WorldWideScience

Sample records for faint-end quasar luminosity

  1. The Evolution in the Faint-End Slope of the Quasar Luminosity Function

    OpenAIRE

    Hopkins, Philip F.; Hernquist, Lars; Cox, Thomas J.; Di Matteo, Tiziana; Robertson, Brant; Springel, Volker

    2005-01-01

    (Abridged) Based on numerical simulations of galaxy mergers that incorporate black hole (BH) growth, we predict the faint end slope of the quasar luminosity function (QLF) and its evolution with redshift. Our simulations have yielded a new model for quasar lifetimes where the lifetime depends on both the instantaneous and peak quasar luminosities. This motivates a new interpretation of the QLF in which the bright end consists of quasars radiating at nearly their peak luminosities, but the fai...

  2. The Faint End of the Quasar Luminosity Function at z ~ 4

    Science.gov (United States)

    Glikman, Eilat; Bogosavljević, Milan; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Mahabal, Ashish

    2010-02-01

    The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 law (Φ vprop L β) gives a faint-end slope β = -1.6 ± 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 law LF. Our best fit finds a bright-end slope, α = -2.4 ± 0.2, and faint-end slope, β = -2.3 ± 0.2, without a well-constrained break luminosity. This is effectively a single power law, with β = -2.7 ± 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  3. The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

    Science.gov (United States)

    Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

    2011-02-01

    We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  4. The faint-end of galaxy luminosity functions at the Epoch of Reionization

    Science.gov (United States)

    Yue, B.; Castellano, M.; Ferrara, A.; Fontana, A.; Merlin, E.; Amorín, R.; Grazian, A.; Mármol-Queralto, E.; Michałowski, M. J.; Mortlock, A.; Paris, D.; Parsa, S.; Pilo, S.; Santini, P.; Di Criscienzo, M.

    2018-05-01

    During the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ~ 6, MUVT >~-13.3 for the circular velocity threshold of quenching star formation process, vc* <~ 47 km s-1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies.

  5. Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A

    Science.gov (United States)

    Crnojevic, Denija

    2014-10-01

    We request HST/ACS imaging to follow up 15 new faint candidate dwarfs around the nearest elliptical Centaurus A (3.8 Mpc). The dwarfs were found via a systematic ground-based (Magellan/Megacam) survey out to ~150 kpc, designed to directly confront the "missing satellites" problem in a wholly new environment. Current Cold Dark Matter models for structure formation fail to reproduce the shallow slope of the satellite luminosity function in spiral-dominated groups for which dwarfs fainter than M_V<-14 have been surveyed (the Local Group and the nearby, interacting M81 group). Clusters of galaxies show a better agreement with cosmological predictions, suggesting an environmental dependence of the (poorly-understood) physical processes acting on the evolution of low mass galaxies (e.g., reionization). However, the luminosity function completeness for these rich environments quickly drops due to the faintness of the satellites and to the difficult cluster membership determination. We target a yet unexplored "intermediate" environment, a nearby group dominated by an elliptical galaxy, ideal due to its proximity: accurate (10%) distance determinations for its members can be derived from resolved stellar populations. The proposed observations of the candidate dwarfs will confirm their nature, group membership, and constrain their luminosities, metallicities, and star formation histories. We will obtain the first complete census of dwarf satellites of an elliptical down to an unprecedented M_V<-9. Our results will crucially constrain cosmological predictions for the faint end of the satellite luminosity function to achieve a more complete picture of the galaxy formation process.

  6. The Faint End of the Lyman Alpha Luminosity Function at 2 < z < 3.8

    Science.gov (United States)

    Devarakonda, Yaswant; Livermore, Rachael; Indahl, Briana; Wold, Isak; Davis, Dustin; Finkelstein, Steven

    2018-01-01

    Most current models predict that our universe is mostly composed of small, dim galaxies. Due to these galaxies being so faint, it is very difficult to study these types of galaxies outside of our local universe. This is particularly an issue for studying how these small galaxies evolved over their lifetimes. With the benefit of gravitational lensing, however, we are able to observe galaxies that are farther and fainter than ever before possible. In this particular study, we focus on Lyman-Alpha emitting galaxies between the redshifts of 2-3.8, so that we may study these galaxies during the epoch of peak star formation in the universe. We use the McDonald Observatory 2.7, Harlan Smith telescope with the VIRUS-P IFU spectrograph to observe several Hubble Frontier Field lensing clusters to spectroscopically discover faint galaxies over this redshift range. In addition to providing insight into the faint-end slope of the Lyman alpha luminosity function, the spectroscopic redshifts will allow us to better constrain the mass models of the foreground clusters, such as Abell 370, so that we may better understand lensing effects for this and future studies.

  7. Luminosity function of high redshift quasars

    International Nuclear Information System (INIS)

    Vaucher, B.G.

    1982-01-01

    Data from ten different emission-line surveys are included in a study of the luminosity function of high redshift quasars. Five of the surveys are analyzed through microdensitometric techniques and the data for new quasars are given. The uncertainties in magnitudes, redshifts, and line equivalent widths are assessed and found to be +-0.3 mag. +-0.04 in z and approx. 30%, respectively. Criteria for selecting the redshift range 1.8 less than or equal to z - 1 Mpc - 1 for each of two cosmologies (q 0 = 1 and q 0 = 0). For either cosmology, the function exhibits a steep increase with magnitude at high luminosities and a gentler increase at intermediate luminosities. Data from the new surveys indicate a possible turnover at the faint end of the distribution. Total volume densities of quasars are computed for each of three extrapolations of the trend of the data to low luminosities. These densities are compared to those of active galaxies and field galaxies

  8. The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

    Science.gov (United States)

    Akiyama, Masayuki; He, Wanqiu; Ikeda, Hiroyuki; Niida, Mana; Nagao, Tohru; Bosch, James; Coupon, Jean; Enoki, Motohiro; Imanishi, Masatoshi; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Onoue, Masafusa; Ouchi, Masami; Schulze, Andreas; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Terashima, Yuichi; Toba, Yoshiki; Ueda, Yoshihiro

    2018-01-01

    We present the luminosity function of z ˜ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ˜ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29 mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ˜ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

  9. The luminosity function of quasars

    Science.gov (United States)

    Pei, Yichuan C.

    1995-01-01

    We propose a new evolutionary model for the optical luminosity function of quasars. Our analytical model is derived from fits to the empirical luminosity function estimated by Hartwick and Schade and Warren, Hewett, and Osmer on the basis of more than 1200 quasars over the range of redshifts 0 approximately less than z approximately less than 4.5. We find that the evolution of quasars over this entire redshift range can be well fitted by a Gaussian distribution, while the shape of the luminosity function can be well fitted by either a double power law or an exponential L(exp 1/4) law. The predicted number counts of quasars, as a function of either apparent magnitude or redshift, are fully consistent with the observed ones. Our model indicates that the evolution of quasars reaches its maximum at z approximately = 2.8 and declines at higher redshifts. An extrapolation of the evolution to z approximately greater than 4.5 implies that quasars may have started their cosmic fireworks at z(sub f) approximately = 5.2-5.5. Forthcoming surveys of quasars at these redshifts will be critical to constrain the epoch of quasar formation. All the results we derived are based on observed quasars and are therefore subject to the bias of obscuration by dust in damped Ly alpha systems. Future surveys of these absorption systems at z approximately greater than 3 will also be important if the formation epoch of quasars is to be known unambiguously.

  10. The Evolution of the Faint End of the UV Luminosity Function during the Peak Epoch of Star Formation (1 < z < 3)

    Science.gov (United States)

    Alavi, Anahita; Siana, Brian; Richard, Johan; Rafelski, Marc; Jauzac, Mathilde; Limousin, Marceau; Freeman, William R.; Scarlata, Claudia; Robertson, Brant; Stark, Daniel P.; Teplitz, Harry I.; Desai, Vandana

    2016-11-01

    We present a robust measurement of the rest-frame UV luminosity function (LF) and its evolution during the peak epoch of cosmic star formation at 1\\lt z\\lt 3. We use our deep near-ultraviolet imaging from WFC3/UVIS on the Hubble Space Telescope and existing Advanced Camera for Surveys (ACS)/WFC and WFC3/IR imaging of three lensing galaxy clusters, Abell 2744 and MACS J0717 from the Hubble Frontier Field survey and Abell 1689. Combining deep UV imaging and high magnification from strong gravitational lensing, we use photometric redshifts to identify 780 ultra-faint galaxies with {M}{UV}\\lt -12.5 AB mag at 1\\lt z\\lt 3. From these samples, we identified five new, faint, multiply imaged systems in A1689. We run a Monte Carlo simulation to estimate the completeness correction and effective volume for each cluster using the latest published lensing models. We compute the rest-frame UV LF and find the best-fit faint-end slopes of α =-1.56+/- 0.04, α =-1.72+/- 0.04, and α =-1.94+/- 0.06 at 1.0\\lt z\\lt 1.6, 1.6\\lt z\\lt 2.2, and 2.2\\lt z\\lt 3.0, respectively. Our results demonstrate that the UV LF becomes steeper from z˜ 1.3 to z˜ 2.6 with no sign of a turnover down to {M}{UV}=-14 AB mag. We further derive the UV LFs using the Lyman break “dropout” selection and confirm the robustness of our conclusions against different selection methodologies. Because the sample sizes are so large and extend to such faint luminosities, the statistical uncertainties are quite small, and systematic uncertainties (due to the assumed size distribution, for example) likely dominate. If we restrict our analysis to galaxies and volumes above \\gt 50 % completeness in order to minimize these systematics, we still find that the faint-end slope is steep and getting steeper with redshift, though with slightly shallower (less negative) values (α =-1.55+/- 0.06, -1.69 ± 0.07, and -1.79 ± 0.08 for z˜ 1.3, 1.9, and 2.6, respectively). Finally, we conclude that the faint star

  11. On the type Ia supernovae 2007on and 2011iv: evidence for Chandrasekhar-mass explosions at the faint end of the luminosity-width relationship

    Science.gov (United States)

    Ashall, C.; Mazzali, P. A.; Stritzinger, M. D.; Hoeflich, P.; Burns, C. R.; Gall, C.; Hsiao, E. Y.; Phillips, M. M.; Morrell, N.; Foley, Ryan J.

    2018-06-01

    Radiative transfer models of two transitional type Ia supernovae (SNe Ia) have been produced using the abundance stratification technique. These two objects - designated SN 2007on and SN 2011iv - both exploded in the same galaxy, NGC 1404, which allows for a direct comparison. SN 2007on synthesized 0.25 M_{⊙} of 56Ni and was less luminous than SN 2011iv, which produced 0.31 M_{⊙} of 56Ni. SN 2007on had a lower central density (ρc) and higher explosion energy (Ekin ˜1.3 ± 0.3 × 1051erg) than SN 2011iv, and it produced less nuclear statistical equilibrium (NSE) elements (0.06 M_{⊙}). Whereas, SN 2011iv had a larger ρc, which increased the electron capture rate in the lowest velocity regions, and produced 0.35 M_{⊙} of stable NSE elements. SN 2011iv had an explosion energy of ˜Ekin ˜0.9 ± 0.2 × 1051erg. Both objects had an ejecta mass consistent with the Chandrasekhar mass (Ch-mass), and their observational properties are well described by predictions from delayed-detonation explosion models. Within this framework, comparison to the sub-luminous SN 1986G indicates SN 2011iv and SN 1986G have different transition densities (ρtr) but similar ρc. Whereas SN 1986G and SN 2007on had a similar ρtr but different ρc. Finally, we examine the colour-stretch parameter sBV versus Lmax relation and determine that the bulk of SNe Ia (including the sub-luminous ones) are consistent with Ch-mass delayed-detonation explosions, where the main parameter driving the diversity is ρtr. We also find ρc to be driving the second-order scatter observed at the faint end of the luminosity-width relationship.

  12. Reverberation Mapping of High-Luminosity Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Kaspi, Shai [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv (Israel); Brandt, William N. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA (United States); Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA (United States); Department of Physics, Pennsylvania State University, University Park, PA (United States); Maoz, Dan; Netzer, Hagai [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv (Israel); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA (United States); Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park, PA (United States); Shemmer, Ohad, E-mail: shai@wise.tau.ac.il [Department of Physics, University of North Texas, Denton, TX (United States)

    2017-10-30

    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 10{sup 46} 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.

  13. A STEEP FAINT-END SLOPE OF THE UV LUMINOSITY FUNCTION AT z ∼ 2-3: IMPLICATIONS FOR THE GLOBAL STELLAR MASS DENSITY AND STAR FORMATION IN LOW-MASS HALOS

    International Nuclear Information System (INIS)

    Reddy, Naveen A.; Steidel, Charles C.

    2009-01-01

    We use the deep ground-based optical photometry of the Lyman Break Galaxy (LBG) Survey to derive robust measurements of the faint-end slope (α) of the UV luminosity function (LF) at redshifts 1.9 ≤ z ≤ 3.4. Our sample includes >2000 spectroscopic redshifts and ∼31000 LBGs in 31 spatially independent fields over a total area of 3261 arcmin 2 . These data allow us to select galaxies to 0.07L* and 0.10L* at z ∼ 2 and z ∼ 3, respectively. A maximum-likelihood analysis indicates steep values of α(z = 2) = -1.73 ± 0.07 and α(z = 3) = -1.73 ± 0.13. This result is robust to luminosity-dependent systematics in the Lyα equivalent width and reddening distributions, and is similar to the steep values advocated at z ∼> 4, and implies that ∼93% of the unobscured UV luminosity density at z ∼ 2-3 arises from sub-L* galaxies. With a realistic luminosity-dependent reddening distribution, faint to moderately luminous galaxies account for ∼>70% and ∼>25% of the bolometric luminosity density and present-day stellar mass density, respectively, when integrated over 1.9 ≤ z 2 contrasts with the shallower slope inferred locally, suggesting that the evolution in the faint-end slope may be dictated simply by the availability of low-mass halos capable of supporting star formation at z ∼< 2.

  14. THE EVOLUTION OF THE REST-FRAME V-BAND LUMINOSITY FUNCTION FROM z = 4: A CONSTANT FAINT-END SLOPE OVER THE LAST 12 Gyr OF COSMIC HISTORY

    International Nuclear Information System (INIS)

    Marchesini, Danilo; Stefanon, Mauro; Brammer, Gabriel B.; Whitaker, Katherine E.

    2012-01-01

    We present the rest-frame V-band luminosity function (LF) of galaxies at 0.4 ≤ z < 4.0, measured from a near-infrared selected sample constructed from the NMBS, the FIRES, the FIREWORKS, and the ultra-deep NICMOS and WFC3 observations in the HDFN, HUDF, and GOODS-CDFS, all having high-quality optical-to-mid-infrared data. This unique sample combines data from surveys with a large range of depths and areas in a self-consistent way, allowing us to (1) minimize the uncertainties due to cosmic variance; and (2) simultaneously constrain the bright and faint ends with unprecedented accuracy over the targeted redshift range, probing the LF down to 0.1L* at z ∼ 3.9. We find that (1) the faint end is fairly flat and with a constant slope from z = 4, with α = –1.27 ± 0.05; (2) the characteristic magnitude has dimmed by 1.3 mag from z ∼ 3.7 to z = 0.1; (3) the characteristic density has increased by a factor of ∼8 from z ∼ 3.7 to z = 0.1, with 50% of this increase from z ∼ 4 to z ∼ 1.8; and (4) the luminosity density peaks at z ≈ 1-1.5, increasing by a factor of ∼4 from z = 4.0 to z ≈ 1-1.5, and subsequently decreasing by a factor of ∼1.5 by z = 0.1. We find no evidence for a steepening of the faint-end slope with redshift out to z = 4, in contrast with previous observational claims and theoretical predictions. The constant faint-end slope suggests that the efficiency of stellar feedback may evolve with redshift. Alternative interpretations are discussed, such as different masses of the halos hosting faint galaxies at low and high redshifts and/or environmental effects.

  15. NEW CONSTRAINTS ON THE FAINT END OF THE UV LUMINOSITY FUNCTION AT z ∼ 7-8 USING THE GRAVITATIONAL LENSING OF THE HUBBLE FRONTIER FIELDS CLUSTER A2744

    International Nuclear Information System (INIS)

    Atek, Hakim; Kneib, Jean-Paul; Richard, Johan; Clement, Benjamin; Jauzac, Mathilde; Schaerer, Daniel; Limousin, Marceau; Jullo, Eric; Natarajan, Priyamvada; Egami, Eiichi; Ebeling, Harald

    2015-01-01

    Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ∼ 7 and eight candidates at z ∼ 8 in a total survey area of 0.96 arcmin 2 in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ∼ 7 UV LF down to an absolute magnitude of M UV ∼ –15.5. We find a characteristic magnitude of M UV ⋆ =−20.90 −0.73 +0.90  mag and a faint-end slope α=−2.01 −0.28 +0.20 , close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L * . Although prone to large uncertainties, our results at z ∼ 8 also seem to confirm a steep faint-end slope below 0.1 L * . The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization

  16. NEW CONSTRAINTS ON THE FAINT END OF THE UV LUMINOSITY FUNCTION AT z ∼ 7-8 USING THE GRAVITATIONAL LENSING OF THE HUBBLE FRONTIER FIELDS CLUSTER A2744

    Energy Technology Data Exchange (ETDEWEB)

    Atek, Hakim; Kneib, Jean-Paul [Laboratoire d' Astrophysique, Ecole Polytechnique Fédérale de Lausanne, Observatoire de Sauverny, CH-1290 Versoix (Switzerland); Richard, Johan; Clement, Benjamin [CRAL, Observatoire de Lyon, Université Lyon 1, 9 Avenue Ch. André, F-69561 Saint Genis Laval Cedex (France); Jauzac, Mathilde [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Schaerer, Daniel [Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix (Switzerland); Limousin, Marceau; Jullo, Eric [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Natarajan, Priyamvada [Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Egami, Eiichi [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ebeling, Harald [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-02-10

    Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ∼ 7 and eight candidates at z ∼ 8 in a total survey area of 0.96 arcmin{sup 2} in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ∼ 7 UV LF down to an absolute magnitude of M {sub UV} ∼ –15.5. We find a characteristic magnitude of M{sub UV}{sup ⋆}=−20.90{sub −0.73}{sup +0.90} mag and a faint-end slope α=−2.01{sub −0.28}{sup +0.20}, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L {sup *}. Although prone to large uncertainties, our results at z ∼ 8 also seem to confirm a steep faint-end slope below 0.1 L {sup *}. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization.

  17. Seeking the epoch of maximum luminosity for dusty quasars

    International Nuclear Information System (INIS)

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine

    2014-01-01

    Infrared luminosities νL ν (7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 luminosity does not show a maximum at any redshift z < 5, reaching a plateau for z ≳ 3 with maximum luminosity νL ν (7.8 μm) ≳ 10 47 erg s –1 ; luminosity functions show one quasar Gpc –3 having νL ν (7.8 μm) > 10 46.6 erg s –1 for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL ν (0.25 μm), have the largest values of the ratio νL ν (0.25 μm)/νL ν (7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  18. THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82

    International Nuclear Information System (INIS)

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

    2013-01-01

    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 2 , then extend to lower luminosities (M 1450 2 of deep, coadded imaging in the SDSS Stripe 82 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 1450 * ∼-27). The bright-end slope is steep (β ∼ 1450 < –26) from z = 5 to z = 6 than from z = 4 to z = 5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate ∼30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

  19. Luminosity and Redshift dependence of quasar spectral properties

    Energy Technology Data Exchange (ETDEWEB)

    Daniel E. Vanden Berk et al.

    2004-03-09

    Using a large sample of quasar spectra from the SDSS, we examine the composite spectral trends of quasars as functions of both redshift and luminosity, independently of one another. Aside from the well known Baldwin effect (BE)--the decrease of line equivalent width with luminosity--the average spectral properties are remarkably similar. Host galaxy contamination and the BE are the primary causes for apparent changes in the average spectral slope of the quasars. The BE is detected for most emission lines, including the Balmer lines, but with several exceptions including NV1240A. Emission line shifts of several lines are associated with the BE. The BE is mainly a function of luminosity, but also partly a function of redshift in that line equivalent widths become stronger with redshift. Some of the complex iron features change with redshift, particularly near the small blue bump region.

  20. The quasar luminosity function from a variability-selected sample

    Science.gov (United States)

    Hawkins, M. R. S.; Veron, P.

    1993-01-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sign of the 'break' found in the recent UVX sample of Boyle et al. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.

  1. Hints on the Broad Line Region Structure of Quasars at High and Low Luminosities

    Directory of Open Access Journals (Sweden)

    Marziani Paola

    2011-09-01

    Full Text Available Quasars show a considerable spectroscopic diversity. However, the variety of quasar spectra at low redshifts is non-random: a principal component analysis applied to large samples customarily identifies two main eigenvectors. In this contribution we show that the range of quasar optical spectral properties observed at low-z and associated with the first eigenvector is preserved up to z ≈ 2 in a sample of high luminosity quasars. We also describe two major luminosity effects.

  2. Spatial distribution, luminosity function and cosmological evolution of quasars

    International Nuclear Information System (INIS)

    Mathez, G.

    1981-01-01

    The different ways of studying quasars statistics and evolution are reviewed. Attempt is given to deduce, from the observed evolution, some constraints on physical models of energy sources in quasars [fr

  3. A composite plot of far-infrared versus radio luminosity, and the origin of far-infrared luminosity in quasars

    International Nuclear Information System (INIS)

    Sopp, H.M.; Alexander, P.

    1991-01-01

    We have constructed a composite plot of far-infrared versus radioluminosity for late-type galaxies, Seyferts, quasars and radio galaxies. The most striking result is that the radio and far-infrared luminosities of radio-quiet quasars are correlated and follow the same correlation as normal star-forming galaxies and ultra-luminous infrared galaxies, whereas the radio-loud quasars have luminosities in both bands similar to those of radio galaxies. We conclude that the far-infrared emission from radio-quiet quasars is from star-forming host galaxies and not from active galactic nuclei. The far-infrared radio plot may be a powerful discriminator between host galaxy type. (author)

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

    Science.gov (United States)

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

    2018-01-01

    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 < 18.0) quasars in the redshift range of 2.8<= z<=5.0. It effectively uses Random Forest machine-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.

  5. THE REDSHIFT DISTRIBUTION OF INTERVENING WEAK Mg II QUASAR ABSORBERS AND A CURIOUS DEPENDENCE ON QUASAR LUMINOSITY

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Jessica L.; Churchill, Christopher W.; Nielsen, Nikole M.; Klimek, Elizabeth S. [New Mexico State University, Las Cruces, NM 88003 (United States); Murphy, Michael T. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Melbourne, VIC 3122 (Australia)

    2013-05-01

    We have identified 469 Mg II {lambda}{lambda}2796, 2803 doublet systems having W{sub r} {>=} 0.02 A in 252 Keck/High Resolution Echelle Spectrometer and UVES/Very Large Telescope quasar spectra over the redshift range 0.1 < z < 2.6. Using the largest sample yet of 188 weak Mg II systems (0.02 A {<=}W{sub r} < 0.3 A), we calculate their absorber redshift path density, dN/dz. We find clear evidence of evolution, with dN/dz peaking at z {approx} 1.2, and that the product of the absorber number density and cross section decreases linearly with increasing redshift; weak Mg II absorbers seem to vanish above z {approx_equal} 2.7. If the absorbers are ionized by the UV background, we estimate number densities of 10{sup 6}-10{sup 9} Mpc{sup -3} for spherical geometries and 10{sup 2}-10{sup 5} Mpc{sup -3} for more sheetlike geometries. We also find that dN/dz toward intrinsically faint versus bright quasars differs significantly for weak and strong (W{sub r} {>=} 1.0 A) absorbers. For weak absorption, dN/dz toward bright quasars is {approx}25% higher than toward faint quasars (10{sigma} at low redshift, 0.4 {<=} z {<=} 1.4, and 4{sigma} at high redshift, 1.4 < z {<=} 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being {approx}20% higher than toward bright quasars (also 10{sigma} at low redshift and 4{sigma} at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  6. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    International Nuclear Information System (INIS)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu; Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo; Willott, Chris J.; Im, Myungshin; Shimasaku, Kazuhiro; Ouchi, Masami; Hibon, Pascale

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg 2 utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z B ) and (z B -z R ) colors, where z B and z 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 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 1450 = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M 1450 = –22.58 and a narrow Lyα emission with HWHM =427 km s –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

  7. INFRARED CLASSIFICATION AND LUMINOSITIES FOR DUSTY ACTIVE GALACTIC NUCLEI AND THE MOST LUMINOUS QUASARS

    International Nuclear Information System (INIS)

    Weedman, Daniel; Sargsyan, Lusine; Houck, James; Barry, Donald; Lebouteiller, Vianney

    2012-01-01

    Mid-infrared spectroscopic measurements from the Infrared Spectrometer (IRS) on Spitzer are given for 125 hard X-ray active galactic nuclei (AGNs; 14-195 keV) from the Swift Burst Alert Telescope (BAT) sample and for 32 AGNs with black hole masses (BHMs) from reverberation mapping. The 9.7 μm silicate feature in emission or absorption defines an infrared AGN classification describing whether AGNs are observed through dust clouds, indicating that 55% of the BAT AGNs are observed through dust. The mid-infrared dust continuum luminosity is shown to be an excellent indicator of intrinsic AGN luminosity, scaling closely with the hard X-ray luminosity, log νL ν (7.8 μm)/L(X) = –0.31 ± 0.35, and independent of classification determined from silicate emission or absorption. Dust luminosity scales closely with BHM, log νL ν (7.8 μm) = (37.2 ± 0.5) + 0.87 log BHM for luminosity in erg s –1 and BHM in M ☉ . The 100 most luminous type 1 quasars as measured in νL ν (7.8 μm) are found by comparing Sloan Digital Sky Survey (SDSS) optically discovered quasars with photometry at 22 μm from the Wide-Field Infrared Survey Explorer (WISE), scaled to rest frame 7.8 μm using an empirical template determined from IRS spectra. The most luminous SDSS/WISE quasars have the same maximum infrared luminosities for all 1.5 IR = 10 14.4 L ☉ . Comparing with dust-obscured galaxies from Spitzer and WISE surveys, we find no evidence of hyperluminous obscured quasars whose maximum infrared luminosities exceed the maximum infrared luminosities of optically discovered quasars. Bolometric luminosities L bol estimated from rest-frame optical or ultraviolet luminosities are compared to L IR . For the local AGN, the median log L IR /L bol = –0.35, consistent with a covering factor of 45% for the absorbing dust clouds. For the SDSS/WISE quasars, the median log L IR /L bol = 0.1, with extremes indicating that ultraviolet-derived L bol can be seriously underestimated even for type 1

  8. VizieR Online Data Catalog: Quasar luminosity function (Hawkins+, 1993)

    Science.gov (United States)

    Hawkins, M. R. S.; Veron, P.

    1994-11-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved. (1 data file).

  9. Quasars.

    Science.gov (United States)

    Smith, H J

    1966-11-01

    A short historical outline of the discovery and a description of observed properties of quasars introduces questions as to their nature. Some of the principal arguments concerning their reality, distance, intrinsic properties and age lead to the conclusion that, while there is room for other points of view; a strong case can be made for the interpretation, on which quasars are the most distant observable objects in the known universe. To produce such luminosities over times of thousands to millions of years requires the presence of millions of solar masses. For each quasar this enormous mass may be concentrated into a single object, in which case novel physics comes into play. Whatever the final interpretation, quasars seem certain to illuminate such questions as the origin and evolution of galaxies, perhaps also the structure and origin of the universe.

  10. Cross-correlation of SDSS DR7 quasars and DR10 BOSS galaxies: The weak luminosity dependence of quasar clustering at z ∼ 0.5

    International Nuclear Information System (INIS)

    Shen, Yue; McBride, Cameron K.; Swanson, Molly E. C.; White, Martin; Kirkpatrick, Jessica A.; Ross, Nicholas P.; Schlegel, David J.; Zheng, Zheng; Myers, Adam D.; Guo, Hong; Zehavi, Idit; Padmanabhan, Nikhil; Parejko, John K.; Schneider, Donald P.; Streblyanska, Alina; Pan, Kaike; Bizyaev, Dmitry; Brewington, Howard; Ebelke, Garrett; Malanushenko, Viktor

    2013-01-01

    We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 quasars and 349,608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey at 0.3 < z < 0.9. The CCF can be reasonably well fit by a power-law model ξ QG (r) = (r/r 0 ) –γ on projected scales of r p = 2-25 h –1 Mpc with r 0 = 6.61 ± 0.25 h –1 Mpc and γ = 1.69 ± 0.07. We estimate a quasar linear bias of b Q = 1.38 ± 0.10 at (z) = 0.53 from the CCF measurements, which corresponds to a characteristic host halo mass of ∼4 × 10 12 h –1 M ☉ , compared with a ∼10 13 h –1 M ☉ characteristic host halo mass for CMASS galaxies. Based on the clustering measurements, most quasars at z-bar ∼0.5 are not the descendants of their higher luminosity counterparts at higher redshift, which would have evolved into more massive and more biased systems at low redshift. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db Q /dlog L = 0.20 ± 0.34 or 0.11 ± 0.32 (depending on different luminosity divisions) for quasar luminosities –23.5 > M i (z = 2) > –25.5, implying a weak luminosity dependence of clustering for luminous quasars at z-bar ∼0.5. We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations and ambiguities in modeling the distribution of quasars with the standard HOD approach.

  11. THE BLACK HOLE MASS-GALAXY LUMINOSITY RELATIONSHIP FOR SLOAN DIGITAL SKY SURVEY QUASARS

    International Nuclear Information System (INIS)

    Salviander, S.; Shields, G. A.; Bonning, E. W.

    2015-01-01

    We investigate the relationship between the mass of the central supermassive black hole, M BH , and the host galaxy luminosity, L gal , in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M BH -L gal relationship by examining the redshift dependence of Δ log M BH , the offset in M BH from the local M BH -L gal relationship. There is little systematic trend in Δ log M BH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ * , we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ * in statistical studies

  12. MAD ADAPTIVE OPTICS IMAGING OF HIGH-LUMINOSITY QUASARS: A PILOT PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Liuzzo, E. [Osservatorio di Radioastronomia, INAF, via Gobetti 101, I-40129 Bologna (Italy); Falomo, R.; Paiano, S.; Baruffolo, A.; Farinato, J.; Moretti, A.; Ragazzoni, R. [Osservatorio Astronomico di Padova, INAF, vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Treves, A. [Università dell’Insubria (Como) (Italy); Uslenghi, M. [INAF-IASF, via E. Bassini 15, I-20133 Milano (Italy); Arcidiacono, C.; Diolaiti, E.; Lombini, M. [Osservatorio Astronomico di Bologna, INAF, Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Brast, R. [Dipartimento di Fisica e Astronomia, Università di Bologna, Via Irnerio, 46, I-40126, Bologna (Italy); Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S., E-mail: liuzzo@ira.inaf.it [European Southern Observatory, Karl-Schwarschild-Strasse 2, D-85748 Garching bei München (Germany)

    2016-08-01

    We present near-IR images of five luminous quasars at z ∼ 2 and one at z ∼ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ∼ 0.2 arcsec. We are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2–3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K -magnitude spanning from 15 to 20 (corresponding to absolute magnitude −31 to −26) and host galaxies that are 4 mag fainter than their nuclei.

  13. MAD Adaptive Optics Imaging of High-luminosity Quasars: A Pilot Project

    Science.gov (United States)

    Liuzzo, E.; Falomo, R.; Paiano, S.; Treves, A.; Uslenghi, M.; Arcidiacono, C.; Baruffolo, A.; Diolaiti, E.; Farinato, J.; Lombini, M.; Moretti, A.; Ragazzoni, R.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

    2016-08-01

    We present near-IR images of five luminous quasars at z ˜ 2 and one at z ˜ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ˜ 0.2 arcsec. We are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2-3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K-magnitude spanning from 15 to 20 (corresponding to absolute magnitude -31 to -26) and host galaxies that are 4 mag fainter than their nuclei.

  14. The Size-Luminosity Relationship of Quasar Narrow-Line Regions

    Science.gov (United States)

    Dempsey, Ross; Zakamska, Nadia L.

    2018-04-01

    The presence of an active galactic nucleus (AGN) can strongly affect its host. Due to the copious radiative power of the nucleus, the effects of radiative feedback can be detected over the entire host galaxy and sometimes well into the intergalactic space. In this paper we model the observed size-luminosity relationship of the narrow-line regions (NLRs) of AGN. We model the NLR as a collection of clouds in pressure equilibrium with the ionizing radiation, with each cloud producing line emission calculated by Cloudy. The sizes of the NLRs of powerful quasars are reproduced without any free parameters, as long as they contain massive (105M⊙ to 107M⊙) ionization-bounded clouds. At lower AGN luminosities the observed sizes are larger than the model sizes, likely due to additional unmodeled sources of ionization (e.g., star formation). We find that the observed saturation of sizes at ˜10kpc which is observed at high AGN luminosities (Lion ≃ 1046erg/s) is naturally explained by optically thick clouds absorbing the ionizing radiation and preventing illumination beyond a critical distance. Using our models in combination with observations of the [O III]/IR ratio and the [O III] size - IR luminosity relationship, we calculate the covering factor of the obscuring torus (and therefore the type 2 fraction within the quasar population) to be f = 0.5, though this is likely an upper bound. Finally, because the gas behind the ionization front is invisible in ionized gas transitions, emission-based NLR mass calculations underestimate the mass of the NLR and therefore of the energetics of ionized-gas winds.

  15. THE RADIO AND OPTICAL LUMINOSITY EVOLUTION OF QUASARS. II. THE SDSS SAMPLE

    International Nuclear Information System (INIS)

    Singal, J.; Petrosian, V.; Stawarz, Ł.; Lawrence, A.

    2013-01-01

    We determine the radio and optical luminosity evolutions and the true distribution of the radio-loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining Sloan Digital Sky Survey optical and Faint Images of the Radio Sky at Twenty cm (FIRST) radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. With the luminosity evolutions accounted for, we determine the density evolutions and local radio and optical luminosity functions. The intrinsic distribution of the radio-loudness parameter R is found to be quite different from the observed one and is smooth with no evidence of a bimodality in radio loudness for log R ≥ –1. The results we find are in general agreement with the previous analysis of Singal et al., which used POSS-I optical and FIRST radio data.

  16. What BOSS has taught us about Quasars.

    Science.gov (United States)

    Ross, Nicholas; SDSS-III BOSS Quasar Science Working Group

    2015-01-01

    This talk presents science highlights from the SDSS-III BOSS Quasar Survey, which has obtained spectra for over 300,000 quasars, 200,000 of which are at redshift z>2. Using this dataset, new measurements of the luminosity function have been made, with the faint end of the luminosity function now measured to z~5. New clustering results from DR12 are presented, and the weak luminosity dependence of quasar clustering at z~0.5 is also discussed.New studies of the broad absorption line (BAL) quasar population have also been performed, with a sample of BAL quasars from the original SDSS being re-observed. These new data have shown the disappearance of CIV BAL troughs and indeed the transformation of BAL QSOs to non-BAL QSOs. BAL disappearance, and emergence, events appear to be extremes of general BAL variability, and have shed light on accretion-disk wind models.We highlight the discovery of new classes of quasars including: a population of broad-line Mg II emitters found in a passive galaxy sample; objects with extremely red optical-to-mid infrared colors; objects with very curious UV line (LyA:NV) ratios and potentially the long-sought after high-redshift Type 2 Quasar population.Finally, we describe two new dedicated programs, one focusing on reverberation mapping, the other on X-ray selected quasars.A full list of papers connected to the BOSS Quasar Survey is given at: http://www.sdss3.org/science/publications.php

  17. Statistics of the Hubble diagram. I. Determination of q2 and luminosity evolution with application to quasars

    International Nuclear Information System (INIS)

    Turner, E.L.

    1979-01-01

    A rank statistic version of the magnitude-redshift q 0 test is developed. It may be applied to the Hubble diagram of objects with an arbitrary and unknown luminosity function; in particular, the objects need not be ''standard candles.'' Only the single restriction that the objects' luminosity function does not vary in functional form is placed on the sources' intrinsic properties. Density and/or luminosity evolution are taken into account. Corrections for sample selection biases are incorporated into the analysis. Tests for the presence of luminosity evolution are given. Methods for determining either q 0 or the luminosity evolution when the other is a priori known are described.Application of these techniques to a sample of 119 3CR and 4C quasars leads to the following results: The radio Hubble diagram is consistent with all values of q 0 , suggesting that the quasar radio luminosity function is a featureless power law. The optical Hubble diagram indicates one of these possibilities: (1) the value of q 0 is in the range 2--32, probably near 5; (2) the value of q 0 is more reasonable and there is strong optical luminosity evolution [e.g., if q/sub o/ approx. = 0.05, then the characteristic optical luminosity scales like approx. (1 + Z)/sup 7/3/]; or (3) the data are a low-probability (< or =0.05) statistical fluctuation. The second interpretation is probably the most sensible one.Generalizations of the rank statistic magnitude-redshift test are suggested for application to a variety of extragalactic and stellar problems. Specific examples of applications to unorthodox cosmologies are given. Even for the unfavorable (very broad luminosity function) case of the optical quasar data, the rank statistic analysis is sensitive to relative variations in the distance-modulus-redshift relation as small as approx.0.4 mag for 1/2 < or = Z < or = 2

  18. Clustering of quasars in a wide luminosity range at redshift 4 with Subaru Hyper Suprime-Cam Wide-field imaging

    Science.gov (United States)

    He, Wanqiu; Akiyama, Masayuki; Bosch, James; Enoki, Motohiro; Harikane, Yuichi; Ikeda, Hiroyuki; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nagao, Tohru; Nagashima, Masahiro; Niida, Mana; Nishizawa, Atsushi J.; Oguri, Masamune; Onoue, Masafusa; Oogi, Taira; Ouchi, Masami; Schulze, Andreas; Shirasaki, Yuji; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Toba, Yoshiki; Uchiyama, Hisakazu; Yamashita, Takuji

    2018-01-01

    We examine the clustering of quasars over a wide luminosity range, by utilizing 901 quasars at \\overline{z}_phot˜ 3.8 with -24.73 Strategic Program (HSC-SSP) S16A Wide2 date release and 342 more luminous quasars at 3.4 Digital Sky Survey that fall in the HSC survey fields. We measure the bias factors of two quasar samples by evaluating the cross-correlation functions (CCFs) between the quasar samples and 25790 bright z ˜ 4 Lyman break galaxies in M1450 < -21.25 photometrically selected from the HSC dataset. Over an angular scale of 10.0" to 1000.0", the bias factors are 5.93+1.34-1.43 and 2.73+2.44-2.55 for the low- and high-luminosity quasars, respectively, indicating no significant luminosity dependence of quasar clustering at z ˜ 4. It is noted that the bias factor of the luminous quasars estimated by the CCF is smaller than that estimated by the auto-correlation function over a similar redshift range, especially on scales below 40.0". Moreover, the bias factor of the less-luminous quasars implies the minimal mass of their host dark matter halos is 0.3-2 × 1012 h-1 M⊙, corresponding to a quasar duty cycle of 0.001-0.06.

  19. A Compton-thick Wind in the High Luminosity Quasar, PDS 456

    Science.gov (United States)

    Reeves, J. N.; O'Brien, P. T.; Behar, E.; Miller, L.; Turner, T. J.; Braito, V.; Fabian, A. C.; Kaspi, S.; Mushotzky, R.; Ward, M.

