WorldWideScience

Sample records for high redshift damped

  1. The spin temperature of high-redshift damped Lyman-$\\alpha$ systems

    CERN Document Server

    Kanekar, N; Smette, A; Ellison, S L; Ryan-Weber, E V; Momjian, E; Briggs, F H; Lane, W M; Chengalur, J N; Delafosse, T; Grave, J; Jacobsen, D; de Bruyn, A G

    2013-01-01

    We report results from a programme aimed at investigating the temperature of neutral gas in high-redshift damped Lyman-$\\alpha$ absorbers (DLAs). This involved (1) HI 21cm absorption studies of a large DLA sample, (2) VLBI studies to measure the low-frequency quasar core fractions, and (3) optical/ultraviolet spectroscopy to determine DLA metallicities and velocity widths. Including literature data, our sample consists of 37 DLAs with estimates of the spin temperature $T_s$ and the covering factor. We find a strong $4\\sigma$) difference between the $T_s$ distributions in high-z (z>2.4) and low-z (z1 sub-sample. Since z>1 DLAs have angular diameter distances comparable to or larger than those of the background quasars, they have similar efficiency in covering the quasars. Low covering factors in high-z DLAs thus cannot account for the observed redshift evolution in spin temperatures. (Abstract abridged.)

  2. A deep search for 21-cm absorption in high redshift damped Lyman-alpha systems

    NARCIS (Netherlands)

    Kanekar, N; Chengalur, JN

    2003-01-01

    We present deep GMRT 21-cm absorption spectra of 10 damped Lyman-alpha systems (DLAs), of which 8 are at redshifts zgreater than or similar to1.3. HI absorption was detected in only one DLA, the z=0.5318 absorber toward PKS 1629+12. This absorber has been identified with a luminous spiral galaxy; th

  3. 36 new, high-probability, damped Lyα absorbers at redshift 0.42 < z < 0.70

    Science.gov (United States)

    Turnshek, David A.; Monier, Eric M.; Rao, Sandhya M.; Hamilton, Timothy S.; Sardane, Gendith M.; Held, Ryan

    2015-05-01

    Quasar damped Lyα (DLA) absorption-line systems with redshifts z systems fall in the UV and are rarely found in blind UV spectroscopic surveys. Therefore, it has been difficult to compile a moderate-sized sample of UV DLAs in any narrow cosmic time interval. However, DLAs are easy to identify in low-resolution spectra because they have large absorption rest equivalent widths. We have performed an efficient strong-Mg II-selected survey for UV DLAs at redshifts z = [0.42, 0.70] using Hubble Space Telescope's low-resolution ACS-HRC-PR200L prism. This redshift interval covers ˜1.8 Gyr in cosmic time, i.e. t ≈ [7.2, 9.0] Gyr after the big bang. A total of 96 strong Mg II absorption-line systems identified in Sloan Digital Sky Survey spectra were successfully observed with the prism at the predicted UV wavelengths of Lyα absorption. We found that 35 of the 96 systems had a significant probability of being DLAs. One additional observed system could be a very high N_{H I} DLA (N_{H I} ˜ 2× 10^{22} atoms cm-2 or possibly higher), but since very high N_{H I} systems are extremely rare, it would be unusual for this system to be a DLA given the size of our sample. Here we present information on our prism sample, including our best estimates of N_{H I} and errors for the 36 systems fitted with DLA profiles. This list is valuable for future follow-up studies of low-redshift DLAs in a small redshift interval, although such work would clearly benefit from improved UV spectroscopy to more accurately determine their neutral hydrogen column densities.

  4. Abundances in Damped Lyman-$\\alpha$ Systems and Chemical Evolution of High Redshift Galaxies

    CERN Document Server

    Lü, L; Barlow, T A; Lu, Limin; Sargent, Wallace L.W.; Barlow, Thomas A.

    1997-01-01

    Recent abundance measurements in damped Lyman-alpha galaxies, supplemented with unpublished Keck observations, are discussed. The metallicity distribution with cosmic time is examined for clues about the degree of enrichment, the onset of initial star formation, and the nature of the galxies. The relative abundances of the elements are compared with the abundnce pattern in Galactic halo stars and in the Sun, taking into account of the effects of dust depletion, in order to gain insight into the stellar processes and the time scales by which the enrichment occurred.

  5. The most metal-poor damped Lyman alpha systems: An insight into dwarf galaxies at high redshift

    CERN Document Server

    Cooke, Ryan; Jorgenson, Regina A

    2014-01-01

    In this paper, we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped Lyman alpha 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 alpha-capture and Fe-peak elements when the metallicity is [Fe/H] ~ -2.0. 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 m...

  6. The Most Metal-poor Damped Lyα Systems: An Insight into Dwarf Galaxies at High-redshift

    Science.gov (United States)

    Cooke, Ryan J.; Pettini, Max; Jorgenson, Regina A.

    2015-02-01

    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] sime -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 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. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (VLT program IDs: 60.A-9022(A), 65.O-0063(B), 65.O-0296(A), 67.A-0022(A), 67.A-0078(A), 68.A-0600(A), 68.B-0115(A), 70.A-0425(C), 078.A-0185(A), 080.A-0014(A), 082.A-0544(A), 083.A-0042(A), 083.A-0454(A), 085.A-0109(A), 086.A-0204(A)), and at the

  7. First Detection of NaI D lines in High-Redshift Damped Lyman-alpha Systems

    CERN Document Server

    Kondo, S; Gässler, W; Hayano, Y; Iye, M; Kamata, Y; Kanzawa, T; Kobayashi, N; Minowa, Y; Nedachi, K; Oya, S; Pyo, T S; Saint-Jacques, D; Takami, H; Takato, N; Terada, H; Tokunaga, A; Tsujimoto, T; Churchill, Christopher W.; Gaessler, Wolfgang; Hayano, Yutaka; Iye, Masanori; Kamata, Yukiko; Kanzawa, Tomio; Kobayashi, Naoto; Kondo, Sohei; Minowa, Yosuke; Nedachi, Ko; Oya, Shin; Pyo, Tae-Soo; Takami, Hideki; Takato, Naruhisa; Terada, Hiroshi; Tokunaga, Alan; Tsujimoto, Takuji

    2006-01-01

    A Near-infrared (1.18-1.35 micron) high-resolution spectrum of the gravitationally-lensed QSO APM 08279+5255 was obtained with the IRCS mounted on the Subaru Telescope using the AO system. We detected strong NaI D 5891,5897 doublet absorption in high-redshift DLAs at z=1.062 and 1.181, confirming the presence of NaI, which was first reported for the rest-frame UV NaI 3303.3,3303.9 doublet by Petitjean et al. This is the first detection of NaI D absorption in a high-redshift (z>1) DLA. In addition, we detected a new NaI component in the z=1.062 DLA and four new components in the z=1.181 DLA. Using an empirical relationship between NaI and HI column density, we found that all "components" have large HI column density, so that each component is classified as DLA absorption. We also detected strong NaI D absorption associated with a MgII system at z=1.173. Because no other metal absorption lines were detected in this system at the velocity of the NaI absorption in previously reported optical spectra (observed 3.6...

  8. Moderate resolution spectrophotometry of high redshift quasars

    Science.gov (United States)

    Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

    1991-01-01

    A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.

  9. Thirty-four New, High-Probability, Damped Ly-alpha Absorbers at Redshift z=[0.42, 0.70

    CERN Document Server

    Turnshek, David A; Rao, Sandhya M; Hamilton, Timothy S; Sardane, Gendith M; Held, Ryan

    2014-01-01

    Quasar damped Ly-alpha (DLA) absorption line systems with redshifts z<1.65 are used to trace neutral gas over approximately 70 per cent of the most recent history of the Universe. However, such systems fall in the UV and are rarely found in blind UV spectroscopic surveys. Therefore, it has been difficult to compile a moderate-sized sample of UV DLAs in any narrow cosmic time interval. However, DLAs are easy to identify in low-resolution spectra because they have large absorption rest equivalent widths. We have performed an efficient strong-MgII-selected survey for UV DLAs at redshifts z=[0.42,0.70] using HST's low-resolution ACS-HRC-PR200L prism. This redshift interval covers ~1.8 Gyr in cosmic time, i.e., t~[7.2,9.0] Gyrs after the Big Bang. A total of 95 strong MgII absorption-line systems identified in SDSS spectra were successfully observed with the prism at the predicted UV wavelengths of Ly-alpha absorption. We found that 33 of the 95 systems had a significant probability of being DLAs. One additiona...

  10. High-redshift cosmography

    Energy Technology Data Exchange (ETDEWEB)

    Vitagliano, Vincenzo; Xia, Jun-Qing; Liberati, Stefano [SISSA, Via Beirut 2-4, 34151 Trieste (Italy); Viel, Matteo, E-mail: vitaglia@sissa.it, E-mail: xia@sissa.it, E-mail: liberati@sissa.it, E-mail: viel@oats.inaf.it [INFN sez. Trieste, Via Valerio 2, 34127 Trieste (Italy)

    2010-03-01

    We constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires a very minimal set of assumptions (namely to specify a metric) and does not rely on the dynamical equations for gravity. On the data side, we consider the most recent compilations of Supernovae and Gamma Ray Bursts catalogues. This allows to further extend the cosmographic fit up to z = 6.6, i.e. up to redshift for which one could start to resolve the low z degeneracy among competing cosmological models. In order to reliably control the cosmographic approach at high redshifts, we adopt the expansion in the improved parameter y = z/(1+z). This series has the great advantage to hold also for z > 1 and hence it is the appropriate tool for handling data including non-nearby distance indicators. We find that Gamma Ray Bursts, probing higher redshifts than Supernovae, have constraining power and do require (and statistically allow) a cosmographic expansion at higher order than Supernovae alone. Exploiting the set of data from Union and GRBs catalogues, we show (for the first time in a purely cosmographic approach parametrized by deceleration q{sub 0}, jerk j{sub 0}, snap s{sub 0}) a definitively negative deceleration parameter q{sub 0} up to the 3σ confidence level. We present also forecasts for realistic data sets that are likely to be obtained in the next few years.

  11. High-Redshift Cosmography

    CERN Document Server

    Vitagliano, Vincenzo; Liberati, Stefano; Viel, Matteo

    2009-01-01

    We constrain the parameters describing the kinematical state of the universe using a cosmographic approach, which is fundamental in that it requires a very minimal set of assumptions (namely to specify a metric) and does not rely on the dynamical equations for gravity. On the data side, we consider the most recent compilations of Supernovae and Gamma Ray Bursts catalogs. This allows to further extend the cosmographic fit up to $z=6.6$, i.e. up to redshift for which one could start to resolve the low $z$ degeneracy among competing cosmological models. In order to reliably control the cosmographic approach at high redshifts, we adopt the expansion in the improved parameter $y=z/(1+z)$ (as proposed in Class. Quant. Grav., 24 (2007) 5985). This series has the great advantage to hold also for $z>1$ and hence it is the appropriate tool for handling data including non-nearby distance indicators. We find that Gamma Ray Bursts, probing higher redshifts than Supernovae, have constraining power and do require (and stati...

  12. 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...

  13. CO-dark molecular gas at high redshift: very large H2 content and high pressure in a low-metallicity damped Lyman alpha system

    Science.gov (United States)

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

    2017-09-01

    We present a detailed analysis of an H2-rich, extremely strong intervening damped Ly α absorption system (DLA) at zabs = 2.786 towards the quasar J 0843+0221, observed with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. The total column density of molecular (resp. atomic) hydrogen is log N(H2) = 21.21 ± 0.02 (resp. log N(H i) = 21.82 ± 0.11), making it to be the first case in quasar absorption line studies with H2 column density as high as what is seen in 13CO-selected clouds in the Milky Way. We find that this system has one of the lowest metallicity detected among H2-bearing DLAs, with [Zn/H] = -1.52^{+0.08}_{-0.10}. This can be the reason for the marked differences compared to systems with similar H2 column densities in the local Universe: (i) the kinetic temperature, T ∼ 120 K, derived from the J = 0, 1 H2 rotational levels is at least twice higher than expected; (ii) there is little dust extinction with AV 2 × 1023 cm-2/(km s-1 K), in the very low metallicity gas. Low CO and high H2 contents indicate that this system represents 'CO-dark/faint' gas. We investigate the physical conditions in the H2-bearing gas using the fine-structure levels of C i, C ii, Si ii and the rotational levels of HD and H2. We find the number density to be about n ∼ 260-380 cm-3, implying a high thermal pressure of 3-5 × 104 cm-3 K. We further identify a trend of increasing pressure with increasing total hydrogen column density. This independently supports the suggestion that extremely strong DLAs (with log N(H) ∼22) probe high-z galaxies at low impact parameters.

  14. Very high redshift radio galaxies

    Energy Technology Data Exchange (ETDEWEB)

    van Breugel, W.J.M., LLNL

    1997-12-01

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

  15. Obscured AGN at High Redshift

    Science.gov (United States)

    Stern, Daniel

    2008-01-01

    This viewgraph presentation reviews the obscured sources of Active Galactic Nuclei (AGN) in the universe at high redshift. The cosmic X-ray background, unified models of AGN and clues to galaxy formation/evolution is the motivation for this study.

  16. Damping Bearings In High-Speed Turbomachines

    Science.gov (United States)

    Von Pragenau, George L.

    1994-01-01

    Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).

  17. Damped Lyman Alpha Gas Metallicities at Redshifts z=0.9-2.0 from SDSS Spectra

    CERN Document Server

    Nestor, D B; Turnshek, D A; Vanden Berk, Daniel E; Nestor, Daniel B.; Rao, Sandhya M.; Turnshek, David A.; Berk, Daniel Vanden

    2003-01-01

    Using Sloan Digital Sky Survey (SDSS) early data release spectra, we have identified 370 MgII absorption systems with MgII 2796 rest equivalent widths >= 1A and redshifts z=0.9-2.2. From our previous and ongoing HST UV spectroscopic studies, we estimate that the mean neutral hydrogen column density of a system selected in this manner is N(HI) = 3.6 +/- 1.3 x10^(20) atoms cm^(-2), which corresponds to the damped Ly-alpha (DLA) regime. We have formed high signal-to-noise ratio composite spectra using 223 of these systems with z=0.9-2.0 in order to study the strength of the ZnII and CrII absorption lines corresponding to this mean neutral hydrogen column density. After making a correction for missed DLAs, overall we find that [Zn/H] = -1.13 +/- 0.19. We find [Cr/Zn] = -0.45 +/- 0.13, which indicates that approx 65% of the Cr is depleted on to grains, but this does not correct for the missed DLAs. We have also derived Zn and Cr abundances in two kinematic regimes, and within each regime we consider two redshift i...

  18. Searches for High Redshift Clusters

    CERN Document Server

    Dickinson, M

    1996-01-01

    High redshift galaxy clusters have traditionally been a fruitful place to study galaxy evolution. I review various search strategies for finding clusters at z > 1. Most efforts to date have concentrated on the environments of distant AGN. I illustrate these with data on the cluster around 3C 324 (z=1.2) and other, more distant systems, and discuss possibilities for future surveys with large telescopes.

  19. Old Galaxies at High Redshift

    CERN Document Server

    Dunlop, J

    1997-01-01

    The most passive galaxies at high redshift are unlikely to be identified by either narrow-band emission-line searches, or by Lyman limit searches (both techniques which have been highlighted at this meeting) simply because such selection methods rely on the presence of a strong ultraviolet component. Selection on the basis of extreme radio power has also proved to yield optically active objects with the majority of high-redshift objects studied to date displaying complex elongated optical/UV morphologies, relatively blue optical-ultraviolet continuum colours, and strong emission lines. These features, coupled with the failure to detect any spectral signatures of old stars at $z > 1$, has led to the suggestion that these galaxies are being observed close to or even during a general epoch of formation. However, we have recently demonstrated that radio selection at significantly fainter (mJy) flux densities can be used to identify apparently passively evolving elliptical galaxies at high redshift. Deep Keck spec...

  20. 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...

  1. High redshift quasars monitoring campaign

    Science.gov (United States)

    Botti, Ismael; Lira, Paulina; Martinez, Jorge; Netzer, Hagai; Kaspi, Shai

    2014-07-01

    We present an update of the monitoring campaign we have undertaken to probe the most massive black holes in powerful quasars at high redshift through the reverberation mapping technique. Once this campaign has finished, we will be able to directly measure broad line region (BLR) sizes of quasars at z ~ 2-3, improving dramatically the BLR size-luminosity relation, and therefore, black hole mass estimates based on this relationship. So far, we have identified a dozen highly variable sources suitable for future cross-correlation analysis and reverberation measurements.

  2. High Redshift Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil

    2012-01-01

    The Swift Observatory has been detecting 100 gamma-ray bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from 1 minute after the burst, continuing for days. GRBs are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=9.4 giving information on metallicity, star formation rate and reionization. The talk will present the latest results.

  3. The First Observations of Low Redshift Damped Lyman-alpha Systems with the Cosmic Origins Spectrograph

    CERN Document Server

    Meiring, Joseph D; Prochaska, Jason X; Tumlinson, Jason; Werk, Jessica; Jenkins, Edward B; Thom, Chris; O'Meara, John M; Sembach, Kenneth R

    2011-01-01

    We report on the first Cosmic Origins Spectrograph (COS) observations of damped and sub-damped Lyman-alpha (DLA) systems discovered in a new survey of the gaseous halos of low-redshift galaxies. From observations of 37 sightlines, we have discovered three DLAs and four sub-DLAs. We measure the neutral gas density Omega(HI), and redshift density dN/dz, of DLA and sub-DLA systems at z<0.35. We find dN/dz=0.25 and Omega(HI)=1.4x10^-3 for DLAs, and dN/dz=0.08 with Omega(HI)=4.2x10^-5 for sub-DLAs over a redshift path delta z=11.9. To demonstrate the scientific potential of such systems, we present a detailed analysis of the DLA at z=0.1140 in the spectrum of SDSS J1009+0713. Profile fits to the absorption lines determine log N(H I)=20.68pm0.10 with a metallicity determined from the undepleted element Sulfur of [S/H]=-0.62pm0.18. The abundance pattern of this DLA is similar to that of higher z DLAs, showing mild depletion of the refractory elements Fe and Ti with [S/Fe]=+0.24pm0.22 and [S/Ti]=+0.28pm0.15. Nitro...

  4. Element abundances at high redshift

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, D.M.; Welty, D.E.; York, D.G. (Northwestern Univ., Evanston, IL (USA); Chicago Univ., IL (USA))

    1989-08-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe( ), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value. 25 refs.

  5. Element abundances at high redshift

    Science.gov (United States)

    Meyer, David M.; Welty, D. E.; York, D. G.

    1989-01-01

    Abundances of Si(+), S(+), Cr(+), Mn(+), Fe(_), and Zn(+) are considered for two absorption-line systems in the spectrum of the QSO PKS 0528 - 250. Zinc and sulfur are underabundant, relative to H, by a factor of 10 compared to their solar and Galactic interstellar abundances. The silicon-, chromium-, iron-, and nickel-to-hydrogen ratios are less than the solar values and comparable to the local interstellar ratios. A straightforward interpretation is that nucleosynthesis in these high-redshift systems has led to only about one-tenth as much heavy production as in the gas clouds around the sun, and that the amount of the observed underabundances attributable to grain depletion is small. The dust-to-gas ratio in these clouds is less than 8 percent of the Galactic value.

  6. High Damping Alloys and Their Application

    Institute of Scientific and Technical Information of China (English)

    Fuxing Yin

    2000-01-01

    Damping alloys show prospective applications in the elimination of unwanted vibrations and acoustic noise. The basic definitions and characterization methods of damping capacity are reviewed in this paper. Several physical mechanisms controlled by the alloy microstructure are responsible for the damping behavior in the damping alloys. Composite, dislocation, ferromagnetic and planar defect types are commonly classified for the alloys, which show the different damping behavior against temperature, frequency of vibration,amplitude of vibration and damping modes. Development of practically applicable damping alloys requires the higher mechanical properties and adequate workability, besides the high damping capacity. A new Mn-Cu damping alloy, named as M2052 alloy, is recently developed with possible industrial applications.

  7. IONIZED NITROGEN AT HIGH REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Decarli, R.; Walter, F. [Max-Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Neri, R.; Cox, P. [IRAM, 300 rue de la piscine, F-38406 Saint-Martin d' Heres (France); Bertoldi, F. [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Carilli, C. [NRAO, Pete V. Domenici Array Science Center, P.O. Box O, Socorro, NM 87801 (United States); Kneib, J. P. [Laboratoire d' Astrophysique de Marseille, Observatoire d' Astronomie Marseille-Provence, BP 8, F-13376 Marseille (France); Lestrade, J. F. [Observatoire de Paris, CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Maiolino, R. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monte Porzio Catone (Italy); Omont, A. [Institut d' Astrophysique de Paris, UPMC and CNRS, 98bis Bld. Arago, F-75014 Paris (France); Richard, J. [CRAL, Observatoire de Lyon, Universite Lyon 1, 9 Avenue Ch. Andre, F-69561 Saint Genis Laval Cedex (France); Riechers, D. [Astronomy Department, Caltech, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Thanjavur, K. [Canada-France-Hawaii Telescope Corporation, HI 96743 (United States); Weiss, A., E-mail: decarli@mpia.de [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)

    2012-06-10

    We present secure [N II]{sub 205{mu}m} detections in two millimeter-bright, strongly lensed objects at high redshift, APM 08279+5255 (z = 3.911) and MM 18423+5938 (z = 3.930), using the IRAM Plateau de Bure Interferometer. Due to its ionization energy [N II]{sub 205{mu}m} is a good tracer of the ionized gas phase in the interstellar medium. The measured fluxes are S([N II]{sub 205{mu}m}) = (4.8 {+-} 0.8) Jy km s{sup -1} and (7.4 {+-} 0.5) Jy km s{sup -1}, respectively, yielding line luminosities of L([N II]{sub 205{mu}m}) = (1.8 {+-} 0.3) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for APM 08279+5255 and L([N II]{sub 205{mu}m}) = (2.8 {+-} 0.2) Multiplication-Sign 10{sup 9} {mu}{sup -1} L{sub Sun} for MM 18423+5938. Our high-resolution map of the [N II]{sub 205{mu}m} and 1 mm continuum emission in MM 18423+5938 clearly resolves an Einstein ring in this source and reveals a velocity gradient in the dynamics of the ionized gas. A comparison of these maps with high-resolution EVLA CO observations enables us to perform the first spatially resolved study of the dust continuum-to-molecular gas surface brightness ({Sigma}{sub FIR}{proportional_to}{Sigma}{sup N}{sub CO}, which can be interpreted as the star formation law) in a high-redshift object. We find a steep relation (N = 1.4 {+-} 0.2), consistent with a starbursting environment. We measure a [N II]{sub 205{mu}m}/FIR luminosity ratio in APM 08279+5255 and MM 18423+5938 of 9.0 Multiplication-Sign 10{sup -6} and 5.8 Multiplication-Sign 10{sup -6}, respectively. This is in agreement with the decrease of the [N II]{sub 205{mu}m}/FIR ratio at high FIR luminosities observed in local galaxies.

  8. Molecular Gas at High Redshift

    CERN Document Server

    Solomon, P M

    2005-01-01

    The Early Universe Molecular Emission Line Galaxies (EMGs) are a population of galaxies with only 36 examples that hold great promise for the study of galaxy formation and evolution at high redshift. The classification, luminosity of molecular line emission, molecular mass, far-infrared (FIR) luminosity, star formation efficiency, morphology, and dynamical mass of the currently known sample are presented and discussed. The star formation rates derived from the FIR luminosity range from about 300 to 5000 M(sun)per year and the molecular mass from 4 x 10^9 to 1 x 10^{11} M(sun). At the lower end, these star formation rates, gas masses, and diameters are similar to those of local ultraluminous infrared galaxies, and represent starbursts in centrally concentrated disks, sometimes, but not always, associated with active galactic nuclei. The evidence for large (> 5 kpc) molecular disks is limited. Morphology and several high angular resolution images suggest that some EMGs are mergers with a massive molecular inter...

  9. Gamma-ray bursts at high redshift

    NARCIS (Netherlands)

    R.A.M.J. Wijers

    1999-01-01

    Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive stars

  10. Gamma-ray bursts at high redshift

    NARCIS (Netherlands)

    Wijers, R.A.M.J.

    1999-01-01

    Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive stars

  11. The First Observations of Low-Redshift Damped Lyman-{\\alpha} Systems with the Cosmic Origins Spectrograph: Chemical Abundances and Affiliated Galaxies

    CERN Document Server

    Battisti, A J; Tripp, T M; Prochaska, J X; Werk, J K; Jenkins, E B; Lehner, N; Tumlinson, J; Thom, C

    2011-01-01

    We present Cosmic Origins Spectrograph (COS) measurements of metal abundances in eight 0.083 < zabs < 0.321 damped Lyman-{\\alpha} (DLA) and sub-damped Ly{\\alpha} absorption systems serendipitously discovered in the COS-Halos survey. We find that these systems show a large range in metallicities, with -1.10 < [Z/H] < 0.31, similar to the spread found at higher redshifts. These low-redshift systems on average have subsolar metallicities, but do show a rise in metallicity over cosmic time when compared to higher-redshift systems. Utilizing our sources and those in the literature, we find the average sub-DLA metallicity is higher than the average DLA metallicity at all redshifts. Nitrogen is underabundant with respect to {\\alpha}-group elements in all but perhaps one of the absorbers. In some cases, [N/{\\alpha}] is significantly below the lowest nitrogen measurements in nearby galaxies; the nitrogen abundances are more similar to those observed in high-redshift DLAs. Systems for which depletion patter...

  12. The Physical Conditions of Atomic Gas at High Redshift

    Science.gov (United States)

    Neeleman, Marcel

    In this thesis we provide insight into the chemical composition, physical conditions and cosmic distribution of atomic gas at high redshift. We study this gas in absorption against bright background quasars in absorption systems known as Damped Ly-alpha Systems (DLAs). These systems contain the bulk of the atomic gas at high redshift and are the likely progenitors of modern-day galaxies. In Chapter 2, we find that the atomic gas in DLAs obeys a mass-metallicity relationship that is similar to the mass-metallicity relationship seen in star-forming galaxies. The evolution of this relationship is linear with redshift, allowing for a planar equation to accurately describe this evolution, which provides a more stringent constraint on simulations modeling DLAs. Furthermore, the concomitant evolution of the mass-metallicity relationship of atomic gas and star-forming galaxies suggests an intimate link between the two. We next use a novel way to measure the physical conditions of the gas by using fine-structure line ratios of singly ionized carbon and silicon. By measuring the density of the upper and lower level states, we are able to determine the temperature, hydrogen density and electron density of the gas. We find that the conditions present in this high redshift gas are consistent with the conditions we see in the local interstellar medium (ISM). A few absorbers have higher than expected pressure, which suggests that they probe the ISM of star-forming galaxies. Finally in Chapter 4, we measure the cosmic neutral hydrogen density at redshifts below 1.6. Below this redshift, the Ly-alpha line of hydrogen is absorbed by the atmosphere, making detection difficult. Using the archive of the Hubble Space Telescope, we compile a comprehensive list of quasars for a search of DLAs at redshift below 1.6. We find that the incidence rate of DLAs and the cosmic neutral hydrogen density is smaller than previously measured, but consistent with the values both locally and at

  13. -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.

  14. Cosmography with high-redshift probes

    Science.gov (United States)

    Vitagliano, Vincenzo

    2014-05-01

    I discuss how the cosmographic approach to the determination of cosmological parameters can be implemented with the inclusion of high-redshift data. I argue on the viability of such high-z probes for cosmographic purposes, and resume some statistical issues in finding the most reliable cosmographic truncation.

  15. Observations of GRBs at high redshift.

    Science.gov (United States)

    Tanvir, Nial R; Jakobsson, Páll

    2007-05-15

    The extreme luminosity of gamma-ray bursts and their afterglows means they are detectable, in principle, to very high redshifts. Although the redshift distribution of gamma-ray bursts (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 per cent probably at z>6. Thus, GRBs are potentially powerful probes of the era of reionization and the sources responsible for it. Moreover, it seems probable that they can provide constraints on the star-formation history of the Universe and may also help in the determination of the cosmological parameters.

  16. Diffuse Interstellar Bands in Seven Intermediate Redshift Damped Lyman-Alpha Absorbers

    CERN Document Server

    Lawton, Brandon; York, Brian A; Ellison, Sara L; Snow, Theodore P; Johnson, Rachel A; Ryan, Sean G; Benn, Chris R

    2008-01-01

    We present equivalent width measurements and limits of six diffuse interstellar bands (DIBs) in seven damped Ly-alpha absorbers (DLAs) over the redshift range 0.091

  17. Identifying high-redshift GRBs with RATIR

    CERN Document Server

    Littlejohns, O M; Cucchiara, A; Watson, A M; Kutyrev, A S; Lee, W H; Richer, M G; Klein, C R; Fox, O D; Prochaska, J X; Bloom, J S; Troja, E; Ramirez-Ruiz, E; de Diego, J A; Georgiev, L; González, J; Román-Zúñiga, C G; Gehrels, N; Moseley, H

    2013-01-01

    We present a template fitting algorithm for determining photometric redshifts, $z_{\\rm phot}$, 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 spectrum, 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 RATIR photometry of GRB 130606A, finding $z_{\\rm phot} = 6.01_{-0.08}^{+0.16}$ for a model with negligible host dust extinction, consistent with spectroscopic measurements of the redshift of this GRB. Using simulated RATIR photometry, we find our algorithm provides precise measures of $z_{\\rm phot}$ in the ranges $4 4$. Further testing highlights the required caution in cases of highly dust extincted host galaxies. These tests also show that our algorithm minimizes false negatives thus allowing us to rapidly identify all potential high-redshift eve...

  18. Atomic hydrogen at high redshift

    NARCIS (Netherlands)

    Briggs, FH; Rickman, H

    2002-01-01

    After the production of the ionizing background by the first generation of stars, neutral gas must be confined to sufficiently high density to be self-shielding and remain neutral. Neutral gas is an identifier of the presence of confining gravitational potentials and a tracer of the kinematics of

  19. Atomic hydrogen at high redshift

    NARCIS (Netherlands)

    Briggs, FH; Rickman, H

    2002-01-01

    After the production of the ionizing background by the first generation of stars, neutral gas must be confined to sufficiently high density to be self-shielding and remain neutral. Neutral gas is an identifier of the presence of confining gravitational potentials and a tracer of the kinematics of th

  20. DAMPE

    CERN Multimedia

    Chen, D

    The $\\textbf{DA}$rk $\\textbf{M}$atter $\\textbf{P}$article $\\textbf{E}$xplorer (DAMPE) experiment is a high-energy astroparticle physics satellite mission to search for Dark Matter signatures in space, study the cosmic ray spectrum and composition up to 100 TeV, and perform high-energy gamma astronomy. The launch is planned for end 2015, initially for 3 years, to compliment existing space missions FERMI, AMS and CALET.

  1. Redshift

    CERN Document Server

    Clark, Stuart

    1997-01-01

    The light emitted by celestial objects can have its wavelength "stretched" in different ways before it is observed by astronomers. These stretching phenomena are collectively called "redshift". They influence virtually all aspects of astronomy and even underpin the "Big Bang" theory of the creation of the universe. This book details the types of redshift and explains their myriad of uses. It begins by introducing the nature of light and the problems involved in measuring its properties. After explaining the redshift phenomena and their uses, the book touches on the age and size of the universe; two subjects embroiled in controversy because of our current interpretation of the redshift. Less conventional theories are then expressed. As a by-product of the explanation of redshift, the book offers the reader a basic understanding of Einstein's theory of relativity. Mathematical treatments of the concepts introduced in the text are boxed off and should not detract from the book's readibility, but allow it to be u...

  2. Directly Imaging Damped Ly-Alpha Galaxies at Redshifts Greater Than 2. III: The Star Formation Rates of Neutral Gas Reservoirs at Redshifts of Approximately 2.7

    Science.gov (United States)

    Fumagalli, Michele; OMeara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2014-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Ly alpha systems (DLAs) at redshifts of approximately 2.7. By using the "double-DLA" technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame FUV flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2 sigma limits of psi less than 0.09-0.27 solar mass yr(exp -1), corresponding to SFR surface densities sigma(sub sfr) less than 10(exp -2.6)-10(exp -1.5) solar mass yr(exp -1) kpc(exp -2). The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that less than or equal to 13% of the hosts have psi greater than or equal to 2 solar mass yr(exp -1) at impact parameters b(sub dla) less than or equal to (psi/solar mass yr(exp -1))(exp 0.8) + 6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavor a scenario in which the majority of DLAs arise from bright LBGs at distances 20 less than or equal to b(sub dla) less than 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  3. Chemical Evolution of Damped Ly $\\alpha$ galaxies The [S/Zn] abundance ratio at redshift z > 2

    CERN Document Server

    Centurion, M; Molaro, P; Vladilo, G; Centurion, Miriam; Bonifacio, Piercarlo; Molaro, Paolo; Vladilo, Giovanni

    2000-01-01

    Relative elemental abundances, and in particular the alpha/Fe ratio, are an important diagnostic tool of the chemical evolution of damped Ly alpha systems (DLAs). The S/Zn ratio is not affected by differential dust depletion and is an excellent estimator of the alpha/Fe ratio. We report 6 new determinations of sulphur abundance in DLAs at zabs greater than or equal to 2 with already known zinc abundances. The combination with extant data from the literature provides a measure of the S/Zn abundance ratio for a total of 11 high redshift DLA systems. The observed [S/Zn] ratios do not show the characteristic [alpha/Fe] enhancement observed in metal-poor stars of the Milky Way at comparable level of metallicity ([Zn/H] ~ -1). The behaviour of DLAs data is consistent with a general trend of decreasing [S/Zn] ratio with increasing metallicity [Zn/H]. This would be the first evidence of the expected decrease of the alpha/Fe ratio in the course of chemical evolution of DLA systems. However, in contrast to what observe...

  4. 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).

  5. Structure of the universe at high redshifts

    CERN Document Server

    Doroshkevich, D

    2002-01-01

    We extend the approximate statistical description of the process of formation and evolution of structure of the universe based on the modified Zel'dovich theory of gravitational instability discussed in our previous paper. We show that, in this approach, the mass distribution of different structure elements -- walls, pancakes, filaments and clouds -- is described by the same time dependent function. In all these cases, the mass of formed structure elements is found to be concentrated near the mean mass. At high redshifts, both the mass function and the mean mass of formed elements depend upon the small scale part of the initial power spectrum and, in particular, upon the mass of dominant fraction of dark matter (DM) particles. These results generalize the Press-Schechter approach and allow also to obtain independent estimates of the probable redshifts of the reionization and reheating periods of the Universe. We show that the transverse motions -- expansion and/or compression -- do not change significantly th...

  6. A catalogue of high redshift clusters

    Directory of Open Access Journals (Sweden)

    R. Juncosa

    2007-01-01

    Full Text Available Distant clusters of galaxies provide a powerful method to study the formation and evolution of galaxies and large scale structure of the Universe. However, the number of known clusters at high redshift (z > 0.5 is still limited. As a preparatory work for detailed studies with GTC, we are building a cata- logue of such objects analyzing public deep wide optical and near-IR surveys. In a region of ~9 square degrees, ~100 new clusters (~ 60 of them at z > 0.5 have been detected.

  7. Quasar Elemental Abundances at High Redshifts

    DEFF Research Database (Denmark)

    Dietrich, M.; Hamann, F.; Shields, J. C.

    2003-01-01

    We examine rest-frame ultraviolet spectra of 70 high redshift quasars (z>3.5) to study the chemical enrichment history of the gas closely related to the quasars, and thereby estimate the epoch of first star formation. The fluxes of several ultraviolet emission lines were investigated within...... the framework of the most recent photoionization models to estimate the metallicity of the gas associated with the high-z quasars. Standard photoionization parameters and the assumption of secondary nitrogen enrichment indicate an average abundance of Z/Z_sol = 4 to 5 in the line emitting gas. Assuming a time...... scale of t_evol = 0.5 - 0.8 Gyrs for the chemical enrichment of the gas, the first major star formation for quasars with z>=4 should have started at a redshift of z_f = 6 - 8, corresponding to an age of the universe of several 10^8 yrs (H_o = 65 km/s/Mpc, Omega_M = 0.3, Omega_Lambda = 0.7). We note...

  8. Quasar Elemental Abundances at High Redshifts

    CERN Document Server

    Dietrich, M; Shields, J C; Constantin, A; Heidt, J; Jäger, K; Vestergaard, M; Wagner, S J

    2003-01-01

    We examine rest-frame ultraviolet spectra of 70 high redshift quasars (z>3.5) to study the chemical enrichment history of the gas closely related to the quasars, and thereby estimate the epoch of first star formation. The fluxes of several ultraviolet emission lines were investigated within the framework of the most recent photoionization models to estimate the metallicity of the gas associated with the high-z quasars. Standard photoionization parameters and the assumption of secondary nitrogen enrichment indicate an average abundance of Z/Z_sol = 4 to 5 in the line emitting gas. Assuming a time scale of t_evol = 0.5 - 0.8 Gyrs for the chemical enrichment of the gas, the first major star formation for quasars with z>=4 should have started at a redshift of z_f = 6 - 8, corresponding to an age of the universe of several 10^8 yrs (H_o = 65 km/s/Mpc, Omega_M = 0.3, Omega_Lambda = 0.7). We note that this also appears to be the era of re-ionization of the universe. Finally, there is some evidence for a positive lum...

  9. Survey For Very High-Redshift Quasars

    Science.gov (United States)

    Lemley, S.; MacAlpine, G.

    1997-12-01

    I will present the results from the deep, three color survey for very high redshift quasars. The survey involved direct imaging through Gunn gri filters using a 2048 x 2048 STIS ccd chip and Cerro Tololo's Curtis Scmidt Telescope. Quasar candidates in the range 4.0 < z < 5.4 were selected based on the detection of the Lyman alpha line and the strong drop in the spectrum blueward of this. Because of this response, quasars are clearly located away from the stellar locus on g - r vs. r - i diagrams. Quasar candidates in this redshift range have large values of g - r and small values of r - i. To confirm the candidates as quasars, the multi-fiber spectroscope Hydra, located on the WIYN telescope, was used. To date, spectral confirmation has been completed for ten degrees out of the approximately fifteen square degress of survey area. Several quasars were discovered, and I will present their spectra and information on the viability of this technique.

  10. Magnetic fields during high redshift structure formation

    CERN Document Server

    Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

    2012-01-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

  11. Adaptive Optics Imaging of Low-redshift Damped Lyman-alpha Quasar Absorbers

    CERN Document Server

    Chun, M R; Kulkarni, V P; Takamiya, M; Chun, Mark R.; Gharanfoli, Soheila; Kulkarni, Varsha P.; Takamiya, Marianne

    2005-01-01

    We have carried out a high angular resolution near-infrared imaging study of the fields of 6 quasars with 7 strong absorption line systems at z < 0.5, using the Hokupa'a adaptive optics system and the QUIRC near-infrared camera on the Gemini-North telescope. These absorption systems include 4 classical damped Lyman-alpha absorbers (DLAs), 2 sub-DLAs, and one Lyman-limit system. Images were obtained in the H or K' filters with FWHM between 0.2"-0.5" with the goal of detecting the absorbing galaxies and identifying their morphologies. Features are seen at projected separations of 0.5"-16.0" from the quasars and all of the fields show features at less than 2" separation. We find candidate absorbers in all of the seven systems. With the assumption that some of these are associated with the absorbers, the absorbers are low luminosity < 0.1 L*_H or L*_K; we do not find any large bright candidate absorbers in any of our fields. Some fields show compact features that are too faint for quantitative morphology, b...

  12. High-Redshift Astrophysics Using Every Photon

    Science.gov (United States)

    Breysse, Patrick; Kovetz, Ely; Rahman, Mubdi; Kamionkowski, Marc

    2017-01-01

    Large galaxy surveys have dramatically improved our understanding of the complex processes which govern gas dynamics and star formation in the nearby universe. However, we know far less about the most distant galaxies, as existing high-redshift observations can only detect the very brightest sources. Intensity mapping surveys provide a promising tool to access this poorly-studied population. By observing emission lines with low angular resolution, these surveys can make use of every photon in a target line to study faint emitters which are inaccessible using traditional techniques. With upcoming carbon monoxide experiments in mind, I will demonstrate how an intensity map can be used to measure the luminosity function of a galaxy population, and in turn how these measurements will allow us to place robust constraints on the cosmic star formation history. I will then show how cross-correlating CO isotopologue lines will make it possible to study gas dynamics within the earliest galaxies in unprecedented detail.

  13. High Redshift Lyman-α Hunt

    DEFF Research Database (Denmark)

    Kochiashvili, Ia

    constitute the backbone of thisthesis, I investigated the nature of almost 100 emission-line galaxies selected with thenarrow-band selection method. These candidates can be: galaxies with Hα emissionlines at redshift z ∼ 0.6, [Oiii]/Hβ emission-line galaxies at redshift z ∼ 1.15 and [Oii]emitters at z ∼ 1...

  14. 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.

  15. 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...

  16. Chandra ACIS-S Observations of Three Quasars with Low-Redshift Damped Ly-alpha Absorption Constraints on the Cosmic Neutral-Gas-Phase Metallicity at Redshift z \\approx 0.4

    CERN Document Server

    Turnshek, D A; Ptak, A F; Griffiths, R E; Monier, E M; Turnshek, David A.; Rao, Sandhya M.; Ptak, Andrew F.; Griffiths, Richard E.; Monier, Eric M.

    2003-01-01

    Chandra X-Ray Observatory (CXO) ACIS-S spectra of three quasars which lie behind three foreground damped Lyman alpha (DLA) absorbers are analyzed in order to attempt to determine the amount of photoelectric absorption due to metals present in their x-ray spectra. These absorbers are the three largest neutral hydrogen column density absorption-line systems known at low redshift (0.313 \\le z_abs \\le 0.524). They have HI column densities which lie between 3E21 and 5E21 atoms/cm^2. At these redshifts the amount of photoelectric absorption at x-ray energies is primarily an indicator of the oxygen abundance. Since the column densities of these systems are so high, one would expect accurate metallicity measurements of them to yield a robust estimate of the column-density-weighted cosmic neutral-gas-phase metallicity at z \\approx 0.4. We consider cases where the DLA gas has solar element abundance ratios and ones with the alpha-group element abundance ratios enhanced. For the adopted assumptions, the column-density-w...

  17. 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.

  18. 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...

  19. High Redshift Quasars and Star Formation History

    CERN Document Server

    Dietrich, M; Dietrich, Matthias; Hamann, Fred

    2001-01-01

    Quasars are among the most luminous objects in the universe, and they can be studied in detail up to the highest known redshift. Assuming that the gas associated with quasars is closely related to the interstellar medium of the host galaxy, quasars can be used as tracer of the star formation history in the early universe. We have observed a small sample of quasars at redshifts 3= 10, corresponding to an age of the universe of less than 5*10^8 yrs (H_o = 65 km/s/Mpc, Omega_M = 0.3, Omega_Lambda = 0.7).

  20. 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...

  1. High-redshift major mergers weakly enhance star formation

    Science.gov (United States)

    Fensch, J.; Renaud, F.; Bournaud, F.; Duc, P.-A.; Agertz, O.; Amram, P.; Combes, F.; Di Matteo, P.; Elmegreen, B.; Emsellem, E.; Jog, C. J.; Perret, V.; Struck, C.; Teyssier, R.

    2017-02-01

    Galaxy mergers are believed to trigger strong starbursts. This is well assessed by observations in the local Universe. However, the efficiency of this mechanism has poorly been tested so far for high-redshift, actively star-forming, galaxies. We present a suite of pc-resolution hydrodynamical numerical simulations to compare the star formation process along a merging sequence of high- and low-redshift galaxies, by varying the gas mass fraction between the two models. We show that, for the same orbit, high-redshift gas-rich mergers are less efficient than low-redshift ones at producing starbursts; the star formation rate excess induced by the merger and its duration are both around 10 times lower than in the low gas fraction case. The mechanisms that account for the star formation triggering at low redshift - the increased compressive turbulence, gas fragmentation, and central gas inflows - are only mildly, if not at all, enhanced for high gas fraction galaxy encounters. Furthermore, we show that the strong stellar feedback from the initially high star formation rate in high-redshift galaxies does not prevent an increase of the star formation during the merger. Our results are consistent with the observed increase of the number of major mergers with increasing redshift being faster than the respective increase in the number of starburst galaxies.

  2. HI content, metallicities and spin temperatures of damped and sub-damped Lyman alpha systems in the redshift desert (0.6 < z < 1.7)

    CERN Document Server

    Ellison, Sara L; Prochaska, J Xavier; Momjian, Emmanuel; Worseck, Gabor

    2012-01-01

    The HI 21cm absorption optical depth and the N(HI) derived from Lya absorption can be combined to yield the spin temperature (Ts) of DLAs. Although Ts measurements exist for samples of DLAs with z 1.7, the intermediate redshift regime currently contains only 2 HI 21cm detections, leading to a `redshift desert' that spans 4 Gyrs of cosmic time. To connect the low and high z regimes, we present observations of the Lya line of six 0.6redshift desert, but is also the first to use a fully f-corrected dataset to look for metallicity-based trends. In agreement with trends found in Galactic sightlines, we find that the lowest N(HI) absorbers tend to be dominated by warm gas. In the DLA regime, spin tempera...

  3. 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...

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

    CERN Document Server

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

    2013-01-01

    Due to their highly luminous nature, gamma-ray bursts (GRBs) are useful tools in studying the early Universe (up to z = 10). We consider whether the available subset of Swift high redshift GRBs are unusual when compared to analogous simulations of a bright low redshift sample. By simulating data from the Burst Alert Telescope (BAT; Barthelmy et al. 2005) the light curves of these bright bursts are obtained over an extensive range of redshifts, revealing complicated evolution in properties of the prompt emission such as T90.

  5. Galaxies at High Redshift and Reionization

    CERN Document Server

    Bunker, Andrew; Ellis, Richard; Lacy, Mark; McMahon, Richard; Eyles, Laurence; Stark, Daniel; Chiu, Kuenley

    2009-01-01

    The quest to discover the most distant galaxies has developed rapidly in the last decade. We are now exploring redshifts of 6 and beyond, when the Universe was less than a billion years old, an epoch when the previously-neutral intergalactic medium was reionized. The continuing discovery of galaxies at progressively higher and higher redshifts has been driven by the availability of large telescopes on the ground and in space, improvements in detector technology, and new search strategies. Over the past 4 years, the Lyman break technique has been shown to be effective in isolating z~6 star-forming i'-drop galaxies through spectroscopic confirmation with large ground-based telescopes (Keck, Gemini and the ESO VLTs). Narrow-band imaging, notably with the wide field of the Subaru telescope, has also produced samples of Lyman-alpha emitters at these redshifts. A The discovery of this i'-drop galaxy population has been used to infer the global star formation rate density at this epoch (z~6), and we are now beginnin...

  6. Damping in high-temperature superconducting levitation systems

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R.

    2009-12-15

    Methods and apparatuses for improved damping in high-temperature superconducting levitation systems are disclosed. A superconducting element (e.g., a stator) generating a magnetic field and a magnet (e.g. a rotor) supported by the magnetic field are provided such that the superconducting element is supported relative to a ground state with damped motion substantially perpendicular to the support of the magnetic field on the magnet. Applying this, a cryostat housing the superconducting bearing may be coupled to the ground state with high damping but low radial stiffness, such that its resonant frequency is less than that of the superconducting bearing. The damping of the cryostat may be substantially transferred to the levitated magnetic rotor, thus, providing damping without affecting the rotational loss, as can be derived applying coupled harmonic oscillator theory in rotor dynamics. Thus, damping can be provided to a levitated object, without substantially affecting the rotational loss.

  7. Damping in high-temperature superconducting levitation systems

    Science.gov (United States)

    Hull, John R.

    2009-12-15

    Methods and apparatuses for improved damping in high-temperature superconducting levitation systems are disclosed. A superconducting element (e.g., a stator) generating a magnetic field and a magnet (e.g. a rotor) supported by the magnetic field are provided such that the superconducting element is supported relative to a ground state with damped motion substantially perpendicular to the support of the magnetic field on the magnet. Applying this, a cryostat housing the superconducting bearing may be coupled to the ground state with high damping but low radial stiffness, such that its resonant frequency is less than that of the superconducting bearing. The damping of the cryostat may be substantially transferred to the levitated magnetic rotor, thus, providing damping without affecting the rotational loss, as can be derived applying coupled harmonic oscillator theory in rotor dynamics. Thus, damping can be provided to a levitated object, without substantially affecting the rotational loss.

  8. Design Rules for High Damping in Mobile Hydraulic Systems

    OpenAIRE

    Axin, Mikael; Krus, Petter

    2013-01-01

    This paper analyses the damping in pressure compensated closed centre mobile working hydraulic systems. Both rotational and linear loads are covered and the analysis applies to any type of pump controller. Only the outlet orifice in the directional valve will provide damping to a pressure compensated system. Design rules are proposed for how the system should be dimensioned in order to obtain a high damping. The volumes on each side of the load have a high impact on the damping. In case of a ...

  9. Detecting Dual AGN at High Redshift

    Science.gov (United States)

    Barrows, Robert S.

    2012-01-01

    The existence of supermassive black holes (SMBHs) in most, if not all, galaxies, along with observations of galaxy mergers, suggests that pairs of SMBHs should exist for some time in the merger remnant. Observational evidence for these systems at kpc-scale separations (i.e. dual AGN) has dramatically increased recently through a combination of spectral and morphological selections. I discuss observations of CXOXBJ142607.6+353351 (CXOJ1426+35), a candidate dual AGN at z=1.175, and put its properties, including significant obscuration, within the context of other candidate/confirmed dual AGN at lower redshifts. Though dual AGN are expected to be more common at higher redshifts, they are more difficult to detect. Furthermore, adding to the difficulties of detection are a number of other physical mechanisms which can mimic the spectroscopic signature of two Type 2 AGN. In particular, I will discuss the possibility of strong outflows from an AGN. These outflow phenomena can be an important feedback mechanism in galaxies and are apparently common in AGN, making them a viable alternative to the dual AGN scenario. Based on our candidate's luminosity and emission line intensities, we find that an outflow is a possibility. If this is the case, such an outflow would be especially strong and has implications for AGN feedback in galaxies. However, the dual AGN scenario cannot be ruled out, and at z=1.175, the two putative AGN could potentially be resolved with Chandra. Other candidate dual AGN at similar redshifts and with significant obscuration could also be confirmed this way. This research was sponsored by the Strategic University Research Partnership Program, the National Aeronautics and Space Administration and the Arkansas NASA EPSCoR program.

  10. Imaging of Three Possible Low Redshift Analogs to High Redshift Compact Red Galaxies

    CERN Document Server

    Shih, Hsin-Yi

    2011-01-01

    As part of a larger program to identify and characterize possible low-redshift analogs to massive compact red galaxies found at high redshift, we have examined the morphologies of three low-redshift compact galaxies drawn from the sample of Trujillo et al. (2009). Using deeper and higher resolution images, we have found faint and relatively extensive outer structures in addition to the compact cores identified in the earlier measurements. One object appears to have a small companion that may be involved in an ongoing minor merger of the sort that could be responsible for building up the outer parts of these galaxies. The ages of the dominant stellar populations in these objects are found to be around 2--4 Gyr, in good agreement with the previous estimates. The presence of diffuse outer structures in these galaxies indicates that truly compact and massive red galaxies are exceedingly rare at low redshift. The relatively young stellar populations suggest that the accretion of the extensive outer material must o...

