; Garavini, G.; Folatelli, G.; Nobili, S.; Aldering, G.; Amanullah, R.; Antilogus, P.; Astier, P.; Blanc, G.; Bronder, J.; Burns, M.S.; Conley, A.; Deustua, S. E.; Doi, M.; Fabbro, S.; Fadeyev, V.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hook, I.; Howell, D. A.; Kashikawa, N.; Kim, A. G.; Kowalski, M.; Kuznetsova, N.; Lee, B. C.; Lidman, C.; Mendez, J.; Morokuma, T.; Motohara, K.; Nugent, P. E.; Pain, R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2008-03-24

    We develop a method to measure the strength of the absorption features in type Ia supernova (SN Ia) spectra and use it to make a quantitative comparisons between the spectra of type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 = z = 0.912) SNe Ia observed by the Supernova Cosmology Project. Through measurements of the strengths of these features and of the blueshift of theabsorption minimum in Ca ii H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z< 0.15). One supernova in our high redshift sample, SN 2002fd at z = 0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.

  17. Quantitative comparison between type Ia supernova spectra at low and high redshifts: a case study

    Science.gov (United States)

    Garavini, G.; Folatelli, G.; Nobili, S.; Aldering, G.; Amanullah, R.; Antilogus, P.; Astier, P.; Blanc, G.; Bronder, T.; Burns, M. S.; Conley, A.; Deustua, S. E.; Doi, M.; Fabbro, S.; Fadeyev, V.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D. E.; Hook, I.; Howell, D. A.; Kashikawa, N.; Kim, A. G.; Kowalski, M.; Kuznetsova, N.; Lee, B. C.; Lidman, C.; Mendez, J.; Morokuma, T.; Motohara, K.; Nugent, P. E.; Pain, R.; Perlmutter, S.; Quimby, R.; Raux, J.; Regnault, N.; Ruiz-Lapuente, P.; Sainton, G.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.; Yasuda, N.

    2007-08-01

    We develop a method to measure the strength of the absorption features in type Ia supernova (SN Ia) spectra and use it to make a quantitative comparisons between the spectra of type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 ≤ z ≤ 0.912) SNe Ia observed by the Supernova Cosmology Project. Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca ii H&K, we show that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z = 0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.

  18. XMM-Newton analysis of a newly discovered, extremely X-ray luminous galaxy cluster at high redshift

    Science.gov (United States)

    Thoelken, S.; Schrabback, T.

    2016-06-01

    Galaxy clusters, the largest virialized structures in the universe, provide an excellent method to test cosmology on large scales. The galaxy cluster mass function as a function of redshift is a key tool to determine the fundamental cosmological parameters and especially measurements at high redshifts can e.g. provide constraints on dark energy. The fgas test as a direct cosmological probe is of special importance. Therefore, relaxed galaxy clusters at high redshifts are needed but these objects are considered to be extremely rare in current structure formation models. Here we present first results from an XMM-Newton analysis of an extremely X-ray luminous, newly discovered and potentially cool core cluster at a redshift of z=0.9. We carefully account for background emission and PSF effects and model the cluster emission in three radial bins. Our preliminary results suggest that this cluster is indeed a good candidate for a cool core cluster and thus potentially of extreme value for cosmology.

  19. A search for moderate-redshift survivors from the population of luminous compact passive galaxies at high redshift

    International Nuclear Information System (INIS)

    From a search of a ∼2400 deg2 region covered by both the Sloan Digital Sky Survey and UKIRT Infrared Deep Sky Survey databases, we have attempted to identify galaxies at z ∼ 0.5 that are consistent with their being essentially unmodified examples of the luminous passive compact galaxies found at z ∼ 2.5. After isolating good candidates via deeper imaging, we further refine the sample with Keck moderate-resolution spectroscopy and laser guide star adaptive-optics imaging. For four of the five galaxies that so far remain after passing through this sieve, we analyze plausible star-formation histories based on our spectra in order to identify galaxies that may have survived with little modification from the population formed at high redshift. We find two galaxies that are consistent with having formed ≳ 95% of their mass at z > 5. We attempt to estimate masses both from our stellar population determinations and from velocity dispersions. Given the high frequency of small axial ratios, both in our small sample and among samples found at high redshifts, we tentatively suggest that some of the more extreme examples of passive compact galaxies may have prolate morphologies.

  20. Blazar Demographics Using Multiwavelength Data

    Science.gov (United States)

    Mao, Peiyuan; Massaro, F.; Urry, C. Megan

    2016-01-01

    Blazars are ideal laboratories to study relativistic jets in AGN, which are thought to be an important channel for feeding energy into galaxies and clusters. We present multi-wavelength SEDs of 2214 blazars with known redshifts, based on the Roma-BZCAT data across 12 frequency bands ranging from radio to gamma-ray. We confirm the anti-correlation between radio luminosity and synchrotron peak frequency, (part of what defines the "blazar sequence"), although with greater scatter than seen previously in studies of far fewer blazars. We describe an empirical estimator of luminosities in those 12 frequency bands using only the radio luminosity at 1.4 GHz and the redshift as inputs. Using this estimator, we study the demographics of blazars by comparing Monte-Carlo simulations to blazar surveys at several different frequencies and flux limits. We recover the observed evolutionary parameter for both low-frequency peaked (V/Vmax≈0.6) and high-frequency peaked (V/Vmax≈0.4) blazars, proving that selection effects cause the high-frequency-peaked sources to appear to anti-evolve even though the same underlying evolution was assumed in the simulation. We also show that the if instead we randomly assign fluxes independent of radio luminosity, the simulated blazar samples disagree strongly with the observed ones. These simulations confirm that luminosity and SED shape must indeed be linked in a physical blazar sequence.

  1. The Proton Blazar

    OpenAIRE

    Mannheim, Karl

    1993-01-01

    Considering shock-accelerated protons in addition to electrons in a synchrotron radio jet naturally produces the observed X- through gamma ray continuum emission of flat-spectrum radio-loud AGN, whereas the corresponding shock-accelerated electrons produce the infrared through optical continuum. All of these emission components are rapidly variable on short time scales which can be accounted for by a common origin of the blazar emission in a relativistic sub-parsec scale jet. Moreover, neutri...

  2. Variability of Blazars

    Indian Academy of Sciences (India)

    J. H. Fan; Y. Liu; Y. Li; Q. F. Zhang; J. Tao; O. Kurtanidze

    2011-03-01

    Variability is one of the characteristics of blazars. The rapid variability is superposed on the long term variation. In this work, the variability on different time scales, such as intra-day (IDV), short-term (STV) and long-term (LTV) variations are presented for some sources. We also presented our own observations of some selected objects, for which the historical data were compiled for periodicity analysis using several methods. The parameters of the binary black hole system OJ 287 are determined.

  3. A Spectroscopic Search for Protoclusters at High Redshift

    Science.gov (United States)

    Avruch, I. M.; Burke, B. F.; Davis, M. M.; Horowitz, P.; Leigh, D.; Weintroub, J.

    1995-12-01

    Between recombination (z ~ 1100) and the quasars (z ~ 5) structures formed which today we observe in the hierarchy of galaxies, clusters, voids, and sheets. Theories of what happened in that interval are constrained by observations of the diffuse CMB and the appearance of discrete objects. We want to extend the lower bound by detecting protoclusters in collapse. We are trying to observe these in the hydrogen hyperfine line (lambda 21 cm), at redshifts 4.7 mixers, and a custom power-accumulating FFT spectrometer with 10 kHz resolution and 32 MHz instantaneous bandwidth centered at 235 MHz (4 k channels per feed). The spectrometer output is time tagged and logged to disk on a control PC, and digital audio data tapes are shipped biweekly to Cambridge. We present the current status of the experiment. Strong RFI is a problem except for a few early morning hours, and spillover losses are unexpectedly high. We are redesigning our feed to lower horizon sensitivity and maximize overall SNR. Design requirements are derived by modeling with candidate feeds the effects of spherical aberration and squint on system gain and noise temperature.

  4. ZEN and the search for high-redshift galaxies

    Science.gov (United States)

    Willis, Jon; Courbin, Frédéric; Kneib, Jean-Paul; Minniti, Dante

    2006-03-01

    We present the ZEN ( z equals nine) survey: a deep, narrow J-band search for proto-galactic Ly α emission at redshifts z ˜ 9. In the first phase of the survey, dubbed ZEN1, we combine an exceptionally deep image of the Hubble Deep Field South, obtained using a narrow-band filter centred on the wavelength 1.187 μm, with existing deep, broad band images covering optical to near infrared wavelengths. Candidate z ˜ 9 Ly α-emitting galaxies display a significant narrow-band excess relative to the Js-band that are undetected at optical wavelengths. We detect no sources consistent with this criterion to the 90% point source flux limit of the NB image, FNB = 3.28 × 10 -18 ergs s -1 cm -2. The survey selection function indicates that we have sampled a volume of approximately 340 h -3 Mpc 3 to a Ly α emission luminosity of 10 43 h -2 ergs s -1. When compared to the predicted properties of z ˜ 9 galaxies based upon no evolution of observed z ˜ 6 Ly α-emitting galaxies, the 'volume shortfall' of the current survey, i.e., the volume required to detect this putative population, is a factor of at least 8-10. We also discuss continuing narrow J-band imaging surveys that will reduce the volume shortfall factor to the point where the no-evolution prediction from z ˜ 6 is probed in a meaningful manner.

  5. THE ENVIRONMENTS OF HIGH-REDSHIFT QUASI-STELLAR OBJECTS

    International Nuclear Information System (INIS)

    We present a sample of i 775-dropout candidates identified in five Hubble Advanced Camera for Surveys (ACS) fields centered on Sloan Digital Sky Survey quasi-stellar objects (QSOs) at redshift z ∼ 6. Our fields are as deep as the GOODS ACS images, which are used as a reference field sample. We find them to be overdense in two fields, underdense in two fields, and as dense as the average density of GOODS in one field. The two excess fields show significantly different color distributions from that of GOODS at the 99% confidence level, strengthening the idea that the excess objects are indeed associated with the QSO. The distribution of i 775-dropout counts in the five fields is broader than that derived from GOODS at the 80%-96% confidence level, depending on which selection criteria were adopted to identify i 775-dropouts; its width cannot be explained by cosmic variance alone. Thus, QSOs seem to affect their environments in complex ways. We suggest the picture where the highest redshift QSOs are located in very massive overdensities and are therefore surrounded by an overdensity of lower mass halos. Radiative feedback by the QSO can in some cases prevent halos from becoming galaxies, thereby generating in extreme cases an underdensity of galaxies. The presence of both enhancement and suppression is compatible with the expected differences between lines of sight at the end of reionization as the presence of residual diffuse neutral hydrogen would provide young galaxies with shielding from the radiative effects of the QSO.

  6. Gamma Rays From Blazars

    CERN Document Server

    Tavecchio, F

    2016-01-01

    Blazars are high-energy engines providing us natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics, black hole physics. Key informations are provided by observations at high-energy (in particular by Fermi/LAT) and very-high energy (by Cherenkov telescopes). I give a short account of the current status of the field, with particular emphasis on the theoretical challenges connected to the observed ultra-fast variability events and to the emission of flat spectrum radio quasars in the very high energy band.

  7. Probing the dark ages: Observations of the high-redshift universe

    Science.gov (United States)

    Stevens, Daniel Keith

    This thesis attempts to describe some of the earliest phases in the collapse of galaxies from an observational standpoint. The work is composed of an assortment of projects which sample objects at very high redshift, probing the Universe 1-3 Gyr after the Big Bang. The first section of the thesis concerns high-redshift galaxies. Search techniques for identifying distant galaxies are extensively reviewed. Radio selection was once the primary vehicle to targeting the early Universe. Keck spectroscopy of high-redshift radio galaxies from the MIT-Greenbank radio catalog (S5GHz >~ 50 mJy) are discussed. We synthesize a composite radio galaxy spectrum, which we compare with other composite active galaxy spectra. Our data suggests a correlation between radio power and ionization state in high-redshift radio galaxies. The following three chapters detail individual galaxies confirmed at z > 5. These galaxies are among the half-dozen most distant sources known at the close of the 20th Century. Two of the galaxies were photometrically-selected from the Hubble Deep Field (HDF 4-473.0 at z = 5.60 and HDF 3-951.0 at z = 5.34 +/- 0.01). The third is TN J0924-2201, a radio galaxy at z = 5.19 selected on the basis of steep radio spectral index and faint K-band brightness. This source contains the most distant active galactic nucleus currently known, requiring early formation of supermassive blackholes within a Gyr after the Big Bang. The second section of the thesis concerns searches for high-redshift Lyα emission, identified either from deep, narrow-band imaging surveys or deep slit spectra. We discuss in detail one faint, high equivalent width line-emitter. Conventional wisdom would suggest identifying the 9185 Å line with Lyα at z = 6.55. We argue [O II] λ3727 at z = 1.46 is the more likely identification and discuss observational tests to distinguish Lyα-emitters at high redshift from foreground (active) sources. The final section of the thesis concerns high-redshift

  8. AGN Winds and Blazar Phenomenology

    Science.gov (United States)

    Kazanas, Demos

    2012-01-01

    The launch of {\\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

  9. Blazar jets the spectra

    CERN Document Server

    Ghisellini, G

    2000-01-01

    The radiation observed by blazars is believed to originate from the transformation of bulk kinetic energy of relativistic jets into random energy. A simple way to achieve this is to have an intermittent central power source, producing shells of plasma with different bulk Lorentz factors. These shells will collide at some distance from the center, producing shocks and then radiation. This scenario, called internal shock model, is thought to be at the origin of the gamma-rays observed in gamma-ray bursts and can work even better in blazars. It accounts for the observed key characteristics of these objects, including the fact that radiation must be preferentially produced at a few hundreds of Schwarzschild radii from the center, but continues to be produced all along the jet. At the kpc scale and beyond, the slowly moving parts of a (straight) jet can be illuminated by the beamed radiation of the core, while the fast parts of the jet will see enhanced cosmic microwave radiation. In both cases the Inverse Compton...

  10. The CLASS blazar survey: testing the blazar sequence

    CERN Document Server

    Caccianiga, A

    2004-01-01

    We discuss the properties of the sources in the CLASS Blazar survey which aims at the selection of low radio power (P(5GHz)<10^25 W Hz^-1) blazars. We use VLA data from available catalogues and from our own observations to constrain the radio core-dominance of the sample which, together with the flat radio spectral index, is a signature of the blazar activity. X-ray data from the ROSAT All Sky Survey were also collected in order to constrain the radio-to-X-ray luminosity ratio (alpha_RX) of the sources. The data analysis shows that more than 30% of sources at low radio power (P(5 GHz)<10^25 W Hz^-1) have an alpha_RX steeper than that expected in the framework of the ``blazar sequence'' recently put forward to unify the high and low power blazars. The possibility that this result is influenced by contaminating sources in the current sample is discussed. The conclusion is that, even if a number of non-blazars (typically CSO/GPS sources) are expected in the survey, it is unlikely that this constitutes the ...

  11. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data II: The Spring Equatorial Stripe

    OpenAIRE

    SDSS Collaboration; Fan, Xiaohui

    1999-01-01

    This is the second paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from ~250 deg^2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of sky. Our success rate of identifying high-redshift quasars is ...

  12. Weak line quasars at high redshift: extremely high accretion rates or anemic broad-line regions?

    NARCIS (Netherlands)

    O. Shemmer; B. Trakhtenbrot; S.F. Anderson; W.N. Brandt; A.M. Diamond-Stanic; X. Fan; P. Lira; H. Netzer; R.M. Plotkin; G.T. Richards; D.P. Schneider; M.A. Strauss

    2010-01-01

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak

  13. Spectra of High-Redshift Type Ia Supernovae and a Comparison withtheir Low-Redshift Counterparts

    Energy Technology Data Exchange (ETDEWEB)

    Hook, I.M.; Howell, D.A.; Aldering, G.; Amanullah, R.; Burns,M.S.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fadeyev, V.; Folatelli, G.; Garavini, G.; Gibbons, R.; Goldhaber, G.; Goobar, A.; Groom, D.E.; Kim, A.G.; Knop, R.A.; Kowalski, M.; Lidman, C.; Nobili, S.; Nugent, P.E.; Pain, R.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente,P.; Sainton, G.; Schaefer, B.E.; Smith, E.; Spadafora, A.L.; Stanishev,V.; Thomas, R.C.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.

    2005-07-20

    We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted Ca H&K are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these low- and high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift.

  14. ON THE EFFECT OF THE COSMIC MICROWAVE BACKGROUND IN HIGH-REDSHIFT (SUB-)MILLIMETER OBSERVATIONS

    International Nuclear Information System (INIS)

    Modern (sub-)millimeter interferometers enable the measurement of the cool gas and dust emission of high-redshift galaxies (z > 5). However, at these redshifts the cosmic microwave background (CMB) temperature is higher, approaching, and even exceeding, the temperature of cold dust and molecular gas observed in the local universe. In this paper, we discuss the impact of the warmer CMB on (sub-)millimeter observations of high-redshift galaxies. The CMB affects the observed (sub-)millimeter dust continuum and the line emission (e.g., carbon monoxide, CO) in two ways: (1) it provides an additional source of (both dust and gas) heating and (2) it is a non-negligible background against which the line and continuum emission are measured. We show that these two competing processes affect the way we interpret the dust and gas properties of high-redshift galaxies using spectral energy distribution models. We quantify these effects and provide correction factors to compute what fraction of the intrinsic dust (and line) emission can be detected against the CMB as a function of frequency, redshift, and temperature. We discuss implications on the derived properties of high-redshift galaxies from (sub-)millimeter data. Specifically, the inferred dust and molecular gas masses can be severely underestimated for cold systems if the impact of the CMB is not properly taken into account.

  15. On high-redshift quasar absorption spectra and the Riemannian geometry of the Universe

    International Nuclear Information System (INIS)

    It is studied the observed small deviations of high-redshift quasar absorption spectra that are interpreted as a possible evidence for a variable fine structure constant. On the contrary, it was claimed that the effect could be completely attributed to the small amount of cosmic shear beyond the standard Friedmann expanding Universe

  16. The rest-frame submillimeter spectrum of high-redshift, dusty, star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Spilker, J. S.; Marrone, D. P. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Aguirre, J. E. [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Aravena, M. [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001 Vitacura Santiago (Chile); Ashby, M. L. N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Béthermin, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Université Paris Diderot, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Bradford, C. M. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Bothwell, M. S. [Cavendish Laboratory, University of Cambridge, JJ Thompson Ave, Cambridge CB3 0HA (United Kingdom); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Carlstrom, J. E.; Crawford, T. M. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Chapman, S. C. [Dalhousie University, Halifax, Nova Scotia (Canada); De Breuck, C.; Gullberg, B. [European Southern Observatory, Karl Schwarzschild Straße 2, D-85748 Garching (Germany); Fassnacht, C. D. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, A. H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Hezaveh, Y. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Holzapfel, W. L., E-mail: jspilker@as.arizona.edu [Department of Physics, University of California, Berkeley, CA 94720 (United States); and others

    2014-04-20

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250 to 770 GHz. This spectrum was constructed by stacking Atacama Large Millimeter/submillimeter Array (ALMA) 3 mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z = 2.0-5.7. In addition to multiple bright spectral features of {sup 12}CO, [C I], and H{sub 2}O, we also detect several faint transitions of {sup 13}CO, HCN, HNC, HCO{sup +}, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the {sup 13}CO brightness in these objects is comparable to that of the only other z > 2 star-forming galaxy in which {sup 13}CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO{sup +}, and CN is consistent with a warm, dense medium with T {sub kin} ∼ 55 K and n{sub H{sub 2}}≳10{sup 5.5} cm{sup –3}. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlikely to be significant for the bulk of these systems. We quantify the average emission from several species with no individually detected transitions, and find emission from the hydride CH and the linear molecule CCH for the first time at high redshift, indicating that these molecules may be powerful probes of interstellar chemistry in high-redshift systems. These observations represent the first constraints on many molecular species with rest-frame transitions from 0.4 to 1.2 mm in star-forming systems at high redshift, and will be invaluable in making effective use of ALMA in full science operations.

  17. Blazar sequence - an artefact of Doppler boosting

    OpenAIRE

    Nieppola, E.; Valtaoja, E.; Tornikoski, M.; Hovatta, T.; Kotiranta, M.

    2008-01-01

    The blazar sequence is a scenario in which the bolometric luminosity of the blazar governs the appearance of its spectral energy distribution. The most prominent result is the significant negative correlation between the synchrotron peak frequencies and the synchrotron peak luminosities of the blazar population. Observational studies of the blazar sequence have, in general, neglected the effect of Doppler boosting. We study the dependence of both the synchrotron peak frequency and luminosity ...

  18. A New Relativistic Jet Model of Blazars

    Science.gov (United States)

    Webb, James; Benitez, Erika; Howard, Emily

    1998-11-01

    The subclass of Active galaxies called Blazars encompass the most intrinsically luminous and rapidly variable sources known to astrophysicists. Attempts to model these sources has largely been frustrated due in part to observational difficulties, but also due to the lack of theoretical models capable of explaining the different characteristics of the observed sources. Leading candidate models all incorporate a massive, rotating black hole which is accreting galactic material, with some of this material being ejected out the ratational axis of the hole in the form of relativistically expanding jets. These jets are thought to emit energy via the synchrotron process across the entire spectrum from radio frequences all the way through the GEV (sometimes TEV) gamma-ray frequencies. Attempts to model these sources with single relativistic jets has proven difficult. We present a new model which features concentric interacting jets that do a much better job of explaining the types of Blazars we observe. We also discuss ways of testing this new model against multifreuqency observations.

  19. First Structure Formation A Simulation of Small Scale Structure at High Redshift

    CERN Document Server

    Jang-Condell, H; Jang-Condell, Hannah; Hernquist, Lars

    2000-01-01

    We describe the results of a simulation of collisionless cold dark matter in a LambdaCDM universe to examine the properties of objects collapsing at high redshift (z=10). We analyze the halos that form at these early times in this simulation and find that the results are similar to those of simulations of large scale structure formation at low redshift. In particular, we consider halo properties such as the mass function, density profile, halo shape, spin parameter, and angular momentum alignment with the minor axis. By understanding the properties of small scale structure formation at high redshift, we can better understand the nature of the first structures in the universe, such as Population III stars.

  20. Age of high redshift objects-a litmus test for the dark energy models

    International Nuclear Information System (INIS)

    The discovery of the quasar, the APM 08279+5255 at z=3.91 whose age is 2-3 Gyr has once again led to 'age crisis'. The noticeable fact about this object is that it cannot be accommodated in a universe with Ωm=0.27, currently accepted value of matter density parameter and ω=const. In this work, we explore the concordance of various dark energy parameterizations (w(z) models) with the age estimates of the old high redshift objects. It is alarming to note that the quasar cannot be accommodated in any dark energy model even for Ωm=0.23, which corresponds to 1σ deviation below the best fit value provided by WMAP. There is a need to look for alternative cosmologies or some other dark energy parameterizations which allow the existence of the high redshift objects

  1. Cosmic star formation, gamma-ray burst rate at high redshift and cosmic chemical evolution

    International Nuclear Information System (INIS)

    Recent optical observations and Gamma-ray burst rate determinations have led to significant progress in establishing the star formation rate (SFR) at high redshift. The SFR in turn is used to predict the ionization history of the Universe (using last results from CMB WMAP mission), the cosmic chemical abundances, and supernova rates. These predictions are done using a hierarchical model for structure formation (Press and Schechter). (author)

  2. Expected Number and Flux Distribution of Gamma-Ray-Burst Afterglows with High Redshifts

    OpenAIRE

    Ciardi, Benedetta; Loeb, Abraham

    2000-01-01

    If Gamma-Ray-Bursts (GRBs) occur at high redshifts, then their bright afterglow emission can be used to probe the ionization and metal enrichment histories of the intervening intergalactic medium during the epoch of reionization. In contrast to other sources, such as galaxies or quasars, which fade rapidly with increasing redshift, the observed infrared flux from a GRB afterglow at a fixed observed age is only a weak function of its redshift. This results from a combination of the spectral sl...

  3. A Systematic Meta-Survey of High Redshift Quasars Probing their Environments and Evolution

    Science.gov (United States)

    Gobeille, Doug B. P.

    We have constructed a meta-survey of 298 quasars in the window from 7 to 17.5 hours in right ascension and 0 to 65 degrees in declination. These quasars span three decades of total power and redshifts from 0.158 to 5.284. All sources had a flux density of greater than 70 mJy at 1.4 GHz. At redshifts z > 2.5 our sample is complete. It is also complete for z 1027.55 W/Hz. Our quasar sample is built from archival Very Large Array (VLA) observations, as well as three observations in 2007 and 2008. This sample represents one of the most complete meta-surveys to date of the high redshift universe. In the 1980's, two competing groups (Ne, Gower and Hutchings, and Barthel, Miley, and Lonsdale) investigated the high redshift universe, seeking to investigate the dependence of largest linear size (LLS) and bending angles on redshift, core power, and extended power. Using our sample we test the differing results of these groups and build our own model of source evolution with redshift and power. We also seek a relationship between bending angles and core dominance, modeling this dependence on the thoughts of Orr & Browne showing that projected bending angles grow as the angle to the line of sight approaches the intrinsic bending angle of the quasar. We will also present an additional component of our high redshift quasar observations seeking arcsecond scale jets to be observed with the space based Chandra x-ray telescope. These observations will be used to investigate the nature of x-ray emission from the knots of kiloparsec jets in the high redshift universe.

  4. Evolution of Neutral Gas at High Redshift -- Implications for the Epoch of Galaxy Formation

    OpenAIRE

    Storrie-Lombardi, L. J.; McMahon, R. G.; Irwin, M J

    1996-01-01

    Though observationally rare, damped Lya absorption systems dominate the mass density of neutral gas in the Universe. Eleven high redshift damped Lya systems covering 2.83.5 in number density per unit redshift of damped systems with column densities log N(HI)>21 atoms cm^-2, these results point to an epoch at z>3 prior to which the highest column density damped systems are still forming. We find that over the redshift range 2

  5. UV Spectroscopy of Type Ia Supernovae at Low- and High-Redshift

    International Nuclear Information System (INIS)

    In the past three years two separate programs were initiated to study the restframe UV properties of Type Ia Supernovae. The low-redshift study was carried out using several ground-based facilities coupled with HST/STIS observations. The high-redshift program is an offshoot of the CFHT Legacy Survey and uses Keck/LRIS to obtain spectra. Here we present the preliminary results from each program and their implications for current cosmology measurements

  6. Are globular clusters the natural outcome of regular high-redshift star formation?

    Science.gov (United States)

    Kruijssen, J. M. Diederik

    2016-02-01

    We summarise the recent progress in understanding the formation and evolution of globular clusters (GCs) in the context of galaxy formation and evolution. It is discussed that an end-to-end model for GC formation and evolution should capture four different phases: (1) star and cluster formation in the high-pressure interstellar medium of high-redshift galaxies, (2) cluster disruption by tidal shocks in the gas-rich host galaxy disc, (3) cluster migration into the galaxy halo, and (4) the final evaporation-dominated evolution of GCs until the present day. Previous models have mainly focussed on phase 4. We present and discuss a simple model that includes each of these four steps - its key difference with respect to previous work is the simultaneous addition of the high-redshift formation and early evolution of young GCs, as well as their migration into galaxy haloes. The new model provides an excellent match to the observed GC mass spectrum and specific frequency, as well as the relations of GCs to the host dark matter halo mass and supermassive black hole mass. These results show (1) that the properties of present-day GCs are reproduced by assuming that they are the natural outcome of regular high-redshift star formation (i.e. they form according to same physical processes that govern massive cluster formation in the local Universe), and (2) that models only including GC evaporation strongly underestimate their integrated mass loss over a Hubble time.

  7. Predictions for the Counts of Faint, High-Redshift Galaxies in the Mid-Infrared

    CERN Document Server

    Haiman, Z; Turner, E L; Haiman, Zoltan; Spergel, David N.; Turner, Edwin L.

    2003-01-01

    Deep mid-infrared (MIR) observations could reveal a population of faint, high-redshift (z>3) dusty starburst galaxies that are the progenitors of present-day spheroids or bulges, and are beyond the reach of current instruments. We utilize a semi-analytic galaxy formation scheme to find an extreme model for the MIR galaxy counts, designed to maximize the number of detectable sources down to a flux level of a few nJy. The model incorporates the formation of heavily dust-enshrouded stellar populations at high redshift, and is consistent with existing observations, including faint counts at 1.6um in the NICMOS Hubble Deep Field, and the upper limit on the extragalactic MIR background from TeV gamma rays. Our models predict upto 0.5 galaxies/sq.arcsec at the threshold of 100 nJy at 6um, with a comparable or larger surface density at longer MIR wavelengths. We conclude that a significant new population of high-redshift galaxies could be detected by the Space Infrared Telescope Facility (SIRTF) and Next Generation S...

  8. The impact of nebular emission on the broadband fluxes of high-redshift galaxies

    CERN Document Server

    Zackrisson, E; Leitet, E

    2008-01-01

    A substantial fraction of the light emitted from young or star-forming galaxies at ultraviolet to near-infrared wavelengths comes from the ionized interstellar medium in the form of emission lines and a nebular continuum. At high redshifts, star formation rates are on average higher and stellar populations younger than in the local Universe. Both of these effects act to boost the impact of nebular emission on the overall spectrum of galaxies. Even so, the broadband fluxes and colours of high-redshift galaxies are routinely analyzed under the assumption that the light observed originates directly from stars. Here, we assess the impact of nebular emission on broadband fluxes in Johnson/Cousins BVRIJHK, Sloan Digital Sky Survey griz and Spitzer IRAC/MIPS filters as a function of observed redshift (up to z=15) for galaxies with different star formation histories. We find that nebular emission may account for a non-negligible fraction of the light received from high-redshift galaxies. The ages and masses inferred ...

  9. The escape of ionising radiation from high-redshift dwarf galaxies

    CERN Document Server

    Paardekooper, Jan-Pieter; Altay, Gabriel; Kruip, Chael

    2011-01-01

    The UV escape fraction from high-redshift galaxies plays a key role in models of cosmic reionisation. Because it is currently not possible to deduce the escape fractions during the epoch of reionisation from observations, we have to rely on numerical simulations. Our aim is to better constrain the escape fraction from high-redshift dwarf galaxies, as these are the most likely sources responsible for reionising the Universe. We employ a N-body/SPH method that includes realistic prescriptions for the physical processes that are important for the evolution of dwarf galaxies. These models are post-processed with radiative transfer to determine the escape fraction of ionising radiation. We perform a parameter study to assess the influence of the spin parameter, gas fraction and formation redshift of the galaxy and study the importance of numerical parameters as resolution, source distribution and local gas clearing. We find that the UV escape fraction from high-redshift dwarf galaxies that have formed a rotational...

  10. High-Redshift Galaxy Kinematics: Constraints on Models of Disk Formation

    CERN Document Server

    Robertson, Brant E

    2008-01-01

    Integral field spectroscopy of galaxies at redshift z~2 has revealed a population of early-forming, rotationally-supported disks. These high-redshift systems provide a potentially important clue to the formation processes that build disk galaxies in the universe. A particularly well-studied example is the z=2.38 galaxy BzK-15504, which was shown by Genzel et al. (2006) to be a rotationally supported disk despite the fact that its high star formation rate and short gas consumption timescale require a very rapid acquisition of mass. Previous kinematical analyses have suggested that z~2 disk galaxies like BzK-15504 did not form through mergers because their line-of-sight velocity fields display low levels of asymmetry. We perform the same kinematical analysis on a set of simulated disk galaxies formed in gas-rich mergers of the type that may be common at high redshift, and show that the remnant disks display low velocity field asymmetry and satisfy the criteria that have been used to classify high-redshift galax...

  11. On the effect of the Cosmic Microwave Background in high-redshift (sub-)millimeter observations

    CERN Document Server

    da Cunha, Elisabete; Walter, Fabian; Decarli, Roberto; Weiss, Axel; Carilli, Chris; Daddi, Emanuele; Elbaz, David; Ivison, Rob; Maiolino, Roberto; Riechers, Dominik; Rix, Hans-Walter; Sargent, Mark; Smail, Ian

    2013-01-01

    Modern (sub-)millimeter interferometers enable the measurement of the cool gas and dust emission of high-redshift galaxies (z>5). However, at these redshifts the cosmic microwave background (CMB) temperature is higher, approaching, and even exceeding, the temperature of cold dust and molecular gas observed in the local Universe. In this paper, we discuss the impact of the warmer CMB on (sub-)millimeter observations of high-redshift galaxies. The CMB affects the observed (sub-)millimeter dust continuum and the line emission (e.g. carbon monoxide, CO) in two ways: (i) it provides an additional source of (both dust and gas) heating; and (ii) it is a non-negligible background against which the line and continuum emission are measured. We show that these two competing processes affect the way we interpret the dust and gas properties of high-redshift galaxies using spectral energy distribution models. We quantify these effects and provide correction factors to compute what fraction of the intrinsic dust (and line) ...

  12. Strong clustering of high-redshift Lyman-$\\alpha$ forest absorption systems

    CERN Document Server

    Fernández-Soto, A; Barcons, X; Carswell, R F; Webb, J K; Yahil, A

    1996-01-01

    We use new observations of very weak CIV absorption lines associated with high-redshift Lyman-alpha absorption systems to measure the high-redshift Lyman-alpha line two-point correlation function (TPCF). These very weak CIV absorption lines trace small-scale velocity structure that cannot be resolved by Lyman-alpha absorption lines. We find that (1) high-redshift Lyman-alpha absorption systems with N(HI) > 3.10^14 cm^{-2} are strongly clustered in redshift, (2) previous measurements of the Lyman-alpha line TPCF underestimated the actual clustering of the absorbers due to unresolved blending of overlapping velocity components, (3) the present observations are consistent with the hypothesis that clustering of Lyman-alpha absorption systems extends to lower column densities, but maybe with smaller amplitude in the correlation function, and (4) the observed clustering is broadly compatible with that expected for galaxies at z \\sim 2-3. We interpret these results as suggesting that many or most Lyman-alpha absorbe...

  13. RAPID, MACHINE-LEARNED RESOURCE ALLOCATION: APPLICATION TO HIGH-REDSHIFT GAMMA-RAY BURST FOLLOW-UP

    International Nuclear Information System (INIS)

    As the number of observed gamma-ray bursts (GRBs) continues to grow, follow-up resources need to be used more efficiently in order to maximize science output from limited telescope time. As such, it is becoming increasingly important to rapidly identify bursts of interest as soon as possible after the event, before the afterglows fade beyond detectability. Studying the most distant (highest redshift) events, for instance, remains a primary goal for many in the field. Here, we present our Random Forest Automated Triage Estimator for GRB redshifts (RATE GRB-z ) for rapid identification of high-redshift candidates using early-time metrics from the three telescopes onboard Swift. While the basic RATE methodology is generalizable to a number of resource allocation problems, here we demonstrate its utility for telescope-constrained follow-up efforts with the primary goal to identify and study high-z GRBs. For each new GRB, RATE GRB-z provides a recommendation—based on the available telescope time—of whether the event warrants additional follow-up resources. We train RATE GRB-z using a set consisting of 135 Swift bursts with known redshifts, only 18 of which are z > 4. Cross-validated performance metrics on these training data suggest that ∼56% of high-z bursts can be captured from following up the top 20% of the ranked candidates, and ∼84% of high-z bursts are identified after following up the top ∼40% of candidates. We further use the method to rank 200 + Swift bursts with unknown redshifts according to their likelihood of being high-z.

  14. Quasi Periodic Oscillations in Blazars

    Indian Academy of Sciences (India)

    Alok C. Gupta

    2014-09-01

    Here we report our recent discoveries of Quasi-Periodic Oscillations (QPOs) in blazars time series data in X-ray and optical electromagnetic bands. Any such detection can give important clues of the location and nature of the processes of emission mechanism. In the case of radio-quiet AGN, the detected QPOs are very likely to be associated with the accretion disk. But in the case of blazars, it may be associated with jets in the high and outburst states, and in the low-state, it is probably associated with the accretion disk. In this brief review, I summarize the recent QPO detections in blazars. There is one strong evidence of QPO detection in XMM–Newton time series data of narrow line Seyfert 1 galaxy RE J1034+396 about which we will also discuss briefly.

  15. Blazars at Low Radio Frequencies

    Science.gov (United States)

    Trüstedt, J.; Kadler, M.; Brüggen, M.; Falcke, H.; Heald, G.; McKean, J.; Mueller, C.; Ros, E.; Schulz, R.; Wilms, J.

    We explore the low radio-frequency properties of the MOJAVE 1 blazar sample using the LOFAR Multi-Frequency Snapshot Sky Survey (MSSS). We find the characteristically flat blazar spectrum to extend down to the LOFAR bands, demonstrating that the emission at these low radio frequencies is still dominated by relativistically beamed emission. As most sources remain unresolved at the MSSS angular resolution, we are reimaging these data using LOFAR baselines beyond the standard MSSS uv-range resulting in an angular resolution of ~24 arcsec. We present first LOFAR images of MOJAVE sources from this project.

  16. Mining the Herschel-ATLAS: submillimeter-selected blazars in equatorial fields

    CERN Document Server

    López-Caniego, M; Massardi, M; Bonavera, L; Herranz, D; Negrello, M; De Zotti, G; Carrera, F J; Danese, L; Fleuren, S; Hardcastle, M; Jarvis, M J; Klöckner, H -R; Mauch, T; Procopio, P; Righini, S; Sutherland, W; Auld, R; Baes, M; Buttiglione, S; Clark, C J R; Cooray, A; Dariush, A; Dunne, L; Dye, S; Eales, S; Hopwood, R; Hoyos, C; Ibar, E; Ivison, R J; Maddox, S; Valiante, E

    2012-01-01

    The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35 mJy at 500{\\mu}m in the \\sim 135 square degrees of the sky covered by the H-ATLAS equatorial fields at 9 h and 15 h, plus half of the field at 12 h. We found that 379 of the H-ATLAS sources have a FIRST counterpart within 10 arcsec, including 8 catalogued blazars (plus one known blazar that was found at the edge of one the H-ATLAS maps). To search for additional blazar candidates we have devised new diagnostic diagrams and found that known blazars occupy a region of the log(S500{\\mu}m/S350{\\mu}m) vs. log(S500{\\mu}m/S1.4GHz) plane separated from that of the other sub-mm sources with radio counterparts. Using this diagnostic we have selected 12 further candidates that turn out to be scattered in the (r-z) vs. (u-r) plane or in the WISE colour-colour diagram proposed by Massaro ...

  17. Debeamed Sequence of LBAS Blazars

    Indian Academy of Sciences (India)

    Bangrong Huang; Xiong Zhang; Dingrong Xiong; Haojin Zhang

    2014-09-01

    We have collected a sample of 71 -ray blazars selected from the Fermi LAT Bright AGN Sample (LBAS). The correlation between synchrotron peak luminosities p and synchrotron peak frequencies p have been studied and there is a weak negative correlation. But after correcting the effect of redshift and Doppler boosting, the relation between intrinsic 'p and 'p show significant positive correlation.

  18. The Perugia Blazar Monitoring Program

    Science.gov (United States)

    Tosti, G.; Fiorucci, M.; Luciani, M.

    We here present a summary of the Perugia blazar monitoring program. To date it is the only ongoing monitoring program carried out in an automatic way. In three years, we were able to collect about 12000 BVR_cI_c photometric points, contributing to get knowledge on the history of many sources brighter than V=3D17.0.

  19. High redshift galaxies in the ALHAMBRA survey: I. selection method and number counts based on redshift PDFs

    CERN Document Server

    Viironen, K; López-Sanjuan, C; Varela, J; Chaves-Montero, J; Cristóbal-Hornillos, D; Molino, A; Fernández-Soto, A; Ascaso, B; Cenarro, A J; Cerviño, M; Cepa, J; Ederoclite, A; Márquez, I; Masegosa, J; Moles, M; Oteo, I; Pović, M; Aguerri, J A L; Alfaro, E; Aparicio-Villegas, T; Benítez, N; Broadhurst, T; Cabrera-Caño, J; Castander, J F; Del Olmo, A; Delgado, R M González; Husillos, C; Infante, L; Martínez, V J; Perea, J; Prada, F; Quintana, J M

    2015-01-01

    Context. Most observational results on the high redshift restframe UV-bright galaxies are based on samples pinpointed using the so called dropout technique or Ly-alpha selection. However, the availability of multifilter data allows now replacing the dropout selections by direct methods based on photometric redshifts. In this paper we present the methodology to select and study the population of high redshift galaxies in the ALHAMBRA survey data. Aims. Our aim is to develop a less biased methodology than the traditional dropout technique to study the high redshift galaxies in ALHAMBRA and other multifilter data. Thanks to the wide area ALHAMBRA covers, we especially aim at contributing in the study of the brightest, less frequent, high redshift galaxies. Methods. The methodology is based on redshift probability distribution functions (zPDFs). It is shown how a clean galaxy sample can be obtained by selecting the galaxies with high integrated probability of being within a given redshift interval. However, reach...

  20. THE X-RAY PROPERTIES OF TYPICAL HIGH-REDSHIFT RADIO-LOUD QUASARS

    International Nuclear Information System (INIS)

    We report spectral, imaging, and variability results from four new XMM-Newton observations and two new Chandra observations of high-redshift (z ∼> 4) radio-loud quasars (RLQs). Our targets span lower, and more representative, values of radio loudness than those of past samples of high-redshift RLQs studied in the X-ray regime. Our spectral analyses show power-law X-ray continua with a mean photon index, (Γ) = 1.74 ± 0.11, that is consistent with measurements of lower redshift RLQs. These continua are likely dominated by jet-linked X-ray emission, and they follow the expected anticorrelation between photon index and radio loudness. We find no evidence of iron Kα emission lines or Compton-reflection continua. Our data also constrain intrinsic X-ray absorption in these RLQs. We find evidence for significant absorption (NH ∼ 1.7 x 1022cm-2) in one RLQ of our sample (SDSS J0011+1446); the incidence of X-ray absorption in our sample appears plausibly consistent with that for high-redshift RLQs that have higher values of radio loudness. In the Chandra observation of PMN J2219-2719 we detect apparent extended (∼14 kpc) X-ray emission that is most likely due to a jet; the X-ray luminosity of this putative jet is ∼2% that of the core. The analysis of a 4.9 GHz Very Large Array image of PMN J2219-2719 reveals a structure that matches the X-ray extension found in this source. We also find evidence for long-term (450-460 days) X-ray variability by 80%-100% in two of our targets.

  1. Semi-analytical galaxy formation models and the high redshift universe

    CERN Document Server

    Lacey, C; Cole, S; Frenk, C S; Governato, F; Lacey, Cedric; Baugh, Carlton; Cole, Shaun; Frenk, Carlos; Governato, Fabio

    1998-01-01

    Semi-analytical models of galaxy formation based on hierarchical clustering now make a wide range of predictions for observable properties of galaxies at low and high redshift. This article concentrates on 2 aspects: (1) Self-consistent modelling of dust absorption predicts a mean UV extinction A_{UV} ~ 1 mag, depending only weakly on redshift, and similar to observational estimates. (2) The models predict that the Lyman-break galaxies found at z ~ 3 should be strongly clustered with a comoving correlation length r_0 = 4-7 Mpc/h (depending on the cosmology), in good agreement with subsequent observational determinations.

  2. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data

    OpenAIRE

    SDSS Collaboration; Fan, X

    1999-01-01

    We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg^2 of five-color (u'g'r'i'z') imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have redshifts higher than 4.6 (z=4.63, 4.75, 4.90 and 5.00, the latter being the highest redshift quasar yet known). In addition, two previously known z > 4 obje...

  3. High-Redshift Quasars as Probes of Primordial Large-Scale Structure and Galaxy Formation

    OpenAIRE

    Djorgovski, S. G.

    1998-01-01

    Several arguments suggest that quasars at z > 4 may be in the cores of future giant ellipticals, and forming at the very highest peaks of the primordial density field. A strong bias-driven primordial clustering is then expected in these fields, which are naturally interpreted as the cores of future rich clusters. High-redshift quasars can thus be used as markers of some of the earliest galaxy formation sites. Recent discoveries of (proto)galaxy companions of z > 4 quasars, and hints of strong...

  4. The red damping wing of Gunn-Peterson trough in the high redshift GRBs

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We calculate the red damping wing of Gunn-Peterson trough taking the evolution of the neutral fraction into consideration and take a clear look at the ionized region around the ionizing sources. We get the result that the damping wing flux feature is mainly determined by the neutral hydrogen outside the ionized bubble and the cut off in the damping wing would be useful to get the size of the ionized bubble. We also fit the red damping wing of the recently discovered high redshift GRB080913 and find that the ionized bubble is too small to create apparent cut off in the spectrum of this burst.

  5. The red damping wing of Gunn-Peterson trough in the high redshift GRBs

    Institute of Scientific and Technical Information of China (English)

    XU Zhou; WEI DaMing

    2009-01-01

    We calculate the red damping wing of Gunn-Petereon trough taking the evolution of the neutral fraction into consideration and take a clear look at the ionized region around the ionizing sources.We get the result that the damping wing flux feature is mainly determined by the neutral hydrogen outside the ionized bubble and the cut off in the damping wing would be useful to get the size of the ionized bubble.We also fit the red damping wing of the recently discovered high redshift GRB080913 and find that the ionized bubble is too small to create apparent cut off in the spectrum of this buret.

  6. Observational Signatures of High-Redshift Quasars and Local Relics of Black Hole Seeds

    CERN Document Server

    Reines, Amy

    2016-01-01

    Observational constraints on the birth and early evolution of massive black holes (BHs) come from two extreme regimes. At high redshift, quasars signal the rapid growth of billion-solar-mass BHs and indicate that these objects began remarkably heavy and/or accreted mass at rates above the Eddington limit. At low redshift, the smallest nuclear BHs known are found in dwarf galaxies and provide the most concrete limits on the mass of BH seeds. Here we review current observational work in these fields that together are critical for our understanding of the origin of massive BHs in the Universe.

  7. Infrared Properties of High Redshift and X-ray Selected AGN Samples

    OpenAIRE

    Wilkes, Belinda J.; Hooper, Eric J.; McLeod, Kim K.; Elvis, Martin S.; Hughes, David H.; Impey, Chris D.; Kuraszkiewicz, Joanna K.; Lonsdale, Carol S.; Malkan, Matt A.; McDowell, Jonathan C.

    2000-01-01

    The NASA/ISO Key Project on active galactic nuclei (AGN) seeks to better understand the broad-band spectral energy distributions (SEDs) of these sources from radio to X-rays, with particular emphasis on infrared properties. The ISO sample includes a wide variety of AGN types and spans a large redshift range. Two subsamples are considered herein: 8 high-redshift (1 < z < 4.7) quasars; and 22 hard X-ray selected sources. The X-ray selected AGN show a wide range of IR continuum shapes, extending...

  8. On the faint end of the high redshift AGN luminosity function

    OpenAIRE

    Shankar, Francesco; Mathur, Smita

    2007-01-01

    Using the results of recent optical surveys we conclude that the {\\it non}-detection of quasars down to faint magnitudes implies a significant flattening of the high redshift (z~6) optical active galactic nuclei (AGN) luminosity function for M_{1450}>-24.7. We find that all the data are consistent with a faint-end slope for the optical AGN luminosity function of \\beta=-2.2 and \\beta=-2.8, at the 90% and 99% confidence level respectively, flatter than the bright-end slope of \\beta'~ -3.2. We a...

  9. Time-Dependent Behavior of Lyman$\\alpha$ Photon Transfer in High Redshift Optically Thick Medium

    OpenAIRE

    Xu, Wen; Wu, Xiang-Ping; Fang, Li-Zhi

    2011-01-01

    With Monte Carlo simulation method, we investigate the time dependent behavior of Ly$\\alpha$ photon transfer in optically thick medium of the concordance $\\Lambda$CDM universe. At high redshift, the Ly$\\alpha$ photon escaping from optically thick medium has a time scale as long as the age of the luminous object, or even comparable to the age of the universe. In this case, time-independent, or stationary solutions of the Ly$\\alpha$ photon transfer with resonant scattering will overlook importa...

  10. Are globular clusters the natural outcome of regular high-redshift star formation?

    CERN Document Server

    Kruijssen, J M Diederik

    2015-01-01

    We summarise some of the recent progress in understanding the formation and evolution of globular clusters (GCs) in the context of galaxy formation and evolution. It is discussed that an end-to-end model for GC formation and evolution should capture four different phases: (1) star and cluster formation in the high-pressure interstellar medium of high-redshift galaxies, (2) cluster disruption by tidal shocks in the gas-rich host galaxy disc, (3) cluster migration into the galaxy halo, and (4) the final evaporation-dominated evolution of GCs until the present day. Previous models have mainly focussed on phase 4. We present and discuss a simple model that includes each of these four steps - its key difference with respect to previous work is the simultaneous addition of the high-redshift formation and early evolution of young GCs, as well as their migration into galaxy haloes. The new model provides an excellent match to the observed GC mass spectrum and specific frequency, as well as the relations of GCs to the...

  11. On the Contribution of Active Galactic Nuclei to the High-Redshift Metagalactic Ionizing Background

    CERN Document Server

    D'Aloisio, Anson; McQuinn, Matthew; Trac, Hy; Shapiro, Paul R

    2016-01-01

    Motivated by the claimed detection of a large population of faint active galactic nuclei (AGN) at high redshift, recent studies have proposed models in which AGN contribute significantly to the z > 4 H I ionizing background. In some models, AGN are even the chief sources of reionization. If correct, these models would make necessary a complete revision to the standard view that galaxies dominated the high-redshift ionizing background. It has been suggested that AGN-dominated models can better account for two recent observations that appear to be in conflict with the standard view: (1) large opacity variations in the z ~ 5.5 H I Lyman-alpha forest, and (2) slow evolution in the mean opacity of the He II Lyman-alpha forest. Large spatial fluctuations in the ionizing background from the brightness and rarity of AGN may account for the former, while the earlier onset of He II reionization in these models may account for the latter. Here we show that models in which AGN emissions source >~ 50 % of the ionizing bac...

  12. Discovery and identification of the very high redshift afterglow of GRB 050904

    CERN Document Server

    Haislip, J; Reichart, D; Levan, A; Tanvir, N; Cenko, S; Fox, D; Price, P; Castro-Tirado, A J; Gorosabel, J; Evans, C; Figueredo, E; MacLeod, C; Kirschbrown, J; Jelinek, M; Guziy, S; De Postigo, A U; Cypriano, E S; La Cluyze, A; Graham, J; Priddey, R; Chapman, R; Rhoads, J; Fruchter, A; Lamb, D; Kouveliotou, C; Wijers, R A M J; Schmidt, B; Soderberg, A M; Kulkarni, S; Harrison, F; Moon, D; Gal-Yam, A; Kasliwal, M; Hudec, R; Vítek, S; Kubánek, P; Crain, J; Foster, A; Bayliss, M; Clemens, J; Bartelme, J

    2005-01-01

    In 2000, Lamb and Reichart predicted that gamma-ray bursts (GRBs) and their afterglows occur in sufficient numbers and at sufficient brightnesses at very high redshifts (z > 5) to eventually replace quasars as the preferred probe of element formation and reionization in the early universe and to be used to characterize the star-formation history of the early universe, perhaps back to when the first stars formed. Here we report the discovery of the afterglow of GRB 050904 and the identification of GRB 050904 as the first very high redshift GRB. We measure its redshift to be 6.39(+0.11,-0.12), which is consistent with the reported spectroscopic redshift (6.29 +/- 0.01). Furthermore, just redward of Ly-alpha the flux is suppressed by a factor of three on the first night, but returns to expected levels by the fourth night. We propose that this is due to absorption by molecular hydrogen that was excited to rovibrational states by the GRB's prompt emission, but was then overtaken by the jet. Now that very high reds...

  13. Dust Formation, Evolution, and Obscuration Effects in the Very High-Redshift Universe

    Science.gov (United States)

    Dwek, Eli; Staguhn, Johannes; Arendt, Richard G.; Kovacs, Attila; Su, Ting; Benford, Dominic J.

    2014-01-01

    The evolution of dust at redshifts z > or approx. 9, and consequently the dust properties, differs greatly from that in the local universe. In contrast to the local universe, core collapse supernovae (CCSNe) are the only source of thermally-condensed dust. Because of the low initial dust-to-gas mass ratio, grain destruction rates are low, so that CCSNe are net producers of interstellar dust. Galaxies with large initial gas mass or high mass infall rate will therefore have a more rapid net rate of dust production comported to galaxies with lower gas mass, even at the same star formation rate. The dust composition is dominated by silicates, which exhibit a strong rise in the UV opacity near the Lyman break. This "silicate-UV break" may be confused with the Lyman break, resulting in a misidentification of a galaxies' photometric redshift. In this paper we demonstrate these effects by analyzing the spectral energy distribution (SED) of MACS1149-JD, a lensed galaxy at z = 9.6. A potential 2mm counterpart of MACS1149-JD has been identified with GISMO. While additional observations are required to corroborate this identification, we use this possible association to illustrate the physical processes and the observational effects of dust in the very high redshift universe. Subject headings: galaxies: high-redshift - galaxies: evolution - galaxies: individual (MACS1149- JD) - Interstellar medium (ISM), nebulae: dust, extinction - physical data and processes: nuclear reactions, nucleosynthesis, abundances.

  14. Probing the very high redshift universe with the broadband emission of GRBS

    Science.gov (United States)

    Inoue, S.; Omukai, K.; Ciardi, B.; Miniati, F.

    Due to their high luminosities and close association with massive stars, gamma-ray bursts hold the promise of being unique and crucial probes of the very high redshift universe. The following topics will be discussed. 1) Dispersion in the low frequency radio emission of GRBs may offer an important probe of the cosmic reionization history. The observational prospects can be particularly interesting for facilities such as LOFAR, if GRBs emit strong, coherent radio emission (Inoue 2004, MNRAS, 348, 999). 2) Due to the contribution of the reverse shock, GRBs at a few hours after the burst are brightest in the millimeter to infrared band, with peak fluxes reaching ˜ mJy from z ˜ 5--30. Atomic and molecular absorption lines in these bands are potentially observable by telescopes such as ALMA, providing an important probe of early star-forming regions (Inoue, Omukai & Ciardi, in prep). 3) The possibility of probing the high redshift UV background utilizing gamma-ray absorption in the GeV-TeV emission of GRBs is briefly discussed (Inoue & Miniati, in prep).

  15. Physical Conditions in the Interstellar Medium of High-Redshift Galaxies: Mass Budget and Gas Excitation

    CERN Document Server

    Riechers, Dominik A

    2013-01-01

    Following the first pioneering efforts in the 1990s that have focused on the detection of the molecular interstellar medium in high redshift galaxies, recent years have brought great advances in our understanding of the actual physical properties of the gas that set the conditions for star formation. Observations of the ground-state CO J=1-0 line have furnished crucial information on the total masses of the gas reservoirs, as well as reliable dynamical mass and size estimates. Detailed studies of rotational ladders of CO have provided insight on the temperature and density of the gas. Investigations of the very dense gas associated with actively star-forming regions in the interstellar medium, most prominently through HCN and HCO+, have enabled a better understanding of the nature of the extreme starbursts found in many high-redshift galaxies, which exceed the star formation rates of their most active present-day counterparts by an order of magnitude. Key progress in this area has been made through targeted s...

  16. Predictions for the abundance and colours of galaxies in high redshift clusters in hierarchical models

    CERN Document Server

    Merson, Alexander I; Abdalla, Filipe B; Gonzalez-Perez, Violeta; Lagos, Claudia del P; Mei, Simona

    2015-01-01

    High redshift galaxy clusters allow us to examine galaxy formation in extreme environments. Here we compile data for $z>1$ galaxy clusters to test the predictions from one of the latest semi-analytical models of galaxy formation. The model gives a good match to the slope and zero-point of the cluster red sequence. The model is able to match the cluster galaxy luminosity function at faint and bright magnitudes, but under-estimates the number of galaxies around the break in the luminosity function. We find that simply assuming a weaker dust attenuation improves the model predictions for the cluster galaxy luminosity function, but worsens the predictions for the red sequence at bright magnitudes. Examination of the properties of the bright cluster galaxies suggests that the default dust attenuation is very large due to these galaxies having large reservoirs of cold gas as well as small radii. We find that matching the luminosity function and colours of high redshift cluster galaxies, whilst remaining consistent ...

  17. Gravitational wave source counts at high redshift and in models with extra dimensions

    CERN Document Server

    García-Bellido, Juan; Trashorras, Manuel

    2016-01-01

    Gravitational wave (GW) source counts have been recently shown to be able to test how gravitational radiation propagates with the distance from the source. Here, we extend this formalism to cosmological scales, i.e. the high redshift regime, and we also allow for models with large or compactified extra dimensions like in the Kaluza-Klein (KK) model. We found that in the high redshift regime one would potentially expect two windows where observations above the minimum signal-to-noise threshold can be made, assuming there are no higher order corrections in the redshift dependence of the signal-to-noise $S/N(z)$ for the expected prediction. Furthermore, we also considered the case of intermediate redshifts, i.e. $0

  18. The evolution of quiescent galaxies at high redshift (z > 1.4)

    CERN Document Server

    Pozzi, F; Cimatti, A; Ilbert, O; Pozzetti, L; McCracken, H; Capak, P; Floch, E Le; Salvato, M; Zamorani, G; Carollo, C M; Contini, T; Kneib, J P; Févre, O Le; Lilly, S J; Mainieri, V; Renzini, A; Scodeggio, M; Bardelli, S; Bolzonella, M; Bongiorno, A; Caputi, K; Coppa, G; Cucciati, O; de la Torre, S; de Ravel, L; Franzetti, P; Garilli, B; Iovino, A; Kampczyk, P; Knobel, C; Kovac, K; Lamareille, F; Borgne, J F Le; Brun, V Le; Maier, C; Mignoli, M; Pelló, R; Peng, Y; Pérez-Montero, E; Ricciardelli, E; Silverman, J D; Tanaka, M; Tasca, L A M; Tresse, L; Vergani, D; Zucca, E

    2011-01-01

    We have studied the evolution of high redshift quiescent galaxies over an effective area of ~1.7 deg^2 in the COSMOS field. Galaxies have been divided according to their star-formation activity and the evolution of the different populations has been investigated in detail. We have studied an IRAC (mag_3.6 1.4 with multi-wavelength coverage. We have derived accurate photometric redshifts (sigma=0.06) and other important physical parameters through a SED-fitting procedure. We have divided our sample into actively star-forming, intermediate and quiescent galaxies depending on their specific star formation rate. We have computed the galaxy stellar mass function of the total sample and the different populations at z=1.4-3.0. We have studied the properties of high redshift quiescent galaxies finding that they are old (1-4 Gyr), massive (log(M/M_sun)~10.65), weakly star forming stellar populations with low dust extinction (E(B-V) 11, while the quiescent population increases from 10% to 50% at the same redshift and...

  19. High redshift X-ray galaxy clusters. II. The L_X-T relationship revisited

    CERN Document Server

    Branchesi, M; Fanti, C; Fanti, R

    2007-01-01

    In this paper we re-visit the observational relation between X-ray luminosity and temperature for high-z galaxy clusters and compare it with the local L_X-T and with theoretical models. To these ends we use a sample of 17 clusters extracted from the Chandra archive supplemented with additional clusters from the literature, either observed by Chandra or XMM-Newton, to form a final sample of 39 high redshift (0.25 < z < 1.3) objects. Different statistical approaches are adopted to analyze the L_X-T relation. The slope of the L_X-T relation of high redshift clusters is steeper than expected from the self-similar model predictions and steeper, even though still compatible within the errors, than the local L_X-T slope. The distant cluster L_X-T relation shows a significant evolution with respect to the local Universe: high-z clusters are more luminous than the local ones by a factor ~2 at any given temperature. The evolution with redshift of the L_X-T relation cannot be described by a single power law nor by...

  20. FINDING HIGH-REDSHIFT DARK STARS WITH THE JAMES WEBB SPACE TELESCOPE

    International Nuclear Information System (INIS)

    The first stars in the history of the universe are likely to form in the dense central regions of ∼105-106 Msun cold dark matter halos at z ∼ 10-50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive, and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 103 Msun are intrinsically too faint to be detected by JWST at z > 6. However, by exploiting foreground galaxy clusters as gravitational telescopes do, certain varieties of cool (Teff ≤ 30, 000 K) dark stars should be within reach at redshifts up to z ∼ 10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least ∼1% of the total stellar mass in such objects.

  1. Identifying clustering at high redshift through actively star-forming galaxies

    CERN Document Server

    Davies, L J M; Stanway, E R; Husband, K; Lehnert, M D; Mannering, E J A

    2013-01-01

    Identifying galaxy clustering at high redshift (i.e. z > 1) is essential to our understanding of the current cosmological model. However, at increasing redshift, clusters evolve considerably in star-formation activity and so are less likely to be identified using the widely-used red sequence method. Here we assess the viability of instead identifying high redshift clustering using actively star-forming galaxies (SMGs associated with over-densities of BzKs/LBGs). We perform both a 2- and 3-D clustering analysis to determine whether or not true (3D) clustering can be identified where only 2D data are available. As expected, we find that 2D clustering signals are weak at best and inferred results are method dependant. In our 3D analysis, we identify 12 SMGs associated with an over-density of galaxies coincident both spatially and in redshift - just 8% of SMGs with known redshifts in our sample. Where an SMG in our target fields lacks a known redshift, their sightline is no more likely to display clustering than ...

  2. The Rest-Frame Submillimeter Spectrum of High-Redshift, Dusty, Star-Forming Galaxies

    CERN Document Server

    Spilker, J S; Aguirre, J E; Aravena, M; Ashby, M L N; Bethermin, M; Bradford, C M; Bothwell, M S; Brodwin, M; Carlstrom, J E; Chapman, S C; Crawford, T M; de Breuck, C; Fassnacht, C D; Gonzalez, A H; Greve, T R; Gullberg, B; Hezaveh, Y; Holzapfel, W L; Husband, K; Ma, J; Malkan, M; Murphy, E J; Reichardt, C L; Rotermund, K M; Stalder, B; Stark, A A; Strandet, M; Vieira, J D; Weiss, A; Welikala, N

    2014-01-01

    We present the average rest-frame spectrum of high-redshift dusty, star-forming galaxies from 250-770GHz. This spectrum was constructed by stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral features of 12CO, [CI], and H2O, we also detect several faint transitions of 13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to characterize the typical properties of the interstellar medium of these high-redshift starburst galaxies. We find that the 13CO brightness in these objects is comparable to that of the only other z>2 star-forming galaxy in which 13CO has been observed. We show that the emission from the high-critical density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen densities are required to reproduce the observed line ratios, and we demonstrate that alternatives to purely collisional excitation are unlik...

  3. VLP - High-Redshift AGNs and the X-SERVS Survey

    Science.gov (United States)

    Brandt, W.

    2016-06-01

    In the first part of this talk, I will review how X-ray observations of high-redshift AGNs at z = 4-7 have played a critical role in understanding their basic demographics as well as their physical processes; e.g., accretion rates, jet emission, X-ray absorption by nuclear material and winds. Since 2000, XMM-Newton and Chandra have provided new X-ray detections for more than 120 such objects, and well-defined samples of z > 4 AGNs now allow reliable basic X-ray population studies. I will point out key remaining areas of uncertainty, highlighting where further XMM-Newton and Chandra observations can advance understanding. I will then describe the X-SERVS project which aims to go ``beyond COSMOS'' via a 12 deg^2 survey of three prime sky regions: W-CDF-S, XMM-LSS, and ELAIS-S1. The X-SERVS survey will allow outstanding studies of the detected AGNs and groups/clusters by powerfully leveraging multiple intensive radio-to-UV surveys: ATLAS/HerMES/SERVS/VIDEO/DES/HSC/PS1MD/VOICE/ CSI/PRIMUS. We aim to dramatically advance studies of SMBH growth across the full range of cosmic environments, links between SMBH accretion and star formation, exceptional AGNs at high redshifts, protoclusters, etc. The targeted X-SERVS fields will have extraordinary legacy value as MOONS massive spectroscopy fields, prime ALMA fields, and DES/LSST deep-drilling fields.

  4. High-redshift supernova rates measured with the gravitational telescope A1689

    CERN Document Server

    Petrushevska, Tanja; Goobar, Ariel; Fabbro, Sebastien; Johansson, Joel; Kjellsson, Tor; Lidman, Chris; Paech, Kerstin; Richard, Johan; Dahle, Hakon; Ferretti, Raphael; Kneib, Jean-Paul; Limousin, Marceau; Nordin, Jakob; Stanishev, Vallery

    2016-01-01

    We present a ground-based near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z=0.18, one of the most powerful gravitational telescopes that nature provides. Our survey was based on multi-epoch $J$-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope. Our search resulted in the discovery of five high-redshift, $0.671high-redshifts, $z$$\\sim$$3$, albeit for a limited region of space. We present a study of the core-collapse supernova rates for $0.4\\leq z< 2.9$, and find good agreement with both previous estimates, and the predictions from the star formation history. During our survey, we also discovered 2 type Ia supernov...

  5. Distortion of the luminosity function of high-redshift galaxies by gravitational lensing

    CERN Document Server

    Fialkov, Anastasia

    2015-01-01

    The observed properties of high redshift galaxies depend on the underlying foreground distribution of large scale structure, which distorts their intrinsic properties via gravitational lensing. We focus on the regime where the dominant contribution originates from a single lens and examine the statistics of gravitational lensing by a population of virialized and non-virialized structures using sub-mm galaxies at z ~ 2.6 and Lyman-break galaxies at redshifts z ~ 6-15 as the background sources. We quantify the effect of lensing on the luminosity function of the high redshift sources, focusing on the intermediate and small magnifications (mu < 3) which affect the majority of the background galaxies. We show that depending on the intrinsic properties of the background galaxies, gravitational lensing can significantly affect the observed luminosity function even when no obvious strong lenses are present. Finally, we find that in the case of the Lyman-break galaxies it is important to account for the surface bri...

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

    Science.gov (United States)

    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.

  7. Evolution of star formation conditions from high-redshift to low-redshift

    Science.gov (United States)

    Shirazi, Maryam

    2015-08-01

    There are some hints indicating extreme interstellar medium (ISM) conditions at high redshift e.g., harder ionsing radiation fields and higher electron densities. By analysing the ionisation state of galaxies using their [OIII]5007/[OII]3727 line ratios we recently showed that star-forming galaxies at z~ 1. 5 -- 3. 5 have higher ionisation parameters and higher gas densities relative to that of local galaxies with similar global properties (Shirazi et al. 2014). This means the intrinsic properties e.g., the density of star forming regions at high redshift is different from what we observe in the local Universe. Based on the distribution of galaxies in the BPT diagram, it is proposed that the transition to nearby like conditions happen at 0. 8 MUSE to indirectly trace the ISM conditions at those redshifts. We measure the spatially-resolved ionisation parameter using [OIII ]5007/ [O II]3727 ratio and we measure the spatially resolved gas density using the [OII] 3727,3729 doublet. We probe the spatial distributions of the ionisation parameter and gas density and search for systematic differences between high, intermediate and low redshift galaxies in terms of their global galaxy properties.

  8. Resolved properties of high-redshift lensed galaxies seen with MUSE

    Science.gov (United States)

    Patricio, Vera; Richard, Johan; Verhamme, Anne; Christensen, Lise; Lagattuta, David; Clément, Benjamin; Mahler, Guillaume

    2015-08-01

    Spatially resolved properties of high redshift galaxies provide important insights into galaxy formation processes. However, with the current instrumentation we have been limited to the analysis of the Lyman alpha line and UV continuum through long-slit observations of individual galaxies or stacking. Combining the power of the newly commissioned integral field spectrograph MUSE on VLT with strong gravitational lensing, it is now possible to spatially probe the rest-frame UV properties of individual high-z galaxies.I will present the study of a 109 M⊙ galaxy at z = 3.5 strongly lensed by the SMACS2031 cluster for which we were able to obtain 2D resolved spatial information of Lyman alpha, and, for the fist time, CIII] emission. The exceptional signal to noise of the data also allows the study of the UV continuum as well as emission and absorption lines rarely measured at these redshifts. We compare the spatial Lyman alpha information and continuum properties with radiative transfer models, resulting in a unique view of an individual high-z galaxy.Additionally, I will present the first results from a sample of 8 high redshift (z = 0.7 - 1.5) extended lensed arcs in the Frontier Fields, also observed with MUSE.With this sample, wederive gas kinematics from both emission and absorption lines, as well as properties of resolved stellar populations.

  9. ON THE OCCUPATION FRACTION OF SEED BLACK HOLES IN HIGH-REDSHIFT DARK MATTER HALOS

    International Nuclear Information System (INIS)

    It is well known that an initial population of seed black holes (BHs), formed in the nuclei of low-mass galaxies at high redshift, can simultaneously explain, through their subsequent growth by mergers and accretion, both the observed evolution of the quasar luminosity function (LF) and the distribution of remnant supermassive black hole (SMBH) masses measured in local galactic nuclei. Here we consider three very different initial conditions for this scenario: models in which initial seed BHs form in either all, or only a small fraction (f bh = 0.1 or 0.01) of high-redshift dark matter halos (with M halo = 5 x 109 M sun at z = 6-10). We show that with a suitable and relatively minor adjustment of two global physical parameters (the radiative efficiency and mass accretion time-scale of quasar episodes), models with f bh ∼ 0.1 and 1 can accurately reproduce the observed quasar LF at redshifts 0 bh ∼bh is varied; this should allow LISA to deliver useful constraints on otherwise degenerate models.

  10. Optical Spectral Variability of Blazars

    Indian Academy of Sciences (India)

    Haritma Gaur

    2014-09-01

    It is well established that blazars show flux variations in the complete electromagnetic (EM) spectrum on all possible time scales ranging from a few tens of minutes to several years. Here, we report the review of optical flux and spectral variability properties of different classes of blazars on IDV and STV time-scales. Our analysis show HSPs are less variable in optical bands as compared to LSPs. Also, we investigated the spectral slope variability and found that the average spectral slopes of LSPs showed a good agreement with the synchrotron self-Compton loss-dominated model. However, spectra of the HSPs and FSRQs have significant additional emission components. In general, spectra of BL Lacs get flatter when they become brighter, while for FSRQs the opposite trend appears to hold.

  11. Rapid VHE variability in blazars

    OpenAIRE

    Volpe, Francesca; Rieger, Frank M.

    2011-01-01

    Active Galactic Nuclei (AGN) are known to show significant variability over a wide frequency range. We review observational results on the variability characteristics of blazars in the very high energy (VHE) domain, focusing on recent findings of rapid VHE variability and evidence for an underlying multiplicative driving process in PKS 2155-304. We explore a physical scenario where the variability is assumed to arise due to accretion disk fluctuations transmitted to the jet, and discuss its i...

  12. The VLT observations of the HDF-S NICMOS field photometric catalog and high redshift galaxy candidates

    CERN Document Server

    Fontana, A; Fosbury, R A E; Giallongo, E; Hook, R N; Poli, F; Renzini, A; Rosati, P; Viezzer, R

    1999-01-01

    We present the deep UBVRI observations of the HDF-S NICMOS field obtained as part of the Science Verification of the VLT Unit 1 telescope. The images have been used to construct object catalogs and to obtain photometric redshifts. The effective field of view is $\\simeq 70\\times70$ arcsec$^2$, and the formal $5\\sigma$ limiting magnitudes (in a 2 FWHM aperture) are 26.3, 27.8, 27.5, 26.9, 25.2 in the $U$, $B$, $V$, $R$ and $I$ bands, respectively. Thanks to the sub-arcsecond image quality, relatively long exposure time, and large collecting area of the VLT, this is the deepest set of multicolor images ever obtained from a ground-based telescope. Galaxy counts have been derived independently in each band, and show no significant departures from previous data from wider areas. A multicolor photometric catalog of all the galaxies selected in the $R$ band has also been obtained and used to derive photometric redshifts for all galaxies with $R \\leq 26.5 $, using also the J,H and K magnitudes from the NICMOS deep obs...

  13. 搜寻高红移类星体%The search for high-redshift quasars

    Institute of Scientific and Technical Information of China (English)

    左文文; 吴学兵

    2016-01-01

    2015年,以中国天文学家为主的国际研究团队宣布发现了目前已知的宇宙早期发光本领最强、中心黑洞质量最大的类星体.这颗类星体SDSS J0100+2802如同一座最明亮的灯塔照亮了人类探索神秘的早期宇宙的道路,它的发现刷新了人类使用2米级望远镜发现高红移类星体的纪录,更对宇宙早期黑洞的成长理论提出了新的挑战.文章将着重介绍:(1)类星体的发现;(2)类星体的本质以及描述其物理性质的参数;(3)研究类星体的重大科学意义;(4)类星体尤其是高红移类星体的搜寻方法;(5)最亮的高红移类星体的发现历程;(6)对今后高红移类星体研究的展望.%In 2015, an international team consisting of mainly Chinese astronomers an-nounced the discovery of the most luminous quasar in the early Universe, powered by the most massive black hole known at the time. The discovery of this quasar, named SDSS J0100+2802, set a new record in the discovery of high redshift quasars with 2-meter telescopes, and sheds light just like a lighthouse to help us know more about the early Universe. Moreover, it presents sub-stantial challenges to theories of the formation and growth of black holes in the early Universe. This article will discuss the following topics:(1) the historical discovery of quasars;(2) the nature of quasars and parameters to describe them;(3) the scientific motivation to study quasars;(4) the ways to select quasars, especially high redshift quasars;(5) how we discovered the quasar SDSS J0100+2802;(6) a perspective of future research on high redshift quasars.

  14. Clusters of Galaxies at High Redshift The LMT\\/GTM Perspective

    CERN Document Server

    López-Cruz, O; Lopez-Cruz, Omar; Gaztanaga, Enrique

    2000-01-01

    The lack of reliable cluster samples at intermediate and high redshift has motivated many optical/infrared and X-ray cluster searches. The motivation of such searches is well justified: the abundance of massive collapsed regions gives a direct constraint on Omega(matter). Alternatively, the Sunyaev-Zeldovich effect (SZE) offers a robust method for the detection of clusters which is, almost, independent of redshift. In this paper we comment on the possibility of mapping the SZE at high resolution in the millimeter regime using the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT/GTM) and the bolometer array BOLOCAM. The construction of the LMT/GTM facility is underway atop Cerro La Negra (latitude=18deg 59min; height=4600 m) in Mexico.

  15. Constraining High Redshift X-ray Sources with Next Generation 21 cm Power Spectrum Measurements

    CERN Document Server

    Ewall-Wice, Aaron; Mesinger, Andrei; Dillon, Joshua S; Liu, Adrian; Pober, Jonathan

    2015-01-01

    We use the Fisher matrix formalism and semi-numerical simulations to derive quantitative predictions of the constraints that power spectrum measurements on next-generation interferometers, such as the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA), will place on the characteristics of the X-ray sources that heated the high redshift intergalactic medium. Incorporating observations between $z=5$ and $z=25$, we find that the proposed 331 element HERA and SKA phase 1 will be capable of placing $\\lesssim 10\\%$ constraints on the spectral properties of these first X-ray sources, even if one is unable to perform measurements within the foreground contaminated "wedge" or the FM band. When accounting for the enhancement in power spectrum amplitude from spin temperature fluctuations, we find that the observable signatures of reionization extend well beyond the peak in the power spectrum usually associated with it. We also find that lower redshift degeneracies between the signatures of ...

  16. High redshift signatures in the 21 cm forest due to cosmic string wakes

    International Nuclear Information System (INIS)

    Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ''21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (z∼>10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10−7. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10−8 for the single frequency band case and 4.0 × 10−8 for the multi-frequency band case

  17. FeII/MgII Emission Line Ratio in High Redshift Quasars

    DEFF Research Database (Denmark)

    Dietrich, M.; Hamann, F.; Appenzeller, I.;

    2003-01-01

    We present results of the analysis of near infrared spectroscopic observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of the ultraviolet FeII/MgII emission line strength in order to estimate the beginning of intense star formation in the early universe. To investigate the...... evolution of the FeII/MgII ratio over a wider range in cosmic time, we measured this ratio for composite quasar spectra which cover a redshift range of 0 4 quasars must have started already at an epoch corresponding to z_f = 6 to 9, when the age of the universe was ~0.5 Gyr (H_o = 72 km/s/Mpc, Omega_M = 0...

  18. Dual-frequency VSOP Imaging of a High-redshift Radio Quasar PKS 1402+044

    CERN Document Server

    Yang, J; Lobanov, A; Frey, S; Hong, X Y; Yang, Jun; Gurvits, Leonid; Lobanov, Andrei; Frey, Sandor; Hong, Xiao-Yu

    2006-01-01

    Based on the VLBI Space Observatory Programme (VSOP) observations at 1.6 and 5 GHz, we find that the luminous high-redshift (z=3.215) quasar PKS 1402+044 (J1405+0415) has a pronounced 'core--jet' structure. The jet shows a steeper spectral index and lower brightness temperature with the increase of the distance from the core. The variation of brightness temperature is basically consistent with the shock-in-jet model. Assuming that the jet is collimated by the ambient magnetic field, we estimate the mass of the central object as ~10^9 M_sun. The upper limit of the jet proper motion of PKS 1402+044 is 0.03 mas/yr (~3c) in the east-west direction.

  19. On the injection spectrum of relativistic electrons in high-redshift radio galaxies

    CERN Document Server

    Gopal-Krishna,; Mangalam, A

    2011-01-01

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

  20. 1WGAJ1226.9+3332: a high redshift cluster discovered by Chandra

    OpenAIRE

    Cagnoni, I.; Elvis, M.; Kim, D. -W.; Mazzotta, P.; Huang, J. -S.; Celotti, A.

    2001-01-01

    We report the detection of 1WGAJ1226.9+3332 as an arcminute scale extended X-ray source with the Chandra X-ray Observatory. The Chandra observation and R and K band imaging strongly support the identification of 1WGAJ1226.9+3332 as a high redshift cluster of galaxies, most probably at z=0.85 +- 0.15, with an inferred temperature kT =10 (+4;-3) keV and an unabsorbed luminosity (in a r=120" aperture) of 1.3 (+0.16;-0.14) x 1e45 erg/s (0.5-10 keV). This indication of redshift is also supported b...

  1. Gravitational wave source counts at high redshift and in models with extra dimensions

    Science.gov (United States)

    García-Bellido, Juan; Nesseris, Savvas; Trashorras, Manuel

    2016-07-01

    Gravitational wave (GW) source counts have been recently shown to be able to test how gravitational radiation propagates with the distance from the source. Here, we extend this formalism to cosmological scales, i.e. the high redshift regime, and we discuss the complications of applying this methodology to high redshift sources. We also allow for models with compactified extra dimensions like in the Kaluza-Klein model. Furthermore, we also consider the case of intermediate redshifts, i.e. 0 dark energy model. Our analysis is as general as possible, but it depends on two important factors: a source model for the black hole binary mergers and the GW source to galaxy bias. This methodology also allows us to obtain the higher order corrections of the source counts in terms of the signal-to-noise S/N. We then forecast the sensitivity of future observations in constraining GW physics but also the underlying cosmology by simulating sources distributed over a finite range of signal-to-noise with a number of sources ranging from 10 to 500 sources as expected from future detectors. We find that with 500 events it will be possible to provide constraints on the matter density parameter at present Ωm,0 on the order of a few percent and with the precision growing fast with the number of events. In the case of extra dimensions we find that depending on the degeneracies of the model, with 500 events it may be possible to provide stringent limits on the existence of the extra dimensions if the aforementioned degeneracies can be broken.

  2. COSMOLOGICAL CONCORDANCE OR CHEMICAL COINCIDENCE? DEUTERATED MOLECULAR HYDROGEN ABUNDANCES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    We report two detections of deuterated molecular hydrogen (HD) in QSO absorption-line systems at z>2. Toward J2123-0500, we find N(HD) =13.84 ± 0.2 for a sub-Damped Lyman Alpha system (DLA) with metallicity ≅0.5Zsun and N(H2) = 17.64 ± 0.15 at z = 2.0594. Toward FJ0812+32, we find N(HD) =15.38 ± 0.3 for a solar-metallicity DLA with N(H2) = 19.88 ± 0.2 at z = 2.6265. These systems have ratios of HD to H2 above that observed in dense clouds within the Milky Way disk and apparently consistent with a simple conversion from the cosmological ratio of D/H. These ratios are not readily explained by any available model of HD chemistry, and there are no obvious trends with metallicity or molecular content. Taken together, these two systems and the two published z>2 HD-bearing DLAs indicate that HD is either less effectively dissociated or more efficiently produced in high-redshift interstellar gas, even at low molecular fraction and/or solar metallicity. It is puzzling that such diverse systems should show such consistent HD/H2 ratios. Without clear knowledge of all the aspects of HD chemistry that may help determine the ratio HD/H2, we conclude that these systems are potentially more revealing of gas chemistry than of D/H itself and that it is premature to use such systems to constrain D/H at high redshift.

  3. EXTENDED Lyα EMISSION FROM INTERACTING GALAXIES AT HIGH REDSHIFTS

    International Nuclear Information System (INIS)

    Recent observations have discovered a population of extended Lyα sources, dubbed Lyα blobs (LABs), at high redshift z ∼ 2-6.6. These LABs typically have a luminosity of L ∼ 1042-1044 erg s–1, and a size of tens of kiloparsecs, with some giant ones reaching up to D ∼ 100 kpc. However, the origin of these LABs is not well understood. In this paper, we investigate a merger model for the formation of LABs by studying Lyα emission from interacting galaxies at high redshifts by means of a combination of hydrodynamics simulations with three-dimensional radiative transfer calculations. Our galaxy simulations focus on a set of binary major mergers of galaxies with a mass range of 3-7 × 1012 M☉ in the redshift range z ∼ 3-7, and we use the newly improved ART2 code to perform the radiative transfer calculations, which couple multi-wavelength continuum, ionization of hydrogen, and Lyα line emission. We find that intense star formation and enhanced cooling induced by gravitational interaction produce strong Lyα emission from these merging galaxies. The Lyα emission appears to be extended due to the extended distribution of sources and gas. During the close encounter of galaxy progenitors when the star formation rate peaks at ∼103 M☉ yr–1, our model produces LABs with luminosity of L ∼ 1042-1044 erg s–1, and size of D ∼ 10-20 kpc at z > 6 and D ∼ 20-50 kpc at z ∼ 3, in broad agreement with observations in the same redshift range. Our results suggest that merging galaxies may produce some typical LABs as observed, but the giant ones may be produced by mergers more massive than those in our model, or a combination of mergers and cold accretion from filaments on a large scale

  4. Reionisation and High-Redshift Galaxies: The View from Quasar Absorption Lines

    Science.gov (United States)

    Becker, George D.; Bolton, James S.; Lidz, Adam

    2015-12-01

    Determining when and how the first galaxies reionised the intergalactic medium promises to shed light on both the nature of the first objects and the cosmic history of baryons. Towards this goal, quasar absorption lines play a unique role by probing the properties of diffuse gas on galactic and intergalactic scales. In this review, we examine the multiple ways in which absorption lines trace the connection between galaxies and the intergalactic medium near the reionisation epoch. We first describe how the Ly α forest is used to determine the intensity of the ionising ultraviolet background and the global ionising emissivity budget. Critically, these measurements reflect the escaping ionising radiation from all galaxies, including those too faint to detect directly. We then discuss insights from metal absorption lines into reionisation-era galaxies and their surroundings. Current observations suggest a buildup of metals in the circumgalactic environments of galaxies over z ~ 6 to 5, although changes in ionisation will also affect the evolution of metal line properties. A substantial fraction of metal absorbers at these redshifts may trace relatively low-mass galaxies. Finally, we review constraints from the Ly α forest and quasar near zones on the timing of reionisation. Along with other probes of the high-redshift Universe, absorption line data are consistent with a relatively late end to reionisation (5.5 ≲ z ≲ 7); however, the constraints are still fairly week. Significant progress is expected to come through improved analysis techniques, increases in the number of known high-redshift quasars from optical and infrared sky surveys, large gains in sensitivity from next-generation observing facilities, and synergies with other probes of the reionisation era.

  5. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    Science.gov (United States)

    Giroletti, M.; Massaro, F.; D'Abrusco, R.; Lico, R.; Burlon, D.; Hurley-Walker, N.; Johnston-Hollitt, M.; Morgan, J.; Pavlidou, V.; Bell, M.; Bernardi, G.; Bhat, R.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Ewall-Rice, A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hindson, L.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Feng, L.; Jacobs, D.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Pindor, B.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2016-04-01

    Context. Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. Aims: We characterize the spectral properties of the blazar population at low radio frequency, compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. Methods: We cross-correlated the 6100 deg2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. Results: We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120-180 MHz) blazar spectral index is ⟨αlow⟩ = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Conclusions: Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population. Tables 5-7 are only available at the CDS via anonymous ftp to http

  6. The role of plasma instabilities in the propagation of gamma-rays from distant Blazars

    International Nuclear Information System (INIS)

    The observation in the GeV band of distant blazars has been recently used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Fields (EGMF). To support such claims one has to assume that the leptonic component of the electromagnetic cascade initiated by blazar gamma-rays is deflected away by strong enough EGMF, suppressing the signal in the Fermi window. Apart from magnetic fields, the development of such a cascade might be affected by plasma instabilities due to interactions with the ionized component of the Intergalactic Medium (IGM). In this paper we model the electromagnetic cascade through a Monte Carlo simulation in which both effects are taken into account separately, and we derive constraints on these scenarios from the combined Fermi-HESS data set. In the specific case of 1ES 0229+200 observations, we show that both explanations of the GeV flux suppression are compatible with the available data, specifically by assuming a magnetic field of B >or similar 10-16 G or an IGM temperature of T 4 K along the line of sight. Future observations of the spectra of high redshift (z < or similar 1) TeV objects will help to distinguish magnetic field and plasma effects on electromagnetic cascades in the IGM.

  7. The role of plasma instabilities in the propagation of gamma-rays from distant Blazars

    Energy Technology Data Exchange (ETDEWEB)

    Saveliev, A.; Evoli, C.; Sigl, G. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

    2013-11-15

    The observation in the GeV band of distant blazars has been recently used to put constraints on the Extragalactic Background Light (EBL) and Extragalactic Magnetic Fields (EGMF). To support such claims one has to assume that the leptonic component of the electromagnetic cascade initiated by blazar gamma-rays is deflected away by strong enough EGMF, suppressing the signal in the Fermi window. Apart from magnetic fields, the development of such a cascade might be affected by plasma instabilities due to interactions with the ionized component of the Intergalactic Medium (IGM). In this paper we model the electromagnetic cascade through a Monte Carlo simulation in which both effects are taken into account separately, and we derive constraints on these scenarios from the combined Fermi-HESS data set. In the specific case of 1ES 0229+200 observations, we show that both explanations of the GeV flux suppression are compatible with the available data, specifically by assuming a magnetic field of B >or similar 10{sup -16} G or an IGM temperature of T high redshift (z

  8. Beaming Effect in Fermi Blazars

    OpenAIRE

    Fan, J.H.; Yang, J. H.; Zhang, J Y; Hua, T. X.; Liu, Y.; Qin, Y. P.; Huang, Y.

    2012-01-01

    The \\gamma-ray loud blazars (flat spectrum radio quasars--FSRQs and BL Lacertae objects-BLs) are very bright in the \\gamma-ray bands, which is perhaps associated with a beaming effect. Therefore, one can expect that the \\gamma-ray luminosity is correlated with the beaming factor. In this paper, we investigated the relation between the radio Doppler factors and the gamma-ray luminosities. Our analysis suggests that the \\gamma-ray luminosity be strongly correlated with the factor of \\delta_R fo...

  9. Radio core dominance of Fermi blazars

    Science.gov (United States)

    Pei, Zhi-Yuan; Fan, Jun-Hui; Liu, Yi; Yuan, Yi-Hai; Cai, Wei; Xiao, Hu-Bing; Lin, Chao; Yang, Jiang-He

    2016-07-01

    During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, R = S_{core}/ S_{ext.}, where S_{core} is the core emission, while S_{ext.} is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have γ-ray emission (from 3FGL). We compared the core-dominance parameters, log R, between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are V.I.) in the γ-ray band for FDBs, and we found V.I.=(0.12 ±0.07) log R+(2.25±0.10), suggesting that a source with larger log R has larger V.I. value. Thirdly, we compared the mean values of radio spectral index for FDBs and non-FDBs, and we obtained relationship, we found that the spectral index for the core component is α_{γ}|_{core} = 1.11 (a photon spectral index of α_{γ}^{ph}|_{core} = 2.11) and that for the extended component is α_{γ}|_{ext.} = 0.70 (a photon spectral index of α_{γ}^{ph}|_{ext.} = 1.70). Some discussions are also presented.

  10. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data. II. The Spring Equatorial Stripe

    International Nuclear Information System (INIS)

    This is the second paper in a series aimed at finding high-redshift quasars from five-color (u' g' r' i' z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from ∼250 deg2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of the sky. Our success rate in identifying high-redshift quasars is 68%. Five of the newly discovered quasars have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92, and 5.03). All the quasars have i* B 0 =0.5). Several of the quasars show unusual emission and absorption features in their spectra, including an object at z=4.62 without detectable emission lines, and a broad absorption line (BAL) quasar at z=4.92. (c) (c) 2000. The American Astronomical Society

  11. THE GEOMETRY EFFECTS OF AN EXPANDING UNIVERSE ON THE DETECTION OF COOL NEUTRAL GAS AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    Recent high-redshift surveys for 21 cm absorption in damped Lyα absorption systems (DLAs) take the number of published searches at zabs > 2 to 25, the same number as at zabs < 2, although the detection rate at high redshift remains significantly lower (20% compared to 60%). Using the known properties of the DLAs to estimate the unknown profile widths of the 21 cm non-detections and including the limits via a survival analysis, we show that the mean spin temperature/covering factor degeneracy at high redshift is, on average, double that of the low-redshift sample. This value is significantly lower than the previous factor of eight for the spin temperatures and is about the same factor as in the angular diameter distance ratios between the low- and high-redshift samples. That is, without the need for the several pivotal assumptions, which lead to an evolution in the spin temperature, we show that the observed distribution of 21 cm detections in DLAs can be accounted for by the geometry effects of an expanding universe. That is, as yet there is no evidence of the spin temperature of gas-rich galaxies evolving with redshift.

  12. Warm molecular Hydrogen at high redshift with the James Webb Space Telescope

    Science.gov (United States)

    Guillard, P.; Boulanger, F.; Lehnert, M. D.; Appleton, P. N.; Pineau des Forêts, G.

    2015-12-01

    The build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation. Spitzer Space Telescope infrared spectroscopy revealed a population of galaxies with weak star formation and unusually powerful H_2 line emission. This is a signature of turbulent dissipation, sustained by large-scale mechanical energy injection. The cooling of the multiphase interstellar medium is associated with emission in the H_2 lines. These results have profound consequences on our understanding of regulation of star formation, feedback and energetics of galaxy formation in general. The fact that H_2 lines can be strongly enhanced in high-redshift turbulent galaxies will be of great importance for the James Webb Space Telescope observations which will unveil the role that H_2 plays as a cooling agent in the era of galaxy assembly.

  13. High redshift galaxies and the Lyman-alpha forest in a CDM universe

    CERN Document Server

    Croft, R A C; Springel, V; Westover, M; White, M; Croft, Rupert A.C.; Hernquist, Lars; Springel, Volker; Westover, Michael; White, Martin

    2002-01-01

    We use a cosmological hydrodynamic simulation of a cold dark matter universe to investigate theoretically the relationship between high redshift galaxies and the Lyman=alpha forest at redshift z=3. Galaxies in the simulation are surrounded by halos of hot gas, which nevertheless contain enough neutral hydrogen to cause a Ly-alpha flux decrement, its strength increasing with galaxy mass. A comparison with recent observational data by Adelberger et. al on the Ly-alpha forest around galaxies reveals that actual galaxies may have systematically less Ly-alpha absorption within 1 Mpc of them than our simulated galaxies. In order to investigate this possibility, we add several simple prescriptions for galaxy feedback on the IGM to the evolved simulation. These include the effect of photoionizing background radiation coming from galactic sources, galactic winds whose only effect is to deposit thermal energy into the IGM, and another, kinetic model for winds, which are assumed to evacuate cavities in the IGM around ga...

  14. High redshift signatures in the 21 cm forest due to cosmic string wakes

    Energy Technology Data Exchange (ETDEWEB)

    Tashiro, Hiroyuki [Physics Department, Arizona State University, Tempe, AZ, 85287 (United States); Sekiguchi, Toyokazu [Department of Physics and Astrophysics, Nagoya University, Nagoya, 464–8602 (Japan); Silk, Joseph, E-mail: hiroyuki.tashiro@asu.edu, E-mail: toyokazu.sekiguchi@nagoya-u.jp, E-mail: silk@astro.ox.ac.uk [Institut d' Astrophysique, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis Blvd Arago, Paris, 75014 (France)

    2014-01-01

    Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a ''21 cm forest'' against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift (z∼>10), even if the string tension is below the current upper bound, Gμ < 1.5 × 10{sup −7}. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with Gμ ≈ 7.5 × 10{sup −8} for the single frequency band case and 4.0 × 10{sup −8} for the multi-frequency band case.

  15. A Stellar Feedback Origin for Neutral Hydrogen in High-Redshift Quasar-Mass Halos

    CERN Document Server

    Faucher-Giguere, C -A; Quataert, E; Keres, D; Hopkins, P F; Murray, N

    2016-01-01

    Observations of quasar pairs reveal that quasar host halos at z~2 have large covering fractions of cool dense gas (>~60% for Lyman limit systems within a projected virial radius). Most simulations have so far failed to explain these large observed covering fractions. We analyze a new set of 15 simulated massive halos with explicit stellar feedback from the FIRE project, covering the halo mass range M_h~2x10^12-10^13 Msun at z=2. This extends our previous analysis of the circum-galactic medium of high-redshift galaxies to more massive halos. Feedback from active galactic nuclei (AGN) is not included in these simulations. We find covering fractions consistent with those observed around z~2 quasars. The large HI covering fractions arise from star formation-driven galactic winds, including winds from low-mass satellite galaxies that interact with the cosmological infalling filaments in which they are typically embedded. The simulated covering fractions increase with both halo mass and redshift over the ranges cov...

  16. GRB 120521C at z~6 and the Properties of High-redshift GRBs

    CERN Document Server

    Laskar, T; Tanvir, N; Zauderer, B; Margutti, R; Levan, A; Perley, D; Fong, W; Wiersema, K; Cucchiara, A; Menten, K; Hrudkova, M

    2013-01-01

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength dataset, we derive a photometric redshift of z~6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of 0.05/cm^3. The radio observations reveal the presence of a jet break at 7 d, corresponding to a jet opening angle of ~ 3 deg. The beaming-corrected gamma-ray and kinetic energies are both ~ 3e50 erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z>6 with radio detections (GRBs 050904 and 090423). We find a jet break at ~ 15 d for GRB 090423, in contrast to pre...

  17. Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation

    CERN Document Server

    Henry, Alaina; Dominguez, Alberto; Malkan, Matthew; Martin, Crystal L; Siana, Brian; Atek, Hakim; Bedregal, Alejandro G; Colbert, James W; Rafelski, Marc; Ross, Nathaniel; Teplitz, Harry; Bunker, Andrew J; Dressler, Alan; Hathi, Nimish; Masters, Daniel; McCarthy, Patrick; Straughn, Amber

    2013-01-01

    We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10^{8}10^{9.5} M_{\\sun} and z~2.3. Within the statistical uncertainties, our MZ relation agrees with the z~2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift z=1.76 of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M_{*} relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high SFRs. Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.

  18. The high-redshift gamma-ray burst GRB140515A

    CERN Document Server

    Melandri, A; D'Avanzo, P; Sanchez-Ramirez, R; Nappo, F; Nava, L; Japelj, J; Postigo, A de Ugarte; Oates, S; Campana, S; Covino, S; D'Elia, V; Ghirlanda, G; Gafton, E; Ghisellini, G; Gnedin, N; Goldoni, P; Gorosabel, J; Libbrecht, T; Malesani, D; Salvaterra, R; Thone, C C; Vergani, S D; Xu, D; Tagliaferri, G

    2015-01-01

    High-redshift gamma-ray bursts have several advantages for the study of the distant universe, providing unique information about the structure and properties of the galaxies in which they exploded. Spectroscopic identification with large ground-based telescopes has improved our knowledge of the class of such distant events. We present the multi-wavelength analysis of the high-$z$ Swift gamma-ray burst GRB140515A ($z = 6.327$). The best estimate of the neutral hydrogen fraction of the intergalactic medium (IGM) towards the burst is $x_{HI} \\leq 0.002$. The spectral absorption lines detected for this event are the weakest lines ever observed in gamma-ray burst afterglows, suggesting that GRB140515A exploded in a very low density environment. Its circum-burst medium is characterised by an average extinction (A$_{\\rm V} \\sim 0.1$) that seems to be typical of $z \\ge 6$ events. The observed multi-band light curves are explained either with a very flat injected spectrum ($p = 1.7$) or with a multi-component emission...

  19. Constraining the high redshift formation of black hole seeds in nuclear star clusters with gas inflows

    CERN Document Server

    Lupi, Alessandro; Devecchi, Bernadetta; Galanti, Giorgio; Volonteri, Marta

    2014-01-01

    In this paper we explore a possible route of black hole seed formation that appeal to a model by Davies, Miller & Bellovary who considered the case of the dynamical collapse of a dense cluster of stellar black holes subjected to an inflow of gas. Here, we explore this case in a broad cosmological context. The working hypotheses are that (i) nuclear star clusters form at high redshifts in pre-galactic discs hosted in dark matter halos, providing a suitable environment for the formation of stellar black holes in their cores, (ii) major central inflows of gas occur onto these clusters due to instabilities seeded in the growing discs and/or to mergers with other gas-rich halos, and that (iii) following the inflow, stellar black holes in the core avoid ejection due to the steepening to the potential well, leading to core collapse and the formation of a massive seed of $<~ 1000\\, \\rm M_\\odot$. We simulate a cosmological box tracing the build up of the dark matter halos and there embedded baryons, and explore...

  20. DUST FORMATION, EVOLUTION, AND OBSCURATION EFFECTS IN THE VERY HIGH-REDSHIFT UNIVERSE

    International Nuclear Information System (INIS)

    The evolution of dust at redshifts z ≳ 9, and consequently the dust properties, differs greatly from that in the local universe. In contrast to the local universe, core collapse supernovae (CCSNe) are the only source of thermally condensed dust. Because of the low initial dust-to-gas mass ratio, grain destruction rates are low, so that CCSNe are net producers of interstellar dust. Galaxies with large initial gas mass or high mass infall rate will therefore have a more rapid net rate of dust production compared to galaxies with lower gas mass, even at the same star formation rate. The dust composition is dominated by silicates, which exhibit a strong rise in the UV opacity near the Lyman break. This ''silicate-UV break'' may be confused with the Lyman break, resulting in a misidentification of a galaxy's photometric redshift. In this Letter we demonstrate these effects by analyzing the spectral energy distribution of MACS1149-JD, a lensed galaxy at z = 9.6. A potential 2 mm counterpart of MACS1149-JD has been identified with GISMO. While additional observations are required to corroborate this identification, we use this possible association to illustrate the physical processes and the observational effects of dust in the very high-redshift universe

  1. Detecting Relativistic X-ray Jets in High-Redshift Quasars

    CERN Document Server

    McKeough, Kathryn; Cheung, C C; Stawarz, Lukasz; Kashyap, Vinay L; Stein, Nathan; Stampoulis, Vasileios; van Dyk, David A; Wardle, J F C; Lee, N P; Harris, D E; Schwartz, D A; Donato, Davide; Maraschi, Laura; Tavecchio, Fabrizio

    2016-01-01

    We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift (z >= 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 < z < 2.9) quasars. The dataset includes four sources with integrated steep radio spectra and seven with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet, and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p-value upper bounds on the significance that an X- ray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional 6 marginally. We also find residual emission in the cores of 3 quasars and in the background of 1 quasar...

  2. Inflow velocities of cold flows streaming into massive galaxies at high redshifts

    CERN Document Server

    Goerdt, Tobias

    2015-01-01

    We study the velocities of the accretion along streams from the cosmic web into massive galaxies at high redshift with the help of three different suites of AMR hydrodynamical cosmological simulations. The results are compared to free-fall velocities and to the sound speeds of the hot ambient medium. The sound speed of the hot ambient medium is calculated using two different methods to determine the medium's temperature. We find that the simulated cold stream velocities are in violent disagreement with the corresponding free-fall profiles. The sound speed is a better albeit not always correct description of the cold flows' velocity. Using these calculations as a first order approximation for the gas inflow velocities $v_{\\rm inflow} = 0.9 \\ v_{\\rm vir}$ is given. We conclude from the hydrodynamical simulations as our main result that the velocity profiles for the cold streams are constant with radius. These constant inflow velocities have in units of the virial velocity a "parabola-like" dependency on the hos...

  3. Dark-ages Reionization & Galaxy Formation Simulation I: The dynamical lives of high redshift galaxies

    CERN Document Server

    Poole, Gregory B; Mutch, Simon J; Power, Chris; Duffy, Alan R; Geil, Paul M; Mesinger, Andrei; Wyithe, Stuart B

    2015-01-01

    We present the Dark-ages Reionization and Galaxy-formation Observables from Numerical Simulations (DRAGONS) program and Tiamat, the collisionless N-body simulation program upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programs is its density of outputs at high redshift (100 from z=35 to z=5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from "universal" behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (~20%) of galactic halos are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: i) halo...

  4. Balancing the Energy Budget between Star-Formation and AGN in High Redshift Infrared Luminous Galaxies

    CERN Document Server

    Murphy, E J; Alexander, D M; Dickinson, M; Magnelli, B; Morrison, G; Pope, A; Teplitz, H I

    2008-01-01

    (abridged) We present deep Spitzer mid-infrared spectroscopy, along with 16, 24, 70, and 850 um photometry, for 22 galaxies located in GOODS-N. The sample spans a redshift range of 0.6 25 mag) sources. We find that infrared (IR; 8-1000 um) luminosities are overestimated by a factor of ~5 in the redshift range between 1.4 < z < 2.6 by fitting local spectral energy distributions (SEDs) with 24 um photometry alone compared to when having additional mid-infrared spectroscopic and longer wavelength photometric data. This result arises partly due to the fact that high redshift galaxies exhibit aromatic feature equivalent widths that are large compared to local galaxies of similar luminosities. Using improved estimates for the IR luminosities of these sources, we investigate whether their infrared emission is found to be in excess relative to that expected based on extinction corrected UV star formation rates (SFRs), possibly suggesting the presence of an obscured AGN. Through a spectral decomposition of mid-i...

  5. The Connection Between Reddening, Gas Covering Fraction, and the Escape of Ionizing Radiation at High Redshift

    CERN Document Server

    Reddy, Naveen A; Pettini, Max; Bogosavljevic, Milan; Shapley, Alice

    2016-01-01

    We use a large sample of galaxies at z~3 to establish a relationship between reddening, neutral gas covering fraction (fcov(HI)), and the escape of ionizing photons at high redshift. Our sample includes 933 galaxies at z~3, 121 of which have very deep spectroscopic observations (>7 hrs) in the rest-UV (lambda=850-1300 A) with Keck/LRIS. Based on the high covering fraction of outflowing optically-thick HI indicated by the composite spectra of these galaxies, we conclude that photoelectric absorption, rather than dust attenuation, dominates the depletion of ionizing photons. By modeling the composite spectra as the combination of an unattenuated stellar spectrum including nebular continuum emission with one that is absorbed by HI and reddened by a line-of-sight extinction, we derive an empirical relationship between E(B-V) and fcov(HI). Galaxies with redder UV continua have larger covering fractions of HI characterized by higher line-of-sight extinctions. Our results are consistent with the escape of Lya throug...

  6. XMM-Newton observations of three high-redshift radio galaxies

    CERN Document Server

    Belsole, E; Hardcastle, M J; Birkinshaw, M; Lawrence, C R

    2004-01-01

    We present the results of XMM-Newton observations of three high-redshift powerful radio galaxies 3C 184, 3C 292 and 3C 322. Although none of the sources lies in as rich an X-ray-emitting environment as is seen for some powerful radio galaxies at low redshift, the environments provide sufficient pressure to confine the radio lobes. The weak gas emission is particularly interesting for 3C 184, where a gravitational arc is seen, suggesting the presence of a massive cluster. Here Chandra data complement the XMM-Newton measurements by spatially separating X-rays from the extended atmosphere, the nucleus and the small-scale radio source. For 3C 292 the X-ray-emitting gas has a temperature of ~2 keV and luminosity of 6.5E43 erg/s, characteristic of a poor cluster. In all three cases, structures where the magnetic-field strength can be estimated through combining measurements of radio-synchrotron and inverse-Compton-X-ray emission, are consistent with being in a state of minimum total energy. 3C 184 and 3C 292 (and p...

  7. The gas distribution in the high-redshift cluster MS 1054-0321

    CERN Document Server

    Mirakhor, M S

    2016-01-01

    We investigate the gas mass distribution in the high redshift cluster MS 1054-0321 using Chandra X-ray and OCRA SZ effect data. We use a superposition of offset $\\beta$-type models to describe the composite structure of MS 1054-0321. We find gas mass fractions $f_{gas}^\\rm{X\\mbox{-}ray} = 0.087_{-0.001}^{+0.005}$ and $f_{gas}^\\rm{SZ} = 0.094_{-0.001}^{+0.003}$ for the (main) eastern component of MS 1054-0321 using X-ray or SZ data, but $f_{gas}^\\rm{X\\mbox{-}ray} = 0.030 _{-0.014}^{+0.010}$ for the western component. The gas mass fraction for the eastern component is in agreement with some results reported in the literature, but inconsistent with the cosmic baryon fraction. The low gas mass fraction for the western component is likely to be a consequence of gas stripping during the ongoing merger. The gas mass fraction of the integrated system is $0.060_{-0.009}^{+0.004}$: we suggest that the missing baryons from the western component are present as hot diffuse gas which is poorly represented in existing X-ray...

  8. Dark-ages reionization & galaxy formation simulation IV: UV luminosity functions of high-redshift galaxies

    CERN Document Server

    Liu, Chuanwu; Angel, P W; Duffy, Alan R; Geil, Paul M; Poole, Gregory B; Mesinger, Andrei; Wyithe, J Stuart B

    2015-01-01

    In this paper we present calculations of the UV luminosity function predictions from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations (DRAGONS) project, which combines N-body, semi-analytic and semi-numerical modeling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from $z{\\sim}5$ through to $z{\\sim}10$. We investigate the predicted luminosity-star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the mean relation of $0.1$-$0.3$ dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our predicted luminosities to investigate the luminosity function below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below cu...

  9. Globular clusters as the relics of regular star formation in 'normal' high-redshift galaxies

    CERN Document Server

    Kruijssen, J M Diederik

    2015-01-01

    We present an end-to-end, two-phase model for the origin of globular clusters (GCs). In the model, populations of stellar clusters form in the high-pressure discs of high-redshift ($z>2$) galaxies (a rapid-disruption phase due to tidal perturbations from the dense interstellar medium), after which the galaxy mergers associated with hierarchical galaxy formation redistribute the surviving, massive clusters into the galaxy haloes, where they remain until the present day (a slow-disruption phase due to tidal evaporation). The high galaxy merger rates of $z>2$ galaxies allow these clusters to be `liberated' into the galaxy haloes before they are disrupted within the high-density discs. This physically-motivated toy model is the first to include the rapid-disruption phase, which is shown to be essential for simultaneously reproducing the wide variety of properties of observed GC systems, such as their universal characteristic mass-scale, the dependence of the specific frequency on metallicity and galaxy mass, the ...

  10. AGN-driven outflows without quenching in simulations of high-redshift disk galaxies

    CERN Document Server

    Gabor, Jared M

    2014-01-01

    Recent observations have revealed nuclear outflows in high-redshift, star forming galaxies. We study outflows driven by Active Galactic Nuclei (AGNs) using high- resolution simulations of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the star formation rate (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e. unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively "off." The highest velocity outflows are concentrated within 2-3 kpc of the galactic center during the peak accretion. With our purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (10^6 K) and diffuse (nH<10^(-2) cm-3), but includes a cold component entrained in the ho...

  11. The ionization mechanism of the extended gas in high redshift radio galaxies shocks or AGN photoionization?

    CERN Document Server

    Villar-Martin, M; Clark, N E

    1997-01-01

    We have compared the UV line ratios of a sample of very high redshift radio galaxies with shock and AGN photoionization models, with the goal of determining the balance between jet-induced shocks and AGN illumination in the extended emission line regions. We find that the UV line ratios cannot be explained in terms of photoionization of solar abundance gas by the classical power law of index $\\alpha=$-1.5, which successfully reproduces the general trends defined by the optical line ratios of low redshift radio galaxies. Pure shock models also provide a poor fit to the data. However, photoionization by a power law of index -1.0 provides an excellent fit to the UV line ratios. This suggests that the ionizing continuum spectral shape may depend on radio luminosity and/or redshift, such that it becomes harder as the radio power and/or redshift increase. However, an alternative possibility is that we are seeing the first signs of chemical evolution in these objects, since a power-law of index -1.5 with low metalli...

  12. The origin of dust in high redshift QSOs: the case of SDSS J1148+5251

    CERN Document Server

    Valiante, Rosa; Salvadori, Stefania; Bianchi, Simone

    2011-01-01

    We present a semi-analytical model for the formation and evolution of a high redshift quasar (QSO). We reconstruct a set of hierarchical merger histories of a 10^13 Msun dark matter halo and model the evolution of the corresponding galaxy and of its central super massive black hole. The code GAMETE/QSODUST consistently follows: the black hole assembly via both coalescence with other black holes and gas accretion; the build up and star formation history of the quasar host galaxy, driven by binary mergers and mass accretion; the evolution of gas, stars, metals in the interstellar medium (ISM), accounting for mass exchanges with the external medium (infall and outflow processes); dust formation in Supernova (SN) ejecta and in the stellar atmosphere of Asymptotic Giant Branch (AGB) stars, dust destruction by interstellar shocks and grain growth in molecular clouds; the AGN feedback which powers a galactic-scale wind, self-regulating the black hole growth and eventually halting star formation.We use this model to ...

  13. The origin and evolution of dust in high-redshift galaxies

    CERN Document Server

    Dwek, Eli; Jones, Anthony P

    2007-01-01

    Dusty hyperluminous galaxies in the early universe provide unique environments for studying the role of massive stars in the formation and destruction of dust. At redshifts above 6, when the universe was less than 1 Gyr old, dust could have only condensed in the explosive ejecta of Type II supernovae (SNe), since most of the progenitors of the AGB stars, the major alternative source of interstellar dust, did not have time to evolve off the main sequence. We present analytical models for the evolution of the gas, dust, and metals in high redshift galaxies, with a special application to SDSS J1148+5251, a hyperluminous quasar at z = 6.4. We show that an average SN must condense at least 1 Msun of dust to account for the mass of dust in this object, when grain destruction by supernova remnants (SNRs) is taken into account. This required yield is in excess of ~0.05 Msun, the largest mass of dust inferred from infrared observations of Cas A. If the yield of Cas A is typical, then other processes, such as accretion...

  14. The Coevolution of Supermassive Black Holes and Massive Galaxies at High Redshift

    CERN Document Server

    Lapi, A; Aversa, R; Cai, Z -Y; Negrello, M; Celotti, A; De Zotti, G; Danese, L

    2013-01-01

    We exploit the recent, wide samples of far-infrared (FIR) selected galaxies followed-up in X rays and of X-ray/optically selected active galactic nuclei (AGNs) followed-up in the FIR band, along with the classic data on AGN and stellar luminosity functions at high redshift z>1.5, to probe different stages in the coevolution of supermassive black holes (BHs) and host galaxies. The results of our analysis indicate the following scenario: (i) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ~0.5-1 Gyr, and then abruptly declines due to quasar feedback; over the same timescale, (ii) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the star formation and is temporarily stored into a massive reservoir/proto-torus wherefrom it can be promptly accreted; (iii) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington...

  15. The Star-Forming Molecular Gas in High Redshift Submillimeter Galaxies

    CERN Document Server

    Narayanan, Desika; Hayward, Christopher; Younger, Joshua D; Hernquist, Lars

    2009-01-01

    We present a model for the CO molecular line emission from high redshift Submillimeter Galaxies (SMGs). By combining hydrodynamic simulations of gas rich galaxy mergers with the polychromatic radiative transfer code, Sunrise, and the 3D non-LTE molecular line radiative transfer code, Turtlebeach, we show that if SMGs are typically a transient phase of major mergers, their observed compact CO spatial extents, broad line widths, and high excitation conditions (CO SED) are naturally explained. In this sense, SMGs can be understood as scaled-up analogs to local ULIRGs. We utilize these models to investigate the usage of CO as an indicator of physical conditions. We find that care must be taken when applying standard techniques. The usage of CO line widths as a dynamical mass estimator from SMGs can possibly overestimate the true enclosed mass by a factor ~1.5-2. At the same time, assumptions of line ratios of unity from CO J=3-2 (and higher lying lines) to CO (J=1-0) will oftentimes lead to underestimates of the ...

  16. Infrared Properties of High Redshift and X-ray Selected AGN Samples

    CERN Document Server

    Wilkes, B J; McLeod, K K; Elvis, M; Hughes, D H; Impey, C D; Kuraszkiewicz, J K; Lonsdale, C S; Malkan, M A; McDowell, J C; Wilkes, Belinda J.; Hooper, Eric J.; Leod, Kim K. Mc; Elvis, Martin S.; Hughes, David H.; Impey, Chris D.; Kuraszkiewicz, Joanna K.; Lonsdale, Carol S.; Malkan, Matt A.; Dowell, Jonathan C. Mc

    2000-01-01

    The NASA/ISO Key Project on active galactic nuclei (AGN) seeks to better understand the broad-band spectral energy distributions (SEDs) of these sources from radio to X-rays, with particular emphasis on infrared properties. The ISO sample includes a wide variety of AGN types and spans a large redshift range. Two subsamples are considered herein: 8 high-redshift (1 < z < 4.7) quasars; and 22 hard X-ray selected sources. The X-ray selected AGN show a wide range of IR continuum shapes, extending to cooler colors than the optical/radio sample of Elvis et al. (1994). Where a far-IR turnover is clearly observed, the slopes are < 2.5 in all but one case so that non-thermal emission remains a possibility. The highest redshift quasars show extremely strong, hot IR continua requiring ~ 100 solar masses of 500 - 1000 Kelvin dust with ~ 100 times weaker optical emission. Possible explanations for these unusual properties include: reflection of the optical light from material above/below a torus; strong obscurati...

  17. A high-redshift IRAS galaxy with huge luminosity - hidden quasar or protogalaxy?

    International Nuclear Information System (INIS)

    During a survey intended to measure redshifts for 1,400 galaxies identified with faint sources detected by the Infrared Astronomy Satellite, we found an emission-line galaxy at a redshift of 2.286, and with the enormous far-infrared luminosity of 3 x 1014 times that of the sun (Lsun) The spectrum is very unusual, showing lines of high excitation but with very weak Lyman-α emission. A self-absorbed synchrotron model for the infrared energy distribution cannot be ruled out, but a thermal origin seems more plausible. A radio-quiet quasar embedded in a very dusty galaxy could account for the infrared emission, as might a starburst embedded in 1-10 x 109 Msun of dust. The latter case demands so much dust that the object would probably be a massive galaxy in the process of formation. In either case, this is a remarkable object, and the presence of a large amount of dust in an object of such high redshift implies the generation of heavy elements at an early cosmological epoch. (author)

  18. Updated f(T) gravity constraints from high-redshift cosmography

    Science.gov (United States)

    Piedipalumbo, Ester; Moglie, Enrica Della; Cianci, Roberto

    2015-09-01

    In the last dozen years, a wide and variegated mass of observational data revealed that the universe is now expanding at an accelerated rate. In the absence of a well-based theory to interpret the observations, cosmography provides information about the evolution of the universe from measured distances, only assuming that the geometry can be described by the Friedmann-Lemaitre-Robertson-Walker metric. In this paper, we perform a high-redshift analysis which allows us to put constraints on the cosmographic parameters up to the fifth-order, thus inducing indirect constraints on any gravity theory. Here, we are interested in the so-called teleparallel gravity theory, f(T). Actually, we use the analytical expressions of the present day values of f(T) and its derivatives as functions of the cosmographic parameters to map the cosmography region of confidences into confidence ranges for f(T) and its derivative. Moreover, we show how these can be used to test some teleparallel gravity models without solving the dynamical equations. Our analysis is based on the Union2 Type Ia supernovae (SNIa) data set, a set of 28 measurements of the Hubble parameter, the Hubble diagram constructed from some gamma ray bursts (GRB) luminosity distance indicators and Gaussian priors on the distance from the baryon acoustic oscillations (BAOs) and the Hubble constant h. To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters, we use the Markov chain Monte Carlo (MCMC) method.

  19. The AzTEC/SMA Interferometric Imaging Survey of Submillimeter-Selected High-Redshift Galaxies

    CERN Document Server

    Younger, J D; Huang, J -S; Yun, M S; Wilson, G W; Ashby, M L N; Gurwell, M A; Peck, A B; Petitpas, G R; Wilner, D J; Hughes, D H; Aretxaga, I; Kim, S; Scott, K S; Austermann, J; Perera, T; Lowenthal, J D

    2009-01-01

    We present results from a continuing interferometric survey of high-redshift submillimeter galaxies with the Submillimeter Array, including high-resolution (beam size ~2 arcsec) imaging of eight additional AzTEC 1.1mm selected sources in the COSMOS Field, for which we obtain six reliable (peak S/N>5 or peak S/N>4 with multiwavelength counterparts within the beam) and two moderate significance (peak S/N>4) detections. When combined with previous detections, this yields an unbiased sample of millimeter-selected SMGs with complete interferometric followup. With this sample in hand, we (1) empirically confirm the radio-submillimeter association, (2) examine the submillimeter morphology - including the nature of submillimeter galaxies with multiple radio counterparts and constraints on the physical scale of the far infrared - of the sample, and (3) find additional evidence for a population of extremely luminous, radio-dim submillimeter galaxies that peaks at higher redshift than previous, radio-selected samples. I...

  20. The Quest for Dusty Star-forming Galaxies at High Redshift z>4

    CERN Document Server

    Mancuso, C; Shi, J; Gonzalez-Nuevo, J; Aversa, R; Danese, L

    2016-01-01

    We exploit the continuity equation approach and the `main sequence' star-formation timescales to show that the observed high abundance of galaxies with stellar masses > a few 10^10 M_sun at redshift z>4 implies the existence of a galaxy population featuring large star formation rates (SFRs) > 10^2 M_sun/yr in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z30 M_sun/yr cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from AzTEC-LABOCA, SCUBA-2 and ALMA-SPT surveys are already digging into it. We substantiate how an observational strategy based on a color preselection in the far-IR or (sub-)mm band with Herschel and SCUBA-2, supplemented by photometric data...

  1. Star formation in high redshift galaxies including Supernova feedback: effect on stellar mass and luminosity functions

    CERN Document Server

    Samui, Saumyadip

    2014-01-01

    We present a semi-analytical model of high redshift galaxy formation. In our model the star formation inside a galaxy is regulated by the feedback from supernova (SNe) driven outflows. We derive a closed analytical form for star formation rate in a single galaxy taking account of the SNe feedback in a self-consistent manner. We show that our model can explain the observed correlation between the stellar mass and the circular velocity of galaxies from dwarf galaxies to massive galaxies of $10^{12} M_\\odot$. For small mass dwarf galaxies additional feedback other than supernova feedback is needed to explain the spread in the observational data. Our models reproduce the observed 3-D fundamental correlation between the stellar mass, gas phase metallicity and star formation rate in galaxies establishing that the SNe feedback plays a major role in building this relation. Further, the observed UV luminosity functions of Lyman-Break galaxies (LBGs) are well explained by our feedback induced star formation model for a...

  2. Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology

    CERN Document Server

    Jorgenson, Regina A; Prochaska, J Xavier

    2010-01-01

    We probe the physical conditions in high redshift galaxies, specifically, the Damped Lyman-alpha Systems (DLAs) using neutral carbon (CI) fine structure lines and molecular hydrogen (H2). We report five new detections of CI and analyze the CI in an additional 2 DLAs with previously published data. We also present one new detection of H2 in a DLA. We present a new method of analysis that simultaneously constrains \\emph{both} the volume density and the temperature of the gas, as opposed to previous studies that a priori assumed a gas temperature. We use only the column density of CI measured in the fine structure states and the assumption of ionization equilibrium in order to constrain the physical conditions in the gas. We present a sample of 11 CI velocity components in 6 DLAs and compare their properties to those derived by the global CII* technique. The resulting median values for this sample are: = 69 cm^{-3}, = 50 K, and = 3.86 cm^{-3} K, with standard deviations, sigma_{n(HI)} = 134 cm^{-3}, sigma_T =...

  3. Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

    CERN Document Server

    Bournaud, F; Weiss, A; Renaud, F; Mastropietro, C; Teyssier, R

    2014-01-01

    We model the intensity of emission lines from the CO molecule, based on hydrodynamic simulations of spirals, mergers, and high-redshift galaxies with very high resolutions (3pc and 10^3 Msun) and detailed models for the phase-space structure of the interstellar gas including shock heating, stellar feedback processes and galactic winds. The simulations are analyzed with a Large Velocity Gradient (LVG) model to compute the local emission in various molecular lines in each resolution element, radiation transfer and opacity effects, and the intensity emerging from galaxies, to generate synthetic spectra for various transitions of the CO molecule. This model reproduces the known properties of CO spectra and CO-to-H2 conversion factors in nearby spirals and starbursting major mergers. The high excitation of CO lines in mergers is dominated by an excess of high-density gas, and the high turbulent velocities and compression that create this dense gas excess result in broad linewidths and low CO intensity-to-H2 mass r...

  4. Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey

    CERN Document Server

    Canameras, R; Guery, D; McKenzie, T; Koenig, S; Petitpas, G; Dole, H; Frye, B; Flores-Cacho, I; Montier, L; Negrello, M; Beelen, A; Boone, F; Dicken, D; Lagache, G; Floch, E Le; Altieri, B; Bethermin, M; Chary, R; De Zotti, G; Giard, M; Kneissl, R; Krips, M; Malhotra, S; Martinache, C; Omont, A; Pointecouteau, E; Puget, J -L; Scott, D; Soucail, G; Valtchanov, I; Welikala, N; Yan, L

    2015-01-01

    We present an analysis of 11 bright far-IR/submm sources discovered through a combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each source has a redshift z=2.2-3.6 obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA, and optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um and 2 mm, respectively. All objects are bright, isolated point sources in the 18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking either near the 350 um or the 500 um bands of SPIRE, and with apparent far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes, CO line widths and luminosities, dust temperatures, and far-infrared luminosities provide additional empirical evidence that these are strongly gravitationally lensed high-redshift gala...

  5. Feeding cosmic star formation: Exploring high-redshift molecular gas with CO intensity mapping

    CERN Document Server

    Breysse, Patrick C

    2016-01-01

    The study of molecular gas is crucial for understanding star formation, feedback, and the broader ecosystem of a galaxy as a whole. However, we have limited understanding of its physics and distribution in all but the nearest galaxies. We present a new technique for studying the composition and distribution of molecular gas in high-redshift galaxies inaccessible to existing methods. Our proposed approach is an extension of carbon monoxide intensity mapping methods, which have garnered significant experimental interest in recent years. These intensity mapping surveys target the 115 GHz $^{12}$CO (1-0) line, but also contain emission from the substantially fainter 110 GHz $^{13}$CO (1-0) transition. The method leverages the information contained in the $^{13}$CO line by cross-correlating pairs of frequency channels in an intensity mapping survey. Since $^{13}$CO is emitted from the same medium as the $^{12}$CO, but saturates at a much higher column density, this cross-correlation provides valuable information a...

  6. Supermassive Black Hole Formation at High Redshifts via Direct Collapse: Physical Processes in the Early Stage

    CERN Document Server

    Choi, Jun-Hwan; Begelman, Mitchell C

    2013-01-01

    We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. We follow the evolution of gas within slowly tumbling DM halos of 2 x 10^8 Mo and 1 kpc. We adopt cosmologically motivated density profiles and j-distributions. Our goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation. We find that the collapse leads either to a central runaway or to off-center fragmentation. A disk-like configuration is formed inside the centrifugal barrier. For more cuspy DM distribution, the gas collapses more and experiences a bar-like perturbation and a central runaway. We have followed this inflow down to ~10^{-4} pc. The flow remains isothermal and the specific angular momentum is efficiently transferred by gravitational torques in a cascade of nested bars. This cascade supports a self-similar, disk-like collapse. In the collapsing phase, virial supersonic turbulence dev...

  7. Colour gradients of high-redshift Early-Type Galaxies from hydrodynamical monolithic models

    CERN Document Server

    Tortora, C; D'Ercole, A; Napolitano, N R; Matteucci, F

    2013-01-01

    We analyze the evolution of colour gradients predicted by the hydrodynamical models of early type galaxies (ETGs) in Pipino et al. (2008), which reproduce fairly well the chemical abundance pattern and the metallicity gradients of local ETGs. We convert the star formation (SF) and metal content into colours by means of stellar population synthetic model and investigate the role of different physical ingredients, as the initial gas distribution and content, and eps_SF, i.e. the normalization of SF rate. From the comparison with high redshift data, a full agreement with optical rest-frame observations at z < 1 is found, for models with low eps_SF, whereas some discrepancies emerge at 1 < z < 2, despite our models reproduce quite well the data scatter at these redshifts. To reconcile the prediction of these high eps_SF systems with the shallower colour gradients observed at lower z we suggest intervention of 1-2 dry mergers. We suggest that future studies should explore the impact of wet galaxy mergings...

  8. A scientific case for future X-ray Astronomy: Galaxy Clusters at high redshifts

    CERN Document Server

    Tozzi, Paolo

    2013-01-01

    Clusters of galaxies at high redshift (z>1) are vitally important to understand the evolution of the large scale structure of the Universe, the processes shaping galaxy populations and the cycle of the cosmic baryons, and to constrain cosmological parameters. After 13 years of operation of the Chandra and XMM-Newton satellites, the discovery and characterization of distant X-ray clusters is proceeding at a slow pace, due to the low solid angle covered so far, and the time-expensive observations needed to physically characterize their intracluster medium (ICM). At present, we know that at z>1 many massive clusters are fully virialized, their ICM is already enriched with metals, strong cool cores are already in place, and significant star formation is ongoing in their most massive galaxies, at least at z>1.4. Clearly, the assembly of a large and well characterized sample of high-z X-ray clusters is a major goal for the future. We argue that the only means to achieve this is a survey-optimized X-ray mission capa...

  9. Outflows Driven by Quasars in High-Redshift Galaxies with Radiation Hydrodynamics

    CERN Document Server

    Bieri, Rebekka; Rosdahl, Joakim; Wagner, Alexander Y; Silk, Joseph; Mamon, Gary A

    2016-01-01

    The quasar mode of Active Galactic Nuclei (AGN) in the high-redshift Universe is routinely observed in gas-rich galaxies together with large-scale AGN-driven winds. It is crucial to understand how photons emitted by the central AGN source couple to the ambient interstellar-medium to trigger large-scale outflows. By means of radiation-hydrodynamical simulations of idealised galactic discs, we study the coupling of photons with the multiphase galactic gas, and how it varies with gas cloud sizes, and the radiation bands included in the simulations, which are ultraviolet (UV), optical, and infrared (IR). We show how a quasar with a luminosity of $10^{46}$ erg/s can drive large-scale winds with velocities of $10^2-10^3$ km/s and mass outflow rates around $10^3$ M$_\\odot$/yr for times of order a few million years. Infrared radiation is necessary to efficiently transfer momentum to the gas via multi-scattering on dust in dense clouds. However, IR multi-scattering, despite being extremely important at early times, qu...

  10. Warm molecular Hydrogen at high redshift with the James Webb Space Telescope

    CERN Document Server

    Guillard, P; Lehnert, M D; Appleton, P N; Forêts, G Pineau des

    2015-01-01

    The build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation. The energy released by these processes has to dissipate for gas to cool, condense, and form stars. How gas cools is thus a key to understand galaxy formation. \\textit{Spitzer Space Telescope} infrared spectroscopy revealed a population of galaxies with weak star formation and unusually powerful H$_2$ line emission. This is a signature of turbulent dissipation, sustained by large-scale mechanical energy injection. The cooling of the multiphase interstellar medium is associated with emission in the H$_2$ lines. These results have profound consequences on our understanding of regulation of star formation, feedback and energetics of galaxy formation in general. The fact that H$_2$ lines can be strongly enhanced in high-redshift turbulent galaxies will be of great importance for the \\textit{James Webb Space Telescope} observations which will unveil the role tha...

  11. Different star formation laws for disks versus starbursts at low and high redshifts

    CERN Document Server

    Daddi, E; Walter, F; Bournaud, F; Salmi, F; Carilli, C; Dannerbauer, H; Dickinson, M; Monaco, P; Riechers, D

    2010-01-01

    We present evidence that 'bona fide' disks and starburst systems occupy distinct regions in the gas mass versus star formation (SF) rate plane, both for the integrated quantities and for the respective surface densities. This result is based on CO observations of galaxy populations at low and high redshifts, and on the current consensus for the CO luminosity to gas mass conversion factors. The data suggest the existence of two different star formation regimes: a long-lasting mode for disks and a more rapid mode for starbursts, the latter probably occurring during major mergers or in dense nuclear SF regions. Both modes are observable over a large range of SF rates. The detection of CO emission from distant near-IR selected galaxies reveals such bimodal behavior for the first time, as they allow us to probe gas in disk galaxies with much higher SF rates than are seen locally. The different regimes can potentially be interpreted as the effect of a top-heavy IMF in starbursts. However, we favor a different physi...

  12. Evolution of Neutral Gas at High Redshift -- Implications for the Epoch of Galaxy Formation

    CERN Document Server

    Storrie-Lombardi, L J; Irwin, M J

    1996-01-01

    Though observationally rare, damped Lya absorption systems dominate the mass density of neutral gas in the Universe. Eleven high redshift damped Lya systems covering 2.84 QSO Survey, extending these absorption system surveys to the highest redshifts currently possible. Combining our new data set with previous surveys we find that the cosmological mass density in neutral gas, omega_g, does not rise as steeply prior to z~2 as indicated by previous studies. There is evidence in the observed omega_g for a flattening at z~2 and a possible turnover at z~3. When combined with the decline at z>3.5 in number density per unit redshift of damped systems with column densities log N(HI)>21 atoms cm^-2, these results point to an epoch at z>3 prior to which the highest column density damped systems are still forming. We find that over the redshift range 2

  13. The first XMM-Newton spectrum of a high redshift quasar - PKS 0537-286

    CERN Document Server

    Reeves, J N; Bennie, P J; Pounds, K A; Short, A; O'Brien, P T; Boller, T; Kuster, M; Tiengo, A; Boller, Th.

    2001-01-01

    We present XMM-Newton observations of the high redshift z=3.104, radio-loud quasar PKS 0537-286. The EPIC CCD cameras provide the highest signal-to-noise spectrum of a high-z quasar to date. The EPIC observations show that PKS 0537-286 is extremely X-ray luminous (Lx=2x10^47 erg/s), with an unusually hard X-ray spectrum (Gamma=1.27+/-0.02). The flat power-law emission extends over the whole observed energy range; there is no evidence of intrinsic absorption, which has been claimed in PKS 0537-286 and other high z quasars. However, there is evidence for weak Compton reflection. A redshifted iron K line, observed at 1.5 keV - corresponding to 6.15 keV in the quasar rest frame - is detected at 95% confidence. If confirmed, this is the most distant iron K line known. The line equivalent width is small (33eV), consistent with the `X-ray Baldwin effect' observed in other luminous quasars. The reflected continuum is also weak (R=0.25). We find the overall spectral energy distribution of PKS 0537-286 is dominated by ...

  14. Infrared-Faint Radio Sources in the SERVS deep fields: Pinpointing AGNs at high redshift

    CERN Document Server

    Maini, Alessandro; Norris, Ray P; Spitler, Lee R; Mignano, Arturo; Lacy, Mark; Morganti, Raffaella

    2016-01-01

    Infrared-Faint Radio Sources (IFRS) represent an unexpected class of objects relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S_{1.4GHz} >= 10 mJy) has provided evidence that most of them (if not all) contain an AGN. Still uncertain is the nature of the radio-faintest ones (S_{1.4GHz} 4). We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 mum IR counterparts of the 64 sources located in the SERVS fields were searched for, and, when detected, their IR properties were studied. We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that they are mostly consistent with a mixture of high-redshift (z >= 3) radio-loud AGNs. The faintest ones (S_{1.4GHz} ~ 100 muJy), however, could be also associated with nearer (z ~ 2) dust-enshrouded...

  15. The high-redshift (z>3) AGN population in the 4 Ms Chandra Deep Field South

    CERN Document Server

    Vito, F; Gilli, R; Comastri, A; Iwasawa, K; Brandt, W N; Alexander, D M; Brusa, M; Lehmer, B; Bauer, F E; Schneider, D P; Xue, Y Q; Luo, B

    2012-01-01

    We present results from a spectral analysis of a sample of high-redshift (z>3) X-ray selected AGN in the 4 Ms Chandra Deep Field South (CDF-S), the deepest X-ray survey to date. The sample is selected using the most recent spectroscopic and photometric information available in this field. It consists of 34 sources with median redshift z=3.7, 80 median net counts in the 0.5-7 keV band and median rest-frame absorption-corrected luminosity $L_{2-10 \\rmn{keV}}\\approx1.5\\times10^{44}\\rmn{erg} \\rmn{s^{-1}}$. Spectral analysis for the full sample is presented and the intrinsic column density distribution, corrected for observational biases using spectral simulations, is compared with the expectations of X-ray background (XRB) synthesis models. We find that $\\approx57$ per cent of the sources are highly obscured ($N_H>10^{23}\\rmn{cm^{-2}}$). Source number counts in the $0.5-2\\rmn{keV}$ band down to flux $F_{0.5-2 \\rmn{keV}}\\approx4\\times10^{-17}\\rmn{erg} \\rmn{s^{-1}cm^{-2}}$ are also presented. Our results are consis...

  16. 1WGAJ1226.9+3332 a high redshift cluster discovered by Chandra

    CERN Document Server

    Cagnoni, I; Kim, D W; Mazzotta, P; Huang, J S; Celotti, A

    2001-01-01

    We report the detection of 1WGAJ1226.9+3332 as an arcminute scale extended X-ray source with the Chandra X-ray Observatory. The Chandra observation and R and K band imaging strongly support the identification of 1WGAJ1226.9+3332 as a high redshift cluster of galaxies, most probably at z=0.85 +- 0.15, with an inferred temperature kT =10 (+4;-3) keV and an unabsorbed luminosity (in a r=120" aperture) of 1.3 (+0.16;-0.14) x 1e45 erg/s (0.5-10 keV). This indication of redshift is also supported by the K and R band imaging, and is in agreement with the spectroscopic redshift of 0.89 found by Ebeling et al. (2001). The surface brightness profile is consistent with a beta-model with beta=0.770 +- 0.025, rc=(18.1 +-0.9)" (corresponding to 101 +- 5 kpc at z=0.89), and S(0)=1.02 +- 0.08 counts/arcsec**2. 1WGAJ1226.9+3332 was selected as an extreme X-ray loud source with FX/FV>60; this selection method, thanks to the large area sampled, seems to be a highly efficient method for finding luminous high z clusters of galaxi...

  17. Nearby Clumpy, Gas Rich, Star Forming Galaxies: Local Analogs of High Redshift Clumpy Galaxies

    CERN Document Server

    Garland, C A; Mac Low, M -M; Kreckel, K; Rabidoux, K; Guzmán, R

    2015-01-01

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates and compact morphologies. We combine Sloan Digital Sky Survey data with HI data of 29 LCBGs at redshift z~0 to understand their nature. We find that local LCBGs have high atomic gas fractions (~50%) and star formation rates per stellar mass consistent with some high redshift star forming galaxies. Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy star forming galaxies commonly observed at z~1-3. Local LCBGs separate into three groups: 1. Interacting galaxies (~20%); 2. Clumpy spirals (~40%); 3. Non-clumpy, non-spirals with regular shapes and smaller effective radii and stellar masses (~40%). It seems that the method of building up a high gas fraction, which then triggers star formation, is not the same for all local LCBGs. This may lead to a dichotomy in galaxy characteristics. We consider possible gas delivery scenarios and sugges...

  18. WEAK LINE QUASARS AT HIGH REDSHIFT: EXTREMELY HIGH ACCRETION RATES OR ANEMIC BROAD-LINE REGIONS?

    International Nuclear Information System (INIS)

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak broad Hβ line and place tight upper limits on the strengths of their [O III] lines. Virial, Hβ-based black hole mass determinations indicate normalized accretion rates of L/L Edd=0.4 for these sources, which is well within the range observed for typical quasars with similar luminosities and redshifts. We also present high-quality XMM-Newton imaging spectroscopy of SDSS J114153.34+021924.3 and find a hard-X-ray photon index of Γ = 1.91+0.24-0.22, which supports the virial L/L Edd determination in this source. Our results suggest that the weakness of the broad emission lines in WLQs is not a consequence of an extreme continuum-emission source but instead due to abnormal broad emission line region properties.

  19. An Increasing Stellar Baryon Fraction in Bright Galaxies at High Redshift

    CERN Document Server

    Finkelstein, Steven L; Behroozi, Peter; Somerville, Rachel S; Papovich, Casey; Milosavljevic, Milos; Dekel, Avishai; Narayanan, Desika; Ashby, Matthew L N; Cooray, Asantha; Fazio, Giovanni G; Ferguson, Henry C; Koekemoer, Anton M; Salmon, Brett W; Willner, S P

    2015-01-01

    Recent observations have shown that the characteristic luminosity of the rest-frame ultraviolet (UV) luminosity function does not significantly evolve at 4 < z < 7 and is approximately M*_UV ~ -21. We investigate this apparent non-evolution by examining a sample of 190 bright, M_UV < -21 galaxies at z=4 to 7, analyzing their stellar populations and host halo masses. Including deep Spitzer/IRAC imaging to constrain the rest-frame optical light, we find that M*_UV galaxies at z=4-7 have similar stellar masses of log(M/Msol)=9.8-9.9 and are thus relatively massive for these high redshifts. However, bright galaxies at z=4-7 are less massive and have younger inferred ages than similarly bright galaxies at z=2-3, even though the two populations have similar star formation rates and levels of dust attenuation. We match the abundances of these bright z=4-7 galaxies to halo mass functions from the Bolshoi Lambda-CDM simulation to estimate the halo masses. We find that the typical halo masses in ~M*_UV galaxie...

  20. Giant clumps in the FIRE simulations: a case study of a massive high-redshift galaxy

    CERN Document Server

    Oklopcic, Antonija; Feldmann, Robert; Keres, Dusan; Faucher-Giguere, Claude-Andre; Murray, Norman

    2016-01-01

    The morphology of massive star-forming galaxies at high redshift is often dominated by giant clumps of mass ~10^8-10^9 Msun and size ~100-1000 pc. Previous studies have proposed that giant clumps might have an important role in the evolution of their host galaxy, particularly in building the central bulge. However, this depends on whether clumps live long enough to migrate from their original location in the disc or whether they get disrupted by their own stellar feedback before reaching the centre of the galaxy. We use cosmological hydrodynamical simulations from the FIRE (Feedback in Realistic Environments) project that implement explicit treatments of stellar feedback and ISM physics to study the properties of these clumps. We follow the evolution of giant clumps in a massive (stellar mass ~10^10.8 Msun at z=1), discy, gas-rich galaxy from redshift z>2 to z=1. Even though the clumpy phase of this galaxy lasts over a gigayear, individual gas clumps are short-lived, with mean lifetime of massive clumps of ~2...

  1. Atomic carbon as a tracer of molecular gas in high-redshift galaxies: perspectives for ALMA

    CERN Document Server

    Tomassetti, Matteo; Romano-Diaz, Emilio; Ludlow, Aaron D; Papadopoulos, Padelis P

    2014-01-01

    We use a high-resolution simulation that tracks the non-equilibrium abundance of molecular hydrogen, H2, within a massive high-redshift galaxy to produce mock ALMA maps of the fine-structure lines of atomic carbon CI 1-0 and CI 2-1. Inspired by recent observational and theoretical work, we assume that CI is thoroughly mixed in giant molecular clouds and demonstrate that its emission is an excellent proxy for H2. The entire H2 mass of a galaxy at redshift z<4 can be detected using a compact interferometric configuration with a large synthesized beam (that does not resolve the target galaxy) in less than 1 hour of integration time. Low-resolution imaging of the CI lines (in which the target galaxy is resolved into 3-4 beams) will detect nearly 50-60 per cent of the molecular hydrogen in less than 12 hours. In this case, the data cube also provides valuable information regarding the dynamical state of the galaxy. We conclude that ALMA observations of the CI 1-0 and 2-1 emission will widely extend the interval...

  2. GISMO, a 2 mm Bolometer Camera Optimized for the Study of High Redshift Galaxies

    Science.gov (United States)

    Staguhn, J.

    2007-01-01

    The 2mm spectral range provides a unique terrestrial window enabling ground based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. We present a progress report for our bolometer camera GISMO (the Goddard-IRAM Superconducting 2-Millimeter Observer), which will obtain large and sensitive sky maps at this wavelength. The instrument will be used at the IRAM 30 m telescope and we expect to install it at the telescope in 2007. The camera uses an 8 x 16 planar array of multiplexed TES bolometers, which incorporates our recently designed Backshort Under Grid (BUG) architecture. GISMO will be very efficient at detecting sources serendipitously in large sky surveys. With the background limited performance of the detectors, the camera provides significantly greater imaging sensitivity and mapping speed at this wavelength than has previously been possible. The major scientific driver for the instrument is to provide the IRAM 30 m telescope with the capability to rapidly observe galactic and extragalactic dust emission, in particular from high-zeta ULI RGs and quasar s, even in the summer season. The instrument will fill in the SEDs of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Our source count models predict that GISMO will serendipitously detect one galaxy every four hours on the blank sky, and that one quarter of these galaxies will be at a redshift of zeta 6.5.

  3. THE POPULATION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE CHANDRA-COSMOS SURVEY

    International Nuclear Information System (INIS)

    We present the high-redshift (3 phot phot + 1σ > 3. Eighty-one sources are selected in the 0.5-2 keV band, fourteen are selected in the 2-10 keV and six in the 0.5-10 keV bands. We sample the high-luminosity (log L(2-10keV) > 44.15 erg s–1) space density up to z ∼ 5 and a fainter luminosity range (43.5 erg s–1 (2-10keV) –1) than previous studies, up to z = 3.5. We weighted the contribution to the number counts and the space density of the sources with photometric redshift by using their probability of being at z > 3. We find that the space density of high-luminosity AGNs declines exponentially at all the redshifts, confirming the trend observed for optically selected quasars. At lower luminosity, the measured space density is not conclusive, and a larger sample of faint sources is needed. Comparisons with optical luminosity functions and black hole formation models are presented together with prospects for future surveys.

  4. The gas distribution in the high-redshift cluster MS 1054-0321

    Science.gov (United States)

    Mirakhor, M. S.; Birkinshaw, M.

    2016-04-01

    We investigate the gas mass distribution in the high-redshift cluster MS 1054-0321 using Chandra X-ray and One Centimetre Receiver array Sunyaev-Zel'dovich (SZ) effect data. We use a superposition of offset β-type models to describe the composite structure of MS 1054-0321. We find gas mass fractions f_{gas}^{X {-}ray} = 0.087_{-0.001}^{+0.005} and f_{gas}^SZ=0.094_{-0.001}^{+0.003} for the (main) eastern component of MS 1054-0321 using X-ray or SZ data, but f_{gas}^{X {-}ray}=0.030_{-0.014}^{+0.010} for the western component. The gas mass fraction for the eastern component is in agreement with some results reported in the literature, but inconsistent with the cosmic baryon fraction. The low-gas mass fraction for the western component is likely to be a consequence of gas stripping during the ongoing merger. The gas mass fraction of the integrated system is 0.060_{-0.009}^{+0.004}: we suggest that the missing baryons from the western component are present as hot diffuse gas which is poorly represented in existing X-ray images. The missing gas could appear in sensitive SZ maps.

  5. Accretion Disks, Jets and Blazar Variability

    OpenAIRE

    Wiita, Paul J.

    2005-01-01

    Although blazar variability is probably dominated by emission from relativistic jets, accretion disks should be present in all blazars. These disks produce emission over most of the electromagnetic spectrum; various unstable processes operate in those disks which lead to variable emission. Here I summarize some of the most relevant disk mechanisms for AGN variability. I also discuss some aspects of jet variability, focusing on the possibility that ultrarelativisitic jets of modest opening ang...

  6. Gravitational microlensing of gamma-ray blazars

    DEFF Research Database (Denmark)

    F. Torres, Diego; E. Romero, Gustavo; F. Eiroa, Ernesto;

    2003-01-01

    We present a detailed study of the effects of gravitational microlensing on compact and distant $\\gamma$-ray blazars. These objects have $\\gamma$-ray emitting regions which are small enough as to be affected by microlensing effects produced by stars lying in intermediate galaxies. We analyze the...... galactic latitude whose gamma-ray statistical properties are very similar to detected $\\gamma$-ray blazars) are indeed the result of gravitational lensing magnification of background undetected Active Galactic Nuclei (AGNs)....

  7. Clustering of High Redshift (z>2.9) Quasars from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E.Vanden; Anderson, Scott F.; Bahcall, Neta A.; /KIPAC, Menlo Park

    2006-11-30

    We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 {le} z {le} 5.4 selected over 4041 deg{sup 2} from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form {zeta}(r) = (r/r{sub 0}){sup -{gamma}}, the fitted parameters in comoving coordinates are r{sub 0} = 15.2 {+-} 2.7 h{sup -1} Mpc and {gamma} = 2.0 {+-} 0.3, over a scale range 4 {le} r{sub p} {le} 150 h{sup -1} Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z {approx} 1.5 counterparts, which have a comoving clustering length r{sub 0} {approx} 6.5 h{sup -1} Mpc. Dividing our sample into two redshift bins: 2.9 {le} z {le} 3.5 and z {ge} 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r{sub 0} = 16.9 {+-} 1.7 h{sup -1} Mpc for the former, and r{sub 0} = 24.3 {+-} 2.4 h{sup -1} Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 {approx} 50 Myr for quasars with 2.9 {le} z {le} 3.5; and 30 {approx} 600 Myr for quasars with z {ge} 3.5. The corresponding duty cycles are 0.004 {approx} 0.05 for the lower redshift bin and 0.03 {approx} 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with 2.9 {le} z {le} 3.5 and 4-6 x 10{sup 12} h{sup -1} M{sub {circle_dot}} for quasars with z {ge} 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b

  8. Globular clusters as the relics of regular star formation in `normal' high-redshift galaxies

    Science.gov (United States)

    Kruijssen, J. M. Diederik

    2015-12-01

    We present an end-to-end, two-phase model for the origin of globular clusters (GCs). In the model, populations of stellar clusters form in the high-pressure discs of high-redshift (z > 2) galaxies (a rapid-disruption phase due to tidal perturbations from the dense interstellar medium), after which the galaxy mergers associated with hierarchical galaxy formation redistribute the surviving, massive clusters into the galaxy haloes, where they remain until the present day (a slow-disruption phase due to tidal evaporation). The high galaxy merger rates of z > 2 galaxies allow these clusters to be `liberated' into the galaxy haloes before they are disrupted within the high-density discs. This physically motivated toy model is the first to include the rapid-disruption phase, which is shown to be essential for simultaneously reproducing the wide variety of properties of observed GC systems, such as their universal characteristic mass-scale, the dependence of the specific frequency on metallicity and galaxy mass, the GC system mass-halo mass relation, the constant number of GCs per unit supermassive black hole mass, and the colour bimodality of GC systems. The model predicts that most of these observables were already in place at z = 1-2, although under rare circumstances GCs may still form in present-day galaxies. In addition, the model provides important constraints on models for multiple stellar populations in GCs by putting limits on initial GC masses and the amount of pristine gas accretion. The paper is concluded with a discussion of these and several other predictions and implications, as well as the main open questions in the field.

  9. Narrow-band surveys for very high redshift Lyman-α emitters

    Science.gov (United States)

    Nilsson, K. K.; Orsi, A.; Lacey, C. G.; Baugh, C. M.; Thommes, E.

    2007-11-01

    Context: Many current and future surveys aim to detect the highest redshift (z ⪆ 7) sources through their Lyman-α (Lyα) emission, using the narrow-band imaging method. However, to date the surveys have only yielded non-detections and upper limits as no survey has reached the necessary combination of depth and area to detect these very young star forming galaxies. Aims: We aim to calculate model luminosity functions and mock surveys of Lyα emitters at z ⪆ 7 based on a variety of approaches calibrated and tested on observational data at lower redshifts. Methods: We calculate model luminosity functions at different redshifts based on three different approaches: a semi-analytical model based on CDM, a simple phenomenological model, and an extrapolation of observed Schechter functions at lower redshifts. The results of the first two models are compared with observations made at redshifts z ˜ 5.7 and z ˜ 6.5, and they are then extrapolated to higher redshift. Results: We present model luminosity functions for redshifts between z = 7{-}12.5 and give specific number predictions for future planned or possible narrow-band surveys for Lyα emitters. We also investigate what constraints future observations will be able to place on the Lyα luminosity function at very high redshift. Conclusions: It should be possible to observe z = 7{-}10 Lyα emitters with present or near-future instruments if enough observing time is allocated. In particular, large area surveys such as ELVIS (Emission Line galaxies with VISTA Survey) will be useful in collecting a large sample. However, to get a large enough sample to constrain well the z ≥ 10 Lyα luminosity function, instruments further in the future, such as an ELT, will be necessary.

  10. The Quest for Dusty Star-forming Galaxies at High Redshift z ≳ 4

    Science.gov (United States)

    Mancuso, C.; Lapi, A.; Shi, J.; Gonzalez-Nuevo, J.; Aversa, R.; Danese, L.

    2016-06-01

    We exploit the continuity equation approach and “main-sequence” star formation timescales to show that the observed high abundance of galaxies with stellar masses ≳ a few 1010 M ⊙ at redshift z ≳ 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ ≳ 102 M ⊙ yr‑1 in heavily dust-obscured conditions. These galaxies constitute the high-redshift counterparts of the dusty star-forming population already surveyed for z ≲ 3 in the far-IR band by the Herschel Space Observatory. We work out specific predictions for the evolution of the corresponding stellar mass and SFR functions out to z ∼ 10, determining that the number density at z ≲ 8 for SFRs ψ ≳ 30 M ⊙ yr‑1 cannot be estimated relying on the UV luminosity function alone, even when standard corrections for dust extinction based on the UV slope are applied. We compute the number counts and redshift distributions (including galaxy-scale gravitational lensing) of this galaxy population, and show that current data from the AzTEC-LABOCA, SCUBA-2, and ALMA-SPT surveys are already addressing it. We demonstrate how an observational strategy based on color preselection in the far-IR or (sub-)millimeter band with Herschel and SCUBA-2, supplemented by photometric data from on-source observations with ALMA, can allow us to reconstruct the bright end of the SFR functions out to z ≲ 8. In parallel, such a challenging task can be managed by exploiting current UV surveys in combination with (sub-)millimeter observations by ALMA and NIKA2 and/or radio observations by SKA and its precursors.

  11. LOW MASSES AND HIGH REDSHIFTS: THE EVOLUTION OF THE MASS-METALLICITY RELATION

    International Nuclear Information System (INIS)

    We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 108 ∼☉ ∼10, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 ∼23 metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 109.8 M ☉, to 12+log(O/H) = 8.2 at M = 108.2 M ☉. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M ∼> 109.5 M ☉ and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M * relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation

  12. What Powers Diffuse Lyα Emission around High-Redshift Galaxies?

    Science.gov (United States)

    Xue, Rui; Lee, Kyoung-Soo

    2016-06-01

    We report the detection of diffuse Lyα emission, or Lyman-α halos (LAHs), around high-redshift star-forming galaxies. Our samples consist of ~1400 galaxies at z~2.66 and z~3.78 within the total area of 2.0 deg2 where several massive protoclusters are known to reside. Taking advantage of the wide range of galaxy parameters spanned by our samples, we investigate how the LAH characteristics depend on UV and Lyα properties and local environmental galaxy density. We find that the median size of the LAHs depends strongly on UV continuum luminosities (and thus UV star formation rates), while it does not correlate with Lyα equivalent widths and galaxy overdensity. The galaxies in our sample – the majority are continuum-faint Lyα line emitters (LAEs) – have the median LAH size of 5-6 kpc with 40-50% of the Lyα emission originating from the diffuse Lyα halo. However, the most UV-luminous galaxies show more extended halos (6-9 kpc). Most of the discrepancies found among the existing studies may be reconciled if the LAH size is primarily driven by the UV luminosity of the host galaxy, while other parameters themselves weakly correlate with UV luminosities but with large scatter. Based on the considerations of the observed trends and detailed comparisons of the measured Lyα radial profile with theoretical predictions, we conclude that diffuse Lyα emission is largely powered by central star formation while the contribution from gravitational cooling and faint satellites is at best secondary.

  13. The coevolution of supermassive black holes and massive galaxies at high redshift

    International Nuclear Information System (INIS)

    We exploit the recent, wide samples of far-infrared (FIR) selected galaxies followed up in X-rays and of X-ray/optically selected active galactic nuclei (AGNs) followed up in the FIR band, along with the classic data on AGNs and stellar luminosity functions at high redshift z ≳ 1.5, to probe different stages in the coevolution of supermassive black holes (BHs) and host galaxies. The results of our analysis indicate the following scenario: (1) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ≲ 0.5-1 Gyr and then abruptly declines due to quasar feedback, over the same timescale; (2) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the star formation, and is temporarily stored in a massive reservoir/proto-torus wherefrom it can be promptly accreted; (3) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit L/L Edd ≲ 4, particularly at the highest redshifts; (4) for massive BHs, the ensuing energy feedback at its maximum exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (5) afterward, if the latter has retained enough gas, a phase of supply-limited accretion follows, exponentially declining with a timescale of about two e-folding times. We also discuss how the detailed properties and the specific evolution of the reservoir can be investigated via coordinated, high-resolution observations of star-forming, strongly lensed galaxies in the (sub-)mm band with ALMA and in the X-ray band with Chandra and the next-generation X-ray instruments.

  14. The coevolution of supermassive black holes and massive galaxies at high redshift

    Energy Technology Data Exchange (ETDEWEB)

    Lapi, A.; Raimundo, S.; Aversa, R.; Cai, Z.-Y.; Celotti, A.; De Zotti, G.; Danese, L. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Negrello, M. [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2014-02-20

    We exploit the recent, wide samples of far-infrared (FIR) selected galaxies followed up in X-rays and of X-ray/optically selected active galactic nuclei (AGNs) followed up in the FIR band, along with the classic data on AGNs and stellar luminosity functions at high redshift z ≳ 1.5, to probe different stages in the coevolution of supermassive black holes (BHs) and host galaxies. The results of our analysis indicate the following scenario: (1) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ≲ 0.5-1 Gyr and then abruptly declines due to quasar feedback, over the same timescale; (2) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the star formation, and is temporarily stored in a massive reservoir/proto-torus wherefrom it can be promptly accreted; (3) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit L/L {sub Edd} ≲ 4, particularly at the highest redshifts; (4) for massive BHs, the ensuing energy feedback at its maximum exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (5) afterward, if the latter has retained enough gas, a phase of supply-limited accretion follows, exponentially declining with a timescale of about two e-folding times. We also discuss how the detailed properties and the specific evolution of the reservoir can be investigated via coordinated, high-resolution observations of star-forming, strongly lensed galaxies in the (sub-)mm band with ALMA and in the X-ray band with Chandra and the next-generation X-ray instruments.

  15. Massive Clumps in Local Galaxies: Comparisons with High-redshift Clumps

    Science.gov (United States)

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Sánchez Almeida, J.; Muñoz-Tuñón, C.; Dewberry, J.; Putko, J.; Teich, Y.; Popinchalk, M.

    2013-09-01

    Local UV-bright galaxies in the Kiso survey include clumpy systems with kiloparsec-size star complexes that resemble clumpy young galaxies in surveys at high redshift. We compare clump masses and underlying disks in several dozen galaxies from each of these surveys to the star complexes and disks of normal spirals. Photometry and spectroscopy for the Kiso and spiral sample come from the Sloan Digital Sky Survey. We find that the largest Kiso clumpy galaxies resemble Ultra Deep Field (UDF) clumpies in terms of the star formation rates, clump masses, and clump surface densities. Clump masses and surface densities in normal spirals are smaller. If the clump masses are proportional to the turbulent Jeans mass in the interstellar medium, then for the most luminous galaxies in the sequence of normal:Kiso:UDF, the turbulent speeds and surface densities increase in the proportions 1.0:4.7:5.0 and 1.0:4.0:5.1, respectively, for fixed restframe B-band absolute magnitude. For the least luminous galaxies in the overlapping magnitude range, the turbulent speed and surface density trends are 1.0:2.7:7.4 and 1.0:1.4:3.0, respectively. We also find that while all three types have radially decreasing disk intensities when measured with ellipse-fit azimuthal averages, the average profiles are more irregular for UDF clumpies (which are viewed in their restframe UV) than for Kiso galaxies (viewed at g-band), and major axis intensity scans are even more irregular for the UDF than Kiso galaxies. Local clumpy galaxies in the Kiso survey appear to be intermediate between UDF clumpies and normal spirals.

  16. From nearby low-mass protostars to high redshift starbursts: protostellar outflows tracing the IMF

    Science.gov (United States)

    Kristensen, Lars E.; Bergin, Edwin

    2015-08-01

    Embedded low-mass protostars are notoriously difficult to observe even in the nearest Galactic high-mass clusters where they outnumber the high-mass protostars by orders of magnitude. Thus, without a good tracer of the low-mass population, we do not have a good handle on the shape of the initial (core) mass function, leaving little hope for extrapolating to extragalactic regions where we will never have neither the sensitivity nor the resolution to directly observe this population. A good tracer of the low-mass population is needed.One such physical tracer is outflows. Outflow emission is directly proportional to envelope mass, and outflows are predominantly active during the deeply embedded phases of star formation. What is required for this method to work is species and transitions tracing outflows uniquely such that any signal is not diluted by the surrounding cloud, such as certain methanol transitions, water, high-J CO (J > 10).I will present a statistical model of a forming high-mass cluster. The model includes what we currently know about Galactic high-mass clusters and incorporates outflow emission from low-mass protostars. The latter component is obtained from observations of tens of nearby embedded low-mass protostellar outflows in the above-mentioned tracers. The model is benchmarked against ALMA and Herschel-HIFI observations of Galactic clusters proving the concept, and preliminary extrapolations to the extragalactic regime are presented. With this new probe, and traditional probes of the distant star formation which predominantly trace high mass stars, we will be able to explore the IMF in starburst galaxies from low to high redshift.

  17. Harnessing High Redshift Beacons: IRS Spectra of Lensed Lyman Break Galaxies

    Science.gov (United States)

    Siana, Brian; Coppin, Kristen; Ebeling, Harald; Edge, Alastair; Ellis, Richard; Kneib, Jean-Paul; Pettini, Max; Richard, Johan; Smail, Ian; Swinbank, Mark; Teplitz, Harry

    2007-05-01

    Star-formation at high redshift occurs in two types of galaxies: dusty Ultra-Luminous Infrared Galaxies (ULIRGs) and UV-bright Lyman Break Galaxies (LBGs). In both populations dust absorbs most of the ultraviolet (UV) light from young stars and re-emits the energy in the infrared (IR). Therefore, detailed studies of the dust and the infrared SEDs of these galaxies are critical for understanding these important evolutionary stages in galaxy formation. ULIRGs at z ~ 2-3 are luminous enough for both submm detection and Spitzer IRS spectroscopy, so much has been learned recently about their interstellar medium and IR SEDs. LBGs are too faint to be detected with submm imaging or IRS spectroscopy so little can be discovered about their dust content and IR SEDs prior to JWST and ALMA. Fortunately, there exist a few rare examples of LBGs which are strongly lensed by a foreground cluster or galaxy, and are magnified by factors of 10-30. We can therefore study in detail the infrared properties of this otherwise inaccessible population. Our group will obtain (in an approved Cycle-3 program) IRS spectroscopy of the most famous LBG, cB58, but it is clearly dangerous to draw wide-ranging conclusions about the LBG population based on this single object. We therefore propose for a detailed Spitzer study of the only other known bright lensed LBGs: the 'Cosmic Eye' and the '8-O'clock Arc'. The requested program uses IRS spectroscopy, IRS Peak-Up 16 micron, MIPS 70 micron, and IRAC imaging to fully characterize the gas and dust in the ISM of these galaxies and determine the shape of the IR SEDs. Together, the three lensed sources span the full range of star-formation rates and dust attenuation levels observed in LBGs. Therefore, we can correlate these properties with the infrared SEDs and emission-line properties (PAHs) and apply the correlations when examining the entire LBG population.

  18. SHOCK BREAKOUT IN TYPE II PLATEAU SUPERNOVAE: PROSPECTS FOR HIGH-REDSHIFT SUPERNOVA SURVEYS

    International Nuclear Information System (INIS)

    Shock breakout is the brightest radiative phenomenon in a supernova (SN) but is difficult to be observed owing to the short duration and X-ray/ultraviolet (UV)-peaked spectra. After the first observation from the rising phase reported in 2008, its observability at high redshift is attracting enormous attention. We perform multigroup radiation hydrodynamics calculations of explosions for evolutionary presupernova models with various main-sequence masses M MS, metallicities Z, and explosion energies E. We present multicolor light curves of shock breakouts in Type II plateau SNe, being the most frequent core-collapse SNe, and predict apparent multicolor light curves of shock breakout at various redshifts z. We derive the observable SN rate and reachable redshift as functions of filter x and limiting magnitude m x,lim by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. We propose a realistic survey strategy optimized for shock breakout. For example, the g'-band observable SN rate for m g',lim = 27.5 mag is 3.3 SNe deg-2 day-1 and half of them are located at z ≥ 1.2. It is clear that the shock breakout is a beneficial clue for probing high-z core-collapse SNe. We also establish ways to identify shock breakout and constrain SN properties from the observations of shock breakout, brightness, timescale, and color. We emphasize that the multicolor observations in blue optical bands with ∼hour intervals, preferably over ≥2 continuous nights, are essential to efficiently detect, identify, and interpret shock breakout.

  19. GALEX FAR-ULTRAVIOLET COLOR SELECTION OF UV-BRIGHT HIGH-REDSHIFT QUASARS

    International Nuclear Information System (INIS)

    We study the small population of high-redshift (zem>2.7) quasars detected by the Galaxy Evolution Explorer(GALEX), whose far-UV emission is not extinguished by intervening H I Lyman limit systems. These quasars are of particular importance to detect intergalactic He II absorption along their sight lines. We correlate almost all verified zem>2.7 quasars to the GALEX GR4 source catalog covering ∼ 25,000 deg2, yielding 304 sources detected at signal-to-noise ratio (S/N) >3. However, ∼50% of these are only detected in the GALEX NUV band, signaling the truncation of the FUV flux by low-redshift optically thick Lyman limit systems. We exploit the GALEX UV color mFUV - mNUV to cull the most promising targets for follow-up studies, with blue (red) GALEX colors indicating transparent (opaque) sight lines. Extensive Monte Carlo simulations indicate an He II detection rate of ∼60% for quasars with mFUV - mNUV ∼em ∼3 to be most promising for Hubble Space Telescope follow-up, with an additional 114 quasars if we consider S/N >2 detections in the FUV. Combining the statistical properties of H I absorbers with the Sloan Digital Sky Survey (SDSS) quasar luminosity function, we predict a large all-sky population of ∼200 quasars with zem>2.7 and i ∼304 em ∼em ∼em ∼< 3.5 quasars have likely underestimated their space density by selecting intergalactic medium sight lines with an excess of strong H I absorbers.

  20. Effects of dark matter decay and annihilation on the high-redshift 21 cm background

    International Nuclear Information System (INIS)

    The radiation background produced by the 21 cm spin-flip transition of neutral hydrogen at high redshifts can be a pristine probe of fundamental physics and cosmology. At z∼30-300, the intergalactic medium (IGM) is visible in 21 cm absorption against the cosmic microwave background (CMB), with a strength that depends on the thermal (and ionization) history of the IGM. Here we examine the constraints this background can place on dark matter decay and annihilation, which could heat and ionize the IGM through the production of high-energy particles. Using a simple model for dark matter decay, we show that, if the decay energy is immediately injected into the IGM, the 21 cm background can detect energy injection rates(greater-or-similar sign)10-24 eV cm-3 sec-1. If all the dark matter is subject to decay, this allows us to constrain dark matter lifetimes(less-or-similar sign)1027 sec. Such energy injection rates are much smaller than those typically probed by the CMB power spectra. The expected brightness temperature fluctuations at z∼50 are a fraction of a mK and can vary from the standard calculation by up to an order of magnitude, although the difference can be significantly smaller if some of the decay products free stream to lower redshifts. For self-annihilating dark matter, the fluctuation amplitude can differ by a factor(less-or-similar sign)2 from the standard calculation at z∼50. Note also that, in contrast to the CMB, the 21 cm probe is sensitive to both the ionization fraction and the IGM temperature, in principle allowing better constraints on the decay process and heating history. We also show that strong IGM heating and ionization can lead to an enhanced H2 abundance, which may affect the earliest generations of stars and galaxies

  1. Constraining sub-grid physics with high-redshift spatially-resolved metallicity distributions

    Science.gov (United States)

    Gibson, B. K.; Pilkington, K.; Brook, C. B.; Stinson, G. S.; Bailin, J.

    2013-06-01

    Aims: We examine the role of energy feedback in shaping the distribution of metals within cosmological hydrodynamical simulations of L∗ disc galaxies. While negative abundance gradients today provide a boundary condition for galaxy evolution models, in support of inside-out disc growth, empirical evidence as to whether abundance gradients steepen or flatten with time remains highly contradictory. Methods: We made use of a suite of L∗ discs, realised with and without "enhanced" feedback. All the simulations were produced using the smoothed particle hydrodynamics code Gasoline, and their in situ gas-phase metallicity gradients traced from redshift z ~ 2 to the present-day. Present-day age-metallicity relations and metallicity distribution functions were derived for each system. Results: The "enhanced" feedback models, which have been shown to be in agreement with a broad range of empirical scaling relations, distribute energy and re-cycled ISM material over large scales and predict the existence of relatively "flat" and temporally invariant abundance gradients. Enhanced feedback schemes reduce significantly the scatter in the local stellar age-metallicity relation and, especially, the [O/Fe]-[Fe/H] relation. The local [O/Fe] distribution functions for our L∗ discs show clear bimodality, with peaks at [O/Fe] = -0.05 and + 0.05 (for stars with [Fe/H] > -1), consistent with our earlier work on dwarf discs. Conclusions: Our results with "enhanced" feedback are inconsistent with our earlier generation of simulations realised with "conservative" feedback. We conclude that spatially-resolved metallicity distributions, particularly at high-redshift, offer a unique and under-utilised constraint on the uncertain nature of stellar feedback processes.

  2. EXPLORING THE CHEMICAL LINK BETWEEN LOCAL ELLIPTICALS AND THEIR HIGH-REDSHIFT PROGENITORS

    Energy Technology Data Exchange (ETDEWEB)

    Leja, Joel; Van Dokkum, Pieter G.; Momcheva, Ivelina; Nelson, Erica [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Brammer, Gabriel [European Southern Observatory, Alonson de Córdova 3107, Casilla 19001, Vitacura, Santiago (Chile); Skelton, Rosalind E. [South African Astronomical Observatory, Observatory Road, Cape Town (South Africa); Whitaker, Katherine E. [Astrophysics Science Division, Goddard Space Center, Greenbelt, MD 20771 (United States); Andrews, Brett H. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Franx, Marijn; Patel, Shannon G. [Leiden Observatory, Leiden University, P.O. Box 9513, NL 2300 RA, Leiden (Netherlands); Kriek, Mariska [Astronomy Department, University of California at Berkeley, Berkeley, CA 94720 (United States); Van der Wel, Arjen [Max-Planck Institute for Astronomy (MPIA), Königstuhl 17, D-69117 Heidelberg (Germany); Bezanson, Rachel [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Conroy, Charlie [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA (United States); Förster Schreiber, Natascha [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)

    2013-12-01

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z ∼ 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]λ6584/Hα ratio of 0.27 ± 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Hα ratios depends on the calibration method, and ranges from 12+log(O/H){sub gas} = 8.57 for the Pettini and Pagel calibration to 12+log(O/H){sub gas} = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H){sub stars} = 8.95, similar to the gas-phase abundances of the z ∼ 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z ∼ 2.3 sample: the galaxies with detected Hα tend to be larger and have higher star formation rates than the galaxies without detected Hα, and we may still be missing the most dust-obscured progenitors.

  3. Exploring the Chemical Link Between Local Ellipticals and Their High-Redshift Progenitors

    Science.gov (United States)

    Leja, Joel; Van Dokkum, Pieter G.; Momcheva, Ivelina; Brammer, Gabriel; Skelton, Rosalind E.; Whitaker, Katherine E.; Andrews, Brett H.; Franx, Marijn; Kriek, Mariska; Van Der Wel, Arjen; Bezanson, Rachel; Conroy, Charlie; Schreiber, Natascha Foerster; Nelson, Erica; Patel, Shannon G.

    2013-01-01

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z approximately 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]lambda6584/H-alpha ratio of 0.27 +/- 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Halpha ratios depends on the calibration method, and ranges from 12+log(O/H)(sub gas) = 8.57 for the Pettini & Pagel calibration to 12+log(O/H)(sub gas) = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H)(sub stars) = 8.95, similar to the gas-phase abundances of the z approximately 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z approximately 2.3 sample: the galaxies with detected Ha tend to be larger and have higher star formation rates than the galaxies without detected H-alpha, and we may still be missing the most dust-obscured progenitors.

  4. EXPLORING THE CHEMICAL LINK BETWEEN LOCAL ELLIPTICALS AND THEIR HIGH-REDSHIFT PROGENITORS

    International Nuclear Information System (INIS)

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at z ∼ 2.3. Targets are selected from the 3D-Hubble Space Telescope Treasury survey. The six detected galaxies have a mean [N II]λ6584/Hα ratio of 0.27 ± 0.01, with a small standard deviation of 0.05. This mean value is similar to that of UV-selected galaxies of the same mass. The mean gas-phase oxygen abundance inferred from the [N II]/Hα ratios depends on the calibration method, and ranges from 12+log(O/H)gas = 8.57 for the Pettini and Pagel calibration to 12+log(O/H)gas = 8.87 for the Maiolino et al. calibration. Measurements of the stellar oxygen abundance in nearby quiescent galaxies with the same number density indicate 12+log(O/H)stars = 8.95, similar to the gas-phase abundances of the z ∼ 2.3 galaxies if the Maiolino et al. calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies. The main uncertainties are the absolute calibration of the gas-phase oxygen abundance and the incompleteness of the z ∼ 2.3 sample: the galaxies with detected Hα tend to be larger and have higher star formation rates than the galaxies without detected Hα, and we may still be missing the most dust-obscured progenitors

  5. The impact of foregrounds on redshift space distortion measurements with the highly redshifted 21-cm line

    Science.gov (United States)

    Pober, Jonathan C.

    2015-02-01

    The highly redshifted 21-cm line of neutral hydrogen has become recognized as a unique probe of cosmology from relatively low redshifts (z ˜ 1) up through the Epoch of Reionization (EoR) (z ˜ 8) and even beyond. To date, most work has focused on recovering the spherically averaged power spectrum of the 21-cm signal, since this approach maximizes the signal to noise in the initial measurement. However, like galaxy surveys, the 21-cm signal is affected by redshift space distortions, and is inherently anisotropic between the line of sight and transverse directions. A measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter power spectrum from astrophysical effects. However, in interferometric measurements, foregrounds also have an anisotropic footprint between the line of sight and transverse directions: the so-called foreground `wedge'. Although foreground subtraction techniques are actively being developed, a `foreground avoidance' approach of simply ignoring contaminated modes has arguably proven most successful to date. In this work, we analyse the effect of this foreground anisotropy in recovering the redshift space distortion signature in 21-cm measurements at both high and intermediate redshifts. We find the foreground wedge corrupts nearly all of the redshift space signal for even the largest proposed EoR experiments (Hydrogen Epoch of Reionization Array and the Square Kilometre Array), making cosmological information unrecoverable without foreground subtraction. The situation is somewhat improved at lower redshifts, where the redshift-dependent mapping from observed coordinates to cosmological coordinates significantly reduces the size of the wedge. Using only foreground avoidance, we find that a large experiment like Canadian Hydrogen Intensity Mapping Experiment can place non-trivial constraints on cosmological parameters.

  6. VERITAS OBSERVATIONS OF SIX BRIGHT, HARD-SPECTRUM FERMI-LAT BLAZARS

    International Nuclear Information System (INIS)

    We report on VERITAS very high energy (VHE; E ≥ 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and X-Ray Telescope data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars shows a synchrotron peak bordering between the intermediate- and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.

  7. VERITAS OBSERVATIONS OF SIX BRIGHT, HARD-SPECTRUM FERMI-LAT BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    Aliu, E.; Errando, M. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Aune, T.; Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Boettcher, M. [Astrophysical Institute, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Cui, W. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Duke, C. [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Falcone, A., E-mail: afurniss@ucsc.edu, E-mail: pafortin@cfa.harvard.edu, E-mail: deirdre@llr.in2p3.fr [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Collaboration: VERITAS Collaboration; and others

    2012-11-10

    We report on VERITAS very high energy (VHE; E {>=} 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and X-Ray Telescope data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars shows a synchrotron peak bordering between the intermediate- and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.

  8. Fourier Analysis of Blazar Variability

    CERN Document Server

    Finke, Justin D

    2014-01-01

    Blazars display strong variability on multiple timescales and in multiple radiation bands. Their variability is often characterized by power spectral densities (PSDs) and time lags plotted as functions of the Fourier frequency. We develop a new theoretical model based on the analysis of the electron transport (continuity) equation, carried out in the Fourier domain. The continuity equation includes electron cooling and escape, and a derivation of the emission properties includes light travel time effects associated with a radiating blob in a relativistic jet. The model successfully reproduces the general shapes of the observed PSDs and predicts specific PSD and time lag behaviors associated with variability in the synchrotron, synchrotron self-Compton (SSC), and external Compton (EC) emission components, from sub-mm to gamma-rays. We discuss applications to BL Lacertae objects and to flat-spectrum radio quasars (FSRQs), where there are hints that some of the predicted features have already been observed. We a...

  9. The Impact of Foregrounds on Redshift Space Distortion Measurements With the Highly-Redshifted 21 cm Line

    CERN Document Server

    Pober, Jonathan C

    2014-01-01

    The highly redshifted 21 cm line of neutral hydrogen has become recognized as a unique probe of cosmology from relatively low redshifts (z ~ 1) up through the Epoch of Reionization (z ~ 8) and even beyond. To date, most work has focused on recovering the spherically averaged power spectrum of the 21 cm signal, since this approach maximizes the signal-to-noise in the initial measurement. However, like galaxy surveys, the 21 cm signal is effected by redshift space distortion effects, and is inherently anisotropic between the line-of-sight and transverse directions. A full measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter power spectrum from astrophysical effects at high redshifts. However, foregrounds also have an anisotropic footprint between the line-of-sight and transverse directions: the so-called foreground "wedge". Although techniques to subtract foregrounds are actively being developed, a "foreground avoidance" approach of simply ignoring cont...

  10. The Galaxy Mass Function at High-Redshift from the Largest Available Spitzer-Based Survey (SERVS)

    Science.gov (United States)

    Morice-Atkinson, Xan; Maraston, Claudia; Lacy, Mark; Capozzi, Diego

    2015-08-01

    We exploit the largest (18 deg2) and deepest (AB = 23.1) galaxy and QSO survey available up to date of five highly observed astronomical fields (SERVS) to derive the galaxy stellar mass function and detailed galaxy properties as a function of cosmic time. SERVS obtained Spitzer 3.6µm and 4.5µm magnitudes for ~1 million galaxies up to redshift ~6, which we complement with multi-wavelength data from other on-going surveys, including VIDEO, GALEX, CFHTLS, UKIDSS, etc. in order to perform full SED fitting to models. The power of Spitzer data is its sensitivity to evolved stars at high-redshift, which allows us to better constrain the galaxy star formation histories. The wide area and depth of SERVS was designed precisely to capture the light from the most massive galaxies up to high-redshift. Results and comparison with the literature will be presented.

  11. Dark matter and Modified Newtonian Dynamics in a sample of high-redshift galaxy clusters observed with Chandra

    OpenAIRE

    Blaksley, Carl; Bonamente, Massimiliano

    2009-01-01

    We compare the measurement of the gravitational mass of 38 high-redshift galaxy clusters observed by Chandra using Modified Newtonian Dynamics (MOND) and standard Newtonian gravity. Our analysis confirms earlier findings that MOND cannot explain the difference between the baryonic mass and the total mass inferred from the assumption of hydrostatic equilibrium. We also find that the baryon fraction at $r_{2500}$ using MOND is consistent with the Wilkinson Microwave Anisotropy Probe (WMAP) valu...

  12. A PARAMETRIC STUDY OF POSSIBLE SOLUTIONS TO THE HIGH-REDSHIFT OVERPRODUCTION OF STARS IN MODELED DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    White, Catherine E. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Somerville, Rachel S. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Ferguson, Henry C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2015-02-01

    Both numerical hydrodynamic and semi-analytic cosmological models of galaxy formation struggle to match observed star formation histories of galaxies in low-mass halos (M {sub H} ≲ 10{sup 11} M {sub ☉}), predicting more star formation at high redshift and less star formation at low redshift than observed. The fundamental problem is that galaxies' gas accretion and star formation rates are too closely coupled in the models: the accretion rate largely drives the star formation rate. Observations point to gas accretion rates that outpace star formation at high redshift, resulting in a buildup of gas and a delay in star formation until lower redshifts. We present three empirical adjustments of standard recipes in a semi-analytic model motivated by three physical scenarios that could cause this decoupling: (1) the mass-loading factors of outflows driven by stellar feedback may have a steeper dependence on halo mass at earlier times, (2) the efficiency of star formation may be lower in low-mass halos at high redshift, and (3) gas may not be able to accrete efficiently onto the disk in low-mass halos at high redshift. These new recipes, once tuned, better reproduce the evolution of f {sub *}≡ M {sub *}/M {sub H} as a function of halo mass as derived from abundance matching over redshifts z = 0 to 3, though they have different effects on cold gas fractions, star formation rates, and metallicities. Changes to gas accretion and stellar-driven winds are promising, while direct modification of the star formation timescale requires drastic measures that are not physically well motivated.

  13. Constraining Emission Models of Luminous Blazar Sources

    International Nuclear Information System (INIS)

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy (γ-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line-region, or dusty molecular torus. The lack or weakness of bulk Compton and Klein-Nishina features indicated by the presently available data favors production of γ-rays via up-scattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical and γ-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intra-day flares occasionally observed in powerful blazars sources.

  14. CONSTRAINING EMISSION MODELS OF LUMINOUS BLAZAR SOURCES

    International Nuclear Information System (INIS)

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broadband spectra characterized by a large luminosity ratio of their high-energy (γ-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars also typically have very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high-energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line region, or dusty molecular torus. The lack or weakness of bulk-Compton and Klein-Nishina features indicated by the presently available data favors the production of γ-rays via upscattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical, and γ-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intraday flares occasionally observed in powerful blazar sources.

  15. The deepest X-ray view of high-redshift galaxies: constraints on low-rate black-hole accretion

    CERN Document Server

    Vito, Fabio; Vignali, Cristian; Brandt, William N; Comastri, Andrea; Yang, Guang; Lehmer, Bret D; Luo, Bin; Basu-Zych, Antara; Bauer, Franz E; Cappelluti, Nico; Koekemoer, Anton; Mainieri, Vincenzo; Paolillo, Maurizio; Ranalli, Piero; Shemmer, Ohad; Trump, Jonathan; Wang, Junxian; Xue, Yongquan

    2016-01-01

    We exploit the 7 Ms \\textit{Chandra} observations in the \\chandra\\,Deep Field-South (\\mbox{CDF-S}), the deepest X-ray survey to date, coupled with CANDELS/GOODS-S data, to measure the total X-ray emission arising from 2076 galaxies at $3.5\\leq z 3.7\\sigma$) X-ray emission from massive galaxies at $z\\approx4$. We also report the detection of massive galaxies at $z\\approx5$ at a $99.7\\%$ confidence level ($2.7\\sigma$), the highest significance ever obtained for X-ray emission from galaxies at such high redshifts. No significant signal is detected from galaxies at even higher redshifts. The stacking results place constraints on the BHAD associated with the known high-redshift galaxy samples, as well as on the SFRD at high redshift, assuming a range of prescriptions for X-ray emission due to X- ray binaries. We find that the X-ray emission from our sample is likely dominated by processes related to star formation. Our results show that low-rate mass accretion onto SMBHs in individually X-ray-undetected galaxies i...

  16. Serendipitous discovery of an extended X-ray jet without a radio counterpart in a high-redshift quasar

    CERN Document Server

    Simionescu, A; Ichinohe, Y; Cheung, C C; Jamrozy, M; Siemiginowska, A; Hagino, K; Gandhi, P; Werner, N

    2015-01-01

    A recent Chandra observation of the nearby galaxy cluster Abell 585 has led to the discovery of an extended X-ray jet associated with the high-redshift background quasar B3 0727+409, a luminous radio source at redshift z=2.5. This is one of only few examples of high-redshift X-ray jets known to date. It has a clear extension of about 10-12", corresponding to a projected length of 80-100 kpc, with a possible hot spot as far as 35" from the quasar. The archival high resolution VLA maps surprisingly reveal no extended jet emission, except for one knot about 1.4" away from the quasar. The high X-ray to radio luminosity ratio for this source appears consistent with the $\\propto (1+z)^{4}$ amplification expected from the inverse Compton radiative model. This serendipitous discovery may signal the existence of an entire population of similar systems with bright X-ray and faint radio jets at high redshift, a selection bias which must be accounted for when drawing any conclusions about the redshift evolution of jet pr...

  17. LENSING MAGNIFICATION: A NOVEL METHOD TO WEIGH HIGH-REDSHIFT CLUSTERS AND ITS APPLICATION TO SpARCS

    International Nuclear Information System (INIS)

    We introduce a novel method to measure the masses of galaxy clusters at high redshift selected from optical and IR Spitzer data via the red-sequence technique. Lyman-break galaxies are used as a well-understood, high-redshift background sample allowing mass measurements of lenses at unprecedented high redshifts using weak lensing magnification. By stacking a significant number of clusters at different redshifts with average masses of ∼(1-3) x 1014 Msun, as estimated from their richness, we can calibrate the normalization of the mass-richness relation. With the current data set (area: 6 deg2) we detect a magnification signal at the >3σ level. There is good agreement between the masses estimated from the richness of the clusters and the average masses estimated from magnification, albeit with large uncertainties. We perform tests that suggest the absence of strong systematic effects and support the robustness of the measurement. This method-when applied to larger data sets in the future-will yield an accurate calibration of the mass-observable relations at z ∼> 1 which will represent an invaluable input for cosmological studies using the galaxy cluster mass function and astrophysical studies of cluster formation. Furthermore, this method will probably be the least expensive way to measure masses of large numbers of z > 1 clusters detected in future IR-imaging surveys.

  18. ACCOUNTING FOR COSMIC VARIANCE IN STUDIES OF GRAVITATIONALLY LENSED HIGH-REDSHIFT GALAXIES IN THE HUBBLE FRONTIER FIELD CLUSTERS

    International Nuclear Information System (INIS)

    Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ∼35% at redshift z ∼ 7 to ≳ 65% at z ∼ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program

  19. ON THE RADIATIVE EFFICIENCIES, EDDINGTON RATIOS, AND DUTY CYCLES OF LUMINOUS HIGH-REDSHIFT QUASARS

    International Nuclear Information System (INIS)

    We investigate the characteristic radiative efficiency ε, Eddington ratio λ, and duty cycle P 0 of high-redshift active galactic nuclei (AGNs), drawing on measurements of the AGN luminosity function at z = 3-6 and, especially, on recent measurements of quasar clustering at z = 3-4.5 from the Sloan Digital Sky Survey. The free parameters of our models are ε, λ, and the normalization, scatter, and redshift evolution of the relation between black hole (BH) mass M BH and halo virial velocity Vvir. We compute the luminosity function from the implied growth of the BH mass function and the quasar correlation length from the bias of the host halos. We test our adopted formulae for the halo mass function and halo bias against measurements from the large N-body simulation developed by the MICE collaboration. The strong clustering of AGNs observed at z = 3 and, especially, at z = 4 implies that massive BHs reside in rare, massive dark matter halos. Reproducing the observed luminosity function then requires high efficiency ε and/or low Eddington ratio λ, with a lower limit (based on 2σ agreement with the measured z = 4 correlation length) ε ∼> 0.7λ/(1 + 0.7λ), implying ε ∼> 0.17 for λ>0.25. Successful models predict high duty cycles, P0 ∼ 0.2, 0.5, and 0.9 at z = 3.1, 4.5, and 6, respectively, and they require that the fraction of halo baryons locked in the central BH is much larger than the locally observed value. The rapid drop in the abundance of the massive and rare host halos at z > 7 implies a proportionally rapid decline in the number density of luminous quasars, much stronger than simple extrapolations of the z = 3-6 luminosity function would predict. For example, our most successful model predicts that the highest redshift quasar in the sky with true bolometric luminosity L > 1047.5 erg s-1 should be at z ∼ 7.5, and that all quasars with higher apparent luminosities would have to be magnified by lensing.

  20. LOW MASSES AND HIGH REDSHIFTS: THE EVOLUTION OF THE MASS-METALLICITY RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Alaina; Straughn, Amber [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Scarlata, Claudia; Bedregal, Alejandro G. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States); Domínguez, Alberto; Siana, Brian; Masters, Daniel [Department of Physics and Astronomy, University of California, Riverside, Riverside, CA 92521 (United States); Malkan, Matthew; Ross, Nathaniel [Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA 90095 (United States); Martin, Crystal L. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Atek, Hakim [Laboratoire d' astrophysique, École Polytechniuqe Fédérale de Lausanne, Observatoire de Sauverny, 1290 Versoix (Switzerland); Colbert, James W.; Rafelski, Marc [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Teplitz, Harry [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States); Bunker, Andrew J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, OX1 3RH (United Kingdom); Dressler, Alan; Hathi, Nimish; McCarthy, Patrick, E-mail: alaina.henry@nasa.gov [Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)

    2013-10-20

    We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10{sup 8} ∼< M/M {sub ☉} ∼< 10{sup 10}, obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 ∼< z ∼< 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R {sub 23} metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10{sup 9.8} M {sub ☉}, to 12+log(O/H) = 8.2 at M = 10{sup 8.2} M {sub ☉}. After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M ∼> 10{sup 9.5} M {sub ☉} and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M {sub *} relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high star formation rates (SFRs). Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation.

  1. Supermassive Black Hole Formation at High Redshifts via Direct Collapse: Physical Processes in the Early Stage

    Science.gov (United States)

    Choi, Jun-Hwan; Shlosman, Isaac; Begelman, Mitchell C.

    2013-09-01

    We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. Using the adaptive mesh refinement code ENZO, we follow the evolution of gas within slowly tumbling dark matter (DM) halos of M vir ~ 2 × 108 M ⊙ and R vir ~ 1 kpc. For our idealized simulations, we adopt cosmologically motivated DM and baryon density profiles and angular momentum distributions. Our principal goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation which can potentially lead to star formation, decreasing the seed SMBH mass. We find that the collapse proceeds from inside out and leads either to a central runaway or to off-center fragmentation. A disk-like configuration is formed inside the centrifugal barrier, growing via accretion. For models with a more cuspy DM distribution, the gas collapses more and experiences a bar-like perturbation and a central runaway on scales of damped. Models with progressively larger initial DM cores evolve similarly, but the timescales become longer. In models with more organized initial rotation—when the rotation of spherical shells is constrained to be coplanar—a torus forms on scales ~20-50 pc outside the disk, and appears to be supported by turbulent motions driven by accretion from the outside. The overall evolution of the models depends on the competition between two timescales, corresponding to the onset of the central runaway and of off-center fragmentation. In models with less organized rotation—when the rotation of spherical shells is randomized (but the total angular momentum remains unchanged)—the torus is greatly weakened, the central accretion timescale is shortened, and off-center fragmentation is suppressed—triggering the central runaway even in previously "stable" models. The resulting seed SMBH masses is found in the range M • ~ 2 × 104 M ⊙-2 × 106 M ⊙, substantially

  2. Spatially Resolved Emission of a High-redshift DLA Galaxy with the Keck/OSIRIS IFU

    Science.gov (United States)

    Jorgenson, Regina A.; Wolfe, Arthur M.

    2014-04-01

    We present the first Keck/OSIRIS infrared IFU observations of a high-redshift damped Lyα (DLA) galaxy detected in the line of sight to a background quasar. By utilizing the Laser Guide Star Adaptive Optics to reduce the quasar point-spread function to FWHM ~ 0.''15, we were able to search for and map the foreground DLA emission free from the quasar contamination. We present maps of the Hα and [O III] λλ5007, 4959 emission of DLA 2222-0946 at a redshift of z ~ 2.35. From the composite spectrum over the Hα emission region, we measure a star formation rate of 9.5 ± 1.0 M ⊙ yr-1 and a dynamical mass of M dyn = 6.1 × 109 M ⊙. The average star formation rate surface density is langΣSFRrang = 0.55 M ⊙ yr-1 kpc-2, with a central peak of 1.7 M ⊙ yr-1 kpc-2. Using the standard Kennicutt-Schmidt relation, this corresponds to a gas mass surface density of Σgas = 243 M ⊙ pc-2. Integrating over the size of the galaxy, we find a total gas mass of M gas = 4.2 × 109 M ⊙. We estimate the gas fraction of DLA 2222-0946 to be f gas ~ 40%. We detect [N II] λ6583 emission at 3σ significance with a flux corresponding to a metallicity of 75% solar. Comparing this metallicity with that derived from the low-ion absorption gas ~6 kpc away, ~30% solar, indicates possible evidence for a metallicity gradient or enriched in/outflow of gas. Kinematically, both Hα and [O III] emission show relatively constant velocity fields over the central galactic region. While we detect some red and blueshifted clumps of emission, they do not correspond with rotational signatures that support an edge-on disk interpretation. The data presented herein were obtained 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.

  3. Fermi detected blazars seen by INTEGRAL

    CERN Document Server

    Beckmann, V; Soldi, S

    2009-01-01

    Multiwavelength observations are essential to constrain physical parameters of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were detected. 15 of these sources allowed significant spectral extraction. They show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars are also visible in the first 16 months of the Fermi/LAT data, thus allowing to constrain the inverse Compton branch in these cases. Among others, we analyse the LAT data of four blazars which were not included in the Fermi LAT Bright AGN Sample based on the first 3 months of the mission: QSO B0836+710, H 1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during bright outbursts, as already observed simultaneously by INTEGRAL and Fermi (e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to several hundred keV. We pr...

  4. Recent highlights in the X-ray study of blazars

    CERN Document Server

    Pian, E

    2002-01-01

    Blazars exhibit flux and spectral variations of largest amplitude at the highest frequencies. Therefore, monitoring their variability at X- and gamma-rays is the most effective tool to peer into the mighty powerhouse of these sources. High energy observations of the brightest blazars with the latest generation of satellites have allowed a detailed study of their behavior and have critically improved our understanding of the physics of blazar jets. I will review some of the recent results of blazar multiwavelength monitoring with emphasis on the X-ray campaigns accomplished with BeppoSAX and I will describe some of the future programs for blazar investigation from space, particularly with INTEGRAL.

  5. An integral field spectroscopic survey for high redshift damped Lyman-α galaxies

    Science.gov (United States)

    Christensen, L.; Wisotzki, L.; Roth, M. M.; Sánchez, S. F.; Kelz, A.; Jahnke, K.

    2007-06-01

    Aims:We search for galaxy counterparts to damped Lyman-α absorbers (DLAs) at z > 2 towards nine quasars, which have 14 DLAs and 8 sub-DLAs in their spectra. Methods: We use integral field spectroscopy to search for Lyα emission line objects at the redshifts of the absorption systems. Results: Besides recovering two previously confirmed objects, we find six statistically significant candidate Lyα emission line objects. The candidates are identified as having wavelengths close to the DLA line where the background quasar emission is absorbed. In comparison with the six currently known Lyα emitting DLA galaxies the candidates have similar line fluxes and line widths, while velocity offsets between the emission lines and systemic DLA redshifts are larger. The impact parameters are larger than 10 kpc, and lower column density systems are found at larger impact parameters. Conclusions: Assuming that a single gas cloud extends from the QSO line of sight to the location of the candidate emission line, we find that the average candidate DLA galaxy is surrounded by neutral gas with an exponential scale length of ~5 kpc. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA), operated by the Max-Planck Institut für Astronomie and the Instituto Astrofisica de Andalucia (CSIC). Full Fig. [see full text] is only available in electronic form at http://www.aanda.org

  6. An integral field spectroscopic survey for high redshift damped Lyman-alpha galaxies

    CERN Document Server

    Christensen, L; Roth, M M; Sánchez, S F; Kelz, A; Jahnke, K

    2007-01-01

    We search for galaxy counterparts to damped Lyman-alpha absorbers (DLAs) at z>2 towards nine quasars, which have 14 DLAs and 8 sub-DLAs in their spectra. We use integral field spectroscopy to search for Ly-alpha emission line objects at the redshifts of the absorption systems. Besides recovering two previously confirmed objects, we find six statistically significant candidate Ly-alpha emission line objects. The candidates are identified as having wavelengths close to the DLA line where the background quasar emission is absorbed. In comparison with the six currently known Ly-alpha emitting DLA galaxies the candidates have similar line fluxes and line widths, while velocity offsets between the emission lines and systemic DLA redshifts are larger. The impact parameters are larger than 10 kpc, and lower column density systems are found at larger impact parameters. Assuming that a single gas cloud extends from the QSO line of sight to the location of the candidate emission line, we find that the average candidate ...

  7. An integral field spectroscopic survey for high redshift damped Lyman-alpha galaxies

    OpenAIRE

    Christensen, L; Wisotzki, L.; Roth, M. M.; Sanchez, S. F.; Kelz, A.; Jahnke, K.

    2007-01-01

    We search for galaxy counterparts to damped Lyman-alpha absorbers (DLAs) at z>2 towards nine quasars, which have 14 DLAs and 8 sub-DLAs in their spectra. We use integral field spectroscopy to search for Ly-alpha emission line objects at the redshifts of the absorption systems. Besides recovering two previously confirmed objects, we find six statistically significant candidate Ly-alpha emission line objects. The candidates are identified as having wavelengths close to the DLA line where the ba...

  8. Observations of WIBRaLS Blazars with K2

    Science.gov (United States)

    Carini, Michael T.; Brown, Rebecca

    2016-01-01

    We report on the recent results of our ongoing program to characterize the rapid variability of a sample of IR and optically bright blazars with K2. The K2 mission, through its superb photometric precision and its ability to continuously sample light curves on timescales of minutes to months is providing unrivaled information on blazar variability. In its previous incarnation as the Kepler mission, only a few blazars were present in its field of view. Nevertheless, Kepler's observations of blazars uncovered rich and complicated variability down to the most rapid timescales it could sample and indicated a need for more roboust time-series analysis techniques. Our K2 sample of IR and optically bright blazars will be a unique set of blazars with light curves sampled on timescales not possible with ground based observatories. We present our recent blazar results from the K2 mission and discuss the analysis challenges they pose.

  9. High Energy Neutrinos from Recent Blazar Flares

    CERN Document Server

    Halzen, Francis

    2016-01-01

    The energy density of cosmic neutrinos measured by IceCube matches the one observed by Fermi in extragalactic photons that predominantly originate in blazars. This has inspired attempts to match Fermi sources with IceCube neutrinos. A spatial association combined with a coincidence in time with a flaring source may represent a smoking gun for the origin of the IceCube flux. In June 2015, the Fermi Large Area Telescope observed an intense flare from blazar 3C 279 that exceeded the steady flux of the source by a factor of forty for the duration of a day. We show that IceCube is likely to observe neutrinos, if indeed hadronic in origin, in data that are still blinded at this time. We also discuss other opportunities for coincident observations that include a recent flare from blazar 1ES 1959+650 that previously produced an intriguing coincidence with AMANDA observations.

  10. Powers and Magnetization of Blazar Jets

    CERN Document Server

    Sikora, Marek

    2016-01-01

    In this work I review the observational constraints imposed on the energetics and magnetisation of quasar jets, in the context of theoretical expectations. The discussion is focused on issues regarding the jet production efficiency, matter content, and particle acceleration. I show that if the ratio of electron-positron-pairs to protons is of order $15$, as is required to achieve agreement between jet powers computed using blazar spectral fits and those computed using radio-lobe calorimetry, the magnetization of blazar jets in flat-spectrum-radio-quasars (FSRQ) must be significant. This result favors the reconnection mechanism for particle acceleration and explains the large Compton-dominance of blazar spectra that is often observed, without the need to postulate very low jet magnetization.

  11. TeV blazars and their distance

    CERN Document Server

    Prandini, Elisa; Maraschi, Laura; Mariotti, Mose'; Tavecchio, Fabrizio

    2011-01-01

    Recently, a new method to constrain the distance of blazars with unknown redshift using combined observations in the GeV and TeV regimes has been developed, with the underlying assumption that the Very High Energy (VHE) spectrum corrected for the absorption of TeV photons by the Extragalactic Background Light (EBL) via photon-photon interaction should still be softer than the gamma-ray spectrum observed by Fermi/LAT. The constraints found are related to the real redshifts by a simple linear relation, that has been used to infer the unknown distance of blazars. The sample will be revised with the up-to-date spectra in both TeV and GeV bands, the method tested with the more recent EBL models and finally applied to the unknown distance blazars detected at VHE.

  12. Relativistic Beaming Effect in Fermi Blazars

    Indian Academy of Sciences (India)

    J. H. Fan; D. Bastieri; J. H. Yang; Y. Liu; D. X. Wu; S. H. Li

    2014-09-01

    The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the -ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral -ray luminosity in the range of 1–100 GeV. It is interesting that the integral -ray luminosity is closely correlated with the estimated Doppler factor, log = (2.95 ± 0.09) log + 43.59 ± 0.08 for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the -ray emissions are strongly beamed.

  13. What determines the observational differences of blazars?

    CERN Document Server

    Fan, Xu-Liang; Mao, Jirong

    2016-01-01

    We examine the scenario that the Doppler factor determines the observational differences of blazars in this paper. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency further has a tightly linear relation with the Doppler factor. It is more interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction of the kinetic jet powers between BL Lacs and FSRQs disappears after the boosting factor $\\delta^2$ is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsui...

  14. Multiwavelength Emission from Blazars – Conference Summary

    Indian Academy of Sciences (India)

    Meg Urry

    2011-03-01

    Presentations at the Guangzhou Conference on Multiwave-length Emission from Blazars confirmed our understanding of blazars as relativistic jets closely aligned with the line of sight. Powerful new studies have been enabled by the Fermi gamma-ray satellite and new ground-based TeV facilities, which are an order of magnitude more sensitive than their predecessors. Combining gamma-ray data with VLBA radio and with optical/IR photometry has shed new light on the emission mechanisms and the jet geometry. This conference summary sets the context for the 4th blazar conference and presents some of the highlights from the meeting, as well as the questions that remain outstanding.

  15. SUPERMASSIVE BLACK HOLE FORMATION AT HIGH REDSHIFTS VIA DIRECT COLLAPSE: PHYSICAL PROCESSES IN THE EARLY STAGE

    International Nuclear Information System (INIS)

    We use numerical simulations to explore whether direct collapse can lead to the formation of supermassive black hole (SMBH) seeds at high redshifts. Using the adaptive mesh refinement code ENZO, we follow the evolution of gas within slowly tumbling dark matter (DM) halos of Mvir ∼ 2 × 108 M☉ and Rvir ∼ 1 kpc. For our idealized simulations, we adopt cosmologically motivated DM and baryon density profiles and angular momentum distributions. Our principal goal is to understand how the collapsing flow overcomes the centrifugal barrier and whether it is subject to fragmentation which can potentially lead to star formation, decreasing the seed SMBH mass. We find that the collapse proceeds from inside out and leads either to a central runaway or to off-center fragmentation. A disk-like configuration is formed inside the centrifugal barrier, growing via accretion. For models with a more cuspy DM distribution, the gas collapses more and experiences a bar-like perturbation and a central runaway on scales of ∼–4 pc (∼10 AU), where it is estimated to become optically thick. The flow remains isothermal and the specific angular momentum, j, is efficiently transferred by gravitational torques in a cascade of nested bars. This cascade is triggered by finite perturbations from the large-scale mass distribution and by gas self-gravity, and supports a self-similar, disk-like collapse where the axial ratios remain constant. The mass accretion rate shows a global minimum on scales of ∼1-10 pc at the time of the central runaway. In the collapsing phase, virial supersonic turbulence develops and fragmentation is damped. Models with progressively larger initial DM cores evolve similarly, but the timescales become longer. In models with more organized initial rotation—when the rotation of spherical shells is constrained to be coplanar—a torus forms on scales ∼20-50 pc outside the disk, and appears to be supported by turbulent motions driven by accretion from the

  16. SDSS J114657.79+403708.6: the third most distant blazar at z=5.0

    CERN Document Server

    Ghisellini, G; Tagliaferri, G; Foschini, L; Tavecchio, F; Ghirlanda, G; Braito, V; Gehrels, N

    2014-01-01

    The radio-loud quasar SDSS J114657.79+403708.6 at a redshift z=5.0 is one of the most distant radio-loud objects. The IR-optical luminosity and spectrum suggest that its black hole has a very large mass: M=(5+-1)x 1e9 Msun. The radio-loudness (ratio of the radio to optical flux) of the source is large (around 100), suggesting that the source is viewed at small angles from the jet axis, and could be a blazar. The X-ray observations fully confirm this hypothesis, due to the high level and hardness of the flux. This makes SDSS J114657.79+403708.6 the third most distant blazar known, after Q0906+693 (z=5.47) and B2 1023+25 (z=5.3). Among those, SDSS J114657.79+403708.6 has the largest black hole mass, setting interesting constraints on the mass function of heavy (larger than one billion solar masses) black holes at high redshifts.

  17. ANTARES Constrains a Blazar Origin of Two IceCube PeV Neutrino Events

    CERN Document Server

    Adrián-Martínez, S; André, M; Anton, G; Ardid, M; Aubert, J -J; Baret, B; Barrios, J; Basa, S; Bertin, V; Biagi, S; Bogazzi, C; Bormuth, R; Bou-Cabo, M; Bouwhuis, M C; Bruijn, R; Brunner, J; Busto, J; Capone, A; Caramete, L; Carr, J; Chiarusi, T; Circella, M; Coniglione, R; Core, L; Costantini, H; Coyle, P; Creusot, A; De Rosa, G; Dekeyser, I; Deschamps, A; De Bonis, G; Distefano, C; Donzaud, C; Dornic, D; Dorosti, Q; Drouhin, D; Dumas, A; Eberl, T; Enzenhöfer, A; Escoffier, S; Fehn, K; Felis, I; Fermani, P; Folger, F; Fusco, L A; Galatà, S; Gay, P; Geißelsöder, S; Geyer, K; Giordano, V; Gleixner, A; Gómez-González, J P; Graf, K; Guillard, G; van Haren, H; Heijboer, A J; Hello, Y; Hernández-Rey, J J; Herold, B; Herrero, A; Hößl, J; Hofestädt, J; Hugon, C; James, C W; de Jong, M; Kalekin, O; Katz, U; Kießling, D; Kooijman, P; Kouchner, A; Kulikovskiy, V; Lahmann, R; Lambard, E; Lambard, G; Lefèvre, D; Leonora, E; Loehner, H; Loucatos, S; Mangano, S; Marcelin, M; Margiotta, A; Martínez-Mora, J A; Martini, S; Mathieu, A; Michael, T; Migliozzi, P; Neff, M; Nezri, E; Palioselitis, D; Păvălaş, G E; Pellegrino, C; Perrina, C; Piattelli, P; Popa, V; Pradier, T; Racca, C; Riccobene, G; Richter, R; Roensch, K; Rostovtsev, A; Saldaña, M; Samtleben, D F E; Sánchez-Losa, A; Sanguineti, M; Sapienza, P; Schmid, J; Schnabel, J; Schulte, S; Schüssler, F; Seitz, T; Sieger, C; Spies, A; Spurio, M; Steijger, J J M; Stolarczyk, Th; Taiuti, M; Tamburini, C; Tayalati, Y; Trovato, A; Vallage, B; Vallée, C; Van Elewyck, V; Visser, E; Vivolo, D; Wagner, S; de Wolf, E; Yatkin, K; Yepes, H; Zornoza, J D; Zúñiga, J; :,; Krauß, F; Kadler, M; Mannheim, K; Schulz, R; Trüstedt, J; Wilms, J; Ojha, R; Ros, E; Baumgartner, W; Beuchert, T; Blanchard, J; Bürkel, C; Carpenter, B; Edwards, P G; Glawion, D Eisenacher; Elsässer, D; Fritsch, U; Gehrels, N; Gräfe, C; Großberger, C; Hase, H; Horiuchi, S; Kappes, A; Kreikenbohm, A; Kreykenbohm, I; Langejahn, M; Leiter, K; Litzinger, E; Lovell, J E J; Müller, C; Phillips, C; Plötz, C; Quick, J; Steinbring, T; Stevens, J; Thompson, D J; Tzioumis, A K

    2015-01-01

    The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Such objects are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons - and hence their neutrino progenitors - from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for different possible source neutrino spectra. A...

  18. Multi-TeV flaring from blazars: Markarian 421 as a case study

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, Sarira; Miranda, Luis Salvador [Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Mexico, DF (Mexico); Rajpoot, Subhash [California State University, Department of Physics and Astronomy, Long Beach, CA (United States)

    2016-03-15

    The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observations in the X-ray and TeV energies were made. It was observed that the TeV outbursts had no counterparts in the lower energy range. One implication of this is that it might be an orphan flare. We show that Fermi-accelerated protons of energy ≤ 168 TeV can interact with the low energy tail of the background synchrotron self-Compton photons in the inner region of the blazar to produce the multi-TeV flare and our results fit very well with the observed spectrum. Based on our study, we predict that the blazars with a deep valley in between the end of the synchrotron spectrum and the beginning of the SSC spectrum are possible candidates for orphan flaring. Future possible candidates for this scenario are the HBLs Mrk 501 and PG 1553 + 113 objects. (orig.)

  19. Fourier analysis of blazar variability

    Energy Technology Data Exchange (ETDEWEB)

    Finke, Justin D. [U.S. Naval Research Laboratory, Code 7653, 4555 Overlook Avenue SW, Washington, DC 20375-5352 (United States); Becker, Peter A., E-mail: justin.finke@nrl.navy.mil [School of Physics, Astronomy, and Computational Sciences, MS 5C3, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)

    2014-08-10

    Blazars display strong variability on multiple timescales and in multiple radiation bands. Their variability is often characterized by power spectral densities (PSDs) and time lags plotted as functions of the Fourier frequency. We develop a new theoretical model based on the analysis of the electron transport (continuity) equation, carried out in the Fourier domain. The continuity equation includes electron cooling and escape, and a derivation of the emission properties includes light travel time effects associated with a radiating blob in a relativistic jet. The model successfully reproduces the general shapes of the observed PSDs and predicts specific PSD and time lag behaviors associated with variability in the synchrotron, synchrotron self-Compton, and external Compton emission components, from submillimeter to γ-rays. We discuss applications to BL Lacertae objects and to flat-spectrum radio quasars (FSRQs), where there are hints that some of the predicted features have already been observed. We also find that FSRQs should have steeper γ-ray PSD power-law indices than BL Lac objects at Fourier frequencies ≲ 10{sup –4} Hz, in qualitative agreement with previously reported observations by the Fermi Large Area Telescope.

  20. VERITAS Blazar Observations - Recent Results

    CERN Document Server

    Cogan, Peter

    2008-01-01

    We present the discovery of very high energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 0806+524 (z=0.138) and the intermediate-frequency-peaked BL Lac object W Comae (z=0.102) with VERITAS. VHE emission was discovered from these objects during the 2007/2008 observing campaign, with a strong outburst from W Comae detected in mid-March, lasting a few days. Quasi-simultaneous spectral energy distributions are presented, incorporating optical (AAVSO), and X-ray (Swift/RXTE) observations. We also present the energy spectrum of the distant BL Lac (z=0.182) 1ES 1218+304 which was detected by VERITAS during the 2006/2007 observing campaign. The energy spectrum is discussed in the context of different models of absorption from the diffuse extragalactic background radiation. We present multiwavelength observations of the blazar Markarian 421 (z=0.03), including a strong flare initially detected by the Whipple 10m gamma-ray telescope. Finally we present a broadband spectral energy distrib...

  1. Astronomical Plate Archives and Binary Blazars Studies

    Czech Academy of Sciences Publication Activity Database

    Hudec, René

    2011-01-01

    Roč. 32, 1-2 (2011), s. 91-95. ISSN 0250-6335. [Conference on Multiwavelength Variability of Blazars. Guangzhou, 22,09,2010-24,09,2010] R&D Projects: GA ČR GA205/08/1207 Grant ostatní: GA ČR(CZ) GA102/09/0997; MŠMT(CZ) ME09027 Institutional research plan: CEZ:AV0Z10030501 Keywords : astronomical plates * plate archives archives * binary blazars Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 0.400, year: 2011

  2. Probes of the inner jets of blazars.

    OpenAIRE

    A. P. Marscher(Institute for Astrophysical Research, Boston University, Boston, USA)

    1995-01-01

    I review models for the "inner jet" in blazars, the section that connects the central engine with the radio jet. I discuss how the structure and physics of the inner jet can be explored using millimeter-wave VLBI (very-long-baseline radio interferometry) as well as multiwaveband observations of blazars. Flares at radio to gamma-ray frequencies should exhibit time delays at different wavebands that can test models for both the high-energy emission mechanisms and the nature of the inner jet in ...

  3. Monitoring of bright blazars with MAGIC telescope

    OpenAIRE

    Hsu, C. C.; Satalecka, K.; Thom, M; Backes, M.; Bernardini, E.; Bonnoli, G.; Galante, N.; Goebel, F; Lindfors, E.; Majumdar, P.; Stamerra, A.; Wagner, R. M.

    2009-01-01

    Blazars, a class of Active Galactic Nuclei (AGN) characterized by a close orientation of their relativistic outflows (jets) towards the line of sight, are a well established extragalactic TeV $\\gamma$-ray emitters. Since 2006, three nearby and TeV bright blazars, Markarian (Mrk) 421, Mrk 501 and 1ES 1959+650, are regularly observed by the MAGIC telescope with single exposures of 30 to 60 minutes. The sensitivity of MAGIC allows to establish a flux level of 30% of the Crab flux for each such o...

  4. Multi-TeV flaring from blazars: Markarian 421 a case study

    CERN Document Server

    Sahu, Sarira; Rajpoot, Subhash

    2015-01-01

    The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observed in x-ray and TeV energies. It was observed that the TeV outbursts had no counterparts in the lower energies, which implies that this might be an orphan flare. In the context of hadronic model, we have shown that this multi-TeV flaring can be produced due to the interaction of Fermi-accelerated protons of energy $\\lesssim 168$ TeV with the background photons in the low energy tail of the synchrotron self-Compton spectrum of the blazar jet. We fit very well the flaring spectrum with this model. Based on this study, we speculate that Mrk 501 and PG 1553+113 are possible candidates for orphan flaring in the future.

  5. Photometric redshifts and selection of high redshift galaxies in the NTT and Hubble Deep Fields

    CERN Document Server

    Fontana, A; Poli, F; Giallongo, E; Arnouts, S; Cristiani, S; Moorwood, A F M; Saracco, P

    2000-01-01

    We present and compare in this paper new photometric redshift catalogs of the galaxies in three public fields: the NTT Deep Field, the HDF-N and the HDF-S. Photometric redshifts have been obtained for thewhole sample, by adopting a $\\chi^2$ minimization technique on a spectral library drawn from the Bruzual and Charlot synthesis models, with the addition of dust and intergalactic absorption. The accuracy, determined from 125 galaxies with known spectroscopic redshifts, is $\\sigma_z\\sim 0.08 (0.3)$ in the redshift intervals $z=0-1.5 (1.5-3.5)$. The global redshift distribution of I-selected galaxies shows a distinct peak at intermediate redshifts, z~0.6 at I_{AB}5 candidates in the HDF filter set and that the 4 brightest candidates at $z>5$ in the HDF-S are indeed most likely M stars. (ABRIDGED)

  6. Using young massive star clusters to understand star formation and feedback in high-redshift-like environments

    OpenAIRE

    Longmore, Steven; Barnes, Ashley; Battersby, Cara; Bally, John; Kruijssen, J. M. Diederik; Dale, James; Henshaw, Jonathan; Walker, Daniel; Rathborne, Jill; Testi, Leonardo; Ott, Juergen; Ginsburg, Adam

    2016-01-01

    The formation environment of stars in massive stellar clusters is similar to the environment of stars forming in galaxies at a redshift of 1 - 3, at the peak star formation rate density of the Universe. As massive clusters are still forming at the present day at a fraction of the distance to high-redshift galaxies they offer an opportunity to understand the processes controlling star formation and feedback in conditions similar to those in which most stars in the Universe formed. Here we desc...

  7. IGMtransmission: A Java GUI to model the effects of the Intergalactic Medium on the colours of high redshift galaxies

    CERN Document Server

    Harrison, Christopher M; Stock, David

    2011-01-01

    IGMtransmission is a Java graphical user interface that implements Monte Carlo simulations to compute the corrections to colours of high-redshift galaxies due to intergalactic attenuation based on current models of the Intergalactic Medium. The effects of absorption due to neutral hydrogen are considered, with particular attention to the stochastic effects of Lyman Limit Systems. Attenuation curves are produced, as well as colours for a wide range of filter responses and model galaxy spectra. Alternative filter response curves and spectra may be readily uploaded. The code is freely available from http://code.google.com/p/igmtransmission. It is licensed under the GNU General Public License v.3.

  8. Weak-Line Quasars at High Redshift: Extremely High Accretion Rates or Anemic Broad-Line Regions?

    OpenAIRE

    Shemmer, Ohad; Trakhtenbrot, Benny; Anderson, Scott F.; Brandt, W. N.; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Lira, Paulina; Netzer, Hagai; Plotkin, Richard M.; Richards, Gordon T.; Donald P. Schneider(Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802, USA); Strauss, Michael A.

    2010-01-01

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z=3.55 and SDSS J123743.08+630144.9 at z=3.49. In both sources we detect an unusually weak broad H_beta line and we place tight upper limits on the strengths of their [O III] lines. Virial, H_beta-based black-hole mass determinations indicate normalized accretion rates of L/L_Edd=0.4 for the...

  9. Astronomical plate archives and blazar monitoring

    Czech Academy of Sciences Publication Activity Database

    Hudec, René

    Torino : OAT Torino, 1999 - (Raiteri, C.; Villata, M.; Takalo, L.), s. 63-65 [Blazar monitoring towards the third millenium. Torino (IT), 19.05.1999-21.05.1999] Institutional research plan: CEZ:AV0Z1003909 Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  10. Estimating Black Hole Masses of Blazars

    Indian Academy of Sciences (India)

    Xue-Bing Wu; F. K. Liu; M. Z. Kong; R. Wang; J. L. Han

    2011-03-01

    Estimating black hole masses of blazars is still a big challenge. Because of the contamination of jets, using the previously suggested size–continuum luminosity relation can overestimate the broad line region (BLR) size and black hole mass for radio-loud AGNs, including blazars. We propose a new relation between the BLR size and emission line luminosity and present evidences for using it to get more accurate black hole masses of radio-loud AGNs. For extremely radio-loud AGNs such as blazars with weak/absent emission lines, we suggest the use of fundamental plane relation of their elliptical host galaxies to estimate the central velocity dispersions and black hole masses, if their velocity dispersions are not known but the host galaxies can be mapped. The black hole masses of some well-known blazars, such as OJ 287, AO 0235+164 and 3C 66B are obtained using these two methods and the – relation. The implications of their black hole masses on other related studies are also discussed.

  11. The Cosmological Impact of Luminous TeV Blazars. I. Implications of Plasma Instabilities for the Intergalactic Magnetic Field and Extragalactic Gamma-Ray Background

    Science.gov (United States)

    Broderick, Avery E.; Chang, Philip; Pfrommer, Christoph

    2012-06-01

    Inverse Compton cascades (ICCs) initiated by energetic gamma rays (E >~ 100 GeV) enhance the GeV emission from bright, extragalactic TeV sources. The absence of this emission from bright TeV blazars has been used to constrain the intergalactic magnetic field (IGMF), and the stringent limits placed on the unresolved extragalactic gamma-ray background (EGRB) by Fermi have been used to argue against a large number of such objects at high redshifts. However, these are predicated on the assumption that inverse Compton scattering is the primary energy-loss mechanism for the ultrarelativistic pairs produced by the annihilation of the energetic gamma rays on extragalactic background light photons. Here, we show that for sufficiently bright TeV sources (isotropic-equivalent luminosities >~ 1042 erg s-1) plasma beam instabilities, specifically the "oblique" instability, present a plausible mechanism by which the energy of these pairs can be dissipated locally, heating the intergalactic medium. Since these instabilities typically grow on timescales short in comparison to the inverse Compton cooling rate, they necessarily suppress the ICCs. As a consequence, this places a severe constraint on efforts to limit the IGMF from the lack of a discernible GeV bump in TeV sources. Similarly, it considerably weakens the Fermi limits on the evolution of blazar populations. Specifically, we construct a TeV-blazar luminosity function from those objects currently observed and find that it is very well described by the quasar luminosity function at z ~ 0.1, shifted to lower luminosities and number densities, suggesting that both classes of sources are regulated by similar processes. Extending this relationship to higher redshifts, we show that the magnitude and shape of the EGRB above ~10 GeV are naturally reproduced with this particular example of a rapidly evolving TeV-blazar luminosity function.

  12. Unveiling the nature of dark matter with high redshift 21 cm line experiments

    OpenAIRE

    Evoli, Carmelo; Mesinger , Andrei; Ferrara, Andrea

    2014-01-01

    Observations of the redshifted 21 cm line from neutral hydrogen will open a new window on the early Universe. By influencing the thermal and ionization history of the intergalactic medium (IGM), annihilating dark matter (DM) can leave a detectable imprint in the 21 cm signal. Building on the publicly available 21cmFAST code, we compute the 21 cm signal for a 10 GeV WIMP DM candidate. The most pronounced role of DM annihilations is in heating the IGM earlier and more uniformly than astrophysic...

  13. Geometrical tests of cosmological models. I. Probing dark energy using the kinematics of high-redshift galaxies

    CERN Document Server

    Marinoni, C; Giovanelli, R; Haynes, M P; Masters, K L; Le Fèvre, O; Mazure, A; Taxil, P; Virey, J -M

    2007-01-01

    We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test. We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to measure the amplitude of the dark energy density parameter, or to constrain the cosmic equation of state parameter for a smooth dark energy component. We evaluate how systematics may affect the proposed tests, and find that a linear standard rod evolution, causing galaxy dimensions to be up to 30% smaller at z=1.5, can be uniquely diagnosed, and will minimally bias the confidence level contours in the [Omega_Q, w] plane....

  14. A LINK TO THE PAST: USING MARKOV CHAIN MONTE CARLO FITTING TO CONSTRAIN FUNDAMENTAL PARAMETERS OF HIGH-REDSHIFT GALAXIES

    International Nuclear Information System (INIS)

    We have developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 2'. It allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in two sections. In the first, we test πMC2 using simulated SEDs to not only confirm the recovery of the known inputs but to assess the limitations of the method and identify potential hazards of SED fitting when applied specifically to high-redshift (z > 4) galaxies. In the second part of the paper we apply πMC2 to thirty-three 4 6 galaxies. Using πMC2, we are able to constrain the stellar mass of these objects and in some cases their stellar age and find no evidence that any of these sources formed at a redshift larger than z = 8, a time when the universe was ≈0.6 Gyr old.

  15. PROSPECTS FOR MEASURING THE MASS OF BLACK HOLES AT HIGH REDSHIFTS WITH RESOLVED KINEMATICS USING GRAVITATIONAL LENSING

    Energy Technology Data Exchange (ETDEWEB)

    Hezaveh, Yashar D. [Kavli Institute for Particle Astrophysics and Cosmology Stanford University, Stanford, CA (United States)

    2014-08-20

    Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and 30m class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z ∼ 1-6), using resolved gas kinematics with these instruments. We show that in ∼15% and ∼20% of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of ≳ 10{sup 8} M {sub ☉} black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-σ relation at high redshifts.

  16. FIR-detected Lyman break galaxies at z ~ 3: Dust attenuation and dust correction factors at high redshift

    CERN Document Server

    Oteo, I; Bongiovanni, Á; Pérez-García, A M; Cedrés, B; Sánchez, H Domínguez; Ederoclite, A; Sánchez-Portal, M; Pintos-Castro, I; Pérez-Martínez, R

    2013-01-01

    Lyman break galaxies (LBGs) represent one of the kinds of star-forming galaxies that are found in the high-redshift universe. The detection of LBGs in the FIR domain can provide very important clues on their dust attenuation and total SFR, allowing a more detailed study than those performed so far. In this work we explore the FIR emission of a sample of 16 LBGs at z ~ 3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100um or PACS-160um. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. We find that PACS-detected LBGs at z ~ 3 are highly obscured galaxies which belong to the Ultra luminous IR galaxies or Hyper luminous IR galaxies class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope or their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results for most of the galaxies. Comparing with a sample of PACS...

  17. PROSPECTS FOR MEASURING THE MASS OF BLACK HOLES AT HIGH REDSHIFTS WITH RESOLVED KINEMATICS USING GRAVITATIONAL LENSING

    International Nuclear Information System (INIS)

    Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and 30m class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z ∼ 1-6), using resolved gas kinematics with these instruments. We show that in ∼15% and ∼20% of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of ≳ 108 M ☉ black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-σ relation at high redshifts

  18. The evolution of the dust-to-metals ratio in high-redshift galaxies probed by GRB-DLAs

    CERN Document Server

    Wiseman, P; Bolmer, J; Krühler, T; Yates, R M; Greiner, J; Fynbo, J P U

    2016-01-01

    Context: Several issues regarding the nature of dust at high redshift remain unresolved: its composition, its production and growth mechanisms, and its effect on background sources. Aims: This paper aims to provide a more accurate relation between dust depletion levels and dust-to-metals ratio (DTM), and to use the DTM to investigate the origin and evolution of dust in the high redshift Universe via GRB-DLAs. Methods: We use absorption-line measured metal column densities for a total of 19 GRB-DLAs, including five new GRB afterglow spectra from VLT/X-shooter. We use the latest linear models to calculate the dust depletion strength factor in each DLA. Using this we calculate total dust and metal column densities to determine a DTM. We explore the evolution of DTM with metallicity, and compare this to previous trends in DTM measured with different methods. Results: We find significant dust depletion in 16 of our 19 GRB-DLAs, yet 18 of the 19 have a DTM significantly lower than the Milky Way. We find that DTM is...

  19. Non-linear violent disc instability with high Toomre's Q in high-redshift clumpy disc galaxies

    Science.gov (United States)

    Inoue, Shigeki; Dekel, Avishai; Mandelker, Nir; Ceverino, Daniel; Bournaud, Frédéric; Primack, Joel

    2016-02-01

    We utilize zoom-in cosmological simulations to study the nature of violent disc instability in clumpy galaxies at high redshift, z = 1-5. Our simulated galaxies are not in the ideal state assumed in Toomre instability, of linear fluctuations in an isolated, uniform, rotating disc. There, instability is characterized by a Q parameter below unity, and lower when the disc is thick. Instead, the high-redshift discs are highly perturbed. Over long periods they consist of non-linear perturbations, compact massive clumps and extended structures, with new clumps forming in interclump regions. This is while the galaxy is subject to frequent external perturbances. We compute the local, two-component Q parameter for gas and stars, smoothed on a ˜1 kpc scale to capture clumps of 108-9 M⊙. The Q VDI may be stimulated by the external perturbations such as mergers and counter-rotating streams. The high Q may represent excessive compressive modes of turbulence, possibly induced by tidal interactions.

  20. Non-linear violent disc instability with high Toomre's Q in high-redshift clumpy disc galaxies

    CERN Document Server

    Inoue, Shigeki; Mandelker, Nir; Ceverino, Daniel; Bournaud, Frederic; Primack, Joel

    2015-01-01

    We utilize zoom-in cosmological simulations to study the nature of violent disc instability (VDI) in clumpy galaxies at high redshift, $z=1$--$5$. Our simulated galaxies are not in the ideal state assumed in Toomre instability, of linear fluctuations in an isolated, uniform, rotating disk. There, instability is characterised by a $Q$ parameter below unity, and lower when the disk is thick. Instead, the high-redshift discs are highly perturbed. Over long periods they consist of non-linear perturbations, compact massive clumps and extended structures, with new clumps forming in inter-clump regions. This is while the galaxy is subject to frequent external perturbances. We compute the local, two-component $Q$ parameter for gas and stars, smoothed on a $\\sim1~{\\rm kpc}$ scale to capture clumps of $10^{8-9}~{\\rm M}_\\odot$. The $Q<1$ regions are confined to collapsed clumps due to the high surface density there, while the inter-clump regions show $Q$ significantly higher than unity. Tracing the clumps back to the...

  1. Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars

    CERN Document Server

    Stern, D; Allen, L; Bian, C; Blain, A; Brand, K; Brodwin, M; Brown, M J I; Cool, R; Desai, V; Dey, A; Eisenhardt, P; González, A; Jannuzi, B T; Menendez-Delmestre, K; Smith, H A; Soifer, B T; Tiede, G P; Wright, E

    2006-01-01

    We discuss color selection of rare objects in a wide-field, multiband survey spanning from the optical to the mid-infrared. Simple color criteria simultaneously identify and distinguish two of the most sought after astrophysical sources: the coolest brown dwarfs and the most distant quasars. We present spectroscopically-confirmed examples of each class identified in the IRAC Shallow Survey of the Bootes field of the NOAO Deep Wide-Field Survey. ISS J142950.9+333012 is a T4.5 brown dwarf at a distance of approximately 42 pc, and ISS J142738.5+331242 is a radio-loud quasar at redshift z=6.12. Our selection criteria identify a total of four candidates over 8 square degrees of the Bootes field. The other two candidates are both confirmed 5.5

  2. UV and X-ray Variability of Blazars

    Indian Academy of Sciences (India)

    Alok C. Gupta

    2011-03-01

    It is well established that the blazars show flux variations in the complete electromagnetic (EM) spectrum on all possible time scales ranging from a few tens of minutes to several years. Here we report the review of various UV and X-ray flux variability properties of blazars. Our analysis show that UV variability amplitude is smaller than X-rays, mostly soft X-rays hardness ratio show correlations with blazar luminosity and different modes of variability might be operating for different time scales and epochs. Quasi periodic oscillations are seen on a few occasions in blazars, higher fraction of high energy peaked blazars show intra day and short term variabilities in X-rays but variability duty cycle is much less in optical bands on intra day time scale compared to low energy peaked blazars. But these results are yet to be established.

  3. Correlation Analysis of Multi-Wavelength Luminosity of Fermi Blazars

    Indian Academy of Sciences (India)

    Xiongwei Bi; Wanquan He; Jiajin Tian; Zhimei Ding; Shuping Ge

    2014-09-01

    We have studied the correlations between luminosities (R, O, X, ) in radio, optical, X-ray and -ray wave bands for Fermi blazars, and found that there are significant correlations between R and , X and and O and for blazars, BL Lacs and FSRQs, but no correlation between and O for BL Lacs. These results suggest that for Fermi blazars, the high energy -ray emission can be related with radio, X-ray and optical emissions.

  4. A Search for Stellar Dust Production in Leo P, a Nearby Analog of High Redshift Galaxies

    Science.gov (United States)

    Boyer, Martha; McDonald, Iain; McQuinn, Kristen; Skillman, Evan; Sonneborn, George; Srinivasan, Sundar; van Loon, Jacco Th.; Zijlstra, Albert; Sloan, Greg

    2016-08-01

    The origin of dust in the early Universe is a matter of debate. One of the main potential dust contributors are Asymptotic Giant Branch (AGB) stars, and several studies have been devoted to investigating whether and how AGB dust production changes in metal-poor environments. Of particular interest are the most massive AGB stars (8-10 Msun), which can in principle enter the dust-producing phase material (unlike carbon AGB stars), so the efficiency of dust production decreases with metallicity. Evidence for dust production in massive AGB stars more metal-poor than the Magellanic Clouds is scarce due both to the rarity of chemically-unevolved, star-forming systems reachable in the infrared and to the short lifetimes of these stars. The recently discovered galaxy Leo P provides an irresistible opportunity to search for these massive AGB stars: Leo P is a gas-rich, star-forming galaxy, it is nearby enough for resolved star photometry with Spitzer, and its interstellar medium is 0.4 dex more metal-poor than any other accessible star-forming galaxy. Models predict ~3 massive AGB stars may be present in Leo P, and optical HST observations reveal 7 candidates. We propose to use Spitzer to determine whether these stars are dusty, providing valuable constraints to the dust contribution from AGB stars up to at least redshift 3.2, or 11.7 Gyr ago, when massive spheroidals and Galactic globular clusters were still forming. This is a gain of 2.8 Gyr compared to other accessible galaxies. We also request 1 orbit of joint HST time to confirm whether the AGB candidates in Leo P are indeed massive AGB stars belonging to the galaxy. These observations will provide information crucial for potential JWST followup spectroscopy.

  5. ASCA and other contemporaneous observations of the blazar B2 1308+326

    CERN Document Server

    Watson, D; Hanlon, L O; McBreen, B; Quilligan, F; Tashiro, M; Metcalfe, L; Doyle, P G; Teraesranta, H; Carramiñana, A; Guichard, J P

    2000-01-01

    The high redshift (z=0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data from two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model. The break in the x-ray spectrum is interpreted, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (m_V=18.3+/-0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component. MgII emission was detected with an equivalent width (EW) significantly different from previously reported values. Absorption at a level of in excess of the Galactic value was detected, indicating ...

  6. Redshift measurement of the BL-Lac gamma-ray blazar PKS 1424+240

    CERN Document Server

    Rovero, A C; Pichel, A; Muriel, H

    2015-01-01

    PKS 1424+240 is a BL-Lac blazar with unknown redshift detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. It was first detected at very-high-energy by VERITAS and latter confirmed by MAGIC. Attempts to find limits on its redshift include three estimations by modeling gamma-ray observations, and one obtained by analyzing Lyb and Lyg absorption lines observed in the far-UV spectra (from HST/COS) caused by absorbing gas along the line of sight. They allowed to constrain the redshift range to 0:6candidates to be the most distant blazars detected at very-high-energy gamma rays. Redshift determination of BL-Lac objects are difficult to achieve. We have found that redshift of blazars can be determined by its association to a galaxy group or cluster. To explore this possibility for PKS 1424+240, we have carried out spectroscopic measurements with the Gemini North telescope of galaxies in its field of view...

  7. Current and Future X-ray Studies of High-Redshift AGNs and the First Supermassive Black Holes

    Science.gov (United States)

    Brandt, Niel

    2016-01-01

    X-ray observations of high-redshift AGNs at z = 4-7 have played a critical role in understanding the physical processes at work inthese objects as well as their basic demographics. Since 2000, Chandra and XMM-Newton have provided new X-ray detections for more than 120 such objects, and well-defined samples of z > 4 AGNs now allow reliable X-ray population studies. Once luminosity effectsare considered, the basic X-ray continuum properties of most high-redshift AGNs appear remarkably similar to those of local AGNs, although there are some notable apparent exceptions (e.g., highly radio-loud quasars). Furthermore, the X-ray absorption found in some objects has been used as a diagnostic of outflowing winds and circumnuclear material. Demographically, the X-ray data now support an exponential decline in the number density of luminous AGNs above z ~ 3, and quantitative space-density comparisons for optically selected and X-ray selected quasars indicate basic statistical agreement.The current X-ray discoveries point the way toward the future breakthroughs that will be possible with, e.g., Athena and the X-raySurveyor. These missions will execute powerful blank-field surveys to elucidate the demographics of the first growing supermassive black holes (SMBHs), including highly obscured systems, up to z ~ 10. They will also carry out complementary X-ray spectroscopic and variability investigations of high-redshift AGNs by targeting the most-luminous z = 7-10 quasars found in wide-field surveys by, e.g., Euclid, LSST, and WFIRST. X-ray spectroscopic and variability studies of the X-ray continuum and reflection signatures will help determine Eddington ratios and disk/corona properties; measuring these will clarify how the first quasars grew so quickly. Furthermore, absorption line/edge studies will reveal how outflows from the first SMBHs influenced the growth of the first galaxies. I will suggest some efficient observational strategies for Athena and the X-ray Surveyor.

  8. GOODS-HERSCHEL: IMPACT OF ACTIVE GALACTIC NUCLEI AND STAR FORMATION ACTIVITY ON INFRARED SPECTRAL ENERGY DISTRIBUTIONS AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    We explore the effects of active galactic nuclei (AGNs) and star formation activity on the infrared (0.3-1000 μm) spectral energy distributions (SEDs) of luminous infrared galaxies from z = 0.5 to 4.0. We have compiled a large sample of 151 galaxies selected at 24 μm (S 24 ∼> 100 μJy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-IR spectrum into contributions from star formation and AGN activity. A significant portion (∼25%) of our sample is dominated by an AGN (>50% of the mid-IR luminosity) in the mid-IR. Based on the mid-IR classification, we divide our full sample into four sub-samples: z ∼ 1 star-forming (SF) sources, z ∼ 2 SF sources, AGNs with clear 9.7 μm silicate absorption, and AGNs with featureless mid-IR spectra. From our large spectroscopic sample and wealth of multi-wavelength data, including deep Herschel imaging at 100, 160, 250, 350, and 500 μm, we use 95 galaxies with complete spectral coverage to create a composite SED for each sub-sample. We then fit a two-temperature component modified blackbody to the SEDs. We find that the IR SEDs have similar cold dust temperatures, regardless of the mid-IR power source, but display a marked difference in the warmer dust temperatures. We calculate the average effective temperature of the dust in each sub-sample and find a significant (∼20 K) difference between the SF and AGN systems. We compare our composite SEDs to local templates and find that local templates do not accurately reproduce the mid-IR features and dust temperatures of our high-redshift systems. High-redshift IR luminous galaxies contain significantly more cool dust than their local counterparts. We find that a full suite of photometry spanning the IR peak is necessary to accurately account for the dominant dust temperature components in high-redshift IR luminous galaxies.

  9. THE ORIGIN OF [O II] IN POST-STARBURST AND RED-SEQUENCE GALAXIES IN HIGH-REDSHIFT CLUSTERS

    International Nuclear Information System (INIS)

    We present the first results from a near-IR spectroscopic campaign of the Cl1604 supercluster at z ∼ 0.9 and the cluster RX J1821.6+6827 at z ∼ 0.82 to investigate the nature of [O II] λ3727 emission in cluster galaxies at high redshift. Of the 401 members in Cl1604 and RX J1821+6827 confirmed using the Keck II/DEIMOS spectrograph, 131 galaxies have detectable [O II] emission with no other signs of current star formation activity, as well as strong absorption features indicative of a well-established older stellar population. The combination of these features suggests that the primary source of [O II] emission in these galaxies is not a result of star formation processes, but rather due to the presence of a low-ionization nuclear emission-line region (LINER) or Seyfert component. Using the NIRSPEC spectrograph on the Keck II 10 m telescope, 19 such galaxies were targeted, as well as 6 additional [O II]-emitting cluster members that exhibited signs of ongoing star formation activity. Nearly half (∼47%) of the 19 [O II]-emitting, absorption-line-dominated galaxies exhibit [O II] to Hα equivalent width (EW) ratios higher than unity, the typical observed value for star-forming galaxies, with an EW distribution similar to that observed for LINERs at low redshift. A majority (∼68%) of these 19 galaxies are classified as LINER/Seyfert based primarily on the emission-line ratio of [N II] λ6584 and Hα. The fraction of LINER/Seyferts increases to ∼85% for red [O II]-emitting, absorption-line-dominated galaxies. The LINER/Seyfert galaxies in our Cl1604 sample exhibit average L([O II])/L(Hα) ratios that are significantly higher than that observed in populations of star-forming galaxies, suggesting that [O II] is a poor indicator of star formation in a significant fraction of high-redshift cluster members. From the prevalence of [O II]-emitting, absorption-line-dominated galaxies in both systems and the fraction of such galaxies that are classified as LINER

  10. Unveiling the nature of dark matter with high redshift 21 cm line experiments

    CERN Document Server

    Evoli, Carmelo; Ferrara, Andrea

    2014-01-01

    Observations of the redshifted 21 cm line from neutral hydrogen will open a new window on the early Universe. By influencing the thermal and ionization history of the intergalactic medium (IGM), annihilating dark matter (DM) can leave a detectable imprint in the 21 cm signal. Building on the publicly available 21cmFAST code, we compute the 21 cm signal for a 10 GeV WIMP DM candidate. The most pronounced role of DM annihilations is in heating the IGM earlier and more uniformly than astrophysical sources of X-rays. This leaves several unambiguous, qualitative signatures in the redshift evolution of the large-scale ($k\\approx0.1$ Mpc$^{-1}$) 21 cm power amplitude: (i) the local maximum (peak) associated with IGM heating can be lower than the other maxima; (ii) the heating peak can occur while the IGM is in emission against the cosmic microwave background (CMB); (iii) there can be a dramatic drop in power (a global minimum) corresponding to the epoch when the IGM temperature is comparable to the CMB temperature. ...

  11. Sub-mm detection of a high redshift Type 2 QSO

    CERN Document Server

    Mainieri, V; Lehmann, I; Scott, S; Matute, I; Almaini, O; Tozzi, P; Hasinger, G; Dunlop, J S

    2004-01-01

    We report on the first SCUBA detection of a Type 2 QSO at z=3.660 in the Chandra Deep Field South. This source is X-ray absorbed, shows only narrow emission lines in the optical spectrum and is detected in the sub-mm: it is the ideal candidate in an evolution scheme for AGN (e.g. Fabian (1999); Page et al. (2004)) of an early phase corresponding to the main growth of the host galaxy and formation of the central black hole. The overall photometry (from the radio to the X-ray energy band) of this source is well reproduced by the spectral energy distribution (SED) of NGC 6240, while it is incompatible with the spectrum of a Type 1 QSO (3C273) or a starburst galaxy (Arp 220). Its sub-mm (850 \\mu m) to X-ray (2 keV) spectral slope (alpha_SX) is close to the predicted value for a Compton-thick AGN in which only 1% of the nuclear emission emerges through scattering. Using the observed flux at 850 \\mu m we have derived a SFR=550--680 M$_odot/yr and an estimate of the dust mass, M$_dust=4.2 10^8 M_odot

  12. Growth of Black Holes and Their Host Spheroids in (Sub)mm-loud High-Redshift QSOs

    Institute of Scientific and Technical Information of China (English)

    Cai-Na Hao; Xiao-Yang Xia; Shu-De Mao; Zu-Gan Deng; Hong Wu

    2008-01-01

    We study the growth of black holes and stellar population in spheroids at high redshift using several (sub)mm-loud QSO samples. Applying the same criteria established in an earlier work, we find that, similar to IR QSOs at low redshift, the far-infrared emission of these (sub)mm-loud QSOs mainly originates from dust heated by starbursts. By combining low-z IR QSOs and high-z (sub)mm-loud QSOs, we find a trend that the star formation rate (M★) increases with the accretion rate (Macc). We compare the values of M★/Macc for submm emitting galaxies (SMGs), far-infrared ultraluminous/hyperluminous QSOs and typical QSOs, and construct a likely evolution scenario for these objects. The (sub)mm-loud QSO transition phase has both high Macc and M★ and hence is important for establishing the correlation between the masses of black holes and spheroids.

  13. DEEP SPITZER OBSERVATIONS OF INFRARED-FAINT RADIO SOURCES: HIGH-REDSHIFT RADIO-LOUD ACTIVE GALACTIC NUCLEI?

    International Nuclear Information System (INIS)

    Infrared-faint radio sources (IFRSs) are a rare class of objects which are relatively bright at radio wavelengths but very faint at infrared and optical wavelengths. Here we present sensitive near-infrared observations of a sample of these sources taken as part of the Spitzer Extragalactic Representative Volume Survey. Nearly all the IFRSs are undetected at a level of ∼1 μJy in these new deep observations, and even the detections are consistent with confusion with unrelated galaxies. A stacked image implies that the median flux density is S3.6μm ∼ 0.2 μJy or less, giving extreme values of the radio-infrared flux density ratio. Comparison of these objects with known classes of object suggests that the majority are probably high-redshift radio-loud galaxies, possibly suffering from significant dust extinction.

  14. Warm gas at high redshift clues to gravitational structure formation from optical spectroscopy of Lyman $\\alpha$ absorption systems

    CERN Document Server

    Rauch, M

    1995-01-01

    We discuss the effects of gravitational collapse on the shape of absorption line profiles for low column density (log N(HI) < 14) Lyman Alpha forest clouds and argue by comparison with cosmological simulations that Lyman alpha forest observations show the signs of ongoing gravitational structure formation at high redshift. The departures of observed line profiles from thermal Voigt profiles (caused by bulk motion of infalling gas and compressional heating) are evident from the results of profile fitting as a correlation in velocity space among pairs of components with discrepant Doppler parameters. This correlation also allows us to qualitatively understand the meaning of the Doppler parameter - column density (b vs. N(HI)) diagram for intergalactic gas.

  15. Quasar ionization of Lyman-alpha clouds - the proximity effect, a probe of the ultraviolet background at high redshift

    International Nuclear Information System (INIS)

    The distribution of lines in the Ly-alpha forests in quasar spectra is examined using spectral data from 19 quasars with emission lines redshifts z sub Q ranging from 1.7 to 3.8. The number density of Ly-alpha lines generally increases with resdhift z, but there exists a countervailing trend of diminishing number density within individual quasar spectra as z tends to z sub Q. Evidence is presented that this countervailing trend is due to enhanced ionization of Ly-alpha clouds by the bright nearby quasars in whose spectra they are observed. It is suggested that this proximity effect should be used as a powerful tool to measure locally the ionizing flux emitted by high-redshift objects. 44 references

  16. Multi-Waveband Emission Maps of Blazars

    Indian Academy of Sciences (India)

    Alan Marscher; Svetlana G. Jorstad; Valeri M. Larionov; Margo F. Aller; Anne Lähteenmäki

    2011-03-01

    We are leading a comprehensive multi-waveband monitoring program of 34 -ray bright blazars designed to locate the emission regions of blazars from radio to -ray frequencies. The `maps’ are anchored by sequences of images in both total and polarized intensity obtained with the VLBA at an angular resolution of ∼ 0.1 milliarcseconds. The time-variable linear polarization at radio to optical wavelengths and radio to -ray light curves allow us to specify the locations of flares relative to bright stationary features seen in the images and to infer the geometry of the magnetic field in different regions of the jet. Our data reveal that some flares occur simultaneously at different wavebands and others are only seen at some of the frequencies. The flares are often triggered by a superluminal knot passing through the stationary `core’ on the VLBA images. Other flares occur upstream or even parsecs downstream of the core.

  17. THERMAL AND RADIATIVE ACTIVE GALACTIC NUCLEUS FEEDBACK HAVE A LIMITED IMPACT ON STAR FORMATION IN HIGH-REDSHIFT GALAXIES

    International Nuclear Information System (INIS)

    The effects of active galactic nuclei (AGNs) on their host galaxies depend on the coupling between the injected energy and the interstellar medium (ISM). Here, we model and quantify the impact of long-range AGN ionizing radiation—in addition to the often considered small-scale energy deposition—on the physical state of the multi-phase ISM of the host galaxy and on its total star formation rate (SFR). We formulate an AGN spectral energy distribution matched with observations, which we use with the radiative transfer (RT) code Cloudy to compute AGN ionization in a simulated high-redshift disk galaxy. We use a high-resolution (∼6 pc) simulation including standard thermal AGN feedback and calculate RT in post-processing. Surprisingly, while these models produce significant AGN-driven outflows, we find that AGN ionizing radiation and heating reduce the SFR by a few percent at most for a quasar luminosity (L bol = 1046.5 erg s–1). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 102 – 3 cm–3) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm–3)—which are the sites of future star formation (SF; 100-200 Myr), are generally too dense to be significantly affected. Our analysis ignores any absorption from a putative torus, making our results upper limits on the effects of ionizing radiation. Therefore, while the AGN-driven outflows can remove substantial amounts of gas in the long term, the impact of AGN feedback on the SF efficiency in the interstellar gas in high-redshift galaxies is marginal, even when long-range radiative effects are accounted for

  18. ALMA Imaging and Gravitational Lens Models of South Pole Telescope—Selected Dusty, Star-Forming Galaxies at High Redshifts

    Science.gov (United States)

    Spilker, J. S.; Marrone, D. P.; Aravena, M.; Béthermin, M.; Bothwell, M. S.; Carlstrom, J. E.; Chapman, S. C.; Crawford, T. M.; de Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y.; Litke, K.; Ma, J.; Malkan, M.; Rotermund, K. M.; Strandet, M.; Vieira, J. D.; Weiss, A.; Welikala, N.

    2016-08-01

    The South Pole Telescope has discovered 100 gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0.″5 resolution 870 μ {{m}} Atacama Large Millimeter/submillimeter Array imaging of a sample of 47 DSFGs spanning z=1.9{--}5.7, and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies ({μ }870μ {{m}}\\gt 2), with a median magnification of {μ }870μ {{m}}=6.3, extending to {μ }870μ {{m}}\\gt 30. We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the dust optical depth is unity and find this wavelength to be correlated with the dust temperature. This correlation leads to discrepancies in dust mass estimates of a factor of two compared to estimates using a single value for this wavelength. We investigate the relationship between the [C ii] line and the far-infrared luminosity and find that the same correlation between the [C ii]/{L}{{FIR}} ratio and {{{Σ }}}{{FIR}} found for low-redshift star-forming galaxies applies to high-redshift galaxies and extends at least two orders of magnitude higher in {{{Σ }}}{{FIR}}. This lends further credence to the claim that the compactness of the IR-emitting region is the controlling parameter in establishing the “[C ii] deficit.”

  19. THERMAL AND RADIATIVE ACTIVE GALACTIC NUCLEUS FEEDBACK HAVE A LIMITED IMPACT ON STAR FORMATION IN HIGH-REDSHIFT GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Roos, Orianne; Juneau, Stéphanie; Bournaud, Frédéric; Gabor, Jared M., E-mail: orianne.roos@cea.fr [CEA-Saclay, F-91190 Gif-sur-Yvette (France)

    2015-02-10

    The effects of active galactic nuclei (AGNs) on their host galaxies depend on the coupling between the injected energy and the interstellar medium (ISM). Here, we model and quantify the impact of long-range AGN ionizing radiation—in addition to the often considered small-scale energy deposition—on the physical state of the multi-phase ISM of the host galaxy and on its total star formation rate (SFR). We formulate an AGN spectral energy distribution matched with observations, which we use with the radiative transfer (RT) code Cloudy to compute AGN ionization in a simulated high-redshift disk galaxy. We use a high-resolution (∼6 pc) simulation including standard thermal AGN feedback and calculate RT in post-processing. Surprisingly, while these models produce significant AGN-driven outflows, we find that AGN ionizing radiation and heating reduce the SFR by a few percent at most for a quasar luminosity (L {sub bol} = 10{sup 46.5} erg s{sup –1}). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 10{sup 2} {sup –} {sup 3} cm{sup –3}) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm{sup –3})—which are the sites of future star formation (SF; 100-200 Myr), are generally too dense to be significantly affected. Our analysis ignores any absorption from a putative torus, making our results upper limits on the effects of ionizing radiation. Therefore, while the AGN-driven outflows can remove substantial amounts of gas in the long term, the impact of AGN feedback on the SF efficiency in the interstellar gas in high-redshift galaxies is marginal, even when long-range radiative effects are accounted for.

  20. Precise Strong Lensing Mass Modeling of Four Hubble Frontier Field Clusters and a Sample of Magnified High-redshift Galaxies

    Science.gov (United States)

    Kawamata, Ryota; Oguri, Masamune; Ishigaki, Masafumi; Shimasaku, Kazuhiro; Ouchi, Masami

    2016-03-01

    We conduct precise strong lensing mass modeling of four Hubble Frontier Field (HFF) clusters, Abell 2744, MACS J0416.1-2403, MACS J0717.5+3745, and MACS J1149.6+2223, for which HFF imaging observations are completed. We construct a refined sample of more than 100 multiple images for each cluster by taking advantage of the full-depth HFF images, and conduct mass modeling using the glafic software, which assumes simply parametrized mass distributions. Our mass modeling also exploits a magnification constraint from the lensed SN Ia HFF14Tom for Abell 2744 and positional constraints from the multiple images S1-S4 of the lensed supernova SN Refsdal for MACS J1149.6+2223. We find that our best-fitting mass models reproduce the observed image positions with rms errors of ˜0.″4, which are smaller than rms errors in previous mass modeling that adopted similar numbers of multiple images. Our model predicts a new image of SN Refsdal with a relative time delay and magnification that are fully consistent with a recent detection of reappearance. We then construct catalogs of z ˜ 6-9 dropout galaxies behind the four clusters and estimate magnification factors for these dropout galaxies with our best-fitting mass models. The dropout sample from the four cluster fields contains ˜120 galaxies at z ≳ 6, about 20 of which are predicted to be magnified by a factor of more than 10. Some of the high-redshift galaxies detected in the HFF have lensing-corrected magnitudes of MUV ˜ -15 to -14. Our analysis demonstrates that the HFF data indeed offer an ideal opportunity to study faint high-redshift galaxies. All lensing maps produced from our mass modeling will be made available on the Space Telescope Science Institute website (https://archive.stsci.edu/prepds/frontier/lensmodels/).

  1. FEEDBACK FROM HIGH-MASS X-RAY BINARIES ON THE HIGH-REDSHIFT INTERGALACTIC MEDIUM: MODEL SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Power, Chris [International Centre for Radio Astronomy Research, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); James, Gillian; Wynn, Graham [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Combet, Celine, E-mail: chris.power@icrar.org [Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph Fourier Grenoble 1/CNRS/IN2P3/INPG, 53 avenue des Martyrs, F-38026 Grenoble (France)

    2013-02-10

    Massive stars at redshifts z {approx}> 6 are predicted to have played a pivotal role in cosmological reionization as luminous sources of ultraviolet (UV) photons. However, the remnants of these massive stars could be equally important as X-ray-luminous (L{sub X} {approx} 10{sup 38} erg s{sup -1}) high-mass X-ray binaries (HMXBs). Because the absorption cross section of neutral hydrogen decreases sharply with photon energy ({sigma}{proportional_to}E {sup -3}), X-rays can escape more freely than UV photons from the star-forming regions in which they are produced, allowing HMXBs to make a potentially significant contribution to the ionizing X-ray background during reionization. In this paper, we explore the ionizing power of HMXBs at redshifts z {approx}> 6 using a Monte Carlo model for a coeval stellar population of main-sequence stars and HMXBs. Using the archetypal Galactic HMXB Cygnus X-1 as our template, we propose a composite HMXB spectral energy distribution consisting of blackbody and power-law components, whose contributions depend on the accretion state of the system. We determine the time-dependent ionizing power of a combined population of UV-luminous stars and X-ray-luminous HMXBs and deduce fitting formulae for the boost in the population's ionizing power arising from HMXBs; these fits allow for simple implementation of HMXB feedback in numerical simulations. Based on this analysis, we estimate the contribution of high-redshift HMXBs to the present-day soft X-ray background, and we show that it is a factor of {approx}100-1000 smaller than the observed limit. Finally, we discuss the implications of our results for the role of HMXBs in reionization and in high-redshift galaxy formation.

  2. Supermassive black hole seed formation at high redshifts: long-term evolution of the direct collapse

    Science.gov (United States)

    Shlosman, Isaac; Choi, Jun-Hwan; Begelman, Mitchell C.; Nagamine, Kentaro

    2016-02-01

    We use cosmological adaptive mesh refinement code ENZO zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ˜0.01-10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. Their growth is negligible with the sole exception of the central seed which grows dramatically to Mseed ˜ 2 × 106 M⊙ in ˜2 Myr, confirming the feasibility of this path to the SMBH. The variability of angular momentum in the accreted gas results in the formation of two misaligned discs. Both discs lie within the Roche limit of the central seed. While the inner disc is geometrically thin and weakly asymmetric, the outer disc flares due to turbulent motions as a result of the massive inflow along a pair of penetrating filaments. The filamentary inflow determines the dominant Fourier modes in this disc - these modes have a non-self-gravitational origin. We do not confirm that m = 1 is a dominant mode that drives the inflow in the presence of a central massive object. The overall configuration appears to be generic, and is expected to form when the central seed becomes sufficiently massive.

  3. Constraining blazar physics with polarization signatures

    Science.gov (United States)

    Zhang, Haocheng; Boettcher, Markus; Li, Hui

    2016-01-01

    Blazars are active galactic nuclei whose jets are directed very close to our line of sight. They emit nonthermal-dominated emission from radio to gamma-rays, with the radio to optical emissions known to be polarized. Both radiation and polarization signatures can be strongly variable. Observations have shown that sometimes strong multiwavelength flares are accompanied by drastic polarization variations, indicating active participation of the magnetic field during flares. We have developed a 3D multi-zone time-dependent polarization-dependent radiation transfer code, which enables us to study the spectral and polarization signatures of blazar flares simultaneously. By combining this code with a Fokker-Planck nonthermal particle evolution scheme, we are able to derive simultaneous fits to time-dependent spectra, multiwavelength light curves, and time-dependent optical polarization signatures of a well-known multiwavelength flare with 180 degree polarization angle swing of the blazar 3C279. Our work shows that with detailed consideration of light travel time effects, the apparently symmetric time-dependent radiation and polarization signatures can be naturally explained by a straight, helically symmetric jet pervaded by a helical magnetic field, without the need of any asymmetric structures. Also our model suggests that the excess in the nonthermal particles during flares can originate from magnetic reconnection events, initiated by a shock propagating through the emission region. Additionally, the magnetic field should generally revert to its initial topology after the flare. We conclude that such shock-initiated magnetic reconnection event in an emission environment with relatively strong magnetic energy can be the driver of multiwavelength flares with polarization angle swings. Future statistics on such observations will constrain general features of such events, while magneto-hydrodynamic simulations will provide physical scenarios for the magnetic field evolution

  4. Blazar microvariability at hard X-rays

    OpenAIRE

    Foschini, L.; Gliozzi, M.; Pian, E.; Tagliaferri, G.; Tavecchio, F.; Bianchin, V.; L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy); Sambruna, R. M.; Di Cocco, G.; Ghisellini, G.; Malaguti, G.; Tosti, G.; Treves, A.

    2007-01-01

    Blazars are known to display strong and erratic variability at almost all the wavelengths of electromagnetic spectrum. Presently, variability studies at high-energies (hard X-rays, gamma-rays) are hampered by low sensitivity of the instruments. Nevertheless, the latest generation of satellites (INTEGRAL, Swift) have given suggestions not yet fully confirmed of variability on intraday timescales. Some specific cases recently observed are presented and physical implications are discussed (e.g. ...

  5. Astronomical Plate Archives and Binary Blazars Studies

    Indian Academy of Sciences (India)

    Rene Hudec

    2011-03-01

    There are about 3 million astronomical photographic plates around the globe, representing an important data source for various aspects of astrophysics. The main advantage is the large time coverage of 100 years or even more. Recent digitization efforts, together with the development of dedicated software, enables for the first time, effective data mining and data analyses by powerful computers with these archives. Examples of blazars proposed and/or investigated on the astronomical plates are presented and discussed.

  6. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    Margo F. Aller; Hugh D. Aller; Philip A. Hughes

    2011-03-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the -ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially selfabsorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

  7. Cosmology with high-redshift galaxy survey: Neutrino mass and inflation

    International Nuclear Information System (INIS)

    High-z galaxy redshift surveys open up exciting possibilities for precision determinations of neutrino masses and inflationary models. The high-z surveys are more useful for cosmology than low-z ones owing to much weaker nonlinearities in matter clustering, redshift-space distortion, and galaxy bias, which allows us to use the galaxy power spectrum down to the smaller spatial scales that are inaccessible by low-z surveys. We can then utilize the two-dimensional information of the linear power spectrum in angular and redshift space to measure the scale-dependent suppression of matter clustering due to neutrino free-streaming as well as the shape of the primordial power spectrum. To illustrate capabilities of high-z surveys for constraining neutrino masses and the primordial power spectrum, we compare three future redshift surveys covering 300 square degrees at 0.5ν,tot)=0.059, 0.043, and 0.025 eV, respectively, thus yielding a positive detection of the neutrino mass rather than an upper limit, as σ(mν,tot) is smaller than the lower limits to the neutrino masses implied from the neutrino oscillation experiments, by up to a factor of 4 for the highest redshift survey. The accuracies of constraining the tilt and running index of the primordial power spectrum, σ(ns)=(3.8,3.7,3.0)x10-3 and σ(αs)=(5.9,5.7,2.4)x10-3 at k0=0.05 Mpc-1, respectively, are smaller than the current uncertainties by more than an order of magnitude, which will allow us to discriminate between candidate inflationary models. In particular, the error on αs from the future highest redshift survey is not very far away from the prediction of a class of simple inflationary models driven by a massive scalar field with self-coupling, αs=-(0.8-1.2)x10-3

  8. Gamma-Ray and Multiwavelength Emission from Blazars

    Indian Academy of Sciences (India)

    Meg Urry

    2011-03-01

    Blazars are now well understood as approaching relativistic jets aligned with the line of sight. The long-time uncertainty about the demographics of blazars is starting to become clearer: since the Fermi blazar sample includes a larger fraction of high-frequency peaked blazars (like the typical X-ray-selected blazars in, say, the Einstein Slew Survey sample) than did the higher-flux-limit EGRET blazar sample, these low-luminosity sources must be more common than their higher luminosity, low-frequency-peaked cousins. Blazar spectral energy distributions have a characteristic two-component form, with synchrotron radiation at radio through optical (UV, X-ray) frequencies and gamma-rays from X-ray through GeV (TeV) energies.Multiwavelength monitoring has suggested that gamma-ray flares can result from acceleration of electrons at shocks in the jet, and there appears to be an association between the creation of outflowing superluminal radio components in VLBI maps and the gamma-ray flares. In many cases, the gamma-ray emission is produced by inverse Compton upscattering of ambient optical-UV photons, although the contribution from energetic hadrons cannot be ruled out. The next few years of coordinated gamma-ray, X-ray, UV, optical, infrared and radio monitoring of blazars will be important for characterizing jet content, structure, and total power.

  9. Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217

    CERN Document Server

    Worsley, M A; Pooley, G G; Chandler, C J

    2006-01-01

    We report on the extreme behaviour of the high redshift blazar GB B1428+4217 at z=4.72. A continued programme of radio measurements has revealed an exceptional flare in the lightcurve, with the 15.2 GHz flux density rising by a factor ~3 from ~140 mJy to ~430 mJy in a rest-frame timescale of only ~4 months -- much larger than any previous flares observed in this source. In addition to new measurements of the 1.4-43 GHz radio spectrum we also present the analysis and results of a target-of-opportunity X-ray observation using XMM-Newton, made close to the peak in radio flux. Although the X-ray data do not show a flare in the high energy lightcurve, we are able to confirm the X-ray spectral variability hinted at in previous observations. GB B1428+4217 is one of several high-redshift radio-loud quasars that display a low energy break in the X-ray spectrum, probably due to the presence of excess absorption in the source. X-ray spectral analysis of the latest XMM-Newton data is shown to be consistent with the warm ...

  10. Connection between optical and gamma-ray variability in blazars

    CERN Document Server

    Hovatta, T; King, O G; Mahabal, A; Sesar, B; Dancikova, R; Djorgovski, S G; Drake, A; Laher, R; Levitan, D; Max-Moerbeck, W; Ofek, E O; Pearson, T J; Prince, T A; Readhead, A C S; Richards, J L; Surace, J

    2014-01-01

    We use optical data from the Palomar Transient Factory (PTF) and the Catalina Real-Time Transient Survey (CRTS) to study the variability of gamma-ray detected and non-detected objects in a large population of active galactic nuclei (AGN) selected from the Candidate Gamma-Ray Blazar Survey and Fermi Gamma-Ray Space Telescope catalogs. Our samples include 714 sources with PTF data and 1244 sources with CRTS data. We calculate the intrinsic modulation index to quantify the optical variability amplitude in these samples. We find the gamma-ray detected objects to be more variable than the non-detected ones. The flat spectrum radio quasars (FSRQs) are more variable than the BL Lac objects in our sample, but the significance of the difference depends on the sample used. When dividing the objects based on their synchrotron peak frequency, we find the low synchrotron peaked (LSP) objects to be significantly more variable than the high synchrotron peaked (HSP) ones, explaining the difference between the FSRQs and BL La...

  11. Magnetic Field Amplification and Blazar Flares

    Directory of Open Access Journals (Sweden)

    Chen Xuhui

    2013-12-01

    Full Text Available Recent multiwavelength observations of PKS 0208-512 by SMARTS, Fermi, and Swift revealed that γ-ray and optical light curves of this flat spectrum radio quasars are highly correlated, but with an exception of one large optical flare having no corresponding gamma-ray activity or even detection. On the other hand, recent advances in SNRs observations and plasma simulations both reveal that magnetic field downstream of astrophysical shocks can be largely amplified beyond simple shock compression. These amplifications, along with their associated particle acceleration, might contribute to blazar flares, including the peculiar flare of PKS 0208-512. Using our time dependent multizone blazar emission code, we evaluate several scenarios that may represent such phenomena. This code combines Monte Carlo method that tracks the radiative processes including inverse Compton scattering, and Fokker-Planck equation that follows the cooling and acceleration of particles. It is a comprehensive time dependent code that fully takes into account the light travel time effects. In this study, both the changes of the magnetic field and acceleration efficiency are explored as the cause of blazar flares. Under these assumption, synchrotron self-Compton and external Compton scenarios produce distinct features that favor the external Compton scenario. The optical flares with/without gamma-ray counterparts can be explained by different allocations of energy between the magnetization and particle acceleration, which in turn can be affected by the relative orientation between the magnetic field and the shock flow. We compare the details of the observations and simulation, and highlight what implications this study has on our understanding of relativistic jets.

  12. The contribution of high-redshift galaxies to cosmic reionization: new results from deep WFC3 imaging of the Hubble Ultra Deep Field

    Science.gov (United States)

    Bunker, Andrew J.; Wilkins, Stephen; Ellis, Richard S.; Stark, Daniel P.; Lorenzoni, Silvio; Chiu, Kuenley; Lacy, Mark; Jarvis, Matt J.; Hickey, Samantha

    2010-12-01

    We have searched for star-forming galaxies at z ~ 7-10 by applying the Lyman-break technique to newly released Y-, J- and H-band images (1.1, 1.25 and 1.6μm) from Wide Field Camera 3 (WFC3) on the Hubble Space Telescope. By comparing these images of the Hubble Ultra Deep Field with the Advanced Camera for Surveys (ACS) z'-band (0.85μm) images, we identify objects with red colours, (z' - Y)AB > 1.3, consistent with the Lyman α forest absorption at z ~ 6.7-8.8. We identify 12 of these z'-drops down to a limiting magnitude YAB image to eliminate contaminant low-mass Galactic stars, which typically have redder colours than z ~ 7 galaxies. One of our z'-drops is probably a T-dwarf star. The z ~ 7z'-drops appear to have much bluer spectral slopes than Lyman-break galaxies at lower redshift. Our brightest z'-drop is not present in the NICMOS J-band image of the same field taken 5 years before, and is a possible transient object. From the 10 remaining z ~ 7 candidates we determine a lower limit on the star formation rate density of 0.0017Msolaryr-1Mpc-3 for a Salpeter initial mass function, which rises to 0.0025-0.004Msolaryr-1Mpc-3 after correction for luminosity bias. The star formation rate density is a factor of ~10 less than that of Lyman-break galaxies at z = 3-4, and is about half the value at z ~ 6. We also present the discovery of seven Y-drop objects with (Y - J)AB > 1.0 and JAB 0.5), and the clumping factor of the Universe is low. Even then, we need to invoke a large contribution from galaxies below our detection limit (a steep faint-end slope). The apparent shortfall in ionizing photons might be alleviated if stellar populations at high redshift are of low metallicity or have a top-heavy initial mass function.

  13. A sample of weak blazars at milli-arcsecond resolution

    CERN Document Server

    Mantovani, F; Mack, K -H; Alef, W; Ros, E; Zensus, J A

    2015-01-01

    We started a follow-up investigation of the Deep X-ray Radio Blazar Survey objects with declination >-10 deg. We undertook a survey with the EVN at 5GHz to make the first images of a complete sample of weak blazars, aiming at a comparison between high- and low-power samples of blazars. All of the 87 sources observed were detected. Point-like sources are found in 39 cases, and 48 show core-jet structure. According to the spectral indices previously obtained, 58 sources show a flat spectral index, and 29 sources show a steep spectrum or a spectrum peaking at a frequency around 1-2 GHz. Adding to the DXRBS objects we observed those already observed with ATCA in the southern sky, we found that 14 blazars and a SSRQ, are associated to gamma-ray emitters. We found that 56 sources can be considered blazars. We also detected 2 flat spectrum NLRGs. About 50% of the blazars associated to a gamma-ray object are BL Lacs, confirming that they are more likely detected among blazars gamma-emitters. We confirm the correlatio...

  14. Observations of High-Redshift X-Ray Selected Clusters with the Sunyaev-Zel'dovich Array

    CERN Document Server

    Muchovej, S; Cartwright, J; Greer, C; Hawkins, D; Hennessy, R; Joy, M; Lamb, J W; Leitch, E M; Loh, M; Miller, A D; Mroczkowski, T; Pryke, C; Reddall, B; Runyan, M; Sharp, M; Wood, D; Muchovej, Stephen; Carlstrom, John E.; Cartwright, John; Greer, Christopher; Hawkins, David; Hennessy, Ryan; Joy, Marshall; Lamb, James W.; Leitch, Erik M.; Loh, Michael; Miller, Amber D.; Mroczkowski, Tony; Pryke, Clem; Reddall, Ben; Runyan, Marcus; Sharp, Matthew; Wood, and David

    2006-01-01

    We report measurements of the Sunyaev-Zel'dovich (SZ) effect in three high-redshift (0.89 < z < 1.03), X-ray selected galaxy clusters. The observations were obtained at 30 GHz during the commissioning period of a new, eight-element interferometer -- the Sunyaev-Zel'dovich Array (SZA) -- built for dedicated SZ effect observations. The SZA observations are sensitive to angular scales larger than those subtended by the virial radii of the clusters. Assuming isothermality and hydrostatic equilibrium for the intracluster medium, and gas-mass fractions consistent with those for clusters at moderate redshift, we calculate electron temperatures, gas masses, and total cluster masses from the SZ data. The SZ-derived masses, integrated approximately to the virial radii, are 1.9 ^{+0.5}_{-0.4}x10^{14} solar masses for CLl1415.1+3612, 3.4^{+0.6}_{-0.5}x10^{14} solar masses for CL1429.0+4241, and 7.2^{+1.3}_{-0.9}x10^{14} solar masses for CL1226.9+3332. The SZ-derived quantities are in good agreement with the cluster...

  15. Approximate Bayesian Computation for Astronomical Model Analysis: A Case Study in Galaxy Demographics and Morphological Transformation at High Redshift

    CERN Document Server

    Cameron, E

    2012-01-01

    "Approximate Bayesian Computation" (ABC) represents a powerful methodology for the analysis of complex stochastic systems for which the likelihood of the observed data under an arbitrary set of input parameters may be entirely intractable-the latter condition rendering useless the standard machinery of tractable likelihood-based, Bayesian statistical inference (e.g. conventional Markov Chain Monte Carlo simulation; MCMC). In this article we demonstrate the potential of ABC for astronomical model analysis by application to a case study in the morphological transformation of high redshift galaxies. To this end we develop, first, a stochastic model for the competing processes of merging and secular evolution in the early Universe; and second, through an ABC-based comparison against the observed demographics of the first generation of massive (M_gal > 10^11 M_sun) galaxies (at 1.5 < z < 3) in the CANDELS/EGS dataset we derive posterior probability densities for the key parameters of this model. The "Sequent...

  16. The effects of the small-scale DM power on the cosmological neutral hydrogen (\\HI) distribution at high redshifts

    CERN Document Server

    Sarkar, Abir; Das, Subinoy; Sethi, Shiv K; Bharadwaj, Somnath; Marsh, David J E

    2015-01-01

    The particle nature of dark matter remains a mystery. In this paper, we consider two dark matter models---Late Forming Dark Matter (LFDM) and Ultra-Light Axion (ULA) models---where the matter power spectra show novel effects on small scales. The high redshift universe offers a powerful probe of their parameters. In particular, we study two cosmological observables: the neutral hydrogen (HI) redshifted 21-cm signal from the epoch of reionization, and the evolution of the collapsed fraction of HI in the redshift range $2 4 \\times 10^5$ (for LFDM) and the axion mass $m_a > 2.6 \\times 10^{-23} \\, \\rm eV$ (for ULA). The comparison of the collapsed mass fraction inferred from damped Lyman-$\\alpha$ observations to the theoretical predictions of our models lead to the weaker bounds: $z_f > 2 \\times 10^5$ and $m_a > 10^{-23} \\, \\rm eV$. These bounds are consistent with other constraints in the literature using different observables and, in the case of ULAs, are also consistent with a solution to the cusp-core problem...

  17. Properties of high-redshift Lyman-alpha clouds. I - Statistical analysis of the Schneider-Schmidt-Gunn quasars

    Science.gov (United States)

    Press, William H.; Rybicki, George B.; Schneider, Donald P.

    1993-01-01

    Techniques for statistical analysis of the Lyman-alpha forest in high-redshift quasars are developed, and applied to the low-resolution (25 A) spectra of 29 of the 33 quasars in the Schneider-Schmidt-Gunn sample. We extrapolate each quasar's continuum shortward of Lyman-alpha emission, then consider each spectral bin of each quasar to be an (approximately) independent measurement of the absorption due to the Lyman-alpha clouds. With several thousand such measurements thus available, we can obtain good determinations of some interesting properties of clouds in the redshift range 2.5-4.3 without actually resolving any single cloud. We find that the mean absorption increases with z approximately as a power law (1 + z) exp (gamma + 1) with gamma = 2.46 +/- 0.37. The mean ratio of Lyman-alpha to Lyman-beta absorption in the clouds is 0.476 +/- 0.054. We also detect, and obtain ratios, for Lyma-gamma, delta, and possibly epsilon.

  18. A simple model to link the properties of quasars to the properties of dark matter halos out to high redshift

    CERN Document Server

    Croton, Darren J

    2009-01-01

    We present a simple model of how quasars occupy dark matter halos from z=0 to z=5 using the observed mBH-sigma relation and quasar luminosity functions. This provides a way for observers to statistically infer host halo masses for quasar observations using luminosity and redshift alone. Our model is deliberately simple and sidesteps any need to explicitly describe the physics. In spite of its simplicity, the model reproduces many key observations and has predictive power: 1) model quasars have the correct luminosity function (by construction) and spatial clustering (by consequence); 2) we predict high redshift quasars of a given luminosity live in less massive dark matter halos than the same luminosity quasars at low redshifts; 3) we predict a factor of ~5 more 10^8.5Msun black holes at z~2 than is currently observed; 4) we predict a factor of ~20 evolution in the amplitude of the mBH-Mhalo relation between z=5 and the present day; 5) we expect luminosity dependent quasar lifetimes of between tQ~10^(7-8)yr, b...

  19. The XMM Cluster Survey: The build up of stellar mass in Brightest Cluster Galaxies at high redshift

    CERN Document Server

    Stott, J P; Sahlen, M; Hilton, M; Lloyd-Davies, E; Capozzi, D; Hosmer, M; Liddle, A R; Mehrtens, N; Miller, C J; Romer, A K; Stanford, S A; Viana, P T P; Davidson, M; Hoyle, B; Kay, S T; Nichol, R C

    2010-01-01

    We present deep J and Ks band photometry of 20 high redshift galaxy clusters between z=0.8-1.5, 19 of which are observed with the MOIRCS instrument on the Subaru Telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at ~9e11MSol since z~1.5. We investigate the effect on this result of differing star formation histories generated by three well known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar ma...

  20. High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence

    CERN Document Server

    Burkert, A; Bouche, N; Cresci, G; Khochfar, S; Sommer-Larsen, J; Sternberg, A; Naab, T; Foerster-Schreiber, N; Tacconi, L; Shapiro, K; Hicks, E; Lutz, D; Davies, R; Buschkamp, P; Genel, S

    2009-01-01

    The structure of a sample of high-redshift (z=2), rotating galaxies with high star formation rates and turbulent gas velocities of sigma=40-80 km/s is investigated. Fitting the observed disk rotational velocities and radii with a Mo, Mao, White (1998) (MMW) model leads to unusually large spin parameters in the range of lambda=0.05-0.2. In addition, the ratios of disk-to-dark halo masses md are extreme and in several cases exceed the cosmic baryon fraction. The galaxies segregate into dispersion-dominated systems with 1200 km/s, vmax/sigma>3 and rd=4-8 kpc. For the dispersion-dominated sample, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities. Including this pressure effect in the MMW model leads to spin parameters lambda=0.035 and disk mass fractions md=0.1 that are in good agreement with cosmological expectations. For the rotation-dominated sample, pressure effects are small and better agreement with theoretical expectations can only be achieved if the da...

  1. Searching High Redshift Large-Scale Structures: Photomety of Four Fields Around Quasar Pairs at $z \\sim 1$

    CERN Document Server

    Boris, N V; Cypriano, E S; Santos, W A; De Oliveira, C M; West, M

    2007-01-01

    We have studied the photometric properties of four fields around the high-redshift quasar pairs QP1310+0007, QP1355-0032, QP0110-0219, and QP0114-3140 at z $\\sim$ 1 with the aim of identifying large-scale structures- galaxy clusters or groups- around them. This sample was observed with GMOS in Gemini North and South telescopes in the $g'$, $r'$, $i'$, and $z'$ bands, and our photometry is complete to a limiting magnitude of $i' \\sim 24$ mag (corresponding to $\\sim M_{i'}^* + 2$ at the redshift of the pairs). Our analysis shows that QP1310+0007, QP1355-0032 and QP0110-0219 are probably in rich clusters environments. For the pair QP0114-3140, the evidence for existence of galaxy clustering at the pair redshift is less compeling. This work suggest that $z \\sim 1$ quasar pairs are excellent tracers of high density environments and this same technique may be useful to find clusters at higher redshifts.

  2. A Link to the Past: Using Markov Chain Monte Carlo Fitting to Constrain Fundamental Parameters of High-Redshift Galaxies

    CERN Document Server

    Pirzkal, N; Nilsson, Kim K; Finkelstein, S; Koekemoer, Anton; Malhotra, Sangeeta; Rhoads, James

    2011-01-01

    We have a developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 4) galaxies. Our tests reveal five critical results: 1) the ability to confidently constrain metallicity, population ages, and Av all require photometric accuracy better than what is currently achievable (i.e. less than a few percent); 2) the ability to confidently constrain stellar masses (within a factor of two) can be achieved without the need for high-precision photometry; 3) the addition of IRAC photometry does not guarantee that tighter constraints of the stellar masses and ages can be defined; 4) different assumptions about the star formation history can lead to significant biases in mass and age estimates; and 5) we are able to constrain stellar age and Av of objects that are both young and relatively dust free. In the second part of the paper we apply PiMC^2 to 17 46 galaxies. Using PiMC^2, we are able to constrain the stellar mass of these objects an...

  3. The role of relativistic jets in the heaviest and most active supermassive black holes at high redshift

    CERN Document Server

    Ghisellini, G; Della Ceca, R; Volonteri, M; Sbarrato, T

    2013-01-01

    In powerful radio-quiet active galactic nuclei (AGN), black holes heavier than one billion solar masses form at a redshift ~1.5-2. Supermassive black holes in jetted radio-loud AGN seems to form earlier, at a redshift close to 4. The ratio of active radio-loud to radio-quiet AGN hosting heavy black holes is therefore a rather a strong function of redshift. We report on some recent evidence supporting this conclusion, gathered from the Burst Alert Telescope (BAT, onboard Swift) and by the Large Area Telescope (LAT, onboard Fermi). We suggest that the more frequent occurrence of relativistic jets in the most massive black holes at high redshifts, compared to later times, could be due to the average black hole spin being greater in the distant past, or else to the jet helping a fast accretion rate (or some combination of the two scenarios). We emphasize that the large total accretion efficiency of rapidly spinning black holes inhibits a fast growth, unless a large fraction of the available gravitational energy o...

  4. Clustering of High Redshift ($z\\ge 2.9$) Quasars from the Sloan Digital Sky Survey

    CERN Document Server

    Shen, Y; Oguri, M; Hennawi, J F; Fan, X; Richards, G T; Hall, P B; Gunn, J E; Schneider, D P; Szalay, A S; Thakar, A R; Vanden Berk, D E; Anderson, S F; Bahcall, N A; Connolly, A J; Knapp, G R; Shen, Yue; Strauss, Michael A.; Oguri, Masamune; Hennawi, Joseph F.; Fan, Xiaohui; Richards, Gordon T.; Hall, Patrick B.; Gunn, James E.; Schneider, Donald P.; Szalay, Alexander S.; Thakar, Anirudda R.; Berk, Daniel E. Vanden; Anderson, Scott F.; Bahcall, Neta A.; Connolly, Andrew J.; Knapp, Gillian R.

    2007-01-01

    (Abridged) We study the two-point correlation function of a uniformly selected sample of 4,426 luminous optical quasars with redshift $2.9 \\le z\\le 5.4$ selected over 4041 deg$^2$ from the Fifth Data Release of the Sloan Digital Sky Survey. For a real-space correlation function of the form $\\xi(r)=(r/r_0)^{-\\gamma}$, the fitted parameters in comoving coordinates are $r_0 = 15.2 \\pm 2.7 h^{-1}$ Mpc and $\\gamma = 2.0 \\pm 0.3$, over a scale range $4\\le r_p\\le 150 h^{-1}$ Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their $z \\approx 1.5$ counterparts, which have a comoving clustering length $r_0 \\approx 6.5 h^{-1}$ Mpc. Dividing our sample into two redshift bins: $2.9\\le z\\le 3.5$ and $z\\ge 3.5$, and assuming a power-law index $\\gamma=2.0$, we find a correlation length of $r_0 = 16.9 \\pm 1.7 h^{-1}$ Mpc for the former, and $r_0 = 24.3 \\pm 2.4 h^{-1}$ Mpc for the latter. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifet...

  5. ALMA Imaging and Gravitational Lens Models of South Pole Telescope-Selected Dusty, Star-Forming Galaxies at High Redshifts

    CERN Document Server

    Spilker, Justin; Aravena, Manuel; Bethermin, Matthieu; Bothwell, Matt; Carlstrom, John; Chapman, Scott; Crawford, Tom; de Breuck, Carlos; Fassnacht, Chris; Gonzalez, Anthony; Greve, Thomas; Hezaveh, Yashar; Litke, Katrina; Ma, Jingzhe; Malkan, Matt; Rotermund, Kaja; Strandet, Maria; Vieira, Joaquin; Weiss, Axel; Welikala, Niraj

    2016-01-01

    The South Pole Telescope has discovered one hundred gravitationally lensed, high-redshift, dusty, star-forming galaxies (DSFGs). We present 0.5" resolution 870um Atacama Large Millimeter/submillimeter Array imaging of a sample of 47 DSFGs spanning z=1.9-5.7, and construct gravitational lens models of these sources. Our visibility-based lens modeling incorporates several sources of residual interferometric calibration uncertainty, allowing us to properly account for noise in the observations. At least 70% of the sources are strongly lensed by foreground galaxies (mu_870um > 2), with a median magnification mu_870um = 6.3, extending to mu_870um > 30. We compare the intrinsic size distribution of the strongly lensed sources to a similar number of unlensed DSFGs and find no significant differences in spite of a bias between the magnification and intrinsic source size. This may indicate that the true size distribution of DSFGs is relatively narrow. We use the source sizes to constrain the wavelength at which the du...

  6. Constraints on photoionization feedback from number counts of ultra-faint high-redshift galaxies in the Frontier Fields

    CERN Document Server

    Castellano, M; Ferrara, A; Merlin, E; Fontana, A; Amorín, R; Grazian, A; Mármol-Queralto, E; Michałowski, M J; Mortlock, A; Paris, D; Parsa, S; Pilo, S; Santini, P

    2016-01-01

    We exploit a sample of ultra-faint high-redshift galaxies (demagnified HST $H_{160}$ magnitude $>30$) in the Frontier Fields clusters A2744 and M0416 to constrain a theoretical model for the UV luminosity function (LF) in the presence of photoionization feedback. The objects have been selected on the basis of accurate photometric redshifts computed from multi-band photometry including 7 HST bands and deep $K_s$ and IRAC observations. Magnification is computed on an object-by-object basis from all available lensing models of the two clusters. We take into account source detection completeness as a function of luminosity and size, magnification effects and systematics in the lens modeling of the clusters under investigation. We find that our sample of high-$z$ galaxies constrain the cut-off halo circular velocity below which star-formation is suppressed by photo-ionization feedback to $v_c^{\\rm cut} < 50$ km s$^{-1}$. This circular velocity corresponds to a halo mass of $\\approx5.6\\times10^9~M_\\odot$ and $\\a...

  7. Dark-ages reionization and galaxy formation simulation--VII. The sizes of high-redshift galaxies

    CERN Document Server

    Liu, Chuanwu; Poole, Gregory; Angel, Paul; Duffy, Alan; Geil, Paul; Mesinger, Andrei; Wyithe, Stuart

    2016-01-01

    We investigate high-redshift galaxy sizes using a semi-analytic model constructed for the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulation project. Our fiducial model, including strong feedback from supernovae and photoionization background, accurately reproduces the evolution of the stellar mass function and luminosity function. Using this model, we study the size--luminosity relation of galaxies and find that the effective radius scales with UV luminosity as $R_\\mathrm{e}\\propto L^{0.25}$ at $z{\\sim}5$--$9$. We show that recently discovered very luminous galaxies at $z{\\sim}7$ (Bowler et al. 2016) and $z{\\sim}11$ (Oesch et al. 2016) lie on our predicted size--luminosity relations. We find that a significant fraction of galaxies at $z>6$ will not be resolved by JWST, but GMT will have the ability to resolve all galaxies in haloes above the atomic cooling limit. We show that our fiducial model successfully reproduces the redshift evolution of average galaxy sizes at $z>5$. We ...

  8. ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxies

    CERN Document Server

    Decarli, Roberto; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Elbaz, David; Riechers, Dominik; Smail, Ian; Swinbank, Mark; Weiss, Axel; Bacon, Roland; Bauer, Franz; Bell, Eric F; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C; Cox, Pierre; Gónzalez-López, Jorge; Inami, Hanae; Ivison, Rob; Hodge, Jacqueline; Karim, Alex; Magnelli, Benjamin; Ota, Kazuaki; Popping, Gergö; Rix, Hans-Walter; Sargent, Mark; van der Wel, Arjen; van der Werf, Paul

    2016-01-01

    We study the molecular gas properties of high-$z$ galaxies observed in the ALMA Spectroscopic Survey (ASPECS) that targets a $\\sim1$ arcmin$^2$ region in the Hubble Ultra Deep Field (UDF), a blind survey of CO emission (tracing molecular gas) in the 3mm and 1mm bands. Of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. Among these, 11 have infrared luminosities $L_{\\rm{}IR}>10^{11}$ L$_\\odot$, i.e. a detection in CO emission was expected. Out these, 7 are detected at various significance in CO, and 4 are undetected in CO emission. In the CO-detected sources, we find CO excitation conditions that are lower than typically found in starburst/SMG/QSO environments. We use the CO luminosities (including limits for non-detections) to derive molecular gas masses. We discuss our findings in context of previous molecular gas observations at high redshift (star-formation law, gas depletion times, gas fractions): The CO-detected galaxies in the U...

  9. Theoretical predictions for the effect of nebular emission on the broad band photometry of high-redshift galaxies

    CERN Document Server

    Wilkins, Stephen M; Caruana, Joseph; Croft, Rupert; Di Matteo, Tiziana; Khandai, Nishikanta; Feng, Yu; Bunker, Andrew; Elbert, Holly

    2013-01-01

    By combining optical and near-IR observations from the Hubble Space Telescope with NIR photometry from the Spitzer Space Telescope it is possible to measure the rest-frame UV-optical colours of galaxies at z=4-8. The UV-optical spectral energy distribution of star formation dominated galaxies is the result of several different factors. These include the joint distribution of stellar masses, ages, and metallicities, and the subsequent reprocessing by dust and gas in the ISM. Using a large cosmological hydrodynamical simulation we investigate the predicted spectral energy distributions of galaxies at high-redshift with a particular emphasis on assessing the potential contribution of nebular emission. We find that the average pure stellar UV-optical colour correlates with both luminosity and redshift such that galaxies at lower-redshift and higher-luminosity are typically redder. Assuming the escape fraction of ionising photons is close to zero, the effect of nebular emission is to redden the UV-optical 1500-V_w...

  10. Primordial pollution of globular clusters within their host dwarfs embedded in dark matter halos at high redshifts

    CERN Document Server

    Bekki, K

    2006-01-01

    Recent observational studies have revealed star-to-star abundance inhomogeneity among light elements (e.g., C, N, O, Na, and Al) of stars on the main sequence in the Galactic globular clusters (GCs). One of promising interpretations for this result is that the observed abundance inhomogeneity is due to the second generation of stars formed from ejecta of the first generation of evolved stars (e.g., AGB stars) within GCs. However it remains unclear whether and how this primordial pollution can occur within GCs. We here propose a new scenario in which primordial pollution of GCs is highly likely to occur if GCs are located in the central regions of high redshift dark matter subhalos that can host low-mass dwarf galaxies. In this scenario, gas ejected from the first generation of stars of GCs can be effectively trapped in the deep gravitational potential of their host halos and consequently can be consumed for the formation of the second generation of stars without losing a significant amount of gas by ram press...

  11. Enabling the next generation of cm-wavelength studies of high-redshift molecular gas with the SKA

    CERN Document Server

    Wagg, J; Carilli, C L; Walter, F; Aravena, M; Heywood, I; Hodge, J; Murphy, E; Riechers, D; Sargent, M; Wang, R

    2014-01-01

    The Square Kilometre Array will be a revolutionary instrument for the study of gas in the distant Universe. SKA1 will have sufficient sensitivity to detect and image atomic 21 cm HI in individual galaxies at significant cosmological distances, complementing ongoing ALMA imaging of redshifted high-J CO line emission and far-infrared interstellar medium lines such as [CII] 157.7 um. At frequencies below ~50 GHz, observations of redshifted emission from low-J transitions of CO, HCN, HCO+, HNC, H2O and CS provide insight into the kinematics and mass budget of the cold, dense star-forming gas in galaxies. In advance of ALMA band 1 deployment (35 to 52 GHz), the most sensitive facility for high-redshift studies of molecular gas operating below 50~GHz is the Karl G. Jansky Very Large Array (VLA). Here, we present an overview of the role that the SKA could play in molecular emission line studies during SKA1 and SKA2, with an emphasis on studies of the dense gas tracers directly probing regions of active star-formatio...

  12. High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data VI. Sloan Digital Sky Survey Spectrograph Observations

    CERN Document Server

    Anderson, S F; Richards, G T; Schneider, D P; Strauss, M A; Vanden Berk, Daniel E; Gunn, J E; Anderson, Scott F.; Fan, Xiaohui; Richards, Gordon T.; Schneider, Donald P.; Strauss, Michael A.; Berk, Daniel E. Vanden; Gunn, James E.

    2001-01-01

    We present results on over 100 high-redshift quasars found in the Sloan Digital Sky Survey (SDSS), using automated selection algorithms applied to SDSS imaging data and with spectroscopic confirmation obtained during routine spectroscopic operations of the Sloan 2.5-m telescope. The SDSS spectra cover the wavelength range 3900--9200 Angstroms at a spectral resolution of 1800, and have been obtained for 116 quasars with redshifts greater than 3.94; 92 of these objects were previously uncataloged, significantly increasing the current tally of published z>4 quasars. The paper also reports observations of five additional new z>4.6 quasars; all were found from the SDSS imaging survey and spectroscopically confirmed with data from the Apache Point Observatory's 3.5-m telescope. The i' magnitudes of the quasars range from 18.03 to 20.56. Of the 97 new objects in this paper, 13 are Broad Absorption Line quasars. Five quasars, including one object at a redshift of 5.11, have 20 cm peak flux densities greater than 1 mJ...

  13. The Argo Simulation: I. Quenching of Massive Galaxies at High Redshift as a Result of Cosmological Starvation

    CERN Document Server

    Feldmann, Robert

    2014-01-01

    Observations show a prevalence of high redshift galaxies with large stellar masses and predominantly passive stellar populations. A variety of processes have been suggested that could reduce the star formation in such galaxies to observed levels, including quasar mode feedback, virial shock heating, or galactic winds driven by stellar feedback. However, the main quenching mechanisms have yet to be identified. Here we study the origin of star formation quenching using Argo, a cosmological zoom-in simulation that follows the evolution of a massive galaxy at $z\\geq{}2$. This simulation adopts the same sub-grid recipes of the Eris simulations, which have been shown to form realistic disk galaxies, and, in one version, adopts also a mass and spatial resolution identical to Eris. The resulting galaxy has properties consistent with those of observed, massive (M_* ~ 1e11 M_sun) galaxies at z~2 and with abundance matching predictions. Our models do not include AGN feedback indicating that supermassive black holes like...

  14. Pressure distribution of the high-redshift cluster of galaxies CL J1226.9+3332 with NIKA

    CERN Document Server

    Adam, R; Macías-Pérez, J -F; Adane, A; Ade, P; André, P; Beelen, A; Belier, B; Benoît, A; Bideaud, A; Billot, N; Blanquer, G; Bourrion, O; Calvo, M; Catalano, A; Coiffard, G; D'Addabbo, A; Désert, F -X; Doyle, S; Goupy, J; Kramer, C; Leclercq, S; Martino, J; Mauskopf, P; Mayet, F; Monfardini, A; Pajot, F; Pascale, E; Perotto, L; Pointecouteau, E; Ponthieu, N; Revéret, V; Ritacco, A; Rodriguez, L; Savini, G; Schuster, K; Sievers, A; Tucker, C; Zylka, R

    2014-01-01

    The thermal Sunyaev-Zel'Dovich (tSZ) effect is expected to provide a low scatter mass proxy for galaxy clusters since it is directly proportional to the cluster thermal energy. tSZ observations have proven to be a powerful tool to detect and study them but high angular resolution observations are now necessary to push their investigation at higher redshift. In this paper, we report high angular (< 20 arcsec) resolution tSZ observations of the high-redshift cluster CLJ1226.9+3332 (z=0.89). It was imaged at 150 and 260 GHz using the NIKA camera at the IRAM 30-meter telescope. The 150 GHz map shows that CLJ1226.9+3332 is morphologically relaxed on large scales with evidence of a disturbed core, while the 260 GHz channel is used mostly to identify point source contamination. NIKA data are combined with those of Planck and X-ray from Chandra to infer the cluster radial pressure, density, temperature and entropy distributions. The total mass profile of the cluster is derived, and we find $M_{500} = 5.96^{+1.02}_...

  15. Evolution of grain size distribution in high-redshift dusty quasars: Integrating large amounts of dust and unusual extinction curves

    CERN Document Server

    Nozawa, Takaya; Hirashita, Hiroyuki; Takeuchi, Tsutomu T

    2014-01-01

    The discoveries of huge amounts of dust and unusual extinction curves in high-redshift quasars (z > 4) cast challenging issues on the origin and properties of dust in the early universe. In this Letter, we investigate the evolutions of dust content and extinction curve in a high-z quasar, based on the dust evolution model taking account of grain size distribution. First, we show that the Milky-Way extinction curve is reproduced by introducing a moderate fraction (~0.2) of dense molecular-cloud phases in the interstellar medium for a graphite-silicate dust model. Then we show that the peculier extinction curves in high-z quasars can be explained by taking a much higher molecular-cloud fraction (>0.5), which leads to more efficient grain growth and coagulation, and by assuming amorphous carbon instead of graphite. The large dust content in high-z quasar hosts is also found to be a natural consequence of the enhanced dust growth. These results indicate that grain growth and coagulation in molecular clouds are ke...

  16. High Redshift Intergalactic C IV Abundance Measurements from the Near-Infrared Spectra of Two z~6 QSOs

    CERN Document Server

    Simcoe, R A

    2006-01-01

    New measurements of the z~6 intergalactic CIV abundance are presented, using moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South. These data were systematically searched for high redshift CIV absorption lines, using objective selection criteria. Comprehensive tests were performed to quantify sample incompleteness, as well as the rate of false positive CIV identifications. The trend of constant $\\Omega_{CIV}(z)$ observed at z~2-5 appears to continue to z~6, the highest observed redshift. The CIV sample is also consistent with the redshift-invariant form of the CIV column density distribution reported by Songaila (2001) at lower redshift, although with fairly large uncertainties due to a smaller sample size and noisier infrared data. The constant value of $\\Omega_{CIV}$ does not necessarily imply that the IGM was infused with an early metallicity ``floor,'' but the presence of early CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big Bang. The lack of a decline...

  17. X-ray Variability of Blazars

    OpenAIRE

    Pian, Elena

    2002-01-01

    Critical progress in our understanding of high energy emission from AGN has been determined in the last 10 years by X-ray monitoring campaigns with many space missions, notably ROSAT, ASCA, RXTE, BeppoSAX, and XMM, often in conjunction with observations at other frequencies. The emphasis of the present review is on recent findings about X-ray variability of blazars. Among AGN, these exhibit the largest amplitude variations of the X-ray emission, often well correlated with variations at higher...

  18. Looking for High Energy Peaked Blazars

    OpenAIRE

    Costamante, L.; Ghisellini, G.; Celotti, A.; Giommi, P.; Padovani, P.; Tagliaferri, G.; Wolter, A.; Chiaberge, M.; Fossati, G; Pian, E.; L. Maraschi(INAF National Institute for Astrophysics, I-00136 Rome, Italy); Tavecchio, F.; Treves, A.

    2000-01-01

    Blazars can be classified on the basis of their overall Spectral Energy Distribution (SED). BL Lac objects are usually divided in LBL or HBL (Low or High energy peaked BL Lacs), according to the peak frequency of the synchrotron emission, if in the optical or UV-soft-X band respectively. FSRQs instead are characterized by synchrotron peaks mainly at IR-optical frequencies, similarly to LBLs. Here we report on recent BeppoSAX observations which are unveiling the high energy branch of the range...

  19. The Spectral Energy Distribution of Fermi bright blazars

    CERN Document Server

    Abdo, A A; Ajello, M; Axelsson, M; 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; 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; Charles, E; Chaty, S; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Silva, E do Couto e; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fuhrmann, L; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Healey, S E; Horan, D; Hughes, R E; Itoh, R; Jackson, M S; Johannesson, G; Johnson, A S; Johnson, W N; Kadler, M; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knodlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Max-Moerbeck, W; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F

    2009-01-01

    (Abridged) We have conducted a detailed investigation of the broad-band spectral properties of the \\gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous Spectral Energy Distributions (SED) for 48 LBAS blazars.The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual Log $\

  20. Correlation between -Ray and Radio Bands for -Ray Loud Blazars

    Indian Academy of Sciences (India)

    D. X. Wu; J. H. Fan; S. H. Li

    2014-09-01

    The most identified sources observed by Fermi are blazars (Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BLs). In this paper, we obtained 124 -ray loud blazars with available -ray and radio (core and total) data. It is interesting that the -ray luminosity have a good correlation with the radio luminosity. This phenomenon exists in the core radio luminosity (c) and total radio luminosity (t). The correlation between the -ray and the radio luminosities is still stronger even after we eliminated the redshift effect, which suggests that the -ray radiations in the -ray loud blazars are strongly beamed.

  1. High-energy properties of the high-redshift flat spectrum radio quasar PKS 2149-306

    CERN Document Server

    D'Ammando, F

    2015-01-01

    We investigate the gamma-ray and X-ray properties of the flat spectrum radio quasar PKS 2149-306 at redshift z = 2.345. A strong gamma-ray flare from this source was detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope satellite in 2013 January, reaching on January 20 a daily peak flux of (301$\\pm$36)$\\times$10$^{-8}$ ph/cm$^2$/s in the 0.1-100 GeV energy range. This flux corresponds to an apparent isotropic luminosity of (1.5$\\pm$0.2)$\\times$10$^{50}$ erg/s, comparable to the highest values observed by a blazar so far. During the flare the increase of flux was accompanied by a significant change of the spectral properties. Moreover significant flux variations on a 6-h time-scale were observed, compatible with the light crossing time of the event horizon of the central black hole. The broad band X-ray spectra of PKS 2149-306 observed by Swift-XRT and NuSTAR are well described by a broken power-law model, with a very hard spectrum ($\\Gamma$$_1$ $\\sim$ 1) below the break energy, at ...

  2. Central black hole mass determination for blazars

    Institute of Scientific and Technical Information of China (English)

    Yuan Yu-Hai; Fan Jun-Hui; Huang Yong

    2008-01-01

    In this paper, we use a method to determine some basic parameters for the (r)-ray loud blazars. The parameters include the central black mass (M), the boosting factor (δ), the propagation angle (φ), the distance along the axis to the site of the (r)-ray production (d). A sample including 32 (r)-ray loud blazars with available variability time scaleshas been used to discuss the above properties. In this method, the (r)-ray energy, the emission size and the property of the accretion disc determine the absorption effect. If we take the intrinsic(γ)-ray luminosity to be λ Times the Eddington luminosity, I.e. Lin(r) =λLedd, then we have the following results: the mass of the black hole is in the range of (0.59 - 67.99) ⊙ (λ= 1.0) or (0.90 - 104.13) ⊙ (λ = 0.1); the boosting factor (δ) in the range of 0.16 - 2.09(λ=1.0) or 0.24 - 2.86 (λ=0.1); the angle (φ) in the range of 9.53 (λ =1.0) or 7.36°=0.1); and the distance (d/Rg) in the range of 22.39 - 609.36 (λ= 1.0) or 17.54 - 541.88 (λ = 0.1).

  3. FACT. Flare alerts from blazar monitoring

    International Nuclear Information System (INIS)

    One of the major goals of the First G-APD Cherenkov Telescope is the longterm monitoring of bright TeV blazars. For more than three years, FACT has observed the blazars Mrk 421 and Mrk 501 and a few other sources on a regular basis. To understand these highly variable objects, simultaneous data at different wavelengths are very useful. FACT is not only taking part in multi-wavelength campaigns, but also sending alerts to other instruments in case of enhanced flux, to study flares within the multi-wavelength frame. To send fast alerts, an automatic quick look analysis was set up on site. Once the data are written on disk, they are automatically processed, and the analysis results are published on a website where other observers can monitor the activity of the source in the very high energy band. In addition, alerts are sent in case the flux is higher than a certain predefined value. In 2014, more than five alerts have been sent. Results from three years of monitoring are presented.

  4. FACT. Flare alerts from blazar monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Dorner, Daniela [Universitaet Wuerzburg (Germany); Bretz, Thomas [RWTH Aachen (Germany); Collaboration: FACT-Collaboration

    2015-07-01

    One of the major goals of the First G-APD Cherenkov Telescope is the longterm monitoring of bright TeV blazars. For more than three years, FACT has observed the blazars Mrk 421 and Mrk 501 and a few other sources on a regular basis. To understand these highly variable objects, simultaneous data at different wavelengths are very useful. FACT is not only taking part in multi-wavelength campaigns, but also sending alerts to other instruments in case of enhanced flux, to study flares within the multi-wavelength frame. To send fast alerts, an automatic quick look analysis was set up on site. Once the data are written on disk, they are automatically processed, and the analysis results are published on a website where other observers can monitor the activity of the source in the very high energy band. In addition, alerts are sent in case the flux is higher than a certain predefined value. In 2014, more than five alerts have been sent. Results from three years of monitoring are presented.

  5. THE XMM CLUSTER SURVEY: THE BUILD-UP OF STELLAR MASS IN BRIGHTEST CLUSTER GALAXIES AT HIGH REDSHIFT

    International Nuclear Information System (INIS)

    We present deep J- and Ks -band photometry of 20 high redshift galaxy clusters between z = 0.8 and1.5, 19 of which are observed with the MOIRCS instrument on the Subaru telescope. By using near-infrared light as a proxy for stellar mass we find the surprising result that the average stellar mass of Brightest Cluster Galaxies (BCGs) has remained constant at ∼9 x 1011 M sun since z ∼ 1.5. We investigate the effect on this result of differing star formation histories generated by three well-known and independent stellar population codes and find it to be robust for reasonable, physically motivated choices of age and metallicity. By performing Monte Carlo simulations we find that the result is unaffected by any correlation between BCG mass and cluster mass in either the observed or model clusters. The large stellar masses imply that the assemblage of these galaxies took place at the same time as the initial burst of star formation. This result leads us to conclude that dry merging has had little effect on the average stellar mass of BCGs over the last 9-10 Gyr in stark contrast to the predictions of semi-analytic models, based on the hierarchical merging of dark matter halos, which predict a more protracted mass build-up over a Hubble time. However, we discuss that there is potential for reconciliation between observation and theory if there is a significant growth of material in the intracluster light over the same period.

  6. GRB 120521C at z ∼ 6 and the properties of high-redshift γ-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Laskar, Tanmoy; Berger, Edo; Zauderer, B. Ashley; Margutti, Raffaella; Fong, Wen-fai [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Tanvir, Nial; Wiersema, Klaas [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Levan, Andrew [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Perley, Daniel [Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Menten, Karl [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Hrudkova, Marie [Isaac Newton Group of Telescopes, Apartado de Correos 321, E-387 00 Santa Cruz de la Palma, Canary Islands (Spain)

    2014-01-20

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm{sup –3}. The radio observations reveal the presence of a jet break at t {sub jet} ≈ 7 d, corresponding to a jet opening angle of θ{sub jet} ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E {sub γ} ≈ E{sub K} ≈ 3 × 10{sup 50} erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z ≳ 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t {sub jet} ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ∼ 8.

  7. THE MOST METAL-POOR DAMPED Lyα SYSTEMS: AN INSIGHT INTO DWARF GALAXIES AT HIGH-REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, Ryan J. [Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Pettini, Max [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Jorgenson, Regina A., E-mail: rcooke@ucolick.org [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-02-10

    In this paper we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyα systems (DLAs), to uncover their links to modern-day galaxies. We present evidence that the DLA population as a whole exhibits a ''knee'' in the relative abundances of the α-capture and Fe-peak elements when the metallicity is [Fe/H] ≅ –2.0, assuming that Zn traces the buildup of Fe-peak elements. In this respect, the chemical evolution of DLAs is clearly different from that experienced by Milky Way halo stars, but resembles that of dwarf spheroidal galaxies in the Local Group. We also find a close correspondence between the kinematics of Local Group dwarf galaxies and of high-redshift metal-poor DLAs, which further strengthens this connection. On the basis of such similarities, we propose that the most metal-poor DLAs provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. To this end, we have measured some of the key physical properties of the DLA gas, including their neutral gas mass, size, kinetic temperature, density, and turbulence. We find that metal-poor DLAs contain a warm neutral medium with T {sub gas} ≅ 9600 K predominantly held up by thermal pressure. Furthermore, all of the DLAs in our sample exhibit a subsonic turbulent Mach number, implying that the gas distribution is largely smooth. These results are among the first empirical descriptions of the environments where the first few generations of stars may have formed in the universe.

  8. Dark-ages Reionization and Galaxy formation simulation - I. The dynamical lives of high-redshift galaxies

    Science.gov (United States)

    Poole, Gregory B.; Angel, Paul W.; Mutch, Simon J.; Power, Chris; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, Stuart B.

    2016-07-01

    We present the Dark-ages Reionization and Galaxy formation Observables from Numerical Simulations (DRAGONS) programme and Tiamat, the collisionless N-body simulation programme upon which DRAGONS is built. The primary trait distinguishing Tiamat from other large simulation programme is its density of outputs at high redshift (100 from z = 35 to z = 5; roughly one every 10 Myr) enabling the construction of very accurate merger trees at an epoch when galaxy formation is rapid and mergers extremely frequent. We find that the friends-of-friends halo mass function agrees well with the prediction of Watson et al. at high masses, but deviates at low masses, perhaps due to our use of a different halo finder or perhaps indicating a break from `universal' behaviour. We then analyse the dynamical evolution of galaxies during the Epoch of Reionization finding that only a small fraction (˜20 per cent) of galactic haloes are relaxed. We illustrate this using standard relaxation metrics to establish two dynamical recovery time-scales: (i) haloes need ˜1.5 dynamical times following formation, and (ii) ˜2 dynamical times following a major (3:1) or minor (10:1) merger to be relaxed. This is remarkably consistent across a wide mass range. Lastly, we use a phase-space halo finder to illustrate that major mergers drive long-lived massive phase-space structures which take many dynamical times to dissipate. This can yield significant differences in the inferred mass build-up of galactic haloes and we suggest that care must be taken to ensure a physically meaningful match between the galaxy formation physics of semi-analytic models and the halo finders supplying their input.

  9. GRB 120521C at z ∼ 6 and the properties of high-redshift γ-ray bursts

    International Nuclear Information System (INIS)

    We present optical, near-infrared, and radio observations of the afterglow of GRB 120521C. By modeling the multi-wavelength data set, we derive a photometric redshift of z ≈ 6.0, which we confirm with a low signal-to-noise ratio spectrum of the afterglow. We find that a model with a constant-density environment provides a good fit to the afterglow data, with an inferred density of n ≲ 0.05 cm–3. The radio observations reveal the presence of a jet break at t jet ≈ 7 d, corresponding to a jet opening angle of θjet ≈ 3°. The beaming-corrected γ-ray and kinetic energies are E γ ≈ EK ≈ 3 × 1050 erg. We quantify the uncertainties in our results using a detailed Markov Chain Monte Carlo analysis, which allows us to uncover degeneracies between the physical parameters of the explosion. To compare GRB 120521C to other high-redshift bursts in a uniform manner we re-fit all available afterglow data for the two other bursts at z ≳ 6 with radio detections (GRBs 050904 and 090423). We find a jet break at t jet ≈ 15 d for GRB 090423, in contrast to previous work. Based on these three events, we find that γ-ray bursts (GRBs) at z ≳ 6 appear to explode in constant-density environments, and exhibit a wide range of energies and densities that span the range inferred for lower redshift bursts. On the other hand, we find a hint for narrower jets in the z ≳ 6 bursts, potentially indicating a larger true event rate at these redshifts. Overall, our results indicate that long GRBs share a common progenitor population at least to z ∼ 8.

  10. Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

    Science.gov (United States)

    Ledoux, C.; Vreeswijk, P. M.; Smette, A.; Fox, A. J.; Petitjean, P.; Ellison, S. L.; Fynbo, J. P. U.; Savaglio, S.

    2009-11-01

    Aims: We aim to understand the nature of the absorbing neutral gas in the galaxies hosting high-redshift long-duration gamma-ray bursts (GRBs) and to determine their physical conditions. Methods: A detailed analysis of high-quality VLT/UVES spectra of the optical afterglow of GRB 050730 and other Swift-era bursts is presented. Results: We report the detection of a significant number of previously unidentified allowed transition lines of Fe^+, involving the fine structure of the ground term ( ^6D{7/2}, ^6D{5/2}, ^6D{3/2}, ^6D{1/2}) and that of other excited levels (^4F{9/2}, ^4F{7/2}, ^4F{5/2}, ^4F{3/2}, ^4D{7/2}, ^4D{5/2}), from the zabs = 3.969, log N(H^0) = 22.10, damped Lyman-α (DLA) system located in the host galaxy of GRB 050730. No molecular hydrogen (H2) is detected down to a molecular fraction of log f 1.8 GRB host galaxies observed with VLT/UVES. We show that the lack of H2 can be explained by the low metallicities, [X/H] Fiore, and 075.A-0385, 077.D-0661, 080.D-0526, and 081.A-0856, P.I. Vreeswijk, with the Ultraviolet and Visual Echelle Spectrograph (UVES) installed at the Nasmyth-B focus of the Very Large Telescope (VLT), Unit 2 - Kueyen, operated by the European Southern Observatory (ESO) on Cerro Paranal in Chile.

  11. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Smolcic, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. Muenchen (Germany); Navarrete, F.; Bertoldi, F. [Argelander Institut for Astronomy, Auf dem Huegel 71, Bonn D-53121 (Germany); Aravena, M.; Sheth, K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Ilbert, O. [Laboratoire d' Astrophysique de Marseille, Universite de Provence, CNRS, BP 8, Traverse du Siphon, F-13376 Marseille Cedex 12 (France); Yun, M. S. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Salvato, M.; Finoguenov, A. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); McCracken, H. J. [Institut d' Astrophysique de Paris, UMR7095 CNRS, Universit Pierre et Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Diener, C. [Institute for Astronomy, ETH Zrich, Wolfgang-Pauli-strasse 27, 8093 Zurich (Switzerland); Aretxaga, I.; Hughes, D.; Wilson, G. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Aptdo. Postal 51 y 216, 72000 Puebla, Pue. (Mexico); Riechers, D. A.; Capak, P.; Scoville, N. Z. [Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Karim, A.; Schinnerer, E. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, Heidelberg D-69117 (Germany)

    2012-05-01

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F{sub 1m} > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, {approx}10''-30'', resolution. All three sources-AzTEC/C1, Cosbo-3, and Cosbo-8-are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution ({approx}2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z {approx}> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 {+-} 1.2, 1.9{sup +0.9}{sub -0.5}, and {approx}4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of {approx}> 1000 M{sub Sun} yr{sup -1}and IR luminosities of {approx}10{sup 13} L{sub Sun} consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z {approx} 2 and today's passive galaxies.

  12. Quasars as the formation sites of high-redshift ellipticals: a signature in the `associated' absorption-line systems?

    Science.gov (United States)

    Franceschini, A.; Gratton, R.

    1997-03-01

    Published data on the average metallicities and abundance ratios for absorption-line systems in high-redshift quasars suggest that a dichotomy may exist between the chemical composition of damped Lyman alpha (Lyalpha) systems (interpreted as intervening galaxies in the QSO line of sight) and the z_abs~=z_em absorption- line systems associated with the quasar. Intervening systems have smaller than solar metallicities, whereas associated absorbers have solar or greater than solar metallicities and small N/C ratios. While these results have to be confirmed by more precise abundance determinations, we argue that they may be explained by an early phase of efficient metal enrichment occurring only in the close environment of high-z QSOs, and characterized by an excess type-II supernova (SNII) activity. This is reminiscent of the SNII phase required to explain the abundance ratios (favouring alpha- over Fe-group elements) observed in the intracluster (IC) medium of local galaxy clusters. We explore the following scenario, to be tested by forthcoming observations of QSO absorption lines using very large optical telescopes. (a) Well-studied damped- Lyalpha, Lyalpha and metal lines in intervening systems trace only part of the history of metal production in the Universe - the one concerning slowly star-forming discs or dwarf irregulars. (b) The complementary class of early-type and bulge-dominated galaxies formed quickly (at z>~4-5) through a huge episode of star formation favouring high-mass stars. (c) The nucleus of the latter is the site of the subsequent formation of a quasar, which partly hides from view the dimmer host galaxy. (d) The products of a galactic wind, following the violent episode of star formation in the host galaxy and metal pollution of the IC medium in the forming cluster, could be directly observable in the z_abs~=z_em associated absorption systems on the QSO line of sight.

  13. QUEST FOR COSMOS SUBMILLIMETER GALAXY COUNTERPARTS USING CARMA AND VLA: IDENTIFYING THREE HIGH-REDSHIFT STARBURST GALAXIES

    International Nuclear Information System (INIS)

    We report on interferometric observations at 1.3 mm at 2''-3'' resolution using the Combined Array for Research in Millimeter-wave Astronomy. We identify multi-wavelength counterparts of three submillimeter galaxies (SMGs; F1m > 5.5 mJy) in the COSMOS field, initially detected with MAMBO and AzTEC bolometers at low, ∼10''-30'', resolution. All three sources—AzTEC/C1, Cosbo-3, and Cosbo-8—are identified to coincide with positions of 20 cm radio sources. Cosbo-3, however, is not associated with the most likely radio counterpart, closest to the MAMBO source position, but with that farther away from it. This illustrates the need for intermediate-resolution (∼2'') mm-observations to identify the correct counterparts of single-dish-detected SMGs. All of our three sources become prominent only at NIR wavelengths, and their mm-to-radio flux based redshifts suggest that they lie at redshifts z ∼> 2. As a proof of concept, we show that photometric redshifts can be well determined for SMGs, and we find photometric redshifts of 5.6 ± 1.2, 1.9+0.9–0.5, and ∼4 for AzTEC/C1, Cosbo-3, and Cosbo-8, respectively. Using these we infer that these galaxies have radio-based star formation rates of ∼> 1000 M☉ yr–1and IR luminosities of ∼1013 L☉ consistent with properties of high-redshift SMGs. In summary, our sources reflect a variety of SMG properties in terms of redshift and clustering, consistent with the framework that SMGs are progenitors of z ∼ 2 and today's passive galaxies.

  14. Blazar flares powered by plasmoids in relativistic reconnection

    CERN Document Server

    Petropoulou, Maria; Sironi, Lorenzo

    2016-01-01

    Powerful flares from blazars with short ($\\sim$ min) variability timescales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e., plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours--days powered by the largest and slowest moving plasmoids th...

  15. Optical Counterparts of Undetermined Type -Ray Active Galactic Nuclei with Blazar-Like Spectral Energy Distributions

    Indian Academy of Sciences (India)

    Giovanni La Mura; Graziano Chiaro; Stefano Ciroi; Piero Rafanelli; David Salvetti; Marco Berton; Valentina Cracco; Fermi-LAT collaboration

    2015-12-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 -ray sources above a 4 significance level. Although most of the extra-galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections (∼30%) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN -ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet, which, in the case of blazars, is oriented very close to our line-of-sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with -rays, providing a much better source localization potential, we focused our attention on a sample of -ray Blazar Candidates of Undetermined type (BCUs), starting a campaign of optical spectroscopic observations. The main aims of our investigation include a census of the AGN families that contribute to -ray emission and a study of their redshift distribution, with the subsequent implications on the intrinsic source power. We furthermore analyze which -ray properties can better constrain the nature of the source, thus helping in the study of objects not yet associated with a reliable low frequency counterpart. Here we report on the instruments and techniques used to identify the optical counterparts of -ray sources, we give an overview on the status of our work, and we discuss the implications of a large scale study of -ray emitting AGNs.

  16. Relaxation of Blazar Induced Pair Beams in Cosmic Voids

    OpenAIRE

    Miniati, Francesco; Elyiv, Andrii

    2012-01-01

    The stability properties of a low density ultra relativistic pair beam produced in the intergalactic medium by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could affect considerably the thermal history of the intergalactic medium and structure formation. We use a Monte Carlo method to quantify the properties of the blazar induced electromagnetic...

  17. Swift BAT, Fermi LAT, and the Blazar Sequence

    CERN Document Server

    Sambruna, R M; Ajello, M; Maraschi, L

    2009-01-01

    Using public \\fermi LAT and \\swift BAT observations, we constructed the first sample of blazars selected at both hard X-rays and gamma-rays. Studying its spectral properties, we find a luminosity dependence of the spectral slopes at both energies. Specifically, luminous blazars, generally classified as FSRQs, have {\\it hard} continua in the medium-hard X-ray range but {\\it soft} continua in the LAT gamma-ray range (photon indices $\\Gamma_X$ \\ltsima 2 and $\\Gamma_G$ \\gtsima 2), while lower luminosity blazars, classified as BL Lacs, have opposite behavior, i.e., {\\it soft} X-ray and {\\it hard} gamma-ray continua ($\\Gamma_X$ \\gtsima 2.4 and $\\Gamma_G < 2$). The trends are confirmed by detailed Monte Carlo simulations explicitly taking into account the observational biases of both instruments. Our results support the so-called ``blazar sequence'' which was originally based on radio samples of blazars and radio luminosities. We also argue that the X-ray-to-gamma-ray continua of blazars may provide independent i...

  18. Time Variability Analysis of the SMARTS Monitoring of Fermi Blazars

    CERN Document Server

    Chatterjee, Ritaban; Bonning, E W; Buxton, M; Coppi, P; Isler, J; Urry, C M

    2011-01-01

    We present the time variability properties of a sample of six blazars, AO 0235+164, 3C 273, 3C 279, PKS 1510-089, PKS 2155-304, and 3C 454.3, at optical-near IR frequencies as well as Gamma-ray energies observed as a part of the Yale/SMARTS program during 2008-2010 that has followed the variations in emission of the bright Fermi-LAT-monitored blazars in the southern sky with closely-spaced observations at BVRJK bands. The discrete auto-correlation function of the variability of these six blazars at optical-IR and Gamma-ray energies do not show any periodicity or characteristic timescale. The power spectral density (PSD) functions of the R-band variability of all six blazars are fit well by simple power-law functions with negative slope implying there is higher amplitude variability on longer than on shorter timescales. Average slope of the PSD of R-band variability of these blazars is similar to what was found by the Fermi team for the Gamma-ray variability of a larger sample of bright blazars. The shortest t...

  19. Modeling the flaring activity of the high z, hard X-ray selected blazar IGR J22517+2217

    CERN Document Server

    Lanzuisi, G; Ghisellini, G; Ubertini, P; Panessa, F; Ajello, M; Bassani, L; Fukazawa, Y; D'Ammando, F

    2011-01-01

    We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray data from INTEGRAL and Swift-BAT survey, to investigate the physical properties of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217, through the modelization of its broad band spectral energy distribution (SED) in two different activity states. Through the analysis of the new Suzaku data and the flux selected data from archival hard X-ray observations, we build the source SED in two different states, one for the newly discovered flare occurred in 2005 and one for the following quiescent period. Both SEDs are strongly dominated by the high energy hump peaked at 10^20 -10^22 Hz, that is at least two orders of magnitude higher than the low energy (synchrotron) one at 10^11 -10^14 Hz, and varies by a factor of 10 between the two states. In both states the high energy hump is modeled as inverse Compton emission between relativistic electrons and seed photons produced externally to the jet, while the synchrotron self-Co...

  20. Gamma-ray flaring activity from the gravitationally lensed blazar PKS 1830-211 observed by Fermi LAT

    CERN Document Server

    Abdo, A A; Ajello, M; Allafort, A; Amin, M A; Baldini, L; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Blandford, R D; Bonamente, E; Borgland, A W; Bregeon, J; Brigida, M; Buehler, R; Bulmash, D; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cavazzuti, E; Cecchi, C; Charles, E; Cheung, C C; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Corbet, R H D; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Dermer, C D; Drell, P S; Drlica-Wagner, A; Favuzzi, C; Finke, J; Focke, W B; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Grenier, I A; Grove, J E; Guiriec, S; Hadasch, D; Hayashida, M; Hays, E; Hughes, R E; Inoue, Y; Jackson, M S; Jogler, T; Jòhannesson, G; Johnson, A S; Kamae, T; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Mazziotta, M N; Mehault, J; Michelson, P F; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohno, M; Ohsugi, T; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reyes, L C; Ritz, S; Romoli, C; Roth, M; Parkinson, P M Saz; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Takahashi, H; Takeuchi, Y; Tanaka, T; Thayer, J G; Thayer, J B; Thompson, D J; Tibaldo, L; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Tronconi, V; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Werner, M; Winer, B L; Wood, K S

    2014-01-01

    The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope routinely detects the highly dust-absorbed, reddened, and MeV-peaked flat spectrum radio quasar PKS 1830-211 (z=2.507). Its apparent isotropic gamma-ray luminosity (E>100 MeV) averaged over $\\sim$ 3 years of observations and peaking on 2010 October 14/15 at 2.9 X 10^{50} erg s^{-1}, makes it among the brightest high-redshift Fermi blazars. No published model with a single lens can account for all of the observed characteristics of this complex system. Based on radio observations, one expects time delayed variability to follow about 25 days after a primary flare, with flux about a factor 1.5 less. Two large gamma-ray flares of PKS 1830-211 have been detected by the LAT in the considered period and no substantial evidence for such a delayed activity was found. This allows us to place a lower limit of about 6 on the gamma rays flux ratio between the two lensed images. Swift XRT observations from a dedicated Target of Opportunity program ...

  1. Optical counterparts of undetermined type $\\gamma$-ray Active Galactic Nuclei with blazar-like Spectral Energy Distributions

    CERN Document Server

    La Mura, G; Ciroi, S; Rafanelli, P; Salvetti, D; Berton, M; Cracco, V

    2015-01-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 $\\gamma$-ray sources above a 4$\\sigma$ significance level. Although most of the extra-Galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections ($\\sim 30\\%$) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN $\\gamma$-ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet that, in the case of blazars, is oriented very close to our line of sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with $\\gamma$-rays, providing a much better source localization potential, we focused our attention on a sample of $\\gamma$-ray Blazar Candidates of Undetermined Type (BCUs), starting a campaign of optical spectroscopic observations. The...

  2. Why Have Many of the Brightest Radio-loud Blazars Not Been Detected in Gamma-Rays by Fermi?

    Science.gov (United States)

    Lister, M. L.; Aller, M. F.; Aller, H. D.; Hovatta, T.; Max-Moerbeck, W.; Readhead, A. C. S.; Richards, J. L.; Ros, E.

    2015-09-01

    We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1 GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below {10}13.4 Hz also tend to have high-energy peaks that lie below the 0.1 GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5 Jy sample also have significantly lower 15 GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the 3FGL catalog. Based on their observed properties, we have identified several bright radio-selected blazars that are strong candidates for future detection by Fermi.

  3. The line emissions and polarization in blazars

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The correlations between broad-line emission,polarization,and core-dominance parameters are investigated for a sample of 148 blazars(BL Lacertae objects-BLs and flat spectrum radio quasars-FSRQs). An anti-correlation between the broad-line luminosity and the linear polarization is found. The broad-line and polarization relation can be explained by using a relativistic beaming model,which perhaps suggests that BL Lacs and FSRQs are a single class. We also investigated the relation between the ratio of the broad-line luminosity to the Eddington luminosity and linear polarization,and that between the ratio of the broad-line luminosity to the Eddington luminosity and the core-dominance parameter.

  4. Multi-waveband Behavior of Blazars

    Directory of Open Access Journals (Sweden)

    Marscher Alan P.

    2013-12-01

    Full Text Available The author reviews recent progress toward understanding blazars that multi-waveband monitoring observations have advanced. The primary techniques include the compilation of multi-waveband light curves, multi-epoch VLBI images at radio wavelengths, plots of linear polarization vs. time at radio through optical wavelengths, and spectral energy distributions (SEDs. Correlations and the coincidence or lag of events across wavebands and in the images indicate where the events take place relative to the “core” that lies ≳ 0.5 pc from the central engine. Rotations of the polarization electric vector suggest a helical geometry of the magnetic field upstream of the millimeter-wave core, while rapid fluctuations in degree and position angle of polarization imply that the jet plasma is turbulent in and downstream of the core. The author is developing a numerical model that simulates the emission from such turbulence as it interacts with a conical standing shock in the core region.

  5. BLAZAR MONITORING WITH THE WATCHER ROBOTIC TELESCOPE

    Directory of Open Access Journals (Sweden)

    Pete Tisdall

    2014-01-01

    Full Text Available Presentamos informaci ́on sobre una intensa campa ̃na de obs ervaciones de blazars de rayos gamma en el ́optico que estamos llevando a cabo capaz de observar variabilidad ́ optica de corta y larga duraci ́on para fuentes del hemisferio sur. Diez fuentes est ́an siendo observadas dent ro de este programa con ́enfasis en PKS 2155-304 y PKS 2005-489 durante el invierno austral de 2013. Ambas fuen tes fueron observadas con 3 filtros (V, R e I obteniendo alrededor de 20,000 im ́agenes durante un period o de 5 meses. Un an ́alisis preliminar parcial de los datos indica que no hubo episodios de gran actividad en la ban da ́optica.

  6. FACT - Monitoring Blazars at Very High Energies

    CERN Document Server

    Dorner, D; Bergmann, M; Biland, A; Balbo, M; Bretz, T; Buss, J; Einecke, S; Freiwald, J; Hempfling, C; Hildebrand, D; Hughes, G; Lustermann, W; Mannheim, K; Meier, K; Mueller, S; Neise, D; Neronov, A; Overkemping, A -K; Paravac, A; Pauss, F; Rhode, W; Steinbring, T; Temme, F; Thaele, J; Toscano, S; Vogler, P; Walter, R; Wilbert, A

    2015-01-01

    The First G-APD Cherenkov Telescope (FACT) was built on the Canary Island of La Palma in October 2011 as a proof of principle for silicon based photosensors in Cherenkov Astronomy. The scientific goal of the project is to study the variability of active galatic nuclei (AGN) at TeV energies. Observing a small sample of TeV blazars whenever possible, an unbiased data sample is collected. This allows to study the variability of the selected objects on timescales from hours to years. Results from the first three years of monitoring will be presented. To provide quick flare alerts to the community and trigger multi-wavelength observations, a quick look analysis has been installed on-site providing results publicly online within the same night. In summer 2014, several flare alerts were issued. Results of the quick look analysis are summarized.

  7. BALANCING THE ENERGY BUDGET BETWEEN STAR FORMATION AND ACTIVE GALACTIC NUCLEI IN HIGH-REDSHIFT INFRARED LUMINOUS GALAXIES

    International Nuclear Information System (INIS)

    We present deep Spitzer mid-infrared spectroscopy, along with 16, 24, 70, and 850 μm photometry, for 22 galaxies located in the Great Observatories Origins Deep Survey-North (GOODS-N) field. The sample spans a redshift range of 0.6 ∼AB > 25 mag) sources. We find that infrared (IR; 8-1000 μm) luminosities derived by fitting local spectral energy distributions (SEDs) with 24 μm photometry alone are well matched to those when additional mid-infrared spectroscopic and longer wavelength photometric data are used for galaxies having z ∼12 L sun. However, for galaxies in the redshift range between 1.4 ∼3 x 1012 L sun, IR luminosities are overestimated by an average factor of ∼5 when SED fitting with 24 μm photometry alone. This result arises partly due to the fact that high-redshift galaxies exhibit aromatic feature equivalent widths that are large compared to local galaxies of similar luminosities. Using improved estimates for the IR luminosities of these sources, we investigate whether their infrared emission is found to be in excess relative to that expected based on extinction-corrected UV star formation rates (SFRs), possibly suggesting the presence of an obscured AGN. Through a spectral decomposition of mid-infrared spectroscopic data, we are able to isolate the fraction of IR luminosity arising from an AGN as opposed to star formation activity. This fraction is only able to account for ∼30% of the total IR luminosity among the entire sample and ∼35% of the 'excess' IR emission among these sources, on average, suggesting that AGNs are not the dominant cause of the inferred 'mid-infrared excesses' in these systems. Of the sources identified as having mid-infrared excesses, half are accounted for by using proper bolometric corrections while half show the presence of obscured AGNs. This implies sky and space densities for Compton-thick AGNs of ∼1600 deg.-2 and ∼1.3 x 10-4 Mpc-3, respectively. We also note that IR luminosities derived from SED

  8. HIGH-REDSHIFT STAR-FORMING GALAXIES: ANGULAR MOMENTUM AND BARYON FRACTION, TURBULENT PRESSURE EFFECTS, AND THE ORIGIN OF TURBULENCE

    International Nuclear Information System (INIS)

    The structure of a sample of high-redshift (z ∼ 2), rotating galaxies with high star formation rates and turbulent gas velocities of σ ∼ 40-80 km s-1 is investigated. Fitting the observed disk rotational velocities and radii with a Mo et al. (MMW) model requires unusually large disk spin parameters λd>0.1 and disk-to-dark halo mass fractions of md ∼ 0.2, close to the cosmic baryon fraction. The galaxies segregate into dispersion-dominated systems with 1 ≤ vmax/σ ≤ 3, maximum rotational velocities vmax≤ 200 km s-1, and disk half-light radii r1/2∼ 1-3 kpc, and rotation-dominated systems with vmax> 200 km s-1, vmax/σ>3, and r1/2∼ 4-8 kpc. For the dispersion-dominated sample, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities. Including this pressure effect in the MMW model, dispersion-dominated galaxies can be fitted well with spin parameters of λd = 0.03-0.05 for high disk mass fractions of md ∼ 0.2 and with λd = 0.01-0.03 for md ∼ 0.05. These values are in good agreement with cosmological expectations. For the rotation-dominated sample, however, pressure effects are small and better agreement with theoretically expected disk spin parameters can only be achieved if the dark halo mass contribution in the visible disk regime (2-3 x r1/2) is smaller than predicted by the MMW model. We argue that these galaxies can still be embedded in standard cold dark matter halos if the halos do not contract adiabatically in response to disk formation. In this case, the data favor models with small disk mass fractions of md = 0.05 and disk spin parameters of λd ∼ 0.035. It is shown that the observed high turbulent gas motions of the galaxies are consistent with a Toomre instability parameter Q = 1 which is equal to the critical value, expected for gravitational disk instability to be the major driver of turbulence. The dominant energy source of turbulence is then the potential energy of the gas in the

  9. Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program

    CERN Document Server

    Richards, Joseph L; Pavlidou, Vasiliki; King, Oliver G; Pearson, Timothy J; Readhead, Anthony C S; Reeves, Rodrigo; Shepherd, Martin C; Stevenson, Matthew A; Weintraub, Lawrence C; Fuhrmann, Lars; Angelakis, Emmanouil; Zensus, J Anton; Healey, Stephen E; Romani, Roger W; Shaw, Michael S; Grainge, Keith; Birkinshaw, Mark; Lancaster, Katy; Worrall, Diana M; Taylor, Gregory B; Cotter, Garret; Bustos, Ricardo

    2010-01-01

    The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40-m telescope at the Owens Valley Radio Observatory (OVRO). This program began with the 1158 northern (declination>-20 deg) sources from the Candidate Gamma-ray Blazar Survey (CGRaBS) and now encompasses over 1500 sources, each observed twice per week with a ~4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrat...

  10. Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets

    CERN Document Server

    Baring, Matthew G; Summerlin, Errol J

    2016-01-01

    Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broadband continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-LAT spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multi-wavelength spectra spanning optical to X-ray to gamma-ray bands can be used to probe diffusive acceleration in relativistic, oblique, magnetohydrodynamic (MHD) shocks in blazar jets. Diagnostics on the MHD turbulence near such shocks are obtained using thermal and non-thermal particle distributions resulting from detailed Monte Carlo simulations of DSA. These probes are afforded by the characteristic property that the synchrotron $\

  11. A spine-sheath model for strong-line blazars

    Science.gov (United States)

    Sikora, Marek; Rutkowski, Mieszko; Begelman, Mitchell C.

    2016-04-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of `the blazar zone'. We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why γ-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme γ-ray events.

  12. Spectral and Polarization Signatures of Relativistic Shocks in Blazars

    CERN Document Server

    Boettcher, Markus

    2016-01-01

    Relativistic shocks are one of the most plausible sites of the emission of strongly variable, polarized multi-wavelength emission from relativistic jet sources such as blazars, via diffusive shock acceleration (DSA) of relativistic particles. This paper summarizes recent results on a self-consistent coupling of diffusive shock acceleration and radiation transfer in blazar jets. We demonstrate that the observed spectral energy distributions (SEDs) of blazars strongly constrain the nature of hydromagnetic turbulence responsible for pitch-angle scattering by requiring a strongly energy-dependent pitch-angle mean free path. The prominent soft X-ray excess ("Big Blue Bump") in the SED of the BL Lac object AO 0235+164 can be modelled as the signature of bulk Compton scattering of external radiation fields by the thermal electron population, which places additional constraints on the level of hydromagnetic turbulence. It has further been demonstrated that internal shocks propagating in a jet pervaded by a helical ma...

  13. Polarization Swings Reveal Magnetic Energy Dissipation in Blazars

    CERN Document Server

    Zhang, Haocheng; Boettcher, Markus; Guo, Fan; Li, Hui

    2015-01-01

    The polarization signatures of the blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, sometimes large (> 180^o) polarization angle swings are observed. We suggest that such p henomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change of its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.

  14. Intrinsic brightness temperatures of blazar jets at 15 GHz

    Directory of Open Access Journals (Sweden)

    Hovatta Talvikki

    2013-12-01

    Full Text Available We have developed a new Bayesian Markov Chain Monte Carlo method to deconvolve light curves of blazars into individual flares, including proper estimation of the fit errors. We use the method to fit 15GHzlight curves obtained within the OVRO 40-m blazar monitoring program where a large number of AGN have been monitored since 2008 in support of the Fermi Gamma-Ray Space Telescope mission. The time scales obtained from the fitted models are used to calculate the variability brightness temperature of the sources. Additionally, we have calculated brightness temperatures of a sample of these objects using Very Long Baseline Array data from the MOJAVE survey. Combining these two data sets enables us to study the intrinsic brightness temperature distribution in these blazars at 15 GHz. Our preliminary results indicate that the mean intrinsic brightness temperature in a sample of 14 sources is near the equipartition brightness temperature of ~ 1011K.

  15. The Candidate

    OpenAIRE

    Osborn, John C

    2013-01-01

    ABSTRACT   The Candidate is an attempt to marry elements of journalism and gaming into a format that both entertains and educates the player. The Google-AP Scholarship, a new scholarship award that is given to several journalists a year to work on projects at the threshold of technology and journalism, funded the project. The objective in this prototype version of the game is to put the player in the shoes of a congressional candidate during an off-year election, specificall...

  16. Rotation on sub-kpc scales in the strongly lensed z~3 'arc&core' and implications for high-redshift galaxy dynamics

    OpenAIRE

    Nesvadba, N. P. H.; Lehnert, M. D.; Frye, B. L.

    2008-01-01

    Strongly lensed galaxies at high redshift provide a unique window into the early universe. We compare the internal kinematics of the strongly lensed Lyman-break galaxy (LBG) 'arc&core' at z=3.2 (the first strongly lensed z~3 LBG with the signs of rotation on sub-kiloparsec scales) with an LBG that is not gravitationally lensed, as well as with a larger sample of actively star-forming galaxies at slightly lower redshifts. All galaxies have deep rest-frame optical integral-field spectroscopy ob...

  17. A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

    Science.gov (United States)

    Tanaka, Yasuyuki T.; Becerra Gonzalez, Josefa; Itoh, Ryosuke; Finke, Justin D.; Inoue, Yoshiyuki; Ojha, Roopesh; Carpenter, Bryce; Lindfors, Elina; Krauß, Felicia; Desiante, Rachele; Shiki, Kensei; Fukazawa, Yasushi; Longo, Francesco; McEnery, Julie E.; Buson, Sara; Nilsson, Kari; Fallah Ramazani, Vandad; Reinthal, Riho; Takalo, Leo; Pursimo, Tapio; Boschin, Walter

    2016-08-01

    We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1-compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ± 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous ( 100 MeV) and a hard spectral index of ΓGeV up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.

  18. Parsec-Scale Blazar Monitoring Proper Motions

    CERN Document Server

    Homan, D C; Wardle, J F C; Roberts, D H; Aller, M F; Aller, H D; Hughes, P A

    2001-01-01

    We present proper motions obtained from a dual frequency, six-epoch, VLBA polarization experiment monitoring a sample of 12 blazars. The observations were made at 15 GHz and 22 GHz at bi-monthly intervals over 1996. Ten of the eleven sources for which proper motion could be reliably determined are superluminal. Only J2005+77 has no superluminal components. Three sources (OJ287, J1224+21, and J1512-09) show motion faster than 10h^{-1}c, requiring $\\gamma_{pattern}$ of at least 10h^{-1}c (H_0 = 100h km/s/Mpc). We compare our results to those in the literature and find motions outside the previously observed range for four sources. While some jet components exhibit significant non-radial motion, most motion is radial. In at least two sources there are components moving radially at significantly different structural position angles. In five of six sources (3C120, J1224+21, 3C273, 3C279, J1512-09, and J1927+73) that have multiple components with measurable proper motion, the innermost component is significantly sl...

  19. VERA monitoring of a blazar OJ 287

    Directory of Open Access Journals (Sweden)

    Sawada-Satoh S.

    2013-12-01

    Full Text Available We present the frequent VLBI monitoring results of blazar OJ 287 at 22 GHz band using the VLBI Exploration of Radio Astrometry (VERA from 2010 November to 2012 September. Time interval of the monitoring is typically once or twice per month. The 22-GHz light curve of OJ 287 show three obvious increasing activities around 2011 May, 2011 October, and 2012 March, with a timescale of < 4 months. The second radio increasing events occurred at the same time as the γ-ray flare in 2011 October detected by the Fermi Large Area Telescope (LAT, and the third one seemed to precede the γ-ray flares in 2012, exhibiting different behaviour from the previous γ-ray flaring events in 2009. The relative motion of one jet component from the core was rectilinear super luminal motion (~ 8c from the 2011 February to 2011 November toward the south direction, and then it changed the direction backward. The direction variation of the relative motion was seen from 2011 November to 2012 August, simultaneously with the γ-ray flares. It could be caused by a new ejected component in the innermost region.

  20. Applying Relativistic Reconnection to Blazar Jets

    CERN Document Server

    Nalewajko, Krzysztof

    2016-01-01

    Rapid and luminous flares of non-thermal radiation observed in blazars require an efficient mechanism of energy dissipation and particle acceleration in relativistic active galactic nuclei (AGN) jets. Particle acceleration in relativistic magnetic reconnection is being actively studied by kinetic numerical simulations. Relativistic reconnection produces hard power-law electron energy distributions N(gamma) = N_0 gamma^(-p) exp(-gamma/gamma_max) with index p -> 1 and exponential cut-off Lorentz factor gamma_max ~ sigma in the limit of magnetization sigma = B^2/(4 pi w) >> 1 (where w is the relativistic enthalpy density). Reconnection in electron-proton plasma can additionally boost gamma_max by the mass ratio m_p/m_e. Hence, in order to accelerate particles to gamma_max ~ 10^6 in the case of BL Lacs, reconnection should proceed in plasma of very high magnetization sigma_max >~ 10^3. On the other hand, moderate mean jet magnetization values are required for magnetic bulk acceleration of relativistic jets, sigma...