    2009-01-01

    PDS 456 is a nearby (z=0.184), luminous (L(sub bol) approximately equal to 10(exp 47) ergs(exp -1) type I quasar. A deep 190 ks Suzaku observation in February 2007 revealed the complex, broad band X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly statistically significant absorption features near 9 keV in the quasar rest-frame. We show that the most plausible origin of the absorption is from blue-shifted resonance (1s-2p) transitions of hydrogen-like iron (at 6.97 keV in the rest frame). This indicates that a highly ionized outflow may be present moving at near relativistic velocities (0.26-0.31c). A possible hard X-ray excess is detected above 15 keV with HXD (at 99.8% confidence), which may arise from high column density gas (N(sub H) greater than 10(exp 24)cm(exp -2) partially covering the X-ray emission, or through strong Compton reflection. Here we propose that the iron K-shell absorption in PDS 456 is associated with a thick, possibly clumpy outflow, covering about 20% of 4(pi) steradian solid angle. The outflow is likely launched from the inner accretion disk, within 15-100 gravitational radii of the black hole. The kinetic power of the outflow may be similar to the bolometric luminosity of PDS 456. Such a powerful wind could have a significant effect on the co-evolution of the host galaxy and its supermassive black hole, through feedback.

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

    Energy Technology Data Exchange (ETDEWEB)

    Rowan-Robinson, M; Broadhurst, T [Queen Mary Coll., London (UK). School of Mathematical Sciences; Lawrence, A [Queen Mary Coll., London (UK). Dept. of Physics; McMahon, R G [Cambridge Univ. (UK). Inst. of Astronomy; Lonsdale, C J [California Inst. of Tech., Pasadena, CA (USA). Infrared Processing and Analysis Center; Oliver, S J; Taylor, A N [Queen Mary Coll., London (UK). School of Mathematical Sciences; Hacking, P B; Conrow, T [California Inst. of Tech., Pasadena, CA (USA). Infrared Processing and Analysis Center; Saunders, W [Oxford Univ. (UK). Dept. of Astrophysics; Ellis, R S [Durham Univ. (UK). Dept. of Physics; Efstathiou, G P [Oxford Univ. (UK). Dept. of Astrophysics; Condon, J J [National Radio Astronomy Observatory, Charlottesville, VA (USA)

    1991-06-27

    During a survey intended to measure redshifts for 1,400 galaxies identified with faint sources detected by the Infrared Astronomy Satellite, we found an emission-line galaxy at a redshift of 2.286, and with the enormous far-infrared luminosity of 3 x 10{sup 14} times that of the sun (L{sub sun}) The spectrum is very unusual, showing lines of high excitation but with very weak Lyman-{alpha} emission. A self-absorbed synchrotron model for the infrared energy distribution cannot be ruled out, but a thermal origin seems more plausible. A radio-quiet quasar embedded in a very dusty galaxy could account for the infrared emission, as might a starburst embedded in 1-10 x 10{sup 9} M{sub sun} of dust. The latter case demands so much dust that the object would probably be a massive galaxy in the process of formation. In either case, this is a remarkable object, and the presence of a large amount of dust in an object of such high redshift implies the generation of heavy elements at an early cosmological epoch. (author).

  1. STELLAR VELOCITY DISPERSION MEASUREMENTS IN HIGH-LUMINOSITY QUASAR HOSTS AND IMPLICATIONS FOR THE AGN BLACK HOLE MASS SCALE

    Energy Technology Data Exchange (ETDEWEB)

    Grier, C. J.; Martini, P.; Peterson, B. M.; Pogge, R. W.; Zu, Y. [Department of Astronomy, Ohio State University, 140 W 18th Avenue, Columbus, OH 43210 (United States); Watson, L. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bentz, M. C. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Dasyra, K. M. [Observatoire de Paris, LERMA (CNRS:UMR8112), 61 Avenue de l' Observatoire, F-75014, Paris (France); Dietrich, M. [Department of Physics and Astronomy, Ohio University, Athens, OH 45601 (United States); Ferrarese, L. [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria BV V9E 2E7 (Canada)

    2013-08-20

    We present new stellar velocity dispersion measurements for four luminous quasars with the Near-Infrared Integral Field Spectrometer instrument and the ALTAIR laser guide star adaptive optics system on the Gemini North 8 m telescope. Stellar velocity dispersion measurements and measurements of the supermassive black hole (BH) masses in luminous quasars are necessary to investigate the coevolution of BHs and galaxies, trace the details of accretion, and probe the nature of feedback. We find that higher-luminosity quasars with higher-mass BHs are not offset with respect to the M{sub BH}-{sigma}{sub *} relation exhibited by lower-luminosity active galactic nuclei (AGNs) with lower-mass BHs, nor do we see correlations with galaxy morphology. As part of this analysis, we have recalculated the virial products for the entire sample of reverberation-mapped AGNs and used these data to redetermine the mean virial factor (f) that places the reverberation data on the quiescent M{sub BH}-{sigma}{sub *} relation. With our updated measurements and new additions to the AGN sample, we obtain (f) = 4.31 {+-} 1.05, which is slightly lower than, but consistent with, most previous determinations.

  2. Statistics of the hubble diagram. II. The form of the luminosity function and density variations with application to quasars

    International Nuclear Information System (INIS)

    Turner, E.L.

    1979-01-01

    New techniques for deriving a luminosity function LF and a spatial density distribution rho (r) from magnitude-redshift data are presented. These techniques do not require iterative improvement of an initially guessed solution or the adoption of arbitrary analytic forms; instead, they provide explicit numerical estimates of the LF and rho (r). Thus, sources of systematic uncertainty are eliminated. This is achieved at the cost of an increase in the statistical noise. As in Paper I of this series, it is necessary to assume that the LF does not vary in functional form. An internal test of this assumption is described.These techniques are illustrated by application to a sample of 3 CR and 4C quasars. The radio luminosity function is found to be a steep power law with no features. The optical luminosity function is found to be a shallow power law cut off roughly exponentially above a characteristic luminosity L/sub opt/* (Z) corresponding roughly to M/sub B/=-22-6 log (1+Z) The comoving density evolution is not well fitted by any simple function of 1+Z [e.g., (1+Z) 6 errs by factors as large as approx.5 at some redshifts] but is well represented by an exponential of look-back time. Specific analytic fits and numerical tabulations are given for each of these functions. The constant LF form assumption is found to be a reasonable first approximation for the quasars.Other possible applications of the new methods to problems in extragalactic and stellar astronomy are suggested

  3. The Luminosity Function of Fermi-Detected Flat-Spectrum Radio Quasars

    Science.gov (United States)

    2012-05-11

    extensively studied at radio (Dunlop & Peacock 1990; Wall et al. 2005), soft X-ray (Giommi & Padovani 1994; Rector et al. 2000; Wolter & Celotti 2001...FSRQs) evolve positively (i.e., there were more blazars in the past, Dunlop & Peacock 1990) up to a redshift cutoff which depends on luminosity (e.g...luminosity of 1048 erg s−1. The LDDE model provides a good fit to the LAT data and is able to reproduce the observed distribution in Figure 2. The log

  4. 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.

    2012-04-16

    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.

  5. Recalculating the quasar luminosity function of the extended Baryon Oscillation Spectroscopic Survey

    Science.gov (United States)

    Caditz, David M.

    2017-12-01

    Aims: The extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey provides a uniform sample of over 13 000 variability selected quasi-stellar objects (QSOs) in the redshift range 0.68 based on this survey may be in error because the k-correction has apparently been misapplied, which results in underestimating the intrinsic brightness of roughly half of the eBOSS sources. This work provides new estimates of the QLF based on a corrected eBOSS dataset. Methods: Intrinsic luminosities were recalculated using the appropriate g-band k-correction function. The QLF was determined for the corrected dataset using a model-weighted estimator, and parametric models were refit to the corrected luminosity function. Projected number counts based on the corrected models are also provided. Results: At redshifts higher than the "pivot" redshift, zp = 2.2, the original and recalculated results differ significantly; in particular, the new results show stronger high-redshift evolution in the best-fit models than the original eBOSS analysis. A new seven-parameter QLF model is provided that fits the corrected eBOSS dataset.

  6. SDSS J013127.34–032100.1: A NEWLY DISCOVERED RADIO-LOUD QUASAR AT z = 5.18 WITH EXTREMELY HIGH LUMINOSITY

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Wei-Min; Bai, Jin-Ming; Zhang, Ju-jia; Wang, Fang; Wang, Jian-Guo; Fan, Yu-Feng; Chang, Liang; Wang, Chuan-Jun; Lun, Bao-Li [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Wang, Feige; Wu, Xue-Bing; Yang, Jinyi; Ho, Luis C.; Zuo, Wenwen; Yang, Qian; Ai, Yanli [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui [Steward Observatory, University of Arizona, Tucson, AZ 85721-0065 (United States); Brandt, William N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Kim, Minjin [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Wang, Ran [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); and others

    2014-11-10

    Very few of the z > 5 quasars discovered to date have been radio-loud, with radio-to-optical flux ratios (radio-loudness parameters) higher than 10. Here we report the discovery of an optically luminous radio-loud quasar, SDSS J013127.34–032100.1 (J0131–0321 in short), at z = 5.18 ± 0.01 using the Lijiang 2.4 m and Magellan telescopes. J0131–0321 has a spectral energy distribution consistent with that of radio-loud quasars. With an i-band magnitude of 18.47 and a radio flux density of 33 mJy, its radio-loudness parameter is ∼100. The optical and near-infrared spectra taken by Magellan enable us to estimate its bolometric luminosity to be L {sub bol} ∼ 1.1 × 10{sup 48} erg s{sup –1}, approximately 4.5 times greater than that of the most distant quasar known to date. The black hole mass of J0131–0321 is estimated to be 2.7 × 10{sup 9} M {sub ☉}, with an uncertainty up to 0.4 dex. Detailed physical properties of this high-redshift, radio-loud, potentially super-Eddington quasar can be probed in the future with more dedicated and intensive follow-up observations using multi-wavelength facilities.

  7. THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. II. BLACK HOLE MASS AND EDDINGTON RATIO FUNCTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Brandon C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Shen, Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States)

    2013-02-10

    We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of {approx}58, 000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M {sub BH} {approx}< 3 Multiplication-Sign 10{sup 8} M {sub Sun} or L/L {sub Edd} {approx}< 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L {sub Edd} {approx} 3. Consistent with our results in Shen and Kelly, we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.

  8. Evolution of the Quasar Luminosity Function: Implications for EoR-21cm

    Science.gov (United States)

    Kulkarni, Girish; Choudhury, Tirthankar Roy; Puchwein, Ewald; Haehnelt, Martin G.

    2018-05-01

    We present predictions for the spatial distribution of 21 cm brightness temperature fluctuations from high-dynamic-range simulations for AGN-dominated reionization histories that have been tested against available Lyα and CMB data. We model AGN by extrapolating the observed Mbh-σ relation to high redshifts and assign them ionizing emissivities consistent with recent UV luminosity function measurements. AGN-dominated reionization histories increase the variance of the 21 cm emission by a factor of up to ten compared to similar reionization histories dominated by faint galaxies, to values close to 100 mK2 at scales accessible to experiments (k <~ 1 cMpc-1h). This is lower than the sensitivity reached by ongoing experiments by only a factor of about two or less. AGN dominated reionization should be easily detectable by LOFAR (and later HERA and SKA1) at their design sensitivity.

  9. Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ≳ 6 studied with ALMA

    Science.gov (United States)

    Izumi, Takuma; Onoue, Masafusa; Shirakata, Hikari; Nagao, Tohru; Kohno, Kotaro; Matsuoka, Yoshiki; Imanishi, Masatoshi; Strauss, Michael A.; Kashikawa, Nobunari; Schulze, Andreas; Silverman, John D.; Fujimoto, Seiji; Harikane, Yuichi; Toba, Yoshiki; Umehata, Hideki; Nakanishi, Kouichiro; Greene, Jenny E.; Tamura, Yoichi; Taniguchi, Akio; Yamaguchi, Yuki; Goto, Tomotsugu; Hashimoto, Yasuhiro; Ikarashi, Soh; Iono, Daisuke; Iwasawa, Kazushi; Lee, Chien-Hsiu; Makiya, Ryu; Minezaki, Takeo; Tang, Ji-Jia

    2018-04-01

    We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L_[C II] = (3.8-10.2)× 108 L_{⊙} and LFIR = (1.2-2.0) × 1011 L_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≃ 23-40 M_{⊙} yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L_[C II]/L_FIR ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 M_{⊙}. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ˜ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

  10. Ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to z 3

    Science.gov (United States)

    Cao, Shuo; Zheng, Xiaogang; Biesiada, Marek; Qi, Jingzhao; Chen, Yun; Zhu, Zong-Hong

    2017-09-01

    Context. Ultra-compact structure in radio sources (especially in quasars that can be observed up to very high redshifts), with milliarcsecond angular sizes measured by very-long-baseline interferometry (VLBI), is becoming an important astrophysical tool for probing both cosmology and the physical properties of AGN. Aims: We present a newly compiled data set of 120 milliarcsec. compact radio sources representing intermediate-luminosity quasars covering the redshift range 0.46 RDE) or the Dvali-Gabadadze-Porrati (DGP) brane-world scenario. While no significant change in w with redshift is detected, there is still considerable room for evolution in w and the transition redshift at which w departing from -1 is located at z 2.0. Our results demonstrate that the method extensively investigated in our work on observational radio quasar data can be used to effectively derive cosmological information. Finally, we find the combination of high-redshift quasars and low-redshift clusters may provide an important source of angular diameter distances, considering the redshift coverage of these two astrophysical probes.

  11. Quasars in galaxy cluster environments

    International Nuclear Information System (INIS)

    Ellingson, E.

    1989-01-01

    The evolution of radio loud quasars is found to be strongly dependent upon their galaxy cluster environment. Previous studies have shown that bright quasars are found in rich clusters, while high luminosity quasars are found only in poorer environments. The analysis of low luminosity radio quiet quasars indicate that they are never found in rich environments, suggesting that they are a physically different class of objects. Properties of the quasar environment are investigated to determine constraints on the physical mechanisms of quasar formation and evolution. The optical cluster morphology indicates that the cluster cores have smaller radii and higher galaxy densities than are typical for low redshift clusters of similar richness. Radio morphologies may indicate that the formation of a dense intra-cluster medium is associated with the quasars' fading at these epochs. Galaxy colors appear to be normal, but there may be a tendency for clusters associated with high luminosity quasars to contain a higher fraction of gas-rich galaxies than those associated with low luminosity quasars. Multislit spectroscopic observations of galaxies associated with high luminosity quasars indicate that quasars are preferentially located in regions of low relative velocity dispersion, either in rich clusters of abnormally low dispersion, or in poor groups which are dynamically normal. This suggests that galaxy-galaxy interactions may play a role in quasar formation and sustenanace. Virialization of rich clusters and the subsequent increase in galaxy velocities may therefore be responsible for the fading of quasars in rich environments

  12. Superconducting cosmic string evolution of quasars

    International Nuclear Information System (INIS)

    Liu Yulin.

    1988-09-01

    The quasars may have been undergoing two evolutionary processes after they formed. As a result of the string loops shrinking at the first stage, the luminosities of the quasars increased gradually up to their maximum value at the redshift z ∼ 2, after then the second evolutionary stage began and the luminosity reduced. This result can be fitted by luminosity counting of quasars. Observable limit of quasars can be obtained naturally. Many phenomena, such as radiomorphology, density distribution between fuzz structure and broad line region and rotational curve may also originate from the first evolutionary stage of quasars as cosmic string. (author). 10 refs

  13. Quasars: Cosmological evolution and x-ray background contribution

    International Nuclear Information System (INIS)

    Schmidt, M.; Green, R.F.

    1986-01-01

    The luminosity function of quasars varies with redshift or cosmic epoch. The authors discuss how the luminosity function and its evolution can be determined from complete samples of quasars. They first concentrate on optical survey of quasars. For quasars of medium luminosity, the co-moving space density rises very steeply with redshift. Quasars of lower luminosity exhibit a slower increase of density with redshift, resulting in luminosity-dependent evolution of the space density. They also discuss evidence for a cutoff of quasar redshift and for a possible dependence of the cutoff on luminosity. They evaluate X-ray counts of quasars and show the need for negative X-ray luminosity evolution in order to explain the counts and the low average redshifts of X-ray quasars. As a consequence, the quasar contribution to the X-ray background is lower than originally suspected. They discuss other extragalactic contributors to the X-ray background and conclude that they, together with the quasars, contribute about 60 percent of the observed background. About half of this is contributed by active galactic nuclei with optical luminosities below those of quasars

  14. QUASAR CLUSTERING FROM SDSS DR5: DEPENDENCES ON PHYSICAL PROPERTIES

    International Nuclear Information System (INIS)

    Shen Yue; Strauss, Michael A.; Lin, Yen-Ting; Bahcall, Neta A.; Ross, Nicholas P.; Schneider, Donald P.; Vanden Berk, Daniel E.; Hall, Patrick B.; Richards, Gordon T.; Weinberg, David H.; Shankar, Francesco; Connolly, Andrew J.; Fan Xiaohui; Hennawi, Joseph F.; Brunner, Robert J.

    2009-01-01

    Using a homogenous sample of 38,208 quasars with a sky coverage of ∼4000 deg. 2 drawn from the Sloan Digital Sky Survey Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole (BH) mass, quasar color, and radio loudness. At z 13 h -1 M sun , compared to ∼2 x 10 12 h -1 M sun for radio-quiet quasar hosts at z ∼ 1.5.

  15. The statistics of radio emission from quasars

    International Nuclear Information System (INIS)

    Peacock, J.A.; Miller, L.; Longair, M.S.; Edinburgh Univ.

    1986-01-01

    The radio properties of quasars have traditionally been discussed in terms of the radio-to-optical flux-density ratio R, implying a correlation between emission in these wavebands. It is here shown that, for bright quasars, this apparent correlation is largely due to an abrupt change in the radio properties of the quasar population near absolute magnitude Msub(B)=-24. It is suggested that this change in due to the existence of two classes of quasar with differing host galaxies: a proportion of quasars brighter than Msub(B)approx.=-24 lie in elliptical galaxies and thus generate powerful radio sources, while elliptical galaxies with weaker nuclear quasar components are classified as N-galaxies rather than quasars; quasars fainter than Msub(B)approx.=-24 lie in spiral galaxies and thus are high-luminosity analogues of radio-quiet Seyfert galaxies. (author)

  16. A main sequence for quasars

    Science.gov (United States)

    Marziani, Paola; Dultzin, Deborah; Sulentic, Jack W.; Del Olmo, Ascensión; Negrete, C. A.; Martínez-Aldama, Mary L.; D'Onofrio, Mauro; Bon, Edi; Bon, Natasa; Stirpe, Giovanna M.

    2018-03-01

    The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called “main sequence” associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.

  17. A Main Sequence for Quasars

    Directory of Open Access Journals (Sweden)

    Paola Marziani

    2018-03-01

    Full Text Available The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called “main sequence” associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.

  18. Are quasars local

    International Nuclear Information System (INIS)

    Terrell, J.

    1974-01-01

    The problems of interpreting quasars as galaxies, at distances of billions of light-years, seem to be increasing with time and with observational knowledge. The incredibly large energy and brightness requirements, the very small size and thus high surface brightness required by their rapid fluctuations in luminosity, the recently-discovered radio-source separation speeds apparently much greater than the speed of light, their general lack of association with distant galaxies, and many other properties are all very difficult to explain on the basis of cosmological distance. The very local quasar model, involving much less massive and bright objects--perhaps similar to Type O stars--emitted at relativistic speeds by the center of our own galaxy, greatly eases these difficulties. Since such ejected objects also seem necessary to explain the similarly strange properties of radio galaxies, the emission of local quasars from some galaxies might be deduced on this basis alone. (6 figures) (U.S.)

  19. GALACTIC-SCALE ABSORPTION OUTFLOW IN THE LOW-LUMINOSITY QUASAR IRAS F04250-5718: HUBBLE SPACE TELESCOPE/COSMIC ORIGINS SPECTROGRAPH OBSERVATIONS

    International Nuclear Information System (INIS)

    Edmonds, Doug; Borguet, Benoit; Arav, Nahum; Dunn, Jay P.; Penton, Steve; Kriss, Gerard A.; Korista, Kirk; Bautista, Manuel; Costantini, Elisa; Kaastra, Jelle; Steenbrugge, Katrien; Ignacio Gonzalez-Serrano, J.; Benn, Chris; Aoki, Kentaro; Behar, Ehud; Micheal Crenshaw, D.; Everett, John; Gabel, Jack; Moe, Maxwell; Scott, Jennifer

    2011-01-01

    We present absorption line analysis of the outflow in the quasar IRAS F04250-5718. Far-ultraviolet data from the Cosmic Origins Spectrograph on board the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e.g., C IV, N V, and O VI) as well as low ionization ions (e.g., C II and Si III). We identify three kinematic components with central velocities ranging from ∼-50 to ∼-230 km s -1 . Velocity-dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is ∼ -3 . Photoionization analysis yields an ionization parameter log U H ∼ -1.6 ± 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is ∼>3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.

  20. THE PROPERTIES OF QUASAR HOSTS AT THE PEAK OF THE QUASAR ACTIVITY

    International Nuclear Information System (INIS)

    Kotilainen, Jari K.; Falomo, Renato; Decarli, Roberto; Treves, Aldo; Uslenghi, Michela; Scarpa, Riccardo

    2009-01-01

    We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of 16 low luminosity radio-quiet quasars (RQQs) at the epoch around the peak of the quasar activity (2 2. The luminosity trend with a cosmic epoch resembles that observed for massive inactive galaxies, suggesting a similar star formation history. In particular, both quasar host galaxies and massive inactive galaxies appear mostly assembled already at the peak age of the quasar activity. This result is of key importance for testing the models of joint formation and evolution of galaxies and their active nuclei.

  1. X-ray, optical, and radio properties of quasars

    International Nuclear Information System (INIS)

    Blumenthal, G.R.; Keel, W.C.; Miller, J.S.

    1982-01-01

    We have examined a sample of 26 low-redshift quasars for the relationships between X-ray luminosity and optical spectroscopic features. All quasars were observed with the Einstein Observatory and with the IDS on the Lick 3 meter telescope. We find evidence for correlations between quasar X-ray luminosity and both optical continuum luminosity and Hβ luminosity. In the latter case, there is a smooth relationship connecting quasars, Seyfert 1, and Seyfert 2 galaxies. For the quasars in this sample, there is also a strong correlation between optical continuum luminosity and both the Hβ luminosity and equivalent width. Unlike the case for Seyfert 1 nuclei, there is no evidence for a correlation between X-ray luminosity and either the Hβ/[O III] ratio or the width at zero intensity of the Hβ line. However, we do find some evidence for a weak correlation between α'/sub o/x, the mean continuum spectral index between 5000 A and 2 keV, and Fe II equivalent width, Hβ equivalent width, Hβ line width at zero intensity, and the ratio of Hβ equivalent width to its line width at zero intensity. Overall, we found few strong correlations between optical spectroscopic quanitites and X-ray properties of quasars. Some of the implications of these results for models of quasars and quasar emission line regions are discussed

  2. Quasars as Cosmological Standard Candles

    International Nuclear Information System (INIS)

    Negrete, C. Alenka; Dultzin, Deborah; Marziani, Paola; Sulentic, Jack W.; Esparza-Arredondo, Donají; Martínez-Aldama, Mary L.; Del Olmo, Ascensión

    2017-01-01

    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.

  3. Quasars as Cosmological Standard Candles

    Energy Technology Data Exchange (ETDEWEB)

    Negrete, C. Alenka [CONACYT Research Fellow - Instituto de Astronomía, UNAM, Mexico City (Mexico); Dultzin, Deborah [Instituto de Astronomía, UNAM, Mexico City (Mexico); Marziani, Paola [INAF, Osservatorio Astronomico di Padova, Padua (Italy); Sulentic, Jack W. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada (Spain); Esparza-Arredondo, Donají [Instituto de Radioastronomía y Astrofísica, Morelia (Mexico); Martínez-Aldama, Mary L.; Del Olmo, Ascensión, E-mail: alenka@astro.unam.mx [Instituto de Astrofísica de Andalucía, IAA-CSIC, Granada (Spain)

    2017-12-15

    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.

  4. Radio-continuum emission from quasar host galaxies

    International Nuclear Information System (INIS)

    Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)

    1987-01-01

    Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references

  5. Mass and environment as drivers of galaxy evolution. III. The constancy of the faint-end slope and the merging of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Ying-jie; Lilly, Simon J.; Carollo, Marcella [Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland); Renzini, Alvio [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2014-08-01

    Using our continuity approach, we explore the underlying connections between the evolution of the faint-end slope α{sub s} of the stellar mass function of star-forming galaxies, the logarithmic slope β of the specific star formation rate (sSFR)-mass relation, and the merging of galaxies. We derive analytically the consequences of the observed constancy of α{sub s} since redshifts of at least z ∼ 2. If the logarithmic slope β of the sSFR-mass relation is negative, then the faint-end slope α{sub s} should quickly diverge due to the differential mass increase of galaxies on the star-forming main sequence, and this will also quickly destroy the Schechter form of the mass function. This problem can be solved by removing low-mass galaxies by merging them into more massive galaxies. We quantify this process by introducing the specific merger mass rate (sMMR) as the specific rate of mass added to a given galaxy through mergers. For a modest negative value of β ∼ –0.1, an average sMMR ∼ 0.1 sSFR across the population is required to keep α{sub s} constant with epoch, as observed. This in turn implies a merger rate of ∼0.2 sSFR for major mergers, which is consistent with the available observational estimates. More negative values of β require higher sMMR and higher merger rates, and the steepening of the mass function becomes impossible to control for β < –(α{sub s} + 2). The close link that is required between the in situ sSFR and the sMMR probably arises because both are closely linked to the buildup of dark matter halos. These new findings further develop the formalism for the evolving galaxy population that we introduced earlier and show how striking symmetries in the galaxy population can emerge as the result of deep links between the physical processes involved.

  6. Discovery of a bright quasar without a massive host galaxy.

    Science.gov (United States)

    Magain, Pierre; Letawe, Géraldine; Courbin, Frédéric; Jablonka, Pascale; Jahnke, Knud; Meylan, Georges; Wisotzki, Lutz

    2005-09-15

    A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy. Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars. Since then, the connection between quasars and galaxies has been well established. Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole.

  7. First observation of a quasar with a redshift of 4

    International Nuclear Information System (INIS)

    Warren, S.J.; Hewett, P.C.; Irwin, M.J.; McMahon, R.G.; Bridgeland, M.T.; Bunclark, P.S.; Kibblewhite, E.J.

    1987-01-01

    The authors report the discovery of a quasar (0046-293) with a redshift z = 4.01 and another (0044-276) with a redshift z 3.42. The redshift of the former quasar is the highest yet detected and compares with the z = 3.80 of the previous most distant known quasar. The new quasars lie in the same field as three other known high-redshift quasars and were identified in a preliminary analysis of new multi-colour data derived from measurements of direct photographic plates taken with the United Kingdom Schmidt Telescope. The two new quasars are significantly fainter (msub(R) > 19) than previously known high-redshift quasars discovered by optical techniques, and demonstrate that the luminosity function of optically selected high-redshift quasars extends over at least two magnitudes. (author)

  8. RADIO-SELECTED QUASARS IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Helfand, David J.; White, Richard L.

    2009-01-01

    We have conducted a pilot survey for z > 3.5 quasars by combining the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves the discovery rate by using strict astrometric criteria for matching the radio and optical positions. Our method allows for selection of high-redshift quasars with less color bias than with optical selection, as using radio selection essentially eliminates stellar contamination. We report the results of spectroscopy for 45 candidates, including 29 quasars in the range 0.37 3.5. We compare quasars selected using radio and optical criteria, and find that radio-selected quasars have a much higher fraction of moderately reddened objects. We derive a radio-loud quasar luminosity function at 3.5 < z < 4.0, and find that it is in good agreement with expectations from prior SDSS results.

  9. High-redshift quasars in the Cold Dark Matter cosmogony

    International Nuclear Information System (INIS)

    Efstathiou, G.; Rees, M.J.

    1988-01-01

    The relationship between high-redshift quasars and the epoch of galaxy formation in the Cold Dark Matter (CDM) cosmogony is investigated. Luminous quasars could only form after galactic sized systems had collapsed. A constant comoving density of luminous quasars between z = 2 and z = 4 is compatible with the CDM model if quasars are short-lived and radiate at about the Eddington limit. However, according to the CDM model the abundance of high-luminosity quasars must decline exponentially at higher redshifts. Even if all protogalaxies form quasars, and about 1 per cent of the baryons within a protogalaxy collapse into a compact object, a steep fall in the density of quasars with L > 10 47 erg s -1 at redshifts z ≥ 5. The existence of a 'cut-off' in the quasar numbers at high redshift could therefore supply an important test of the CDM theory. (author)

  10. Galaxy luminosity function: evolution at high redshift

    Science.gov (United States)

    Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

    2014-12-01

    There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4luminosity functions (GLFs) based on photometric redshifts for 30 clusters in B, V, R and I restframe bands. We show that completeness is a key parameter to understand the different observed behaviors when fitting the GLFs. We also investigate the evolution of GLFs with redshift for red and blue galaxy populations separately. We find a drop of the faint end of red GLFs which is more important at higher redshift while the blue GLF faint end remains flat in our redshift range. These results can be interpreted in terms of galaxy quenching. Faint blue galaxies transform into red ones which enrich the red sequence from high to low redshifts in clusters while some blue galaxies are still accreted from the environment, compensating for this evolution so that the global GLF does not seem to evolve.

  11. The WISSH quasars project. II. Giant star nurseries in hyper-luminous quasars

    Science.gov (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.

    2017-08-01

    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 code to account for the contribution of the quasar-related emission to the far-IR fluxes. Results: Most SEDs are well described by a 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

  12. Moderate resolution spectrophotometry of high redshift quasars

    Science.gov (United States)

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

    1991-01-01

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

  13. Space Density of Optically Selected Type 2 Quasars

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

    2008-12-01

    Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [O III]5007 luminosity function (LF) for 108.3 L sun < L [O III] < 1010 L sun (corresponding to intrinsic luminosities up to M[2500 Å] ~= -28 mag or bolometric luminosities up to 4 × 1047 erg s-1). This LF provides robust lower limits to the actual space density of obscured quasars due to our selection criteria, the details of the spectroscopic target selection, and other effects. We derive the equivalent LF for the complete sample of type 1 (unobscured) quasars and determine the ratio of type 2 to type 1 quasar number densities. Our data constrain this ratio to be at least ~1.5:1 for 108.3 L sun < L [O III] < 109.5 L sun at z < 0.3, and at least ~1.2:1 for L [O III] ~ 1010 L sun at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby universe (z <~ 0.8) for the highest luminosities.

  14. Quasar energy distributions. I. Soft X-ray spectra of quasars

    International Nuclear Information System (INIS)

    Wilkes, B.J.; Elvis, M.

    1987-01-01

    As the initial stage of a study of quasar energy distributions (QEDs), Einstein IPC spectra of 24 quasars are presented. These are combined with previously reported IPC spectra to form a sample of 33 quasars with well-determined soft X-ray slopes. A correlation analysis shows that radio loudness, rather than redshift or luminosity, is fundamentally related to the X-ray slope. This correlation is not followed by higher energy spectra of active galaxies. Two components are required to explain both sets of results. The best-fit column densities are systematically smaller than the Galactic values. The same effect is not present in a sample of BL Lac objects, implying that the effect is intrinsic to the quasars and is caused by a low-energy turnup in the quasar spectra. 74 references

  15. The kinetically dominated quasar 3C 418

    Science.gov (United States)

    Punsly, Brian; Kharb, Preeti

    2017-06-01

    The existence of quasars that are kinetically dominated, where the jet kinetic luminosity, Q, is larger than the total (infrared to X-ray) thermal luminosity of the accretion flow, Lbol, provides a strong constraint on the fundamental physics of relativistic jet formation. Since quasars have high values of Lbol by definition, only ˜10 kinetically dominated quasars (with \\overline{Q}/L_{bol}>1) have been found, where \\overline{Q} is the long-term time-averaged jet power. We use low-frequency (151 MHz-1.66 GHz) observations of the quasar 3C 418 to determine \\overline{Q}≈ 5.5 ± 1.3 × 10^{46} {erg s^{-1}}. Analysis of the rest-frame ultraviolet spectrum indicates that this equates to 0.57 ± 0.28 times the Eddington luminosity of the central supermassive black hole and \\overline{Q}/L_{bol} ≈ 4.8 ± 3.1, making 3C 418 one of the most kinetically dominated quasars found to date. It is shown that this maximal \\overline{Q}/L_{bol} is consistent with models of magnetically arrested accretion of jet production in which the jet production reproduces the observed trend of a decrement in the extreme ultraviolet continuum as the jet power increases. This maximal condition corresponds to an almost complete saturation of the inner accretion flow with vertical large-scale magnetic flux (maximum saturation).

  16. Far-infrared properties of optically selected quasars

    International Nuclear Information System (INIS)

    Edelson, R.A.

    1986-01-01

    The far-infrared properties of 10, optically selected quasars were studied on the basis of pointed IRAS observations and ground-based near-infrared and radio measurements. Nine of these quasars were detected in at least three IRAS bands. The flat spectral energy distributions characterizing these optically selected quasars together with large 60-100-micron luminosities suggest that the infrared emission is dominated by nonthermal radiation. Seven of the nine quasars with far-infrared detections were found to have low-frequency turnovers. 12 references

  17. Luminosity monitor

    International Nuclear Information System (INIS)

    Underwood, D. G.

    1998-01-01

    Luminosity monitors are needed in each experiment doing spin physics at RHIC. They concentrate on the luminosity aspects here because, for example, with a 10 -3 raw asymmetry in an experiment, an error of 10 -4 in the luminosity is as significant as a 10% polarization error. Because luminosity is a property of how two beams overlap, the luminosity at an interaction region must be measured at that interaction region in order to be relevant to the experiment at that interaction region. The authors will have to do the physics and the luminosity measurements by using labels on the event sums according to the polarization labels on the colliding bunches. Most likely they will not have independent polarization measurement on each bunch, but only on all the filled bunches in a ring, or perhaps all the bunches that are actually used in an experiment. Most analyses can then be handled by using the nine combinations gotten from three kinds of bunches in each ring, +, - and empty bunches. The empty bunches are needed to measure beam-gas background, (and some, like six in a row, are needed for the beam abort). Much of the difficulty comes from the fact that they must use a physics process to represent the luminosity. This process must have kinematic and geometric cuts both to reduce systematics such as beam-gas backgrounds, and to make it representative of the part of the interaction diamond from which the physics events come

  18. Companions of low-redshift radio-quiet quasars

    International Nuclear Information System (INIS)

    Yee, H.K.C.

    1987-01-01

    Using imaging data from a relatively complete subset of low-redshift radio-quiet quasars, the frequency of finding associated companion galaxies of the quasars is determined statistically. With an average completeness limit of M/sub r/ of about -19, it is found that about 40 percent of the quasars have at least one close physical companion within a projected distance of 100 kpc. The percentage of quasars with detected companions is consistent with all quasars in the sample having a companion of luminosity brighter than about -16.5 mag. It is estimated that the frequency of finding close companions to quasars is about six times higher than that expected for field galaxies. This frequency is similar to that found for lower-luminosity Seyfert galaxies. The properties of the companions appear to be uncorrelated with the level of activity in the quasars. This suggests that, for radio-quiet quasars, the companions act mainly as triggers of the activity and are probably not a strong determining factor of the detailed properties of the quasars. 28 references

  19. SPITZER OBSERVATIONS OF YOUNG RED QUASARS

    International Nuclear Information System (INIS)

    Urrutia, Tanya; Lacy, Mark; Spoon, Henrik; Glikman, Eilat; Petric, Andreea; Schulz, Bernhard

    2012-01-01

    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 Å emission line profile, suggesting that the quasar activity is driving thermal winds in at least some members of our sample.

  20. Overdensity of galaxies in the environment of quasar pairs

    Science.gov (United States)

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

    2018-03-01

    We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation 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.

  1. The luminosity function for different morphological types in the CfA Redshift Survey

    Science.gov (United States)

    Marzke, Ronald O.; Geller, Margaret J.; Huchra, John P.; Corwin, Harold G., Jr.

    1994-01-01

    We derive the luminosity function for different morphological types in the original CfA Redshift Survey (CfA1) and in the first two slices of the CfA Redshift Survey Extension (CfA2). CfA1 is a complete sample containing 2397 galaxies distributed over 2.7 steradians with m(sub z) less than or equal 14.5. The first two complete slices of CfA2 contain 1862 galaxies distributed over 0.42 steradians with m(sub z)=15.5. The shapes of the E-S0 and spiral luminosity functions (LF) are indistinguishable. We do not confirm the steeply decreasing faint end in the E-S0 luminosity function found by Loveday et al. for an independent sample in the southern hemisphere. We demonstrate that incomplete classification in deep redshift surveys can lead to underestimates of the faint end of the elliptical luminosity function and could be partially responsible for the difference between the CfA survey and other local field surveys. The faint end of the LF for the Magellanic spirals and irregulars is very steep. The Sm-Im luminosity function is well fit by a Schechter function with M*=-18.79, alpha=-1.87, and phi*=0.6x10(exp -3) for M(sub z) less than or equal to -13. These galaxies are largely responsible for the excess at the faint end of the general CfA luminosity function. The abundance of intrinsically faint, blue galaxies nearby affects the interpretation of deep number counts. The dwarf population increases the expected counts at B=25 in a no-evolution, q(sub 0)=0.05 model by a factor of two over standard no-evolution estimates. These dwarfs change the expected median redshift in deep redshift surveys by less than 10 percent . Thus the steep Sm-Im LF may contribute to the reconciliation of deep number counts with deep redshift surveys.

  2. THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS

    International Nuclear Information System (INIS)

    Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue

    2012-01-01

    We present an estimate of the projected two-point correlation function (2PCF) of quasars in the Sloan Digital Sky Survey (SDSS) over the full range of one- and two-halo scales, 0.02 h –1 Mpc p –1 Mpc. This was achieved by combining data from SDSS DR7 on large scales and Hennawi et al. (with appropriate statistical corrections) on small scales. Our combined clustering sample is the largest spectroscopic quasar clustering sample to date, containing ∼48, 000 quasars in the redshift range 0.4 ∼ sat = (7.4 ± 1.4) × 10 –4 , be satellites in dark matter halos. At z ∼ 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M cen = 4.1 +0.3 –0.4 × 10 12 h –1 M ☉ and M sat = 3.6 +0.8 –1.0 × 10 14 h –1 M ☉ , respectively. To investigate the redshift evolution of the quasar-halo relationship, we also perform HOD modeling of the projected 2PCF measured by Shen et al. for SDSS quasars with median redshift 3.2. We find tentative evidence for an increase in the mass scale of quasar host halos—the inferred median mass of halos hosting central quasars at z ∼ 3.2 is M cen = 14.1 +5.8 –6.9 × 10 12 h –1 M ☉ . The cutoff profiles of the mean occupation functions of central quasars reveal that quasar luminosity is more tightly correlated with halo mass at higher redshifts. The average quasar duty cycle around the median host halo mass is inferred to be f q = 7.3 +0.6 –1.5 × 10 –4 at z ∼ 1.4 and f q = 8.6 +20.4 –7.2 × 10 –2 at z ∼ 3.2. We discuss the implications of our results for quasar evolution and quasar-galaxy co-evolution.

  3. X-ray studies of quasars with the Einstein observatory. II

    International Nuclear Information System (INIS)

    Zamorani, G.; Henry, J.P.; Maccacaro, T.; Tananbaum, H.; Soltan, A.; Avni, Y.; Liebert, J.; Stocke, J.; Strittmatter, P.A.; Weymann, R.J.; Smith, M.G.; Condon, J.J.

    1981-01-01

    Using the Einstein Observatory, we have carried out X-ray observations of 107 quasars and have detected 79. From the analysis of this sample of objects we find a correlation between optical emission and X-ray emission. Our data for radio-loud quasars also show a correlation between radio emission and X-ray emission. For a given optical luminosity, the average X-ray emission of radio-loud quasars is approx.3 times higher than that of ratio-quiet quasars. In addition, our data suggest that the radio of X-ray to optical luminosity is decreasing with increasing redshift and/or optical luminosity. Taking into account the differences in X-ray luminosity between radio-loud and radio-quiet quasars, and between low-redshift and high-redshift quasars, we estimate that approx.30% of the observed X-ray background is contributed by quasars brighter than m/sub B/roughly-equal20, while much of the remainder can be contributed by still fainter quasars. Our data also imply that the optical log N--m/sub B/ relation for quasars cannot be extrapolated much beyond m/sub B/roughly-equal20 with the steep slope used to characterize optical source counts at brighter magnitudes. This situation supports the picture in which luminosity evolution, rather than pure density evolution, describes the quasar behavior as a function of redshift. We briefly discuss the observed correlation of X-ray luminosity with radio luminosity in the context of current quasar models

  4. Effect of undetected gravitational lenses on statistical measures of quasar evolution

    International Nuclear Information System (INIS)

    Turner, E.L.

    1980-01-01

    Brightness amplifications by undetected gravitational lenses could be responsible in part for the apparent evolution of quasars, particularly for those which appear to be of high luminosity. It is shown that values of Vover-bar/over-barVover-bar/sub M/> or =0.6 and number-magnitude slopes > or =0.9 need not necessarily imply source density evolution if lensing events are common. Quasar samples which are defined by flux limits and minimum luminosities will preferentially include gravitational lens systems. Even if lensing events are quite rare, a large fraction of the lensed quasars will appear more luminous than the most luminous unlensed quasar

  5. Quasars Probing Quasars: the Circumgalactic Medium Surrounding z ~ 2 Quasars

    Science.gov (United States)

    Lau, Marie; Quasars Probing Quasars survey

    2018-01-01

    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.

  6. Probing black hole accretion in quasar pairs at high redshift

    Science.gov (United States)

    Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

    2018-06-01

    Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here, we present the X-ray properties of two systems of dual quasars at z = 3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z = 5 (separation of 21 arcsec, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3 per cent probability that it is by chance.

  7. Probing black hole accretion in quasar pairs at high redshift

    Science.gov (United States)

    Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

    2018-03-01

    Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here we present the X-ray properties of two systems of dual quasars at z=3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z=5 (separation of 21″, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3% probability that it is by chance.

  8. A CONSTRAINT ON QUASAR CLUSTERING AT z = 5 FROM A BINARY QUASAR

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Fan, Xiaohui; Eftekharzadeh, Sarah; Myers, Adam D.

    2016-01-01

    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 0 ) −2 , this discovery implies a correlation length of r 0 ≳ 20h −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. A CONSTRAINT ON QUASAR CLUSTERING AT z = 5 FROM A BINARY QUASAR

    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: imcgreer@as.arizona.edu [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)

    2016-03-15

    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.

  10. Luminosity function of the brightest galaxies in the IRAS survey

    International Nuclear Information System (INIS)

    Soifer, B.T.; Sanders, D.B.; Madore, B.F.; Neugebauer, G.; Persson, C.J.; Persson, S.E.; Rice, W.L.

    1987-01-01

    Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume

  11. Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission

    Science.gov (United States)

    Richards, Gordon T.; Kratzer, R.

    2014-01-01

    We explore the evolution of the fraction of radio loud quasars and the mean radio properties of quasars. Although any quasar has only a ~10% chance of being radio loud and the average quasar has a radio luminosity of ~4x10^30 ergs/s/Hz, these properties are strong functions of not only luminosity, redshift, black hole mass, and accretion rate, but also the strength of the accretion disk wind (as characterized by CIV emission line properties). Quasars with higher optical luminosity and/or lower redshift have a higher than average probability of being radio loud, but their median radio luminosity (relative to optical) is much lower than average. We find that, while radio properties of quasars generally cannot be predicted from their optical properties, objects where one expects a strong radiation line driven wind (based on emission line features) have virtually no chance of being radio loud. The redder quasars are in the optical, the more radio flux (relative to optical) they have; this trend holds even for quasars that are not expected to be significantly dust reddened/extincted in the optical. Finally, we consider the radio properties of quasars in the framework of models which describe the radio loud extrema as being due to particularly high spin resulting from second generation mergers and in the context of star formation at lower levels of radio flux. This work was supported by NSF AAG grant 1108798.

  12. Quasars Probing Quasars. X. The Quasar Pair Spectral Database

    Science.gov (United States)

    Findlay, Joseph R.; Prochaska, J. Xavier; Hennawi, Joseph F.; Fumagalli, Michele; Myers, Adam D.; Bartle, Stephanie; Chehade, Ben; DiPompeo, Michael A.; Shanks, Tom; Lau, Marie Wingyee; Rubin, Kate H. R.

    2018-06-01

    The rare close projection of two quasars on the sky provides the opportunity to study the host galaxy environment of a foreground quasar in absorption against the continuum emission of a background quasar. For over a decade the “Quasars probing quasars” series has utilized this technique to further the understanding of galaxy formation and evolution in the presence of a quasar at z > 2, resolving scales as small as a galactic disk and from bound gas in the circumgalactic medium to the diffuse environs of intergalactic space. Presented here is the public release of the quasar pair spectral database utilized in these studies. In addition to projected pairs at z > 2, the database also includes quasar pair members at z useful for small-scale clustering studies. In total, the database catalogs 5627 distinct objects, with 4083 lying within 5‧ of at least one other source. A spectral library contains 3582 optical and near-infrared spectra for 3028 of the cataloged sources. As well as reporting on 54 newly discovered quasar pairs, we outline the key contributions made by this series over the last 10 years, summarize the imaging and spectroscopic data used for target selection, discuss the target selection methodologies, describe the database content, and explore some avenues for future work. Full documentation for the spectral database, including download instructions, is supplied at http://specdb.readthedocs.io/en/latest/.

  13. Quasars and galactic evolution

    CERN Document Server

    Woltjer, L

    1978-01-01

    The evolution of quasars is discussed. It is noted that substantial clustering may be present at faint magnitudes. The relationship between quasar evolution and galactic evolution is considered. (4 refs).

  14. Altered luminosity functions for relativistically beamed objects. II - Distribution of Lorentz factors and parent populations with complex luminosity functions

    International Nuclear Information System (INIS)

    Urry, C.M.; Padovani, P.

    1991-01-01

    In a previous paper, Urry and Shafer (1984) showed that the observed luminosity function (LF) of objects that have part or all of their emission relativistically beamed was a double power law, flat at the faint end and steep at the bright end, so that the ratio of beamed sources to parents was a strong function of luminosity. These calculations are extended here for more realistic LFs required for actual tests of a unified theory of AGN. The observed LF of the beam-dominated objects is generally flatter than the parent LF, so that the number density ratio is a strong function of luminosity and can easily be greater than unity at high luminosities, even for gradual low-luminosity cutoffs in the parent LF. Several characteristic break points can be identified depending on the details of the parent LF. The calculations can be used to test unified theories by predicting the observed LF for aligned objects from the LF of the proposed parent population. 6 refs

  15. DISSECTING THE QUASAR MAIN SEQUENCE: INSIGHT FROM HOST GALAXY PROPERTIES

    International Nuclear Information System (INIS)

    Sun, Jiayi; Shen, Yue

    2015-01-01

    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 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 * (hence, the BH mass via the M–σ * relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ * 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 * 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

  16. Space density of optically-selected type 2 quasars

    OpenAIRE

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon; Anderson, Scott; Schneider, Donald

    2008-01-01

    Type 2 quasars are luminous active galactic nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey (SDSS), selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is six times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [OIII]5008 luminosity function for...

  17. The Quasar Fraction in Low-Frequency Selected Complete Samples and Implications for Unified Schemes

    Science.gov (United States)

    Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

    2000-01-01

    Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines - the 'quasar fraction' - as a function of redshift and of radio and narrow emission line luminosity. We find that the quasar fraction is more strongly dependent upon luminosity (both narrow line and radio) than it is on redshift. Above a narrow [OII] emission line luminosity of log(base 10) (L(sub [OII])/W) approximately > 35 [or radio luminosity log(base 10) (L(sub 151)/ W/Hz.sr) approximately > 26.5], the quasar fraction is virtually independent of redshift and luminosity; this is consistent with a simple unified scheme with an obscuring torus with a half-opening angle theta(sub trans) approximately equal 53 deg. For objects with less luminous narrow lines, the quasar fraction is lower. We show that this is not due to the difficulty of detecting lower-luminosity broad emission lines in a less luminous, but otherwise similar, quasar population. We discuss evidence which supports at least two probable physical causes for the drop in quasar fraction at low luminosity: (i) a gradual decrease in theta(sub trans) and/or a gradual increase in the fraction of lightly-reddened (0 approximately quasar luminosity; and (ii) the emergence of a distinct second population of low luminosity radio sources which, like M8T, lack a well-fed quasar nucleus and may well lack a thick obscuring torus.

  18. IRAS bright galaxy sample. II. The sample and luminosity function

    International Nuclear Information System (INIS)

    Soifer, B.T.; Sanders, D.B.; Neugebauer, G.; Madore, B.F.; Danielson, G.E.; David Dunlap Observatory, Richmond Hill, Canada; Palomar Observatory; California Institute of Technology, Pasadena)

    1987-01-01

    A statistically complete sample of 324 of the brightest infrared galaxies discovered at 60 microns in the IRAS all-sky survey is described. The results show that far-infrared emission is a significant luminosity component in the local universe, representing 25 percent of the luminosity emitted by stars in the same volume. Above 10 to the 11th solar luminosities, the infrared luminous galaxies are the dominant population of objects in the universe, being as numerous as the Seyfert galaxies and more numerous than quasars at higher luminosities. The infrared luminosity appears to be independent of the optical luminosity of galaxies. Most infrared bright galaxies appear to require much of the interstellar matter to be contributing to the observed infrared luminosity. Approximately 60-80 percent of the far-infrared luminosity of the local universe can be attributed, directly or indirectly, to recent or ongoing star formation. 67 references

  19. What are quasars. 3. ed.

    International Nuclear Information System (INIS)

    Dautcourt, G.

    1982-01-01

    The subject is covered under the following headings: gigantic explosions in galaxies, the puzzle of far radio sources, all records are broken, the quasar light - a messenger from the far past, the radio mantle of quasars, where do spectral lines originate, mysterious absorption, restless quasars, quasars as infrared sources, what is the gist of the matter, was Einstein wrong, when is a quasar no quasar, quasars and cosmology, youthful escapades of a galaxy, and once again the red shift

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

    DEFF Research Database (Denmark)

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

    2014-01-01

    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...

  1. MEASURING THE LUMINOSITY AND VIRIAL BLACK HOLE MASS DEPENDENCE OF QUASAR–GALAXY CLUSTERING AT z ∼ 0.8

    International Nuclear Information System (INIS)

    Krolewski, Alex G.; Eisenstein, Daniel J.

    2015-01-01

    We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasars at 0.2–6.4 h −1 Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity

  2. MEASURING THE LUMINOSITY AND VIRIAL BLACK HOLE MASS DEPENDENCE OF QUASAR–GALAXY CLUSTERING AT z ∼ 0.8

    Energy Technology Data Exchange (ETDEWEB)

    Krolewski, Alex G.; Eisenstein, Daniel J., E-mail: akrolewski@college.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2015-04-10

    We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasars at 0.2–6.4 h{sup −1} Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity.

  3. Highly Accreting Quasars at High Redshift

    Directory of Open Access Journals (Sweden)

    Mary L. Martínez-Aldama

    2018-01-01

    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. Highly Accreting Quasars at High Redshift

    Science.gov (United States)

    Martínez-Aldama, Mary L.; Del Olmo, Ascensión; Marziani, Paola; Sulentic, Jack W.; Negrete, C. Alenka; Dultzin, Deborah; Perea, Jaime; D'Onofrio, Mauro

    2017-12-01

    We present preliminary results of a spectroscopic analysis for a sample of type 1 highly accreting quasars (LLedd>0.2) 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 AlIII, SiIII and CIII. 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.

  5. Quasars Probing Quasars: The Circumgalactic Medium Surrounding Z 2 Quasars

    Science.gov (United States)

    Lau, Marie Wingyee

    Models of galaxy formation make the most direct predictions on gas related processes. Specifically, a picture on how gas flows through dark matter halos and onto galaxies to fuel star formation. A major prediction is that massive halos, including those hosting the progenitors of massive elliptical galaxies, exhibit a higher fraction of hot gas with T 107 K. Another prediction is that some mechanism must be invoked to quench the supply of cool gas in massive systems. Under the current galaxy formation paradigm, every massive galaxy has undergone a quasar phase, making high-redshift quasars the progenitors of inactive supermassive black holes found in the center of nearly all galaxies. Moreover, quasars clustering implies Mhalo = 1012.5 Msun , making quasar-host galaxies the progenitors of present day, massive, red and dead galaxies. The Quasars Probing Quasars survey is well-suited to examine gas related processes in the context of massive galaxy formation, as well as quasar feedback. To date the survey has selected 700 closely projected quasar pairs. To study the circumgalactic medium, a sub-sample of pairs with projected separation within 300 kpc at the foreground quasar's redshift are selected. From the first to seventh paper in the Quasars Probing Quasars series, the statistical results had been limited to covering fractions, equivalent widths, and without precise redshift measurements of the foreground quasars. Signatures of quasar feedback in the cool circumgalactic medium had not been identified. Hence, a sub-sample of 14 pairs with echellette spectra are selected for more detailed analysis. It is found that the low and high ions roughly trace each other in velocity structure. The HI and low ion surface densities decline with projected distance. HI absorption is strong even beyond the virial radius. Unresolved Lyalpha emission in one case and NV detection in another case together imply that a fraction of transverse sightlines are illuminated. The ionization

  6. The Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Quasar Survey: Quasar Properties from Data Release Two and Three

    Science.gov (United States)

    Dong, X. Y.; Wu, Xue-Bing; Ai, Y. L.; Yang, J. Y.; Yang, Q.; Wang, F.; Zhang, Y. X.; Luo, A. L.; Xu, H.; Yuan, H. L.; Zhang, J. N.; Wang, M. X.; Wang, L. L.; Li, Y. B.; Zuo, F.; Hou, W.; Guo, Y. X.; Kong, X.; Chen, X. Y.; Wu, Y.; Yang, H. F.; Yang, M.

    2018-05-01

    This is the second installment for the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Quasar Survey, which includes quasars observed from 2013 September to 2015 June. There are 9024 confirmed quasars in DR2 and 10911 in DR3. After cross-match with the Sloan Digital Sky Survey (SDSS) quasar catalogs and NED, 12126 quasars are discovered independently. Among them, 2225 quasars were released by SDSS DR12 QSO catalog in 2014 after we finalized the survey candidates. 1801 sources were identified by SDSS DR14 as QSOs. The remaining 8100 quasars are considered as newly founded, and among them, 6887 quasars can be given reliable emission line measurements and the estimated black hole masses. Quasars found in LAMOST are mostly located at low-to-moderate redshifts, with a mean value of 1.5. The highest redshift observed in DR2 and DR3 is 5. We applied emission line measurements to Hα, Hβ, Mg II, and C IV. We deduced the monochromatic continuum luminosities using photometry data, and estimated the virial black hole masses for the newly discovered quasars. Results are compiled into a quasar catalog, which will be available online.

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i P1 dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z P1 magnitude of 19.4, a luminosity of 3.8 × 10 47 erg s –1 , and a black hole mass of 6.9 × 10 9 M ☉ . It is a broad absorption line quasar with a prominent Lyβ peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i P1 dropout quasars and could potentially find more than 10 z P1 dropout (z > 6.8) quasars.

  8. A search for changing look quasars in second epoch imaging

    Science.gov (United States)

    Findlay, Joseph; Myers, Adam; McGreer, Ian

    2018-01-01

    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.

  9. Cosmic Star Formation History and Evolution of the Galaxy UV Luminosity Function for z < 1

    Science.gov (United States)

    Zhang, Keming; Schiminovich, David

    2018-01-01

    We present the latest constraints on the evolution of the far-ultraviolet luminosity function of galaxies (1500 Å, UVLF hereafter) for 0 NSA, GAMA, VIPERS, and COSMOS photo-z. Our final sample consists of ~170000 galaxies, which represents the largest sample used in such studies. By integrating wide NSA and GAMA data and deep VIPERS and COSMOS photo-z data, we have been able to constrain both the bright end and the faint end of the luminosity function with high accuracy over the entire redshift range. We fit a Schechter function to our measurements of the UVLF, both to parameterize its evolution, and to integrate for SFR densities. From z~1 to z~0, the characteristic absolute magnitude of the UVLF increases linearly by ~1.5 magnitudes, while the faint end slope remains shallow (alpha < 1.5). However, the Schechter function fit exhibits an excess of galaxies at the bright end, which is accounted for by contributions from AGN. We also describe our methodology, which can be applied more generally to any combination of wide-shallow and deep-narrow surveys.

  10. Quasars and superclusters

    International Nuclear Information System (INIS)

    Osmer, P.S.

    1983-01-01

    The evidence for quasar superclusters is discussed, together with implications and survey techniques. The data base of clusters of pairs of quasars with similar redshifts, which is supportive of theories of gravitational lenses, indicates that quasar superclusters do exist. Surveys of large redshift quasars have shown that the quasars do not necessarily cluster. It is cautioned that randomness in an observational scheme, followed by assumptions of uniformity in analyses, will produce results that support a uniformity that may not exist. It is suggested that clusters observed in one survey should be sought in other direction using the same techniques. Continuing expanded surveys of large redshift quasars are recommended in order to form an all-sky distribution of the objects. 18 references

  11. V/V/sub m/ test for quasars: A new interpretation

    International Nuclear Information System (INIS)

    Hawkins, M.R.S.; Stewart, N.J.

    1981-01-01

    The V/V/sub m/ test is discussed, and it is suggested that if certain problem of misidentification are not taken into account, the expected value for without evolution is not 1/2 , but depends on the quasar luminosity function and is compatible with currently observed values of about 0.68. A complete sample of quasars is examined, and it appears that beyond a redshift of about 0.5, the evidence for evolution is not strong. Differences in the value of for steep and flat spectrum quasars can be simply explained as differences in luminosity function

  12. A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

    Science.gov (United States)

    Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

    2002-01-01

    Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe.

  13. FIRST-2MASS RED QUASARS: TRANSITIONAL OBJECTS EMERGING FROM THE DUST

    International Nuclear Information System (INIS)

    Glikman, Eilat; Urrutia, Tanya; Lacy, Mark; Djorgovski, S. George; Mahabal, Ashish; Myers, Adam D.; Ross, Nicholas P.; Petitjean, Patrick; Ge, Jian; Schneider, Donald P.; York, Donald G.

    2012-01-01

    We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey with the near-infrared Two Micron All Sky Survey catalog and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B – V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1 ∼< z ∼< 3, 0.1 ∼< E(B – V) ∼< 1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a 'normal' blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up ∼< 15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.

  14. Space Density Of Optically-Selected Type II Quasars From The SDSS

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, N. L.; Strauss, M. A.; Green, J.; Krolik, J. H.; Shen, Y.; Richards, G. T.

    2007-12-01

    Type II quasars are luminous Active Galactic Nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this poster, we present a catalog of 887 type II quasars with redshifts z<0.83 from the Sloan Digital Sky Survey (SDSS), selected based on their emission lines, and derive the 1/Vmax [OIII] 5007 luminosity function from this sample. Since some objects may not be included in the sample because they lack strong emission lines, the derived luminosity function is only a lower limit. We also derive the [OIII] 5007 luminosity function for a sample of type I (broad-line) quasars in the same redshift range. Taking [OIII] 5007 luminosity as a tracer of intrinsic luminosity in both type I and type II quasars, we obtain lower limits to the type II quasar fraction as a function of [OIII] 5007 luminosity, from L[OIII] = 108.3 to 1010 Lsun, which roughly correspond to bolometric luminosities of 1044 to 1046 erg/s.

  15. Discovery of a very Lyman-α-luminous quasar at z = 6.62.

    Science.gov (United States)

    Koptelova, Ekaterina; Hwang, Chorng-Yuan; Yu, Po-Chieh; Chen, Wen-Ping; Guo, Jhen-Kuei

    2017-02-02

    Distant luminous quasars provide important information on the growth of the first supermassive black holes, their host galaxies and the epoch of reionization. The identification of quasars is usually performed through detection of their Lyman-α line redshifted to 0.9 microns at z > 6.5. Here, we report the discovery of a very Lyman-α luminous quasar, PSO J006.1240 + 39.2219 at redshift z = 6.618, selected based on its red colour and multi-epoch detection of the Lyman-α emission in a single near-infrared band. The Lyman-α line luminosity of PSO J006.1240 + 39.2219 is unusually high and estimated to be 0.8 × 10 12 Solar luminosities (about 3% of the total quasar luminosity). The Lyman-α emission of PSO J006.1240 + 39.2219 shows fast variability on timescales of days in the quasar rest frame, which has never been detected in any of the known high-redshift quasars. The high luminosity of the Lyman-α line, its narrow width and fast variability resemble properties of local Narrow-Line Seyfert 1 galaxies which suggests that the quasar is likely at the active phase of the black hole growth accreting close or even beyond the Eddington limit.

  16. Statistics of gravitational lenses. III. Astrophysical consequences of quasar lensing

    International Nuclear Information System (INIS)

    Ostriker, J.P.; Vietri, M.

    1986-01-01

    The method of Schmidt and Green (1983) for calculating the luminosity function of quasars is combined with gravitational-lensing theory to compute expected properties of lensed systems. Multiple quasar images produced by galaxies are of order 0.001 of the observed quasars, with the numbers over the whole sky calculated to be (0.86, 120, 1600) to limiting B magnitudes of (16, 19, 22). The amount of false evolution is small except for an interesting subset of apparently bright, large-redshift objects for which minilensing by starlike objects may be important. Some of the BL Lac objects may be in this category, with the galaxy identified as the parent object really a foreground object within which stars have lensed a background optically violent variable quasar. 24 references

  17. DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

    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: yjkim@astro.snu.ac.kr, E-mail: mim@astro.snu.ac.kr [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)

    2015-11-10

    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.

  18. A Long-Term Space Astrophysics Research Program. The Evolution of the Quasar Continuum

    Science.gov (United States)

    Elvis, M.

    1998-01-01

    The grant "The Evolution of the Quasar Continuum" resulted in over 53 published referred papers and conference proceedings. The more significant of these papers are listed below, and abstracts are attached. The papers address a wide range of issues involving the evolution of quasars, their electromagnetic emissions, and their environment, from nearby low luminosity Seyfert galaxies to quasars at the highest redshifts. Primarily observational in content the work nonetheless included theoretical studies of quasar accretion disks that attempt to explain the observed time variability of quasars, and the overall 'demographics' of the quasar population. The work carried out under this grant has laid a strong foundation for ongoing and future research with AXAF, HST and other new facilities.

  19. X-ray spectra of PG quasars. I. The continuum from X-rays to infrared

    International Nuclear Information System (INIS)

    Elvis, M.; Green, R.F.; Bechtold, J.; Schmidt, M.; Neugebauer, G.; Kitt Peak National Observatory, Tucson, AZ; Steward Observatory, Tucson, AZ; Palomar Observatory, Pasadena, CA)

    1986-01-01

    Einstein IPC X-ray spectra for a sample of eight optically selected quasars from the Palomar Bright Quasar survey are presented. The quasars have a mean power law energy slope which in five individual cases is inconsistent with the value found in hard X-ray selection criterion rather than luminosity, redshift, or U-B color. New IUE and optical continuum spectra and infrared photometry are presented for these quasars. The data are combined into log vf(v) and log v distributions which support the decomposition of the overall quasar spectrum into a power law plus a superposed optical-UV big bump which may be due to an accretion disk. At least six of the quasars have vf(v)s which are roughly constant between their infrared and X-ray power laws, suggesting a strong link between the two regions. 104 references

  20. Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

    Science.gov (United States)

    Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

    2011-01-01

    We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

  1. DEEP ULTRAVIOLET LUMINOSITY FUNCTIONS AT THE INFALL REGION OF THE COMA CLUSTER

    International Nuclear Information System (INIS)

    Hammer, D. M.; Hornschemeier, A. E.; Jenkins, L.; Salim, S.; Smith, R.; Mobasher, B.; Miller, N.; Ferguson, H.

    2012-01-01

    We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M UV = –10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (α ≈ –1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of α ≈ –1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than α = –1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M UV ≈ –14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M * = 10 8 M ☉ . A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

  2. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander

    2013-01-01

    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...

  3. Radio structure in quasars

    International Nuclear Information System (INIS)

    Barthel, P.D.

    1984-01-01

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  4. Clustering of quasars in SDSS-IV eBOSS: study of potential systematics and bias determination

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, Pierre; Goff, Jean-Marc Le; Burtin, Etienne; Bourboux, Hélion du Mas des; Palanque-Delabrouille, Nathalie [IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Eftekharzadeh, Sarah; Myers, Adam [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); White, Martin [Lawrence Berkeley National Lab, 1 Cyclotron Rd, Berkeley CA 94720 (United States); Ross, Ashley J. [Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, OH 43210 (United States); Tinker, Jeremy [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, 10003 (United States); Tojeiro, Rita [School of Physics and Astronomy, North Haugh, St. Andrews KY16 9SS (United Kingdom); Bautista, Julian; Dawson, Kyle [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Brinkmann, Jonathan [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349 (United States); Comparat, Johan [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching (Germany); Kneib, Jean-Paul [Laboratoire d' Astrophysique, École Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); McGreer, Ian D. [Steward Observatory, University of Arizona, Tucson, AZ 85721–0065 (United States); Percival, Will J. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama building, PO1 3FX, Portsmouth (United Kingdom); Prada, Francisco, E-mail: jmlegoff@cea.fr [Instituto de Fìsica Teórica (IFT) UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); and others

    2017-07-01

    We study the first year of the eBOSS quasar sample in the redshift range 0.9< z <2.2 which includes 68,772 homogeneously selected quasars. We show that the main source of systematics in the evaluation of the correlation function arises from inhomogeneities in the quasar target selection, particularly related to the extinction and depth of the imaging data used for targeting. We propose a weighting scheme that mitigates these systematics. We measure the quasar correlation function and provide the most accurate measurement to date of the quasar bias in this redshift range, b {sub Q} = 2.45 ± 0.05 at z-bar =1.55, together with its evolution with redshift. We use this information to determine the minimum mass of the halo hosting the quasars and the characteristic halo mass, which we find to be both independent of redshift within statistical error. Using a recently-measured quasar-luminosity-function we also determine the quasar duty cycle. The size of this first year sample is insufficient to detect any luminosity dependence to quasar clustering and this issue should be further studied with the final ∼500,000 eBOSS quasar sample.

  5. Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission

    Energy Technology Data Exchange (ETDEWEB)

    Lyu, Jianwei; Rieke, G. H. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Shi, Yong, E-mail: jianwei@email.arizona.edu [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)

    2017-02-01

    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.

  6. First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey

    International Nuclear Information System (INIS)

    Wang, Feige; Yang, Jinyi; Wu, Xue-Bing; Yang, Qian; Li, Zefeng; Fan, Xiaohui; McGreer, Ian D.; Ding, Jiani; Green, Richard; Bian, Fuyan; Li, Jiang-Tao; Dey, Arjun; Dye, Simon; Findlay, Joseph R.; Myers, Adam D.; James, David; Jiang, Linhua; Lang, Dustin; Lawrence, Andy; Ross, Nicholas P.

    2017-01-01

    We present the first discoveries from a survey of z ≳ 6 quasars using imaging data from the DECam Legacy Survey (DECaLS) in the optical, the UKIRT Deep Infrared Sky Survey (UKIDSS) and a preliminary version of the UKIRT Hemisphere Survey (UHS) in the near-IR, and ALLWISE in the mid-IR. DECaLS will image 9000 deg 2 of sky down to z AB ∼ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching J VEGA ∼ 19.6 (5- σ ). The combination of these data sets allows us to discover quasars at redshift z ≳ 7 and to conduct a complete census of the faint quasar population at z ≳ 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z ≳ 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z ∼ 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 Å being M 1450 = −25.83 and M 1450 = −25.76, respectively. These discoveries suggest that we can find quasars close to or fainter than the break magnitude of the Quasar Luminosity Function (QLF) at z ≳ 6. The new z = 6.63 quasar has an absolute magnitude of M 1450 = −25.95. This demonstrates the potential of using the combined DECaLS and UKIDSS/UHS data sets to find z ≳ 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield ∼200 z ∼ 6 quasars to z AB < 21.5, ∼1000 z ∼ 6 quasars to z AB < 23, and ∼30 quasars at z > 6.5 to J VEGA < 19.5.

  7. Quasar X-Ray Spectra At z=1.5

    Science.gov (United States)

    Siemiginowska, Aneta

    2001-01-01

    The predicted counts for ASCA observation was much higher than actually observed counts in the quasar. However, there are three weak hard x-ray sources in the GIS field. We are adding them to the source counts in modeling of hard x-ray background. The work is in progress. We have published a paper in Ap.J. on the luminosity function and the quasar evolution. Based on the theory described in this paper we are predicting a number of sources and their contribution to the x-ray background at different redshifts. These model predictions will be compared to the observed data in the final paper.

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

    Energy Technology Data Exchange (ETDEWEB)

    Morganson, Eric; De Rosa, Gisella; Decarli, Roberto; Walter, Fabian; Rix, Hans-Walter [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Chambers, Ken; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Sweeney, Bill; Waters, Christopher [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); McGreer, Ian; Fan, Xiaohui [Steward Observatory, University of Arizona, 933 N Cherry Ave., Tucson, AZ 85721 (United States); Greiner, Jochen [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching (Germany); Price, Paul, E-mail: morganson@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-06-15

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i{sub P1} dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z{sub P1} magnitude of 19.4, a luminosity of 3.8 Multiplication-Sign 10{sup 47} erg s{sup -1}, and a black hole mass of 6.9 Multiplication-Sign 10{sup 9} M{sub Sun }. It is a broad absorption line quasar with a prominent Ly{beta} peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i{sub P1} dropout quasars and could potentially find more than 10 z{sub P1} dropout (z > 6.8) quasars.

  9. UV Luminosity Functions at z~4, 5, and 6 from the Hubble Ultra Deep Field and Other Deep Hubble Space Telescope ACS Fields: Evolution and Star Formation History

    Science.gov (United States)

    Bouwens, R. J.; Illingworth, G. D.; Franx, Marijn; Ford, Holland

    2007-12-01

    We use the ACS BViz data from the HUDF and all other deep HST ACS fields (including the GOODS fields) to find large samples of star-forming galaxies at z~4 and ~5 and to extend our previous z~6 sample. These samples contain 4671, 1416, and 627 B-, V-, and i-dropouts, respectively, and reach to extremely low luminosities [(0.01-0.04)L*z=3 or MUV~-16 to -17], allowing us to determine the rest-frame UV LF and faint-end slope α at z~4-6 to high accuracy. We find faint-end slopes α=-1.73+/-0.05, -1.66+/-0.09, and -1.74+/-0.16 at z~4, ~5, and ~6, respectively, suggesting that the faint-end slope is very steep and shows little evolution with cosmic time. We find that M*UV brightens considerably in the 0.7 Gyr from z~6 to ~4 (by ~0.7 mag from M*UV=-20.24+/-0.19 to -20.98+/-0.10). The observed increase in the characteristic luminosity over this range is almost identical to that expected for the halo mass function, suggesting that the observed evolution is likely due to the hierarchical coalescence and merging of galaxies. The evolution in φ* is not significant. The UV luminosity density at z~6 is modestly lower than (0.45+/-0.09 times) that at z~4 (integrated to -17.5 mag) although a larger change is seen in the dust-corrected SFR density. We thoroughly examine published LF results and assess the reasons for their wide dispersion. We argue that the results reported here are the most robust available. The extremely steep faint-end slopes α found here suggest that lower luminosity galaxies play a significant role in reionizing the universe. Finally, recent search results for galaxies at z~7-8 are used to extend our estimates of the evolution of M* from z~7-8 to z~4. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 9425, 9575, 9803, 9978, 10189, 10339, 10340, and 10632.

  10. Are quasars really far away

    International Nuclear Information System (INIS)

    Narlikar, J.V.

    1983-01-01

    Most astrophysicists think that quasars are distant objects. But new data, based on red-shift anomalies, and new theories embracing non-cosmological doppler effect and gravitational effects could account for the peculiarities of quasars. (U.K.)

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

    DEFF Research Database (Denmark)

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

    2007-01-01

    We present low-resolution ultraviolet spectra of 14 low redshift (z zz 1.4 Large Bright Quasar samples. By design, our objects sample luminosities in between these two surveys, and our four absorbed objects are consistent with the v ~ L^0.62 relation derived by Laor & Brandt (2002). Another quasar......, 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...... the spectra of the quasars PG1407+265, SDSSJ1136+0242, and PKS1004+13 for which several possible explanations have been entertained....

  12. Luminosity monitor at PEP

    International Nuclear Information System (INIS)

    Fox, J.D.; Franklin, M.E.B.

    1981-02-01

    The luminosity monitor system utilized by the MKII Detector and by the PEP operators is described. This system processes information from 56 photomultipliers and calculates independent luminosities for each of the 3 colliding bunches in PEP. Design considerations, measurement techniques, and sources of error in the luminosity measurement are discussed

  13. What makes red quasars red?. Observational evidence for dust extinction from line ratio analysis

    Science.gov (United States)

    Kim, Dohyeong; Im, Myungshin

    2018-02-01

    Red quasars are very red in the optical through near-infrared (NIR) wavelengths, which is possibly due to dust extinction in their host galaxies as expected in a scenario in which red quasars are an intermediate population between merger-driven star-forming galaxies and unobscured type 1 quasars. However, alternative mechanisms also exist to explain their red colors: (i) an intrinsically red continuum; (ii) an unusual high covering factor of the hot dust component, that is, CFHD = LHD/Lbol, where the LHD is the luminosity from the hot dust component and the Lbol is the bolometric luminosity; and (iii) a moderate viewing angle. In order to investigate why red quasars are red, we studied optical and NIR spectra of 20 red quasars at z 0.3 and 0.7, where the usage of the NIR spectra allowed us to look into red quasar properties in ways that are little affected by dust extinction. The Paschen to Balmer line ratios were derived for 13 red quasars and the values were found to be 10 times higher than unobscured type 1 quasars, suggesting a heavy dust extinction with AV > 2.5 mag. Furthermore, the Paschen to Balmer line ratios of red quasars are difficult to explain with plausible physical conditions without adopting the concept of the dust extinction. The CFHD of red quasars are similar to, or marginally higher than, those of unobscured type 1 quasars. The Eddington ratios, computed for 19 out of 20 red quasars, are higher than those of unobscured type 1 quasars (by factors of 3-5), and hence the moderate viewing angle scenario is disfavored. Consequently, these results strongly suggest the dust extinction that is connected to an enhanced nuclear activity as the origin of the red color of red quasars, which is consistent with the merger-driven quasar evolution scenario. Full Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A31

  14. A high signal-to-noise ratio composite quasar spectrum

    International Nuclear Information System (INIS)

    Francis, P.J.; Hewett, P.C.; Foltz, C.B.; Chaffee, F.H.; Weymann, R.J.

    1991-01-01

    A very high signal-to-noise ratio (S/N of about 400) composite spectrum of the rest-frame ultraviolet and optical region of high luminosity quasars is presented. The spectrum is derived from 718 individual spectra obtained as part of the Large Bright Quasar Survey. The moderate resolution, 4A or less, and high signal-to-noise ratio allow numerous weak emission features to be identified. Of particular note is the large equivalent-width of the Fe II emission in the rest-frame ultraviolet and the blue continuum slope of the composite. The primary aim of this paper is to provide a reference spectrum for use in line identifications, and a series of large-scale representations of the composite spectrum are shown. A measure of the standard deviation of the individual quasar spectra from the composite spectrum is also presented. 12 refs

  15. Emission Line Correlations as Diagnostics of Quasar Winds

    Science.gov (United States)

    Sheldon, Keziah; Richards, Gordon

    2018-01-01

    We investigate correlations between UV and optical emission line properties for a sample of z~0.5 SDSS (Sloan Digital Sky Survey) quasars that have recently been observed by HST. The sample is designed to be comparable in luminosity to the existing reverberation mapping (RM) sample, but less biased in terms of their "eigenvector 1" properties. We seek to understand the conditions under which high-ionization emission lines become dominated by a wind. Our analysis takes advantage of spectral decomposition through Independent Component Analysis (ICA) and archival UV HST spectroscopy of SDSS quasars. With these data we will clarify the needs for RM analysis of quasars with wind-dominated emission features.

  16. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    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)

    2012-11-01

    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.

  17. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    International Nuclear Information System (INIS)

    Baloković, M.; Smolčić, V.; Ivezić, Ž.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-01-01

    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.

  18. Quasar Absorption Studies

    Science.gov (United States)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  20. Outflow and hot dust emission in broad absorption line quasars

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-01

    We have investigated a sample of 2099 broad absorption line (BAL) quasars with z = 1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature and is refined by our new algorithm. Correlations of outflow velocity and strength with a hot dust indicator (β{sub NIR}) and other quasar physical parameters—such as an Eddington ratio, luminosity, and a UV continuum slope—are explored in order to figure out which parameters drive outflows. Here β{sub NIR} is the near-infrared continuum slope, which is a good indicator of the amount of hot dust emission relative to the accretion disk emission. We confirm previous findings that outflow properties moderately or weakly depend on the Eddington ratio, UV slope, and luminosity. For the first time, we report moderate and significant correlations of outflow strength and velocity with β{sub NIR} in BAL quasars. It is consistent with the behavior of blueshifted broad emission lines in non-BAL quasars. The statistical analysis and composite spectra study both reveal that outflow strength and velocity are more strongly correlated with β{sub NIR} than the Eddington ratio, luminosity, and UV slope. In particular, the composites show that the entire C IV absorption profile shifts blueward and broadens as β{sub NIR} increases, while the Eddington ratio and UV slope only affect the high and low velocity part of outflows, respectively. We discuss several potential processes and suggest that the dusty outflow scenario, i.e., that dust is intrinsic to outflows and may contribute to the outflow acceleration, is most likely.

  1. Quasar outflow energetics from broad absorption line variability

    Science.gov (United States)

    McGraw, S. M.; Shields, J. C.; Hamann, F. W.; Capellupo, D. M.; Herbst, H.

    2018-03-01

    Quasar outflows have long been recognized as potential contributors to the co-evolution between supermassive black holes (SMBHs) and their host galaxies. The role of outflows in active galactic nucleus (AGN) feedback processes can be better understood by placing observational constraints on wind locations and kinetic energies. We utilize broad absorption line (BAL) variability to investigate the properties of a sample of 71 BAL quasars with P V broad absorption. The presence of P V BALs indicates that other BALs like C IV are saturated, such that variability in those lines favours clouds crossing the line of sight. We use these constraints with measurements of BAL variability to estimate outflow locations and energetics. Our data set consists of multiple-epoch spectra from the Sloan Digital Sky Survey and MDM Observatory. We detect significant (4σ) BAL variations from 10 quasars in our sample over rest-frame time-scales between ≤0.2-3.8 yr. Our derived distances for the 10 variable outflows are nominally ≲ 1-10 pc from the SMBH using the transverse-motion scenario, and ≲ 100-1000 pc from the central source using ionization-change considerations. These distances, in combination with the estimated high outflow column densities (i.e. NH ≳ 1022 cm-2), yield outflow kinetic luminosities between ˜ 0.001 and 1 times the bolometric luminosity of the quasar, indicating that many absorber energies within our sample are viable for AGN feedback.

  2. The evolution of the intergalactic medium and the origin of the galaxy luminosity function

    Science.gov (United States)

    Valls-Gabaud, David; Blanchard, Alain; Mamon, Gary

    1993-01-01

    The coupling of the Press and Schechter prescription with the CDM scenario and the Hoyle-Rees-Ostriker cooling criterion leads to a galaxy formation scenario in which galaxies are overproduced by a large factor. Although star formation might be suppressed in the smaller halos, a large amount of energy per galactic mass is needed to account for the present number density of galaxies. The evolution of the intergalactic medium (IGM) provides a simple criterion to prevent galaxy formation without requiring feedback, since halos with small virial temperatures are not able to retain the infalling hot gas of the IGM. If the ionizing background has decreased since z is approximately 1 - 2, then this criterion explains the slope of the luminosity function at the faint end. In addition, this scenario predicts two populations of dwarf galaxies, well differentiated in age, gas content, stellar populations, and clustering properties, which can be identified with dE and dIm galaxies.

  3. The evolution of the cluster optical galaxy luminosity function between z = 0.4 and 0.9 in the DAFT/FADA survey

    Science.gov (United States)

    Martinet, Nicolas; Durret, Florence; Guennou, Loïc; Adami, Christophe; Biviano, Andrea; Ulmer, Melville P.; Clowe, Douglas; Halliday, Claire; Ilbert, Olivier; Márquez, Isabel; Schirmer, Mischa

    2015-03-01

    Context. There is some disagreement about the abundance of faint galaxies in high-redshift clusters, with contradictory results in the literature arising from studies of the optical galaxy luminosity function (GLF) for small cluster samples. Aims: We compute GLFs for one of the largest medium-to-high-redshift (0.4 ≤ z DAFT/FADA survey in the B,V,R, and I rest-frame bands. We used photometric redshifts computed from BVRIZJ images to constrain galaxy cluster membership. We carried out a detailed estimate of the completeness of our data. We distinguished the red-sequence and blue galaxies using a V - I versus I colour-magnitude diagram. We studied the evolution of these two populations with redshift. We fitted Schechter functions to our stacked GLFs to determine average cluster characteristics. Results: We find that the shapes of our GLFs are similar for the B,V,R, and I bands with a drop at the red GLF faint ends that is more pronounced at high redshift: αred ~ -0.5 at 0.40 ≤ z 0.1 at 0.65 ≤ z < 0.90. The blue GLFs have a steeper faint end (αblue ~ -1.6) than the red GLFs, which appears to be independent of redshift. For the full cluster sample, blue and red GLFs meet at MV = -20, MR = -20.5, and MI = -20.3. A study of how galaxy types evolve with redshift shows that late-type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour. Conclusions: Our results indicate that these clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today. This effect is consistent with the evolution of the faint-end slope of the red sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field

  4. Black hole feedback in the luminous quasar PDS 456

    DEFF Research Database (Denmark)

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

    2015-01-01

    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....

  5. Clusters of galaxies associated with quasars. I. 3C 206

    International Nuclear Information System (INIS)

    Ellingson, E.; Yee, H.K.C.; Green, R.F.; Kinman, T.D.

    1989-01-01

    Multislit spectroscopy and three-color CCD photometry of the galaxies in the cluster associated with the quasar 3C 206 (PKS 0837-12) at z = 0.198 are presented. This cluster is the richest environment of any low-redshift quasar observed in an Abell richness class 1 cluster. The cluster has a very flattened structure and a very concentrated core about the quasar. Most of the galaxies in this field have colors and luminosities consistent with normal galaxies at this redshift. The background-corrected blue fraction of galaxies is consistent with values for other rich clusters. The existence of several blue galaxies in the concentrated cluster core is an anomaly for a region of such high galaxy density, however, suggesting the absence of a substantial intracluster medium. This claim is supported by the Fanaroff-Riley (1974) class II morphology of the radio source. The velocity dispersion calculated from 11 spectroscopically confirmed cluster members is 500 + or - 110 km/s, which is slightly lower than the average for Abell class 1 clusters. A high frequency of interaction between the quasar host galaxy and cluster core members at low relative velocities, and a low intracluster gas pressure, may comprise a favorable environment for quasar activity. The properties of the cluster of galaxies associated with 3C 206 are consistent with this model. 59 refs

  6. The Sloan Digital Sky Survey Quasar Catalog: Fourteenth data release

    Science.gov (United States)

    Pâris, Isabelle; Petitjean, Patrick; Aubourg, Éric; Myers, Adam D.; Streblyanska, Alina; Lyke, Brad W.; Anderson, Scott F.; Armengaud, Éric; Bautista, Julian; Blanton, Michael R.; Blomqvist, Michael; Brinkmann, Jonathan; Brownstein, Joel R.; Brandt, William Nielsen; Burtin, Étienne; Dawson, Kyle; de la Torre, Sylvain; Georgakakis, Antonis; Gil-Marín, Héctor; Green, Paul J.; Hall, Patrick B.; Kneib, Jean-Paul; LaMassa, Stephanie M.; Le Goff, Jean-Marc; MacLeod, Chelsea; Mariappan, Vivek; McGreer, Ian D.; Merloni, Andrea; Noterdaeme, Pasquier; Palanque-Delabrouille, Nathalie; Percival, Will J.; Ross, Ashley J.; Rossi, Graziano; Schneider, Donald P.; Seo, Hee-Jong; Tojeiro, Rita; Weaver, Benjamin A.; Weijmans, Anne-Marie; Yèche, Christophe; Zarrouk, Pauline; Zhao, Gong-Bo

    2018-05-01

    We present the data release 14 Quasar catalog (DR14Q) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV). This catalog includes all SDSS-IV/eBOSS objects that were spectroscopically targeted as quasar candidates and that are confirmed as quasars via a new automated procedure combined with a partial visual inspection of spectra, have luminosities Mi [z = 2] < -20.5 (in a Λ CDM cosmology with H0 = 70 km s-1 Mpc-1, Ω M =0.3, and Ω Λ = 0.7), and either display at least one emission line with a full width at half maximum larger than 500 km s-1 or, if not, have interesting/complex absorption features. The catalog also includes previously spectroscopically-confirmed quasars from SDSS-I, II, and III. The catalog contains 526 356 quasars (144 046 are new discoveries since the beginning of SDSS-IV) detected over 9376 deg2 (2044 deg2 having new spectroscopic data available) with robust identification and redshift measured by a combination of principal component eigenspectra. The catalog is estimated to have about 0.5% contamination. Redshifts are provided for the Mg II emission line. The catalog identifies 21 877 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3610-10 140 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Science Archiver Server. http://www.sdss.org/dr14/algorithms/qso_catalog

  7. THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z ∼ 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN

    International Nuclear Information System (INIS)

    Schenker, Matthew A.; Ellis, Richard S.; Robertson, Brant E.; Schneider, Evan; Ono, Yoshiaki; Ouchi, Masami; Stark, Daniel P.; McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Curtis-Lake, Emma; Rogers, Alexander B.; Cirasuolo, Michele; Koekemoer, Anton; Charlot, Stephane; Furlanetto, Steven R.

    2013-01-01

    We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z ≅ 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe ∼0.65 (0.25) mag fainter in absolute UV magnitude, at z ∼ 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z ∼ 7 and 27 at z ∼ 8. Incorporating brighter archival and ground-based samples, we measure the z ≅ 7 UV luminosity function to an absolute magnitude limit of M UV = –17 and find a faint end Schechter slope of α=-1.87 +0.18 -0.17 . Using a similar color-color selection at z ≅ 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z ≅ 8, α=-1.94 +0.21 -0.24 . We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique.

  8. THE UV LUMINOSITY FUNCTION OF STAR-FORMING GALAXIES VIA DROPOUT SELECTION AT REDSHIFTS z {approx} 7 AND 8 FROM THE 2012 ULTRA DEEP FIELD CAMPAIGN

    Energy Technology Data Exchange (ETDEWEB)

    Schenker, Matthew A.; Ellis, Richard S. [Department of Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Robertson, Brant E.; Schneider, Evan [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Ono, Yoshiaki; Ouchi, Masami; Stark, Daniel P. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa City, Chiba 277-8582 (Japan); McLure, Ross J.; Dunlop, James S.; Bowler, Rebecca A. A.; Curtis-Lake, Emma; Rogers, Alexander B.; Cirasuolo, Michele [Institute for Astronomy, University of Edinburgh, Edinburgh EH9 3HJ (United Kingdom); Koekemoer, Anton [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Charlot, Stephane [UPMC-CNRS, UMR7095, Institut d' Astrophysique de Paris, F-75014 Paris (France); Furlanetto, Steven R., E-mail: schenker@astro.caltech.edu [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095 (United States)

    2013-05-10

    We present a catalog of high-redshift star-forming galaxies selected to lie within the redshift range z {approx_equal} 7-8 using the Ultra Deep Field 2012 (UDF12), the deepest near-infrared (near-IR) exposures yet taken with the Hubble Space Telescope (HST). As a result of the increased near-IR exposure time compared to previous HST imaging in this field, we probe {approx}0.65 (0.25) mag fainter in absolute UV magnitude, at z {approx} 7 (8), which increases confidence in a measurement of the faint end slope of the galaxy luminosity function. Through a 0.7 mag deeper limit in the key F105W filter that encompasses or lies just longward of the Lyman break, we also achieve a much-refined color-color selection that balances high redshift completeness and a low expected contamination fraction. We improve the number of dropout-selected UDF sources to 47 at z {approx} 7 and 27 at z {approx} 8. Incorporating brighter archival and ground-based samples, we measure the z {approx_equal} 7 UV luminosity function to an absolute magnitude limit of M{sub UV} = -17 and find a faint end Schechter slope of {alpha}=-1.87{sup +0.18}{sub -0.17}. Using a similar color-color selection at z {approx_equal} 8 that takes our newly added imaging in the F140W filter into account, and incorporating archival data from the HIPPIES and BoRG campaigns, we provide a robust estimate of the faint end slope at z {approx_equal} 8, {alpha}=-1.94{sup +0.21}{sub -0.24}. We briefly discuss our results in the context of earlier work and that derived using the same UDF12 data but with an independent photometric redshift technique.

  9. On the Role of the Environments and Star Formation for Quasar Activity

    International Nuclear Information System (INIS)

    Bettoni, Daniela; Falomo, Renato; Kotilainen, Jari K.; Karhunen, Kalle

    2017-01-01

    We investigate the host galaxy and environment properties of a sample of 400 low z (<0.5) quasars that were imaged in the SDSS Stripe82. We can detect and study the properties of the host galaxy for more than 75% of the data sample. We discover that quasar are mainly hosted in luminous galaxies of absolute magnitude M * − 3 < M(R) < M *1 and that in the quasar environments the galaxy number density is comparable to that of inactive galaxies of similar luminosities. For these quasars we undertake also a study in u,g,r,i, and z SDSS bands and again we discover that the mean colors of the quasar host galaxy it is not very different with respect to the values of the sample of inactive galaxies. For a subsample of low z sources the imaging study is complemented by spectroscopy of quasar hosts and of close companion galaxies. This study suggests that the supply and cause of the nuclear activity depends only weakly on the local environment of quasars. Contrary to past suggestions, for low redshift quasar there is a very modest connection between recent star formation and the nuclear activity.

  10. On the Role of the Environments and Star Formation for Quasar Activity

    Directory of Open Access Journals (Sweden)

    Daniela Bettoni

    2017-11-01

    Full Text Available We investigate the host galaxy and environment properties of a sample of 400 low z (<0.5 quasars that were imaged in the SDSS Stripe82. We can detect and study the properties of the host galaxy for more than 75% of the data sample. We discover that quasar are mainly hosted in luminous galaxies of absolute magnitude M* − 3 < M(R < M*1 and that in the quasar environments the galaxy number density is comparable to that of inactive galaxies of similar luminosities. For these quasars we undertake also a study in u,g,r,i, and z SDSS bands and again we discover that the mean colors of the quasar host galaxy it is not very different with respect to the values of the sample of inactive galaxies. For a subsample of low z sources the imaging study is complemented by spectroscopy of quasar hosts and of close companion galaxies. This study suggests that the supply and cause of the nuclear activity depends only weakly on the local environment of quasars. Contrary to past suggestions, for low redshift quasar there is a very modest connection between recent star formation and the nuclear activity.

  11. On the Role of the Environments and Star Formation for Quasar Activity

    Energy Technology Data Exchange (ETDEWEB)

    Bettoni, Daniela; Falomo, Renato [INAF - Osservatorio Astronomico di Padova, Padua (Italy); Kotilainen, Jari K. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Turku (Finland); Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Turku (Finland); Karhunen, Kalle, E-mail: daniela.bettoni@oapd.inaf.it [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Turku (Finland)

    2017-11-16

    We investigate the host galaxy and environment properties of a sample of 400 low z (<0.5) quasars that were imaged in the SDSS Stripe82. We can detect and study the properties of the host galaxy for more than 75% of the data sample. We discover that quasar are mainly hosted in luminous galaxies of absolute magnitude M{sup *} − 3 < M(R) < M{sup *1} and that in the quasar environments the galaxy number density is comparable to that of inactive galaxies of similar luminosities. For these quasars we undertake also a study in u,g,r,i, and z SDSS bands and again we discover that the mean colors of the quasar host galaxy it is not very different with respect to the values of the sample of inactive galaxies. For a subsample of low z sources the imaging study is complemented by spectroscopy of quasar hosts and of close companion galaxies. This study suggests that the supply and cause of the nuclear activity depends only weakly on the local environment of quasars. Contrary to past suggestions, for low redshift quasar there is a very modest connection between recent star formation and the nuclear activity.

  12. GNIRS-DQS: A Gemini Near Infrared Spectrograph Distant Quasar Survey

    Science.gov (United States)

    Matthews, Brandon; Shemmer, Ohad; Brotherton, Michael S.; Andruchow, Ileana; Boroson, Todd A.; Brandt, W. Niel; Cellone, Sergio; Ferrero, Gabriel; Gallagher, Sarah; Green, Richard F.; Hennawi, Joseph F.; Lira, Paulina; Myers, Adam D.; Plotkin, Richard; Richards, Gordon T.; Runnoe, Jessie; Schneider, Donald P.; Shen, Yue; Strauss, Michael A.; Willott, Chris J.; Wills, Beverley J.

    2018-06-01

    We describe an ongoing three-year Gemini survey, launched in 2017, that will obtain near-infrared spectroscopy of 416 Sloan Digital Sky Survey (SDSS) quasars between redshifts of 1.5 and 3.5 in the ~1.0-2.5 μm band. These spectra will cover critical diagnostic emission lines, such as Mg II, Hβ, and [O III], in each source. This project will more than double the existing inventory of near-infrared spectra of luminous quasars at these redshifts, including the era of fast quasar growth. Additional rest frame ultraviolet coverage of at least the C IV emission line is provided by the SDSS spectrum of each source. We will utilize the spectroscopic inventory to determine the most accurate and precise quasar black hole masses, accretion rates, and redshifts, and use the results to derive improved prescriptions for UV-based proxies for these parameters. The improved redshifts will establish velocities of quasar outflows that interact with the host galaxies, and will help constrain how imprecise distance estimates bias quasar clustering measurements. Furthermore, our measurements will facilitate a more complete understanding of how the rest-frame UV-optical spectral properties depend on redshift and luminosity, and test whether the physical properties of the quasar central engine evolve over cosmic time. We will make our data immediately available to the public, provide reduced spectra via a dedicated website, and produce a catalog of measurements and fundamental quasar properties.

  13. Evolution of optically selected quasars with z<2.2 and B<20

    International Nuclear Information System (INIS)

    Marshall, H.L.

    1985-01-01

    Several complete samples of optically selected quasars are combined to give details of the quasar luminosity function and its evolution for redshifts less than 2.2. Sufficient coverage of the Hubble diagram is obtained that luminosity-dependent density evolution models can be tested and compared against pure luminosity evolution models. Although luminosity-dependent evolution is indicated if the evolution function has an exponential form, the data are consistent with a power-law evolution model that is independent of luminosity. When the sample is split into halves by redshift, a better fit is obtained with a power-law evolution model than with an exponential model. Furthermore, the luminosity function is consistent with a power-law shape whose slope is independent of redshift. Pure luminosity evolution models wherein luminosities evolve as (1+z)/sup 3.5/ and the luminosity functioin is given by dN/dLproportionalL/sup -3.6/ are consistent with these results and fit the data very well. These results suggest that the same mass supply and energy generation mechanisms apply over several decades of optical luminosity and for z<2.2

  14. Optical spectral properties of active galactic nuclei and quasars

    International Nuclear Information System (INIS)

    Yee, H.K.C.

    1981-01-01

    Four separate investigations dealing with the properties of optical continuum and emission-lines of active galactic nuclei (AGN) and quasars are presented. Multichannel scans of 3CR radio galaxies are decomposed by using a two-component model-an elliptical galaxy and a power-law nonthermal component. It is found that there is a strong correlation between the luminosity of the power-law component and the strength of the Balmer emission-lines. In most cases, by extrapolating to the Lyman continuum, the power-law models derived provide enough ionizing radiation to account for the Balmer line strengths. Extending the study of radio galaxies to include Seyfert galaxies and quasars, it is found that there is a strong continuity between broad-line AGN's and quasars in terms of similarities in the correlations between line luminosities and nonthermal continuum luminosity. Next, a study of the variability of absolute optical energy distribution and emission-lines of the N-galaxies 3C382 and 3C390.3 is made. Lastly, a preliminary study of surface photometry of Markarian Seyfert galaxies are presented. It is found that the properties of the underlying galaxies such as scale-length and surface brightness of the disk, color, and total brightness, do not depart systematically from those of luminous normal spiral galaxies

  15. Imprints of quasar duty cycle on the 21cm signal from the Epoch of Reionization

    Science.gov (United States)

    Bolgar, Florian; Eames, Evan; Hottier, Clément; Semelin, Benoit

    2018-05-01

    Quasars contribute to the 21-cm signal from the Epoch of Reionization (EoR) primarily through their ionizing UV and X-ray emission. However, their radio continuum and Lyman-band emission also regulates the 21-cm signal in their direct environment, potentially leaving the imprint of their duty cycle. We develop a model for the radio and UV luminosity functions of quasars from the EoR, and constrain it using recent observations. Our model is consistent with the recent discovery of the quasar J1342+0928 at redshift ˜7.5, and also predicts only a few quasars suitable for 21-cm forest observations (˜10 mJy) in the sky. We exhibit a new effect on the 21-cm signal observed against the CMB: a radio-loud quasar can leave the imprint of its duty cycle on the 21-cm tomography. We apply this effect in a cosmological simulation and conclude that the effect of typical radio-loud quasars is most likely negligible in an SKA field of view. For a ˜10mJy quasar the effect is stronger though hardly observable at SKA resolution. Then we study the contribution of the lyman band (Ly-α to Ly-β) emission of quasars to the Wouthuisen-Field coupling. The collective effect of quasars on the 21-cm power spectrum is larger than the thermal noise at low k, though featureless. However, a distinctive pattern around the brightest quasars in an SKA field of view may be observable in the tomography, encoding the duration of their duty cycle. This pattern has a high signal-to-noise ratio for the brightest quasar in a typical SKA shallow survey.

  16. LHC Luminosity Performance

    CERN Document Server

    AUTHOR|(CDS)2091107; Fuchsberger, Kajetan; Papotti, Giulia

    This thesis adresses several approaches with the common goal of assessing, understanding and improving the luminosity of the Large Hadron Collider (LHC). To better exploit existing margins for maximum luminosity while fulfilling the requirements of the LHC experiments, new techniques for luminosity levelling are studied and developed to an operational state, such as changing the crossing angle or $\\beta^*$ (beam size) at the interaction points with the beams in collisions. In 2017 LHC operation, the crossing angle reduction in collisions improved the integrated luminosity by $\\mathrm{\\sim} 2\\,\\mathrm{fb^{-1}}$ ($\\mathrm{\\sim} 4\\,\\mathrm{\\%}$ of the yearly production). For additional diagnostics, a new method for measuring beam sizes and orbits for each circulating bunch using the luminosity measurement during beam separation scans is shown. The results of these Emittance Scans improved the understanding of the LHC luminosity reach and of the orbit offsets introduced by beam-beam long-range effects.

  17. THE JET POWER AND EMISSION-LINE CORRELATIONS OF RADIO-LOUD OPTICALLY SELECTED QUASARS

    International Nuclear Information System (INIS)

    Punsly, Brian; Zhang Shaohua

    2011-01-01

    In this Letter, the properties of the extended radio emission form Sloan Digital Sky Survey Data Release 7 quasars with 0.4 20-30 kpc). The frequency of quasars with FR II level extended radio emission is ∼2.3% and >0.4% of quasars have FR I level extended radio emission. The lower limit simply reflects the flux density limit of the survey. The distribution of the long-term time-averaged jet powers of these quasars, Q-bar , has a broad peak ∼3 x 10 44 erg s -1 that turns over below 10 44 erg s -1 and sources above 10 45 erg s -1 are extremely rare. It is found that the correlation between the bolometric (total thermal) luminosity of the accretion flow, L bol , and Q-bar is not strong. The correlation of Q-bar with narrow line luminosity is stronger than the correlation with broad line luminosity and the continuum luminosity. It is therefore concluded that previous interpretations of correlations of Q-bar with narrow line strengths in radio galaxies as a direct correlation of jet power and accretion power have been overstated. It is explained why this interpretation mistakenly overlooks the sizeable fraction of sources with weak accretion luminosity and powerful jets discovered by Ogle et al.

  18. UV-luminous, star-forming hosts of z ˜ 2 reddened quasars in the Dark Energy Survey

    Science.gov (United States)

    Wethers, C. F.; Banerji, M.; Hewett, P. C.; Lemon, C. A.; McMahon, R. G.; Reed, S. L.; Shen, Y.; Abdalla, F. B.; Benoit-Lévy, A.; Brooks, D.; Buckley-Geer, E.; Capozzi, D.; Carnero Rosell, A.; CarrascoKind, M.; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jeltema, T.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Miquel, R.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Walker, A. R.

    2018-04-01

    We present the first rest-frame UV population study of 17 heavily reddened, high-luminosity [E(B - V)QSO ≳ 0.5; Lbol > 1046 erg s-1] broad-line quasars at 1.5 VISTA Hemisphere Survey and UKIDSS Large Area Survey data, from which the reddened quasars were initially identified. We demonstrate that the significant dust reddening towards the quasar in our sample allows host galaxy emission to be detected at the rest-frame UV wavelengths probed by the DES photometry. By exploiting this reddening effect, we disentangle the quasar emission from that of the host galaxy via spectral energy distribution fitting. We find evidence for a relatively unobscured, star-forming host galaxy in at least 10 quasars, with a further three quasars exhibiting emission consistent with either star formation or scattered light. From the rest-frame UV emission, we derive instantaneous, dust-corrected star formation rates (SFRs) in the range 25 < SFRUV < 365 M⊙ yr-1, with an average SFRUV = 130 ± 95 M⊙ yr-1. We find a broad correlation between SFRUV and the bolometric quasar luminosity. Overall, our results show evidence for coeval star formation and black hole accretion occurring in luminous, reddened quasars at the peak epoch of galaxy formation.

  19. A very bright (i = 16.44) quasar in the 'redshift desert' discovered by the Guoshoujing Telescope (LAMOST)

    International Nuclear Information System (INIS)

    Wu Xuebing; Chen Zhaoyu; Jia Zhendong; Zuo Wenwen; Zhao Yongheng; Luo Ali; Bai Zhongrui; Chen Jianjun; Zhang Haotong; Yan Hongliang; Ren Juanjuan; Sun Shiwei; Wu Hong; Zhang Yong; Li Yeping; Lu Qishuai; Wang You; Ni Jijun; Wang Hai; Kong Xu

    2010-01-01

    The redshift range from 2.2 to 3 is known as the 'redshift desert' of quasars because quasars with redshifts in this range have similar optical colors as normal stars and are thus difficult to find in optical sky surveys. A quasar candidate, SDSS J085543.40-001517.7, which was selected by a recently proposed criterion involving near-IR Y - K and optical g - z colors, was identified spectroscopically as a new quasar with a redshift of 2.427 by the Guoshoujing Telescope (LAMOST) commissioning observation in 2009 December and confirmed by the observation made with the NAOC/Xinglong 2.16 m telescope in 2010 March. This quasar was not identified in the SDSS spectroscopic survey. Comparing with other SDSS quasars, we found that this new quasar, with an i magnitude of 16.44, is apparently the brightest one in the redshift range from 2.3 to 2.7. From its spectral properties, we derived its central black hole mass to be (1.4 ∼ 3.9) x 10 10 M o-dot and its bolometric luminosity to be 3.7 x 10 48 erg s -1 , which indicates that this new quasar is intrinsically very bright and belongs to the class of the most luminous quasars in the universe. Our identification supports the notion that quasars in the redshift desert can be found by the quasar selection criterion involving the near-IR colors. More missing quasars are expected to be uncovered by future LAMOST spectroscopic surveys, which is important to the study of the cosmological evolution of quasars at redshifts higher than 2.2. (research papers)

  20. Distribution in depth of quasars

    International Nuclear Information System (INIS)

    Schmidt, M.; Green, R.F.

    1980-01-01

    The authors discuss the distribution in depth of different kinds of quasars: quasi-stellar radio sources with steep radio spectrum, those with flat radio spectrum, and optically selected quasars. All exhibit an increase of space density with distance to a different degree. The optically selected quasars, in particular, show a steep increase of surface density with magnitude. The steepness of the increase is inconsistent with a uniform distribution of quasars in the local hypothesis. In the cosmological hypothesis the co-moving space density of optically selected quasars increases by a factor of 100,000 to a redshift of 2, and by factors of 1000 and 10 for steep-spectrum and flat-spectrum radio quasars, respectively. (Auth.)

  1. ARE THE VARIATIONS IN QUASAR OPTICAL FLUX DRIVEN BY THERMAL FLUCTUATIONS?

    International Nuclear Information System (INIS)

    Kelly, Brandon C.; Siemiginowska, Aneta; Bechtold, Jill

    2009-01-01

    We analyze a sample of optical light curves for 100 quasars, 70 of which have black hole mass estimates. Our sample is the largest and broadest used yet for modeling quasar variability. The sources in our sample have z 42 ∼ λ (5100 A) ∼ 46 , and 10 6 ∼ BH /M sun ∼ 10 . We model the light curves as a continuous time stochastic process, providing a natural means of estimating the characteristic timescale and amplitude of quasar variations. We employ a Bayesian approach to estimate the characteristic timescale and amplitude of flux variations; our approach is not affected by biases introduced from discrete sampling effects. We find that the characteristic timescales strongly correlate with black hole mass and luminosity, and are consistent with disk orbital or thermal timescales. In addition, the amplitude of short-timescale variations is significantly anticorrelated with black hole mass and luminosity. We interpret the optical flux fluctuations as resulting from thermal fluctuations that are driven by an underlying stochastic process, such as a turbulent magnetic field. In addition, the intranight variations in optical flux implied by our empirical model are ∼<0.02 mag, consistent with current microvariability observations of radio-quiet quasars. Our stochastic model is therefore able to unify both long- and short-timescale optical variations in radio-quiet quasars as resulting from the same underlying process, while radio-loud quasars have an additional variability component that operates on timescales ∼<1 day.

  2. Study of the optical and x-ray properties of quasars

    International Nuclear Information System (INIS)

    Bradley, S.E.

    1985-01-01

    It is now widely believed that photoionization by the central nucleus is primarily responsible for the emission lines observed in quasars. If this view is correct, x-ray wavelength photons from the nucleus could play a role in determining the emission line strengths of the various chemical species present in quasars. Indeed, recent photoionization models predict the enhancement of some emission lines arising from an extended ionized zone heated by soft x-rays. In an attempt to investigate this possibility, a sample of 17 quasars exhibiting a wide range of x-ray to optical luminosities has been observed spectrophotometrically in an effort to correlate their optical spectroscopic features with published x-ray and radio luminosities. Such correlations are known to exist for Seyfert galaxies, but at present it is unclear whether quasars also exhibit these correlations. All of the quasars in this sample have been previously observed with the Einstein Observatory. Strengths of the broad permitted emission lines as well as the narrow forbidden lines are analyzed for correlations with the x-ray strength and the optical strength; also, ratios of lines such as Hβ to [O III] and Fe II to Hβ are considered, as well as high excitation lines such as [Ne V]. Because of the difficulty in obtaining high signal-to-noise data for objects as faint as quasars, resolving this issue may well require many such studies as this one, each contributing a fraction of knowledge to the whole, before the question can adequately be answered

  3. AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-01

    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.

  4. AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?

    International Nuclear Information System (INIS)

    Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi; Yin, Jun

    2015-01-01

    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 ν12 (1000 ∼ 2000 Å) and α ν24 (2000 ∼ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher α ν ) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both α ν12 and α 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 ν − z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσ v ∼ 10 −5 h Mpc −1 at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed

  5. Compact features in radio galaxies and quasars

    International Nuclear Information System (INIS)

    Purvis, A.

    1981-05-01

    The structure of compact features ('hotspots') in the outer lobes of classical double radio sources over a large flux density interval at 81.5 MHz is investigated in order to understand more fully the structural evolution of radio sources with both luminosity and redshift. The technique of interplanetary scintillations is used. An account is given of the development of a new telescope, the 3.6-hectare Array. A method for eliminating zero level and phase drifts from interferometric records and a method for analysing data scattered according to a skewed probability distribution are described. New observations of hotspots in complete samples of bright 3CR sources and 4C quasars having an intermediate flux density are then presented. The problems of interpreting scintillation data are then considered and three methods are suggested to reduce the difficulties imposed by the observational limitation known as 'blending', whereby the whole outer lobe may scintillate and distort the measured hotspot size. Finally, all the new observational data are assimilated and this leads to models for (a) the dependence of source structure on luminosity and (b) for the dependence of observed hotspot size on both luminosity and redshift. (author)

  6. Paired quasars near NGC 2639: Evidence for quasars in superclusters

    International Nuclear Information System (INIS)

    Ford, H.; Ciardullo, R.; Harms, R.

    1983-01-01

    Arp found 10 quasars near a low-redshift galaxy 27' SSE of NGC 2639. Six of the quasars can be grouped into three redshift pairs which align across the anonymous galaxy. The large number of quasars and pairings could show an association with the low-redshift galaxy, or alternatively, might be due to superclusters seen along the line of sight. We tested the latter hypothesis by using deep, red-sensitive Lick 3 m prime focus plates to search for a supercluster associated with the z = 0.3 quasar pair. The plates show extended nebulosity associated with the quasar U10 (thetaapprox.7'', or 20 kpc at z = 0.3) and a richness class 1, Bautz-Morgan type III cluster 4' NW of U10. A spectrum of one the cluster's brightest galaxies gives z = 0.34, suggesting that the cluster and quasar are unassociated. We obtained spectra of eight of the quasars and find that (i) two of the quasars have very strong absorption shortward of Lyα, and (ii) two of Arp's redshifts (including one which Arp considered uncertain) are incorrect. Our redshifts break two of the redshift pairs, including the pair at z = 0.3. We use the redshift distribution of optically selected quasars to argue that the third pair has no statistical significance, and conclude that there is no basis for associating the quasars with the low-redshift anonymous galaxy. The disappearance of the redshift pairs vitiates the possibility of testing the paired-quasars-in-superclusters hypothesis in the NGC 2639 field

  7. SDSS J1254+0846: A BINARY QUASAR CAUGHT IN THE ACT OF MERGING

    International Nuclear Information System (INIS)

    Green, Paul J.; Cox, Thomas J.; Aldcroft, Thomas L.; Myers, Adam D.; Barkhouse, Wayne A.; Mulchaey, John S.; Bennert, Vardha N.

    2010-01-01

    We present the first luminous, spatially resolved binary quasar that clearly inhabits an ongoing galaxy merger. SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1 (SDSS J1254+0846 hereafter) are two luminous z = 0.44 radio-quiet quasars, with a radial velocity difference of just 215 km s -1 , separated on the sky by 21 kpc in a disturbed host galaxy merger showing obvious tidal tails. The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry. We present follow-up optical imaging which shows broad, symmetrical tidal arm features spanning some 75 kpc at the quasars' redshift. Previously, the triggering of two quasars during a merger had only been hypothesized but our observations provide strong evidence of such an event. SDSS J1254+0846, as a face-on, pre-coalescence merger hosting two luminous quasars separated by a few dozen kpc, provides a unique opportunity to probe quasar activity in an ongoing gas-rich merger. Numerical modeling suggests that the system consists of two massive disk galaxies prograde to their mutual orbit, caught during the first passage of an active merger. This demonstrates rapid black hole growth during the early stages of a merger between galaxies with pre-existing bulges. Neither of the two luminous nuclei show significant intrinsic absorption by gas or dust in our optical or X-ray observations, illustrating that not all merging quasars will be in an obscured, ultraluminous phase. We find that the Eddington ratio for the fainter component B is rather normal, while for the A component L/L Edd is quite (>3σ) high compared to quasars of similar luminosity and redshift, possibly evidence for strong merger-triggered accretion. More such mergers should be identifiable at higher redshifts using binary quasars as tracers.

  8. Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Rumbaugh, N.; Shen, Yue; Morganson, Eric; Liu, Xin; Banerji, M.; McMahon, R. G.; Abdalla, F. B.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Frieman, J.; García-Bellido, J.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Plazas, A. A.; Reil, K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sheldon, E.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Walker, A. R.; Wester, W.

    2018-02-20

    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.

  9. A DESCRIPTION OF QUASAR VARIABILITY MEASURED USING REPEATED SDSS AND POSS IMAGING

    International Nuclear Information System (INIS)

    MacLeod, Chelsea L.; Ivezić, Željko; Becker, Andrew C.; Anderson, Scott F.; Sesar, Branimir; De Vries, Wim; Kochanek, Christopher S.; Kelly, Brandon C.; Lupton, Robert H.; Hall, Patrick B.; Richards, Gordon T.; Schneider, Donald P.

    2012-01-01

    We provide a quantitative description and statistical interpretation of the optical continuum variability of quasars. The Sloan Digital Sky Survey (SDSS) has obtained repeated imaging in five UV-to-IR photometric bands for 33,881 spectroscopically confirmed quasars. About 10,000 quasars have an average of 60 observations in each band obtained over a decade along Stripe 82 (S82), whereas the remaining ∼25,000 have 2-3 observations due to scan overlaps. The observed time lags span the range from a day to almost 10 years, and constrain quasar variability at rest-frame time lags of up to 4 years, and at rest-frame wavelengths from 1000 Å to 6000 Å. We publicly release a user-friendly catalog of quasars from the SDSS Data Release 7 that have been observed at least twice in SDSS or once in both SDSS and the Palomar Observatory Sky Survey, and we use it to analyze the ensemble properties of quasar variability. Based on a damped random walk (DRW) model defined by a characteristic timescale and an asymptotic variability amplitude that scale with the luminosity, black hole mass, and rest wavelength for individual quasars calibrated in S82, we can fully explain the ensemble variability statistics of the non-S82 quasars such as the exponential distribution of large magnitude changes. All available data are consistent with the DRW model as a viable description of the optical continuum variability of quasars on timescales of ∼5-2000 days in the rest frame. We use these models to predict the incidence of quasar contamination in transient surveys such as those from the Palomar Transient Factory and Large Synoptic Survey Telescope.

  10. The QUASAR facility

    Science.gov (United States)

    Gates, David

    2013-10-01

    The QUAsi-Axisymmetric Research (QUASAR) stellarator is a new facility which can solve two critical problems for fusion, disruptions and steady-state, and which provides new insights into the role of magnetic symmetry in plasma confinement. If constructed it will be the only quasi-axisymmetric stellarator in the world. The innovative principle of quasi-axisymmetry (QA) will be used in QUASAR to study how ``tokamak-like'' systems can be made: 1) Disruption-free, 2) Steady-state with low recirculating power, while preserving or improving upon features of axisymmetric tokamaks, such as 1) Stable at high pressure simultaneous with 2) High confinement (similar to tokamaks), and 3) Scalable to a compact reactor Stellarator research is critical to fusion research in order to establish the physics basis for a magnetic confinement device that can operate efficiently in steady-state, without disruptions at reactor-relevant parameters. The two large stellarator experiments - LHD in Japan and W7-X under construction in Germany are pioneering facilities capable of developing 3D physics understanding at large scale and for very long pulses. The QUASAR design is unique in being QA and optimized for confinement, stability, and moderate aspect ratio (4.5). It projects to a reactor with a major radius of ~8 m similar to advanced tokamak concepts. It is striking that (a) the EU DEMO is a pulsed (~2.5 hour) tokamak with major R ~ 9 m and (b) the ITER physics scenarios do not presume steady-state behavior. Accordingly, QUASAR fills a critical gap in the world stellarator program. This work supported by DoE Contract No. DEAC02-76CH03073.

  11. Quasars and cosmology

    International Nuclear Information System (INIS)

    Fliche, H.-H.; Souriau, J.-M.

    1978-03-01

    On the basis of colorimetric data a composite spectrum of quasars is established from the visible to the Lyman's limit. Its agreement with the spectrum of the quasar 3C273, obtained directly, confirms the homogeneity of these objects. The compatibility of the following hypotheses: negligible evolution of quasars, Friedmann type model of the universe with cosmological constant, is studied by means of two tests: a non-correlation test adopted to the observation conditions and the construction of diagrams (absolute magnitude, volume) using the K-correction deduced from the composite spectrum. This procedure happens to give relatively well-defined values of the parameters; the central values of the density parameter, the reduced curvature and the reduced cosmological constant are: Ω 0 =0.053, k 0 =0.245, lambda-zero=1.19, which correspond to a big bang model, eternally expanding, spatially finite, in which Hubble's parameter H is presently increasing. This model responds well to different cosmological tests: density of matter, diameter of radio sources, age of the universe. Its characteristics suggest various cosmogonic mechanisms, espacially mass formation by growth of empty spherical bubbles [fr

  12. Luminosity measurement at AMY

    International Nuclear Information System (INIS)

    Kurihara, Y.

    1995-01-01

    A precise measurement of a luminosity is required by experiments with high statistics. The largest sources of a systematic error of a luminosity measurement are an alignment of the tube chambers which measure a polar angle of Bhabha events and a higher order correction for the Bhabha cross section calculation. We describe a resent study for these uncertainties and how to reduce the systematic errors from these sources. The total systematic error of the luminosity measurement of 1.8% can be reduced to 1.0% by this study. (author)

  13. In quest of axionic hairs in quasars

    Science.gov (United States)

    Banerjee, Indrani; Mandal, Bhaswati; SenGupta, Soumitra

    2018-03-01

    The presence of axionic field can provide plausible explanation to several long standing problems in physics such as dark matter and dark energy. The pseudo-scalar axion whose derivative corresponds to the Hodge dual of the Kalb-Ramond field strength in four dimensions plays crucial roles in explaining several astrophysical and cosmological observations. Therefore, the detection of axionic hairs/Kalb-Ramond field which appears as closed string excitations in the heterotic string spectrum may provide a profound insight to our understanding of the current universe. The current level of precision achieved in solar-system based tests employed to test general relativity, is not sufficient to detect the presence of axion. However, the near horizon regime of quasars where the curvature effects are maximum seems to be a natural laboratory to probe such additions to the matter sector. The continuum spectrum emitted from the accretion disk around quasars encapsulates the imprints of the background spacetime and hence acts as a storehouse of information regarding the nature of gravitational interaction in extreme situations. The surfeit of data available in the electromagnetic domain provides a further motivation to explore such systems. Using the optical data for eighty Palomar Green quasars we demonstrate that the theoretical estimates of optical luminosity explain the observations best when the axionic field is assumed to be absent. However, axion which violates the energy condition seems to be favored by observations which has several interesting consequences. Error estimators, including reduced χ2, Nash-Sutcliffe efficiency, index of agreement and modified versions of the last two are used to solidify our conclusion and the implications of our result are discussed.

  14. High redshift quasars and high metallicities

    Science.gov (United States)

    Ferland, Gary J.

    1997-01-01

    A large-scale code called Cloudy was designed to simulate non-equilibrium plasmas and predict their spectra. The goal was to apply it to studies of galactic and extragalactic emission line objects in order to reliably deduce abundances and luminosities. Quasars are of particular interest because they are the most luminous objects in the universe and the highest redshift objects that can be observed spectroscopically, and their emission lines can reveal the composition of the interstellar medium (ISM) of the universe when it was well under a billion years old. The lines are produced by warm (approximately 10(sup 4)K) gas with moderate to low density (n less than or equal to 10(sup 12) cm(sup -3)). Cloudy has been extended to include approximately 10(sup 4) resonance lines from the 495 possible stages of ionization of the lightest 30 elements, an extension that required several steps. The charge transfer database was expanded to complete the needed reactions between hydrogen and the first four ions and fit all reactions with a common approximation. Radiative recombination rate coefficients were derived for recombination from all closed shells, where this process should dominate. Analytical fits to Opacity Project (OP) and other recent photoionization cross sections were produced. Finally, rescaled OP oscillator strengths were used to compile a complete set of data for 5971 resonance lines. The major discovery has been that high redshift quasars have very high metallicities and there is strong evidence that the quasar phenomenon is associated with the birth of massive elliptical galaxies.

  15. Seeing the Unseen: MIR Spectroscopic Constraints on Quasar Big Blue Bumps

    Science.gov (United States)

    Gallagher, Sarah; Hines, Dean; Leighly, Karen; Ogle, Patrick; Richards, Gordon

    2008-03-01

    The IRS on Spitzer offers an exciting opportunity for detailed, mid-infrared spectroscopy of z~2 quasars for the first time. This epoch, sampling the peak of the quasar luminosity evolution, is particularly important for understanding the nature of quasar activity in the most massive galaxies. We aim to use this powerful tool to constrain the shape and power of the far-ultraviolet through soft-X-ray ionizing continuum of luminous quasars. Though these so-called `big blue bumps' dominate the power of quasar spectral energy distributions, they are largely unobservable as a result of hydrogen opacity in the Universe. However, we can determine the properties of the big blue bump by studying emission lines from ions in the coronal line region that emit in the mid-infrared and are created by those same energetic and elusive photons. We propose deep, high quality IRS observations of 5 luminous quasars with a range of HeII emission properties to investigate the mid-infrared spectral region in depth and constrain the shape of the ionizing continuum in each quasar. In addition, these high S/N spectra will provide templates for interpreting lower resolution, lower S/N IRS spectra.

  16. Rest-frame optical photometry of a z-7.54 quasar and its environment

    Science.gov (United States)

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

    2017-10-01

    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.

  17. QUASARS ARE NOT LIGHT BULBS: TESTING MODELS OF QUASAR LIFETIMES WITH THE OBSERVED EDDINGTON RATIO DISTRIBUTION

    International Nuclear Information System (INIS)

    Hopkins, Philip F.; Hernquist, Lars

    2009-01-01

    We use the observed distribution of Eddington ratios as a function of supermassive black hole (BH) mass to constrain models of quasar/active galactic nucleus (AGN) lifetimes and light curves. Given the observed (well constrained) AGN luminosity function, a particular model for AGN light curves L(t) or, equivalently, the distribution of AGN lifetimes (time above a given luminosity t(>L)) translates directly and uniquely (without further assumptions) to a predicted distribution of Eddington ratios at each BH mass. Models for self-regulated BH growth, in which feedback produces a self-regulating 'decay' or 'blowout' phase after the AGN reaches some peak luminosity/BH mass and begins to expel gas and shut down accretion, make specific predictions for the light curves/lifetimes, distinct from, e.g., the expected distribution if AGN simply shut down by gas starvation (without feedback) and very different from the prediction of simple phenomenological 'light bulb' scenarios. We show that the present observations of the Eddington ratio distribution, spanning nearly 5 orders of magnitude in Eddington ratio, 3 orders of magnitude in BH mass, and redshifts z = 0-1, agree well with the predictions of self-regulated models, and rule out phenomenological 'light bulb' or pure exponential models, as well as gas starvation models, at high significance (∼5σ). We also compare with observations of the distribution of Eddington ratios at a given AGN luminosity, and find similar good agreement (but show that these observations are much less constraining). We fit the functional form of the quasar lifetime distribution and provide these fits for use, and show how the Eddington ratio distributions place precise, tight limits on the AGN lifetimes at various luminosities, in agreement with model predictions. We compare with independent estimates of episodic lifetimes and use this to constrain the shape of the typical AGN light curve, and provide simple analytic fits to these for use in

  18. Starburst-driven Superwinds in Quasar Host Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Barthel, Peter; Podigachoski, Pece [Kapteyn Astronomical Institute, University of Groningen, Groningen (Netherlands); Wilkes, Belinda [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Haas, Martin, E-mail: pdb@astro.rug.nl, E-mail: podigachoski@astro.rug.nl [Astronomisches Institut, Ruhr Universität, Bochum (Germany)

    2017-07-01

    During the past five decades astronomers have been puzzled by the presence of strong absorption features including metal lines, observed in the optical and ultraviolet spectra of quasars, signaling inflowing and outflowing gas winds with relative velocities up to several thousands of km s{sup −1}. In particular, the location of these winds—close to the quasar, further out in its host galaxy, or in its direct environment—and the possible impact on their surroundings have been issues of intense discussion and uncertainty. Using our Herschel Space Observatory data, we report a tendency for this so-called associated metal absorption to occur along with prodigious star formation in the quasar host galaxy, indicating that the two phenomena are likely to be interrelated, that the gas winds likely occur on the kiloparsec scale and would then have a strong impact on the interstellar medium of the galaxy. This correlation moreover would imply that the unusually high cold dust luminosities in these quasars are connected with ongoing star formation. Given that we find no correlation with the AGN strength, the wind feedback that we establish in these radio-loud objects is most likely associated with their host star formation rather than with their black hole accretion.

  19. THE MICROLENSING PROPERTIES OF A SAMPLE OF 87 LENSED QUASARS

    International Nuclear Information System (INIS)

    Mosquera, A. M.; Kochanek, C. S.

    2011-01-01

    Gravitational microlensing is a powerful tool for probing the physical properties of quasar accretion disks and properties of the lens galaxy such as its dark matter fraction and mean stellar mass. Unfortunately, the number of lensed quasars (∼90) exceeds our monitoring capabilities. Thus, estimating their microlensing properties is important for identifying good microlensing candidates as well as for the expectations of future surveys. In this work, we estimate the microlensing properties of a sample of 87 lensed quasars. While the median Einstein radius crossing timescale is 20.6 years, the median source crossing timescale is 7.3 months. Broadly speaking, this means that on ∼10 year timescales roughly half the lenses will be quiescent, with the source in a broad demagnified valley, and roughly half will be active with the source lying in the caustic ridges. We also found that the location of the lens system relative to the cosmic microwave background dipole has a modest effect on microlensing timescales, and in theory microlensing could be used to confirm the kinematic origin of the dipole. As a corollary of our study we analyzed the accretion rate parameters in a sub-sample of 32 lensed quasars. At fixed black hole mass, it is possible to sample a broad range of luminosities (i.e., Eddington factors) if it becomes feasible to monitor fainter lenses.

  20. Outshining the quasars at reionization

    DEFF Research Database (Denmark)

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

    2006-01-01

    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...

  1. Erratum: "Space Density of Optically Selected Type 2 Quasars" (2008, AJ, 136, 2373)

    Science.gov (United States)

    Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

    2010-03-01

    Figure 12 of the paper "Space Density of Optically Selected Type 2 Quasars" compares the obscured quasar fractions derived in our work with those of other studies. Unfortunately, some of the points from these other studies were shown incorrectly. Specifically, the results from X-ray data—Hasinger (2004; open circles) and Ueda et al. (2003; open squares)—which we had taken from Figure 16 of Hopkins et al. (2006), were affected by a luminosity conversion error, in the sense that the displayed luminosities for these data were too high by ~1 dex. With this erratum, we correct this problem and update the figure. The new version (Figure 12) shows more recent results from Hasinger (2008), in lieu of the Hasinger (2004) data points. These are based on data in the redshift range z = 0.2-3.2 (open circles) in that work. The best linear fit to these data (black dashed line) is consistent with that derived for the redshift slice z = 0.4-0.8, which overlaps with the highest redshift bin in our study, and is higher than that derived for redshifts smaller than 0.4 (corresponding to a shift of ~0.7 dex in luminosity). Figure 12 also shows estimates of the obscured quasar fraction derived from the ratio of IR to bolometric luminosities of an AGN sample at redshift z ~ 1 (Treister et al. 2008; filled triangles). Because the obscured quasar fractions derived from our analysis (colored arrows) are strict lower limits, there was already a hint in the previous version of Figure 12 that at high quasar luminosities, we find higher obscured quasar fractions than X-ray surveys. The correction and updates of Figure 12 strengthen this conclusion. At face value, our derived obscured quasar fractions are consistent with those from IR data (Treister et al. 2008; filled triangles). However, we find that they are significantly higher than those derived from X-ray surveys at L_[O\\,\\mathsc {iii]}\\gtrsim 10^{9.5}\\;L_{\\odot }, especially those from the recent analysis by Hasinger (2008). This

  2. Studies of Quasar Outflows

    Science.gov (United States)

    Arav, Nahum

    2002-01-01

    The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

  3. First Discoveries of z > 6 Quasars with the DECam Legacy Survey and UKIRT Hemisphere Survey

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Feige; Yang, Jinyi; Wu, Xue-Bing; Yang, Qian; Li, Zefeng [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui; McGreer, Ian D.; Ding, Jiani; Green, Richard [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Bian, Fuyan [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Li, Jiang-Tao [Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Avenue, Ann Arbor, MI, 48109 (United States); Dey, Arjun [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Dye, Simon [School of Physics and Astronomy, Nottingham University, University Park, Nottingham, NG7 2RD (United Kingdom); Findlay, Joseph R.; Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); James, David [Cerro Tololo Inter-American Observatory, Casilla 603 La Serena (Chile); Jiang, Linhua [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Lang, Dustin [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario, M5S 3H4 (Canada); Lawrence, Andy; Ross, Nicholas P. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); and others

    2017-04-10

    We present the first discoveries from a survey of z ≳ 6 quasars using imaging data from the DECam Legacy Survey (DECaLS) in the optical, the UKIRT Deep Infrared Sky Survey (UKIDSS) and a preliminary version of the UKIRT Hemisphere Survey (UHS) in the near-IR, and ALLWISE in the mid-IR. DECaLS will image 9000 deg{sup 2} of sky down to z {sub AB} ∼ 23.0, and UKIDSS and UHS will map the northern sky at 0 < decl. < +60°, reaching J {sub VEGA} ∼ 19.6 (5- σ ). The combination of these data sets allows us to discover quasars at redshift z ≳ 7 and to conduct a complete census of the faint quasar population at z ≳ 6. In this paper, we report on the selection method of our search, and on the initial discoveries of two new, faint z ≳ 6 quasars and one new z = 6.63 quasar in our pilot spectroscopic observations. The two new z ∼ 6 quasars are at z = 6.07 and z = 6.17 with absolute magnitudes at rest-frame wavelength 1450 Å being M {sub 1450} = −25.83 and M {sub 1450} = −25.76, respectively. These discoveries suggest that we can find quasars close to or fainter than the break magnitude of the Quasar Luminosity Function (QLF) at z ≳ 6. The new z = 6.63 quasar has an absolute magnitude of M {sub 1450} = −25.95. This demonstrates the potential of using the combined DECaLS and UKIDSS/UHS data sets to find z ≳ 7 quasars. Extrapolating from previous QLF measurements, we predict that these combined data sets will yield ∼200 z ∼ 6 quasars to z {sub AB} < 21.5, ∼1000 z ∼ 6 quasars to z {sub AB} < 23, and ∼30 quasars at z > 6.5 to J {sub VEGA} < 19.5.

  4. The optical variability of SDSS quasars from multi-epoch spectroscopy. I. Results from 60 quasars with ≥ six-epoch spectra

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hengxiao; Gu, Minfeng, E-mail: hxguo@shao.ac.cn, E-mail: gumf@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

    2014-09-01

    In a sample of 60 quasars selected from the Sloan Digital Sky Survey with at least six-epoch spectroscopy, we investigate the variability of emission lines and continuum luminosity at various aspects. A strong anti-correlation between the variability and continuum luminosity at 2500 Å is found for the sample, which is consistent with previous works. In individual sources, we find that half of the sample objects follow the trend of being bluer when brighter, while the remaining half follow the redder-when-brighter (RWB) trend. Although the mechanism for RWB is unclear, the effects of host galaxy contribution due to seeing variations cannot be completely ruled out. As expected from the photoionization model, the positive correlations between the broad emission line and continuum luminosity are found in most individual sources, as well as for the whole sample. We confirm the Baldwin effect in most individual objects and the whole sample, while a negative Baldwin effect is also found in several quasars, which can be at least partly (if not all) due to the host galaxy contamination. We find positive correlations between the broad emission line luminosity and line width in most individual quasars, as well as the whole sample, implying a line base that is more variable than the line core.

  5. The galaxy cluster mid-infrared luminosity function at 1.3 < z < 3.2

    Energy Technology Data Exchange (ETDEWEB)

    Wylezalek, Dominika; Vernet, Joël; De Breuck, Carlos [European Southern Observatory, Karl-Schwarzschildstr.2, D-85748 Garching bei München (Germany); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Brodwin, Mark [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Galametz, Audrey [INAF-Osservatorio di Roma, Via Frascati 33, I-00040, Monteporzio (Italy); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Jarvis, Matt [Astrophysics, Department of Physics, Keble Road, Oxford OX1 3RH (United Kingdom); Hatch, Nina [School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Seymour, Nick [CASS, P.O. Box 76, Epping, NSW, 1710 (Australia); Stanford, Spencer A. [Physics Department, University of California, Davis, CA 95616 (United States)

    2014-05-01

    We present 4.5 μm luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3 < z < 3.2. The clusters were identified as Spitzer/Infrared Array Camera (IRAC) color-selected overdensities in the Clusters Around Radio-Loud AGN project, which imaged 420 powerful radio-loud active galactic nuclei (RLAGNs) at z > 1.3. The luminosity functions are derived for different redshift and richness bins, and the IRAC imaging reaches depths of m* + 2, allowing us to measure the faint end slopes of the luminosity functions. We find that α = –1 describes the luminosity function very well in all redshift bins and does not evolve significantly. This provides evidence that the rate at which the low mass galaxy population grows through star formation gets quenched and is replenished by in-falling field galaxies does not have a major net effect on the shape of the luminosity function. Our measurements for m* are consistent with passive evolution models and high formation redshifts (z{sub f} ∼ 3). We find a slight trend toward fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. Modeling shows that a contribution of a star-forming population of up to 40% cannot be ruled out. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z ∼ 1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of RLAGNs—which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift—and they may therefore be older and more evolved systems than the general protocluster population.

  6. The galaxy cluster mid-infrared luminosity function at 1.3 < z < 3.2

    International Nuclear Information System (INIS)

    Wylezalek, Dominika; Vernet, Joël; De Breuck, Carlos; Stern, Daniel; Brodwin, Mark; Galametz, Audrey; Gonzalez, Anthony H.; Jarvis, Matt; Hatch, Nina; Seymour, Nick; Stanford, Spencer A.

    2014-01-01

    We present 4.5 μm luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3 < z < 3.2. The clusters were identified as Spitzer/Infrared Array Camera (IRAC) color-selected overdensities in the Clusters Around Radio-Loud AGN project, which imaged 420 powerful radio-loud active galactic nuclei (RLAGNs) at z > 1.3. The luminosity functions are derived for different redshift and richness bins, and the IRAC imaging reaches depths of m* + 2, allowing us to measure the faint end slopes of the luminosity functions. We find that α = –1 describes the luminosity function very well in all redshift bins and does not evolve significantly. This provides evidence that the rate at which the low mass galaxy population grows through star formation gets quenched and is replenished by in-falling field galaxies does not have a major net effect on the shape of the luminosity function. Our measurements for m* are consistent with passive evolution models and high formation redshifts (z f ∼ 3). We find a slight trend toward fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. Modeling shows that a contribution of a star-forming population of up to 40% cannot be ruled out. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z ∼ 1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of RLAGNs—which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift—and they may therefore be older and more evolved systems than the general protocluster population.

  7. properties and luminosity functions

    Directory of Open Access Journals (Sweden)

    Hektor Monteiro

    2007-01-01

    Full Text Available In this article, we present an investigation of a sample of 1072 stars extracted from the Villanova Catalog of Spectroscopically Identified White Dwarfs (2005 on-line version, studying their distribution in the Galaxy, their physical properties and their luminosity functions. The distances and physical properties of the white dwarfs are determined through interpolation of their (B-V or (b-y colors in model grids. The solar position relative to the Galactic plane, luminosity function, as well as separate functions for each white dwarf spectral type are derived and discussed. We show that the binary fraction does not vary significantly as a function of distance from the Galactic disk out to 100 pc. We propose that the formation rates of DA and non-DAs have changed over time and/or that DAs evolve into non-DA types. The luminosity functions for DAs and DBs have peaks possibly related to a star burst event.

  8. Luminosity measurement at CMS

    CERN Document Server

    Leonard, Jessica Lynn

    2014-01-01

    The measurement of the luminosity delivered by the LHC is pivotal for several key physics analyses. During the first three years of running, tremendous steps forwards have been made in the comprehension of the subtleties related to luminosity monitoring and calibration, which led to an unprecedented accuracy at a hadron collider. The detectors and corresponding algorithms employed to estimate online and offline the luminosity in CMS are described. Details are given concerning the procedure based on the Van der Meer scan technique that allowed a very precise calibration of the luminometers from the determination of the LHC beams parameters. What is being prepared in terms of detector and online software upgrades for the next LHC run is also summarized.

  9. CLIC Luminosity Monitoring

    CERN Document Server

    Apyan, Armen; Gschwendtner, Edda; Lefevre, Thibault; Tygier, Sam; Appleby, Robert B

    2012-01-01

    The CLIC post-collision line is designed to transport the un-collided beams and the products of the collided beams with a total power of 14 MW to the main beam dump. Luminosity monitoring for CLIC is based on high energy muons produced by beamstrahlung photons in the main dump. Threshold Cherenkov counters are proposed for the detection of these muons. The expected rates and layout for these detectors is presented. Another method for luminosity monitoring is to directly detect the beamstrahlung photons in the post-collision line. Full Monte Carlo simulation has been performed to address its feasibility.

  10. Luminosity enhancements at SLAC

    International Nuclear Information System (INIS)

    Coward, D.H.

    1984-04-01

    Several ideas are discussed that have been proposed to improve the luminosity at the SPEAR and PEP electron-positron storage rings and to insure good luminosity at the SLAC Linear Collider. There have been two proposals studied recently for SPEAR: a Microbeta insertion using Samarium Cobalt permanent magnets, and a Minibeta insertion using conventional quadrupole magnets. The notations Microbeta and minibeta used here are somewhat arbitrary since the front faces of the first quadrupole magnets for both insertions are at nearly the same distance from the interaction point

  11. Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

    Science.gov (United States)

    Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

    2018-04-01

    We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

  12. X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

    International Nuclear Information System (INIS)

    Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta; Janiuk, Agnieszka

    2009-01-01

    We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jet can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.

  13. Intergalactic dust and quasar distribution

    International Nuclear Information System (INIS)

    Soltan, A.

    1979-01-01

    Non-homogeneous intergalactic extinction may considerably affect the quasar distribution. Especially samples of quasars isolated on the basis of B-V colours are subject to this phenomenon. Apparent grouping and close pairs of quasars reported in the literature may be a result of intergalactic dust. Using surface distribution of faint blue objects selected by Hawkins and Reddish it is estimated that intergalactic extinction in B should reach approximately 1 mag out to the redshift of approximately 1. This is slightly larger than predicted by theory and comparable to the mean dust density derived from observations. (Author)

  14. THE INTRINSIC FRACTIONS AND RADIO PROPERTIES OF LOW-IONIZATION BROAD ABSORPTION LINE QUASARS

    International Nuclear Information System (INIS)

    Dai Xinyu; Shankar, Francesco; Sivakoff, Gregory R.

    2012-01-01

    Low-ionization (Mg II, Fe II, and Fe III) broad absorption line quasars (LoBALs) probe a relatively obscured quasar population and could be at an early evolutionary stage for quasars. We study the intrinsic fractions of LoBALs using the Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, and Faint Images of the Radio Sky at Twenty cm survey. We find that the LoBAL fractions of the near-infrared (NIR) and radio samples are approximately 5-7 times higher than those measured in the optical sample. This suggests that the fractions measured in the NIR and radio bands are closer to the intrinsic fractions of the populations, and that the optical fractions are significantly biased due to obscuration effects, similar to high-ionization broad absorption line quasars (HiBALs). Considering a population of obscured quasars that do not enter the SDSS, which could have a much higher LoBAL fraction, we expect that the intrinsic fraction of LoBALs could be even higher. We also find that the LoBAL fractions decrease with increasing radio luminosities, again, similarly to HiBALs. In addition, we find evidence for increasing fractions of LoBALs toward higher NIR luminosities, especially for FeLoBALs with a fraction of ∼18% at M K s < -31 mag. This population of NIR-luminous LoBALs may be at an early evolutionary stage of quasar evolution. To interpret the data, we use a luminosity-dependent model for LoBALs that yields significantly better fits than those from a pure geometric model.

  15. Evolution of radio quasars from redshift 0.6-3.7

    International Nuclear Information System (INIS)

    Neff, S.G.; Hutchings, J.B.

    1990-01-01

    This paper presents the results of VLA radio imaging of 58 radio-loud quasars with redshift 2.0 or higher, which fill the redshift-luminosity plane as evenly as possible. This work completes a survey of about 250 quasars covering redshifts from 0.6-3.7, which attempts to sample luminosity and look-back time in a uniform way. Within the constraints of possible selection effects it is found that the relative population of extended and unresolved sources changes with redshift in a way that suggests that radio quasars may live longer and spend more time as large triple sources in the present epoch than in the earlier universe. There appear to be few low-luminosity radio quasars at high redshift. Ejection of material appears to occur on one side at a time, with usually at least one reversal of direction in the source lifetime. The velocity of ejection appears to be mildly relativistic at high redshift, but of lower velocity in the present epoch. There is also evidence suggestive of changes in the IGM with cosmic time; however, the data presented do not show the minimum in density at z about 2 that has been suggested for cluster environments. 11 refs

  16. 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)

    2017-08-15

    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.)

  17. An Anthropology of Luminosity

    DEFF Research Database (Denmark)

    Bille, Mikkel; Sørensen, Tim Flohr

    2007-01-01

    of luminosity in the practice of day-to-day activities. The article surveys an array of past conceptions of light within philosophy, natural science and more recent approaches to light in the fields of anthropology and material culture studies. A number of implications are discussed, and by way of three case...

  18. High luminosity particle colliders

    International Nuclear Information System (INIS)

    Palmer, R.B.; Gallardo, J.C.

    1997-03-01

    The authors consider the high energy physics advantages, disadvantages and luminosity requirements of hadron (pp, p anti p), lepton (e + e - , μ + μ - ) and photon-photon colliders. Technical problems in obtaining increased energy in each type of machine are presented. The machines relative size are also discussed

  19. Luminosity measurement at CMS

    CERN Document Server

    Karacheban, Olena

    2017-01-01

    Luminosity is a key quantity of any collider, since it allows for the determinationof the absolute cross sections from the observed rates in a detector. Since theHiggs boson discovery in 2012, the highest priority at the Large Hadron Collider(LHC) has been given to an accurate understanding of the electroweak scale anda search for new physics. Precise luminosity measurements in such conditions areof crucial importance, as they determine the precision of any physics cross sectionmeasurement.To increase the production of particles of interest, usually of low cross section,the LHC is running at the highest possible luminosity. After the first Long Shutdown (LS1) the original performance goal for the luminosity of 1 × 1034 cm−2 s−1was reached with 1011 protons per bunch and a bunch spacing of 25 ns. In suchconditions radiation hard detectors with extremely fast response time are required,especially for instrumentation near the beam.The Compact Muon Solenoid experiment is equipped with three online luminomet...

  20. Characterizing the evolution of WISE-selected obscured and unobscured quasars using HOD models.

    Science.gov (United States)

    Myers, Adam D.; DiPompeo, Michael A.; Mitra, Kaustav; Hickox, Ryan C.; Chatterjee, Suchetana; Whalen, Kelly

    2018-06-01

    Large-area imaging surveys in the infrared are now beginning to unlock the links between the activity of supermassive black holes and the cosmic evolution of dark matter halos during the significant times when black hole growth is enshrouded in dust. With data from the Wide-Field Infrared Survey Explorer (WISE) and complementary optical photometry, we construct samples of nearly half-a-million obscured and unobscured quasars around redshift 1. We study the dark matter halos of these populations using both angular autocorrelation functions and CMB lensing cross-correlations, carefully characterizing the redshift distribution of the obscured quasar sample using cross-correlations. Independent of our measurement technique, we find that obscured quasars occupy dark matter halos a few times more massive than their unobscured counterparts, despite being matched in luminosity at 12 and 22 microns. Modeling the two-point correlation function using a four-parameter Halo Occupation Distribution (HOD) formalism, we determine that purely optically selected quasars reside in dark matter halos that are about half the mass of WISE-selected obscured quasars, and that satellite fractions are somewhat larger for obscured quasars. We investigate scenarios such as merger-driven fueling and Eddington-dependent obscuration to explore what combinations of physical effects can reproduce our observed halo mass measurements. This work was, in part, supported by NASA ADAP award NNX16AN48G.

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

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2012-01-01

    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...... and the few BALs detected in this quasar sample obey key predictions of models of radiatively driven disk-winds in which (1) the local disk luminosity launches the wind, (2) the central UV radiation drives it outwards, and (3) the wind acceleration (i.e., terminal velocity) depends on the strength of the X...

  2. Discovery of an infrared nucleus in Cygnus A - An obscured quasar revealed?

    International Nuclear Information System (INIS)

    Djorgovski, S.; Weir, N.; Matthews, K.; Graham, J.R.

    1991-01-01

    This paper reports on the discovery of a compact, unresolved infrared nucleus, coincident with the radio core, in the prototypical powerful radio galaxy Cygnus A (3C 405). The infrared colors and magnitudes of the nucleus can be explained as a highly reddened extension of the radio continuum. The implied restframe extinction is A(V) equal to about 50 + or - 30 magnitudes. The extinction-corrected luminosity of the object is in the quasar range. This discovery gives some support to the unification models for quasars and powerful radio galaxies. 35 refs

  3. Fast Molecular Outflows in Luminous Galaxy Mergers: Evidence for Quasar Feedback from Herschel

    Science.gov (United States)

    Veilleux, S.; Melendez, M.; Sturm, E.; Garcia-Carpio, J.; Fischer, J.; Gonzalez-Alfonso, E.; Contursi, A.; Lutz, D.; Poglitsch, A.; Davies, R.; hide

    2013-01-01

    We report the results from a systematic search for molecular (OH 119 micron) outflows with Herschel/PACS in a sample of 43 nearby (z 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. However, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

  4. A Hubble Diagram for Quasars

    Directory of Open Access Journals (Sweden)

    Susanna Bisogni

    2018-01-01

    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.

  5. Using Quasars as Standard Candles for Studying Dark Energy

    DEFF Research Database (Denmark)

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

    2012-01-01

    , which relies on the technique of reverberation mapping to measure time delays between the quasar continuum and emission line variability signatures. Measuring this time delay effectively measures the radius between the central source and the emission-line gas. The emission line gas is photo-ionized...... by the continuum photons, and the radius to this emission-line region scales tightly with the nuclear luminosity - a consequence of the photoionization physics responsible for regulating the production of line-emitting photons. Hence, measuring the radius of the emission-line gas provides a measure...

  6. Relativistic beaming and quasar statistics

    International Nuclear Information System (INIS)

    Orr, M.J.L.; Browne, I.W.A.

    1982-01-01

    The statistical predictions of a unified scheme for the radio emission from quasars are explored. This scheme attributes the observed differences between flat- and steep-spectrum quasars to projection and the effects of relativistic beaming of the emission from the nuclear components. We use a simple quasar model consisting of a compact relativistically beamed core with spectral index zero and unbeamed lobes, spectral index - 1, to predict the proportion of flat-spectrum sources in flux-limited samples selected at different frequencies. In our model this fraction depends on the core Lorentz factor, γ and we find that a value of approximately 5 gives satisfactory agreement with observation. In a similar way the model is used to construct the expected number/flux density counts for flat-spectrum quasars from the observed steep-spectrum counts. Again, good agreement with the observations is obtained if the average core Lorentz factor is about 5. Independent estimates of γ from observations of superluminal motion in quasars are of the same order of magnitude. We conclude that the statistical properties of quasars are entirely consistent with the predictions of simple relativistic-beam models. (author)

  7. Gaia Space Mission and Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Zwitter, Tomaž, E-mail: tomaz.zwitter@fmf.uni-lj.si [Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana (Slovenia)

    2017-11-15

    Quasars are often considered to be point-like objects. This is largely true and allows for an excellent alignment of the optical positional reference frame of the ongoing ESA mission Gaia with the International Celestial Reference Frame. But presence of optical jets in quasars can cause shifts of the optical photo-centers at levels detectable by Gaia. Similarly, motion of emitting blobs in the jet can be detected as proper motion shifts. Gaia's measurements of spectral energy distribution for around a million distant quasars is useful to determine their redshifts and to assess their variability on timescales from hours to years. Spatial resolution of Gaia allows to build a complete magnitude limited sample of strongly lensed quasars. The mission had its first public data release in September 2016 and is scheduled to have the next and much more comprehensive one in April 2018. Here we briefly review the capabilities and current results of the mission. Gaia's unique contributions to the studies of quasars are already being published, a highlight being a discovery of a number of quasars with optical jets.

  8. An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30.

    Science.gov (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

    2015-02-26

    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. Luminosity measurement at CMS

    Energy Technology Data Exchange (ETDEWEB)

    Karacheban, Olena

    2017-10-15

    Luminosity is a key quantity of any collider, since it allows for the determination of the absolute cross sections from the observed rates in a detector. Since the Higgs boson discovery in 2012, the highest priority at the Large Hadron Collider (LHC) has been given to an accurate understanding of the electroweak scale and a search for new physics. Precise luminosity measurements in such conditions are of crucial importance, as they determine the precision of any physics cross section measurement. To increase the production of particles of interest, usually of low cross section, the LHC is running at the highest possible luminosity. After the first Long Shutdown (LS1) the original performance goal for the luminosity of 1 x 10{sup 34} cm{sup -2} s{sup -1} was reached with 10{sup 11} protons per bunch and a bunch spacing of 25 ns. In such conditions radiation hard detectors with extremely fast response time are required, especially for instrumentation near the beam. The Compact Muon Solenoid experiment is equipped with three online luminometers, which fulfill the listed requirements: the Fast Beam Conditions Monitor (BCM1F), the Pixel Luminosity Telescope (PLT) and the Forward Hadron calorimeter (HF). The BCM1F was upgraded during LS1 from 8 to 24 diamond sensors and is read out by a dedicated fast ASIC. The back-end comprises a deadtime-less histogramming unit, with 6.25 ns bin width and analog-to-digital converters with 2 ns sampling time in the VME standard. A microTCA system with better time resolution is in development. Particles originating from collisions and machine induced background arrive with 12 ns time difference. Because of its excellent time resolution BCM1F measures separately both luminosity and machine induced background particles. The performance of the detector in the first running period and radiation damage monitoring of the sensors and electronics chain form the first part of this thesis. Calibration of the luminometers at the LHC is done using

  10. Luminosity measurement at CMS

    International Nuclear Information System (INIS)

    Karacheban, Olena

    2017-10-01

    Luminosity is a key quantity of any collider, since it allows for the determination of the absolute cross sections from the observed rates in a detector. Since the Higgs boson discovery in 2012, the highest priority at the Large Hadron Collider (LHC) has been given to an accurate understanding of the electroweak scale and a search for new physics. Precise luminosity measurements in such conditions are of crucial importance, as they determine the precision of any physics cross section measurement. To increase the production of particles of interest, usually of low cross section, the LHC is running at the highest possible luminosity. After the first Long Shutdown (LS1) the original performance goal for the luminosity of 1 x 10 34 cm -2 s -1 was reached with 10 11 protons per bunch and a bunch spacing of 25 ns. In such conditions radiation hard detectors with extremely fast response time are required, especially for instrumentation near the beam. The Compact Muon Solenoid experiment is equipped with three online luminometers, which fulfill the listed requirements: the Fast Beam Conditions Monitor (BCM1F), the Pixel Luminosity Telescope (PLT) and the Forward Hadron calorimeter (HF). The BCM1F was upgraded during LS1 from 8 to 24 diamond sensors and is read out by a dedicated fast ASIC. The back-end comprises a deadtime-less histogramming unit, with 6.25 ns bin width and analog-to-digital converters with 2 ns sampling time in the VME standard. A microTCA system with better time resolution is in development. Particles originating from collisions and machine induced background arrive with 12 ns time difference. Because of its excellent time resolution BCM1F measures separately both luminosity and machine induced background particles. The performance of the detector in the first running period and radiation damage monitoring of the sensors and electronics chain form the first part of this thesis. Calibration of the luminometers at the LHC is done using van der Meer (Vd

  11. OLYMPUS luminosity monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Ates, Ozgur [Hampton University, Hampton, Virginia (United States); Collaboration: OLYMPUS-Collaboration

    2013-07-01

    The OLYMPUS experiment at DESY has been measuring the ratio of positron-proton and electron-proton elastic scattering cross sections to quantify the effect of two-photon exchange, which is widely considered to be responsible for the discrepancy between measurements of the proton electric to magnetic form factor ratio with the Rosenbluth and polarization transfer methods. In order to control the systematic uncertainties to the percent level, the luminosities are monitored redundantly with high precision by measuring the rates for symmetric Moller and Bhabha scattering, and by measuring the ep-elastic count rates at forward angles and low momentum transfer with tracking telescopes based on GEM (Gas Electron Multiplier) and MWPC (Multi Wire Proportional Chamber) technology. During two data taking periods, performances of GEM and MWPC luminosity monitors are presented.

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

    International Nuclear Information System (INIS)

    Worseck, Gabor; Prochaska, J. Xavier

    2011-01-01

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

  13. Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

    Science.gov (United States)

    Rumbaugh, N.; Shen, Yue; Morganson, Eric; Liu, Xin; Banerji, M.; McMahon, R. G.; Abdalla, F. B.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D’Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Frieman, J.; García-Bellido, J.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Martini, P.; Menanteau, F.; Plazas, A. A.; Reil, K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sheldon, E.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Walker, A. R.; Wester, W.; (DES Collaboration

    2018-02-01

    We perform a systematic search for long-term extreme variability quasars (EVQs) in the overlapping Sloan Digital Sky Survey and 3 Year Dark Energy Survey imaging, which provide light curves spanning more than 15 years. We identified ∼1000 EVQs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. The EVQs have L bol ∼ 1045–1047 erg s‑1 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 yr. We performed detailed multi-wavelength, spectral, and variability analyses for the EVQs and compared them 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 suggests 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 rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales.

  14. Star formation quenching in quasar host galaxies

    Science.gov (United States)

    Carniani, Stefano

    2017-10-01

    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 ionised 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 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, 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.

  15. Discovery of three z > 6.5 quasars in the VISTA kilo-degree infrared galaxy (VIKING) survey

    Energy Technology Data Exchange (ETDEWEB)

    Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Findlay, J. R. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Sutherland, W. J. [Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, London, E1 4NS (United Kingdom); De Rosa, G. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); McMahon, R. G.; González-Solares, E. A.; Lewis, J. R. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Simcoe, R. [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Kuijken, K., E-mail: venemans@mpia.de [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands)

    2013-12-10

    Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z ≅ 6.4, a limit set by the use of the z-band and CCD detectors. Only one z ≳ 6.4 quasar has been discovered, namely the z = 7.08 quasar ULAS J1120+0641, using near-infrared imaging. Here we report the discovery of three new z ≳ 6.4 quasars in 332 deg{sup 2} of the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, thus extending the number from 1 to 4. The newly discovered quasars have redshifts of z = 6.60, 6.75, and 6.89. The absolute magnitudes are between –26.0 and –25.5, 0.6-1.1 mag fainter than ULAS J1120+0641. Near-infrared spectroscopy revealed the Mg II emission line in all three objects. The quasars are powered by black holes with masses of ∼(1-2) × 10{sup 9} M {sub ☉}. In our probed redshift range of 6.44 < z < 7.44 we can set a lower limit on the space density of supermassive black holes of ρ(M {sub BH} > 10{sup 9} M {sub ☉}) > 1.1 × 10{sup –9} Mpc{sup –3}. The discovery of three quasars in our survey area is consistent with the z = 6 quasar luminosity function when extrapolated to z ∼ 7. We do not find evidence for a steeper decline in the space density of quasars with increasing redshift from z = 6 to z = 7.

  16. A large sample of Kohonen-selected SDSS quasars with weak emission lines: selection effects and statistical properties

    Science.gov (United States)

    Meusinger, H.; Balafkan, N.

    2014-08-01

    Aims: A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains puzzling. The aim of this study was to create a sizeable sample of WLQs and WLQ-like objects and to evaluate various properties of this sample. Methods: We performed a search for WLQs in the spectroscopic data from the Sloan Digital Sky Survey Data Release 7 based on Kohonen self-organising maps for nearly 105 quasar spectra. The final sample consists of 365 quasars in the redshift range z = 0.6 - 4.2 (z¯ = 1.50 ± 0.45) and includes in particular a subsample of 46 WLQs with equivalent widths WMg iiattention was paid to selection effects. Results: The WLQs have, on average, significantly higher luminosities, Eddington ratios, and accretion rates. About half of the excess comes from a selection bias, but an intrinsic excess remains probably caused primarily by higher accretion rates. The spectral energy distribution shows a bluer continuum at rest-frame wavelengths ≳1500 Å. The variability in the optical and UV is relatively low, even taking the variability-luminosity anti-correlation into account. The percentage of radio detected quasars and of core-dominant radio sources is significantly higher than for the control sample, whereas the mean radio-loudness is lower. Conclusions: The properties of our WLQ sample can be consistently understood assuming that it consists of a mix of quasars at the beginning of a stage of increased accretion activity and of beamed radio-quiet quasars. The higher luminosities and Eddington ratios in combination with a bluer spectral energy distribution can be explained by hotter continua, i.e. higher accretion rates. If quasar activity consists of subphases with different accretion rates, a change towards a higher rate is probably accompanied by an only slow development of the broad line region. The composite WLQ spectrum can be reasonably matched by the

  17. The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1.

    Science.gov (United States)

    Wilkes, Belinda J.; Tananbaum, Harvey; Worrall, D. M.; Avni, Yoram; Oey, M. S.; Flanagan, Joan

    1994-01-01

    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.

  18. THE BRIGHTEST OF REIONIZING GALAXIES SURVEY: CONSTRAINTS ON THE BRIGHT END OF THE z {approx} 8 LUMINOSITY FUNCTION

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, L. D.; Stiavelli, M.; Pirzkal, N. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Trenti, M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Oesch, P. A. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Treu, T. [Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States); Bouwens, R. J. [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Shull, J. M. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Holwerda, B. W. [European Space Agency (ESTEC), Keplerlaan 1, NL-2200 AG, Noordwijk (Netherlands)

    2012-12-01

    We report the discovery of 33 Lyman-break galaxy candidates at z {approx} 8 detected in Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging as part of the Brightest of Reionizing Galaxies (BoRG) pure-parallel survey. The ongoing BoRG survey currently has the largest area (274 arcmin{sup 2}) with Y {sub 098} (or Y {sub 105}), J {sub 125}, and H {sub 160} band coverage needed to search for z {approx} 8 galaxies, about three times the current CANDELS area, and slightly larger than what will be the final CANDELS wide component with Y {sub 105} data (required to select z {approx} 8 sources). Our sample of 33 relatively bright Y {sub 098}-dropout galaxies have J {sub 125}-band magnitudes between 25.5 and 27.4 mag. This is the largest sample of bright (J {sub 125} {approx}< 27.4) z {approx} 8 galaxy candidates presented to date. Combining our data set with the Hubble Ultra-Deep Field data set, we constrain the rest-frame ultraviolet galaxy luminosity function at z {approx} 8 over the widest dynamic range currently available. The combined data sets are well fitted by a Schechter function, i.e., {phi} (L) = {phi}{sub *} (L/L{sub *}){sup {alpha}} e{sup -(}L{sup /L{sub *})}, without evidence for an excess of sources at the bright end. At 68% confidence, for h = 0.7 we derive {phi}{sub *} = (4.3{sup +3.5} {sub -2.1}) Multiplication-Sign 10{sup -4} Mpc{sup -3}, M {sub *} = -20.26{sup +0.29} {sub -0.34}, and a very steep faint-end slope {alpha} = -1.98{sup +0.23} {sub -0.22}. While the best-fit parameters still have a strong degeneracy, especially between {phi}{sub *} and M {sub *}, our improved coverage at the bright end has reduced the uncertainty of the faint-end power-law slope at z {approx} 8 compared to the best previous determination at {+-}0.4. With a future expansion of the BoRG survey, combined with planned ultradeep WFC3/IR observations, it will be possible to further reduce this uncertainty and clearly demonstrate the steepening of the faint-end slope compared

  19. The luminosity function at z ∼ 8 from 97 Y-band dropouts: Inferences about reionization

    International Nuclear Information System (INIS)

    Schmidt, Kasper B.; Treu, Tommaso; Kelly, Brandon C.; Trenti, Michele; Bradley, Larry D.; Stiavelli, Massimo; Oesch, Pascal A.; Holwerda, Benne W.; Shull, J. Michael

    2014-01-01

    We present the largest search to date for Y-band dropout galaxies (z ∼ 8 Lyman break galaxies, LBGs) based on 350 arcmin 2 of Hubble Space Telescope observations in the V, Y, J, and H bands from the Brightest of Reionizing Galaxies (BoRG) survey. In addition to previously published data, the BoRG13 data set presented here includes approximately 50 arcmin 2 of new data and deeper observations of two previous BoRG pointings, from which we present 9 new z ∼ 8 LBG candidates, bringing the total number of BoRG Y-band dropouts to 38 with 25.5 ≤ m J ≤ 27.6 (AB system). We introduce a new Bayesian formalism for estimating the galaxy luminosity function, which does not require binning (and thus smearing) of the data and includes a likelihood based on the formally correct binomial distribution as opposed to the often-used approximate Poisson distribution. We demonstrate the utility of the new method on a sample of 97 Y-band dropouts that combines the bright BoRG galaxies with the fainter sources published in Bouwens et al. from the Hubble Ultra Deep Field and Early Release Science programs. We show that the z ∼ 8 luminosity function is well described by a Schechter function over its full dynamic range with a characteristic magnitude M ⋆ =−20.15 −0.38 +0.29 , a faint-end slope of α=−1.87 −0.26 +0.26 , and a number density of log 10  ϕ ⋆ [Mpc −3 ]=−3.24 −0.24 +0.25 . Integrated down to M = –17.7, this luminosity function yields a luminosity density log 10  ϵ[erg s −1 Hz −1 Mpc −3 ]=25.52 −0.05 +0.05 . Our luminosity function analysis is consistent with previously published determinations within 1σ. The error analysis suggests that uncertainties on the faint-end slope are still too large to draw a firm conclusion about its evolution with redshift. We use our statistical framework to discuss the implication of our study for the physics of reionization. By assuming theoretically motivated priors on the clumping factor and the photon

  20. The luminosity function at z ∼ 8 from 97 Y-band dropouts: Inferences about reionization

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Kasper B.; Treu, Tommaso; Kelly, Brandon C. [Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States); Trenti, Michele [Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Bradley, Larry D.; Stiavelli, Massimo [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Oesch, Pascal A. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Holwerda, Benne W. [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Shull, J. Michael, E-mail: kschmidt@physics.ucsb.edu [CASA, Department of Astrophysical and Planetary Science, University of Colorado, Center for Astrophysics and Space Astronomy, 389-UCB, Boulder, CO 80309 (United States)

    2014-05-01

    We present the largest search to date for Y-band dropout galaxies (z ∼ 8 Lyman break galaxies, LBGs) based on 350 arcmin{sup 2} of Hubble Space Telescope observations in the V, Y, J, and H bands from the Brightest of Reionizing Galaxies (BoRG) survey. In addition to previously published data, the BoRG13 data set presented here includes approximately 50 arcmin{sup 2} of new data and deeper observations of two previous BoRG pointings, from which we present 9 new z ∼ 8 LBG candidates, bringing the total number of BoRG Y-band dropouts to 38 with 25.5 ≤ m{sub J} ≤ 27.6 (AB system). We introduce a new Bayesian formalism for estimating the galaxy luminosity function, which does not require binning (and thus smearing) of the data and includes a likelihood based on the formally correct binomial distribution as opposed to the often-used approximate Poisson distribution. We demonstrate the utility of the new method on a sample of 97 Y-band dropouts that combines the bright BoRG galaxies with the fainter sources published in Bouwens et al. from the Hubble Ultra Deep Field and Early Release Science programs. We show that the z ∼ 8 luminosity function is well described by a Schechter function over its full dynamic range with a characteristic magnitude M{sup ⋆}=−20.15{sub −0.38}{sup +0.29}, a faint-end slope of α=−1.87{sub −0.26}{sup +0.26}, and a number density of log{sub 10} ϕ{sup ⋆}[Mpc{sup −3}]=−3.24{sub −0.24}{sup +0.25}. Integrated down to M = –17.7, this luminosity function yields a luminosity density log{sub 10} ϵ[erg s{sup −1} Hz{sup −1} Mpc{sup −3}]=25.52{sub −0.05}{sup +0.05}. Our luminosity function analysis is consistent with previously published determinations within 1σ. The error analysis suggests that uncertainties on the faint-end slope are still too large to draw a firm conclusion about its evolution with redshift. We use our statistical framework to discuss the implication of our study for the physics of

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

    International Nuclear Information System (INIS)

    Ubachukwu, A.A.; Chukwude, A.E.

    2002-07-01

    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-ll radio galaxies form the unbeamed parent population of both the lobe- and core-dominated 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 core-dominated quasars are highly relativistic, with optimum bulk Lorentz factor, γ opt ∼6-16, and also highly anisotropic, with an average viewing angle, ∼ 9 deg. - 16 deg. Furthermore, the largest boosting occurs within a critical cone angle of ∼ 4 deg. - 10 deg. The results suggest that relativistic bulk flow appears to extend to kilo-parsec scales in these sources. (author)

  2. The diversity of quasars unified by accretion and orientation.

    Science.gov (United States)

    Shen, Yue; Ho, Luis C

    2014-09-11

    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.

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

    DEFF Research Database (Denmark)

    Jiang, Linhua; Fan, Xiaohui; Vestergaard, Marianne

    2007-01-01

    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 Gemini-North/NIRI. We calculate line strengths for all detected emission lines and use their ratios to estimate gas metallicity in the broad-line regions of the quasars. The metallicity is found to be supersolar with a typical value of $\\sim$4 Z_{\\sun}, and a comparison with low-redshift observations...... shows no strong evolution in metallicity up to z$\\sim$6. The FeII/MgII ratio of the quasars is 4.9+/-1.4, consistent with low-redshift measurements. We estimate central BH masses of 10^9 to 10^{10} M_{\\sun} and Eddington luminosity ratios of order unity. We identify two MgII $\\lambda\\lambda$2796...

  4. Far infrared peculiar behavior of quasars

    International Nuclear Information System (INIS)

    Liu Yulin; Liu Jiying

    1988-09-01

    Many quasars possibly have nebulous envelopes with far infrared radiation. These nebulosities may be similar to fuzz in the optical region in morphology. These quasars have many properties in common. (author). Refs, 3 figs

  5. Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships

    DEFF Research Database (Denmark)

    Vestergaard, Marianne; Peterson, B. M.

    2006-01-01

    We present four improved empirical relationships useful for estimating the central black hole mass in nearby AGNs and distant luminous quasars alike using either optical or UV single-epoch spectroscopy. These mass-scaling relationships between line widths and luminosity are based on recently...

  6. 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.

    2016-04-06

    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.

  7. Microlensing as a possible probe of event-horizon structure in quasars

    Science.gov (United States)

    Tomozeiu, Mihai; Mohammed, Irshad; Rabold, Manuel; Saha, Prasenjit; Wambsganss, Joachim

    2018-04-01

    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 disc 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.

  8. Quasars at the Cosmic Dawn: effects on Reionization properties in cosmological simulations

    Science.gov (United States)

    Garaldi, Enrico; Compostella, Michele; Porciani, Cristiano

    2018-05-01

    We study a model of cosmic reionization where quasars (QSOs) are the dominant source of ionizing photons at all relevant epochs. We employ a suite of adaptive hydrodynamical simulations post-processed with a multi-wavelength Monte Carlo radiative-transfer code and calibrate them in order to accurately reproduce the observed quasar luminosity function and emissivity evolution. Our results show that the QSO-only model fails in reproducing key observables linked to the Helium reionization, as the temperature evolution of the inter-galactic medium (IGM) and the HeII effective optical depth in synthetic Lyα spectra. Nevertheless, we find hints that an increased quasar contribution can explain recent measurements of a large inhomogeneity in the IGM at redshift z ~ 5. Finally, we devise a method capable of constraining the QSOs contribution to the reionization from the properties of the HeII Lyα forest at z ~ 3.5.

  9. Constraining the neutrino emission of gravitationally lensed Flat-Spectrum Radio Quasars with ANTARES data

    Energy Technology Data Exchange (ETDEWEB)

    Adrián-Martínez, S.; Ardid, M.; Bou-Cabo, M. [Institut d' Investigació per a la Gestió Integrada de les Zones Costaneres (IGIC), Universitat Politècnica de València, C/ Paranimf 1, Gandia, 46730 Spain (Spain); Albert, A. [GRPHE - Institut universitaire de technologie de Colmar, 34 rue du Grillenbreit BP 50568, Colmar, 68008 France (France); André, M. [Technical University of Catalonia, Laboratory of Applied Bioacoustics, Rambla Exposició, Vilanova i la Geltrú, Barcelona, 08800 Spain (Spain); Anton, G. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, Erlangen, 91058 Germany (Germany); Aubert, J.-J.; Bertin, V.; Brunner, J.; Busto, J. [Aix Marseille Université, CNRS/IN2P3, CPPM UMR 7346, Marseille, 13288 France (France); Baret, B. [APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, Paris Cedex 13, F-75205 France (France); Barrios-Martí, J. [IFIC - Instituto de Física Corpuscular, Edificios Investigación de Paterna, CSIC - Universitat de València, Apdo de Correos 22085, Valencia, 46071 Spain (Spain); Basa, S. [LAM - Laboratoire d' Astrophysique de Marseille, Pôle de l' Étoile Site de Château-Gombert, rue Frédéric Joliot-Curie 38, Marseille Cedex 13, 13388 France (France); Biagi, S. [INFN - Sezione di Bologna, Viale Berti-Pichat 6/2, Bologna, 40127 Italy (Italy); Bogazzi, C.; Bormuth, R.; Bouwhuis, M.C.; Bruijn, R. [Nikhef, Science Park 105, Amsterdam, 1098XG The Netherlands (Netherlands); Capone, A. [INFN -Sezione di Roma, P.le Aldo Moro 2, Roma, 00185 Italy (Italy); Caramete, L., E-mail: antares.spokesperson@in2p3.fr [Institute for Space Sciences, Bucharest, Măgurele, R-77125 Romania (Romania); and others

    2014-11-01

    This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08× 10{sup 46} erg s{sup -1}. This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.

  10. Hadron collider luminosity limitations

    CERN Document Server

    Evans, Lyndon R

    1992-01-01

    The three colliders operated to date have taught us a great deal about the behaviour of both bunched and debunched beams in storage rings. The main luminosity limitations are now well enough understood that most of them can be stronglu attenuated or eliminated by approriate design precautions. Experience with the beam-beam interaction in both the SPS and the Tevatron allow us to predict the performance of the new generation of colliders with some degree of confidence. One of the main challenges that the accelerator physicist faces is the problem of the dynamic aperture limitations due to the lower field quality expected, imposed by economic and other constraints.

  11. THE FIFTH DATA RELEASE SLOAN DIGITAL SKY SURVEY/XMM-NEWTON QUASAR SURVEY

    International Nuclear Information System (INIS)

    Young, M.; Elvis, M.; Risaliti, G.

    2009-01-01

    We present a catalog of 792 Fifth Data Release Sloan Digital Sky Survey quasars with optical spectra that have been observed serendipitously in the X-rays with the XMM-Newton. These quasars cover a redshift range of z = 0.11-5.41 and a magnitude range of i = 15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at ≥2σ account for 87% of the sample (685 quasars), and 473 quasars are detected at ≥6σ, sufficient to allow X-ray spectral fits. For detected sources, ∼60% have X-ray fluxes between F 2-10keV = (1-10) x10 -14 erg cm -2 s -1 . We fit a single power law, a fixed power law with intrinsic absorption left free to vary, and an absorbed power-law model to all quasars with X-ray signal-to-noise ratio ≥ 6, resulting in a weighted mean photon index Γ = 1.91 ± 0.08, with an intrinsic dispersion σ Γ = 0.38. For the 55 sources (11.6%) that prefer intrinsic absorption, we find a weighted mean N H = 1.5 ± 0.3 x 10 21 cm -2 . We find that Γ correlates significantly with optical color, Δ(g - i), the optical-to-X-ray spectral index (α ox ), and the X-ray luminosity. While the first two correlations can be explained as artifacts of undetected intrinsic absorption, the correlation between Γ and X-ray luminosity appears to be a real physical correlation, indicating a pivot in the X-ray slope.

  12. 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)

    2015-02-01

    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.

  13. The Intrinsic Far-infrared Continua of Type-1 Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Lyu, Jianwei; Rieke, George H., E-mail: jianwei@email.arizona.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2017-06-01

    The range of currently proposed active galactic nucleus (AGN) far-infrared templates results in uncertainties in retrieving host galaxy information from infrared observations and also undermines constraints on the outer part of the AGN torus. We discuss how to test and reconcile these templates. Physically, the fraction of the intrinsic AGN IR-processed luminosity compared with that from the central engine should be consistent with the dust-covering factor. In addition, besides reproducing the composite spectral energy distributions (SEDs) of quasars, a correct AGN IR template combined with an accurate library of star-forming galaxy templates should be able to reproduce the IR properties of the host galaxies, such as the luminosity-dependent SED shapes and aromatic feature strengths. We develop tests based on these expected behaviors and find that the shape of the AGN intrinsic far-IR emission drops off rapidly starting at ∼20 μ m and can be matched by an Elvis et al.-like template with a minor modification. Despite the variations in the near- to mid-IR bands, AGNs in quasars and Seyfert galaxies have remarkably similar intrinsic far-IR SEDs at λ ∼ 20–100 μ m, suggesting a similar emission character of the outermost region of the circumnuclear torus. The variations of the intrinsic AGN IR SEDs among the type-1 quasar population can be explained by the changing relative strengths of four major dust components with similar characteristic temperatures, and there is evidence for compact AGN-heated dusty structures at sub-kiloparsec scales in the far-IR.

  14. MODELING THE TIME VARIABILITY OF SDSS STRIPE 82 QUASARS AS A DAMPED RANDOM WALK

    International Nuclear Information System (INIS)

    MacLeod, C. L.; Ivezic, Z.; Bullock, E.; Kimball, A.; Sesar, B.; Westman, D.; Brooks, K.; Gibson, R.; Becker, A. C.; Kochanek, C. S.; Kozlowski, S.; Kelly, B.; De Vries, W. H.

    2010-01-01

    We model the time variability of ∼9000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk (DRW). Using 2.7 million photometric measurements collected over 10 yr, we confirm the results of Kelly et al. and Kozlowski et al. that this model can explain quasar light curves at an impressive fidelity level (0.01-0.02 mag). The DRW model provides a simple, fast (O(N) for N data points), and powerful statistical description of quasar light curves by a characteristic timescale (τ) and an asymptotic rms variability on long timescales (SF ∞ ). We searched for correlations between these two variability parameters and physical parameters such as luminosity and black hole mass, and rest-frame wavelength. Our analysis shows SF ∞ to increase with decreasing luminosity and rest-frame wavelength as observed previously, and without a correlation with redshift. We find a correlation between SF ∞ and black hole mass with a power-law index of 0.18 ± 0.03, independent of the anti-correlation with luminosity. We find that τ increases with increasing wavelength with a power-law index of 0.17, remains nearly constant with redshift and luminosity, and increases with increasing black hole mass with a power-law index of 0.21 ± 0.07. The amplitude of variability is anti-correlated with the Eddington ratio, which suggests a scenario where optical fluctuations are tied to variations in the accretion rate. However, we find an additional dependence on luminosity and/or black hole mass that cannot be explained by the trend with Eddington ratio. The radio-loudest quasars have systematically larger variability amplitudes by about 30%, when corrected for the other observed trends, while the distribution of their characteristic timescale is indistinguishable from that of the full sample. We do not detect any statistically robust differences in the characteristic timescale and variability amplitude between the full sample and the small subsample of quasars detected

  15. Star Formation in Dusty Quasars

    Science.gov (United States)

    Lumsden, Stuart; Croom, Scott

    2012-04-01

    Quasar mode feedback is thought to be a crucial ingredient in galaxy formation for luminous merging and star-bursting systems at high redshift. The energy from the active nucleus should cause significant gas outflows, reducing the available free gas reservoir for future star formation. It is currently unknown which observational state best corresponds to the stage at which this "blowout" should occur. We intend to test one possible source population for this transition phase, by studying the molecular gas content in a small, statistically complete sample of 3 K-band selected reddened quasars from the AUS survey. All lie in the redshift range 2quasar activity in typical galaxies, where we also expect the bulk of the stars for form as well.

  16. A DISTANT QUASAR'S BRILLIANT LIGHT

    Science.gov (United States)

    2002-01-01

    The arrow in this image, taken by a ground-based telescope, points to a distant quasar, the brilliant core of an active galaxy residing billions of light-years from Earth. As light from this faraway object travels across space, it picks up information on galaxies and the vast clouds of material between galaxies as it moves through them. The Space Telescope Imaging Spectrograph aboard NASA's Hubble Space Telescope decoded the quasar's light to find the spectral 'fingerprints' of highly ionized (energized) oxygen, which had mixed with invisible clouds of hydrogen in intergalactic space. The quasar's brilliant beam pierced at least four separate filaments of the invisible hydrogen laced with the telltale oxygen. The presence of oxygen between the galaxies implies there are huge quantities of hydrogen in the universe. Credits: WIYN Telescope at Kitt Peak National Observatory in Arizona. The telescope is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.

  17. A luminous quasar at a redshift of z = 7.085.

    Science.gov (United States)

    Mortlock, Daniel J; Warren, Stephen J; Venemans, Bram P; Patel, Mitesh; Hewett, Paul C; McMahon, Richard G; Simpson, Chris; Theuns, Tom; Gonzáles-Solares, Eduardo A; Adamson, Andy; Dye, Simon; Hambly, Nigel C; Hirst, Paul; Irwin, Mike J; Kuiper, Ernst; Lawrence, Andy; Röttgering, Huub J A

    2011-06-29

    The intergalactic medium was not completely reionized until approximately a billion years after the Big Bang, as revealed by observations of quasars with redshifts of less than 6.5. It has been difficult to probe to higher redshifts, however, because quasars have historically been identified in optical surveys, which are insensitive to sources at redshifts exceeding 6.5. Here we report observations of a quasar (ULAS J112001.48+064124.3) at a redshift of 7.085, which is 0.77 billion years after the Big Bang. ULAS J1120+0641 has a luminosity of 6.3 × 10(13)L(⊙) and hosts a black hole with a mass of 2 × 10(9)M(⊙) (where L(⊙) and M(⊙) are the luminosity and mass of the Sun). The measured radius of the ionized near zone around ULAS J1120+0641 is 1.9 megaparsecs, a factor of three smaller than is typical for quasars at redshifts between 6.0 and 6.4. The near-zone transmission profile is consistent with a Lyα damping wing, suggesting that the neutral fraction of the intergalactic medium in front of ULAS J1120+0641 exceeded 0.1.

  18. Quenching star formation with quasar outflows launched by trapped IR radiation

    Science.gov (United States)

    Costa, Tiago; Rosdahl, Joakim; Sijacki, Debora; Haehnelt, Martin G.

    2018-06-01

    We present cosmological radiation-hydrodynamic simulations, performed with the code RAMSES-RT, of radiatively-driven outflows in a massive quasar host halo at z = 6. Our simulations include both single- and multi-scattered radiation pressure on dust from a quasar and are compared against simulations performed with thermal feedback. For radiation pressure-driving, we show that there is a critical quasar luminosity above which a galactic outflow is launched, set by the equilibrium of gravitational and radiation forces. While this critical luminosity is unrealistically high in the single-scattering limit for plausible black hole masses, it is in line with a ≈ 3 × 10^9 M_⊙ black hole accreting at its Eddington limit, if infrared (IR) multi-scattering radiation pressure is included. The outflows are fast (v ≳ 1000 km s^{-1}) and strongly mass-loaded with peak mass outflow rates ≈ 10^3 - 10^4 M_⊙ yr^{-1}, but short-lived (star formation in the bulge. We hence argue that radiation pressure-driven feedback may be an important ingredient in regulating star formation in compact starbursts, especially during the quasar's `obscured' phase.

  19. Continuing Long Term Optical and Infrared Reverberation Mapping of 17 Sloan Digital Sky Survey Quasars

    Science.gov (United States)

    Gorjian, Varoujan; Barth, Aaron; Brandt, Niel; Dawson, Kyle; Green, Paul; Ho, Luis; Horne, Keith; Jiang, Linhua; McGreer, Ian; Schneider, Donald; Shen, Yue; Tao, Charling

    2018-05-01

    Previous Spitzer reverberation monitoring projects searching for UV/optical light absorbed and re-emitted in the IR by dust have been limited to low luminosity active galactic nuclei (AGN) that could potentially show reverberation within a single cycle ( 1 year). Cycle 11-12's two year baseline allowed for the reverberation mapping of 17 high-luminosity quasars from the Sloan Digital Sky Survey Reverberation Mapping project. We continued this monitoring in Cycle 13 and now propose to extend this program in Cycle 14. By combining ground-based monitoring from Pan-STARRS, CFHT, and Steward Observatory telescopes with Spitzer data we have for the first time detected dust reverberation in quasars. By continuing observations with this unqiue combination of resources we should detect reverberation in more objects and reduce the uncertainties for the remaining sources.

  20. NuSTAR unveils a compton-thick 2 quasar in MrK 34

    DEFF Research Database (Denmark)

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

    2014-01-01

    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...... standard" CT QSO2 and is the nearest non-merging system in this class, in contrast to the other local CT quasar NGC 6240, which is currently undergoing a major merger coupled with strong star formation. For typical X-ray bolometric correction factors, the accretion luminosity of Mrk 34 is high enough...... to potentially power the total infrared luminosity. X-ray spectral fitting also shows that thermal emission related to star formation is unlikely to drive the observed bright soft component below similar to 3 keV, favoring photoionization instead....

  1. The statistics of quasar-galaxy separations

    International Nuclear Information System (INIS)

    Phillips, S.

    1983-01-01

    One of the arguments put forward in favor of physical associations between low redshift galaxies and high redshift quasars is shown to be void. The argument is based on the form of the relationship for 'close' pairs of quasars and galaxies and on the size of their separations. Simple statistical reasoning based on selection effects shows that the relationship for quasar-galaxy pairs is expected if the objects are not physically associated. Further, the actual separations of the closest pairs are in close agreement with those expected given the observed numbers of nearby galaxies and the total number of known quasars. This argument avoids the controversial number density of quasars

  2. Cosmological Evolution of the Central Engine in High-Luminosity, High-Accretion Rate AGN

    Directory of Open Access Journals (Sweden)

    Matteo Guainazzi

    2014-12-01

    Full Text Available In this paper I discuss the status of observational studies aiming at probing the cosmological evolution of the central engine in high-luminosity, high-accretion rate Active Galactic Nuclei (AGN. X-ray spectroscopic surveys, supported by extensive multi-wavelength coverage, indicate a remarkable invariance of the accretion disk plus corona system, and of their coupling up to redshifts z≈6. Furthermore, hard X-ray (E >10 keV surveys show that nearby Seyfert Galaxies share the same central engine notwithstanding their optical classication. These results suggest that the high-luminosity, high accretion rate quasar phase of AGN evolution is homogeneous over cosmological times.

  3. A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

    Science.gov (United States)

    Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

    2001-01-01

    Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe. The major study of a sample of z=3 and its comparison with a sample of z=0.l quasars across the whole X-ray to radio spectrum was completed and accepted for publication in ApJ Supplements. This study comprises the thesis work of Olga Kuhn. The two samples are matched in evolved luminosity, and so should be sampling the same black hole population at different z, and in different accretion states. Despite this no strong differences were found between the samples, except in the 'small bump' region of the optical/UV. This region is dominated by FeII emission, and may indicate abundance evolution in quasars. The lack of overall spectral changes argues strongly against a single population of quasars fading over cosmic time, and for a multiple generation, or multiple outburst model for quasars. A study of the total luminosity absorbed from quasars and re-emitted in the infrared produced two results (reported in two papers): The minimum intrinsic luminosity/Gpc(3) from AGN compared with the measured mass density in supermassive black holes [Gpc(-3)] requires a conversion efficiency of accreted mass into luminosity of greater than 15%. Non-rotating black holes cannot exceed 5% efficiency, while rapidly rotating black holes can reach 47%. Hence our result requires that most supermassive black holes must be rapidly rotating. The second result comes from considering the contribution that the re-radiated quasar

  4. EFFECTS OF BIASES IN VIRIAL MASS ESTIMATION ON COSMIC SYNCHRONIZATION OF QUASAR ACCRETION

    International Nuclear Information System (INIS)

    Steinhardt, Charles L.

    2011-01-01

    Recent work using virial mass estimates and the quasar mass-luminosity plane has yielded several new puzzles regarding quasar accretion, including a sub-Eddington boundary (SEB) on most quasar accretion, near-independence of the accretion rate from properties of the host galaxy, and a cosmic synchronization of accretion among black holes of a common mass. We consider how these puzzles might change if virial mass estimation turns out to have a systematic bias. As examples, we consider two recent claims of mass-dependent biases in Mg II masses. Under any such correction, the surprising cosmic synchronization of quasar accretion rates and independence from the host galaxy remain. The slope and location of the SEB are very sensitive to biases in virial mass estimation, and various mass calibrations appear to favor different possible physical explanations for feedback between the central black hole and its environment. The alternative mass estimators considered do not simply remove puzzling quasar behavior, but rather replace it with new puzzles that may be more difficult to solve than those using current virial mass estimators and the Shen et al. catalog.

  5. Proper motions and distances of quasars

    International Nuclear Information System (INIS)

    Varshni, Y.P.

    1982-01-01

    The author's theory that quasars are stars raises the question of their proper motions. From the evidence presented in a previous paper, it is hypothesised that planetary nuclei and quasars are related objects and that their distributions in the galaxy are not very different. Proper motions of 30 quasars, calculated from existing measurements, are discussed. It is shown that three of these, namely PHL 1033, LB 8956 and LB 8991, have proper motions comparable to the largest proper motion known amongst the planetary nuclei. From this it is estimated that these three quasars lie within a few hundred parsecs from the sun. The evidence presented in a previous paper and the present one clearly supports the theory that quasars are stars. The possibility of using the interstellar K and H lines as distance indicators of quasars is discussed and the available evidence summarised. The desirability of determining more accurate values of the proper motions of quasars is emphasised. (Auth.)

  6. Flare colours and luminosities

    International Nuclear Information System (INIS)

    Cristaldi, S.; Rodono, M.

    1975-01-01

    Flare colours determined from simultaneous UBV observations made at Catania Observatory and from sequential UBV observations made at McDonald Observatory are presented. They fit fairly well with the theoretical colours computed according to the Gurzadian's (1970) non-thermal model. Only part of the observed flare colours are consistent with the solar type models by Gershberg (1967) and Kunkel (1970). From a B-band patrol of UV Cet-type stars carried out from 1967 to 1972, some quantitative estimates of flare frequencies and luminosities and their average contributions to the stellar radiation are given. The corresponding parameters for the Sun, which were estimated from 'white light' flare activity, are also given for comparison. The Sun and V 1216 Sgr can be regarded as low-activity flare stars of the type found by Kunkel (1973). (Auth.)

  7. An Archival Chandra and XMM-Newton Survey of Type 2 Quasars

    Science.gov (United States)

    Jia, Jianjun; Ptak, Andrew Francis; Heckman, Timothy; Zakamska, Nadia L.

    2013-01-01

    In order to investigate obscuration in high-luminosity type 2 active galactic nuclei (AGNs), we analyzed Chandra and XMM-Newton archival observations for 71 type 2 quasars detected at 0.05 100 eV in the rest frame) and we detect this line in the other sources through a joint fit (spectral stacking). The correlation between the Fe K alpha and [O III] fluxes and the inverse correlation of the equivalent width of the Fe Ka line with the ratio of hard X-ray and [O III] fluxes is consistent with previous results for lower luminosity Seyfert 2 galaxies. We conclude that obscuration is the cause of the weak hard X-ray emission rather than intrinsically low X-ray luminosities. We find that about half of the population of optically selected type 2 quasars are likely to be Compton thick. We also find no evidence that the amount of X-ray obscuration depends on the AGN luminosity (over a range of more than three orders of magnitude in luminosity).

  8. Storm in a Teacup: X-Ray View of an Obscured Quasar and Superbubble

    Science.gov (United States)

    Lansbury, George B.; Jarvis, Miranda E.; Harrison, Chris M.; Alexander, David M.; Del Moro, Agnese; Edge, Alastair C.; Mullaney, James R.; Thomson, Alasdair P.

    2018-03-01

    We present the X-ray properties of the “Teacup AGN” (SDSS J1430+1339), a z = 0.085 type 2 quasar that is interacting dramatically with its host galaxy. Spectral modeling of the central quasar reveals a powerful, highly obscured active galactic nucleus (AGN) with a column density of N H = (4.2–6.5) × 1023 cm‑2 and an intrinsic luminosity of L 2–10 keV = (0.8–1.4) × 1044 erg s‑1. The current high bolometric luminosity inferred (L bol ≈1045–1046 erg s‑1) has ramifications for previous interpretations of the Teacup as a fading/dying quasar. High-resolution Chandra imaging data reveal a ≈10 kpc loop of X-ray emission, cospatial with the “eastern bubble” previously identified in luminous radio and ionized gas (e.g., [O III] line) emission. The X-ray emission from this structure is in good agreement with a shocked thermal gas, with T = (4–8) × 106 K, and there is evidence for an additional hot component with T ≳ 3 × 107 K. Although the Teacup is a radiatively dominated AGN, the estimated ratio between the bubble power and the X-ray luminosity is in remarkable agreement with observations of ellipticals, groups, and clusters of galaxies undergoing AGN feedback.

  9. Remarks on the maximum luminosity

    Science.gov (United States)

    Cardoso, Vitor; Ikeda, Taishi; Moore, Christopher J.; Yoo, Chul-Moon

    2018-04-01

    The quest for fundamental limitations on physical processes is old and venerable. Here, we investigate the maximum possible power, or luminosity, that any event can produce. We show, via full nonlinear simulations of Einstein's equations, that there exist initial conditions which give rise to arbitrarily large luminosities. However, the requirement that there is no past horizon in the spacetime seems to limit the luminosity to below the Planck value, LP=c5/G . Numerical relativity simulations of critical collapse yield the largest luminosities observed to date, ≈ 0.2 LP . We also present an analytic solution to the Einstein equations which seems to give an unboundedly large luminosity; this will guide future numerical efforts to investigate super-Planckian luminosities.

  10. Axions and polarisation of quasars

    International Nuclear Information System (INIS)

    Payez, A.; Cudell, J. R.; Hutsemekers, D.

    2008-01-01

    We present results showing that, thanks to axion-photon mixing in external magnetic fields, it is actually possible to produce an effect similar to the one needed to explain the large-scale coherent orientations of quasar polarisation vectors in visible light that have been observed in some regions of the sky

  11. IRAS 10479 - 2808: a quasar

    International Nuclear Information System (INIS)

    Clowes, R.G.; Leggett, S.K.; Savage, A.

    1991-01-01

    The IRAS point source 10479-2808 is a quasar with B J ∼ 16 and z = 0.190. It is not in the Parkes and Molonglo radio catalogues. At the resolution of the UK and ESO Schmidt telescopes it appears to be star-like, with no sign of surrounding fuzz or interactions; it is probably optically variable. (author)

  12. Star Formation Quenching in Quasar Host Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Carniani, Stefano, E-mail: sc888@mrao.cam.ac.uk [Cavendish Laboratory, University of Cambridge, Cambridge (United Kingdom); Kavli Institute for Cosmology, University of Cambridge, Cambridge (United Kingdom)

    2017-10-16

    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{sub ⊙} yr{sup −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.

  13. Star Formation Quenching in Quasar Host Galaxies

    Directory of Open Access Journals (Sweden)

    Stefano Carniani

    2017-10-01

    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.

  14. Star Formation Quenching in Quasar Host Galaxies

    International Nuclear Information System (INIS)

    Carniani, Stefano

    2017-01-01

    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.

  15. NuSTAR observations of heavily obscured quasars at z ∼ 0.5

    Energy Technology Data Exchange (ETDEWEB)

    Lansbury, G. B.; Alexander, D. M.; Moro, A. Del; Gandhi, P.; Aird, J. [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Assef, R. J. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M.; Grefenstette, B. W.; Harrison, F. A. [Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catlica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Christensen, F. E.; Craig, W. W. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Elvis, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hailey, C. J. [Columbia Astrophysics Laboratory, 550 W 120th Street, Columbia University, NY 10027 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Koss, M., E-mail: g.b.lansbury@durham.ac.uk [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); and others

    2014-04-10

    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 diagnostics, their X-ray absorbing column densities (N {sub H}) are poorly known. In this analysis, (1) we study X-ray emission at >10 keV, where X-rays from the central black hole are relatively unabsorbed, in order to better constrain N {sub H}. (2) We further characterize the physical properties of the sources through broad-band near-UV to mid-IR spectral energy distribution analyses. One of the quasars is detected with NuSTAR at >8 keV with a no-source probability of <0.1%, and its X-ray band ratio suggests near Compton-thick absorption with N {sub H} ≳ 5 × 10{sup 23} cm{sup –2}. The other two quasars are undetected, and have low X-ray to mid-IR luminosity ratios in both the low-energy (2-10 keV) and high-energy (10-40 keV) X-ray regimes that are consistent with extreme, Compton-thick absorption (N {sub H} ≳ 10{sup 24} cm{sup –2}). We find that for quasars at z ∼ 0.5, NuSTAR provides a significant improvement compared to lower energy (<10 keV) Chandra and XMM-Newton observations alone, as higher column densities can now be directly constrained.

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

    Science.gov (United States)

    Lansbury, G. B.; Gandhi, P.; Alexander, D. M.; Assef, R. J.; Aird, J.; Annuar, A.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Del Moro, A.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; LaMassa, S. M.; Luo, B.; Puccetti, S.; Stern, D.; Treister, E.; Vignali, C.; Zappacosta, L.; Zhang, W. W.

    2015-08-01

    The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z 1.5 × 1024 cm-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z < 0.5, have observed [O iii] luminosities in the range 8.4\\lt {log}({L}[{{O} {{III}}]}/{L}⊙ )\\lt 9.6, and show evidence for extreme, Compton-thick absorption when indirect absorption diagnostics are considered. Among the nine candidate CTQSO2s, five are detected by NuSTAR in the high-energy (8-24 keV) band: two are weakly detected at the ≈3σ confidence level and three are strongly detected with sufficient counts for spectral modeling (≳90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic active galactic nucleus properties are feasible, and we measure column densities ≈2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ≈10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH 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 fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable.

  17. On The Dark Side of Quasar Evolution

    OpenAIRE

    Menou, Kristen; Haiman, Zoltan

    2004-01-01

    Recent improved determinations of the mass density rho_BH of supermassive black holes (SMBHs) in the local universe have allowed accurate comparisons of rho_BH with the amount of light received from past quasar activity. These comparisons support the notion that local SMBHs are ``dead quasars'' and yield a value epsilon >~ 0.1 for the average radiative efficiency of cosmic SMBH accretion. BH coalescences may represent an important component of the quasar mass assembly and yet not produce any ...

  18. Various Approaches for Targeting Quasar Candidates

    Science.gov (United States)

    Zhang, Y.; Zhao, Y.

    2015-09-01

    With the establishment and development of space-based and ground-based observational facilities, the improvement of scientific output of high-cost facilities is still a hot issue for astronomers. The discovery of new and rare quasars attracts much attention. Different methods to select quasar candidates are in bloom. Among them, some are based on color cuts, some are from multiwavelength data, some rely on variability of quasars, some are based on data mining, and some depend on ensemble methods.

  19. INFRARED SPECTRA AND PHOTOMETRY OF COMPLETE SAMPLES OF PALOMAR-GREEN AND TWO MICRON ALL SKY SURVEY QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yong [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Rieke, G. H.; Su, K. Y. L. [Department of Astronomy And Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ogle, P. M. [Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Balog, Z., E-mail: yshipku@gmail.com [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-10-01

    As a step toward a comprehensive overview of the infrared (IR) diagnostics of the central engines and host galaxies of quasars at low redshift, we present Spitzer Space Telescope spectroscopic (5-40 μm) and photometric (24, 70, and 160 μm) measurements of all Palomar-Green (PG) quasars at z < 0.5 and Two Micron All Sky Survey (2MASS) quasars at z < 0.3. We supplement these data with Herschel measurements at 160 μm. The sample is composed of 87 optically selected PG quasars and 52 near-IR-selected 2MASS quasars. Here we present the data, measure the prominent spectral features, and separate emission due to star formation from that emitted by the dusty circumnuclear torus. We find that the mid-IR (5-30 μm) spectral shape for the torus is largely independent of quasar IR luminosity with scatter in the spectral energy distribution (SED) shape of ≲0.2 dex. Except for the silicate features, no large difference is observed between PG (unobscured—silicate emission) and 2MASS (obscured—silicate absorption) quasars. Only mild silicate features are observed in both cases. When in emission, the peak wavelength of the silicate feature tends to be longer than 9.7 μm, possibly indicating effects on grain properties near the active galactic nucleus. The IR color is shown to correlate with the equivalent width of the aromatic features, indicating that the slope of the quasar mid- to far-IR SED is to first order driven by the fraction of radiation from star formation in the IR bands.

  20. Quasar Photometric Redshifts and Candidate Selection: A New Algorithm Based on Optical and Mid-infrared Photometric Data

    Science.gov (United States)

    Yang, Qian; Wu, Xue-Bing; Fan, Xiaohui; Jiang, Linhua; McGreer, Ian; Green, Richard; Yang, Jinyi; Schindler, Jan-Torge; Wang, Feige; Zuo, Wenwen; Fu, Yuming

    2017-12-01

    We present a new algorithm to estimate quasar photometric redshifts (photo-zs), by considering the asymmetries in the relative flux distributions of quasars. The relative flux models are built with multivariate Skew-t distributions in the multidimensional space of relative fluxes as a function of redshift and magnitude. For 151,392 quasars in the SDSS, we achieve a photo-z accuracy, defined as the fraction of quasars with the difference between the photo-z z p and the spectroscopic redshift z s , | {{Δ }}z| =| {z}s-{z}p| /(1+{z}s) within 0.1, of 74%. Combining the WISE W1 and W2 infrared data with the SDSS data, the photo-z accuracy is enhanced to 87%. Using the Pan-STARRS1 or DECaLS photometry with WISE W1 and W2 data, the photo-z accuracies are 79% and 72%, respectively. The prior probabilities as a function of magnitude for quasars, stars, and galaxies are calculated, respectively, based on (1) the quasar luminosity function, (2) the Milky Way synthetic simulation with the Besançon model, and (3) the Bayesian Galaxy Photometric Redshift estimation. The relative fluxes of stars are obtained with the Padova isochrones, and the relative fluxes of galaxies are modeled through galaxy templates. We test our classification method to select quasars using the DECaLS g, r, z, and WISE W1 and W2 photometry. The quasar selection completeness is higher than 70% for a wide redshift range 0.5publicly available.

  1. Luminosity class of neutron reflectometers

    Energy Technology Data Exchange (ETDEWEB)

    Pleshanov, N.K., E-mail: pnk@pnpi.spb.ru

    2016-10-21

    The formulas that relate neutron fluxes at reflectometers with differing q-resolutions are derived. The reference luminosity is defined as a maximum flux for measurements with a standard resolution. The methods of assessing the reference luminosity of neutron reflectometers are presented for monochromatic and white beams, which are collimated with either double diaphragm or small angle Soller systems. The values of the reference luminosity for unified parameters define luminosity class of reflectometers. The luminosity class characterizes (each operation mode of) the instrument by one number and can be used to classify operating reflectometers and optimize designed reflectometers. As an example the luminosity class of the neutron reflectometer NR-4M (reactor WWR-M, Gatchina) is found for four operation modes: 2.1 (monochromatic non-polarized beam), 1.9 (monochromatic polarized beam), 1.5 (white non-polarized beam), 1.1 (white polarized beam); it is shown that optimization of measurements may increase the flux at the sample up to two orders of magnitude with monochromatic beams and up to one order of magnitude with white beams. A fan beam reflectometry scheme with monochromatic neutrons is suggested, and the expected increase in luminosity is evaluated. A tuned-phase chopper with a variable TOF resolution is recommended for reflectometry with white beams.

  2. A QUASAR CATALOG WITH SIMULTANEOUS UV, OPTICAL, AND X-RAY OBSERVATIONS BY SWIFT

    International Nuclear Information System (INIS)

    Wu Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Porterfield, Blair L.; Vanden Berk, Daniel; Wesolowski, Sarah

    2012-01-01

    We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ∼60% which rises to ∼85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about ∼0.3 dex to the quasar luminosity. We re-visit the α ox -L 2500Å relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L bol /L Edd and α UV . We do not find significant correlations between α x and α ox , α ox and α UV , and α x and log L(0.3-10 keV). The correlations between α UV and α x , α ox and α x , α ox and α UV , L bol /L Edd and α x , and L bol /L Edd and α ox are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

  3. 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

    2007-04-01

    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.

  4. A Hubble Space Telescope imaging study of four FeLoBAL quasar host galaxies

    Science.gov (United States)

    Lawther, D.; Vestergaard, M.; Fan, X.

    2018-04-01

    We study the host galaxies of four Iron Low-Ionization Broad Absorption-line Quasars (FeLoBALs), using Hubble Space Telescope imaging data, investigating the possibility that they represent a transition between an obscured active galactic nucleus (AGN) and an ordinary optical quasar. In this scenario, the FeLoBALs represent the early stage of merger-triggered accretion, in which case their host galaxies are expected to show signs of an ongoing or recent merger. Using PSF subtraction techniques, we decompose the images into host galaxy and AGN components at rest-frame ultraviolet and optical wavelengths. The ultraviolet is sensitive to young stars, while the optical probes stellar mass. In the ultraviolet we image at the BAL absorption trough wavelengths so as to decrease the contrast between the quasar and host galaxy emission. We securely detect an extended source for two of the four FeLoBALs in the rest-frame optical; a third host galaxy is marginally detected. In the rest-frame UV we detect no host emission; this constrains the level of unobscured star formation. Thus, the host galaxies have observed properties that are consistent with those of non-BAL quasars with the same nuclear luminosity, i.e. quiescent or moderately star-forming elliptical galaxies. However, we cannot exclude starbursting hosts that have the stellar UV emission obscured by modest amounts of dust reddening. Thus, our findings also allow the merger-induced young quasar scenario. For three objects, we identify possible close companion galaxies that may be gravitationally interacting with the quasar hosts.

  5. Is 1146+111B, C a lensed quasar or a quasar pair

    International Nuclear Information System (INIS)

    Huchra, J.P.

    1986-01-01

    It has been speculated that the quasar pair 1146+B, C are two bright images of a single quasar produced by a gravitational lens. The author reports additional observations of these objects, made with an ultraviolet-sensitive spectrograph on the Multiple Mirror Telescope. The ultraviolet spectra of the two quasars are different. There are also different velocity shifts between the quasars as measured by the C III] and Mg II lines. Although it is impossible to rule out the lensing hypothesis, these observations increase the probability that these objects are just two quasars at nearly the same redshift. (author)

  6. The Physical Relation between Disc and Coronal Emission in Quasars

    Directory of Open Access Journals (Sweden)

    Elisabeta Lusso

    2018-01-01

    Full Text Available We propose a modified version of the observed non-linear relation between the X-ray (2 keV and the ultraviolet (2,500 Å emission in quasars (i.e., LX∝LUVγ which involves the full width at half-maximum, FWHM, of the broad emission line, i.e., LX∝LUVγ^ FWHMβ^. By analyzing a sample of 550 optically selected non-jetted quasars in the redshift range of 0.36–2.23 from the Sloan Digital Sky Survey cross matched with the XMM-Newton catalog 3XMM-DR6, we found that the additional dependence of the observed LX − LUV correlation on the FWHM of the Mgii broad emission line is statistically significant. Our statistical analysis leads to a much tighter relation with respect to the one neglecting FWHM, and it does not evolve with redshift. We interpret this new relation within an accretion disc corona scenario where reconnection and magnetic loops above the accretion disc can account for the production of the primary X-ray radiation. For a broad line region size depending on the disc luminosity as Rblr∝Ldisc0.5, we find that LX∝LUV4/7 FWHM4/7, which is in very good agreement with the observed correlation.

  7. Quasar Massive Ionized Outflows Traced by CIV λ1549 and [OIII]λλ4959,5007

    Energy Technology Data Exchange (ETDEWEB)

    Marziani, Paola [National Institute for Astrophysics, Osservatorio Astronomico di Padova, Rome (Italy); Negrete, C. Alenka; Dultzin, Deborah [Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Mexico City (Mexico); Martínez-Aldama, Mary L.; Del Olmo, Ascensión [Instituto de Astrofísica de Andalucía (CSIC), Granada (Spain); D' Onofrio, Mauro [Dipartimento di Fisica e Astronomia, Università di Padova, Padova (Italy); Stirpe, Giovanna M., E-mail: paola.marziani@oapd.inaf.it [Osservatorio Astronomico di Bologna (INAF), Bologna (Italy)

    2017-09-27

    The most luminous quasars (with bolometric luminosities are ≳ 10{sup 47} 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.

  8. Quasar Massive Ionized Outflows Traced by CIV λ1549 and [OIII]λλ4959,5007

    Directory of Open Access Journals (Sweden)

    Paola Marziani

    2017-09-01

    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.

  9. Luminosity lifetime in the Tevatron

    International Nuclear Information System (INIS)

    Jackson, G.; Finley, D.; Johnson, R.P.; Kerns, Q.; McCarthy, J.; Siemann, R.; Zhang, P.

    1988-01-01

    Since the inauguration of colliding proton-antiproton operations in 1987, the Tevatron has exhibited luminosity lifetimes shorter than expected. During a typical colliding beam storage period, called a store, luminosity is calculated periodically by measuring the charge and emittances of each bunch. The growth of the transverse bunch emittances is the dominant cause of luminosity deterioration. Throughout, this period, the position spectrum of the bunches exhibited betatron signals larger than expected from Schottky noise. A model assuming externally driven betatron oscillations explains both the betatron signals and the emittance growth. A program is underway to improve the Tevatron luminosity lifetime. The abort kickers have been identified as sources of emittance growth, and some quadrupole power supplies are further candidates. Because the horizontal dispersion through the RF cavities is nonzero, RF phase noise has been investigated. Noise in the main dipole regulation circuit has also been studied. 13 refs., 4 figs

  10. LHC luminosity upgrade detector challenges

    CERN Multimedia

    CERN. Geneva; de Roeck, Albert; Bortoletto, Daniela; Wigmans, Richard; Riegler, Werner; Smith, Wesley H

    2006-01-01

    LHC luminosity upgrade: detector challenges The upgrade of the LHC machine towards higher luminosity (1035 cm -2s-1) has been studied over the last few years. These studies have investigated scenarios to achieve the increase in peak luminosity by an order of magnitude, as well as the physics potential of such an upgrade and the impact of a machine upgrade on the LHC DETECTORS. This series of lectures will cover the following topics: • Physics motivation and machine scenarios for an order of magnitude increase in the LHC peak luminosity (lecture 1) • Detector challenges including overview of ideas for R&D programs by the LHC experiments: tracking and calorimetry, other new detector developments (lectures 2-4) • Electronics, trigger and data acquisition challenges (lecture 5) Note: the much more ambitious LHC energy upgrade will not be covered

  11. High Luminosity LHC Project Description

    CERN Document Server

    Apollinari, Giorgio; Rossi, Lucio

    2014-01-01

    The High Luminosity LHC (HL-LHC) is a novel configuration of the Large Hadron Collider, aiming at increasing the luminosity by a factor five or more above the nominal LHC design, to allow increasing the integrated luminosity, in the high luminosity experiments ATLAS and CMS, from the 300 fb-1 of the LHC original design up to 3000 fb-1 or more. This paper contains a short description of the main machine parameters and of the main equipment that need to be developed and installed. The preliminary cost evaluation and the time plan are presented, too. Finally, the international collaboration that is supporting the project, the governance and the project structure are discussed, too.

  12. DETERMINING QUASAR BLACK HOLE MASS FUNCTIONS FROM THEIR BROAD EMISSION LINES: APPLICATION TO THE BRIGHT QUASAR SURVEY

    International Nuclear Information System (INIS)

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

    2009-01-01

    We describe a Bayesian approach to estimating quasar black hole mass functions (BHMF) using the broad emission lines to estimate black hole mass. We show how using the broad-line mass estimates in combination with statistical techniques developed for luminosity function estimation (e.g., the 1/V a correction) leads to statistically biased results. We derive the likelihood function for the BHMF based on the broad-line mass estimates, and derive the posterior distribution for the BHMF, given the observed data. We develop our statistical approach for a flexible model where the BHMF is modeled as a mixture of Gaussian functions. Statistical inference is performed using Markov chain Monte Carlo (MCMC) methods, and we describe a Metropolis-Hastings algorithm to perform the MCMC. The MCMC simulates random draws from the probability distribution of the BHMF parameters, given the data, and we use a simulated data set to show how these random draws may be used to estimate the probability distribution for the BHMF. In addition, we show how the MCMC output may be used to estimate the probability distribution of any quantities derived from the BHMF, such as the peak in the space density of quasars. Our method has the advantage that it is able to constrain the BHMF even beyond the survey detection limits at the adopted confidence level, accounts for measurement errors and the intrinsic uncertainty in broad-line mass estimates, and provides a natural way of estimating the probability distribution of any quantities derived from the BHMF. We conclude by using our method to estimate the local active BHMF using the z BH ∼> 10 8 M sun . Our analysis implies that at a given M BH , z < 0.5 broad-line quasars have a typical Eddington ratio of ∼0.4 and a dispersion in Eddington ratio of ∼<0.5 dex.

  13. Weak hard X-ray emission from broad absorption line quasars: evidence for intrinsic X-ray weakness

    International Nuclear Information System (INIS)

    Luo, B.; Brandt, W. N.; Scott, A. E.; Alexander, D. M.; Gandhi, P.; Stern, D.; Teng, S. H.; Arévalo, P.; Bauer, F. E.; Boggs, S. E.; Craig, W. W.; Christensen, F. E.; Comastri, A.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Koss, M.; Ogle, P.; Puccetti, S.; Saez, C.

    2014-01-01

    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 < 1.3. However, their rest-frame ≈2 keV luminosities are 14 to >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 are not detected. The hard X-ray (8-24 keV) weakness observed by NuSTAR requires Compton-thick absorption if these objects have nominal underlying X-ray emission. However, a soft stacked effective photon index (Γ eff ≈ 1.8) for this sample disfavors Compton-thick absorption in general. The uniform hard X-ray weakness observed by NuSTAR for this and the pilot samples selected with <10 keV weakness also suggests that the X-ray weakness is intrinsic in at least some of the targets. We conclude that the NuSTAR observations have likely discovered a significant population (≳ 33%) of intrinsically X-ray weak objects among the BAL quasars with significantly weak <10 keV emission. We suggest that intrinsically X-ray weak quasars might be preferentially observed as BAL quasars.

  14. The MEXSAS2 Sample and the Ensemble X-ray Variability of Quasars

    Energy Technology Data Exchange (ETDEWEB)

    Serafinelli, Roberto [Dipartimento di Fisica, Università di Roma Tor Vergata, Rome (Italy); Dipartimento di Fisica, Università di Roma Sapienza, Rome (Italy); Vagnetti, Fausto; Chiaraluce, Elia [Dipartimento di Fisica, Università di Roma Tor Vergata, Rome (Italy); Middei, Riccardo, E-mail: roberto.serafinelli@roma2.infn.it [Dipartimento di Matematica e Fisica, Università Roma Tre, Rome (Italy)

    2017-10-11

    We present the second Multi-Epoch X-ray Serendipitous AGN Sample (MEXSAS2), extracted from the 6th release of the XMM Serendipitous Source Catalog (XMMSSC-DR6), cross-matched with Sloan Digital Sky Survey quasar Catalogs DR7Q and DR12Q. Our sample also includes the available measurements for masses, bolometric luminosities, and Eddington ratios. Analyses of the ensemble structure function and spectral variability are presented, together with their dependences on such parameters. We confirm a decrease of the structure function with the X-ray luminosity, and find a weak dependence on the black hole mass. We introduce a new spectral variability estimator, taking errors on both fluxes and spectral indices into account. We confirm an ensemble softer when brighter trend, with no dependence of such estimator on black hole mass, Eddington ratio, redshift, X-ray and bolometric luminosity.

  15. The MEXSAS2 Sample and the Ensemble X-ray Variability of Quasars

    Directory of Open Access Journals (Sweden)

    Roberto Serafinelli

    2017-10-01

    Full Text Available We present the second Multi-Epoch X-ray Serendipitous AGN Sample (MEXSAS2, extracted from the 6th release of the XMM Serendipitous Source Catalog (XMMSSC-DR6, cross-matched with Sloan Digital Sky Survey quasar Catalogs DR7Q and DR12Q. Our sample also includes the available measurements for masses, bolometric luminosities, and Eddington ratios. Analyses of the ensemble structure function and spectral variability are presented, together with their dependences on such parameters. We confirm a decrease of the structure function with the X-ray luminosity, and find a weak dependence on the black hole mass. We introduce a new spectral variability estimator, taking errors on both fluxes and spectral indices into account. We confirm an ensemble softer when brighter trend, with no dependence of such estimator on black hole mass, Eddington ratio, redshift, X-ray and bolometric luminosity.

  16. Fast luminosity monitor at LEP

    International Nuclear Information System (INIS)

    Bini, C.; De Pedis, D.; De Zorzi, G.; Diambrini-Palazzi, G.; Di Cosimo, G.; Di Domenico, A.; Gauzzi, P.; Zanello, D.

    1994-01-01

    In 1990 the LEP-5 experiment measured luminosity at LEP by detecting the single bremsstrahlung photons emitted in the e + e - collisions. In 1991 the experiment was upgraded to exploit the intrinsic high speed of the method which allows luminosity measurement of the single bunches of LEP. In this paper the LEP-5 upgrade is described and the results of a test performed are discussed. ((orig.))

  17. A Full Year's Chandra Exposure on Sloan Digital Sky Survey Quasars from the Chandra Multiwavelength Project

    Science.gov (United States)

    Green, Paul J.; Aldcroft, T. L.; Richards, G. T.; Barkhouse, W. A.; Constantin, A.; Haggard, D.; Karovska, M.; Kim, D.-W.; Kim, M.; Vikhlinin, A.; Anderson, S. F.; Mossman, A.; Kashyap, V.; Myers, A. D.; Silverman, J. D.; Wilkes, B. J.; Tananbaum, H.

    2009-01-01

    We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2 3, substantially expanding the known sample. We find no evidence for evolution out to z ~ 5 for either the X-ray photon index Γ or for the ratio of optical/UV to X-ray flux αox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022 cm-2, but the fraction might reach ~1/3 if most nondetections are absorbed. We confirm a significant correlation between αox and optical luminosity, but it flattens or disappears for fainter (MB gsim -23) active galactic nucleus (AGN) alone. We report significant hardening of Γ both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, we find no evidence for unusual distributions of either αox or Γ.

  18. The High Luminosity LHC Project

    Science.gov (United States)

    Rossi, Lucio

    The High Luminosity LHC is one of the major scientific project of the next decade. It aims at increasing the luminosity reach of LHC by a factor five for peak luminosity and a factor ten in integrated luminosity. The project, now fully approved and funded, will be finished in ten years and will prolong the life of LHC until 2035-2040. It implies deep modifications of the LHC for about 1.2 km around the high luminosity insertions of ATLAS and CMS and relies on new cutting edge technologies. We are developing new advanced superconducting magnets capable of reaching 12 T field; superconducting RF crab cavities capable to rotate the beams with great accuracy; 100 kA and hundred meter long superconducting links for removing the power converter out of the tunnel; new collimator concepts, etc... Beside the important physics goals, the High Luminosity LHC project is an ideal test bed for new technologies for the next hadron collider for the post-LHC era.

  19. MILLIMETER OBSERVATIONS OF A SAMPLE OF HIGH-REDSHIFT OBSCURED QUASARS

    International Nuclear Information System (INIS)

    Martinez-Sansigre, Alejo; Karim, Alexander; Schinnerer, Eva

    2009-01-01

    We present observations at 1.2 mm with Max-Planck Millimetre Bolometer Array (MAMBO-II) of a sample of z ∼> 2 radio-intermediate obscured quasars, as well as CO observations of two sources with the Plateau de Bure Interferometer. The typical rms noise achieved by the MAMBO observations is 0.55 mJy beam -1 and five out of 21 sources (24%) are detected at a significance of ≥3σ. Stacking all sources leads to a statistical detection of (S 1.2mm ) = 0.96 ± 0.11 mJy and stacking only the non-detections also yields a statistical detection, with (S 1.2mm ) = 0.51 ± 0.13 mJy. At the typical redshift of the sample, z = 2, 1 mJy corresponds to a far-infrared luminosity L FIR ∼4 x 10 12 L sun . If the far-infrared luminosity is powered entirely by star formation, and not by active galactic nucleus heated dust, then the characteristic inferred star formation rate is ∼700 M sun yr -1 . This far-infrared luminosity implies a dust mass of M d ∼3 x 10 8 M sun , which is expected to be distributed on ∼kpc scales. We estimate that such large dust masses on kpc scales can plausibly cause the obscuration of the quasars. Combining our observations at 1.2 mm with mid- and far-infrared data, and additional observations for two objects at 350 μm using SHARC-II, we present dust spectral energy distributions (SEDs) for our sample and derive a mean SED for our sample. This mean SED is not well fitted by clumpy torus models, unless additional extinction and far-infrared re-emission due to cool dust are included. This additional extinction can be consistently achieved by the mass of cool dust responsible for the far-infrared emission, provided the bulk of the dust is within a radius ∼2-3 kpc. Comparison of our sample to other samples of z ∼ 2 quasars suggests that obscured quasars have, on average, higher far-infrared luminosities than unobscured quasars. There is a hint that the host galaxies of obscured quasars must have higher cool-dust masses and are therefore often

  20. Chandra X-Rays from the Redshift 7.54 Quasar ULAS J1342+0928

    Science.gov (United States)

    Bañados, Eduardo; Connor, Thomas; Stern, Daniel; Mulchaey, John; Fan, Xiaohui; Decarli, Roberto; Farina, Emanuele P.; Mazzucchelli, Chiara; Venemans, Bram P.; Walter, Fabian; Wang, Feige; Yang, Jinyi

    2018-04-01

    We present a 45 ks Chandra observation of the quasar ULAS J1342+0928 at z = 7.54. We detect {14.0}-3.7+4.8 counts from the quasar in the observed-frame energy range 0.5–7.0 keV (6σ detection), representing the most distant non-transient astronomical source identified in X-rays to date. The present data are sufficient only to infer rough constraints on the spectral parameters. We find an X-ray hardness ratio of { \\mathcal H }{ \\mathcal R }=-{0.51}-0.28+0.26 between the 0.5–2.0 keV and 2.0–7.0 keV ranges and derive a power-law photon index of {{Γ }}={1.95}-0.53+0.55. Assuming a typical value for high-redshift quasars of Γ = 1.9, ULAS J1342+0928 has a 2–10 keV rest-frame X-ray luminosity of {L}2-10={11.6}-3.5+4.3× {10}44 {erg} {{{s}}}-1. Its X-ray-to-optical power-law slope is {α }OX}=-{1.67}-0.10+0.16, consistent with the general trend indicating that the X-ray emission in the most bolometrically powerful quasars is weaker relative to their optical emission.

  1. Quasars: Active nuclei of young galaxies

    Science.gov (United States)

    Komberg, B. V.

    1980-01-01

    The hypothetical properties of 'young' galaxies and possible methods of observing them are discussed. It is proposed that star formation first takes place in the central regions of protogalaxies which may appear as quasar-like objects. An evolutionary scheme is outlined in which the radio quasars are transformed in time into the nuclei of radio galaxies.

  2. Galaxies at z ~ 6: The UV Luminosity Function and Luminosity Density from 506 HUDF, HUDF Parallel ACS Field, and GOODS i-Dropouts

    Science.gov (United States)

    Bouwens, R. J.; Illingworth, G. D.; Blakeslee, J. P.; Franx, M.

    2006-12-01

    We have detected 506 i-dropouts (z~6 galaxies) in deep, wide-area HST ACS fields: HUDF, enhanced GOODS, and HUDF parallel ACS fields (HUDF-Ps). The contamination levels are ~92% are at z~6). With these samples, we present the most comprehensive, quantitative analyses of z~6 galaxies yet and provide optimal measures of the UV luminosity function (LF) and luminosity density at z~6, and their evolution to z~3. We redetermine the size and color evolution from z~6 to z~3. Field-to-field variations (cosmic variance), completeness, flux, and contamination corrections are modeled systematically and quantitatively. After corrections, we derive a rest-frame continuum UV (~1350 Å) LF at z~6 that extends to M1350,AB~-17.5 (0.04L*z=3). There is strong evidence for evolution of the LF between z~6 and z~3, most likely through a brightening (0.6+/-0.2 mag) of M* (at 99.7% confidence), although the degree depends on the faint-end slope. As expected from hierarchical models, the most luminous galaxies are deficient at z~6. Density evolution (φ*) is ruled out at >99.99% confidence. Despite large changes in the LF, the luminosity density at z~6 is similar to (0.82+/-0.21 times) that at z~3. Changes in the mean UV color of galaxies from z~6 to z~3 suggest an evolution in dust content, indicating that the true evolution is substantially larger: at z~6 the star formation rate density is just ~30% of the z~3 value. Our UV LF is consistent with z~6 galaxies providing the necessary UV flux to reionize the universe. Based on observations made with the NASA/ESA Hubble Space Telescope, 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 9803. Observations have been carried out using the Very Large Telescope at the European Southern Observatory (ESO) Paranal Observatory, under program ID LP168.A-0485.

  3. Phylogenetic Analyses of Quasars and Galaxies

    Science.gov (United States)

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

    2017-10-01

    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 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 1500 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.

  4. 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.

    2010-04-01

    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.

  5. Effects of Galaxy collisions on the structure and evolution of Galaxy clusters. I. Mass and luminosity functions and background light

    International Nuclear Information System (INIS)

    Miller, G.E.; Department of Astronomy, University of Texas at Austin)

    1983-01-01

    The role of galaxy collisions in controlling the form of the galaxy mass and luminosity functions and in creating a diffuse background light is investigated by means of a direct computer simulation. Galaxy collisions are treated in a realistic manner, including both galaxy mergers and tidal encounters. A large number of theoretical studies of a galaxy collisions were consulted to formulate the basic input physics of collision cross sections. Despite this large number of studies, there remains considerable uncertainty in the effects of a collision on a galaxy due mainly to our lack of knowledge of the orbital distribution of matter in galaxies. To improve this situation, some methods of semiempirical calibration are suggested: for example, a survey of background light in clusters of different richness and morphological classes. If real galaxies are represented by galaxy models where the bulk of the matter is on radial, rather than circular, orbits, then tidal collisions are more damaging and there are a number of interesting effects: Repeated tidal encounters lead to galaxy mass and luminosity functions which are largely independent of model parameters and the initial galaxy mass function. It appears unlikely that the form of the average present-day luminosity function characteristic of both field and cluster galaxies is due to collisions, but certain observed deviations from the average found by Heiligman and Turner and by Dressler may be a signature of collisions, in particular a flat faint-end slope. The amount of luminous matter stripped from the galaxies in the simulations agrees with the amount of diffuse background light seen in the Coma Cluster

  6. Galaxy evolution. Black hole feedback in the luminous quasar PDS 456.

    Science.gov (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

    2015-02-20

    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.

  7. The Clustering of High-redshift (2.9 ≤ z ≤ 5.1) Quasars in SDSS Stripe 82

    Science.gov (United States)

    Timlin, John D.; Ross, Nicholas P.; Richards, Gordon T.; Myers, Adam D.; Pellegrino, Andrew; Bauer, Franz E.; Lacy, Mark; Schneider, Donald P.; Wollack, Edward J.; Zakamska, Nadia L.

    2018-05-01

    We present a measurement of the two-point autocorrelation function of photometrically selected high-z quasars over ∼100 deg2 on the Sloan Digital Sky Survey Stripe 82 field. Selection is performed using three machine-learning algorithms in a six-dimensional optical/mid-infrared color space. Optical data from the Sloan Digital Sky Survey are combined with overlapping deep mid-infrared data from the Spitzer IRAC Equatorial Survey and the Spitzer-HETDEX Exploratory Large-Area survey. Our selection algorithms are trained on the colors of known high-z quasars. The selected quasar sample consists of 1378 objects and contains both spectroscopically confirmed quasars and photometrically selected quasar candidates. These objects span a redshift range of 2.9 ≤ z ≤ 5.1 and are generally fainter than i = 20.2, a regime that has lacked sufficient number density to perform autocorrelation function measurements of photometrically classified quasars. We compute the angular correlation function of these data, marginally detecting quasar clustering. We fit a single power law with an index of δ = 1.39 ± 0.618 and amplitude of θ 0 = 0.‧71 ± 0.‧546 . A dark matter model is fit to the angular correlation function to estimate the linear bias. At the average redshift of our survey ( =3.38), the bias is b = 6.78 ± 1.79. Using this bias, we calculate a characteristic dark matter halo mass of 1.70–9.83× {10}12{h}-1 {M}ȯ . Our bias estimate suggests that quasar feedback intermittently shuts down the accretion of gas onto the central supermassive black hole at early times. If confirmed, these results hint at a level of luminosity dependence in the clustering of quasars at high-z.

  8. THE WYOMING SURVEY FOR Hα. II. Hα LUMINOSITY FUNCTIONS AT z∼ 0.16, 0.24, 0.32, AND 0.40

    International Nuclear Information System (INIS)

    Dale, Daniel A.; Cook, David O.; Moore, Carolynn A.; Staudaher, Shawn M.; Barlow, Rebecca J.; Cohen, Seth A.; Johnson, L. Clifton; Kattner, ShiAnne M.; Schuster, Micah D.

    2010-01-01

    The Wyoming Survey for Hα, or WySH, is a large-area, ground-based imaging survey for Hα-emitting galaxies at redshifts of z ∼ 0.16, 0.24, 0.32, and 0.40. The survey spans up to 4 deg 2 in a set of fields of low Galactic cirrus emission, using twin narrowband filters at each epoch for improved stellar continuum subtraction. Hα luminosity functions are presented for each Δz ∼ 0.02 epoch based on a total of nearly 1200 galaxies. These data clearly show an evolution with look-back time in the volume-averaged cosmic star formation rate. Integrals of Schechter fits to the incompleteness- and extinction-corrected Hα luminosity functions indicate star formation rates per comoving volume of 0.010, 0.013, 0.020, 0.022 h 70 M sun yr -1 Mpc -3 at z ∼ 0.16, 0.24, 0.32, and 0.40, respectively. Combined statistical and systematic measurement uncertainties are on the order of 25%, while the effects of cosmic variance are at the 20% level. The bulk of this evolution is driven by changes in the characteristic luminosity L * of the Hα luminosity functions, with L * for the earlier two epochs being a factor of 2 larger than L * at the latter two epochs; it is more difficult with this data set to decipher systematic evolutionary differences in the luminosity function amplitude and faint-end slope. Coupling these results with a comprehensive compilation of results from the literature on emission line surveys, the evolution in the cosmic star formation rate density over 0 ∼< z ∼< 1.5 is measured.

  9. Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization

    Science.gov (United States)

    Ishigaki, Masafumi; Kawamata, Ryota; Ouchi, Masami; Oguri, Masamune; Shimasaku, Kazuhiro; Ono, Yoshiaki

    2018-02-01

    We present UV luminosity functions of dropout galaxies at z∼ 6{--}10 with the complete Hubble Frontier Fields data. We obtain a catalog of ∼450 dropout-galaxy candidates (350, 66, and 40 at z∼ 6{--}7, 8, and 9, respectively), with UV absolute magnitudes that reach ∼ -14 mag, ∼2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at z∼ 6{--}8 have steep faint-end slopes, α ∼ -2, and likely steeper slopes, α ≲ -2 at z∼ 9{--}10. We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond z∼ 8 in the case of {M}trunc}=-15, but an accelerated one in the case of {M}trunc}=-17. We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction Q H II at z≲ 7 based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of {f}esc}={0.17}-0.03+0.07 and {M}trunc}> -14.0 for {log}{ξ }ion}/[{erg}}-1 {Hz}]=25.34, where {f}esc} is the escape fraction, M trunc is the faint limit of the UV luminosity function, and {ξ }ion} is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be {{Δ }}z={3.9}-1.6+2.0 (for 0.1< {Q}{{H}{{II}}}< 0.99), consistent with the recent estimate from Planck.

  10. Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yan-Fei [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Green, Paul J.; Pancoast, Anna; MacLeod, Chelsea L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Morganson, Eric; Shen, Yue [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Grier, C. J. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Rix, H.-W. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Protopapas, Pavlos [Institute for Applied Computational Science, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 (United States); Scott, Caroline [Astrophysics, Imperial College London, Blackett Laboratory, London SW7 2AZ (United Kingdom); Burgett, W. S.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States); and others

    2017-02-20

    We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band ( g , r , i , z ) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN , we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g − r to g − i and then to g − z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.

  11. Phylogenetic Analyses of Quasars and Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Fraix-Burnet, Didier [University Grenoble Alpes, CNRS, IPAG, Grenoble (France); D' Onofrio, Mauro [Osservatorio Astronomico di Padova (INAF), Padua (Italy); Marziani, Paola, E-mail: didier.fraix-burnet@univ-grenoble-alpes.fr [Dipartimento di Fisica e Astronomia, Università di Padova, Padua (Italy)

    2017-10-10

    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.

  12. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    Science.gov (United States)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  13. The FIRST-2MASS Red Quasar Survey

    International Nuclear Information System (INIS)

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

    2007-01-01

    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 ∼ 50% success rate for discovering quasars substantially redder than those found in optical surveys. Comparison with UVX- and optical color-selected samples shows that ∼> 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%

  14. Phylogenetic Analyses of Quasars and Galaxies

    International Nuclear Information System (INIS)

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

    2017-01-01

    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.

  15. LUCID: The ATLAS Luminosity Detector

    CERN Document Server

    Cabras, Grazia; The ATLAS collaboration

    2018-01-01

    After the long shut-down, the LHC Run2 has started with new running conditions with respect to Run1: in particular the centre of mass energy has reached 13 TeV and the bunch-spacing is now 25 ns. In order to cope with these changes, the ATLAS luminosity monitor LUCID and its electronics have been completely rebuilt. This note describes the new detector and electronics, the new luminosity algorithms and the new calibration systems, with a brief review of the first results about the stability of the measurement and evaluation of systematic uncertainties for the 2015 data-taking.

  16. LUCID: the ATLAS Luminosity Detector

    CERN Document Server

    Fabbri, Laura; The ATLAS collaboration

    2018-01-01

    A precise measurement of luminosity is a key component of the ATLAS program: its uncertainty is a systematics for all cross-section measurements, from Standard Model processes to new discoveries, and for some precise measurements it can be dominant. To be predictive a precision compatible with PDF uncertainty ( 1-2%) is desired. LUCID (LUminosity Cherenkov Integrating Detector) is sensitive to charged particles generated by the pp collisions. It is the only ATLAS dedicated detector for this purpose and the referred one during the second run of LHC data taking.

  17. Radio and optical studies of high luminosity Iras galaxies

    International Nuclear Information System (INIS)

    Wolstencroft, R.D.; Parker, Q.A.; Savage, A.; MacGillivray, H.T.; Leggett, S.K.; Clowes, R.G.; Unger, S.W.; Pedlar, A.; Heasley, J.N.; Menzies, J.W.

    1987-01-01

    Follow-up observations of a complete sample of 154 IRAS galaxies, optically identified down to B=21, indicate that between 3 and 9% of the sample are ultraluminous depending on the choice of H 0 . VLA observations at 20 cm of the complete sample indicate that 85% are detected above 1mJy and for the most part the radio emission is centrally concentrated. The tight linear relation between radio and infrared luminosities is valid at the highest luminosities. Of the 11 most luminous objects one is a quasar: it fits the radio infrared relation very well which suggests that the infrared and radio emission has the same origin as in the other IRAS galaxies, ie. it probably originates primarily in regions of star formation in the host galaxy. The other 10 very luminous galaxies are either close but resolved mergers or double galaxies, presumably interacting. Radio observations of the 10 original empty field sources in our sample with no optical counterpart (B ≤ 21) allow us to conclude that 4 of these are fainter galaxies just outside the IRAS error ellipse with high values of L IR /L B . One other object, with a radio source at the edge of the error ellipse but no optical counterpart brighter than B = 23, may prove to be a highly luminous galaxy with L IR /L B > ∼ 1250

  18. 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.,

    2005-03-01

    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.

  19. DETECTING RELATIVISTIC X-RAY JETS IN HIGH-REDSHIFT QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    McKeough, Kathryn [Department of Statistics, Harvard University, Cambridge, MA 02138 (United States); Siemiginowska, Aneta; Kashyap, Vinay L.; Lee, N. P.; Harris, D. E.; Schwartz, D. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Stawarz, Łukasz [Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244, Kraków (Poland); Stein, Nathan [Department of Statistics, The Wharton School, University of Pennsylvania, 400 Jon M. Huntsman Hall, 3730 Walnut Street, Philadelphia, PA 19104-6340 (United States); Stampoulis, Vasileios; Dyk, David A. van [Statistics Section, Imperial College London, Huxley Building, South Kensington Campus, London SW7 (United Kingdom); Wardle, J. F. C. [Department of Physics, MS 057, Brandeis University, Waltham, MA 02454 (United States); Donato, Davide [CRESST and Astroparticle Physics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States); Maraschi, Laura; Tavecchio, Fabrizio, E-mail: kathrynmckeough@g.harvard.edu [INAF Osservatorio Astronomico di Brera, via Brera 28, I-20124, Milano (Italy)

    2016-12-10

    We analyze Chandra X-ray images of a sample of 11 quasars that are known to contain kiloparsec scale radio jets. The sample consists of five high-redshift ( z  ≥ 3.6) flat-spectrum radio quasars, and six intermediate redshift (2.1 <  z  < 2.9) quasars. The data set includes four sources with integrated steep radio spectra and seven with flat radio spectra. A total of 25 radio jet features are present in this sample. We apply a Bayesian multi-scale image reconstruction method to detect and measure the X-ray emission from the jets. We compute deviations from a baseline model that does not include the jet, and compare observed X-ray images with those computed with simulated images where no jet features exist. This allows us to compute p -value upper bounds on the significance that an X-ray jet is detected in a pre-determined region of interest. We detected 12 of the features unambiguously, and an additional six marginally. We also find residual emission in the cores of three quasars and in the background of one quasar that suggest the existence of unresolved X-ray jets. The dependence of the X-ray to radio luminosity ratio on redshift is a potential diagnostic of the emission mechanism, since the inverse Compton scattering of cosmic microwave background photons (IC/CMB) is thought to be redshift dependent, whereas in synchrotron models no clear redshift dependence is expected. We find that the high-redshift jets have X-ray to radio flux ratios that are marginally inconsistent with those from lower redshifts, suggesting that either the X-ray emissions are due to the IC/CMB rather than the synchrotron process, or that high-redshift jets are qualitatively different.

  20. On the Gas Content and Efficiency of AGN Feedback in Low-redshift Quasars

    Science.gov (United States)

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

    2018-02-01

    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 2MASS, WISE, and Herschel, combined with Spitzer mid-infrared (5–40 μm) spectra. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. This procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. Most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive 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.

  1. Peering Through the Dust: NuSTAR Observations of Two First-2Mass Red Quasars

    Science.gov (United States)

    Lamassa, Stephanie M.; Ricarte, Angelo; Glikman, Eilat; Urry, C. Megan; Stern, Daniel; Yaqoob, Tahir; Lansbury, George B.; Civano, Francesca; Boggs, Steve E.; Zhang, Will

    2016-01-01

    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 NuSTAR and XMM-Newton/Chandra observations of FIRST-2MASS-selected red quasars F2M 0830+3759 and F2M 1227+3214. We find that though F2M 0830 +3759 is moderately obscured N(sub H) = (2.1 +/- 0.2) x 10 (exp 22) per square centimeter) and F2M 1227+3214 is mildly absorbed (N(sub H),Z =3.4(+0.8/-0.7) X 10(exp -2) along the line of sight, heavier global obscuration may be present in both sources, with N(sub H) = 3.7 (+4.1/-2.6) X 10 (exp 23) per square centimeter) and less than 5.5 X 10(exp 23) per square centimeter) for F2M 0830+3759 and F2M 1227+ 3214, respectively. F2M 0830+3759 also has an excess of soft X-ray emission below 1 of dust and gas. Hard X-ray observations are able to peer through this gas and dust, revealing the properties of circumnuclear obscuration. Here, we present keV, which is well accommodated by a model where 7% of the intrinsic X-ray emission from the active galactic nucleus (AGN) is scattered into the line of sight. While F2M 1227+3214 has a dust-to-gas ratio (E(B - V)/NH) consistent with the Galactic value, the value of E(B - V)/NH for F2M 0830+3759 is lower than the Galactic standard, consistent with the paradigm that the dust resides on galactic scales while the X-ray reprocessing gas originates within the dust sublimation zone of the broad-line region. The X-ray and 6.1 µm luminosities of these red quasars are consistent with the empirical relations derived for high-luminosity, unobscured quasars, extending the parameter space of obscured AGNs previously observed by NuSTAR to higher luminosities.

  2. Precision luminosity measurements at LHCb

    CERN Document Server

    Aaij, Roel; Adinolfi, Marco; Affolder, Anthony; Ajaltouni, Ziad; Akar, Simon; Albrecht, Johannes; Alessio, Federico; Alexander, Michael; Ali, Suvayu; Alkhazov, Georgy; Alvarez Cartelle, Paula; Alves Jr, Antonio Augusto; Amato, Sandra; Amerio, Silvia; Amhis, Yasmine; An, Liupan; Anderlini, Lucio; Anderson, Jonathan; Andreassen, Rolf; Andreotti, Mirco; Andrews, Jason; Appleby, Robert; Aquines Gutierrez, Osvaldo; Archilli, Flavio; Artamonov, Alexander; Artuso, Marina; Aslanides, Elie; Auriemma, Giulio; Baalouch, Marouen; Bachmann, Sebastian; Back, John; Badalov, Alexey; Baesso, Clarissa; Baldini, Wander; Barlow, Roger; Barschel, Colin; Barsuk, Sergey; Barter, William; Batozskaya, Varvara; Battista, Vincenzo; Bay, Aurelio; Beaucourt, Leo; Beddow, John; Bedeschi, Franco; Bediaga, Ignacio; Belogurov, Sergey; Belous, Konstantin; Belyaev, Ivan; Ben-Haim, Eli; Bencivenni, Giovanni; Benson, Sean; Benton, Jack; Berezhnoy, Alexander; Bernet, Roland; Bettler, Marc-Olivier; van Beuzekom, Martinus; Bien, Alexander; Bifani, Simone; Bird, Thomas; Bizzeti, Andrea; Bjørnstad, Pål Marius; Blake, Thomas; Blanc, Frédéric; Blouw, Johan; Blusk, Steven; Bocci, Valerio; Bondar, Alexander; Bondar, Nikolay; Bonivento, Walter; Borghi, Silvia; Borgia, Alessandra; Borsato, Martino; Bowcock, Themistocles; Bowen, Espen Eie; Bozzi, Concezio; Brambach, Tobias; Bressieux, Joël; Brett, David; Britsch, Markward; Britton, Thomas; Brodzicka, Jolanta; Brook, Nicholas; Brown, Henry; Bursche, Albert; Buytaert, Jan; Cadeddu, Sandro; Calabrese, Roberto; Calvi, Marta; Calvo Gomez, Miriam; Campana, Pierluigi; Campora Perez, Daniel; Carbone, Angelo; Carboni, Giovanni; Cardinale, Roberta; Cardini, Alessandro; Carson, Laurence; Carvalho Akiba, Kazuyoshi; Casse, Gianluigi; Cassina, Lorenzo; Castillo Garcia, Lucia; Cattaneo, Marco; Cauet, Christophe; Cenci, Riccardo; Charles, Matthew; Charpentier, Philippe; Chefdeville, Maximilien; Chen, Shanzhen; Cheung, Shu-Faye; Chiapolini, Nicola; Chrzaszcz, Marcin; Ciba, Krzystof; Cid Vidal, Xabier; Ciezarek, Gregory; Clarke, Peter; Clemencic, Marco; Cliff, Harry; Closier, Joel; Coco, Victor; Cogan, Julien; Cogneras, Eric; Cojocariu, Lucian; Collazuol, Gianmaria; Collins, Paula; Comerma-Montells, Albert; Contu, Andrea; Cook, Andrew; Coombes, Matthew; Coquereau, Samuel; Corti, Gloria; Corvo, Marco; Counts, Ian; Couturier, Benjamin; Cowan, Greig; Craik, Daniel Charles; Cruz Torres, Melissa Maria; Cunliffe, Samuel; Currie, Robert; D'Ambrosio, Carmelo; Dalseno, Jeremy; David, Pascal; David, Pieter; Davis, Adam; De Bruyn, Kristof; De Capua, Stefano; De Cian, Michel; De Miranda, Jussara; De Paula, Leandro; De Silva, Weeraddana; De Simone, Patrizia; Dean, Cameron Thomas; Decamp, Daniel; Deckenhoff, Mirko; Del Buono, Luigi; Déléage, Nicolas; Derkach, Denis; Deschamps, Olivier; Dettori, Francesco; Di Canto, Angelo; Dijkstra, Hans; Donleavy, Stephanie; Dordei, Francesca; Dorigo, Mirco; Dosil Suárez, Alvaro; Dossett, David; Dovbnya, Anatoliy; Dreimanis, Karlis; Dujany, Giulio; Dupertuis, Frederic; Durante, Paolo; Dzhelyadin, Rustem; Dziurda, Agnieszka; Dzyuba, Alexey; Easo, Sajan; Egede, Ulrik; Egorychev, Victor; Eidelman, Semen; Eisenhardt, Stephan; Eitschberger, Ulrich; Ekelhof, Robert; Eklund, Lars; El Rifai, Ibrahim; Elsasser, Christian; Ely, Scott; Esen, Sevda; Evans, Hannah Mary; Evans, Timothy; Falabella, Antonio; Färber, Christian; Farinelli, Chiara; Farley, Nathanael; Farry, Stephen; Fay, Robert; Ferguson, Dianne; Fernandez Albor, Victor; Ferreira Rodrigues, Fernando; Ferro-Luzzi, Massimiliano; Filippov, Sergey; Fiore, Marco; Fiorini, Massimiliano; Firlej, Miroslaw; Fitzpatrick, Conor; Fiutowski, Tomasz; Fol, Philip; Fontana, Marianna; Fontanelli, Flavio; Forty, Roger; Francisco, Oscar; Frank, Markus; Frei, Christoph; Frosini, Maddalena; Fu, Jinlin; Furfaro, Emiliano; Gallas Torreira, Abraham; Galli, Domenico; Gallorini, Stefano; Gambetta, Silvia; Gandelman, Miriam; Gandini, Paolo; Gao, Yuanning; García Pardiñas, Julián; Garofoli, Justin; Garra Tico, Jordi; Garrido, Lluis; Gascon, David; Gaspar, Clara; Gauld, Rhorry; Gavardi, Laura; Geraci, Angelo; Gersabeck, Evelina; Gersabeck, Marco; Gershon, Timothy; Ghez, Philippe; Gianelle, Alessio; Gianì, Sebastiana; Gibson, Valerie; Giubega, Lavinia-Helena; Gligorov, V.V.; Göbel, Carla; Golubkov, Dmitry; Golutvin, Andrey; Gomes, Alvaro; Gotti, Claudio; Grabalosa Gándara, Marc; Graciani Diaz, Ricardo; Granado Cardoso, Luis Alberto; Graugés, Eugeni; Graziani, Giacomo; Grecu, Alexandru; Greening, Edward; Gregson, Sam; Griffith, Peter; Grillo, Lucia; Grünberg, Oliver; Gui, Bin; Gushchin, Evgeny; Guz, Yury; Gys, Thierry; Hadjivasiliou, Christos; Haefeli, Guido; Haen, Christophe; Haines, Susan; Hall, Samuel; Hamilton, Brian; Hampson, Thomas; Han, Xiaoxue; Hansmann-Menzemer, Stephanie; Harnew, Neville; Harnew, Samuel; Harrison, Jonathan; He, Jibo; Head, Timothy; Heijne, Veerle; Hennessy, Karol; Henrard, Pierre; Henry, Louis; Hernando Morata, Jose Angel; van Herwijnen, Eric; Heß, Miriam; Hicheur, Adlène; Hill, Donal; Hoballah, Mostafa; Hombach, Christoph; Hulsbergen, Wouter; Hunt, Philip; Hussain, Nazim; Hutchcroft, David; Hynds, Daniel; Idzik, Marek; Ilten, Philip; Jacobsson, Richard; Jaeger, Andreas; Jalocha, Pawel; Jans, Eddy; Jaton, Pierre; Jawahery, Abolhassan; Jing, Fanfan; John, Malcolm; Johnson, Daniel; Jones, Christopher; Joram, Christian; Jost, Beat; Jurik, Nathan; Kandybei, Sergii; Kanso, Walaa; Karacson, Matthias; Karbach, Moritz; Karodia, Sarah; Kelsey, Matthew; Kenyon, Ian; Ketel, Tjeerd; Khanji, Basem; Khurewathanakul, Chitsanu; Klaver, Suzanne; Klimaszewski, Konrad; Kochebina, Olga; Kolpin, Michael; Komarov, Ilya; Koopman, Rose; Koppenburg, Patrick; Korolev, Mikhail; Kozlinskiy, Alexandr; Kravchuk, Leonid; Kreplin, Katharina; Kreps, Michal; Krocker, Georg; Krokovny, Pavel; Kruse, Florian; Kucewicz, Wojciech; Kucharczyk, Marcin; Kudryavtsev, Vasily; Kurek, Krzysztof; Kvaratskheliya, Tengiz; La Thi, Viet Nga; Lacarrere, Daniel; Lafferty, George; Lai, Adriano; Lambert, Dean; Lambert, Robert W; Lanfranchi, Gaia; Langenbruch, Christoph; Langhans, Benedikt; Latham, Thomas; Lazzeroni, Cristina; Le Gac, Renaud; van Leerdam, Jeroen; Lees, Jean-Pierre; Lefèvre, Regis; Leflat, Alexander; Lefrançois, Jacques; Leo, Sabato; Leroy, Olivier; Lesiak, Tadeusz; Leverington, Blake; Li, Yiming; Likhomanenko, Tatiana; Liles, Myfanwy; Lindner, Rolf; Linn, Christian; Lionetto, Federica; Liu, Bo; Lohn, Stefan; Longstaff, Iain; Lopes, Jose; Lopez-March, Neus; Lowdon, Peter; Lu, Haiting; Lucchesi, Donatella; Luo, Haofei; Lupato, Anna; Luppi, Eleonora; Lupton, Oliver; Machefert, Frederic; Machikhiliyan, Irina V; Maciuc, Florin; Maev, Oleg; Malde, Sneha; Malinin, Alexander; Manca, Giulia; Mancinelli, Giampiero; Mapelli, Alessandro; Maratas, Jan; Marchand, Jean François; Marconi, Umberto; Marin Benito, Carla; Marino, Pietro; Märki, Raphael; Marks, Jörg; Martellotti, Giuseppe; Martens, Aurelien; Martín Sánchez, Alexandra; Martinelli, Maurizio; Martinez Santos, Diego; Martinez Vidal, Fernando; Martins Tostes, Danielle; Massafferri, André; Matev, Rosen; Mathe, Zoltan; Matteuzzi, Clara; Maurin, Brice; Mazurov, Alexander; McCann, Michael; McCarthy, James; McNab, Andrew; McNulty, Ronan; McSkelly, Ben; Meadows, Brian; Meier, Frank; Meissner, Marco; Merk, Marcel; Milanes, Diego Alejandro; Minard, Marie-Noelle; Moggi, Niccolò; Molina Rodriguez, Josue; Monteil, Stephane; Morandin, Mauro; Morawski, Piotr; Mordà, Alessandro; Morello, Michael Joseph; Moron, Jakub; Morris, Adam Benjamin; Mountain, Raymond; Muheim, Franz; Müller, Katharina; Mussini, Manuel; Muster, Bastien; Naik, Paras; Nakada, Tatsuya; Nandakumar, Raja; Nasteva, Irina; Needham, Matthew; Neri, Nicola; Neubert, Sebastian; Neufeld, Niko; Neuner, Max; Nguyen, Anh Duc; Nguyen, Thi-Dung; Nguyen-Mau, Chung; Nicol, Michelle; Niess, Valentin; Niet, Ramon; Nikitin, Nikolay; Nikodem, Thomas; Novoselov, Alexey; O'Hanlon, Daniel Patrick; Oblakowska-Mucha, Agnieszka; Obraztsov, Vladimir; Oggero, Serena; Ogilvy, Stephen; Okhrimenko, Oleksandr; Oldeman, Rudolf; Onderwater, Gerco; Orlandea, Marius; Otalora Goicochea, Juan Martin; Owen, Patrick; Oyanguren, Maria Arantza; Pal, Bilas Kanti; Palano, Antimo; Palombo, Fernando; Palutan, Matteo; Panman, Jacob; Papanestis, Antonios; Pappagallo, Marco; Pappalardo, Luciano; Parkes, Christopher; Parkinson, Christopher John; Passaleva, Giovanni; Patel, Girish; Patel, Mitesh; Patrignani, Claudia; Pearce, Alex; Pellegrino, Antonio; Pepe Altarelli, Monica; Perazzini, Stefano; Perret, Pascal; Perrin-Terrin, Mathieu; Pescatore, Luca; Pesen, Erhan; Pessina, Gianluigi; Petridis, Konstantin; Petrolini, Alessandro; Picatoste Olloqui, Eduardo; Pietrzyk, Boleslaw; Pilař, Tomas; Pinci, Davide; Pistone, Alessandro; Playfer, Stephen; Plo Casasus, Maximo; Polci, Francesco; Poluektov, Anton; Polycarpo, Erica; Popov, Alexander; Popov, Dmitry; Popovici, Bogdan; Potterat, Cédric; Price, Eugenia; Price, Joseph David; Prisciandaro, Jessica; Pritchard, Adrian; Prouve, Claire; Pugatch, Valery; Puig Navarro, Albert; Punzi, Giovanni; Qian, Wenbin; Rachwal, Bartolomiej; Rademacker, Jonas; Rakotomiaramanana, Barinjaka; Rama, Matteo; Rangel, Murilo; Raniuk, Iurii; Rauschmayr, Nathalie; Raven, Gerhard; Redi, Federico; Reichert, Stefanie; Reid, Matthew; dos Reis, Alberto; Ricciardi, Stefania; Richards, Sophie; Rihl, Mariana; Rinnert, Kurt; Rives Molina, Vincente; Robbe, Patrick; Rodrigues, Ana Barbara; Rodrigues, Eduardo; Rodriguez Perez, Pablo; Roiser, Stefan; Romanovsky, Vladimir; Romero Vidal, Antonio; Rotondo, Marcello; Rouvinet, Julien; Ruf, Thomas; Ruiz, Hugo; Ruiz Valls, Pablo; Saborido Silva, Juan Jose; Sagidova, Naylya; Sail, Paul; Saitta, Biagio; Salustino Guimaraes, Valdir; Sanchez Mayordomo, Carlos; Sanmartin Sedes, Brais; Santacesaria, Roberta; Santamarina Rios, Cibran; Santovetti, Emanuele; Sarti, Alessio; Satriano, Celestina; Satta, Alessia; Saunders, Daniel Martin; Savrina, Darya; Schiller, Manuel; Schindler, Heinrich; Schlupp, Maximilian; Schmelling, Michael; Schmidt, Burkhard; Schneider, Olivier; Schopper, Andreas; Schubiger, Maxime; Schune, Marie Helene; Schwemmer, Rainer; Sciascia, Barbara; Sciubba, Adalberto; Semennikov, Alexander; Sepp, Indrek; Serra, Nicola; Serrano, Justine; Sestini, Lorenzo; Seyfert, Paul; Shapkin, Mikhail; Shapoval, Illya; Shcheglov, Yury; Shears, Tara; Shekhtman, Lev; Shevchenko, Vladimir; Shires, Alexander; Silva Coutinho, Rafael; Simi, Gabriele; Sirendi, Marek; Skidmore, Nicola; Skwarnicki, Tomasz; Smith, Anthony; Smith, Edmund; Smith, Eluned; Smith, Jackson; Smith, Mark; Snoek, Hella; Sokoloff, Michael; Soler, Paul; Soomro, Fatima; Souza, Daniel; Souza De Paula, Bruno; Spaan, Bernhard; Sparkes, Ailsa; Spradlin, Patrick; Sridharan, Srikanth; Stagni, Federico; Stahl, Marian; Stahl, Sascha; Steinkamp, Olaf; Stenyakin, Oleg; Stevenson, Scott; Stoica, Sabin; Stone, Sheldon; Storaci, Barbara; Stracka, Simone; Straticiuc, Mihai; Straumann, Ulrich; Stroili, Roberto; Subbiah, Vijay Kartik; Sun, Liang; Sutcliffe, William; Swientek, Krzysztof; Swientek, Stefan; Syropoulos, Vasileios; Szczekowski, Marek; Szczypka, Paul; Szumlak, Tomasz; T'Jampens, Stephane; Teklishyn, Maksym; Tellarini, Giulia; Teubert, Frederic; Thomas, Christopher; Thomas, Eric; van Tilburg, Jeroen; Tisserand, Vincent; Tobin, Mark; Tolk, Siim; Tomassetti, Luca; Tonelli, Diego; Topp-Joergensen, Stig; Torr, Nicholas; Tournefier, Edwige; Tourneur, Stephane; Tran, Minh Tâm; Tresch, Marco; Trisovic, Ana; Tsaregorodtsev, Andrei; Tsopelas, Panagiotis; Tuning, Niels; Ubeda Garcia, Mario; Ukleja, Artur; Ustyuzhanin, Andrey; Uwer, Ulrich; Vacca, Claudia; Vagnoni, Vincenzo; Valenti, Giovanni; Vallier, Alexis; Vazquez Gomez, Ricardo; Vazquez Regueiro, Pablo; Vázquez Sierra, Carlos; Vecchi, Stefania; Velthuis, Jaap; Veltri, Michele; Veneziano, Giovanni; Vesterinen, Mika; Viaud, Benoit; Vieira, Daniel; Vieites Diaz, Maria; Vilasis-Cardona, Xavier; Vollhardt, Achim; Volyanskyy, Dmytro; Voong, David; Vorobyev, Alexey; Vorobyev, Vitaly; Voß, Christian; de Vries, Jacco; Waldi, Roland; Wallace, Charlotte; Wallace, Ronan; Walsh, John; Wandernoth, Sebastian; Wang, Jianchun; Ward, David; Watson, Nigel; Websdale, David; Whitehead, Mark; Wicht, Jean; Wiedner, Dirk; Wilkinson, Guy; Williams, Matthew; Williams, Mike; Wilschut, Hans; Wilson, Fergus; Wimberley, Jack; Wishahi, Julian; Wislicki, Wojciech; Witek, Mariusz; Wormser, Guy; Wotton, Stephen; Wright, Simon; Wyllie, Kenneth; Xie, Yuehong; Xing, Zhou; Xu, Zhirui; Yang, Zhenwei; Yuan, Xuhao; Yushchenko, Oleg; Zangoli, Maria; Zavertyaev, Mikhail; Zhang, Liming; Zhang, Wen Chao; Zhang, Yanxi; Zhelezov, Alexey; Zhokhov, Anatoly; Zhong, Liang; Zvyagin, Alexander

    2014-12-05

    Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy $\\sqrt{s}$. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for $\\sqrt{s}$ = 2.76, 7 and 8 TeV (proton-proton collisions) and for $\\sqrt{s_{NN}}$ = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at $\\sqrt{s}$ = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determin...

  3. Optical spectra and radio properties of quasars

    International Nuclear Information System (INIS)

    Wills, B.J.

    1982-01-01

    Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

  4. SELECTING QUASARS BY THEIR INTRINSIC VARIABILITY

    International Nuclear Information System (INIS)

    Schmidt, Kasper B.; Rix, Hans-Walter; Jester, Sebastian; Hennawi, Joseph F.; Marshall, Philip J.; Dobler, Gregory

    2010-01-01

    We present a new and simple technique for selecting extensive, complete, and pure quasar samples, based on their intrinsic variability. We parameterize the single-band variability by a power-law model for the light-curve structure function, with amplitude A and power-law index γ. We show that quasars can be efficiently separated from other non-variable and variable sources by the location of the individual sources in the A-γ plane. We use ∼60 epochs of imaging data, taken over ∼5 years, from the SDSS stripe 82 (S82) survey, where extensive spectroscopy provides a reference sample of quasars, to demonstrate the power of variability as a quasar classifier in multi-epoch surveys. For UV-excess selected objects, variability performs just as well as the standard SDSS color selection, identifying quasars with a completeness of 90% and a purity of 95%. In the redshift range 2.5 < z < 3, where color selection is known to be problematic, variability can select quasars with a completeness of 90% and a purity of 96%. This is a factor of 5-10 times more pure than existing color selection of quasars in this redshift range. Selecting objects from a broad griz color box without u-band information, variability selection in S82 can afford completeness and purity of 92%, despite a factor of 30 more contaminants than quasars in the color-selected feeder sample. This confirms that the fraction of quasars hidden in the 'stellar locus' of color space is small. To test variability selection in the context of Pan-STARRS 1 (PS1) we created mock PS1 data by down-sampling the S82 data to just six epochs over 3 years. Even with this much sparser time sampling, variability is an encouragingly efficient classifier. For instance, a 92% pure and 44% complete quasar candidate sample is attainable from the above griz-selected catalog. Finally, we show that the presented A-γ technique, besides selecting clean and pure samples of quasars (which are stochastically varying objects), is also

  5. Dust in the Quasar Wind (Artist Concept)

    Science.gov (United States)

    2007-01-01

    Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the dust in our young universe come from? Dust is crucial for efficient star formation as it allows the giant clouds where stars are born to cool quickly and collapse into new stars. Once a star has formed, dust is also needed to make planets and living creatures. Dust has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most dust in our current epoch forms in the winds of evolved stars that did not exist when the universe was young. Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this dust. While the environment close to a quasar is too hot for large molecules like dust grains to survive, dust has been found in the cooler, outer regions. Astronomers now have evidence that dust is created in these outer winds. Using Spitzer's infrared spectrograph instrument, scientists found a wealth of dust grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.

  6. A z = 3 Lyα BLOB ASSOCIATED WITH A DAMPED Lyα SYSTEM PROXIMATE TO ITS BACKGROUND QUASAR

    International Nuclear Information System (INIS)

    Hennawi, Joseph F.; Prochaska, J. Xavier; Kollmeier, Juna; Zheng Zheng

    2009-01-01

    We report on the discovery of a bright Lyα blob associated with the z = 3 quasar SDSS J124020.91+145535.6 which is also coincident with strong damped Lyα absorption from a foreground galaxy (a so-called proximate damped Lyα (PDLA) system). The one-dimensional spectrum acquired by the Sloan Digital Sky Survey (SDSS) shows a broad Lyα emission line with a FWHM ≅500 km s -1 and a luminosity of L Lyα = 3.9 x 10 43 erg s -1 superposed on the trough of the PDLA. Follow-up observations using the Keck/LRIS spectrometer confirm that this source has a Lyα nebula with spatial extent exceeding 5'', corresponding to a proper size >39 kpc. Mechanisms for powering the large Lyα luminosity in this nebula are discussed. We use a Monte Carlo radiative transfer simulation to investigate the possibility that the line emission is fluorescent recombination radiation from a kpc-scale PDLA galaxy powered by the ionizing flux of the quasar, but find that the predicted Lyα flux is several orders of magnitude lower than observed. We conclude that the Lyα emission is not associated with the PDLA galaxy at all, but instead is intrinsic to the quasar's host and similar to the extended Lyα f uzzwhich is detected around many active galactic nuclei. PDLAs are natural coronagraphs that block their background quasar at Lyα and we discuss how systems similar to SDSS J124020.91+145535.6 might be used to image the neutral hydrogen in the PDLA galaxy in silhouette against the screen of extended Lyα emission from the background quasar.

  7. The CTIO surveys for large redshift quasars

    International Nuclear Information System (INIS)

    Osmer, P.S.

    1978-01-01

    Lyman α emission in large redshift quasars is readily detectable on slitless spectrograms taken with an objective combination on the 4m telescope. This provides a new survey method, independent of color for finding radio-quiet quasars in large numbers. Surveys by Smith with the Curtis Schmidt and Hoag and Smith with the 4 m telescope, have produced more than 200 candidates with 1.5< z<3.5 and 16< m<21. Spectroscopic observations with the CTIO SIT vidicon system have been carried out for more than 50 of the candidates, with the result that the basic properties of the surveys are known. To date three 16th magnitude quasars with zapproximately2.2 and six quasars with 3.0< z<3.25 have been found. One of the most important uses of the surveys will be the determination of the surface and surface densities of large redshift quasars. A preliminary analysis of the data indicates that the space density of quasars is at least constant, if not increasing, over the interval 1.0< z<3.25. However, the Hoag-Smith sample has only one candidate with z<3.2.(Auth.)

  8. Using the Properties of Broad Absorption Line Quasars to Illuminate Quasar Structure

    Science.gov (United States)

    Yong, Suk Yee; King, Anthea L.; Webster, Rachel L.; Bate, Nicholas F.; O'Dowd, Matthew J.; Labrie, Kathleen

    2018-06-01

    A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted emission lines provides a crucial clue to the structure of quasar emitting regions. To learn whether it is possible to discriminate between the BALQ and non-BALQ populations given the observed spectral properties of a quasar, we employ two approaches: one based on statistical methods and the other supervised machine learning classification, applied to quasar samples from the Sloan Digital Sky Survey. The features explored include continuum and emission line properties, in particular the absolute magnitude, redshift, spectral index, line width, asymmetry, strength, and relative velocity offsets of high-ionisation C IV λ1549 and low-ionisation Mg II λ2798 lines. We consider a complete population of quasars, and assume that the statistical distributions of properties represent all angles where the quasar is viewed without obscuration. The distributions of the BALQ and non-BALQ sample properties show few significant differences. None of the observed continuum and emission line features are capable of differentiating between the two samples. Most published narrow disk-wind models are inconsistent with these observations, and an alternative disk-wind model is proposed. The key feature of the proposed model is a disk-wind filling a wide opening angle with multiple radial streams of dense clumps.

  9. BLACK HOLE MASS ESTIMATES AND RAPID GROWTH OF SUPERMASSIVE BLACK HOLES IN LUMINOUS z ∼ 3.5 QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Zuo, Wenwen; Wu, Xue-Bing [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China); Fan, Xiaohui; Green, Richard [Steward Observatory, The University of Arizona, Tucson, AZ 85721 (United States); Wang, Ran [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Bian, Fuyan [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston ACT 2611 (Australia)

    2015-02-01

    We present new near-infrared (IR) observations of the Hβ λ4861 and Mg II λ2798 lines for 32 luminous quasars with 3.2 < z < 3.9 using the Palomar Hale 200 inch telescope and the Large Binocular Telescope. We find that the Mg II FWHM is well correlated with the Hβ FWHM, confirming itself as a good substitute for the Hβ FWHM in the black hole mass estimates. The continuum luminosity at 5100 Å well correlates with the continuum luminosity at 3000 Å and the broad emission line luminosities (Hβ and Mg II). With simultaneous near-IR spectroscopy of the Hβ and Mg II lines to exclude the influences of flux variability, we are able to evaluate the reliability of estimating black hole masses based on the Mg II line for high redshift quasars. With the reliable Hβ line based black hole mass and Eddington ratio estimates, we find that the z ∼ 3.5 quasars in our sample have black hole masses 1.90 × 10{sup 9} M {sub ☉} ≲ M {sub BH} ≲ 1.37 × 10{sup 10} M {sub ☉}, with a median of ∼5.14 × 10{sup 9} M {sub ☉} and are accreting at Eddington ratios between 0.30 and 3.05, with a median of ∼1.12. Assuming a duty cycle of 1 and a seed black hole mass of 10{sup 4} M {sub ☉}, we show that the z ∼ 3.5 quasars in this sample can grow to their estimated black hole masses within the age of the universe at their redshifts.

  10. THE REST-FRAME OPTICAL LUMINOSITY FUNCTION OF CLUSTER GALAXIES AT z < 0.8 AND THE ASSEMBLY OF THE CLUSTER RED SEQUENCE

    International Nuclear Information System (INIS)

    Rudnick, Gregory; Von der Linden, Anja; De Lucia, Gabriella; White, Simon; Pello, Roser; Aragon-Salamanca, Alfonso; Marchesini, Danilo; Clowe, Douglas; Halliday, Claire; Jablonka, Pascale; Milvang-Jensen, Bo; Poggianti, Bianca; Saglia, Roberto; Simard, Luc; Zaritsky, Dennis

    2009-01-01

    We present the rest-frame optical luminosity function (LF) of red-sequence galaxies in 16 clusters at 0.4 < z < 0.8 drawn from the ESO Distant Cluster Survey (EDisCS). We compare our clusters to an analogous sample from the Sloan Digital Sky Survey (SDSS) and match the EDisCS clusters to their most likely descendants. We measure all LFs down to M ∼ M * + (2.5-3.5). At z < 0.8, the bright end of the LF is consistent with passive evolution but there is a significant buildup of the faint end of the red sequence toward lower redshift. There is a weak dependence of the LF on cluster velocity dispersion for EDisCS but no such dependence for the SDSS clusters. We find tentative evidence that red-sequence galaxies brighter than a threshold magnitude are already in place, and that this threshold evolves to fainter magnitudes toward lower redshifts. We compare the EDisCS LFs with the LF of coeval red-sequence galaxies in the field and find that the bright end of the LFs agree. However, relative to the number of bright red galaxies, the field has more faint red galaxies than clusters at 0.6 < z < 0.8 but fewer at 0.4 < z < 0.6, implying differential evolution. We compare the total light in the EDisCS cluster red sequences to the total red-sequence light in our SDSS cluster sample. Clusters at 0.4 < z < 0.8 must increase their luminosity on the red sequence (and therefore stellar mass in red galaxies) by a factor of 1-3 by z = 0. The necessary processes that add mass to the red sequence in clusters predict local clusters that are overluminous as compared to those observed in the SDSS. The predicted cluster luminosities can be reconciled with observed local cluster luminosities by combining multiple previously known effects.

  11. THE UDF05 FOLLOW-UP OF THE HUBBLE ULTRA DEEP FIELD. III. THE LUMINOSITY FUNCTION AT z ∼ 6

    International Nuclear Information System (INIS)

    Su Jian; Stiavelli, Massimo; Bergeron, Eddie; Bradley, Larry; Dahlen, Tomas; Ferguson, Henry C.; Koekemoer, Anton; Lucas, Ray A.; Panagia, Nino; Pavlovsky, Cheryl; Oesch, Pascal; Carollo, Marcella; Lilly, Simon; Trenti, Michele; Giavalisco, Mauro; Mobasher, Bahram

    2011-01-01

    In this paper, we present a derivation of the rest-frame 1400 A luminosity function (LF) at redshift six from a new application of the maximum likelihood method by exploring the five deepest Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) fields, i.e., the Hubble Ultra Deep Field, two UDF05 fields, and two Great Observatories Origins Deep Survey fields. We work on the latest improved data products, which makes our results more robust than those of previous studies. We use unbinned data and thereby make optimal use of the information contained in the data set. We focus on the analysis to a magnitude limit where the completeness is larger than 50% to avoid possibly large errors in the faint end slope that are difficult to quantify. We also take into account scattering in and out of the dropout sample due to photometric errors by defining for each object a probability that it belongs to the dropout sample. We find the best-fit Schechter parameters to the z ∼ 6 LF are α = 1.87 ± 0.14, M * = -20.25 ± 0.23, and φ * = 1.77 +0.62 -0.49 x 10 -3 Mpc -3 . Such a steep slope suggests that galaxies, especially the faint ones, are possibly the main sources of ionizing photons in the universe at redshift six. We also combine results from all studies at z ∼ 6 to reach an agreement in the 95% confidence level that -20.45 * < -20.05 and -1.90 < α < -1.55. The luminosity density has been found not to evolve significantly between z ∼ 6 and z ∼ 5, but considerable evolution is detected from z ∼ 6 to z ∼ 3.

  12. Ultra-faint ultraviolet galaxies at z ∼ 2 behind the lensing cluster A1689: The luminosity function, dust extinction, and star formation rate density

    Energy Technology Data Exchange (ETDEWEB)

    Alavi, Anahita; Siana, Brian; Freeman, William R.; Dominguez, Alberto [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Richard, Johan [Centre de Recherche Astrophysique de Lyon, Université Lyon 1, 9 Avenue Charles André, F-69561 Saint Genis Laval Cedex (France); Stark, Daniel P.; Robertson, Brant [Department of Astronomy, Steward Observatory, University of Arizona, 933 North Cherry Avenue, Rm N204, Tucson, AZ 85721 (United States); Scarlata, Claudia [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States); Teplitz, Harry I.; Rafelski, Marc [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States); Kewley, Lisa, E-mail: anahita.alavi@email.ucr.edu [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia)

    2014-01-10

    We have obtained deep ultraviolet imaging of the lensing cluster A1689 with the WFC3/UVIS camera onboard the Hubble Space Telescope in the F275W (30 orbits) and F336W (4 orbits) filters. These images are used to identify z ∼ 2 star-forming galaxies via their Lyman break, in the same manner that galaxies are typically selected at z ≥ 3. Because of the unprecedented depth of the images and the large magnification provided by the lensing cluster, we detect galaxies 100× fainter than previous surveys at this redshift. After removing all multiple images, we have 58 galaxies in our sample in the range –19.5 < M {sub 1500} < –13 AB mag. Because the mass distribution of A1689 is well constrained, we are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing for accurate determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be α = –1.74 ± 0.08, which is consistent with the values obtained for 2.5 < z < 6. Notably, there is no turnover in the luminosity function down to M {sub 1500} = –13 AB mag. We fit the UV spectral slopes with photometry from existing Hubble optical imaging. The observed trend of increasingly redder slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of (E(B – V)) = 0.15 mag. We assume the stars in these galaxies are metal poor (0.2 Z {sub ☉}) compared to their brighter counterparts (Z {sub ☉}), resulting in bluer assumed intrinsic UV slopes and larger derived values for dust extinction. The total UV luminosity density at z ∼ 2 is 4.31{sub −0.60}{sup +0.68}×10{sup 26} erg s{sup –1} Hz{sup –1} Mpc{sup –3}, more than 70% of which is emitted by galaxies in the luminosity range of our sample. Finally, we determine the global star formation rate density from UV-selected galaxies at z ∼ 2 (assuming a constant dust

  13. X-Ray Observations of Optically Selected, Radio-quiet Quasars. I. The ASCA Results

    Science.gov (United States)

    George, I. M.; Turner, T. J.; Yaqoob, T.; Netzer, H.; Laor, A.; Mushotzky, R. F.; Nandra, K.; Takahashi, T.

    2000-03-01

    We present the result of 27 ASCA observations of 26 radio-quiet quasars (RQQs) from the Palomar-Green (PG) survey. The sample is not statistically complete, but it is reasonably representative of RQQs in the PG survey. For many of the sources, the ASCA data are presented here for the first time. All the RQQs were detected except for two objects, both of which contain broad absorption lines in the optical band. We find the variability characteristics of the sources to be consistent with Seyfert 1 galaxies. A power law offers an acceptable description of the time-averaged spectra in the 2-10 keV (quasar frame) band for all but one data set. The best-fitting values of the photon index vary from object to object over the range 1.5~=2 and dispersion σ(Γ2-10)~=0.25. The distribution of Γ2-10 is therefore similar to that observed in other RQ active galactic nuclei (AGNs) and seems to be unrelated to X-ray luminosity. No single model adequately describes the full 0.6-10 keV (observed frame) continuum of all the RQQs. Approximately 50% of the sources can be adequately described by a single power law or by a power law with only very subtle deviations. All but one of the remaining data sets were found to have convex spectra (flattening as one moves to higher energies). The exception is PG 1411+442, in which a substantial column density (NH,z~2x1023 cm-2) obscures ~98% of the continuum. We find only five (maybe six) of 14 objects with z<~0.25 to have ``soft excesses'' at energies <~1 keV, but we find no universal shape for these spectral components. The spectrum of PG 1244+026 contains a rather narrow emission feature centered at an energy ~1 keV (quasar frame). The detection rate of absorption due to ionized material in these RQQs is lower than that seen in Seyfert 1 galaxies. In part, this may be due to selection effects. However, when detected, the absorbers in the RQQs exhibit a similar range of column density and ionization parameter as Seyfert 1 galaxies. We find

  14. Detectors and luminosity for hadron colliders

    International Nuclear Information System (INIS)

    Diebold, R.

    1983-01-01

    Three types of very high energy hadron-hadron coliders are discussed in terms of the trade-off between energy and luminosity. The usable luminosity depends both on the physics under study and the rate capabilities of the detector

  15. MICROLENSING OF QUASAR BROAD EMISSION LINES: CONSTRAINTS ON BROAD LINE REGION SIZE

    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)

    2013-02-20

    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.

  16. THE ULTRAVIOLET-TO-MID-INFRARED SPECTRAL ENERGY DISTRIBUTION OF WEAK EMISSION LINE QUASARS

    International Nuclear Information System (INIS)

    Lane, Ryan A.; Shemmer, Ohad; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Plotkin, Richard M.; Richards, Gordon T.; Strauss, Michael A.

    2011-01-01

    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 spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame ∼0.1-5 μm spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line of sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.

  17. THE ULTRAVIOLET-TO-MID-INFRARED SPECTRAL ENERGY DISTRIBUTION OF WEAK EMISSION LINE QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Ryan A.; Shemmer, Ohad [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Diamond-Stanic, Aleksandar M. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States); Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Plotkin, Richard M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam (Netherlands); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A., E-mail: RyanLane@my.unt.edu, E-mail: ohad@unt.edu [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States)

    2011-12-20

    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 spectra and ground-based, near-infrared (IR) photometry of these sources to produce a large inventory of spectral energy distributions (SEDs) of WLQs across the rest-frame {approx}0.1-5 {mu}m spectral band. The SEDs of our sources are inconsistent with those of BL Lacertae objects which are dominated by synchrotron emission due to a jet aligned close to our line of sight, but are consistent with the SED of ordinary quasars with similar luminosities and redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust emission. This indicates that broad emission lines in WLQs are intrinsically weak, rather than suffering continuum dilution from a jet, and that such sources cannot be selected efficiently from traditional photometric surveys.

  18. Objective-prism spectrophotometry of quasars

    International Nuclear Information System (INIS)

    Clowes, R.G.

    1980-01-01

    A procedure is derived for obtaining low-resolution spectrophotometry of quasars directly from the objective-prism plates on which they were discovered. Measurements with a PDS microdensitometer of approximately 130 quasar candidates in approximately the central 19 square degrees of the UK Schmidt prism plate UJ3682P were used in the application of the procedure. The success of the objective-prism spectrophotometry is demonstrated in a comparison with 12 slit spectra. Redshifts and equivalent widths can be determined with typical discrepancies of 1% and 40% respectively. This work on objective-prism spectrophotometry leads to a quantification of the selection effects that operate in the searches for emission-line objects on objective-prism plates. The quantification successfully explains an apparent discrepancy in the detection efficiencies of the CTIO-4m and Curtis Schmidt surveys for quasars. Spectra of quasars that were observed with the Image Photon Counting System on the Anglo-Australian Telescope are presented. The observations of quasars with broad absorption troughs indicate the ejection of matter with velocities up to approximately 22000kms -1 and with velocity dispersions up to approximately 11000kms -1 . Data on the wavelength dependences of the contrast γ and the grain response function g of the Kodak emulsion IIIaJ are presented. (author)

  19. IRAS 14348-1447, an Ultraluminous Pair of Colliding, Gas-Rich Galaxies: The Birth of a Quasar?

    Science.gov (United States)

    Sanders, D B; Scoville, N Z; Soifer, B T

    1988-02-05

    Ground-based observations of the object IRAS 14348-1447, which was discovered with the Infrared Astronomical Satellite, show that it is an extremely luminous colliding galaxy system that emits more than 95 percent of its energy at far-infrared wavelengths. IRAS 14348-1447, which is receeding from the sun at 8 percent of the speed of light, has a bolometric luminosity more than 100 times larger than that of our galaxy, and is therefore as luminous as optical quasars. New optical, infrared, and spectroscopic measurements suggest that the dominant luminosity source is a dustenshrouded quasar. The fuel for the intense activity is an enormous supply of molecular gas. Carbon monoxide emission has been detected at a wavelength of 2.6 millimeters by means of a new, more sensitive receiver recently installed on the 12-meter telescope of the National Radio Astronomy Observatory. IRAS 14348-1447 is the most distant and luminous source of carbon monoxide line emission yet detected. The derived mass of interstellar molecular hydrogen is 6 x 10(10) solar masses. This value is approximately 20 times that of the molecular gas content of the Milky Way and is similar to the largest masses of atomic hydrogen found in galaxies. A large mass of molecular gas may be a prerequisite for the formation of quasars during strong galactic collisions.

  20. Spectroscopy of the fuzz associated with four quasars

    International Nuclear Information System (INIS)

    Balick, B.; Heckman, T.M.

    1983-01-01

    The spectroscopic properties of the ''fuzz'' near four quasars are consistent with starlight in a galactic environment at essentially the same redshift as the quasar. Apparently, then, the same processes that determine the redshifts of galaxies also determine the redshifts of quasars

  1. RESOLVED DUST EMISSION IN A QUASAR AT z = 3.65

    International Nuclear Information System (INIS)

    Clements, D. L.; Babbedge, T.; Rowan-Robinson, M.; Petitpas, G.; Farrah, D.; Hatziminaoglou, E.; