Sample records for bright radio-quiet quasar

  1. The radio structure of radio-quiet quasars

    NARCIS (Netherlands)

    Leipski, C.; Falcke, H.D.E.; Bennert, N.; Hüttemeister, S.


    Aims.We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies.
    Methods: .We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert

  2. The Far-Infrared Emission of Radio Loud and Radio Quiet Quasars (United States)

    Polletta, M.; Courvoisier, T. J.-L.; Wilkes, B. J.; Hooper, E. J.


    Continuum observations at radio, millimeter, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large observational datasets provided by ISOPHOT on board the Infrared Space Observatory, by the IRAM interferometer, by the sub-millimetre array SCUBA on JCMT, and by the European Southern Observatory (ESO) facilities IRAC1 on the 2.2 m telescope and SEST. The spectral energy distributions of all quasars from radio to IR energies are analyzed and modeled with non-thermal and thermal spectral components. The dominant mechanism emitting in the far/mid-IR is thermal dust emission in all quasars, with the exception of flat spectrum radio loud quasars for which the presence of thermal IR emission remains rather uncertain, since it is difficult to separate it from the bright non-thermal component. The dust is predominantly heated by the optical/ultraviolet radiation emitted from the external components of the AGN. A starburst contributes to the IR emission at different levels, but always less than the AGN (<= 27%). The distribution of temperatures, sizes, masses, and luminosities of the emitting dust are independent of the quasar type.

  3. Evidence that the AGN dominates the radio emission in z ˜ 1 radio-quiet quasars (United States)

    White, Sarah V.; Jarvis, Matt J.; Kalfountzou, Eleni; Hardcastle, Martin J.; Verma, Aprajita; Cao Orjales, José M.; Stevens, Jason


    In order to understand the role of radio-quiet quasars (RQQs) in galaxy evolution, we must determine the relative levels of accretion and star-formation activity within these objects. Previous work at low radio flux densities has shown that accretion makes a significant contribution to the total radio emission, in contrast with other quasar studies that suggest star formation dominates. To investigate, we use 70 RQQs from the Spitzer-Herschel Active Galaxy Survey. These quasars are all at z ˜ 1, thereby minimizing evolutionary effects, and have been selected to span a factor of ˜100 in optical luminosity, so that the luminosity dependence of their properties can be studied. We have imaged the sample using the Karl G. Jansky Very Large Array (JVLA), whose high sensitivity results in 35 RQQs being detected above 2σ. This radio data set is combined with far-infrared luminosities derived from grey-body fitting to Herschel photometry. By exploiting the far-infrared-radio correlation observed for star-forming galaxies, and comparing two independent estimates of the star-formation rate, we show that star formation alone is not sufficient to explain the total radio emission. Considering RQQs above a 2σ detection level in both the radio and the far-infrared, 92 per cent are accretion dominated, and the accretion process accounts for 80 per cent of the radio luminosity when summed across the objects. The radio emission connected with accretion appears to be correlated with the optical luminosity of the RQQ, whilst a weaker luminosity dependence is evident for the radio emission connected with star formation.


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    Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Edge, A. C.; Hogan, M. T.; Swinbank, A. M. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontifica Universidad Católica de Chile, 306, Santiago 22 (Chile); Mullaney, J. R., E-mail: [Department of Physics and Astronomy, University of Sheffield, Sheffield S7 3RH (United Kingdom)


    We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L {sub 1.4} {sub GHz} ≈ 5 × 10{sup 23} W Hz{sup –1} and L {sub AGN} ≈ 2 × 10{sup 45} erg s{sup –1}). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the ''Teacup'' active galactic nucleus (AGN) in the literature. We identify ''bubbles'' of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the ''Teacup'' AGN hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = –740 km s{sup –1}. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on ≳ 10 kpc scales. Our study highlights that even when a quasar is formally ''radio-quiet'' the radio emission can be extremely effective for observing the effects of AGN feedback.

  5. Exploratory X-Ray Monitoring of Luminous Radio-quiet Quasars at High Redshift: No Evidence for Evolution in X-Ray Variability (United States)

    Shemmer, Ohad; Brandt, W. N.; Paolillo, Maurizio; Kaspi, Shai; Vignali, Cristian; Lira, Paulina; Schneider, Donald P.


    We report on the second installment of an X-ray monitoring project of seven luminous radio-quiet quasars (RQQs). New Chandra observations of four of these, at 4.10≤slant z≤slant 4.35, yield a total of six X-ray epochs per source, with temporal baselines of ˜ 850{--}1600 days in the rest frame. These data provide the best X-ray light curves for RQQs at z> 4 to date, enabling qualitative investigations of the X-ray variability behavior of such sources for the first time. On average, these sources follow the trend of decreasing variability amplitude with increasing luminosity, and there is no evidence for X-ray variability increasing toward higher redshifts, in contrast with earlier predictions of potential evolutionary scenarios. An ensemble variability structure function reveals that their variability level remains relatively flat across ≈ 20{--}1000 days in the rest frame and it is generally lower than that of three similarly luminous RQQs at 1.33≤slant z≤slant 2.74 over the same temporal range. We discuss possible explanations for the increased variability of the lower-redshift subsample and, in particular, whether higher accretion rates play a leading role. Near-simultaneous optical monitoring of the sources at 4.10≤slant z≤slant 4.35 indicates that none is variable on ≈ 1 day timescales, although flux variations of up to ˜25% are observed on ≈ 100 day timescales, typical of RQQs at similar redshifts. Significant optical-X-ray spectral slope variations observed in two of these sources are consistent with the levels observed in luminous RQQs and are dominated by X-ray variations.

  6. Optical microvariability of bright type 2 quasars (United States)

    Polednikova, Jana; Ederoclite, Alessandro; Cepa, Jordi; de Diego Onsurbe, José Antonio; González-Serrano, José Ignacio


    We present results from a project focused on searching optical microvariabilty (also known as ``intra-night'' variability) in type 2 - obscured - quasars. Optical microvariability can be described as very small changes in the flux, typically in the order of hundredths of magnitude, which can be observed on timescales of hours. Such studies have been so far conducted for samples of blazars and type 1, unobscured, AGNs, where the optical microvariability was detected with success. We have focused on obscured targets which would pose a challenge to the AGN standard model. In the present work, however, we have observed a sample of three bright (g mag < 17) type 2 quasar, based on the catalog of type 2 quasars from SDSS of Reyes et al. (2008). The observations were carried out with the 1.5 meter telescope at San Pedro Martir observatory in Mexico. The sample was observed during an observation period of four days in Johnsons V filter, resulting in at least two continuous intervals of observations per target during the observational run. We have obtained differential light curves for our sources as well as for the comparison stars. They were analyzed using one-way analysis of variance statistical test (ANOVA), which has been repeatedly used in the past for studies of unobscured targets. Based on the results from the statistical analysis, we show that at least two out of three observed targets appear to be variable on time scales of hours. So far, this is the first study which confirmed existence of optical microvariability in type 2 quasars.

  7. Multi-epoch intranight optical monitoring of eight radio-quiet BL Lac candidates (United States)

    Kumar, P.; Gopal-Krishna; Stalin, C. S.; Chand, H.; Srianand, R.; Petitjean, P.


    For a new sample of eight weak-line quasars (WLQs) we report a sensitive search in 20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and longer time-scale (day/month/year-like). The sample consists exclusively of the WLQs that are not radio-loud and either have been classified as 'radio-weak probable BL Lac candidates' and/or are known to have exhibited at least one episode of large, blazar-like optical variability. Whereas only a hint of intranight variability is seen for two of these WLQs, J104833.5+620305.0 (z = 0.219) and J133219.6+622715.9 (z = 3.15), statistically significant internight variability at a few per cent level is detected for three of the sources, including the radio-intermediate WLQ J133219.6+622715.9 (z = 3.15) and the well-known bona fide radio-quiet WLQs J121221.5+534128.0 (z = 3.10) and WLQ J153259.9-003944.1 (z = 4.62). In the rest frame, this variability is intraday and in the far-ultraviolet band. On the time-scale of a decade, we find for three of the WLQs large brightness changes, amounting to 1.655 ± 0.009, 0.163 ± 0.010 and 0.144 ± 0.018 mag, for J104833.5+620305.0, J123743.1+630144.9 and J232428.4+144324.4, respectively. Whereas the latter two are confirmed radio-quiet WLQs, the extragalactic nature of J104833.5+620305.0 remains to be well established, thanks to the absence of any feature(s) in its available optical spectra. This study forms a part of our ongoing campaign of intranight optical monitoring of radio-quiet WLQs, in order to improve the understanding of this enigmatic class of active galactic nuclei and to look among them for a possible tiny, elusive population of radio-quiet BL Lacs.

  8. Radio-quiet Gamma-ray Pulsars

    Directory of Open Access Journals (Sweden)

    Lupin Chun-Che Lin


    Full Text Available A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400 of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on are also to specified discuss their common and specific features.

  9. The Extremely Luminous Quasar Survey (ELQS) in SDSS and the high-z bright-end Quasar Luminosity Function (United States)

    Schindler, Jan-Torge; Fan, Xiaohui; McGreer, Ian


    Studies of the most luminous quasars at high redshift directly probe the evolution of the most massive black holes in the early Universe and their connection to massive galaxy formation. Unfortunately, extremely luminous quasars at high redshift are very rare objects. Only wide area surveys have a chance to constrain their population. The Sloan Digital Sky Survey (SDSS) nd the Baryon Oscillation Spectroscopic Survey (BOSS) have so far provided the most widely adopted measurements of the type I quasar luminosity function (QLF) at z>3. However, a careful re-examination of the SDSS quasar sample revealed that the SDSS quasar selection is in fact missing a significant fraction of $z~3$ quasars at the brightest end.We have identified the purely optical color selection of SDSS, where quasars at these redshifts are strongly contaminated by late-type dwarfs, and the spectroscopic incompleteness of the SDSS footprint as the main reasons. Therefore we have designed the Extremely Luminous Quasar Survey (ELQS), based on a novel near-infrared JKW2 color cut using WISE AllWISE and 2MASS all-sky photometry, to yield high completeness for very bright (i learning algorithms on SDSS and WISE photometry for quasar-star classification and photometric redshift estimation.The ELQS is spectroscopically following up ~230 new quasar candidates in an area of ~12000 deg2 in the SDSS footprint, to obtain a well-defined and complete quasar sample for an accurate measurement of the bright-end quasar luminosity function (QLF) at 2.8<= z<=5.0. So far the ELQS has identified 75 bright new quasars in this redshift range and observations of the fall sky will continue until the end of the year. At the AAS winter meeting we will present the full spectroscopic results of the survey, including a re-estimation and extension of the high-z QLF toward higher luminosities.

  10. The SDSS view of the Palomar-Green bright quasar survey

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    Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.; Green, Richard F.; Schmidt, Maarten; Hall, Patrick B.; Strauss, Michael A.; Vanden Berk, Daniel E.; Stoughton, Chris; Gunn, James E.; Brinkmann, Jon; Kent, Stephen M.; Smith, J.Allyn; Tucker, Douglas, L.; Yanny, Brian; /Fermilab /Penn State U., Astron. Astrophys. /Princeton U.


    The author investigates the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, they define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U-B cut in the PG survey is U-B < -0.71, implying a color-related incompleteness. As the color distribution of bright quasars peaks near U-B = -0.7 and the 2-{sigma} error in U-B is comparable to the full width of the color distribution of quasars, the color incompleteness of the BQS is approximately 50% and essentially random with respect to U-B color for z < 0.5. There is however, a bias against bright quasars at 0.5 < z < 1, which is induced by the color-redshift relation of quasars (although quasars at z > 0.5 are inherently rare in bright surveys in any case). They find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects which are blue in g-i, in particular compared to the full range of g-i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.


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    Hennawi, Joseph F.; Prochaska, J. Xavier, E-mail: [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)


    We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantly radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar-powered fluorescence


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    Kovalev, Y. Y.; Kardashev, N. S.; Voitsik, P. A.; Kovalev, Yu. A.; Lisakov, M. M.; Sokolovsky, K. V. [Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow (Russian Federation); Kellermann, K. I. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Lobanov, A. P.; Zensus, J. A.; Anderson, J. M.; Bach, U.; Kraus, A. [Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 (Germany); Johnson, M. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gurvits, L. I. [Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Jauncey, D. L. [CSIRO Astronomy and Space Sciences, Epping, NSW 1710 (Australia); Ghigo, F. [National Radio Astronomy Observatory, Rt. 28/92, Green Bank, WV 24944-0002 (United States); Ghosh, T.; Salter, C. J. [Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo, Puerto Rico, PR 00612 (United States); Petrov, L. Yu. [Astrogeo Center, 7312 Sportsman Drive, Falls Church, VA 22043 (United States); Romney, J. D. [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States)


    Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of 10{sup 11.5} K. Relativistic boosting can increase its observed value, but apparent brightness temperatures much in excess of 10{sup 13} K are inaccessible using ground-based very long baseline interferometry (VLBI) at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as small as 26 μas (2.7 light months) and brightness temperature in excess of 10{sup 13} K. These measurements challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive black holes and require a much higher Doppler factor than what is determined from jet apparent kinematics.

  13. Evidence for Higher Black Hole Spin in Radio-loud Quasars (United States)

    Schulze, Andreas; Done, Chris; Lu, Youjun; Zhang, Fupeng; Inoue, Yoshiyuki


    One of the major unsolved questions concerning the understanding of the active galactic nucleus population is the origin of the dichotomy between radio-quiet and radio-loud quasars. The most promising explanation is provided by the spin paradigm, which suggests that radio-loud quasars have a higher black hole spin. However, the measurement of black hole spin remains extremely challenging. We here aim at comparing the mean radiative efficiencies of carefully matched samples of radio-loud and radio-quiet Sloan Digital Sky Survey (SDSS) quasars at 0.3paradigm.

  14. Milliarcsecond Imaging of the Radio Emission from the Quasar with the Most Massive Black Hole at Reionization (United States)

    Wang, Ran; Momjian, Emmanuel; Carilli, Chris L.; Wu, Xue-Bing; Fan, Xiaohui; Walter, Fabian; Strauss, Michael A.; Wang, Feige; Jiang, Linhua


    We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas ×5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 ± 9.0 μJy beam-1 and a total flux density of 88 ± 19 μJy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 ± 3.5) mas × (3.1 ± 1.7) mas. This corresponds to a physical scale of (40 ± 20) pc × (18 ± 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be TB = (1.6 ± 1.2) × 107 K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.

  15. Milliarcsecond Imaging of the Radio Emission from the Quasar with the Most Massive Black Hole at Reionization

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    Wang, Ran; Wu, Xue-Bing; Jiang, Linhua [Kavli Institute of Astronomy and Astrophysics at Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China); Momjian, Emmanuel; Carilli, Chris L. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States); Fan, Xiaohui [Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Walter, Fabian [Max-Planck-Institute for Astronomy, Königsstuhl 17, D-69117 Heidelberg (Germany); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Wang, Feige [Department of Astronomy, School of Physics, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China)


    We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas ×5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 ± 9.0 μ Jy beam{sup −1} and a total flux density of 88 ± 19 μ Jy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 ± 3.5) mas × (3.1 ± 1.7) mas. This corresponds to a physical scale of (40 ± 20) pc × (18 ± 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be T {sub B} = (1.6 ± 1.2) × 10{sup 7} K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.

  16. Narrow CIV lambda 1549A Absorption Lines in Moderate-Redshift Quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne


    A large, high-quality spectral data base of well-selected, moderate-redshift radio-loud and radio-quiet quasars is used to characterize the incidence of narrow associated CIV lambda 1549 absorption, and how this may depend on some quasar properties, including radio-type. Preliminary results...

  17. A catalogue of optical to X-ray spectral energy distributions of z ≈ 2 quasars observed with Swift - I. First results (United States)

    Lawther, D.; Vestergaard, M.; Raimundo, S.; Grupe, D.


    We present the Swift optical to X-ray spectral energy distributions (SEDs) of 44 quasars at redshifts z ≈ 2 observed by Swift, part of a larger program to establish and characterize the optical through X-ray SEDs of moderate-redshift quasars. Here, we outline our analysis approach and present preliminary analysis and results for the first third of the full quasar sample. Not all quasars in the sample are detected in X-rays; all of the X-ray-detected objects so far are radio loud. As expected for radio-loud objects, they are X-ray bright relative to radio-quiet quasars of comparable optical luminosities, with an average αox =1.39 ± 0.03 (where αox is the power-law slope connecting the monochromatic flux at 2500 Å and at 2 keV), and display hard X-ray spectra. We find integrated 3000 Å-25 keV accretion luminosities of between 0.7 × 1046 erg s-1 and 5.2 × 1047 erg s-1. Based on single-epoch spectroscopic virial black hole mass estimates, we find that these quasars are accreting at substantial Eddington fractions, 0.1 ≲ L/LEdd ≲ 1.

  18. Determination of the coronal properties of luminous quasars at cosmological redshifts (United States)

    Kammoun, E.; Risaliti, G.; Stern, D.; Celotti, A.


    Several precise measurements of high-energy cutoffs in the X-ray spectra of bright local AGN have been reported recently. These measurements can be also done for luminous quasars at cosmological redshifts. The shift of the high-energy cutoff to lower energies, in the observer frame, compensates for the relative faintness of the source, allowing an estimate of the coronal temperature analogous to the ones done for local, low luminosity but very bright AGN. We present the analysis of the joint XMM-Newton and NuSTAR observations of the luminous radio-quiet quasar QSO B2202-209 (z=0.53; L(2-10 keV)= 1.93× 10^{45} erg/s). Assuming a Comptonization model, we estimated a coronal temperature of kT_{e} = (42± 3) keV and KT_{e}=(56 ± 3) keV for a spherical and a slab geometry, respectively, for B2202-209. The unusual X-ray loudness of this quasar (α_{OX} = 1.00 ± 0.02) and the exceptionally strong optical [O III] line, that we found, can be explained by a nearly edge-on disc, leading to a reduction in the observed ultraviolet continuum light.

  19. Mass Functions of the Active Black Holes in Distant Quasars from the Large Bright Quasar Survey, the Bright Quasar Survey, and the Color-Selected Sample of the SDSS Fall Equatorial Stripe

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Osmer, Patrick S.


    functions at similar redshifts based on the SDSS Data Release 3 quasar catalog presented by Vestergaard et al. We see clear evidence of cosmic downsizing in the comoving space density distribution of active black holes in the LBQS sample alone. In forthcoming papers, further analysis, comparison...

  20. Occurrence and Global Properties of Narrow CIV lambda 1549 Absorption Lines in Moderate-Redshift Quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne


    A statistical study is presented of (a) the frequency of narrow CIV lambda 1549 absorption lines in 1.5 ~50%) of narrow CIV absorbers is detected for the radio-quiet and radio-loud quasars, and a constant ~25% of all the quasars, irrespective of radio type display associated CIV absorbers stronger...... than a rest equivalent width of 0.5A. Both radio-quiet and radio-loud quasars with narrow absorption lines have systematically redder continua, especially strongly absorbed objects. There is evidence of inclination dependent dust reddening and absorption for the radio quasars. An additional key result...... is that the most strongly absorbed radio quasars have the largest radio source extent. This result is in stark contrast to a recent study of the low-frequency selected Molonglo survey in which a connection between the strength of the narrow absorbers and the (young) age of the radio source has been proposed...

  1. Blind search for radio-quiet and radio-loud gamma-ray pulsars with Fermi-LAT data (United States)

    Rubtsov, G. I.; Sokolova, E. V.


    The Fermi Large Area Telescope (LAT) has observed more than a hundred of gamma-ray pulsars, about one third of which are radio-quiet, i.e., not detected at radio frequencies. The most of radio-loud pulsars are detected by Fermi LAT by using the radio timing models, while the radio-quiet ones are discovered in a blind search. The difference in the techniques introduces an observational selection bias and, consequently, the direct comparison of populations is complicated. In order to produce an unbiased sample, we perform a blind search of gamma-ray pulsations using Fermi-LAT data alone. No radio data or observations at optical or X-ray frequencies are involved in the search process. We produce a gamma-ray selected catalog of 25 non-recycled gamma-ray pulsars found in a blind search, including 16 radio-quiet and 9 radio-loud pulsars. This results in the direct measurement of the fraction of radio-quiet pulsars ɛRQ = 64 ± 10%, which is in agreement with the existing estimates from the population modeling in the outer magnetosphere model. The Polar cap models are disfavored due to a lower expected fraction and the prediction of age dependence. The age, gamma-ray energy flux, spin-down luminosity and sky location distributions of the radio-loud and radio-quiet pulsars from the catalog do not demonstrate any statistically significant difference. The results indicate that the radio-quiet and radio-loud pulsars belong to one and the same population. The catalog shows no evidence for the radio beam evolution.

  2. Multiwavelength polarization observations of the γ-ray bright quasar PKS 0420-014

    Directory of Open Access Journals (Sweden)

    Troitskiy I.S.


    Full Text Available We analyze total and polarized intensity images of the quasar PKS 0420-014 obtained monthly with the VLBA at 43 GHz during 2008–2012 along with γ-ray data provided by the Fermi Large Area Telescope and multi-color photometric and polarimetric measurements collected by different optical telescopes. During this period the quasar underwent a number of optical flares, which were accompanied by rapid rotation of polarization angle, an increase of activity in γ-rays, and the appearance of new superluminal knots in the parsec-scale jet. We investigate the fine structure of the flares at different wavelengths and in polarized light, and determine kinematic parameters of the knots. We compare the rapid evolution of the optical polarization with the polarization of the VLBI core and knots. We interpret the multi-wavelength behavior within a model that places the blazar “dissipation zone” at the millimeter-wave core of the parsec-scale jet.

  3. Soft X-ray Variability of the Bright Quasar 3C273

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy; Volume 22; Issue 4. Soft X-ray Variability of the Bright ... no correlation between them. There is no distinct variation of the photon index in the case of simple power law model fitting. For power law + free absorption model fitting, the average photon index () is 2.08.

  4. Differences between Radio-loud and Radio-quiet Gamma-ray Pulsars as Revealed by Fermi (United States)

    Hui, C. Y.; Lee, Jongsu; Takata, J.; Ng, C. W.; Cheng, K. S.


    By comparing the properties of non-recycled radio-loud γ-ray pulsars and radio-quiet γ-ray pulsars, we have searched for the differences between these two populations. We found that the γ-ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled γ-ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We note that this might result from an observational bias. By reexamining the previously reported difference of γ-ray-to-X-ray flux ratios, we found that the significance can be hampered by their statistical uncertainties. In the context of the outer gap model, we discuss the expected properties of these two populations and compare with the possible differences that are identified in our analysis.

  5. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs: III - Location and Energetics (United States)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Braito, V.


    Using the results of a previous X-ray photo-ionization modelling of blue-shifted Fe K absorption lines on a sample of 42 local radio-quiet AGNs observed with XMM-Newton, in this letter we estimate the location and energetics of the associated ultrafast outflows (UFOs). Due to significant uncertainties, we are essentially able to place only lower/upper limits. On average, their location is in the interval approx.0.0003-0.03pc (approx.10(exp 2)-10(exp 4)tau(sub s) from the central black hole, consistent with what is expected for accretion disk winds/outflows. The mass outflow rates are constrained between approx.0.01- 1 Stellar Mass/y, corresponding to approx. or >5-10% of the accretion rates. The average lower-upper limits on the mechanical power are logE(sub K) approx. or = 42.6-44.6 erg/s. However, the minimum possible value of the ratio between the mechanical power and bolometric luminosity is constrained to be comparable or higher than the minimum required by simulations of feedback induced by winds/outflows. Therefore, this work demonstrates that UFOs are indeed capable to provide a significant contribution to the AGN r.osmological feedback, in agreement with theoretical expectations and the recent observation of interactions between AGN outflows and the interstellar medium in several Seyferts galaxies .

  6. A unique UV flare in the optical light curve of the quasar J004457.9+412344

    Directory of Open Access Journals (Sweden)

    Hatzidimitriou D.


    Full Text Available We found that the nova candidate J004457.9+412344 is a radio-quiet quasar at z ∼ 2. Its optical long-term light curve, covering more than half a century, shows quasar typical flux variations superimposed by a spectacular single flare lasting more than one year (observer frame. We could not find comparable light curves among the several thousand catalogued radio-quiet quasars in the stripe 82 of the Sloan Digital Sky Survey. The decreasing part of the flare light curve roughly follows a power law t−5/3. The quasar spectrum, the total energy of the flare, and the decline of the light curve are consistent with the tidal disruption of a ∼10 Mʘ giant star by a supermassive black hole of a few 108 Mʘ. We argue that the alternative explanation by gravitational microlensing is less likely, though it cannot be definitely excluded.


    Energy Technology Data Exchange (ETDEWEB)

    Clark, C. J.; Pletsch, H. J.; Allen, B.; Aulbert, C.; Beer, C.; Bock, O.; Cuéllar, A.; Eggenstein, H. B.; Fehrmann, H.; Machenschalk, B.; Nieder, L. [Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-30167 Hannover (Germany); Wu, J.; Guillemot, L.; Kramer, M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Camilo, F. [SKA South Africa, Pinelands, 7405 (South Africa); Johnson, T. J. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Kerr, M., E-mail: [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia)


    We report the discovery and timing measurements of PSR J1208−6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home . No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit at 1369 MHz of 30 μ Jy. By timing this pulsar’s gamma-ray pulsations, we measure its braking index over five years of LAT observations to be n = 2.598 ± 0.001 ± 0.1, where the first uncertainty is statistical and the second estimates the bias due to timing noise. Assuming its braking index has been similar since birth, the pulsar has an estimated age of around 2700 years, making it the youngest pulsar to be found in a blind search of gamma-ray data and the youngest known radio-quiet gamma-ray pulsar. Despite its young age, the pulsar is not associated with any known supernova remnant or pulsar wind nebula. The pulsar’s inferred dipolar surface magnetic field strength is 3.8 × 10{sup 13} G, almost 90% of the quantum-critical level. We investigate some potential physical causes of the braking index deviating from the simple dipole model but find that LAT data covering a longer time interval will be necessary to distinguish between these.

  8. Spectral differences between the jets in `radio-loud' and `radio-quiet' hard-state black hole binaries (United States)

    Espinasse, M.; Fender, R.


    We have compiled from the available literature a large set of radio measurements of black hole binaries in the hard X-ray state for which measurements of the gigahertz frequency radio spectral index are possible. We separate the sample into 'radio-loud' and 'radio-quiet' subsets based upon their distribution in the radio-X-ray plane and investigate the distribution of radio spectral indices within each subset. The distribution of spectral indices of the 'radio-loud' subset is well described by a Gaussian distribution with mean spectral index α = +0.2 and standard deviation 0.2 (here spectral index is defined such that a positive spectral index means more flux at higher frequencies). The sparser sample for the 'radio-quiet' subset can be approximated, less well, by a Gaussian with mean α = -0.2 and standard deviation 0.3; alternatively, the simple mean of the distribution of the radio-quiet subset is -0.3. The two spectral index distributions are different at high statistical significance. Confirming previous work in the literature, we test to see if the differences in observed spectra could result from different distributions of jet viewing angles, but find no evidence for this. We conclude therefore that the jets in the two groups are physically different in some way, and briefly discuss possible origins and further possible diagnostics. Finally, we note that extrapolating to lower frequencies the two subsets move closer together in the radio-X-ray plane, and approximately merge into a single distribution at around 400 MHz.

  9. Phylogenetic Analyses of Quasars and Galaxies

    Directory of Open Access Journals (Sweden)

    Didier Fraix-Burnet


    Full Text Available Phylogenetic approaches have proven to be useful in astrophysics. We have recently published a Maximum Parsimony (or cladistics analysis on two samples of 215 and 85 low-z quasars (z < 0.7 which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. Cladistics is not only able to group sources radiating at higher Eddington ratios, to separate radio-quiet (RQ and radio-loud (RL quasars and properly distinguishes core-dominated and lobe-dominated quasars, but it suggests a black hole mass threshold for powerful radio emission as already proposed elsewhere. An interesting interpretation from this work is that the phylogeny of quasars may be represented by the ontogeny of their central black hole, i.e. the increase of the black hole mass. However these exciting results are based on a small sample of low-z quasars, so that the work must be extended. We are here faced with two difficulties. The first one is the current lack of a larger sample with similar observables. The second one is the prohibitive computation time to perform a cladistic analysis on more that about one thousand objects. We show in this paper an experimental strategy on about 1,500 galaxies to get around this difficulty. Even if it not related to the quasar study, it is interesting by itself and opens new pathways to generalize the quasar findings.

  10. Search for Differences between Radio-loud and Radio-quiet Gamma-Ray Pulsar Populations with Fermi-LAT Data (United States)

    Sokolova, E. V.; Rubtsov, G. I.


    Observations by the Fermi-Large Area Telescope (LAT) have enabled us to explore the population of non-recycled gamma-ray pulsars with a set of 112 objects. It was recently noted that there are apparent differences in the properties of radio-quiet and radio-loud subsets. In particular, the average observed radio-loud pulsar is younger than the average radio-quiet one and is located at lower Galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most radio-loud pulsars are first discovered in the radio band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi-LAT data alone, using all point sources from the 3FGL catalog as the candidates. Unlike our previous work, the present catalog is constructed with a semi-coherent method based on the time-differencing technique and covers the full range of characteristic ages down to 1 kyr. The search resulted in a catalog of 40 non-recycled pulsars, 25 of which are radio-quiet. All pulsars found in the search were previously known gamma-ray pulsars. We find no statistically significant differences in age or in distributions in Galactic latitude for the radio-loud and radio-quiet pulsars, while the distributions in rotation period are marginally different with a statistical probability of 4× {10}-3. The fraction of radio-quiet pulsars is estimated as {ɛ }{RQ}=(63+/- 8) % . The results are in agreement with the predictions of the outer magnetosphere models, while the polar cap models are disfavored.

  11. Is optical Fe II emission related to the soft X-ray properties of quasars? (United States)

    Wilkes, Belinda J.; Elvis, Martin; McHardy, Ian


    Radio-quiet quasars generally show broad, blended multiplets of Fe II emission in their optical and UV spectra. Radio-loud quasars also show UV Fe II emission, but their optical Fe II emission is generally weaker. No satisfactory theory connecting the generation of Fe II and radio emission has been found to explain this effect. A second, well-established distinction between the two clases of quasar is in their X-ray properties: radio-loud quasars are more X-ray luminous, and recent results have shown that they also have systematically flatter soft X-ray slopes. Here it is proposed that the second effect causes the first; i.e., that the primary factor controlling the optical Fe II emission is the soft X-ray spectrum. This proposition is supported by X-ray and optical data for nine quasars, which shows a correlation between the soft X-ray slope and the strength of the optical Fe II emission. One of these quasars (1803+676) is radio-quiet, and yet its optical spectrum shows no evidence for Fe II emission. This quasar is also unusual in that it has a flat X-ray spectrum. This further supports the proposal that the X-ray spectrum is important in determining the relative strengths of UV and optical Fe II emission.

  12. Testing Disk-Wind Models with Quasar CIV 1549Å Associated Absorption Lines

    DEFF Research Database (Denmark)

    Vestergaard, Marianne


    Narrow associated C IV 1549Å absorption lines (NALs) with a rest equivalent width EW =3 Å detected in z ˜ 2 radio-loud and radio-quiet quasars, (a) exhibit evidence of an origin in radiatively accelerated gas, and (b) may be closely related to broad absorption line (BAL) outflows. These NALs......-ray to UV emission ratio, i.e., aOX. The latter means that quasars with flat aOX (like radio-louds) should not have strong, high-velocity (BAL-like) outflows. These results are of interest not only to studies of disk wind scenarios and quasar structure, but also to studies of quasar feedback: NALs...... that originate in powerful outflows are potential probes of quasar feedback on its environment, since NALs are more commonly occuring than BALs, irrespective of quasar radio properties (Vestergaard 2003)....

  13. PKS 0347+05: a radio-loud/radio-quiet double active galactic nucleus system triggered in a major galaxy merger

    NARCIS (Netherlands)

    Tadhunter, C. N.; Ramos Almeida, C.; Morganti, R.; Holt, J.; Rose, M.; Dicken, D.; Inskip, K.


    We present optical, infrared (IR) and radio observations of the powerful Fanaroff-Riley type II (FR II) radio source PKS 0347+05 (z = 0.3390), and demonstrate that it is a rare example of a radio-loud/radio-quiet double active galactic nucleus (AGN) system, comprising a weak-line radio galaxy (WLRG)

  14. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander


    The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...

  15. Intrinsic, Narrow N V Absorption Reveals a Clumpy Outflow in z < 0.4 Radio-Loud Quasars (United States)

    DeMarcy, Bryan; Serra, Viktoriah; Culliton, Chris; Ganguly, Rajib; Runnoe, Jessie; Charlton, Jane; Eracleous, Michael; Misawa, Toru; Narayanan, Anand


    Quasar outflows are often invoked in models for galaxy evolution to inject energy and momentum into the gas in the host galaxy and influence its star formation history. Thus, the study of quasar outflows is essential for understanding galaxy evolution. N V absorption systems within the associated region (|Δv| ≤ 5000 km s-1) of the quasar are thought to be intrinsic since many show evidence for partial covering of the quasar. A recent archival study of quasar spectra taken with COS/G130M or G160M found 39/181 radio-quiet quasars show intrinsic N V absorption, while none of the 31 radio-loud quasars have N V absorption detected (Culliton et al. 2017). Further investigation of these radio-loud quasars showed a clear bias towards compact morphologies as revealed by FIRST 1.4 GHz imaging and comparatively flat radio spectra. This suggests we are viewing more face-on orientations which prevent us from seeing absorption outflows. The cause for such bias within the HST archive is still unknown; however, it could explain the lack of radio-loud intrinsic N V absorption seen by Culliton et al. (2017). Alternatively, the quasar wind structure may be fundamentally different between radio-loud and radio-quiet objects. We used COS/G130M or G160M to obtain rest-frame UV spectra (1195 Å - 1250 Å) of 14 low-redshift SDSS radio-loud quasars which show lobe-dominated FIRST morphologies to distinguish between these possibilities. Intrinsic N V absorption was detected in 6 of our 14 quasars. This suggests the lack of detections in the archival study was a result of an orientation effect/sampling bias rather than to differences in wind structure between radio-loud and radio-quiet quasars. Interestingly, we find significant overlap in radio core fractions between quasars with and without N V detection. Quasars in our sample with N V detection span a range of core fractions from < 0.01 up to 0.89 while those without detected N V range from 0.04 up to 0.93. A laminar outflow with a


    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Mignani, R. P.; Luca, A. De; Salvetti, D. [INAF—Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133, Milano (Italy); Parkinson, P. M. Saz [Santa Cruz Institute for Particle Physics, Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Hartog, P. R. Den [Stanford University HEPL/KIPAC, 452 Lomita Mall, Stanford, CA 94305-4085 (United States); Wolff, M. T., E-mail: [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)


    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet (RQ) γ-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from γ-ray pulsar timing. For PSR J2030+4415 we found evidence for a ∼10″-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. and confirm that, on average, the γ-ray-to-X-ray flux ratios (F{sub γ}/F{sub X}) of RQ pulsars are higher than for the radio-loud (RL) ones. Furthermore, while the F{sub γ}/F{sub X} distribution features a single peak for the RQ pulsars, the distribution is more dispersed for the RL ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  17. On the Radio and Optical Luminosity Evolution of Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; /KIPAC, Menlo Park /SLAC; Petrosian, V.; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.; Lawrence, A.; /Edinburgh U., Inst. Astron.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.


    We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness R defined as the ratio of radio and optical luminosities, using a flux limited data set containing 636 quasars with radio and optical fluxes from White et al. We first note that when dealing with multivariate data it is imperative to first determine the true correlations among the variables, not those introduced by the observational selection effects, before obtaining the individual distributions of the variables. We use the methods developed by Efron and Petrosian which are designed to obtain unbiased correlations, distributions, and evolution with redshift from a data set truncated due to observational biases. It is found that as expected the population of quasars exhibits strong positive correlation between the radio and optical luminosities and that this correlation deviates from a simple linear relation in a way indicating that more luminous quasars are more radio loud. We also find that there is a strong luminosity evolution with redshift in both wavebands, with significantly higher radio than optical evolution. We conclude that the luminosity evolution obtained by arbitrarily separating the sources into radio loud (R > 10) and radio quiet (R < 10) populations introduces significant biases that skew the result considerably. We also construct the local radio and optical luminosity functions and the density evolution. Finally, we consider the distribution of the radio loudness parameter R obtained from careful treatment of the selection effects and luminosity evolutions with that obtained from the raw data without such considerations. We find a significant difference between the two distributions and no clear sign of bi-modality in the true distribution. Our results indicate therefore, somewhat surprisingly, that there is no critical switch in the efficiency of the production of disk outflows/jets between very radio quiet and very radio

  18. Astronomy: Quasars signpost massive galaxies (United States)

    Bouwens, Rychard


    The neighbourhoods of extremely bright astronomical objects called quasars in the early Universe have been incompletely probed. Observations suggest that these regions harbour some of the most massive known galaxies. See Letter p.457

  19. MUSE-inspired view of the quasar Q2059-360, its Lyman α blob, and its neighborhood (United States)

    North, P. L.; Marino, R. A.; Gorgoni, C.; Hayes, M.; Sluse, D.; Chelouche, D.; Verhamme, A.; Cantalupo, S.; Courbin, F.


    The radio-quiet quasar Q2059-360 at redshift z = 3.08 is known to be close to a small Lyman α blob (LAB) and to be absorbed by a proximate damped Lyα (PDLA) system. Here, we present the Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy follow-up of this quasi-stellar object (QSO). Our primary goal is to characterize this LAB in detail by mapping it both spatially and spectrally using the Lyα line, and by looking for high-ionization lines to constrain the emission mechanism. Combining the high sensitivity of the MUSE integral field spectrograph mounted on the Yepun telescope at ESO-VLT with the natural coronagraph provided by the PDLA, we map the LAB down to the QSO position, after robust subtraction of QSO light in the spectral domain. In addition to confirming earlier results for the small bright component of the LAB, we unveil a faint filamentary emission protruding to the south over about 80 pkpc (physical kpc); this results in a total size of about 120 pkpc. We derive the velocity field of the LAB (assuming no transfer effects) and map the Lyα line width. Upper limits are set to the flux of the N v λ1238 - 1242, C iv λ1548 - 1551, He II λ1640, and C III] λ1548 - 1551 lines. We have discovered two probable Lyα emitters at the same redshift as the LAB and at projected distances of 265 kpc and 207 kpc from the QSO; their Lyα luminosities might well be enhanced by the QSO radiation. We also find an emission line galaxy at z = 0.33 near the line of sight to the QSO. This LAB shares the same general characteristics as the 17 others surrounding radio-quiet QSOs presented previously. However, there are indications that it may be centered on the PDLA galaxy rather than on the QSO. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 60.A-9331(A).


    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; Petrosian, V. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory and Stanford University, 382 Via Pueblo Mall, Stanford, CA 94305-4060 (United States); Lawrence, A. [Institute for Astronomy, Scottish Universities Physics Alliance (SUPA), University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Stawarz, L., E-mail: [Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5510 (Japan)


    We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness R defined as the ratio of radio and optical luminosities, using a flux-limited data set containing 636 quasars with radio and optical fluxes from White et al. We first note that when dealing with multi-variate data it is imperative to first determine the true correlations among the variables, not those introduced by the observational selection effects, before obtaining the individual distributions of the variables. We use the methods developed by Efron and Petrosian which are designed to obtain unbiased correlations, distributions, and evolution with redshift from a data set truncated due to observational biases. It is found that the population of quasars exhibits strong positive correlation between the radio and optical luminosities. With this correlation, whether intrinsic or observationally induced accounted for, we find that there is a strong luminosity evolution with redshift in both wavebands, with significantly higher radio than optical evolution. We conclude that the luminosity evolution obtained by arbitrarily separating the sources into radio-loud (R > 10) and radio-quiet (R < 10) populations introduces significant biases that skew the result considerably. We also construct the local radio and optical luminosity functions and the density evolution. Finally, we consider the distribution of the radio-loudness parameter R obtained from careful treatment of the selection effects and luminosity evolutions with that obtained from the raw data without such considerations. We find a significant difference between the two distributions and no clear sign of bi-modality in the true distribution for the range of R values considered. Our results indicate therefore, somewhat surprisingly, that there is no critical switch in the efficiency of the production of disk outflows/jets between very radio-quiet and very radio-loud quasars, but rather a

  1. The Hard X-Ray Spectrum as a Probe for Black Hole Growth in Radio-Quiet Active Galactic Nuclei (United States)

    Shemmer, Ohad; Brandt, W. N.; Netzer, Hagai; Maiolino, Roberto; Kaspi, Shai


    We study the hard X-ray spectral properties of 10 highly luminous radio-quiet (RQ) active galactic nuclei (AGNs) at z = 1.3-3.2, including new XMM-Newton observations of four of these sources. We find a significant correlation between the normalized accretion rate (L/LEdd) and the hard X-ray photon index (Γ) for 35 moderate- to high-luminosity RQ AGNs, including our 10 highly luminous sources. Within the limits of our sample, we show that a measurement of Γ and LX can provide an estimate of L/LEdd and black hole mass (MBH) with a mean uncertainty of a factor of lesssim3 on the predicted values of these properties. This may provide a useful probe for tracing the history of BH growth in the universe, utilizing samples of X-ray-selected AGNs for which L/LEdd and MBH have not yet been determined systematically. It may prove to be a useful way to probe BH growth in distant Compton-thin type 2 AGNs. We also find that the optical-X-ray spectral slope (αox) depends primarily on optical-UV luminosity rather than on L/LEdd in a sample of RQ AGNs spanning 5 orders of magnitude in luminosity and over 2 orders of magnitude in L/LEdd. We detect a significant Compton-reflection continuum in two of our highly luminous sources, and in the stacked X-ray spectrum of seven other sources with similar luminosities, we obtain a mean relative Compton reflection of R = 0.9+ 0.6-0.5 and an upper limit on the rest-frame equivalent width of a neutral Fe Kα line of 105 eV. We do not detect a significant steepening of the X-ray power-law spectrum below rest-frame 2 keV in any of our highly luminous sources, suggesting that a soft-excess feature, commonly observed in local AGNs, either does not depend strongly on L/LEdd, or is not accessible at high redshifts using current X-ray detectors.

  2. Feedback from Broad Absorption Line Quasars (United States)

    Chartas, George; Saez, C.


    The fraction of the total bolometric energy released over an AGN's lifetime into the ISM and IGM in the form kinetic energy injection scales as the outflow velocity to the third power so we expect that powerful broad absorption line (BAL) quasars may have mass outflow rates that are large enough to influence significantly the formation of the host galaxy and to regulate the growth of the central black hole. One of the most promising radio quiet quasars for studying the properties of the outflow is the lensed BAL quasar APM 08279+5255. The large flux magnification by a factor of about 100 provided by the gravitational lens effect combined with the large redshift (z = 3.91) of the quasar have provided the highest S/N X-ray spectra of a quasar containing X-ray BALs. We present results from recent monitoring observations of APM 08279+5255. performed with the Suzaku, XMM-Newton and Chandra observatories. Significant variability of the X-ray BALs is detected on timescales as short as 4 days (proper time) implying launching radii of about 6 times the Schwarzschild radius. The fitted width of the X-ray absorption troughs imply a large gradient in the outflow velocity of the X-ray absorbers with projected outflow velocities of up to 0.5c. The notch-like shape of the detected X-ray BALs are similar to those produced in recent numerical simulations (i.e. Schurch & Done 2007) that include radiative transfer calculations through highly ionized X-ray absorbers outflowing at near relativistic velocities. We provide preliminary constraints of the outflows properties.

  3. Quasar-mode Feedback in Nearby Type 1 Quasars: Ubiquitous Kiloparsec-scale Outflows and Correlations with Black Hole Properties (United States)

    Rupke, David S. N.; Gültekin, Kayhan; Veilleux, Sylvain


    The prevalence and properties of kiloparsec-scale outflows in nearby Type 1 quasars have been the subject of little previous attention. This work presents Gemini integral field spectroscopy of 10 Type 1 radio-quiet quasars at z \\equiv ) of 200–1300 {km} {{{s}}}-1 and peak velocities (maximum {v}98 % ) of 500–2600 {km} {{{s}}}-1. These minor-axis outflows are powered primarily by the central active galactic nucleus, reach scales of 3–12 kpc, and often fill the field of view. Including molecular data and Type 2 quasar measurements, nearby quasars show a wide range in mass outflow rates ({dM}/{dt}=1 to > 1000 {M}ȯ {{yr}}-1) and momentum boosts [(c {dp}/{dt})/{L}{AGN}=0.01{--}20]. After extending the mass scale to Seyferts, dM/dt and dE/dt correlate with black hole mass ({dM}/{dt}∼ {M}{BH}0.7+/- 0.3 and {dE}/{dt}∼ {M}{BH}1.3+/- 0.5). Thus, the most massive black holes in the local universe power the most massive and energetic quasar-mode winds.

  4. The phylogeny of quasars and the ontogeny of their central black holes (United States)

    Fraix-Burnet, Didier; Marziani, Paola; D'Onofrio, Mauro; Dultzin, Deborah


    The connection between multifrequency quasar observational and physical parameters related to accretion processes is still open to debate. In the last 20 year, Eigenvector 1-based approaches developed since the early papers by Boroson and Green (1992) and Sulentic et al. (2000b) have been proved to be a remarkably powerful tool to investigate this issue, and have led to the definition of a quasar "main sequence". In this paper we perform a cladistic analysis on two samples of 215 and 85 low-z quasars (z ~ 0.7) which were studied in several previous works and which offer a satisfactory coverage of the Eigenvector 1-derived main sequence. The data encompass accurate measurements of observational parameters which represents key aspects associated with the structural diversity of quasars. Cladistics is able to group sources radiating at higher Eddington ratios, as well as to separate radio-quiet (RQ) and radio-loud (RL) quasars. The analysis suggests a black hole mass threshold for powerful radio emission and also properly distinguishes core-dominated and lobe-dominated quasars, in accordance with the basic tenet of RL unification schemes. Considering that black hole mass provides a sort of "arrow of time" of nuclear activity, a phylogenetic interpretation becomes possible if cladistic trees are rooted on black hole mass: the ontogeny of black holes is represented by their monotonic increase in mass. More massive radio-quiet Population B sources at low-z become a more evolved counterpart of Population A i.e., wind dominated sources to which the "local" Narrow-Line Seyfert 1s belong.

  5. A Quasar Turns On (United States)

    Kohler, Susanna


    The intermediate Palomar Transient Factory (iPTF) has discovered a quasar the brightly-shining, active nucleus of a galaxy abruptly turning on in what appears to be the fastest such transition ever seen in such an object.A Rapid TransitionQuasars are expected to show variations in brightness on timescales of hours to millions of years, but its not often that we get to study their major variability in real time! So far, weve discovered only a dozen changing-look quasars active galactic nuclei that exhibit major changes in their spectral class and brightness between observations. Roughly half of these were quasars that turned on and half were quasars that turned off, generally on timescales of maybe 5 or 10 years.The dramatic change in spectrum of iPTF 16bco between the archival SDSS data from 2004 (bottom) and the follow-up spectroscopy from Keck 2+DEIMOS in 2016 (top). [Adapted from Gezari et al. 2017]In June 2016, however, a team of scientists led by Suvi Gezari (University of Maryland) discovered iPTF 16bco, a nuclear transient that wasnt there the last time Palomar checked in 2012. A search through archival Sloan Digital Sky Survey and GALEX data in addition to some follow-up X-ray imaging and spectroscopic observations told the team what they needed to know: iPTF 16bco is a quasar that only just turned on within the 500 days preceding the iPTF observations.This source, in fact, is a 100-million-solar-mass black hole located at the center of a galaxy at a redshift of z= 0.237. In just over a year, the source changed classification from a galaxy with weak narrow-line emission to a quasar with characteristic strong, broad emission lines and a ten-fold increase in continuum brightness! What caused this sudden transition?Instabilities at Fault?iPTF 16bco and the other known changing-look quasars with disappearing (red circles) and appearing (blue circles) broad-line emission. [Adapted from Gezari et al. 2017]Gezari and collaborators used the large number of recent

  6. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines (United States)

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.


    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.


    Energy Technology Data Exchange (ETDEWEB)

    Balokovic, M. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Smolcic, V. [Argelander-Institut fuer Astronomie, Auf dem Hugel 71, D-53121 Bonn (Germany); Ivezic, Z. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Zamorani, G. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Schinnerer, E. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)


    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 {+-} 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.


    Energy Technology Data Exchange (ETDEWEB)

    Punsly, Brian, E-mail: [1415 Granvia Altamira, Palos Verdes Estates CA, USA 90274 and ICRANet, Piazza della Repubblica 10 Pescara I-65100 (Italy)


    Hubble Space Telescope (HST) spectra of the EUV, the optically thick emission from the innermost accretion flow onto the central supermassive black hole, indicate that radio loud quasars (RLQs) tend to be EUV weak compared to the radio-quiet quasars; yet the remainder of the optically thick thermal continuum is indistinguishable. The deficit of EUV emission in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. This article is an examination of the evidence for a distribution of magnetic flux tubes in the innermost accretion flow that results in magnetically arrested accretion (MAA) and creates the EUV deficit. These same flux tubes and possibly the interior magnetic flux that they encircle are the sources of the jet power as well. In the MAA scenario, islands of large-scale vertical magnetic flux perforate the innermost accretion flow of RLQs. The first prediction of the theory that is supported by the HST data is that the strength of the (large-scale poloidal magnetic fields) jets in the MAA region is regulated by the ram pressure of the accretion flow in the quasar environment. The second prediction that is supported by the HST data is that the rotating magnetic islands remove energy from the accretion flow as a Poynting flux dominated jet in proportion to the square of the fraction of the EUV emitting gas that is displaced by these islands.


    Energy Technology Data Exchange (ETDEWEB)

    Eitan, Assaf; Behar, Ehud, E-mail:, E-mail: [Physics Department, Technion, Haifa 32000 (Israel)


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

  10. On the puzzling high-energy pulsations of the energetic radio-quiet γ-ray pulsar J1813–1246

    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Pizzocaro, D.; De Luca, A.; Caraveo, P.; Salvetti, D. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Harding, A. [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Saz Parkinson, P. M. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Acero, F., E-mail: [Laboratoire AIM, CEA-IRFU/CNRS/Universit Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)


    We have analyzed the new deep XMM-Newton and Chandra observations of the energetic, radio-quiet pulsar J1813–1246. The X-ray spectrum is nonthermal, very hard, and absorbed. Based on spectral considerations, we propose that J1813 is located at a distance further than 2.5 kpc. J1813 is highly pulsed in the X-ray domain, with a light curve characterized by two sharp, asymmetrical peaks, separated by 0.5 in phase. We detected no significant X-ray spectral changes during the pulsar phase. We extended the available Fermi ephemeris to five years. We found two glitches. The γ-ray light curve is characterized by two peaks, separated by 0.5 in phase, with a bridge in between and no off-pulse emission. The spectrum shows clear evolution in phase, being softer at the peaks and hardening toward the bridge. Surprisingly, both X-ray peaks lag behind the γ-ray ones by a quarter of phase. We found a hint of detection in the 30-500 keV band with INTEGRAL, which is consistent with the extrapolation of both the soft X-ray and γ-ray emission of J1813. The unique X-ray and γ-ray phasing suggests a singular emission geometry. We discuss some possibilities within the current pulsar emission models. Finally, we develop an alternative geometrical model where the X-ray emission comes from polar cap pair cascades.


    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun, E-mail: [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)


    We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., α{sub ν12} (1000 ∼ 2000 Å) and α{sub ν24} (2000 ∼ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher α{sub ν}) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both α{sub ν12} and α{sub ν24} show significant anti-correlations with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed α{sub ν} − z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσ{sub v} ∼ 10{sup −5}h Mpc{sup −1} at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed.

  12. Exploration of quasars with the Gaia mission (United States)

    Proft, Svea; Wambsganss, Joachim


    We analyze the opportunities in and limits to investigating quasars with the Gaia satellite by studying Gaia's low- and high-resolution quasar spectra, with consideration of their signal-to-noise ratios. Furthermore, we explore bright quasars from the Sloan Digital Sky Survey with broad emission lines (BELs) redshifted into the spectral range of Gaia's Radial Velocity Spectrograph (RVS). We find that Gaia low-resolution spectra of quasars enable a determination of equivalent widths, continuum variability, and the Baldwin effect. Additionally, it will be feasible to analyze BEL reverberation mapping with Gaia data for a small sample of objects. These quasars should have a high cadence of measurements or higher time lags due to large redshifts, high quasar luminosities, or selected low-ionization lines. More than 500 known quasars will also get high-resolution spectra of individual BELs in the small wavelength range of the RVS. This allows an investigation of broad emission line shapes and their variabilities to get information on the spatial structure and kinematics of the broad line region. We identify six known variable SDSS quasars with BELs in the RVS that have interesting spectra for a potential intrinsic line variability investigation. However, the signal-to-noise ratio of the RVS is too small for studying narrow and broad absorption lines in quasar spectra.

  13. Investigating Quasar Diversity using UV, X-ray, and Emission-line Properties (United States)

    Briana Rivera, Angelica; Richards, Gordon; Shemmer, Ohad; Gallagher, Sarah


    We investigate the diversity of quasars through the analysis of their UV (Sheldon et al, these proceedings), X-ray, and emission-line properties. We concentrate on a sample of 25 radio-quiet SDSS quasars with HST observations that all have similar optical luminosities and redshifts (z~0.5). These objects fill gaps in the sample of “reverberation mapped (RM)” quasars in terms of their CIV parameter space (CIV EQW vs. CIV blueshift). In addition to exploring their UV properties, we use Chandra observations to analyze their X-ray properties (Γ, αox, Δαox), in order to determine how accretion disk winds (which are regulated by αox) contribute to the diversity of UV emission-line properties in quasars. We compare optical and X-ray derived values of L/LEdd , as Γ has been shown to be an indicator of the accretion rate. We are able to determine Γ for 7 quasars from the Chandra sample with over 100 counts. Preliminary data reduction demonstrates that all of the quasars observed with over 100 counts have similar values of αox and Δαox (averaging ~ -1.56 and ~0.42, respectively), while those below 100 counts lie within a wider, weaker range (average αox ~ -1.78, and average Δαox ~0.2). With the combined UV and X-ray data, we explore the differences between quasars and attempt to understand how/when quasars can have high L/LEdd, but show little evidence for strong winds.

  14. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

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


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

  15. A 100 kpc nebula associated with the `Teacup' fading quasar (United States)

    Villar-Martín, M.; Cabrera-Lavers, A.; Humphrey, A.; Silva, M.; Ramos Almeida, C.; Piqueras-López, J.; Emonts, B.


    We report the discovery of an ˜100 kpc ionized nebula associated with the radio-quiet type 2 quasar (QSO2) nicknamed the `Teacup' (z = 0.085). The giant nebula is among the largest known around active galaxies at any z. We propose that it is part of the circumgalactic medium (CGM) of the QSO2 host, which has been populated with tidal debris by galactic interactions. This rich gaseous medium has been rendered visible due to the illumination by the powerful active nucleus (AGN). Subsolar abundances (˜0.5 Z⊙) are tentatively favoured by AGN photoionization models. We also report the detection of coronal emission (Fe+6) from the NE bubble, at ˜9 kpc from the AGN. The detection of coronal lines at such large distances from the AGN and the [N II] λ6583/Hα, [S II] λλ6716,6731/Hα, [O I] λ6300/Hα optical emission-line ratios of the giant nebula are consistent with the fading quasar scenario proposed by Gagne et al. The fading rate appears to have been faster in the last ˜46 000 yr. Deep wide field integral field spectroscopy of giant nebulae around powerful AGN such as the `Teacup's' with instruments such as MUSE on VLT opens up a way to detect and study the elusive material from the CGM around massive active galaxies thanks to the illumination by the luminous AGN.

  16. Evidence for the Thermal Sunyaev Zeldovich Effect Associated with Quasar Feedback (United States)

    Crichton, Devin; Gralla, Megan B.; Hall, Kirsten; Marriage, Tobias A.; Zakamska, Nadia L.; Battaglia, Nick; Bond, J. Richard; Devlin, Mark J.; Hill, J. Colin; Hilton, Matt; hide


    Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalogue, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We constrain the form of the far-infrared emission and find 3 sigma-4 sigma evidence for the thermal Sunyaev-Zel'dovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy (6.2 plus or minus 1.7) × 10 (exp 60) erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of (1-5) × 10(exp 12) h(exp -1) solar mass that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. Our measurements are consistent with quasars depositing up to (14.5 +/- 3.3)tau (sub 8)(exp -1) per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is tau(sub 8) x 108 yr. For high quasar host masses, approximately 10(exp 13) h(exp -1) solar mass, this percentage will be reduced. Furthermore, the uncertainty on this percentage is only statistical and additional systematic uncertainties enter at the 40 per cent level. The SEDs are dust dominated in all bands and we consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 3 sigma-4 sigma level for most models.

  17. Imprints of the super-Eddington accretion on the quasar clustering (United States)

    Oogi, Taira; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Makiya, Ryu; Nagashima, Masahiro; Okamoto, Takashi; Shirakata, Hikari


    Super-Eddington mass accretion has been suggested as an efficient mechanism to grow supermassive black holes. We investigate the imprint left by the radiative efficiency of the super-Eddington accretion process on the clustering of quasars using a new semi-analytic model of galaxy and quasar formation based on large-volume cosmological N-body simulations. Our model includes a simple model for the radiative efficiency of a quasar, which imitates the effect of photon trapping for a high mass accretion rate. We find that the model of radiative efficiency affects the relation between the quasar luminosity and the quasar host halo mass. The quasar host halo mass has only weak dependence on quasar luminosity when there is no upper limit for quasar luminosity. On the other hand, it has significant dependence on quasar luminosity when the quasar luminosity is limited by its Eddington luminosity. In the latter case, the quasar bias also depends on the quasar luminosity, and the quasar bias of bright quasars is in agreement with observations. Our results suggest that the quasar clustering studies can provide a constraint on the accretion disc model.

  18. GALEX observations of quasar variability in the ultraviolet (United States)

    Welsh, B. Y.; Wheatley, J. M.; Neil, J. D.


    rollover in the NUV SF for all redshift values, which is also observed (with a lower signiÞcance) in the FUV variability data. Although we find no strong relationship between UV variability and redshift, our data do show that higher redshift quasars appear to be more variable than their low redshift counterparts. Our data also show that, for all values of time-lag, the more luminous quasars tend to be slightly less UV variable, with perhaps the exception of FUV variable quasars for short time-lags. Although our data sample is small, we find that radio-loud quasars are marginally more variable than radio quiet ones by a factor ~2 in the NUV and by a factor 1 - 3 in the FUV. Therefore, our present observations support the notion in which the radio properties of quasars have a limited influence on the observed UV variability of these objects. In summation, our present analysis favors a quasar model in which UV variability is mainly due to stochastic changes in the underlying continuum level, rather than models that favor gravitational microlensing or discrete-event processes.

  19. FR-II Broad Absorption Line Quasars and the Life Cycle of Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Gregg, M D; Becker, R H; de Vries, W


    By combining the Sloan Digitized Sky Survey Third Data Release quasar list with the VLA FIRST survey, we have identified five objects having both broad absorption lines in their optical spectra and FR-II radio morphologies. We identify an additional example of this class from the FIRST Bright Quasar Survey, J1408+3054. Including the original FR-II-BAL object, J1016+5209, brings the number of such objects to eight. These quasars are relatively rare; finding this small handful has required the 45,000-large quasar sample of SDSS. The FR-II-BAL quasars exhibit a significant anti-correlation between radio-loudness and the strength of the BAL features. This is easily accounted for by the evolutionary picture in which quasars emerge from cocoons of BAL-producing material which stifle the development of radio jets and lobes. There is no such simple explanation for the observed properties of FR-II-BALs in the unification-by-orientation model of quasars. The rarity of the FR-II-BAL class implies that the two phases do not coexist for very long in a single quasar, perhaps less than 10{sup 5} years, with the combined FR-II, high ionization broad absorption phase being even shorter by another factor of 10 or more.

  20. The z = 5 Quasar Luminosity Function from SDSS Stripe 82 (United States)

    McGreer, Ian D.; Jiang, Linhua; Fan, Xiaohui; Richards, Gordon T.; Strauss, Michael A.; Ross, Nicholas P.; White, Martin; Shen, Yue; Schneider, Donald P.; Myers, Adam D.; Brandt, W. Niel; DeGraf, Colin; Glikman, Eilat; Ge, Jian; Streblyanska, Alina


    We present a measurement of the Type I quasar luminosity function at z = 5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M 1450 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7 confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of ~2 greater decrease in the number density of luminous quasars (M 1450 joint facility of the Smithsonian Institution and the University of Arizona. This paper also includes data gathered with the 6.5 m Magellan telescopes located at Las Campanas Observatory, Chile.

  1. Quasars Probing Quasars: the Circumgalactic Medium Surrounding z ~ 2 Quasars (United States)

    Lau, Marie; Quasars Probing Quasars survey


    Understanding the circumgalactic medium--the gaseous halo surrounding a galaxy, is an integral part to understanding galaxy evolution. The z ~ 2-3 universe is interesting as this is when the star formation rate and AGN activity peak. My thesis concludes the decade-long Quasars Probing Quasars survey designed for studying massive galaxy formation and quasar feedback. I use background quasar sightlines that pass close to foreground quasars to study the circumgalactic medium of quasar-host galaxies in absorption. My sample of 149 quasar pairs involve spectra taken with 17 different optical and near IR instruments. I present results on the statistical and physical properties of the circumgalactic medium. The circumgalactic medium is enriched even beyond the virial radius. The alpha/Fe abundance ratio is enhanced, suggesting enrichment from core-collapse supernovae. The cool gas mass within the virial radius is enough to fuel star formation for another Gyr, and may account for 1/3 of the baryonic budget of the galaxy halo. The ionization state increases with projected distance from the quasar, which implies the quasar does not dominate the ionizing radiation flux. However, detection of fluorescent Lyman-alpha emission and NV absorption imply these transverse absorbers are partially illuminated by the quasar. In one peculiar case, the absorbing clump has density >100 cm^-3 and sub-parsec size. The average absorption in the circumgalactic medium exhibits large velocity widths, and is asymmetric about the systemic redshift of the galaxies. The widths are consistent with gravitational motions and Hubble flow, and outflows are not required to explain them. The asymmetry can be explained if the ionizing radiation from the quasar is anisotropic or intermittent and the gas is not in inflow. My results pose challenges for cosmological hydrodynamic simulations to produce a substantial cool gas reservoir surrounding quasars, that is also enriched and shows extreme kinematics.

  2. Towards a comprehensive picture of powerful quasars, their host galaxies and quasar winds at z ˜ 0.5 (United States)

    Wylezalek, Dominika; Zakamska, Nadia L.; Liu, Guilin; Obied, Georges


    Luminous type-2 quasars in which the glow from the central black hole is obscured by dust are ideal targets for studying their host galaxies and the quasars' effect on galaxy evolution. Such feedback appears ubiquitous in luminous obscured quasars where high-velocity-ionized nebulae have been found. We present rest-frame yellow-band (˜5000 Å) observations using the Hubble Space Telescope (HST) for a sample of 20 luminous quasar host galaxies at 0.2 host galaxy observations with geometric measurements of quasar illumination using blue-band HST observations and [O III] integral field unit observations probing the quasar winds. The HST images reveal bright merger signatures in about half the galaxies; a significantly higher fraction than in comparison inactive ellipticals. We show that the host galaxies are primarily bulge-dominated, with masses close to M*, but belong to host galaxies' high star formation rates and bright merger signatures, we suggest that this low-redshift outbreak of luminous quasar activity is triggered by recent minor mergers. Combining these novel observations, we present new quasar unification tests, which are in agreement with expectations of the orientation-based unification model for quasars.

  3. The Final SDSS High-redshift Quasar Sample of 52 Quasars at z>5.7 (United States)

    Jiang, Linhua; McGreer, Ian D.; Fan, Xiaohui; Strauss, Michael A.; Bañados, Eduardo; Becker, Robert H.; Bian, Fuyan; Farnsworth, Kara; Shen, Yue; Wang, Feige; Wang, Ran; Wang, Shu; White, Richard L.; Wu, Jin; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian


    We present the discovery of nine quasars at z˜ 6 identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of z˜ 6 quasars in the SDSS footprint. Our final sample consists of 52 quasars at 5.7\\lt z≤slant 6.4, including 29 quasars with {z}{AB}≤slant 20 mag selected from 11,240 deg2 of the SDSS single-epoch imaging survey (the main survey), 10 quasars with 20≤slant {z}{AB}≤slant 20.5 selected from 4223 deg2 of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to {z}{AB}≈ 22 mag from the 277 deg2 in Stripe 82. They span a wide luminosity range of -29.0≤slant {M}1450≤slant -24.5. This well-defined sample is used to derive the quasar luminosity function (QLF) at z˜ 6. After combining our SDSS sample with two faint ({M}1450≥slant -23 mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope β of the QLF is well constrained to be β =-2.8+/- 0.2. Due to the small number of low-luminosity quasars, the faint-end slope α and the characteristic magnitude {M}1450* are less well constrained, with α =-{1.90}-0.44+0.58 and {M}* =-{25.2}-3.8+1.2 mag. The spatial density of luminous quasars, parametrized as ρ ({M}1450\\lt -26,z)=ρ (z=6){10}k(z-6), drops rapidly from z˜ 5 to 6, with k=-0.72+/- 0.11. Based on our fitted QLF and assuming an intergalactic medium (IGM) clumping factor of C = 3, we find that the observed quasar population cannot provide enough photons to ionize the z˜ 6 IGM at ˜90% confidence. Quasars may still provide a significant fraction of the required photons, although much larger samples of faint quasars are needed for more stringent constraints on the quasar contribution to reionization.

  4. Mean and extreme radio properties of quasars and the origin of radio emission

    Energy Technology Data Exchange (ETDEWEB)

    Kratzer, Rachael M.; Richards, Gordon T. [Department of Physics, Drexel University, Philadelphia, PA (United States)


    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  5. Quasar Saleem Padiath

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Genetics. Quasar Saleem Padiath. Articles written in Journal of Genetics. Volume 83 Issue 2 August 2004 pp 117-119 Perspectives. Chance in our strands? Quasar Saleem Padiath B. Jagadeeshwara Rao · More Details Fulltext PDF ...


    Energy Technology Data Exchange (ETDEWEB)

    Teng, Stacy H.; Mushotzky, Richard F.; Reynolds, Christopher S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Sambruna, Rita M. [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States); Davis, David S., E-mail: [CRESST and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States)


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

  7. Weak hard X-ray emission from two broad absorption line quasars observed with NuSTAR: Compton-thick absorption or intrinsic X-ray weakness?

    DEFF Research Database (Denmark)

    Luo, B.; Brandt, W. N.; Alexander, D. M.


    We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus...... and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain ≈ 400-600 hard X-ray (≳ 10 keV) photons with NuSTAR, provided that these photons...... are not significantly absorbed (NH ≲ 1024 cm-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain...


    Energy Technology Data Exchange (ETDEWEB)

    McGreer, Ian D.; Fan, Xiaohui [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Eftekharzadeh, Sarah; Myers, Adam D., E-mail: [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)


    We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada–France–Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ∼135 kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5; the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r{sub 0}){sup −2}, this discovery implies a correlation length of r{sub 0} ≳ 20h{sup −1} Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift.

  9. Merging Galaxies Create a Binary Quasar (United States)


    Astronomers have found the first clear evidence of a binary quasar within a pair of actively merging galaxies. Quasars are the extremely bright centers of galaxies surrounding super-massive black holes, and binary quasars are pairs of quasars bound together by gravity. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution's Magellan telescope in Chile show two distinct galaxies with "tails" produced by tidal forces from their mutual gravitational attraction. "This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting," says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger. Most, if not all, large galaxies, such as our galaxy the Milky Way, host super-massive black holes at their centers. Because galaxies regularly interact and merge, astronomers have assumed that binary super-massive black holes have been common in the Universe, especially during its early history. Black holes can only be detected as quasars when they are actively accreting matter, a process that releases vast amounts of energy. A leading theory is that galaxy mergers trigger accretion, creating quasars in both galaxies. Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve. The binary quasar, labeled SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a large scale astronomical survey of galaxies and over 120,000 quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues* using NASA's Chandra's X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar


    Energy Technology Data Exchange (ETDEWEB)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu [Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo [Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 (Japan); Willott, Chris J. [Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Im, Myungshin [Center for the Exploration of the Origin of the Universe (CEOU), Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-rho, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Ouchi, Masami [Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Hibon, Pascale, E-mail: [Gemini Observatory, La Serena (Chile)


    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.

  11. The Extremely Luminous Quasar Survey in the SDSS Footprint. I. Infrared-based Candidate Selection (United States)

    Schindler, Jan-Torge; Fan, Xiaohui; McGreer, Ian D.; Yang, Qian; Wu, Jin; Jiang, Linhua; Green, Richard


    Studies of the most luminous quasars at high redshift directly probe the evolution of the most massive black holes in the early universe and their connection to massive galaxy formation. However, extremely luminous quasars at high redshift are very rare objects. Only wide-area surveys have a chance to constrain their population. The Sloan Digital Sky Survey (SDSS) has so far provided the most widely adopted measurements of the quasar luminosity function at z> 3. However, a careful re-examination of the SDSS quasar sample revealed that the SDSS quasar selection is in fact missing a significant fraction of z≳ 3 quasars at the brightest end. We identified the purely optical-color selection of SDSS, where quasars at these redshifts are strongly contaminated by late-type dwarfs, and the spectroscopic incompleteness of the SDSS footprint as the main reasons. Therefore, we designed the Extremely Luminous Quasar Survey (ELQS), based on a novel near-infrared JKW2 color cut using Wide-field Infrared Survey Explorer mission (WISE) AllWISE and 2MASS all-sky photometry, to yield high completeness for very bright ({m}{{i}}learning algorithms on SDSS and WISE photometry for quasar-star classification and photometric redshift estimation. The ELQS will spectroscopically follow-up ˜230 new quasar candidates in an area of ˜12,000 deg2 in the SDSS footprint to obtain a well-defined and complete quasar sample for an accurate measurement of the bright-end quasar luminosity function (QLF) at 3.0≤slant z≤slant 5.0. In this paper, we present the quasar selection algorithm and the quasar candidate catalog.

  12. Kinematics of the ionized gas around the quasar MR 2251-178

    NARCIS (Netherlands)

    Mulder, P.S.; Valentijn, E. A.

    O III forbidden line observations of the nearby quasar MR 2251-178 were made with the Taurus II imaging Fabry-Perot instrument. The line emission around the quasar is found to consist of several regions of high surface brightness located in two half-cones with an opening angle of about 37 deg

  13. New quasar survey with WIRO: The light curves of quasars over ~15 year timescales (United States)

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


    Quasars, a type of active galactic nuclei (AGN), are known to vary in brightness on 10 day to 7 year timescales. While it has been proposed that this variability is caused by instability in the accretion disk, Poisson processes, or microlensing, the exact cause remains mysterious. Understanding the physical mechanisms that drive quasar variability will require imaging of quasars over a wide range of timescales. In particular, the observations required to constrain longer timescales can be difficult to conduct. This summer ~1000 quasars in Stripe 82 were observed in ugriz wavelength bands using WIRO, the University of Wyoming’s 2.3-meter telescope. Using these images, earlier data from the Sloan Digital Sky Survey's observations of Stripe 82, as well as various data reduction methods, the quasars’ magnitude can be studied on our extended 3 day to 15 year timescale. Here, we present the light curves of ~1000 quasars in ugriz bands as observed over the last 15 years. Thiswork is supported by the National Science Foundation under REU grant AST 1560461.

  14. Detection of Rest-frame Optical Lines from X-shooter Spectroscopy of Weak Emission Line Quasars (United States)

    Plotkin, Richard M.; Shemmer, Ohad; Trakhtenbrot, Benny; Anderson, Scott F.; Brandt, W. N.; Fan, Xiaohui; Gallo, Elena; Lira, Paulina; Luo, Bin; Richards, Gordon T.; Schneider, Donald P.; Strauss, Michael A.; Wu, Jianfeng


    Over the past 15 yr, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we present spectroscopy of seven such weak emission line quasars (WLQs) at moderate redshifts (z = 1.4-1.7) using the X-shooter spectrograph, which provides simultaneous optical and near-infrared spectroscopy covering the rest-frame ultraviolet (UV) through optical. These new observations effectively double the number of WLQs with spectroscopy in the optical rest-frame, and they allow us to compare the strengths of (weak) high-ionization emission lines (e.g., C iv) to low-ionization lines (e.g., Mg ii, Hβ, Hα) in individual objects. We detect broad Hβ and Hα emission in all objects, and these lines are generally toward the weaker end of the distribution expected for typical quasars (e.g., Hβ has rest-frame equivalent widths ranging from 15-40 Å). However, these low-ionization lines are not exceptionally weak, as is the case for high-ionization lines in WLQs. The X-shooter spectra also display relatively strong optical Fe ii emission, Hβ FWHM ≲ 4000 km s-1, and significant C iv blueshifts (≈1000-5500 km s-1) relative to the systemic redshift; two spectra also show elevated UV Fe ii emission, and an outflowing component to their (weak) Mg ii emission lines. These properties suggest that WLQs are exotic versions of “wind-dominated” quasars. Their BELRs either have unusual high-ionization components, or their BELRs are in an atypical photoionization state because of an unusually soft continuum. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program IDs 088.B-0355 and 090.B-0438.

  15. Physical Properties of 15 Quasars at z ≳ 6.5 (United States)

    Mazzucchelli, C.; Bañados, E.; Venemans, B. P.; Decarli, R.; Farina, E. P.; Walter, F.; Eilers, A.-C.; Rix, H.-W.; Simcoe, R.; Stern, D.; Fan, X.; Schlafly, E.; De Rosa, G.; Hennawi, J.; Chambers, K. C.; Greiner, J.; Burgett, W.; Draper, P. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E.; Metcalfe, N.; Waters, C.; Wainscoat, R. J.


    Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at z> 6.5 (big bang). In this work, we present six additional z≳ 6.5 quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 z≳ 6.5 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of z≳ 6.5 quasars show large blueshifts of the broad C IV λ1549 emission line compared to the systemic redshift of the quasars, with a median value ˜3× higher than a quasar sample at z˜ 1; (2) we estimate the quasars’ black hole masses ({M}{BH} ˜ (0.3-5) × 109 M ⊙) via modeling of the Mg II λ2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with =0.39) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe II/Mg II abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for z˜ 6 quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C II] 158 μm emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C II]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.

  16. Characterizing Mass Outflows in Palomar Green Quasars: evidence for AGN feedback? (United States)

    Kraemer, Steven


    The correlation between the masses of galaxy bulges and the super-massive black holes (BH) at their gravitational centers suggests that they co-evolve. The process thought to regulate bulge/BH growth is ''AGN feedback'', either in the form of radiation-driven (''quasar mode'') or mechanically driven (e.g., ''radio mode'') outflows. Our recent HST/ACS/STIS study of QSO2s has, indeed, revealed outflows, but they do not extend beyond 1.5 kpc, which calls into question their relevance to feedback processes. However, the morphologies of these objects suggest that they may be in an early state of activity, before the outflows can clear the bulges. To explore whether large-scale outflows are present, we propose to extend our study to the 7 [O III] brightest, radio quiet, PG QSO1s. Previous HST/WFPC2 images reveal that these targets possess extended emission-line regions. Therefore, we propose to obtain HST/ACS images and STIS long-slit spectra of these targets with which we will measure and model the extended emisision-line gas kinematics, probe the dynamics of the gas, and, ultimately, determine whether AGN-driven outflows exist in these QSOs. Ground-based observations lack the sensitivity to probe the extended emission-line gas, hence this study can only be accomplished with HST. These results will have profound implications towards our understanding of AGN feedback.

  17. Gravitationally lensed quasars in Gaia: I. Resolving small-separation lenses (United States)

    Lemon, Cameron A.; Auger, Matthew W.; McMahon, Richard G.; Koposov, Sergey E.


    Gaia's exceptional resolution (FWHM $\\sim$ 0.1$^{\\prime\\prime}$) allows identification and cataloguing of the multiple images of gravitationally lensed quasars. We investigate a sample of 49 known lensed quasars in the SDSS footprint, with image separations less than 2$^{\\prime\\prime}$, and find that 8 are detected with multiple components in the first Gaia data release. In the case of the 41 single Gaia detections, we generally are able to distinguish these lensed quasars from single quasars when comparing Gaia flux and position measurements to those of Pan-STARRS and SDSS. This is because the multiple images of these lensed quasars are typically blended in ground-based imaging and therefore the total flux and a flux-weighted centroid are measured, which can differ significantly from the fluxes and centroids of the individual components detected by Gaia. We compare the fluxes through an empirical fit of Pan-STARRS griz photometry to the wide optical Gaia bandpass values using a sample of isolated quasars. The positional offsets are calculated from a recalibrated astrometric SDSS catalogue. Applying flux and centroid difference criteria to spectroscopically confirmed quasars, we discover 4 new sub-arcsecond-separation lensed quasar candidates which have two distinct components of similar colour in archival CFHT or HSC data. Our method based on single Gaia detections can be used to identify the $\\sim$ 1400 lensed quasars with image separation above 0.5$^{\\prime\\prime}$, expected to have only one image bright enough to be detected by Gaia.

  18. Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs): New z > 6 Quasar Survey with Subaru/HSC (United States)

    Matsuoka, Yoshiki; SHELLQs Collaboration


    Quasars at high redshift are an important and unique probe of the distant Universe, for understanding the origin and progress of cosmic reionization, the early growth of supermassive black holes, and the evolution of quasar host galaxies and their dark matter halos, among other topics. We are currently carrying out a new spectroscopic survey, called SHELLQs (Subaru High-z Exploration of Low-Luminosity Quasars), to search for low-luminosity quasars at z > 6. By exploiting the exquisite imaging data produced by the Subaru Hyper Suprime-Cam (HSC) survey, we aim to probe quasar luminosities down to M1450 ~ -22 mag, i.e., below the classical threshold between quasars and Seyfert galaxies. Candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm. A large spectroscopic observing program is underway, using Subaru/FOCAS, GTC/OSIRIS, and Gemini/GMOS; in particular, SHELLQs has been approved as a Subaru intensive program to use 20 nights in the coming four semesters. As of August 2016, we have discovered ~40 quasars and bright galaxies at z ~ 6 and beyond, from the first 100 deg2 of the HSC survey (Matsuoka et al. 2016, ApJ, 828, 26). Surprisingly, we are starting to see the steep rise of the luminosity function of high-z galaxies, compared with that of quasars, at magnitudes fainter than M1450 ~ -22 mag or zAB ~ 24 mag. Multi-wavelength follow-up studies of the discovered objects as well as further survey observations are ongoing.

  19. Photometric classification of quasars from RCS-2 using Random Forest (United States)

    Carrasco, D.; Barrientos, L. F.; Pichara, K.; Anguita, T.; Murphy, D. N. A.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.; Hsieh, B. C.; López, S.


    The classification and identification of quasars is fundamental to many astronomical research areas. Given the large volume of photometric survey data available in the near future, automated methods for doing so are required. In this article, we present a new quasar candidate catalog from the Red-Sequence Cluster Survey 2 (RCS-2), identified solely from photometric information using an automated algorithm suitable for large surveys. The algorithm performance is tested using a well-defined SDSS spectroscopic sample of quasars and stars. The Random Forest algorithm constructs the catalog from RCS-2 point sources using SDSS spectroscopically-confirmed stars and quasars. The algorithm identifies putative quasars from broadband magnitudes (g, r, i, z) and colors. Exploiting NUV GALEX measurements for a subset of the objects, we refine the classifier by adding new information. An additional subset of the data with WISE W1 and W2 bands is also studied. Upon analyzing 542 897 RCS-2 point sources, the algorithm identified 21 501 quasar candidates with a training-set-derived precision (the fraction of true positives within the group assigned quasar status) of 89.5% and recall (the fraction of true positives relative to all sources that actually are quasars) of 88.4%. These performance metrics improve for the GALEX subset: 6529 quasar candidates are identified from 16 898 sources, with a precision and recall of 97.0% and 97.5%, respectively. Algorithm performance is further improved when WISE data are included, with precision and recall increasing to 99.3% and 99.1%, respectively, for 21 834 quasar candidates from 242 902 sources. We compiled our final catalog (38 257) by merging these samples and removing duplicates. An observational follow up of 17 bright (r classification of point sources with Random Forest algorithms to search for quasars within current and future large-area photometric surveys. Full Tables 1-3 are only available at the CDS via anonymous ftp to http

  20. Far-infrared emission in luminous quasars accompanied by nuclear outflows (United States)

    Maddox, Natasha; Jarvis, M. J.; Banerji, M.; Hewett, P. C.; Bourne, N.; Dunne, L.; Dye, S.; Eales, S.; Furlanetto, C.; Maddox, S. J.; Smith, M. W. L.; Valiante, E.


    Combining large-area optical quasar surveys with the new far-infrared (FIR) Herschel-ATLAS Data Release 1, we search for an observational signature associated with the minority of quasars possessing bright FIR luminosities. We find that FIR-bright quasars show broad C IV emission-line blueshifts in excess of that expected from the optical luminosity alone, indicating particularly powerful nuclear outflows. The quasars show no signs of having redder optical colours than the general ensemble of optically selected quasars, ruling out differences in line-of-sight dust within the host galaxies. We postulate that these objects may be caught in a special evolutionary phase, with unobscured, high black hole accretion rates and correspondingly strong nuclear outflows. The high FIR emission found in these objects is then either a result of star formation related to the outflow, or is due to dust within the host galaxy illuminated by the quasar. We are thus directly witnessing coincident small-scale nuclear processes and galaxy-wide activity, commonly invoked in galaxy simulations that rely on feedback from quasars to influence galaxy evolution.

  1. Rest-frame optical photometry of a z-7.54 quasar and its environment (United States)

    Decarli, Roberto; Banados, Eduardo; Fan, Xiaohui; Walter, Fabian; Venemans, Bram; Paolo, Emanuele; Mazzucchelli, Chiara; Wang, Feige; Stern, Daniel


    Bright quasars are unique tools to study the dawn of galaxy and black hole formation, and to investigate the properties of the universe at the earliest cosmic epochs. We recently discovered the luminous quasar ULAS J1342+0928 at a record-breaking redshift of z=7.54 (whereas the previous quasar redshift record holder was at z=7.08). The presence of a damping wing in the quasar's spectrum, associated with a highly neutral intergalactic medium, and the high bolometric luminosity, powered by accretion on a supermassive, 8e8 Msun black hole, set unparalleled constraints on the history of reionization and on the formation and evolution of first massive black holes, only 690 Myr after the Big Bang. Here we propose to obtain sensitive Spitzer observations to sample the rest-frame optical emission of this quasar and of potential bright companion galaxies. By complementing our already secured observations with HST, IRAM/NOEMA, ALMA, and many other facilities, the proposed dataset will allow us (1) to constrain the Spectral Energy Distribution of the quasar, thus disentangling the contribution of its various components at optical wavelengths; (2) to investigate the quasar environment; and (3) to lay the foundation for high-resolution imaging and sensitive spectroscopy at MIR wavelengths with the James Webb Space Telescope.

  2. Outshining the quasars at reionization

    DEFF Research Database (Denmark)

    Watson, D.; Reeves, J.N.; Hjorth, J.


    Gamma Rays: Bursts, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines, X-Rays: Galaxies, X-Rays: General Udgivelsesdato: 19 January......Gamma Rays: Bursts, Galaxies: Intergalactic Medium, Galaxies: Quasars: Absorption Lines, X-Rays: Galaxies, X-Rays: General Udgivelsesdato: 19 January...

  3. Quasars in the Cosmic Environment

    NARCIS (Netherlands)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Dultzin, Deborah; Richards, Gordon; Knapen, Johan; Shlosman, Isaac; Morganti, Raffaella; Falomo, Renato; Hawkins, Mike; Cavaliere, Alfonso; McLure, Ross; Shields, Greg; Netzer, Hagai; Proga, Daniel; Franceschini, Alberto; Fan, Xiaoui; Elvis, Martin


    We now consider the environment of quasars in the widest possible sense, from the circumnuclear regions to very large scales of hundreds of kiloparsecs. The circumgalactic environment of nearby quasars has been widely studied since the late 1960s in an attempt to test its influence on the triggering

  4. The space distribution of quasars

    NARCIS (Netherlands)

    Pilipenko, S. V.


    The space distribution of quasars from the 2dF and SDSS DR5 catalogs in the redshift interval 0.3 quasars in both catalogs are found to have the following common features: (1) when the distance between the nearest objects exceeds 35h (-1) Mpc (where h = H

  5. The jet-disk symbiosis. I. Radio to X-ray emission models for quasars. (United States)

    Falcke, H.; Biermann, P. L.


    Starting from the assumption that radio jets and accretion disks are symbiotic features present in radio loud and radio quiet quasars we scale the bulk power of radio jets with the accretion power by adding mass- and energy conservation of the whole jet-disk system to the standard Blandford & Koenigl theory for compact radio cores. The jet is described as a conically expanding plasma with maximal sound speed c/sqrt(3) enclosing relativistic particles and a magnetic field. Relativistic speeds of γ_jbeta_ j_>5 make an additional confinement unnecessary and the shape is solely given by the Mach cone. The model depends on only few parameters and can be constrained by observations. Thus we are able to show that radio and X-ray fluxes (SSC emission) of cores and lobes and typical dimensions of radio loud quasars are consistent with a jet being produced in the central engine. We present a synthetic broadband spectrum from radio to X-ray for a jet-disk system. The only way to explain the high efficiency of radio loud objects is to postulate that these objects consist of `maximal jets' with `total equipartition' where the magnetic energy flow of the jet is comparable to the kinetic jet power and the total jet power is a large fraction of the disk power. As the number of electrons is limited by the accretion flow, such a situation is only possible when the minimum Lorentz factor of the electron distribution is γ_e,min_>100(E>50MeV) or/and a large number of pairs are present. Such an electron/positron population would be a necessary consequence of hadronic interactions and may lead to some interesting effects in the low frequency self-absorbed spectrum. Emission from radio weak quasars can be explained with an initially identical jet. The difference between radio loud and radio weak could be due to a different efficiency in accelerating relativistic electrons on the sub-parsec scale only. Finally we demonstrate that in order to appease the ravenous hunger of radio loud jets

  6. Spectral Variability in Radio-Loud Quasars Minfeng Gu

    Indian Academy of Sciences (India)

    when-brighter trend, which is in contrast to our previous results. Eight of 18 SSRQs display a BWB. We found an anticorrelation between the. Eddington ratio and the variability amplitude in the r band for SSRQs, which is similar to that in radio-quiet AGNs. This implies that the thermal emission from the accretion disk may be ...

  7. Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Rumbaugh, N.; et al.


    We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey (SDSS) and 3-Year Dark Energy Survey (DES) imaging, which provide light curves spanning more than 15 years. We identified ~1000 EVQs with a maximum g band magnitude change of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L_bol~10^45-10^47 erg/s and L/L_Edd~0.01-1. Accounting for selection effects, we estimate an intrinsic EVQ fraction of ~30-50% among all g<~22 quasars over a baseline of ~15 years. These EVQs are good candidates for so-called "changing-look quasars", where a spectral transition between the two types of quasars (broad-line and narrow-line) is observed between the dim and bright states. We performed detailed multi-wavelength, spectral and variability analyses for the EVQs and compared to their parent quasar sample. We found that EVQs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their UV broad emission lines have larger equivalent widths; (2) their Eddington ratios are systematically lower; and (3) they are more variable on all timescales. The intrinsic difference in quasar properties for EVQs suggest that internal processes associated with accretion are the main driver for the observed extreme long-term variability. However, despite their different properties, EVQs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. We speculate that EVQs are normal quasars accreting at relatively low accretion rates, where the accretion flow is more likely to experience instabilities that drive the factor of few changes in flux on multi-year timescales.

  8. Calan Tololo Survey: Bright Quasars at High Redshifts (United States)

    Maza, Jose; Ruiz, Maria Teresa; Gonzalez, Luis E.; Wischnjewsky, Marina

    An objective prism survey has been started at Cerro Tololo Inter-American Observatory using the thin UV prism (1,360 Å/mm at Hγ and 1,740 Å/mm at Hβ) on the Curtis Schmidt telescope. Unfiltered baked IIIaJ plates exposed 90 minutes have been obtained for 163 fields. Unwiden spectra taken in good seeing reach B ≅ 19. This survey is an extension of the original Tololo survey (Smith 1975; Smith, Aguirre and Zemelman 1986).

  9. VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars (United States)

    Doi, Akihiro; Kawaguchi, Noriyuki; Kono, Yusuke; Oyama, Tomoaki; Fujisawa, Kenta; Takaba, Hiroshi; Sudou, Hiroshi; Wakamatsu, Ken-Ichi; Yamauchi, Aya; Murata, Yasuhiro; Mochizuki, Nanako; Wajima, Kiyoaki; Omodaka, Toshihiro; Nagayama, Takumi; Nakai, Naomasa; Sorai, Kazuo; Kawai, Eiji; Sekido, Mamoru; Koyama, Yasuhiro; VLBI Group At Geographical Survey Institute,; Asano, Shoichiro; Uose, Hisao


    We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network. We aimed to select BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of the quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 105K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources, or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.

  10. Understanding the Nature of X-ray Weak Quasars (United States)

    Brandt, William

    We propose a program of archival X-ray and related studies designed to advance understanding of the remarkable active galactic nucleus (AGN) population of X-ray weak quasars. These exceptional objects reveal phenomena that are more generally applicable but are difficult to investigate when more subtly expressed in the overall quasar population. X-ray weak quasars furthermore challenge a central tenet of X-ray astronomy that luminous X-ray emission is a universal property of efficiently accreting supermassive black holes; this idea underlies the utility of X-ray surveys for identifying AGNs throughout the Universe. Our previous findings indicate that understanding of Xray weak quasars is now primed for rapid further advances. Our studies of X-ray weak quasars will employ data from the vast archives of forefront X-ray missions, particularly XMM-Newton and Chandra, and they will also benefit greatly from the use of NuSTAR, ROSAT, Suzaku, Swift, GALEX, and WISE data. They are largely enabled by the enormous quasar samples delivered by modern widefield sky surveys. In particular, we will identify X-ray weak quasars using the serendipitous X-ray coverage of the 380,000 relatively bright quasars spectroscopically identified by the Sloan Digital Sky Survey (SDSS) from z 0.1-5.5; these are wellmatched to the depths of typical archival X-ray observations. The number of SDSS spectroscopic quasars has more than tripled in recent years, and the sample-size improvements at redshifts of z = 2-4, important for our investigations, are even more dramatic. We will construct an unprecedented new sample of X-ray weak quasars, about 20 times larger than those used currently, to enable systematic studies of the X-ray weakness phenomenon. This work should reveal the cause of X-ray weakness for quasars with weak emission lines, allowing testing of a model that relies upon small-scale shielding of ionizing photons by a thick inner accretion disk around a black hole accreting at a high

  11. Extreme Variability in a Broad Absorption Line Quasar

    Energy Technology Data Exchange (ETDEWEB)

    Stern, Daniel; Jun, Hyunsung D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Graham, Matthew J.; Djorgovski, S. G.; Donalek, Ciro; Drake, Andrew J.; Mahabal, Ashish A.; Steidel, Charles C. [California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125 (United States); Arav, Nahum; Chamberlain, Carter [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Barth, Aaron J. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Glikman, Eilat, E-mail: [Department of Physics, Middlebury College, Middlebury, VT 05753 (United States)


    CRTS J084133.15+200525.8 is an optically bright quasar at z = 2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V ∼ 17.3 between 2002 and 2008. Then, over the following five years, the source slowly brightened by approximately one magnitude, to V ∼ 16.2. Only ∼1 in 10,000 quasars show such extreme variability, as quantified by the extreme parameters derived for this quasar assuming a damped random walk model. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line quasar with extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. We report the first definitive redshift for this source, based on the detection of broad H α in a Keck/MOSFIRE spectrum. Absorption systems separated by several 1000 km s{sup −1} in velocity show coordinated weakening in the depths of their troughs as the continuum flux increases. We interpret the broad absorption line variability to be due to changes in photoionization, rather than due to motion of material along our line of sight. This source highlights one sort of rare transition object that astronomy will now be finding through dedicated time-domain surveys.

  12. Microlensing as a Possible Probe of Event-Horizon Structure in Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Tomozeiu, Mihai [Zurich U.; Mohammed, Irshad [Fermilab; Rabold, Manuel [Zurich U.; Saha, Prasenjit [Zurich U.; Wambsganss, Joachim [Heidelberg U.


    In quasars which are lensed by galaxies, the point-like images sometimes show sharp and uncorrelated brightness variations (microlensing). These brightness changes are associated with the innermost region of the quasar passing through a complicated pattern of caustics produced by the stars in the lensing galaxy. In this paper, we study whether the universal properties of optical caustics could enable extraction of shape information about the central engine of quasars. We present a toy model with a crescent-shaped source crossing a fold caustic. The silhouette of a black hole over an accretion disk tends to produce roughly crescent sources. When a crescent-shaped source crosses a fold caustic, the resulting light curve is noticeably different from the case of a circular luminosity profile or Gaussian source. With good enough monitoring data, the crescent parameters, apart from one degeneracy, can be recovered.

  13. A counter-jet in the Quasar 1049+616? | Akujor | Nigerian Journal of ...

    African Journals Online (AJOL)

    Multi-frequency and high fidelity radio observations of the quasar 1049 + 616 have been made in the frequency range 1.3 - 8.4 Ghz with the NRAO'S VLA and Jodrell Bank's MERLIN. Our new images reveal a prominent knotty jet and a possible counter-jet with an identifiable knot. The jet-to-counter-jet brightness ratio is ...

  14. Simultaneous observations of the quasar 3C 273 with INTEGRAL, XMM-Newton and RXTE

    DEFF Research Database (Denmark)

    Courvoisier, T.J.L.; Beckmann, V.; Bourban, G.


    INTEGRAL has observed the bright quasar 3C 273 on 3 epochs in January 2003 as one of the first observations of the open programme. The observation on January 5 was simultaneous with RXTE and XMM-Newton observations. We present here a first analysis of the continuum emission as observed by these 3...

  15. Quasar Jet Acceleration (United States)

    Polito, Nicholas; Hough, David


    We observed radio jets in six lobe-dominated quasars (LDQs) from 1995 to 2008 using the NRAO VLBA at 8.4 and 15 GHz. These observations have tracked jet component positions and velocities over that time period. There is a correlation between apparent jet speed and projected core distance in these LDQs at greater than 99 per cent confidence levels (Hough 2008, Extragalactic Jets, eds: Rector and DeYoung, ASP, p. 274). Four of our sources show this effect particularly strongly. We only tracked single jet components over relatively short distances, but the assumption of a unique velocity profile allows us to study component motion on an effective timescale of approximately 20-50 years. Results for 3C207 and 3C263 show a good fit using a constant acceleration model. The cause of such acceleration is still unknown, though ``magnetic acceleration'' by a gradient in magnetic field pressure is one possibility.

  16. A Hubble Diagram for Quasars

    Directory of Open Access Journals (Sweden)

    Susanna Bisogni


    Full Text Available The cosmological model is at present not tested between the redshift of the farthest observed supernovae (z ~ 1.4 and that of the Cosmic Microwave Background (z ~ 1,100. Here we introduce a new method to measure the cosmological parameters: we show that quasars can be used as “standard candles” by employing the non-linear relation between their intrinsic UV and X-ray emission as an absolute distance indicator. We built a sample of ~1,900 quasars with available UV and X-ray observations, and produced a Hubble Diagram up to z ~ 5. The analysis of the quasar Hubble Diagram, when used in combination with supernovae, provides robust constraints on the matter and energy content in the cosmos. The application of this method to forthcoming, larger quasar samples, will also provide tight constraints on the dark energy equation of state and its possible evolution with time.

  17. Quasars as Cosmological Standard Candles

    Directory of Open Access Journals (Sweden)

    C. Alenka Negrete


    Full Text Available We propose the use of quasars with accretion rate near the Eddington ratio (extreme quasars as standard candles. The selection criteria are based on the Eigenvector 1 (E1 formalism. Our first sample is a selection of 334 optical quasar spectra from the SDSS DR7 database with a S/N > 20. Using the E1, we define primary and secondary selection criteria in the optical spectral range. We show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Our results are consistent with concordance cosmology but we need to work with other spectral ranges to take into account the quasar orientation, among other constrains.

  18. Galaxies on Top of Quasars: Probing Dwarf Galaxies in the SDSS (United States)

    Straka, Lorrie; York, D. G.; Noterdaeme, P.; Srianand, R.; Bowen, D. V.; Khare, P.; Bishof, M.; Whichard, Z.; Kulkarni, V. P.


    Absorption lines from galaxies at intervening redshifts in quasar spectra are sensitive probes of metals and gas that are otherwise invisible due to distance or low surface brightness. However, in order to determine the environments these absorption lines arise in, we must detect these galaxies in emission as well. Galaxies on top of quasars (GOTOQs) are low-z galaxies found intervening with background quasars in the SDSS. These galaxies have been flagged for their narrow galactic emission lines present in quasar spectra in the SDSS. Typically, the low-z nature of these galaxies allows them to be easily detected in SDSS imaging. However, a number of GOTOQs (about 10%), despite being detected in spectral emission, are NOT seen in SDSS imaging. This implies that these may be dark galaxies, dwarf galaxies, or similarly low surface brightness galaxies. Additionally, about 25% of those detected in imaging are dwarf galaxies according to their L* values. Dwarf galaxies have long been underrepresented in observations compared to theory and are known to have large extents in dark matter. Given their prevalence here in our sample we must ask what role they play in quasar absorption line systems (QSOALS). Recent detections of 21-cm galaxies with few stars imply that aborted star formation in dark matter sub halos may produce QSOALS. Thus, this sub sample of galaxies offers a unique technique for probing dark and dwarf galaxies. The sample and its properties will be discussed, including star formation rates and dust estimates, as well as prospects for the future.

  19. Confirmation of the Most Distant Quasar (United States)

    Tilvi, Vithal


    We propose for 8-orbit G141 grism observations to confirm the AGN nature of a z=7.51 galaxy, currently the most distant quasar candidate identified via NV line detection using deep G102 grism observations. The AGN evidence is further supported by a weak line detection in the ground-based MOSFIRE spectrum. Here we request grism observations to better understand the physical processes occurring in this unique galaxy, and confirm its AGN nature via additional lines: CIV, HeII and CIII. Detection of CIV alone will unambiguously confirm its AGN nature. Currently, WFC3 grism is the most efficient instrument for observing these lines as our recent work shows that the flux loss from ground-based slit-spectrographs is significant (>4x) compared with the grism measurements. Furthermore, the CIII line falls on to a bright atmospheric line making it nearly impossible to observe from the ground. Confirmation of the AGN nature of our target will be a tremendous achievement because this discovery implies that the black hole accretion was already in place within the first few million years after the big bang. This also means that at least some fraction of Lyman-break selected galaxies host AGNs, which can enhance the escape of ionizing radiation and thus contribute to the reionization of the intergalactic medium (IGM). Currently there are no observations of faint quasars, M(UV)>-23.2 mag, at z>7. Our proposed observations will push the discoveries to fainter limits, which consequently will start building an excellent base-sample for James Webb Space Telescope for studying the physical nature of sources responsible for reionizing the universe.

  20. A Quasar's Identity May Simply Be In The Eye Of The Beholder (United States)


    Using NASA's Chandra X-ray Observatory, astronomers have made the first detailed study of a peculiar type of quasar that is shrouded in clouds of gas and dust flowing outward at millions of miles per hour. The results support the idea that this outflow is a common feature of all quasars, highly active supermassive black holes that give the illusion of being different when viewed from various angles. Quasars are some of the most energetic and distant known objects in the universe. Most quasars are extremely bright in optical light, but about 10 percent appear 'shrouded,'or hidden, by absorbing clouds of gas and dust. In addition to these obscuring clouds, the same subset of quasars shows evidence of extremely energetic winds blasting outwards from the central regions. Astronomers have debated whether these shrouded quasars represent an early evolutionary stage of black holes when they vigorously consume matter, or whether these energetic outflows are present in all quasars, but detectable only when viewed in certain orientations. "Because high-energy X-rays can pierce through these clouds, we can use Chandra to observe close to the underlying black hole," said Paul Green of the Harvard-Smithsonian Center for Astrophysics and lead author of a paper to appear in The Astrophysical Journal. "Looking through these veils, we find that the extremely hot gas around these supermassive black holes shines just the same way as in non-shrouded quasars." Green and his colleagues used Chandra to survey ten shrouded quasars through a process known as spectroscopy, the study of how atoms absorb and emit light. X-ray spectroscopy provides astronomers with a unique ability to "fingerprint" very high-energy objects at great distances. BALQSO These two Chandra images demonstrate the different appearances of "normal" and "shrouded" quasars. Credit: NASA/CfA/P.Green et al. "Chandra is beginning to show us that these quasars are all the same underneath, regardless of what they are wearing

  1. Fractal Quasar Clouds (United States)

    Bottorff, Mark; Ferland, Gary


    This paper examines whether a fractal cloud geometry can reproduce the emission-line spectra of active galactic nuclei (AGNs). The nature of the emitting clouds is unknown, but many current models invoke various types of magnetohydrodynamic confinement. Recent studies have argued that a fractal distribution of clouds, in which subsets of clouds occur in self-similar hierarchies, is a consequence of such confinement. Whatever the confinement mechanism, fractal cloud geometries are found in nature and may be present in AGNs too. We first outline how a fractal geometry can apply at the center of a luminous quasar. Scaling laws are derived that establish the number of hierarchies, typical sizes, column densities, and densities. Photoionization simulations are used to predict the integrated spectrum from the ensemble. Direct comparison with observations establishes all model parameters so that the final predictions are fully constrained. Theory suggests that denser clouds might form in regions of higher turbulence and that larger turbulence results in a wider dispersion of physical gas densities. An increase in turbulence is expected deeper within the gravitational potential of the black hole, resulting in a density gradient. We mimic this density gradient by employing two sets of clouds with identical fractal structuring but different densities. The low-density clouds have a lower column density and large covering factor similar to the warm absorber. The high-density clouds have high column density and smaller covering factor similar to the broad-line region (BLR). A fractal geometry can simultaneously reproduce the covering factor, density, column density, BLR emission-line strengths, and BLR line ratios as inferred from observation. Absorption properties of the model are consistent with the integrated line-of-sight column density as determined from observations of X-ray absorption, and when scaled to a Seyfert galaxy, the model is consistent with the number of

  2. New results on quasar outflows

    NARCIS (Netherlands)

    Hamann, Fred; Kanekar, Nissem; Prochaska, Jason X.; Murphy, Michael T.; Milutinovic, Nikola; Ellison, Sara; Ubachs, Wim; Ferland, Gary

    Accretion disk outflows are an important part of the quasar phenomenon. They might play a major role in distributing metals to the galactic surroundings, halting growth of the central black hole and providing kinetic energy "feedback" to regulate star formation in the host galaxies. Some models of

  3. Population mixtures and searches of lensed and extended quasars across photometric surveys (United States)

    Williams, Peter; Agnello, Adriano; Treu, Tommaso


    Wide-field photometric surveys enable searches of rare yet interesting objects, such as strongly lensed quasars or quasars with a bright host galaxy. Past searches for lensed quasars based on their optical and near-infrared properties have relied on photometric cuts and spectroscopic preselection (as in the Sloan Quasar Lens Search), or neural networks applied to photometric samples. These methods rely on cuts in morphology and colours, with the risk of losing many interesting objects due to scatter in their population properties, restrictive training sets, systematic uncertainties in catalogue-based magnitudes and survey-to-survey photometric variations. Here, we explore the performance of a Gaussian mixture model to separate point-like quasars, quasars with an extended host and strongly lensed quasars using griz psf and model magnitudes and WISE W1, W2. The choice of optical magnitudes is due to their presence in all current and upcoming releases of wide-field surveys, whereas UV information is not always available. We then assess the contamination from blue galaxies and the role of additional features such as W3 magnitudes or psf-model terms as morphological information. As a demonstration, we conduct a search in a random 10 per cent of the SDSS footprint, and provide the catalogue of the 43 SDSS object with the highest 'lens' score in our selection that survive visual inspection, and are spectroscopically confirmed to host active nuclei. We inspect archival data and find images of 5/43 objects in the Hubble Legacy Archive, including two known lenses. The code and materials are available to facilitate follow-up.

  4. The XMM-Newton Very Large Program on Cosmology with High-Redshift Quasars (United States)

    Risaliti, G.


    The non-linear relation between the X-ray and UV emission in quasars can be used to estimate the distance of quasars with a precision of 0.2 dex. Based on this property, we built a Hubble Diagram of quasars up to z˜6. This provides a new way to test the cosmological model at high redshift, and to measure the cosmological parameters. So far, we filled the Hubble Diagram with SDSS quasars with serendipitous XMM observation. This is an efficient method up to z˜2-2.5, but at higher redshifts pointed observations are needed in order to constrain the cosmological models. XMM-Newton will observe 30 optically bright quasars at z 3, allowing to measure the expansion rate of the Universe at z=3 with a 8% precision. This will provide a tight test of the standard LCDM model, and an improvement of the constraints on the possible evolution of the equation of state of the dark energy.

  5. BrightFocus Foundation (United States)

    ... sooner. More science news Help us find a cure. Give to BrightFocus BrightFocus Updates BrightFocus Foundation Lauds Bill Gates Alzheimer’s Initiative “BrightFocus Foundation lauds today’s historic announcement by ...

  6. Formation et Evolution des Quasars et Contraintes cosmologiques (United States)

    Hatziminaoglou, Evanthia


    Cette thèse porte sur l'étude de l'évolution des quasars. Elle en aborde certains aspects théoriques et observationnels, ainsi que la construction des grands échantillons de quasars dans le but à long terme de combiner le tout dans un test cosmologique géométrique pour déterminer les valeurs des paramètres cosmologiques Omega et Lambda. Les paramètres cosmologiques Omegaspan>et Lambdaspan>décrivent la géométrie globale de l'Univers. En faisant des hypothèses raisonnables sur la distribution spatiale et l'évolution des objets astrophysiques (galaxies, amas des galaxies, quasars), on peut déterminer les valeurs de ces paramètres qui sont cohérentes avec ces hypothèses. Les tests cosmologiques traditionnels ont besoin de ''chandelles standards'', objets dont les propriétés intrinsèques sont indépendantes des distances. De tels objets sont probablement fictifs. Néanmoins, certains de ces tests cosmologiques peuvent être adaptés si l'évolution individuelle, ou au moins l'évolution statistique d'une population d'objets est connue. La question de la nature de l'évolution des quasars a très vite été posée et des réponses ''phénoménologiques'' ont d'abord été données. Ces réponses ne faisaient que donner une forme mathématique à l'évolution mais n'expliquaient rien de la physique duphénomène. Les premières tentatives de construction d'un modèle physique, liées au processus d'accrétion sur un trou noir et à la théorie de la formation de l'Univers ont commencé à la fin des années 80. Depuis, des dizaines de modèles tentent d'expliquer les observations, qui sont les résultats de l'étude d'objets de plus en plus nombreux. Au cours de cette thèse, le test V/Vmax a été appliqué sur l'échantillon du Large Bright Quasar Survey en montrant 1) que l'échantillon était biaisé à cause des critères de sélection et 2) que la (simple) loi de Pure Evolution en Luminosité n'était pas une bonne approximation à tout

  7. Spectral Variability in Radio-Loud Quasars

    Indian Academy of Sciences (India)

    The spectral variability of a sample of 44 Flat-Spectrum Radio Quasars (FSRQs) and 18 Steep-Spectrum Radio Quasars (SSRQs) in SDSS stripe 82 region is investigated. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows a redder-when-brighter trend, which is in contrast to our ...

  8. Detecting the First Quasars with ALMA

    NARCIS (Netherlands)

    Schleicher, Dominik R. G.; Spaans, Marco; Klessen, Ralf S.

    We show that ALMA is the first telescope that can probe the dust-obscured central region of quasars at z > 5 with a maximum resolution of ~ 30 pc employing the 18 km baseline. We explore the possibility of detecting the first quasars with ALMA (Schleicher, Spaans, & Klessen 2009). For this purpose,

  9. Quasar polarization with ultralight (pseudo-)scalars

    Indian Academy of Sciences (India)

    Abstract. Recently, it was shown that the absence of circular polarization of visible light from quasars severely constrains the interpretation of axion-like particles (ALPs) as a solution for the generation of linear polarization. Furthermore, the new observation of linear polarization in radio wavelength from quasars, similar to ...

  10. Quasar polarization with ultralight (pseudo-) scalars

    Indian Academy of Sciences (India)

    Recently, it was shown that the absence of circular polarization of visible light from quasars severely constrains the interpretation of axion-like particles (ALPs) as a solution for the generation of linear polarization. Furthermore, the new observation of linear polarization in radio wavelength from quasars, similar to the earlier ...

  11. Dark-ages reionization and galaxy formation simulation - X. The small contribution of quasars to reionization (United States)

    Qin, Yuxiang; Mutch, Simon J.; Poole, Gregory B.; Liu, Chuanwu; Angel, Paul W.; Duffy, Alan R.; Geil, Paul M.; Mesinger, Andrei; Wyithe, J. Stuart B.


    Motivated by recent measurements of the number density of faint AGN at high redshift, we investigate the contribution of quasars to reionization by tracking the growth of central supermassive black holes in an update of the MERAXES semi-analytic model. The model is calibrated against the observed stellar mass function at z ∼ 0.6-7, the black hole mass function at z ≲ 0.5, the global ionizing emissivity at z ∼ 2-5 and the Thomson scattering optical depth. The model reproduces a Magorrian relation in agreement with observations at z < 0.5 and predicts a decreasing black hole mass towards higher redshifts at fixed total stellar mass. With the implementation of an opening angle of 80 deg for quasar radiation, corresponding to an observable fraction of ∼23.4 per cent due to obscuration by dust, the model is able to reproduce the observed quasar luminosity function at z ∼ 0.6-6. The stellar light from galaxies hosting faint active galactic nucleus (AGN) contributes a significant or dominant fraction of the UV flux. At high redshift, the model is consistent with the bright end quasar luminosity function and suggests that the recent faint z ∼ 4 AGN sample compiled by Giallongo et al. (2015) includes a significant fraction of stellar light. Direct application of this luminosity function to the calculation of AGN ionizing emissivity consequently overestimates the number of ionizing photons produced by quasars by a factor of 3 at z ∼ 6. We conclude that quasars are unlikely to make a significant contribution to reionization.

  12. The FIRST-2MASS Red Quasar Survey

    Energy Technology Data Exchange (ETDEWEB)

    Glikman, E; Helfand, D J; White, R L; Becker, R H; Gregg, M D; Lacy, M


    Combining radio observations with optical and infrared color selection--demonstrated in our pilot study to be an efficient selection algorithm for finding red quasars--we have obtained optical and infrared spectroscopy for 120 objects in a complete sample of 156 candidates from a sky area of 2716 square degrees. Consistent with our initial results, we find our selection criteria--J-K > 1.7,R-K > 4.0--yield a {approx} 50% success rate for discovering quasars substantially redder than those found in optical surveys. Comparison with UVX- and optical color-selected samples shows that {approx}> 10% of the quasars are missed in a magnitude-limited survey. Simultaneous two-frequency radio observations for part of the sample indicate that a synchrotron continuum component is ruled out as a significant contributor to reddening the quasars spectra. We go on to estimate extinctions for our objects assuming their red colors are caused by dust. Continuum fits and Balmer decrements suggest E(B-V) values ranging from near zero to 2.5 magnitudes. Correcting the K-band magnitudes for these extinctions, we find that for K {le} 14.0, red quasars make up between 25% and 60% of the underlying quasar population; owing to the incompleteness of the 2MASS survey at fainter K-band magnitudes, we can only set a lower limit to the radio-detected red quasar population of > 20-30%.

  13. Robotic Monitoring of Gravitationally Lensed Quasars

    Directory of Open Access Journals (Sweden)

    Luis J. Goicoechea


    Full Text Available We report on the first observational phase of the Liverpool Quasar Lens Monitoring (LQLM project. This mainly consisted of the optical follow-up of three lensed quasars using the 2 m Liverpool Robotic Telescope. The observational subprogram started in January 2005 and was completed in July 2007. We also describe our photometric approaches (including two pipelines to extract accurate and reliable fluxes of images of lensed quasars, the performance of the telescope when taking modest nightly exposures of lens systems, and the main scientific results from the observed light curves. The LQLM archive and the current status of the project (second phase are also outlined.

  14. Observations of a Radio-Quiet Solar Preflare (United States)

    Benz, Arnold O.; Battaglia, Marina; Güdel, Manuel


    The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, in that it was covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and because it showed three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that no associated radio emission at 17 GHz was found either, despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is higher by more than one order of magnitude than the ratio in regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.

  15. Burkina Faso - BRIGHT II (United States)

    Millennium Challenge Corporation — Millennium Challenge Corporation hired Mathematica Policy Research to conduct an independent evaluation of the BRIGHT II program. The three main research questions...


    Energy Technology Data Exchange (ETDEWEB)

    Dahle, H.; Groeneboom, N. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, NO-0315 Oslo (Norway); Gladders, M. D.; Abramson, L. E. [Department of Astronomy and Astrophysics, The University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637 (United States); Sharon, K. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Bayliss, M. B. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Wuyts, E. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbackstrasse 1, D-85748 Garching bei Muenchen (Germany); Koester, B. P. [Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, MI 48109 (United States); Brinckmann, T. E.; Kristensen, M. T.; Lindholmer, M. O.; Nielsen, A.; Krogager, J.-K.; Fynbo, J. P. U., E-mail: [Dark Cosmology Centre, Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark)


    We report the discovery of a unique gravitational lens system, SDSS J2222+2745, producing five spectroscopically confirmed images of a z{sub s} = 2.82 quasar lensed by a foreground galaxy cluster at z{sub l} = 0.49. We also present photometric and spectroscopic evidence for a sixth lensed image of the same quasar. The maximum separation between the quasar images is 15.''1. Both the large image separations and the high image multiplicity are in themselves rare among known lensed quasars, and observing the combination of these two factors is an exceptionally unlikely occurrence in present data sets. This is only the third known case of a quasar lensed by a cluster, and the only one with six images. The lens system was discovered in the course of the Sloan Giant Arcs Survey, in which we identify candidate lenses in the Sloan Digital Sky Survey and target these for follow-up and verification with the 2.56 m Nordic Optical Telescope. Multi-band photometry obtained over multiple epochs from 2011 September to 2012 September reveals significant variability at the {approx}10%-30% level in some of the quasar images, indicating that measurements of the relative time delay between quasar images will be feasible. In this lens system, we also identify a bright (g = 21.5) giant arc corresponding to a strongly lensed background galaxy at z{sub s} = 2.30. We fit parametric models of the lens system, constrained by the redshift and positions of the quasar images and the redshift and position of the giant arc. The predicted time delays between different pairs of quasar images range from {approx}100 days to {approx}6 yr.

  17. Twin Quasars Tango And It's No Mirage (United States)


    Scientists have unraveled a longstanding mystery about a rare double quasar system 11 billion light years from Earth using NASA's Chandra X-ray Observatory. These "twin" quasars, previously thought to be an optical illusion, were instead probably created by merging galaxies and may have been more common in the dense universe soon after the Big Bang. "When galaxies interact or merge, they become more active and luminous and can excite quasar activity in their centers," said Paul Green of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., who led the research team. "The quasars that make up these nearly identical twins appear to have been hatched in the same nest." The Chandra data show that the quasars - luminous galaxies powered by central supermassive black holes - are not mirror images caused by a cosmic phenomenon known as a "gravitational lens." Rather, these two quasars are distinct objects that were probably spawned when their host galaxies collided, energizing the flow of gas onto their central black holes. Quasar pairs that are seen close to one another on the sky and are at the same distance from Earth often turn out to be an illusion as part of a gravitationally lensed system. In these cases, the image of a single quasar has been split into two or more images as its light has been bent and focused on its way to Earth by the gravity of an intervening massive object like a galaxy, or a cluster of galaxies. Usually, the intervening mass shows up as a fainter galaxy or cluster of galaxies seen between or among the quasar images, confirming the cause of the illusion. The quasar pair Q2345+007 A, B was thought to be such an illusion because of the remarkably similar patterns of the light, or spectra, from the pair at both optical and ultraviolet wavelengths. Quasar Pair Q2345+007A,B X-ray/Optical Composite However, almost two decades after its discovery by optical astronomers, the identification of enough intervening material to "split" the

  18. New Discoveries Fill the Quasar Gap (United States)

    Kohler, Susanna


    Quasars active and luminous galactic centers can be difficult to find at some high redshifts due to their camouflaging color. A team of scientists has now come up with a way to detect these distant monsters in spite of their disguise.Quasar CamouflageThe color track of quasars between 5 z 6 in the commonly used i z and r i bands. Each dot on the red line marks a 0.1 difference in redshift. The contours show the colors of M dwarfs, from early type to late type. Quasars at a redshift of 5.3 z 5.7 are clearly contaminated by M dwarfs, making them difficult to identify. [Adapted from Yang et al. 2017]One of the key ways we can study the early universe is by building a large sample of high-redshift quasars. In particular, we believe that reionization of the universe is just completing around z 6. Quasars near this redshift are crucial tools for probing the post-reionization epoch and exploring the evolution of the intergalactic medium, quasar evolution, and early supermassive black hole growth.But quasars at this redshift are difficult to detect! The problem is contamination: quasars at this distance are the same color in commonly used optical bands as cool M-dwarf stars. As a result, surveys searching for quasars have often just cut out that entire section of the color space in order to avoid this contamination.This means that theres a huge gap in our sample of quasars around z 5.5: of the more than 300,000 quasars known, only 30 have been found in the redshift range of 5.3 z 5.7.The addition of new colorcolor selection criteria using infrared bands (bottom two plots) allows the authors to differentiate quasars (blue) from M dwarfs (grey), which isnt possible when only the traditional optical colorcolor selection criteria are used (top plot). [Adapted from Yang et al. 2017]A New ApproachIn a recent publication led by Jinyi Yang (Peking University, China and Steward Observatory, University of Arizona), a team of scientists has demonstrated a new technique for finding

  19. Expanding space, quasars and St. Augustine's fireworks

    CERN Document Server

    Chashchina, O I


    An attempt is made to explain time non-dilation allegedly observed in quasar light curves. The explanation is based on the assumption that quasar black holes are, in some sense, foreign for our Friedmann-Robertson-Walker universe and do not participate in the Hubble flow. Although at first sight such a weird explanation requires unreasonably fine-tuned Big Bang initial conditions, we find a natural justification for it using the Milne cosmological model as an inspiration.


    Energy Technology Data Exchange (ETDEWEB)

    Prochaska, J. Xavier; Cantalupo, Sebastiano; Lau, Marie Wingyee [Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Hennawi, Joseph F.; Lee, Khee-Gan; Myers, Adam; Rubin, Kate H. R. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69115 Heidelberg (Germany); Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Djorgovski, S. G. [California Institute of Technology, Pasadena, CA 91125 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Finnerty Road, Victoria, British Columbia V8P 1A1 (Canada); Martin, Crystal L. [Department of Physics, University of California, Santa Barbara, Santa Barbara, CA 93106 (United States); Simcoe, Robert A. [MIT-Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)


    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ∼ 2 quasars at proper separations of 30 kpc < R < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc){sup –0.46}. We also observe a high (≅ 60%) covering factor of strong, optically thick H I absorbers (H I column N{sub H{sub I}}>10{sup 17.3} cm{sup -2}) at separations R < 200 kpc, which decreases to ∼20% at R ≅ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ{sub QA}(r) = (r/r{sub 0}){sup γ} with a large correlation length r{sub 0} = 12.5{sup +2.7}{sub -1.4} h{sup -1} Mpc (comoving) and γ=1.68{sup +0.14}{sub -0.30}. The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M{sub halo} ≈ 10{sup 12.5} M{sub ☉} at z ∼ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ∼ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  1. Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6. (United States)

    Decarli, R; Walter, F; Venemans, B P; Bañados, E; Bertoldi, F; Carilli, C; Fan, X; Farina, E P; Mazzucchelli, C; Riechers, D; Rix, H-W; Strauss, M A; Wang, R; Yang, Y


    The existence of massive (1011 solar masses) elliptical galaxies by redshift z ≈ 4 (refs 1, 2, 3; when the Universe was 1.5 billion years old) necessitates the presence of galaxies with star-formation rates exceeding 100 solar masses per year at z > 6 (corresponding to an age of the Universe of less than 1 billion years). Surveys have discovered hundreds of galaxies at these early cosmic epochs, but their star-formation rates are more than an order of magnitude lower. The only known galaxies with very high star-formation rates at z > 6 are, with one exception, the host galaxies of quasars, but these galaxies also host accreting supermassive (more than 109 solar masses) black holes, which probably affect the properties of the galaxies. Here we report observations of an emission line of singly ionized carbon ([C ii] at a wavelength of 158 micrometres) in four galaxies at z > 6 that are companions of quasars, with velocity offsets of less than 600 kilometres per second and linear offsets of less than 100 kiloparsecs. The discovery of these four galaxies was serendipitous; they are close to their companion quasars and appear bright in the far-infrared. On the basis of the [C ii] measurements, we estimate star-formation rates in the companions of more than 100 solar masses per year. These sources are similar to the host galaxies of the quasars in [C ii] brightness, linewidth and implied dynamical mass, but do not show evidence for accreting supermassive black holes. Similar systems have previously been found at lower redshift. We find such close companions in four out of the twenty-five z > 6 quasars surveyed, a fraction that needs to be accounted for in simulations. If they are representative of the bright end of the [C ii] luminosity function, then they can account for the population of massive elliptical galaxies at z ≈ 4 in terms of the density of cosmic space.

  2. Ultraviolet Echoes of Quasar Accretion Disks (United States)

    Trump, Jonathan


    We propose a novel ultraviolet monitoring campaign with WFC3/UVIS to measure quasar accretion disk structure. The bulk of supermassive black hole growth occurs in luminous quasar phases of rapid accretion, yet the governing physics remains poorly understood. Continuum reverberation mapping (RM) measures the accretion disk size via the time lag between short- and long-wavelength emission: the proposed UV monitoring forms the foundation for simultaneous optical observations (expected to continue for our quasars through 2019). Currently only 4 Seyfert AGNs have UV/optical RM accretion-disk sizes, all low-luminosity and at z<0.02. We propose to monitor 5 new quasars, spanning an order of magnitude higher accretion rate and out to z 1. The 5 quasar targets are drawn from SDSS-RM, a pioneering multi-object spectroscopic RM campaign, and have been monitored with optical photometry and spectroscopy since 2014. The higher luminosity and accurate RM masses of our sample enable the first measurements of accretion-rate effects on accretion-disk size, with UV monitoring directly probing changes in the inner disk suggested by theory and previous indirect observations. Our proposed HST monitoring campaign is unusually efficient, targeting 5 quasars per orbit using the DASH method with UVIS subarray readouts. We use simulations to demonstrate that our 2-day cadence over 32 epochs will accurately measure continuum lags and accretion-disk structure. Ultraviolet monitoring of these 5 quasars will enable critical new measurements of accretion-disk structure during the rapid accretion mode that dominates black hole growth.

  3. Highly Accreting Quasars at High Redshift

    Directory of Open Access Journals (Sweden)

    Mary L. Martínez-Aldama


    Full Text Available We present preliminary results of a spectroscopic analysis for a sample of type 1 highly accreting quasars (L/LEdd ~ 1.0 at high redshift, z ~2–3. The quasars were observed with the OSIRIS spectrograph on the GTC 10.4 m telescope located at the Observatorio del Roque de los Muchachos in La Palma. The highly accreting quasars were identified using the 4D Eigenvector 1 formalism, which is able to organize type 1 quasars over a broad range of redshift and luminosity. The kinematic and physical properties of the broad line region have been derived by fitting the profiles of strong UV emission lines such as Aliiiλ1860, Siiii]λ1892 and Ciii]λ1909. The majority of our sources show strong blueshifts in the high-ionization lines and high Eddington ratios which are related with the productions of outflows. The importance of highly accreting quasars goes beyond a detailed understanding of their physics: their extreme Eddington ratio makes them candidates standard candles for cosmological studies.

  4. The WISSH quasars project. II. Giant star nurseries in hyper-luminous quasars (United States)

    Duras, F.; Bongiorno, A.; Piconcelli, E.; Bianchi, S.; Pappalardo, C.; Valiante, R.; Bischetti, M.; Feruglio, C.; Martocchia, S.; Schneider, R.; Vietri, G.; Vignali, C.; Zappacosta, L.; La Franca, F.; Fiore, F.


    Context. Studying the coupling between the energy output produced by the central quasar and the host galaxy is fundamental to fully understand galaxy evolution. Quasar feedback is indeed supposed to dramatically affect the galaxy properties by depositing large amounts of energy and momentum into the interstellar medium (ISM). Aims: In order to gain further insights on this process, we study the spectral energy distributions (SEDs) of sources at the brightest end of the quasar luminosity function, for which the feedback mechanism is assumed to be at its maximum, given their high efficiency in driving powerful outflows. Methods: We modelled the rest-frame UV-to-far-IR SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 standard combination of accretion disc plus torus and cold dust emission. However, about 30% of SEDs require an additional emission component in the near-IR, with temperatures peaking at 750 K, which indicates that a hotter dust component is present in these powerful quasars. We measure extreme values of both AGN bolometric luminosity (LBOL > 1047 erg/s) and star formation rate (up to 2000 M⊙/yr) based on the quasar-corrected, IR luminosity of the host galaxy. A new relation between quasar and star formation luminosity is derived (LSF ∝ L0.73QSO) by combining several Herschel-detected quasar samples from z 0 to 4. WISSH quasars have masses ( 108M⊙) and temperatures ( 50 K) of cold dust in agreement with those found for other high-z IR luminous quasars. Conclusions: Thanks to their extreme nuclear and star formation luminosities, the WISSH quasars are ideal targets to shed light on the feedback mechanism and its effect on the evolution of their host galaxies, as well as on the merger-induced scenario that is commonly assumed to explain these exceptional luminosities. Future observations will be crucial to measure the molecular gas content in these systems, probe the effect between quasar-driven outflows and on-going star formation

  5. Probing Extragalactic Planets Using Quasar Microlensing (United States)

    Dai, Xinyu; Guerras, Eduardo


    Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fe Kα line energy shifts observed in the gravitationally lensed quasar RXJ 1131–1231 at a lens redshift of z = 0.295 or 3.8 billion lt-yr away. We constrain the planet mass-fraction to be larger than 0.0001 of the halo mass, which is equivalent to 2000 objects ranging from Moon to Jupiter mass per main-sequence star.

  6. Black-hole masses of distant quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne


    A brief overview of the methods commonly used to determine or estimate the black hole mass in quiescent or active galaxies is presented and it is argued that the use of mass-scaling relations is both a reliable and the preferred method to apply to large samples of distant quasars. The method uses...... that the black hole masses are very large, of order 1 to 10 billion solar masses, even at the highest redshifts of 4 to 6. The black holes must build up their mass very fast in the early universe. Yet they do not grow much larger than that: a maximum mass of about 10 billion solar masses is also observed....... Preliminary mass functions of active black holes are presented for several quasar samples, including the Sloan Digital Sky Survey. Finally, common concerns related to the application of the mass scaling relations, especially for high redshift quasars, are briefly discussed....

  7. Quasar Elemental Abundances at High Redshifts

    DEFF Research Database (Denmark)

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


    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...... 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...


    Energy Technology Data Exchange (ETDEWEB)

    Urrutia, Tanya [Leibniz Institut fuer Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Lacy, Mark [NRAO, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Spoon, Henrik [Department of Astronomy, Cornell University, 219 Space Sciences Building, Ithaca, NY 14853 (United States); Glikman, Eilat [Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06520 (United States); Petric, Andreea [Astronomy Department, California Institute of Technology, Pasadena, CA 91125 (United States); Schulz, Bernhard, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Infrared Processing and Analysis Center, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States)


    We present mid-infrared spectra and photometry of 13 redshift 0.4 < z < 1 dust reddened quasars obtained with Spitzer IRS and MIPS. We compare properties derived from their infrared spectral energy distributions (intrinsic active galactic nucleus (AGN) luminosity and far-infrared luminosity from star formation) to the host luminosities and morphologies from Hubble Space Telescope imaging, and black hole masses estimated from optical and/or near-infrared spectroscopy. Our results are broadly consistent with models in which most dust reddened quasars are an intermediate phase between a merger-driven starburst triggering a completely obscured AGN, and a normal, unreddened quasar. We find that many of our objects have high accretion rates, close to the Eddington limit. These objects tend to fall below the black hole mass-bulge luminosity relation as defined by local galaxies, whereas most of our low accretion rate objects are slightly above the local relation, as typical for normal quasars at these redshifts. Our observations are therefore most readily interpreted in a scenario in which galaxy stellar mass growth occurs first by about a factor of three in each merger/starburst event, followed sometime later by black hole growth by a similar amount. We do not, however, see any direct evidence for quasar feedback affecting star formation in our objects, for example, in the form of a relationship between accretion rate and star formation. Five of our objects, however, do show evidence for outflows in the [O III]5007 A emission line profile, suggesting that the quasar activity is driving thermal winds in at least some members of our sample.

  9. The Global Jet Structure of the Archetypical Quasar 3C 273

    Directory of Open Access Journals (Sweden)

    Kazunori Akiyama


    Full Text Available A key question in the formation of the relativistic jets in active galactic nuclei (AGNs is the collimation process of their energetic plasma flow launched from the central supermassive black hole (SMBH. Recent observations of nearby low-luminosity radio galaxies exhibit a clear picture of parabolic collimation inside the Bondi accretion radius. On the other hand, little is known of the observational properties of jet collimation in more luminous quasars, where the accretion flow may be significantly different due to much higher accretion rates. In this paper, we present preliminary results of multi-frequency observations of the archetypal quasar 3C 273 with the Very Long Baseline Array (VLBA at 1.4, 15, and 43 GHz, and Multi-Element Radio Linked Interferometer Network (MERLIN at 1.6 GHz. The observations provide a detailed view of the transverse structure resolved on a broad range of spatial scales from sub-parsec to kilo parsecs, allowing us to profile the jet width as a function of the distance from the core for the first time in jets of bright quasars. We discovered a transition from a parabolic stream to a conical stream, which has been seen in much lower-luminosity radio galaxies. The similarity in the profile to the much lower-powered radio galaxy M87 suggests the universality of jet collimation among AGNs with different accretion rates.

  10. The Gamma-ray Activity of the high-z Quasar 0836+71

    Directory of Open Access Journals (Sweden)

    Jorstad Svetlana


    Full Text Available The Fermi LAT detected an increase in γ-ray activity of the quasar 0836+710 (z=2.17 in Spring 2011 that culminated in a sharp γ-ray flare at the end of 2011 when the source reached a flux of 2.9×10−6 phot s−1cm−2 at 0.1-200 GeV. We monitor the quasar at optical wavelengths in photometric and polarimetric modes, at millimeter and centimeter wavelengths, and with the VLBA at 43 GHz. The optical brightness of the quasar increased by ~0.5 mag in R band and the degree of polarization oscillated between ~1% and ~6% during the highest γ-ray state, while the position angle of polarization rotated by ~300°. We have identified in the VLBA images a strong, highly polarized component that moves with an apparent speed of ~20 c. The component emerged from the core in the beginning of the γ-ray event and reached a flux maximum at the peak of the γ-ray outburst. We present the results of a correlative analysis of variations at different wavelengths along with the kinematic parameters of the parsec scale jet. We discuss the location of the high γ-ray emission in the relativistic jet, as well as the emission mechanisms responsible for γ-ray production.

  11. Discovery of the First Quadruple Gravitationally Lensed Quasar Candidate with Pan-STARRS (United States)

    Berghea, C. T.; Nelson, George J.; Rusu, C. E.; Keeton, C. R.; Dudik, R. P.


    We report the serendipitous discovery of the first gravitationally lensed quasar candidate from Pan-STARRS. The grizy images reveal four point-like images with magnitudes between 14.9 and 18.1 mag. The colors of the point sources are similar, and they are more consistent with quasars than with stars or galaxies. The lensing galaxy is detected in the izy bands, with an inferred photometric redshift of ∼0.6, lower than that of the point sources. We successfully model the system with a singular isothermal ellipsoid with shear, using the relative positions of the five objects as constraints. While the brightness ranking of the point sources is consistent with that of the model, we find discrepancies between the model-predicted and observed fluxes, likely due to microlensing by stars and millilensing due to the dark matter substructure. In order to fully confirm the gravitational lens nature of this system and add it to the small but growing number of the powerful probes of cosmology and astrophysics represented by quadruply lensed quasars, we require further spectroscopy and high-resolution imaging.

  12. XMM-Newton observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326 (United States)

    Ai, Yanli; Fabian, A. C.; Fan, Xiaohui; Walker, S. A.; Ghisellini, G.; Sbarrato, T.; Dou, Liming; Wang, Feige; Wu, Xue-Bing; Feng, Longlong


    A brief Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326 showed it to be a relatively bright, soft X-ray source with a count rate of about 1 count ks-1. In this article, we present results for the quasar from a 65-ks XMM-Newton observation, which constrains its spectral shape well. The quasar is clearly detected with a total of ˜460 net counts in the 0.2-10 keV band. The spectrum is characterized by a simple power-law model with a photon index of Γ = 2.30^{+0.10}_{-0.10} and the intrinsic 2-10 keV luminosity is 3.14 × 1045 erg s-1. The 1σ upper limit to any intrinsic absorption column density is NH = 6.07 × 1022 cm-2. No significant iron emission lines were detected. We derive an X-ray-to-optical flux ratio αox of -1.74 ± 0.01, consistent with the values found in other quasars of comparable ultraviolet luminosity. We did not detect significant flux variations either in the XMM-Newton exposure or between XMM-Newton and Chandra observations, which are separated by ˜8 months. The X-ray observation enables the bolometric luminosity to be calculated after modelling the spectral energy distribution: the accretion rate is found to be sub-Eddington.

  13. A Time-domain Analysis of Nitrogen-rich Quasars. (United States)

    Dittmann, Alexander; Liu, Xin; Shen, Yue; Jiang, Linhua


    A small population of quasars exhibit anomalously high nitrogen-to-carbon ratios (N/C) in their emission lines. These “nitrogen-rich” (N-rich) quasars have been difficult to explain. Few of the possible mechanism are natural, since stellar populations with abnormally high metallicities are required to produce an N-rich interstellar medium. N-rich quasars are also more likely to be “radio-loud” than average quasars, which is difficult to explain by invoking higher metallicity alone. Recently, tidal disruption events (TDEs) have been proposed as a mechanism for N-rich quasars. Such a TDE would occur between a supersolar mass star and a supermassive black hole. The CNO cycle creates a surplus of N-rich and carbon-deficient material that could naturally explain the N/C observed in N-rich quasars. The TDE hypothesis explains N-rich quasars without requiring extremely exotic stellar populations. A testable difference differentiating the TDE explanation and exotic stellar population scenarios is that TDEs do not produce enough N-rich material to pollute the quasar environment for extended periods of time, in which case N-rich phenomena in quasars would be transient. By analyzing changes in nitrogen and carbon line widths in time-separated spectra of N-rich quasars, we have studied nitrogen abundance in quasars which had previously been identified as nitrogen rich. We have found that over time-frames of greater than one year in the quasar rest frame, nitrogen abundance tends to systematically decrease. The observed decrease is larger than our estimate of the effects of noise based on spectra separated by smaller time frames. Additionally, x-ray observations of one N-rich quasar have demonstrated that its x-ray emission is an outlier among the quasar population, but similar to confirmed TDEs.

  14. Simple stellar population modelling of low S/N galaxy spectra and quasar host galaxy applications (United States)

    Mosby, G.; Tremonti, C. A.; Hooper, E. J.; Wolf, M. J.; Sheinis, A. I.; Richards, J. W.


    To study the effect of supermassive black holes (SMBHs) on their host galaxies it is important to study the hosts when the SMBH is near its peak activity. A method to investigate the host galaxies of high luminosity quasars is to obtain optical spectra at positions offset from the nucleus where the relative contribution of the quasar and host is comparable. However, at these extended radii the galaxy surface brightness is often low (20-22 mag arcsec-2) and the resulting spectrum might have such low signal-to-noise ratio (S/N) that it hinders analysis with standard stellar population modelling techniques. To address this problem, we have developed a method that can recover galaxy star formation histories (SFHs) from rest-frame optical spectra with S/N ˜ 5 Å-1. This method uses the statistical technique diffusion k-means to tailor the stellar population modelling basis set. Our diffusion k-means minimal basis set, composed of four broad age bins, is successful in recovering a range of galaxy SFHs. Additionally, using an analytic prescription for seeing conditions, we are able to simultaneously model scattered quasar light and the SFH of quasar host galaxies (QHGs). We use synthetic data to compare results of our novel method with previous techniques. We also present the modelling results on a previously published QHG and show that galaxy properties recovered from a diffusion k-means basis set are less sensitive to noise added to this QHG spectrum. Our new method has a clear advantage in recovering information from QHGs and could also be applied to the analysis of other low S/N galaxy spectra such as those typically obtained for high redshift objects or integral field spectroscopic surveys.

  15. Inspiraling halo accretion mapped in Ly α emission around a z ˜ 3 quasar (United States)

    Arrigoni Battaia, Fabrizio; Prochaska, J. Xavier; Hennawi, Joseph F.; Obreja, Aura; Buck, Tobias; Cantalupo, Sebastiano; Dutton, Aaron A.; Macciò, Andrea V.


    In an effort to search for Ly α emission from circum- and intergalactic gas on scales of hundreds of kpc around z ∼ 3 quasars, and thus characterize the physical properties of the gas in emission, we have initiated an extensive fast survey with the Multi-Unit Spectroscopic Explorer (MUSE): Quasar Snapshot Observations with MUse: Search for Extended Ultraviolet eMission (QSO MUSEUM). In this work, we report the discovery of an enormous Ly α nebula (ELAN) around the quasar SDSS J102009.99+104002.7 at z = 3.164, which we followed-up with deeper MUSE observations. This ELAN spans ∼297 projected kpc, has an average Ly α surface brightness SBLy α ∼ 6.04 × 10-18 erg s-1 cm-2 arcsec-2(within the 2σ isophote) and is associated with an additional four previously unknown embedded sources: two Ly α emitters and two faint active galactic nuclei (one type-1 and one type-2 quasar). By mapping at high significance, the line-of-sight velocity in the entirety of the observed structure, we unveiled a large-scale coherent rotation-like pattern spanning ∼300 km s-1 with a velocity dispersion of complement our MUSE observations and are definitely needed to fully characterize such a complex system. None the less, our observations reveal the potential of new sensitive integral-field spectrographs to characterize the dynamical state of diffuse gas on large scales in the young Universe, and thereby witness the assembly of galaxies.


    Energy Technology Data Exchange (ETDEWEB)

    Ai, Y. L.; Wu, Xue-Bing; Yang, Jinyi; Yang, Qian; Wang, Feige; Guo, Rui; Dong, Xiaoyi [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Zuo, Wenwen; Shen, S.-Y. [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Zhang, Y.-X.; Yuan, H.-L.; Song, Y.-H.; Yang, M.; Wu, H.; Shi, J.-R.; He, B.-L.; Lei, Y.-J.; Li, Y.-B. [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences 100012, Beijing (China); Wang, Jianguo; Dong, Xiaobo, E-mail: [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); and others


    We present preliminary results of the quasar survey in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes the pilot survey and the first year of the regular survey. There are 3921 quasars reliably identified, among which 1180 are new quasars discovered in the survey. These quasars are at low to median redshifts, with a highest z of 4.83. We compile emission line measurements around the Hα, Hβ, Mg ii, and C iv regions for the new quasars. The continuum luminosities are inferred from SDSS photometric data with model fitting, as the spectra in DR1 are non-flux-calibrated. We also compile the virial black hole mass estimates, with flags indicating the selection methods, and broad absorption line quasars. The catalog and spectra for these quasars are also available. Of the 3921 quasars, 28% are independently selected with optical–infrared colors, indicating that the method is quite promising for the completeness of the quasar survey. LAMOST DR1 and the ongoing quasar survey will provide valuable data for studies of quasars.

  17. Quasar Mass Functions Across Cosmic Time

    DEFF Research Database (Denmark)

    Vestergaard, Marianne


    I present mass functions of actively accreting black holes detected in different quasar surveys which in concert cover a wide range of cosmic history. I briefly address what we learn from these mass functions. I summarize the motivation for such a study and the methods by which we determine black...

  18. High Brightness OLED Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Spindler, Jeffrey [OLEDWorks LLC; Kondakova, Marina [OLEDWorks LLC; Boroson, Michael [OLEDWorks LLC; Hamer, John [OLEDWorks LLC


    In this work we describe the technology developments behind our current and future generations of high brightness OLED lighting panels. We have developed white and amber OLEDs with excellent performance based on the stacking approach. Current products achieve 40-60 lm/W, while future developments focus on achieving 80 lm/W or higher.

  19. X-Ray Continua of Broad Absorption Line Quasars (United States)

    Mathur, S.


    The targets for this program, PG1416-129 and LBQS 2212-1759 were known to be Broad Absorption Line Quasars (BALQSOs). BALQSOs are highly absorbed in soft X-rays. Good high energy response of Rossi-XTE made them ideal targets for observation. We observed LBQS 2212-1759 with PCA. We have now analyzed the data and found that the source was not detected. Since our target was expected to be faint, reliable estimate of background was very important. With the release of new FTOOLS (version 4.1) we were able to do so. We also analyzed a well known bright object and verified our results with the published data. This gave us confidence in the non-detection of our target LBQS 2212-1759. We are currently investigating the implications of this non-detection. Due to some scheduling problems, our second target PG1416-129 was not observed in A01. It was observed on 06/26/98. This target was detected with RXTE. We are now working on the spectral analysis with XSPEC.


    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Shen, Yue [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); McGreer, Ian D.; Fan, Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Morganson, Eric [National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Windhorst, Rogier A., E-mail: [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)


    We present a reverberation mapping (RM) experiment that combines broad- and intermediate-band photometry; it is the first such attempt targeting 13 quasars at 0.2 < z < 0.9. The quasars were selected to have strong Hα or Hβ emission lines that are located in one of three intermediate bands (with FWHM around 200 Å) centered at 8045, 8505, and 9171 Å. The imaging observations were carried out in the intermediate bands and the broad i and z bands using the prime-focus imager 90Prime on the 2.3 m Bok telescope. Because of the large (∼1 deg{sup 2}) field of view (FOV) of 90Prime, we included the 13 quasars within only five telescope pointings or fields. The five fields were repeatedly observed over 20–30 epochs that were unevenly distributed over a duration of 5–6 months. The combination of the broad- and intermediate-band photometry allows us to derive accurate light curves for both optical continuum emission (from the accretion disk) and line emission (from the broad-line region, or BLR). We detect Hα time lags between the continuum and line emission in six quasars. These quasars are at relatively low redshifts 0.2 < z < 0.4. The measured lags are consistent with the current BLR size–luminosity relation for Hβ at z < 0.3. While this experiment appears successful in detecting lags of the bright Hα line, further investigation is required to see if it can also be applied to the fainter Hβ line for quasars at higher redshifts. Finally we demonstrate that, by using a small telescope with a large FOV, intermediate-band photometric RM can be efficiently executed for a large sample of quasars at z > 0.2.

  1. The brightness of colour.

    Directory of Open Access Journals (Sweden)

    David Corney

    Full Text Available The perception of brightness depends on spatial context: the same stimulus can appear light or dark depending on what surrounds it. A less well-known but equally important contextual phenomenon is that the colour of a stimulus can also alter its brightness. Specifically, stimuli that are more saturated (i.e. purer in colour appear brighter than stimuli that are less saturated at the same luminance. Similarly, stimuli that are red or blue appear brighter than equiluminant yellow and green stimuli. This non-linear relationship between stimulus intensity and brightness, called the Helmholtz-Kohlrausch (HK effect, was first described in the nineteenth century but has never been explained. Here, we take advantage of the relative simplicity of this 'illusion' to explain it and contextual effects more generally, by using a simple Bayesian ideal observer model of the human visual ecology. We also use fMRI brain scans to identify the neural correlates of brightness without changing the spatial context of the stimulus, which has complicated the interpretation of related fMRI studies.Rather than modelling human vision directly, we use a Bayesian ideal observer to model human visual ecology. We show that the HK effect is a result of encoding the non-linear statistical relationship between retinal images and natural scenes that would have been experienced by the human visual system in the past. We further show that the complexity of this relationship is due to the response functions of the cone photoreceptors, which themselves are thought to represent an efficient solution to encoding the statistics of images. Finally, we show that the locus of the response to the relationship between images and scenes lies in the primary visual cortex (V1, if not earlier in the visual system, since the brightness of colours (as opposed to their luminance accords with activity in V1 as measured with fMRI.The data suggest that perceptions of brightness represent a robust

  2. Overdensity of galaxies in the environment of quasar pairs (United States)

    Sandrinelli, A.; Falomo, R.; Treves, A.; Scarpa, R.; Uslenghi, M.


    We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation Digital Sky Survey images, we evaluated the galaxy overdensity around these quasars in pairs and then compare it with that of a sample of isolated quasars with same redshift and luminosity. It is found that on average there is a systematic larger overdensity of galaxies around quasars in pairs with respect to that of isolated quasars. This may represent a significant link between nuclear activity and galaxy environment. However, at odds with that, the closest quasar pairs seem to inhabit poorer environments. Implications of present results and perspectives for future work are briefly discussed.

  3. The SCUBA-2 850 μm Follow-up of WISE-selected, Luminous Dust-obscured Quasars (United States)

    Fan, Lulu; Jones, Suzy F.; Han, Yunkun; Knudsen, Kirsten K.


    Hot dust-obscured galaxies (Hot DOGs) are a new population recently discovered in the Wide-field Infrared Survey Explorer All-Sky survey. Multiwavelength follow-up observations suggest that they are luminous, dust-obscured quasars at high redshift. Here we present the JCMT SCUBA-2 850 μm follow-up observations of 10 Hot DOGs. Four out of ten Hot DOGs have been detected at >3σ level. Based on the IR SED decomposition approach, we derive the IR luminosities of AGN torus and cold dust components. Hot DOGs in our sample are extremely luminous with most of them having {L}{IR}{tot}> {10}14 {L}⊙ . The torus emissions dominate the total IR energy output. However, the cold dust contribution is still non-negligible, with the fraction of the cold dust contribution to the total IR luminosity (˜8%-24%) being dependent on the choice of torus model. The derived cold dust temperatures in Hot DOGs are comparable to those in UV bright quasars with similar IR luminosity, but much higher than those in SMGs. Higher dust temperatures in Hot DOGs may be due to the more intense radiation field caused by intense starburst and obscured AGN activities. Fourteen and five submillimeter serendipitous sources in the 10 SCUBA-2 fields around Hot DOGs have been detected at >3σ and >3.5σ levels, respectively. By estimating their cumulative number counts, we confirm the previous argument that Hot DOGs lie in dense environments. Our results support the scenario in which Hot DOGs are luminous, dust-obscured quasars lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars.

  4. Multiwavelength observations of the γ-ray flaring quasar S4 1030+61 in 2009-2014 (United States)

    Kravchenko, E. V.; Kovalev, Y. Y.; Hovatta, T.; Ramakrishnan, V.


    We present a study of the parsec-scale multifrequency properties of the quasar S4 1030+61 during a prolonged radio and γ-ray activity. Observations were performed within Fermi γ-ray telescope, Owens Valley Radio Observatory 40-m telescope and MOJAVE Very Long Baseline Array (VLBA) monitoring programmes, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24 and 43 GHz, which were triggered by the bright γ-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4 ± 0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and γ-ray emission implies a spatial separation between emitting regions at these bands of about 12 pc and locates the γ-ray emission within a parsec from the central engine. We detected changes in the value and direction of the linear polarization and the Faraday rotation measure. The value of the intrinsic brightness temperature of the core is above the equipartition state, while its value as a function of distance from the core is well approximated by the power law. Altogether these results show that the radio flaring activity of the quasar is accompanied by injection of relativistic particles and energy losses at the jet base, while S4 1030+61 has a stable, straight jet well described by standard conical jet theories.

  5. Do Quasar Ley Lines Really Exist (United States)

    Webster, A.


    The hypothesis that the distribution of the quasars on the celestial sphere contains an unexpectedly large number of well-aligned triples is tested by applying, to the Cerro Tololo objective-prism sample, a shape-statistic which was originally developed to investigate whether neolithic standing stones were deliberately sited on ley lines. It is found that alignment in triples is not a conspicuous feature of the quasars in this sample. The sample does contain one well-aligned triple whose properties resemble those of two triples found earlier in a different field by Arp & Hazard, but the probability of this being a chance alignment is not low. The same authors have noted a total of four well-collimated triples which they consider remarkable, but an approximate probability calculation based on the shape-statistic indicates that they need not have a low probability of occurring by chance.

  6. Microlensing of quasar ultraviolet iron emission

    Energy Technology Data Exchange (ETDEWEB)

    Guerras, E.; Mediavilla, E. [Instituto de Astrofísica de Canarias, Vía Láctea S/N, La Laguna 38200, Tenerife (Spain); Jimenez-Vicente, J. [Departamento de Física Teórica y del Cosmos, Universidad de Granada, Campus de Fuentenueva, 18071 Granada (Spain); Kochanek, C. S. [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, The Ohio State University, 4055 McPherson Lab, 140 West 18th Avenue, Columbus, OH 43221 (United States); Muñoz, J. A. [Departamento de Astronomía y Astrofísica, Universidad de Valencia, 46100 Burjassot, Valencia (Spain); Falco, E. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Motta, V.; Rojas, K. [Departamento de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso (Chile)


    We measure the differential microlensing of the UV Fe II and Fe III emission line blends between 14 quasar image pairs in 13 gravitational lenses. We find that the UV iron emission is strongly microlensed in four cases with amplitudes comparable to that of the continuum. Statistically modeling the magnifications, we infer a typical size of r{sub s}∼4√(M/M{sub ⊙}) light-days for the Fe line-emitting regions, which is comparable to the size of the region generating the UV continuum (∼3-7 light-days). This may indicate that a significant part of the UV Fe II and Fe III emission originates in the quasar accretion disk.

  7. Clustering of quasars from the ROE/ESO large-scale Automated Quasar Detection (AQD)

    Energy Technology Data Exchange (ETDEWEB)

    Clowes, R.G.; Iovino, A.; Shaver, P.


    The new ROE/ESO large-scale AQD survey for quasars forms a connected area of approx. 200 deg/sup 2/ near the South Galactic Pole, and has resulted in the discovery of a total number of quasar candidates that is comparable to the number previously published from all other sources. This paper describes a three-dimensional clustering analysis of approx. 1100 'high-probability' candidates occupying the assigned-redshift band of 1.8-2.4. The analysis is sensitive to very weak clustering - to a level of 7 per cent of the quasars occurring in pairs on scales approx. 5h/sup -1/ Mpc - but none is found.

  8. Reverberation Mapping of High-Luminosity Quasars

    Directory of Open Access Journals (Sweden)

    Shai Kaspi


    Full Text Available Over the past three decades reverberation mapping (RM has been applied to about 100 AGNs. Their broad line region (BLR sizes were measured and yielded mass estimates of the black holes in their center. However, very few attempts were carried out for high-luminosity quasars, at luminosities higher than 1046 erg/sec in the optical. Most of these attempts failed since RM of such quasars is difficult due to a number of reasons, mostly due to the long time needed to monitor these objects. During the past two decades we carried out a RM campaign on six high-luminosity quasars. This contribution presents some of the final light curves of that RM campaign in which we measured the BLR size in C iv of three of the objects (S5 0836+71, SBS 1116+603, and SBS 1425+606. We present the C iv BLR size and luminosity relation over eight orders of magnitude in luminosity, pushing the luminosity limit to its highest point so far.

  9. Discovery of 16 New z ˜ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection (United States)

    Yang, Jinyi; Fan, Xiaohui; Wu, Xue-Bing; Wang, Feige; Bian, Fuyan; Yang, Qian; McGreer, Ian D.; Yi, Weimin; Jiang, Linhua; Green, Richard; Yue, Minghao; Wang, Shu; Li, Zefeng; Ding, Jiani; Dye, Simon; Lawrence, Andy


    We present initial results from the first systematic survey of luminous z ˜ 5.5 quasars. Quasars at z ˜ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution, and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 ≤ z ≤ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ˜ 5.5 quasars based on optical, near-IR, and mid-IR photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys—Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS), and Wide Field Infrared Survey Explorer. From our pilot observations in the SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 ≤ z ≤ 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ˜ 5.5 quasars already published in our previous work, we now construct a uniform quasar sample at 5.3 ≤ z ≤ 5.7, with 17 quasars in a ˜4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J-band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ˜ 5.5 quasar.

  10. HI Surface brightness mapping (United States)

    Pen, Ue-Li; Staveley-Smith, Lister; Chang, Tzu-Ching; Peterson, Jeff; Bandura, Kevin


    We propose to scan the 2dF survey field with Parkes multibeam in driftscan mode to make a map to cross correlate with galaxy redshifts. This allows a statistical detection of HI large scale structure out to z=0.15. In this cross correlation, the HI in ALL galaxies contributes, not only the bright ones, which significantly boosts the sensitivity. The proposed 40 hours on the fields result in a forecasted 20 sigma detection. The survey volume is 10 million cubic megaparsec, which contain 10^15 solar masses of hydrogen.

  11. ALMA Examines a Distant Quasar Host (United States)

    Kohler, Susanna


    The dust continuum (top) and the [CII] emission (bottom) maps for the region around J1120+0641. [Adapted from Venemans et al. 2017]A team of scientists has used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the host galaxy of the most distant quasar known. Their observations may help us to build a picture of how the first supermassive black holes in the universe formed and evolved.Faraway Monsters and Their GalaxiesWe know that quasars the incredibly luminous and active centers of some distant galaxies are powered by accreting, supermassive black holes. These monstrous powerhouses have been detected out to redshifts of z 7, when the universe was younger than a billion years old.Though weve observed over a hundred quasars at high redshift, we still dont understand how these early supermassive black holes formed, or whether the black holes and the galaxies that host them co-evolved. In order to answer questions like these, however, we first need to gather information about the properties and behavior of various supermassive black holes and their host galaxies.A team of scientists led by Bram Venemans (Max-Planck Institute for Astronomy, Germany) recently used the unprecedented sensitivity and angular resolution of ALMA as well as the Very Large Array and the IRAM Plateau de Bure Interferometer to examine the most distant quasar currently known, J1120+0641, located at a redshift of z = 7.1.A High-Resolution LookThe teams observations of the dust and gas emission from the quasars host galaxy revealed a number of intriguing things:The red and blue sides of the [CII] emission line are shown here as contours, demonstrating that theres no ordered rotational motion of the gas on kpc scales. [Adapted from Venemans et al. 2017]The majority of the galaxys emission is very compact. Around 80% of the observed flux came from a region of only 11.5 kpc in diameter.Despite the fact that the 2.4-billion-solar-mass black hole at the galaxys center is accreting at

  12. Soft X-ray Variability of the Bright Quasar 3C273

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    By encouraging this discovery, we try to analyze the four ROSAT PSPC data sets of. 3C273 which were not included in the investigation by Leach et al. (1995) in order to search any periodic long-term soft X-ray variation. We present the observation in section 2, an analysis and the results in section 3, and discussion and ...

  13. Lightness, brightness, and anchoring. (United States)

    Anderson, Barton L; Whitbread, Michael; de Silva, Chamila


    The majority of work in lightness perception has evaluated the perception of lightness using flat, matte, two-dimensional surfaces. In such contexts, the amount of light reaching the eye contains a conflated mixture of the illuminant and surface lightness. A fundamental puzzle of lightness perception is understanding how it is possible to experience achromatic surfaces as specific achromatic shades in the face of this ambiguity. It has been argued that the perception of lightness in such contexts implies that the visual system imposes an "anchoring rule" whereby a specific relative luminance (the highest) serves as a fixed point in the mapping of image luminance onto the lightness scale ("white"). We conducted a series of experiments to explicitly test this assertion in contexts where this mapping seemed most unlikely-namely, low-contrast images viewed in dim illumination. Our results provide evidence that the computational ambiguity in mapping luminance onto lightness is reflected in perceptual experience. The perception of the highest luminance in a two-dimensional Mondrian display varied monotonically with its brightness, ranging from midgray to white. Similar scaling occurred for the lowest luminance and, by implication, all other luminance values. We conclude that the conflation between brightness and lightness in two-dimensional Mondrian displays is reflected in perception and find no support for the claim that any specific relative luminance value acts as a fixed anchor point in this mapping function. © 2014 ARVO.

  14. Q-3D: Imaging Spectroscopy of Quasar Hosts with JWST Analyzed with a Powerful New PSF Decomposition and Spectral Analysis Package (United States)

    Wylezalek, Dominika; Veilleux, Sylvain; Zakamska, Nadia; Barrera-Ballesteros, J.; Luetzgendorf, N.; Nesvadba, N.; Rupke, D.; Sun, A.


    In the last few years, optical and near-IR IFU observations from the ground have revolutionized extragalactic astronomy. The unprecedented infrared sensitivity, spatial resolution, and spectral coverage of the JWST IFUs will ensure high demand from the community. For a wide range of extragalactic phenomena (e.g. quasars, starbursts, supernovae, gamma ray bursts, tidal disruption events) and beyond (e.g. nebulae, debris disks around bright stars), PSF contamination will be an issue when studying the underlying extended emission. We propose to provide the community with a PSF decomposition and spectral analysis package for high dynamic range JWST IFU observations allowing the user to create science-ready maps of relevant spectral features. Luminous quasars, with their bright central source (quasar) and extended emission (host galaxy), are excellent test cases for this software. Quasars are also of high scientific interest in their own right as they are widely considered to be the main driver in regulating massive galaxy growth. JWST will revolutionize our understanding of black hole-galaxy co-evolution by allowing us to probe the stellar, gas, and dust components of nearby and distant galaxies, spatially and spectrally. We propose to use the IFU capabilities of NIRSpec and MIRI to study the impact of three carefully selected luminous quasars on their hosts. Our program will provide (1) a scientific dataset of broad interest that will serve as a pathfinder for JWST science investigations in IFU mode and (2) a powerful new data analysis tool that will enable frontier science for a wide swath of astrophysical research.

  15. Clues to quasar broad-line region geometry and kinematics

    NARCIS (Netherlands)

    Vestergaard, M; Wilkes, BJ; Barthel, PD


    We present evidence that the high-velocity C IV lambda 1549 emission-line gas of radio-loud quasars may originate in a disklike configuration, in close proximity to the accretion disk often assumed to emit the low-ionization lines. For a sample of 36 radio-loud z approximate to 2 quasars, we find

  16. Emission line imaging of 3CR quasars and radio galaxies

    NARCIS (Netherlands)

    Hes, R; Barthel, PD; Fosbury, RAE

    Optical emission line images and spectra of sixteen 3CR powerful radio galaxies and quasars are presented. Extended line emission is detected in both radio galaxies and quasars. We show that line luminosities, derived from the spatially integrated [OII]lambda 3727 narrow emission line, are on

  17. Using Quasars as Standard Clocks for Measuring Cosmological Redshift (United States)

    Dai, De-Chang; Starkman, Glenn D.; Stojkovic, Branislav; Stojkovic, Dejan; Weltman, Amanda


    We report hitherto unnoticed patterns in quasar light curves. We characterize segments of the quasar’s light curves with the slopes of the straight lines fit through them. These slopes appear to be directly related to the quasars’ redshifts. Alternatively, using only global shifts in time and flux, we are able to find significant overlaps between the light curves of different pairs of quasars by fitting the ratio of their redshifts. We are then able to reliably determine the redshift of one quasar from another. This implies that one can use quasars as standard clocks, as we explicitly demonstrate by constructing two independent methods of finding the redshift of a quasar from its light curve.

  18. Parsec-scale radio structures in Quasars (United States)

    Coldwell, G.; Paragi, Z.; Gurvits, L.

    Very Long Baseline Interferometry (VLBI) con su nueva extensión para el radio telescopio orbital, VSOP/HALCA, ofrece una incomparable resolución angular alcanzando escalas de milisegundos y submilisegundos de arco a longitudes de onda de centímetros. En este trabajo presentamos observaciones y análisis de estructuras en radio, en escalas de parsec, para 3 radio fuentes extragalácticas de la muestra de VSOP Survey y 1 quasar, 1442+101, del proyecto `VSOP High Redshift'.

  19. Camera for Quasars in Early Universe (CQUEAN) (United States)

    Park, Won-Kee; Pak, Soojong; Im, Myungshin; Choi, Changsu; Jeon, Yiseul; Chang, Seunghyuk; Jeong, Hyeonju; Lim, Juhee; Kim, Eunbin


    We describe the overall characteristics and the performance of an optical CCD camera system, Camera for Quasars in Early Universe (CQUEAN), which has been used at the 2.1 m Otto Struve Telescope of the McDonald Observatory since 2010 August. CQUEAN was developed for follow-up imaging observations of red sources such as high-redshift quasar candidates (z ≳ 5), gamma-ray bursts, brown dwarfs, and young stellar objects. For efficient observations of the red objects, CQUEAN has a science camera with a deep-depletion CCD chip, which boasts a higher quantum efficiency at 0.7-1.1 μm than conventional CCD chips. The camera was developed in a short timescale () and has been working reliably. By employing an autoguiding system and a focal reducer to enhance the field of view on the classical Cassegrain focus, we achieve a stable guiding in 20 minute exposures, an imaging quality with FWHM≥0.6‧‧ over the whole field (4.8‧ × 4.8‧), and a limiting magnitude of z = 23.4 AB mag at 5-σ with 1 hr total integration time. This article includes data taken at the McDonald Observatory of The University of Texas at Austin.

  20. LSST survey: millions and millions of quasars (United States)

    Ivezić, Željko

    The Large Synoptic Survey Telescope (LSST), the next-generation optical imaging survey sited at Cerro Pachon in Chile, will provide hundreds of detections for a sample of more than ten million quasars with redshifts up to about seven. The LSST design, with an 8.4m (6.7m effective) primary mirror, a 9.6 sq. deg. field of view, and a 3.2 Gigapixel camera, will allow about 10,000 sq. deg. of sky to be covered twice per night, every three to four nights on average, with typical 5-sigma depth for point sources of r=24.5 (AB). With about 1000 observations in ugrizy bands over a 10-year period, these data will enable a deep stack reaching r=27.5 (about 5 magnitudes deeper than SDSS) and faint time-domain astronomy. The measured properties of newly discovered and known astrometric and photometric transients will be publicly reported within 60 sec after closing the shutter. In addition to a brief introduction to LSST, I review optical quasar selection techniques, with emphasis on methods based on colors, variability properties, and astrometric behavior.

  1. Impact of quasar proper motions on the alignment between the International Celestial Reference Frame and the Gaia reference frame (United States)

    Liu, J.-C.; Malkin, Z.; Zhu, Z.


    The International Celestial Reference Frame (ICRF) is currently realized by the very long baseline interferometry (VLBI) observations of extragalactic sources with the zero proper motion assumption, while Gaia will observe proper motions of these distant and faint objects to an accuracy of tens of microarcseconds per year. This paper investigates the difference between VLBI and Gaia quasar proper motions and it aims to understand the impact of quasar proper motions on the alignment of the ICRF and Gaia reference frame. We use the latest time series data of source coordinates from the International VLBI Service analysis centres operated at Goddard Space Flight Center (GSF2017) and Paris observatory (OPA2017), as well as the Gaia auxiliary quasar solution containing 2191 high-probability optical counterparts of the ICRF2 sources. The linear proper motions in right ascension and declination of VLBI sources are derived by least-squares fits while the proper motions for Gaia sources are simulated taking into account the acceleration of the Solar system barycentre and realistic uncertainties depending on the source brightness. The individual and global features of source proper motions in GSF2017 and OPA2017 VLBI data are found to be inconsistent, which may result from differences in VLBI observations, data reduction and analysis. A comparison of the VLBI and Gaia proper motions shows that the accuracies of the components of rotation and glide between the two systems are 2-4 μas yr- 1 based on about 600 common sources. For the future alignment of the ICRF and Gaia reference frames at different wavelengths, the proper motions of quasars must necessarily be considered.

  2. Ultra-Bright Optical Transients Are Linked With Type Ic Supernovae (United States)


    stel- lar explosions. Ultra-bright supernovae (SNe) associated with faint and, presumably, metal-poor host galaxies are the most spectacular recent...associated with no obvious host galaxy (although a weak source, 1.′′5 from the transient, was marginally detected at magnitude z ∼ 25.8).15 Without robust...Possible scenarios proposed by Barbary et al. (2009) for SCP-06F6 were an outburst of a Galactic C-rich white dwarf (WD), a broad ab- sorption lines quasar

  3. Ultraviolet spectropolarimetry of high-redshift quasars with the Hubble Space Telescope (United States)

    Impey, C. D.; Malkan, Matthew A.; Webb, Wayne; Petry, C. E.


    Ultraviolet spectropolarimetry of three bright high-redshift low-polarization quasars (LPQs) was obtained with the Faint Object Spectrograph of the Hubble Space Telescope (HST). Two of the quasars, PG 1634+706 and PG 2302+029, had polarizations p approximately = 0.5%-1.0% throughout the ultraviolet, and showed no significant variation of polarization amplitude or position angle with wavelength. PG 2302+029 was also marginally (2.4 sigma) circularly polarized in the optical continuum. For the highest redshift quasar, PG 1222+228 (Ton 1530), the polarization was measured down to rest wavelengths below 800 A. Although the continuum of PG 1222+228 was weakened by Lyman limit absorption from an intergalactic gas cloud, the polarization increased sharply from 1% to about 4.5%, a change of 4 sigma significance. This abrupt rise in polarization does not appear attributable to any known instrumental artifact. These UV polarizations were only slightly less than those previously observed for these same objects in the optical. The polarization spectra were flat with a typical slope of the polarized flux pF(sub nu) proportional to nu(exp -0.8 +/- 0.5). Unlike the case of several high luminosity Seyfert 1 nuclei studied previously, polarization caused by scattering from dust grains does not provide the best fit to the polarization spectra of these luminous quasars. These observed spectra are consistent with a wavelength-independent polarization proportional to the total nonstellar light or, possibly, to the contribution of the blue thermal component. The polarization spectra have insufficient signal-to-noise to locate the scatterers with respect to the continuum source and the much larger broad line region. A decrease in amplitude and rotation of the position angle of the polarization vector at the shortest wavelengths, which could result from general relativistic effects near a spinning black hole, was not observed. In fact, in PG 1222+228, the polarization was observed to

  4. Tracing a high redshift cosmic web with quasar systems (United States)

    Einasto, Maret; Tago, Erik; Lietzen, Heidi; Park, Changbom; Heinämäki, Pekka; Saar, Enn; Song, Hyunmi; Liivamägi, Lauri Juhan; Einasto, Jaan


    Context. To understand the formation, evolution, and present-day properties of the cosmic web we need to study it at low and high redshifts. Aims: We trace the cosmic web at redshifts that range from 1.0 ≤ z ≤ 1.8 by using the quasar (QSO) data from the SDSS DR7 QSO catalogue. Methods: We apply a friend-of-friend algorithm to the quasar and random catalogues to determine systems at a series of linking length and analyse richness and sizes of these systems. Results: At the linking lengths l ≤ 30 h-1 Mpc, the number of quasar systems is larger than the number of systems detected in random catalogues, and the systems themselves have smaller diameters than random systems. The diameters of quasar systems are comparable to the sizes of poor galaxy superclusters in the local Universe. The richest quasar systems have four members. The mean space density of quasar systems, ≈ 10-7 (h-1 Mpc)-3, is close to the mean space density of local rich superclusters. At intermediate linking lengths (40 ≤ l ≤ 70 h-1 Mpc), the richness and length of quasar systems are similar to those derived from random catalogues. Quasar system diameters are similar to the sizes of rich superclusters and supercluster chains in the local Universe. The percolating system, which penetrate the whole sample volume appears in a quasar sample at a smaller linking length than in random samples (85 h-1 Mpc). At the linking length 70 h-1 Mpc, the richest systems of quasars have diameters exceeding 500 h-1 Mpc. Quasar luminosities in systems are not correlated with the system richness. Conclusions: Quasar system catalogues in our web pages and at the Strasbourg Astronomical Data Center (CDS) serve as a database for searching superclusters of galaxies and for tracing the cosmic web at high redshifts. Appendix A is available in electronic form at http://www.aanda.orgThe catalogues are only available at the CDS via anonymous ftp to ( or via http://cdsarc

  5. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

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


    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...... 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...

  6. A survey of z > 5.7 quasars in the sloan digital sky survey. 4. discovery of seven additional quasars

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiao-Hui; Strauss, Michael A.; Richards, Gordon T.; Hennawi, Joseph F.; Becker, Robert H.; White, Richard L.; Diamond-Stanic, Aleksandar M.; onley, Jennifer L.D; Jiang, Lin-Hua; Kim, J.Serena; Vestergaard, Marianne; Young, Jason E.; Gunn, James E.; Lupton, Robert H.; Knapp, Gillian R.; Schneider, Donald P.; Brandt, W.N.; Bahcall, Neta A.; Barentine, J.C.; Brinkmann, J.; Brewington, Howard J.; /Arizona U., Astron. Dept. - Steward Observ. /Princeton U. Observ. /Johns Hopkins U. /UC, Berkeley, Astron. Dept. /UC, Davis


    We present the discovery of seven quasars at z > 5.7, selected from {approx}2000 deg{sup 2} of multicolor imaging data of the Sloan Digital Sky Survey (SDSS). The new quasars have redshifts z from 5.79 to 6.13. Five are selected as part of a complete flux-limited sample in the SDSS Northern Galactic Cap; two have larger photometric errors and are not part of the complete sample. One of the new quasars, SDSS J1335+3533 (z = 5.93), exhibits no emission lines; the 3-{sigma} limit on the rest-frame equivalent width of Ly{alpha} + NV line is 5 {angstrom}. It is the highest redshift lineless quasar known, and could be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z > 6 quasars, SDSS 1250+3130 (z = 6.13) and SDSS J1137+3549 (z = 6.01), show deep Gunn-Peterson absorption gaps in Ly{alpha}. These gaps are narrower the complete Gunn-Peterson absorption troughs observed among quasars at z > 6.2 and do not have complete Ly{beta} absorption.

  7. Quasar Absorption Lines and SDSS Galaxies (United States)

    Shoemaker, Emileigh Suzanne; Scott, Jennifer E.; Oldak, Katarzyna


    We present the results of a study of the sightlines of 45 low redshift quasars (0.06 footprint of the Sloan Digital Sky Survey. We use both the SDSS DR12 galaxy photometric data, including photometric redshifts, and the measured properties of the absorbers along with the known absorption characteristics of the intergalactic medium and the circumgalactic medium of galaxies to assign the most probable galaxy matches for each absorber in the sample, using estimated galaxy luminosities and virial radii as a discriminator. We show that the scheme can recover known galaxy-absorber matches found from spectroscopic data and thus provides a method for identifying likely pairs in photometric data sets as well as targets for spectroscopic follow up.

  8. Are high-redshift quasars hidden by dusty galaxies? (United States)

    Wright, Edward L.


    A Monte Carlo technique has been developed to compute the joint probability distribution for the reddening and extinction of quasars by galaxies along the line of sight with a realistic dust extinction curve including the 220 nm feature. Galaxies are treated as disks with random inclinations, having exponential or modified Gaussian radial profiles. This technique is used to find the distribution of the reddened quasars on multicolor diagrams such as the (U-J, J-F) plots used by Koo and Kron (1982) to find faint quasars. The multicolor search technique is not a simple UV excess approach, and the resulting color selection does not add significantly to the flux selection discussed by Wright (1981), Ostriker and Heisler (1984), and Heisler and Ostriker (1988). The quasar reddening trend observed by Wright and Malkan (1987) is about 0.35 + or - 0.50 times the mean reddening of the selected sample predicted by the Heisler and Ostriker model.

  9. The Doppler Effect: A Consideration of Quasar Redshifts. (United States)

    Gordon, Kurtiss J.


    Provides information on the calculation of the redshift to blueshift ratio introduced by the transverse Doppler effect at relativistic speeds. Indicates that this shift should be mentioned in discussions of whether quasars are "local" rather than "cosmological" objects. (GS)

  10. How Quasar Feedback May Shape the Co-evolutionary Paths

    Directory of Open Access Journals (Sweden)

    Wako Ishibashi


    Full Text Available Observations point toward some form of “co-evolutionary sequence,” from dust-enshrouded starbursts to luminous unobscured quasars. Active galactic nucleus (AGN feedback is generally invoked to expel the obscuring dusty gas in a blow-out event, eventually revealing the hidden central quasar. However, the physical mechanism driving AGN feedback, either due to winds or radiation, remains uncertain and is still a source of much debate. We consider quasar feedback, based on radiation pressure on dust, which directly acts on the obscuring dusty gas. We show that AGN radiative feedback is capable of efficiently removing the obscuring cocoon, and driving powerful outflows on galactic scales, consistent with recent observations. I will discuss how such quasar feedback may provide a natural physical interpretation of the observed evolutionary path, and the physical implications in the broader context of black hole-host galaxy co-evolution.

  11. ELM-KNN for photometric redshift estimation of quasars (United States)

    Zhang, Yanxia; Tu, Yang; Zhao, Yongheng; Tian, Haijun


    We explore photometric redshift estimation of quasars with the SDSS DR12 quasar sample. Firstly the quasar sample is separated into three parts according to different redshift ranges. Then three classifiers based on Extreme Learning Machine (ELM) are created in the three redshift ranges. Finally k-Nearest Neighbor (kNN) approach is applied on the three samples to predict photometric redshifts of quasars with multiwavelength photometric data. We compare the performance with different input patterns by ELM-KNN with that only by kNN. The experimental results show that ELM-KNN is feasible and superior to kNN (e.g. rms is 0.0751 vs. 0.2626 for SDSS sample), in other words, the ensemble method has the potential to increase regressor performance beyond the level reached by an individual regressor alone and will be a good choice when facing much more complex data.

  12. Development of SED Camera for Quasars in Early Universe (SQUEAN)


    Kim, Sanghyuk; Jeon, Yiseul; Lee, Hye-In; Park, Woojin; Ji, Tae-Geun; Hyun, Minhee; Choi, Changsu; Im, Myungshin; Pak, Soojong


    We describe the characteristics and performance of a camera system, Spectral energy distribution Camera for Quasars in Early Universe (SQUEAN). It was developed to measure SEDs of high redshift quasar candidates (z $\\gtrsim$ 5) and other targets, e.g., young stellar objects, supernovae, and gamma-ray bursts, and to trace the time variability of SEDs of objects such as active galactic nuclei (AGNs). SQUEAN consists of an on-axis focal plane camera module, an auto-guiding system, and mechanical...

  13. Probing Planets in Extragalactic Galaxies Using Quasar Microlensing


    Dai, Xinyu; Guerras, Eduardo


    Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fek...

  14. Recent Seven Years of Radio and Optical Variabilities of Quasar ...

    Indian Academy of Sciences (India)

    Abstract. We analyzed the radio (4.8, 8.0 and 14.5 GHz) light curves from UMRAO database and the optical data of quasar 1156 + 295 and found that the quasar exhibited remarkable quasi-periodic long-term flux variations in both radio and optical bands with a similar variability timescale of 1.2 ± 0.3 yr. In addition, when a ...

  15. A search for changing look quasars in second epoch imaging (United States)

    Findlay, Joseph; Myers, Adam; McGreer, Ian


    Over nearly two decades, the Sloan Digital Sky Survey has compiled a catalog of over half a million confirmed quasars. During that period approximately ten percent of these objects have been spectroscopically observed in two or more epochs over baselines of ten or more years. This led recently to the discovery of the largest change in luminosity ever before observed in a quasar. The dimming emission was a reflection of very significant changes in continuum and broad line properties, the source had effectively transitioned from a Type I quasar to a Type II AGN. Since then several more "changing look" quasars have been discovered in multi-epoch SDSS spectroscopy. Among them are objects with rising and falling luminosities, appearing and disappearing broad lines. The origin of this behavior is still very uncertain, currently favored is the scenario in which an accreting black hole is simply starved of fuel. Other plausible scenarios include flaring due to stellar tidal disruption close to the black hole or large changes in accretion flow, which can occur during transitions between radiatively efficient and inefficient accretion regimes. Monitoring of larger numbers of changing look quasars will help to elucidate these ideas.In this poster, we report on the progress of a pilot study in which we hope to learn how to select changing look quasars in multi-epoch imaging. This will allow us to take advantage of the entire SDSS quasar catalog rather than just the ten percent of objects with multi-epoch spectroscopy. Comparing archival SDSS and more recent Legacy Survey imaging over ten-year baselines we select objects whose photometry is consistent with the large changes in luminosity expected in changing look quasars. We aim to build up a catalog of both transitioned and transitioning objects for future monitoring.

  16. Host galaxies of high-redshift quasars with extreme outflows (United States)

    Zakamska, Nadia


    Feedback from accreting supermassive black holes is now a standard ingredient in galaxy formation models. It has long been speculated that powerful quasars, triggered in major gas-rich mergers, had a profound impact on galaxy formation via quasar-driven winds. This process must have been at its peak during the epoch of most active galaxy formation and quasar activity at z=2-3, yet there is not yet any direct observational support for this long-hypothesized process. We have discovered a population of extremely luminous (L>1e47 erg/s) red quasars with peculiar line properties at z=2-3 which show unprecedented signatures of powerful v>2000 km/s outflows in their [OIII]5007A lines. We propose to image eleven of these objects with the HST in two filters, one probing rest-frame UV and one probing the rest-frame optical. The rest-frame optical observations will directly probe the dynamical state and extent of the hosts of luminous obscured quasars and search for companions and merger signatures. We will determine the masses of the stellar component to determine if the bulges of the quasar hosts have already become apparent in this epoch. Using the rest-frame UV observations, we will probe the distribution of the gas in quasar hosts by observing the morphology of ongoing star formation and scattered light from the central engine. Our targets are the best candidates to probe the long-speculated merger-driven scenario for quasar activity, and our proposed HST observations will definitively determine whether this process drives the evolution of massive galaxies.

  17. The X-ray properties of z 6 luminous quasars (United States)

    Nanni, R.; Vignali, C.; Gilli, R.; Moretti, A.; Brandt, W. N.


    We present a systematic analysis of X-ray archival data of all the 29 quasars (QSOs) at z> 5.5 observed so far with Chandra, XMM-Newton and Swift-XRT, including the most-distant quasar ever discovered, ULAS J1120+0641 (z = 7.08). This study allows us to place constraints on the mean spectral properties of the primordial population of luminous Type 1 (unobscured) quasars. Eighteen quasars are detected in the X-ray band, and we provide spectral-fitting results for their X-ray properties, while for the others we provide upper limits to their soft (0.5-2.0 keV) X-ray flux. We measured the power-law photon index and derived an upper limit to the column density for the five quasars (J1306+0356, J0100+2802, J1030+0524, J1148+5251, J1120+0641) with the best spectra (>30 net counts in the 0.5-7.0 keV energy range) and find that they are consistent with values from the literature and lower-redshift quasars. By stacking the spectra of ten quasars detected by Chandra in the redshift range 5.7 ≤ z ≤ 6.1 we find a mean X-ray power-law photon index of Γ = 1.92-0.27+0.28 and a neutral intrinsic absorption column density of NH ≤ 1023 cm-2. These results suggest that the X-ray spectral properties of luminous quasars have not evolved up to z ≈ 6. We also derived the optical-X-ray spectral slopes (αox) of our sample and combined them with those of previous works, confirming that αox strongly correlates with UV monochromatic luminosity at 2500 Å. These results strengthen the non-evolutionary scenario for the spectral properties of luminous active galactic nuclei (AGN).

  18. Teradiode's high brightness semiconductor lasers (United States)

    Huang, Robin K.; Chann, Bien; Burgess, James; Lochman, Bryan; Zhou, Wang; Cruz, Mike; Cook, Rob; Dugmore, Dan; Shattuck, Jeff; Tayebati, Parviz


    TeraDiode is manufacturing multi-kW-class ultra-high brightness fiber-coupled direct diode lasers for industrial applications. A fiber-coupled direct diode laser with a power level of 4,680 W from a 100 μm core diameter, world-record brightness levels for direct diode lasers. The fiber-coupled output corresponds to a Beam Parameter Product (BPP) of 3.5 mm-mrad and is the lowest BPP multi-kW-class direct diode laser yet reported. This laser is suitable for industrial materials processing applications, including sheet metal cutting and welding. This 4-kW fiber-coupled direct diode laser has comparable brightness to that of industrial fiber lasers and CO2 lasers, and is over 10x brighter than state-of-the-art direct diode lasers. We have also demonstrated novel high peak power lasers and high brightness Mid-Infrared Lasers.


    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jiayi [Tsinghua Center for Astrophysics, Department of Physics, Tsinghua University, Beijing 100084 (China); Shen, Yue [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)


    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L{sub Edd}) of the black hole (BH) accretion. Shen and Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ{sub *} (hence, the BH mass via the M–σ{sub *} relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ{sub *} systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ{sub *} on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  20. Application of Independent Component Analysis to Legacy UV Quasar Spectra (United States)

    Richards, Gordon


    We propose to apply a novel analysis technique to UV spectroscopy ofquasars in the HST archive. We endeavor to analyze all of thearchival quasar spectra, but will first focus on those quasars thatalso have optical spectroscopy from SDSS. An archival investigationby Sulentic et al. (2007) revealed 130 known quasars with UV coverageof CIV complementing optical emission line coverage. Today, thesample has grown considerably and now includes COS spectroscopy. Ourproposal includes a proof-of-concept demonstration of the power of atechnique called Independent Component Analysis (ICA). ICA allows usto reduce complexity of of quasar spectra to just a handful ofnumbers. In addition to providing a uniform set of traditional linemeasurements (and carefully calibrated redshifts), we will provide ICAweights to the community with examples of how they can be used to doscience that previously would have been quite difficult. The time isripe for such an investigation because 1) it has been a decade sincethe last significant archival investigation of UV emission lines fromHST quasars, 2) the future is uncertain for obtaining new UV quasarspectroscopy, and 3) the rise of machine learning has provided us withpowerful new tools. Thus our proposed work will provide a true UVlegacy database for quasar-based investigations.


    Energy Technology Data Exchange (ETDEWEB)

    LaMassa, Stephanie M.; Cales, Sabrina; Urry, C. Megan [Yale Center for Astronomy and Astrophysics, Physics Department, P.O. Box 208120, New Haven, CT 06520 (United States); Moran, Edward C. [Astronomy Department, Wesleyan University, Middletown, CT 06459 (United States); Myers, Adam D. [Department of Physics and Astronomy 3905, University of Wyoming, 1000 E. University, Laramaie, WY 82071 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Eracleous, Michael [Department of Astronomy and Astrophysics, and Institute for Gravitation and the Cosmos, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Heckman, Timothy M. [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Gallo, Luigi [Department of Astronomy and Physics, Saint Mary’s University, Halifax, NS B3H 3C3 (Canada)


    SDSS J015957.64+003310.5 is an X-ray selected, z = 0.31 active galactic nucleus (AGN) from the Stripe 82X survey that transitioned from a Type 1 quasar to a Type 1.9 AGN between 2000 and 2010. This is the most distant AGN, and first quasar, yet observed to have undergone such a dramatic change. We re-observed the source with the double spectrograph on the Palomar 5 m telescope in 2014 July and found that the spectrum is unchanged since 2010. From fitting the optical spectra, we find that the AGN flux dropped by a factor of 6 between 2000 and 2010 while the broad Hα emission faded and broadened. Serendipitous X-ray observations caught the source in both the bright and dim state, showing a similar 2–10 keV flux diminution as the optical while lacking signatures of obscuration. The optical and X-ray changes coincide with g-band magnitude variations over multiple epochs of Stripe 82 observations. We demonstrate that variable absorption, as might be expected from the simplest AGN unification paradigm, does not explain the observed photometric or spectral properties. We interpret the changing state of J0159+0033 to be caused by dimming of the AGN continuum, reducing the supply of ionizing photons available to excite gas in the immediate vicinity around the black hole. J0159+0033 provides insight into the intermittency of black hole growth in quasars, as well as an unprecedented opportunity to study quasar physics (in the bright state) and the host galaxy (in the dim state), which has been impossible to do in a single sources until now.

  2. Structure of Quasar Continuum Emission Regions and Cosmology from Optical and X-Ray Microlensing in Gravitationally Lensed Quasars (United States)


    15. NUMBER OF PAGES 42 14. SUBJECT TERMS cosmology : observations — accretion, accretion disks — dark matter — gravitational hole. Subject headings: cosmology : observations — accretion, accretion disks — dark matter — gravitational lensing — quasars: general 2...U.S.N.A. – Trident Scholar project report; no. 365 (2008) STRUCTURE OF QUASAR CONTINUUM EMISSION REGIONS AND COSMOLOGY FROM OPTICAL AND X-RAY

  3. Lightness, brightness, and brightness contrast: 2. Reflectance variation. (United States)

    Arend, L E; Spehar, B


    Changes of annulus luminance in traditional disk-and-annulus patterns can be perceived to be either reflectance or illuminance changes. In the present experiments, we examined the effect of varying annulus reflectance. In Experiment 1, we placed test and standard patch-and-surround patterns in identical Mondrian patchworks. Only the luminance of the test surround changed from trial to trial, appearing as reflectance variation under constant illumination. Lightness matches were identical to brightness matches, as expected. In Experiment 2, we used only the patch and surround (no Mondrian). Instructions said that the illumination would change from trial to trial. Lightness and brightness-contrast data were identical; illumination gradients were indistinguishable from reflectance gradients. In Experiment 3, the patterns were the same, but the instructions said that the shade of gray of the test surround would change from trial to trial. Lightness matches were identical to brightness matches, again confirming the ambiguity of disk-and-annulus patterns.

  4. Measuring Quasar Variability with Pan-STARRS1 and SDSS (United States)

    Morganson, E.; Burgett, W. S.; Chambers, K. C.; Green, P. J.; Kaiser, N.; Magnier, E. A.; Marshall, P. J.; Morgan, J. S.; Price, P. A.; Rix, H.-W.; Schlafly, E. F.; Tonry, J. L.; Walter, F.


    We measure quasar variability using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS1 or PS1) and the Sloan Digital Sky Survey (SDSS) and establish a method of selecting quasars via their variability in 104 deg2 surveys. We use 105 spectroscopically confirmed quasars that have been well measured in both PS1 and SDSS and take advantage of the decadal timescales that separate SDSS measurements and PS1 measurements. A power law model fits the data well over the entire time range tested, 0.01-10 yr. Variability in the current PS1-SDSS data set can efficiently distinguish between quasars and nonvarying objects. It improves the purity of a griz quasar color cut from 4.1% to 48% while maintaining 67% completeness. Variability will be very effective at finding quasars in data sets with no u band and in redshift ranges where exclusively photometric selection is not efficient. We show that quasars' rest-frame ensemble variability, measured as a root mean squared in Δ magnitudes, is consistent with V(z, L, t) = A 0(1 + z)0.37(L/L 0)-0.16(t/1 yr)0.246, where L 0 = 1046 erg s-1 and A 0 = 0.190, 0.162, 0.147, or 0.141 in the g P1, r P1, i P1, or z P1filter, respectively. We also fit across all four filters and obtain median variability as a function of z, L, and λ as V(z, L, λ, t) = 0.079(1 + z)0.15(L/L 0)-0.2(λ/1000 nm)-0.44(t/1 yr)0.246.

  5. Star Formation Quenching in Quasar Host Galaxies

    Directory of Open Access Journals (Sweden)

    Stefano Carniani


    Full Text Available Galaxy evolution is likely to be shaped by negative feedback from active galactic nuclei (AGN. In the whole range of redshifts and luminosities studied so far, galaxies hosting an AGN frequently show fast and extended outflows consisting in both ionized and molecular gas. Such outflows could potentially quench the start formation within the host galaxy, but a clear evidence of negative feedback in action is still missing. Hereby I will analyse integral-field spectroscopic data for six quasars at z ~ 2.4 obtained with SINFONI in the H- and K-band. All the quasars show [Oiii]λ5007 line detection of fast, extended outflows. Also, the high signal-to-noise SINFONI observations allow the identification of faint narrow Hα emission (FWHM < 500 km/s, which is spatially extended and associated with star formation in the host galaxy. On paper fast outflows are spatially anti-correlated with star-formation powered emission, i.e., star formation is suppressed in the area affected by the outflow. Nonetheless as narrow, spatially-extended Hα emission, indicating star formation rates of at least 50–100 M⊙ yr−1, has been detected, either AGN feedback is not affecting the whole host galaxy, or star formation is completely quenched only by several feedback episodes. On the other hand, a positive feedback scenario, supported by narrow emission in Hα extending along the edges of the outflow cone, suggests that galaxy-wide outflows could also have a twofold role in the evolution of the host galaxy. Finally, I will present CO(3-2 ALMA data for three out of the six QSOs observed with SINFONI. Flux maps obtained for the CO(3-2 transition suggest that molecular gas within the host galaxy is swept away by fast winds. A negative-feedback scenario is supported by the inferred molecular gas mass in all three objects, which is significantly below what observed in non-active main-sequence galaxies at high-z.

  6. Fifty Years of Quasars From Early Observations and Ideas to Future Research

    CERN Document Server

    Marziani, Paola; Sulentic, Jack


    The 50th anniversary of the discovery of quasars in 1963 presents an interesting opportunity to ask questions about the current state of quasar research. Formatted as a series of interviews with noted researchers in the field, each of them asked to address a specific set of questions covering topics selected by the editors, this book deals with the historical development of quasar research and discusses how advances in instrumentation and computational capabilities have benefitted quasar astronomy and have changed our basic understanding of quasars. In the last part of the book the interviews address the current topic of the role of quasars in galaxy evolution. They summarise open issues in understanding active galactic nuclei and quasars and present an outlook regarding what future observational facilities both on the ground and in space might reveal. Its interview format, the fascinating topic of quasars and black holes, and the lively recollections and at times controversial views of the contributors make ...

  7. Bright Light Treatment in Psychiatry

    Directory of Open Access Journals (Sweden)

    Pinar Guzel Ozdemir


    Full Text Available Bright light treatment is a treatment modality that leads elevation of mood due to attenuation in depressive symptoms, regulation in circadian rhythm activity, increase the effect of antidepressants and amelioration in sleep quality. Bright light treatment is considered among the first-line treatments for seasonal affective disorder because of high response rates. Additionally, bright light treatment being extended to other conditions, including non-seasonal mood disorders, Alzheimer's disease, circadian rhythm sleep disorders, eating disorders, attention deficit hyperactivity disorder and other behavioral syndromes is likely to have a far reached use. Side effects are often temporary and can generally be overcome by reducing exposure time. The central focus on this paper is to review the action mechanisms, efficacy, usage areas, the ways of administration and side effects of the light treatment. [Psikiyatride Guncel Yaklasimlar - Current Approaches in Psychiatry 2017; 9(2.000: 177-188

  8. Are Quasar Jets Dominated by Poynting Flux?

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, M


    The formation of relativistic astrophysical jets is presumably mediated by magnetic fields threading accretion disks and central, rapidly rotating objects. As it is accelerated by magnetic stresses, the jet's kinetic energy flux grows at the expense of its Poynting flux. However, it is unclear how efficient is the conversion from magnetic to kinetic energy and whether there are any observational signatures of this process. We address this issue in the context of jets in quasars. Using data from all spatial scales, we demonstrate that in these objects the conversion from Poynting-flux-dominated to matter-dominated jets is very likely to take place closer to the black hole than the region where most of the Doppler boosted radiation observed in blazars is produced. We briefly discuss the possibility that blazar activity can be induced by global MHD instabilities, e.g., via the production of localized velocity gradients that lead to dissipative events such as shocks or magnetic reconnection, where acceleration of relativistic particles and production of non-thermal flares is taking place.

  9. Illuminating Radio Dim/Gamma-ray Bright Active Galactic Nuclei (United States)

    Macomb, Daryl J.; Bohney, Amanda; Shrader, Chris R.


    A recent survey of high-latitude gamma-ray sources by Schinzel et al. (arXiv:1702.070336), reveals a sample of about 100 objects which are not detected in the 4-10 GHz radio band to a limiting flux of about 2mJy. This apparent lack of radio flux is puzzling, and may indicate either an extreme Compton-dominated sample, or copious gamma-ray emission from a heretofore unknown population such as a subclass of radio-quiet AGN. To further investigate the nature sources, we have undertaken the task of searching for transient or faint steady emission in the ~15-100-keV X-ray band using the Swift/BAT archive. Here we discuss the analysis, detection's (or not) , and any spectral or temporal information that may enable us to assess the nature of these sources.

  10. Serendipitous discovery of quadruply-imaged quasars:Two diamonds (United States)

    Lucey, John R.; Schechter, Paul L.; Smith, Russell J.; Anguita, T.


    Gravitationally lensed quasars are powerful and versatile astrophysical tools, but they are challengingly rare. In particular, only ˜25 well-characterized quadruple systems are known to date. To refine the target catalogue for the forthcoming Taipan Galaxy Survey, the images of a large number of sources are being visually inspected in order to identify objects that are confused by a foreground star or galaxies that have a distinct multi-component structure. An unexpected by-product of this work has been the serendipitous discovery of about a dozen galaxies that appear to be lensing quasars, i.e. pairs or quartets of foreground stellar objects in close proximity to the target source. Here we report two diamond-shaped systems. Follow-up spectroscopy with the IMACS instrument on the 6.5m Magellan Baade telescope confirms one of these as a z = 1.975 quasar quadruply lensed by a double galaxy at z = 0.293. Photometry from publicly available survey images supports the conclusion that the other system is a highly sheared quadruply-imaged quasar. In starting with objects thought to be galaxies, our lens finding technique complements the conventional approach of first identifying sources with quasar-like colours and subsequently finding evidence of lensing.

  11. Camera for Quasars in the Early Universe (CQUEAN) (United States)

    Kim, Eunbin; Park, W.; Lim, J.; Jeong, H.; Kim, J.; Oh, H.; Pak, S.; Im, M.; Kuehne, J.


    The early universe of z ɳ is where the first stars, galaxies, and quasars formed, starting the re-ionization of the universe. The discovery and the study of quasars in the early universe allow us to witness the beginning of history of astronomical objects. In order to perform a medium-deep, medium-wide, imaging survey of quasars, we are developing an optical CCD camera, CQUEAN (Camera for QUasars in EArly uNiverse) which uses a 1024*1024 pixel deep-depletion CCD. It has an enhanced QE than conventional CCD at wavelength band around 1μm, thus it will be an efficient tool for observation of quasars at z > 7. It will be attached to the 2.1m telescope at McDonald Observatory, USA. A focal reducer is designed to secure a larger field of view at the cassegrain focus of 2.1m telescope. For long stable exposures, auto-guiding system will be implemented by using another CCD camera viewing an off-axis field. All these instruments will be controlled by the software written in python on linux platform. CQUEAN is expected to see the first light during summer in 2010.

  12. Hubble Space Telescope Ultraviolet spectroscopy of 14 low-redshift quasars

    NARCIS (Netherlands)

    Ganguly, R.; Kaastra, J.S.|info:eu-repo/dai/nl/070911134


    We present low-resolution ultraviolet spectra of 14 low-redshift quasars observed with the Hubble Space Telescope STIS as part of a Snapshot project to understand the relationship between quasar outflows and luminosity. The quasar is radio-loud but has a steep spectral index and a lobe-dominated

  13. Probability distributions for the magnification of quasars due to microlensing (United States)

    Wambsganss, Joachim


    Gravitational microlensing can magnify the flux of a lensed quasar considerably and therefore possibly influence quasar source counts or the observed quasar luminosity function. A large number of distributions of magnification probabilities due to gravitational microlensing for finite sources are presented, with a reasonable coverage of microlensing parameter space (i.e., surface mass density, external shear, mass spectrum of lensing objects). These probability distributions were obtained from smoothing two-dimensional magnification patterns with Gaussian source profiles. Different source sizes ranging from 10 exp 14 cm to 5 x 10 exp 16 cm were explored. The probability distributions show a large variety of shapes. Coefficients of fitted slopes for large magnifications are presented.

  14. Network based sky Brightness Monitor (United States)

    McKenna, Dan; Pulvermacher, R.; Davis, D. R.


    We have developed and are currently testing an autonomous 2 channel photometer designed to measure the night sky brightness in the visual wavelengths over a multi-year campaign. The photometer uses a robust silicon sensor filtered with Hoya CM500 glass. The Sky brightness is measured every minute at two elevation angles typically zenith and 20 degrees to monitor brightness and transparency. The Sky Brightness monitor consists of two units, the remote photometer and a network interface. Currently these devices use 2.4 Ghz transceivers with a free space range of 100 meters. The remote unit is battery powered with day time recharging using a solar panel. Data received by the network interface transmits data via standard POP Email protocol. A second version is under development for radio sensitive areas using an optical fiber for data transmission. We will present the current comparison with the National Park Service sky monitoring camera. We will also discuss the calibration methods used for standardization and temperature compensation. This system is expected to be deployed in the next year and be operated by the International Dark Sky Association SKYMONITOR project.

  15. The near-to-mid infrared spectrum of quasars (United States)

    Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena; Mateos, Silvia


    We analyse a sample of 85 luminous (log (νLν(3 μm)/erg s-1) > 45.5) quasars with rest frame ˜2-11 μm spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disc and two blackbodies for the dust emission successfully reproduces the 0.1-10 μm spectral energy distributions (SEDs). Excess emission at 1-2 μm over the best-fitting model suggests that hotter dust is necessary in addition to the ˜1200 K blackbody and the disc to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disc and in the relative strength of the disc and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disc luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the rest-frame range 0.1-11 μm, and separate templates for the disc and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2-4 μm range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 μm bump.

  16. Camera for QUasars in EArly uNiverse (CQUEAN)


    Park, Won-Kee; Pak, Soojong; Im, Myungshin; Choi, Changsu; Jeon, Yiseul; Chang, Seunghyuk; Jeong, Hyeonju; Lim, Juhee; Kim, Eunbin


    We describe the overall characteristics and the performance of an optical CCD camera system, Camera for QUasars in EArly uNiverse (CQUEAN), which is being used at the 2.1 m Otto Struve Telescope of the McDonald Observatory since 2010 August. CQUEAN was developed for follow-up imaging observations of red sources such as high redshift quasar candidates (z >= 5), Gamma Ray Bursts, brown dwarfs, and young stellar objects. For efficient observations of the red objects, CQUEAN has a science camera ...

  17. Measuring Quasar Spin via X-ray Continuum Fitting (United States)

    Jenkins, Matthew; Pooley, David; Rappaport, Saul; Steiner, Jack


    We have identified several quasars whose X-ray spectra appear very soft. When fit with power-law models, the best-fit indices are greater than 3. This is very suggestive of thermal disk emission, indicating that the X-ray spectrum is dominated by the disk component. Galactic black hole binaries in such states have been successfully fit with disk-blackbody models to constrain the inner radius, which also constrains the spin of the black hole. We have fit those models to XMM-Newton spectra of several of our identified soft X-ray quasars to place constraints on the spins of the supermassive black holes.

  18. Clues to Quasar Broad Line Region Geometry and Kinematics

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Wilkes, B. J.; Barthel, P. D.


    We present evidence that the high-velocity CIV lambda 1549 emission line gas of radio-loud quasars may originate in a disk-like configuration, in close proximity to the accretion disk often assumed to emit the low-ionization lines. For a sample of 36 radio-loud z~2 quasars we find the 20--30% peak...... width to show significant inverse correlations with the fractional radio core-flux density, R, the radio axis inclination indicator. Highly inclined systems have broader line wings, consistent with a high-velocity field perpendicular to the radio axis. By contrast, the narrow line-core shows...

  19. Quasar Formation and Energy Emission in Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Zhang T. X.


    Full Text Available Formation and energy emission of quasars are investigated in accord with the black hole universe, a new cosmological model recently developed by Zhang. According to this new cosmological model, the universe originated from a star-like black hole and grew through a supermassive black hole to the present universe by accreting ambient matter and merging with other black holes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe have been fully ex- plained in Paper I and II. This study as Paper III explains how a quasar forms, ignites and releases energy as an amount of that emitted by dozens of galaxies. A main sequence star, after its fuel supply runs out, will, in terms of its mass, form a dwarf, a neutron star, or a black hole. A normal galaxy, after its most stars have run out of their fuels and formed dwarfs, neutron stars, and black holes, will eventually shrink its size and collapse towards the center by gravity to form a supermassive black hole with billions of solar masses. This collapse leads to that extremely hot stellar black holes merge each other and further into the massive black hole at the center and meantime release a huge amount of radiation energy that can be as great as that of a quasar. Therefore, when the stellar black holes of a galaxy collapse and merge into a supermassive black hole, the galaxy is activated and a quasar is born. In the black hole universe, the observed dis- tant quasars powered by supermassive black holes can be understood as donuts from the mother universe. They were actually formed in the mother universe and then swallowed into our universe. The nearby galaxies are still very young and thus quiet at the present time. They will be activated and further evolve into quasars after billions of years. At that time, they will enter the universe formed by the currently observed distant quasars as similar to the distant quasars entered our universe

  20. NuSTAR and XMM-Newton Observations of Luminous, Heavily Obscured, WISE-Selected Quasars at z ~ 2

    DEFF Research Database (Denmark)

    Stern, D.; Lansbury, G. B.; Assef, Roberto J.


    faintly detected by XMM-Newton. A third source was observed only with XMM-Newton, yielding a faint detection. The X-ray data require gas column densities N(H)>1e24 /cm2, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population......We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected AGN at z~2 in a broad X-ray band (0.1 - 79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4um (W1) and 4.6um (W2) bands but bright at 12um...... L(sun). The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10)~4e45 erg/s for typical quasar templates. These are amongst the most luminous AGN known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even...

  1. Discovery of 16 New z  ∼ 5.5 Quasars: Filling in the Redshift Gap of Quasar Color Selection

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jinyi; Wu, Xue-Bing; Wang, Feige; Yang, Qian; Yue, Minghao; Wang, Shu; Li, Zefeng [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui; Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); McGreer, Ian D.; Green, Richard; Ding, Jiani [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Yi, Weimin [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Dye, Simon [School of Physics and Astronomy, Nottingham University, University Park, Nottingham, NG7 2RD (United Kingdom); Lawrence, Andy [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom)


    We present initial results from the first systematic survey of luminous z  ∼ 5.5 quasars. Quasars at z ∼ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution, and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 ≤ z ≤ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ∼ 5.5 quasars based on optical, near-IR, and mid-IR photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys—Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS), and Wide Field Infrared Survey Explorer . From our pilot observations in the SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 ≤ z ≤ 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ∼ 5.5 quasars already published in our previous work, we now construct a uniform quasar sample at 5.3 ≤ z ≤ 5.7, with 17 quasars in a ∼4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J-band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ∼ 5.5 quasar.

  2. Helmholtz bright and boundary solitons

    Energy Technology Data Exchange (ETDEWEB)

    Christian, J M [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); McDonald, G S [Joule Physics Laboratory, School of Computing, Science and Engineering, Institute for Materials Research, University of Salford, Salford M5 4WT (United Kingdom); Chamorro-Posada, P [Departmento de TeorIa de la Senal y Comunicaciones e IngenierIa Telematica, Universidad de Valladolid, ETSI Telecomunicacion, Campus Miguel Delibes s/n, 47011 Valladolid (Spain)


    We report, for the first time, exact analytical boundary solitons of a generalized cubic-quintic nonlinear Helmholtz (NLH) equation. These solutions have a linked-plateau topology that is distinct from conventional dark soliton solutions; their amplitude and intensity distributions are spatially delocalized and connect regions of finite and zero wave-field disturbances (suggesting also the classification as 'edge solitons'). Extensive numerical simulations compare the stability properties of recently derived Helmholtz bright solitons, for this type of polynomial nonlinearity, to those of the new boundary solitons. The latter are found to possess a remarkable stability characteristic, exhibiting robustness against perturbations that would otherwise lead to the destabilizing of their bright-soliton counterparts.

  3. Iapetus Bright and Dark Terrains (United States)


    Saturn's outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this Voyager 2 image taken on August 22, 1981. Amazingly, the dark material covers precisely the side of Iapetus that leads in the direction of orbital motion around Saturn (except for the poles), whereas the bright material occurs on the trailing hemisphere and at the poles. The bright terrain is made of dirty ice, and the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes. Iapetus' dark hemisphere has been likened to tar or asphalt and is so dark that no details within this terrain were visible to Voyager 2. The bright icy hemisphere, likened to dirty snow, shows many large impact craters. The closest approach by Voyager 2 to Iapetus was a relatively distant 600,000 miles, so that our best images, such as this, have a resolution of about 12 miles. The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin. Two theories have been developed, but neither is fully satisfactory--(1) the dark material may be organic dust knocked off the small neighboring satellite Phoebe and 'painted' onto the leading side of Iapetus as the dust spirals toward Saturn and Iapetus hurtles through the tenuous dust cloud, or (2) the dark material may be made of icy-cold carbonaceous 'cryovolcanic' lavas that were erupted from Iapetus' interior and then blackened by solar radiation, charged particles, and cosmic rays. A determination of the actual cause, as well as discovery of any other geologic features smaller than 12 miles across, awaits the Cassini Saturn orbiter to arrive in 2004.

  4. LSST Site: Sky Brightness Data (United States)

    Burke, Jamison; Claver, Charles


    The Large Synoptic Survey Telescope (LSST) is an upcoming robotic survey telescope. At the telescope site on Cerro Pachon in Chile there are currently three photodiodes and a Canon camera with a fisheye lens, and both the photodiodes and Canon monitor the night sky continuously. The NIST-calibrated photodiodes directly measure the flux from the sky, and the sky brightness can also be obtained from the Canon images via digital aperture photometry. Organizing and combining the two data sets gives nightly information of the development of sky brightness across a swath of the electromagnetic spectrum, from blue to near infrared light, and this is useful for accurately predicting the performance of the LSST. It also provides data for models of moonlight and twilight sky brightness. Code to accomplish this organization and combination was successfully written in Python, but due to the backlog of data not all of the nights were processed by the end of the summer.Burke was supported by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  5. The Scale Invariant Synchrotron Jet of Flat Spectrum Radio Quasars

    Indian Academy of Sciences (India)


    Jan 27, 2016 ... In this paper, the scale invariance of the synchrotron jet of Flat Spectrum Radio Quasars has been studied using a sample of combined sources from FKM04 and from SDSS DR3 catalogue. Since the research of scale invariance has been focused on sub-Eddington cases that can be fitted onto the ...

  6. The Scale Invariant Synchrotron Jet of Flat Spectrum Radio Quasars ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, the scale invariance of the synchrotron jet of Flat. Spectrum Radio Quasars has been studied using a sample of combined sources from FKM04 and from SDSS DR3 catalogue. Since the research of scale invariance has been focused on sub-Eddington cases that can be fitted onto the fundamental ...


    NARCIS (Netherlands)


    10.7 GHz VLBI observations of the giant double-lobed quasar 4C 34.47 (1721 + 343) are presented. Previous VLBI monitoring at 5 GHz indicated the presence of superluminal motion in the core of this large radio source, at velocities of approximately 2.5h-1 c (Barthel et al. 1989). In the present

  8. Measurement of Black Hole Mass Radio-Loud Quasars

    Indian Academy of Sciences (India)


    Jan 27, 2016 ... In this work, we construct a sample of 1585 radio-loud quasars to measure their black hole masses using broad emission lines. We compare our black hole masses with the virial black hole masses measured by Shen et al. (2010).We find that there is a large deviation between them if our black hole mass is ...

  9. Rapid interstellar scintillation of quasar PKS 1257-326

    NARCIS (Netherlands)

    Bignall, Hayley E.; Jauncey, David L.; Lovell, James E. J.; Tzioumis, Anastasios K.; Macquart, Jean-Pierre; Kedziora-Chudczer, Lucyna; Engvold, O


    PKS 1257-326 is one of three quasars known to show unusually large and rapid, intra-hour intensity variations, as a result of scintillation in the turbulent Galactic interstellar medium. We have measured time delays in the variability pattern arrival times at the VLA and the ATCA, as well as an

  10. Microlensing makes lensed quasar time delays significantly time variable (United States)

    Tie, S. S.; Kochanek, C. S.


    The time delays of gravitationally lensed quasars are generally believed to be unique numbers whose measurement is limited only by the quality of the light curves and the models for the contaminating contribution of gravitational microlensing to the light curves. This belief is incorrect - gravitational microlensing also produces changes in the actual time delays on the ∼day(s) light-crossing time-scale of the emission region. This is due to a combination of the inclination of the disc relative to the line of sight and the differential magnification of the temperature fluctuations producing the variability. We demonstrate this both mathematically and with direct calculations using microlensing magnification patterns. Measuring these delay fluctuations can provide a physical scale for microlensing observations, removing the need for priors on either the microlens masses or the component velocities. That time delays in lensed quasars are themselves time variable likely explains why repeated delay measurements of individual lensed quasars appear to vary by more than their estimated uncertainties. This effect is also a new important systematic problem for attempts to use time delays in lensed quasars for cosmology or to detect substructures (satellites) in lens galaxies.

  11. Radio imaging of core-dominated high redshift quasars

    NARCIS (Netherlands)

    Barthel, PD; Vestergaard, M; Lonsdale, CJ

    VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many;objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum quasars, consistent with these objects being observed at sight

  12. Determination of astrophysical parameters of quasars within the Gaia mission (United States)

    Delchambre, L.


    We describe methods designed to determine the astrophysical parameters of quasars based on spectra coming from the red and blue spectrophotometers of the Gaia satellite. These methods principally rely on two already published algorithms that are the weighted principal component analysis and the weighted phase correlation. The presented approach benefits from a fast implementation, an intuitive interpretation as well as strong diagnostic tools on the potential errors that may arise during predictions. The production of a semi-empirical library of spectra as they will be observed by Gaia is also covered and subsequently used for validation purpose. We detail the pre-processing that is necessary in order for these spectra to be fully exploitable by our algorithms along with the procedures that are used to predict the redshifts of the quasars, their continuum slopes, the total equivalent width of their emission lines and whether these are broad absorption line (BAL) quasars or not. Performances of these procedures were assessed in comparison with the extremely randomized trees learning method and were proven to provide better results on the redshift predictions and on the ratio of correctly classified observations though the probability of detection of BAL quasars remains restricted by the low resolution of these spectra as well as by their limited signal-to-noise ratio. Finally, the triggering of some warning flags allows us to obtain an extremely pure subset of redshift predictions where approximately 99 per cent of the observations come along with absolute errors that are below 0.1.

  13. Gemini Near-infrared Spectroscopy of Luminous z~6 Quasars

    DEFF Research Database (Denmark)

    Jiang, Linhua; Fan, Xiaohui; Vestergaard, Marianne


    We present Gemini near-infrared spectroscopic observations of six luminous quasars at z=5.8$\\sim$6.3. Five of them were observed using Gemini-South/GNIRS, which provides a simultaneous wavelength coverage of 0.9--2.5 $\\mu$m in cross dispersion mode. The other source was observed in K band with Ge...

  14. Report on the Dynamical Evolution of an Axially Symmetric Quasar ...

    Indian Academy of Sciences (India)

    The role of the angular momentum in the regular or chaotic character of motion in an axially symmetric quasar model is examined. It is found that, for a given value of the critical angular momentum , there are two values of the mass of the nucleus for which transition from regular to chaotic motion occurs.

  15. Using Quasars as Standard Candles for Studying Dark Energy

    DEFF Research Database (Denmark)

    Denney, Kelly D.; Vestergaard, Marianne; Watson, D.


    We have recently demonstrated (Watson et al. 2011, ApJ, 740, L49) that quasars, or more generally active galactic nuclei (AGNs), can be used as standard candles for measuring distances in the universe, similar to Type Ia supernovae (SNe). Here, we present the initial findings of this new method...

  16. A multi-wavelength perspective on quasar fundamental properties (United States)

    Runnoe, Jessie C.

    The goal of this thesis is to use a multi-wavelength perspective to advance the methods used to estimate fundamental properties of quasars. Based on a sample of the 85 most detailed quasar spectral energy distributions (SEDs) observed to date, this work focuses on calculating bolometric luminosity and black hole mass and understanding the role of orientation in determining these properties. Because quasars emit over a broad range of wavelengths, it can be challenging to determine bolometric luminosity and accretion rate (expressed as the Eddington ratio). I determine new bolometric corrections, taking particular care to address the difficulties that arise during the derivation process. Of the bolometric corrections in the infrared, optical, ultraviolet, and X-ray, those in the ultraviolet have the least dispersion and are preferred. X-ray bolometric corrections have very large dispersion and should be avoided. Black hole masses can be estimated for any quasar with a single-epoch spectrum using the single-epoch mass scaling relationships that are calibrated for a variety of emission lines, including Hbeta, Mg II lambda2798, and C IV lambda1549. I identify two sources of scatter, orientation and contamination from emission of non-virialized gas in the C IV line, between masses estimated from different emission lines and determine corrections for these effects. The application of both of these corrections reduces scatter between black hole masses estimated from different emission lines. Orientation plays an important role in determining the observed SEDs of quasars. In order to quantify this effect, I investigate quasar SEDs and their properties as a function of orientation. I find that infrared through X-ray monochromatic luminosities are orientation dependent, although the shape of the SED and estimates of the covering fraction of the circumnuclear dust are not. The sum of these investigations is to motivate the field to use a multi-wavelength approach and multi

  17. Chemical enrichment and accretion of nitrogen-loud quasars (United States)

    Matsuoka, K.; Nagao, T.; Maiolino, R.; Marconi, A.; Park, D.; Taniguchi, Y.


    We present rest-frame optical spectra of 12 "nitrogen-loud" quasars at z 2.2, whose rest-frame ultraviolet (UV) spectra show strong nitrogen broad emission lines. To investigate their narrow-line region (NLR) metallicities, we measure the equivalent width (EW) of the [O III]λ5007 emission line: if the NLR metallicity is remarkably high, as suggested by the strong UV nitrogen lines, the [O III]λ5007 line flux should be very weak due to the low equilibrium temperature of the ionized gas owing to significant metal cooling. In the result we found that our spectra show moderate EW of the [O III]λ5007 line similar to general quasars. This indicates that nitrogen-loud quasars do not have extremely metal-rich gas clouds in NLRs. This suggests that strong nitrogen lines from broad-line regions (BLRs) originate from exceptionally high abundances of nitrogen relative to oxygen without very high BLR metallicities. This result indicates that broad emission lines of nitrogen are not good indicators of the BLR metallicity in some cases. On the other hand, we also investigate virial black hole masses and Eddington ratios by using the Hβ and C IVλ1549 lines for our sample. As a result, we found that black hole masses and Eddington ratios of nitrogen-loud quasars tend to be low and high relative to normal quasars, suggesting that nitrogen-loud quasars seem to be in a rapidly accreting phase. This can be explained in terms of a positive correlation between Eddington ratios and nitrogen abundances of quasars, which is probably caused by the connection between the mass accretion onto black holes and nuclear star formation. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 088.B-0191(A), and at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.Reduced spectra (FITS files) are available at the CDS via anonymous ftp to (http://130

  18. Chandra Observes Cosmic Traffic Pile-Up In Energetic Quasar Jet (United States)


    produced in gamma rays, a question that researchers are unable to resolve with current telescopes. The energy emitted from the jet in 3C273 probably comes from gas that falls toward a supermassive black hole at the center of the quasar, but is redirected by strong electromagnetic fields into a collimated jet. While the black hole itself is not observed directly, scientists can discern properties of the black hole by studying the jet. The formation of the jet from the matter that falls into the black hole is a process that remains poorly understood. The quasar 3C273 is no stranger to making astronomical news. Discovered in the 1960s, 3C273 was one of the first objects to be recognized a "quasi-stellar" object, due to its incredible optical and radio brightness, but perplexing properties. Only after careful consideration did astronomers determine that 3C273 and others of its ilk were not nearby stars, but instead incredibly powerful objects billions of light years away. The Chandra observation of 3C273 was made with both the Low Energy Transmission Grating (LETG) and the High Energy Transmission Grating (HETG), in conjunction with the High Resolution Camera (HRC) and the Advanced CCD Imaging Spectrometer (ACIS). In addition to Dr. Marshall, the team of researchers includes J.J. Drake, A. Fruscione, J. Grimes, D. Harris, M. Juda, R. Kraft, S.S. Murray, D. Pease, A. Siemiginowska, S. Vrtilek, and B.J. Wargelin (Harvard-Smithsonian Center for Astrophysics), P.M. Ogle (MIT), and S. Mathur (Ohio State University.) The HRC was built for NASA by the Smithsonian Astrophysical Observatory. The HETG and ACIS instruments were built for NASA by the Massachusetts Institute of Technology, Cambridge, MA, and Pennsylvania State University, University Park. The LETG was built by the Space Research Organization of the Netherlands and the Max Plank Institute. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW, Inc., Redondo Beach, Calif., is the prime

  19. Measuring the Outflow Properties of FeLoBAL Quasars (United States)

    Dabbieri, Collin; Choi, Hyunseop; MacInnis, Francis; Leighly, Karen; Terndrup, Donald


    Roughly 20 percent of the quasar population shows broad absorption lines, which are indicators of an energetic wind. Within the broad absorption line class of quasars exist FeLoBAL quasars, which show strong absorption lines from the Fe II and Fe III transitions as well as other low-ionization lines. FeLoBALs are of particular interest because they are thought to possibly be a short-lived stage in a quasar's life where it expels its shroud of gas and dust. This means the winds we see from FeLoBALs are one manifestation of galactic feedback. This idea is supported by Farrah et al. (2012) who found an anti correlation between outflow strength and contribution from star formation to the total IR luminosity of the host galaxy when examining a sample of FeLoBAL quasars. We analyze the sample of 26 FeLoBALs from Farrah et al. (2012) in order to measure the properties of their outflows, including ionization, density, column density and covering fraction. The absorption and continuum profiles of these objects are modeled using SimBAL, a program which creates synthetic spectra using a grid of Cloudy models. A Monte-Carlo method is employed to determine posterior probabilities for the physical parameters of the outflow. From these probabilities we extract the distance of the outflow, the mass outflow rate and the kinetic luminosity. We demonstrate SimBAL is capable of modeling a wide range of spectral morphologies. From the 26 objects studied we observe interesting correlations between ionization parameter, distance and density. Analysis of our sample also suggests a dearth of objects with velocity widths greater than or equal to 300 km/s at distances greater than or equal to 100 parsecs.

  20. Flamingos 2 Spectroscopy of Obscured and Unobscured Quasars (United States)

    Ridgway, Susan; Lacy, Mark; Urrutia, Tanya; Petric, Andreea


    We will use Flamingos-2 to obtain spectra of luminous AGN and quasars selected in the mid-infrared. Mid-infrared selection is much less biased with respect to obscuration than optical and X-ray techniques, and hence allows for finding obscured (Type-2) quasars as well as Type-1 quasars. Our survey so far has been very successful and has provided an unique opportunity to construct luminosity functions for both Type-1 and Type-2 quasars selected in the same way and covering similar redshifts and luminosities. We have quantifed the change in the obscured fraction with luminosity and redshift for the first time, and find interesting indications that at high redshift the obscured fraction rises, consistent with models for the joint formation of the galaxy and black hole populations. Our samples are, however, still quite incomplete at low fluxes (and therefore lower luminosities at a given redshift), particularly in the southern hemisphere. Near-infrared spectroscopy, such as that we have previously obtained with NIRI at Gemini N, offers us the best possibility of bringing these southern samples to a reasonable completeness level, and will greatly increase the number of high z quasars in our sample. This will allow us to better judge our tantalizing initial results on the redshift evolution of the obscured fraction. In addition, these southern targets can be followed up with ALMA and GEMS/GSAOI to study the morphologies and star-formation properties of the hosts, allowing further exploration of the relationship between the formation of massive bulges and supermassive blackholes in the early universe.


    Energy Technology Data Exchange (ETDEWEB)

    Mechtley, M.; Windhorst, R. A.; Cohen, S. H.; Jansen, R. A.; Scannapieco, E. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States); Ryan, R. E.; Koekemoer, A. M. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Schneider, G.; Fan, X. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Hathi, N. P. [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Keel, W. C. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Roettgering, H. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden (Netherlands); Schneider, D. P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Strauss, M. A. [Princeton University Observatory, Princeton, NJ 08544 (United States); Yan, H. J. [Department of Physics and Astronomy, The University of Missouri, 701 South College Ave, Columbia, MO 65211 (United States)


    We report on deep near-infrared F125W (J) and F160W (H) Hubble Space Telescope Wide Field Camera 3 images of the z = 6.42 quasar J1148+5251 to attempt to detect rest-frame near-ultraviolet emission from the host galaxy. These observations included contemporaneous observations of a nearby star of similar near-infrared colors to measure temporal variations in the telescope and instrument point-spread function (PSF). We subtract the quasar point source using both this direct PSF and a model PSF. Using direct subtraction, we measure an upper limit for the quasar host galaxy of m{sub J} > 22.8 and m{sub H} > 23.0 AB mag (2 {sigma}). After subtracting our best model PSF, we measure a limiting surface brightness from 0.''3 to 0.''5 radius of {mu}{sub J} > 23.5 and {mu}{sub H} > 23.7 AB mag arcsec{sup -2} (2 {sigma}). We test the ability of the model subtraction method to recover the host galaxy flux by simulating host galaxies with varying integrated magnitude, effective radius, and Sersic index, and conducting the same analysis. These models indicate that the surface brightness limit ({mu}{sub J} > 23.5 AB mag arcsec{sup -2}) corresponds to an integrated upper limit of m{sub J} > 22-23 AB mag, consistent with the direct subtraction method. Combined with existing far-infrared observations, this gives an infrared excess log (IRX) > 1.0 and corresponding ultraviolet spectral slope {beta} > -1.2 {+-} 0.2. These values match those of most local luminous infrared galaxies, but are redder than those of almost all local star-forming galaxies and z {approx_equal} 6 Lyman break galaxies.

  2. The Curious Molecular Gas Conditions in a z=2.6 Radio-loud Quasar (United States)

    Sharon, Chelsea; Riechers, Dominik A.; Kuk Leung, Tsz; Weiss, Axel; Walter, Fabian; Carilli, Chris; Kraiburg Knudsen, Kirsten; Hodge, Jacqueline


    Theoretical work suggests that AGN play an important role in quenching star formation in massive galaxies. In addition to molecular outflows observed in the local universe, emission from very high-J CO rotational transitions has been one of the key pieces of evidence for AGN directly affecting the molecular gas reservoirs that fuel star formation. However, very few observations of Jupper>9 transitions exist for galaxies in the early universe. Here we will present the peculiar molecular gas conditions in MG 0414+0534 (MG 0414 hereafter), one of the few high-z galaxies with very high-J CO detections. MG 0414 is a strongly lensed IR-bright radio-loud quasar with broad Hα emission at z=2.6390. We recently confirmed the CO(3–2) detection from Barvainis et al. (1998), but were unable to detect the CO(1–0) line. The 3σ lower limit on the 3–2/1–0 line ratio (in units of brightness temperature) is r3,1>5.72, which is significantly higher than the r3,1≤1 typical for thermalized optically thick emission in other z˜2–3 AGN host galaxies. In addition, the CO(11–10) line was detected to high significance using the Atacama Large Millimeter/submillimeter Array, and the CO(11–10) line FWHM is nearly double that of the CO(3–2) line. We will discuss possible explanations for the peculiar line ratios in MG 0414 (such as optically thin emission, molecular outflows, and differential lensing) and what the origin of these ratios imply for molecular gas observations of other high-z AGN host galaxies.

  3. Parsec-scale jet properties of the gamma-ray quasar 3C 286 (United States)

    An, T.; Lao, B.-Q.; Zhao, W.; Mohan, P.; Cheng, X.-P.; Cui, Y.-Z.; Zhang, Z.-L.


    The quasar 3C 286 is one of two compact steep-spectrum sources detected by the Fermi/Large Area Telescope. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the gamma-ray emission in 3C 286. The Very Long Baseline Interferometry (VLBI) images at various frequencies reveal a one-sided core-jet structure extending to the south-west at a projected distance of ˜1 kpc. The component at the jet base showing an inverted spectrum is identified as the core, with a mean brightness temperature of 2.8 × 109 K. The jet bends at about 600 pc (in projection) away from the core, from a position angle of -135° to -115°. Based on the available VLBI data, we inferred the proper-motion speed of the inner jet as 0.013 ± 0.011 mas yr-1 (βapp = 0.6 ± 0.5), corresponding to a jet speed of about 0.5 c at an inclination angle of 48° between the jet and the line of sight of the observer. The brightness temperature, jet speed and Lorentz factor are much lower than those of gamma-ray-emitting blazars, implying that the pc-scale jet in 3C 286 is mildly relativistic. Unlike blazars in which gamma-ray emission is in general thought to originate from the beamed innermost jet, the location and mechanism of gamma-ray emission in 3C 286 may be different as indicated by the current radio data. Multiband spectrum fitting may offer a complementary diagnostic clue of the gamma-ray production mechanism in this source.

  4. Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission (United States)

    Lyu, Jianwei; Rieke, G. H.; Shi, Yong


    To elucidate the intrinsic broadband infrared (IR) emission properties of active galactic nuclei (AGNs), we analyze the spectral energy distributions (SEDs) of 87 z ≲ 0.5 Palomar-Green (PG) quasars. While the Elvis AGN template with a moderate far-IR correction can reasonably match the SEDs of the AGN components in ˜60% of the sample (and is superior to alternatives such as that by Assef), it fails on two quasar populations: (1) hot-dust-deficient (HDD) quasars that show very weak emission thoroughly from the near-IR to the far-IR, and (2) warm-dust-deficient (WDD) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-IR. After building composite AGN templates for these dust-deficient quasars, we successfully fit the 0.3-500 μm SEDs of the PG sample with the appropriate AGN template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 HDD and 12 WDD quasars are identified from the SED decomposition, including seven ambiguous cases. Compared with normal quasars, the HDD quasars have AGNs with relatively low Eddington ratios and the fraction of WDD quasars increases with AGN luminosity. Moreover, both the HDD and WDD quasar populations show relatively stronger mid-IR silicate emission. Virtually identical SED properties are also found in some quasars from z = 0.5 to 6. We propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch.

  5. Chandra Finds Well-Established Black Holes In Distant Quasars (United States)


    Pushing further back toward the first generation of objects to form in the universe, NASA's Chandra X-ray Observatory has observed the three most distant known quasars and found them to be prodigious producers of X-rays. This indicates that the supermassive black holes powering them were already in place when the Universe was only about one billion years old. "Chandra's superb sensitivity has allowed the detection of X-rays from the dawn of the modern universe, when the first massive black holes and galaxies were forming," said Niel Brandt of Penn State University, leader of one the teams involved. "These results indicate that future X-ray surveys should be able to detect the first black holes to form in the Universe." The three quasars were recently discovered at optical wavelengths by the Sloan Digital Sky Survey and are 13 billion light years from Earth, making them the most distant known quasars. The X-rays Chandra detected were emitted when the universe was only a billion years old, about 7 percent of the present age of the Universe. Since X-rays reveal conditions in the immediate vicinity of supermassive black holes, Brandt proposed that Chandra look at these objects in three snapshots of about two hours each to see if they were different from their older counterparts. The observations on January 29, 2002 were made public immediately and the four different teams quickly went to work on them. Brandt's team concluded that the quasars looked similar to ones that were at least twice as old, so the conditions around the central black hole had not changed much in that time, contrary to some theoretical expectations. A team led by Smita Mathur of Ohio State University reached a similar conclusion. "These young quasars do not appear to be any different from their older cousins, based upon our current understanding and assumptions," said Mathur. "Perhaps the most remarkable thing about them may be that they are so absolutely unremarkable." Jill Bechtold of the

  6. Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8 (United States)

    Matsuoka, Yoshiki; Onoue, Masafusa; Kashikawa, Nobunari; Iwasawa, Kazushi; Strauss, Michael A.; Nagao, Tohru; Imanishi, Masatoshi; Lee, Chien-Hsiu; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Foucaud, Sébastien; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E.; Harikane, Yuichi; Ikeda, Hiroyuki; Izumi, Takuma; Kawaguchi, Toshihiro; Kikuta, Satoshi; Kohno, Kotaro; Komiyama, Yutaka; Lupton, Robert H.; Minezaki, Takeo; Miyazaki, Satoshi; Morokuma, Tomoki; Murayama, Hitoshi; Niida, Mana; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Ouchi, Masami; Price, Paul A.; Sameshima, Hiroaki; Schulze, Andreas; Shirakata, Hikari; Silverman, John D.; Sugiyama, Naoshi; Tait, Philip J.; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Tang, Ji-Jia; Toba, Yoshiki; Utsumi, Yousuke; Wang, Shiang-Yu


    We present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 galaxies, two [O III] emitters at z ˜ 0.8, and 15 Galactic brown dwarfs. The new quasars have considerably lower luminosity (M1450 ˜ -25 to -22 mag) than most of the previously known high-z quasars. Several of these quasars have luminous (>1043 erg s-1) and narrow (galaxies have extremely high luminosities (M1450 ˜ -24 to -22 mag) compared to other galaxies found at similar redshifts. With the discovery of these new classes of objects, we are opening up new parameter spaces in the high-z Universe. Further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ˜ 6, are ongoing.

  7. Mining the Infrared Sky for High-Redshift Quasars (United States)

    Richards, Gordon

    The Spitzer and WISE satellites have opened up new avenues for the study of active galactic nuclei (AGN) by peering through the dust shrouding half (or more) of AGNs. However, despite being more sensitive to shrouded AGNs, current selection methods being used in the mid-IR are still largely blind to the highest redshift quasars-both those that are shrouded and those that are not (and should therefore be easy to find). We describe projects to identify both unobscured (at z>3) and obscured quasars (at z>2) that have heretofore been missed in significant numbers. Finding the high-z obscured quasars in large numbers is crucial for fulfilling the legacy of NASA missions in the IR and X-ray. With these quasars we will be able to perform clustering analyses that break the degeneracy of models describing how black holes can ``feed back" energy to the large-scale host galaxy, significantly influencing its evolution. We will further trace the luminosity function of galaxies undergoing active accretion from low-luminosity AGNs to luminous quasars—probing the growth of the supermassive black holes that we see today in the local universe. Our new insights come about from leveraging new Spitzer data, primarily from the PI's SpitzerIRAC Equatorial Survey (SpIES). The Spitzer data are 2.5 magnitudes deeper than the "AllWISE" survey in a 125 square degree, multiwavelength-rich, equatorial region known as SDSS "Stripe 82". These data are crucial for extending mid-IR investigations to higher redshifts, both for unobscured and obscured sources. The PI's team are among the world's experts in using the proposed machine learning techniques to find both unobscured (type-1) and obscured (type- 2) quasars and in using quasar clustering and luminosity functions to do cutting-edge science. The luminosity function and clustering algorithms are already in place, allowing for timely completion of this project once the multi-wavelength NASA data have been incorporated. This project is directly

  8. The X-ray variability properties of radio-quiet AGN (United States)

    Papadakis, Iosif

    The X-ray variability properties of AGN have been extensively studied during the past twenty years. I will present a summary of the significant progress has been achieved in the estimation of their X-ray power spectral density functions, which (among other things) can be helpful in the search for characteristic time scales in these objects. This progress has been made possible with the combined use of monitoring RXTE light curves (which are up to 5-10 years long in many cases) and shorter (1 to a few days long), high signal-to-noise, XMM-Newton and Chandra light curves. The results have shown that the PSD has a -2 power law shape at high frequencies and then, below a characteristic "break -frequency", it flattens to a slope of -1. I will review the evidence which suggests that the corresponding "break time scale" increases with increasing black hole (BH) mass, and for a given mass, it decreases with increasing accretion rate (in units of the Eddington limit). This relation can explain the recent results which show that the X-ray variability amplitude in AGN decreases with increasing BH mass. It seems "natural" to associate this PSD "break time scale" with one of the characteristic time scales in the innermost region of the accretion disc, even if the disc itself is too cold to emit X-rays (at least in AGN), and I will discuss possible consequences that result from such an association. Finally, I will also discuss briefly the relation between the "optical variability amplitude and BH mass" in AGN, and its comparison with the same relation in the X-ray domain.

  9. Sources of the Radio Background Considered

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; /KIPAC, Menlo Park /Stanford U.; Stawarz, L.; /KIPAC, Menlo Park /Stanford U. /Jagiellonian U., Astron. Observ.; Lawrence, A.; /Edinburgh U., Inst. Astron. /KIPAC, Menlo Park /Stanford U.; Petrosian, V.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.


    We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio background is produced by radio point sources that dominate at sub {mu}Jy fluxes. We show that a truly diffuse background produced by elections far from galaxies is ruled out because such energetic electrons would overproduce the observed X-ray/{gamma}-ray background through inverse Compton scattering of the other photon fields. Unrecognized flux from low surface brightness regions of extended radio sources, or moderate flux sources missed entirely by radio source count surveys, cannot explain the bulk of the observed background, but may contribute as much as 10%. We consider both radio supernovae and radio quiet quasars as candidate sources for the background, and show that both fail to produce it at the observed level because of insufficient number of objects and total flux, although radio quiet quasars contribute at the level of at least a few percent. We conclude that the most important population for production of the background is likely ordinary starforming galaxies above redshift 1 characterized by an evolving radio far-infrared correlation, which increases toward the radio loud with redshift.

  10. Microlensing Constraints on Quasar Spins and X-ray Reflection Regions (United States)

    Dai, Xinyu


    Gravitational microlensing provides a unique probe of the innermost parts of quasar accretion disks, close to the event horizon of supermassive black holes. Using Chandra monitoring data of six lenses from two Large Programs in Cycles 11 and 14/15, we identified two microlensing effects that can be used to constrain black hole spins and X-ray reflection regions for high redshift quasars. The first effect is the excess iron line equivalent widths of lensed quasars compared to normal AGN, and the second is the distribution of iron line peak energies of lensed quasars. A microlensing analysis of the iron line equivalent widths prefers high spin values and very steep iron line emissivity profiles for quasars at z~2. We will also discuss the prospect of measuring quasar spins with microlensing using the next generation of X-ray telescopes.

  11. A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey IV

    DEFF Research Database (Denmark)

    Fan, Xiaohui; Strauss, Michael A.; Richards, Gordon T.


    be a gravitational lensed galaxy, a BL Lac object or a new type of quasar. Two new z>6 quasars, SDSS 1250+3130 (z=6.13) and SDSS J1137+3549 (z=6.01), show deep Gunn-Peterson absorption gaps in Ly alpha. These gaps are narrower the complete Gunn-Peterson absorption troughs observed among quasars at z>6.2 and do...

  12. The Distance of Quasar outflows: VLT/X-SHOOTER Survey (United States)

    Xu, Xinfeng; Arav, Nahum; Reid Miller, Timothy


    We observed 13 BAL and mini-BAL quasars using the VLT X-Shooter spectrograph. In 7 of these we find outflow troughs from S IV and S IV*. Using collisional excitation models of the measured S IV and S IV* column densities, we determine the electron number density (ne) of the outflow; and combining this value of ne with photoionization simulations, we derive the distance of each outflow from the central source. We find that 6 out of 8 outflows (one quasar shows two such outflows) are located at a distances of more than 100 pc from the central source. The spectral region covering the S IV and S IV* troughs was not observed in our targets prior to the VLT observations; and therefore this sample is unbiased towards a specific distance scale. Thus, these results are representitive (albeit in a small sample) for the general population of the high ionization BAL and mini-BAL outflows.

  13. An XMM-Newton Study of the Bright Ultrasoft Narrow-Line Quasar NAB 0205+024 (United States)

    Brandt, Niel


    The broad-band X-ray continuum of NAB 0205424 is well constrained due to the excellent photon statistics obtained (about 97,700 counts), and its impressive soft X-ray excess is clearly apparent. The hard X-ray power law has become notably steeper than when NAB 0205424 was observed with ASCA, attesting to the presence of significant X-ray spectral variability. A strong and broad emission feature is detected from about 5 to 6.4 keV, and we have modeled this as a relativistic line emitted close to the black hole from a narrow annulus of the accretion disk. Furthermore, a strong X-ray flare is detected with a hard X-ray spectrum; this flare may be responsible for illuminating the inner line-emitting part of the accretion disk. The combined observational results can be broadly interpreted in terms of the "thundercloud model proposed by Merloni & Fabian (2001).

  14. Black hole feedback in the luminous quasar PDS 456

    DEFF Research Database (Denmark)

    Nardini, E.; Reeves, J. N.; Gofford, J.


    The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different...... gas. The outflow’s kinetic power larger than 1046 ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution....

  15. Fundamental Plane of FSRQs from SDSS DR5 Quasar Catalogue

    Indian Academy of Sciences (India)

    In this work, we explore a sample of 362 flat-spectrum radio quasars (FSRQs) to investigate the jet formation. We find that the fundamental plane for our FSRQs can be expressed as 5\\;GHz ∝ bh − 0.19 2\\; keV 1.08 . We also find that the 5 GHz luminosities are tightly related to both black hole mass and Eddington ratio, ...

  16. Insights into quasar UV spectra using unsupervised clustering analysis (United States)

    Tammour, A.; Gallagher, S. C.; Daley, M.; Richards, G. T.


    Machine learning techniques can provide powerful tools to detect patterns in multidimensional parameter space. We use K-means - a simple yet powerful unsupervised clustering algorithm which picks out structure in unlabelled data - to study a sample of quasar UV spectra from the Quasar Catalog of the 10th Data Release of the Sloan Digital Sky Survey (SDSS-DR10) of Paris et al. Detecting patterns in large data sets helps us gain insights into the physical conditions and processes giving rise to the observed properties of quasars. We use K-means to find clusters in the parameter space of the equivalent width (EW), the blue- and red-half-width at half-maximum (HWHM) of the Mg II 2800 Å line, the C IV 1549 Å line, and the C III] 1908 Å blend in samples of broad absorption line (BAL) and non-BAL quasars at redshift 1.6-2.1. Using this method, we successfully recover correlations well-known in the UV regime such as the anti-correlation between the EW and blueshift of the C IV emission line and the shape of the ionizing spectra energy distribution (SED) probed by the strength of He II and the Si III]/C III] ratio. We find this to be particularly evident when the properties of C III] are used to find the clusters, while those of Mg II proved to be less strongly correlated with the properties of the other lines in the spectra such as the width of C IV or the Si III]/C III] ratio. We conclude that unsupervised clustering methods (such as K-means) are powerful methods for finding `natural' binning boundaries in multidimensional data sets and discuss caveats and future work.

  17. Quasars in the Central Region of the Virgo Cluster

    Indian Academy of Sciences (India)


    The answer from the binomial distribution function is 2 ×10-4. But, of course, this is an overestimate of the probability because one of the associations has a probability of much less than 2 × 10. -3. A more simple and straightforward calculation is that the chance of finding the closest quasar to one of the 11 Ε galaxies is 11× ...

  18. Observational Constraints on Quasar Black Hole Mass Distributions, Eddington Ratio Distributions, and Lifetimes

    DEFF Research Database (Denmark)

    Kelly, Brandon C.; Vestergaard, Marianne; Fan, X.


    I will present the black hole mass function (BHMF) of broad line quasars in the SDSS DR3. We employ a powerful Bayesian statistical technique that corrects for incompleteness and the statistical uncertainty in the mass estimates. We find evidence that the most massive black hole appeared as quasars...... earlier in the universe, and that most quasars are not radiating at or near the Eddington limit. I will also present constraints on the quasar lifetime and maximum black hole mass, derived from the mass functions....


    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yongjung; Im, Myungshin; Jeon, Yiseul; Choi, Changsu; Hong, Jueun; Hyun, Minhee; Jun, Hyunsung David; Kim, Dohyeong; Kim, Duho; Kim, Jae-Woo; Lee, Seong-Kook; Taak, Yoon Chan; Yoon, Yongmin [Center for the Exploration of the Origin of the Universe (CEOU), Building 45, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Minjin; Park, Won-Kee [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Karouzos, Marios [Astronomy Program, FPRD, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Ji Hoon [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720 (United States); Pak, Soojong, E-mail:, E-mail: [School of Space Research and Institute of Natural Sciences, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 446-701 (Korea, Republic of)


    Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to z = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.

  20. Two to Tango? Binary Quasars, their Environments, and the Merger Hypothesis (United States)

    Green, Paul


    Merger/feedback scenarios linking AGN and galaxy evolution to cosmological structure formation seem wildly successful. Close quasar pairs, which are rare but show a significant excess over the extrapolated large-scale quasar correlation function, are the strongest candidates for merger triggering we have. But a competing theory posits that their excess is only due to their inhabiting locally overdense environments. To address this controversy, we propose to observe 9 close quasar pairs. Their X-ray luminosity, spectra, and broadband SEDs will be compared to hundreds of isolated SDSS quasars already imaged and analyzed. Proposed NOAO 4-meter imaging provides complementary tests for environmental overdensities.

  1. Kinematics of the active region of the quasar 3C 345 (United States)

    Matveyenko, L. I.; Sivakon', S. S.


    The fine structure of the quasar 3C 345 in polarized emission at 7 mm and 2 cm has been investigated. The kinematics is shown to correspond to an anticentrifuge: the thermal plasma of the surrounding space accretes onto the disk, flows to the center, and is ejected in the form of a rotating bipolar outflow that carries away the excess angular momentum as it accumulates. The bipolar outflow consists of a high-velocity central jet surrounded by a low-velocity component. The low-velocity flows are the rotating hollow tubes ejected from the peripheral part of the disk with a diameter ˜Ø1 = 2.2 pc and from the region Ø2 = 1 pc. The high-velocity jet with a diameter Ø3 = 0.2 pc is ejected from the central part of the disk, while the remnant falls onto the forming central body. The ejection velocity of the high-velocity flow is v ⩾ 0.06 c. At a distance up to ˜1 pc, the jet accelerates to an apparent velocity v ˜ 8 c. Further out, uniform motion is observed within ˜2 pc following which deceleration occurs. The jet structure corresponding to a conical diverging helix with an increasing pitch is determined by gasdynamic instability. The counterjet structure is a mirror reflection of the nearby part of the jet. The brightness temperature of the fragment of the high-velocity flow at the exit from the counterjet nozzle is T b ≈ (1012-1013) K. The disk inclined at an angle of 60° to the plane of the sky shadows the jet ejector region. Ring currents observed in the tangential directions as parallel chains of components are excited in the rotating flows. The magnetic fields of the rotating bipolar outflow and the disk are aligned and oriented along the rotation axis. The translational motions of the jet and counterjet are parallel and antiparallel to the magnetic field, which determines their acceleration or deceleration. The quasar core is surrounded by a thermal plasma. The sizes of the HII region reach ˜30 pc. The electron density decreases with increasing

  2. Relativistic beaming and orientation effects in core-dominated quasars

    CERN Document Server

    Ubachukwu, A A


    In this paper, we investigate the relativistic beaming effects in a well-defined sample of core-dominated quasars using the correlation between the relative prominence of the core with respect to the extended emission (defined as the ratio of the core- to the lobe- flux density measured in the rest frame of the source) and the projected linear size as an indicator of relativistic beaming and source orientation. Based on the orientation-dependent relativistic beaming and unification paradigm for high luminosity sources in which the Fanaroff-Riley class-II radio galaxies form the unbeamed parent population of both the lobe- and coredominated quasars which are expected to lie at successively smaller angles to the line of sight, we find that the flows in the cores of these coredominated quasars are highly relativistic, with optimum bulk Lorentz factor, $\\gamma_{opt}\\sim6-16$, and also highly anisotropic, with an average viewing angle, $\\sim9^0-16^0$. Furthermore, the largest boosting occurs within a critical cone...

  3. High-frequency monitoring of quasars with absorption lines (United States)

    Cegłowski, Maciej; Hayashi, Takayuki J.; Kunert-Bajraszewska, Magdalena; Katarzyński, Krzysztof


    An investigation of the origin of the broad absorption lines observed in some quasars was performed. We selected a sample of the most luminous objects and observed them with the VERA interferometer at 22 GHz. We also used a single 32-meter antenna, located near Toruń in Poland, to monitor variability of these quasars at 30 GHz. We succeed in detecting 16 out of 19 initially selected objects. The main aim of our observations was to determine the spacial orientation of the observed sources and their evolutionary status. We investigated their radio maps, performed the variability studies, and examined their radio spectra as well as the emission in the broadband frequency range. Most of the quasars from our sample seem to evolve in a similar way to young radio objects. However, radio structures of two sources may suggest that these objects are restarted active galactic nuclei. This may indicate a diversity of evolutionary stages in our sample. Six of the investigated sources were classified as candidates for the variable objects.

  4. The diversity of quasars unified by accretion and orientation (United States)

    Shen, Yue; Ho, Luis C.


    Quasars are rapidly accreting supermassive black holes at the centres of massive galaxies. They display a broad range of properties across all wavelengths, reflecting the diversity in the physical conditions of the regions close to the central engine. These properties, however, are not random, but form well-defined trends. The dominant trend is known as `Eigenvector 1', in which many properties correlate with the strength of optical iron and [O III] emission. The main physical driver of Eigenvector 1 has long been suspected to be the quasar luminosity normalized by the mass of the hole (the `Eddington ratio'), which is an important parameter of the black hole accretion process. But a definitive proof has been missing. Here we report an analysis of archival data that reveals that the Eddington ratio indeed drives Eigenvector 1. We also find that orientation plays a significant role in determining the observed kinematics of the gas in the broad-line region, implying a flattened, disk-like geometry for the fast-moving clouds close to the black hole. Our results show that most of the diversity of quasar phenomenology can be unified using two simple quantities: Eddington ratio and orientation.

  5. [Galaxy/quasar classification based on nearest neighbor method]. (United States)

    Li, Xiang-Ru; Lu, Yu; Zhou, Jian-Ming; Wang, Yong-Jun


    With the wide application of high-quality CCD in celestial spectrum imagery and the implementation of many large sky survey programs (e. g., Sloan Digital Sky Survey (SDSS), Two-degree-Field Galaxy Redshift Survey (2dF), Spectroscopic Survey Telescope (SST), Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) program and Large Synoptic Survey Telescope (LSST) program, etc.), celestial observational data are coming into the world like torrential rain. Therefore, to utilize them effectively and fully, research on automated processing methods for celestial data is imperative. In the present work, we investigated how to recognizing galaxies and quasars from spectra based on nearest neighbor method. Galaxies and quasars are extragalactic objects, they are far away from earth, and their spectra are usually contaminated by various noise. Therefore, it is a typical problem to recognize these two types of spectra in automatic spectra classification. Furthermore, the utilized method, nearest neighbor, is one of the most typical, classic, mature algorithms in pattern recognition and data mining, and often is used as a benchmark in developing novel algorithm. For applicability in practice, it is shown that the recognition ratio of nearest neighbor method (NN) is comparable to the best results reported in the literature based on more complicated methods, and the superiority of NN is that this method does not need to be trained, which is useful in incremental learning and parallel computation in mass spectral data processing. In conclusion, the results in this work are helpful for studying galaxies and quasars spectra classification.

  6. How Bright Can Supernovae Get? (United States)

    Kohler, Susanna


    Supernovae enormous explosions associated with the end of a stars life come in a variety of types with different origins. A new study has examined how the brightest supernovae in the Universe are produced, and what limits might be set on their brightness.Ultra-Luminous ObservationsRecent observations have revealed many ultra-luminous supernovae, which haveenergies that challenge our abilities to explain them usingcurrent supernova models. An especially extreme example is the 2015 discovery of the supernova ASASSN-15lh, which shone with a peak luminosity of ~2*1045 erg/s, nearly a trillion times brighter than the Sun. ASASSN-15lh radiated a whopping ~2*1052 erg in the first four months after its detection.How could a supernova that bright be produced? To explore the answer to that question, Tuguldur Sukhbold and Stan Woosley at University of California, Santa Cruz, have examined the different sources that could produce supernovae and calculated upper limits on the potential luminosities ofeach of these supernova varieties.Explosive ModelsSukhbold and Woosley explore multiple different models for core-collapse supernova explosions, including:Prompt explosionA stars core collapses and immediately explodes.Pair instabilityElectron/positron pair production at a massive stars center leads to core collapse. For high masses, radioactivity can contribute to delayed energy output.Colliding shellsPreviously expelled shells of material around a star collide after the initial explosion, providing additional energy release.MagnetarThe collapsing star forms a magnetar a rapidly rotating neutron star with an incredibly strong magnetic field at its core, which then dumps energy into the supernova ejecta, further brightening the explosion.They then apply these models to different types of stars.Setting the LimitThe authors show that the light curve of ASASSN-15lh (plotted in orange) can be described by a model (black curve) in which a magnetar with an initial spin period of 0.7 ms

  7. The origin of the far-infrared continuum of z ~ 6 quasars. A radiative transfer model for SDSS J1148+5251 (United States)

    Schneider, R.; Bianchi, S.; Valiante, R.; Risaliti, G.; Salvadori, S.


    Context. Understanding the history of formation of z > 6 quasars is a major challenge to theoretical models. Physical insights on the connection between the central black hole and its host galaxy can be gained by means of the quasar infrared properties. Aims: Here we investigate the origin of the far-infrared continuum of SDSS J1148+5251, using it as a prototype for the more general class of high-luminosity high-redshift quasars. Methods: We run the radiative transfer code TRADING to follow the transfer of radiation from the central source and from stellar sources through the dusty environment of the host galaxy. We adopt simple models for the central source, including all the radiation that can travel beyond the dusty torus. The radiation from stellar sources is modelled using the code PÉGASE. The model is based on the output of the semi-analytical merger tree code, GAMETE/QSOdust, which lets us predict the evolution of the host galaxy and of its nuclear black hole, following the star formation history and chemical evolution - including dust - in all the progenitor galaxies of SDSS J1148+5251. Results: We find that the radiation emitted by the central source, which dominates the observed spectral energy distribution from UV/optical to near- and mid-infrared wavelengths, can also provide an important source of heating for the dust distributed in the host galaxy, powering at least 30% and up to 70% of the observed far-infrared emission at rest-frame wavelengths [20-1000] μm. The remaining fraction is contributed by stellar sources and can only be achieved if the host galaxy is able to sustain a star formation rate of ≈900 M⊙/yr at z = 6.4. This points to a co-evolution scenario where, during their hierarchical assembly, the first super-massive black holes and their host galaxies grow at the same pace until the black hole reaches a mass of ~2 × 108 M⊙; it then starts growing faster than its host, reaching the bright quasar phase when the black hole and

  8. Giant Gas Cloud Made of Atoms Formed in First Stars Revealed in Universe's Most Distant Quasar (United States)


    Astronomers studying the most distant quasar yet found in the Universe have discovered a massive reservoir of gas containing atoms made in the cores of some of the first stars ever formed. The carbon-monoxide gas was revealed by the National Science Foundation's Very Large Array (VLA) and the Plateau de Bure radio interferometer in Europe. The gas, along with the young galaxy containing it, is seen as it was when the Universe was only one-sixteenth its current age, just emerging from the primeval "Dark Ages" before light could travel freely through the cosmos. VLA Image of Quasar VLA Image of J1148+5251 CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) "Our discovery of this much carbon monoxide gas in such an extremely distant and young galaxy is surprising. It means that, even at a very early time in the history of the Universe, galaxies already had huge amounts of molecular gas that would eventually form new generations of stars," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The distant galaxy, dubbed J1148+5251, contains a bright quasar powered by a black hole at least a billion times more massive than the Sun. The galaxy is seen as it was only 870 million years after the Big Bang. The Universe now is 13.7 billion years old. J1148+5251 would have been among the first luminous objects in the Universe. The original atoms formed in the Universe within the first three minutes of the Big Bang were only hydrogen and helium. Carbon and oxygen -- the atoms making up carbon monoxide -- had to be made in the thermonuclear furnaces at the cores of the earliest stars. "The carbon and oxygen atoms in the gas we detected were made by some of the first stars ever formed, only about 650 million years after the Big Bang. In the next 200 million years or so, those stars -- probably very different stars from those we see today -- exploded as supernovae, spreading the carbon and oxygen out into space. Those atoms then cooled

  9. Brightness and darkness as perceptual dimensions

    NARCIS (Netherlands)

    Vladusich, T.; Lucassen, M.P.; Cornelissen, F.W.


    A common-sense assumption concerning visual perception states that brightness and darkness cannot coexist at a given spatial location. One corollary of this assumption is that achromatic colors, or perceived grey shades, are contained in a one-dimensional (1-D) space varying from bright to dark. The


    NARCIS (Netherlands)



    Low surface brightness (LSB) galaxies are galaxies dominated by an exponential disc whose central surface brightness is much fainter than the value of mu(B)(0) = 21.65 +/- 0.30 mag arcsec(-2) found by Freeman. In this paper we present broadband photometry of a sample of 21 late-type LSB galaxies.

  11. Brightness Alteration with Interweaving Contours

    Directory of Open Access Journals (Sweden)

    Sergio Roncato


    Full Text Available Chromatic induction is observed whenever the perceived colour of a target surface shifts towards the hue of a neighbouring surface. Some vivid manifestations may be seen in a white background where thin coloured lines have been drawn (assimilation or when lines of different colours are collinear (neon effect or adjacent (watercolour to each other. This study examines a particular colour induction that manifests in concomitance with an opposite effect of colour saturation (or anti-spread. The two phenomena can be observed when a repetitive pattern is drawn in which outline thin contours intercept wider contours or surfaces, colour spreading appear to fill the surface occupied by surfaces or thick lines whereas the background traversed by thin lines is seen as brighter or filled of a saturated white. These phenomena were first observed by Bozzi (1975 and Kanizsa (1979 in figural conditions that did not allow them to document their conjunction. Here we illustrate various manifestations of this twofold phenomenon and compare its effects with the known effects of brightness and colour induction. Some conjectures on the nature of these effects are discussed.

  12. Android application and REST server system for quasar spectrum presentation and analysis (United States)

    Wasiewicz, P.; Pietralik, K.; Hryniewicz, K.


    This paper describes the implementation of a system consisting of a mobile application and RESTful architecture server intended for the analysis and presentation of quasars' spectrum. It also depicts the quasar's characteristics and significance to the scientific community, the source for acquiring astronomical objects' spectral data, used software solutions as well as presents the aspect of Cloud Computing and various possible deployment configurations.


    NARCIS (Netherlands)



    Measurements at 60 mu wavelength of 3CR quasars and powerful radio galaxies in the redshift range 0.3 quasars being

  14. NuSTAR observations of heavily obscured quasars at z ~ 0.5

    DEFF Research Database (Denmark)

    Lansbury, G. B.; Alexander, D. M.; Del Moro, A.


    We present NuSTAR hard X-ray observations of three Type 2 quasars at z ≈ 0.4-0.5, optically selected from the Sloan Digital Sky Survey. Although the quasars show evidence for being heavily obscured, Compton-thick systems on the basis of the 2-10 keV to [O III] luminosity ratio and multiwavelength...

  15. Observing broad-absorption line quasars with Spectrum-Rontgen-Gamma

    DEFF Research Database (Denmark)

    Singh, K.P.; Schnopper, H.W.; Westergaard, Niels Jørgen Stenfeldt


    Broad-absorption line quasars are found to have extremely weak soft X-ray emission when compared with other optically selected quasars. In the only example of PHL 5200 for which a detailed X-ray spectrum has been obtained with ASCA, strong absorption in the source appears to be responsible...

  16. The ultraviolet-to-mid-infrared spectral energy distribution of weak emission line quasars

    NARCIS (Netherlands)

    Lane, R.A.; Shemmer, O.; Diamond-Stanic, A.M.; Fan, X.; Anderson, S.F.; Brandt, W.N.; Plotkin, R.M.; Richards, G.T.; Schneider, D.P.; Strauss, M.A.


    We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey (SDSS) quasars at 2.7 ≤ z ≤ 5.9 which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet (UV) spectra (hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with SDSS

  17. Hubble Space Telescope Ultraviolet Spectroscopy of Fourteen Low-Redshift Quasars

    DEFF Research Database (Denmark)

    Ganguly, Rajib; Brotherton, Michael S.; Arav, Nahum


    , HE0441-2826, contains extremely weak emission lines and our spectrum is consistent with a simple power-law continuum. The quasar is radio-loud, but has a steep spectral index and a lobe-dominated morphology, which argues against it being a blazar. The unusual spectrum of this quasar resembles...


    NARCIS (Netherlands)


    Multi-epoch VLBI observations are presented of two large double-lobed quasars, 4C 28.45 (1830 + 285) and 4C 21.35 (1222 + 216). On mas-scales, both quasars contain a multi-component asymmetric radio structure. In 4C 28.45 the nuclear emission was seen to expand, the observed proper motions

  19. A Sample of Quasars with Strong Nitrogen Emission Lines from the Sloan Digital Sky Survey

    DEFF Research Database (Denmark)

    Jiang, Linhua; Fan, Xiaohui; Vestergaard, Marianne


    We report on 293 quasars with strong NIV] lambda 1486 or NIII] lambda 1750 emission lines (rest-frame equivalent width > 3 \\AA) at 1.7......We report on 293 quasars with strong NIV] lambda 1486 or NIII] lambda 1750 emission lines (rest-frame equivalent width > 3 \\AA) at 1.7...

  20. Quasar lenses and galactic streams: outlier selection and Gaia multiplet detection (United States)

    Agnello, Adriano


    I describe two novel techniques originally devised to select strongly lensed quasar candidates in wide-field surveys. The first relies on outlier selection in optical and mid-infrared magnitude space; the second combines mid-infrared colour selection with Gaia spatial resolution, to identify multiplets of objects with quasar-like colours. Both methods have already been applied successfully to the Sloan Digital Sky Survey, ATLAS and Dark Energy Survey footprints: besides recovering known lenses from previous searches, they have led to new discoveries, including quadruply lensed quasars, which are rare within the rare-object class of quasar lenses. As a serendipitous by-product, at least four candidate Galactic streams in the South have been identified among foreground contaminants. There is considerable scope for tailoring the WISE-Gaia multiplet search to stellar-like objects, instead of quasar-like, and to automatically detect Galactic streams.

  1. Quasars in the 4D Eigenvector 1 Context: a stroll down memory lane

    Directory of Open Access Journals (Sweden)

    Jack W. Sulentic


    Full Text Available Recently some pessimism has been expressed about our lack of progress in understanding quasars over more than fifty year since their discovery. It is worthwhile to look back at some of the progress that has been made – but still lies under the radar – perhaps because few people are working on optical/UV spectroscopy in this field. Great advances in understanding quasar phenomenology have emerged using eigenvector techniques. The 4D eigenvector 1 context provides a surrogate H-R Diagram for quasars with a source main sequence driven by Eddington ratio convolved with line-of-sight orientation. Appreciating the striking differences between quasars at opposite ends of the main sequence (so-called population A and B sources opens the door towards a unified model of quasar physics, geometry and kinematics. We present a review of some of the progress that has been made over the past 15 years, and point out unsolved issues.

  2. Spitzer observations of the field of the hyperluminous quasar HE0515-4414 (United States)

    Lacy, Mark; Surace, Jason; Nyland, Kristina; Mason, Brian; Rowe, Barnaby; Chatterjee, Sutechana; Rocha, Graca; Kimball, Amy


    We have used unique, ultradeep ALMA 140GHz data to obtain a tentative first direct detection of a thermal quasar wind via the SZ effect. We are requesting Spitzer time to image the environment of the quasar. In particular, we will map the galaxy distribution in the vicinity of our tentative detection of the quasar wind to rule out any contribution to the SZ decrement due to an intracluster or intragroup medium associated with a compact cluster or group of galaxies around the quasar or along the line of sight. In addition, the data will be used to quantify the environment of one of the most luminous quasars known, as well as study the serendipitous ALMA sources in the field, the deepest ever at this frequency.

  3. Spectral Properties of Bright Fermi-Detected Blazars in the Gamma-Ray Band (United States)

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


    The gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample (LBAS) are investigated using Fermi-LAT data. Spectral properties (hardness, curvature, and variability) established using a data set accumulated over 6 months of operation are presented and discussed for different blazar classes and subclasses: flat spectrum radio quasars (FSRQs), low-synchrotron peaked BLLacs (LSP-BLLacs), intermediate-synchrotron peaked BLLacs (ISP-BLLacs), and high-synchrotron peaked BLLacs (HSP-BLLacs). The distribution of photon index (Γ, obtained from a power-law fit above 100 MeV) is found to correlate strongly with blazar subclass. The change in spectral index from that averaged over the 6 months observing period is < 0.2-0.3 when the flux varies by about an order of magnitude, with a tendency toward harder spectra when the flux is brighter for FSRQs and LSP-BLLacs. A strong departure from a single power-law spectrum appears to be a common feature for FSRQs. This feature is also present for some high-luminosity LSP-BLLacs, and a small number of ISP-BLLacs. It is absent in all LBAS HSP-BLLacs. For 3C 454.3 and AO 0235+164, the two brightest FSRQ source and LSP-BLLac source, respectively, a broken power law (BPL) gives the most acceptable of power law, BPL, and curved forms. The consequences of these findings are discussed.

  4. Bright Sparks of Our Future! (United States)

    Riordan, Naoimh


    My name is Naoimh Riordan and I am the Vice Principal of Rockboro Primary School in Cork City, South of Ireland. I am a full time class primary teacher and I teach 4th class, my students are aged between 9-10 years. My passion for education has developed over the years and grown towards STEM (Science, Technology, Engineering and Mathematics) subjects. I believe these subjects are the way forward for our future. My passion and beliefs are driven by the unique after school programme that I have developed. It is titled "Sparks" coming from the term Bright Sparks. "Sparks" is an after school programme with a difference where the STEM subjects are concentrated on through lessons such as Science, Veterinary Science Computer Animation /Coding, Eco engineering, Robotics, Magical Maths, Chess and Creative Writing. All these subjects are taught through activity based learning and are one-hour long each week for a ten-week term. "Sparks" is fully inclusive and non-selective which gives all students of any level of ability an opportunity to engage into these subjects. "Sparks" is open to all primary students in County Cork. The "Sparks" after school programme is taught by tutors from the different Universities and Colleges in Cork City. It works very well because the tutor brings their knowledge, skills and specialised equipment from their respective universities and in turn the tutor gains invaluable teaching practise, can trial a pilot programme in a chosen STEM subject and gain an insight into what works in the physical classroom.

  5. Probing Quasar Winds Using Intrinsic Narrow Absorption Lines (United States)

    Culliton, Christopher S.; Charlton, Jane C.; Eracleous, Michael; Roberts, Amber; Ganguly, Rajib; Misawa, Toru; Muzahid, Sowgat


    Quasar outflows are important for understanding the accretion and growth processes of the central black hole. Furthermore, outflows potentially have a role in providing feedback to the galaxy, and halting star formation and infall of gas. The geometry and density of these outflows remain unknown, especially as a function of ionization and velocity. Having searched ultraviolet spectra at both high redshift (VLT/UVES; 1.4CIV systems with black Lya and with a separate low ionization gas phase to partially covered NV systems with partially covered Lya and without detected low ionization gas. Additionally, we construct a model describing the spatial distributions, geometries, and varied ionization structures of intrinsic NALs.

  6. Luminosity function of quasars at large redshifts from grism surveys (United States)

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


    We have carried out a systematic search for emission-line objects through photometrically calibrated CCD grism surveys with the Palomar 200-inch telescope in transit mode, covering 62 square degrees. These surveys have yielded 141 quasars detected by their C IV or Ly-alpha emission in the redshift range 2.0 - 4.7. We use this sample and the known flux limits to derive the slope of the luminosity function and the space density above a given line luminosity, as a function of redshift. While space densities are approximately constant at redshifts 2.0 - 3.0, they are declining steeply for redshifts larger than 3.

  7. Radio imaging of core-dominated high redshift quasars

    DEFF Research Database (Denmark)

    Barthel, Peter D.; Vestergaard, Marianne; Lonsdale, Colin J.


    VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum quasars, consistent with these objects being observed...... at sight lines close to their (relativistic, $\\gamma \\approx$ 4-7) jet axes. The usefulness of the radio source orientation indicator R_V, being defined as ratio of radio core and rest frame optical V-band luminosity, is confirmed....

  8. Space Brightness Evaluation for a Daylit Room

    Directory of Open Access Journals (Sweden)

    Takashi Maruyama


    Full Text Available One of the most important problems for lighting design is how to reduce an electric energy. One way to solve this problem is use of daylight, but little is known how to perceive a brightness of a room illuminated by daylight come in through a window and artificial light. Although the horizontal illuminance increases because of daylight, we would not perceive the room as bright as brightness estimated by the illuminance. The purpose of this study is to measure the space brightness for daylit room and to propose a evaluation method. The experiment was conducted with a couple of miniature office rooms, standard room and test room. Test room has several types of windows and standard room has no window. Subject was asked to evaluate the brightness of the test room relative to the standard room with method of magnitude estimation. It was found that brightness of daylit room did not increase simply with horizontal illuminance. Subject perceived a daylit room darker than a room illuminated only by the artificial light even if horizontal illuminance of these room was same. The effect of daylight on space brightness would vary with the window size and intensity of daylight or artificial light.

  9. Bright boys the making of information technology

    CERN Document Server

    Green, Tom


    Everything has a beginning. None was more profound-and quite as unexpected-than Information Technology. Here for the first time is the untold story of how our new age came to be and the bright boys who made it happen. What began on the bare floor of an old laundry building eventually grew to rival in size the Manhattan Project. The unexpected consequence of that journey was huge---what we now know as Information Technology. For sixty years the bright boys have been totally anonymous while their achievements have become a way of life for all of us. "Bright Boys" brings them home. By 1950 they'd

  10. Revealing the Star-Forming Hosts of Luminous Quasars at z~2: A Multi-Wavelength Study (United States)

    Wethers, Clare; Banerji, Manda; Hewett, Paul; Dark Energy Survey (DES)


    Quasars are thought to govern many fundamental processes within galaxies, from quenching star formation to shaping the galaxy itself. In an evolutionary picture of quasars, the most luminous systems (Lbol~1047erg) are thought to evolve from merger-driven starbursts, appearing heavily obscured during their transition to UV-luminous quasars as dust from the decaying starburst is being cleared out of the galaxy. Understanding the connection between dust obscuration, black hole accretion and star formation in luminous quasars undergoing this transition is therefore an important test of such evolutionary models. Host galaxy studies of the most massive and luminous quasars at z>1.5 remain challenging, particularly in the rest-frame UV where a quasar will typically outshine its host galaxy by several orders of magnitude. I will present the first rest-frame UV study for a population of obscured type-1 quasars at z~2 - a peak epoch in both star formation and black hole accretion. By combining deep ground-based imaging from the Dark Energy Survey (DES) with near infra-red observations, I exploit dust obscuration towards the quasar to isolate host galaxy emission, finding obscured quasars to reside in prodigiously star-forming hosts at z~2, with the most actively star-forming galaxies appearing to host the most luminous quasars. Combining these results with new sub-mm observations from SCUBA2, I will present a direct comparison of the unobscured and obscured star formation in this population of dusty quasar hosts.

  11. The Spectral Energy Distribution of Fermi Bright Blazars (United States)

    Abdo, A. A.; Ackermann, M.; Agudo, I.; Ajello, M.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Arkharov, A. A.; Axelsson, M.; Bach, U.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Benitez, E.; Berdyugin, A.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Boettcher, M.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Burrows, D.; Buson, S.; Caliandro, G. A.; Calzoletti, L.; Cameron, R. A.; Capalbi, M.; Caraveo, P. A.; Carosati, D.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chaty, S.; Chekhtman, A.; Chen, W. P.; Chiang, J.; Chincarini, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Colafrancesco, S.; Cominsky, L. R.; Conrad, J.; Costamante, L.; Cutini, S.; D'ammando, F.; Deitrick, R.; D'Elia, V.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Donnarumma, I.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dultzin, D.; Dumora, D.; Falcone, A.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Forné, E.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gómez, J. L.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giuliani, A.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Gronwall, C.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Gurwell, M. A.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Healey, S. E.; Heidt, J.; Hiriart, D.; Horan, D.; Hoversten, E. A.; Hughes, R. E.; Itoh, R.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Jorstad, S. G.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kennea, J.; Kerr, M.; Kimeridze, G.; Knödlseder, J.; Kocian, M. L.; Kopatskaya, E. N.; Koptelova, E.; Konstantinova, T. S.; Kovalev, Y. Y.; Kovalev, Yu. A.; Kurtanidze, O. M.; Kuss, M.; Lande, J.; Larionov, V. M.; Latronico, L.; Leto, P.; Lindfors, E.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Marchegiani, P.; Marscher, A. P.; Marshall, F.; Max-Moerbeck, W.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nestoras, I.; Nilsson, K.; Nizhelsky, N. A.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Ojha, R.; Omodei, N.; Orlando, E.; Ormes, J. F.; Osborne, J.; Ozaki, M.; Pacciani, L.; Padovani, P.; Pagani, C.; Page, K.; Paneque, D.; Panetta, J. H.; Parent, D.; Pasanen, M.; Pavlidou, V.; Pelassa, V.; Pepe, M.; Perri, M.; Pesce-Rollins, M.; Piranomonte, S.; Piron, F.; Pittori, C.; Porter, T. A.; Puccetti, S.; Rahoui, F.; Rainò, S.; Raiteri, C.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Richards, J. L.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Romani, R. W.; Ros, J. A.; Roth, M.; Roustazadeh, P.; Ryde, F.; Sadrozinski, H. F.-W.; Sadun, A.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sellerholm, A.; Sgrò, C.; Shaw, M. S.; Sigua, L. A.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J.-L.; Stevenson, M.; Stratta, G.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Takalo, L. O.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Verrecchia, F.; Vilchez, N.; Villata, M.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Zensus, J. A.; Zhekanis, G. V.; Ziegler, M.


    We have conducted a detailed investigation of the broadband spectral properties of the γ-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi γ-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/γ-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these γ-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log ν-log ν F ν representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, αro, and optical to X-ray, αox, spectral slopes) and from the γ-ray spectral index. Our data show that the synchrotron peak frequency (ν S peak) is positioned between 1012.5 and 1014.5 Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 1013 and 1017 Hz in featureless BL Lacertae objects. We find that the γ-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are

  12. Development of SED Camera for Quasars in Early Universe (SQUEAN) (United States)

    Kim, Sanghyuk; Jeon, Yiseul; Lee, Hye-In; Park, Woojin; Ji, Tae-Geun; Hyun, Minhee; Choi, Changsu; Im, Myungshin; Pak, Soojong


    We describe the characteristics and performance of a camera system, Spectral energy distribution Camera for Quasars in Early Universe (SQUEAN). It was developed to measure SEDs of high-redshift quasar candidates (z ≳ 5) and other targets, e.g., young stellar objects, supernovae, and gamma-ray bursts, and to trace the time variability of SEDs of objects such as active galactic nuclei (AGNs). SQUEAN consists of an on-axis focal plane camera module, an autoguiding system, and mechanical supporting structures. The science camera module is composed of a focal reducer, a customizable filter wheel, and a CCD camera on the focal plane. The filter wheel uses filter cartridges that can house filters with different shapes and sizes, enabling the filter wheel to hold 20 filters of 50 mm × 50 mm size, 10 filters of 86 mm × 86 mm size, or many other combinations. The initial filter mask was applied to calibrate the filter wheel with high accuracy, and we verified that the filter position is repeatable at much less than one pixel accuracy. We installed and tested 50 nm medium bandwidth filters of 600-1050 nm and other filters at the commissioning observation in 2015 February. We found that SQUEAN can reach limiting magnitudes of 23.3-25.3 AB mag at 5σ in a one-hour total integration time.

  13. Apparent superluminal motion in the quasar NRAO 140 (United States)

    Marscher, A. P.; Broderick, J. J.


    Very long baseline interferometer (VLBI) measurements of the compact radio structure in the quasar NRAO 140 (z = 1.258) have been obtained at three epochs at a wavelength of 2.8 cm. These observations indicate that the two most compact radio components are separating at an angular rate of 0.10-0.14 milli-arcsec per year. For cosmological distances H sub 0 = 50 and q sub 0 = 0, this corresponds to a velocity of separation (in the quasar's rest frame) of 10 + or - 2 times the speed of light, c; for H sub 0 = 100 and q sub 0 = 1, the value is (3.1 + or - 0.6) c. Other interpretations of the temporal changes in correlated flux density and closure phase are discussed and are considered unlikely. The derived velocities are consistent with an earlier prediction that the separation velocity should be greater than about 4 c. Extrapolation back to the epoch of zero separation indicates that the expansion originated between late 1963 and late 1968 (under the assumption of constant velocity). This range includes the beginning of an isolated outburst in flux density at 2.8 cm. These results cannot be used to make any statements concerning the validity of cosmological interpretations of QSO redshifts.

  14. First light with Trident: multi-platform synthetic quasar spectra (United States)

    Silvia, Devin W.; Hummels, Cameron B.; Smith, Britton


    Observational efforts to better understand the nature of the intergalactic and circumgalactic media have relied heavily on the information encoded in the absorption line systems of quasar spectra. Numerical simulations of large-scale structure and galaxy evolution are well-suited to explore the properties of those same media owing to the relative ease with which one can access physical quantities from complex, three-dimensional data. However, a difficulty arises when one tries to make direct “apple-to-apples” comparisons between observed spectra and simulated data. In an effort to provide a common language capable of linking theory and observation, we announce the release of Trident. Trident is a publicly available software tool that enables the creation of realistic synthetic absorption spectra from virtually all widely-used hydrodynamics simulation codes. Through user-controlled levels of spectral realism, direct comparisons between simulated and observed data become not only possible, but greatly simplified. We present the methods for extracting artificial quasar sightlines and generating spectra as well as early-stage applications of those spectra to intergalactic and circumgalactic absorption line studies.

  15. Jet evolution in Steep Spectrum Radio Quasars: a multiwavelength study

    Directory of Open Access Journals (Sweden)

    Torresi Eleonora


    Full Text Available Thanks to the Fermi γ-ray satellite, it is now confirmed that Misaligned Active Galactic Nuclei (MAGN, i.e. radio galaxies and steep spectrum radio quasars, are a new class of GeV emitters. In this work we present the first γ-ray and multiwavelength study of the two steep spectrum radio quasars, i.e. 3C 207 and 3C 380, belonging to the MAGN sample. From the γ -ray variability study we estimate the physical size of the zone where high-energy photons are dissipated: for both sources this region should be very compact, not larger than 0.05 pc. As a successive step, we build multiwavelength light curves of 3C 207 and 3C 380 to search for possible simultaneous outbursts in different wavebands with the aim of localizing the compact emitting region. This is an important issue with strong impact on theoretical models: indeed, knowing where highenergy photons are dissipated (at sub-pc or pc-scale provides information on the nature of the seed photons involved in the production of the GeV radiation.

  16. A Left and Right Truncated Schechter Luminosity Function for Quasars

    Directory of Open Access Journals (Sweden)

    Lorenzo Zaninetti


    Full Text Available The luminosity function for quasars (QSOs is usually fitted by a Schechter function. The dependence of the number of quasars on the redshift, both in the low and high luminosity regions, requires the inclusion of a lower and upper boundary in the Schechter function. The normalization of the truncated Schechter function is forced to be the same as that for the Schechter function, and an analytical form for the average value is derived. Three astrophysical applications for QSOs are provided: deduction of the parameters at low redshifts, behavior of the average absolute magnitude at high redshifts, and the location (in redshift of the photometric maximum as a function of the selected apparent magnitude. The truncated Schechter function with the double power law and an improved Schechter function are compared as luminosity functions for QSOs. The chosen cosmological framework is that of the flat cosmology, for which we provided the luminosity distance, the inverse relation for the luminosity distance, and the distance modulus.

  17. A spectroscopic atlas of bright stars

    CERN Document Server

    Martin, Jack


    Suitable for amateur astronomers interested in practical spectroscopy or spectrography, this reference book identifies more than 70 (northern hemisphere) bright stars that are suitable observational targets. It provides finder charts for locating these sometimes-familiar stars.

  18. Nimbus-5 ESMR Polar Gridded Brightness Temperatures (United States)

    National Aeronautics and Space Administration — The Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR) data set consists of gridded brightness temperature arrays for the Arctic and Antarctic, spanning 11...

  19. The Luminosity Function of Fermi-detected Flat-Spectrum Radio Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Ajello, M.; Shaw, M.S.; Romani, R.W.; Dermer, C.D.; Costamante, L.; King, O.G.; Max-Moerbeck, W.; Readhead, A.; Reimer, A.; Richards, J.L.; Stevenson, M.


    Fermi has provided the largest sample of {gamma}-ray selected blazars to date. In this work we use a complete sample of FSRQs detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift {approx}0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of {gamma}-ray FSRQs follows a luminosity-dependent density evolution similarly to that of radio-quiet AGN. Also using data from the Swift Burst Alert Telescope we derive the average spectral energy distribution of FSRQs in the 10 keV-100GeV band and show that there is no correlation of the peak {gamma}-ray luminosity with {gamma}-ray peak frequency. The coupling of the SED and LF allows us to predict that the contribution of FSRQs to the Fermi isotropic {gamma}-ray background is 9.3{sub -1.0}{sup +1.6}% ({+-}3% systematic uncertainty) in the 0.1-100GeV band. Finally we determine the LF of unbeamed FSRQs, finding that FSRQs have an average Lorentz factor of {gamma} = 11.7{sub -2.2}{sup +3.3}, that most are seen within 5{sup o} of the jet axis, and that they represent only {approx}0.1% of the parent population.

  20. Magnetic topological analysis of coronal bright points (United States)

    Galsgaard, K.; Madjarska, M. S.; Moreno-Insertis, F.; Huang, Z.; Wiegelmann, T.


    Context. We report on the first of a series of studies on coronal bright points which investigate the physical mechanism that generates these phenomena. Aims: The aim of this paper is to understand the magnetic-field structure that hosts the bright points. Methods: We use longitudinal magnetograms taken by the Solar Optical Telescope with the Narrowband Filter Imager. For a single case, magnetograms from the Helioseismic and Magnetic Imager were added to the analysis. The longitudinal magnetic field component is used to derive the potential magnetic fields of the large regions around the bright points. A magneto-static field extrapolation method is tested to verify the accuracy of the potential field modelling. The three dimensional magnetic fields are investigated for the presence of magnetic null points and their influence on the local magnetic domain. Results: In nine out of ten cases the bright point resides in areas where the coronal magnetic field contains an opposite polarity intrusion defining a magnetic null point above it. We find that X-ray bright points reside, in these nine cases, in a limited part of the projected fan-dome area, either fully inside the dome or expanding over a limited area below which typically a dominant flux concentration resides. The tenth bright point is located in a bipolar loop system without an overlying null point. Conclusions: All bright points in coronal holes and two out of three bright points in quiet Sun regions are seen to reside in regions containing a magnetic null point. An as yet unidentified process(es) generates the brigh points in specific regions of the fan-dome structure. The movies are available at

  1. Formación estelar y AGNs en los entornos de quasars (United States)

    Coldwell, G.; García Lambas, D.

    En este trabajo utilizamos las galaxias del catálogo 2dF (2dF public 100K data release) y muestras de quasars tomados del catálogo Verón-Cetty & Verón (2001) para estudiar la naturaleza de estas galaxias en los entornos de quasars con redshift en el rango 0.1 3.5, en los entornos de quasars comparado con la fracción presente en las vecindades de galaxias típicas del 2dF. Analizamos las distribuciones de luminosidad para estas galaxias (eta > 3.5) encontrando un exceso de galaxias mas luminosas que M ˜ -19.5 en las vecindades de quasars, indicativo de la posible presencia de AGNs. Por otro lado, estimamos la tasa de formación estelar promedio para objetos a distintas distancias de quasars, galaxias y cúmulos de galaxias detectando una actividad de formacion estelar significativamente alta dentro de 1.5 Mpc h-1 de quasars con respecto a las galaxias del 2dF. Estos resultados proveen evidencia de un particular entorno de galaxias alrededor de Quasars.

  2. Effect of Interior Chromaticness on Space Brightness

    Directory of Open Access Journals (Sweden)

    Hidenari Takada


    Full Text Available To design a lighting environment, horizontal illuminance is generally used as the brightness of a room. But it is reported that a subjective brightness does not always match the horizontal illuminance. For example, the room furnished with high saturated colored objects is perceived brighter than the room furnished with achromatic objects, even though the horizontal illuminance is the same. To investigate a effect of interior chromaticness on space brightness, we conducted the experiment in four miniature rooms that were different in terms of chromaticness of interior decorating surfaces, but kept lightness of surfaces constant. Subjects were asked to set the illuminance of reference room, that is furnished with achromatic objects, to equate the brightness of the test room, that is with chromatic objects. Four of seven subjects needed less illuminance to get the equality of space brightness if the test room had a saturated objects. The illuminance ratio of test to reference room was about 1.4. Other three subjects set the illuminance of reference room almost equal to test room. Thus, there are differences between individuals so further work would be needed to estimate the quantitative effect of interior chromaticness on space brightness.

  3. Dust reddened quasars in first and UKIDSS: Beyond the tip of the iceberg

    Energy Technology Data Exchange (ETDEWEB)

    Glikman, Eilat [Department of Physics, Middlebury College, Middlebury, VT 05753 (United States); Urrutia, Tanya [Leibniz Institut fr Astrophysik, An der Sternwarte 16, D-14482 Potsdam (Germany); Lacy, Mark [National Radio Astronomy Observatory, Charlottesville, VA (United States); Djorgovski, S. G.; Mahabal, Ashish; Graham, Matthew [California Institute of Technology, Pasadena, CA 91125 (United States); Urry, Meg [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Croom, Scott [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Ge, Jian, E-mail: [Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States)


    We present the results of a pilot survey to find dust-reddened quasars by matching the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) radio catalog to the UKIDSS near-infrared survey and using optical data from Sloan Digital Sky Survey to select objects with very red colors. The deep K-band limit provided by UKIDSS allows for finding more heavily reddened quasars at higher redshifts as compared with previous work using FIRST and Two Micron All Sky Survey (2MASS). We selected 87 candidates with K ≤ 17.0 from the UKIDSS Large Area Survey (LAS) First Data Release (DR1), which covers 190 deg{sup 2}. These candidates reach up to ∼1.5 mag below the 2MASS limit and obey the color criteria developed to identify dust-reddened quasars. We have obtained 61 spectroscopic observations in the optical and/or near-infrared, as well as classifications in the literature, and have identified 14 reddened quasars with E(B – V) > 0.1, including 3 at z > 2. We study the infrared properties of the sample using photometry from the Wide-Field Infrared Survey Explorer and find that infrared colors improve the efficiency of red quasar selection, removing many contaminants in an infrared-to-optical color-selected sample alone. The highest-redshift quasars (z ≳ 2) are only moderately reddened, with E(B – V) ∼ 0.2-0.3. We find that the surface density of red quasars rises sharply with faintness, comprising up to 17% of blue quasars at the same apparent K-band flux limit. We estimate that to reach more heavily reddened quasars (i.e., E(B – V) ≳ 0.5) at z > 2 and a depth of K = 17, we would need to survey at least ∼2.5 times more area.

  4. Investigations of Short-Timescale Outflow Variability in Quasars of the Sloan Digital Sky Survey (United States)

    Hemler, Zachary; Grier, Catherine; Brandt, William; Hall, Patrick; Schneider, Donald; Shen, Yue; Fernandez-Trincado, Jose; SDSS-RM Collaboration


    Quasar outflows are hypothesized to regulate the growth of a quasar's host galaxy and the supermassive black hole (SMBH) itself. Thus, understanding the physics of these outflows is imperative to understanding galactic evolution. The physical properties of these outflows, such as density, radial distance from the SMBH, and kinetic energy can be investigated by measuring both the strength and shape variability of broad absorption lines (BALs) in quasar spectra. However, the accuracy of physical properties calculated using BAL variability methods is limited by the time resolution of the observations. Recent spectral data from the Sloan Digital Sky Survey Reverberation Mapping program (SDSS-RM) provides a novel opportunity to investigate the short-term BAL variability of many quasars at many epochs. The SDSS-RM program took many epochs of spectra for a large sample of quasars over a period of several years, many of which exhibit BALs. The median rest-frame time resolution of these observations is roughly 2 days, in contrast to previous large-sample studies, which typically have time spacing on the order of hundred of days. We are using the SDSS-RM dataset to conduct a BAL variability study that will further constrain outflow properties and provide significant insights into the variability mechanisms of quasar outflows. We are searching for variability in BALs on timescales of less than 2 days among our sample of 22 quasars and determining whether this behavior is common among quasars. We are also investigating the general short-term (less than 10 days) variability characteristics of the entire sample. We will present preliminary results from this study and the possible implications to our understanding of quasar outflows.

  5. Composite Spectral Energy Distributions and Infrared–Optical Colors of Type 1 and Type 2 Quasars (United States)

    Hickox, Ryan C.; Myers, Adam D.; Greene, Jenny E.; Hainline, Kevin N.; Zakamska, Nadia L.; DiPompeo, Michael A.


    We present observed mid-infrared and optical colors and composite spectral energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars selected from Sloan Digital Sky Survey (SDSS) spectroscopy. A significant fraction of powerful quasars are obscured by dust and are difficult to detect in optical photometric or spectroscopic surveys. However, these may be more easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using samples of SDSS type 1 and 2 matched in redshift and [O III] luminosity, we produce composite rest-frame 0.2–15 μm SEDs based on SDSS, UKIDSS, and Wide-field Infrared Survey Explorer photometry and perform model fits using simple galaxy and quasar SED templates. The SEDs of type 1 and 2 quasars are remarkably similar, with the differences explained primarily by the extinction of the quasar component in the type 2 systems. For both types of quasar, the flux of the active galactic nucleus (AGN) relative to the host galaxy increases with AGN luminosity ({L}[{{O}{{III}}]}) and redder observed MIR color, but we find only weak dependencies of the composite SEDs on mechanical jet power as determined through radio luminosity. We conclude that luminous quasars can be effectively selected using simple MIR color criteria similar to those identified previously ({{W}}1{--}{{W}}2> 0.7; Vega), although these criteria miss many heavily obscured objects. Obscured quasars can be further identified based on optical–IR colors (for example, (u{--}{{W}}3 [{AB}])> 1.4({{W}}1{--}{{W}}2 [{Vega}])+3.2). These results illustrate the power of large statistical studies of obscured quasars selected on the basis of MIR and optical photometry.

  6. Energy-exchange collisions of dark-bright-bright vector solitons. (United States)

    Radhakrishnan, R; Manikandan, N; Aravinthan, K


    We find a dark component guiding the practically interesting bright-bright vector one-soliton to two different parametric domains giving rise to different physical situations by constructing a more general form of three-component dark-bright-bright mixed vector one-soliton solution of the generalized Manakov model with nine free real parameters. Moreover our main investigation of the collision dynamics of such mixed vector solitons by constructing the multisoliton solution of the generalized Manakov model with the help of Hirota technique reveals that the dark-bright-bright vector two-soliton supports energy-exchange collision dynamics. In particular the dark component preserves its initial form and the energy-exchange collision property of the bright-bright vector two-soliton solution of the Manakov model during collision. In addition the interactions between bound state dark-bright-bright vector solitons reveal oscillations in their amplitudes. A similar kind of breathing effect was also experimentally observed in the Bose-Einstein condensates. Some possible ways are theoretically suggested not only to control this breathing effect but also to manage the beating, bouncing, jumping, and attraction effects in the collision dynamics of dark-bright-bright vector solitons. The role of multiple free parameters in our solution is examined to define polarization vector, envelope speed, envelope width, envelope amplitude, grayness, and complex modulation of our solution. It is interesting to note that the polarization vector of our mixed vector one-soliton evolves in sphere or hyperboloid depending upon the initial parametric choices.


    Energy Technology Data Exchange (ETDEWEB)

    Lu Rusen; Fish, Vincent L.; Doeleman, Sheperd S.; Crew, Geoffrey; Cappallo, Roger J. [Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States); Akiyama, Kazunori; Honma, Mareki [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Algaba, Juan C.; Ho, Paul T. P.; Inoue, Makoto [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan, R.O.C. (China); Bower, Geoffrey C.; Dexter, Matt [Department of Astronomy, Radio Astronomy Laboratory, University of California Berkeley, 601 Campbell, Berkeley, CA 94720-3411 (United States); Brinkerink, Christiaan [Department of Astrophysics, IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Chamberlin, Richard [Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Freund, Robert [Arizona Radio Observatory, Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Friberg, Per [James Clerk Maxwell Telescope, Joint Astronomy Centre, 660 North A' ohoku Place, University Park, Hilo, HI 96720 (United States); Gurwell, Mark A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Jorstad, Svetlana G. [Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States); Krichbaum, Thomas P. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Loinard, Laurent, E-mail: [Centro de Radiostronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, 58089 Morelia, Michoacan (Mexico); and others


    We report results from five day very long baseline interferometry observations of the well-known quasar 3C 279 at 1.3 mm (230 GHz) in 2011. The measured nonzero closure phases on triangles including stations in Arizona, California, and Hawaii indicate that the source structure is spatially resolved. We find an unusual inner jet direction at scales of {approx}1 pc extending along the northwest-southeast direction (P.A. = 127 Degree-Sign {+-} 3 Degree-Sign ), as opposed to other (previously) reported measurements on scales of a few parsecs showing inner jet direction extending to the southwest. The 1.3 mm structure corresponds closely with that observed in the central region of quasi-simultaneous super-resolution Very Long Baseline Array images at 7 mm. The closure phase changed significantly on the last day when compared with the rest of observations, indicating that the inner jet structure may be variable on daily timescales. The observed new direction of the inner jet shows inconsistency with the prediction of a class of jet precession models. Our observations indicate a brightness temperature of {approx}8 Multiplication-Sign 10{sup 10} K in the 1.3 mm core, much lower than that at centimeter wavelengths. Observations with better uv coverage and sensitivity in the coming years will allow the discrimination between different structure models and will provide direct images of the inner regions of the jet with 20-30 {mu}as (5-7 light months) resolution.

  8. Milliarcsecond polarization structure of the superluminal quasar 3C 273

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, D.H.; Kollgaard, R.I.; Brown, L.F.; Gabuzda, D.C.; Wardle, J.F. C. (Brandeis Univ., Waltham, MA (USA))


    A 2 x 10 marcsec-resolution determination is presented for the total intensity and linear polarization structures of the superluminal quasar 3C 273 at 5 GHz. Substantial polarized flux was detected from several superluminal components of the jet, whose fractional polarization increased symmetrically with distance from the core; the most distant component is highly polarized and exhibits a highly ordered magnetic field. Within a few marcsec of the core, the inferred magnetic field orientation varies rapidly with position along the jet. The primarily longitudinal magnetic field orientation is concluded to become established within 20 marcsec of the core. A highly disorganized magnetic field is the most plausible explanation for the low degree of polarization in the innermost regions of the jet. 48 refs.

  9. MERLIN observations of the unusual superluminal quasar 3C395

    Energy Technology Data Exchange (ETDEWEB)

    Saikia, D.J. (Nuffield Radio Astronomy Labs., Jodrell Bank (UK) Tata Inst. of Fundamental Research, Poona Univ. Campus, Pune (India)); Muxlow, T.W.B. (Nuffield Radio Astronomy Labs., Jodrell Bank (UK)); Junor, W. (National Radio Astronomy Observatory, Socorro, NM (USA))


    We present MERLIN observations at 73, 18 and 6 cm of the quasar 3C395 (1901 + 319) which has a superluminal component moving towards a stationary knot located at a distance of 15.8 mas from the VLBI core. The observations help to clarify the radiostructure of 3C395 on scales ranging from a few tens to a few hundreds of milliarcsec. They show evidence of a highly curved jet-like structure extending beyond the stationary VLBI component. The radio images of 3C395 are consistent with a two-sided structure inclined at a small angle to the line-of-sight, with the approaching jet being decelerated and distorted within {approx} 15 mas of the nucleus. (author).

  10. Multifrequency observations of the superluminal quasar 3C 345 (United States)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Neugebauer, G.; Soifer, B. T.; Matthews, K.; Roellig, T. P. L.; Bregman, J. D.; Witteborn, F. C.; Lester, D. F.


    Attention is given to the continuum properties of the superluminal quasar 3C 345, on the basis of radio, optical, IR, and X-ray frequency monitorings, as well as by means of simultaneous multifrequency spectra extending from the radio through the X-ray bands. Radio outbursts, which appear to follow IR-optical outbursts by about one year, first occur at the highest frequencies, as expected from optical depth effects; the peak flux is nevertheless often reached at several frequencies at once. The beginning of outbursts, as defined by mm-measurements, corresponds to the appearance of the three known 'superluminal' components. An increase in the X-ray flux during 1979-1980 corresponds to increased radio flux, while the IR flux changes in the opposite sense.

  11. Highly accreting quasars: sample definition and possible cosmological implications (United States)

    Marziani, P.; Sulentic, J. W.


    We propose a method to identify quasars radiating closest to the Eddington limit, defining primary and secondary selection criteria in the optical, UV and X-ray spectral range based on the 4D eigenvector 1 formalism. We then show that it is possible to derive a redshift-independent estimate of luminosity for extreme Eddington ratio sources. Using preliminary samples of these sources in three redshift intervals (as well as two mock samples), we test a range of cosmological models. Results are consistent with concordance cosmology but the data are insufficient for deriving strong constraints. Mock samples indicate that application of the method proposed in this paper using dedicated observations would allow us to set stringent limits on ΩM and significant constraints on ΩΛ.

  12. ESO 113-IG45 galaxy and/or quasar?

    CERN Document Server

    West, R M; Danks, A C


    Spectroscopy, UBV photometry and photography have been obtained of the extraordinary 13th magnitude object ESO 113-IG45 identified as a Seyfert galaxy by Fairall (1977); R.A.=01/sup h/ 21/sup m/.9; Decl .=-59 degrees 04' (1950). V/sub 0/=13630+or-50 km s/sup -1/; M/sub V /=-24/sup m/.0; largest diameter 75 kpc or more (with H/sub 0/=55 km s /sup -1/ Mpc/sup -1/). The nucleus is stellar-like and several times more luminous than the surrounding envelope which has a well-developed lane-structure. It is the intrinsically most luminous Seyfert nuclear yet known, and may be described as a 'quasar in the center of a (spiral) galaxy'. It is probably associated with the X-ray source 2A0120-591. (14 refs).

  13. Are Quasar Jets Matter Or Poynting Flux Dominated?

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Marek; /Warsaw, Copernicus Astron. Ctr.; Madejski, Greg M.; /SLAC /KIPAC, Menlo Park; Lasota, Jean-Pierre; /Paris, Inst. Astrophys.; Begelman, Mitchell C.; /JILA,


    If quasar jets are accelerated by magnetic fields but terminate as matter dominated, where and how does the transition occur between the Poynting-dominated and matter-dominated regimes? To address this question, we study constraints which are imposed on the jet structure by observations at different spatial scales. We demonstrate that observational data are consistent with a scenario where the acceleration of a jet occurs within 10{sup 3-4}R{sub g}. In this picture, the non-thermal flares--important defining attributes of the blazar phenomenon--are produced by strong shocks formed in the region where the jet inertia becomes dominated by matter. Such shocks may be formed due to collisions between the portions of a jet accelerated to different velocities, and the acceleration differentiation is very likely to be related to global MHD instabilities.

  14. On the Gas Content and Efficiency of AGN Feedback in Low-redshift Quasars (United States)

    Shangguan, Jinyi; Ho, Luis C.; Xie, Yanxia


    The interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. However, direct gas measurements are limited by sensitivity and other uncertainties. Dust provides an efficient indirect probe of the total gas. We apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. We present a comprehensive study of the full (1 to 500 μm) infrared spectral energy distributions of 87 redshift early-type galaxies. This result indicates that “quasar mode” feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. We also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. This cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate.

  15. The intrinsic far-UV spectrum of the high-redshift quasar B1422+231 (United States)

    O'Dowd, M.; Bate, N. F.; Webster, R. L.; Labrie, K.; King, A. L.; Yong, S.-. Y.


    We present new spectroscopy of the z = 3.62 gravitationally lensed quasar B1422+117 from the Gemini North GMOS integral field spectrograph. We observe significant differential magnifications between the broad emission lines and the continuum, as well as across the velocity structure of the Lyman-α line. We take advantage of this differential microlensing to algebraically decompose the quasar spectrum into the absorbed broad emission line and absorbed continuum components. We use the latter to derive the intrinsic Ly α forest absorption spectrum. The proximity effect is clearly detected, with a proximity zone edge of 8.6-17.3 Mpc from the quasar, implying (perhaps intermittent) activity over at least 28 Myr. The Ly α line profile exhibits a blue excess that is inconsistent with a symmetric fit to the unabsorbed red side. This has important implications for the use of this fitting technique in estimating the absorbed blue Ly α wings of Gunn-Peterson trough quasars.

  16. Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe. (United States)

    Hennawi, Joseph F; Prochaska, J Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio


    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations. Copyright © 2015, American Association for the Advancement of Science.

  17. Probing the gravitational Faraday rotation using quasar X-ray microlensing. (United States)

    Chen, Bin


    The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission.

  18. A selective deficit in the appreciation and recognition of brightness: brightness agnosia?

    NARCIS (Netherlands)

    Nijboer, T.C.W.; Nys, G.M.S.; van der Smagt, M.J.; de Haan, E.H.F.


    We report a patient with extensive brain damage in the right hemisphere who demonstrated a severe impairment in the appreciation of brightness. Acuity, contrast sensitivity as well as luminance discrimination were normal, suggesting her brightness impairment is not a mere consequence of low-level

  19. Stellar Populations of Quasar Host Galaxies Using WIYN (United States)

    Mosby, Gregory; Moravec, E.; Kotulla, R. C.


    We now know that most galaxies have supermassive black holes (SMBH) in their centers, and somewhat unexpectedly, there are relationships—such as the M-sigma relation—between the mass of the central black hole and the velocity dispersion of the host galaxy's stellar spheroid (bulge), even though they lie outside the black hole's influence. Galaxy merger models show reasonable evidence for coevolution of the bulge and black hole since the merging process initiates simultaneous growth of the black hole and galaxy by supplying gas to the nucleus for accretion onto the black hole and triggering bursts of star formation. The merging process truncates the growth of both by removing the gas reservoir via feedback from these processes. But recently, it’s been shown that this relation could arise from central limit-like arguments alone. To really judge connections between SMBH and their host, it’s crucial to study these galaxies at the peak of black hole growth—during the quasar phase. Using 3-d spectroscopy methods, namely Sparsepak, an integral field units (IFU) on WIYN, it is possible to successfully recover information about the host galaxy's integrated star formation history that can be used to check merger-induced galaxy evolution predicted by the models. However, it is critical to have a robust and careful analysis of the stellar population modeling. The research presented in this poster focuses on new results from Sparsepak and preliminary WHIRC H-band light profiles of select quasar host galaxies. The stellar populations are derived using a new statistical method called diffusion k-means, and the WHIRC data are analyzed using a Python code written by Ralf Kotulla.

  20. A selective deficit in the appreciation and recognition of brightness: brightness agnosia? (United States)

    Nijboer, Tanja C W; Nys, Gudrun M S; van der Smagt, Maarten J; de Haan, Edward H F


    We report a patient with extensive brain damage in the right hemisphere who demonstrated a severe impairment in the appreciation of brightness. Acuity, contrast sensitivity as well as luminance discrimination were normal, suggesting her brightness impairment is not a mere consequence of low-level sensory impairments. The patient was not able to indicate the darker or the lighter of two grey squares, even though she was able to see that they differed. In addition, she could not indicate whether the lights in a room were switched on or off, nor was she able to differentiate between normal greyscale images and inverted greyscale images. As the patient recognised objects, colours, and shapes correctly, the impairment is specific for brightness. As low-level, sensory processing is normal, this specific deficit in the recognition and appreciation of brightness appears to be of a higher, cognitive level, the level of semantic knowledge. This appears to be the first report of 'brightness agnosia'.

  1. The Thermal Proximity Effect: A New Probe of the He II Reionization History and Quasar Lifetime (United States)

    Khrykin, I. S.; Hennawi, J. F.; McQuinn, M.


    Despite decades of effort, the timing and duration of He II reionization and the properties of the quasars believed to drive it are still not well constrained. We present a new method to study both via the thermal proximity effect—the heating of the intergalactic medium (IGM) around quasars when their radiation doubly ionizes helium. We post-process hydrodynamical simulations with 1D radiative transfer and study how the thermal proximity effect depends on the He II fraction, {x}{He{{II}},0}, which prevailed in the IGM before the quasar turned on, and the quasar lifetime {t}{{Q}}. We find that the amplitude of the temperature boost in the quasar environment depends on {x}{He{{II}},0}, with a characteristic value of {{Δ }}T≃ {10}4 {{K}} for {x}{He{{II}},0}=1.0, whereas the size of the thermal proximity zone is sensitive to {t}{{Q}}, with typical sizes of ≃ 100 {cMpc} for {t}{{Q}}={10}8 {yr}. This temperature boost increases the thermal broadening of H I absorption lines near the quasar. We introduce a new Bayesian statistical method based on measuring the Lyα forest power spectrum as a function of distance from the quasar, and demonstrate that the thermal proximity effect should be easily detectable. For a mock data set of 50 quasars at z≃ 4, we predict that one can measure {x}{He{{II}},0} to an (absolute) precision ≈ 0.04 and {t}{{Q}} to a precision of ≈ 0.1 dex. By applying our formalism to existing high-resolution Lyα forest spectra, one should be able to reconstruct the He II reionization history, providing a global census of hard photons in the high-z universe.

  2. GBT Detection of Polarization-Dependent HI Absorption and HI Outflows in Local ULIRGs and Quasars (United States)

    Teng, Stacy H.; Veilleux, Sylvain; Baker, Andrew J.


    We present the results of a 21-cm HI survey of 27 local massive gas-rich late-stage mergers and merger remnants with the Green Bank Telescope (GBT). These remnants were selected from the Quasar/ULIRG Evolution Study (QUEST) sample of ultraluminous infrared galaxies (ULIRGs; L(sub 8 - 1000 micron) > 10(exp 12) solar L) and quasars; our targets are all bolometrically dominated by active galactic nuclei (AGN) and sample the later phases of the proposed ULIRG-to-quasar evolutionary sequence. We find the prevalence of HI absorption (emission) to be 100% (29%) in ULIRGs with HI detections, 100% (88%) in FIR-strong quasars, and 63% (100%) in FIR-weak quasars. The absorption features are associated with powerful neutral outflows that change from being mainly driven by star formation in ULIRGs to being driven by the AGN in the quasars. These outflows have velocities that exceed 1500 km/s in some cases. Unexpectedly, we find polarization-dependent HI absorption in 57% of our spectra (88% and 63% of the FIR-strong and FIR-weak quasars, respectively). We attribute this result to absorption of polarized continuum emission from these sources by foreground HI clouds. About 60% of the quasars displaying polarized spectra are radio-loud, far higher than the approx 10% observed in the general AGN population. This discrepancy suggests that radio jets play an important role in shaping the environments in these galaxies. These systems may represent a transition phase in the evolution of gas-rich mergers into "mature" radio galaxies.

  3. High brightness semiconductor lasers with reduced filamentation

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter.; Skovgaard, Peter M. W.


    High brightness semiconductor lasers have applications in spectroscopy, fiber lasers, manufacturing and materials processing, medicine and free space communication or energy transfer. The main difficulty associated with high brightness is that, because of COD, high power requires a large aperture....... Large apertures result in high order transverse modes, filamentation and spatio-temporal instabilities, all of which degrade spatial coherence and therefore brightness. We shall describe a combined assault on three fronts: (1) minimise aperture size required for a given power by maximising the facet...... damage threshold, (2) for a given aperture, minimise self-focusing and filamentation by minimising the effective nonlinear coefficient (the alpha parameter), and (3) for a given aperture and nonlinear coefficient, develop optical cavities and propagation structures to suppress filamentation and high...

  4. On the Brightness of Supernova Ia

    CERN Document Server

    Zheng, Yijia


    Before 1998 the universe expansion was thought to be slowing down. After 1998 the universe expansion is thought to be accelerating up. The key evidence came from the observed brightness of high redshift supernovae Ia in 1998. Astronomers found that the observed brightness of high redshift supernovae Ia is fainter than expected. Astronomers believe this means that the universe expansion is accelerating up. In this paper it is argued that if the ionized gas in the universe space is taken into account, then the brightness of the high redshift supernova Ia should be fainter than expected. The universe expansion does not need to be accelerating up. The exotic form of energy (dark energy) does not need to be introduce

  5. Increasing the brightness of light sources

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Ling


    In this work the principle of light recycling is applied to artificial light sources in order to achieve brightness enhancement. Firstly, the feasibilities of increasing the brightness of light sources via light recycling are examined theoretically, based on the fundamental laws of thermodynamics including Kirchhoff's law on radiation, Planck's law, Lambert-Beer's law, the etendue conservation and the brightness theorem. From an experimental viewpoint, the radiation properties of three different kinds of light sources including short-arc lamps, incandescent lamps and LEDs characterized by their light-generating mechanisms are investigated. These three types of sources are used in light recycling experiments, for the purpose of 1. validating the intrinsic light recycling effect in light sources, e. g. the intrinsic light recycling effect in incandescent lamps stemming from the coiled filament structure. 2. acquiring the required parameters for establishing physical models, e.g. the emissivity/absorptivity of the short-arc lamps, the intrinsic reflectivity and the external quantum efficiency of LEDs. 3. laying the foundations for designing optics aimed at brightness enhancement according to the characteristics of the sources and applications. Based on the fundamental laws and experiments, two physical models for simulating the radiance distribution of light sources are established, one for thermal filament lamps, the other for luminescent sources, LEDs. As validation of the theoretical and experimental investigation of the light recycling effect, an optical device, the Carambola, is designed for achieving deterministic and multiple light recycling. The Carambola has the function of a concentrator. In order to achieve the maximum possible brightness enhancement with the Carambola, several combinations of sources and Carambolas are modelled in ray-tracing simulations. Sources with different light-emitting mechanisms and different radiation properties


    Energy Technology Data Exchange (ETDEWEB)

    De Diego, José A.; De Leo, Mario A.; Verdugo, Tomás [Instituto de Astronomía, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Ciudad Universitaria, C.P. 04510, Distrito Federal (Mexico); Polednikova, Jana; Bongiovanni, Angel; Pérez García, Ana M.; Cepa, Jordi, E-mail: [Instituto de Astrofísica de Canarias-Universidad de La Laguna (Spain)


    Microvariability consists of small timescale variations of low amplitude in the photometric light curves of quasars and represents an important tool to investigate their inner core. Detection of quasar microvariations is challenging because of their non-periodicity, as well as the need for high monitoring frequency and a high signal-to-noise ratio. Statistical tests developed for the analysis of quasar differential light curves usually show either low power or low reliability, or both. In this paper we compare two statistical procedures to perform tests on several stars with enhanced power and high reliability. We perform light curve simulations of variable quasars and non-variable stars and analyze them with statistical procedures developed from the F-test and the analysis of variance. The results show a large improvement in the power of both statistical probes and a larger reliability when several stars are included in the analysis. The results from the simulations agree with those obtained from observations of real quasars. The high power and high reliability of the tests discussed in this paper improve the results that can be obtained from short and long timescale variability studies. These techniques are not limited to quasar variability; on the contrary, they can be easily implemented for other sources, such as variable stars. Their applications to future research and to the analysis of large-field photometric monitoring archives could reveal new variable sources.

  7. The Sloan Digital Sky Survey Reverberation Mapping Project: Quasar Reverberation Mapping Studies (United States)

    Grier, Catherine; SDSS-RM Collaboration


    The Sloan Digital Sky Survey Reverberation Mapping Project (SDSS-RM) has completed its first three years of spectroscopic observations of a sample of ~850 quasars with the SDSS-III BOSS spectrograph. From January-July in 2014, 2015, and 2016, more than 55 epochs of spectroscopy were obtained for this quasar sample, and continued monitoring has been approved for 2017. Supporting photometric observations were also carried out at the Canada-France-Hawaii Telescope and the Steward Observatory Bok telescope. In addition, the SDSS-RM field overlaps with the Pan-STARRS 1 Medium Deep Field MD07, so we have photometric data for three years prior to the SDSS-RM observations, which considerably extends the time delay sensitivity of the campaign. Preliminary reverberation mapping results were presented by Shen et al. (2015) and the program has also yielded ancillary science results in regimes such as broad absorption line variability, quasar ensemble variability characteristics, quasar emission line studies, SDSS quasar redshift measurements, and host galaxy properties. I will discuss the current status of the SDSS-RM program, including recent reverberation mapping results from the wider 850-quasar sample using the full set of first-year photometric and spectroscopic data.

  8. Microwave brightness temperature imaging and dielectric properties ...

    Indian Academy of Sciences (India)

    material collected by former Soviet Union robots and Apollo astronauts. With the completion of the first round of lunar exploration by human beings, the study of lunar microwave brightness tempe- rature was completely forgotten. Accompanied by a new upcoming era of lunar exploration and the development of science and ...

  9. Dark matter in low surface brightness galaxies

    NARCIS (Netherlands)

    de Blok, WJG; McGaugh, SS; Persic, M; Salucci, P


    Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that LSB

  10. Robust fitting of diurnal brightness temperature cycle

    CSIR Research Space (South Africa)

    Udahemuka, G


    Full Text Available for a pixel concerned. Robust fitting of observed Diurnal Temperature Cycle (DTC) taken over a day of a given pixel without cloud cover and other abnormally conditions such as fire can give a data based brightness temperature model for a given pixel...

  11. Simultaneous brightness contrast of foraging Papilio butterflies (United States)

    Kinoshita, Michiyo; Takahashi, Yuki; Arikawa, Kentaro


    This study focuses on the sense of brightness in the foraging Japanese yellow swallowtail butterfly, Papilio xuthus. We presented two red discs of different intensity on a grey background to butterflies, and trained them to select one of the discs. They were successfully trained to select either a high intensity or a low intensity disc. The trained butterflies were tested on their ability to perceive brightness in two different protocols: (i) two orange discs of different intensity presented on the same intensity grey background and (ii) two orange discs of the same intensity separately presented on a grey background that was either higher or lower in intensity than the training background. The butterflies trained to high intensity red selected the orange disc of high intensity in protocol 1, and the disc on the background of low intensity grey in protocol 2. We obtained similar results in another set of experiments with purple discs instead of orange discs. The choices of the butterflies trained to low intensity red were opposite to those just described. Taken together, we conclude that Papilio has the ability to learn brightness and darkness of targets independent of colour, and that they have the so-called simultaneous brightness contrast. PMID:22179808

  12. Microwave brightness temperature imaging and dielectric properties ...

    Indian Academy of Sciences (India)

    In this paper,we give a rough analysis of the microwave brightness temperature images of the lunar disc observed using the NRAO 12 meter Telescope and Siberian Solar Radio Telescope.We also ... Center for Space Science and Applied Research, Chinese Academy of Sciences, P.O. Box 8701, Beijing 100 080, China.

  13. Dark Matter in Low Surface Brightness Galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; McGaugh, S. S.


    Abstract: Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that

  14. The nature of solar brightness variations (United States)

    Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Cameron, R. H.; Yeo, K. L.; Schmutz, W. K.


    Determining the sources of solar brightness variations1,2, often referred to as solar noise3, is important because solar noise limits the detection of solar oscillations3, is one of the drivers of the Earth's climate system4,5 and is a prototype of stellar variability6,7—an important limiting factor for the detection of extrasolar planets. Here, we model the magnetic contribution to solar brightness variability using high-cadence8,9 observations from the Solar Dynamics Observatory (SDO) and the Spectral And Total Irradiance REconstruction (SATIRE)10,11 model. The brightness variations caused by the constantly evolving cellular granulation pattern on the solar surface were computed with the Max Planck Institute for Solar System Research (MPS)/University of Chicago Radiative Magnetohydrodynamics (MURaM)12 code. We found that the surface magnetic field and granulation can together precisely explain solar noise (that is, solar variability excluding oscillations) on timescales from minutes to decades, accounting for all timescales that have so far been resolved or covered by irradiance measurements. We demonstrate that no other sources of variability are required to explain the data. Recent measurements of Sun-like stars by the COnvection ROtation and planetary Transits (CoRoT)13 and Kepler14 missions uncovered brightness variations similar to that of the Sun, but with a much wider variety of patterns15. Our finding that solar brightness variations can be replicated in detail with just two well-known sources will greatly simplify future modelling of existing CoRoT and Kepler as well as anticipated Transiting Exoplanet Survey Satellite16 and PLAnetary Transits and Oscillations of stars (PLATO)17 data.

  15. AGN feedback on molecular gas reservoirs in quasars at z 2.4 (United States)

    Carniani, S.; Marconi, A.; Maiolino, R.; Feruglio, C.; Brusa, M.; Cresci, G.; Cano-Díaz, M.; Cicone, C.; Balmaverde, B.; Fiore, F.; Ferrara, A.; Gallerani, S.; La Franca, F.; Mainieri, V.; Mannucci, F.; Netzer, H.; Piconcelli, E.; Sani, E.; Schneider, R.; Shemmer, O.; Testi, L.


    We present new ALMA observations aimed at mapping molecular gas reservoirs through the CO(3-2) transition in three quasars at z ≃ 2.4, LBQS 0109+0213, 2QZ J002830.4-281706, and [HB89] 0329-385. Previous [Oiii]λ5007 observations of these quasars showed evidence for ionised outflows quenching star formation in their host galaxies. Systemic CO(3-2) emission has been detected only in one quasar, LBQS 0109+0213, where the CO(3-2) emission is spatially anti-correlated with the ionised outflow, suggesting that most of the molecular gas may have been dispersed or heated in the region swept by the outflow. In all three sources, including the one detected in CO, our constraints on the molecular gas mass indicate a significantly reduced reservoir compared to main-sequence galaxies at the same redshift, supporting a negative feedback scenario. In the quasar 2QZ J002830.4-281706, we tentatively detect an emission line blob blue-shifted by v - 2000 km s-1 with respect to the galaxy systemic velocity and spatially offset by 0.2'' (1.7 kpc) with respect to the ALMA continuum peak. Interestingly, such emission feature is coincident in both velocity and space with the ionised outflow as seen in [Oiii]λ5007. This tentative detection must be confirmed with deeper observations but, if real, it could represent the molecular counterpart of the ionised gas outflow driven by the Active Galactic Nucleus (AGN). Finally, in all ALMA maps we detect the presence of serendipitous line emitters within a projected distance 160 kpc from the quasars. By identifying these features with the CO(3-2) transition, we find that the serendipitous line emitters would be located within | Δv | < 500 km s-1 from the quasars, hence suggesting an overdensity of galaxies in two out of three quasars.

  16. Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745* (United States)

    Sharon, Keren; Bayliss, Matthew B.; Dahle, Hakon; Florian, Michael K.; Gladders, Michael D.; Johnson, Traci L.; Paterno-Mahler, Rachel; Rigby, Jane R.; Whitaker, Katherine E.; Wuyts, Eva


    SDSS J2222+2745 is a galaxy cluster at z = 0.49, strongly lensing a quasar at z = 2.805 into six widely separated images. In recent Hubble Space Telescope imaging of the field, we identify additional multiply lensed galaxies and confirm the sixth quasar image that was identified by Dahle et al. We used the Gemini-North telescope to measure a spectroscopic redshift of z = 4.56 of one of the lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a lensed galaxy at z = 2.3. This galaxy also appears in absorption in our Gemini spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is in agreement with the recent time delay measurements of Dahle et al., who found T(sub AB) = 47.7 +/- 6.0 days and T(sub AC) = 722 +/- 24 days. We use the observed time delays to further constrain the model, and find that the model-predicted time delays of the three faint images of the quasar are T(sub AD) = 502+/- 68 days, T( sub AE) = 611 +/- 75 days, and T(sub AF) = 415 +/- 72 days. We have initiated a follow-up campaign to measure these time delays with Gemini North. Finally, we present initial results from an X-ray monitoring program with Swift, indicating the presence of hard X-ray emission from the lensed quasar, as well as extended X-ray emission from the cluster itself, which is consistent with the lensing mass measurement and the cluster velocity dispersion.

  17. The large-scale quasar-Lyman α forest cross-correlation from BOSS

    Energy Technology Data Exchange (ETDEWEB)

    Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Arnau, Eduard [Institut de Ciències del Cosmos (IEEC/UB), Martí i Franquès 1, 08028 Barcelona, Catalonia (Spain); Miralda-Escudé, Jordi, E-mail:, E-mail:, E-mail: [Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Catalonia (Spain); and others


    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption in redshift space, using ∼ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 h{sup −1}Mpc. For r > 15 h{sup −1}Mpc, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence. Using previous determinations of the Lyα forest bias factor obtained from the Lyα autocorrelation, we infer the quasar bias factor to be b{sub q} = 3.64{sup +0.13}{sub −0.15} at a mean redshift z = 2.38, in agreement with previous measurements from the quasar auto-correlation. We also obtain a new estimate of the Lyα forest redshift distortion factor, β{sub F} = 1.1±0.15, slightly larger than but consistent with the previous measurement from the Lyα forest autocorrelation. The simple linear model we use fails at separations r < 15h{sup −1}Mpc, and we show that this may reasonably be due to the enhanced ionization due to radiation from the quasars. We also provide the expected correction that the mass overdensity around the quasar implies for measurements of the ionizing radiation background from the line-of-sight proximity effect.

  18. The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines (United States)

    Sun, Mouyuan; Trump, Jonathan R.; Shen, Yue; Brandt, W. N.; Dawson, Kyle; Denney, Kelly D.; Hall, Patrick B.; Ho, Luis C.; Horne, Keith; Jiang, Linhua; Richards, Gordon T.; Schneider, Donald P.; Bizyaev, Dmitry; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey


    We explore the variability of quasars in the Mg ii and {{H}}β broad emission lines and ultraviolet/optical continuum emission using the Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic study of quasar variability to date: our study includes 29 spectroscopic epochs from SDSS-RM over 6 months, containing 357 quasars with Mg ii and 41 quasars with {{H}}β . On longer timescales, the study is also supplemented with two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional 2854 quasars with Mg ii and 572 quasars with {{H}}β . The Mg ii emission line is significantly variable ({{Δ }}f/f∼ 10% on ∼100-day timescales), a necessary prerequisite for its use for reverberation mapping studies. The data also confirm that continuum variability increases with timescale and decreases with luminosity, and the continuum light curves are consistent with a damped random-walk model on rest-frame timescales of ≳ 5 days. We compare the emission-line and continuum variability to investigate the structure of the broad-line region. Broad-line variability shows a shallower increase with timescale compared to the continuum emission, demonstrating that the broad-line transfer function is not a δ-function. {{H}}β is more variable than Mg ii (roughly by a factor of ∼1.5), suggesting different excitation mechanisms, optical depths and/or geometrical configuration for each emission line. The ensemble spectroscopic variability measurements enabled by the SDSS-RM project have important consequences for future studies of reverberation mapping and black hole mass estimation of 1\\lt z\\lt 2 quasars.

  19. Simple Stellar Population Modeling of Quasar Host Galaxies with Diffusion K-Means Test Results (United States)

    Mosby, Gregory; Moravec, E. A.; Tremonti, C. A.; Wolf, M. J.


    In the last decade, the correlation of the masses of supermassive black holes (SMBHs) and their host galaxy stellar spheroid velocity dispersions (the M-sigma relation) was greeted as clear evidence for the co-evolution of host galaxies and their SMBHs. However, studies in the last five years have posited that this relation could arise from central-limit properties of hierarchical formation alone. To address the question of whether and how often the SMBHs evolve with their host galaxies, it is necessary to look at galaxies whose SMBHs are actively growing—quasars—and determine the host galaxy properties. The central nuclei of quasar host galaxies complicate this type of study because their high luminosity tends to wash out their host galaxies. But, by using 3-D spectroscopy with the integral field unit (IFU) Sparsepak on the WIYN telescope, we have shown that the quasar light can be mostly isolated to one fiber in order to obtain the spectra of the quasar and the host galaxy concurrently. We can then model simultaneously the scattered quasar light and the stellar populations in the host galaxy fiber using a new simple stellar population (SSP) modeling method called diffusion k-means (DFK). The objectives of the research presented in this poster are to model synthetic quasar host galaxies using a DFK basis and a more traditional basis, compare the accuracy of both modeling methods, and test the affects of various prescriptions for masking the quasar lines in the host galaxy fiber. We present results from our SSP modeling and Markov Chain Monte Carlo (MCMC) results for DFK and traditional modeling schemes using synthetic data. By determining and then using the more robust stellar population modeling method, we can more confidently study quasar host galaxies to answer remaining questions in galaxy evolution. This work was partially supported by a National Science Foundation Graduate Fellowship (NSF Grant DGE-0718123) and through the NSF's REU program (NSF Award

  20. A search for distant radio-loud quasars in the CLASS survey : three new radio-selected quasars at z > 4

    NARCIS (Netherlands)

    Snellen, IAG; McMahon, RG; Dennett-Thorpe, J; Jackson, N; Mack, KH; Xanthopoulos, E


    We report on the search for distant radio-loud quasars in the Cosmic Lens All Sky Survey (CLASS) of flat spectrum radio sources with S-5GHz > 30 mJy. Unresolved optical counterparts were selected from APM scans of POSS-I plates, with e <19.0 and red o - e > 2.0 colours, in an effective area of

  1. Intermittent Episodes of Bright Light Suppress Myopia in the Chicken More than Continuous Bright Light (United States)

    Lan, Weizhong; Feldkaemper, Marita; Schaeffel, Frank


    Purpose Bright light has been shown a powerful inhibitor of myopia development in animal models. We studied which temporal patterns of bright light are the most potent in suppressing deprivation myopia in chickens. Methods Eight-day-old chickens wore diffusers over one eye to induce deprivation myopia. A reference group (n = 8) was kept under office-like illuminance (500 lux) at a 10∶14 light∶dark cycle. Episodes of bright light (15 000 lux) were super-imposed on this background as follows. Paradigm I: exposure to constant bright light for either 1 hour (n = 5), 2 hours (n = 5), 5 hours (n = 4) or 10 hours (n = 4). Paradigm II: exposure to repeated cycles of bright light with 50% duty cycle and either 60 minutes (n = 7), 30 minutes (n = 8), 15 minutes (n = 6), 7 minutes (n = 7) or 1 minute (n = 7) periods, provided for 10 hours. Refraction and axial length were measured prior to and immediately after the 5-day experiment. Relative changes were analyzed by paired t-tests, and differences among groups were tested by one-way ANOVA. Results Compared with the reference group, exposure to continuous bright light for 1 or 2 hours every day had no significant protective effect against deprivation myopia. Inhibition of myopia became significant after 5 hours of bright light exposure but extending the duration to 10 hours did not offer an additional benefit. In comparison, repeated cycles of 1∶1 or 7∶7 minutes of bright light enhanced the protective effect against myopia and could fully suppress its development. Conclusions The protective effect of bright light depends on the exposure duration and, to the intermittent form, the frequency cycle. Compared to the saturation effect of continuous bright light, low frequency cycles of bright light (1∶1 min) provided the strongest inhibition effect. However, our quantitative results probably might not be directly translated into humans, but rather need further amendments in clinical

  2. Circadian Phase-Shifting Effects of Bright Light, Exercise, and Bright Light + Exercise. (United States)

    Youngstedt, Shawn D; Kline, Christopher E; Elliott, Jeffrey A; Zielinski, Mark R; Devlin, Tina M; Moore, Teresa A


    Limited research has compared the circadian phase-shifting effects of bright light and exercise and additive effects of these stimuli. The aim of this study was to compare the phase-delaying effects of late night bright light, late night exercise, and late evening bright light followed by early morning exercise. In a within-subjects, counterbalanced design, 6 young adults completed each of three 2.5-day protocols. Participants followed a 3-h ultra-short sleep-wake cycle, involving wakefulness in dim light for 2h, followed by attempted sleep in darkness for 1 h, repeated throughout each protocol. On night 2 of each protocol, participants received either (1) bright light alone (5,000 lux) from 2210-2340 h, (2) treadmill exercise alone from 2210-2340 h, or (3) bright light (2210-2340 h) followed by exercise from 0410-0540 h. Urine was collected every 90 min. Shifts in the 6-sulphatoxymelatonin (aMT6s) cosine acrophase from baseline to post-treatment were compared between treatments. Analyses revealed a significant additive phase-delaying effect of bright light + exercise (80.8 ± 11.6 [SD] min) compared with exercise alone (47.3 ± 21.6 min), and a similar phase delay following bright light alone (56.6 ± 15.2 min) and exercise alone administered for the same duration and at the same time of night. Thus, the data suggest that late night bright light followed by early morning exercise can have an additive circadian phase-shifting effect.

  3. Optical Variability Properties of High Luminosity AGN Classes

    Indian Academy of Sciences (India)

    INOV) characteristics of radio-loud and radio-quiet quasars, which involves a systematic intra-night optical monitoring of seven sets of high luminosity AGNs covering the redshift range ≃ 0.2 to ≃ 2.2. The sample, matched in the optical ...

  4. The High AV Quasar Survey: A z = 2.027 metal-rich damped Lyman-α absorber towards a red quasar at z = 3.21 (United States)

    Fynbo, J. P. U.; Krogager, J.-K.; Heintz, K. E.; Geier, S.; Møller, P.; Noterdaeme, P.; Christensen, L.; Ledoux, C.; Jakobsson, P.


    It is important to understand the selection effects behind the quasar samples to fully exploit the potential of quasars as probes of cosmic chemical evolution and the internal gas dynamics of galaxies; in particular, it is vital to understand whether the selection criteria exclude foreground galaxies with certain properties, most importantly a high dust content. Here we present spectroscopic follow-up from the 10.4 m GTC telescope of a dust-reddened quasar, eHAQ0111+0641, from the extended High AV Quasar (HAQ) survey. We find that the z = 3.21 quasar has a foreground damped Lyman-α absorber (DLA) at z = 2.027 along the line of sight. The DLA has very strong metal lines due to a moderately high metallicity with an inferred lower limit of 25% of the solar metallicity, but a very large gas column density along the line of sight in its host galaxy. This discovery is further evidence that there is a dust bias affecting the census of metals, caused by the combined effect of dust obscuration and reddening, in existing samples of z > 2 DLAs. The case of eHAQ0111+0641 illustrates that dust bias is not only caused by dust obscuration, but also dust reddening. The reduced spectrum (FITS file) is only available at the CDS via anonymous ftp to ( or via

  5. HE0359-3959: An Extremely Radiating Quasar

    Directory of Open Access Journals (Sweden)

    M. L. Martínez-Aldama


    Full Text Available We present a multiwavelength spectral study of the quasar HE0359-3959, which has been identified as an extreme radiating source at intermediate redshift (z = 1.5209. Along the spectral range, the different ionic species give information about the substructures in the broad line region. The presence of a powerful outflow with an extreme blueshifted velocity of ~–6,000 ± 500 km s−1 is shown in the Civλ1549 emission line. A prominent blueshifted component is also associated with the 1900Å blend, resembling the one observed in Civλ1549. We detect a strong contribution of very the low–ionization lines, Feii and Near-Infrared Ca ii triplet. We find that the physical conditions for the low, intermediate, and high–ionization emission lines are different, which indicate that the emission lines are emitted in different zones of the broad line region. The asymmetries shown by the profiles reveal different forces over emitter zones. The high–ionization region is strongly dominated by radiation forces, which also affect the low and intermediate–ionization emitter region, commonly governed by virial motions. These results support the idea that highly radiating sources host a slim disk.

  6. Implications of the enthalpy flux carried by powerful quasar jets (United States)

    Schwartz, Daniel; Marshall, Herman L.; Worrall, Diana; Birkinshaw, Mark; Perlman, Eric; Lovell, James; Jauncey, David; Murphy, David; Gelbord, Jonathan; Godfrey, Leith; Bicknell, Geoffrey Vincent


    We have detected 31 X-ray jets as counterparts to radio jets observed in a survey of 54 quasars (Marshall et al., 2005; 2011). With the most likely interpretation that the X-rays result from inverse Compton boosting of the cosmic microwave background photons, one can estimate the rest frame magnetic field strength, and the particle energy density via the minimum total energy assumption. To reconcile these quantities so that the same spectrum of electrons produces the GHz radio synchrotron emission and its extension to lower energy produces the X-ray, the jets must be in relativistic motion. Another approximation, for example that the bulk Lorentz factor of the jet equals the Doppler factor, is needed to estimate the Lorentz factor. That cannot becorrect for individual jets, but for the ensemble of 31 objects it results in reasonable estimates for the angle of the jet to the line of sight. We can then calculate the enthalpy flux of these jets, which are typically (5--10) x 10^46 erg/s if protons balance the electron charge, and about 5 times smaller if the jets contain only electronsand positrons. Either case represents a signficant, and sometimes dominant, portion of the Eddington luminosity of the black hole.

  7. Probing the Intergalactic Medium with high-redshift quasars (United States)

    Calverley, Alexander Peter


    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

  8. Accurate spectroscopic redshift of the multiply lensed quasar PSOJ0147 from the Pan-STARRS survey (United States)

    Lee, C.-H.


    Context. The gravitational lensing time delay method provides a one-step determination of the Hubble constant (H0) with an uncertainty level on par with the cosmic distance ladder method. However, to further investigate the nature of the dark energy, a H0 estimate down to 1% level is greatly needed. This requires dozens of strongly lensed quasars that are yet to be delivered by ongoing and forthcoming all-sky surveys. Aims: In this work we aim to determine the spectroscopic redshift of PSOJ0147, the first strongly lensed quasar candidate found in the Pan-STARRS survey. The main goal of our work is to derive an accurate redshift estimate of the background quasar for cosmography. Methods: To obtain timely spectroscopically follow-up, we took advantage of the fast-track service programme that is carried out by the Nordic Optical Telescope. Using a grism covering 3200-9600 Å, we identified prominent emission line features, such as Lyα, N V, O I, C II, Si IV, C IV, and [C III] in the spectra of the background quasar of the PSOJ0147 lens system. This enables us to determine accurately the redshift of the background quasar. Results: The spectrum of the background quasar exhibits prominent absorption features bluewards of the strong emission lines, such as Lyα, N V, and C IV. These blue absorption lines indicate that the background source is a broad absorption line (BAL) quasar. Unfortunately, the BAL features hamper an accurate determination of redshift using the above-mentioned strong emission lines. Nevertheless, we are able to determine a redshift of 2.341 ± 0.001 from three of the four lensed quasar images with the clean forbidden line [C III]. In addition, we also derive a maximum outflow velocity of 9800 km s-1 with the broad absorption features bluewards of the C IV emission line. This value of maximum outflow velocity is in good agreement with other BAL quasars.

  9. Human CD56bright NK Cells

    DEFF Research Database (Denmark)

    Michel, Tatiana; Poli, Aurélie; Cuapio, Angelica


    Human NK cells can be subdivided into various subsets based on the relative expression of CD16 and CD56. In particular, CD56(bright)CD16(-/dim) NK cells are the focus of interest. They are considered efficient cytokine producers endowed with immunoregulatory properties, but they can also become...... cytotoxic upon appropriate activation. These cells were shown to play a role in different disease states, such as cancer, autoimmunity, neuroinflammation, and infection. Although their phenotype and functional properties are well known and have been extensively studied, their lineage relationship with other...... NK cell subsets is not fully defined, nor is their precise hematopoietic origin. In this article, we summarize recent studies about CD56(bright) NK cells in health and disease and briefly discuss the current controversies surrounding them....

  10. The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars (United States)

    Sherwin, Blake D; Das, Sudeep; Haijian, Amir; Addison, Graeme; Bond, Richard; Crichton, Devin; Devlin, Mark J.; Dunkley, Joanna; Gralla, Megan B.; Halpern, Mark; hide


    We measure the cross-correlation of Atacama cosmology telescope cosmic microwave background (CMB) lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing quasar cross-power spectrum is detected for the first time at a significance of 3.8 sigma, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z > 1. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift z ap 1.4, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of b = 2.5 +/- 0.6. With the signal-to-noise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing crosscorrelations to probe astrophysics at high redshifts.

  11. Five New High-Redshift Quasar Lenses from the Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Inada, Naohisa; Oguri, Masamune; Shin, Min-Su; Kayo, Issha; Strauss, Michael A.; Morokuma, Tomoki; Schneider, Donald P.; Becker, Robert H.; Bahcall, Neta A.; York, Donald G.


    We report the discovery of five gravitationally lensed quasars from the Sloan Digital Sky Survey (SDSS). All five systems are selected as two-image lensed quasar candidates from a sample of high-redshift (z > 2.2) SDSS quasars. We confirmed their lensing nature with additional imaging and spectroscopic observations. The new systems are SDSS J0819+5356 (source redshift z{sub s} = 2.237, lens redshift z{sub l} = 0.294, and image separation {theta} = 4.04 inch), SDSS J1254+2235 (z{sub s} = 3.626, {theta} = 1.56 inch), SDSS J1258+1657 (z{sub s} = 2.702, {theta} = 1.28 inch), SDSS J1339+1310 (z{sub s} = 2.243, {theta} = 1.69 cin), and SDSS J1400+3134 (z{sub s} = 3.317, {theta} = 1.74 inch). We estimate the lens redshifts of the latter four systems to be z{sub l} = 0.4-0.6 from the colors and magnitudes of the lensing galaxies. We find that the image configurations of all systems are well reproduced by standard mass models. Although these lenses will not be included in our statistical sample of z{sub s} < 2.2 lenses, they expand the number of lensed quasars which can be used for high-redshift galaxy and quasar studies.

  12. Polarization of the changing-look quasar J1011+5442 (United States)

    Hutsemékers, D.; Agís González, B.; Sluse, D.; Ramos Almeida, C.; Acosta Pulido, J.-A.


    If the disappearance of the broad emission lines observed in changing-look quasars were caused by the obscuration of the quasar core through moving dust clouds in the torus, high linear polarization typical of type 2 quasars would be expected. We measured the polarization of the changing-look quasar J1011+5442 in which the broad emission lines have disappeared between 2003 and 2015. We found a polarization degree compatible with null polarization. This measurement suggests that the observed change of look is not due to a change of obscuration hiding the continuum source and the broad line region, and that the quasar is seen close to the system axis. Our results thus support the idea that the vanishing of the broad emission lines in J1011+5442 is due to an intrinsic dimming of the ionizing continuum source that is most likely caused by a rapid decrease in the rate of accretion onto the supermassive black hole. Based on observations made with the William Herschel telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  13. Understanding extreme quasar optical variability with CRTS - I. Major AGN flares (United States)

    Graham, Matthew J.; Djorgovski, S. G.; Drake, Andrew J.; Stern, Daniel; Mahabal, Ashish A.; Glikman, Eilat; Larson, Steve; Christensen, Eric


    There is a large degree of variety in the optical variability of quasars and it is unclear whether this is all attributable to a single (set of) physical mechanism(s). We present the results of a systematic search for major flares in active galactic nucleus (AGN) in the Catalina Real-time Transient Survey as part of a broader study into extreme quasar variability. Such flares are defined in a quantitative manner as being atop of the normal, stochastic variability of quasars. We have identified 51 events from over 900 000 known quasars and high-probability quasar candidates, typically lasting 900 d and with a median peak amplitude of Δm = 1.25 mag. Characterizing the flare profile with a Weibull distribution, we find that nine of the sources are well described by a single-point single-lens model. This supports the proposal by Lawrence et al. that microlensing is a plausible physical mechanism for extreme variability. However, we attribute the majority of our events to explosive stellar-related activity in the accretion disc: superluminous supernovae, tidal disruption events and mergers of stellar mass black holes.

  14. Companions of Bright Barred Shapley Ames Galaxies


    Garcia-Barreto, J. Antonio; Carrillo, Rene; Vera-Villamizar, Nelson


    Companion galaxy environment for a subset of 78 bright and nearby barred galaxies from the Shapley Ames Catalog is presented. Among spiral barred galaxies there are Seyfert galaxies, galaxies with circumnuclear structures, galaxies not associated with any large scale galaxy cloud structure, galaxies with peculiar disk morphology (crooked arms) and galaxies with normal disk morphology; the list includes all Hubble types. The companion galaxy list includes number of companion galaxies within 20...

  15. Modular Zero Energy. BrightBuilt Home

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, Robb [Steven Winter Associates, Inc., Norwalk, CT (United States); Butterfield, Karla [Steven Winter Associates, Inc., Norwalk, CT (United States)


    With funding from the Building America Program, part of the U.S. Department of Energy Building Technologies Office, the Consortium for Advanced Residential Buildings (CARB) worked with BrightBuilt Home (BBH) to evaluate and optimize building systems. CARB’s work focused on a home built by Black Bros. Builders in Lincolnville, Maine (International Energy Conservation Code Climate Zone 6). As with most BBH projects to date, modular boxes were built by Keiser Homes in Oxford, Maine.

  16. Gemini long-slit observations of luminous obscured quasars: Further evidence for an upper limit on the size of the narrow-line region

    Energy Technology Data Exchange (ETDEWEB)

    Hainline, Kevin N.; Hickox, Ryan C. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Zakamska, Nadia L.; Liu, Guilin [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 (United States); Liu, Xin [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)


    We examine the spatial extent of the narrow-line regions (NLRs) of a sample of 30 luminous obscured quasars at 0.4 < z < 0.7 observed with spatially resolved Gemini-N GMOS long-slit spectroscopy. Using the [O III] λ5007 emission feature, we estimate the size of the NLR using a cosmology-independent measurement: the radius where the surface brightness falls to 10{sup –15} erg s{sup –1} cm{sup –2} arcsec{sup –2}. We then explore the effects of atmospheric seeing on NLR size measurements and conclude that direct measurements of the NLR size from observed profiles are too large by 0.1-0.2 dex on average, as compared to measurements made to best-fit Sérsic or Voigt profiles convolved with the seeing. These data, which span a full order of magnitude in IR luminosity (log (L {sub 8} {sub μm}/erg s{sup –1}) = 44.4-45.4), also provide strong evidence that there is a flattening of the relationship between NLR size and active galactic nucleus luminosity at a seeing-corrected size of ∼7 kpc. The objects in this sample have high luminosities which place them in a previously under-explored portion of the size-luminosity relationship. These results support the existence of a maximal size of the NLR around luminous quasars; beyond this size, there is either not enough gas or the gas is over-ionized and does not produce enough [O III] λ5007 emission.

  17. A long-term study of AGN X-ray variability . Structure function analysis on a ROSAT-XMM quasar sample (United States)

    Middei, R.; Vagnetti, F.; Bianchi, S.; La Franca, F.; Paolillo, M.; Ursini, F.


    Context. Variability in the X-rays is a key ingredient in understanding and unveiling active galactic nuclei (AGN) properties. In this band, flux variations occur on short timescales (hours) as well as on larger timescales. While short timescale variability is often investigated in single source studies, only a few works are able to explore flux variation on very long timescales. Aims: This work aims to provide a statistical analysis of the AGN long term X-ray variability. We study variability on the largest time interval ever investigated for the 0.2-2 keV band, up to approximately 20 yr rest-frame for a sample of 220 sources. Moreover, we study variability for 2700 quasars up to approximatley eight years rest-frame in the same (soft) band. Methods: We built our source sample using the 3XMM serendipitous source catalogue data release 5, and data from ROSAT All Sky Survey Bright and Faint source catalogues. To ensure that we selected AGN only, we used the Sloan Digital Sky Survey quasar catalogues data releases 7 and 12. Combining ROSAT and XMM-Newton observations, we investigated variability using the structure function analysis which describes the amount of variability as a function of the lag between the observations. Results: Our work shows an increase of the structure function up to 20 yr. We find no evidence of a plateau in the structure function on these long timescales. Conclusions: The increase of the structure function at long time lags suggests that variability in the soft X-rays can be influenced by flux variations originated in the accretion disk or that they take place in a region large enough to justify variation on such long timescales.


    National Aeronautics and Space Administration — The TC4 AMPR Brightness Temperature (TB) dataset consists of brightness temperature data from July 19, 2007 through August 8, 2007. The Tropical Composition, Cloud...

  19. Brightness illusion in the guppy (Poecilia reticulata). (United States)

    Agrillo, Christian; Miletto Petrazzini, Maria Elena; Bisazza, Angelo


    A long-standing debate surrounds the issue of whether human and nonhuman species share similar perceptual mechanisms. One experimental strategy to compare visual perception of vertebrates consists in assessing how animals react in the presence of visual illusions. To date, this methodological approach has been widely used with mammals and birds, while few studies have been reported in distantly related species, such as fish. In the present study we investigated whether fish perceive the brightness illusion, a well-known illusion occurring when 2 objects, identical in physical features, appear to be different in brightness. Twelve guppies (Poecilia reticulata) were initially trained to discriminate which rectangle was darker or lighter between 2 otherwise identical rectangles. Three different conditions were set up: neutral condition between rectangle and background (same background used for both darker and lighter rectangle); congruent condition (darker rectangle in a darker background and lighter rectangle in a lighter background); and incongruent condition (darker rectangle in a lighter background and lighter rectangle in a darker background). After reaching the learning criterion, guppies were presented with the illusory pattern: 2 identical rectangles inserted in 2 different backgrounds. Guppies previously trained to select the darker rectangle showed a significant choice of the rectangle that appears to be darker by human observers (and vice versa). The human-like performance exhibited in the presence of the illusory pattern suggests the existence of similar perceptual mechanisms between humans and fish to elaborate the brightness of objects. (c) 2016 APA, all rights reserved).

  20. The QUASAR reproducibility study, Part II: Results from a multi-center Arterial Spin Labeling test-retest study

    DEFF Research Database (Denmark)

    Petersen, Esben Thade; Mouridsen, Kim; Golay, Xavier


    Quantitative STAR labeling of Arterial Regions or QUASAR), a method providing user independent quantification of CBF in a large test-retest study across sites from around the world, dubbed "The QUASAR reproducibility study". Altogether, 28 sites located in Asia, Europe and North America participated...

  1. Weak Hard X-Ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-Ray Weakness

    DEFF Research Database (Denmark)

    Luo, B.; Brandt, W. N.; Alexander, D. M.


    We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z 330 times weaker than...... expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL...... quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with ≲ 45 counts in the 3-24 keV band, and the other three...

  2. Peering through the dust: NuSTAR observations of two first-2MASS red quasars

    DEFF Research Database (Denmark)

    LaMassa, Stephanie M.; Ricarte, Angelo; Glikman, Eilat


    Some reddened quasars appear to be transitional objects in the paradigm of merger-induced black hole growth/galaxy evolution, where a heavily obscured nucleus starts to be unveiled by powerful quasar winds evacuating the surrounding cocoon of dust and gas. Hard X-ray observations are able to peer...

  3. Catalog of 3 < z < 5.5 Quasar Candidates Selected among XMM-Newton Sources and Its Spectroscopic Verification

    Directory of Open Access Journals (Sweden)

    Georgii Khorunzhev


    Full Text Available We have compiled a catalog of 903 quasar candidates (including known quasars at 3 < z < 5.5 selected among X-ray sources from the XMM-Newton serendipitous survey (3XMM-DR4 catalog. We used photometric SDSS, 2MASS, and WISE data to select the objects. The surface number density of objects in our sample exceeds that in the SDSS spectroscopic quasar sample at the same redshifts by a factor of 1.5. We have performed spectroscopic observations of a subsample of new quasar candidates using a new low- and medium-resolution spectrograph at the 1.6-m AZT-33IK telescope (Mondy, Russia and demonstrated that the purity of these candidates is about 65%. We have discovered one of the most distant (z = 5.08 X-ray selected quasars.

  4. 4C 74. 26 - the largest radio source associated with a quasar

    Energy Technology Data Exchange (ETDEWEB)

    Riley, J.M.; Warner, P.J.; Rawlings, S.; Saunders, R.; Pooley, G.G.; Eales, S.A.


    Observations of the radio source 4C74.26 with the Cambridge Low-Frequency Synthesis Telescope have shown it to be a 10-arcmin double. It is identified with a quasar with a redshift of 0.104, measured with the University of Hawaii 88-inch telescope, giving the source a projected linear size of 1.6 Mpc and making it the largest-known radio source associated with a quasar. The optical spectrum and image, radio maps and JCMT millimetre observations are presented here. The radio properties of 4C74.26 are remarkably similar to those of other giant sources identified with galaxies - despite its very much larger non-stellar optical nuclear luminosity - as well as to those of 4C34.47, the only other giant source associated with a quasar.

  5. NuSTAR Reveals Extreme Absorption in z <0.5 Type 2 Quasars

    DEFF Research Database (Denmark)

    Lansbury, G. B.; Gandhi, P.; Alexander, D. M.


    -ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (N-H > 1.5 x 10(24) cm(-2)) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously......STAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the N-H distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of f(CT) = 36(-12)(+14)%, although higher...

  6. The Sloan Digital Sky Survey Quasar Catalog. 4. Fifth Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Strauss, Michael A.; Vanden Berk, Daniel E.; Anderson, Scott F.; Brandt, W.N.; Fan, Xiao-Hui; Jester,; Gray, Jim; Gunn, James E.; /Penn State U., Astron. Astrophys. /York U., Canada /Johns Hopkins U. /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona


    We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition. The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 5740 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than four, of which 36 are at redshifts greater than five. Approximately half of the catalog quasars have i < 19; nearly all have i < 21. For each object the catalog presents positions accurate to better than 0.2-minutes rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains basic radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. The average SDSS colors of quasars as a function of redshift, derived from the catalog entries, are presented in tabular form. Approximately 96% of the objects in the catalog were discovered by the SDSS.


    Energy Technology Data Exchange (ETDEWEB)

    Jiang Peng; Zhou Hongyan; Ji Tuo; Shu Xinwen; Liu Wenjuan; Dong Xiaobo; Wang Huiyuan; Wang Tinggui [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui, 230026 (China); Wang Jianguo [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011 (China); Bai Jinming, E-mail: [Polar Research Institute of China, Jinqiao Road 451, Shanghai 200136 (China)


    A fraction of the heavily reddened quasars require a reddening curve that is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we derive a reddening curve in the rest-frame wavelength range of 1200-10000 A. It has a steep rise at wavelengths shorter than 3000 A, but no significant reddening at longer wavelengths. The absence of dust reddening in the optical continuum is confirmed by the normal broad-line Balmer decrement (the H{alpha}/H{beta} ratio) in IRAS 14026+4341. The anomalous reddening curve can be satisfactorily reproduced with a dust model containing silicate grains in a power-law size distribution, dn(a)/da{proportional_to}a {sup -1.4}, truncated at a maximum size of a{sub max} = 70 nm. The unusual size distribution may be caused by the destruction of large 'stardust' grains by quasar activities or a different dust formation mechanism (i.e., the in situ formation of dust grains in quasar outflows). It is also possible that the analogies of the dust grains observed near the Galactic center are responsible for the steep reddening curve. In addition, we find that IRAS 14026+4341 is a weak emission-line quasar (i.e., PHL 1811 analogies) with heavy dust reddening and blueshifted broad absorption lines.

  8. Joint Bayesian Estimation of Quasar Continua and the Lyα Forest Flux Probability Distribution Function (United States)

    Eilers, Anna-Christina; Hennawi, Joseph F.; Lee, Khee-Gan


    We present a new Bayesian algorithm making use of Markov Chain Monte Carlo sampling that allows us to simultaneously estimate the unknown continuum level of each quasar in an ensemble of high-resolution spectra, as well as their common probability distribution function (PDF) for the transmitted Lyα forest flux. This fully automated PDF regulated continuum fitting method models the unknown quasar continuum with a linear principal component analysis (PCA) basis, with the PCA coefficients treated as nuisance parameters. The method allows one to estimate parameters governing the thermal state of the intergalactic medium (IGM), such as the slope of the temperature-density relation γ -1, while marginalizing out continuum uncertainties in a fully Bayesian way. Using realistic mock quasar spectra created from a simplified semi-numerical model of the IGM, we show that this method recovers the underlying quasar continua to a precision of ≃ 7 % and ≃ 10 % at z = 3 and z = 5, respectively. Given the number of principal component spectra, this is comparable to the underlying accuracy of the PCA model itself. Most importantly, we show that we can achieve a nearly unbiased estimate of the slope γ -1 of the IGM temperature-density relation with a precision of +/- 8.6 % at z = 3 and +/- 6.1 % at z = 5, for an ensemble of ten mock high-resolution quasar spectra. Applying this method to real quasar spectra and comparing to a more realistic IGM model from hydrodynamical simulations would enable precise measurements of the thermal and cosmological parameters governing the IGM, albeit with somewhat larger uncertainties, given the increased flexibility of the model.


    Energy Technology Data Exchange (ETDEWEB)

    Brescia, M.; Mercurio, A. [INAF-Astronomical Observatory of Capodimonte, via Moiariello 16, I-80131 Napoli (Italy); Cavuoti, S.; Longo, G. [Department of Physics, University Federico II, via Cinthia 6, I-80126 Napoli (Italy); D' Abrusco, R., E-mail: [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)


    The Multi Layer Perceptron with Quasi Newton Algorithm (MLPQNA) is a machine learning method that can be used to cope with regression and classification problems on complex and massive data sets. In this paper, we give a formal description of the method and present the results of its application to the evaluation of photometric redshifts for quasars. The data set used for the experiment was obtained by merging four different surveys (Sloan Digital Sky Survey, GALEX, UKIDSS, and WISE), thus covering a wide range of wavelengths from the UV to the mid-infrared. The method is able (1) to achieve a very high accuracy, (2) to drastically reduce the number of outliers and catastrophic objects, and (3) to discriminate among parameters (or features) on the basis of their significance, so that the number of features used for training and analysis can be optimized in order to reduce both the computational demands and the effects of degeneracy. The best experiment, which makes use of a selected combination of parameters drawn from the four surveys, leads, in terms of {Delta}z{sub norm} (i.e., (z{sub spec} - z{sub phot})/(1 + z{sub spec})), to an average of {Delta}z{sub norm} = 0.004, a standard deviation of {sigma} = 0.069, and a median absolute deviation, MAD = 0.02, over the whole redshift range (i.e., z{sub spec} {<=} 3.6), defined by the four-survey cross-matched spectroscopic sample. The fraction of catastrophic outliers, i.e., of objects with photo-z deviating more than 2{sigma} from the spectroscopic value, is <3%, leading to {sigma} = 0.035 after their removal, over the same redshift range. The method is made available to the community through the DAMEWARE Web application.

  10. Auto-Guiding System for CQUEAN (Camera for QUasars in EArly uNiverse)


    Kim, Eunbin; Park, Won-Kee; Jeong, Hyeonju; Kim, Jinyoung; Kuehne, John; Kim, Dong Han; Kim, Han Geun; Odoms, Peter S.; Chang, Seunghyuk; Im, Myungshin; Pak, Soojong


    To perform imaging observation of optically red objects such as high redshift quasars and brown dwarfs, the Center for the Exploration of the Origin of the Universe (CEOU) recently developed an optical CCD camera, Camera for QUasars in EArly uNiverse(CQUEAN), which is sensitive at 0.7-1.1 um. To enable observations with long exposures, we developed an auto-guiding system for CQUEAN. This system consists of an off-axis mirror, a baffle, a CCD camera, a motor and a differential decelerator. To ...

  11. VLBI limits on the proper motion of the 'core' of the superluminal quasar 3C345 (United States)

    Bartel, N.; Herring, T. A.; Ratner, M. I.; Shapiro, I. I.; Corey, B. E.


    VLBI (very-long-baseline interferometry) observations between 1971 and 1983 have been used to determine the positions of the 'core' of the quasar 3C345 relative to the more distant compact quasar NRAO512 with a fractional uncertainty as small as two parts in a hundred million. The core of 3C345 appears stationary in right ascension to within 20 arc microsec/yr, a subluminal bound corresponding to 0.7c. The apparent velocities of the jets are superluminal, up to 14c in magnitude.

  12. Superluminal motion in the double-lobed quasar 3C263 (United States)

    Zensus, J. A.; Hough, D. H.; Porcas, R. W.


    The detection of superluminal motion in the quasar 3C263 is reported. The milliarcsecond structure of this source consists of two nearly unresolved components whose separation is increasing at a rate of 0.06 + or - 0.02 marcsec/yr. This corresponds to an expansion speed of 2.7 + or - 0.9 c (H/0/ = 55 km/s/Mpc, q/0/ = 0.05). This quasar is the weakest superluminal source found so far, and there are indications that superluminal motion occurs frequently in this class of object.

  13. Flux and color variations of the quadruply imaged quasar HE 0435-1223

    DEFF Research Database (Denmark)

    Ricci, D.; Poels, J.; Elyiv, A.


    Aims: We present VRi photometric observations of the quadruply imaged quasarHE0435-1223, carried out with the Danish 1.54 m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. Methods. We monitored...... lensed components in the three filters. We also found a significant increase (≈ 0.05-0.015) in their V - R and R - i color indices. Conclusions. These flux and color variations are very likely caused by intrinsic variations of the quasar between the observed epochs. Microlensing effects probably also...

  14. The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; /Penn State U.; Richards, Gordon T.; /Drexel U.; Hall, Patrick B.; /York U., Canada; Strauss, Michael A.; /Princeton U. Observ.; Anderson, Scott F.; /Washington U., Seattle, Astron. Dept.; Boroson, Todd A.; /Kitt Peak Observ.; Ross, Nicholas P.; /Penn State U.; Shen, Yue; /Princeton U. Observ.; Brandt, W.N.; /Penn State U.; Fan, Xiaohui; /Arizona U., Astron. Dept. - Steward Observ.; Inada, Naohisa; /Wako, RIKEN /Southampton U. /Heidelberg, Max Planck Inst. Astron.


    We present the fifth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog, which is based upon the SDSS Seventh Data Release. The catalog, which contains 105,783 spectroscopically confirmed quasars, represents the conclusion of the SDSS-I and SDSS-II quasar survey. The catalog consists of the SDSS objects that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The catalog covers an area of {approx} 9380 deg{sup 2}. The quasar redshifts range from 0.065 to 5.46, with a median value of 1.49; the catalog includes 1248 quasars at redshifts greater than 4, of which 56 are at redshifts greater than 5. The catalog contains 9210 quasars with i < 18; slightly over half of the entries have i < 19. For each object the catalog presents positions accurate to better than 0.1-inch rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the SDSS public database using the information provided in the catalog. Over 96% of the objects in the catalog were discovered by the SDSS. We also include a supplemental list of an additional 207 quasars with SDSS spectra whose archive photometric information is incomplete.

  15. Study of Three-Dimensional Image Brightness Loss in Stereoscopy


    Hsing-Cheng Yu; Xie-Hong Tsai; An-Chun Luo; Ming Wu; Sei-Wang Chen


    When viewing three-dimensional (3D) images, whether in cinemas or on stereoscopic televisions, viewers experience the same problem of image brightness loss. This study aims to investigate image brightness loss in 3D displays, with the primary aim being to quantify the image brightness degradation in the 3D mode. A further aim is to determine the image brightness relationship to the corresponding two-dimensional (2D) images in order to adjust the 3D-image brightness values. In addition, the ph...

  16. Investigating the Bright End of LSST Photometry (United States)

    Ojala, Elle; Pepper, Joshua; LSST Collaboration


    The Large Synoptic Survey Telescope (LSST) will begin operations in 2022, conducting a wide-field, synoptic multiband survey of the southern sky. Some fraction of objects at the bright end of the magnitude regime observed by LSST will overlap with other wide-sky surveys, allowing for calibration and cross-checking between surveys. The LSST is optimized for observations of very faint objects, so much of this data overlap will be comprised of saturated images. This project provides the first in-depth analysis of saturation in LSST images. Using the PhoSim package to create simulated LSST images, we evaluate saturation properties of several types of stars to determine the brightness limitations of LSST. We also collect metadata from many wide-field photometric surveys to provide cross-survey accounting and comparison. Additionally, we evaluate the accuracy of the PhoSim modeling parameters to determine the reliability of the software. These efforts will allow us to determine the expected useable data overlap between bright-end LSST images and faint-end images in other wide-sky surveys. Our next steps are developing methods to extract photometry from saturated images.This material is based upon work supported in part by the National Science Foundation through Cooperative Agreement 1258333 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory. Additional LSST funding comes from private donations, grants to universities, and in-kind support from LSSTC Institutional Members.Thanks to NSF grant PHY-135195 and the 2017 LSSTC Grant Award #2017-UG06 for making this project possible.

  17. Dark and Bright Ridges on Europa (United States)


    This high-resolution image of Jupiter's moon Europa, taken by NASA's Galileo spacecraft camera, shows dark, relatively smooth region at the lower right hand corner of the image which may be a place where warm ice has welled up from below. The region is approximately 30 square kilometers in area. An isolated bright hill stands within it. The image also shows two prominent ridges which have different characteristics; youngest ridge runs from left to top right and is about 5 kilometers in width (about 3.1 miles). The ridge has two bright, raised rims and a central valley. The rims of the ridge are rough in texture. The inner and outer walls show bright and dark debris streaming downslope, some of it forming broad fans. This ridge overlies and therefore must be younger than a second ridge running from top to bottom on the left side of the image. This dark 2 km wide ridge is relatively flat, and has smaller-scale ridges and troughs along its length.North is to the top of the picture, and the sun illuminates the surface from the upper left. This image, centered at approximately 14 degrees south latitude and 194 degrees west longitude, covers an area approximately 15 kilometers by 20 kilometers (9 miles by 12 miles). The resolution is 26 meters (85 feet) per picture element. This image was taken on December 16, 1997 at a range of 1300 kilometers (800 miles) by Galileo's solid state imaging system.The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL galileo.

  18. An exceptionally bright, compact starburst nucleus (United States)

    Margon, Bruce; Anderson, Scott F.; Mateo, Mario; Fich, Michel; Massey, Philip


    Observations are reported of a remarkably bright (V about 13) starburst nucleus, 0833 + 652, which has been detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the 'prototypical' example of the starburst phenomenon, 0833 + 652 appears to be a previously uncataloged object. Its ease of detectability throughout the electromagnetic spectrum should make it useful for a variety of problems in the study of compact emission-line galaxies.

  19. Broadband bright twin beams and their upconversion (United States)

    Chekhova, Maria V.; Germanskiy, Semen; Horoshko, Dmitri B.; Kitaeva, Galiya Kh.; Kolobov, Mikhail I.; Leuchs, Gerd; Phillips, Chris R.; Prudkovskii, Pavel A.


    We report on the observation of broadband (40 THz) bright twin beams through high-gain parametric down-conversion in an aperiodically poled lithium niobate crystal. The output photon number is shown to scale exponentially with the pump power and not with the pump amplitude, as in homogeneous crystals. Photon-number correlations and the number of frequency/temporal modes are assessed by spectral covariance measurements. By using sum-frequency generation on the surface of a non-phasematched crystal, we measure a cross-correlation peak with the temporal width 90 fs.

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  1. Radio-quiet neutron star 1E 1207.4-5209: a possible strong gravitational-wave source. (United States)

    Gong, Biping


    There are four puzzles on 1E 1207.4-5209: (1) The characteristic age of the pulsar is much higher than the estimated age of the supernova remnant; (2) the magnetic field inferred from spin down is significantly different from the value obtained from the cyclotron absorption lines; (3) the spinning down of the pulsar is nonmonotonic; (4) the magnitude of the frequency's first derivative varies significantly and its sign is also variable. The third puzzle can be explained by a wide binary system, with orbital period from 0.2 to 6 yr. This Letter proposes that all four puzzles can be explained naturally by an ultracompact binary with an orbital period between 0.5 and 3.3 min. With the shortest orbital period and a close distance of 2 kpc, the characteristic amplitude of gravitational waves is h approximately 3 x 10(-21). It would be an excellent source for gravitational-wave detectors such as the Laser Interferometer Space Antenna.

  2. Coronal bright points associated with minifilament eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Junchao; Jiang, Yunchun; Yang, Jiayan; Bi, Yi; Li, Haidong [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Yang, Bo; Yang, Dan, E-mail: [Also at Graduate School of Chinese Academy of Sciences, Beijing, China. (China)


    Coronal bright points (CBPs) are small-scale, long-lived coronal brightenings that always correspond to photospheric network magnetic features of opposite polarity. In this paper, we subjectively adopt 30 CBPs in a coronal hole to study their eruptive behavior using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. About one-quarter to one-third of the CBPs in the coronal hole go through one or more minifilament eruption(s) (MFE(s)) throughout their lifetimes. The MFEs occur in temporal association with the brightness maxima of CBPs and possibly result from the convergence and cancellation of underlying magnetic dipoles. Two examples of CBPs with MFEs are analyzed in detail, where minifilaments appear as dark features of a cool channel that divide the CBPs along the neutral lines of the dipoles beneath. The MFEs show the typical rising movements of filaments and mass ejections with brightenings at CBPs, similar to large-scale filament eruptions. Via differential emission measure analysis, it is found that CBPs are heated dramatically by their MFEs and the ejected plasmas in the MFEs have average temperatures close to the pre-eruption BP plasmas and electron densities typically near 10{sup 9} cm{sup –3}. These new observational results indicate that CBPs are more complex in dynamical evolution and magnetic structure than previously thought.

  3. Subpicosecond, high-brightness excimer laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, A.J.; Gosnell, T.R.; Roberts, J.P.; Lester, C.S.; Gibson, R.B.; Harper, S.E.; Tallman, C.R.


    Subpicosecond, high-brightness excimer laser systems are being used to explore the interaction of intense coherent ultraviolet radiation with matter. Applications of current systems include generation of picosecond x-ray pulses, investigation of possible x-ray laser pumping schemes, studies of multiphoton phenomena in atomic species, and time-resolved photochemistry. These systems, based on the amplification of subpicosecond pulses in small aperture (/approximately/1 cm/sup 2/) XeCl or KrF amplifiers, deliver focal spot intensities of /approximately/10/sup 17/ W/cm/sup 2/. Scaling to higher intensities, however, will require an additional large aperture amplifier which preserves near-diffraction-limited beam quality and subpicosecond pulse duration. We describe here both a small aperture KrF system which routinely provides intensities >10/sup 17/ W/cm/sup 2/ to several experiments, and a large aperture XeCl system designed to deliver /approximately/1 J subpicosecond pulses and yield intensities on target in excess of 10/sup 19/W/cm/sup 2/. We also discuss the effects of two-photon absorption on large-aperture, high-brightness excimer lasers. 4 refs., 2 figs.

  4. Optical Sky Brightness at Dome C, Antarctica (United States)

    Kenyon, S.; Storey, J. W. V.; Burton, M. G.


    Dome C, Antarctica is a prime site for astronomical observations in terms of climate, wind speeds and turbulence. The infrared and terahertz sky backgrounds are the lowest of any inhabited place on Earth. However, at present little is known about the optical sky brightness and atmospheric extinction. Using a variety of modelling techniques together with data from the South Pole, we estimate the brightness of the night sky including the contributions from scattered sunlight, moonlight, aurorae, airglow, zodiacal light and artificial sources. We compare our results to another prime astronomical site, Mauna Kea. We find moonlight has significantly less effect at Dome C than at Mauna Kea. Aurorae are expected to have a minor impact at both sites, and zodiacal light is expected to be less at Dome C than at Mauna Kea. Airglow emissions at Dome C are expected to be similar to those at temperate sites. With proper planning, artificial sources of light pollution should be non-existent. The overall atmospheric extinction, or opacity, is expected to be the minimum possible. We conclude that Dome C is a very promising site not only for infrared and terahertz astronomy, but for optical astronomy as well..

  5. Sublimation in bright spots on (1) Ceres (United States)

    Nathues, A.; Hoffmann, M.; Schaefer, M.; Le Corre, L.; Reddy, V.; Platz, T.; Cloutis, E. A.; Christensen, U.; Kneissl, T.; Li, J.-Y.; Mengel, K.; Schmedemann, N.; Schaefer, T.; Russell, C. T.; Applin, D. M.; Buczkowski, D. L.; Izawa, M. R. M.; Keller, H. U.; O'Brien, D. P.; Pieters, C. M.; Raymond, C. A.; Ripken, J.; Schenk, P. M.; Schmidt, B. E.; Sierks, H.; Sykes, M. V.; Thangjam, G. S.; Vincent, J.-B.


    The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5, 6, 7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the ‘snow line’, which is the distance from the Sun at which water molecules condense.

  6. Crowdsourcing Broad Absorption Line Properties and Other Features of Quasar Outflow Using Zooniverse Citizen Science Project Platform (United States)

    Crowe, Cassie; Lundgren, Britt; Grier, Catherine


    The Sloan Digital Sky Survey (SDSS) regularly publishes vast catalogs of quasars and other astronomical objects. Previously, the SDSS collaboration has used visual inspection to check quasar redshift validity and flag instances of broad absorption lines (BALs). This information helps researchers to easily single out the quasars with BAL properties and study their outflows and other intervening gas clouds. Due to the ever-growing number of new SDSS quasar observations, visual inspections are no longer possible using previous methods. Currently, BAL information is being determined entirely computationally, and the accuracy of that information is not precisely known. This project uses the Zooniverse citizen science platform to visually inspect quasar spectra for BAL properties, to check the accuracy of the current autonomous methods, and to flag multi-phase outflows and find candidates for in-falling gas into the quasar central engine. The layout and format of a Zooniverse project provides an easier way to inspect and record data on each spectrum and share the workload via crowdsourcing. Work done by the SDSS collaboration members is serving as a beta test for a public project upon the official release of the DR14 quasar catalog by SDSS.


    Sanmartim, David; Storchi-Bergmann, Thaisa


    Post-Starburst Quasars (PSQs) are an intriguing set of galaxies that simultaneously host AGNs and post-starburst stellar populations, making them one of the most suitable objects to investigate the nature of the connection between these two components. The simultaneous presence of a post-starburst population and nuclear activity may be explained by two possible scenarios. In the secular evolutionary scenario star formation may cease due to exhaustion of the gas, while in the quenching one it may cease abruptly when the nuclear activity is triggered. In order to test these scenarios we have mapped the star formation history, manifestations of nuclear activity and excitation mechanisms in the central kpc of two nearby PSQs by using GMOS-IFU observations. In these two first exploratory studies, we have found that the young and intermediate age populations are located in a ring at ≈300-500 kpc, with some contribution of the intermediate age component also in the central region. In both of them, the gas outflow does not coincide with the young stellar population ring, which suggests that the ring is not being affected by the AGN feedback, but only the innermost regions. The individual study one of the PSQs of the sample has supported the evolutionary scenario, since the post-starburst population is not located close enough to the nucleus, where the outflow is observed. As a general behaviour, we found that outflows velocity are on the order of ~600-800 km/s and the mass outflow rates of ≈0.03-0.1 M⊙/yr, one order of magnitude greater than the AGN accretion rate, which suggests a scenario where the AGN-driven wind has entrained material from the circumnuclear region. In order to increase the statistical significance of our previous results and to distinguish between the proposed scenarios, we are conducting the same analysis to a wider sample of PSQs, which we hope will indicate more conclusively which is the favored scenario. During the meeting, we will present


    NARCIS (Netherlands)



    We report detection of superluminal motion in the core of 4C 38.41, associated with the z = 1.814 quasar 1633+382. The dominant nucleus in the similar to 30 kpc triple morphology of the radio source displays a core-jet structure on the milliarcsecond scale, and a jet component is found moving

  9. The parsec-scale evolution of the superluminal quasar 1642+690

    NARCIS (Netherlands)

    Venturi, T; Pearson, TJ; Barthel, PD; Unwin, SC

    We present the results of a 6 cm VLBI monitoring program of the core dominated, radio loud quasar 1642+690. 3.6 cm VLBI observations are also presented. The 6 cm observations, carried out in 1986.4, 1988.2, 1992.2 and 1994.7 confirm that the source is variable, both in morphology and in flux

  10. Quasar feedback in the early Universe : The case of SDSS J1148+5251

    NARCIS (Netherlands)

    Valiante, Rosa; Schneider, Raffaella; Maiolino, Roberto; Salvadori, Stefania; Bianchi, Simone


    Galaxy-scale gas outflows triggered by active galactic nuclei have been proposed as a key physical process to regulate the co-evolution of nuclear black holes and their host galaxies. The recent detection of a massive gas outflow in one of the most distant quasars, SDSS J1148+5251 at z = 6.4,

  11. Quasar feedback in the early Universe: the case of SDSS J1148+5251

    NARCIS (Netherlands)

    Valiante, Rosa; Schneider, Raffaella; Maiolino, Roberto; Salvadori, Stefania; Bianchi, Simone


    Galaxy-scale gas outflows triggered by active galactic nuclei have been proposed as a key physical process to regulate the co-evolution of nuclear black holes and their host galaxies. The recent detection of a massive gas outflow in one of the most distant quasars, SDSS J1148+5251 at z= 6.4,

  12. Observations of the Ca II IR Triplet in High Luminosity Quasars ...

    Indian Academy of Sciences (India)

    Abstract. We present a new spectroscopic sample of 11 quasars at intermediate redshift observed with the Infrared Spectrometer and Array. Camera (ISAAC) on the ESO Very Large Telescope (VLT), covering O I λ8446 and the Ca II triplet 8498, 8542, 8662. The new observations – that supplement the sample presented by ...

  13. Spectral Variability of Quasar SDSS J030639.57+000343.1 ...

    Indian Academy of Sciences (India)

    Spectral Variability of Quasar SDSS J030639.57+000343.1. Hengxiao Guo1,2,∗ & Minfeng Gu1. 1Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical. Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China. 2University of Chinese Academy of Sciences, 19A ...

  14. Nature and statistical properties of quasar associated absorption systems in the XQ-100 Legacy Survey

    DEFF Research Database (Denmark)

    Perrotta, Serena; D'Odorico, Valentina; Prochaska, J. Xavier


    We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and intervening NALs without taking into account any a priori definition or velocity cut-off. We analyze the spectra of 100 quasars...

  15. The mass function of primordial rogue planet MACHOs in quasar nano-lensing

    NARCIS (Netherlands)

    Schild, R.E; Nieuwenhuizen, T.M.; Gibson, C.H.


    The recent Sumi et al (2010 Astrophys. J. 710 1641; 2011 Nature 473 349) detection of free roaming planet mass MACHOs in cosmologically significant numbers recalls their original detection in quasar microlening studies (Colley and Schild 2003 Astrophys. J. 594 97; Schild R E 1996 Astrophys. J. 464


    NARCIS (Netherlands)


    We report the results of fourth epoch VLBI observations at 4990.99 MHz, with a resolution of approximately 1 mas, of the compact steep-spectrum quasar 3C 216. Superluminal motion in this object is confirmed. Although a constant superluminal expansion at upsilon(app) = 3.9c +/- 0.6 is not ruled out,

  17. Emergence and disappearance of microarcsecond structure in the scintillating quasar J1819+3845

    NARCIS (Netherlands)

    Macquart, J.-P.; de Bruyn, A. G.


    The 4.8-GHz light curves of the scintillating intraday variable quasar J1819+3845 during 2004-2005 exhibit sharp structure, down to a time-scale of 15 min, that was absent from light curves taken prior to this period and from the 2006 light curves. Analysis of the light curve power spectra show that

  18. High-redshift quasars host galaxies: is there a stellar mass crisis?

    NARCIS (Netherlands)

    Valiante, Rosa; Schneider, Raffaella; Salvadori, Stefania; Gallerani, Simona


    We investigate the evolutionary properties of a sample of quasars (QSOs) at 5

  19. Elemental Abundances in the Broad Emission Line Region of Quasars at Redshifts larger than 4

    DEFF Research Database (Denmark)

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


    We present observations of 11 high redshift quasars ($3.9 \\la z \\la 5.0$) observed with low spectral resolution in the restframe ultraviolet using FORS 1 at the VLT UT 1. The emission-line fluxes of strong permitted and intercombination ultraviolet emission lines are measured to estimate the chem...

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

    DEFF Research Database (Denmark)

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


    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...

  1. How Far Is Quasar UV/Optical Variability from a Damped Random Walk at Low Frequency? (United States)

    Guo, Hengxiao; Wang, Junxian; Cai, Zhenyi; Sun, Mouyuan


    Studies have shown that UV/optical light curves of quasars can be described using the prevalent damped random walk (DRW) model, also known as the Ornstein-Uhlenbeck process. A white noise power spectral density (PSD) is expected at low frequency in this model; however, a direct observational constraint to the low-frequency PSD slope is difficult due to the limited lengths of the light curves available. Meanwhile, quasars show scatter in their DRW parameters that is too large to be attributed to uncertainties in the measurements and dependence on the variation of known physical factors. In this work we present simulations showing that, if the low-frequency PSD deviates from the DRW, the red noise leakage can naturally produce large scatter in the variation parameters measured from simulated light curves. The steeper the low-frequency PSD slope, the larger scatter we expect. Based on observations of SDSS Stripe 82 quasars, we find that the low-frequency PSD slope should be no steeper than -1.3. The actual slope could be flatter, which consequently requires that the quasar variabilities should be influenced by other unknown factors. We speculate that the magnetic field and/or metallicity could be such additional factors.


    NARCIS (Netherlands)


    We present radio maps of a collection of intermediate redshift quasars and radio galaxies mostly taken from the 3C and 4C catalogues. The sources were observed with the Very Large Array (VLA) at one or more of the following frequencies: 15 GHz, 8.4 GHz or 1.4 GHz. Several basic source parameters axe

  3. Testing and selecting cosmological models with ultra-compact radio quasars

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaolei [Beijing Normal University, Department of Astronomy, Beijing (China); University of Michigan, Department of Physics, Ann Arbor, MI (United States); Cao, Shuo; Qi, Jingzhao; Zhu, Zong-Hong [Beijing Normal University, Department of Astronomy, Beijing (China); Zheng, Xiaogang; Biesiada, Marek [Beijing Normal University, Department of Astronomy, Beijing (China); University of Silesia, Department of Astrophysics and Cosmology, Institute of Phyisics, Katowice (Poland)


    In this paper, we place constraints on four alternative cosmological models under the assumption of the spatial flatness of the Universe: CPL, EDE, GCG and MPC. A new compilation of 120 compact radio quasars observed by very-long-baseline interferometry, which represents a type of new cosmological standard rulers, are used to test these cosmological models. Our results show that the fits on CPL obtained from the quasar sample are well consistent with those obtained from BAO. For other cosmological models considered, quasars provide constraints in agreement with those derived with other standard probes at 1σ confidence level. Moreover, the results obtained from other statistical methods including figure of merit, Om(z) and statefinder diagnostics indicate that: (1) Radio quasar standard ruler could provide better statistical constraints than BAO for all cosmological models considered, which suggests its potential to act as a powerful complementary probe to BAO and galaxy clusters. (2) Turning to Om(z) diagnostics, CPL, GCG and EDE models cannot be distinguished from each other at the present epoch. (3) In the framework of statefinder diagnostics, MPC and EDE will deviate from the ΛCDM model in the near future, while GCG model cannot be distinguished from the ΛCDM model unless much higher precision observations are available. (orig.)

  4. NuSTAR unveils a compton-thick 2 quasar in MrK 34

    DEFF Research Database (Denmark)

    Gandhi, P.; Lansbury, G. B.; Alexander, D. M.


    We present Nuclear Spectroscopic Telescope Array (NuSTAR) 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM-Newton data can be fitted self-consistently with a reflection-dominated continuum...

  5. New observational constraints on f(T) cosmology from radio quasars

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Jing-Zhao; Cao, Shuo; Zhu, Zong-Hong [Beijing Normal University, Department of Astronomy, Beijing (China); Biesiada, Marek; Zheng, Xiaogang [Beijing Normal University, Department of Astronomy, Beijing (China); University of Silesia, Department of Astrophysics and Cosmology, Institute of Physics, Katowice (Poland)


    Using a new recently compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range 0.46 < z < 2.76, whose statistical linear sizes show negligible dependence on redshifts and intrinsic luminosity and thus represent standard rulers in cosmology, we constrain three viable and most popular f(T) gravity models, where T is the torsion scalar in teleparallel gravity. Our analysis reveals that constraining power of the quasars data (N = 120) is comparable to the Union2.1 SN Ia data (N = 580) for all three f(T) models. Together with other standard ruler probes such as cosmic microwave background and baryon acoustic oscillation distance measurements, the present value of the matter density parameter Ω{sub m} obtained by quasars is much larger than that derived from other observations. For one of the models considered (f{sub 1}CDM) a small but noticeable deviation from ΛCDM cosmology is present, while in the framework of f{sub 3}CDM the effective equation of state may cross the phantom divide line at lower redshifts. These results indicate that intermediate-luminosity quasars could provide an effective observational probe comparable to SN Ia at much higher redshifts, and f(T) gravity is a reasonable candidate for the modified gravity theory. (orig.)

  6. The asymmetric radio structure and record jet of giant quasar 4C 34.47

    NARCIS (Netherlands)

    Hocuk, S.; Barthel, P. D.


    Context. Unification models for active galactic nuclei, AGN, predict that all quasars (radio sources associated with quasi-stellar objects) should be at a substantial angle with the sky plane. Aims. We test the predictions of the orientation unification model with the morphological and polarization

  7. The Angular Structure of Quasar 3C 47 in the Decameter Waveband (United States)

    Lozinskiy, A. B.; Lozinskiy, R. A.; Ivantishin, O. L.; Romanchev, Y. V.; Rashkovskiy, S. L.; Shepelev, V. A.; Brazhenko, A. I.; Vashchishin, R. V.; Litvinenko, O. A.

    The quasar 3C47 was observed with the URAN network at decameter wavelengths. A model of its angular structure consisting of four components was fitted. Lobes of the source are enlarged significantly in the range if compare with their high frequency dimensions. The hot spots emission is detected at low frequencies but a radio core is disappeared completely due to its flat spectrum.

  8. A glimpse at quasar host galaxy far-UV emission using damped Lyα's as natural coronagraphs

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zheng; Fan, Xiaohui; Wang, Ran; McGreer, Ian, E-mail: [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Noterdaeme, Pasquier; Finley, Hayley; Petitjean, Patrick [Institut d' Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Carithers, Bill [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Canberra, Weston Creek, ACT, 2611 (Australia); Miralda-Escudé, Jordi [Institució Catalana de Recerca i Estudis Avançats, Barcelona (Spain); Pâris, Isabelle [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Zakamska, Nadia L. [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States); Ge, Jian [Department of Astronomy, University of Florida, Gainesville, FL (United States); Slosar, Anze [Brookhaven National Laboratory, Upton, NY 11973 (United States)


    In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of ∼2000 DLA systems (N {sub H} {sub I} > 10{sup 20.6} cm{sup –2}) with a median absorption redshift (z) = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift (z) = 3.1) that is not blocked by the intervening DLA. Assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminosity bin ((L) = 2.5 × 10{sup 13} L {sub ☉}), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 10{sup 40} erg s{sup –1} Å{sup –1}; this corresponds to an unobscured UV star formation rate of 9 M {sub ☉} yr{sup –1}.

  9. Statistical Detection of the He ii Transverse Proximity Effect: Evidence for Sustained Quasar Activity for >25 Million Years

    Directory of Open Access Journals (Sweden)

    Tobias M. Schmidt


    Full Text Available The reionization of helium at z ~ 3 is the final phase transition of the intergalactic medium and supposed to be driven purely by quasars. The He ii transverse proximity effect—enhanced He ii transmission in a background sightline caused by the ionizing radiation of a foreground quasar—therefore offers a unique opportunity to probe the morphology of He ii reionization and to investigate the emission properties of quasars, e.g., ionizing emissivity, lifetime and beaming geometry. We use the most-recent HST/COS far-UV dataset of 22 He ii absorption spectra and conduct our own dedicated optical spectroscopic survey to find foreground quasars around these He ii sightlines. Based on a set of 66 foreground quasars, we perform the first statistical analysis of the He ii transverse proximity effect. Despite a large object-to-object variance, our stacking analysis reveals an excess in the average He ii transmission near the foreground quasars at 3σ significance. This statistical evidence for the transverse proximity effect is corroborated by a clear dependence of the signal strength on the inferred He ii ionization rate at the background sightline. Our detection places, based on the transverse light crossing time, a geometrical limit on the quasar lifetime of tQ > 25 Myr. This evidence for sustained activity of luminous quasars is relevant for the morphology of H i and He ii reionization and helps to constrain AGN triggering mechanisms, accretion physics and models of black hole mass assembly. We show how future modeling of the transverse proximity effect can additionally constrain quasar emission geometries and e.g., clarify if the large observed object-to-object variance can be explained by current models of quasar obscuration.

  10. New Distant Comet Headed for Bright Encounter (United States)


    How Impressive Will Comet Hale-Bopp Become in 1997 ? A very unusual comet was discovered last month, on its way from the outer reaches of the solar system towards the Sun. Although it is still situated beyond the orbit of Jupiter, it is so bright that it can be observed in even small telescopes. It has been named `Hale-Bopp' after the discoverers and is already of great interest to cometary astronomers. No less than seven telescopes have been used at the ESO La Silla observatory for the first observations of the new object. Together with data gathered at other sites, their aim is to elucidate the nature of this comet and also to determine whether there is reason to hope that it will become a bright and beautiful object in the sky from late 1996 and well into 1997. Further observations are now being planned at ESO and elsewhere to monitor closely the behaviour of this celestial visitor during the coming months. Discovery circumstances The comet was discovered on 23 July 1995, nearly simultaneously by two American amateur astronomers, Alan Hale of Cloudcroft (New Mexico) and Thomas Bopp of Glendale (Arizona). Although the chronology is slightly uncertain, it appears that Hale first saw it some 10 - 20 minutes before Bopp, at 06:10 - 06:15 UT on that day. In any case, he informed the IAU Central Bureau for Astronomical Telegrams (CBAT) in Cambridge (Massachussetts) about his discovery by email already at 06:50 UT, while Bopp's message was filed more than 2 hours later, after he had driven back to his home, 140 km from where he had been observing. Upon receipt of these messages, Brian Marsden at the CBAT assigned the designation `1995 O1' (indicating that it is the first comet found in the second half of July 1995). After further sightings had been made by other observers, and according to the venerable astronomical tradition, the new object was named after the discoverers. The magnitude, reported as 10.5 by Hale, is not unusual for a comet that is discovered within


    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jianfeng; Brandt, W. N.; Garmire, Gordon P.; Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Miller, Brendan P. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Vignali, Cristian, E-mail: [Dipartimento di Astronomia, Universita degli Studi di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)


    We present a systematic study of the X-ray and multiwavelength properties of a sample of 17 highly radio-loud quasars (HRLQs) at z > 4 with sensitive X-ray coverage from new Chandra and archival Chandra, XMM-Newton, and Swift observations. Eight of the new and archival observations are reported in this work for the first time. New Chandra observations of two moderately radio-loud and highly optically luminous quasars at z {approx}> 4 are also reported. Our HRLQ sample represents the top {approx}5% of radio-loud quasars (RLQs) in terms of radio loudness. We found that our HRLQs have an X-ray emission enhancement over HRLQs at lower redshifts (by a typical factor of Almost-Equal-To 3), and this effect, after controlling for several factors which may introduce biases, has been solidly estimated to be significant at the 3{sigma}-4{sigma} level. HRLQs at z = 3-4 are also found to have a similar X-ray emission enhancement over z < 3 HRLQs, which further supports the robustness of our results. We discuss models for the X-ray enhancement's origin including a fractional contribution from inverse Compton scattering of cosmic microwave background photons. No strong correlations are found between the relative X-ray brightness and optical/UV emission-line rest-frame equivalent widths (REWs) for RLQs. However, the line REWs are positively correlated with radio loudness, which suggests that relativistic jets make a negligible contribution to the optical/UV continua of these HRLQs (contrary to the case where the emission lines are diluted by the relativistically boosted continuum). Our HRLQs are generally consistent with the known anti-correlation between radio loudness and X-ray power-law photon index. We also found that the two moderately radio-loud quasars appear to have the hardest X-ray spectra among our objects, suggesting that intrinsic X-ray absorption (N {sub H} {approx} 10{sup 23} cm{sup -2}) may be present. Our z > 4 HRLQs generally have higher X-ray luminosities

  12. Studying low-redshift universe through observation of Damped Lyman-alpha quasar absorbers (United States)

    Gharanfoli, Soheila


    In recent years, an extremely successful method to study galaxy formation and evolution, has been provided by observation of quasar absorbers. Quasar absorbers are systems intercepting our line-of-sight to a given quasar and thus produce a feature in the quasar spectrum, the so-called absorption lines. The Damped Lyman-a (DLA) and sub-Damped Lyman-a (sub-DLA) absorption features in quasar spectra are believed to be produced by intervening galaxies. However, the connection of quasar absorbers to galaxies is not well-understood, since attempts to image the absorbing galaxies have often failed. DLAs and sub-DLAs were originally thought to be the precursors of present day disk galaxies, but there is evidence that they may be dominated by gas-rich, proto-dwarf galaxies representing the basic building blocks of hierarchical growth of structure. While most DLAs appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs, has been discovered in recent spectroscopic studies. It is of great interest to image these metal-rich absorbers, especially with high spatial resolution, to understand the connection between the stellar and interstellar content of the underlying galaxies. This dissertation consists of several projects designed to further our understanding of galaxies and galactic structures associated with intervening quasar absorption lines. Two projects were completed that involved the imaging of 13 DLA/sub-DLA galaxies at z projects, follow-up spectroscopy was performed to confirm the spectroscopic redshifts of the candidate absorbers. In addition, optical and near-infrared spectroscopy provide necessary information to understand the luminosities, dust extinction, and star formation rates and thus the nature of these galaxies. Spectroscopy of 5 DLA/sub-DLA galaxies was performed using the 10-m Keck telescope with LRIS spectrograph, and 8-m Gemini- North telescope with the GMOS spectrograph. Several emission lines (e.g., Ha, Hb, [N II], [O II], [O

  13. Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745 (United States)

    Sharon, Keren; Bayliss, Matthew B.; Dahle, Håkon; Florian, Michael K.; Gladders, Michael D.; Johnson, Traci L.; Paterno-Mahler, Rachel; Rigby, Jane R.; Whitaker, Katherine E.; Wuyts, Eva


    SDSS J2222+2745 is a galaxy cluster at z = 0.49, strongly lensing a quasar at z = 2.805 into six widely separated images. In recent Hubble Space Telescope imaging of the field, we identify additional multiply lensed galaxies and confirm the sixth quasar image that was identified by Dahle et al. We used the Gemini-North telescope to measure a spectroscopic redshift of z = 4.56 of one of the lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a lensed galaxy at z = 2.3. This galaxy also appears in absorption in our Gemini spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is in agreement with the recent time delay measurements of Dahle et al., who found τAB = 47.7 ± 6.0 days and τAC = -722 ± 24 days. We use the observed time delays to further constrain the model, and find that the model-predicted time delays of the three faint images of the quasar are τAD = 502 ± 68 days, τAE = 611 ± 75 days, and τAF = 415 ± 72 days. We have initiated a follow-up campaign to measure these time delays with Gemini North. Finally, we present initial results from an X-ray monitoring program with Swift, indicating the presence of hard X-ray emission from the lensed quasar, as well as extended X-ray emission from the cluster itself, which is consistent with the lensing mass measurement and the cluster velocity dispersion. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-13337.

  14. The Sloan Digital Sky Survey Quasar Catalog. 3. Third data release

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Vanden Berk, Daniel E.; Anderson, Scott F.; Fan, Xiao-Hui; Jester, Sebastian; Stoughton, Chris; Strauss,; SubbaRao, Mark; Brandt, W.N.; Gunn, James E.; Yanny, Brian; Bahcall, Neta A.; Barentine, J.C.; Blanton, Michael R.; Boroski, William N.; Brewington, Howard J.; Brinkmann, J.; Brunner, Robert; Csabai, Istvan; /Penn State U., Astron. Astrophys. /York U., Canada /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona U.,


    We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than M{sub i} = -22 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 4188 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than four, of which 17 are at redshifts greater than five. For each object the catalog presents positions accurate to better than 0.2'' rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 at a spectral resolution of {approx} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.

  15. Quasar Rain: The Broad Emission Line Region as Condensations in the Warm Accretion Disk Wind (United States)

    Elvis, Martin


    The origin of the broad emission line region (BELR) in quasars and active galactic nuclei is still unclear. I propose that condensations form in the warm, radiation-pressure-driven, accretion disk wind of quasars creating the BEL clouds and uniting them with the other two manifestations of cool (˜104 K) gas in quasars, the low ionization phase of the warm absorbers (WAs) and the clouds causing X-ray eclipses. The cool clouds will condense quickly (days to years), before the WA outflows reach escape velocity (which takes months to centuries). Cool clouds form in equilibrium with the warm phase of the wind because the rapidly varying X-ray quasar continuum changes the force multiplier, causing pressure waves to move gas into stable locations in pressure-temperature space. The narrow range of two-phase equilibrium densities may explain the (luminosity){}1/2 scaling of the BELR size, while the scaling of cloud formation timescales could produce the Baldwin effect. These dense clouds have force multipliers of order unity and so cannot be accelerated to escape velocity. They fall back on a dynamical timescale (months to centuries), producing an inflow that rains down toward the central black hole. As they soon move at Mach ˜10-100 with respect to the WA outflow, these “raindrops” will be rapidly destroyed within months. This rain of clouds may produce the elliptical BELR orbits implied by velocity-resolved reverberation mapping in some objects and can explain the opening angle and destruction timescale of the narrow “cometary” tails of the clouds seen in X-ray eclipse observations. Some consequences and challenges of this “quasar rain” model are presented, along with several avenues for theoretical investigation.

  16. Bright sneezes and dark coughs, loud sunlight and soft moonlight. (United States)

    Marks, L E


    Synesthetic metaphors (such as "the dawn comes up like thunder") are expressions in which words or phrases describing experiences proper to one sense modality transfer their meanings to another modality. In a series of four experiments, subjects used scales of loudness, pitch, and brightness to evaluate the meanings of a variety of synesthetic (auditory-visual) metaphors. Loudness and pitch expressed themselves metaphorically as greater brightness; in turn, brightness expressed itself as greater loudness and as higher pitch. Although loudness thus shared with brightness a metaphorical connection, pitch and brightness showed a connection that was closer and that applied more generally to different kinds of visual brightness. The ways that people evaluate synesthetic metaphors emulate the characteristics of synesthetic perception, thereby suggesting that synesthesia in perception and synesthesia in language both may emenate from the same source-from a phenomenological similarity in the makeup of sensory experiences of different modalities.

  17. Bright photoluminescent hybrid mesostructured silica nanoparticles. (United States)

    Miletto, Ivana; Bottinelli, Emanuela; Caputo, Giuseppe; Coluccia, Salvatore; Gianotti, Enrica


    Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods.

  18. Bioinspired bright noniridescent photonic melanin supraballs. (United States)

    Xiao, Ming; Hu, Ziying; Wang, Zhao; Li, Yiwen; Tormo, Alejandro Diaz; Le Thomas, Nicolas; Wang, Boxiang; Gianneschi, Nathan C; Shawkey, Matthew D; Dhinojwala, Ali


    Structural colors enable the creation of a spectrum of nonfading colors without pigments, potentially replacing toxic metal oxides and conjugated organic pigments. However, significant challenges remain to achieve the contrast needed for a complete gamut of colors and a scalable process for industrial application. We demonstrate a feasible solution for producing structural colors inspired by bird feathers. We have designed core-shell nanoparticles using high-refractive index (RI) (~1.74) melanin cores and low-RI (~1.45) silica shells. The design of these nanoparticles was guided by finite-difference time-domain simulations. These nanoparticles were self-assembled using a one-pot reverse emulsion process, which resulted in bright and noniridescent supraballs. With the combination of only two ingredients, synthetic melanin and silica, we can generate a full spectrum of colors. These supraballs could be directly added to paints, plastics, and coatings and also used as ultraviolet-resistant inks or cosmetics.

  19. Kappa-effect and brightness oscillations of stars (United States)

    Zhugzhda, Y. D.; Roth, M.; Herzberg, W.


    In this paper the theory of visibility and darkening functions for the brightness oscillations of stars is outlined. For this the non-grey approximation is used and the effect of opacity disturbances on stellar brightness oscillations is explored for different types of stars. An explanation of the Procyon paradox is proposed. Special features of the brightness oscillations are discussed. The effect of opacity fluctuations on the damping of p-mode oscillations is considered. Furthermore, the photospheric kappa-mechanism is discussed.

  20. Study of Three-Dimensional Image Brightness Loss in Stereoscopy

    Directory of Open Access Journals (Sweden)

    Hsing-Cheng Yu


    Full Text Available When viewing three-dimensional (3D images, whether in cinemas or on stereoscopic televisions, viewers experience the same problem of image brightness loss. This study aims to investigate image brightness loss in 3D displays, with the primary aim being to quantify the image brightness degradation in the 3D mode. A further aim is to determine the image brightness relationship to the corresponding two-dimensional (2D images in order to adjust the 3D-image brightness values. In addition, the photographic principle is used in this study to measure metering values by capturing 2D and 3D images on television screens. By analyzing these images with statistical product and service solutions (SPSS software, the image brightness values can be estimated using the statistical regression model, which can also indicate the impact of various environmental factors or hardware on the image brightness. In analysis of the experimental results, comparison of the image brightness between 2D and 3D images indicates 60.8% degradation in the 3D image brightness amplitude. The experimental values, from 52.4% to 69.2%, are within the 95% confidence interval

  1. The night sky brightness at McDonald Observatory (United States)

    Kalinowski, J. K.; Roosen, R. G.; Brandt, J. C.


    Baseline observations of the night sky brightness in B and V are presented for McDonald Observatory. In agreement with earlier work by Elvey and Rudnick (1937) and Elvey (1943), significant night-to-night and same-night variations in sky brightness are found. Possible causes for these variations are discussed. The largest variation in sky brightness found during a single night is approximately a factor of two, a value which corresponds to a factor-of-four variation in airglow brightness. The data are used to comment on the accuracy of previously published surface photometry of M 81.

  2. Do the outflow properties in the most luminous quasars correlate with X-ray radiative output and host dynamical state? (United States)

    Zappacosta, Luca


    We are following up the multiwavelength properties of the WISSH sample of hyperluminous MIR-selected Type 1 quasars at z 2-3. In these objects we expect both powerful AGN feedback and galaxy mergers to manifest themselves in full force. We are finding in LBT/LUCI near infrared data that they are composed by two populations showing powerful mutually exclusive outflows in [OIII] and CIV. Interestingly they seem to show a dichotomy in their X-ray luminosities. Furthermore a HST-WFC3 follow-up of a WISSH quasar with [OIII] outflows show no sign of galaxy mergers. We propose here Chandra (280 ks) and HST (6 orbits) observations of WISSH quasars with the aim of establishing whether the two populations are linked to: (i) different quasar X-ray output and (ii) distinct host dynamical state.

  3. Unveiling hidden black holes in the cosmic web: Dark matter halos of WISE quasars from Planck CMB lensing (United States)

    Hickox, Ryan

    The WISE and Planck surveys have now produced groundbreaking data sets which, in concert, can be exploited to obtain revolutionary constraints on the evolution of structure in the Universe. One particularly powerful application of WISE has been to uncover millions of the previously "hidden" obscured quasars, rapidly growing supermassive black holes that are shrouded in gas and dust and so are not detectable using traditional ground-based optical and near-IR techniques. Recently, Planck has produced the most precise all-sky map to date of dark matter structures via the lensing of the cosmic microwave background (CMB). We propose to combine these data sets to obtain a uniquely powerful measurement of the link between rapidly growing black holes and their host dark matter structures, by cross-correlating the density field of WISE-selected quasars with the CMB lensing convergence maps obtained from Planck. This proposal will build on our current ADAP program (NNX12AE38G), which studies the host dark matter halos of WISE-selected quasars via spatial clustering. NNX12AE38G involves a detailed characterization of the redshifts, luminosities, and spectral energy distributions of WISE-selected quasars and uses new techniques to measure how quasars cluster around themselves. NNX12AE38G has contributed to more than 10 journal articles and 5 conference proceedings. Building on our current work, an even more complete understanding of the link between black holes and their host dark matter structures is possible if we employ an independent method for measuring the clustering bias (and thus characteristic halo mass) of the quasar population. This has recently become possible using CMB lensing maps. In the past two years, our team has conducted an initial analysis covering 2500 square degrees using WISE-selected quasars and lensing maps from the South Pole Telescope (Geach, Hickox, Myers et al., 2013), and have implemented this technique with Planck over part of the SDSS region


    Energy Technology Data Exchange (ETDEWEB)

    Hilbert, B.; Chiaberge, M.; Kotyla, J. P.; Sparks, W. B.; Macchetto, F. D. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Tremblay, G. R. [Yale University, Department of Astronomy, 260 Whitney Avenue, New Haven, CT 06511 (United States); Stanghellini, C. [INAF—Istituto di Radioastronomia, Via P. Gobetti, 101 I-40129 Bologna (Italy); Baum, S.; O’Dea, C. P. [University of Manitoba, Dept of Physics and Astronomy, 66 Chancellors Circle, Winnipeg, MB R3T 2N2 (Canada); Capetti, A. [Osservatorio Astronomico de Torino, Corso Savona, I-10024 Moncalieri TO (Italy); Miley, G. K. [Universiteit Leiden, Rapenburg 70, 2311 EZ Leiden (Netherlands); Perlman, E. S. [Florida Institute of Technology, 150 W University Boulevard, Melbourne, FL 32901 (United States); Quillen, A. [Rochester Institute of Technology, School of Physics and Astronomy, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States)


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

  5. The Molecular ISM of Quasar Host Galaxies in the Early Universe (United States)

    Riechers, D. A.


    Detailed studies of the molecular gas phase in the host galaxies of the highest redshift quasars are important for our understanding of the formation and evolution of quasars and their bulges, since the molecular gas is the prerequisite material for star formation. This investigation capitalizes on state-of-the-art observations in the radio/millimeter wavelength regime to study the key properties of the molecular interstellar medium in some of the most distant, gas-rich quasars. To search for evolutionary, luminosity-dependent, or galaxy type-dependent trends in the conditions under which star formation takes place, results are interpreted in the context of studies of nearby galaxies and high redshift galaxy populations. From the first high-resolution CO(J=1→0) spectroscopy of high-z quasars, the total molecular gas mass of their host galaxies is determined. By more than doubling the number of molecules known in the distant universe [from 2 (CO/HCN) to 5], it is found that multiple molecular probes of dense gas predict similar star formation rates within the dense molecular regions of high redshift galaxies, out to the first 2Gyr after the Big Bang. Together with other studies, these results indicate an increase in star formation efficiency toward the most luminous distant gas-rich systems, possibly due to a higher median gas density. In a connected, time consuming interferometric study, the host galaxies of three z>4 quasars are resolved, for the first time, both spatially (at up to 0.15", or 1.0 kpc) and in velocity space, revealing that the molecular reservoirs show a wealth of morphologies. The derived dynamical masses are large enough to account for both the central supermassive black holes and the full reservoirs of molecular gas, but do not leave much room for a stellar bulge as predicted by the local relation between black hole mass and bulge velocity dispersion. Quasar host galaxies are thus prime laboratories to study the coevolution of supermassive

  6. Signals from the Noise: Image Stacking for Quasars in the FIRST Survey

    Energy Technology Data Exchange (ETDEWEB)

    White, R L; Helfand, D J; Becker, R H; Glikman, E; deVries, W


    We present a technique to explore the radio sky into the nanoJansky regime by employing image stacking using the FIRST radio sky survey. We begin with a discussion of the non-intuitive relationship between the mean and median values of a non-Gaussian distribution in which measurements of the members of the distribution are dominated by noise. Following a detailed examination of the systematic effects present in the 20 cm VLA snapshot images that comprise FIRST, we demonstrate that image stacking allows us to recover the average properties of source populations with flux densities a factor of 30 or more below the rms noise level. With the calibration described herein, mean estimates of radio flux density, luminosity, radio loudness, etc. are derivable for any undetected source class having arcsecond positional accuracy. We demonstrate the utility of this technique by exploring the radio properties of quasars found in the Sloan Digital Sky Survey. We compute the mean luminosities and radio-loudness parameters for 41,295 quasars in the SDSS DR3 catalog. There is a tight correlation between optical and radio luminosity, with the radio luminosity increasing as the 0.72 power of optical luminosity. This implies declining radio-loudness with optical luminosity, with the most luminous objects (M{sub UV} = -30) having on average ten times lower radio-to-optical ratios than the least luminous objects (M{sub UV} = -21). There is also a striking correlation between optical color and radio loudness: quasars that are either redder or bluer than the norm are brighter radio sources. Quasars having g-r {approx} 0.8 magnitudes redder than the SDSS composite spectrum are found to have radio-loudness ratios that are higher by a factor of 8. We examine the radio properties of the subsample of quasars with broad absorption lines, finding, surprisingly, that BAL quasars have higher mean radio flux densities at all redshifts, with the greatest disparity arising in the rare low

  7. The LBT/WISSH quasar survey: revealing powerful winds in the most luminous AGN (United States)

    Vietri, Giustina


    The systematic, multi-frequency investigation of hyper-luminous quasars shining at the golden epoch of AGN activity offers the unique opportunity of studying the power and the effect of AGN feedback at its extreme.The WISE/SDSS selected hyper-luminous (WISSH) quasar survey is an extensive multi-band observing program (from millimeter wavelengths to hard X rays) designed to accurately probe the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows.Our on-going project aims at constraining both AGN and host galaxy ISM and star-formation properties in a large sample of ~ 90 broad-line quasars at the brightest end of the AGN luminosity function (L_bol > 1e14 L_sun), and at the peak of their number density (z ~ 2.5 - 3.5).I will review the most important results of the near-IR spectroscopic follow-up of WISSH quasars (available for ~40% of the total sample) performed with the LUCI at LBT. These observations were carried out to obtain a reliable Hbeta-based estimate of the SMBH masses and a census of the ionized outflows in these hyper-luminous quasars.We found that WISSH AGN are typically powered by highly accreting (0.3-3 Ledd), ten billion solar masses SMBHs, demonstrating that WISSH provides a simple and valuable tool to complete the census of the extreme SMBH population in the universe.We also succeeded in discovering [OIII] emission lines with a broad, skewed profile and exceptional luminosities (> 6e44 erg/s), tracing very powerful ionized outflows (up to ~4% of L_bol) in ~30% of the sample.Remarkably, the remaining 70% of quasars lacks [OIII] emission but shows strong winds traced by 3,000-8,000 km/s blueshifts of the high-ionization (CIV) with respect to low-ionization (Hbeta) broad emission lines, revealing strong radiatively driven winds that dominate the BLR kinematics.I will discuss the possible origins of this intriguing dichotomy which involves fundamental parameters such as bolometric luminosity, SMBH mass, Eddington ratio

  8. An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30. (United States)

    Wu, Xue-Bing; Wang, Feige; Fan, Xiaohui; Yi, Weimin; Zuo, Wenwen; Bian, Fuyan; Jiang, Linhua; McGreer, Ian D; Wang, Ran; Yang, Jinyi; Yang, Qian; Thompson, David; Beletsky, Yuri


    So far, roughly 40 quasars with redshifts greater than z = 6 have been discovered. Each quasar contains a black hole with a mass of about one billion solar masses (10(9) M Sun symbol). The existence of such black holes when the Universe was less than one billion years old presents substantial challenges to theories of the formation and growth of black holes and the coevolution of black holes and galaxies. Here we report the discovery of an ultraluminous quasar, SDSS J010013.02+280225.8, at redshift z = 6.30. It has an optical and near-infrared luminosity a few times greater than those of previously known z > 6 quasars. On the basis of the deep absorption trough on the blue side of the Lyman-α emission line in the spectrum, we estimate the proper size of the ionized proximity zone associated with the quasar to be about 26 million light years, larger than found with other z > 6.1 quasars with lower luminosities. We estimate (on the basis of a near-infrared spectrum) that the black hole has a mass of ∼1.2 × 10(10) M Sun symbol, which is consistent with the 1.3 × 10(10) M Sun symbol derived by assuming an Eddington-limited accretion rate.

  9. Discovery of a z = 0.65 post-starburst BAL quasar in the DES supernova fields

    Energy Technology Data Exchange (ETDEWEB)

    Mudd, Dale; Martini, Paul; Tie, Suk Sien; Lidman, Chris; McMahon, Richard; Banerji, Manda; Davis, Tamara; Peterson, Bradley; Sharp, Rob; Seymour, Nicholas; Childress, Michael; Lewis, Geraint; Tucker, Brad; Yuan, Fang; Abbot, Tim; Abdalla, Filipe; Allam, Sahar; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Camero Rosell, A.; Carrasco Kind, Matias; Carretero, Jorge; da Costa, Luiz N.; Desai, Shantanu; Diehl, Thomas; Eifler, Tim; Finley, David; Flaugher, Brenna; Glazebrook, Karl; Gruen, Daniel; Gruendl, Robert; Gutierrez, Gaston; Hinton, Samuel; Honscheid, Klaus; James, David; Kuehn, Kyler; Kuropatkin, Nikolav; Macaulay, Edward; Maia, Marcio A. G.; Miquel, Ramon; Ogando, Ricardo; Plazas, Andres; Riel, Kevin; Sanchez, Eusebio; Santiago, Basillio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Smith, Robert C.; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly; Tarle, Gregory; Thomas, Daniel; Uddin, Syed; Walker, Alistair; Zhang, Bonnie


    We present the discovery of a z=0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad FeII (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario.

  10. Discovery of a z = 0.65 post-starburst BAL quasar in the DES supernova fields (United States)

    Mudd, Dale; Martini, Paul; Tie, Suk Sien; Lidman, Chris; McMahon, Richard; Banerji, Manda; Davis, Tamara; Peterson, Bradley; Sharp, Rob; Seymour, Nicholas; Childress, Michael; Lewis, Geraint; Tucker, Brad; Yuan, Fang; Abbot, Tim; Abdalla, Filipe; Allam, Sahar; Benoit-Lévy, Aurélien; Bertin, Emmanuel; Brooks, David; Camero Rosell, A.; Carrasco Kind, Matias; Carretero, Jorge; da Costa, Luiz N.; Desai, Shantanu; Diehl, Thomas; Eifler, Tim; Finley, David; Flaugher, Brenna; Glazebrook, Karl; Gruen, Daniel; Gruendl, Robert; Gutierrez, Gaston; Hinton, Samuel; Honscheid, Klaus; James, David; Kuehn, Kyler; Kuropatkin, Nikolav; Macaulay, Edward; Maia, Marcio A. G.; Miquel, Ramon; Ogando, Ricardo; Plazas, Andres; Riel, Kevin; Sanchez, Eusebio; Santiago, Basillio; Schubnell, Michael; Sevilla-Noarbe, Ignacio; Smith, Robert C.; Soares-Santos, Marcelle; Sobreira, Flavia; Suchyta, Eric; Swanson, Molly; Tarle, Gregory; Thomas, Daniel; Uddin, Syed; Walker, Alistair; Zhang, Bonnie


    We present the discovery of a z = 0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad Fe II (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario.

  11. A new perspective on the infrared brightness temperature ...

    Indian Academy of Sciences (India)

    And Johnson SB parameters are observed to be best in discriminating the Johnson SB distribution of infrared brightness temperatures of deep convective systems for each season. Due to these properties of Johnson SB function, it can be utilized in the modelling of the histogram of infrared brightness temperature of deep ...

  12. A new perspective on the infrared brightness temperature ...

    Indian Academy of Sciences (India)

    It is observed that Johnson SB function is the best continuous distribution function in explaining the histogram of infrared brightness temperatures of the convective clouds. The best fit is confirmed by Kolmogorov–Smirnov statistic. Johnson SB's distribution of histogram of infrared brightness temperatures clearly ...

  13. Analysis of Bright Harvest Remote Analysis for Residential Solar Installations

    Energy Technology Data Exchange (ETDEWEB)

    Nangle, John [National Renewable Energy Lab. (NREL), Golden, CO (United States); Simon, Joseph [National Renewable Energy Lab. (NREL), Golden, CO (United States)


    Bright Harvest provides remote shading analysis and design products for residential PV system installers. The National Renewable Energy Laboratory (NREL) through the NREL Commercialization Assistance Program, completed comparative assessments between on-site measurements and remotely calculated values to validate the accuracy of Bright Harvest’s remote shading and power generation.

  14. Edge integration and the perception of brightness and darkness

    NARCIS (Netherlands)

    Vladusich, T.; Lucassen, M.P.; Cornelissen, F.W.


    How do induced brightness and darkness signals from local and remote surfaces interact to determine the final achromatic color percept of a target surface? An emerging theory of achromatic color perception posits that brightness and darkness percepts are computed by weighting and summing the

  15. The ASAS-SN bright supernova catalogue - III. 2016

    DEFF Research Database (Denmark)

    Holoien, T. W. -S.; Brown, J. S.; Stanek, K. Z.


    This catalogue summarizes information for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) and all other bright (m(peak)d......This catalogue summarizes information for all supernovae discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) and all other bright (m(peak)d...

  16. Lamp spectrum and spatial brightness at photopic levels

    DEFF Research Database (Denmark)

    Fotios, Steve; Atli, Deniz; Cheal, Chris


    Light sources are available in a variety of spectral power distributions (SPDs) and this affects spatial brightness in a manner not predicted by quantities such as illuminance. Tuning light source SPD to better match the sensitivity of visual perception may allow the same spatial brightness...

  17. Brightness limitations of cold field emitters caused by Coulomb interactions

    NARCIS (Netherlands)

    Cook, B.J.; Verduin, T.; Hagen, C.W.; Kruit, P.


    Emission theory predicts that high brightness cold field emitters can enhance imaging in the electron microscope. This (neglecting chromatic aberration) is because of the large (coherent) probe current available from a high brightness source and is based on theoretically determined values of reduced

  18. Surface photometry of bulge dominated low surface brightness galaxies

    NARCIS (Netherlands)

    Beijersbergen, M; de Blok, WJG; van der Hulst, JM


    We present results of broad band BVRI observations of a sample of galaxies with a low surface brightness (LSB) disk and a bulge. These galaxies are well described as exponential disks and exponential bulges with no preferred value for either scale length or central surface brightness. The median B

  19. Spatial Model of Sky Brightness Magnitude in Langkawi Island, Malaysia (United States)

    Redzuan Tahar, Mohammad; Kamarudin, Farahana; Umar, Roslan; Khairul Amri Kamarudin, Mohd; Sabri, Nor Hazmin; Ahmad, Karzaman; Rahim, Sobri Abdul; Sharul Aikal Baharim, Mohd


    Sky brightness is an essential topic in the field of astronomy, especially for optical astronomical observations that need very clear and dark sky conditions. This study presents the spatial model of sky brightness magnitude in Langkawi Island, Malaysia. Two types of Sky Quality Meter (SQM) manufactured by Unihedron are used to measure the sky brightness on a moonless night (or when the Moon is below the horizon), when the sky is cloudless and the locations are at least 100 m from the nearest light source. The selected locations are marked by their GPS coordinates. The sky brightness data obtained in this study were interpolated and analyzed using a Geographic Information System (GIS), thus producing a spatial model of sky brightness that clearly shows the dark and bright sky areas in Langkawi Island. Surprisingly, our results show the existence of a few dark sites nearby areas of high human activity. The sky brightness of 21.45 mag arcsec{}-2 in the Johnson-Cousins V-band, as the average of sky brightness equivalent to 2.8 × {10}-4{cd} {{{m}}}-2 over the entire island, is an indication that the island is, overall, still relatively dark. However, the amount of development taking place might reduce the number in the near future as the island is famous as a holiday destination.

  20. An isolated, bright cusp aurora at Saturn (United States)

    Kinrade, J.; Badman, S. V.; Bunce, E. J.; Tao, C.; Provan, G.; Cowley, S. W. H.; Grocott, A.; Gray, R. L.; Grodent, D.; Kimura, T.; Nichols, J. D.; Arridge, C. S.; Radioti, A.; Clarke, J. T.; Crary, F. J.; Pryor, W. R.; Melin, H.; Baines, K. H.; Dougherty, M. K.


    Saturn's dayside aurora displays a number of morphological features poleward of the main emission region. We present an unusual morphology captured by the Hubble Space Telescope on 14 June 2014 (day 165), where for 2 h, Saturn's FUV aurora faded almost entirely, with the exception of a distinct emission spot at high latitude. The spot remained fixed in local time between 10 and 15 LT and moved poleward to a minimum colatitude of 4°. It was bright and persistent, displaying intensities of up to 49 kR over a lifetime of 2 h. Interestingly, the spot constituted the entirety of the northern auroral emission, with no emissions present at any other local time—including Saturn's characteristic dawn arc, the complete absence of which is rarely observed. Solar wind parameters from propagation models, together with a Cassini magnetopause crossing and solar wind encounter, indicate that Saturn's magnetosphere was likely to have been embedded in a rarefaction region, resulting in an expanded magnetosphere configuration during the interval. We infer that the spot was sustained by reconnection either poleward of the cusp or at low latitudes under a strong component of interplanetary magnetic field transverse to the solar wind flow. The subsequent poleward motion could then arise from either reconfiguration of successive open field lines across the polar cap or convection of newly opened field lines. We also consider the possible modulation of the feature by planetary period rotating current systems.

  1. Intercomparisons of Nine Sky Brightness Detectors

    Directory of Open Access Journals (Sweden)

    Henk Spoelstra


    Full Text Available Nine Sky Quality Meters (SQMs have been intercompared during a night time measurement campaign held in the Netherlands in April 2011. Since then the nine SQMs have been distributed across the Netherlands and form the Dutch network for monitoring night sky brightness. The goal of the intercomparison was to infer mutual calibration factors and obtain insight into the variability of the SQMs under different meteorological situations. An ensemble average is built from the individual measurements and used as a reference to infer the mutual calibration factors. Data required additional synchronization prior to the calibration determination, because the effect of moving clouds combined with small misalignments emerges as time jitter in the measurements. Initial scatter of the individual instruments lies between ±14%. Individual night time sums range from −16% to +20%. Intercalibration reduces this to 0.5%, and −7% to +9%, respectively. During the campaign the smallest luminance measured was 0.657 ± 0.003 mcd/m2 on 12 April, and the largest value was 5.94 ± 0.03 mcd/m2 on 2 April. During both occurrences interfering circumstances like snow cover or moonlight were absent.

  2. The Los Alamos high-brightness photoinjector

    Energy Technology Data Exchange (ETDEWEB)

    O' Shea, P.G.


    For a number of years Los Alamos National Laboratory has been developing photocathode RF guns for high-brightness electron beam applications such as free-electron lasers (FELs). Previously thermionic high-voltage guns have been the source of choice for the electron accelerators used to drive FELs. The performance of such FELs is severely limited by the emittance growth produced by the subharmonic bunching process and also by the low peak current of the source. In a photoinjector, a laser driven photocathode is placed directly in a high-gradient RF accelerating cavity. A photocathode allows unsurpassed control over the current, and the spatial and temporal profile of the beam. In addition the electrodeless emission'' avoids many of the difficulties associated with multi-electrode guns, i.e. the electrons are accelerated very rapidly to relativistic energies, and there are no electrodes to distort the accelerating fields. For the past two years we have been integrating a photocathode into our existing FEL facility by replacing our thermionic gun and subharmonic bunchers with a high-gradient 1.3 GHz photoinjector. The photoinjector, which is approximately 0.6 m in length, produces 6 MeV, 300 A, 15 ps linac, and accelerated to a final energy of 40 MeV. We have recently begun lasing at wavelengths near 3 {mu}m. 16 refs., 2 figs., 5 tabs.

  3. Dark Skies, Bright Kids Year 6 (United States)

    Liss, Sandra; Troup, Nicholas William; Johnson, Kelsey E.; Barcos-Munoz, Loreto D.; Beaton, Rachael; Bittle, Lauren; Borish, Henry J.; Burkhardt, Andrew; Corby, Joanna; Dean, Janice; Hancock, Danielle; King, Jennie; Prager, Brian; Romero, Charles; Sokal, Kimberly R.; Stierwalt, Sabrina; Wenger, Trey; Zucker, Catherine


    Now entering our sixth year of operation, Dark Skies, Bright Kids (DSBK) is an entirely volunteer-run outreach organization based out of the Department of Astronomy at the University of Virginia. Our core mission is to enhance elementary science education and literacy in central Virginia through fun, hands-on activities that introduce basic Astronomy concepts beyond Virginia's Standards of Learning. Our primary focus is hosting an 8-10 week after-school astronomy club at underserved elementary and middle schools. Each week, DSBK volunteers take the role of coaches to introduce astronomy-related concepts ranging from the Solar System to galaxies to astrobiology, and to lead students in interactive learning activities. Another hallmark of DSBK is hosting our Annual Central Virginia Star Party, a free event open to the community featuring star-gazing and planetarium shows.DSBK has amassed over 15,000 contact hours since 2009 and we continue to broaden our impact. One important step we have taken in the past year is to establish a graduate student led assessment program to identify and implement directed learning goals for DSBK outreach. The collection of student workbooks, observations, and volunteer surveys indicates broad scale success for the program both in terms of student learning and their perception of science. The data also reveal opportunities to improve our organizational and educational practices to maximize student achievement and overall volunteer satisfaction for DSBK's future clubs and outreach endeavors.

  4. Dark Skies, Bright Kids Year 9 (United States)

    Burkhardt, Andrew Michael; Mathews, Allison M.; Johnson, Kelsey E.; Avilez, Ian; Beale, Luca; Bittle, Lauren E.; Bordenave, David; Finn, Molly; Firebaugh, Ariel; Hancock, Danielle; Hughes, Paul; Rochford Hayes, Christian; Lewis, Hannah; Linden, Sean; Liss, Sandra; Liu, Mengyao; McNair, Shunlante; Murphy, Edward; Prager, Brian; Pryal, Matthew; Richardson, Whitney; Song, Yiqing; Troup, Nicholas; Villadsen, Jackie; Wenger, Trey V.; Wilson, Robert Forrest


    We present updates from the ninth year of operation of Dark Skies, Bright Kids (DSBK) including new club content, continued assessments, and our seventh annual Star Party. DSBK is an entirely volunteer-run outreach organization based out of the Department of Astronomy at the University of Virginia. Our core mission is to enhance elementary science education and literacy in Virginia through fun, hands-on activities that introduce basic Astronomy concepts. DSBK’s most fundamental program is an 8-10 week long after-school Astronomy camp at surrounding local elementary schools, where each week introduces new concepts through interactive hands-on activities. Over the past two summers, we have traveled to four rural Virginia locations to bring week-long Astronomy camps to otherwise overlooked elementary school districts. These programs aim to inspire a curiosity for science and include inquiry based activities in topics ranging from the electromagnetic spectrum to the classification and evolution of galaxies. We strive to be self-reflective in our mission to inspire scientific curiosity in the minds of underserved demographics. In this effort, we continually assess the effectiveness of each activity through feedback in student-kept journal pages and observed excitement levels. This self-reflection has initiated the development of new curriculum. In addition, differing from our normal collaboration with local elementary schools, we have found great success partnering with local youth organizations, who may better represent DSBK's target demographics and have infrastructure to support incoming outreach groups.

  5. Bright visible light emission from graphene. (United States)

    Kim, Young Duck; Kim, Hakseong; Cho, Yujin; Ryoo, Ji Hoon; Park, Cheol-Hwan; Kim, Pilkwang; Kim, Yong Seung; Lee, Sunwoo; Li, Yilei; Park, Seung-Nam; Yoo, Yong Shim; Yoon, Duhee; Dorgan, Vincent E; Pop, Eric; Heinz, Tony F; Hone, James; Chun, Seung-Hyun; Cheong, Hyeonsik; Lee, Sang Wook; Bae, Myung-Ho; Park, Yun Daniel


    Graphene and related two-dimensional materials are promising candidates for atomically thin, flexible and transparent optoelectronics. In particular, the strong light-matter interaction in graphene has allowed for the development of state-of-the-art photodetectors, optical modulators and plasmonic devices. In addition, electrically biased graphene on SiO2 substrates can be used as a low-efficiency emitter in the mid-infrared range. However, emission in the visible range has remained elusive. Here, we report the observation of bright visible light emission from electrically biased suspended graphene devices. In these devices, heat transport is greatly reduced. Hot electrons (∼2,800 K) therefore become spatially localized at the centre of the graphene layer, resulting in a 1,000-fold enhancement in thermal radiation efficiency. Moreover, strong optical interference between the suspended graphene and substrate can be used to tune the emission spectrum. We also demonstrate the scalability of this technique by realizing arrays of chemical-vapour-deposited graphene light emitters. These results pave the way towards the realization of commercially viable large-scale, atomically thin, flexible and transparent light emitters and displays with low operation voltage and graphene-based on-chip ultrafast optical communications.

  6. Modular Zero Energy. BrightBuilt Home

    Energy Technology Data Exchange (ETDEWEB)

    Aldrich, Robb [Consortium for Advanced Residential Buildings (CARB), Norwalk, CT (United States). Steven Winters Associates, Inc.; Butterfield, Karla [Consortium for Advanced Residential Buildings (CARB), Norwalk, CT (United States). Steven Winters Associates, Inc.


    Kaplan Thompson Architects (KTA) has specialized in sustainable, energy-efficient buildings, and they have designed several custom, zero-energy homes in New England. These zero-energy projects have generally been high-end, custom homes with budgets that could accommodate advanced energy systems. In an attempt to make zero energy homes more affordable and accessible to a larger demographic, KTA explored modular construction as way to provide high-quality homes at lower costs. In the mid-2013, KTA formalized this concept when they launched BrightBuilt Home (BBH). The BBH mission is to offer a line of architect-designed, high-performance homes that are priced to offer substantial savings off the lifetime cost of a typical home and can be delivered in less time. For the past two years, CARB has worked with BBH and Keiser Homes (the primary modular manufacturer for BBH) to discuss challenges related to wall systems, HVAC, and quality control. In Spring of 2014, CARB and BBH began looking in detail on a home to be built in Lincolnville, ME by Black Bros. Builders. This report details the solution package specified for this modular plan and the challenges that arose during the project.

  7. Intrinsic brightness temperatures of blazar jets at 15 GHz

    Directory of Open Access Journals (Sweden)

    Hovatta Talvikki


    Full Text Available We have developed a new Bayesian Markov Chain Monte Carlo method to deconvolve light curves of blazars into individual flares, including proper estimation of the fit errors. We use the method to fit 15GHzlight curves obtained within the OVRO 40-m blazar monitoring program where a large number of AGN have been monitored since 2008 in support of the Fermi Gamma-Ray Space Telescope mission. The time scales obtained from the fitted models are used to calculate the variability brightness temperature of the sources. Additionally, we have calculated brightness temperatures of a sample of these objects using Very Long Baseline Array data from the MOJAVE survey. Combining these two data sets enables us to study the intrinsic brightness temperature distribution in these blazars at 15 GHz. Our preliminary results indicate that the mean intrinsic brightness temperature in a sample of 14 sources is near the equipartition brightness temperature of ~ 1011K.

  8. X-Ray Bright Optically Faint AGNs Found in XMM-Newton and Subaru Hyper Suprime-Cam Surveys (United States)

    Terashima, Y.; Suganuma, M.; Akiyama, M.; Greene, J.; Kawaguchi, T.; Iwasawa, K.; Nagao, T.; Toba, Y.; Ueda, Y.; Yamashita, T.


    We present a new sample of X-ray bright optically faint active galactic nuclei selected by combining XMM-Newton and Subaru Hyper Suprime-Cam surveys. 53 X-ray sources satisfying i band magnitude fainter than 23.5 mag and X-ray counts with EPIC-PN detector larger than 70 are selected from 9 deg^2 in the XMM-XXL field, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. 46 objects with an X-ray to i band flux ratio F_{X}/F_{i}>10 are classified as extreme X-ray-to-optical flux sources. SEDs of 48 among 53 are represented by templates of type 2 AGNs or starforming galaxies and show signature of stellar emission from host galaxies in the optical in the source rest frame. X-ray spectra are fitted by an absorbed power law model, and the intrinsic absorption column densities are modest (best-fit log N_{H} = 20.5-23.5 cm^{-2} in most cases). The absorption corrected X-ray luminosities are in a range of 6×10^{42}-2×10^{45} erg s^{-1}. 20 objects are classified as type 2 quasars. The optical faintness is explained by a combination of redshifts (mostly z>1.0), strong dust extinction, and in part a large ratio of dust/gas.


    Energy Technology Data Exchange (ETDEWEB)

    Hainline, Laura J.; Morgan, Christopher W.; Beach, Joseph N.; Le, Truong X. [Department of Physics, United States Naval Academy, 572C Holloway Road, Annapolis, MD 21402 (United States); Kochanek, C. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Harris, Hugh C.; Tilleman, Trudy [United States Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001-8521 (United States); Fadely, Ross [Department of Astronomy, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041 (United States); Falco, Emilio E., E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)


    We present evidence for ultraviolet/optical microlensing in the gravitationally lensed quasar Q 0957+561. We combine new measurements from our optical monitoring campaign at the United States Naval Observatory, Flagstaff, with measurements from the literature and find that the time-delay-corrected r-band flux ratio m{sub A} - m{sub B} has increased by {approx}0.1 mag over a period of five years beginning in the fall of 2005. We apply our Monte Carlo microlensing analysis procedure to the composite light curves, obtaining a measurement of the optical accretion disk size, log ((r{sub s} /cm)[cos (i)/0.5]{sup 1/2}) = 16.2 {+-} 0.5, that is consistent with the quasar accretion disk size-black hole mass relation.

  10. Galaxy evolution. Black hole feedback in the luminous quasar PDS 456. (United States)

    Nardini, E; Reeves, J N; Gofford, J; Harrison, F A; Risaliti, G; Braito, V; Costa, M T; Matzeu, G A; Walton, D J; Behar, E; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Matt, G; Miller, J M; O'Brien, P T; Stern, D; Turner, T J; Ward, M J


    The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution. Copyright © 2015, American Association for the Advancement of Science.

  11. Hunting for Intrinsically X-ray Weak Quasars: The Case of PHL 1811 Analogs (United States)

    Brandt, William


    A central dogma of X-ray astronomy is that luminous X-ray emission is a universal property of efficiently accreting supermassive black holes. One interesting challenge to this idea has come from the quasar PHL 1811 which appears to be intrinsically X-ray weak and also has distinctive emission-line properties. We propose to observe a sample of eight SDSS quasars, selected to have similar UV emission-line properties to that of PHL 1811, to test if they are also X-ray weak. Our analyses of the currently available X-ray data appear to support this hypothesis but do not provide a proper test. Our results will have implications for the nature of accretion-disk coronae, emission-line formation, and AGN selection.

  12. Black Holes, Quasars, Blazars, and all that. . . How to explain them to a lay audience? (United States)

    Hamidani, Hamid; Mimouni, Jamal


    The popularisation of science is central to the culture of the citizen, and if astronomy make poets dream (and many others), astrophysics attracts young and old talents to science. To reveal in simple terms the stellar bestiary from the black holes to the quasars proceeds along this line. Black hole is still the object which is subject to most questions in any public talk on astronomy. How indeed does contemporary physics link the black hole, this stellar gravitational tomb, with the quasar, a galaxy gone mad? The tale is worth telling and makes indeed a beautiful story for contemporary young audience. Can it be told to our high school students with their modest scientific background? This is what we intend to do in this paper, spicing the sauce at the end with some new insights on the unified model of AGN.

  13. Major galaxy mergers and the growth of supermassive black holes in quasars. (United States)

    Treister, Ezequiel; Natarajan, Priyamvada; Sanders, David B; Urry, C Megan; Schawinski, Kevin; Kartaltepe, Jeyhan


    Despite observed strong correlations between central supermassive black holes (SMBHs) and star formation in galactic nuclei, uncertainties exist in our understanding of their coupling. We present observations of the ratio of heavily obscured to unobscured quasars as a function of cosmic epoch up to z congruent with 3 and show that a simple physical model describing mergers of massive, gas-rich galaxies matches these observations. In the context of this model, every obscured and unobscured quasar represents two distinct phases that result from a massive galaxy merger event. Much of the mass growth of the SMBH occurs during the heavily obscured phase. These observations provide additional evidence for a causal link between gas-rich galaxy mergers, accretion onto the nuclear SMBH, and coeval star formation.

  14. A swirling jet in the quasar 1308+326 (United States)

    Britzen, S.; Qian, S.-J.; Steffen, W.; Kun, E.; Karouzos, M.; Gergely, L.; Schmidt, J.; Aller, M.; Aller, H.; Krause, M.; Fendt, C.; Böttcher, M.; Witzel, A.; Eckart, A.; Moser, L.


    Context. Despite numerous and detailed studies of the jets of active galactic nuclei (AGN) on pc-scales, many questions are still debated. The physical nature of the jet components is one of the most prominent unsolved problems, as is the launching mechanism of jets in AGN. The quasar 1308+326 (z = 0.997) allows us to study the overall properties of its jet in detail and to derive a more physical understanding of the nature and origin of jets in general. The long-term data provided by the Monitoring Of Jets in Active galactic nuclei with Very Long Baseline Array (VLBA) experiments (MOJAVE) survey permit us to trace out the structural changes in 1308+326 that we present here. The long-lived jet features in this source can be followed for about two decades. Aims: We investigate the very long baseline interferomety (VLBI) morphology and kinematics of the jet of 1308+326 to understand the physical nature of this jet and jets in general, the role of magnetic fields, and the causal connection between jet features and the launching process. Methods: Fifty VLBA observations performed at 15 GHz from the MOJAVE survey were re-modeled with Gaussian components and re-analyzed (the time covered: 20 Jan. 1995-25 Jan. 2014). The analysis was supplemented by multi-wavelength radio-data (UMRAO, at 4.8, 8.0, and 14.5 GHz) in polarization and total intensity. We fit the apparent motion of the jet features with the help of a model of a precessing nozzle. Results: The jet features seem to be emitted with varying viewing angles and launched into an ejection cone. Tracing the component paths yields evidence for rotational motion. Radio flux-density variability can be explained as a consequence of enhanced Doppler boosting corresponding to the motion of the jet relative to the line of sight. Based on the presented kinematics and other indicators, such as electric-vector polarization position-angle (EVPA) rotation, we conclude that the jet of 1308+326 has a helical structure, meaning that

  15. A Microlensing Analysis of the Central Engine in the Lensed Quasar WFI J2033-4723 (United States)

    Hyer, Gregory Edward; Morgan, Christopher; Bonvin, Vivien; Courbin, Fredric; Kochanek, Christopher; Falco, Emilio


    We report a detection of uncorrelated variability in 12 season optical light curves of the gravitationally lensed quasar WFI J2033-4723 from the 1.3m SMARTS telescope at CTIO and the 1.5m EULER telescope in La Silla. We analyzed this variability using the Monte Carlo technique of Kochanek (2004) to yield the first measurement of the size of this quasar’s accretion disk.

  16. Deep Learning of Quasar Spectra to Discover and Characterize Damped Lyα Systems (United States)

    Parks, David; Xavier Prochaska, J.; Dong, Shawfeng; Cai, Zheng


    We have designed, developed, and applied a convolutional neural network (CNN) architecture using multi-task learning to search for and characterize strong HI Lyα absorption in quasar spectra. Without any explicit modeling of the quasar continuum nor application of the predicted line-profile for Lyα from quantum mechanics, our algorithm predicts the presence of strong HI absorption and estimates the corresponding redshift zabs and HI column density NHI, with emphasis on damped Lyα systems (DLAs, absorbers with NHI ≥ 2 × 1020 cm-2). We tuned the CNN model using a custom training set of DLAs injected into DLA-free quasar spectra from the Sloan Digital Sky Survey (SDSS), data release 5 (DR5). Testing on a held-back validation set demonstrates a high incidence of DLAs recovered by the algorithm (97.4% as DLAs and 99% as an HI absorber with NHI > 1019.5 cm-2) and excellent estimates for zabs and NHI. Similar results are obtained against a human-generated survey of the SDSS DR5 dataset. The algorithm yields a low incidence of false positives and negatives but is challenged by overlapping DLAs and/or very high NHI systems. We have applied this CNN model to the quasar spectra of SDSS-DR7 and the Baryonic Oscillation Spectroscopic Survey (BOSS, data release 12) and provide catalogs of 4,913 and 50,969 DLAs respectively (including 1,659 and 9,230 high-confidence DLAs that were previously unpublished). This work validates the application of deep learning techniques to astronomical spectra for both classification and quantitative measurements.

  17. Exploring a Potential Bias in Dark Matter Investigations Using Strongly Lensed Quasars (United States)

    Hsueh, Jen-Wei; Fassnacht, Christopher; Vegetti, Simona; Springola, Cristiana; Oldham, Lindsay; Despali, Giulia; Auger, Matthew; Xu, Dandan; Metcalf, Benton; McKean, John; Koopmans, Leon; Lagattuta, David


    Simulations based on ΛCDM cosmology predict thousands of substructures under galactic scale have not been detected in the local universe. One hypothesis proposes that most of these substructures are dark for various astrophysical reasons. Gravitational lensing provides a powerful alternative way to probe dark substructures in distant galaxies by detecting their gravitational perturbations and therefore provides insights into the nature of dark matter. Lensed quasars with certain image configurations are especially promising for probing substructure abundance in lens galaxy halos. When the observed flux ratios of the lensed quasar images deviate from the smooth mass model predictions, these “flux-ratio anomalies” are considered to be the evidence of gravitational perturbations. While the standard analysis of flux-ratio anomalies assumes that substructures are the only cause of anomalies, we found that in two edge-on disk lenses, B1555+375 and B0712+472, their flux anomalies can be explained by including disk components into their mass models. Our results bring up a concern with a potential bias in the previous analyses of flux-ratio anomalies. To further investigate the baryonic effects in flux-ratio anomalies, we create mock quasar lenses by selecting disk and elliptical galaxies in the Illustris simulation. Our analysis shows that baryon-induced flux anomalies can be found in all morphological types of lens galaxies. The baryonic effects increase the probability of finding lenses with strong anomalies by 8% in ellipticals and 10~20% in disk lenses, showing that the baryonic effects are unneglectable in the analysis. As future large-scale surveys are expected to bring numerous lensed quasar samples, further investigations on baryonic effects should be done in order to achieve precise constraints on dark matter in the future.

  18. Collapse of primordial gas clouds and the formation of quasar black holes (United States)

    Loeb, Abraham; Rasio, Frederic A.


    The formation of quasar black holes during the hydrodynamic collapse of protogalactic gas clouds is discussed. The dissipational collapse and long-term dynamical evolution of these systems is analyzed using three-dimensional numerical simulations. The calculations focus on the final collapse stages of the inner baryonic component and therefore ignore the presence of dark matter. Two types of initial conditions are considered: uniformly rotating spherical clouds, and iirotational ellipsoidal clouds. In both cases the clouds are initially cold, homogeneous, and not far from rotational support (T/(absolute value of W) approximately equals 0.1). Although the details of the dynamical evolution depend sensitively on the initial conditions, the qualitative features of the final configurations do not. Most of the gas is found to fragment into small dense clumps, that eventually make up a spheroidal component resembling a galactic bulge. About 5% of the initial mass remains in the form of a smooth disk of gas supported by rotation in the gravitational potential potential well of the outer spheroid. If a central seed black hole of mass approximately greater than 10(exp 6) solar mass forms, it can grow by steady accretion from the disk and reach a typical quasar black hole mass approximately 10(exp 8) solar mass in less than 5 x 10(exp 8) yr. In the absence of a sufficiently massive seed, dynamical instabilities in a strongly self-gravitating inner region of the disk will inhibit steady accretion of gas and may prevent the immediate formation of quasar.

  19. Quasar-Lyman α forest cross-correlation from BOSS DR11: Baryon Acoustic Oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Kirkby, David; Blomqvist, Michael [Department of Physics and Astronomy, University of California, 4129 Frederick Reines Hall, Irvine, CA, 92697 (United States); Busca, Nicolas; Aubourg, Éric; Bautista, Julian [APC, Université Paris Diderot-Paris 7, CNRS/IN2P3, CEA, Observatoire de Paris, 10, rue A. Domon and L. Duquet, Paris (France); Miralda-Escudé, Jordi [Institut de Ciències del Cosmos (IEEC/UB), Martí i Franquès 1, Barcelona, 08028 Catalonia (Spain); Ross, Nicholas P.; Bailey, Stephen; Beutler, Florian; Carithers, Bill [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States); Slosar, Anže [Brookhaven National Laboratory, Blgd 510, Upton, NY, 11375 (United States); Rich, James; Delubac, Timothée [CEA, Centre de Saclay, IRFU, Gif-sur-Yvette, 91191 France (France); Bhardwaj, Vaishali; Bizyaev, Dmitry [Department of Astronomy, University of Washington, Box 351580, Seattle, WA, 98195 (United States); Brewington, Howard; Brinkmann, Jon [Apache Point Observatory and New Mexico State University, P.O. Box 59, Sunspot, NM, 88349-0059 (United States); Brownstein, Joel R.; Dawson, Kyle S., E-mail: [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Salt Lake City, UT, 84112 (United States); and others


    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption, using over 164,000 quasars from Data Release 11 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We extend the previous study of roughly 60,000 quasars from Data Release 9 to larger separations, allowing a measurement of the Baryonic Acoustic Oscillation (BAO) scale along the line of sight c/(H(z = 2.36)r{sub s}) = 9.0±0.3 and across the line of sight D{sub A}(z = 2.36)/r{sub s} = 10.8±0.4, consistent with CMB and other BAO data. Using the best fit value of the sound horizon from Planck data (r{sub s} = 147.49 Mpc), we can translate these results to a measurement of the Hubble parameter of H(z = 2.36) = 226±8 km s{sup −1} Mpc{sup −1} and of the angular diameter distance of D{sub A}(z = 2.36) = 1590±60 Mpc. The measured cross-correlation function and an update of the code to fit the BAO scale (baofit) are made publicly available.

  20. The Relationship between Mg ii Broad Emission and Quasar Inclination Angle

    Directory of Open Access Journals (Sweden)

    Conor Wildy


    Full Text Available Several observed spectral properties of quasars are believed to be influenced by quasar orientation. In this investigation we examine the effect of orientation on the Mg ii line located at 2,798 Å in a sample of 36 radio-loud quasars, with orientation angles having been obtained in a previous study using radio observations. We find no significant relationship between orientation angle and either Mg ii line full-width at half-maximum or equivalent width. The lack of correlation with inclination angle contradicts previous studies which also use radio data as a proxy for inclination angle and suggests the Mg ii emission region does not occupy a disk-like geometry. The lack of correlation with Mg ii equivalent width, however, is reported in at least one previous study. Although the significance is not very strong (86%, there is a possible negative relationship between inclination angle and Fe ii strength which, if true, could explain the Fe ii anti-correlation with [O iii] strength associated with Eigenvector 1. Interestingly, there are objects having almost edge-on inclinations while still exhibiting broad lines. This could be explained by a torus which is either clumpy (allowing sight lines to the central engine or mis-aligned with the accretion disk.

  1. New constraints on quasar broad absorption and emission line regions from gravitational microlensing (United States)

    Hutsemékers, Damien; Braibant, Lorraine; Sluse, Dominique; Anguita, Timo; Goosmann, René


    Gravitational microlensing is a powerful tool allowing one to probe the structure of quasars on sub-parsec scale. We report recent results, focusing on the broad absorption and emission line regions. In particular microlensing reveals the intrinsic absorption hidden in the P Cygni-type line profiles observed in the broad absorption line quasar H1413+117, as well as the existence of an extended continuum source. In addition, polarization microlensing provides constraints on the scattering region. In the quasar Q2237+030, microlensing differently distorts the Hα and CIV broad emission line profiles, indicating that the low- and high-ionization broad emission lines must originate from regions with distinct kinematical properties. We also present simulations of the effect of microlensing on line profiles considering simple but representative models of the broad emission line region. Comparison of observations to simulations allows us to conclude that the Hα emitting region in Q2237+030 is best represented by a Keplerian disk.

  2. AKARI Spectroscopy of Quasars at 2.5 - 5 μm (United States)

    Im, Myungshin; Jun, Hyunsung; Kim, Dohyeong; Lee, Hyung Mok; Ohyama, Youichi; Ji, Hoon~Kim; Nakagawa, Takao; QSONG Team


    Utilizing a unique capability of AKARI that allows deep spectroscopy at 2.5 - 5.0 μm, we performed a spectroscopy study of more than 200 quasars through one of the AKARI mission programs, QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG targeted 155 high redshift (3.3 3.3. The low redshift part of QSONG is geared to uncover the rest-frame 2.5 - 5.0 μm spectral features of active galactic nuclei to gain useful information such as the dust-extinction-free black hole mass estimators based on the Brackett lines and the temperatures of the hot dust torus. We outline the program strategy, and present some of the scientific highlights from QSONG, including the detection of the Hα line from a quasar at z > 4.5 which indicates a rigorous growth of black holes in the early universe, and the Brβ-based black hole mass estimators and the hot dust temperatures (˜1100 K) of low redshift AGNs.


    Energy Technology Data Exchange (ETDEWEB)

    Guerras, E.; Mediavilla, E. [Instituto de Astrofisica de Canarias, Via Lactea S/N, La Laguna E-38200, Tenerife (Spain); Jimenez-Vicente, J. [Departamento de Fisica Teorica y del Cosmos, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada (Spain); Kochanek, C. S. [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, The Ohio State University, 4055 McPherson Lab, 140 West 18th Avenue, Columbus, OH 43221 (United States); Munoz, J. A. [Departamento de Astronomia y Astrofisica, Universidad de Valencia, E-46100 Burjassot, Valencia (Spain); Falco, E. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Motta, V. [Departamento de Fisica y Astronomia, Universidad de Valparaiso, Avda. Gran Bretana 1111, Valparaiso (Chile)


    We measure the differential microlensing of the broad emission lines between 18 quasar image pairs in 16 gravitational lenses. We find that the broad emission lines are in general weakly microlensed. The results show, at a modest level of confidence (1.8{sigma}), that high ionization lines such as C IV are more strongly microlensed than low ionization lines such as H{beta}, indicating that the high ionization line emission regions are more compact. If we statistically model the distribution of microlensing magnifications, we obtain estimates for the broad line region size of r{sub s} = 24{sup +22} {sub -15} and r{sub s} = 55{sup +150} {sub -35} lt-day (90% confidence) for the high and low ionization lines, respectively. When the samples are divided into higher and lower luminosity quasars, we find that the line emission regions of more luminous quasars are larger, with a slope consistent with the expected scaling from photoionization models. Our estimates also agree well with the results from local reveberation mapping studies.


    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Anne H. [Institut de Ciencies de l' Espai, CSIC/IEEC, F. de Ciencies, Torre C5 par-2, Barcelona 08193 (Spain); Baltay, Charles; Ellman, Nancy; Jerke, Jonathan; Rabinowitz, David; Scalzo, Richard, E-mail: [Yale University, Department of Physics, P.O. Box 208120, New Haven, CT 06520-8120 (United States)


    Accurate measurement of galaxy cluster masses is an essential component not only in studies of cluster physics but also for probes of cosmology. However, different mass measurement techniques frequently yield discrepant results. The Sloan Digital Sky Survey MaxBCG catalog's mass-richness relation has previously been constrained using weak lensing shear, Sunyaev-Zeldovich (SZ), and X-ray measurements. The mass normalization of the clusters as measured by weak lensing shear is {approx}>25% higher than that measured using SZ and X-ray methods, a difference much larger than the stated measurement errors in the analyses. We constrain the mass-richness relation of the MaxBCG galaxy cluster catalog by measuring the gravitational lensing magnification of type I quasars in the background of the clusters. The magnification is determined using the quasars' variability and the correlation between quasars' variability amplitude and intrinsic luminosity. The mass-richness relation determined through magnification is in agreement with that measured using shear, confirming that the lensing strength of the clusters implies a high mass normalization and that the discrepancy with other methods is not due to a shear-related systematic measurement error. We study the dependence of the measured mass normalization on the cluster halo orientation. As expected, line-of-sight clusters yield a higher normalization; however, this minority of haloes does not significantly bias the average mass-richness relation of the catalog.

  5. New Constraints on Quasar Broad Absorption and Emission Line Regions from Gravitational Microlensing

    Directory of Open Access Journals (Sweden)

    Damien Hutsemékers


    Full Text Available Gravitational microlensing is a powerful tool allowing one to probe the structure of quasars on sub-parsec scale. We report recent results, focusing on the broad absorption and emission line regions. In particular microlensing reveals the intrinsic absorption hidden in the P Cygni-type line profiles observed in the broad absorption line quasar H1413+117, as well as the existence of an extended continuum source. In addition, polarization microlensing provides constraints on the scattering region. In the quasar Q2237+030, microlensing differently distorts the Hα and CIV broad emission line profiles, indicating that the low- and high-ionization broad emission lines must originate from regions with distinct kinematical properties. We also present simulations of the effect of microlensing on line profiles considering simple but representative models of the broad emission line region. Comparison of observations to simulations allows us to conclude that the Hα emitting region in Q2237+030 is best represented by a Keplerian disk.

  6. Dark Skies, Bright Kids: Year 2 (United States)

    Carlberg, Joleen K.; Johnson, K.; Lynch, R.; Walker, L.; Beaton, R.; Corby, J.; de Messieres, G.; Drosback, M.; Gugliucci, N.; Jackson, L.; Kingery, A.; Layman, S.; Murphy, E.; Richardson, W.; Ries, P.; Romero, C.; Sivakoff, G.; Sokal, K.; Trammell, G.; Whelan, D.; Yang, A.; Zasowski, G.


    The Dark Skies, Bright Kids (DSBK) outreach program brings astronomy education into local elementary schools in central Virginia's Southern Albemarle County through an after-school club. Taking advantage of the unusually dark night skies in the rural countryside, DSBK targets economically disadvantaged schools that tend to be underserved due to their rural locale. The goals of DSBK are to foster children's natural curiosity, demonstrate that science is a fun and creative process, challenge students' conceptions of what a scientist is and does, and teach some basic astronomy. Furthermore, DSBK works to assimilate families into students' education by holding family observing nights at the school. Now in its third semester, DSBK has successfully run programs at two schools with very diverse student populations. Working with these students has helped us to revise our activities and to create new ones. A by-product of our work has been the development of lesson plans, complete with learning goals and detailed instructions, that we make publically available on our website. This year we are expanding our repertoire with our new planetarium, which allows us to visualize topics in novel ways and supplements family observing on cloudy nights. The DSBK volunteers have also created a bilingual astronomy artbook --- designed, written, and illustrated by UVa students --- that we will publish and distribute to elementary schools in Virginia. Our book debuted at the last AAS winter meeting, and since then it has been extensively revised and updated with input from many individuals, including parents, professional educators, and a children's book author. Because the club is currently limited to serving a few elementary schools, this book will be part of our efforts to broaden our impact by bringing astronomy to schools we cannot go to ourselves and reaching out to Spanish-speaking communities at the same time.

  7. Visual features underlying perceived brightness as revealed by classification images.

    Directory of Open Access Journals (Sweden)

    Ilmari Kurki

    Full Text Available Along with physical luminance, the perceived brightness is known to depend on the spatial structure of the stimulus. Often it is assumed that neural computation of the brightness is based on the analysis of luminance borders of the stimulus. However, this has not been tested directly. We introduce a new variant of the psychophysical reverse-correlation or classification image method to estimate and localize the physical features of the stimuli which correlate with the perceived brightness, using a brightness-matching task. We derive classification images for the illusory Craik-O'Brien-Cornsweet stimulus and a "real" uniform step stimulus. For both stimuli, classification images reveal a positive peak at the stimulus border, along with a negative peak at the background, but are flat at the center of the stimulus, suggesting that brightness is determined solely by the border information. Features in the perceptually completed area in the Craik-O'Brien-Cornsweet do not contribute to its brightness, nor could we see low-frequency boosting, which has been offered as an explanation for the illusion. Tuning of the classification image profiles changes remarkably little with stimulus size. This supports the idea that only certain spatial scales are used for computing the brightness of a surface.

  8. Quantitative Brightness Analysis of Fluorescence Intensity Fluctuations in E. Coli.

    Directory of Open Access Journals (Sweden)

    Kwang-Ho Hur

    Full Text Available The brightness measured by fluorescence fluctuation spectroscopy specifies the average stoichiometry of a labeled protein in a sample. Here we extended brightness analysis, which has been mainly applied in eukaryotic cells, to prokaryotic cells with E. coli serving as a model system. The small size of the E. coli cell introduces unique challenges for applying brightness analysis that are addressed in this work. Photobleaching leads to a depletion of fluorophores and a reduction of the brightness of protein complexes. In addition, the E. coli cell and the point spread function of the instrument only partially overlap, which influences intensity fluctuations. To address these challenges we developed MSQ analysis, which is based on the mean Q-value of segmented photon count data, and combined it with the analysis of axial scans through the E. coli cell. The MSQ method recovers brightness, concentration, and diffusion time of soluble proteins in E. coli. We applied MSQ to measure the brightness of EGFP in E. coli and compared it to solution measurements. We further used MSQ analysis to determine the oligomeric state of nuclear transport factor 2 labeled with EGFP expressed in E. coli cells. The results obtained demonstrate the feasibility of quantifying the stoichiometry of proteins by brightness analysis in a prokaryotic cell.

  9. Probing the Interstellar Medium and Star Formation of the Most Luminous Quasar at z = 6.3 (United States)

    Wang, Ran; Wu, Xue-Bing; Neri, Roberto; Fan, Xiaohui; Walter, Fabian; Carilli, Chris L.; Momjian, Emmanuel; Bertoldi, Frank; Strauss, Michael A.; Li, Qiong; Wang, Feige; Riechers, Dominik A.; Jiang, Linhua; Omont, Alain; Wagg, Jeff; Cox, Pierre


    We report new IRAM/PdBI, JCMT/SCUBA-2, and VLA observations of the ultraluminous quasar SDSS J010013.02+280225.8 (hereafter, J0100+2802) at z = 6.3, which hosts the most massive supermassive black hole (SMBH), 1.24× {10}10 {M}⊙ , that is known at z > 6. We detect the [C II] 158 μm fine structure line and molecular CO(6-5) line and continuum emission at 353, 260, and 3 GHz from this quasar. The CO(2-1) line and the underlying continuum at 32 GHz are also marginally detected. The [C II] and CO detections suggest active star formation and highly excited molecular gas in the quasar host galaxy. The redshift determined with the [C II] and CO lines shows a velocity offset of ˜ 1000 {km} {{{s}}}-1 from that measured with the quasar Mg II line. The CO (2-1) line luminosity provides a direct constraint on the molecular gas mass, which is about (1.0+/- 0.3)× {10}10 {M}⊙ . We estimate the FIR luminosity to be (3.5+/- 0.7)× {10}12 {L}⊙ , and the UV-to-FIR spectral energy distribution of J0100+2802 is consistent with the templates of the local optically luminous quasars. The derived [C II]-to-FIR luminosity ratio of J0100+2802 is 0.0010 ± 0.0002, which is slightly higher than the values of the most FIR luminous quasars at z ˜ 6. We investigate the constraint on the host galaxy dynamical mass of J0100+2802 based on the [C II] line spectrum. It is likely that this ultraluminous quasar lies above the local SMBH-galaxy mass relationship, unless we are viewing the system at a small inclination angle.

  10. High-speed CuBr brightness amplifier beam profile (United States)

    Evtushenko, G. S.; Torgaev, S. N.; Trigub, M. V.; Shiyanov, D. V.; Evtushenko, T. G.; Kulagin, A. E.


    This paper addresses the experimental study of the beam profile of the CuBr brightness amplifier operating at a wide range of pulse repetition frequencies. The use of a medium-size gas discharge tube (2 cm) ensures the operation of the brightness amplifier both at typical PRFs (520 kHz) and at higher PRFs (up to 100 kHz), either with or without HBr additive. The effect of the active additive on the beam profile is demonstrated. The testing results on kinetic modeling of radial processes in the laser (brightness amplifier) plasma are also discussed.

  11. Intervening Mg II absorption systems from the SDSS DR12 quasar spectra (United States)

    Raghunathan, Srinivasan; Clowes, Roger G.; Campusano, Luis E.; Söchting, Ilona K.; Graham, Matthew J.; Williger, Gerard M.


    We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the 12th data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0σ level respectively for the two lines of the doublet. The catalogue was constrained to an absorption line redshift of 0.35 ≤ z2796 ≤ 2.3. The rest-frame equivalent width of the λ2796 line ranges between 0.2 ≤ Wr ≤ 6.2 Å. Using Gaussian noise-only simulations, we estimate a false positive rate of 7.7 per cent in the catalogue. We measured the number density ∂N2796/∂z of Mg II absorbers and find evidence for steeper evolution of the systems with Wr ≥ 1.2 Å at low redshifts (z2796 ≤ 1.0), consistent with other earlier studies. A suite of null tests over the redshift range 0.5 ≤ z2796 ≤ 1.5 was used to study the presence of systematics and selection effects like the dependence of the number density evolution of the absorption systems on the properties of the background quasar spectra. The null tests do not indicate the presence of any selection effects in the absorption catalogue if the quasars with spectral signal-to-noise level less than 5.0 are removed. The resultant catalogue contains 36,981 absorption systems. The Mg II absorption catalogue is publicly available and can be downloaded from the link

  12. A Study of Galaxies and Quasars in the Background of the Andromeda Galaxy (United States)

    Dhara, Atirath; McConnell, Kaela; Guhathakurta, Puragra; Roy, Namrata; Waite, Jurij


    The SPLASH (Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo) survey is based on wide-field ground-based optical images (KPNO 4-m/Mosaic, CFHT 3.6-m/MegaCam imager, and Subaru 8-m/Suprime-Cam), deep Hubble Space Telescope ultraviolet/optical/near infrared images (ACS and WFC3), and medium resolution spectra (Keck II 10-m/DEIMOS). The SPLASH survey data set contains two main categories of (non-M31) contaminants (SPLASH trash, if you will): foreground Milky Way stars and compact background galaxies/quasars. In this poster, we present the discovery and characterization of galaxies and quasars behind M31. Such objects were identified based on the presence of redshifted emission lines and other galaxy/quasar spectral features (e.g., Ca H+K absorption and IGM absorption). The redshift of each galaxy was measured by cross-correlating its spectrum against an emission line galaxy spectral template. The cross-correlation results (spectrum and best-fit template) were visually inspected to identify cases of incorrect matching of emission lines. Many of these incorrect redshift estimates were corrected by using the second or third highest cross-correlation peak. Quasar redshifts were determined based on cross-correlation against a quasar spectral template. Most of the galaxies in our sample are star forming galaxies with strong emission lines. We analyze their emission line flux ratios in a BPT diagram to learn more about the ionization source and metallicity. Finally, the properties of these compact galaxies behind M31 are compared to those of galaxies selected in a more standard way in the DEEP2 redshift survey to explore the effects of morphological pre-selection (compact vs. extended) on the properties of the resulting galaxy sample.This research was supported by NASA/STScI and the National Science Foundation. Most of this work was carried out by high school students working under the auspices of the Science Internship Program (SIP) at UC Santa Cruz.

  13. An Optically Faint Quasar Survey at z ˜ 5 in the CFHTLS Wide Field: Estimates of the Black Hole Masses and Eddington Ratios (United States)

    Ikeda, H.; Nagao, T.; Matsuoka, K.; Kawakatu, N.; Kajisawa, M.; Akiyama, M.; Miyaji, T.; Morokuma, T.


    We present the result of our spectroscopic follow-up observation for faint quasar candidates at z ˜ 5 in part of the Canada-France-Hawaii Telescope Legacy Survey wide field. We select nine photometric candidates and identify three z ˜ 5 faint quasars, one z ˜ 4 faint quasar, and a late-type star. Since two faint quasar spectra show the C IV emission line without suffering from a heavy atmospheric absorption, we estimate their black hole masses ({M}{BH}) and Eddington ratios (L/{L}{Edd}). The inferred {log}{M}{BH} are 9.04 ± 0.14 and 8.53 ± 0.20, respectively. In addition, the inferred {log}(L/{L}{Edd}) are -1.00 ± 0.15 and -0.42 ± 0.22, respectively. If we adopt that L/{L}{Edd}={constant} {or}\\propto {(1+z)}2, the seed black hole masses ({M}{seed}) of our z ˜ 5 faint quasars are expected to be > {10}5 {M}⊙ in most cases. We also compare the observational results with a mass accretion model, where angular momentum is lost due to supernova explosions. Accordingly, {M}{BH} of the z ˜ 5 faint quasars in our sample can be explained even if {M}{seed} is ˜ {10}3 {M}⊙ . Since z ˜ 6 luminous qusars and our z ˜ 5 faint quasars are not on the same evolutionary track, z ˜ 6 luminous quasars and our z ˜ 5 quasars are not the same populations but different populations, due to the difference of a period of the mass supply from host galaxies. Furthermore, we confirm that one can explain {M}{BH} of z ˜ 6 luminous quasars and our z ˜ 5 faint quasars even if their seed black holes are formed at z ˜ 7.

  14. Identifying Bright X-Ray Beasts (United States)

    Kohler, Susanna


    Ultraluminous X-ray sources (ULXs) are astronomical sources of X-rays that, while dimmer than active galactic nuclei, are nonetheless brighter than any known stellar process. What are these beasts and why do they shine so brightly?Exceeding the LimitFirst discovered in the 1980s, ULXs are rare sources that have nonetheless been found in all types of galaxies. Though the bright X-ray radiation seems likely to be coming from compact objects accreting gas, theres a problem with this theory: ULXs outshine the Eddington luminosity for stellar-mass compact objects. This means that a stellar-mass object couldnt emit this much radiation isotropically without blowing itself apart.There are two alternative explanations commonly proposed for ULXs:Rather than being accreting stellar-mass compact objects, they are accreting intermediate-mass black holes. A hypothetical black hole of 100 solar masses or more would have a much higher Eddington luminosity than a stellar-mass black hole, making the luminosities that we observe from ULXs feasible.An example of one of the common routes the authors find for a binary system to become a ULX. In this case, the binary begins as two main sequence stars. As one star evolves off the main sequence, the binary undergoes a common envelope phase and a stage of mass transfer. The star ends its life as a supernova, and the resulting neutron star then accretes matter from the main sequence star as a ULX. [Wiktorowicz et al. 2017]They are ordinary X-ray binaries (a stellar-mass compact object accreting matter from a companion star), but they are undergoing a short phase of extreme accretion. During this time, their emission is beamed into jets, making them appear brighter than the Eddington luminosity.Clues from a New DiscoveryA few years ago, a new discovery shed some light on ULXs: M82 X-2, a pulsing ULX. Two more pulsing ULXs have been discovered since then, demonstrating that at least some ULXs contain pulsars i.e., neutron stars as the

  15. Millimeter-wave Imaging Radiometer Brightness Temperatures, Wakasa Bay, Japan (United States)

    National Aeronautics and Space Administration — This data set includes calibrated brightness temperatures measured over Wakasa Bay in the Sea of Japan in January and February 2003. The MIR was carried on a...

  16. Nimbus-5 ESMR Polar Gridded Brightness Temperatures, Version 2 (United States)

    National Aeronautics and Space Administration — The Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR) data set consists of gridded brightness temperature arrays for the Arctic and Antarctic, spanning 11...

  17. SMEX03 SSM/I Brightness Temperature Data, Alabama (United States)

    National Aeronautics and Space Administration — This data set provides brightness temperature data acquired during the Soil Moisture Experiment 2003 (SMEX03) by the Special Sensor Microwave/Imager (SSM/I). The...

  18. Binocular Coordination in Reading When Changing Background Brightness

    Directory of Open Access Journals (Sweden)

    Köpsel Anne


    Full Text Available Contradicting results concerning binocular coordination in reading have been reported: Liversedge et al. (2006 reported a dominance of uncrossed fixations, whereas Nuthmann and Kliegl (2009 observed more crossed fixations in reading. Based on both earlier and continuing studies, we conducted a reading experiment involving varying brightness of background and font. Calibration was performed using Gabor patches presented on grey background. During the experimental session, text had to be read either on dark, bright, or grey background. The data corroborates former results that showed a predominance of uncrossed fixations when reading on dark background, as well as those showing a predominance of crossed fixations, when reading on bright background. Besides these systematic shifts, the new results show an increase in unsystematic variability when changing the overall brightness from calibration to test. The origins of the effects need to be clarified in future research.

  19. CLPX-Satellite: AVHRR/HRPT Brightness Temperatures and Reflectances (United States)

    National Aeronautics and Space Administration — This data set includes AVHRR/HRPT (Advanced Very High Resolution Radiometer/High Resolution Picture Transmission) brightness temperatures and reflectances over the...

  20. SMEX03 SSM/I Brightness Temperature Data, Brazil (United States)

    National Aeronautics and Space Administration — This data set provides brightness temperature data acquired during the Soil Moisture Experiment 2003 (SMEX03) by the Special Sensor Microwave/Imager (SSM/I). The...

  1. Ultra High Brightness/Low Cost Fiber Coupled Packaging Project (United States)

    National Aeronautics and Space Administration — The focus of the proposed effort is maximizing the brightness of fiber coupled laser diode pump sources at a minimum cost. The specific innovation proposed is to...

  2. DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures (United States)

    National Aeronautics and Space Administration — NSIDC produces daily gridded brightness temperature data from orbital swath data generated by the Special Sensor Microwave/Imager (SSM/I) aboard the Defense...


    National Aeronautics and Space Administration — This volume contains the archive of Lunar brightness temperature data derived from images acquired by the Clementine Long Wavelength Infrared (LWIR) camera. The LWIR...

  4. SMEX02 SSM/I Brightness Temperature Data, Iowa (United States)

    National Aeronautics and Space Administration — The Special Sensor Microwave/Imager (SSM/I) is a seven-channel, four-frequency, linearly polarized passive microwave radiometric system. Data are brightness...

  5. CLASIC07 PALS Brightness Temperature Data V001 (United States)

    National Aeronautics and Space Administration — This data set contains brightness temperature data obtained by the Passive Active L-band System (PALS) microwave aircraft radiometer instrument as part of the Cloud...

  6. Operational Bright-Band Snow Level Detection Using Doppler Radar (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A method to detect the bright-band snow level from radar reflectivity and Doppler vertical velocity data collection with an atmospheric profiling Doppler radar. The...

  7. Visible Color and Photometry of Bright Materials on Vesta (United States)

    Schroder, S. E.; Li, J. Y.; Mittlefehldt, D. W.; Pieters, C. M.; De Sanctis, M. C.; Hiesinger, H.; Blewett, D. T.; Russell, C. T.; Raymond, C. A.; Keller, H. U.


    The Dawn Framing Camera (FC) collected images of the surface of Vesta at a pixel scale of 70 m in the High Altitude Mapping Orbit (HAMO) phase through its clear and seven color filters spanning from 430 nm to 980 nm. The surface of Vesta displays a large diversity in its brightness and colors, evidently related to the diverse geology [1] and mineralogy [2]. Here we report a detailed investigation of the visible colors and photometric properties of the apparently bright materials on Vesta in order to study their origin. The global distribution and the spectroscopy of bright materials are discussed in companion papers [3, 4], and the synthesis results about the origin of Vestan bright materials are reported in [5].

  8. The Sloan Digital Sky Survey Quasar Lens Search. IV. Statistical Lens Sample from the Fifth Data Release

    Energy Technology Data Exchange (ETDEWEB)

    Inada, Naohisa; /Wako, RIKEN /Tokyo U., ICEPP; Oguri, Masamune; /Natl. Astron. Observ. of Japan /Stanford U., Phys. Dept.; Shin, Min-Su; /Michigan U. /Princeton U. Observ.; Kayo, Issha; /Tokyo U., ICRR; Strauss, Michael A.; /Princeton U. Observ.; Hennawi, Joseph F.; /UC, Berkeley /Heidelberg, Max Planck Inst. Astron.; Morokuma, Tomoki; /Natl. Astron. Observ. of Japan; Becker, Robert H.; /LLNL, Livermore /UC, Davis; White, Richard L.; /Baltimore, Space Telescope Sci.; Kochanek, Christopher S.; /Ohio State U.; Gregg, Michael D.; /LLNL, Livermore /UC, Davis /Exeter U.


    We present the second report of our systematic search for strongly lensed quasars from the data of the Sloan Digital Sky Survey (SDSS). From extensive follow-up observations of 136 candidate objects, we find 36 lenses in the full sample of 77,429 spectroscopically confirmed quasars in the SDSS Data Release 5. We then define a complete sample of 19 lenses, including 11 from our previous search in the SDSS Data Release 3, from the sample of 36,287 quasars with i < 19.1 in the redshift range 0.6 < z < 2.2, where we require the lenses to have image separations of 1 < {theta} < 20 and i-band magnitude differences between the two images smaller than 1.25 mag. Among the 19 lensed quasars, 3 have quadruple-image configurations, while the remaining 16 show double images. This lens sample constrains the cosmological constant to be {Omega}{sub {Lambda}} = 0.84{sub -0.08}{sup +0.06}(stat.){sub -0.07}{sup + 0.09}(syst.) assuming a flat universe, which is in good agreement with other cosmological observations. We also report the discoveries of 7 binary quasars with separations ranging from 1.1 to 16.6, which are identified in the course of our lens survey. This study concludes the construction of our statistical lens sample in the full SDSS-I data set.

  9. The Photometric Brightness Variation of Geostationary Orbit Satellite

    Directory of Open Access Journals (Sweden)

    Haingja Seo


    Full Text Available Photometric observation is one of the most effective techniques for determining the physical characteristics of unknown space objects and space debris. In this research, we examine the change in brightness of the Communication, Ocean, Meteorological Satellite-1 (COMS-1 Geostationary Orbit Satellite (GEO, and compare it to our estimate model. First, we calculate the maximum brightness time using our calculation method and then derive the light curve shape using our rendering model. The maximum brightness is then calculated using the induced equation from Pogson's formula. For a comparison with our estimation, we carried out photometric observation using an optical telescope. The variation in brightness and the shape of the light curve are similar to the calculations achieved using our model, but the maximum brightness shows a slightly different value from our calculation result depending on the input parameters. This paper examines the photometric phenomenon of the variation in brightness of a GEO satellite, and the implementation of our approach to understanding the characteristics of space objects.

  10. Global View of the Bright Material on Vesta (United States)

    Zambon, F.; DeSanctis, C.; Schroeder, S.; Tosi, F.; Li, J.-Y.; Longobardo, A.; Ammannito, E.; Blewett, D. T.; Palomba, E.; Capaccioni, F.; hide


    At 525 km in mean diameter, Vesta is the second-most massive and one of the brightest asteroids of the main-belt. Here we give a global view of the bright material (BM) units on Vesta. We classified the BMs according to the normal visual albedo. The global albedo map of Vesta allows to be divided the surface into three principal types of terrains: bright regions, dark regions and intermediate regions. The distribution of bright regions is not uniform. The mid-southern latitudes contain the most bright areas, while the northern hemisphere is poor in bright regions. The analysis of the spectral parameters and the normal visual albedo show a dependence between albedo and the strength (depth) of ferrous iron absorption bands, strong bands correspond with high albedo units. Vesta's average albedo is 0.38, but there are bright material whose albedo can exceed 0.50. Only the E-Type asteroids have albedos comparable to those of the BMs on Vesta. The Dawn mission observed a large fraction of Vesta's surface at high spatial resolution, allowing a detailed study of the morphology and mineralogy of it. In particular, reflectance spectra provided by the Visible and InfraRed spectrometer (VIR), confirmed that Vesta's mineralogy is dominated by pyroxenes. All Vesta spectra show two strong absorption bands at approx 0.9 and 1.9 micron, typical of the pyroxenes and associated with the howardite, eucrite and diogenite (HED) meteorites.

  11. Synthesizing SMOS Zero-Baselines with Aquarius Brightness Temperature Simulator (United States)

    Colliander, A.; Dinnat, E.; Le Vine, D.; Kainulainen, J.


    SMOS [1] and Aquarius [2] are ESA and NASA missions, respectively, to make L-band measurements from the Low Earth Orbit. SMOS makes passive measurements whereas Aquarius measures both passive and active. SMOS was launched in November 2009 and Aquarius in June 2011.The scientific objectives of the missions are overlapping: both missions aim at mapping the global Sea Surface Salinity (SSS). Additionally, SMOS mission produces soil moisture product (however, Aquarius data will eventually be used for retrieving soil moisture too). The consistency of the brightness temperature observations made by the two instruments is essential for long-term studies of SSS and soil moisture. For resolving the consistency, the calibration of the instruments is the key. The basis of the SMOS brightness temperature level is the measurements performed with the so-called zero-baselines [3]; SMOS employs an interferometric measurement technique which forms a brightness temperature image from several baselines constructed by combination of multiple receivers in an array; zero-length baseline defines the overall brightness temperature level. The basis of the Aquarius brightness temperature level is resolved from the brightness temperature simulator combined with ancillary data such as antenna patterns and environmental models [4]. Consistency between the SMOS zero-baseline measurements and the simulator output would provide a robust basis for establishing the overall comparability of the missions.

  12. The z=0.0912 and z=0.2212 damped Ly alpha galaxies along the sight line toward the quasar OI 363

    NARCIS (Netherlands)

    Turnshek, DA; Rao, S; Nestor, D; Lane, W; Monier, E; Bergeron, J; Smette, A


    New optical and infrared observations along the sight line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding quasars selectively observed because they were known to be located behind gas-rich galaxies and systems which lack confirming UV spectroscopic observations of the

  13. Optical linear polarization measurements of quasars obtained with the 3.6 m telescope at the La Silla Observatory (United States)

    Hutsemékers, D.; Hall, P.; Sluse, D.


    We report 192 previously unpublished optical linear polarization measurements of quasars obtained in April 2003, April 2007, and October 2007 with the European Southern Observatory Faint Object Spectrograph and Camera (EFOSC2) instrument attached to the 3.6 m telescope at the La Silla Observatory. Each quasar was observed once. Among the 192 quasars, 89 have a polarization degree p ≥ 0.6%, 18 have p ≥ 2%, and two have p ≥ 10%. Based on observations made with the ESO 3.6 m Telescope at the La Silla Observatory under program ID 071.B-0460, 079.A-0625, 080.A-0017.Full Table 4 is only available at the CDS via anonymous ftp to ( or via

  14. The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1. (United States)

    Wilkes, Belinda J.; Tananbaum, Harvey; Worrall, D. M.; Avni, Yoram; Oey, M. S.; Flanagan, Joan


    We present the first volume of the Einstein quasar database. The database includes estimates of the X-ray count rates, fluxes, and luminosities for 514 quasars and Seyfert 1 galaxies observed with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. All were previously known optically selected or radio-selected objects, and most were the targets of the X-ray observations. The X-ray properties of the Active Galactic Nuclei (AGNs) have been derived by reanalyzing the IPC data in a systematic manner to provide a uniform database for general use by the astronomical community. We use the database to extend earlier quasar luminosity studies which were made using only a subset of the currently available data. The database can be accessed on internet via the SAO Einstein on-line system ('Einline') and is available in ASCII format on magnetic tape and DOS diskette.

  15. Quasar Massive Ionized Outflows Traced by CIV λ1549 and [OIII]λλ4959,5007

    Directory of Open Access Journals (Sweden)

    Paola Marziani


    Full Text Available The most luminous quasars (with bolometric luminosities are ≳ 1047 erg/s show a high prevalence of CIV λ1549 and [OIII]λλ4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]λλ4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars.

  16. Quasar massive ionized outflows traced by CIV λ1549 and [OIII]λλ4959,5007 (United States)

    Marziani, Paola; Negrete, C. Alenka; Dultzin, Deborah; Martínez-Aldama, Mary L.; Del Olmo, Ascensión; D'Onofrio, Mauro; Stirpe, Giovanna M.


    The most luminous quasars (with bolometric luminosities are 1047 erg/s) show a high prevalence of CIV λ1549 and [OIII]λλ4959,5007 emission line profiles with strong blueshifts. Blueshifts are interpreted as due to Doppler effect and selective obscuration, and indicate outflows occurring over a wide range of spatial scales. We found evidence in favor of the nuclear origin of the outflows diagnosed by [OIII]λλ 4959,5007. The ionized gas mass, kinetic power, and mechanical thrust are extremely high, and suggest widespread feedback effects on the host galaxies of very luminous quasars, at cosmic epochs between 2 and 6 Gyr from the Big Bang. In this mini-review we summarize results obtained by our group and reported in several major papers in the last few years with an eye on challenging aspects of quantifying feedback effects in large samples of quasars.

  17. Solving the puzzle of discrepant quasar variability on monthly time-scales implied by SDSS and CRTS data sets (United States)

    Suberlak, Krzysztof; Ivezić, Željko; MacLeod, Chelsea L.; Graham, Matthew; Sesar, Branimir


    We present an improved photometric error analysis for the 7 100 CRTS (Catalina Real-Time Transient Survey) optical light curves for quasars from the SDSS (Sloan Digital Sky Survey) Stripe 82 catalogue. The SDSS imaging survey has provided a time-resolved photometric data set, which greatly improved our understanding of the quasar optical continuum variability: Data for monthly and longer time-scales are consistent with a damped random walk (DRW). Recently, newer data obtained by CRTS provided puzzling evidence for enhanced variability, compared to SDSS results, on monthly time-scales. Quantitatively, SDSS results predict about 0.06 mag root-mean-square (rms) variability for monthly time-scales, while CRTS data show about a factor of 2 larger rms, for spectroscopically confirmed SDSS quasars. Our analysis has successfully resolved this discrepancy as due to slightly underestimated photometric uncertainties from the CRTS image processing pipelines. As a result, the correction for observational noise is too small and the implied quasar variability is too large. The CRTS photometric error correction factors, derived from detailed analysis of non-variable SDSS standard stars that were re-observed by CRTS, are about 20-30 per cent, and result in reconciling quasar variability behaviour implied by the CRTS data with earlier SDSS results. An additional analysis based on independent light curve data for the same objects obtained by the Palomar Transient Factory provides further support for this conclusion. In summary, the quasar variability constraints on weekly and monthly time-scales from SDSS, CRTS and PTF surveys are mutually compatible, as well as consistent with DRW model.

  18. The Properties of Quasar 2175 Å Dust Absorbers at z = 1.0-2.5 (United States)

    Ma, Jingzhe; Ge, Jian; Prochaska, Jason; Zhao, Yinan; Zhang, Shaohua; Ji, Tuo; Lundgren, Britt; Zhou, Hongyan; Lu, Honglin; Schneider, Donald


    Quasar 2175 Å dust absorbers (2DAs) are a population of quasar absorption line systems identified by the broad absorption feature centered around rest-frame 2175 Å, which is ubiquitously seen in the Milky Way extinction curves. These absorbers are excellent tracers of gas and dust properties, metal abundances, chemical evolution, physical conditions, as well as kinematics in the absorbing galaxies. We present the metallicity, depletion pattern, kinematics, and the cold neutral content (HI and CI gas) of a sample of 2DAs at z = 1.0-2.5 that were initially selected from the Sloan Digital Sky Survey and followed up with Keck and MMT spectrographs. We perform a correlation analysis between metallicity, redshift, depletion level, velocity width, and explore relationships between 2DAs and other absorption line systems. The 2DAs on average have higher metallicity, higher depletion levels, and larger velocity widths than Damped Lyman-α absorbers (DLAs) or subDLAs. The correlation between [Zn/H] and [Fe/Zn] or [Zn/H] and logΔV90 can be used as alternative stellar mass estimators based on the well-established mass-metallicity relation. The relationship with other quasar absorption line systems can be described as (1) 2DAs are a subset of Mg II and Fe II absorbers, (2) 2DAs are preferentially metal-strong DLAs/subDLAs, (3) More importantly, all of the 2DAs show CI detections with N(CI) > 14.0 cm-2, (4) 2DAs can be used as molecular gas tracers. Their host galaxies are likely to be chemically enriched, evolved, and massive galaxies (more massive than typical DLA/subDLA galaxies). In addition, we have, for the first time, identified the host galaxy of a 2DA beyond the local Universe using HST IR direct imaging and grism spectroscopy.

  19. C IV and C III] Reverberation Mapping of the Luminous Quasar PG 1247+267 (United States)

    Trevese, D.; Perna, M.; Vagnetti, F.; Saturni, F. G.; Dadina, M.


    So far the masses of about 50 active galactic nuclei (AGNs) have been measured through the reverberation mapping technique (RM). Most measurements have been performed for objects of moderate luminosity and redshift, based on Hβ, which is also used to calibrate the scaling relation that allows single-epoch (SE) mass determination based on AGN luminosity and the width of different emission lines. Due to the complex structure and gas dynamics of the relevant emission region, the SE masses obtained from the C IV(1549 Å) line show a large spread around the mean values. Direct RM measures of C IV exist for only six AGNs of low luminosity and redshift, and only one luminous quasar. Since 2003, we have collected photometric and spectroscopic observations of PG1247+267, the most luminous quasar ever analyzed for RM. We provide light curves for the continuum and for C IV(1549 Å) and C III](1909 Å), and measures of the reverberation time lags based on the SPEAR method. The sizes of the line emission regions assume a ratio of R C III]/R C IV ~ 2, similar to the case of Seyfert galaxies, indicating for the first time a similar ionization stratification in a luminous quasar and low-luminosity nuclei. Due to the relatively small size of the broad line region and the relatively narrow line widths, we estimate a small mass and an anomalously high Eddington ratio. We discuss the possibility that either the shape of the emission region or an amplification of the luminosity caused by gravitational lensing may be partly responsible for the result.

  20. C IV and C III] reverberation mapping of the luminous quasar PG 1247+267

    Energy Technology Data Exchange (ETDEWEB)

    Trevese, D.; Saturni, F. G. [Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro, 5, I-00185 Roma (Italy); Perna, M. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Vagnetti, F. [Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Dadina, M. [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy)


    So far the masses of about 50 active galactic nuclei (AGNs) have been measured through the reverberation mapping technique (RM). Most measurements have been performed for objects of moderate luminosity and redshift, based on Hβ, which is also used to calibrate the scaling relation that allows single-epoch (SE) mass determination based on AGN luminosity and the width of different emission lines. Due to the complex structure and gas dynamics of the relevant emission region, the SE masses obtained from the C IV(1549 Å) line show a large spread around the mean values. Direct RM measures of C IV exist for only six AGNs of low luminosity and redshift, and only one luminous quasar. Since 2003, we have collected photometric and spectroscopic observations of PG1247+267, the most luminous quasar ever analyzed for RM. We provide light curves for the continuum and for C IV(1549 Å) and C III](1909 Å), and measures of the reverberation time lags based on the SPEAR method. The sizes of the line emission regions assume a ratio of R {sub C} {sub III]}/R {sub C} {sub IV} ∼ 2, similar to the case of Seyfert galaxies, indicating for the first time a similar ionization stratification in a luminous quasar and low-luminosity nuclei. Due to the relatively small size of the broad line region and the relatively narrow line widths, we estimate a small mass and an anomalously high Eddington ratio. We discuss the possibility that either the shape of the emission region or an amplification of the luminosity caused by gravitational lensing may be partly responsible for the result.

  1. Spectroscopic CCD surveys for quasars at large redshift. 3: The Palomar Transit Grism Survey catalog (United States)

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


    This paper reports the initial results of the Palomar Transit Grism Survey (PTGS). The PTGS was designed to produce a sample of z greater than 2.7 quasars that were identified by well-defined selection criteria. The survey consists of six narrow (approximately equal to 8.5 min wide) strips of sky; the total effective area is 61.47 sq deg. Low-resolution slitless spectra, covering the wavelength range from 4400 to 7500 A, were obtained for approximately 600 000 objects. The wavelength- and flux-calibrated spectra were searched for emission lines with an automatic software algorithm. A total to 1655 emission features in the grism data satisfied our signal-to-noise ratio and equivalent width selection criteria; subsequent slit spectroscopy of the candidates confirmed the existence of 1052 lines (928 different objects). Six groups of emission lines were detected in the survey: Lyman alpha + N V, C IV, C III1, Mg II, H Beta + (O III), and H alpha + (S II). More than two-thirds of the candidates are low-redshift (z less than 0.45) emission-line galaxies; ninety objects are high-redshift quasars (z greater than 2.7) detected via their Lyman alpha + N V emission lines. The survey contains three previously unknown quasars brighter than 17th magnitude; all three have redshifts of approximately equal to 1.3. In this paper we present the observational properties of the survey, the algorithms used to select the emission-line candidates, and the catalog of emission-line objects.

  2. Time Delay Measurements for the Cluster-lensed Sextuple Quasar SDSS J2222+2745 (United States)

    Dahle, H.; Gladders, M. D.; Sharon, K.; Bayliss, M. B.; Rigby, J. R.


    We report first results from an ongoing monitoring campaign to measure time delays between the six images of the quasar SDSS J2222+2745, gravitationally lensed by a galaxy cluster. The time delay between A and B, the two most highly magnified images, is measured to be {τ }{{AB}}=47.7+/- 6.0 days (95% confidence interval), consistent with previous model predictions for this lens system. The strong intrinsic variability of the quasar also allows us to derive a time delay value of {τ }{{CA}}=722+/- 24 days between image C and A, in spite of modest overlap between their light curves in the current data set. Image C, which is predicted to lead all the other lensed quasar images, has undergone a sharp, monotonic flux increase of 60%-75% during 2014. A corresponding brightening is firmly predicted to occur in images A and B during 2016. The amplitude of this rise indicates that time delays involving all six known images in this system, including those of the demagnified central images D-F, will be obtainable from further ground-based monitoring of this system during the next few years. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and including observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnologi´a e Innovación Productiva (Argentina).


    Energy Technology Data Exchange (ETDEWEB)

    Negrete, C. Alenka [Instituto Nacional de Astrofisica, Optica y Electronica (Mexico); Dultzin, Deborah [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico (Mexico); Marziani, Paola [INAF, Astronomical Observatory of Padova, I-35122 Padova (Italy); Sulentic, Jack W., E-mail:, E-mail:, E-mail:, E-mail: [Instituto de Astrofisica de Andalucia, E-18008 Granada (Spain)


    Black hole mass estimation in quasars, especially at high redshift, involves the use of single-epoch spectra with signal-to-noise ratio and resolution that permit accurate measurement of the width of a broad line assumed to be a reliable virial estimator. Coupled with an estimate of the radius of the broad-line region (BLR) this yields the black hole mass M{sub BH}. The radius of the BLR may be inferred from an extrapolation of the correlation between source luminosity and reverberation-derived r{sub BLR} measures (the so-called Kaspi relation involving about 60 low-z sources). We are exploring a different method for estimating r{sub BLR} directly from inferred physical conditions in the BLR of each source. We report here on a comparison of r{sub BLR} estimates that come from our method and from reverberation mapping. Our ''photoionization'' method employs diagnostic line intensity ratios in the rest-frame range 1400-2000 A (Al III {lambda}1860/Si III] {lambda}1892, C IV {lambda}1549/Al III {lambda}1860) that enable derivation of the product of density and ionization parameter with the BLR distance derived from the definition of the ionization parameter. We find good agreement between our estimates of the density, ionization parameter, and r{sub BLR} and those from reverberation mapping. We suggest empirical corrections to improve the agreement between individual photoionization-derived r{sub BLR} values and those obtained from reverberation mapping. The results in this paper can be exploited to estimate M{sub BH} for large samples of high-z quasars using an appropriate virial broadening estimator. We show that the width of the UV intermediate emission lines are consistent with the width of H{beta}, thereby providing a reliable virial broadening estimator that can be measured in large samples of high-z quasars.

  4. DES meets Gaia: discovery of strongly lensed quasars from a multiplet search

    Energy Technology Data Exchange (ETDEWEB)

    Agnello, A.; et al.


    We report the discovery, spectroscopic confirmation and first lens models of the first two, strongly lensed quasars from a combined search in WISE and Gaia over the DES footprint. The four-image lensWGD2038-4008 (r.a.=20:38:02.65, dec.=-40:08:14.64) has source- and lens-redshifts $z_{s}=0.777 \\pm 0.001$ and $z_l = 0.230 \\pm 0.002$ respectively. Its deflector has effective radius $R_{\\rm eff} \\approx 3.4^{\\prime\\prime}$, stellar mass $\\log(M_{\\star}/M_{\\odot}) = 11.64^{+0.20}_{-0.43}$, and shows extended isophotal shape variation. Simple lens models yield Einstein radii $R_{\\rm E}=(1.30\\pm0.04)^{\\prime\\prime},$ axis ratio $q=0.75\\pm0.1$ (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. The two-image lensWGD2021-4115 (r.a.=20:21:39.45, dec.=--41:15:57.11) has $z_{s}=1.390\\pm0.001$ and $z_l = 0.335 \\pm 0.002$, and Einstein radius $R_{\\rm E} = (1.1\\pm0.1)^{\\prime\\prime},$ but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. We also show high-rank candidate doubles selected this way, some of which have been independently identified with different techniques, and discuss a DES+WISE quasar multiplet selection.

  5. New Constraints on the Hard Ionizing Photon Budget and the Lifetime and Obscuration of Quasars During the Epoch of Helium Reionization (United States)

    Davies, Frederick


    The epoch of helium reionization was a major milestone in the history of the Universe, a direct consequence of supermassive black hole growth and the cumulative output of hard ionizing photons by quasars. Our observations of the He II Ly-alpha forest with HST/COS in 26 quasar sightlines show strong fluctuations at z 3, consistent with our state-of-the-art simulations of the He II reionization epoch. However, our detection of transmission at z > 3.5 is inconsistent with all He II reionization models. Resolving this puzzle requires an extensive parameter study of He II reionization, which we propose to carry out using our fast, efficient simulations. The He II Ly-alpha forest is also sensitive to the effect of quasar radiation illuminating the intergalactic medium, known as the proximity effect. We have performed an ambitious ground-based imaging and spectroscopic survey for z 3 quasars in the foreground of HeII sightlines observed with HST/COS, and statistically detected the transverse proximity effect for the first time. The strength of this effect depends on both the quasar lifetime and the opening angle of quasar emission (or the fraction of obscured quasars), and we propose to use our He II reionization simulations to interpret this new measurement. Finally, the line-of-sight proximity effect due to the background quasar provides an independent constraint on the quasar lifetime. Our preliminary comparison of He II spectra to our radiative transfer simulations suggests a quasar lifetime > 10 Myr. We propose to use our He II reionization simulations to model this diverse set of observations and fully capitalize on the far-UV legacy of HST.

  6. RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz (United States)

    Lobanov, A. P.; Gómez, J. L.; Bruni, G.; Kovalev, Y. Y.; Anderson, J.; Bach, U.; Kraus, A.; Zensus, J. A.; Lisakov, M. M.; Sokolovsky, K. V.; Voytsik, P. A.


    Context. Polarization of radio emission in extragalactic jets at a sub-milliarcsecond angular resolution holds important clues for understanding the structure of the magnetic field in the inner regions of the jets and in close vicinity of the supermassive black holes in the centers of active galaxies. Aims: Space VLBI observations provide a unique tool for polarimetric imaging at a sub-milliarcsecond angular resolution and studying the properties of magnetic field in active galactic nuclei on scales of less than 104 gravitational radii. Methods: A space VLBI observation of high-redshift quasar TXS 0642+449 (OH 471), made at a wavelength of 18 cm (frequency of 1.6 GHz) as part of the early science programme (ESP) of the RadioAstron mission, is used here to test the polarimetric performance of the orbiting Space Radio Telescope (SRT) employed by the mission, to establish a methodology for making full Stokes polarimetry with space VLBI at 1.6 GHz, and to study the polarized emission in the target object on sub-milliarcsecond scales. Results: Polarization leakage of the SRT at 18 cm is found to be within 9% in amplitude, demonstrating the feasibility of high fidelity polarization imaging with RadioAstron at this wavelength. A polarimetric image of 0642+449 with a resolution of 0.8 mas (signifying an ~4 times improvement over ground VLBI observations at the same wavelength) is obtained. The image shows a compact core-jet structure with low (≈2%) polarization and predominantly transverse magnetic field in the nuclear region. The VLBI data also uncover a complex structure of the nuclear region, with two prominent features possibly corresponding to the jet base and a strong recollimation shock. The maximum brightness temperature at the jet base can be as high as 4 × 1013 K.

  7. A New Microlensing Event in the Doubly-Imaged Quasar Q0957+561


    Hainline, Laura J.; Morgan, Christopher W.; Beach, J. N.; Kochanek, C. S.; Harris, Hugh C.; Tilleman, T.; Fadely, Ross; Falco, Emilio E.; Le, T. X.


    We present evidence for ultraviolet/optical microlensing in the gravitationally lensed quasar Q0957+561. We combine new measurements from our optical monitoring campaign at the United States Naval Observatory, Flagstaff (USNO) with measurements from the literature and find that the time-delay-corrected r-band flux ratio m_A - m_B has increased by ~0.1 magnitudes over a period of five years beginning in the fall of 2005. We apply our Monte Carlo microlensing analysis procedure to the composite...

  8. A large anisotropy in the sky distribution of 3CRR quasars and other radio galaxies (United States)

    Singal, Ashok K.


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

  9. The Sloan Digital Sky Survey Quasar Catalog I. Early Data Release


    Donald P. Schneider(Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802, USA); Richards, Gordon T.; Fan, Xiaohui; Hall, Patrick B.; Strauss, Michael A; Berk, Daniel E. Vanden; Gunn, James E.; Newberg, Heidi Jo; Reichard, Timothy A.; Stoughton, C.; Voges, Wolfgang; Yanny, Brian


    We present the first edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 3814 objects (3000 discovered by the SDSS) in the initial SDSS public data release that have at least one emission line with a full width at half maximum larger than 1000 km/s, luminosities brighter than M_i^* = -23, and highly reliable redshifts. The area covered by the catalog is 494 square degrees; the majority of the objects were found in SDSS commissioning data using a multicol...

  10. Models of the Strongly Lensed Quasar DES J0408-5354

    Energy Technology Data Exchange (ETDEWEB)

    Agnello, A.; et al.


    We present gravitational lens models of the multiply imaged quasar DES J0408-5354, recently discovered in the Dark Energy Survey (DES) footprint, with the aim of interpreting its remarkable quad-like configuration. We first model the DES single-epoch $grizY$ images as a superposition of a lens galaxy and four point-like objects, obtaining spectral energy distributions (SEDs) and relative positions for the objects. Three of the point sources (A,B,D) have SEDs compatible with the discovery quasar spectra, while the faintest point-like image (G2/C) shows significant reddening and a `grey' dimming of $\\approx0.8$mag. In order to understand the lens configuration, we fit different models to the relative positions of A,B,D. Models with just a single deflector predict a fourth image at the location of G2/C but considerably brighter and bluer. The addition of a small satellite galaxy ($R_{\\rm E}\\approx0.2$") in the lens plane near the position of G2/C suppresses the flux of the fourth image and can explain both the reddening and grey dimming. All models predict a main deflector with Einstein radius between $1.7"$ and $2.0",$ velocity dispersion $267-280$km/s and enclosed mass $\\approx 6\\times10^{11}M_{\\odot},$ even though higher resolution imaging data are needed to break residual degeneracies in model parameters. The longest time-delay (B-A) is estimated as $\\approx 85$ (resp. $\\approx125$) days by models with (resp. without) a perturber near G2/C. The configuration and predicted time-delays of J0408-5354 make it an excellent target for follow-up aimed at understanding the source quasar host galaxy and substructure in the lens, and measuring cosmological parameters. We also discuss some lessons learnt from J0408-5354 on lensed quasar finding strategies, due to its chromaticity and morphology.

  11. Flux and color variations of the doubly imaged quasar UM673

    DEFF Research Database (Denmark)

    Ricci, D.; Elyiv, A.; Finet, F.


    Aims. With the aim of characterizing the flux and color variations of the multiple components of the gravitationally lensed quasar UM673 as a function of time, we have performed multiepoch and multiband photometric observations with the Danish telescope at the La Silla Observatory. Methods...... seasons (+ 0.09/+ 0.11/+ 0.05 mag) and a subsequent increase during the following ones (- 0.11/- 0.11/- 0.10 mag) in the V/R/i spectral bands, respectively. Comparing our results with previous studies, we find smaller color variations between these seasons as compared with previous ones. We also separate...

  12. The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars (United States)

    Chen, Chien-Ting J.; Hickox, Ryan C.; Goulding, Andrew D.; Stern, Daniel; Assef, Roberto; Kochanek, Christopher S.; Brown, Michael J. I.; Harrison, Chris M.; Hainline, Kevin N.; Alberts, Stacey; Alexander, David M.; Brodwin, Mark; Del Moro, Agnese; Forman, William R.; Gorjian, Varoujan; Jones, Christine; Murray, Stephen S.; Pope, Alexandra; Rovilos, Emmanouel


    Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity ({L}{MIR}) and the rest-frame 2-10 keV luminosity (L X) for luminous quasars. To understand the origin of the difference in the observed {L}{{X}}{--}{L}{MIR} relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed {L}{{X}}{--}{L}{MIR} relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different {L}{{X}}{--}{L}{MIR} relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 μ {{m}}, or {L}6μ {{m}}) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: {log}{L}{{X}}=(0.84+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s-1 + (44.60 ± 0.01) for {L}6μ {{m}}< {10}44.79 erg s-1, and {log}{L}{{X}}=(0.40+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s-1 + (44.51 ± 0.01) for {L}6μ {{m}} ≥slant {10}44.79 erg s-1. This suggests that the luminous type 1 quasars have a shallower {L}{{X}}{--}{L}6μ {{m}} correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent {L}{{X}}{--}{L}{MIR} relation and implies that assuming a linear {L}{{X}}{--}{L}6μ {{m}} relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.

  13. Extent and structure of intervening absorbers from absorption lines redshifted on quasar emission lines (United States)

    Bergeron, J.; Boissé, P.


    Aims: We wish to study the extent and sub-parsec spatial structure of intervening quasar absorbers, mainly those involving cold neutral and molecular gas. Methods: We have selected quasar absorption systems with high spectral resolution and a good signal-to-noise ratio data, with some of their lines falling on quasar emission features. By investigating the consistency of absorption profiles seen for lines formed either against the quasar continuum source or on the much more extended (Lyα-N v, C iv or Lyβ-O vi) emission line region (ELR), we can probe the extent and structure of the foreground absorber over the extent of the ELR ( 0.3-1 pc). The spatial covering analysis provides constraints on the transverse size of the absorber and thus is complementary to variability or photoionisation modelling studies, which yield information on the absorber size along the line of sight. The methods we used to identify spatial covering or structure effects involve line profile fitting and curve-of-growth analysis. Results: We have detected three absorbers with unambiguous non-uniformity effects in neutral gas. For the extreme case of the Fe I absorber at zabs = 0.45206 towards HE 0001-2340, we derive a coverage factor of the ELR of at most 0.10 and possibly very close to zero; this implies an overall absorber size no larger than 0.06 pc. For the zabs = 2.41837 C I absorber towards QSO J1439+1117, absorption is significantly stronger towards the ELR than towards the continuum source in several C I and C I⋆ velocity components, pointing to spatial variations of their column densities of about a factor of two and to structures at the 100 au-0.1 pc scale. The other systems with firm or possible effects can be described in terms of a partial covering of the ELR, with coverage factors in the range 0.7-1. The overall results for cold neutral absorbers imply a transverse extent of about five times the ELR size or smaller, which is consistent with other known constraints. Although

  14. Consistency of spherical, gravity-dominated dynamics with quasar high-ionization emission-line profiles


    Kallman, T. R.; Wilkes, Belinda Jane; Krolik, J. H.; Green, Richard


    Line profile data are used to test a simple kinematic model - spherically symmetric gravitational free fall - in which the number of free parameters is limited by requiring physical self-consistency. The predictions of this model are fitted to high-resolution spectra of the stronger rest-frame UV emission lines in 12 quasars with z of about 2. It is found that if all the lines are radiated predominantly from the illuminated faces of the emission-line clouds, the profiles of Ly-alpha, N V 1240...

  15. PROFFIT: Analysis of X-ray surface-brightness profiles (United States)

    Eckert, Dominique


    PROFFIT analyzes X-ray surface-brightness profiles for data from any X-ray instrument. It can extract surface-brightness profiles in circular or elliptical annuli, using constant or logarithmic bin size, from the image centroid, the surface-brightness peak, or any user-given center, and provides surface-brightness profiles in any circular or elliptical sectors. It offers background map support to extract background profiles, can excise areas using SAO DS9-compatible (ascl:0003.002) region files to exclude point sources, provides fitting with a number of built-in models, including the popular beta model, double beta, cusp beta, power law, and projected broken power law, uses chi-squared or C statistic, and can fit on the surface-brightness or counts data. It has a command-line interface similar to HEASOFT’s XSPEC (ascl:9910.005) package, provides interactive help with a description of all the commands, and results can be saved in FITS, ROOT or TXT format.

  16. A neurodynamical model of brightness induction in v1.

    Directory of Open Access Journals (Sweden)

    Olivier Penacchio

    Full Text Available Brightness induction is the modulation of the perceived intensity of an area by the luminance of surrounding areas. Recent neurophysiological evidence suggests that brightness information might be explicitly represented in V1, in contrast to the more common assumption that the striate cortex is an area mostly responsive to sensory information. Here we investigate possible neural mechanisms that offer a plausible explanation for such phenomenon. To this end, a neurodynamical model which is based on neurophysiological evidence and focuses on the part of V1 responsible for contextual influences is presented. The proposed computational model successfully accounts for well known psychophysical effects for static contexts and also for brightness induction in dynamic contexts defined by modulating the luminance of surrounding areas. This work suggests that intra-cortical interactions in V1 could, at least partially, explain brightness induction effects and reveals how a common general architecture may account for several different fundamental processes, such as visual saliency and brightness induction, which emerge early in the visual processing pathway.

  17. Bright light therapy of subsyndromal seasonal affective disorder in the workplace: morning vs. afternoon exposure. (United States)

    Avery, D H; Kizer, D; Bolte, M A; Hellekson, C


    Bright light therapy in seasonal affective disorder (SAD) has been studied extensively. However, little attention has been given to subsyndromal seasonal affective disorder (SSAD) or the use of bright light in the workplace. Many patients using bright light boxes complain of the inconvenience of use. Much of this inconvenience involves the often-recommended early timing of the bright light therapy. Patients, who already have difficulty awakening, often have difficulty using the bright light therapy soon after awakening before going to work. If bright light could be used effectively in the workplace, the treatment would be more convenient; the improved convenience would probably improve compliance. In this study, we studied the effectiveness of bright light therapy in subjects with SSAD in the workplace, comparing morning bright light with afternoon bright light. Morning and afternoon bright light treatment (2500 lux) were compared in 30 subsyndromal seasonal affective disorder patients using the bright light therapy in the workplace. Hamilton Depression Ratings and subjective measures of mood, energy, alertness and productivity were assessed before and after 2 weeks of light therapy. Both morning and evening bright light significantly decreased the depression ratings and improved the subjective mood, energy, alertness and productivity scores. However, there were no significant differences between the two times of administration of the bright light treatment. Both bright light treatments were well tolerated. Bright light given in the workplace improves subjective ratings of mood, energy, alertness and productivity in SSAD subjects. Morning and afternoon bright lights resulted in similar levels of improvement.

  18. Bright and Not-So-Bright Prospects for Women in Physics in China-Beijing (United States)

    Wu, Ling-An; Yang, Zhongqin; Ma, Wanyun


    Science in China-Beijing is enjoying a healthy increase in funding year by year, so the prospects for physicists are also bright. However, employment discrimination against women, formerly unthinkable, is becoming more and more explicit as the country evolves toward a market economy. Some recruitment notices bluntly state that only men will be considered, or impose restrictions upon potential female candidates. Female associate professors in many institutions are forced to retire at age 55, compared with 60 for men. This double-pinching discrimination against both younger and older women threatens to lead to a "pincer" effect, more serious than the "scissors" effect. Indeed, the ratio of senior-level women physicists in general has dropped significantly in recent years in China. Ironically, the number of female students applying for graduate studies is on the rise, as it is becoming increasingly difficult for them to compete with men in the job market with just an undergraduate degree. The Chinese Physical Society has made certain efforts to promote the image of women physicists, but it will take time and effort to reverse the trend.

  19. High-brightness ultra-cold metastable neon-beam

    CERN Document Server

    Shimizu, Fujio


    This paper presents detailed characteristics of an ultra-cold bright metastable neon atomic beam which we have been using for atom-interferometric applications. The basis of the device is an atomic beam released from a magneto-optical trap (MOT) which is operated with a high intensity trapping laser, high magnetic quadrupole field, and large laser detuining. Mainly due to the complex structure of three dimensional magnetic field and laser beams, a bright small spot of atoms is formed near the center of the quadrupole magnetic field under an appropriate operating condition. We obtained the minimum trap diameter of 50 micron meter, the atomic density nearly 10^{13}cm^{-3}, and the atomic temperature slightly less than the Doppler limited temperature of 200 micro-K. By releasing trapped atoms we obtained an bright cold atomic beam which is not far from the collision limited atomic density.

  20. A high brightness probe of polymer nanoparticles for biological imaging (United States)

    Zhou, Sirong; Zhu, Jiarong; Li, Yaping; Feng, Liheng


    Conjugated polymer nanoparticles (CPNs) with high brightness in long wavelength region were prepared by the nano-precipitation method. Based on fluorescence resonance energy transfer (FRET) mechanism, the high brightness property of the CPNs was realized by four different emission polymers. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) displayed that the CPNs possessed a spherical structure and an average diameter of 75 nm. Analysis assays showed that the CPNs had excellent biocompatibility, good photostability and low cytotoxicity. The CPNs were bio-modified with a cell penetrating peptide (Tat, a targeted element) through covalent link. Based on the entire wave fluorescence emission, the functionalized CPNs1-4 can meet multichannel and high throughput assays in cell and organ imaging. The contribution of the work lies in not only providing a new way to obtain a high brightness imaging probe in long wavelength region, but also using targeted cell and organ imaging.