  11. Cosmological simulations of the high-redshift radio universe

    OpenAIRE

    Kawata, Daisuke; Gibson, Brad K.; Windhorst, Rogier A.

    2004-01-01

    Using self-consistent cosmological simulations of disc galaxy formation, we analyse the 1.4 GHz radio flux from high-redshift progenitors of present-day normal spirals within the context of present-day and planned next-generation observational facilities. We demonstrate that while current radio facilities such as the Very Large Array (VLA) are unlikely to trace these progenitors beyond redshifts z

  12. Structure of the Universe at Small and High Redshifts

    Science.gov (United States)

    Doroshkevich, A.; Turchaninov, V.

    1998-12-01

    The approximate theoretical description of the formation and evolution of the structure of the universe proposed by Demianski and Doroshkevich (1998) is compared with observed and simulated matter distribution at small and high redshifts. It is found that for the CDM-like power spectrum and suitable parameters of the cosmological model the effective matter compression reaches at small redshifts the observed scales Rwall ~20 - 25h^{-1}Mpc with the typical mean separation of wall-like elements DSLSS 50 - 70h^{-1}Mpc. We show that the same theoretical model explains well both the redshift, temperature and NHI distributions of absorption lines observed in the spectra of quasars at redshifts 2 <= z <= 3.5. The models with 0.3 <= Omega_m <= 0.5 give better description of the observed structure parameters.

  13. Spectroscopy of moderately high-redshift RCS-1 clusters

    CERN Document Server

    Gilbank, David G; Blindert, K; Ellingson, E; Gladders, M D; Yee, H K C

    2007-01-01

    We present spectroscopic observations of 11 moderately high-redshift (z~0.7- 1.0) clusters from the first Red-Sequence Cluster Survey (RCS-1). We find excellent agreement between the red-sequence estimated redshift and the spectroscopic redshift, with a scatter of 10% at z>0.7. At the high-redshift end (z>~0.9) of the sample, we find two of the systems selected are projections of pairs of comparably rich systems, with red-sequences too close to discriminate in (R-z') colour. In one of these systems, the two components are close enough to be physically associated. For a subsample of clusters with sufficient spectroscopic members, we examine the correlation between B_gcR (optical richness) and the dynamical mass inferred from the velocity dispersion. We find these measurements to be compatible, within the relatively large uncertainties, with the correlation established at lower redshift for the X-ray selected CNOC1 clusters and also for a lower redshift sample of RCS-1 clusters. Confirmation of this and calibra...

  14. Observations of the High Redshift Universe

    CERN Document Server

    Ellis, Richard S

    2007-01-01

    (Abridged) In these lectures aimed for non-specialists, I review progress in understanding how galaxies form and evolve. Both the star formation history and assembly of stellar mass can be empirically traced from redshifts z~6 to the present, but how the various distant populations inter-relate and how stellar assembly is regulated by feedback and environmental processes remains unclear. I also discuss how these studies are being extended to locate and characterize the earlier sources beyond z~6. Did early star-forming galaxies contribute significantly to the reionization process and over what period did this occur? Neither theory nor observations are well-developed in this frontier topic but the first results presented here provide important guidance on how we will use more powerful future facilities.

  15. Cosmochemistry, cosmology and fundamental constants: High-resolution spectroscopy of damped Lyman-alpha systems

    CERN Document Server

    Quast, R; Smette, A; Garcet, O; Ledoux, C; López, S; Wisotzki, L

    2004-01-01

    Spectroscopy of QSO absorption lines provides essential observational input for the study of nucleosynthesis and chemical evolution of galaxies at high redshift. But new observations may indicate that present chemical abundance data are biased due to deficient spectral resolution and unknown selection effects: Recent high-resolution spectra reveal the hitherto unperceived chemical nonuniformity of molecular hydrogen-bearing damped Lyman-alpha (DLA) systems, and the novel H/ESO DLA survey produces compelling evidence for faint QSOs being attenuated by dust. We present a revised analysis of the molecular hydrogen-bearing DLA complex toward HE 0515-4414 showing nonuniform differential depletion of chemical elements onto dust grains, and introduce to the H/ESO DLA survey and its implications. Conclusively, we aim at starting an unbiased chemical abundance database established on high-resolution spectroscopic observations. New data to probe the temperature-redshift relation predicted by standard cosmology and to t...

  16. Fast damping in mismatched high intensity beam transportation

    Directory of Open Access Journals (Sweden)

    V. Variale

    2001-08-01

    Full Text Available A very fast damping of beam envelope oscillation amplitudes was recently observed in simulations of high intensity beam transport, through periodic FODO cells, in mismatched conditions [V. Variale, Nuovo Cimento Soc. Ital. Fis. 112A, 1571–1582 (1999 and T. Clauser et al., in Proceedings of the Particle Accelerator Conference, New York, 1999 (IEEE, Piscataway, NJ, 1999, p. 1779]. A Landau damping mechanism was proposed at the origin of observed effect. In this paper, to further investigate the source of this fast damping, extensive simulations have been carried out. The results presented here support the interpretation of the mechanism at the origin of the fast damping as a Landau damping effect.

  17. 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...

  18. Flaring γ-Ray Emission from High Redshift Blazars

    Directory of Open Access Journals (Sweden)

    Monica Orienti

    2016-09-01

    Full Text Available High redshift blazars are among the most powerful objects in the Universe. Although they represent a significant fraction of the extragalactic hard X-ray sky, they are not commonly detected in γ-rays. High redshift ( z > 2 objects represent < 10 per cent of the active galactic nuclei (AGN population observed by Fermi so far, and γ-ray flaring activity from these sources is even more uncommon. The characterization of the radio-to-γ-ray properties of high redshift blazars represents a powerful tool for the study of the energetics of such extreme objects and the Extragalactic Background Light. This contribution will present results of multi-band campaigns, from radio to γ-rays, on PKS 0836+710, PKS 2149−306, and TXS 0536+145. The latter is the highest redshift detection of a flaring γ-ray blazar so far. At the peaks of their respective flares these sources reached an apparent isotropic gamma-ray luminosity of about 10 50 erg·s − 1 , which is comparable with the luminosity observed from the most powerful blazars. The physical properties derived from the multi-wavelength observations of these sources are then compared with those shown by the high redshift population.

  19. The IMF from Low to High Redshift

    CERN Document Server

    Greggio, Laura

    2012-01-01

    From time to time, and quite more frequently in recent years, claims appear favoring a variable Initial Mass Function (IMF), one way or another, either in time or space. In this chapter we add our two pennies of wisdom, illustrating how the IMF affects various properties of galaxies and galaxy clusters. We start by showing that even relatively small variations of the IMF slope have large effects on the demography of stellar populations, moving the bulk of the stellar mass from one end to the other of the distribution. We then point out how the slope of the IMF in different mass ranges controls specific major properties of galaxies and clusters. The slope of the IMF below ~1 solar mass controls the M/L ratio of local ellipticals, whereas the slope between ~1 and ~1.4 solar masses controls the evolution with redshift of such ratio, hence of the fundamental plane of elliptical galaxies. Similarly, the slope between ~1 and ~40 solar masses drives the ratio of the global metal mass in clusters of galaxies to their...

  20. 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 ...

  1. 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.

  2. Galaxy Merger Candidates in High-redshift Cluster Environments

    Science.gov (United States)

    Delahaye, A. G.; Webb, T. M. A.; Nantais, J.; DeGroot, A.; Wilson, G.; Muzzin, A.; Yee, H. K. C.; Foltz, R.; Noble, A. G.; Demarco, R.; Tudorica, A.; Cooper, M. C.; Lidman, C.; Perlmutter, S.; Hayden, B.; Boone, K.; Surace, J.

    2017-07-01

    We compile a sample of spectroscopically and photometrically selected cluster galaxies from four high-redshift galaxy clusters (1.59contamination from interlopers, {11.0}-5.6+7.0 % of the cluster members are involved in potential mergers, compared to {24.7}-4.6+5.3 % of the field galaxies. We see no evidence of merger enhancement in the central cluster environment with respect to the field, suggesting that galaxy-galaxy merging is not a stronger source of galaxy evolution in cluster environments compared to the field at these redshifts.

  3. High Redshift Galaxies in the Hubble Ultra Deep Field

    CERN Document Server

    Hathi, Nimish P

    2008-01-01

    My dissertation presents results from three recent investigations in the Hubble Ultra Deep Field (HUDF) focusing on understanding structural and physical properties of high redshift galaxies. Here I summarize results from these studies. This thesis work was conducted at Arizona State University under the guidance of Prof. Rogier Windhorst and Prof. Sangeeta Malhotra.

  4. CMB quenching of high-redshift radio-loud AGNs

    CERN Document Server

    Ghisellini, G; Ciardi, B; Sbarrato, T; Gallo, E; Tavecchio, F; Celotti, A

    2015-01-01

    The very existence of a dozen of high-redshift (z>4) blazars indicates that a much larger population of misaligned powerful jetted AGN was already in place when the Universe was <1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High redshift blazars themselves seem to be failing in producing extended radio-lobes, raising questions about the connection between such class and the vaster population of radio-galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) radiation explains the lack of extended radio emission in high redshift blazars and in their parent population, possibly accounting for the apparently missing misaligned counterparts of high redshift blazars. We then model the spectral energy distribution of blazar lobes following simple prescriptions, finding that most of them should be detectable by low frequency deep radio observations, e.g., by LOw-Frequency ARray for radio as...

  5. Population synthesis and the diagnostics of high-redshift galaxies

    Science.gov (United States)

    Buzzoni, Alberto

    The effect of redshift on the observation of distant galaxies is briefly discussed emphasizing the possible sources of bias in the interpretation of high-z data. A general energetic criterion to assess physical self-consistency of evolutionary population synthesis models is also proposed, for a more appropriate use of this important tool to investigate distinctive properties of primeval galaxies.

  6. Population Synthesis and the Diagnostics of High-redshift Galaxies

    OpenAIRE

    Buzzoni, Alberto

    2001-01-01

    The effect of redshift on the observation of distant galaxies is briefly discussed emphasizing the possible sources of bias in the interpretation of high-z data. A general energetic criterion to assess physical self-consistency of evolutionary population synthesis models is also proposed, for a more appropriate use of this important tool to investigate distinctive properties of primeval galaxies.

  7. 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...

  8. High-redshift major mergers weakly enhance star formation

    CERN Document Server

    Fensch, J; Bournaud, F; Duc, P -A; Agertz, O; Amram, P; Combes, F; Di Matteo, P; Elmegreen, B; Emsellem, E; Jog, C J; Perret, V; Struck, C; Teyssier, R

    2016-01-01

    Galaxy mergers are believed to trigger strong starbursts. This is well assessed by observations in the local Universe. However the efficiency of this mechanism has poorly been tested so far for high redshift, actively star forming, galaxies. We present a suite of pc-resolution hydrodynamical numerical simulations to compare the star formation process along a merging sequence of high and low z galaxies, by varying the gas mass fraction between the two models. We show that, for the same orbit, high-redshift gas- rich mergers are less efficient than low-redshift ones at producing starbursts: the star formation rate excess induced by the merger and its duration are both around 10 times lower than in the low gas fraction case. The mechanisms that account for the star formation triggering at low redshift - the increased compressive turbulence, gas fragmentation, and central gas inflows - are only mildly, if not at all, enhanced for high gas fraction galaxy encounters. Furthermore, we show that the strong stellar fe...

  9. Probing the bias of radio sources at high redshift

    CSIR Research Space (South Africa)

    Passmoor, S

    2012-11-01

    Full Text Available 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...

  10. Stellar Populations and Galaxy Morphology at High Redshift

    CERN Document Server

    Bunker, A J; Stern, D; Thompson, R; Moustakas, L; Davis, M; Dey, A; Bunker, Andrew; Spinrad, Hyron; Stern, Daniel; Thompson, Rodger; Moustakas, Leonidas; Davis, Marc; Dey, Arjun

    2000-01-01

    In this article we investigate the morphology and stellar populations of high-redshift galaxies through multi-waveband HST imaging and ground-based spatially-resolved spectroscopy. We study the redshift evolution of galaxy morphology in the Hubble Deep Field, using the deep IDT-NICMOS near-infrared HST imaging coupled with spectroscopic and photometric redshifts. Using the multi-waveband data to compare the appearance of galaxies at the same rest-frame wavelengths reveals that "morphological k-corrections" (the change in appearance when viewing high-z objects at shorter rest-frame wavelengths) are only important in a minority of cases, and that galaxies were intrinsically more peculiar at high redshift. One example of significant morphological k-corrections is spiral galaxies, which often show more pronounced barred structure in the near-infrared than in the optical. Therefore, the apparent decline in the fraction of barred spirals at faint magnitudes in the optical HDF may be due to band-shifting effects at ...

  11. 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.

  12. THE FIRST OBSERVATIONS OF LOW-REDSHIFT DAMPED Ly{alpha} SYSTEMS WITH THE COSMIC ORIGINS SPECTROGRAPH: CHEMICAL ABUNDANCES AND AFFILIATED GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Battisti, A. J.; Meiring, J. D.; Tripp, T. M. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Prochaska, J. X.; Werk, J. K. [Department of Astronomy and Astrophysics, University of California Observatories-Lick Observatory, UC Santa Cruz, CA 95064 (United States); Jenkins, E. B. [Department of Astrophysical Sciences, Princeton University Observatory, Princeton, NJ 08544 (United States); Lehner, N. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Tumlinson, J.; Thom, C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2012-01-10

    We present Cosmic Origins Spectrograph (COS) measurements of metal abundances in eight 0.083 < z{sub abs} < 0.321 damped Ly{alpha} (DLA) and sub-DLA absorption systems serendipitously discovered in the COS-Halos survey. We find that these systems show a large range in metallicities, with -1.10 < [Z/H] < 0.31, similar to the spread found at higher redshifts. These low-redshift systems on average have subsolar metallicities, but do show a rise in metallicity over cosmic time when compared to higher-redshift systems. We find that the average sub-DLA metallicity is higher than the average DLA metallicity at all redshifts. Nitrogen is underabundant with respect to {alpha}-group elements in all but perhaps one of the absorbers. In some cases, [N/{alpha}] is significantly below the lowest nitrogen measurements in nearby galaxies. Systems for which depletion patterns can be studied show little, if any, depletion, which is characteristic of Milky Way halo-type gas. We also identify affiliated galaxies for three of the sub-DLAs using spectra obtained from a Keck/Low Resolution Imaging Spectrometer (LRIS). None of these sub-DLAs arise in the stellar disks of luminous galaxies; instead, these absorbers may exist in galaxy halos at impact parameters ranging from 38 to 92 kpc. Multiple galaxies are present near two of the sub-DLAs, and galaxy interactions may play a role in the dispersal of the gas. Many of these low-redshift absorbers exhibit simple kinematics, but one sub-DLA has a complicated mix of at least 13 components spread over 150 km s{sup -1}. We find three galaxies near this sub-DLA, which also suggests that galaxy interactions roil the gas. This study reinforces the view that DLAs have a variety of origins, and low-redshift studies are crucial for understanding absorber-galaxy connections.

  13. High Redshift Lyman-α Hunt

    DEFF Research Database (Denmark)

    Kochiashvili, Ia

    . Significant differences between the two selectionmethods have been found. The colour-colour selection method, tends to pick galaxieswith high colour excess and can leave some strong emission-line candidates with relativelylower colour excess out of the sample. The populations of selected galaxies can also...

  14. 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)

  15. "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 ...

  16. Cloning Dropouts: Implications for Galaxy Evolution at High Redshift

    CERN Document Server

    Bouwens, R J; Illingworth, G D; Bouwens, Rychard J.; Broadhurst, Tom; Illingworth, Garth

    2003-01-01

    The evolution of high redshift galaxies in the two Hubble Deep Fields, HDF-N and HDF-S, is investigated using a cloning technique that replicates z~ 2-3 U dropouts to higher redshifts, allowing a comparison with the observed B and V dropouts at higher redshifts (z ~ 4-5). We treat each galaxy selected for replication as a set of pixels that are k-corrected to higher redshift, accounting for resampling, shot-noise, surface-brightness dimming, and the cosmological model. We find evidence for size evolution (a 1.7x increase) from z ~ 5 to z ~ 2.7 for flat geometries (Omega_M+Omega_LAMBDA=1.0). Simple scaling laws for this cosmology predict that size evolution goes as (1+z)^{-1}, consistent with our result. The UV luminosity density shows a similar increase (1.85x) from z ~ 5 to z ~ 2.7, with minimal evolution in the distribution of intrinsic colors for the dropout population. In general, these results indicate less evolution than was previously reported, and therefore a higher luminosity density at z ~ 4-5 (~ 50...

  17. The Formation of High Redshift Submillimeter Galaxies

    CERN Document Server

    Narayanan, Desika; Cox, Thomas J; Hernquist, Lars; Jonsson, Patrik; Younger, Joshua D; Groves, Brent

    2009-01-01

    We describe a model for the formation of z~2 Submillimeter Galaxies (SMGs) which simultaneously accounts for both average and bright SMGs while providing a reasonable match to their mean observed spectral energy distributions (SEDs). By coupling hydrodynamic simulations of galaxy mergers with the high resolution 3D polychromatic radiative transfer code, Sunrise, we find that a mass sequence of merger models which use observational constraints as physical input naturally yield objects which exhibit black hole, bulge, and H2 gas masses similar to those observed in SMGs. The dominant drivers behind the 850 micron flux are the masses of the merging galaxies and the stellar birthcloud covering fraction. The most luminous (S_850 >~ 15 mJy) sources are recovered by ~10^13 Msun 1:1 major mergers with a birthcloud covering fraction close to unity, whereas more average SMGs (S_850 ~ 5-7 mJy) may be formed in lower mass halos (~5 x 10^12 Msun). These models demonstrate the need for high spatial resolution hydrodynamic a...

  18. Demography of High-Redshift AGN

    Directory of Open Access Journals (Sweden)

    Fabrizio Fiore

    2012-01-01

    Universe during its infancy. We review the latest searches for high-z AGN in the deepest X-ray field so far, the Chandra Deep Field South (CDFS 4 Msecond exposure. We do not confirm the positive detection of a signal in the stacked Chandra images at the position of z~6 galaxies recently reported by Treister and collaborators (2011. We present z>3 X-ray sources number counts in the 0.5–2 keV band, obtained joining CDFS faint detections (see Fiore et al. (2011, with Chandra-COSMOS and XMM-COSMOS detections. We use these number counts to make predictions for surveys with three mission concepts: Athena, WFXT, and a Super-Chandra.

  19. FIR line emission from high redshift galaxies

    CERN Document Server

    Vallini, Livia; Ferrara, Andrea; Baek, Sunghye

    2013-01-01

    By combining high resolution, radiative transfer cosmological simulations of z~6 galaxies with a sub-grid multi-phase model of their interstellar medium we derive the expected intensity of several far infrared (FIR) emission lines ([C II] 158 micron, [O I] 63 micron, and [N II] 122 micron) for different values of the gas metallicity, Z. For Z = Z_sun the [C II] spectrum is very complex due to the presence of several emitting clumps of individual size < 3 kpc; the peak is displaced from the galaxy center by ~100 km/s. While the [O I] spectrum is also similarly displaced, the [N II] line comes predominantly from the central ionized regions of the galaxy. When integrated over ~500 km/s, the [C II] line flux is 185 mJy km/s; 95% of such flux originates from the cold (T~250 K) H I phase, and only 5% from the warm (T~5000 K) neutral medium. The [O I] and [N II] fluxes are ~6 and ~90 times lower than the [C II] one, respectively. By comparing our results with observations of Himiko, the most extended and luminous...

  20. 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...

  1. Observed Faraday Effects in Damped Lyα Absorbers and Lyman Limit Systems: The Magnetized Environment of Galactic Building Blocks at Redshift = 2

    Science.gov (United States)

    Farnes, J. S.; Rudnick, L.; Gaensler, B. M.; Haverkorn, M.; O'Sullivan, S. P.; Curran, S. J.

    2017-06-01

    Protogalactic environments are typically identified using quasar absorption lines and can manifest as Damped Lyman-alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). We use radio observations of Faraday effects to test whether these galactic building blocks host a magnetized medium, by combining DLA and LLS detections with 1.4 GHz polarization data from the NRAO VLA Sky Survey (NVSS). We obtain a control, a DLA, and an LLS sample consisting of 114, 19, and 27 lines of sight, respectively. Using a Bayesian framework and weakly informative priors, we are unable to detect either coherent or random magnetic fields in DLAs: the regular coherent fields must be ≤slant 2.8 μG, and the lack of depolarization suggests the weakly magnetized gas in DLAs is non-turbulent and quiescent. However, we find a mild suggestive indication that LLSs have coherent magnetic fields, with a 71.5% probability that LLSs have higher | {RM}| than a control, although this is sensitive to the redshift distribution. We also find a strong indication that LLSs host random magnetic fields, with a 95.5% probability that LLS lines of sight have lower polarized fractions than a control. The regular coherent fields within the LLSs must be ≤slant 2.4 μG, and the magnetized gas must be highly turbulent with a typical turbulent length scale on the order of ≈5-20 pc. Our results are consistent with the standard dynamo paradigm, whereby magnetism in protogalaxies increases in coherence over cosmic time, and with a hierarchical galaxy formation scenario, with the DLAs and LLSs exploring different stages of magnetic field evolution in galaxies.

  2. 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...

  3. 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...

  4. 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...

  5. The nuclear to host galaxy relation of high redshift quasars

    CERN Document Server

    Kotilainen, J K; Labita, M; Treves, A; Uslenghi, M

    2007-01-01

    We present near-infrared imaging with ESO VLT+ISAAC of the host galaxies of low luminosity quasars in the redshift range 1 < z < 2, aimed at investigating the relationship between the nuclear and host galaxy luminosities at high redshift. This work complements our previous study to trace the cosmological evolution of the host galaxies of high luminosity quasars (Falomo et al. 2004). The new sample includes 15 low luminosity quasars, nine radio-loud (RLQ) and six radio-quiet (RQQ). They have similar distribution of redshift and optical luminosity, and together with the high luminosity quasars they cover a large range (~4 mag) of the quasar luminosity function. The host galaxies of both types of quasars are in the range of massive inactive ellipticals between L* and 10 L*. RLQ hosts are systematically more luminous than RQQ hosts by a factor of ~2. This difference is similar to that found for the high luminosity quasars. This luminosity gap appears to be independent of the rest-frame U-band luminosity but...

  6. Damping of High-temperature Shape Memory Alloys

    Science.gov (United States)

    Duffy, Kirsten P.; Padula, Santo A., II; Scheiman, Daniel A.

    2008-01-01

    Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf

  7. 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...

  8. 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...

  9. Protoclusters Traced by High-Redshift Massive Galaxies

    Science.gov (United States)

    Garcia-Vergara, C.

    2017-08-01

    A commonly adopted approach to detect protoclusters is to search for overdensities of galaxies around massive galaxies at high-redshift such as quasars (QSOs) and submillimeter galaxies (SMGs). However, the detection of overdensities in those environments has been elusive, against of theoretical predictions. Here, I present the first measurement of the QSO-LBG and QSO-LAE cross-correlation function at z 4, based in the study of 23 QSO fields. My results indicate that LBG are strongly clustered around QSOs but LAE show similar clustering properties and number density as that observed in blank fields. One possible explanation for the lack of overdensities is that galaxies are highly obscured by dust and thus invisible at optical wavelengths. Additionally, I will present the clustering of SMGs based on spectroscopic redshift information of 52 SMGs recently identified by ALMA. This is critical to test if SMGs trace particularly massive structures. Finally, I will discuss the implications and interpretation of my results, in particular, I give the reasons of why I strongly suggest that the study of high-redshift protoclusters should be done from a combined optical+radio perspective.

  10. Low-Redshift Damped Lyman Alpha Galaxies Towards the Quasars B2 0827+243, PKS 0952+179, PKS 1127-145, and PKS 1629+120

    CERN Document Server

    Rao, S M; Turnshek, D A; Lane, W M; Monier, E M; Bergeron, J; Rao, Sandhya M.; Nestor, Daniel B.; Turnshek, David A.; Lane, Wendy M.; Monier, Eric M.; Bergeron, Jacqueline

    2003-01-01

    We present optical and near-infrared ground-based imaging results on four low-redshift damped Lyman alpha (DLA) galaxies. The corresponding DLA systems were discovered in our Hubble Space Telescope spectroscopic surveys for DLAs in known strong MgII absorption-line systems towards the quasars B2 0827+243 (z{DLA}=0.525), PKS 0952+179 (z{DLA}=0.239), PKS 1127-145 (z_{DLA}=0.313), and PKS 1629+120 (z{DLA}=0.532). The DLA galaxies span a mixture of morphological types from patchy, irregular, and low-surface-brightness to spiral galaxies. The luminosities range from 0.02L_K^* to 1.2L_K^*. We also discovered several extremely red objects (EROs) in two of these fields and discuss the possibility that they are associated with the DLA galaxies. These observations add to the small but growing list of DLA galaxies at low redshift. At the present time, 14 DLA galaxies in the redshift range $0.05 \\lesssim z \\lesssim 1$ have been studied. The distributions of DLA galaxy properties for these 14 cases are discussed and some ...

  11. 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 prominent...... tail of the Lya + N v equivalent width distribution, and we compare them to quasars with more typical emission-line properties and to low-redshift active galactic nuclei with weak/absent emission lines, namely BL Lac objects. We find that WLQs exhibit hot (T ~ 1000 K) thermal dust emission and have...... rest-frame 0.1-5 µm spectral energy distributions that are quite similar to those of normal quasars. The variability, polarization, and radio properties of WLQs are also different from those of BL Lacs, making continuum boosting by a relativistic jet an unlikely physical interpretation. The most...

  12. A Survey for Very High-Redshift Quasars

    Science.gov (United States)

    Lemley, Shelley R.

    1995-12-01

    I have been conducting a deep, three color survey for very high redshift quasars and will present information on how my candidates, which are awaiting spectroscopic confirmation, have been selected. The survey involves direct imaging through Gunn gri filters using a 2048 x 2048 STIS ccd chip and Cerro Tololo's Curtis Scmidt Telescope. Quasar candidates in the range 4.2 5 candidates have large r - i values and g - r values near zero. Before beginning the survey, test observations using this selection method were made of two known quasars with redshifts of 4.5 and 4.7. The quasars were successfully relocated by the technique and several candidates, which will also be observed for spectroscopic confirmation, were selected from those two fields. To date, 13 square degrees have been surveyed.

  13. Kinematics and Formation Mechanisms of High-Redshift Galaxies

    CERN Document Server

    Law, David R; Ellis, Richard S; Erb, Dawn K; Nesvadba, Nicole; Steidel, Charles C; Swinbank, Mark

    2009-01-01

    Recent years have witnessed a substantial increase in our ability to trace the spatially resolved properties of rapidly star-forming galaxies in the high-redshift universe and numerous studies have suggested the importance of turbulent gas-phase kinematics. In this submission to the Astro 2010 Decadal survey we outline some of the major outstanding questions regarding the kinematics and formation history of these galaxies, such as the prevalence of various kinematic models, the relation to lower surface-brightness populations and faint AGN, and the implications for the evolution of gas accretion and cooling mechanisms with redshift. We comment on the capability of future large optical/IR and millimeter wavelength facilities to address these questions.

  14. 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...

  15. 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...

  16. High redshift galaxies in the ALHAMBRA survey . I. Selection method and number counts based on redshift PDFs

    Science.gov (United States)

    Viironen, K.; Marín-Franch, A.; López-Sanjuan, C.; Varela, J.; Chaves-Montero, J.; Cristóbal-Hornillos, D.; Molino, A.; Fernández-Soto, A.; Vilella-Rojo, G.; 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.; González Delgado, R. M.; Husillos, C.; Infante, L.; Martínez, V. J.; Perea, J.; Prada, F.; Quintana, J. M.

    2015-04-01

    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-α selection. However, the availability of multifilter data now allows the dropout selections to be replaced 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 to the study of the brightest, least 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, reaching both a complete and clean sample with this method is challenging. Hence, a method to derive statistical properties by summing the zPDFs of all the galaxies in the redshift bin of interest is introduced. Results: Using this methodology we derive the galaxy rest frame UV number counts in five redshift bins centred at z = 2.5,3.0,3.5,4.0, and 4.5, being complete up to the limiting magnitude at mUV(AB) = 24, where mUV refers to the first ALHAMBRA filter redwards of the Ly-α line. With the wide field ALHAMBRA data we especially contribute to the study of the brightest ends of these counts, accurately sampling the surface densities down to mUV(AB) = 21-22. Conclusions: We show that using the zPDFs it is easy to select a very clean sample of high redshift galaxies. We also show that it is better to do statistical analysis of the properties of galaxies using a probabilistic approach, which takes into account both the incompleteness and contamination issues in a

  17. 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...

  18. On the Evolution of High-redshift Active Galactic Nuclei

    Science.gov (United States)

    Mao, Jirong; Kim, Minsun

    2016-09-01

    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 σ 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˜ 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˜ 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× {10}5 {{years}}. The X-ray AGN LFs and X-ray AGN number counts are also calculated at 2.0\\lt z\\lt 5.0 and z\\gt 3, respectively, using the same parameters adopted in the calculation for the optical AGN LF at z˜ 4. It is estimated that about 30 AGNs per {{{\\deg }}}2 at z\\gt 6 can be detected with a flux limit of 3× {10}-17 {erg} {{cm}}-2 {{{s}}}-1 in the 0.5-2 keV band. Additionally, the cosmic reionization is also investigated. The ultraviolet photons emitted from the high-redshift AGNs mainly contribute to the cosmic reionization, and the central BHs of the high-redshift AGNs have a mass range of {10}6{--}{10}8{M}⊙ . We also discuss some uncertainties in both the AGN LFs and AGN number counts originating from the {M}{{BH}}{--}σ relation, Eddington ratio, AGN lifetime, and X-ray attenuation in our model.

  19. 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...

  20. Dust Attenuation in High Redshift Galaxies -- 'Diamonds in the Sky'

    CERN Document Server

    Scoville, Nick; Capak, Peter; Kakazu, Yuko; Li, Gongjie; Steinhardt, Charles

    2014-01-01

    We use observed optical to near infrared spectral energy distributions (SEDs) of 266 galaxies in the COSMOS survey to derive the wavelength dependence of the dust attenuation at high redshift. All of the galaxies have spectroscopic redshifts in the range z = 2 to 6.5. The presence of the CIV absorption feature, indicating that the rest-frame UV-optical SED is dominated by OB stars, is used to select objects for which the intrinsic, unattenuated spectrum has a well-established shape. Comparison of this intrinsic spectrum with the observed broadband photometric SED then permits derivation of the wavelength dependence of the dust attenuation. The derived dust attenuation curve is similar in overall shape to the Calzetti curve for local starburst galaxies. We also see the 2175 \\AA~bump feature which is present in the Milky Way and LMC extinction curves but not seen in the Calzetti curve. The bump feature is commonly attributed to graphite or PAHs. No significant dependence is seen with redshift between sub-sample...

  1. Radiation-damped profiles of extremely high column density neutral hydrogen: implications of cosmic reionization

    Science.gov (United States)

    Bach, Kiehunn

    2017-01-01

    Incorporating the time-dependent second-order perturbation theory for the Lyman scattering cross-section, we investigate the intergalactic absorption profiles of extremely high column density systems near the end of cosmic reionization. Assuming a representative set of the redshift distribution of neutral hydrogen, we quantitatively examined the impact of inhomogeneous density on the intrinsic absorption profiles. The cumulative absorption by neutral patches in the line of sight mainly affects the far off-centre region of the red damping wing, but the effect is not significant. The shape of the line centre can be modified by the near-zone distribution due to high opacities of the near-resonance scattering. On the other hand, the HWHM (half width at half-maximum) as an effective line width is relatively less sensitive to the local inhomogeneity. Specifically, when the two local damping wings of Lyα and Lyβ are close in spectra of the strongly damped systems, accurate profiles of both lines are required. In the case of N_{H I}≲ 10^{21} { cm^{-2}}, the two-level approximation is marginally applicable for the damping wing fit within 5 - 7 per cent errors. However, as the local column density reaches N_{H I}˜ 10^{22.3} { cm^{-2}}, this classical approximation yields a relative error of a 10 per cent overestimation in the red wing and a 20 per cent underestimation in the blue wing of Lyα. If severe extinction by the Lyα forests is carefully subtracted, the intrinsic absorption profile will provide a better constraint on the local ionized states. For practical applications, an analytic fitting function for the Lyβ scattering is derived.

  2. Radiation Damped Profiles of Extremely High Column Density Neutral Hydrogen : Implications of Cosmic Reionization

    Science.gov (United States)

    Bach, Kiehunn

    2016-09-01

    Incorporating the time-dependent second-order perturbation theory for the Lyman scattering cross-section, we investigate the intergalactic absorption profiles of extremely high column density systems near the end of cosmic reionization. Assuming a representative set of the redshift distribution of neutral hydrogen, we quantitatively examined the impact of inhomogeneous density on the intrinsic absorption profiles. The cumulative absorption by neutral patches in the line-of-sight mainly affects the far off-center region of the red damping wing, but the effect is not significant. The shape of the line-center can be modified by the near-zone distribution due to high opacities of the near-resonance scattering. On the other hand, the HWHM (half width at half maximum) as an effective line-width is relatively less sensitive to the local inhomogeneity. Specifically, when the two local damping wings of Lyα and Lyβ are close in spectra of the strongly damped systems, accurate profiles of both lines are required. In the case of N HI ≲ 1021 cm-2, the two-level approximation is marginally applicable for the damping wing fit within 5 - 7% errors. However, as the local column density reaches N HI ˜ 1022.3 cm-2, this classical approximation yields a relative error of a 10% overestimation in the red wing and a 20% underestimation in the blue wing of Lyα. If severe extinction by the Lyα forests is carefully subtracted, the intrinsic absorption profile will provide a better constraint on the local ionized states. For practical applications, an analytic fitting function for the Lyβ scattering is derived.

  3. Simultaneously high stiffness and damping in nanoengineered microtruss composites.

    Science.gov (United States)

    Meaud, Julien; Sain, Trisha; Yeom, Bongjun; Park, Sei Jin; Shoultz, Anna Brieland; Hulbert, Gregory; Ma, Zheng-Dong; Kotov, Nicholas A; Hart, A John; Arruda, Ellen M; Waas, Anthony M

    2014-04-22

    Materials combining high stiffness and mechanical energy dissipation are needed in automotive, aviation, construction, and other technologies where structural elements are exposed to dynamic loads. In this paper we demonstrate that a judicious combination of carbon nanotube engineered trusses held in a dissipative polymer can lead to a composite material that simultaneously exhibits both high stiffness and damping. Indeed, the combination of stiffness and damping that is reported is quite high in any single monolithic material. Carbon nanotube (CNT) microstructures grown in a novel 3D truss topology form the backbone of these nanocomposites. The CNT trusses are coated by ceramics and by a nanostructured polymer film assembled using the layer-by-layer technique. The crevices of the trusses are then filled with soft polyurethane. Each constituent of the composite is accurately modeled, and these models are used to guide the manufacturing process, in particular the choice of the backbone topology and the optimization of the mechanical properties of the constituent materials. The resulting composite exhibits much higher stiffness (80 times) and similar damping (specific damping capacity of 0.8) compared to the polymer. Our work is a step forward in implementing the concept of materials by design across multiple length scales.

  4. Two Moderate-Redshift Analogs to Compact Massive Early-Type Galaxies at High Redshifts

    CERN Document Server

    Stockton, Alan; Larson, Kirsten

    2009-01-01

    From a search of a portion of the sky covered by the SDSS and UKIDSS databases, we have located 2 galaxies at z~0.5 that have properties similar to those of the luminous passive compact galaxies found at z~2.5. From Keck moderate-resolution spectroscopy and laser-guided adaptive-optics imaging of these galaxies, we can begin to put together a more detailed picture of what their high-redshift counterparts might be like. Spectral-synthesis models that fit the u to K photometry also seem to give good fits to the spectral features. From these models, we estimate masses in the range of 3-4 10^11 M_sun for both galaxies. Under the assumption that these are spheroidal galaxies, our velocity dispersions give estimated masses about a factor of 3 smaller. However, our high-resolution imaging data indicate that these galaxies are not normal spheroids, and the interpretation of the kinematic data depends critically on the actual morphologies and the nature of the stellar orbits. While recent suggestions that the populati...

  5. Large Scale Structures at High Redshift in the GOODS Field

    CERN Document Server

    Castellano, M; Trevese, D; Pentericci, L; Grazian, A; Fontana, A; Giallongo, E; Santini, P; Cristiani, S; Nonino, M; Vanzella, E

    2008-01-01

    We present a catalogue of overdensities in the GOODS-South field. We find various high density peaks that are embedded in structures diffused on the entire field, up to z ~ 2.5. The slope of their colour-magnitude relation does not show significative evolution with z. We find evidence that galaxies forming these structures are more massive than galaxies located in low density regions. We also analyse the variation of galaxy properties with the associated environmental density and we find that the segregation of red galaxies with density is stronger at low redshift and at high luminosities while it gets much weaker for increasing z.

  6. 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...

  7. The effects of the small-scale DM power on the cosmological neutral hydrogen (HI) distribution at high redshifts

    Science.gov (United States)

    Sarkar, Abir; Mondal, Rajesh; Das, Subinoy; Sethi, Shiv. K.; Bharadwaj, Somnath; Marsh, David J. E.

    2016-04-01

    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 × 105 (for LFDM) and the axion mass ma > 2.6 × 10-23 eV (for ULA). The comparison of the collapsed mass fraction inferred from damped Lyman-α observations to the theoretical predictions of our models lead to the weaker bounds: zf > 2 × 105 and ma > 10-23 eV. These bounds are consistent with other constraints in the literature using different observables; we briefly discuss how these bounds compare with possible constraints from the observation of luminosity function of galaxies at high redshifts. In the case of ULAs, these constraints are also consistent with a solution to the cusp-core problem of CDM.

  8. High Redshift Cosmography: New Results and Implications for Dark Energy

    Science.gov (United States)

    Demianski, M.; Piedipalumbo, E.; Rubano, C.; Scudellaro, P.

    2015-01-01

    We use all the publicly available date on high redshift objects to derive constrains on the parameters of FRWL cosmological model without imposing any a priori assumptions about the dynamical equations for gravity and matter content of the Universe. These data sets allow us to put constrains on the cosmographic expansion parameters up to the fifth order. We show that the standard ΛCDM model is marginally compatible with these data, in particular the deceleration parameter confirms the present acceleration phase of the Universe, but there are hints that the dark energy equation of state is changing in time.

  9. High-Redshift Quasars at the Highest Resolution: VSOP Results

    Science.gov (United States)

    Frey, S.; Gurvits, L. I.; Lobanov, A. P.; Schilizzi, R. T.; Paragi, Z.

    2009-08-01

    We studied the radio structure of high-redshift (z>3) quasars with VSOP at 1.6 and 5 GHz. These sources are the most distant objects ever observed with Space VLBI, at rest-frame frequencies up to ˜25 GHz. Here we give an account of the observations and briefly highlight the most interesting cases and results. These observations allowed us, among other things, to estimate the mass of the central black holes powering these quasars, to identify large misalignments between the milli-arcsecond (mas) and sub-mas scale radio structures, and to detect apparent superluminal motion at sub-mas scale.

  10. UV Properties and Evolution of High-redshift Galaxies

    Science.gov (United States)

    Buzzoni, Alberto

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  11. UV properties and evolution of high-redshift galaxies

    OpenAIRE

    Buzzoni, Alberto

    2002-01-01

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for mor...

  12. UV properties and evolution of high-redshift galaxies

    CERN Document Server

    Buzzoni, A

    2002-01-01

    I assess the problem of morphological and photometric evolution of high-redshift galaxies in the ultraviolet wavelength range. My discussion will partly rely on a new set of template galaxy models, in order to infer the expected changes along the Hubble morphological sequence at the different cosmic epochs. The impact of evolution on the faint-end galaxy luminosity function at z~1 and beyond will also be evaluated and briefly discussed. See http://www.merate.mi.astro.it/~eps/home.html for more info and model retrieval.

  13. Integral-field studies of the high-redshift Universe

    OpenAIRE

    Jarvis, Matt J.; van Breuekeln, Caroline; Venemans, Bram P.; Wilman, Richard J.

    2006-01-01

    We present results from a new method of exploring the distant Universe. We use 3-D spectroscopy to sample a large cosmological volume at a time when the Universe was less than 3 billion years old to investigate the evolution of star-formation activity. Within this study we also discovered a high redshift type-II quasar which would not have been identified with imaging studies alone. This highlights the crucial role that integral-field spectroscopy may play in surveying the distant Universe in...

  14. Color and Polarization Models of High Redshift Radio Galaxies

    Science.gov (United States)

    Chambers, K. C.

    2000-05-01

    The scattering of an anisotropic quasar beam by dust swept-up by a bipolar outflow is used to construct model color and polarization images for comparison with high redshift radio galaxies and quasars. The swept-up shell is assumed to be optically thin to dust scattering outside the nuclear region. The spectral energy distributions and polarization characteristics of the extended aligned emission from HZRGs and QSRs can be reproduced using an input quasar spectrum and the Loar & Draine (1993) silicate-graphite grain model.

  15. Photometric Properties of the Most Massive High-Redshift Galaxies

    Science.gov (United States)

    Robertson, Brant; Li, Yuexing; Cox, Thomas J.; Hernquist, Lars; Hopkins, Philip F.

    2007-09-01

    We calculate the observable properties of the most massive high-redshift galaxies in the hierarchical formation scenario where stellar spheroid and supermassive black hole growth are fueled by gas-rich mergers. Combining high-resolution hydrodynamical simulations of the hierarchical formation of a z~6 quasar, stellar population synthesis models, template active galactic nucleus (AGN) spectra, prescriptions for interstellar and intergalactic absorption, and the response of modern telescopes, the photometric evolution of galaxies destined to host z~6 quasars is modeled at redshifts z~4-14. These massive galaxies, with enormous stellar masses of M*~1011.5-1012 Msolar and star formation rates of SFR~103-104 Msolar yr-1 at z>~7, satisfy a variety of photometric selection criteria based on Lyman break techniques, including V-band dropouts at z>~5, i-band dropouts at z>~6, and z-band dropouts at z>~7. The observability of the most massive high-redshift galaxies is assessed and compared with a wide range of existing and proposed photometric surveys, including the Sloan Digital Sky Survey (SDSS), Great Observatories Origins Deep Survey (GOODS)/Hubble Ultra Deep Field (HUDF), National Optical Astronomy Observatory Deep Wide-Field Survey (NDWFS), UKIRT Infared Deep Sky Survey (UKIDSS), Infrared Array Camera (IRAC) Shallow Survey, Ultradeep Visible and Infrared Survey Telescope for Astronomy (VISTA), Dark Universe Explorer (DUNE), Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), Large Synoptic Survey Telescope (LSST), and Supernova/Acceleration Probe (SNAP). Massive stellar spheroids descended from z~6 quasars will likely be detected at z~4 by existing surveys, but owing to their low number densities the discovery of quasar progenitor galaxies at z>7 will likely require future surveys of large portions of the sky (>~0.5%) at wavelengths λ>~1 μm. The detection of rare, starbursting, massive galaxies at redshifts z>~6 would provide support for the

  16. The problematic growth of dust in high-redshift galaxies

    Science.gov (United States)

    Ferrara, A.; Viti, S.; Ceccarelli, C.

    2016-11-01

    Dust growth via accretion of gas species has been proposed as the dominant process to increase the amount of dust in galaxies. We show here that this hypothesis encounters severe difficulties that make it unfit to explain the observed UV and IR properties of such systems, particularly at high redshifts. Dust growth in the diffuse ISM phases is hampered by (a) too slow accretion rates, (b) too high dust temperatures, and (c) the Coulomb barrier that effectively blocks accretion. In molecular clouds these problems are largely alleviated. Grains are cold (but not colder than the CMB temperature, TCMB ≈ 20 K at redshift z = 6). However, in dense environments accreted materials form icy water mantles, perhaps with impurities. Mantles are immediately (≲1 yr) photo-desorbed as grains return to the diffuse ISM at the end of the cloud lifetime, thus erasing any memory of the growth. We conclude that dust attenuating stellar light at high-z must be ready-made stardust largely produced in supernova ejecta.

  17. Silk damping at a redshift of a billion: a new limit on small-scale adiabatic perturbations

    CERN Document Server

    Jeong, Donghui; Chluba, Jens; Kamionkowski, Marc

    2014-01-01

    We study the dissipation of small-scale adiabatic perturbations at early times when the Universe is hotter than T ~ 0.5 keV. When the wavelength falls below the damping scale 1/kD, the acoustic modes diffuse and thermalize, causing entropy production. Before neutrino decoupling, kD is primarily set by the neutrino shear viscosity, and we study the effect of acoustic damping on the relic neutrino number, primordial nucleosynthesis, dark-matter freeze-out, and baryogenesis. This sets a new limit on the amplitude of primordial fluctuations of DeltaR^2 < 0.007 at 10^4/Mpc< k < 10^5/Mpc and a model dependent limit of DeltaR^2 < 0.3 at k < 10^{20-25}/Mpc.

  18. Cosmic Lighthouses : Unveiling the nature of high-redshift galaxies

    CERN Document Server

    Dayal, Pratika

    2011-01-01

    We are in the golden age for the search for high-redshift galaxies, made possible by a combination of new instruments and innovative search techniques. One of the major aims of such searches is to constrain the epoch of reionization (EoR), which marks the second major change in the ionization state of the Universe. Understanding the EoR is difficult since whilst it is galaxy evolution which drives reionization, reionization itself influences galaxy evolution through feedback effects. Unraveling the interplay of reionization and galaxy evolution is further complicated by of a lack of understanding of the metal enrichment and dust distribution in high redshift galaxies. To this end, a class of galaxies called Lyman Alpha Emitters (LAEs) have been gaining enormous popularity as probes of all these three processes. In this thesis, we couple state of the art cosmological SPH simulations (GADGET-2) with a physically motivated, self-consistent model for LAEs, so as to be able to understand the importance of the inte...

  19. Stellar Population Maps of High-Redshift Galaxies

    Science.gov (United States)

    Fetherolf, Tara; Reddy, Naveen; MOSDEF

    2016-06-01

    A comprehensive study of resolved galaxy structure can shed light on the formation and evolution of galactic properties, such as the distribution of stars and interstellar dust that obscures starlight. This requires high-resolution, multi-waveband photometry and spectroscopy to completely characterize the galaxies. Previous studies lacked key spectroscopic information, were comprised of small samples, or focused on the local universe. We use HST ACS/WFC3 high-resolution, multi-waveband imaging from the CANDELS project in parallel with moderate-resolution Keck I MOSFIRE spectra from the MOSFIRE Deep Evolution Field (MOSDEF) survey to produce resolved stellar population and dust maps of ~500 galaxies at redshifts 1.4 < z < 2.6—covering the key epoch when galaxies accreted most of their mass. For data preparation and analysis we develop an automated Python program to process our large, comprehensive dataset. From the multi-waveband imaging and spectroscopic redshifts, we model the spectral energy distribution for every resolution element within each galaxy and compare these results to the spectroscopically measured global properties. From our stellar population and dust maps we identify resolved structures within these galaxies. We also investigate if spectroscopically measured galaxy properties are biased when compared with that of localized sub-galactic structures.

  20. Highly damped quasinormal modes of Kerr black holes

    CERN Document Server

    Berti, E; Kokkotas, K D; Onozawa, H; Berti, Emanuele; Cardoso, Vitor; Kokkotas, Kostas D.; Onozawa, Hisashi

    2003-01-01

    Motivated by recent suggestions that highly damped black hole quasinormal modes (QNM's) may provide a link between classical general relativity and quantum gravity, we present an extensive computation of highly damped QNM's of Kerr black holes. We do not limit our attention to gravitational modes, thus filling some gaps in the existing literature. The frequency of gravitational modes with $l=m=2$ tends to $omega_R=2 Omega$, $Omega$ being the angular velocity of the black hole horizon. If Hod's conjecture is valid, this asymptotic behaviour is related to reversible black hole transformations. Other highly damped modes with $m>0$ that we computed do {it not} show a similar behaviour. The real part of modes with $l=2$ and $m0$ is given by $2pi T_H$ ($T_H$ being the black hole temperature). We conjecture that for all values of $l$ and $m>0$ there is an infinity of modes tending to the critical frequency for superradiance ($omega_R=m$) in the extremal limit. Finally, we study in some detail modes branching off the...

  1. GRB 050505: A high redshift burst discovered by Swift

    CERN Document Server

    Hurkett, C P; Page, K L; Rol, E; Goad, M R; O'Brien, P T; Beardmore, A; Godet, O; Burrows, D N; Tanvir, N R; Levan, A; Zhang, B; Malesani, D; Hill, J E; Kennea, J A; Chapman, R; La Parola, V; Perri, M; Romano, P; Gehrels, R S N

    2006-01-01

    We report the discovery and subsequent multi-wavelength afterglow behaviour of the high redshift (z = 4.27) Gamma Ray Burst GRB 050505. This burst is the third most distant burst, measured by spectroscopic redshift, discovered after GRB 000131 (z = 4.50) and GRB 050904 (z = 6.29). GRB 050505 is a long GRB with a multipeaked gamma-ray light curve, with a duration of T_90 = 63+/-2 s and an inferred isotropic release in gamma-rays of ~4.44 x 10^53 ergs in the 1-10^4 keV rest frame energy range. The Swift X-Ray Telescope followed the afterglow for 14 days, detecting two breaks in the light curve at 7.4(+/-1.5) ks and 58.0 (+9.9/-15.4) ks after the burst trigger. The power law decay slopes before, between and after these breaks were 0.25 (+0.16/-0.17), 1.17 (+0.08/-0.09) and 1.97 (+0.27/-0.28) respectively. The light curve can also be fit with a `smoothly broken' power law model with a break observed at ~ T+18.5 ks, with decay slopes of ~0.4 and ~1.8 before and after the break respectively. The X-ray afterglow sho...

  2. Star formation and mass assembly in high redshift galaxies

    CERN Document Server

    Santini, P; Grazian, A; Salimbeni, S; Fiore, F; Fontanot, F; Boutsia, K; Castellano, M; Cristiani, S; De Santis, C; Gallozzi, S; Giallongo, E; Menci, N; Nonino, M; Paris, D; Pentericci, L; Vanzella, E

    2009-01-01

    We study the star formation and the mass assembly process of 0.30.3, the SFR is well correlated with stellar mass, and this relationship seems to steepen with redshift (using IR-based SFRs); b) The contribution to the global SFRD by massive galaxies increases with redshift up to ~2.5, faster than for galaxies of lower mass, but appears to flatten at higher z; c) Despite this increase, the most important contributors to the SFRD at any z are galaxies around, or immediately below, the characteristic stellar mass; d) At z~2, massive galaxies are actively star-forming, with a median SFR 300 Msun/yr. During this epoch, they assemble a substantial part of their final stellar mass; e) The SSFR shows a clear bimodal distribution. The analysis of the SFRD and the SSFR seems to sup port the downsizing scenario, according to which high mass galaxies have formed their stars earlier and faster than their low mass counterparts. A comparison with recent theoretical models shows that they follow the global increase of the SS...

  3. Dust in High Redshift Gamma Ray Burst Host Galaxies

    Science.gov (United States)

    Liang, Shunlin; Li, A.

    2009-12-01

    The discovery of high-redshift GRBs opens a new window into the nature of dust in the early universe. We explore the dust properties of the host galaxies of a large sample (32 objects) of long-GRBs at 2.0≤ z ≤ 6.7, with a mean redshift of z=3.34 (corresponding to a look-back time of 1.94 Gyr), by fitting their optical-near-IR afterglow spectra. The average dust extinction in the visual band is AV=0.3. The EB-V/NHI and AV/NHI ratios decrease linearly with the dust-to-gas ratio, suggesting that the dust properties remain unchanged at the epoch of 2.0≤ z ≤ 6.7. The inferred extinction curves are closely reproduced in terms of a mixture of amorphous silicate and graphite. The quanities of amorphous silicate and graphite (relative to H) both appear to decrease with, while their cut-off grain sizes show no significant evolution in the interval 2.0≤ z ≤ 6.7.

  4. Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae

    CERN Document Server

    Morokuma, Tomoki; Lidman, Christopher; Doi, Mamoru; Yasuda, Naoki; Aldering, Greg; Amanullah, Rahman; Barbary, Kyle; Dawson, Kyle; Fadeyev, Vitaliy; Fakhouri, Hannah K; Goldhaber, Gerson; Goobar, Ariel; Hattori, Takashi; Hayano, Junji; Hook, Isobel M; Howell, D Andrew; Furusawa, Hisanori; Ihara, Yutaka; Kashikawa, Nobunari; Knop, Rob A; Konishi, Kohki; Meyers, Joshua; Oda, Takeshi; Pain, Reynald; Perlmutter, Saul; Rubin, David; Spadafora, Anthony L; Suzuki, Nao; Takanashi, Naohiro; Totani, Tomonori; Utsunomiya, Hiroyuki; Wang, Lifan

    2009-01-01

    We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These SN surveys specifically targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we obtain redshifts for 32 candidates and spectroscopically identify 7 active candidates as probable SNe Ia, including one at z=1.35, which is the most distant SN Ia to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates are identified as likely SNe Ia from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia are observed within a week of maximum light, we find that we can spectroscopically identify most of them up to z=1.1. Beyond...

  5. Population III Stars and Remnants in High Redshift Galaxies

    CERN Document Server

    Xu, Hao; Norman, Michael L

    2013-01-01

    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 10^9 Msun 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 ~ 10^7 Msun 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} Msun yr^{-1} Mpc^{-3} at redshift 15. The most massive starless halo has a mass of 7 x 10^7 Msun, which could host massive black hole formation...

  6. Frontier Fields: High-Redshift Predictions and Early Results

    CERN Document Server

    Coe, Dan; Zitrin, Adi

    2014-01-01

    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. In this paper, we present high-redshift (z > 6) number count predictions for the full program and candidates in three of the first Hubble Frontier Fields images. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Where previous programs yielded perhaps a dozen z > 9 candidates, the Frontier Fields may yield ~70 (~6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 9. This might suggest a deficit of faint z > 9 galaxies as also reported in the Ultra Deep Field (even while excesses of brighter z > 9 galaxies were reported in shallower fields). At these redshifts, cosmic variance (field-to-field variation) is expected...

  7. Star Formation in High-Redshift Cluster Ellipticals

    CERN Document Server

    Wagner, Cory R; Snyder, Gregory F; Gonzalez, Anthony H; Stanford, S A; Alberts, Stacey; Pope, Alexandra; Stern, Daniel; Zeimann, Gregory R; Chary, Ranga-Ram; Dey, Arjun; Eisenhardt, Peter R M; Mancone, Conor L; Moustakas, John

    2014-01-01

    We measure the star formation rates (SFRs) of massive ($M_{\\star}>10^{10.1}M_{\\odot}$) early-type galaxies (ETGs) in a sample of 11 high-redshift ($1.0 < z < 1.5$) galaxy clusters drawn from the IRAC Shallow Cluster Survey (ISCS). We identify ETGs visually from Hubble Space Telescope imaging and select likely cluster members as having either an appropriate spectroscopic redshift or red sequence color. Mid-infrared SFRs are measured using Spitzer 24 $\\mu$m data for isolated cluster galaxies for which contamination by neighbors, and active galactic nuclei, can be ruled out. Cluster ETGs show enhanced specific star formation rates (sSFRs) compared to cluster galaxies in the local Universe, but have sSFRs more than four times lower than that of field ETGs at $1 < z < 1.5$. Relative to the late-type cluster population, isolated ETGs show substantially quenched mean SFRs, yet still contribute 12% of the overall star formation activity measured in $1 < z < 1.5$ clusters. We find that new ETGs are l...

  8. High Redshift Quasars and Star Formation in the Early Universe

    CERN Document Server

    Dietrich, M; Vestergaard, M; Wagner, S J

    2001-01-01

    In order to derive information on the star formation history in the early universe we observed 6 high-redshift (z=3.4) quasars in the near-infrared to measure the relative iron and \\mgii emission strengths. A detailed comparison of the resulting spectra with those of low-redshift quasars show essentially the same FeII/MgII emission ratios and very similar continuum and line spectral properties, indicating a lack of evolution of the relative iron to magnesium abundance of the gas since z=3.4 in bright quasars. On the basis of current chemical evolution scenarios of galaxies, where magnesium is produced in massive stars ending in type II SNe, while iron is formed predominantly in SNe of type Ia with a delay of ~1 Gyr and assuming as cosmological parameters H_o = 72 km/s Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7$, we conclude that major star formation activity in the host galaxies of our z=3.4 quasars must have started already at an epoch corresponding to z_f ~= 10, when the age of the universe was less than 0....

  9. 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 ...

  10. How Accurately Can We Measure Galaxy Environment at High Redshift Using Only Photometric Redshifts?

    Science.gov (United States)

    Florez, Jonathan; Jogee, Shardha; Sherman, Sydney; Papovich, Casey J.; Finkelstein, Steven L.; Stevans, Matthew L.; Kawinwanichakij, Lalitwadee; Ciardullo, Robin; Gronwall, Caryl; SHELA/HETDEX

    2017-06-01

    We use a powerful synergy of six deep photometric surveys (Herschel SPIRE, Spitzer IRAC, NEWFIRM K-band, DECam ugriz, and XMM X-ray) and a future optical spectroscopic survey (HETDEX) in the Stripe 82 field to study galaxy evolution during the 1.9 nearest neighbor densities, and galaxy counts within some projected aperture) at different photometric redshifts to cosmological simulations in order to quantify the uncertainty in our estimates of environment. We also explore how robustly one can recover the variation of galaxy properties with environment, when using only photometric redshifts. In the era of large photometric surveys, this work has broad implications for studies addressing the impact of environment on galaxy evolution at early cosmic epochs. We acknowledge support from NSF grants AST-1614798, AST-1413652 and NSF GRFP grant DGE-1610403.

  11. The Lyα emission from high- z galaxies hosting strong damped Lyα systems

    Science.gov (United States)

    Joshi, Ravi; Srianand, Raghunathan; Noterdaeme, Pasquier; Petitjean, Patrick

    2017-02-01

    We study the average Lyα emission associated with high-z strong (log N(H I) ≥ 21) damped Lyα systems (DLAs). We report Lyα luminosities (LLyα) for the full as well as various sub-samples based on N(H I), z, (r - i) colours of QSOs and rest equivalent width of Si IIλ1526 line (i.e. W1526). For the full sample, we find LLyα level detection of Lyα emission in the red part of the DLA trough. The LLyα is found to be higher for systems with higher W1526 with its peak, detected at ≥3σ, redshifted by about 300-400 km s-1 with respect to the systemic absorption redshift, as seen in Lyman break galaxies (LBGs) and Lyα emitters. A clear signature of a double-hump Lyα profile is seen when we consider W1526 ≥0.4 Å and (r - i) radiation that is 4-10 times stronger than the metagalactic UV background at these redshifts. The relationship between the SFR and surface mass density of atomic gas seen in DLAs is similar to that of local dwarf and metal-poor galaxies. We show that the low-luminosity galaxies will contribute appreciably to the stacked spectrum if the size-luminosity relation seen for H I at low z is also present at high-z. Alternatively, large Lyα haloes seen around LBGs could also explain our measurements.

  12. High-redshift quasar host galaxies with adaptive optics

    CERN Document Server

    Kuhlbrodt, B; Wisotzki, L; Jahnke, K

    2005-01-01

    We present K band adaptive optics observations of three high-redshift (z ~ 2.2) high-luminosity quasars, all of which were studied for the first time. We also bserved several point spread function (PSF) calibrators, non-simultaneously because of the small field of view. The significant temporal PSF variations on timescales of minutes inhibited a straightforward scaled PSF removal from the quasar images. Characterising the degree of PSF concentration by the radii encircling 20% and 80% of the total flux, respectively, we found that even under very different observing conditions the r20 vs. r80 relation varied coherently between individual short exposure images, delineating a well-defined relation for point sources. Placing the quasar images on this relation, we see indications that all three objects were resolved. We designed a procedure to estimate the significance of this result, and to estimate host galaxy parameters, by reproducing the statistical distribution of the individual short exposure images. We fi...

  13. Elemental Abundances in Two High Column Density Damped Lyman Alpha Systems at z < 1.5

    CERN Document Server

    Rao, S M; Howk, J C; Wolfe, A M; Rao, Sandhya M.; Prochaska, Jason X.; Wolfe, Arthur M.

    2004-01-01

    We present Keck/HIRES abundance measurements and metal-line kinematic profiles of the damped Lyman alpha systems (DLAs) towards the quasars Q0933+733 (z_abs=1.479) and Q0948+433 (z_abs=1.233). These two DLAs have among the five highest HI column densities at any redshift: N(HI)=4.2E21 cm^{-2}. The metal-line data, presented here for the first time, reveal that these DLAs are noteworthy for several other reasons as well. 1) The Q0933+733 DLA exhibits simple kinematic structure with unusually narrow velocity widths as measured from its unsaturated metal lines (delta v=16 km/s). At 2.6% solar, it has the second lowest metallicity at z -1) and a significant alpha-enhancement. The strong metal lines of this DLA have made possible the detection of TiII1910, CoII2012, and MgI2026. 3) We find that the relative gas-phase abundances of both DLAs follow the general trend seen at high redshift, e.g., enhanced Zn/Fe and Si/Fe, and sub-solar Mn/Fe, indicating that there is little evolution in the nucleosynthetic patterns o...

  14. Understanding the dark matter-light connection at high redshifts

    Science.gov (United States)

    Lee, Kyoung-Soo

    Deep, wide-field surveys have enhanced our understanding of galaxy formation and its close connection to the large-scale structures of dark matter in the universe. At high redshifts ( z > 2), in particular, where it is not possible to observe dark matter structures in other methods such as gravitational lensing or galaxy rotation curves, study of galaxy clustering provides a unique view into the formation of galaxies in large look-back times. In this thesis, I present a clustering study of star-forming galaxies at high redshifts ( z ~ 3- 5), observed and selected from two of the deepest multi-wavelength photometric data to date. First, I show that the UV luminosity (or star formation rate) of these galaxies scales closely with the degree of spatial clustering at all cosmic epochs probed from these surveys. In conjunction with the current, well- established theoretical framework of cold dark matter cosmology, this implies that star formation rate is primarily determined by the total mass of the virialized dark matter structures, or dark matter halos. In addition, I show that the measures of galaxy correlation function exhibits a strong upturn on small scales, which cannot be explained with the clustering of halos hosting these galaxies alone. This strongly suggests that multiple galaxies can share a single massive dark matter halo. A simple scaling law between the number of galaxy occupants and halo mass is sufficient to successfully reproduce the observed shape of the correlation function. However, there is uncertainty in drawing physical parameters of the halo-galaxy association which depends on the assumed form of the scaling law, or the halo occupation distribution (HOD). Physical interpretations are further exacerbated by the unknown degree of "fairness" that color-selected galaxies represent. I present an alternative approach which requires precise measurements of both the luminosity function and correlation function (of various luminosity thresholds). By

  15. 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.

  16. 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.

  17. STAR FORMATION IN HIGH-REDSHIFT CLUSTER ELLIPTICALS

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Cory R.; Brodwin, Mark [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Snyder, Gregory F. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gonzalez, Anthony H.; Mancone, Conor L. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Stanford, S. A. [University of California, Davis, CA 95616 (United States); Alberts, Stacey; Pope, Alexandra [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Stern, Daniel; Eisenhardt, Peter R. M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Zeimann, Gregory R. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Chary, Ranga-Ram [Spitzer Science Center, MC 220-6, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91109 (United States); Dey, Arjun [NOAO, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Moustakas, John, E-mail: cwagner@astro.queensu.ca [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States)

    2015-02-20

    We measure the star formation rates (SFRs) of massive (M {sub *} > 10{sup 10.1} M {sub ☉}) early-type galaxies (ETGs) in a sample of 11 high-redshift (1.0 < z < 1.5) galaxy clusters drawn from the IRAC Shallow Cluster Survey (ISCS). We identify ETGs visually from Hubble Space Telescope imaging and select likely cluster members as having either an appropriate spectroscopic redshift or red-sequence color. Mid-infrared SFRs are measured using Spitzer 24 μm data for isolated cluster galaxies for which contamination by neighbors, and active galactic nuclei, can be ruled out. Cluster ETGs show enhanced specific star formation rates (sSFRs) compared to cluster galaxies in the local universe, but have sSFRs more than four times lower than that of field ETGs at 1 < z < 1.5. Relative to the late-type cluster population, isolated ETGs show substantially quenched mean SFRs, yet still contribute 12% of the overall star formation activity measured in 1 < z < 1.5 clusters. We find that new ETGs are likely being formed in ISCS clusters; the fraction of cluster galaxies identified as ETGs increases from 34% to 56% from z ∼ 1.5 → 1.25. While the fraction of cluster ETGs that are highly star-forming (SFR ≥ 26 M {sub ☉} yr{sup –1}) drops from 27% to 10% over the same period, their sSFRs are roughly constant. All these factors taken together suggest that, particularly at z ≳ 1.25, the events that created these distant cluster ETGs—likely mergers, at least among the most massive—were both recent and gas-rich.

  18. High resolution upgrade of the ATF damping ring BPM system

    Energy Technology Data Exchange (ETDEWEB)

    Terunuma, N.; Urakawa, J.; /KEK, Tsukuba; Frisch, J.; May, J.; McCormick, D.; Nelson, J.; Seryi, A.; Smith, T.; Woodley, M.; /SLAC; Briegel, C.; Dysert, R.; /Fermilab

    2008-05-01

    A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished in its first stage, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital downconversion techniques, digital signal processing, and also tests a new automatic gain error correction schema. The technical concept and realization, as well as preliminary results of beam studies are presented.

  19. Probing the Intergalactic Medium with high-redshift quasars

    Science.gov (United States)

    Calverley, Alexander Peter

    2011-11-01

    Clues about the timing of reionization and the nature of the ionizing sources responsible are imprinted in the ionization and thermal state of the IGM. In this thesis, I use high-resolution quasar spectra in conjunction with state-of-the-art hydrodynamical simulations to probe the IGM at high redshift, focusing on the ionization and thermal state of the gas. After reionization, the ionization state of the IGM is set by the intensity of the ultraviolet background (UVB), quantified by the hydrogen photoionization rate, Γ_bkg. At high redshifts this has been estimated by measuring the mean flux in the Lyα forest, and scaling Γ_bkg in simulations such that the simulated mean flux matches the observed value. In Chapter 3 I investigate whether the precision of these estimates can be improved by using the entire flux probability distribution function (PDF) instead of only the mean flux. Although I find it cannot improve the precision directly, the flux PDF can potentially be used to constrain other sources of error in observational estimates of Γ_bkg, and so may increase the precision indirectly. The ionizing output of a quasar will locally dominate over the UVB, and this leads to enhanced transmission bluewards of the quasar Lyα line, known as the proximity effect. In Chapter 4 I present the first measurements of Γ_bkg at z > 5 from the proximity effect. The UVB intensity declines smoothly with redshift over 4.6 6.4. There is a drop in Γ_bkg by roughly a factor of five, which corresponds to a drop in the ionizing emissivity by about a factor of two. Such a redshift evolution in the emissivity cannot continue to much higher redshift without reionization failing to complete, which suggests that reionization cannot have ended much higher than z = 6.4. Estimates of Γ_bkg from the proximity effect and the mean flux are generally discrepant at z ∼ 2-4, with those from the proximity effect systematically higher. This is generally attributed to effects of the

  20. The formation and evolution of high-redshift dusty galaxies

    Science.gov (United States)

    Ma, Jingzhe; Gonzalez, Anthony H.; Ge, Jian; Vieira, Joaquin D.; Prochaska, Jason X.; Spilker, Justin; Strandet, Maria; Ashby, Matthew; Noterdaeme, Pasquier; Lundgren, Britt; Zhao, Yinan; Ji, Tuo; Zhang, Shaohua; Caucal, Paul; SPT SMG Collaboration

    2017-01-01

    Star formation and chemical evolution are among the biggest questions in galaxy formation and evolution. High-redshift dusty galaxies are the best sites to investigate mass assembly and growth, star formation rates, star formation history, chemical enrichment, and physical conditions. My thesis is based on two populations of high-redshift dusty galaxies, submillimeter galaxies (SMGs) and quasar 2175 Å dust absorbers, which are selected by dust emission and dust absorption, respectively.For the SMG sample, I have worked on the gravitationally lensed dusty, star-forming galaxies (DSFGs) at 2.8 thesis is focused on the stellar masses and star formation rates of these objects by means of multi-wavelength spectral energy distribution (SED) modelling. The data include HST/WFC3, Spitzer/IRAC, Herschel/PACS, Herschel/SPIRE, APEX/Laboca and SPT. Compared to the star-forming main sequence (MS), these DSFGs have specific SFRs that lie above the MS, suggesting that we are witnessing ongoing strong starburst events that may be driven by major mergers. SPT0346-52 at z = 5.7, the most extraordinary source in the SPT survey for which we obtained Chandra X-ray and ATCA radio data, was confirmed to have the highest star formation surface density of any known galaxy at high-z.The other half of my thesis is focused on a new population of quasar absorption line systems, 2175 Å dust absorbers, which are excellent probes of gas and dust properties, chemical evolution and physical conditions in the absorbing galaxies. This sample was selected from the SDSS and BOSS surveys and followed up with the Echelle Spectrographs and Imager on the Keck-II telescope, the Red & Blue Channel Spectrograph on the Multiple Mirror Telescope, and the Ultraviolet and Visible Echelle Spectrograph onboard the Very Large Telescope. We found a correlation between the presence of the 2175 Å bump and other ingredients including high metallicity, high depletion level, overall low ionization state of gas, neutral

  1. 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...

  2. High redshift Lya emitters: clues on the Milky Way infancy

    CERN Document Server

    Salvadori, S; Ferrara, A

    2010-01-01

    With the aim of determining if Milky Way (MW) progenitors could be identified as high redshift Lyman Alpha Emitters (LAEs) we have derived the intrinsic properties of z ~ 5.7 MW progenitors, which are then used to compute their observed Lyman-alpha luminosity, L_alpha, and equivalent width, EW. MW progenitors visible as LAEs are selected according to the canonical observational criterion, L_alpha > 10^42 erg/s and EW > 20 A. Progenitors of MW-like galaxies have L_alpha = 10^(39-43.25) erg/s, making some of them visible as LAEs. In any single MW merger tree realization, typically only 1 (out of ~ 50) progenitor meets the LAE selection criterion, but the probability to have at least one LAE is very high, P = 68%. The identified LAE stars have ages, t_* ~ 150-400 Myr at z ~ 5.7 with the exception of five small progenitors with t_* 10% of the halo very metal-poor stars [Fe/H] < -2, thus establishing a potentially fruitful link between high-z galaxies and the Local Universe.

  3. On the Number of Galaxies at High Redshift

    Directory of Open Access Journals (Sweden)

    Lorenzo Zaninetti

    2015-09-01

    Full Text Available The number of galaxies at a given flux as a function of the redshift, z, is derived when the z-distance relation is non-standard. In order to compare different models, the same formalism is also applied to the standard cosmology. The observed luminosity function for galaxies of the zCOSMOS catalog at different redshifts is modeled by a new luminosity function for galaxies, which is derived by the truncated beta probability density function. Three astronomical tests, which are the photometric maximum as a function of the redshift for a fixed flux, the mean value of the redshift for a fixed flux, and the luminosity function for galaxies as a function of the redshift, compare the theoretical values of the standard and non-standard model with the observed value. The tests are performed on the FORS Deep Field (FDF catalog up to redshift z = 1.5 and on the zCOSMOS catalog extending beyond z = 4. These three tests show minimal differences between the standard and the non-standard models.

  4. 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...

  5. 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 ...

  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. Probing the Physical Conditions of Atomic Gas at High Redshift

    CERN Document Server

    Neeleman, Marcel; Wolfe, Arthur M

    2014-01-01

    A new method is used to measure the physical conditions of the gas in damped Lyman-alpha systems (DLAs). Using high resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper to lower fine-structure levels of the ground state of C II and Si II. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov Chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5 % of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ~100 cm-3 and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log(P/k) = 3.4 [K cm-3], which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsec. We sho...

  8. Predicting the High Redshift Galaxy Population for JWST

    Science.gov (United States)

    Flynn, Zoey; Benson, Andrew

    2017-01-01

    The James Webb Space Telescope will be launched in Oct 2018 with the goal of observing galaxies in the redshift range of z = 10 - 15. As redshift increases, the age of the Universe decreases, allowing us to study objects formed only a few hundred million years after the Big Bang. This will provide a valuable opportunity to test and improve current galaxy formation theory by comparing predictions for mass, luminosity, and number density to the observed data. We have made testable predictions with the semi-analytical galaxy formation model Galacticus. The code uses Markov Chain Monte Carlo methods to determine viable sets of model parameters that match current astronomical data. The resulting constrained model was then set to match the specifications of the JWST Ultra Deep Field Imaging Survey. Predictions utilizing up to 100 viable parameter sets were calculated, allowing us to assess the uncertainty in current theoretical expectations. We predict that the planned UDF will be able to observe a significant number of objects past redshift z > 9 but nothing at redshift z > 11. In order to detect these faint objects at redshifts z = 11-15 we need to increase exposure time by at least a factor of 1.66.

  9. Constraining omega from X-ray properties of clusters of galaxies at high redshifts

    DEFF Research Database (Denmark)

    Sadat, R.; Blanchard, A.; Oukbir, J.

    1997-01-01

    Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, L-X - T-X, provides a pow...

  10. The K Band Luminosity Functions of Galaxies in High Redshift Clusters

    CERN Document Server

    Ellis, S C

    2004-01-01

    K band luminosity functions (LFs) of three, massive, high redshift clusters of galaxies are presented. The evolution of K*, the characteristic magnitude of the LF, is consistent with purely passive evolution, and a redshift of forma tion z = 1.5-2.

  11. High-redshift Blazars through NuSTAR Eyes

    Science.gov (United States)

    Marcotulli, L.; Paliya, V. S.; Ajello, M.; Kaur, A.; Hartmann, D. H.; Gasparrini, D.; Greiner, J.; Rau, A.; Schady, P.; Baloković, M.; Stern, D.; Madejski, G.

    2017-04-01

    The most powerful sources among the blazar family are MeV blazars. Often detected at z > 2, they usually display high X- and γ-ray luminosities, larger-than-average jet powers, and black hole masses ≳109 M ⊙. In the present work, we perform a multiwavelength study of three high-redshift blazars: 3FGL J0325.5+2223 (z = 2.06), 3FGL J0449.0+1121 (z = 2.15), and 3FGL J0453.2-2808 (z = 2.56), analyzing quasi-simultaneous data from GROND, Swift-UVOT and XRT, Nuclear Spectroscopic Telescope Array (NuSTAR), and Fermi-LAT. Our main focus is on the hard X-ray band recently unveiled by NuSTAR (3-79 keV) where these objects show a hard spectrum that enables us to constrain the inverse Compton (IC) peak and the jet power. We found that all three targets resemble the most powerful blazars, with the synchrotron peak located in the submillimeter range and the IC peak in the MeV range, and therefore belong to the MeV blazar class. Using a simple one-zone leptonic emission model to reproduce the spectral energy distributions, we conclude that a simple combination of synchrotron and accretion disk emission reproduces the infrared-optical spectra, while the X-ray to γ-ray part is well reproduced by the IC scattering of low-energy photons supplied by the broad-line region. The black hole masses for each of the three sources are calculated to be ≳4 × 108 M ⊙. The three studied sources have jet power at the level of, or beyond, the accretion luminosity.

  12. $\\gamma$-Ray Absorption at High Redshifts and the $\\gamma$-Ray Background

    CERN Document Server

    Stecker, F W

    1997-01-01

    We present results of a calculation of absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high- redshift evolution of the full spectral energy distribution of the intergalactic photon field. For this, we have primarily followed the recent analysis of Fall, Charlot and Pei. We give our results for the gamma-ray opacity as a function of redshift out to a redshift of 3. We then give predicted gamma-ray spectra for selected blazars and also extend our results on the background from unresolved blazars to an energy of 500 GeV. Absorption effects are predicted to significantly steepen the background spectrum above 20 GeV. Our absorption calculations can be used to place limits on the redshifts of gamma-ray bursts. Our background calculations can be used to determine the observability of multi-GeV lines from dark matter neutralino particles.

  13. The High-Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey

    CERN Document Server

    Paterno-Mahler, R; Ashby, M L N; Brodwin, M; Wing, J D; Anand, G; Decker, B; Golden-Marx, E

    2016-01-01

    We present 238 high-redshift galaxy cluster candidates based on galaxy overdensities in the Spitzer/IRAC imaging of the fields surrounding 646 bent, double-lobed radio sources drawn from the Clusters Occupied by Bent Radio AGN (COBRA) Survey. The COBRA sources were chosen as objects in the VLA FIRST survey that lack optical counterparts in the Sloan Digital Sky Survey (SDSS) to a limit of $m_r=22$, making them likely to lie at high redshift. This is confirmed by our observations: the redshift distribution of COBRA sources with estimated redshifts peaks near $z=1$, and extends out to $z\\approx3$. Cluster candidates were identified by comparing our sources to a background field and searching for overdensities. Forty-one of these sources are quasars with known spectroscopic redshifts, which may be tracers of some of the most distant clusters known.

  14. PROBING THE PHYSICAL CONDITIONS OF ATOMIC GAS AT HIGH REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Neeleman, Marcel; Wolfe, Arthur M. [Department of Physics and Center for Astrophysics and Space Sciences, UCSD, La Jolla, CA 92093 (United States); Prochaska, J. Xavier, E-mail: mneeleman@physics.ucsd.edu [Department of Astronomy and Astrophysics, UCO/Lick Observatory, 1156 High Street, University of California, Santa Cruz, CA 95064 (United States)

    2015-02-10

    A new method is used to measure the physical conditions of the gas in damped Lyα systems (DLAs). Using high-resolution absorption spectra of a sample of 80 DLAs, we are able to measure the ratio of the upper and lower fine-structure levels of the ground state of C{sup +} and Si{sup +}. These ratios are determined solely by the physical conditions of the gas. We explore the allowed physical parameter space using a Monte Carlo Markov chain method to constrain simultaneously the temperature, neutral hydrogen density, and electron density of each DLA. The results indicate that at least 5% of all DLAs have the bulk of their gas in a dense, cold phase with typical densities of ∼100 cm{sup –3} and temperatures below 500 K. We further find that the typical pressure of DLAs in our sample is log (P/k{sub B} ) = 3.4 (K cm{sup –3}), which is comparable to the pressure of the local interstellar medium (ISM), and that the components containing the bulk of the neutral gas can be quite small with absorption sizes as small as a few parsecs. We show that the majority of the systems are consistent with having densities significantly higher than expected for a purely canonical warm neutral medium, indicating that significant quantities of dense gas (i.e., n {sub H} > 0.1 cm{sup –3}) are required to match observations. Finally, we identify eight systems with positive detections of Si II*. These systems have pressures (P/k{sub B} ) in excess of 20,000 K cm{sup –3}, which suggest that these systems tag a highly turbulent ISM in young, star-forming galaxies.

  15. Suppression of radiation damping for high precision quantitative NMR.

    Science.gov (United States)

    Bayle, Kevin; Julien, Maxime; Remaud, Gérald S; Akoka, Serge

    2015-10-01

    True quantitative analysis of concentrated samples by (1)H NMR is made very difficult by Radiation Damping. A novel NMR sequence (inspired by the WET NMR sequence and by Outer Volume Saturation methods) is therefore proposed to suppress this phenomenon by reducing the spatial area and consequently the number of spins contributing to the signal detected. The size of the detected volume can be easily chosen in a large range and line shape distortions are avoided thanks to a uniform signal suppression of the outer volume. Composition of a mixture can as a result be determined with very high accuracy (precision and trueness) at the per mille level whatever the concentrations and without hardware modification.

  16. Translational damping on high-frequency flapping wings

    Science.gov (United States)

    Parks, Perry A.

    Flapping fliers such as insects and birds depend on passive translational and rotational damping to terminate quick maneuvers and to provide a source of partial stability in an otherwise unstable dynamic system. Additionally, passive translational and rotational damping reduce the amount of active kinematic changes that must be made to terminate maneuvers and maintain stability. The study of flapping-induced damping phenomena also improves the understanding of micro air vehicle (MAV) dynamics needed for the synthesis of effective flight control strategies. Aerodynamic processes which create passive translational and rotational damping as a direct result of symmetric flapping with no active changes in wing kinematics have been previously studied and were termed flapping counter-force (FCF) and flapping counter-torque (FCT), respectively. In this first study of FCF measurement in air, FCF generation is measured using a pendulum system designed to isolate and measure the relationship of translational flapping-induced damping with wingbeat frequency for a 2.86 gram mechanical flapper equipped with real cicada wings. Analysis reveals that FCF generation and wingbeat frequency are directly proportional, as expected from previous work. The quasi-steady FCF model using Blade-Element-Theory is used as an estimate for translational flapping-induced damping. In most cases, the model proves to be accurate in predicting the relationship between flapping-induced damping and wingbeat frequency. "Forward-backward" motion proves to have the strongest flapping-induced damping while "up-down" motion has the weakest.

  17. Searching for Cool Core Clusters at High redshift

    CERN Document Server

    Santos, Joana S; Tozzi, Paolo; Boehringer, Hans; Ettori, Stefano; Bignamini, Andrea

    2008-01-01

    We investigate the detection of Cool Cores (CCs) in the distant galaxy cluster population, with the purpose of measuring the CC fraction out to redshift 0.7 0.7, and should also be related with the shorter age of distant clusters, implying less time to develop a cool core.

  18. High-Redshift Superwinds as the Source of the Strongest Mg II Absorbers A Feasibility Analysis

    CERN Document Server

    Bond, N A; Charlton, J C; Vogt, S S

    2001-01-01

    We present HIRES/Keck profiles of four extremely strong (W_r > 1.8 A) Mg II absorbers at 1 1.8 A evolve away from z = 2 to the present. We propose that a substantial fraction of these very strong absorbers are due to superwinds and that their evolution is related to the redshift evolution of star-forming galaxies. Based on the observed redshift number density of W_r > 1.8 A Mg II absorbers at 1 < z < 2, we explore whether it is realistic that superwinds from starbursting galaxies could give rise to these absorbers. Finally, we do an analysis of the superwind connection to damped Lya absorbers (DLAs). DLAs and superwinds evolve differently and usually have different kinematic structure, indicating that superwinds probably do not give rise to the majority of DLAs.

  19. A Search for Moderate-Redshift Survivors from the Population of Luminous Compact Passive Galaxies at High Redshift

    CERN Document Server

    Stockton, Alan; Larson, Kirsten; Mann, Andrew W

    2013-01-01

    From a search of a ~ 2400 square degree region covered by both the SDSS and UKIDSS 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 4 of the 5 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 2 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...

  20. Antiknock Performance of Interlayered High-Damping-Rubber Blast Door under Thermobaric Shock Wave

    Directory of Open Access Journals (Sweden)

    Xiudi Li

    2016-01-01

    Full Text Available The long duration and high impulse shock wave of thermobaric bomb threatens the security of underground structures. To obtain high resistance blast door against thermobaric shock wave, firstly, the dynamic mechanic property of high damping rubber was studied by split Hopkinson pressure bar (SHPB equipment and the stress-strain relationship of high damping rubber under average strain rate of 5200/s was obtained. Secondly, the numerical model of interlayered high-damping-rubber blast door was established with ANSYS/LS-DYNA code based on test results, and the antiknock performance of interlayered high-damping-rubber blast door under thermobaric shock wave was analyzed by contrast with ordinary blast door. The results showed that the midspan displacement of the blast door decreased firstly and then increased with the increase of thickness of the high-damping-rubber interlayer, and the optimal thickness of the high-damping-rubber interlayer for energy consuming was 150 mm in the calculation condition of this paper. With the increase of the distance between the interlayer and the front surface of the door, the midspan displacement of the blast door decreased continually. The midspan maximum displacement of interlayered high-damping-rubber blast door decreased 74.5% in comparison to ordinary blast door. It showed that the high-damping-rubber structure can effectively improve the antiknock performance of blast door under thermobaric shock wave.

  1. Damping and support in high-temperature superconducting levitation systems

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R. (Sammamish, WA); McIver, Carl R. (Everett, WA); Mittleider, John A. (Kent, WA)

    2009-12-15

    Methods and apparatuses to provide improved auxiliary damping for superconducting bearings in superconducting levitation systems are disclosed. In a superconducting bearing, a cryostat housing the superconductors is connected to a ground state with a combination of a damping strip of material, a set of linkage arms to provide vertical support, and spring washers to provide stiffness. Alternately, the superconducting bearing may be supported by a cryostat connected to a ground state by posts constructed from a mesh of fibers, with the damping and stiffness controlled by the fiber composition, size, and mesh geometry.

  2. Damping and support in high-temperature superconducting levitation systems

    Science.gov (United States)

    Hull, John R.; McIver, Carl R.; Mittleider, John A.

    2009-12-15

    Methods and apparatuses to provide improved auxiliary damping for superconducting bearings in superconducting levitation systems are disclosed. In a superconducting bearing, a cryostat housing the superconductors is connected to a ground state with a combination of a damping strip of material, a set of linkage arms to provide vertical support, and spring washers to provide stiffness. Alternately, the superconducting bearing may be supported by a cryostat connected to a ground state by posts constructed from a mesh of fibers, with the damping and stiffness controlled by the fiber composition, size, and mesh geometry.

  3. Iron Abundance Diagnostics in High-Redshift QSOs

    CERN Document Server

    Corbin, M R; Freduling, N K W; Corbin, Michael R.; Korista, Kirk T.; Freduling, Nalaka Kodituwakku & Wolfram

    2004-01-01

    The abundance of alpha-process elements such as magnesium and carbon relative to iron measured from the broad emission lines of QSOs can serve as a diagnostic of the star formation and chemical enrichment histories of their host galaxies. We investigate the relationship between Fe/Mg and Fe/C abundance ratios and the resulting Fe II / Mg II 2800A and Fe II / 1900A-blend flux ratios, both of which have been measured in QSOs out to redshifts of approximately six. Using a galactic chemical evolution model based on a starburst in a giant elliptical galaxy, we find that these flux ratios are good tracers of the chemical enrichment of the nuclei. However, the values of these ratios measured in objects at redshifts of approximately six suggest that iron enrichment has occurred more rapidly in these objects than predicted by the assumed elliptical starburst model, under currently favored cosmologies.

  4. A Novel TiNi/AlSi Composite with High Strength and High Damping Capacity

    Institute of Scientific and Technical Information of China (English)

    Shuwei LIU; Xiuyan LI; Desheng YAN; Haichang JIANG; Lijian RONG

    2008-01-01

    A novel TiNi/AlSi composite with high compressive strength and high damping capacity was obtained by infiltrating Al-12%Si alloy into porous TiNi alloy.It had been found that the high compressive strength (440 MPa) of TiNi/AlSi composite is due to the increase of effective carrying area after infiltrating Al-12%Si alloy,while the high damping capacity is contributed to TiNi carcass,Al-12%Si filling material and micro-slipping at the interface.

  5. The Assembly of Supermassive Black Holes at High Redshifts

    CERN Document Server

    Tanaka, Takamitsu

    2008-01-01

    The supermassive black holes (SMBHs) massive enough (>10^9 Msun) to power the bright redshift z=6 quasars observed in the Sloan Digital Sky Survey (SDSS) are thought to have assembled by mergers and/or accretion from less massive ``seed'' BHs. If the seeds are the 100 Msun remnant BHs of the first generation of stars, they must be in place well before redshift z=6, and must avoid being ejected from their parent proto-galaxies by the large (several 100 km/s) kicks they suffer from gravitational-radiation induced recoil during mergers with other BHs. We simulate the SMBH mass function at redshift z>6 using dark matter (DM) halo merger trees, coupled with a prescription for the halo occupation fraction, accretion histories, and radial recoil trajectories of the growing BHs. Our purpose is (i) to map out plausible scenarios for successful assembly of the z=6 quasar BHs by exploring a wide region of parameter space, and (ii) to predict the rate of low-frequency gravitational wave events detectable by the Laser Int...

  6. The luminosity function of high-redshift QSOs

    CERN Document Server

    Fontanot, F; Monaco, P; Vanzella, E; Nonino, M; Brandt, W N; Grazian, A; Mao, J; Fontanot, Fabio; Cristiani, Stefano; Monaco, Pierluigi; Vanzella, Eros; Nonino, Mario; Grazian, Andrea; Mao, Jirong

    2006-01-01

    We measure the luminosity function of QSOs in the redshift range 3.5 < z < 5.2 for the absolute magnitude interval -21 < M_{145} < -28. Suitable criteria are defined to select faint QSOs in the GOODS fields, checking their effectiveness and completeness in detail. The confirmed sample of faint QSOs is compared with a brighter one derived from the SDSS. Using a Monte-Carlo technique we estimate the properties of the luminosity function. Our results show that models based on pure density evolution show better agreement with observation than models based on pure luminosity evolution, even if a different break magnitude with respect to z ~ 2.1 is required at 3.5 < z < 5.2. According to our modeling a faint-end slope steeper than low-redshift observations is required to reproduce the data, moreover models with a steep bright-end slope score a higher probability than models with a bright-end flattening. Determining the faint-end of the luminosity function at these redshifts provides important cons...

  7. WISH: Wide-field Imaging Durvayor for High-redshift

    Science.gov (United States)

    Yamada, Toru

    2015-08-01

    We introduce the concept and current status of WISH project and discuss the science cases. WISH is a proposed space science mission for JAXA, which is dedicated for the deep and wide-field near-infrared imaging surveys. The mission contains the 1.5m cooled telescope as well as the imager with the FoV of ~850 square arcmin. The main goal of WISH is to detect and study galaxies at z=8-15 in the earliest history of structure formation in the universe. The key feature is to conduct WISH Ultra Deep Survey, which images in total of 100 square degrees in 6 broad-band filters at 0.9-4.5 micron down to 28AB magnitude. While more than 10^5 galaxies at z=8-9, 10^4 galaxies at z=11-12 will be detected, WISH-UDS is designed to constrain UV luminosity function at z=15. Depending on the models of the earliest evolution history, 1-1000 galaxies at z~15 (~100 galaxies for the moderate cases) will be detected. The UV spectral properties as well as the clustering properties of galaxies at z=8-15 can be studied as well; UV slope can be measured up to z=15, and the stellar and dark-matter-halo masses can be obtained up to z=9. WISH UDS can provide excellent opportunities for studying SNe at high redshift. Up to ~7000 type Ia SNe at z>1 can be detected and the distance modulus can be constrained with the precision of 0.9-1.5% at z>1.5. More than 100 Super Luminous SNe at z>6, and 10 SLSN at z>10 can also be detected, which allow us to study the earliest history of massive star formation in the universe. WISH imaging surveys as well as WISHSpec, which is an optional parallel-operation simple IFU spectrograph, also provide unique opportunities in various astronomical fields. WISH mission proposal was submitted to JAXA in February 2015 for the first down selection of JAXA Large Strategic Science Mission targeting the launch date in 2020-22. International collaborations including SAO (G.Fazio et al.), LAM (D. Burgarella et al.) and Canada (M.Sawicki et al.) are also actively coordinated.

  8. 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.

  9. Spatially resolved emission of a high-redshift DLA galaxy with the Keck/OSIRIS IFU

    Energy Technology Data Exchange (ETDEWEB)

    Jorgenson, Regina A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822 (United States); Wolfe, Arthur M., E-mail: raj@ifa.hawaii.edu [Department of Physics and Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States)

    2014-04-10

    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 {sub ☉} yr{sup –1} and a dynamical mass of M {sub dyn} = 6.1 × 10{sup 9} M {sub ☉}. The average star formation rate surface density is (Σ{sub SFR}) = 0.55 M {sub ☉} yr{sup –1} kpc{sup –2}, with a central peak of 1.7 M {sub ☉} yr{sup –1} kpc{sup –2}. Using the standard Kennicutt-Schmidt relation, this corresponds to a gas mass surface density of Σ{sub gas} = 243 M {sub ☉} pc{sup –2}. Integrating over the size of the galaxy, we find a total gas mass of M {sub gas} = 4.2 × 10{sup 9} M {sub ☉}. We estimate the gas fraction of DLA 2222–0946 to be f {sub 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.

  10. 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.

  11. 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.

  12. Modulation Voltage of High T c DC Superconducting Quantum Interference Device with Damping Resistance

    Science.gov (United States)

    Enpuku, Keiji; Doi, Hideki; Tokita, Go; Maruo, Taku

    1994-05-01

    The effect of damping resistance on the voltage versus flux (V -Φ) relation of the high T c dc superconducting quantum interference device (SQUID) is studied experimentally. Dc SQUID using YBaCuO step-edge junction and damping resistance in parallel with SQUID inductance is fabricated. Measured values of modulation voltage in the V -Φ relation are compared with those of the conventional SQUID without damping resistance. It is shown that modulation voltage is much improved by using damping resistance. The obtained experimental results agree reasonably with theoretical predictions reported previously.

  13. Multi-wavelength afterglow observations of the high redshift GRB 050730

    OpenAIRE

    2006-01-01

    GRB 050730 is a long duration high-redshift burst (z=3.967) discovered by Swift. The afterglow shows variability and is well monitored over a wide wavelength range. We present comprehensive temporal and spectral analysis of the afterglow of GRB 050730 including observations from the millimeter to X-rays. We use multi-wavelength afterglow data to understand the temporal and spectral decay properties with superimposed variability of this high redshift burst. Five telescopes were used to study t...

  14. Physical properties of absorbers in high redshift quasars

    Directory of Open Access Journals (Sweden)

    L. E. Simon

    2007-01-01

    Full Text Available Recent studies based on quasar emission lines suggest that quasar environments are typicaly metal rich, with metallicities near or above the solar value at even the highest observed redshifts. Due to the large uncertainties in- herent in emission line abundance analysis, we employ another technique, absorption line analysis, to corroborate the evidence gleaned so far in order to better constrain the de- tected metallicities. We are also interested in the physical nature of these absorbers, their relationship to quasar outows, and their role in quasar-host galaxy evolution.

  15. The Main Sequences of Starforming Galaxies and Active Galactic Nuclei at High Redshift

    CERN Document Server

    Mancuso, Claudia; Shi, J; Gonzàlez-Nuevo, J; Bèthermin, M; Danese, L

    2016-01-01

    We provide a novel, unifying physical interpretation on the origin, the average shape, the scatter, and the cosmic evolution for the main sequences of starforming galaxies and active galactic nuclei at high redshift z $\\gtrsim$ 1. We achieve this goal in a model-independent way by exploiting: (i) the redshift-dependent SFR functions based on the latest UV/far-IR data from HST/Herschel, and re- lated statistics of strong gravitationally lensed sources; (ii) deterministic evolutionary tracks for the history of star formation and black hole accretion, gauged on a wealth of multiwavelength observations including the observed Eddington ratio distribution. We further validate these ingredients by showing their consistency with the observed galaxy stellar mass functions and AGN bolometric luminosity functions at different redshifts via the continuity equation approach. Our analysis of the main sequence for high-redshift galaxies and AGNs highlights that the present data are consistently interpreted in terms of an in...

  16. Wide Frequency Band Active Damping Strategy for DFIG System High Frequency Resonance

    DEFF Research Database (Denmark)

    Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    As a popular renewable power generation solution, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer from High Frequency Resonance (HFR) caused by the impedance interaction between the DFIG system and the parallel compensated weak network. A wide frequency band active...... damping strategy for DFIG system HFR, including a high-pass filter and a virtual resistance, is proposed in this paper. The advantages of this active damping strategy are, 1) no resonance frequency detection unit is required, thus the control complexity can be decreased; 2) no active damping parameters...... adjustment is needed within certain wide frequency band, thus the robustness of the proposed active damping strategy can be improved. The parameter design of the high-pass filter cutoff frequency and the virtual resistance are theoretically analyzed with the purpose of satisfactory active damping. A 7.5 k...

  17. Damping of high-lying single-particle modes in heavy nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Gales, S.; Stoyanov, C.; Vdovin, A.I.

    1988-08-01

    The recent experimental and theoretical results on the damping of high-lying single-particle modes in heavy nuclei are reviewed. In one-nucleon transfer reactions these states manifest themselves as broad 'resonance'-like structures superimposed on a large continuum. The advantages and the limitations of the transfer reaction approach will be presented using the results from neutron and proton pick-up and stripping reactions. The problem raised by the subtraction of the underlying background, the assumptions made to describe the reaction process and the method used to extract the strength distributions are presented. The existing empirical systematics is summarized for nuclei ranging from /sup 90/Zr to /sup 208/Pb. The theoretical approaches used to explain the damping of the high-lying single-particle modes are based on the coupling between collective and single-particle degrees of freedom. In a first step the bare single-particle mode is spread over several doorway collective states due to the interaction with surface vibrations. In a second step the doorway states spread their strengths over many other degrees of freedom. These two steps of the damping mechanism are discussed in detail within the framework of the quasiparticle-phonon nuclear model. A large-scale comparison between the measured and calculated average energies, spreading widths and spectroscopic strengths of the high-lying single-particle (hole) states in heavy nuclei is presented. The systematic features of the damping (energy, angular momentum and isotopic dependence) are discussed. Recent advances of the experimental approaches, such as the ..gamma..-decay of the high-lying states or the use of heavy-ion transfer reactions at intermediate energies, are outlined. The detailed study of the damping mechanism of high-lying single-particle modes reveals new features and leads us to a new field in nuclear structure: 'The spectroscopy of inner and outer subshells'.

  18. Dynamic and Seismic Property Experiments of High Damping Concrete and Its Frame Models

    Institute of Scientific and Technical Information of China (English)

    OU Jinping; LIU Tiejun; LI Jilong

    2008-01-01

    The loss tangent and storage modulus of cement mortar containing treated silica fume and styrene-acrylic are measured.Shaking table tests on three groups of 1/4 models of high damping concrete flames are conducted to compare the effects of reducing vibration.A relationship between the viscosity coefficient of high damping concrete and the damping coefficient of structure is established by analyzing dynamic parameters like damping ratio and frequency,and comparing responses of relative displacement and absolute acceleration.Surface treatment of silica fume and styrene-acrylic emulsion prior to incorporation in a cement mortar increases the loss tangent of the resulting composite by 40-400% as compared to the cement mortar without any admixtures,and the damping ratio of the reinforced concrete is raised by 7%-9%.In addition,a theoretical method of determining the viscosity coefficient of the material on the basis of shaking table test results is put forward.

  19. Active Damping of Vibrations in High-Precision Motion Systems

    OpenAIRE

    Babakhani, B.

    2012-01-01

    Technology advancements feed the need for ever faster and more accurate industrial machines. Vibration is a significant source of inaccuracy of such machines. A light-weight design in favor of the speed, and avoiding the use of energy-dissipating materials from the structure to omit any source of inaccuracy, contribute to a low structural damping. The goal of this research is to investigate the addition of damping to the rotational vibration mode of a linearly actuated motion system to •achie...

  20. Were progenitors of local L* galaxies Lyman-alpha emitters at high redshift?

    CERN Document Server

    Yajima, Hidenobu; Zhu, Qirong; Abel, Tom; Gronwall, Caryl; Ciardullo, Robin

    2011-01-01

    The Lya emission has been observed from galaxies over a redshift span z ~ 0 - 8.6. However, the link between high-redshift Lya emitters (LAEs) and local galaxies is largely unknown. Here, we investigate the Lya properties of progenitors of a local L^{*} galaxy by combining cosmological hydrodynamic simulations with three-dimensional radiative transfer calculations using the new ART^2 code. We find that the modeled galaxies are Lya bright in redshift z= 0 - 10. In particular, the Lya luminosities of some massive progenitors at z ~ 2 - 6 are close to the observed characteristic L_{Lya}^{*} of LAEs in that redshift range. Both Lya photon escape fraction and line equivalent width increase with redshift. The Lya escape fraction correlates with a number of physical properties of the galaxy, such as mass, SFR and metallicity. We find a "viewing-angle scatter" in which the photon escape depends strongly on the galaxy morphology and orientation. Moreover, we find that high-redshift LAEs show blue-shifted Lya line prof...

  1. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    Some nontrivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial (depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based...... on a slightly modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical...

  2. Nontrivial effects of high-frequency excitation for strongly damped mechanical systems

    DEFF Research Database (Denmark)

    Fidlin, Alexander; Thomsen, Jon Juel

    2008-01-01

    Some non-trivial effects are investigated, which can occur if strongly damped mechanical systems are subjected to strong high-frequency (HF) excitation. The main result is a theoretical prediction, supported by numerical simulation, that for such systems the (quasi-)equilibrium states can change...... that can be substantial depending on the strength of the HF excitation) for finite values of the damping. The analysis is focused on the differences between the classic results for weakly damped systems, and new effects for which the strong damping terms are responsible. The analysis is based on a slightly...... modified averaging technique, and includes an elementary example of an elliptically excited pendulum for illustration, alongside with a generalization to a broader class of strongly damped dynamical systems with HF excitation. As an application example, the nontrivial behavior of a classical optimally...

  3. Broad Absorption Line Quasars with Redshifted Troughs: High-Velocity Infall or Rotationally Dominated Outflows?

    CERN Document Server

    Hall, Patrick B; Petitjean, P; Paris, I; Ak, N Filiz; Shen, Yue; Gibson, R R; Aubourg, E; Anderson, S F; Schneider, D P; Bizyaev, D; Brinkmann, J; Malanushenko, E; Malanushenko, V; Myers, A D; Oravetz, D J; Ross, N P; Shelden, A; Simmons, A E; Streblyanska, A; Weaver, B A; York, D G

    2013-01-01

    We report the discovery in the Sloan Digital Sky Survey and the SDSS-III Baryon Oscillation Spectroscopic Survey of seventeen broad absorption line (BAL) quasars with high-ionization troughs that include absorption redshifted relative to the quasar rest frame. The redshifted troughs extend to velocities up to v=12,000 km/s and the trough widths exceed 3000 km/s in all but one case. Approximately 1 in 1000 BAL quasars with blueshifted C IV absorption also has redshifted C IV absorption; objects with C IV absorption present only at redshifted velocities are roughly four times rarer. In more than half of our objects, redshifted absorption is seen in C II or Al III as well as C IV, making low-ionization absorption at least ten times more common among BAL quasars with redshifted troughs than among standard BAL quasars. However, the C IV absorption equivalent widths in our objects are on average smaller than those of standard BAL quasars with low-ionization absorption. We consider several possible ways of generatin...

  4. Infrared-faint radio sources are at high redshifts. Spectroscopic redshift determination of infrared-faint radio sources using the Very Large Telescope

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Sharp, R.; Spitler, L. R.; Parker, Q. A.

    2014-07-01

    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 the two classes of object. However, the optical and infrared faintness of IFRS makes their study difficult. Prior to this work, no redshift was known for any IFRS in the Australia Telescope Large Area Survey (ATLAS) fields which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims: This work aims at measuring the first redshifts of IFRS in the ATLAS fields. Furthermore, we test the hypothesis that IFRS are similar to HzRGs, that they are higher-redshift or dust-obscured versions of these massive galaxies. Methods: A sample of IFRS was spectroscopically observed using the Focal Reducer and Low Dispersion Spectrograph 2 (FORS2) at the Very Large Telescope (VLT). The data were calibrated based on the Image Reduction and Analysis Facility (IRAF) and redshifts extracted from the final spectra, where possible. This information was then used to calculate rest-frame luminosities, and to perform the first spectral energy distribution modelling of IFRS based on redshifts. Results: We found redshifts of 1.84, 2.13, and 2.76, for three IFRS, confirming the suggested high-redshift character of this class of object. These redshifts and the resulting luminosities show IFRS to be similar to HzRGs, supporting our hypothesis. We found further evidence that fainter IFRS are at even higher redshifts. Conclusions: Considering the similarities between IFRS and HzRGs substantiated in this work, the detection of IFRS, which have a significantly higher sky density than HzRGs, increases the number of active galactic nuclei in the early universe and adds to the problems of explaining the formation of

  5. Wide Frequency Band Active Damping Strategy for DFIG System High Frequency Resonance

    DEFF Research Database (Denmark)

    Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    As a popular renewable power generation solution, the Doubly Fed Induction Generator (DFIG) based wind power system may suffer from High Frequency Resonance (HFR) caused by the impedance interaction between the DFIG system and the parallel compensated weak network. A wide frequency band active...... damping strategy for DFIG system HFR, including a high-pass filter and a virtual resistance, is proposed in this paper. The advantages of this active damping strategy are, 1) no resonance frequency detection unit is required, thus the control complexity can be decreased; 2) no active damping parameters...

  6. The Ly$\\alpha$ emission from high-$z$ galaxies hosting strong Damped Ly$\\alpha$ systems

    CERN Document Server

    Joshi, Ravi; Noterdaeme, Pasquier; Petitjean, Patrick

    2016-01-01

    We study the average Ly$\\alpha$ emission associated with high-$z$ strong (log $N$(H I) $\\ge$ 21) damped Ly$\\alpha$ systems (DLAs). We report Ly$\\alpha$ luminosities ($L_{\\rm Ly\\alpha}$) for the full as well as various sub-samples based on $N$(H I), $z$, $(r-i)$ colours of QSOs and rest equivalent width of Si II$\\lambda$1526 line (i.e., $W_{1526}$). For the full sample, we find $L_{\\rm Ly\\alpha}$$< 10^{41} (3\\sigma)\\ \\rm erg\\ s^{-1}$ with a $2.8\\sigma$ level detection of Ly$\\alpha$ emission in the red part of the DLA trough. The $L_{\\rm Ly\\alpha}$ is found to be higher for systems with higher $W_{1526}$ with its peak, detected at $\\geq 3\\sigma$, redshifted by about 300-400 $\\rm km\\ s^{-1}$ with respect to the systemic absorption redshift, as seen in Lyman Break Galaxies (LBGs) and Ly$\\alpha$ emitters. A clear signature of a double-hump Ly$\\alpha$ profile is seen when we consider $W_{1526} \\ge 0.4$ \\AA\\ and $(r-i) < 0.05$. Based on the known correlation between metallicity and $W_{1526}$, we interpret our...

  7. A distortion of very-high-redshift galaxy number counts by gravitational lensing.

    Science.gov (United States)

    Wyithe, J Stuart B; Yan, Haojing; Windhorst, Rogier A; Mao, Shude

    2011-01-13

    The observed number counts of high-redshift galaxy candidates have been used to build up a statistical description of star-forming activity at redshift z ≳ 7, when galaxies reionized the Universe. Standard models predict that a high incidence of gravitational lensing will probably distort measurements of flux and number of these earliest galaxies. The raw probability of this happening has been estimated to be ∼0.5 per cent (refs 11, 12), but can be larger owing to observational biases. Here we report that gravitational lensing is likely to dominate the observed properties of galaxies with redshifts of z ≳ 12, when the instrumental limiting magnitude is expected to be brighter than the characteristic magnitude of the galaxy sample. The number counts could be modified by an order of magnitude, with most galaxies being part of multiply imaged systems, located less than 1 arcsec from brighter foreground galaxies at z ≈ 2. This lens-induced association of high-redshift and foreground galaxies has perhaps already been observed among a sample of galaxy candidates identified at z ≈ 10.6. Future surveys will need to be designed to account for a significant gravitational lensing bias in high-redshift galaxy samples.

  8. Exploring The Gas Cycle In High-redshift Galaxies: A Joint Effort Of Theory And Observations

    Science.gov (United States)

    Fumagalli, Michele

    2012-01-01

    The evolution of high-redshift galaxies is regulated by the balance between the inflow of fresh fuel for star formation and the outflow of metal-polluted material from star forming regions. Hydrodynamic cosmological simulations indicate that galaxies at high redshifts are fed by extended streams of cold gas in a smooth component and in merging satellites, but direct evidence of this mode of accretion is lacking. To investigate the signatures of these "cold streams" in observations, we have studied the Lyman-α emission and hydrogen absorption properties in galaxies simulated at high-resolution, using state-of-the-art radiative transfer codes. I will present these model predictions and I will compare and contrast results of simulations with observations of high-redshift Lyman break galaxies. I will also discuss the prospects of mapping the circumgalactic medium with absorption line systems and present preliminary results from ongoing observations.

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

    DEFF Research Database (Denmark)

    Gorosabel, J.; Lund, Niels; Brandt, Søren Kristian

    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 population...... of GRBs. We conclude that, if the GRB rate is proportional to the star formation rate, INTEGRAL's ability to study GRBs are complementary to the ones of missions like SWIFT and HETE 2, devoted to prompt localisations of GRBs. Whereas SWIFT and HETE 2 would detect a higher number of GRBs than INTEGRAL......, 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....

  10. Pressure-driven fragmentation of clouds at high redshift

    CERN Document Server

    Dhanoa, Harpreet; Yates, Jeremy

    2014-01-01

    The discovery of a hyper metal-poor star with total metallicity of $\\le 10^{-5}$ Z$_\\odot$, has motivated new investigations of how such objects can form from primordial gas polluted by a single supernova. In this paper we present a shock-cloud model which simulates a supernova remnant interacting with a cloud in a metal-free environment at redshift $z=10$. Pre-supernova conditions are considered, which include a multiphase neutral medium and H II region. A small dense clump ($n=100$ cm$^{-3}$), located 40 pc from a 40 M$_\\odot$ metal-free star, embedded in a $n=10$ cm$^{-3}$ ambient cloud. The evolution of the supernova remnant (explosion energy $10^{52}$ erg) and its subsequent interaction with the dense clump is examined. This is the first study to include a comprehensive treatment of the non-equilibrium chemistry and associated radiative cooling that is occurring at all stages of the shock-cloud model. We have included a primordial chemistry network that covers the temperature range $10-10^9$ K, and is co...

  11. On the accuracy of the high redshift cluster luminosity function

    CERN Document Server

    Muñoz, Roberto P; Barrientos, Luis F

    2008-01-01

    We study the reliability of the statistical background subtraction method for computing the Ks-band luminosity function of cluster galaxies at z~1 using mock Red-sequence Cluster Survey cluster catalogues constructed from GALFORM semi-analytic galaxies. The underlying cluster luminosity function in the mocks are compatible with recent estimates at z~1 by several authors. We simulate different samples where the number of clusters with Ks-band photometry goes from 5 to a maximum of 50, in order to find the most suitable observational sample to carry out this study; the current observational status in the nIR wavelength range has been reached using 5 real clusters at z~1. We compute the composite luminosity function for several samples of galaxy clusters with masses 1.5x10^14 M_sun assuming a flux limited, complete sample of galaxies down to Ks=21.0 magnitudes. We find that the Schechter fit parameters Ks* and alpha for a sample of galaxies with no redshift information are rather poorly constrained if both param...

  12. Damping mechanisms in high-Q micro and nanomechanical string resonators

    DEFF Research Database (Denmark)

    Schmid, Silvan; Jensen, K. D.; Nielsen, K. H.

    2011-01-01

    been concluded that Q is enhanced due to the high energy stored in the string tension. In this paper, damping mechanisms in string resonators are systematically investigated by varying the geometry and the tensile stress of silicon nitride microstrings. The measured quality factors are compared......Resonant micro and nanostrings were found to have extraordinarily high quality factors (Qs). Since the discovery of the high Qs of silicon nitride nanostrings, the understanding of the underlying mechanisms allowing such high quality factors has been a topic of several investigations. So far it has...... to an analytical model for Q based on bending-related damping mechanisms. It is shown that internal material damping is limiting the quality factor of narrow strings with a width of 3 μm. Q is strongly width dependent and clamping losses evidently seem to be the limiting damping mechanism for wider strings...

  13. High Temperature Damping Behavior of Plasma-Sprayed Thermal Barrier and Protective Coatings

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.; Duffy, Kirsten P.; Ghosn, Louis J.

    2010-01-01

    A high temperature damping test apparatus has been developed using a high heat flux CO 2 laser rig in conjunction with a TIRA S540 25 kHz Shaker and Polytec OFV 5000 Vibrometer system. The test rig has been successfully used to determine the damping performance of metallic and ceramic protective coating systems at high temperature for turbine engine applications. The initial work has been primarily focused on the microstructure and processing effects on the coating temperature-dependence damping behavior. Advanced ceramic coatings, including multicomponent tetragonal and cubic phase thermal barrier coatings, along with composite bond coats, have also been investigated. The coating high temperature damping mechanisms will also be discussed.

  14. New quasar surveys with WIRO: Searching for high redshift (z~6) quasar candidates

    Science.gov (United States)

    Haze Nunez, Evan; Bassett, Neil; Deam, Sophie; Dixon, Don; Griffith, Emily; Harvey, William Bradford; Lee, Daniel; Lyke, Bradley; Parziale, Ryan; Witherspoon, Catherine; Myers, Adam D.; Findlay, Joseph; Kobulnicky, Henry A.; Dale, Daniel A.

    2017-01-01

    High redshift quasars (z~6) are of great interest to fundamental astronomy due to the information they hold about the early universe. With their low number density in the sky, however, they are elusive objects. Reported here is our search for these high redshift quasars using the Wyoming Infrared Observatory (WIRO) 2.3m telescope. We search for potential candidates that have been detected by surveys such as WISE, which have been mostly redshifted out of the optical. The main emission feature of these quasars (the Lyman-Alpha line at ~1216 Angstroms rest-frame) would be redshifted to the z-band or beyond. This means that the quasars should have very low levels of i-band flux. These objects are known as i-dropouts. By imaging the quasars in the i-band and running photometric analysis on our fields, candidates can be identified or rejected by whether or not they appear in our fields. We also provide an analysis of the colors of our candidate high-redshift quasars.This work is supported by the National Science Foundation under REU grant AST1560461

  15. Sub-synchronous resonance damping using high penetration PV plant

    Science.gov (United States)

    Khayyatzadeh, M.; Kazemzadeh, R.

    2017-02-01

    The growing need to the clean and renewable energy has led to the fast development of transmission voltage-level photovoltaic (PV) plants all over the world. These large scale PV plants are going to be connected to power systems and one of the important subjects that should be investigated is the impact of these plants on the power system stability. Can large scale PV plants help to damp sub-synchronous resonance (SSR) and how? In this paper, this capability of a large scale PV plant is investigated. The IEEE Second Benchmark Model aggregated with a PV plant is utilized as the case study. A Wide Area Measurement System (WAMS) based conventional damping controller is designed and added to the main control loop of PV plant in order to damp the SSR and also investigation of the destructive effect of time delay in remote feedback signal. A new optimization algorithm called teaching-learning-based-optimization (TLBO) algorithm has been used for managing the optimization problems. Fast Furrier Transformer (FFT) analysis and also transient simulations of detailed nonlinear system are considered to investigate the performance of the controller. Robustness of the proposed system has been analyzed by facing the system with disturbances leading to significant changes in generator and power system operating point, fault duration time and PV plant generated power. All the simulations are carried out in MATLAB/SIMULINK environment.

  16. Ambient-temperature high damping capacity in TiPd-based martensitic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Dezhen [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Zhou, Yumei, E-mail: zhouyumei@mail.xjtu.edu.cn [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ding, Xiangdong [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Otsuka, Kazuhiro [Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Sun, Jun [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ren, Xiaobing [Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ferroic Physics Group, National Institute for Materials Science, Tsukuba 305-0047, Ibaraki (Japan)

    2015-04-24

    Shape memory alloys (SMAs) have attracted considerable attention for their high damping capacities. Here we investigate the damping behavior of Ti{sub 50}(Pd{sub 50−x}D{sub x}) SMAs (D=Fe, Co, Mn, V) by dynamic mechanical analysis. We find that these alloys show remarkably similar damping behavior. There exists a sharp damping peak associated with the B2–B19 martensitic transformation and a high damping plateau (Q{sup −1}~0.02–0.05) over a wide ambient-temperature range (220–420 K) due to the hysteretic twin boundary motion. After doping hydrogen into the above alloys, a new relaxation-type damping peak appears in the martensite phase over 270–360 K. Such a peak is considered to originate from the interaction of hydrogen atoms with twin boundaries and the corresponding damping capacity (Q{sup −1}~0.05–0.09) is enhanced by roughly twice that of the damping plateau for each alloy. Moreover, the relaxation peaks are at higher temperatures for the TiPd-based alloys (270–370 K) than for the TiNi-based alloys (190–260 K). We discuss the influence of hydrogen diffusion, mobility of twin boundaries and hydrogen–twin boundary interaction on the temperature range of the relaxation peak. Our results suggest that a martensite, with appropriate values for twinning shear and hydrogen doping level, provides a route towards developing high damping SMAs for applications in desired temperature ranges.

  17. A study of massive and evolved galaxies at high redshift

    Energy Technology Data Exchange (ETDEWEB)

    Nayyeri, H.; Mobasher, B.; Hemmati, S.; De Barros, S. [University of California Riverside, Riverside, CA 92512 (United States); Ferguson, H. C.; Wiklind, T.; Dahlen, T.; Kassin, S.; Koekemoer, A. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Dickinson, M. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Giavalisco, M. [University of Massachusetts Amherst, Amherst, MA 01003 (United States); Fontana, A.; Paris, D. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33 Monte Porzio Catone, 00040 Rome (Italy); Ashby, M.; Willner, S. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Barro, G.; Guo, Y. [University of California Santa Cruz, Santa Cruz, CA 95064 (United States); Hathi, N. P. [Laboratoire d' Astrophysique de Marseille, rue Frédéric Joliot Curie, 13013 Marseille (France); Dunlop, J. S.; Targett, T. A. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)

    2014-10-10

    We use data taken as part of Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) observations of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) to identify massive and evolved galaxies at 3 < z < 4.5. This is performed using the strength of the Balmer break feature at rest-frame 3648 Å, which is a diagnostic of the age of the stellar population in galaxies. Using the WFC3 H-band-selected catalog for the CANDELS GOODS-S field and deep multi-waveband photometry from optical (HST) to mid-infrared (Spitzer) wavelengths, we identify a population of old and evolved post-starburst galaxies based on the strength of their Balmer breaks (Balmer break galaxies, BBGs). The galaxies are also selected to be bright in rest-frame near-IR wavelengths and hence massive. We identify a total of 16 BBGs. Fitting the spectral energy distribution of the BBGs shows that the candidate galaxies have average estimated ages of ∼800 Myr and average stellar masses of ∼5 × 10{sup 10} M {sub ☉}, consistent with being old and massive systems. Two of our BBG candidates are also identified by the criteria that are sensitive to star-forming galaxies (Lyman break galaxy selection). We find a number density of ∼3.2 × 10{sup –5} Mpc{sup –3} for the BBGs, corresponding to a mass density of ∼2.0 × 10{sup 6} M {sub ☉} Mpc{sup –3} in the redshift range covering the survey. Given the old age and the passive evolution, it is argued that some of these objects formed the bulk of their mass only a few hundred million years after the big bang.

  18. Optimal Design of High-Order Passive-Damped Filters for Grid-Connected Applications

    DEFF Research Database (Denmark)

    Beres, Remus Narcis; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    design procedures, the proposed method simplifies the iterative design of the overall filter while ensuring the minimum resonance peak with a lower damping capacitor and a lower rated resistor. It is shown that there is only one optimal value of the damping resistor or quality factor to achieve a minimum......Harmonic stability problems caused by the resonance of high-order filters in power electronic systems are ever increasing. The use of passive damping does provide a robust solution to address these issues, but at the price of reduced efficiency due to the presence of additional passive components...

  19. Selection and Physical Properties of High-redshift Galaxies

    Science.gov (United States)

    Fang, G. W.

    2014-09-01

    Extremely Red Objects (EROs) and BzKs continue to attract considerable interest. It has been suggested that they may be the direct progenitors of present-day massive E/S0 galaxies, and can provide crucial constraints on the current galaxy formation and evolution models. Therefore, the key question is to measure the relative fraction of OGs (old galaxies) and DGs (young, and dusty starburst galaxies) in the sample of EROs. Many groups have been currently investigating the fractions of these two ERO populations using a variety of observational approaches, but the fraction of OGs and DGs from different surveys is different. In the meantime, a number of observations suggest that the epoch of z˜2 also plays an important role in galaxy formation and evolution for various reasons: the cosmic star formation rate density (SFRD) begins to drop at z˜2 from a flat plateau at higher redshifts; the morphological type mix of field galaxies changes remarkably at z˜2; the number density of QSOs has a peak at z˜2; and about 50% to 70% of the stellar mass assembly of galaxies took place in the redshift range 1thesis, our main works are as follows: (1) the classification of z˜1 EROs in the UDF and COSMOS field, (2) a study on physical properties of passive and star-forming galaxies at z˜2 in the AEGIS field, and (3) the mid-infrared spectroscopy and multi-wavelength study of ultraluminous infrared galaxies (ULIRGs) at z˜2 in the AEGIS field. Chapter 1 gives a brief review on the research progresses of EROs at z˜1, BzKs at z˜2, and ULIRGs at z˜2, respectively. In Chapter 2 we present a quantitative study of the classification of EROs in the UDF and COSMOS field. Our sample includes 5264 (COSMOS, K_{Vega} ≤19.2) and 24 EROs (UDF, K_{Vega}≤22.0) with (i-K)_{AB}≥2.45. Using the fitting method of spectral energy distribution (SED), [3.6]-[8.0] color, and the nonparametric measures of galaxy morphology, we classify EROs into two classes: DGs and OGs. We find that the

  20. Are z~5 QSOs found in the most massive high redshift over-densities?

    CERN Document Server

    Husband, K; Stanway, E R; Davies, L J M; Lehnert, M D; Douglas, L S

    2013-01-01

    Luminous high-redshift QSOs are thought to exist within the most massive dark matter haloes in the young Universe. As a consequence they are likely to be markers for biased, over-dense regions where early galaxies cluster, regions that eventually grow into the groups and clusters seen in the lower redshift universe. In this paper we explore the clustering of galaxies around z ~ 5 QSOs as traced by Lyman Break Galaxies (LBGs). We target the fields of three QSOs using the same optical imaging and spectroscopy techniques used in the ESO Remote Galaxy Survey (ERGS, Douglas et al. 2009, 2010), which was successful in identifying individual clustered structures of LBGs. We use the statistics of the redshift clustering in ERGS to show that two of the three fields show significant clustering of LBGs at the QSO redshifts. Neither of these fields is obviously over-dense in LBGs from the imaging alone; a possible reason why previous imaging-only studies of high-redshift QSO environments have given ambiguous results. Thi...

  1. Photometric Redshifts for High Resolution Radio Galaxies in the SuperCLASS Field

    Science.gov (United States)

    Manning, Sinclaire; Casey, Caitlin; Battye, Richard; Hales, Christopher A.; Chapman, Scott; Smail, Ian; SuperCLASS Team

    2017-01-01

    SuperCLASS (the Super-Cluster Assisted Shear Survey) is a deep, wide-area (~2 square degrees) extragalactic field with high resolution (0.1”) radio continuum coverage from e-MERLIN (Multi-Element Radio Linked Interferometer Network.) The combination of sensitivity and spatial resolution make e-MERLIN an ideal tool to trace spatially resolved star-formation in heavily obscured, dusty star-forming galaxies (DSFGs). Plus, thanks to the tight relationship between radio continuum and far-IR observations we have an observationally inexpensive and accurate method of mapping star formation density in distant galaxies. We present a photometric redshift catalog for DSFGs located in the SuperCLASS field. Multiwavelength photometric data was obtained with Subaru SuprimeCam (B,V,r,i,z) and photometric redshifts were generated using the public photometric redshift code, EAZY. With these redshifts we aim to conduct the first large sample morphological analysis of z~1-3 obscured galaxies. We plan to address two important questions: 1) Are the majority of obscured SFR>50 Msolar/yr galaxies driven by major collisions? and 2) do luminous active galactic nuclei (AGN) play a crucial role in the quenching of highly obscured star-formation? These photometric redshifts are crucial in determining the physical origins of our DSFG sample and to also conduct radio weak lensing experiments with the e-MERLIN dataset.

  2. The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: The Spitzer Catalog

    Science.gov (United States)

    Paterno-Mahler, R.; Blanton, E. L.; Brodwin, M.; Ashby, M. L. N.; Golden-Marx, E.; Decker, B.; Wing, J. D.; Anand, G.

    2017-07-01

    We present 190 galaxy cluster candidates (most at high redshift) based on galaxy overdensity measurements in the Spitzer/IRAC imaging of the fields surrounding 646 bent, double-lobed radio sources drawn from the Clusters Occupied by Bent Radio AGN (COBRA) Survey. The COBRA sources were chosen as objects in the Very Large Array FIRST survey that lack optical counterparts in the Sloan Digital Sky Survey to a limit of m r = 22, making them likely to lie at high redshift. This is confirmed by our observations: the redshift distribution of COBRA sources with estimated redshifts peaks near z = 1 and extends out to z≈ 3. Cluster candidates were identified by comparing our target fields to a background field and searching for statistically significant (≥slant 2σ ) excesses in the galaxy number counts surrounding the radio sources; 190 fields satisfy the ≥slant 2σ limit. We find that 530 fields (82.0%) have a net positive excess of galaxies surrounding the radio source. Many of the fields with positive excesses but below the 2σ cutoff are likely to be galaxy groups. Forty-one COBRA sources are quasars with known spectroscopic redshifts, which may be tracers of some of the most distant clusters known.

  3. Highly-Damped Spectral Acceleration as a Ground Motion Intensity Measure for Estimating Collapse Vulnerability of Buildings

    Science.gov (United States)

    Buyco, K.; Heaton, T. H.

    2016-12-01

    Current U.S. seismic code and performance-based design recommendations quantify ground motion intensity using 5%-damped spectral acceleration when estimating the collapse vulnerability of buildings. This intensity measure works well for predicting inter-story drift due to moderate shaking, but other measures have been shown to be better for estimating collapse risk.We propose using highly-damped (>10%) spectral acceleration to assess collapse vulnerability. As damping is increased, the spectral acceleration at a given period T begins to behave like a weighted average of the corresponding lowly-damped (i.e. 5%) spectrum at a range of periods. Weights for periods longer than T increase as damping increases. Using high damping is physically intuitive for two reasons. Firstly, ductile buildings dissipate a large amount of hysteretic energy before collapse and thus behave more like highly-damped systems. Secondly, heavily damaged buildings experience period-lengthening, giving further credence to the weighted-averaging property of highly-damped spectral acceleration.To determine the optimal damping value(s) for this ground motion intensity measure, we conduct incremental dynamic analysis for a suite of ground motions on several different mid-rise steel buildings and select the damping value yielding the lowest dispersion of intensity at the collapse threshold. Spectral acceleration calculated with damping as high as 70% has been shown to be a better indicator of collapse than that with 5% damping.

  4. A new analysis methodology for estimating the eigenfrequencies of systems with high modal damping

    Science.gov (United States)

    Ozbek, Muammer; Rixen, Daniel J.

    2016-01-01

    Contemporary system identification algorithms are well proven to provide accurate eigenfrequency estimates in analyzing the systems with low modal damping. Since most engineering structures usually have low damping ratios the corresponding response characteristics can easily be obtained by conventional methods. Indeed, these modes can be extracted by using relatively short measurement durations (150-200 cycles of the lowest frequency included in the data block). However, some specific applications such as analyzing the in-operation vibration behavior of MW scale large wind turbines also require an accurate estimation of the modes with high damping. For a rotating wind turbine, some important turbine modes (e.g. flapwise rotor modes) have very high aeroelastic damping, which make them very difficult (if not impossible) to be detected. Extracting these high damping modes is a challenging task for almost all system identification techniques that are currently in use. In this work, a new method, which is based on Natural Excitation Technique (NExT), is proposed as an alternative approach for extracting the eigenfrequencies of high damping modes in an efficient way. NExT is a well established experimental dynamic analysis tool which was specifically developed to extract the dynamic characteristics of wind turbines in the early 90s. However, during the analyses it was observed that conventional NExT algorithm requires analyzing very long measurement durations (4500-5000 cycles) to be able to estimate the high damping modes accurately. A new method proposed in this work enables the eigenfrequencies of high damping modes to be estimated by using data series which are approximately 30 times shorter (around 150 cycles) than those required for a standard NExT algorithm.

  5. Evolution of the dust-to-metals ratio in high-redshift galaxies probed by GRB-DLAs

    Science.gov (United States)

    Wiseman, P.; Schady, P.; Bolmer, J.; Krühler, T.; Yates, R. M.; Greiner, J.; Fynbo, J. P. U.

    2017-02-01

    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: We 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 gamma-ray burst damped Lyman-alpha absorbers (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 these values we calculate total dust and metal column densities to determine a DTM. We explore the evolution of DTM with metallicity, and compare it 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 positively correlated with metallicity, which supports a dominant ISM grain-growth mode of dust formation. We find a substantial discrepancy between the dust content measured from depletion and that derived from the total V-band extinction, AV, measured by fitting the afterglow SED. We advise against using a measurement from one method to estimate that from the other until the discrepancy can be resolved. Based on observations collected at the European Southern Observatory, Paranal, Chile, Program IDs: 088.A-0051(B), 089.A-0067(B), 091.C-0934, 094.A-0134(A).

  6. The fate of high redshift massive compact galaxies in dense environments

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, Tobias; /Zurich, ETH; Mayer, Lucio; /Zurich U.; Carollo, Marcella; /Zurich, ETH; Feldmann, Robert; /Fermilab /Chicago U., KICP

    2012-01-01

    Massive compact galaxies seem to be more common at high redshift than in the local universe, especially in denser environments. To investigate the fate of such massive galaxies identified at z {approx} 2 we analyse the evolution of their properties in three cosmological hydrodynamical simulations that form virialized galaxy groups of mass {approx} 10{sup 13} M{sub {circle_dot}} hosting a central massive elliptical/S0 galaxy by redshift zero. We find that at redshift {approx} 2 the population of galaxies with M{sub *} > 2 x 10{sup 10} M{sub {circle_dot}} is diverse in terms of mass, velocity dispersion, star formation and effective radius, containing both very compact and relatively extended objects. In each simulation all the compact satellite galaxies have merged into the central galaxy by redshift 0 (with the exception of one simulation where one of such satellite galaxy survives). Satellites of similar mass at z = 0 are all less compact than their high redshift counterparts. They form later than the galaxies in the z = 2 sample and enter the group potential at z < 1, when dynamical friction times are longer than the Hubble time. Also, by z = 0 the central galaxies have increased substantially their characteristic radius via a combination of in situ star formation and mergers. Hence in a group environment descendants of compact galaxies either evolve towards larger sizes or they disappear before the present time as a result of the environment in which they evolve. Since the group-sized halos that we consider are representative of dense environments in the {Lambda}CDM cosmology, we conclude that the majority of high redshift compact massive galaxies do not survive until today as a result of the environment.

  7. The possible detection of high redshift Type II QSOs in deep fields

    OpenAIRE

    Meiksin, Avery

    2005-01-01

    The colours of high redshift Type II QSOs are synthesized from observations of moderate redshift systems. It is shown that Type II QSOs are comparable to starbursts in their success at matching the colours of z_850-dropouts and i_775-drops in the Hubble Ultra Deep Field, and more naturally account for the bluest objects detected. Type II QSOs may also account for some of the i_775-drops detected in the GOODS fields. It is shown that by combining imaging data from the Hubble Space Telescope an...

  8. Early Growth and Efficient Accretion of Massive Black Holes at High Redshift

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2003-01-01

    Black-hole masses of the highest redshift quasars (4 ~ 4 quasars are very massive (>~ 10^9 solar masses). It is argued that the mass estimates of the high-z quasars are not subject to larger uncertainties than those for nearby quasars. Specifically, the large masses are not overestimates and the ...... inefficient (or obscured) phase relative to the stars in their galaxies. Additionally, upper envelopes of black-hole mass of approximately 10^{10} solar masses and bolometric luminosity of ~ 10^{48} erg/s are observed at all redshifts....

  9. 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.

  10. Design and preparation of Zn-based materials possessing both high damping and good mechanical properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new idea of design and manufacture of metal-based materials possessing both high damping and good mechanical properties was proposed. The key of the idea is the combination of fining restriction-damping structures, using all mechanisms and taking advantages of different materials. Based upon this idea a foam ZA27 was prepared by the technology of prefabricated salt-mass centrifugal seeping foundry, its tensile strength and compressive strength are 83~119 MPa and 100~189 MPa, respectively. The damping properties of the foam ZA27 increase remarkably after the carpenter pastern or rosin (the damping-increased materials) was immerged into it, which approaches to the level of viscous-elastic polymer materials (Q-1≥20×10-3).

  11. 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.

  12. 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...

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

    CERN Document Server

    Palle, D

    2001-01-01

    We study the observed small deviations of high-redshift absorption spectra that are interpreted as a possible evidence for a variable fine structure constant. On the contrary, we claim that the effect could be completely attributed to the small amount of cosmic shear beyond the standard Friedmann expanding Universe.

  14. Molecular hydrogen formation on dust grains in the high-redshift universe

    NARCIS (Netherlands)

    Cazaux, S; Spaans, M

    2004-01-01

    We study the formation of molecular hydrogen on dust grain surfaces and apply our results to the high-redshift universe. We find that a range of physical parameters-in particular dust temperature and gas temperature, but not so much dust surface composition-influences the formation rate of H-2. The

  15. Molecular hydrogen formation on dust grains in the high-redshift universe

    NARCIS (Netherlands)

    Cazaux, S; Spaans, M

    2004-01-01

    We study the formation of molecular hydrogen on dust grain surfaces and apply our results to the high-redshift universe. We find that a range of physical parameters-in particular dust temperature and gas temperature, but not so much dust surface composition-influences the formation rate of H-2. The

  16. HIghZ: A search for HI absorption in high-redshift radio galaxies

    Science.gov (United States)

    Allison, J.; Callingham, J.; Sadler, E.; Wayth, R.; Curran, S.; Mahoney, E.

    2017-01-01

    We will use the unique low-frequency spectral capability of the MWA to carry out a pilot survey for neutral gas in the interstellar medium of the most distant (z>5) radio galaxies in the Universe. Through detection of the HI 21-cm line in absorption we aim to place stringent lower limits on the source redshift, confirming its location in the early Universe. Our sample makes use of the excellent wide-band spectral information available from the recently completed MWA GLEAM survey, from which we have selected a sample of ultra-steep peaked-spectrum radio sources that have a spectral turnover below 300 MHz. These sources should be ideal candidates for high-redshift compact radio galaxies since they have (a) spectral peaks that turnover below 1GHz and (b) very steep (alpha environments expected for radio galaxies in the early Universe. Using the MWA, we aim to verify this hypothesis through the detection of significant column densities of cold HI. This pathfinder project will provide important technical information that will inform future absorption surveys both with the MWA and, ultimately, the SKA-LOW telescope.

  17. Testing the Correlation of Ultra-High Energy Cosmic Rays with High Redshift Sources

    CERN Document Server

    Sigl, G; Anchordoqui, L A; Romero, G; Sigl, Guenter; Torres, Diego; Anchordoqui, Luis; Romero, Gustavo

    2001-01-01

    We study the correlation between compact radio quasars and ultra-high energy cosmic rays using an updated list of air shower detections. We estimate the level of positional correlation between both samples and the probability of pure chance association through simulations of random sets of synthetic cosmic ray events. We find that there are no reasons to claim for a physical association and that some previous results appear to be an effect of the small size of the sample used. This is also true when, instead of compact radio quasars, 3EG gamma-ray blazars are considered. Consequently, unless somehow severely deflected, it is unlikely that the high energy CR primaries are new particles or particles with new interactions beyond the electroweak scale, produced in high-redshift active galactic nuclei.

  18. 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.

  19. Confronting predictions of the galaxy stellar mass function with observations at high-redshift

    CERN Document Server

    Wilkins, Stephen M; Croft, Rupert; Khandai, Nishikanta; Feng, Yu; Bunker, Andrew; Coulton, William

    2013-01-01

    We investigate the evolution of the galaxy stellar mass function at high-redshift ($z\\ge 5$) using a pair of large cosmological hydrodynamical simulations: {\\em MassiveBlack} and {\\em MassiveBlack-II}. By combining these simulations we can study the properties of galaxies with stellar masses greater than $10^{8}\\,{\\rm M_{\\odot}}\\,h^{-1}$ and (co-moving) number densities of $\\log_{10}(\\phi\\, [{\\rm Mpc^{-3}\\,dex^{-1}}\\,h^{3}])>-8$. Observational determinations of the galaxy stellar mass function at very-high redshift typically assume a relation between the observed UV luminosity and stellar mass-to-light ratio which is applied to high-redshift samples in order to estimate stellar masses. This relation can also be measured from the simulations. We do this, finding two significant differences with the usual observational assumption: it evolves strongly with redshift and has a different shape. Using this relation to make a consistent comparison between galaxy stellar mass functions we find that at $z=6$ and above ...

  20. 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 ...

  1. The Space Density of High-Redshift QSOs in the GOODS Survey

    CERN Document Server

    Cristiani, S; Bauer, F; Brandt, W N; Chatzichristou, E T; Fontanot, F; Grazian, A; Koekemoer, A M; Lucas, R A; Monaco, P; Nonino, M; Padovani, P; Stern, D; Tozzi, P; Treister, E; Urry, C M; Vanzella, E

    2004-01-01

    We present a sample of 17 high-redshift (3.5redshifts we estimate that the final sample will contain between two and four QSOs with 4high-redshift, moderate-luminosity (M_{145}=~-23) QSOs is observed with respect to predictions based on a) the extrapolation of the z~2.7 luminosity function (LF), according to a pure luminosity evolution calibrated by the results of the Sloan Digital Sky Survey; and b) a constant universal efficiency in the formation of super-massive black holes (SMBHs) in dark-matter halos. Evidence is gathered in favor of a density evolution of the LF at high redshift and of a suppress...

  2. Empirical solutions to the high-redshift overproduction of stars in modeled dwarf galaxies

    CERN Document Server

    White, Catherine E; Ferguson, Henry C

    2014-01-01

    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$_{\\rm{H}} \\lesssim 10^{11}$ \\msun), 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 redsh...

  3. Design of high gradient, high repetition rate damped C -band rf structures

    Science.gov (United States)

    Alesini, David; Bellaveglia, Marco; Bini, Simone; Gallo, Alessandro; Lollo, Valerio; Pellegrino, Luigi; Piersanti, Luca; Cardelli, Fabio; Migliorati, Mauro; Mostacci, Andrea; Palumbo, Luigi; Tocci, Simone; Ficcadenti, Luca; Pettinacci, Valerio

    2017-03-01

    The gamma beam system of the European Extreme Light Infrastructure-Nuclear Physics project foresees the use of a multibunch train colliding with a high intensity recirculated laser pulse. The linac energy booster is composed of 12 traveling wave C -band structures, 1.8 m long with a field phase advance per cell of 2 π /3 and a repetition rate of 100 Hz. Because of the multibunch operation, the structures have been designed with a dipole higher order mode (HOM) damping system to avoid beam breakup (BBU). They are quasiconstant gradient structures with symmetric input couplers and a very effective damping of the HOMs in each cell based on silicon carbide (SiC) rf absorbers coupled to each cell through waveguides. An optimization of the electromagnetic and mechanical design has been done to simplify the fabrication and to reduce the cost of the structures. In the paper, after a review of the beam dynamics issues related to the BBU effects, we discuss the electromagnetic and thermomechanic design criteria of the structures. We also illustrate the criteria to compensate the beam loading and the rf measurements that show the effectiveness of the HOM damping.

  4. Galaxy formation in the PLANCK cosmology IV: the high-redshift universe

    CERN Document Server

    Clay, Scott; Wilkins, Stephen; Henriques, Bruno

    2015-01-01

    We present high-redshift predictions of the star-formation-rate distribution function (SFR DF), UV luminosity function (UV LF), galactic stellar mass function (GSMF), and specific star-formation rates (sSFRs) of galaxies from the latest version of the Munich semi-analytic model L-Galaxies. We find a good fit to both the shape and normalisation of the SFR DF at $z=4-7$, apart from a slight under-prediction at the low SFR end at $z=4$. Likewise, we find a good fit to the faint number counts for the observed UV LF; at brighter magnitudes our predictions lie below the observations, increasingly so at higher redshifts. At all redshifts and magnitudes, the raw (unattenuated) number counts for the UV LF lie above the observations. Because of the good agreement with the SFR we interpret our under-prediction as an over-estimate of the amount of dust in the model for the brightest galaxies, especially at high-redshift. While the shape of our GSMF matches that of the observations, we lie between (conflicting) observatio...

  5. The age of extremely red and massive galaxies at very high redshift

    CERN Document Server

    Castro-Rodriguez, N

    2011-01-01

    Aims. We present a determination of the intrinsic colors and ages of galaxies at very high redshift, in particular old galaxies (OGs) within extremely red objects (EROs). To date, the definition of EROs has been restricted to objects with z2.5). We therefore, refer to these objects as very high-redshift EROs (Z-EROS, herein). Methods. We analyze 63,550 galaxies selected in the XMM-LSS field. To obtain a reasonably sized sample of EROs, it is essential to consider a very wide area surveys. We identify targets within an area of 0.77 square degrees for which optical to mid-infrared data are available from SUBARU, UKIDSS, and Spitzer. We select Z-EROs based on their colors, and then perform a selection of only OGs. One of our novel innovations is to adapt the traditional method of EROs selection based on the filters I and K, to higher redshifts. Using our method, we identify 20 objects that satisfy the conditions required to be Z-EROs/OGs at redshifts 2.5~4.7. After including additional galaxies with z<2.5 ana...

  6. Simulating the COSMOS: The fraction of merging galaxies at high redshift

    CERN Document Server

    Kampczyk, P; Carollo, C M; Scarlata, C; Feldmann, R; Koekemoer, A; Leauthaud, A; Taniguchi, Y; Capak, P

    2006-01-01

    Simulations of nearby (0.015 < z < 0.025) SDSS galaxies have been used to reproduce as accurately as possible the appearance that they would have on COSMOS ACS images if they had been observed at z ~ 0.7 and z ~ 1.2. By adding the SDSS galaxies to random locations in the COSMOS images, we simulate the effects of chance superpositions of high redshift galaxies with unrelated foreground or background objects. We have used these simulated images, together with those of real COSMOS galaxies at these same redshifts, to undertake a "blind" morphological classification of galaxies to identify those that appear to be undergoing mergers and thus to estimate the change in merger fraction with redshift. We find that real mergers are harder to recognize at high redshift, and also that the chance superposition of unrelated galaxies often produces the appearance of mergers where in reality none exists. In particular, we estimate that 1.5 - 2.0% of objects randomly added to ACS images are misclassified as mergers due ...

  7. A study of high-redshift AGN feedback in SZ cluster samples

    Science.gov (United States)

    Bîrzan, L.; Rafferty, D. A.; Brüggen, M.; Intema, H. T.

    2017-10-01

    We present a study of active galactic nucleus (AGN) feedback at higher redshifts (0.3 samples of clusters from the South Pole Telescope and Atacama Cosmology Telescope surveys. In contrast to studies of nearby systems, we do not find a separation between cooling flow (CF) clusters and non-CF clusters based on the radio luminosity of the central radio source (cRS). This lack may be due to the increased incidence of galaxy-galaxy mergers at higher redshift that triggers AGN activity. In support of this scenario, we find evidence for evolution in the radio-luminosity function of the cRS, while the lower luminosity sources do not evolve much, the higher luminosity sources show a strong increase in the frequency of their occurrence at higher redshifts. We interpret this evolution as an increase in high-excitation radio galaxies (HERGs) in massive clusters at z > 0.6, implying a transition from HERG-mode accretion to lower power low-excitation radio galaxy (LERG)-mode accretion at intermediate redshifts. Additionally, we use local radio-to-jet power scaling relations to estimate feedback power and find that half of the CF systems in our sample probably have enough heating to balance cooling. However, we postulate that the local relations are likely not well suited to predict feedback power in high-luminosity HERGs, as they are derived from samples composed mainly of lower luminosity LERGs.

  8. A supernova origin for dust in a high-redshift quasar.

    Science.gov (United States)

    Maiolino, R; Schneider, R; Oliva, E; Bianchi, S; Ferrara, A; Mannucci, F; Pedani, M; Sogorb, M Roca

    2004-09-30

    Interstellar dust plays a crucial role in the evolution of the Universe by assisting the formation of molecules, by triggering the formation of the first low-mass stars, and by absorbing stellar ultraviolet-optical light and subsequently re-emitting it at infrared/millimetre wavelengths. Dust is thought to be produced predominantly in the envelopes of evolved (age >1 Gyr), low-mass stars. This picture has, however, recently been brought into question by the discovery of large masses of dust in the host galaxies of quasars at redshift z > 6, when the age of the Universe was less than 1 Gyr. Theoretical studies, corroborated by observations of nearby supernova remnants, have suggested that supernovae provide a fast and efficient dust formation environment in the early Universe. Here we report infrared observations of a quasar at redshift 6.2, which are used to obtain directly its dust extinction curve. We then show that such a curve is in excellent agreement with supernova dust models. This result demonstrates a supernova origin for dust in this high-redshift quasar, from which we infer that most of the dust at high redshifts probably has the same origin.

  9. ON THE REDSHIFT OF THE VERY HIGH ENERGY BLAZAR 3C 66A

    Energy Technology Data Exchange (ETDEWEB)

    Furniss, A.; Williams, D. A. [Santa Cruz Institute of Particle Physics and Department of Physics, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Fumagalli, M. [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Danforth, C. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Prochaska, J. X. [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-03-20

    As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due to a lack of intrinsic emission and absorption features in optical spectra. We present new far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 3C 66A covering the wavelength range 1132-1800 A. The data show a smooth continuum with intergalactic medium absorption features which can be used to place a firm lower limit on the blazar redshift of z {>=} 0.3347. An upper limit is set by statistically treating the non-detection of additional absorbers beyond z = 0.3347, indicating a redshift of less than 0.41 at 99% confidence and ruling out z {>=} 0.444 at 99.9% confidence. We conclude by showing how the redshift limits derived from the COS spectra remove the potential for this gamma-ray emitting blazar to place an upper limit on the flux of the EBL using high energy data from a flare in 2009 October.

  10. 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

  11. Stellar populations a guide from low to high redshift

    CERN Document Server

    Renzini, Alvio

    2011-01-01

    This up-to-date reference on stellar populations and development models includes coverage of distant galaxies, chemical evolution and supernovae. Written by highly acclaimed authorities in the field, the book makes use of specific problems to reveal the ""kitchen secrets.""

  12. The high redshift star-formation history from carbon-monoxide intensity maps

    CERN Document Server

    Breysse, Patrick C; Kamionkowski, Marc

    2015-01-01

    We demonstrate how cosmic star-formation history can be measured with one-point statistics of carbon-monoxide intensity maps. Using a P(D) analysis, the luminosity function of CO-emitting sources can be inferred from the measured one-point intensity PDF. The star-formation rate density (SFRD) can then be obtained, at several redshifts, from the CO luminosity density. We study the effects of instrumental noise, line foregrounds, and target redshift, and obtain constraints on the CO luminosity density of order 10%. We show that the SFRD uncertainty is dominated by that of the model connecting CO luminosity and star formation. For pessimistic estimates of this model uncertainty, we obtain an error of order 50% on SFRD for surveys targeting redshifts between 2 and 7 with reasonable noise and foregrounds included. However, comparisons between intensity maps and galaxies could substantially reduce this model uncertainty. In this case our constraints on SFRD at these redshifts improve to roughly 5-10%, which is high...

  13. The high-redshift star formation history from carbon-monoxide intensity maps

    Science.gov (United States)

    Breysse, Patrick C.; Kovetz, Ely D.; Kamionkowski, Marc

    2016-03-01

    We demonstrate how cosmic star formation history can be measured with one-point statistics of carbon-monoxide intensity maps. Using a P(D) analysis, the luminosity function of CO-emitting sources can be inferred from the measured one-point intensity PDF. The star formation rate density (SFRD) can then be obtained, at several redshifts, from the CO luminosity density. We study the effects of instrumental noise, line foregrounds, and target redshift, and obtain constraints on the CO luminosity density of the order of 10 per cent. We show that the SFRD uncertainty is dominated by that of the model connecting CO luminosity and star formation. For pessimistic estimates of this model uncertainty, we obtain an error of the order of 50 per cent on SFRD for surveys targeting redshifts between two and seven with reasonable noise and foregrounds included. However, comparisons between intensity maps and galaxies could substantially reduce this model uncertainty. In this case, our constraints on SFRD at these redshifts improve to roughly 5 - 10 per cent, which is highly competitive with current measurements.

  14. Spectral Evolution in High Redshift Quasars from the Final BOSS Sample

    CERN Document Server

    Jensen, Trey W; Dawson, Kyle S; Anderson, Scott F; Bautista, Julian; Bizyaev, Dmitry; Brandt, William N; Brownstein, Joel R; Green, Paul; Harris, David W; Kamble, Vikrant; McGreer, Ian D; Merloni, Andrea; Myers, Adam; Oravetz, Daniel; Pan, Kaike; Pâris, Isabelle; Schneider, Donald P; Simmons, Audrey; Suzuki, Nao

    2016-01-01

    We report on the diversity in quasar spectra from the Baryon Oscillation Spectroscopic Survey. After filtering the spectra to mitigate selection effects and Malmquist bias associated with a nearly flux-limited sample, we create high signal-to-noise ratio composite spectra from 58,656 quasars (2.1 \\le z \\le 3.5), binned by luminosity, spectral index, and redshift. With these composite spectra, we confirm the traditional Baldwin effect (BE, i.e., the anticorrelation of C IV equivalent width (EW) and luminosity) that follows the relation W_\\lambda \\propto L^{\\beta_w} with slope \\beta_w = -0.35 \\pm 0.004, -0.35 \\pm 0.005, and -0.41 \\pm 0.005 for z = 2.25, 2.46, and 2.84, respectively. In addition to the redshift evolution in the slope of the BE, we find redshift evolution in average quasar spectral features at fixed luminosity. The spectroscopic signature of the redshift evolution is correlated at 98% with the signature of varying luminosity, indicating that they arise from the same physical mechanism. At a fixed...

  15. Spectroscopy of High-Redshift Supernovae from the ESSENCE Project: The First Four Years

    CERN Document Server

    Foley, R J; Blondin, S; Chornock, R; Silverman, J M; Challis, P; Clocchiatti, A; Filippenko, A V; Kirshner, R P; Leibundgut, B; Sollerman, J; Spyromilio, J; Tonry, J L; Davis, T M; Garnavich, P M; Jha, S W; Krisciunas, K; Li, W; Pignata, G; Rest, A; Riess, A G; Schmidt, B P; Smith, R C; Stubbs, C W; Tucker, B E; Wood-Vasey, W M

    2008-01-01

    We present the results of spectroscopic observations from the ESSENCE high-redshift supernova (SN) survey during its first four years of operation. This sample includes spectra of all SNe Ia whose light curves were presented by Miknaitis et al. (2007) and used in the cosmological analyses of Davis et al. (2007) and Wood-Vasey et al. (2007). The sample represents 273 hours of spectroscopic observations with 6.5 - 10-m-class telescopes of objects detected and selected for spectroscopy by the ESSENCE team. We present 174 spectra of 156 objects. Combining this sample with that of Matheson et al. (2005), we have a total sample of 329 spectra of 274 objects. From this, we are able to spectroscopically classify 118 Type Ia SNe. As the survey has matured, the efficiency of classifying SNe Ia has remained constant while we have observed both higher-redshift SNe Ia and SNe Ia farther from maximum brightness. Examining the subsample of SNe Ia with host-galaxy redshifts shows that redshifts derived from only the SN Ia sp...

  16. On the Size of HII Regions around High Redshift Quasars

    CERN Document Server

    Maselli, A; Ferrara, A; Choudhury, T R

    2006-01-01

    We investigate the possibility of constraining the ionization state of the Intergalactic Medium (IGM) close to the end of reionization (z ~ 6) by measuring the size of the HII regions in high-z quasars spectra. We perform a combination of multiphase SPH and 3D radiative transfer (RT) simulations to reliably predict the properties of typical high-z quasar HII regions, embedded in a partly neutral IGM. From the analysis of mock spectra along lines of sight through the simulated QSO environment we find that the HII region size derived from quasar spectra is on average 30 % smaller than the physical one. Additional maximum likelihood analysis shows that this offset induces an overestimate of the neutral hydrogen fraction, x_HI, by a factor ~ 3. By applying the same statistical method to a sample of observed QSOs our study favors a mostly ionized (x_HI < 0.06) universe at z=6.1.

  17. Strong magnetic fields in normal galaxies at high redshifts

    CERN Document Server

    Bernet, Martin L; Lilly, Simon J; Kronberg, Philipp P; Dessauges-Zavadsky, Miroslava

    2008-01-01

    The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It has recently been demonstrated that field strengths as traced by rotation measures of distant quasars are comparable to those seen today, but it was unclear whether the high fields were in the exotic environments of the quasars themselves or distributed along the line of sight. Here we demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Since MgII absorption occurs in the haloes of normal galaxies along the sightline to the quasars, this association requires that organized fields of surprisingly high strength are associated with normal galaxies when the Universe was only about one-third of its present age.

  18. Galactic Synchrotron Emission and the Far-infrared-Radio Correlation at High Redshift

    Science.gov (United States)

    Schober, J.; Schleicher, D. R. G.; Klessen, R. S.

    2016-08-01

    Theoretical scenarios, including the turbulent small-scale dynamo, predict that strong magnetic fields already exist in young galaxies. Based on the assumption of energy equipartition between magnetic fields and turbulence, we determine the galactic synchrotron flux as a function of redshift z. Galaxies in the early universe are different from local galaxies, in particular, the former have more intense star formation. To cover a large range of conditions, we consider two different systems: one model galaxy comparable to the Milky Way and one typical high-z starburst galaxy. We include a model of the steady-state cosmic ray spectrum and find that synchrotron emission can be detected up to cosmological redshifts with current and future radio telescopes. The turbulent dynamo theory is in agreement with the origin of the observed correlation between the far-infrared (FIR) luminosity L FIR and the radio luminosity L radio. Our model reproduces this correlation well at z = 0. We extrapolate the FIR-radio correlation to higher redshifts and predict a time evolution with a significant deviation from its present-day appearance already at z≈ 2 for a gas density that increases strongly with z. In particular, we predict a decrease of the radio luminosity with redshift which is caused by the increase of cosmic ray energy losses at high z. The result is an increase of the ratio between L FIR and L radio. Simultaneously, we predict that the slope of the FIR-radio correlation becomes shallower with redshift. This behavior of the correlation could be observed in the near future with ultra-deep radio surveys.

  19. The superluminous supernova PS1-11ap: bridging the gap between low and high redshift

    Science.gov (United States)

    McCrum, M.; Smartt, S. J.; Kotak, R.; Rest, A.; Jerkstrand, A.; Inserra, C.; Rodney, S. A.; Chen, T.-W.; Howell, D. A.; Huber, M. E.; Pastorello, A.; Tonry, J. L.; Bresolin, F.; Kudritzki, R.-P.; Chornock, R.; Berger, E.; Smith, K.; Botticella, M. T.; Foley, R. J.; Fraser, M.; Milisavljevic, D.; Nicholl, M.; Riess, A. G.; Stubbs, C. W.; Valenti, S.; Wood-Vasey, W. M.; Wright, D.; Young, D. R.; Drout, M.; Czekala, I.; Burgett, W. S.; Chambers, K. C.; Draper, P.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Price, P. A.; Sweeney, W.; Wainscoat, R. J.

    2014-01-01

    We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of Mu = -21.4 mag and bolometric luminosity of 8 × 1043 erg s-1 before settling on to a relatively shallow gradient of decline. The observed decline is significantly slower than those of the SLSNe-Ic which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay time-scale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 d before peak to 230 d after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining SLSNe-Ic, and the light-curve evolution can also be quantitatively explained by the magnetar spin-down model. At a redshift of z = 0.524, the observer-frame optical coverage provides comprehensive rest-frame UV data and allows us to compare it with the SLSNe recently found at high redshifts between z = 2 and 4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient.

  20. Vibration damping of superalloys and thermal barrier coatings at high-temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Gregori, Giuliano [California NanoSystems Institute, University of California, Santa Barbara, CA 93160-5050 (United States)], E-mail: g.gregori@fkf.mpg.de; Li Li [Materials Department, University of California, Santa Barbara, CA 93160-5050 (United States); Nychka, John A. [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506-0046 (United States); Clarke, David R. [Materials Department, University of California, Santa Barbara, CA 93160-5050 (United States)

    2007-09-25

    A high-temperature mechanical spectroscopy system, based on non-contact laser vibrometry, has been developed to investigate the temperature dependence of the flexural damping properties of materials and coatings up to 900 deg. C. Results for the damping coefficient and Young's modulus have been obtained for several high temperature alloys (FeCrAlY and a single crystal, Ni-based superalloy PWA 1484), ceramics (polycrystalline alumina and yttria-stabilized zirconia) and an electron-beam deposited thermal barrier coating. The results indicate that the thermally grown oxide, formed by high-temperature oxidation does not confer significant damping, whereas, coatings of the yttria-stabilized zirconia produce measurable damping over the entire temperature range with a peak centered at {approx}200 deg. C. The damping peak appears to be an intrinsic property of the YSZ material whether in the form of a bulk material or a metastable coating. Data on the temperature dependent in-plane Young's modulus of the 7 wt.% yttria-stabilized zirconia thermal barrier coating between room temperature (22 GPa) and 900 deg. C (18 GPa) is also reported for the first time.

  1. High precision spectra at large redshift for dynamical DE cosmologies

    CERN Document Server

    Bonometto, S A; Maccio', A V; Stinson, G

    2010-01-01

    The next generation mass probes will investigate DE nature by measuring non-linear power spectra at various z, and comparing them with high precision simulations. Producing a complete set of them, taking into account baryon physics and for any DE state equation w(z), would really be numerically expensive. Regularities reducing such duty are essential. This paper presents further n-body tests of a relation we found, linking models with DE state parameter w(z) to const.-w models, and also tests the relation in hydro simulations.

  2. High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network

    DEFF Research Database (Denmark)

    Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    When operating in a micro or weak grid which has a relatively large network impedance, the Doubly Fed Induction Generator (DFIG) based wind power generation system is prone to suffer high frequency resonance due to the impedance interaction between DFIG system and the parallel compensated network...... (series RL + shunt C). In order to improve the performance of the DFIG system as well as other units and loads connected to the weak grid, the high frequency resonance needs to be effectively damped. In this paper, the proposed active damping control strategy is able to implement effective damping either...... in the Rotor Side Converter (RSC) or in the Grid Side Converter (GSC), through the introduction of virtual positive capacitor or virtual negative inductor to reshape the DFIG system impedance and mitigate the high frequency resonance. A detailed theoretical explanation on the virtual positive capacitor...

  3. High Frequency Resonance Damping of DFIG based Wind Power System under Weak Network

    DEFF Research Database (Denmark)

    Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede

    2017-01-01

    When operating in a micro or weak grid which has a relatively large network impedance, the Doubly Fed Induction Generator (DFIG) based wind power generation system is prone to suffer high frequency resonance due to the impedance interaction between DFIG system and the parallel compensated network...... (series RL + shunt C). In order to improve the performance of the DFIG system as well as other units and loads connected to the weak grid, the high frequency resonance needs to be effectively damped. In this paper, the proposed active damping control strategy is able to implement effective damping either...... in the Rotor Side Converter (RSC) or in the Grid Side Converter (GSC), through the introduction of virtual positive capacitor or virtual negative inductor to reshape the DFIG system impedance and mitigate the high frequency resonance. A detailed theoretical explanation on the virtual positive capacitor...

  4. On the [CII]-SFR relation in high redshift galaxies

    CERN Document Server

    Vallini, L; Ferrara, A; Pallottini, A; Yue, B

    2015-01-01

    After two ALMA observing cycles, only a handful of [CII] $158\\,\\mu m$ emission line searches in z>6 galaxies have reported a positive detection, questioning the applicability of the local [CII]-SFR relation to high-z systems. To investigate this issue we use the Vallini et al. 2013 (V13) model, based on high-resolution, radiative transfer cosmological simulations to predict the [CII] emission from the interstellar medium of a z~7 (halo mass $M_h=1.17\\times10^{11}M_{\\odot}$) galaxy. We improve the V13 model by including (a) a physically-motivated metallicity (Z) distribution of the gas, (b) the contribution of Photo-Dissociation Regions (PDRs), (c) the effects of Cosmic Microwave Background on the [CII] line luminosity. We study the relative contribution of diffuse neutral gas to the total [CII] emission ($F _{diff}/F_{tot}$) for different SFR and Z values. We find that the [CII] emission arises predominantly from PDRs: regardless of the galaxy properties, $F _{diff}/F_{tot}\\leq 10$% since, at these early epoc...

  5. Metal-rich absorbers at high redshifts: abundance patterns

    CERN Document Server

    Levshakov, S A; Molaro, P; Reimers, D; Hou, J L

    2009-01-01

    (Abbreviated) From six spectra of high-z QSOs, we select eleven metal-rich, Z>=Z_solar, and optically-thin to the ionizing radiation, N(HI)0, which supposes that the nitrogen enrichment occurs irregularly. In some cases, the lines of MgII 2796, 2803 appear to be shifted, probably as a result of an enhanced content of heavy isotopes 25Mg and 26Mg in the absorbing gas relative to the solar isotopic composition. Seven absorbers are characterized by low mean ionization parameter U, log U2 whereas all others are found at z ~= 1.8. Comparing the space number density of metal-rich absorbers with the comoving density of star-forming galaxies at z ~= 2, we estimate that the circumgalactic volume of each galaxy is populated by 10^7 - 10^8 such absorbers with total mass <=1/100th of the stellar galactic mass. Possible effects of high metal content on the peak values of star-forming and AGN activities at z~2 are discussed.

  6. Reconciling the Stellar and Nebular Spectra of High Redshift Galaxies

    CERN Document Server

    Steidel, C C; Pettini, M; Rudie, G C; Reddy, N A; Trainor, R F

    2016-01-01

    We present a combined analysis of rest-frame far-UV (1000-2000 A) and rest-frame optical (3600-7000 A) composite spectra formed from very deep observations of a sample of 30 star-forming galaxies with z=2.4+/-0.1, selected to be representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and the excitation of the observed nebular emission, a self-consistent stellar population synthesis model must simultaneously match the details of the far-UV stellar+nebular continuum and-- when inserted as the excitation source in photoionization models-- account for all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity (Z_*/Z_{sun} ~ 0.1) but relatively high ionized gas-phase oxygen abundances (Z_{neb}/Z_{sun} ~ 0.5), can successfully match all of the observational constraints. We argue that this apparent discrepancy is naturally explained by highly super-solar O/Fe [4-5...

  7. The dust content of QSO hosts at high redshift

    CERN Document Server

    Calura, F; Vignali, C; Pozzi, F; Pipino, A; Matteucci, F

    2013-01-01

    Infrared observations of high-z quasar (QSO) hosts indicate the presence of large masses of dust in the early universe. When combined with other observables, such as neutral gas masses and star formation rates, the dust content of z~6 QSO hosts may help constraining their star formation history. We have collected a database of 58 sources from the literature discovered by various surveys and observed in the FIR. We have interpreted the available data by means of chemical evolution models for forming proto-spheroids, investigating the role of the major parameters regulating star formation and dust production. For a few systems, given the derived small dynamical masses, the observed dust content can be explained only assuming a top-heavy initial mass function, an enhanced star formation efficiency and an increased rate of dust accretion. However, the possibility that, for some systems, the dynamical mass has been underestimated cannot be excluded. If this were the case, the dust mass can be accounted for by stan...

  8. Outflow and hot dust emission in high redshift quasars

    CERN Document Server

    Wang, Huiyuan; Zhang, Kai; Wang, Tinggui; Zhou, Hongyan; Zhang, Shaohua

    2013-01-01

    Correlations of hot dust emission with outflow properties are investigated, based on a large z~2 non-BAL quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near infrared (NIR) slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the emission from accretion disk. In our luminous quasars, these hot dust emission indicators are almost independent of the fundamental parameters, such as luminosity, Eddington ratio and black hole mass, but moderately dependent on the blueshift and asymmetry index (BAI) and FWHM of CIV lines. Interestingly, the latter two correlations dramatically strengthen with increasing Eddington ratio. We suggest that, in high Eddington ratio quasars, CIV regions are dominated by outflows so BAI and FWHM(CIV) can reliably reflect the general property and velocity of outflows, respectively. While in low Eddington ratio quasars, CIV lines are primarily emitted by virialized gas so BAI and FWHM(C...

  9. Characterization and Modeling of Contamination for Lyman Break Galaxy Samples at High Redshift

    Science.gov (United States)

    Vulcani, Benedetta; Trenti, Michele; Calvi, Valentina; Bouwens, Rychard; Oesch, Pascal; Stiavelli, Massimo; Franx, Marijn

    2017-02-01

    The selection of high-redshift sources from broadband photometry using the Lyman-break galaxy (LBG) technique is a well established methodology, but the characterization of its contamination for the faintest sources is still incomplete. We use the optical and near-IR data from four (ultra)deep Hubble Space Telescope legacy fields to investigate the contamination fraction of LBG samples at z∼ 5{--}8 selected using a color–color method. Our approach is based on characterizing the number count distribution of interloper sources, that is, galaxies with colors similar to those of LBGs, but showing detection at wavelengths shorter than the spectral break. Without sufficient sensitivity at bluer wavelengths, a subset of interlopers may not be properly classified, and contaminate the LBG selection. The surface density of interlopers in the sky gets steeper with increasing redshift of LBG selections. Since the intrinsic number of dropouts decreases significantly with increasing redshift, this implies increasing contamination from misclassified interlopers with increasing redshift, primarily by intermediate redshift sources with unremarkable properties (intermediate ages, lack of ongoing star formation and low/moderate dust content). Using Monte-Carlo simulations, we estimate that the CANDELS deep data have contamination induced by photometric scatter increasing from ∼ 2 % at z∼ 5 to ∼ 6 % at z∼ 8 for a typical dropout color ≥slant 1 mag, with contamination naturally decreasing for a more stringent dropout selection. Contaminants are expected to be located preferentially near the detection limit of surveys, ranging from 0.1 to 0.4 contaminants per arcmin2 at {J}125 = 30, depending on the field considered. This analysis suggests that the impact of contamination in future studies of z> 10 galaxies needs to be carefully considered.

  10. Detecting Massive, High-Redshift Galaxy Clusters Using the Thermal Sunyaev-Zel'dovich Effect

    Science.gov (United States)

    Adams, Carson; Steinhardt, Charles L.; Loeb, Abraham; Karim, Alexander; Staguhn, Johannes; Erler, Jens; Capak, Peter L.

    2017-01-01

    We develop the thermal Sunyaev-Zel'dovich (SZ) effect as a direct astrophysical measure of the mass distribution of dark matter halos. The SZ effect increases with cosmological distance, a unique astronomical property, and is highly sensitive to halo mass. We find that this presents a powerful methodology for distinguishing between competing models of the halo mass function distribution, particularly in the high-redshift domain just a few hundred million years after the Big Bang. Recent surveys designed to probe this epoch of initial galaxy formation such as CANDELS and SPLASH report an over-abundance of highly massive halos as inferred from stellar ultraviolet (UV) luminosities and the stellar mass to halo mass ratio estimated from nearby galaxies. If these UV luminosity to halo mass relations hold to high-redshift, observations estimate several orders of magnitude more highly massive halos than predicted by hierarchical merging and the standard cosmological paradigm. Strong constraints on the masses of these galaxy clusters are essential to resolving the current tension between observation and theory. We conclude that detections of thermal SZ sources are plausible at high-redshift only for the halo masses inferred from observation. Therefore, future SZ surveys will provide a robust determination between theoretical and observational predictions.

  11. OUTFLOW AND HOT DUST EMISSION IN HIGH-REDSHIFT QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huiyuan; Xing, Feijun; Wang, Tinggui; Zhou, Hongyan [Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Zhang, Kai [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Zhang, Shaohua, E-mail: whywang@mail.ustc.edu.cn [Polar Research Institute of China, Jinqiao Road 451, Shanghai 200136 (China)

    2013-10-10

    Correlations of hot dust emission with outflow properties are investigated, based on a large z ∼ 2 non-broad absorption line quasar sample built from the Wide-field Infrared Survey and the Sloan Digital Sky Survey data releases. We use the near-infrared slope and the infrared to UV luminosity ratio to indicate the hot dust emission relative to the emission from the accretion disk. In our luminous quasars, these hot dust emission indicators are almost independent of the fundamental parameters, such as luminosity, Eddington ratio and black hole mass, but moderately dependent on the blueshift and asymmetry index (BAI) and FWHM of C IV lines. Interestingly, the latter two correlations dramatically strengthen with increasing Eddington ratio. We suggest that, in high Eddington ratio quasars, C IV regions are dominated by outflows so the BAI and FWHM (C IV) can reliably reflect the general properties and velocity of outflows, respectively. In low Eddington ratio quasars, on the other hand, C IV lines are primarily emitted by virialized gas so the BAI and FWHM (C IV) become less sensitive to outflows. Therefore, the correlations for the highest Eddington ratio quasars are more likely to represent the true dependence of hot dust emission on outflows and the correlations for the entire sample are significantly diluted by the low Eddington ratio quasars. Our results show that an outflow with a large BAI or velocity can double the hot dust emission on average. We suggest that outflows either contain hot dust in themselves or interact with the dusty interstellar medium or torus.

  12. Dusty Star Forming Galaxies and Supermassive Black Holes at High Redshifts: In- Situ Coevolution

    Science.gov (United States)

    Mancuso, Claudia

    2016-10-01

    We have exploited the continuity equation approach and the star-formation timescales derived from the observed 'main sequence' relation (Star Formation Rate vs Stellar Mass), to show that the observed high abundance of galaxies with stellar masses ≥ a few 10^10 M⊙ at redshift z ≥ 4 implies the existence of a galaxy population featuring large star formation rates (SFRs) ψ ≥ 10^2 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-InfraRed (FIR) 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, elucidating that the number density at z ≤ 8 for SFRs ψ ≥ 30 M⊙ yr^-1 cannot be estimated relying on the UltraViolet (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 via on-source observations with ALMA, can allow 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-)mm observations by ALMA and NIKA2. The same could be done with radio observations by SKA and its precursors. In particular we have worked out predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. To do that we

  13. Why do high-redshift galaxies show diverse gas-phase metallicity gradients?

    CERN Document Server

    Ma, Xiangcheng; Feldmann, Robert; Torrey, Paul; Faucher-Giguere, Claude-Andre; Keres, Dusan

    2016-01-01

    Recent spatially resolved observations of galaxies at z=0.6-3 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments (FIRE) project, which include physically motivated models of the multi-phase ISM, star formation, and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z=0-3. Strong negative metallicity gradients only appear in galaxies with a rotating disk, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas...

  14. Comparison of high order modes damping techniques for 800 MHz single cell superconducting cavities

    CERN Document Server

    Shashkov, Ya V; Zobov, M M

    2014-01-01

    Currently, applications of 800 MHz harmonic cavities in both bunch lengthening and shortening regimes are under consideration and discussion in the framework of the High Luminosity LHC project. In this paper we study electromagnetic characteristics of high order modes (HOM) for a single cell 800 MHz superconducting cavity and arrays of such cavities connected by drifts tubes. Different techniques for the HOM damping such as beam pipe grooves, coaxial-notch loads, fluted beam pipes etc. are investigated and compared. The influence of the sizes and geometry of the drift tubes on the HOM damping is analyzed.

  15. High-ion absorption in the proximate damped Lyman-alpha system toward Q0841+129

    CERN Document Server

    Fox, Andrew J; Petitjean, Patrick; Srianand, Raghunathan; Guimarães, Rodney

    2011-01-01

    We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Lyman-alpha (PDLA) absorber at z=2.47621 and a proximate sub-DLA at z=2.50620, both lying close in redshift to the QSO itself at z_em=2.49510+/-0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si IV, C IV, and O VI in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of ~160 km/s, whereas the low ions exist predominantly in a single component spanning just 30 km/s. We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five compone...

  16. Stellar Populations, Outflows, and Morphologies of High-Redshift Galaxies

    Science.gov (United States)

    Kornei, Katherine Anne

    the centroids of FeII interstellar absorption lines, are found to span the interval -217, +155 km s-1. We find that ˜ 40% (10%) of the sample exhibits blueshifted FeII lines at the 1sigma (3sigma) level. We also measure maximal outflow velocities using the profiles of the FeII and MgII lines; we find that MgII frequently traces higher velocity gas than FeII. Using quantitative morphological parameters derived from the HST imaging, we find that mergers are not a prerequisite for driving outflows. More face-on galaxies also show stronger winds than highly inclined systems, consistent with the canonical picture of winds emanating perpendicular to galactic disks. Galactic winds are further explored in the third study of this thesis, where we present a study at z ˜ 1 of the prevalence and kinematics of ultraviolet emission lines from fine-structure FeII* transitions and resonance MgII transitions. Utilizing a multiwavelength dataset of 212 star-forming galaxies, we investigate how the strength and kinematics of FeII* and MgII emission lines vary as a function of galaxy properties. We find that FeII* emission is prevalent in the sample; composite spectra assembled on the basis of a variety of galaxy properties all show FeII* emission, particularly in the stronger 2396 and 2626 A lines. This prevalence of emission is in contrast to observations of local galaxies; the lack of FeII* emission in the small star-forming regions targeted by spectroscopic observations at z ˜ 0 may imply that FeII* emission arises in more extended galaxy halos. The strength of FeII* emission is most strongly modulated by star-formation rate, dust attenuation, and [OII] equivalent width, such that systems with lower star-formation rates, lower dust levels, and larger [OII] equivalent widths show stronger FeII* emission. MgII emission, while not observed in a spectral stack of all the data in our sample, is seen in ˜ 30% of individual objects. We find that objects showing MgII emission have

  17. Seeding high-redshift QSOs by collisional runaway in primordial star clusters

    Science.gov (United States)

    Katz, Harley; Sijacki, Debora; Haehnelt, Martin G.

    2015-08-01

    We study how runaway stellar collisions in high-redshift, metal-poor star clusters form very massive stars (VMSs) that can directly collapse to intermediate-mass black holes (IMBHs). We follow the evolution of a pair of neighbouring high-redshift mini-haloes with high-resolution, cosmological hydrodynamical zoom-in simulations using the adaptive mesh refinement code RAMSES combined with the non-equilibrium chemistry package KROME. The first collapsing mini-halo is assumed to enrich the central nuclear star cluster (NSC) of the other to a critical metallicity, sufficient for Population II (Pop. II) star formation at redshift z ≈ 27. Using the spatial configuration of the flattened, asymmetrical gas cloud forming in the core of the metal-enriched halo, we set the initial conditions for simulations of an initially non-spherical star cluster with the direct summation code NBODY6 which are compared to about 2000 NBODY6 simulations of spherical star clusters for a wide range of star cluster parameters. The final mass of the VMS that forms depends strongly on the initial mass and initial central density of the NSC. For the initial central densities suggested by our RAMSES simulations, VMSs with mass >400 M⊙ can form in clusters with stellar masses of ≈104 M⊙, and this can increase to well over 1000 M⊙ for more massive and denser clusters. The high probability we find for forming a VMS in these mini-haloes at such an early cosmic time makes collisional runaway of Pop. II star clusters a promising channel for producing large numbers of high-redshift IMBHs that may act as the seeds of supermassive black holes.

  18. Probing the EBL evolution at high redshifts using 22 GRBs detected with the Fermi-LAT

    Science.gov (United States)

    Amitbhai Desai, Abhishek; Ajello, Marco; Omodei, Nicola; Hartmann, Dieter; Fermi-LAT Collaboration

    2017-01-01

    The extragalactic background light (EBL) is the collective emission of all the stars and galaxies over the history of the universe. The most efficient method to study the EBL is through the imprint it leaves via photon-photon annihilation in the spectra of distant gamma-ray sources. Here we present a combined analysis of a sample of 22 Gamma Ray Bursts (GRBs) detected by Fermi Large Area Telescope. GRBs are short-lived, bright, high-energy sources detected up to very high redshifts. This allows us to probe the EBL at much higher redshifts than before. We report the first constrain on the EBL when the Universe was one fourth of its present age (z=1.8). This will be discussed in the context of the generation of the UV-optical background and the star-formation activity of the Universe.

  19. Structure formation simulations with momentum exchange: alleviating tensions between high-redshift and low-redshift cosmological probes

    Science.gov (United States)

    Baldi, Marco; Simpson, Fergus

    2017-02-01

    Persisting tensions between the cosmological constraints derived from low-redshift probes and the ones obtained from temperature and polarization anisotropies of the cosmic microwave background (CMB) - although not yet providing compelling evidence against the Λcold dark matter model - seem to consistently indicate a slower growth of density perturbations as compared to the predictions of the standard cosmological scenario. Such behaviour is not easily accommodated by the simplest extensions of General Relativity, such as f(R) models, which generically predict an enhanced growth rate. In this work, we present the outcomes of a suite of large N-body simulations carried out in the context of a cosmological model featuring a non-vanishing scattering cross-section between the dark matter and the dark energy fields, for two different parametrizations of the dark energy equation of state. Our results indicate that these dark scattering models have very mild effects on many observables related to large-scale structures formation and evolution, while providing a significant suppression of the amplitude of linear density perturbations and the abundance of massive clusters. Our simulations therefore confirm that these models offer a promising route to alleviate existing tensions between low-redshift measurements and those of the CMB.

  20. From Nearby Low Luminosity AGN to High Redshift Radio Galaxies: Science Interests with SKA

    CERN Document Server

    Kharb, P; Singh, V; Bagchi, J; Chandra, C H Ishwara; Hota, A; Konar, C; Wadadekar, Y; Shastri, P; Das, M; Baliyan, K; Nath, B B; Pandey-Pommier, M

    2016-01-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

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

    Indian Academy of Sciences (India)

    P. Kharb; D. V. Lal; V. Singh; J. Bagchi; C. H. Ishwara Chandra; A. Hota; C. Konar; Y. Wadadekar; P. Shastri; M. Das; K. Baliyan; B. B. Nath; M. Pandey-Pommier

    2016-12-01

    We present detailed science cases that a large fraction of the Indian AGN community is interested in pursuing with the upcoming Square Kilometre Array (SKA). These interests range from understanding low luminosity active galactic nuclei in the nearby Universe to powerful radio galaxies at high redshifts. Important unresolved science questions in AGN physics are discussed. Ongoing low-frequency surveys with the SKA pathfinder telescope GMRT, are highlighted.

  2. 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.

  3. High performance single-error-correcting quantum codes for amplitude damping

    CERN Document Server

    Shor, Peter W; Smolin, John A; Zeng, Bei

    2009-01-01

    We construct families of high performance quantum amplitude damping codes. All of our codes are nonadditive and most modestly outperform the best possible additive codes in terms of encoded dimension. One family is built from nonlinear error-correcting codes for classical asymmetric channels, with which we systematically construct quantum amplitude damping codes with parameters better than any prior construction known for any block length n > 7 except n=2^r-1. We generalize this construction to employ classical codes over GF(3) with which we numerically obtain better performing codes up to length 14. Because the resulting codes are of the codeword stabilized (CWS) type, easy encoding and decoding circuits are available.

  4. Application of a high-performance damping metal to gravitational wave detectors

    CERN Document Server

    Mio, N; Moriwaki, S

    2002-01-01

    We have investigated applications of a high-performance damping metal, called M2052, which is a manganese-based alloy containing copper, nickel and iron. Using an all-metal prototype of a vibration isolation system, we have tested the property of M2052. As its actual application to a gravitational wave detector, we have used M2052 in the damping system of a suspended optics in TAMA300, which is a 300 m long interferometric gravitational wave detector built at the Mitaka campus of the National Astronomical Observatory in Japan. The results of the experiments are reported.

  5. High frequency electromagnetic characterization of NEG properties for the CLIC damping rings

    CERN Document Server

    Koukovini-Platia, E; Zannini, C

    2014-01-01

    Coating materials will be used in the CLIC damping rings (DR) to suppress two-stream effects. In particular, NEG coating is necessary to suppress fast beam ion instabilities in the electron damping ring (EDR). The electromagnetic (EM) characterization of the material properties up to high frequencies is required for the impedance modeling of the CLIC DR components. The EM properties for frequencies of few GHz are determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D EM simulations. The results obtained from a NEG-coated copper (Cu) waveguide are presented in this paper.

  6. Two high-redshift DLAs towards a z~5 gamma-ray burst

    CERN Document Server

    Sparre, M; Krühler, T; Fynbo, J P U; Watson, D J; Wiersema, K; D'Elia, V; De Cia, A; Afonso, P M J; Covino, S; Postigo, A de Ugarte; Flores, H; Goldoni, P; Greiner, J; Hjorth, J; Jakobsson, P; Kaper, L; Klose, S; Malesani, D; Milvang-Jensen, B; Nardini, M; Piranomonte, S; Sollerman, J; Ramirez, R Sanchez; Schulze, S; Tanvir, N R; Vergani, S D; Wijers, R A M J; Zafar, T

    2013-01-01

    Observations of the afterglows of long gamma-ray bursts (GRBs) allow the study of star-forming galaxies across most of cosmic history. Here we present observations of GRB 111008A from which we can measure abundance patterns, metallicity, dust content and extinction of the GRB host galaxy (z=5.0) as well as a Damped Lyman-alpha Absorber (DLA) galaxy along the line of sight (z=4.6). These systems have column densities of log N =22.30 +/- 0.06 and 21.34 +/- 0.10, respectively. The GRB host galaxy has a metallicity of 2% solar (based on sulfur), and a lower limit of the metallicity for the intervening DLA is 3% (based on silicon). For the intervening absorber we also measure -1.73<[Fe/H]<-1.09, but the true metallicity can be higher, because it is unclear how much the abundances are affected by dust depletion. The presence and variability of fine-structure lines confirms the z=5.0 system as the GRB host. This is the highest redshift where Fe II fine-structure lines have been detected. The afterglow is only ...

  7. 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 ...

  8. Improving Dark Energy Constraints with High Redshift Type Ia Supernovae from CANDELS and CLASH

    CERN Document Server

    Salzano, Vincenzo; Sendra, Irene; Lazkoz, Ruth; Riess, Adam G; Postman, Marc; Broadhurst, Tom; Coe, Dan

    2013-01-01

    Aims. We investigate the degree of improvement in dark energy constraints that can be achieved by extending Type Ia Supernova (SN Ia) samples to redshifts z > 1.5 with the Hubble Space Telescope (HST), particularly in the ongoing CANDELS and CLASH multi-cycle treasury programs. Methods. Using the popular CPL parametrization of the dark energy, w = w0 +wa(1-a), we generate mock SN Ia samples that can be projected out to higher redshifts. The synthetic datasets thus generated are fitted to the CPL model, and we evaluate the improvement that a high-z sample can add in terms of ameliorating the statistical and systematic uncertainties on cosmological parameters. Results. In an optimistic but still very achievable scenario, we find that extending the HST sample beyond CANDELS+CLASH to reach a total of 28 SN Ia at z > 1.0 could improve the uncertainty in the wa parameter by up to 21%. The corresponding improvement in the figure of merit (FoM) would be as high as 28%. Finally, we consider the use of high-redshift SN...

  9. Herschel-ATLAS: The Angular Correlation Function of Submillimetre Galaxies at High and Low Redshift

    Science.gov (United States)

    Maddox, S. J.; Dunne, L.; Rigby, E.; Eales, S.; Cooray, A.; Scott, D.; Peacock, J. A.; Negrello, M.; Smith, D. J. B.; Benford, D.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D.; Burgarella, D.; Buttiglione, S.; Cava, A.; Clements, D.; Dariush, A.; deZotti, G.; Dye, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.

    2010-01-01

    We present measurements of the angular correlation function of galaxies selected from the first field of the H-ATLAS survey. Careful removal of the background from galactic cirrus is essential, and currently dominates the uncertainty in our measurements. For our 250 micrometer-selected sample we detect no significant clustering, consistent with the expectation that the 250 pm-selected sources are mostly normal galaxies at z < or equal to 1. For our 350 micrometer and 500 micrometer-selected samples we detect relatively strong clustering with correlation amplitudes A of 0.2 and 1.2 at 1', but with relatively large uncertainties. For samples which preferentially select high redshift galaxies at z approx. 2-3 we detect significant strong clustering, leading to an estimate of r(0) approx. 7-11/h Mpc. The slope of our clustering measurements is very steep. delta approx. 2. The measurements are consistent with the idea that sub-mm sources consist of a low redshift population of normal galaxies and a high redshift population of highly clustered star-bursting galaxies.

  10. Early Growth and Efficient Accretion of Massive Black Holes at High Redshift

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2003-01-01

    Black-hole masses of the highest redshift quasars (4 ~ 4 quasars are very massive (>~ 10^9 solar masses). It is argued that the mass estimates of the high-z quasars are not subject to larger uncertainties than those for nearby quasars. Specifically, the large masses are not overestimates and the ......Black-hole masses of the highest redshift quasars (4 ~ 4 quasars are very massive (>~ 10^9 solar masses). It is argued that the mass estimates of the high-z quasars are not subject to larger uncertainties than those for nearby quasars. Specifically, the large masses are not overestimates...... and the lack of similarly large black-hole masses in the nearby Universe does not rule out their existence at high-z. However, AGN host galaxies do not typically appear fully formed or evolved at these early epochs. This supports scenarios in which black holes build up mass very fast in a radiatively...... inefficient (or obscured) phase relative to the stars in their galaxies. Additionally, upper envelopes of black-hole mass of approximately 10^{10} solar masses and bolometric luminosity of ~ 10^{48} erg/s are observed at all redshifts....

  11. Seeding High Redshift QSOs by Collisional Runaway in Primordial Star Clusters

    CERN Document Server

    Katz, Harley; Haehnelt, Martin G

    2015-01-01

    We study how runaway stellar collisions in high redshift, metal poor star clusters form very massive stars (VMSs) that can directly collapse to intermediate mass black holes (IMBHs). We follow the evolution of a pair of two neighboring high-redshift mini-halos which are expected to host central nuclear star clusters (NSCs) with very high resolution, cosmological hydrodynamical zoom-in simulations with the adaptive mesh refinement code RAMSES. One of the two mini-halos enriches the central NSC of the other mini-halo to a critical metallicity, sufficient for Pop. II star formation at redshift z~27. We then use the spatial configuration of the flattened, asymmetrical gas cloud forming in the RAMSES simulations at the core of the metal enriched halo to set the initial conditions for simulations of an initially non-spherical star cluster with the direct summation code NBODY6 which are compared to about 2000 NBODY6 simulations of spherical star clusters for a wide range of star cluster parameters. In this way we es...

  12. 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.

  13. 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...

  14. An 80-kpc Lyman-alpha halo around a high redshift type-2 QSO

    CERN Document Server

    Smith, Daniel J B; Simpson, Chris; Martinez-Sansigre, Alejo

    2008-01-01

    We announce the discovery of an extended emission line region associated with a high redshift type-2 QSO. The halo, which was discovered in our new wide-field narrow-band survey, resides at z = 2.85 in the Spitzer First Look Survey region and is extended over ~80 kpc. Deep VLBI observations imply that approximately 50 per cent of the radio emission is extended on scales > 200pc. The inferred AGN luminosity is sufficient to ionize the extended halo, and the optical emission is consistent with being triggered coevally with the radio source. The Lyman-alpha halo is as luminous as those found around high redshift radio galaxies, however the active nucleus is several orders of magnitude less luminous at radio wavelengths than those FRIIs more commonly associated with extended emission line regions. AMS05 appears to be a high-redshift analogue to the radio-quiet quasar E1821+643 which is core dominated but which also exhibits extended FRI-like structure and contains an optically powerful AGN. We also find evidence ...

  15. The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation

    CERN Document Server

    Rahmati, Alireza; Bower, Richard G; Crain, Robert A; Furlong, Michelle; Schaller, Matthieu; Theuns, Tom

    2015-01-01

    The observed high covering fractions of neutral hydrogen (HI) with column densities above $\\sim 10^{17} \\rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ~ 2-3 has been identified as a challenge for simulations of galaxy formation. We use the EAGLE cosmological, hydrodynamical simulation, which has been shown to reproduce a wide range of galaxy properties and for which the subgrid feedback was calibrated without considering gas properties, to study the distribution of HI around high-redshift galaxies. We predict the covering fractions of strong HI absorbers ($N_{\\rm{HI}} \\gtrsim 10^{17} \\rm{cm}^{-2}$) inside haloes to increase rapidly with redshift but to depend only weakly on halo mass. For massive ($M_{200} \\gtrsim 10^{12} {\\rm M_{\\odot}}$) halos the covering fraction profiles are nearly scale-invariant and we provide fitting functions that reproduce the simulation results. While efficient feedback is required to increase the HI covering fractions to the high observed values...

  16. CLASH: EXTREME EMISSION-LINE GALAXIES AND THEIR IMPLICATION ON SELECTION OF HIGH-REDSHIFT GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xingxing; Wang, Junxian; Shu, Xinwen [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zheng, Wei; Ford, Holland; Lemze, Doron [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States); Van der Wel, Arjen [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg (Germany); Zitrin, Adi [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Frye, Brenda L. [Steward Observatory/Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Postman, Marc; Bradley, Larry; Coe, Dan [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Bartelmann, Matthias [Leiden Observatory, Leiden University, P. O. Box 9513, 2300 RA Leiden (Netherlands); Benítez, Narciso [Instituto de Astrofísica de Andalucía (CSIC), C/Camino Bajo de Huétor 24, Granada E-18008 (Spain); Broadhurst, Tom [Department of Theoretical Physics, University of Basque Country UPV/EHU E-Bilbao (Spain); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Infante, Leopoldo, E-mail: hxx@mail.ustc.edu.cn [Departamento de Astronoía y Astrofísica, Pontificia Universidad Católica de Chile, V. Mackenna 4860 Santiago 22 (Chile); and others

    2015-03-01

    We utilize the 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 (Y {sub 105}) and F125W (J {sub 125}), as the flux of the central bands could be enhanced by the presence of [O III] λλ4959, 5007 at redshifts of ∼0.93-1.14 and 1.57-1.79, respectively. The multiband observations help to constrain the equivalent widths (EWs) 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] λλ4959, 5007 EW of ≅ 3700 Å. Our samples include a number of EELGs at lower luminosities that are missed in other surveys, and the extremely high EW can only be found in such faint galaxies. These EELGs can mimic a dropout feature similar to that of high-redshift galaxies and contaminate the color-color selection of high-redshift galaxies when the signal-to-noise ratio is limited or the band coverage is incomplete.

  17. Planck intermediate results. XXXIX. The Planck list of high-redshift source candidates

    Science.gov (United States)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Flores-Cacho, I.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Keihänen, 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.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nesvadba, N. P. H.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-12-01

    The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. A novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been validated and characterized on numerous simulations, and applied to select the most luminous cold submillimetre sources with spectral energy distributions peaking between 353 and 857 GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z > 2, assuming a dust temperature of Txgal = 35 K and a spectral index of βxgal = 1.5. Exhibiting extremely high luminosities, larger than 1014L⊙, the PHZ objects may be made of multiple galaxies or clumps at high redshift, as suggested by a first statistical analysis based on a comparison with number count models. Furthermore, first follow-up observations obtained from optical to submillimetre wavelengths, which can be found in companion papers, have confirmed that this list consists of two distinct populations. A small fraction (around 3%) of the sources have been identified as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample, which is complementary to the Planck Sunyaev-Zeldovich Catalogue (PSZ2); by extending the population of virialized massive galaxy clusters detected below z population of sources at

  18. High-Redshift Clusters form NVSS: The TexOx Cluster (TOC) Survey

    Energy Technology Data Exchange (ETDEWEB)

    Croft, S; Rawlings, S; Hill, G J

    2003-02-11

    The TexOx Cluster (TOC) Survey uses overdensities of radiosources in the NVSS to trace clusters of galaxies. The links between radiosources and rich environments make this a powerful way to find clusters which may potentially be overlooked by other selection techniques. By including constraints from optical surveys, TOC is an extremely efficient way to find clusters at high redshift. One such field, TOC J0233.3+3021, contains at least one galaxy cluster (at z {approx} 1.4) and has been detected using the Sunyaev-Zel'dovich (SZ) effect. Even in targeted deep optical observations, however, distinguishing the cluster galaxies from the background is difficult, especially given the tendency of TOC to select fields containing multiple structures at different redshifts.

  19. 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...

  20. Galactic synchrotron emission and the FIR-radio correlation at high redshift

    CERN Document Server

    Schober, Jennifer; Klessen, Ralf S

    2016-01-01

    Galactic magnetic fields in the local Universe are strong and omnipresent. Now evidence accumulates that galaxies were magnetized already in the early Universe. Theoretical scenarios including the turbulent small-scale dynamo predict magnetic energy densities comparable to the one of turbulence. Based on the assumption of this energy equipartition, we determine the galactic synchrotron flux as a function of redshift. The conditions in the early Universe are different from the present day, in particular the galaxies have more intense star formation. To cover a large range of conditions we consider models based on two different types of galaxies: one model galaxy comparable to the Milky Way and one typical high-z starburst galaxy. We include a model of the steady state cosmic ray spectrum and find that synchrotron emission can be detected up to cosmological redshifts with current and future radio telescopes. Turbulent dynamo theory is in agreement with the origin of the observed correlation between the far-infr...

  1. High-redshift clusters from NVSS The TexOx Cluster (TOC) Survey

    CERN Document Server

    Croft, S; Hill, G J; Croft, Steve; Rawlings, Steve; Hill, Gary J.

    2003-01-01

    The TexOx Cluster (TOC) Survey uses overdensities of radiosources in the NVSS to trace clusters of galaxies. The links between radiosources and rich environments make this a powerful way to find clusters which may potentially be overlooked by other selection techniques. By including constraints from optical surveys, TOC is an extremely efficient way to find clusters at high redshift. One such field, TOC J0233.3+3021, contains at least one galaxy cluster (at z ~ 1.4) and has been detected using the Sunyaev-Zel'dovich (SZ) effect. Even in targetted deep optical observations, however, distinguishing the cluster galaxies from the background is difficult, especially given the tendency of TOC to select fields containing multiple structures at different redshifts.

  2. 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 ...

  3. Gamma-ray Bursts as a Probe of the Very High Redshift Universe

    CERN Document Server

    Lamb, D Q; Lamb, Donald Q.; Reichart, Daniel E.

    1999-01-01

    There is increasingly strong evidence that gamma-ray bursts (GRBs) are associated with star-forming galaxies, and occur near or in the star-forming regions of these galaxies. These associations provide indirect evidence that at least the long GRBs detected by BeppoSAX are a result of the collapse of massive stars. The recent evidence that the light curves and the spectra of the afterglows of GRB 980326 and GRB 970228 appear to contain a supernova component, in addition to a relativistic shock wave component, provide more direct clues that this is the case. We show that, if many GRBs are indeed produced by the collapse of massive stars, GRBs and their afterglows provide a powerful probe of the very high redshift (z > 5) universe. We first establish that GRBs and their afterglows are both detectable out to very high redshifts. We then show that one expects GRBs to occur out to at least z ~ 10 and possibly z ~ 15-20, redshifts that are far larger than those expected for the most distant quasars. This implies tha...

  4. 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...

  5. 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...

  6. Interpreting the observed UV continuum slopes of high-redshift galaxies

    CERN Document Server

    Wilkins, Stephen M; Coulton, William; Croft, Rupert; Di Matteo, Tiziana; Khandai, Nishikanta; Feng, Yu

    2013-01-01

    The observed UV continuum slope of star forming galaxies is strongly affected by the presence of dust. Its observation is then a potentially valuable diagnostic of dust attenuation, particularly at high-redshift where other diagnostics are currently inaccesible. Interpreting the observed UV continuum slope in the context of dust attenuation is often achieved assuming the empirically calibrated Meurer et al. (1999) relation. Implicit in this relation is the assumption of an intrinsic UV continuum slope ($\\beta=-2.23$). However, results from numerical simulations suggest that the intrinsic UV continuum slopes of high-redshift star forming galaxies are bluer than this, and moreover vary with redshift. Using values of the intrinsic slope predicted by numerical models of galaxy formation combined with a Calzetti et al. (2000) reddening law we infer UV attenuations ($A_{1500}$) $0.35-0.5\\,{\\rm mag}$ ($A_{V}$: $0.14-0.2\\,{\\rm mag}$ assuming Calzetti et al. 2000) greater than simply assuming the Meurer relation. This...

  7. Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

    Science.gov (United States)

    Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

    2016-12-01

    Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: 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 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: 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 IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

  8. Structure formation simulations with momentum exchange: alleviating tensions between high-redshift and low-redshift cosmological probes

    CERN Document Server

    Baldi, Marco

    2016-01-01

    Persisting tensions between the cosmological constraints derived from low-redshift probes and the ones obtained from temperature and polarisation anisotropies of the Cosmic Microwave Background -- although not yet providing compelling evidence against the $\\Lambda $CDM model -- seem to consistently indicate a slower growth of density perturbations as compared to the predictions of the standard cosmological scenario. Such behavior is not easily accommodated by the simplest extensions of General Relativity, such as f(R) models, which generically predict an enhanced growth rate. In the present work we present the outcomes of a suite of large N-body simulations carried out in the context of a cosmological model featuring a non-vanishing scattering cross section between the dark matter and the dark energy fields, for two different parameterisations of the dark energy equation of state. Our results indicate that these Dark Scattering models have very mild effects on many observables related to large-scale structure...

  9. Can Life Survive Gamma-Ray Bursts in the High-redshift Universe?

    Science.gov (United States)

    Li, Ye; Zhang, Bing

    2015-09-01

    Nearby gamma-ray bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g., z\\gt 0.5). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies, and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr (˜epoch of the Ordovician mass extinction) is 0.93. The number of lethal GRBs hitting a certain planet increases with redshift, as a result of the increasing star formation rate (SFR) and decreasing metallicity in high-z galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there is still a good fraction of SDSS galaxies beyond z=0.5 where the GRB rate at half-mass radius is lower than this value. We derive the fraction of such benign galaxies as a function of redshift through Monte Carlo simulations, and we find that the fraction is ˜ 50% at z˜ 1.5 and ˜ 10% even at z˜ 3. The mass distribution of benign galaxies is dominated by Milky Way-like ones, due to their commonness, relatively large mass, and low SFR. GRB host galaxies are among the most dangerous ones.

  10. Can life survive Gamma-Ray Bursts in the high-redshift universe?

    CERN Document Server

    Li, Ye

    2015-01-01

    Nearby Gamma-Ray Bursts (GRBs) have been proposed as a possible cause of mass extinctions on Earth. Due to the higher event rate of GRBs at higher redshifts, it has been speculated that life as we know it may not survive above a certain redshift (e.g. $z>0.5$). We examine the duty cycle of lethal (life-threatening) GRBs in the solar neighborhood, in the Sloan Digital Sky Survey (SDSS) galaxies and GRB host galaxies, with the dependence of the long GRB rate on star formation and metallicity properly taken into account. We find that the number of lethal GRBs attacking Earth within the past 500 Myr ($\\sim$ epoch of the Ordovician mass extinction) is $0.93$. The number of lethal GRBs hitting a certain planet increases with redshift, thanks to the increasing star formation rate and decreasing metallicity in high-$z$ galaxies. Taking 1 per 500 Myr as a conservative duty cycle for life to survive, as evidenced by our existence, we find that there are still a good fraction of SDSS galaxies beyond $z=0.5$ where the GR...

  11. Probing cosmic opacity at high redshifts with gamma-ray bursts

    CERN Document Server

    Holanda, R F L

    2014-01-01

    Probing the evolution of the universe at high redshifts with standard candles is a powerful way to discriminate dark energy models, where an open question nowadays is whether this component is constant or evolves with time. One possible source of ambiguity in this kind of analyses comes from cosmic opacity, which can mimick a dark enery behaviour. However, most tests of cosmic opacity have been restricted to the redshift range $z2$) for a flat $\\Lambda$CDM model. A possible degenerescence of the results with the adopted cosmological model is also investigated by considering a flat XCDM model. The limits on cosmic opacity in the redshift range $0

  12. Measuring PAH Emission in Ultradeep Spitzer IRS Spectroscopy of High Redshift IR Luminous Galaxies

    CERN Document Server

    Teplitz, H I; Armus, L; Chary, R; Marshall, J A; Colbert, J W; Frayer, D T; Pope, A; Blain, A; Spoon, H; Charmandaris, V; Scott, D

    2007-01-01

    The study of the dominant population of high redshift IR-luminous galaxies (10^11 - 10^12 Lsun at 1redshift target were taken in the observed-frame 8--21 micron range, while the spectrum of the higher redshift target covered 21--37 microns. We also present the spectra of two secondary sources within the slit. We detect strong PAH emission in all four targets, and compare the spectra to those of local galaxies observed by the IRS. The z=1.09 source appears to be a typical, star-formation dominated IR-luminous galaxy, while the z=2.69 source is a composite source with strong star formation and a prominent AGN. The IRAC colors of this source show no evidence of rest-frame near-infrared stellar photospheric...

  13. Broadband and Narrowband Search for z < 1 Analogs of High Redshift Star Forming Galaxies

    Science.gov (United States)

    Rosenwasser, Benjamin; Barger, Amy J.; Wold, Isak; Lauchlan Cowie, Lennox

    2017-01-01

    Studies of high redshift (z > 6) galaxies rely on extreme broadband colors from Spitzer/IRAC to select samples of low-mass star forming galaxies. These broadband excess searches are biased towards galaxies with the strongest emission lines, and the extent to which existing studies miss fainter galaxies with lower star formation rates remains unknown. Using both broadband (BB) and narrowband (NB) imaging from the HyperSuprimeCam (HSC) and SuprimeCam (SC) on the Subaru Telescope, we have performed a search for z population. The search was performed over roughly 4 square degrees centered on the COSMOS field, and the narrowband filters allow us to probe fainter emission lines than the broadband searches. We carried out spectral followup of our BB excess and NB excess samples using WIYN/Hydra to measure redshifts and line ratios in order to understand the biases in the different selection techniques. We also investigate the rest frame UV properties of our sample using data from GALEX. This study demonstrates the effectiveness of using broadband colors to select intermediate redshift emission line galaxies.

  14. 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.

  15. Building a Better Understanding of the High Redshift BOSS Galaxies as Tools for Cosmology

    CERN Document Server

    Favole, Ginevra; Eisenstein, Daniel J; Prada, Francisco; Swanson, Molly E; Chuang, Chia-Hsun; Schneider, Donald P

    2015-01-01

    We explore the bluer star-forming population of the Sloan Digital Sky Survey (SDSS) III/BOSS CMASS DR11 galaxies at $z>0.55$ to quantify their differences, in terms of redshift-space distortions and large-scale bias, with respect to the luminous red galaxy sample. We perform a qualitative analysis to understand the significance of these differences and whether we can model and reproduce them in mock catalogs. Specifically, we measure galaxy clustering in CMASS on small and intermediate scales ($r\\lesssim 50\\,h^{-1}$Mpc) by computing the two-point correlation function $-$ both projected and redshift-space $-$ of these galaxies, and a new statistic, $\\Sigma(\\pi)$, able to provide robust information about redshift-space distortions and large-scale bias. We interpret our clustering measurements by adopting a Halo Occupation Distribution (HOD) scheme that maps them onto high-resolution N-body cosmological simulations to produce suitable mock galaxy catalogs. The traditional HOD prescription can be applied to the r...

  16. 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...

  17. 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.

  18. High-damping-performance magnetorheological material for passive or active vibration control

    Science.gov (United States)

    Liu, Taixiang; Yang, Ke; Yan, Hongwei; Yuan, Xiaodong; Xu, Yangguang

    2016-10-01

    Optical assembly and alignment system plays a crucial role for the construction of high-power or high-energy laser facility, which attempts to ignite fusion reaction and go further to make fusion energy usable. In the optical assembly and alignment system, the vibration control is a key problem needs to be well handled and a material with higher damping performance is much desirable. Recently, a new kind of smart magneto-sensitive polymeric composite material, named magnetorheological plastomer (MRP), was synthesized and reported as a high-performance magnetorheological material and this material has a magneto-enhanced high-damping performance. The MRP behaves usually in an intermediate state between fluid-like magnetorheological fluid and solid-like magnetorheological elastomer. The state of MRP, as well as the damping performance of MRP, can be tuned by adjusting the ratio of hard segments and soft segments, which are ingredients to synthesize the polymeric matrix. In this work, a series of MRP are prepared by dispersing micron-sized, magneto-sensitive carbonyl iron powders with related additives into polyurethane-based, magnetically insensitive matrix. It is found that the damping performance of MRP depends much on magnetic strength, shear rate, carbonyl iron content and shear strain amplitude. Especially, the damping capacity of MRP can be tuned in a large range by adjusting external magnetic field. It is promising that the MRP will have much application in passive and active vibration control, such as vibration reduction in optical assembly and alignment system, vibration isolation or absorption in vehicle suspension system, etc.

  19. Lyman alpha emitting galaxies at high redshift: Direct detection of young galaxies in a young universe

    Science.gov (United States)

    Dawson, Steven Arthur

    An early result of galaxy formation theory was the prediction that the copious ionizing radiation produced in nascent galaxies undergoing their first starbursts should in turn produce a strong Lya emission line. We report on our efforts to detect and characterize primeval galaxies by searching for this expected Lya signature with two observational techniques: serendipitous slit spectroscopy, and narrowband imaging selection. In Part I, we describe our serendipitous slit spectroscopy survey of the Hubble Deep Field and its environs, which resulted in a catalog of 74 spectroscopic redshifts spanning 0.10 5. Follow-up observations at higher resolution resulted in the additional serendipitous detection of a strong Lya-emitting galaxy at z = 5.190 (ES1). At the time of its discovery, ES1 was one of only nine known galaxies at z > 5, and was the sixth most distant known galaxy. The unprecedented spectral purity of the observation offers evidence for a galaxy-scale outflow with a. velocity of v > 300 km s -1 , consistent with wind speeds observed in powerful local starbursts (typically 10 2 to 10 3 km s -1 ), and with simulations of the late- stage evolution of Lya emission in star-forming systems. Our final serendipitous detection is the remarkable source CXOHDFN J123635.6+621424, which is both the highest redshift known spiral galaxy, and a rare example of a high redshift, hard X-ray-emitting Type II AGN. Significantly, all of these results were acquired with no direct allocation of telescope time. In Part II, we report on our implementation of narrowband imaging selection, with which we traded redshift coverage for survey volume, focusing on the systematic study of galaxies at a particular epoch in favor of chasing that rare, most-distant object. This effort resulted in a catalog of 76 z [approximate] 4.5 Lya-emitting galaxies spectroscopically-confirmed in campaigns of Keck/LRIS and Keck/DEIMOS follow-up observations to candidates selected in the Large Area Lyman

  20. The WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies

    CERN Document Server

    Riemer--Sørensen, Signe; Parkinson, David; Davis, Tamara M; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Croton, Darren; Drinkwater, Michael J; Forster, Karl; Gilbank, David; Gladders, Mike; Glazebrook, Karl; Jelliffe, Ben; Jurek, Russell J; Li, I-hui; Madore, Barry; Martin, D Christopher; Pimbblet, Kevin; Poole, Gregory B; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted K; Yee, H K C

    2011-01-01

    The absolute neutrino mass scale is currently unknown, but can be constrained from cosmology. The WiggleZ high redshift star-forming blue galaxy sample is less sensitive to systematics from non-linear structure formation, redshift-space distortions and galaxy bias than previous surveys. We obtain a upper limit on the sum of neutrino masses of 0.60eV (95% confidence) for WiggleZ+Wilkinson Microwave Anisotropy Probe. Combining with priors on the Hubble Parameter and the baryon acoustic oscillation scale gives an upper limit of 0.29eV, which is the strongest neutrino mass constraint derived from spectroscopic galaxy redshift surveys.

  1. Accounting for Cosmic Variance in Studies of Gravitationally-Lensed High-Redshift Galaxies in the Hubble Frontier Field Clusters

    CERN Document Server

    Robertson, Brant E; Dunlop, James S; McLure, Ross J; Stark, Daniel P; McLeod, Derek

    2014-01-01

    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 {\\it Letter}, we demonstrate 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.

  2. Accounting for Cosmic Variance in Studies of Gravitationally Lensed High-redshift Galaxies in the Hubble Frontier Field Clusters

    Science.gov (United States)

    Robertson, Brant E.; Ellis, Richard S.; Dunlop, James S.; McLure, Ross J.; Stark, Dan P.; McLeod, Derek

    2014-12-01

    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.

  3. Scheduled discoveries of 7+ high-Redshift supernovae: First cosmology results and bounds on q{sub 0}

    Energy Technology Data Exchange (ETDEWEB)

    Perlmutter, S., FNAL

    1998-09-01

    Our search for high-redshift Type Ia supernovae discovered, in its first years, a sample of seven supernovae. Using a ``batch`` search strategy, almost all were discovered before maximum light and were observed over the peak of their light curves. The spectra and light curves indicate that almost all were Type Ia supernovae at redshifts z = 0.35 - 0.5. These high-redshift supernovae can provide a distance indicator and ``standard clock`` to study the cosmological parameters q{sub 0} , {Lambda}, {Omega}{sub 0} , and H{sub 0}. This presentation and the following presentations of Kim et al. (1996), Goldhaber et al. (1996), and Pain et al. (1996) will discuss observation strategies and rates, analysis and calibration issues, the sources of measurement uncertainty, and the cosmological implications, including bounds on q{sub 0} , of these first high-redshift supernovae from our ongoing search.

  4. Planck intermediate results XXXIX. The Planck list of high-redshift source candidates

    DEFF Research Database (Denmark)

    Ade, P. A. R.; Aghanim, N.; Arnaud, M.

    2016-01-01

    Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545 GHz above 500 mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent...... as strongly gravitationally lensed star-forming galaxies at redshift 2 to 4, while the vast majority of the PHZ sources appear as overdensities of dusty star-forming galaxies, having colours consistent with being at z > 2, and may be considered as proto-cluster candidates. The PHZ provides an original sample...

  5. Impact of grain size distributions on the dust enrichment in high-redshift quasars

    OpenAIRE

    Kuo, Tzu-Ming; Hirashita, Hiroyuki

    2012-01-01

    In high-redshift ($z>5$) quasars, a large amount of dust ($\\textstyle\\sim 10^{8} \\mathrm{M}_{\\sun}$) has been observed. In order to explain the large dust content, we focus on a possibility that grain growth by the accretion of heavy elements is the dominant dust source. We adopt a chemical evolution model applicable to nearby galaxies but utilize parameters adequate to high-$z$ quasars. It is assumed that metals and dust are predominantly ejected by Type II supernovae (SNe). We have found th...

  6. Collisional damping of helicon waves in a high density hydrogen linear plasma device

    Science.gov (United States)

    Caneses, Juan F.; Blackwell, Boyd D.

    2016-10-01

    In this paper, we investigate the propagation and damping of helicon waves along the length (50 cm) of a helicon-produced 20 kW hydrogen plasma ({{n}\\text{e}}∼ 1–2 × 1019 m‑3, {{T}\\text{e}}∼ 1–6 eV, H2 8 mTorr) operated in a magnetic mirror configuration (antenna region: 50–200 G and mirror region: 800 G). Experimental results show the presence of traveling helicon waves (4–8 G and {λz}∼ 10–15 cm) propagating away from the antenna region which become collisionally absorbed within 40–50 cm. We describe the use of the WKB method to calculate wave damping and provide an expression to assess its validity based on experimental measurements. Theoretical calculations are consistent with experiment and indicate that for conditions where Coulomb collisions are dominant classical collisionality is sufficient to explain the observed wave damping along the length of the plasma column. Based on these results, we provide an expression for the scaling of helicon wave damping relevant to high density discharges and discuss the location of surfaces for plasma-material interaction studies in helicon based linear plasma devices.

  7. Resonant ultrasound spectroscopy for materials with high damping and samples of arbitrary geometry

    Science.gov (United States)

    Remillieux, Marcel C.; Ulrich, T. J.; Payan, Cédric; Rivière, Jacques; Lake, Colton R.; Le Bas, Pierre-Yves

    2015-07-01

    Resonant ultrasound spectroscopy (RUS) is a powerful and established technique for measuring elastic constants of a material with general anisotropy. The first step of this technique consists of extracting resonance frequencies and damping from the vibrational frequency spectrum measured on a sample with free boundary conditions. An inversion technique is then used to retrieve the elastic tensor from the measured resonance frequencies. As originally developed, RUS has been mostly applicable to (i) materials with small damping such that the resonances of the sample are well separated and (ii) samples with simple geometries for which analytical solutions exist. In this paper, these limitations are addressed with a new RUS approach adapted to materials with high damping and samples of arbitrary geometry. Resonances are extracted by fitting a sum of exponentially damped sinusoids to the measured frequency spectrum. The inversion of the elastic tensor is achieved with a genetic algorithm, which allows searching for a global minimum within a discrete and relatively wide solution space. First, the accuracy of the proposed approach is evaluated against numerical data simulated for samples with isotropic symmetry and transversely isotropic symmetry. Subsequently, the applicability of the approach is demonstrated using experimental data collected on a composite structure consisting of a cylindrical sample of Berea sandstone glued to a large piezoelectric disk. In the proposed experiments, RUS is further enhanced by the use of a 3-D laser vibrometer allowing the visualization of most of the modes in the frequency band studied.

  8. Why do high-redshift galaxies show diverse gas-phase metallicity gradients?

    Science.gov (United States)

    Ma, Xiangcheng; Hopkins, Philip F.; Feldmann, Robert; Torrey, Paul; Faucher-Giguère, Claude-André; Kereš, Dušan

    2017-01-01

    Recent spatially resolved observations of galaxies at z ˜ 0.6-3 reveal that high-redshift galaxies show complex kinematics and a broad distribution of gas-phase metallicity gradients. To understand these results, we use a suite of high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environments (FIRE) project, which include physically motivated models of the multi-phase ISM, star formation, and stellar feedback. Our simulations reproduce the observed diversity of kinematic properties and metallicity gradients, broadly consistent with observations at z ˜ 0-3. Strong negative metallicity gradients only appear in galaxies with a rotating disk, but not all rotationally supported galaxies have significant gradients. Strongly perturbed galaxies with little rotation always have flat gradients. The kinematic properties and metallicity gradient of a high-redshift galaxy can vary significantly on short time-scales, associated with starburst episodes. Feedback from a starburst can destroy the gas disk, drive strong outflows, and flatten a pre-existing negative metallicity gradient. The time variability of a single galaxy is statistically similar to the entire simulated sample, indicating that the observed metallicity gradients in high-redshift galaxies reflect the instantaneous state of the galaxy rather than the accretion and growth history on cosmological time-scales. We find weak dependence of metallicity gradient on stellar mass and specific star formation rate (sSFR). Low-mass galaxies and galaxies with high sSFR tend to have flat gradients, likely due to the fact that feedback is more efficient in these galaxies. We argue that it is important to resolve feedback on small scales in order to produce the diverse metallicity gradients observed.

  9. Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies

    Science.gov (United States)

    Izotov, Y. I.; Schaerer, D.; Thuan, T. X.; Worseck, G.; Guseva, N. G.; Orlitová, I.; Verhamme, A.

    2016-10-01

    Following our first detection reported in Izotov et al., we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. These galaxies, at redshifts of z ˜ 0.3, are characterized by high emission-line flux ratios [O III] λ5007/[O II] λ3727 ≳ 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ˜6-13 per cent, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Ly α emission lines are detected in the spectra of all four galaxies, compatible with predictions for LyC leakers. We find escape fractions of Ly α, fesc(Ly α) ˜ 20-40 per cent, among the highest known for Ly α emitting galaxies. Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the centre and exponential discs in the outskirts with disc scalelengths α in the range ˜0.6-1.4 kpc. Our galaxies are characterized by low metallicity, ˜1/8-1/5 solar, low stellar mass ˜(0.2-4) × 109 M⊙, high star formation rates, SFR ˜ 14-36 M⊙ yr-1, and high SFR densities, Σ ˜ 2-35 M⊙ yr-1 kpc-2. These properties are comparable to those of high-redshift star-forming galaxies. Finally, our observations, combined with our first detection reported in Izotov et al., reveal that a selection for compact star-forming galaxies showing high [O III] λ5007/[O II] λ3727 ratios appears to pick up very efficiently sources with escaping LyC radiation: all five of our selected galaxies are LyC leakers.

  10. A New Determination of the High Redshift Type Ia Supernova Rateswith the Hubble Space Telescope Advanced Camera for Surveys

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsova, N.; Barbary, K.; Connolly, B.; Kim, A.G.; Pain, R.; Roe, N.A.; Aldering, G.; Amanullah, R.; Dawson, K.; Doi, M.; Fadeyev, V.; Fruchter, A.S.; Gibbons, R.; Goldhaber, G.; Goober, A.; Gude, A.; Knop,R.A.; Kowalski, M.; Lidman, C.; Morokuma, T.; Meyers, J.; Perlmutter, S.; Rubin, D.; Schlegel, D.J.; Spadafora, A.L.; Stanishev, V.; Strovink, M.; Suzuki, N.; Wang, L.; Yasuda, N.

    2007-10-01

    We present a new measurement of the volumetric rate of Type Ia supernova up to a redshift of 1.7, using the Hubble Space Telescope (HST) GOODS data combined with an additional HST dataset covering the North GOODS field collected in 2004. We employ a novel technique that does not require spectroscopic data for identifying Type Ia supernovae (although spectroscopic measurements of redshifts are used for over half the sample); instead we employ a Bayesian approach using only photometric data to calculate the probability that an object is a Type Ia supernova. This Bayesian technique can easily be modified to incorporate improved priors on supernova properties, and it is well-suited for future high-statistics supernovae searches in which spectroscopic follow up of all candidates will be impractical. Here, the method is validated on both ground- and space-based supernova data having some spectroscopic follow up. We combine our volumetric rate measurements with low redshift supernova data, and fit to a number of possible models for the evolution of the Type Ia supernova rate as a function of redshift. The data do not distinguish between a flat rate at redshift > 0.5 and a previously proposed model, in which the Type Ia rate peaks at redshift {approx} 1 due to a significant delay from star-formation to the supernova explosion. Except for the highest redshifts, where the signal to noise ratio is generally too low to apply this technique, this approach yields smaller or comparable uncertainties than previous work.

  11. High Resolution BPM Upgrade for the ATF Damping Ring at KEK

    CERN Document Server

    Eddy, N; Fellenz, B; Gianfelice-Wendt, E; Prieto, P; Rechenmacher, R; Semenov, A; Voy, D; Wendt, M; Zhang, D; Terunuma, N; Urakawa, J

    2012-01-01

    A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and processing, and also implements a new automatic gain error correction schema. The technical concept and realization as well as results of beam studies are presented.

  12. Observed Faraday Effects in Damped Lyman-Alpha Absorbers and Lyman Limit Systems: The Magnetised Environment of Galactic Building Blocks at Redshift=2

    CERN Document Server

    Farnes, J S; Gaensler, B M; Haverkorn, M; O'Sullivan, S P; Curran, S J

    2016-01-01

    Protogalactic environments are typically identified using quasar absorption lines, and these galactic building blocks can manifest as Damped Lyman-Alpha Absorbers (DLAs) and Lyman Limit Systems (LLSs). We use radio observations of Faraday effects to test whether DLAs and LLSs host a magnetised medium, by combining DLA and LLS detections throughout the literature with 1.4 GHz polarization data from the NRAO VLA Sky Survey (NVSS). We obtain a control, a DLA, and a LLS sample consisting of 114, 19, and 27 lines-of-sight respectively - all of which are polarized at $\\ge8\\sigma$ to ensure Rician bias is negligible. Using a Bayesian framework, we are unable to detect either coherent or random magnetic fields in DLAs: the regular coherent magnetic fields within the DLAs must be $\\le2.8$ $\\mu$G, and the lack of depolarization is consistent with the weakly magnetised gas in DLAs being non-turbulent and quiescent. However, we find mild suggestive evidence that LLSs have coherent magnetic fields: after controlling for t...

  13. First light: exploring the spectra of high-redshift galaxies in the Renaissance Simulations

    Science.gov (United States)

    Barrow, Kirk S. S.; Wise, John H.; Norman, Michael L.; O'Shea, Brian W.; Xu, Hao

    2017-08-01

    We present synthetic observations for the first generations of galaxies in the Universe and make predictions for future deep field observations for redshifts greater than 6. Due to the strong impact of nebular emission lines and the relatively compact scale of H ii regions, high-resolution cosmological simulations and a robust suite of analysis tools are required to properly simulate spectra. We created a software pipeline consisting of fsps, hyperion, cloudy and our own tools to generate synthetic IR observations from a fully three-dimensional arrangement of gas, dust, and stars. Our prescription allows us to include emission lines for a complete chemical network and tackle the effect of dust extinction and scattering in the various lines of sight. We provide spectra, 2D binned photon imagery for both HST and JWST IR filters, luminosity relationships, and emission-line strengths for a large sample of high-redshift galaxies in the Renaissance Simulations. Our resulting synthetic spectra show high variability between galactic haloes with a strong dependence on stellar mass, metallicity, gas mass fraction, and formation history. Haloes with the lowest stellar mass have the greatest variability in [O iii]/Hβ, [O iii], and C iii], while haloes with higher masses are seen to show consistency in their spectra and [O iii] equivalent widths between 1 and 10 Å. Viewing angle accounted for threefold difference in flux due to the presence of ionized gas channels in a halo. Furthermore, JWST colour plots show a discernible relationship between redshift, colour, and mean stellar age.

  14. A break in the high-redshift stellar mass Tully-Fisher relation

    Science.gov (United States)

    Christensen, Lise; Hjorth, Jens

    2017-09-01

    We investigate the stellar-mass Tully-Fisher relation (TFR) between the stellar mass and the integrated gas velocity dispersion, quantified by the kinematic estimator S0.5 measured from strong emission lines in spectra of galaxies at 0 law slope and normalization of the TFR are independent of redshift out to z ∼ 3. The scatter in the TFR is 3, the scatter increases and the existence of a correlation is not obvious. The high-luminosity sample exhibits a flatter slope of 1.5 ± 0.2 at z natural consequence of galaxy models with a mass-dependent stellar-to-halo mass ratio.

  15. High-Redshift AGNs and the Next Decade of Chandra and XMM-Newton

    CERN Document Server

    Brandt, W N

    2016-01-01

    We briefly review how X-ray observations of high-redshift active galactic nuclei (AGNs) at z = 4-7 have played a critical role in understanding their basic demographics as well as their physical processes; e.g., absorption by nuclear material and winds, accretion rates, and jet emission. We point out some key remaining areas of uncertainty, highlighting where further Chandra and XMM-Newton observations/analyses, combined with new multiwavelength survey data, can advance understanding over the next decade.

  16. Molecular Gas in the Halo Fuels the Growth of a Massive Cluster Galaxy at High Redshift

    CERN Document Server

    Emonts, B H C; Villar-Martin, M; Norris, R P; Ekers, R D; van Moorsel, G A; Dannerbauer, H; Pentericci, L; Miley, G K; Allison, J R; Sadler, E M; Guillard, P; Carilli, C L; Mao, M Y; Rottgering, H J A; De Breuck, C; Seymour, N; Gullberg, B; Ceverino, D; Jagannathan, P; Vernet, J; Indermuehle, B T

    2016-01-01

    The largest galaxies in the Universe reside in galaxy clusters. Using sensitive observations of carbon-monoxide, we show that the Spiderweb Galaxy -a massive galaxy in a distant protocluster- is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched inter-galactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb Galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift.

  17. Identification of (high-redshift) AGN with WFXT: lessons from COSMOS and CDFS

    CERN Document Server

    Brusa, Marcella; Civano, Francesca; Comastri, Andrea; Fiore, Fabrizio; Vignali, Cristian

    2010-01-01

    The Wide Field X-ray Telescope (WFXT) will provide tens of millions of AGN, with more than 4x10^5 expected at z>3. Here we review the issues present in the identification of (large) samples of faint and high-redshift X-ray sources, and describe a statistical, powerful tool that can be applied to WFXT catalogs. The depth of associated optical and near infrared catalogs, needed for a reliable and as much complete as possible identification, are also discussed, along with the combined synergies with existing or planned facilities

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

    Science.gov (United States)

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

    2014-02-01

    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 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 generation X-ray instruments.

  19. 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...

  20. Shocks and Cool Cores: An ALMA View of Massive Galaxy Cluster Formation at High Redshifts

    Science.gov (United States)

    Basu, Kaustuv

    2017-07-01

    These slides present some recent results on the Sunyaev-Zel'dovich (SZ) effect imaging of galaxy cluster substructures. The advantage of SZ imaging at high redshifts or in the low density cluster outskirts is already well-known. Now with ALMA a combination of superior angular resolution and high sensitivity is available. One example is the first ALMA measurement of a merger shock at z=0.9 in the famous El Gordo galaxy cluster. Here comparison between SZ, X-ray and radio data enabled us to put constraints on the shock Mach number and magnetic field strength for a high-z radio relic. Second example is the ALMA SZ imaging of the core region of z=1.4 galaxy cluster XMMU J2235.2-2557. Here ALMA data provide an accurate measurement of the thermal pressure near the cluster center, and from a joint SZ/X-ray analysis we find clear evidence for a reduced core temperature. This result indicate that a cool core establishes itself early enough in the cluster formation history while the gas accumulation is still continuing. The above two ALMA measurements are among several other recent SZ results that shed light on the formation process of massive clusters at high redshifts.

  1. 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.

  2. NIHAO XIII: Clumpy discs or clumpy light in high-redshift galaxies?

    Science.gov (United States)

    Buck, Tobias; Macciò, Andrea V.; Obreja, Aura; Dutton, Aaron A.; Domínguez-Tenreiro, Rosa; Granato, Gian Luigi

    2017-07-01

    Many massive star-forming disc galaxies in the redshift range 3-0.5 are observed to have a clumpy morphology showing giant clumps of size ˜1 kpc and masses of about 107-1010 M⊙. The nature and fate of these giant clumps are still under debate. In this work, we use 19 high-resolution simulations of disc galaxies from the Numerical Investigations of Hundred Astrophysical Objects (NIHAO) sample to study the formation and evolution of clumps in the discs of high-redshift galaxies. We use mock Hubble Space Telescope-CANDELS observations created with the radiative transfer code grasil-3d to carry out, for the first time, a quantitative comparison of the observed fraction of clumpy galaxies and its evolution with redshift with simulations. We find a good agreement between the observed clumpy fraction and the one of the NIHAO galaxies. We find that dust attenuation can suppress intrinsically bright clumps and enhance less luminous ones. In our galaxy sample, we find clumps only in light (U band) from young stars but not in stellar mass surface density maps. This means that the NIHAO sample does not show clumpy stellar discs but rather a clumpy light distribution originating from clumpy star formation events. The clumps found in the NIHAO sample match observed age/colour gradients as a function of distance from the galaxy centre, but they show no sign of inward migration. Clumps in our simulations disperse on time-scales of about a hundred Myr and their contribution to bulge growth is negligible.

  3. 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 < z lesssim 1, where we show it is possible to find an analytical approximation for the source counts dN/d(S/N). This can be done in terms of cosmological parameters, such as the matter density Ωm,0 of the cosmological constant model or the cosmographic parameters for a general 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.

  4. Line and continuum variability of two intermediate-redshift, high-luminosity quasars

    Science.gov (United States)

    Trevese, D.; Paris, D.; Stirpe, G. M.; Vagnetti, F.; Zitelli, V.

    2007-08-01

    Context: It has been shown that the luminosity of active galactic nuclei and the size of their broad line region obey a simple relation of the type R_BLR=a Lγ, from faint Seyfert nuclei to bright quasars, allowing single-epoch determination of the central black hole mass M_BH= b Lγ Δ^2_Hβ from their luminosity L and width of Hβ emission line. Adopting this mass determination for cosmological studies requires the extrapolation to high redshift and luminosity of a relation whose calibration relies so far on reverberation mapping measurements performed for L ⪉ 1046 erg s-1 and redshift z ⪉ 0.4. Aims: We initiated a campaign for the spectrophotometric monitoring of a few luminous, intermediate redshift quasars whose apparent magnitude, V BH from reverberation mapping. Methods: We have repeatedly performed simultaneous spectrophotometric observations of quasars and reference stars to determine relative variability of continuum and emission lines. We describe the observations and methods of analysis. Results: For the quasars PG 1634+706 and PG 1247+268 we obtain light-curves respectively for CIII] (λλ1909 Å), MgII(λλ2798 Å) and for CIV(λλ1549 Å), CIII] (λλ1909 Å) emission lines with the relevant continua. During 3.2 years of observation, in the former case no continuum variability was detected and the evidence for line variability is marginal, while in the latter case both continuum and line variability are detected with high significance and the line variations appear correlated with continuum variations. Conclusions: The detection of the emission line variability in a quasar with L ~ 1047 erg s-1 encourages the continuation of the monitoring campaign which should provide a black hole mass estimate in another 5-6 years, constraining the mass-luminosity relation in a poorly explored range of luminosity.

  5. NEARBY CLUMPY, GAS RICH, STAR-FORMING GALAXIES: LOCAL ANALOGS OF HIGH-REDSHIFT CLUMPY GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Garland, C. A. [Natural Sciences Department, Jeffords Science Center, Castleton State College, Castleton, VT 05735 (United States); Pisano, D. J.; Rabidoux, K. [Department of Physics and Astronomy, West Virginia University, 135 Willey Street, P.O. Box 6315, Morgantown, WV 26506 (United States); Low, M.-M. Mac [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States); Kreckel, K. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Guzmán, R., E-mail: catherine.garland@castleton.edu, E-mail: djpisano@mail.wvu.edu, E-mail: krabidou@mix.wvu.edu, E-mail: mordecai@amnh.org, E-mail: kreckel@mpia.de, E-mail: guzman@astro.ufl.edu [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)

    2015-07-10

    Luminous compact blue galaxies (LCBGs) have enhanced star formation rates (SFRs) and compact morphologies. We combine Sloan Digital Sky Survey data with H i data of 29 LCBGs at redshift z ∼ 0 to understand their nature. We find that local LCBGs have high atomic gas fractions (∼50%) and SFRs per stellar mass consistent with some high-redshift star-forming galaxies (SFGs). Many local LCBGs also have clumpy morphologies, with clumps distributed across their disks. Although rare, these galaxies appear to be similar to the clumpy SFGs commonly observed at z ∼ 1–3. Local LCBGs separate into three groups: (1) interacting galaxies (∼20%); (2) clumpy spirals (∼40%); and (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 suggest that clumpy spirals, preferentially located in clusters and with companions, are smoothly accreting gas from tidally disrupted companions and/or intracluster gas enriched by stripped satellites. Conversely, as non-clumpy galaxies are preferentially located in the field and tend to be isolated, we suggest clumpy, cold streams, which destroy galaxy disks and prevent clump formation, as a likely gas delivery mechanism for these systems. Other possibilities include smooth cold streams, a series of minor mergers, or major interactions.

  6. Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey

    CERN Document Server

    Willott, Chris J; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reyle, Celine; Hill, Gary J; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-01-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshift greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise optical spectra, we use the spectra to investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at z=6.12, we find significant evol...

  7. 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 ...

  8. Planck intermediate results. XXXIX. The Planck list of high-redshift source candidates

    CERN Document Server

    ,

    2015-01-01

    The Planck mission, thanks to its large frequency range and all-sky coverage, has a unique potential for systematically detecting the brightest, and rarest, submillimetre sources on the sky, including distant objects in the high-redshift Universe traced by their dust emission. A novel method, based on a component-separation procedure using a combination of Planck and IRAS data, has been applied to select the most luminous cold submm sources with spectral energy distributions peaking between 353 and 857GHz at 5' resolution. A total of 2151 Planck high-z source candidates (the PHZ) have been detected in the cleanest 26% of the sky, with flux density at 545GHz above 500mJy. Embedded in the cosmic infrared background close to the confusion limit, these high-z candidates exhibit colder colours than their surroundings, consistent with redshifts z>2, assuming a dust temperature of 35K and a spectral index of 1.5. First follow-up observations obtained from optical to submm have confirmed that this list consists of tw...

  9. AWAKENING OF THE HIGH-REDSHIFT BLAZAR CGRaBS J0809+5341

    Energy Technology Data Exchange (ETDEWEB)

    Paliya, Vaidehi S.; Stalin, C. S. [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore 560034 (India); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Ramya, S. [Shanghai Astronomical Observatory, 80 Nandan Road, Shanghai 200030 (China); Covino, S.; Tagliaferri, G. [INAF-Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate (Italy); Sahayanathan, S. [Astrophysical Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Ravikumar, C. D., E-mail: vaidehi@iiap.res.in [Department of Physics, University of Calicut, Malappuram 673635 (India)

    2015-04-20

    CGRaBS J0809+5341, a high-redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by ∼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 Nuclear Spectroscopic Telescope Array, Swift, and ground-based optical facilities. For the first time, the source is detected in γ-rays by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. A high optical polarization of ∼10% is also observed. Using the Sloan Digital Sky Survey spectrum, the accretion disk luminosity and black hole mass are estimated as 1.5 × 10{sup 45} erg s{sup −1} and 10{sup 8.4} M{sub ⊙}, respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source during the flaring activity. This analysis suggests that the emission region is probably located outside the broad-line region, and the jet becomes radiatively efficient. We also show that the overall properties of CGRaBS J0809+5341 seem to not be in agreement with the general properties observed in high-redshift blazars up to now.

  10. The Cosmic Evolution of Galaxies: The Hunt for Hot Gas (and Winds!) at High Redshift

    Science.gov (United States)

    Hornschemeier, Ann; Kilbourne, Caroline; Lehmer, Bret; Yukita, Mihoko; Smith, Randall; Basu-Zych, Antara; Ptak, Andrew; Tatum, Malachi

    Deep surveys with current missions have revealed a population of high-redshift normal galaxies whose X-ray emission is dominated not by accretion onto supermassive black holes, but by the hot interstellar medium and accreting neutron star and black hole binary populations. Enormous progress has been made on the evolution of galaxies in the X-ray band, however there are some glaring holes in our understanding. For one, it is very difficult to measure the properties of the hot phase of the interstellar medium at high redshift, which in many galaxies is tremendously important component. Also, we know from optical, IR and UV studies that outflows from starburst galaxies appear to be relatively ubiquitous; such outflows are thought to be superwinds from the combination of many supernova explosions and stellar winds. Only with high-resolution X-ray spectroscopy will we have the capability of catching the hot phase of these outflows. The outflows remove fuel for subsequent generations of star formation and pollute the Intergalactic Medium with metals. Prospects for observations by next-generation X-ray spectroscopic instruments will be discussed.

  11. Characterization of the Corrosion Behavior of High Damping Alloys in Seawater.

    Science.gov (United States)

    1987-06-01

    the potential is increased, current increases, due to anodic dissolution . However, in some cases, as the specimen is scanned anodically, an oxide...34baseline" alloys were examined during this research. The nominal compositions of the high damping alloys are as follows: Delta Alloy C - 73.0% Cu, 21.0... ferritic stainless steel composition) are 72 ..... ..... presented in Figures 44 and 45, surfaces in Figures 46 to 51. Using the PDP and LPM plots (k

  12. The near-IR properties and continuum shapes of high redshift quasars from the Sloan Digital Sky Survey

    Science.gov (United States)

    Pentericci, L.; Rix, H.-W.; Prada, F.; Fan, X.; Strauss, M. A.; Schneider, D. P.; Grebel, E. K.; Harbeck, D.; Brinkmann, J.; Narayanan, V. K.

    2003-10-01

    We present J-H-K' photometry for a sample of 45 high redshift quasars found by the Sloan Digital Sky Survey. The sample was originally selected on the basis of optical colors and spans a redshift range from 3.6 to 5.03. Our photometry reflects the rest-frame SED longward of Lyalpha for all redshifts. The results show that the near-IR colors of high redshift quasars are quite uniform. We have modelled the continuum shape of the quasars (from just beyond Lyalpha to ~ 4000 Å) with a power law of the form fnu ~ nu \\alpha, and find =-0.57 with a scatter of 0.33. This value is similar to what is found for lower redshift quasars over the same restframe wavelength range, and {we conclude that} there is hardly any evolution in the continuum properties of optically selected quasars up to redshift 5. The spectral indices found by combining near-IR with optical photometry are in general consistent but slightly flatter than what is found for the same quasars using the optical spectra and photometry alone, showing that the continuum region used to determine the spectral indices can somewhat influence the results.

  13. Clustering of galaxies in a hierarchical universe - II. Evolution to high redshift

    Science.gov (United States)

    Kauffmann, Guinevere; Colberg, Jörg M.; Diaferio, Antonaldo; White, Simon D. M.

    1999-08-01

    In hierarchical cosmologies the evolution of galaxy clustering depends both on cosmological quantities such as Omega, Lambda and P(k), which determine how collapsed structures - dark matter haloes - form and evolve, and on the physical processes - cooling, star formation, radiative and hydrodynamic feedback - which drive the formation of galaxies within these merging haloes. In this paper we combine dissipationless cosmological N-body simulations and semi-analytic models of galaxy formation in order to study how these two aspects interact. We focus on the differences in clustering predicted for galaxies of differing luminosity, colour, morphology and star formation rate, and on what these differences can teach us about the galaxy formation process. We show that a `dip' in the amplitude of galaxy correlations between z=0 and z=1 can be an important diagnostic. Such a dip occurs in low-density CDM models, because structure forms early, and dark matter haloes of mass ~10^12M_solar, containing galaxies with luminosities ~L_*, are unbiased tracers of the dark matter over this redshift range; their clustering amplitude then evolves similarly to that of the dark matter. At higher redshifts, bright galaxies become strongly biased and the clustering amplitude increases again. In high density models, structure forms late, and bias evolves much more rapidly. As a result, the clustering amplitude of L_* galaxies remains constant from z=0 to z=1. The strength of these effects is sensitive to sample selection. The dip becomes weaker for galaxies with lower star formation rates, redder colours, higher luminosities and earlier morphological types. We explain why this is the case, and how it is related to the variation with redshift of the abundance and environment of the observed galaxies. We also show that the relative peculiar velocities of galaxies are biased low in our models, but that this effect is never very strong. Studies of clustering evolution as a function of galaxy

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

    Science.gov (United States)

    Oklopčić, Antonija; Hopkins, Philip F.; Feldmann, Robert; Kereš, Dušan; Faucher-Giguère, Claude-André; Murray, Norman

    2017-02-01

    The morphology of massive star-forming galaxies at high redshift is often dominated by giant clumps of mass ˜108-109 M⊙ 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 which implement explicit treatments of stellar feedback and interstellar medium physics to study the properties of these clumps. We follow the evolution of giant clumps in a massive (M* ˜ 1010.8 M⊙ 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 ˜20 Myr. During that time, they turn between 0.1 per cent and 20 per cent of their gas into stars before being disrupted, similar to local giant molecular clouds. Clumps with M ≳ 107 M⊙ account for ˜20 per cent of the total star formation in the galaxy during the clumpy phase, producing ˜1010 M⊙ of stars. We do not find evidence for net inward migration of clumps within the galaxy. The number of giant clumps and their mass decrease at lower redshifts, following the decrease in the overall gas fraction and star formation rate.

  15. Evaluation of Components for the High Precision Inductive Adder for the CLIC Damping Rings

    CERN Document Server

    Holma, J

    2012-01-01

    The CLIC study is exploring the scheme for an electron-positron collider with high luminosity and a nominal centre-of-mass energy of 3 TeV. The CLIC damping rings will produce, through synchrotron radiation, ultra-low emittance beam with high bunch charge, necessary for the luminosity performance of the collider. To limit the beam emittance blow-up due to oscillations, the pulse generators for the damping ring kickers must provide extremely flat high-voltage pulses. The specifications for the extraction kickers of the CLIC damping rings are particularly demanding: the flattop of the output pulse must be 160 ns duration, 12.5 kV and 250 A, with a combined ripple and droop of not more than ±0.02 %. An inductive adder allows the use of different modulation techniques and is therefore a very promising approach to meeting the specifications. In addition to semiconductors working in their saturated region, semiconductors working in their linear region are needed for applying analogue modulation techniques. Simulat...

  16. 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...

  17. 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...

  18. Cosmic dichotomy in the hosts of rapidly star-forming systems at low and high redshifts

    CERN Document Server

    Magliocchetti, Manuela; Negrello, Mattia; De Zotti, Gianfranco; Danese, Luigi

    2013-01-01

    This paper presents a compilation of clustering results taken from the literature for galaxies with highly enhanced (SFR [30-10^3] Msun/yr) star formation activity observed in the redshift range z=[0-3]. We show that, irrespective of the selection technique and only very mildly depending on the star forming rate, the clustering lengths of these objects present a sharp increase of about a factor 3 between z~1 and z~2, going from values of ~5 Mpc to about 15 Mpc and higher. This behaviour is reflected in the trend of the masses of the dark matter hosts of star-forming galaxies which increase from ~10^11.5 Msun to ~10^13.5 Msun between z~1 and z~2. Our analysis shows that galaxies which actively form stars at high redshifts are not the same population of sources we observe in the more local universe. In fact, vigorous star formation in the early universe is hosted by very massive structures, while for z~1 a comparable activity is encountered in much smaller systems, consistent with the down-sizing scenario. The ...

  19. 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...

  20. Jetted Tidal Disruptions of Stars as a Flag of Intermediate Mass Black Holes at High Redshifts

    CERN Document Server

    Fialkov, Anastasia

    2016-01-01

    Tidal disruption events (TDEs) of stars by single or binary supermassive black holes (SMBHs) brighten galactic nuclei and reveal a population of otherwise dormant black holes. Adopting event rates from the literature, we aim to establish general trends in the redshift evolution of the TDE number counts and their observable signals. We pay particular attention to two types of TDEs which are expected to be observable out to high redshifts, namely (i) jetted TDEs whose luminosity is boosted by relativistic beaming, and (ii) TDEs around binary black holes. We show that the brightest (jetted) TDEs are expected to be produced by massive black hole binaries if the occupancy of intermediate mass black holes (IMBHs) in low mass galaxies is high. The same binary population will also provide gravitational wave sources for eLISA. In addition, we find that the shape of the X-ray luminosity function of TDEs strongly depends on the occupancy of IMBHs and could be used to constrain scenarios of SMBH formation. Finally, we ma...

  1. The High Redshift Blazar S5 0836+71: A Broadband Study

    CERN Document Server

    Paliya, Vaidehi S

    2015-01-01

    A broadband study of the high redshift blazar S5 0836+71 (z = 2.172) is presented. Multi-frequency light curves show multiple episodes of X-ray and $\\gamma$-ray flares, while optical-UV fluxes show little variations. During the GeV outburst, the highest $\\gamma$-ray flux measured is (5.22 $\\pm$ 1.10) $\\times$ 10$^{-6}$ ph cm$^{-2}$ s$^{-1}$ in the range of 0.1-300 GeV, which corresponds to an isotropic $\\gamma$-ray luminosity of (1.62 $\\pm$ 0.44) $\\times$ 10$^{50}$ erg s$^{-1}$, thereby making this as one of the most luminous $\\gamma$-ray flare ever observed from any blazar. A fast $\\gamma$-ray flux rising time of $\\sim$3 hours is also noticed which is probably the first measurement of hour scale variability detected from a high redshift (z > 2) blazar. The various activity states of S5 0836+71 are reproduced under the assumption of single zone leptonic emission model. In all the states, the emission region is located inside the broad line region, and the optical-UV radiation is dominated by the accretion dis...

  2. 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...

  3. HCN Observations of Dense Star-Forming Gas in High Redshift Galaxies

    CERN Document Server

    Gao, Y; Solomon, P M; Bout, P A V; Gao, Yu; Carilli, Chris L.; Solomon, Philip M.; Bout, Paul A. Vanden

    2007-01-01

    We present here the sensitive HCN(1-0) observations made with the VLA of two submillimeter galaxies and two QSOs at high-redshift. HCN emission is the signature of dense molecular gas found in GMC cores, the actual sites of massive star formation. We have made the first detection of HCN in a submillimeter galaxy, SMM J16359+6612. The HCN emission is seen with a signal to noise ratio of 4$\\sigma$ and appears to be resolved as a double-source of $\\approxlt 2''$ separation. Our new HCN observations, combined with previous HCN detections and upper limits, show that the FIR/HCN ratios in these high redshift sources lie systematically above the FIR/HCN correlation established for nearby galaxies by about a factor of 2. Even considering the scatter in the data and the presence of upper limits, this is an indication that the FIR/HCN ratios for the early Universe molecular emission line galaxies (EMGs) deviate from the correlation that fits Galactic giant molecular cloud cores, normal spirals, LIRGs, and ULIRGs. This ...

  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. Detecting the integrated Sachs-Wolfe effect with high-redshift 21-cm surveys

    CERN Document Server

    Raccanelli, Alvise; Dai, Liang; Kamionkowski, Marc

    2015-01-01

    We investigate the possibility to detect the integrated Sachs-Wolfe (ISW) effect by cross-correlating 21-cm surveys at high redshifts with galaxies, in a way similar to the usual CMB-galaxy cross-correlation. The high-redshift 21-cm signal is dominated by CMB photons that travel freely without interacting with the intervening matter, and hence its late-time ISW signature should correlate extremely well with that of the CMB at its peak frequencies. Using the 21-cm temperature brightness instead of the CMB would thus be a further check of the detection of the ISW effect, measured by different instruments at different frequencies and suffering from different systematics. We also study the ISW effect on the photons that are scattered by HI clouds. We show that a detection of the unscattered photons is achievable with planned radio arrays, while one using scattered photons will require advanced radio interferometers, either an extended version of the planned Square Kilometre Array or futuristic experiments such as...

  6. Colour gradients of high-redshift early-type galaxies from hydrodynamical monolithic models

    Science.gov (United States)

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

    2013-10-01

    We analyse the evolution of colour gradients predicted by the hydrodynamical models of early-type galaxies (ETGs) in Pipino et al., 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 ɛSF, 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 ɛSF, 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 ɛSF systems with the shallower colour gradients observed at lower z we suggest intervention of one to two dry mergers. We suggest that future studies should explore the impact of wet galaxy merging, interactions with environment, dust content and a variation of the initial mass function from the galactic centres to the peripheries.

  7. Feeding cosmic star formation: exploring high-redshift molecular gas with CO intensity mapping

    Science.gov (United States)

    Breysse, Patrick C.; Rahman, Mubdi

    2017-06-01

    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 12CO (1-0) line, but also contain emission from the substantially fainter 110 GHz 13CO (1-0) transition. The method leverages the information contained in the 13CO line by cross-correlating pairs of frequency channels in an intensity mapping survey. Since 13CO is emitted from the same medium as the 12CO, but saturates at a much higher column density, this cross-correlation provides valuable information about both the gas density distribution and isotopologue ratio, inaccessible from the 12CO alone. Using a simple model of these molecular emission lines, we show that a future intensity mapping survey can constrain the abundance ratio of these two species and the fraction of emission from optically thick regions to order ˜30 per cent. These measurements cannot be made by traditional CO observations, and consequently the proposed method will provide unique insight into the physics of star formation, feedback and galactic ecology at high redshifts.

  8. Fossil HII Regions: Self-Limiting Star Formation at High Redshift

    CERN Document Server

    Oh, S P; Haiman, Zoltan

    2003-01-01

    Recent results by the WMAP satellite suggest that the intergalactic medium was significantly reionized at redshifts as high as z~17. At this early epoch, the first ionizing sources likely appeared in the shallow potential wells of mini-halos with virial temperatures T < 10^4 K. Once such an ionizing source turns off, its surrounding HII region Compton cools and recombines. Nonetheless, we show that the ``fossil'' HII regions left behind remain at high adiabats, prohibiting gas accretion and cooling in subsequent generations of mini-halos. Thus, early star formation is self-limiting. We quantify this effect to show that star formation in mini-halos cannot account for the bulk of the electron scattering opacity measured by WMAP, which must be due to more massive objects. We argue that gas entropy, rather than IGM metallicity, regulates the evolution of the global ionizing emissivity, and impedes full reionization until lower redshifts. We discuss several important consequences of this early entropy floor for...

  9. 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.

  10. Superluminous Supernovae as Standardizable Candles and High-redshift Distance Probes

    Science.gov (United States)

    Inserra, C.; Smartt, S. J.

    2014-12-01

    We investigate the use of type Ic superluminous supernovae (SLSN Ic) as standardizable candles and distance indicators. Their appeal as cosmological probes stems from their remarkable peak luminosities, hot blackbody temperatures, and bright rest-frame ultraviolet emission. We present a sample of 16 published SLSN, from redshifts 0.1 to 1.2, and calculate accurate K corrections to determine uniform magnitudes in 2 synthetic rest-frame filter bandpasses with central wavelengths at 400 nm and 520 nm. At 400 nm, we find an encouragingly low scatter in their uncorrected, raw mean magnitudes with M(400) = -21.86 ± 0.35 mag for the full sample of 16 objects. We investigate the correlation between their decline rates and peak magnitude and find that the brighter events appear to decline more slowly. In a manner similar to the Phillips relation for type Ia SNe (SNe Ia), we define a ΔM 20 decline relation. This correlates peak magnitude and decline over 20 days and can reduce the scatter in standardized peak magnitudes to ±0.22 mag. We further show that M(400) appears to have a strong color dependence. Redder objects are fainter and also become redder faster. Using this peak magnitudecolor evolution relation, a surprisingly low scatter of between ±0.08 mag and ±0.13 mag can be found in peak magnitudes, depending on sample selection. However, we caution that only 8 to 10 objects currently have enough data to test this peak magnitudecolor evolution relation. We conclude that SLSN Ic are promising distance indicators in the high-redshift universe in regimes beyond those possible with SNe Ia. Although the empirical relationships are encouraging, the unknown progenitor systems, how they may evolve with redshift, and the uncertain explosion physics are of some concern. The two major measurement uncertainties are the limited numbers of low-redshift, well-studied objects available to test these relationships and internal dust extinction in the host galaxies.

  11. Novel Slide-Ring Material/Natural Rubber Composites with High Damping Property

    Science.gov (United States)

    Wang, Wencai; Zhao, Detao; Yang, Jingna; Nishi, Toshio; Ito, Kohzo; Zhao, Xiuying; Zhang, Liqun

    2016-03-01

    A novel class of polymers called “slide-ring” (SR) materials with slideable junctions were used for high damping composites for the first time. The SR acts as the high damping phase dispersed in the natural rubber (NR) matrix, and epoxidized natural rubber (ENR) acts as the compatibilizer. The morphological, structural, and mechanical properties of the composites were investigated by atomic force microscope (AFM), transmission electron microscope (TEM), dynamic mechanical thermal analyzer (DMTA), rubber processing analyzer (RPA), and tensile tester. AFM and TEM results showed that the SR phase was uniformly dispersed in the composites, in a small size that is a function of ENR. DMTA and RPA results showed that the damping factor of the composites is much higher than that of NR, especially at room temperatures. Stretch hysteresis was used to study the energy dissipation of the composites at large strains. The results showed that SR and ENR can significantly improve the dissipation efficiency at strains lower than 200% strain. Wide-angle X-ray diffraction was used to study the strain-induced crystallization of the composites. The results indicated that the impact of the SR on the crystallization of NR is mitigated by the insulating effect of ENR.

  12. Highly compliant shape memory polymer gels for tunable damping and reversible adhesion

    Science.gov (United States)

    Mrozek, Randy A.; Berg, Michael C.; Gold, Christopher S.; Leighliter, Brad; Morton, Jeffrey T.; Lenhart, Joseph L.

    2016-02-01

    Materials that can dynamically change their properties to better adapt to the local environment have potential utility in robotics, aerospace, and coatings. For some of these applications, most notably robotics, it is advantageous for these responsive materials to be highly compliant in an effort to provide dynamic changes in adhesion and mechanical damping within a broad temperature operational environment. In this report, non-aqueous, highly compliant shape-memory polymer gels are developed by incorporating a low density of chemical cross-links into a physically cross-linked thermoplastic elastomer gel. Chemical cross-linkers were evaluated by varying there size and degree of functionality to determine the impact on the mechanical and adhesive properties. As a result of the chemical cross-linking, the gels exhibit modulus plateaus around room temperature and at elevated temperatures above 100 °C, where the thermoplastic elastomer gel typically melts. The materials were designed so that moduli in the plateaued regions were above and below the Dahlquist criteria of 4 × 104 Pa, respectively, where materials with a modulus below this value typically exhibit an increase in adhesion. The shape memory polymer gels were also integrated into fiber-reinforced composites to determine the temperature-dependent changes in mechanical damping. It is anticipated that this work will provide insight into materials design to provide dynamic changes in adhesion and damping to improve robotic appendage manipulation and platform mobility.

  13. Damped and sub-damped Lyman-alpha absorbers in z > 4 QSOs

    CERN Document Server

    Guimaraes, Rodney; De Carvalho, Reinaldo Ramos; Djorgovski, George; Noterdaeme, Pasquier; Castro, Sandra; Poppe, Paulo Da Rocha; Aghaee, Ali

    2009-01-01

    We present the results of a survey for damped (DLA, log N(H I) > 20.3) and sub-damped Lyman-? systems (19.5 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 19.5 are detected of which 40 systems are damped Lyman-? systems for an absorption length of ?X = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs. We study the evolution with redshift of the cosmological density of the neutral gas and ?nd, consis- tently with previous studies at similar resolution, that ?DLA,H I decreases at z > 3.5. The overall cosmological evolution of ?HI shows a peak around this redshift. The H I column density distribution for log N(H I) ? 20.3 is ?tted, consistently with previous surveys, with a single power-law of index ? ? -1.8$\\pm$0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a ?attening of the function at lower H I column densities with an index of ? ?...

  14. 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.

  15. Absorption of High Energy $\\gamma$ Rays by Interactions With Starlight Photons in Extragalactic Space at High Redshifts and the High Energy $\\gamma$-Ray Background

    CERN Document Server

    Salamon, M H

    1998-01-01

    We calculate the absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high-redshift evolution of the intergalactic starlight photon field, including its IR-UV spectral energy distribution. To estimate this evolution, we have followed a recent analysis of Fall, Charlot and Pei which gives results consistent with recent data. We give our results for the gamma-ray opacity as a function of redshift out to a redshift of 3. We also give predicted gamma-ray spectra for selected blazars and give an extragalactic unresolved blazar background spectrum up to 500 GeV. Our results indicate that this background should steepen significantly above 20 GeV owing to intergalactic absorption. Future observations of this steepening would provide a test for the blazar background origin hypothesis. We have used our results to discuss upper limits on the redshifts of gamma-ray bursts. We note that the 17 Feb. 1994 burst observed by EGRET must have originated at a redshift less tha...

  16. A search for H$\\alpha$ emission in high-metallicity damped Lyman-$\\alpha$ systems at $z \\sim 2.4$

    CERN Document Server

    Wang, Wei-Hao; Prochaska, J Xavier

    2015-01-01

    We report on a sensitive search for redshifted H$\\alpha$ line-emission from three high-metallicity damped Ly$\\alpha$ absorbers (DLAs) at $z \\approx 2.4$ with the Near-infrared Integral Field Spectrometer (NIFS) on the Gemini-North telescope, assisted by the ALTtitude conjugate Adaptive optics for the InfraRed (ALTAIR) system with a laser guide star. Within the NIFS field-of-view, $\\approx 3.22" \\times 2.92"$ corresponding to $\\approx 25$ kpc $ \\times 23$ kpc at $z=2.4$, we detect no statistically significant line-emission at the expected redshifted H$\\alpha$ wavelengths. The measured root-mean-square noise fluctuations in $0.4"$ apertures are $1-3\\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$. Our analysis of simulated, compact, line-emitting sources yields stringent limits on the star-formation rates (SFRs) of the three DLAs, $< 2.2$~M$_{\\odot}$ yr$^{-1}$ ($3\\sigma$) for two absorbers, and $< 11$~M$_{\\odot}$ yr$^{-1}$ ($3\\sigma$) for the third, at all impact parameters within $\\approx 12.5$~kpc to the quasar s...

  17. Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies

    CERN Document Server

    Izotov, Y I; Thuan, T X; Worseck, G; Orlitova, I; Verhamme, A

    2016-01-01

    Following our first detection reported in Izotov et al. (2016), we present the detection of Lyman continuum (LyC) radiation of four other compact star-forming galaxies observed with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST). These galaxies, at redshifts of z~0.3, are characterized by high emission-line flux ratios [OIII]5007/[OII]3727 > 5. The escape fractions of the LyC radiation fesc(LyC) in these galaxies are in the range of ~6%-13%, the highest values found so far in low-redshift star-forming galaxies. Narrow double-peaked Lyalpha emission lines are detected in the spectra of all four galaxies, compatible with predictions for Lyman continuum leakers. We find escape fractions of Lyalpha, fesc(Lyalpha) ~60%-90%, among the highest known for Lyalpha emitters (LAEs). Surface brightness profiles produced from the COS acquisition images reveal bright star-forming regions in the center and exponential discs in the outskirts with disc scale lengths alpha in the range ~0.6-1.4 k...

  18. 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...

  19. Where is the Cold Neutral Gas in the Hosts of High Redshift AGN?

    CERN Document Server

    Curran, S J; Webb, J K

    2008-01-01

    Previous surveys for HI 21-cm absorption in z > 0.1 radio galaxies and quasars yield a 40% detection rate, which is attributed to unified schemes of active galactic nuclei (AGN). In this paradigm absorption is only witnessed in (close to) type-2 objects, where the central obscuration is viewed (nearly) edge-on and thus absorbs the rest frame 1420 MHz emission along our sight-line. However, we find this mix of detections and non-detections to only apply at low redshift (z 3 radio sources we find no 21-cm absorption, indicating a low abundance of cold neutral gas in (the sight-lines searched in) these objects. Analysing the spectral energy distributions of these sources, we find that our high redshift selection introduces a bias where our sample consists exclusively of quasars with ultra-violet luminosities in excess of 10e23 W/Hz. This may suggest that we have selected a class of particularly UV bright type-1 objects. Whatever the cause, it must also be invoked to explain the non-detections in an equal number...

  20. High-redshift blazar identification for Swift J1656.3-3302

    CERN Document Server

    Masetti, N; Landi, R; Giommi, P; Bassani, L; Malizia, A; Bird, A J; Bazzano, A; Dean, A J; Gehrels, N; Palazzi, E; Ubertini, P

    2008-01-01

    We report on the high-redshift blazar identification of a new gamma-ray source, Swift J1656.3-3302, detected with the BAT imager onboard the Swift satellite and the IBIS instrument on the INTEGRAL satellite. Follow-up optical spectroscopy has allowed us to identify the counterpart as an R-band 19 mag source that shows broad Lyman-alpha, Si IV, He II, C IV, and C III] emission lines at redshift z = 2.40+-0.01. Spectral evolution is observed in X-rays when the INTEGRAL/IBIS data are compared to the Swift/BAT results, with the spectrum steepening when the source gets fainter. The 0.7-200 keV X-ray continuum, observed with Swift/XRT and INTEGRAL/IBIS, shows the power law shape typical of radio loud (broad emission line) active galactic nuclei (with a photon index around 1.6) and a hint of spectral curvature below 2 keV, possibly due to intrinsic absorption (N_H about 7e22 cm-2) local to the source. Alternatively, a slope change (of about 1 in terms of photon index) around 2.7 keV can describe the X-ray spectrum e...

  1. Low-Metallicity Star Formation in High-Redshift Galaxies at z~8

    CERN Document Server

    Taniguchi, Y; Trump, J R

    2010-01-01

    Based on the recent very deep near-infrared imaging of the Hubble Ultra Deep Field with WFC3 on the Hubble Space Telescope, five groups published most probable samples of galaxies at z~8, selected by the so-called dropout method or photometric redshift; e.g., Y_105-dropouts (Y_105-J_125 > 0.8). These studies are highly useful for investigating both the early star formation history of galaxies and the sources of cosmic re-ionization. In order to better understand these issues, we carefully examine if there are low-$z$ interlopers in the samples of z~8 galaxy candidates. We focus on the strong emission-line galaxies at z~2 in this paper. Such galaxies may be selected as Y_105-dropouts since the [OIII] lambda 5007 emission line is redshifted into the J_125-band. We have found that the contamination from such low-$z$ interlopers is negligibly small. Therefore, all objects found by the five groups are free from this type of contamination. However, it remains difficult to extract real z~8 galaxies because all the s...

  2. Complete Ionisation of the Neutral Gas in High Redshift Radio Galaxies and Quasars

    CERN Document Server

    Curran, S J

    2012-01-01

    Cool neutral gas provides the raw material for all star formation in the Universe, and yet, from a survey of the hosts of high redshift radio galaxies and quasars, we find a complete dearth of atomic (HI 21-cm) and molecular (OH, CO, HCO+ & HCN) absorption at redshifts z > 3. Upon a thorough analysis of the optical photometry, we find that all of our targets have ionising ultra-violet continuum luminosities of logL > 23 W/Hz. We therefore attribute this deficit to the traditional optical selection of targets biasing surveys towards the most ultra-violet luminous objects, where the intense radiation excites the neutral gas to the point where it cannot engage in star formation. However, this hypothesis does not explain why there is a critical luminosity, rather than a continuum where the detections gradually become fewer and fewer as the harshness of the radiation increases. We show that by placing a quasar within a galaxy of gas there is always a finite ultra-violet luminosity above which all of the gas is...

  3. New Image Statistics for Detecting Disturbed Galaxy Morphologies at High Redshift

    CERN Document Server

    Freeman, P E; Lee, A B; Newman, J A; Conselice, C J; Koekemoer, A M; Lotz, J M; Mozena, M

    2013-01-01

    Testing theories of hierarchical structure formation requires estimating the distribution of galaxy morphologies and its change with redshift. One aspect of this investigation involves identifying galaxies with disturbed morphologies (e.g., merging galaxies). This is often done by summarizing galaxy images using, e.g., the CAS and Gini-M20 statistics of Conselice (2003) and Lotz et al. (2004), respectively, and associating particular statistic values with disturbance. We introduce three statistics that enhance detection of disturbed morphologies at high-redshift (z ~ 2): the multi-mode (M), intensity (I), and deviation (D) statistics. We show their effectiveness by training a machine-learning classifier, random forest, using 1,639 galaxies observed in the H band by the Hubble Space Telescope WFC3, galaxies that had been previously classified by eye by the CANDELS collaboration (Grogin et al. 2011, Koekemoer et al. 2011). We find that the MID statistics (and the A statistic of Conselice 2003) are the most usef...

  4. A New Diagnostic Diagram of Ionization Source for High Redshift Emission Line Galaxies

    CERN Document Server

    Zhang, Kai

    2016-01-01

    We propose a new diagram, the Kinematic-Excitation diagram (KEx diagram), which uses the [OIII]/H\\beta\\ line ratio and the [OIII]5007 emission line width (\\sigma_{[OIII]}) to diagnose the ionization source and physical properties of the Active Galactic Nuclei (AGNs) and the star-forming galaxies (SFGs). The KEx diagram is a suitable tool to classify emission-line galaxies (ELGs) at intermediate redshift because it uses only the [OIII]5007 and H\\beta\\ emission lines. We use the SDSS DR7 main galaxy sample and the Baldwin-Phillips-Terlevich (BPT) diagnostic to calibrate the diagram at low redshift. We find that the diagram can be divided into 3 regions: one occupied mainly by the pure AGNs (KEx-AGN region), one dominated by composite galaxies (KEx-composite region), and one contains mostly SFGs (KEx-SFG region). AGNs are separated from SFGs in this diagram mainly because they preferentially reside in luminous and massive galaxies and have high [OIII]/H\\beta. The separation of AGN from star-forming galaxies is e...

  5. On the radiative efficiencies, Eddington ratios, and duty cycles of luminous high-redshift quasars

    CERN Document Server

    Shankar, Francesco; Miralda-Escude', Jordi; Fosalba, Pablo; Weinberg, David H

    2008-01-01

    We investigate the characteristic radiative efficiency \\epsilon, Eddington ratio \\lambda, and duty cycle P_0 of high-redshift active galactic nuclei (AGN), 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 \\epsilon, \\lambda, and the normalization, scatter, and redshift evolution of the relation between black hole mass \\mbh and halo virial velocity V_vir. We compute the luminosity function from the implied growth of the black hole 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 black holes reside in rare, massive dark matter halos. Reproducing the observed luminosity functio...

  6. 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...

  7. Massive Close Pairs Measure Rapid Galaxy Assembly in Mergers at High Redshift

    CERN Document Server

    Snyder, Gregory F; Rodriguez-Gomez, Vicente; Guimaraes, Renato da Silva; Torrey, Paul; Hernquist, Lars

    2016-01-01

    We compare mass-selected close pairs at z > 1 with the intrinsic galaxy merger rate in the Illustris Simulations. To do so, we construct three 140 arcmin^2 lightcone catalogs and measure pair fractions, finding that they change little or decrease with increasing redshift at z > 1. Consistent with current surveys, this trend requires a decrease in the merger-pair observability time, roughly as (1 + z)^-2, in order to measure the merger rates of the same galaxies. This implies that major mergers are more common at high redshift than implied by the simplest arguments assuming a constant observability time. Several effects contribute to this trend: (1) The fraction of massive, major (4:1) pairs which merge by today increases weakly from ~0.5 at z=1 to ~0.8 at z=3. (2) The median time elapsed between an observed pair and final remnant decreases by a factor of two from z~1 to z~3. (3) An increasing specific star formation rate (sSFR) decreases the time during which common stellar-mass based pair selection criteria ...

  8. 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...

  9. High-redshift formation and evolution of central massive objects II: The census of BH seeds

    CERN Document Server

    Devecchi, B; Rossi, E M; Colpi, M; Zwart, S Portegies

    2012-01-01

    We present results of simulations aimed at tracing the formation of nuclear star clusters (NCs) and black hole (BH) seeds, in a cosmological context. We focus on two mechanisms for the formation of BHs at high redshifts: as end-products of (1) Population III stars in metal free halos, and of (2) runaway stellar collisions in metal poor NCs. Our model tracks the chemical, radiative and mechanical feedback of stars on the baryonic component of the evolving halos. This procedure allows us to evaluate when and where the conditions for BH formation are met, and to trace the emergence of BH seeds arising from the dynamical channel, in a cosmological context. BHs start to appear already at z~30 as remnants of Population III stars. The efficiency of this mechanism begins decreasing once feedbacks become increasingly important. Around redshift z~15, BHs mostly form in the centre of mildly metal enriched halos inside dense NCs. The seed BHs that form along the two pathways have at birth a mass around 100-1000M\\odot. Th...

  10. Revisiting the Completeness and the Luminosity Function in High-Redshift Low-Luminosity Quasar Surveys

    CERN Document Server

    Niida, Mana; Ikeda, Hiroyuki; Matsuoka, Kenta; Kobayashi, Masakazu A R; Toba, Yoshiki; Taniguchi, Yoshiaki

    2016-01-01

    Recent studies have derived quasar luminosity functions (QLFs) at various redshifts. However, the faint side of the QLF at high redshifts is still too uncertain. An accurate estimate of the survey completeness is essential to derive an accurate QLF for use in studying the luminosity-dependent density evolution of the quasar population. Here we investigate how the luminosity dependence of quasar spectra (the Baldwin effect) and the attenuation model for the inter-galactic medium (IGM) affect the completeness estimates. For this purpose, we revisit the completeness of quasar surveys specifically at $z\\sim4-5$, using the COSMOS images observed with Subaru/Suprime-Cam. As the result, we find that the completeness estimates are sensitive to the luminosity dependence of the quasar spectrum and difference in the IGM attenuation models. At $z\\sim4$, the number density of quasars when we adopt the latest IGM model and take the luminosity dependence of spectra into account are $(3.49\\pm1.62)\\times10^{-7}$ Mpc$^{-3}$ ma...

  11. Detecting quasars at very high redshift with next generation X-ray telescopes

    CERN Document Server

    Rhook, Kirsty J

    2008-01-01

    The next generation of X-ray telescopes have the potential to detect faint quasars at very high redshift and probe the early growth of massive black holes (BHs). We present modelling of the evolution of the optical and X-ray AGN luminosity function at 2 6 for a range of BH growth scenarios. We predict significant numbers of sources at z ~ 6 with fluxes just an order of magnitude below the current detection limits and thus detectable with XEUS and Constellation-X, relatively independently of the fading law chosen. The predicted number of sources at even higher redshift depends sensitively on the early growth history of BHs. For passive evolution models in which BHs grow constantly at their Eddington limit, detectable BHs may be rare beyond z ~ 8 even with Generation-X. However, in the more probable scenario that BH growth at z > 6 can be described by passive evolution with a small duty cycle, or by our merger driven accretion model, then we predict that XEUS and Generation-X will detect significant numbers of...

  12. 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...

  13. Constraining high-redshift X-ray sources with next generation 21-cm power spectrum measurements

    Science.gov (United States)

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

    2016-05-01

    We use the Fisher matrix formalism and seminumerical 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 25, we find that the proposed 331 element HERA and SKA phase 1 will be capable of placing ≲ 10 per cent 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 heating and reionization physics lead to errors on reionization parameters that are significantly greater than previously predicted. Observations over the heating epoch are able to break these degeneracies and improve our constraints considerably. For these two reasons, 21-cm observations during the heating epoch significantly enhance our understanding of reionization as well.

  14. 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.

  15. A Spectral Feature of High-Redshift Gamma-Ray Bursts Probing the Earliest Starlight Background Radiation

    CERN Document Server

    Dai, Z G

    2002-01-01

    Gamma-ray bursts (GRBs) and their afterglows at high redshifts have been widely believed to be detectable. Here we analyze a new feature of the MeV spectra of high-redshift GRBs, which is unlikely to appear in low-redshift GRBs. We generally discuss high-energy emission above a few decades of GeV due to synchrotron self-Compton scattering in the internal shock model. Our discussion seems to be supported by the high-energy spectra of several low-redshift GRBs. However, if GRBs originate at high redshifts (e.g., $z\\ge 6$), such photons cannot be detected because they may collide with cosmic optical and ultraviolet background photons, leading to electron/positron pair production. We show that inverse-Compton scattering of the resulting electron/positron pairs off cosmic microwave background photons will produce an additional multi-MeV component, resulting thus in a spectral "bump". We also derive the scattered photon spectrum of such a bump, $\

  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. Probabilistic Selection of High-redshift Quasars with Subaru/Hyper Suprime-Cam Survey

    Science.gov (United States)

    Onoue, Masafusa

    High-redshift quasars are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. Through pioneering optical and near-infrared wide-area surveys such as the SDSS and the VIKING Survey, about one hundred quasars have been found at z > 6 (e.g., Fan et al. (2006b), Venemans et al. (2013)). However, its current small sample size and the fact that most of them are the most luminous (M 1450 6 quasars, especially low-luminous or z > 7 quasars, is highly desired for further understanding of the early universe. We are now starting a new ground-breaking survey of high-redshift (z > 6) quasars using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. Thanks to its extremely wide coverage and its high sensitivity thorough five optical bands (1,400 deg2 to the depth of r ~ 26 in HSC-Wide layer), it is one of the most powerful contemporary surveys that makes it possible for us to increase the number of z > 6 quasars by almost an order of magnitude, i.e., 300 at z ~ 6 and 50 at z ~ 7, based on the current estimate of the QLF at z > 6 by Willott et al. (2010b). One of the biggest challenges in z > 6 quasar candidate selection is contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to the quasars. To overcome this issue and maximize the selection efficiency, we apply a double-layered approach to the HSC survey products, namely combination of two probabilistic selections: SED-fitting and Bayesian selection. In particular, we have developed a template SED fitting method optimized to high-redshift quasars selection. Its application with 27 photometric bands to the COSMOS quasars at 3 6 quasar selection, and it is expected that the first HSC quasar discovery will be in the near future.

  18. Deep GMRT 150 MHz Observations of the DEEP2 Fields: Searching for High Red-Shift Radio Galaxies Revisited

    Indian Academy of Sciences (India)

    Susanta K. Bisoi; C. H. Ishwara-Chandra; S. K. Sirothia; P. Janardhan

    2011-12-01

    High red-shift radio galaxies are best searched at low radio frequencies, due to its steep radio spectra. Here we present preliminary results from our programme to search for high red-shift radio galaxies to ∼ 10 to 100 times fainter than the known population till date. We have extracted ultra-steep spectrum (USS) samples from deep 150 MHz Giant Meter-wave Radio Telescope (GMRT) observations from one of the three well-studied DEEP2 fields to this effect. From correlating these radio sources with respect to the high-frequency catalogues such as VLA, FIRST and NVSS at 1.4 GHz, we find ∼ 100 steep spectrum (spectral index, > 1) radio sources, which are good candidates for high red-shift radio galaxies.

  19. Using Line Profiles to Test the Fraternity of Type Ia Supernovae at High and Low Redshifts

    Science.gov (United States)

    Blondin, Stéphane; Dessart, Luc; Leibundgut, Bruno; Branch, David; Höflich, Peter; Tonry, John L.; Matheson, Thomas; Foley, Ryan J.; Chornock, Ryan; Filippenko, Alexei V.; Sollerman, Jesper; Spyromilio, Jason; Kirshner, Robert P.; Wood-Vasey, W. Michael; Clocchiatti, Alejandro; Aguilera, Claudio; Barris, Brian; Becker, Andrew C.; Challis, Peter; Covarrubias, Ricardo; Davis, Tamara M.; Garnavich, Peter; Hicken, Malcolm; Jha, Saurabh; Krisciunas, Kevin; Li, Weidong; Miceli, Anthony; Miknaitis, Gajus; Pignata, Giuliano; Prieto, Jose Luis; Rest, Armin; Riess, Adam G.; Salvo, Maria Elena; Schmidt, Brian P.; Smith, R. Chris; Stubbs, Christopher W.; Suntzeff, Nicholas B.

    2006-03-01

    Using archival data of low-redshift (zdatabases) Type Ia supernovae (SNe Ia) and recent observations of high-redshift (0.161.7] SNe Ia, which are also subluminous. In addition, we give the first direct evidence in two high-z SN Ia spectra of a double-absorption feature in Ca II λ3945, an event also observed, although infrequently, in low-redshift SN Ia spectra (6 out of 22 SNe Ia in our local sample). Moreover, echoing the recent studies of Dessart & Hillier in the context of Type II supernovae (SNe II), we see similar P Cygni line profiles in our large sample of SN Ia spectra. First, the magnitude of the velocity location at maximum profile absorption may underestimate that at the continuum photosphere, as observed, for example, in the optically thinner line S II λ5640. Second, we report for the first time the unambiguous and systematic intrinsic blueshift of peak emission of optical P Cygni line profiles in SN Ia spectra, by as much as 8000 km s-1. All the high-z SNe Ia analyzed in this paper were discovered and followed up by the ESSENCE collaboration and are now publicly available. Based in part on observations obtained at the Cerro Tololo Inter-American Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation (NSF); the European Southern Observatory, Chile (ESO program 170.A-0519) the Gemini Observatory, which is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership (the NSF [United States], the Particle Physics and Astronomy Research Council [United Kingdom], the National Research Council [Canada], CONICYT [Chile], the Australian Research Council [Australia], CNPq [Brazil], and CONICET [Argentina]) (programs GN-2002B-Q-14, GN-2003B-Q-11, and GS-2003B-Q-11) the Magellan Telescopes at Las Campanas Observatory; the MMT Observatory, a joint facility of the Smithsonian Institution and the University of

  20. 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

    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.%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.

  1. Fluctuations in radiation backgrounds at high redshift and the first stars

    Science.gov (United States)

    Holzbauer, Lauren Nicole

    The first stars to light up our universe are as yet unseen, but there have been many attempts to elucidate their properties. The characteristics of these stars (`Population/Pop III' stars) that we do know lie mostly within theory; they formed out of metal-free hydrogen and helium gas contained in dark matter minihalos at redshifts z 20-30. The extent to which Pop III star formation reached into later times is unknown. Current and near future instruments are incapable of resolving individual Pop III stars. Consequently, astronomers must devise creative means with which to indirectly predict and measure and their properties. In this thesis, we will investigate a few of those means. We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos that is necessary for star formation. By using a variation of the `halo model', which describes the spatial distribution and clustering of halos, we can efficiently generate power spectra for these backgrounds. Spatial fluctuations in the LW and (indirectly) the Lyman-alpha BG can tell us about the transition from primordial star formation to a more metal-enriched mode that marks the beginning of the second generation of stars in our Universe. The Near Infrared Background (NIRB) has for some time been considered a potential tool with which to indirectly observe the first stars. Ultraviolet (UV) emission from these stars is redshifted into the NIR band, making the NIRB amenable for hunting Pop III stellar signatures. There have been several measurements of the NIRB and subsequent theoretical studies attempting to explain them in recent years. Though controversial, residual levels of the mean NIRB intensity and anisotropies have been

  2. Using young massive star clusters to understand star formation and feedback in high-redshift-like environments

    CERN Document Server

    Longmore, Steven; 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 describe a system of massive clusters and their progenitor gas clouds in the centre of the Milky Way, and outline how detailed observations of this system may be able to: (i) help answer some of the fundamental open questions in star formation and (ii) quantify how stellar feedback couples to the surrounding interstellar medium in this high-pressure, high-redshift analogue environment.

  3. A Revised Host Galaxy Association for GRB 020819B: A High-Redshift Dusty Starburst, Not a Low-Redshift Gas-Poor Spiral

    CERN Document Server

    Perley, Daniel A; Schady, Patricia; Michałowski, Michał J; Thöne, Christina C; Petry, Dirk; Graham, John F; Greiner, Jochen; Schulze, Steve; Kim, Sam

    2016-01-01

    The purported spiral host galaxy of GRB 020819B at z=0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: optical spectroscopy of this host provided evidence that GRBs can form even at high metallicities, while millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from VLT (MUSE and X-shooter) which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star-forming, dusty galaxy at z=1.9621. The revised redshift naturally explains the apparent nondetection of CO(3-2) line emission at the afterglow site from ALMA. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at super-Solar metallicity.

  4. COSMIC RAYS CAN DRIVE STRONG OUTFLOWS FROM GAS-RICH HIGH-REDSHIFT DISK GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Hanasz, M.; Kowalik, K.; Wóltański, D. [Centre for Astronomy, Nicolaus Copernicus University, Faculty of Physics, Astronomy and Informatics, Grudziadzka 5, PL-87100 Toruń (Poland); Lesch, H. [Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München (Germany); Naab, T. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching bei München (Germany); Gawryszczak, A., E-mail: mhanasz@astri.uni.torun.pl [Poznań Supercomputing and Networking Centre, ul. Noskowskiego 10, PL-61-704 Poznań (Poland)

    2013-11-10

    We present simulations of the magnetized interstellar medium (ISM) in models of massive star-forming (40 M {sub ☉} yr{sup –1}) disk galaxies with high gas surface densities (Σ{sub gas} ∼ 100 M {sub ☉} pc{sup –2}) similar to observed star-forming high-redshift disks. We assume that type II supernovae deposit 10% of their energy into the ISM as cosmic rays (CRs) and neglect the additional deposition of thermal energy or momentum. With a typical Galactic diffusion coefficient for CRs (3 × 10{sup 28} cm{sup 2} s{sup –1}), we demonstrate that this process alone can trigger the local formation of a strong low-density galactic wind maintaining vertically open field lines. Driven by the additional pressure gradient of the relativistic fluid, the wind speed can exceed 10{sup 3} km s{sup –1}, much higher than the escape velocity of the galaxy. The global mass loading, i.e., the ratio of the gas mass leaving the galactic disk in a wind to the star formation rate, becomes of order unity once the system has settled into an equilibrium. We conclude that relativistic particles accelerated in supernova remnants alone provide a natural and efficient mechanism to trigger winds similar to observed mass-loaded galactic winds in high-redshift galaxies. These winds also help in explaining the low efficiencies for the conversion of gas into stars in galaxies, as well as the early enrichment of the intergalactic medium with metals. This mechanism may be at least of similar importance to the traditionally considered momentum feedback from massive stars and thermal and kinetic feedback from supernova explosions.

  5. VizieR Online Data Catalog: KMOS AGN Survey at High redshift (KASHz) (Harrison+, 2016)

    Science.gov (United States)

    Harrison, C. M.; Alexander, D. M.; Mullaney, J. R.; Stott, J. P.; Swinbank, A. M.; Arumugam, V.; Bauer, F. E.; Bower, R. G.; Bunker, A. J.; Sharples, R. M.

    2016-08-01

    KASHz is designed to ultimately obtain spatially resolved emission-line kinematics of ~(100-200) high-redshift (z~0.6-3.6) AGN. For our target selection we make use of deep X-ray surveys performed in extragalactic fields (COSMOS, see Scoville et al., 2007, Cat. J/ApJS/171/1; CDF-S, see Giacconi et al. 2001ApJ...551..624G and Xue et al., 2011, Cat. J/ApJS/195/10 (CDFS); UDS, SXDS: see Furusawa et al. 2008, Cat. J/ApJS/176/1 (UDS) and SSA22, see Steidel et al. 1998ApJ...492..428S). (1 data file).

  6. Too big, too early? Multiple High-Redshift Galaxy Clusters: implications

    CERN Document Server

    Hoyle, Ben; Verde, Licia

    2010-01-01

    To date, 15 high-redshift (z>1.0) galaxy clusters with mass measurements have been observed, spectroscopically confirmed and are reported in the literature. These objects should be exceedingly rare in the standard LCDM model. We conservatively approximate the selection functions of these clusters' parent surveys, and quantify the tension between the abundances of massive clusters as predicted by the standard LCDM model and the observed ones. We alleviate the tension considering non-Gaussian primordial perturbations of the local type, characterized by the parameter fnl and derive constraints on fnl arising from the mere existence of these clusters. At the 95% confidence level, fnl>475 with cosmological parameters fixed to their most likely WMAP5 values, or fnl>370 if we marginalize over WMAP5 parameters priors. In combination with fnl constraints from Cosmic Microwave Background and halo bias, this determination implies a scale-dependence of fnl at 3 sigma. Given the assumptions made in the analysis, we expect...

  7. Constraining Sub-Grid Physics with High-Redshift Spatially-Resolved Metallicity Distributions

    CERN Document Server

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

    2013-01-01

    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. 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. 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 invar...

  8. 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.

  9. SU(2)CMB at high redshifts and the value of H0

    Science.gov (United States)

    Hahn, Steffen; Hofmann, Ralf

    2017-07-01

    We investigate a high-z cosmological model to compute the comoving sound horizon rs at baryon-velocity freeze-out towards the end of hydrogen recombination. This model assumes a replacement of the conventional cosmic microwave background (CMB) photon gas by deconfining SU(2) Yang-Mills thermodynamics, three flavours of massless neutrinos (Nν = 3) and a purely baryonic matter sector [no cold dark-matter (CDM)]. The according SU(2) temperature-redshift relation of the CMB is contrasted with recent measurements appealing to the thermal Sunyaev-Zel'dovich effect and CMB-photon absorption by molecular rotation bands or atomic hyperfine levels. Relying on a realistic simulation of the ionization history throughout recombination, we obtain z* = 1693.55 ± 6.98 and zdrag = 1812.66 ± 7.01. Due to considerable widths of the visibility functions in the solutions to the associated Boltzmann hierarchy and Euler equation, we conclude that z* and zdrag overestimate the redshifts for the respective photon and baryon-velocity freeze-out. Realistic decoupling values turn out to be zlf,* = 1554.89 ± 5.18 and zlf, drag = 1659.30 ± 5.48. With rs(zlf, drag) = (137.19 ± 0.45) Mpc and the essentially model independent extraction of rsH0 = constant from low-z data in Bernal, Verde & Riess, we obtain a good match with the value H0 = (73.24 ± 1.74) km s-1 Mpc-1 extracted in Riess et al. by appealing to Cepheid-calibrated Type Ia supernovae, new parallax measurements, stronger constraints on the Hubble flow and a refined computation of distance to NGC 4258 from maser data. We briefly comment on a possible interpolation of our high-z model, invoking percolated and unpercolated U(1) topological solitons of a Planck-scale axion field, to the phenomenologically successful low-z ΛCDM cosmology.

  10. 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.

  11. Exploratory X-ray monitoring of luminous radio-quiet quasars at high redshift: Initial results

    Energy Technology Data Exchange (ETDEWEB)

    Shemmer, Ohad; Stein, Matthew S. [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Paolillo, Maurizio [Dipartimento di Scienze Fisiche, Università Federico II di Napoli, via Cinthia 6, I-80126 Napoli (Italy); Kaspi, Shai [School of Physics and Astronomy and the Wise Observatory, Tel Aviv University, Tel Aviv 69978 (Israel); Vignali, Cristian [Dipartimento di Astronomia, Università degli studi di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Lira, Paulina [Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago (Chile); Gibson, Robert R., E-mail: ohad@unt.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

    2014-03-10

    We present initial results from an exploratory X-ray monitoring project of two groups of comparably luminous radio-quiet quasars (RQQs). The first consists of four sources at 4.10 ≤ z ≤ 4.35, monitored by Chandra, and the second is a comparison sample of three sources at 1.33 ≤ z ≤ 2.74, monitored by Swift. Together with archival X-ray data, the total rest-frame temporal baseline spans ∼2-4 yr and ∼5-13 yr for the first and second group, respectively. Six of these sources show significant X-ray variability over rest-frame timescales of ∼10{sup 2}-10{sup 3} days; three of these also show significant X-ray variability on rest-frame timescales of ∼1-10 days. The X-ray variability properties of our variable sources are similar to those exhibited by nearby and far less luminous active galactic nuclei (AGNs). While we do not directly detect a trend of increasing X-ray variability with redshift, we do confirm previous reports of luminous AGNs exhibiting X-ray variability above that expected from their luminosities, based on simplistic extrapolation from lower luminosity sources. This result may be attributed to luminous sources at the highest redshifts having relatively high accretion rates. Complementary UV-optical monitoring of our sources shows that variations in their optical-X-ray spectral energy distribution are dominated by the X-ray variations. We confirm previous reports of X-ray spectral variations in one of our sources, HS 1700+6416, but do not detect such variations in any of our other sources in spite of X-ray flux variations of up to a factor of ∼4. This project is designed to provide a basic assessment of the X-ray variability properties of RQQs at the highest accessible redshifts that will serve as a benchmark for more systematic monitoring of such sources with future X-ray missions.

  12. Compact High-Redshift Galaxies Are the Cores of Present-Day Massive Spheroids

    CERN Document Server

    Hopkins, Philip F; Murray, Norman; Quataert, Eliot; Lauer, Tod; Ma, Chung-Pei

    2009-01-01

    Observations suggest that effective radii of high-z massive spheroids are as much as a factor ~6 smaller than low-z galaxies of comparable mass. Given the apparent absence of low-z counterparts, this has often been interpreted as indicating that the high density, compact red galaxies must be 'puffed up' by some mechanism. We compare the ensemble of high-z observations with large samples of well-observed low-z ellipticals. At the same physical radii, the stellar surface mass densities of low and high-z systems are comparable. Moreover, the abundance of high surface density material at low redshift is comparable to or larger than that observed at z>1-2, consistent with the continuous buildup of spheroids over this time. The entire population of compact, high-z red galaxies may be the progenitors of the high-density cores of present-day ellipticals, with no need for a decrease in stellar density from z=2 to z=0. The primary difference between low and high-z systems is thus the observed low-density material at la...

  13. Natural rubber/nitrile butadiene rubber/hindered phenol composites with high-damping properties

    Directory of Open Access Journals (Sweden)

    Xiuying Zhao

    2015-10-01

    Full Text Available New natural rubber (NR/nitrile butadiene rubber (NBR/hindered phenol (AO-80 composites with high-damping properties were prepared in this study. The morphological, structural, and mechanical properties were characterized by atomic force microscopy (AFM, polarized Fourier transform infrared spectrometer (FTIR, dynamic mechanical thermal analyzer (DMTA, and a tensile tester. Each composite consisted of two phases: the NR phase and the NBR/AO-80 phase. There was partial compatibility between the NR phase and the NBR/AO-80 phase, and the NR/NBR/AO-80 (50/50/20 composite exhibited a co-continuous morphology. Strain-induced crystallization occurred in the NR phase at strains higher than 200%, and strain-induced orientation appeared in the NBR/AO-80 phase with the increase of strain from 100% to 500%. The composites had a special stress–strain behavior and mechanical properties because of the simultaneous strain-induced orientation and strain-induced crystallization. In the working temperature range of a seismic isolation bearing, the composites (especially the NR/NBR/AO-80 (50/50/20 composite presented a high loss factor, high area of loss peak (TA, and high hysteresis energy. Therefore, the NR/NBR/AO-80 rubber composites are expected to have important application as a high-performance damping material for rubber bearing.

  14. On the Possibility of Using Nonlinear Elements for Landau Damping in High-Intensity Beams

    Energy Technology Data Exchange (ETDEWEB)

    Alexahin, Y. [Fermilab; Gianfelice-Wendt, E. [Fermilab; Lebedev, V. [Fermilab; Valishev, A. [Fermilab

    2016-09-30

    Direct space-charge force shifts incoherent tunes downwards from the coherent ones breaking the Landau mechanism of coherent oscillations damping at high beam intensity. To restore it nonlinear elements can be employed which move back tunes of large amplitude particles. In the present report we consider the possibility of creating a “nonlinear integrable optics” insertion in the Fermilab Recycler to host either octupoles or hollow electron lens for this purpose. For comparison we also consider the classic scheme with distributed octupole families. It is shown that for the Proton Improvement Plan II (PIP II) parameters the required nonlinear tune shift can be created without destroying the dynamic aperture.

  15. Design of a high dynamic range photomultiplier base board for the BGO ECAL of DAMPE

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhiyong; Zhang, Yunlong, E-mail: ylzhang1@mail.ustc.edu.cn; Dong, Jianing; Wen, Sicheng; Feng, Changqing; Wang, Chi; Wei, Yifeng; Wang, Xiaolian; Xu, Zizong; Liu, Shubin

    2015-04-21

    A base board for photomultiplier tube (PMT) with multi-dynode readout has been developed for the BGO electromagnetic calorimeter (ECAL) of the Dark Matter Particle Explorer (DAMPE). In order to cover a high dynamic range of energy measurements, the signals are read out from different sensitive dynodes 2, 5, and 8 (Dy2, Dy5 and Dy8). The performance of this new type of base board is studied with a light-emitting diode (LED) system and cosmic rays. A wide measuring range from 0.5 to 1.0×10{sup 5} MIPs can be achieved using the VA32 readout Application Specific Integrated Circuit (ASIC)

  16. Nuclear Reaction Rates in a Plasma The Effect of Highly Damped Modes

    CERN Document Server

    Opher, M; Opher, Merav; Opher, Reuven

    2000-01-01

    The fluctuation-dissipation theorem is used to evaluate the screening factor of nuclear reactions due to the electromagnetic fluctuations in a plasma. We show that the commonly used Saltpeter factor is obtained if only fluctuations near the plasma eigenfrequency are assumed to be important (\\omega \\sim \\omega_{pe}\\ll T (\\hbar=k_{B}=1)). By taking into account all the fluctuations, the highly damped ones, with \\omega >\\omega_{pe}, as well as those with \\omega\\leq\\omega_{pe}, we find that nuclear reaction rates are higher than those obtained using the Saltpeter factor, for many interesting plasmas.

  17. Big Data in the SHELA Field: Investigating Galaxy Quenching at High Redshifts

    Science.gov (United States)

    Stevans, Matthew L.; Finkelstein, Steven L.; Wold, Isak; Kawinwanichakij, Lalitwadee; Sherman, Sydney; Gebhardt, Karl; Jogee, Shardha; Papovich, Casey J.; Ciardullo, Robin; Gronwall, Caryl; Gawiser, Eric J.; Acquaviva, Viviana; Casey, Caitlin; Florez, Jonathan; HETDEX Team

    2017-06-01

    We present a measurement of the z ~ 4 Lyman break galaxy (LBG) rest-frame UV luminosity function to investigate the onset of quenching in the early universe. The bright-end of the galaxy luminosity function typically shows an exponential decline far steeper than that of the underlying halo mass function. This is typically attributed to negative feedback from past active galactic nuclei (AGN) activity as well as dust attenuation. Constraining the abundance of bright galaxies at early times (z > 3) can provide a key insight into the mechanisms regulating star formation in galaxies. However, existing studies suffer from low number statistics and/or the inability to robustly remove stellar and AGN contaminants. In this study we take advantage of the unprecedentedly large (24 deg^2) Spitzer/HETDEX Exploratory Large Area (SHELA) field and its deep multi-wavelength photometry, which includes DECam ugriz, NEWFIRM K-band, Spitzer/IRAC, Herschel/SPIRE, and X-ray from XMM-Newton and Chandra. With SHELA’s deep imaging over a large area we are uniquely positioned to study statistically significant samples of massive galaxies at high redshifts (z > 3) when the first massive galaxies began quenching. We select our sample using photometric redshifts from the EAZY software package (Brammer et al. 2008) based on the optical and far-infrared imaging. We directly identify and remove stellar contaminants and AGN with IRAC colors and X-ray detections, respectively. By pinning down the exact shape of the bright-end of the z ~ 4 LBG luminosity function, we provide the deepest probe yet into the baryonic physics dominating star formation and quenching in the early universe.

  18. Detection of high frequency oscillations and damping from multi-slit spectroscopic observations of the corona

    CERN Document Server

    Samanta, T; Sindhuja, G; Banerjee, D

    2015-01-01

    During the total solar eclipse of 11 July 2010, multi-slit spectroscopic observations of the solar corona were performed from Easter Island, Chile. To search for high-frequency waves, observations were taken at a high cadence in the green line at 5303 A due to [Fe xiv] and the red line at 6374 A due to [Fe x]. The data are analyzed to study the periodic variations in the intensity, Doppler velocity and line width using wavelet analysis. The data with high spectral and temporal resolution enabled us to study the rapid dynamical changes within coronal structures. We find that at certain locations each parameter shows significant oscillation with periods ranging from 6 - 25 s. For the first time, we could detect damping of high-frequency oscillations with periods of the order of 10 s. If the observed damped oscillations are due to magnetohydrodynamic (MHD) waves then they can contribute significantly in the heating of the corona. From a statistical study we try to characterize the nature of the observed oscillat...

  19. The WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies

    OpenAIRE

    Riemer-Sørensen, Signe; Blake, Chris; Parkinson, David; Davis, Tamara M.; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Croton, Darren; Drinkwater, Michael J.; Forster, Karl; Gilbank, David; Gladders, Mike; Glazebrook, Karl

    2011-01-01

    The absolute neutrino mass scale is currently unknown, but can be constrained from cosmology. The WiggleZ high redshift star-forming blue galaxy sample is less sensitive to systematics from non-linear structure formation, redshift-space distortions and galaxy bias than previous surveys. We obtain a upper limit on the sum of neutrino masses of 0.60eV (95% confidence) for WiggleZ+Wilkinson Microwave Anisotropy Probe. Combining with priors on the Hubble Parameter and the baryon acoustic oscillat...

  20. Damping modeling in Timoshenko beams

    Science.gov (United States)

    Banks, H. T.; Wang, Y.

    1992-01-01

    Theoretical and numerical results of damping model studies for composite material beams using the Timoshenko theory is presented. Based on the damping models developed for Euler-Bernoulli beams, the authors develop damping methods for both bending and shear in investigation of Timoshenko beams. A computational method for the estimation of the damping parameters is given. Experimental data with high-frequency excitation were used to test Timoshenko beam equations with different types of damping models for bending and shear in various combinations.

  1. 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...

  2. Reconciling the Stellar and Nebular Spectra of High-redshift Galaxies

    Science.gov (United States)

    Steidel, Charles C.; Strom, Allison L.; Pettini, Max; Rudie, Gwen C.; Reddy, Naveen A.; Trainor, Ryan F.

    2016-08-01

    We present a combined analysis of rest-frame far-UV (FUV; 1000-2000 Å) and rest-frame optical (3600-7000 Å) composite spectra formed from very deep Keck/LRIS and Keck/MOSFIRE observations of a sample of 30 star-forming galaxies with z=2.40+/- 0.11, selected to be broadly representative of the full KBSS-MOSFIRE spectroscopic survey. Since the same massive stars are responsible for the observed FUV continuum and for the excitation of the observed nebular emission, a self-consistent stellar population synthesis model should simultaneously match the details of the FUV stellar+nebular continuum and—when inserted as the excitation source in photoionization models—predict all observed nebular emission line ratios. We find that only models including massive star binaries, having low stellar metallicity ({Z}* /{Z}⊙ ≃ 0.1) but relatively high nebular (ionized gas-phase) abundances ({Z}{{neb}}/{Z}⊙ ≃ 0.5), can successfully match all of the observational constraints. We show that this apparent discrepancy is naturally explained by highly super-solar O/Fe (≃ 4{--}5 {({{O}}/{Fe})}⊙ ), expected for a gas whose enrichment is dominated by the products of core-collapse supernovae. While O dominates the physics of the ionized gas (and thus the nebular emission lines), Fe dominates the extreme-UV (EUV) and FUV opacity and controls the mass-loss rate from massive stars, resulting in particularly dramatic effects for massive stars in binary systems. This high nebular excitation—caused by the hard EUV spectra of Fe-poor massive stars—is much more common at high redshift (z≳ 2) than low redshift due to systematic differences in the star formation history of typical galaxies. Based on data 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 NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

  3. 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.

  4. Contemporaneous broadband observations of three high-redshift BL Lac Objects

    CERN Document Server

    ,

    2016-01-01

    We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects, 3FGL J0022.1$-$1855 (z=0.689), 3FGL J0630.9$-$2406 (z >~ 1.239), and 3FGL J0811.2$-$7529 (z=0.774), detected by Fermi with relatively flat GeV spectra. By observing simultaneously in the near-IR to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the relativistic jet, we can constrain the underlying particle properties and predict the shape of the GeV Compton component. Standard extragalactic background light (EBL) models explain the high-energy absorption well, with poorer fits for high UV models. The fits show clear evidence for EBL absorption in the Fermi spectrum of our highest redshift source 3FGL J0630.9$-$2406. While synchrotron self-Compton models adequately describe the SEDs, the situation may be complicated by possible external Compton components. For 3FGL J0811.2$-$7529, we also discove...

  5. The High-Ion Content and Kinematics of Low-Redshift Lyman Limit Systems

    CERN Document Server

    Fox, Andrew J; Tumlinson, Jason; Howk, J Christopher; Tripp, Todd M; Prochaska, J Xavier; O'Meara, John M; Werk, Jessica K; Bordoloi, Rongmon; Katz, Neal; Oppenheimer, Benjamin D; Dave, Romeel

    2013-01-01

    We study the high-ionization phase and kinematics of the circumgalactic medium around low-redshift galaxies using a sample of 23 Lyman Limit Systems (LLSs) at 0.08high-ion and kinematic properties of the metal-poor and metal-rich branches. We find that metal-rich LLSs tend to show higher O VI columns and broader O VI profiles than metal-poor LLSs. The total H I line width (dv90 statistic) in LLSs is not correlated with metallicity, indicating that the H I kinematics alone cannot be used to distinguish inflow from outflow and gas recycling. Among the 17 LLSs with O VI detections, all but two show evidence of kinematic sub-structure, in the form of O VI-H I centroid offsets, multiple components, or both. Using various scenarios for how the metallicity in the high-ion and low...

  6. The relation between star formation, morphology and local density in high redshift clusters and groups

    CERN Document Server

    Poggianti, Bianca M; Finn, Rose; Bamford, Steven; De Lucia, Gabriella; Varela, Jesus; Aragon-Salamanca, Alfonso; Halliday, Claire; Noll, Stefan; Saglia, Roberto; Zaritsky, Dennis; Best, Philip; Clowe, Douglas; Milvang-Jensen, Bo; Jablonka, Pascale; Pello, Roser; Rudnick, Gregory; Simard, Luc; von der Linden, Anja; White, Simon

    2008-01-01

    We investigate how the [OII] properties and the morphologies of galaxies in clusters and groups at z=0.4-0.8 depend on projected local galaxy density, and compare with the field at similar redshifts and clusters at low-z. In both nearby and distant clusters, higher-density regions contain proportionally fewer star-forming galaxies, and the average [OII] equivalent width of star-forming galaxies is independent of local density. However, in distant clusters the average current star formation rate (SFR) in star-forming galaxies seems to peak at densities ~15-40 galaxies Mpc^{-2}. At odds with low-z results, at high-z the relation between star-forming fraction and local density varies from high- to low-mass clusters. Overall, our results suggest that at high-z the current star formation (SF) activity in star-forming galaxies does not depend strongly on global or local environment, though the possible SFR peak seems at odds with this conclusion. We find that the cluster SFR normalized by cluster mass anticorrelate...

  7. The Luminosity Function of high-redshift QSOs - A combined analysis of GOODS and SDSS

    CERN Document Server

    Fontanot, F; Monaco, P; Nonino, M; Vanzella, E; Brandt, W N; Grazian, A; Mao, J

    2006-01-01

    Aims: In this work the luminosity function of QSOs is measured in the redshift range 3.53.5. Conclusions: The estimated space density evolution of QSOs indicates a suppression of the formation and/or feeding of Supermassive Black Holes at these redshifts. The QSO contribution to the UV background is insufficient to ionize the IGM at 3.5

  8. ACCOUNTING FOR COSMIC VARIANCE IN STUDIES OF GRAVITATIONALLY LENSED HIGH-REDSHIFT GALAXIES IN THE HUBBLE FRONTIER FIELD CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Brant E.; Stark, Dan P. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ellis, Richard S. [Department of Astronomy, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Dunlop, James S.; McLure, Ross J.; McLeod, Derek, E-mail: brant@email.arizona.edu [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)

    2014-12-01

    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.

  9. 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...

  10. Weak-Line Quasars at High Redshift: Extremely High Accretion Rates or Anemic Broad-Line Regions?

    CERN Document Server

    Shemmer, Ohad; Anderson, Scott F; Brandt, W N; Diamond-Stanic, Aleksandar M; Fan, Xiaohui; Lira, Paulina; Netzer, Hagai; Plotkin, Richard M; Richards, Gordon T; Schneider, Donald P; 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 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 Gamma=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 proper...

  11. A Four-Cell Periodically HOM-Damped RF Cavity for High Current Accelerators

    CERN Document Server

    Wu, G; Wang, H

    2004-01-01

    A periodically Higher Order Mode (HOM) damped RF cavity is a weakly coupled multi-cell RF cavity with HOM couplers periodically mounted between the cells. It was studied as an alternative RF structure between the single cell cavity and superstructure cavity in high beam current application requiring strong damping of the HOMs. The acceleration mode in this design is the lowest frequency mode (Zero Mode) in the pass band, in contrast to the traditional “π” acceleration mode. The acceleration mode of a four-cell Zero Mode cavity has been studied along with the monopole and dipole HOMs. Some HOMs have been modeled in HFSS with waveguide HOM couplers, which were subsequently verified by MAFIA time domain analysis. To understand the tuning challenge for the weakly coupled cavity, ANSYS and SUPERFISH codes were used to simulate the cavity frequency sensitivity and field flatness change within proper tuning range, which will influence the design of the tuner structure. This paper presen...

  12. A high phase advance damped and detuned structure for the main linacs of CLIC

    CERN Document Server

    Khan, V.F.; Grudiev, A.; Jones, R.M.; Wuensch, W.

    2010-01-01

    The main accelerating structures for the CLIC are designed to operate at an average accelerating gradient of 100 MV/m. The accelerating frequency has been optimised to 11.994 GHz with a phase advance of 2π/3 [1] of the main accelerating mode. The moderately damped and detuned structure (DDS) design [2-3] is being studied as an alternative to the strongly damped WDS design [1]. Both these designs are based on the nominal accelerating phase advance. Here we explore high phase advance (HPA) structures in which the group velocity of the rf fields is reduced compared to that of standard (2π/3) structures. The electrical breakdown strongly depends on the fundamental mode group velocity. Hence it is expected that electrical breakdown is less likely to occur in the HPA structures. We report on a study of both the fundamental and dipole modes in a CLIC_DDS_ HPA structure, designed to operate at 5π/6 phase advance per cell. Higher order dipole modes in both the standard and HPA structures are also studied.

  13. Morphology-controlled ZnO nanowire arrays for tailored hybrid composites with high damping.

    Science.gov (United States)

    Malakooti, Mohammad H; Hwang, Hyun-Sik; Sodano, Henry A

    2015-01-14

    Hybrid fiber reinforced composites using a nanoscale reinforcement of the interface have not reached their optimal performance in practical applications due to their complex design and the challenging assembly of their multiscale components. One promising approach to the fabrication of hybrid composites is the growth of zinc oxide (ZnO) nanowire arrays on the surface of carbon fibers to provide improved interfacial strength and out of plane reinforcement. However, this approach has been demonstrated mainly on fibers and thus still requires complex processing conditions. Here we demonstrate a simple approach to the fabrication of such composites through the growth of the nanowires on the fabric. The fabricated composites with nanostructured graded interphase not only exhibit remarkable damping enhancement but also stiffness improvement. It is demonstrated that these two extremely important properties of the composite can be controlled by tuning the morphology of the ZnO nanowires at the interface. Higher damping and flexural rigidity of these composites over traditional ones offer practical high-performance composites.

  14. The Origin and Evolution of Interstellar Dust in the Local and High-redshift Universe

    Science.gov (United States)

    Dwek, Eliahu

    2012-01-01

    In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that approx. 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of sN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history .

  15. Supermassive Black Hole Seed Formation at High Redshifts: Long-Term Evolution of the Direct Collapse

    CERN Document Server

    Shlosman, Isaac; Begelman, Mitchell C; Nagamine, Kentaro

    2015-01-01

    We use cosmological adaptive mesh refinement (AMR) code Enzo zoom-in simulations to study the long term evolution of the collapsing gas within dark matter (DM) halos at high redshifts. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds at high z. To circumvent the Courant condition at small radii, we have used the sink particle method, and focus on the evolution on scales ~0.01-10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc, and with no detected fragmentation. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. Their mass never exceeds ~10^3 Mo, with the sole exception of the central seed which grows dramatically to ~ 2 x 10^6 Mo in ~2 Myr, confirming the feasibility of this path to the SMBH. The time variability of angular momentum axis in the accreted gas results in the formation of two misaligned disks --- a smal...

  16. 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...

  17. Supermassive Black Hole Formation at High Redshifts via Direct Collapse in a Cosmological Context

    CERN Document Server

    Choi, Jun-Hwan; Begelman, Mitchell C

    2014-01-01

    We study the early stage of the formation of seed SMBHs via direct collapse in DM halos, in the cosmological context. We have performed high-resolution zoom-in simulations of such collapse at high redshifts, and have compared it with gas collapse within the isolated DM halo model of Choi et al. Using the AMR code ENZO, we have resolved the formation and growth of a DM halo via cold accretion of the filamentary and diffuse gas, until its virial temperature has reached $\\sim 10^4$K, atomic cooling has turned on, and collapse has ensued. We confirm our previous result that direct collapse proceeds in two stages, although, as expected, they are not as well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing accretion rate with radius, from $\\dot M\\sim 0.1\\,M_\\odot\\,{\\rm yr^{-1}}$ at the halo virial radius to a few $M_\\odot\\,{\\rm yr^{-1}}$, just inside the scale radius $R_{\\rm s}\\sim 30$pc of the NFW DM density profile. The second stage of the runaway collapse co...

  18. The light up and early evolution of high redshift Supermassive Black Holes

    Science.gov (United States)

    Comastri, Andrea; Brusa, Marcella; Aird, James; Lanzuisi, Giorgio

    2016-07-01

    The known AGN population at z > 6 is made by luminous optical QSO hosting Supermassive Black Holes (M > 10 ^{9}solar masses), likely to represent the tip of the iceberg of the luminosity and mass function. According to theoretical models for structure formation, Massive Black Holes (M _{BH} 10^{4-7} solar masses) are predicted to be abundant in the early Universe (z > 6). The majority of these lower luminosity objects are expected to be obscured and severely underepresented in current optical near-infrared surveys. The detection of such a population would provide unique constraints on the Massive Black Holes formation mechanism and subsequent growth and is within the capabilities of deep and large area ATHENA surveys. After a summary of the state of the art of present deep XMM and Chandra surveys, at z >3-6 also mentioning the expectations for the forthcoming eROSITA all sky survey; I will present the observational strategy of future multi-cone ATHENA Wide Field Imager (WFI) surveys and the expected breakthroughs in the determination of the luminosity function and its evolution at high (> 4) and very high (>6) redshifts.

  19. A lower fragmentation mass scale for clumps in high redshift galaxies: a systematic numerical study

    CERN Document Server

    Tamburello, Valentina; Shen, Sijing; Wadsley, James

    2014-01-01

    We perform a systematic study of the effect of sub-grid physics, resolution and structural parameters on the fragmentation of gas-rich galaxy discs into massive star forming clumps due to gravitational instability. We use the state-of-the-art zoom-in cosmological hydrodynamical simulation ARGO (Fiacconi et al. 2015) to set up the initial conditions of our models, and then carry out 26 high resolution controlled SPH simulations of high-z galaxies. We find that when blast-wave feedback is included, the formation of long-lived, gravitationally bound clumps is difficult, requiring disc gas fractions of at least 50% and massive discs, which should have $V_{max} > 200$ km/s at $z \\sim 2$, more massive than the typical galaxies expected at those redshifts. Clumps have typical masses $\\sim 10^7 M_{\\odot}$. Clumps with mass $\\sim 10^8 M_{\\odot}$ are rare, as they require clump-clump merging and sustained mass accretion for a few orbital times, while normally clumps migrate inward and are tidally disrupted on the way o...

  20. Luminosities, Masses and Star Formation Rates of Galaxies at High Redshift (IAU279 conference proceedings)

    CERN Document Server

    Bunker, Andrew

    2013-01-01

    There has been great progress in recent years in discovering star forming galaxies at high redshifts (z>5), close to the epoch of reionization of the intergalactic medium (IGM). The WFC3 and ACS cameras on the Hubble Space Telescope have enabled Lyman break galaxies to be robustly identified, but the UV luminosity function and star formation rate density of this population at z=6-8 seems to be much lower than at z=2-4. High escape fractions and a large contribution from faint galaxies below our current detection limits would be required for star-forming galaxies to reionize the Universe. We have also found that these galaxies have blue rest-frame UV colours, which might indicate lower dust extinction at z>5. There has been some spectroscopic confirmation of these Lyman break galaxies through Lyman-alpha emission, but the fraction of galaxies where we see this line drops at z>7, perhaps due to the onset of the Gunn-Peterson effect (where the IGM is opaque to Lyman-alpha).

  1. High Redshift Radio Galaxies: Laboratories for Massive Galaxy and Cluster Formation in the early Universe

    CERN Document Server

    Miley, G; Taylor, G B; De Breuck, C; Cohen, A

    2009-01-01

    High redshift radio galaxies are among the largest, most luminous, most massive, and most beautiful objects in the Universe. They are generally identified from their radio emission, thought to be powered by accretion of matter onto supermassive black holes in the nuclei of their host galaxies. Observations show that they are energetic sources of radiation throughout most of the electromagnetic spectrum, including relativistic plasma, gas and dust, stars and the active galactic nuclei (AGN). 1 HzRGs are inferred to be extremely massive, including old stars (up to $\\sim$ 10$^{12}$ M$_{\\odot}$), hot gas (up to $\\sim$ 10$^{12}$ M$_{\\odot}$) and molecular gas (up to $\\sim$ 10$^{11}$ M$_{\\odot}$).Because they are highly luminous and (unlike quasars) spatially resolvable from the ground, most components of HzRGs provide important diagnostic information about the spatial distributions of processes within HzRGs and their environment. The fact that the different constituents are present in the same objects and that the...

  2. Lyman alpha emission in starbursts: implications for galaxies at high redshift

    CERN Document Server

    Mas-Hesse, J M; Tenorio-Tagle, G; Leitherer, C; Terlevich, R J; Terlevich, E

    2003-01-01

    We present the results of a high resolution UV 2-D spectroscopic survey of star forming galaxies observed with HST-STIS. Our main aim was to map the Lyman alpha profiles to learn about the gas kinematics and its relation with the escape of Lyman alpha photons and to detect extended Lyman alpha emission due to scattering in gaseous halos. We have combined our data with previously obtained UV spectroscopy on other three star-forming galaxies. We find that the P-Cygni profile is spatially extended, smooth and spans several kiloparsecs covering a region much larger than the starburst itself. We propose a scenario whereby an expanding super-shell is generated by the interaction of the combined stellar winds and supernova ejecta from the young starbursts, with an extended low density halo. The variety of observed Lyman alpha profiles both in our sample and in high redshift starbursts is explained as phases in the time evolution of the super-shell expanding into the disk and halo of the host galaxy. The observed sha...

  3. Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids

    CERN Document Server

    Dekel, Avishai; Ceverino, Daniel

    2009-01-01

    We present a simple theoretical framework for massive galaxies at high redshift, where most of the assembly and star formation occurred. The evolution is governed by the interplay between fueling by smooth and clumpy streams and stabilization by a spheroid, leading to a bimodality in galaxy type by z~3. Disks of giant clumps and high star formation rate (SFR) form when the streams are smoother than average. The streams maintain a dense disk that undergoes gravitational fragmentation into several giant clumps, each a few percent of the disk mass. The disk may reach a disk-to-total mass ratio d~0.5 due to the dark-matter halo before it settles into a steady state with a slowly growing bulge, d=0.5-0.25. The clump interactions self-regulate an unstable disk with a dispersion-to-rotation ratio sigma_r/V=0.3-0.15. Encounters and dynamical friction induce inward clump migration in 10 dynamical times, ~0.5Gyr, while the disk expands in response. The inflowing smooth streams replenish the draining disk and prolong th...

  4. 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...

  5. Formation of High-redshift (z>6) Quasars Driven by Nuclear Starbursts

    CERN Document Server

    Kawakatu, Nozomu

    2009-01-01

    Based on the physical model of a supermassive black hole (SMBH) growth via gas accretion in a circumnuclear disk (CND) proposed by Kawakatu & Wada (2008), we describe the formation of high-$z$ ($z > 6$) quasars (QSOs) whose BH masses are M_{BH}> 10^{9} M_{\\odot}. We derive the necessary conditions to form QSOs at z > 6 by only gas accretion: (i) A large mass supply with M_{sup} > 10^{10}M_{\\odot} from host galaxies to CNDs, because the final BH mass is only 1-10% of the total supplied mass from QSO hosts. (ii) High star formation efficiency for a rapid BH growth. We also find that if the BH growth is limited by the Eddington accretion, the final BH mass is greatly suppressed. Thus, the super-Eddington growth is required for the QSO formation. The evolution of the QSO luminosity depends on the redshift z_{i} at which accretion onto a seed BH is initiated. In other words, the brighter QSOs at z >6 favor the late growth of SMBHs (i.e., z_{i}=10) rather than early growth (i.e., z_{i}=30). Moreover, we predict...

  6. 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...

  7. 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 ...

  8. Probing Pre-galactic Metal Enrichment with High-Redshift Gamma-Ray Bursts

    CERN Document Server

    Wang, F Y; Greif, Thomas H; Stacy, Athena; Dai, Z G; Loeb, Abraham; Cheng, K S

    2012-01-01

    We explore high-redshift gamma-ray bursts (GRBs) as promising tools to probe pre-galactic metal enrichment. We utilize the bright afterglow of a Pop III GRB exploding in a primordial dwarf galaxy as a luminous background source, and calculate the strength of metal absorption lines that are imprinted by the first heavy elements in the intergalactic medium (IGM). To derive the GRB absorption line diagnostics, we use an existing highly-resolved simulation of the formation of a first galaxy which is characterized by the onset of atomic hydrogen cooling in a halo with virial temperature >10^4 K. We explore the unusual circumburst environment inside the systems that hosted Pop III stars, modeling the density evolution with the self-similar solution for a champagne flow. For minihalos close to the cooling threshold, the circumburst density is roughly proportional to (1+z) with values of about a few cm^{-3}. In more massive halos, corresponding to the first galaxies, the density may be larger, n>100 cm^{-3}. The resu...

  9. Star Formation Histories of Nearby Galaxies and the Connection to High Redshift

    CERN Document Server

    Tolstoy, E

    1998-01-01

    It is an obvious statement that all the galaxies we see today in and around our Local Group have been forming and evolving for a significant fraction of the age of the Universe. It is not a great leap of logic to further state that the manner in which they have formed and evolved must be fairly representative of these processes in general. Unless of course we would like to assume that our local region of space is in some way peculiar for which there is no evidence. In other words, if we are able to determine accurate star formation histories for the nearby galaxies back to the ages of the oldest globular clusters then we will also obtain a representative picture of how galaxies have evolved from the earliest times, and predict what nearby galaxies looked like at intermediate and high redshifts. Deep, precision, multi-colour photometry of resolved stellar populations in external galaxies can uniquely determine the star formation histories of nearby galaxies going back many Gyrs. Hubble Space Telescope and high...

  10. On the Kennicutt-Schmidt relation of low-metallicity high-redshift galaxies

    CERN Document Server

    Gnedin, Nickolay Y

    2009-01-01

    We present results of self-consistent, high-resolution cosmological simulations of galaxy formation at z~3. The simulations employ recently developed recipe for star formation based on the local abundance of molecular hydrogen, which is tracked self-consistently during the course of simulation. The phenomenological H2 formation model accounts for the effects of dissociating UV radiation of stars in each galaxy, as well as self-shielding and shielding of H2 by dust, and therefore allows us to explore effects of lower metallicities and higher UV fluxes prevalent in high redshift galaxies on their star formation. We compare stellar masses, metallicities, and star formation rates of the simulated galaxies to available observations of the Lyman Break Galaxies (LBGs) and find a reasonable agreement. We find that the Kennicutt-Schmidt (KS) relation exhibited by our simulated galaxies at z~3 is substantially steeper and has a lower amplitude than the z=0 relation at Sigma_gas < 100 Msun/pc^2. The predicted relatio...

  11. 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.

  12. A revised host galaxy association for GRB 020819B: a high-redshift dusty starburst, not a low-redshift gas-poor spiral

    Science.gov (United States)

    Perley, Daniel A.; Krühler, Thomas; Schady, Patricia; Michałowski, Michał J.; Thöne, Christina C.; Petry, Dirk; Graham, John F.; Greiner, Jochen; Klose, Sylvio; Schulze, Steve; Kim, Sam

    2017-02-01

    The purported spiral host galaxy of GRB 020819B at z = 0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: Optical spectroscopy of this host provided evidence that gamma-ray bursts (GRBs) can form even at high metallicities, whereas millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from the Very Large Telescope (Multi Unit Spectroscopic Explorer and X-shooter), which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star forming, dusty galaxy at z = 1.9621. The revised redshift naturally explains the apparent non-detection of CO(3-2) line emission at the afterglow site from the Atacama Large Millimetre Observatory. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at a super-Solar metallicity.

  13. Far Infrared Spectroscopy of the Nearby Analogues of High-Redshift Galaxies

    Science.gov (United States)

    Hayes, Matthew

    2014-10-01

    We propose far infrared emission line spectroscopy of a sample of 23 local star-forming galaxies, drawn from the Lyman alpha Reference Sample (LARS), for which we have unrivalled high-resolution imaging and spectroscopy from HST, and 21cm HI observations from VLA+GMRT. Moreover the galaxies are selected as the close analogues of the high-redshift Lyman-break galaxies and Spitzer+Herschel selected galaxies found in extragalactic deep fields. The science goal of LARS is to determine what governs the escape of Lyman alpha (Lya) photons from galaxies, and thereby aid interpretation of high-z observations where Lya is the most used spectral probe. However given its clean selection and multiwavelength nature, LARS can equally well improve our understanding of FIR line observations of high-z galaxies. The target emission lines in this proposal are [CII], [OI], and [OIII] at 158, 63, and 88 micron, respectively. The motivations are that these lines: 1. are of increasing interest at high-z as new sensitive submm/radio interferometers come online 2. are proposed quantitative tracers of star formation rates, but their utility must be proven in appropriately analogous well-studied galaxies 3. when combined with models of photodissociation regions, enable estimates of the density and mass of PDR gas and provide vital constraints on our Lya radiative transfer models of galaxies. 4. provide uniquely robust estimates of nebular extinction and metallicity when combined with our optical IFU data. Astrophysical applications are many, especially when combined with the array of existing data. Specifically they will provide vital constraints on ISM structure, that are required for understanding the emission of the cosmologically vital Lya emission line. Moreover, SFR calibrations will be tested in star forming environments that resemble those of early galaxies and the legacy value of the sample is hard to overstate.

  14. 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.

  15. Exploring the chemical link between local ellipticals and their high-redshift progenitors

    CERN Document Server

    Leja, Joel; 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 Forster; Nelson, Erica; Patel, Shannon G

    2013-01-01

    We present Keck/MOSFIRE K-band spectroscopy of the first mass-selected sample of galaxies at $z\\sim2.3$. Targets are selected from the 3D-HST Treasury survey. The six detected galaxies have a mean [NII]$\\lambda$6584/H\\alpha$ ratio of $0.27\\pm0.01$, 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 [NII]/H\\alpha$ ratios depends on the calibration method, and ranges from 12+log(O/H)$_{gas}=8.57$ for the {Pettini} & {Pagel} (2004) calibration to 12+log(O/H)$_{gas}= 8.87$ for the {Maiolino} {et al.} (2008) 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 $z\\sim2.3$ galaxies if the {Maiolino} {et al.} (2008) calibration is used. This suggests that these high-redshift star forming galaxies may be progenitors of today's massive early-type galaxies...

  16. Modeling Gamma-Ray Attenuation in High-Redshift GeV Spectra

    CERN Document Server

    Gilmore, Rudy C; Primack, Joel R; Somerville, Rachel S

    2008-01-01

    We present two models for the cosmological UV background light, and calculate the opacity of GeV gamma--rays out to redshift 9. The contributors to the background include 2 possible quasar emissivities, and output from star--forming galaxies as determined by recent a semi--analytic model (SAM) of structure formation. The SAM used in this work is based upon a hierarchical build-up of structure in a $\\Lambda$CDM universe and is highly successful in reproducing a variety of observational parameters. Above 1 Rydberg energy, ionizing radiation is subject to reprocessing by the IGM, which we treat using our radiative transfer code, CUBA. The two models for quasar emissivity differing above z = 2.3 are chosen to match the ionization rates observed using flux decrement analysis and the higher values of the line-of-sight proximity effect. We also investigate the possibility of a flat star formation rate density at z $>5$. We conclude that observations of gamma--rays from 10 to 100 GeV by Fermi (GLAST) and the next gen...

  17. 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...

  18. 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...

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

    Directory of Open Access Journals (Sweden)

    Kristóf Rozgonyi

    2016-08-01

    Full Text Available 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.

  20. 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...

  1. 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...

  2. 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.

  3. Resolved gas kinematics in a sample of low-redshift high star-formation rate galaxie

    CERN Document Server

    Varidel, Matthew; Croom, Scott; Owers, Matt; Sadler, Elaine

    2016-01-01

    We have used integral field spectroscopy of a sample of six nearby (z~0.01-0.04) high star-formation rate (SFR~10-40 solar masses per year) galaxies to investigate the relationship between local velocity dispersion and star formation rate on sub-galactic scales. The low redshift mitigates, to some extent, the effect of beam smearing which artificially inflates the measured dispersion as it combines regions with different line-of-sight velocities into a single spatial pixel. We compare the parametric maps of the velocity dispersion with the Halpha flux (a proxy for local star-formation rate), and the velocity gradient (a proxy for the local effect of beam smearing). We find, even for these very nearby galaxies, the Halpha velocity dispersion correlates more strongly with velocity gradient than with Halpha flux - implying that beam smearing is still having a significant effect on the velocity dispersion measurements. We obtain a first-order non parametric correction for the unweighted and flux weighted mean vel...

  4. 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.

  5. 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...

  6. 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...

  7. 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...

  8. Long Gamma-Ray Bursts and Their Host Galaxies at High Redshift

    CERN Document Server

    Lapi, A; Bosnjak, Z; Celotti, A; Bressan, A; Granato, G L; Danese, L

    2008-01-01

    Motivated by the recent observational and theoretical evidence that long Gamma-Ray Bursts (GRBs) are likely associated with low metallicity, rapidly rotating massive stars, we examine the cosmological star formation rate (SFR) below a critical metallicity Z_crit~Z_sun/10 - Z_sun/5, to estimate the event rate of high-redshift long GRB progenitors. To this purpose, we exploit a galaxy formation scenario already successfully tested on a wealth of observational data on (proto)spheroids, Lyman break galaxies, Lyman alpha emitters, submm galaxies, quasars, and local early-type galaxies. We find that the predicted rate of long GRBs amounts to about 300 events/yr/sr, of which about 30 per cent occur at z>~6. Correspondingly, the GRB number counts well agree with the bright SWIFT data, without the need for an intrinsic luminosity evolution. Moreover, the above framework enables us to predict properties of the GRB host galaxies. Most GRBs are associated with low mass galaxy halos M_H~10^12 M_sun have larger extinction ...

  9. Physical Conditions in a Young, Unreddened, Low Metallicity Galaxy at High Redshift

    CERN Document Server

    Erb, Dawn K; Shapley, Alice E; Steidel, Charles C; Law, David R; Reddy, Naveen A

    2010-01-01

    Increasingly large samples of galaxies are now being discovered at redshifts z~5-6 and higher. Many of these objects are inferred to be young, low in mass, and relatively unreddened, but detailed analysis of their high quality spectra will not be possible until the advent of future facilities. In this paper we shed light on the physical conditions in a plausibly similar low mass galaxy by presenting the analysis of the rest-frame optical and UV spectra of Q2343-BX418, an L* galaxy at z=2.3 with a very low mass-to-light ratio and unusual properties: BX418 is young (<100 Myr), low mass (M_star ~ 10^9 Msun), low in metallicity (Z ~ 1/6 Zsun), and unreddened (E(B-V)~0.02, UV continuum slope beta=-2.1). We infer a metallicity 12+log(O/H)=7.9 +/- 0.2 from the rest-frame optical emission lines. We also determine the metallicity via the direct, electron temperature method, using the ratio O III] 1661, 1666/[O III] 5007 to determine the electron temperature and finding 12+ log(O/H)=7.8 +/- 0.1. These measurements p...

  10. GRB afterglows: Dust extinction properties from the low to high redshift universe

    Science.gov (United States)

    Zafar, Tayyaba

    2016-11-01

    Long-duration Gamma-ray bursts (GRBs) are excellent probes to study dust extinction due to their occurrence in star-forming regions and having simple synchrotron emission spectra. Inclusion of spectroscopic data to the GRB X-ray to the infrared spectral energy distribution (SED) could better define the continuum and confirm extinction feature. A preliminary SED analysis of GRB afterglows targeted with the VLT/X-Shooter spectrograph finds that all the 60% of extinguished bursts fit-well with featureless extinction curves. The longer wavelength coverage from ultraviolet to the near-infrared of X-Shooter helps to derive individual extinction curves and determine the total-to-selective extinction, RV precisely, suggesting extinction curves steeper (with a mean of RV = 2.66 ± 0.10) than the Small Magellanic Cloud. Moreover, addition of more data to the study of dust-to-metals ratios in GRB afterglows, quasar absorbers, and multiply lensed galaxies still shows the dust-to-metals ratios close to the Galactic value (with a mean value of log - 21.2cm-2mag-1), hinting short time delay between metals and dust formation. Such studies demonstrate the strength of using GRB afterglows to study dust origin and its properties the from low to high redshift Universe.

  11. Lyman {\\alpha} radiative transfer in the high-redshift, dusty Universe

    CERN Document Server

    Laursen, Peter

    2010-01-01

    The significance of the Ly{\\alpha} emission line as a probe of the high-redshift Universe has long been established. Originating mainly in the vicinity of young, massive stars and in association with accretion of large bulks of matter, it is ideal for detecting young galaxies, the fundamental building blocks of our Universe. Since many different processes shape the spectrum and the spatial distribution of the Ly{\\alpha} photons in various ways, a multitude of physical properties of galaxies can be unveiled. However, this also makes the interpretation of Ly{\\alpha} observations notoriously difficult. Because Ly{\\alpha} is a resonant line, it scatters on neutral hydrogen, having its path length from the source to our telescopes vastly increased, and taking it through regions of unknown physical conditions. In this work, a numerical code capable of calculating realistically the radiative transfer of Ly{\\alpha} is presented. The code is capable of performing the radiative transfer in an arbitrary and adaptively r...

  12. 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

  13. Diffuse x-ray emission around high-redshift, radio-loud QSOs

    CERN Document Server

    Bartelmann, M; Matthias Bartelmann; Peter Schneider

    1994-01-01

    We announce the detection of correlations on angular scales of \\ga10' between optically bright, high-redshift, radio-loud QSOs with diffuse X-ray emission seen by ROSAT in the {\\it All-Sky Survey}. These correlations reach significance levels of up to 99.8\\%. A comparison of the results with a sample of control fields, bootstrapping analyses, and Kolmogorov-Smirnov tests provide unambiguous support for the statistical significance of the correlations found. We argue that the detected enhanced diffuse X-ray emission is in the foreground of the QSOs, and that it is probably due to galaxy clusters which magnify the QSOs by their gravitational lensing effect, thereby giving rise to a magnification bias in the background source sample. A comparison of the results presented below with correlations previously found between the same QSO sample and either Lick or IRAS galaxies provides further evidence for this interpretation, and identifies positions in the sky where weak gravitational lensing may be detected by sear...

  14. Fluctuations in the High-Redshift Lyman-Werner and Lyman-alpha Radiation Backgrounds

    CERN Document Server

    Holzbauer, Lauren N

    2011-01-01

    We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons (11.5-13.6 eV) are of particular interest because they dissociate molecular hydrogen, the primary coolant in the first minihalos. By using a variation of the halo model, we efficiently generate power spectra for any choice of radiation background. We find that the LW power spectrum typically traces the matter power spectrum at large scales but turns over at the scale corresponding to the effective `horizon' of LW photons (~100 comoving Mpc), unless the sources are extremely rare. The series of horizons that characterize the Lyman-alpha flux profile shape the fluctuations of that background in a similar fashion, though those imprints are washed out once one considers fluctuations in the brightness temperature of the 21-cm signal. The Lyman-alpha background strongly affects the redshi...

  15. 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...

  16. Disk formation and the origin of clumpy galaxies at high redshift

    CERN Document Server

    Agertz, Oscar; Moore, Ben

    2009-01-01

    Observations of high redshift galaxies have revealed a multitude of large clumpy rapidly star-forming galaxies. Their formation scenario and their link to present day spirals is still unknown. In this Letter we perform AMR simulations of disk formation in a cosmological context that are unrivaled in terms of mass and spatial resolution. We find that the so called "chain-galaxies" and "clump-clusters" are a natural outcome of early epochs of enhanced gas accretion from cold dense streams as well as tidally and ram-pressured stripped material from minor mergers and satellites. Through interaction with the hot halo gas, this freshly accreted cold gas settles into a large disk-like system, not necessarily aligned to an older stellar component, that undergoes fragmentation and subsequent star formation, forming large clumps in the mass range 10^7-10^9 M_sun. Galaxy formation is a complex process at this important epoch when most of the central baryons are being acquired through a range of different mechanisms - we...

  17. A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186.

    Science.gov (United States)

    van Dokkum, Pieter G; Kriek, Mariska; Franx, Marijn

    2009-08-06

    Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the past ten billion years (10 Gyr). A key test of these results is a determination of the stellar kinematics of one of the compact galaxies: if the sizes of these objects are as extreme as has been claimed, their stars are expected to have much higher velocities than those in present-day galaxies of the same mass. Here we report a measurement of the stellar velocity dispersion of a massive compact galaxy at redshift z = 2.186, corresponding to a look-back time of 10.7 Gyr. The velocity dispersion is very high at km s(-1), consistent with the mass and compactness of the galaxy inferred from photometric data. This would indicate significant recent structural and dynamical evolution of massive galaxies over the past 10 Gyr. The uncertainty in the dispersion was determined from simulations that include the effects of noise and template mismatch. However, we cannot exclude the possibility that some subtle systematic effect may have influenced the analysis, given the low signal-to-noise ratio of our spectrum.

  18. 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...

  19. Breaking through the high redshift bottleneck of Observational Hubble parameter Data: The Sandage-Loeb signal Scheme

    CERN Document Server

    Yuan, Shuo; Zhang, Tong-Jie

    2013-01-01

    We propose a valid scheme to measure the Hubble parameter $H(z)$ at high redshifts by detecting the Sandage-Loeb signal (SL signal) which can be realized by the next generation extremely large telescope. It will largely extend the current observational Hubble parameter data (OHD) towards the redshift region of $z \\in [2.0,5.0]$, the so-called "redshift desert", where other dark energy probes are hard to provide useful information of the cosmic expansion. Quantifying the ability of this future measurement by simulating observational data for a CODEX (COsmic Dynamics and EXo-earth experiment)-like survey and constraining various cosmological models, we find that the SL signal scheme brings the redshift upper-limit of OHD from $z_\\mathrm{max}=2.3$ to $z_\\mathrm{max}\\simeq 5.0$, provides more accurate constraints on different dark energy models, and greatly changes the degeneracy direction of the parameters. For the $\\Lambda$CDM case, the accuracy of $\\Omega_m$ is improved by $58\\%$ and the degeneracy between $\\O...

  20. The high-ion content and kinematics of low-redshift Lyman limit systems

    Energy Technology Data Exchange (ETDEWEB)

    Fox, Andrew J.; Tumlinson, Jason; Bordoloi, Rongmon [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Lehner, Nicolas; Howk, J. Christopher [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Tripp, Todd M.; Katz, Neal [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Prochaska, J. Xavier; Werk, Jessica K. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); O' Meara, John M. [Department of Physics, Saint Michael' s College, One Winooski Park, Colchester, VT 05439 (United States); Oppenheimer, Benjamin D. [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Davé, Romeel, E-mail: afox@stsci.edu [University of the Western Cape, Robert Sobukwe Road, Bellville 7535 (South Africa)

    2013-12-01

    We study the high-ion content and kinematics of the circumgalactic medium around low-redshift galaxies using a sample of 23 Lyman limit systems (LLSs) at 0.08 < z < 0.93 observed with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. In Lehner et al., we recently showed that low-z LLSs have a bimodal metallicity distribution. Here we extend that analysis to search for differences between the high-ion and kinematic properties of the metal-poor and metal-rich branches. We find that metal-rich LLSs tend to show higher O VI columns and broader O VI profiles than metal-poor LLSs. The total H I line width (Δv {sub 90} statistic) in LLSs is not correlated with metallicity, indicating that the H I kinematics alone cannot be used to distinguish inflow from outflow and gas recycling. Among the 17 LLSs with O VI detections, all but two show evidence of kinematic sub-structure, in the form of O VI-H I centroid offsets, multiple components, or both. Using various scenarios for how the metallicities in the high-ion and low-ion phases of each LLS compare, we constrain the ionized hydrogen column in the O VI phase to lie in the range log N(H II) ∼ 17.6-20. The O VI phase of LLSs is a substantial baryon reservoir, with M(high-ion) ∼ 10{sup 8.5-10.9} (r/150 kpc){sup 2} M {sub ☉}, similar to the mass in the low-ion phase. Accounting for the O VI phase approximately doubles the contribution of low-z LLSs to the cosmic baryon budget.

  1. High-redshift quasars host galaxies: is there a stellar mass crisis?

    CERN Document Server

    Valiante, Rosa; Salvadori, Stefania; Gallerani, Simona

    2014-01-01

    We investigate the evolutionary properties of a sample of quasars at 5damping the star formation and un-obscuring the line of sight toward the QSO. In this scenario, all the QSOs hosts have final stellar masses in the range $(4-6)\\times 10^{11} M_{sun}$, a factor 3-30 larger than the upper limits allowed by the observations. We discuss alternative scenarios to alleviate this apparent tension: the most likely explanation resides in the large uncertainties that still affect dynamical mass measurements in these high-z galaxies. In addition, during the transition between the starburs...

  2. Herschel-ATLAS: Properties of dusty massive galaxies at low and high redshifts

    CERN Document Server

    Rowlands, K; Dye, S; Aragón-Salamanca, A; Maddox, S; da Cunha, E; Smith, D J B; Bourne, N; Eales, S; Gomez, H L; Smail, I; Alpaslan, M; Clark, C J R; Driver, S; Ibar, E; Ivison, R J; Robotham, A; Smith, M W L; Valiante, E

    2014-01-01

    We present a comparison of the physical properties of a rest-frame $250\\mu$m selected sample of massive, dusty galaxies from $01$ SMGs have an average SFR of $390^{+80}_{-70}\\,$M$_\\odot$yr$^{-1}$ which is 120 times that of the low-redshift sample matched in stellar mass to the SMGs (SFR$=3.3\\pm{0.2}$ M$_\\odot$yr$^{-1}$). The SMGs harbour a substantial mass of dust ($1.2^{+0.3}_{-0.2}\\times{10}^9\\,$M$_\\odot$), compared to $(1.6\\pm0.1)\\times{10}^8\\,$M$_\\odot$ for low-redshift dusty galaxies. At low redshifts the dust luminosity is dominated by the diffuse ISM, whereas a large fraction of the dust luminosity in SMGs originates from star-forming regions. At the same dust mass SMGs are offset towards a higher SFR compared to the low-redshift H-ATLAS galaxies. This is not only due to the higher gas fraction in SMGs but also because they are undergoing a more efficient mode of star formation, which is consistent with their bursty star-formation histories. The offset in SFR between SMGs and low-redshift galaxies is s...

  3. Damping Properties vs. Structure Fineness of the High-zinc Aluminum Alloys

    Directory of Open Access Journals (Sweden)

    Krajewskia W.K.

    2012-09-01

    Full Text Available The subject of this study is the presentation of relation between the degree of structure fineness and ultrasonic wave damping coefficient for the high-zinc aluminium alloys represented in this study by the sand mould cast alloy Al - 20 wt% Zn (AlZn20. The studied alloy was refined with a modifying (Al,Zn-Ti3 ternary master alloy, introducing Ti in the amount of 400 pm into metal. Based on the analysis of the initial and modified alloy macrostructure images and ultrasonic testing, it was found that the addition of (Al,Zn-Ti3 master alloy, alongside a significant fragmentation of grains, does not reduce the coefficient of ultrasonic waves with a frequency of 1 MHz.

  4. THE FUNDAMENTAL PLANE OF DAMPED Ly{alpha} SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Neeleman, Marcel; Wolfe, Arthur M. [Department of Physics and Center for Astrophysics and Space Sciences, UCSD, La Jolla, CA 92093 (United States); Prochaska, J. Xavier [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Rafelski, Marc, E-mail: mneeleman@physics.ucsd.edu [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States)

    2013-05-20

    Using a sample of 100 H I-selected damped Ly{alpha} (DLA) systems, observed with the High Resolution Echelle Spectrometer on the Keck I telescope, we present evidence that the scatter in the well-studied correlation between the redshift and metallicity of a DLA is largely due to the existence of a mass-metallicity relationship at each redshift. To describe the fundamental relations that exist between redshift, metallicity, and mass, we use a fundamental plane description, which is described by the following equation: [M/H] = (- 1.9 {+-} 0.5) + (0.74 {+-} 0.21) {center_dot} log {Delta}v{sub 90} - (0.32 {+-} 0.06) {center_dot} z. Here, we assert that the velocity width, {Delta}v{sub 90}, which is defined as the velocity interval containing 90% of the integrated optical depth, traces the mass of the underlying dark matter halo. This description provides two significant improvements over the individual descriptions of the mass-metallicity correlation and metallicity-redshift correlation. Firstly, the fundamental equation reduces the scatter around both relationships by about 20%, providing a more stringent constraint on numerical simulations modeling DLAs. Secondly, it confirms that the dark matter halos that host DLAs satisfy a mass-metallicity relationship at each redshift between redshifts 2 through 5.

  5. A Novel DFIG Damping Control for Power System with High Wind Power Penetration

    Directory of Open Access Journals (Sweden)

    Aiguo Tan

    2016-07-01

    Full Text Available Aiming at the fact that large-scale penetration of wind power will to some extent weaken the small signal stability of power systems, in this paper, the dynamic model of a doubly fed induction generator (DFIG is established firstly, to analyze the impact of wind generation on power oscillation damping. Then, based on the conventional maximum power point tracking control of variable speed wind turbine, a supplementary control scheme is proposed to increase the damping of power system. To achieve best performance, parameters of the damping control are tuned by using a genetic algorithm. Results of eigenvalue analysis and simulations demonstrate the effectiveness of supplementary damping control with fixed wind speed. At last, due to the problem that fluctuation of output power of wind generators would cause the unstable performance of the DFIG damping controller above, a new algorithm that adapts to the wind variation is added to the supplementary damping control scheme. Results of the simulation show that an improved damping control scheme can stably enhance system damping under various wind speeds and has higher practical value.

  6. Clustering of galaxies near damped Lyman-alpha systems with (z) = 2.6

    Science.gov (United States)

    Wolfe, A. M

    1993-01-01

    The galaxy two-point correlation function, xi, at (z) = 2.6 is determined by comparing the number of Ly-alpha-emitting galaxies in narrowband CCD fields selected for the presence of damped L-alpha absorption to their number in randomly selected control fields. Comparisons between the presented determination of (xi), a density-weighted volume average of xi, and model predictions for (xi) at large redshifts show that models in which the clustering pattern is fixed in proper coordinates are highly unlikely, while better agreement is obtained if the clustering pattern is fixed in comoving coordinates. Therefore, clustering of Ly-alpha-emitting galaxies around damped Ly-alpha systems at large redshifts is strong. It is concluded that the faint blue galaxies are drawn from a parent population different from normal galaxies, the presumed offspring of damped Ly-alpha systems.

  7. 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.

  8. The parameter of the dark energy equation of state for high redshifts

    Energy Technology Data Exchange (ETDEWEB)

    Montiel, Ariadna; Breton, Nora, E-mail: amontiel@fis.cinvestav.mx, E-mail: nora@fis.cinvestav.mx [Physics Department, Centro de Investigacion y de Estudios Avanzados del I.P.N., Mexico City (Mexico)

    2011-09-22

    We study the behavior of the parameter w(z) of the dark-energy equation of state, P{sub x} = w(z){rho}{sub x}, as function of the redshift data from GRBs, to check its deviations from its most accepted value of -1. To this end we first find a reasonable calibration for the GRB in order to extract the luminosity distance d{sub L} as a function of the redshift. Then we proceed to calculate the Hubble function H(z) and w(z).

  9. Validation of High-Resolution CFD Method for Slosh Damping Extraction of Baffled Tanks

    Science.gov (United States)

    Yang, H. Q.; West, Jeff

    2016-01-01

    Determination of slosh damping is a very challenging task as there is no analytical solution. The damping physics involve the vorticity dissipation which requires the full solution of the nonlinear Navier-Stokes equations. As a result, previous investigations and knowledge were mainly carried out by extensive experimental studies. A Volume-Of-Fluid (VOF) based CFD program developed at NASA MSFC was applied to extract slosh damping in a baffled tank from the first principle. First, experimental data using water with subscale smooth wall tank were used as the baseline validation. CFD simulation was demonstrated to be capable of accurately predicting natural frequency and very low damping value from the smooth wall tank at different fill levels. The damping due to a ring baffle at different liquid fill levels from barrel section and into the upper dome was then investigated to understand the slosh damping physics due to the presence of a ring baffle. Based on this study, the Root-Mean-Square error of our CFD simulation in estimating slosh damping was less than 4.8%, and the maximum error was less than 8.5%. Scalability of subscale baffled tank test using water was investigated using the validated CFD tool, and it was found that unlike the smooth wall case, slosh damping with baffle is almost independent of the working fluid and it is reasonable to apply water test data to the full scale LOX tank when the damping from baffle is dominant. On the other hand, for the smooth wall, the damping value must be scaled according to the Reynolds number. Comparison of experimental data, CFD, with the classical and modified Miles equations for upper dome was made, and the limitations of these semi-empirical equations were identified.

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

    Science.gov (United States)

    Bieri, Rebekka; Dubois, Yohan; Rosdahl, Joakim; Wagner, Alexander; Silk, Joseph; Mamon, Gary A.

    2016-09-01

    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 146 erg s-1 can drive large-scale winds with velocities of 102 - 103 km s-1 and mass outflow rates around 10^3 M_⊙ yr^{-1} 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, quickly declines as the central gas cloud expands and breaks up, allowing the radiation to escape through low gas density channels. The typical number of multi-scattering events for an IR photon is only about a quarter of the mean optical depth from the center of the cloud. Our models account for the observed outflow rates of ˜ 500-1000 M_{⊙} {yr}^{-1} and high velocities of ˜ 10^3 km s^{-1}, favouring winds that are energy-driven via extremely fast nuclear outflows, interpreted here as being IR-radiatively-driven winds.

  11. High-redshift supernova rates measured with the gravitational telescope A 1689

    Science.gov (United States)

    Petrushevska, T.; Amanullah, R.; Goobar, A.; Fabbro, S.; Johansson, J.; Kjellsson, T.; Lidman, C.; Paech, K.; Richard, J.; Dahle, H.; Ferretti, R.; Kneib, J. P.; Limousin, M.; Nordin, J.; Stanishev, V.

    2016-10-01

    Aims: We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z = 0.18, which is one of the most powerful gravitational telescopes that nature provides. Methods: 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. Results: Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of 0.671 formula>math id="mml_eq2" type="inline">10-12 SNe L⊙,B-1 yr-1math>formula->), where the error bars indicate 1σ confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10+0.13-0.096±0.02 in SNuM h2 (SNuM ≡10-12SNe M-1⊙ yr-1). Furthermore, we explore the optimal future survey for improving the core-collapse supernova rate measurements at z ≳ 2 using gravitational telescopes, and for detections with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects. Conclusions: Massive clusters can be used as gravitational telescopes to significantly expand the survey range of supernova searches, with important implications for the study of the high-z transient Universe. Based on observations made with European Southern Observatory (ESO) telescopes at the Paranal Observatory under programme ID 082.A-0431; 0.83.A-0398, 091.A-0108 and ID 093.A-0278, PI: A. Goobar.The deep average image (FITS file) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A54

  12. Large turbulent reservoirs of cold molecular gas around high-redshift starburst galaxies

    Science.gov (United States)

    Falgarone, E.; Zwaan, M. A.; Godard, B.; Bergin, E.; Ivison, R. J.; Andreani, P. M.; Bournaud, F.; Bussmann, R. S.; Elbaz, D.; Omont, A.; Oteo, I.; Walter, F.

    2017-08-01

    Starburst galaxies at the peak of cosmic star formation are among the most extreme star-forming engines in the Universe, producing stars over about 100 million years (ref. 2). The star-formation rates of these galaxies, which exceed 100 solar masses per year, require large reservoirs of cold molecular gas to be delivered to their cores, despite strong feedback from stars or active galactic nuclei. Consequently, starburst galaxies are ideal for studying the interplay between this feedback and the growth of a galaxy. The methylidyne cation, CH+, is a most useful molecule for such studies because it cannot form in cold gas without suprathermal energy input, so its presence indicates dissipation of mechanical energy or strong ultraviolet irradiation. Here we report the detection of CH+ (J = 1–0) emission and absorption lines in the spectra of six lensed starburst galaxies at redshifts near 2.5. This line has such a high critical density for excitation that it is emitted only in very dense gas, and is absorbed in low-density gas. We find that the CH+ emission lines, which are broader than 1,000 kilometres per second, originate in dense shock waves powered by hot galactic winds. The CH+ absorption lines reveal highly turbulent reservoirs of cool (about 100 kelvin), low-density gas, extending far (more than 10 kiloparsecs) outside the starburst galaxies (which have radii of less than 1 kiloparsec). We show that the galactic winds sustain turbulence in the 10-kiloparsec-scale environments of the galaxies, processing these environments into multiphase, gravitationally bound reservoirs. However, the mass outflow rates are found to be insufficient to balance the star-formation rates. Another mass input is therefore required for these reservoirs, which could be provided by ongoing mergers or cold-stream accretion. Our results suggest that galactic feedback, coupled jointly to turbulence and gravity, extends the starburst phase of a galaxy instead of quenching it.

  13. Damped Lyman-α Systems

    Science.gov (United States)

    Petitjean, P.; Ledoux, C.

    Recently, Prochaska & Wolfe (1997) have used Keck spectra of 17 DLA absorbers to investigate the kinematics of the neutral gas using unsaturated low excitation transitions such as Si iiλ 1808. They show that the absorption profiles are inconsistent with models of galactic haloes with random motions, spherically infalling gas and slowly rotating hot disks. The CDM model (Kauffmann 1996) is rejected as it produces disks with rotation velocities too small to account for the large observed velocity broadening of the absorption lines. Models of thick disks (h ~0.3 R, where h is the vertical scale and R the radius) with large rotational velocity (v 225kms-1) can reproduce the data. By combining new data on five damped systems with information gathered in the literature, we study the kinematics of the low and high-ionization phases in a sample of 26 damped Lyman-α systems in the redshift range 1.17 - 4.38. We show that the broader the line the more asymmetric, as expected in case rotation dominates the line broadening. However this correlation does not hold for velocities larger than 150 km/s indicating that evidence for rotational motions if any is restricted to velocity broadenings Δ V 200kms-1 are peculiar with kinematics consistent with random motions. They show sub-systems as those expected if the objects are in the process of merging.

  14. MARZ: Redshifting Program

    Science.gov (United States)

    Hinton, Samuel

    2016-05-01

    MARZ analyzes objects and produces high quality spectroscopic redshift measurements. Spectra not matched correctly by the automatic algorithm can be redshifted manually by cycling automatic results, manual template comparison, or marking spectral features. The software has an intuitive interface and powerful automatic matching capabilities on spectra, and can be run interactively or from the command line, and runs as a Web application. MARZ can be run on a local server; it is also available for use on a public server.

  15. A novel high-performance high-frequency SOI MESFET by the damped electric field

    Science.gov (United States)

    Orouji, Ali A.; Khayatian, Ahmad; Keshavarzi, Parviz

    2016-06-01

    In this paper, we introduce a novel silicon-on-insulator (SOI) metal-semiconductor field-effect-transistor (MESFET) using the damped electric field (DEF). The proposed structure is geometrically symmetric and compatible with common SOI CMOS fabrication processes. It has two additional oxide regions under the side gates in order to improve DC and RF characteristics of the DEF structure due to changes in the electrical potential, the electrical field distributions, and rearrangement of the charge carriers. Improvement of device performance is investigated by two-dimensional and two-carrier simulation of fundamental parameters such as breakdown voltage (VBR), drain current (ID), output power density (Pmax), transconductance (gm), gate-drain and gate-source capacitances, cut-off frequency (fT), unilateral power gain (U), current gain (h21), maximum available gain (MAG), and minimum noise figure (Fmin). The results show that proposed structure operates with higher performances in comparison with the similar conventional SOI structure.

  16. Highly red-shifted NIR emission from a novel anthracene conjugated polymer backbone containing Pt( ii ) porphyrins

    KAUST Repository

    Freeman, D. M. E.

    2015-11-30

    © The Royal Society of Chemistry 2016. We present the synthesis of a novel diphenylanthracene (DPA) based semiconducting polymer. The polymer is solubilised by alkoxy groups attached directly to a DPA monomer, meaning the choice of co-monomer is not limited to exclusively highly solubilising moieties. Interestingly, the polymer shows a red-shifted elecroluminescence maximum (510 nm) when compared to its photoluminescence maximum (450 nm) which we attribute to excimer formation. The novel polymer was utilised as a host for a covalently-linked platinum(ii) complexed porphyrin dopant. Emission from these polymers was observed in the NIR and again showed almost a 100 nm red shift from photoluminescence to electroluminescence. This work demonstrates that utilising highly aggregating host materials is an effective tool for inducing red-shifted emission in OLEDs.

  17. The Advanced Camera for Surveys General Catalog: A High Redshift Galaxy Morphology Catalog

    Science.gov (United States)

    Griffith, Roger; Newman, J.; Cooper, M.; Stern, D.; Moustakas, L.; Davis, M.

    2009-05-01

    We use publicly available data obtained with the Advanced Camera for Surveys (ACS) instrument on the Hubble Space Telescope to construct the ACS General Catalog (ACS-GC). The ACS-GC includes over 370,000 astronomical sources (stars + galaxies) derived from the AEGIS, COSMOS, GEMS, and GOODS surveys. We include publicly available redshifts from the DEEP2, COMBO-17, TKRS, PEARS and zCOSMOS surveys to supply redshifts for a considerable fraction ( 52%) of the imaging sample. GALAPAGOS was used to construct photometric (SExtractor) and morphological (GALFIT) catalogs. The morphological analysis assumes a single Sersic model for each object to derive quantitative structural parameters. Galaxy Zoo will measure visual morphologies for 200,000 of these galaxies. The ACS-GC includes color images, GALFIT residual images, a galaxy atlas, and a photometry + morphology + redshift catalog. We use these data to investigate the size-redshift relationship for both early and late-type galaxies out to z 1. The entire data set will be made publicly available through the NASA Extragalactic Database (NED) and LEVEL5.

  18. Why Do Compact Active Galactic Nuclei at High Redshift Scintillate Less?

    CERN Document Server

    Koay, J Y; Rickett, B J; Bignall, H E; Jauncey, D L; Pursimo, T; Reynolds, C; Lovell, J E J; Kedziora-Chudczer, L; Ojha, R

    2012-01-01

    The fraction of compact active galactic nuclei (AGNs) that exhibit interstellar scintillation (ISS) at radio wavelengths, as well as their scintillation amplitudes, have been found to decrease significantly for sources at redshifts z > 2. This can be attributed to an increase in the angular sizes of the \\muas-scale cores or a decrease in the flux densities of the compact \\muas cores relative to that of the mas-scale components with increasing redshift, possibly arising from (1) the space-time curvature of an expanding Universe, (2) AGN evolution, (3) source selection biases, (4) scatter broadening in the ionized intergalactic medium (IGM) and intervening galaxies, or (5) gravitational lensing. We examine the frequency scaling of this redshift dependence of ISS to determine its origin, using data from a dual-frequency survey of ISS of 128 sources at 0 < z < 4. We present a novel method of analysis which accounts for selection effects in the source sample. We determine that the redshift dependence of ISS ...

  19. Resolved Gas Kinematics in a Sample of Low-Redshift High Star-Formation Rate Galaxies

    Science.gov (United States)

    Varidel, Mathew; Pracy, Michael; Croom, Scott; Owers, Matt S.; Sadler, Elaine

    2016-03-01

    We have used integral field spectroscopy of a sample of six nearby (z 0.01-0.04) high star-formation rate (SFR ˜ 10-40 M_⊙ yr^{-1}) galaxies to investigate the relationship between local velocity dispersion and star-formation rate on sub-galactic scales. The low-redshift mitigates, to some extent, the effect of beam smearing which artificially inflates the measured dispersion as it combines regions with different line-of-sight velocities into a single spatial pixel. We compare the parametric maps of the velocity dispersion with the Hα flux (a proxy for local star-formation rate), and the velocity gradient (a proxy for the local effect of beam smearing). We find, even for these very nearby galaxies, the Hα velocity dispersion correlates more strongly with velocity gradient than with Hα flux-implying that beam smearing is still having a significant effect on the velocity dispersion measurements. We obtain a first-order non parametric correction for the unweighted and flux weighted mean velocity dispersion by fitting a 2D linear regression model to the spaxel-by-spaxel data where the velocity gradient and the Hα flux are the independent variables and the velocity dispersion is the dependent variable; and then extrapolating to zero velocity gradient. The corrected velocity dispersions are a factor of 1.3-4.5 and 1.3-2.7 lower than the uncorrected flux-weighted and unweighted mean line-of-sight velocity dispersion values, respectively. These corrections are larger than has been previously cited using disc models of the velocity and velocity dispersion field to correct for beam smearing. The corrected flux-weighted velocity dispersion values are σ m 20-50 km s-1.

  20. Galaxy Evolution at High Redshift: Obscured Star Formation, GRB Rates, Cosmic Reionization, and Missing Satellites

    Science.gov (United States)

    Lapi, A.; Mancuso, C.; Celotti, A.; Danese, L.

    2017-01-01

    We provide a holistic view of galaxy evolution at high redshifts z ≳ 4, which incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic star formation rate (SFR) density from UV/IR surveys and long gamma-ray burst (GRBs) rates, the cosmic reionization history following the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to a UV magnitude limit MUV ≲ ‑13 (or SFR limit around 10‑2 M⊙ yr‑1) produce a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z ≲ Z⊙/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission of the electron scattering optical depth τes ≈ 0.058 remarkably, this result is obtained under a conceivable assumption regarding the average value fesc ≈ 0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance-matching technique that the above constraints concurrently imply galaxy formation becoming inefficient within dark matter halos of mass below a few 108 M⊙ pleasingly, such a limit is also required so as not to run into the missing satellites issue. Finally, we predict a downturn of the Galaxy luminosity function faintward of MUV ≲ ‑12, and stress that its detailed shape, to be plausibly probed in the near future by the JWST, will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter.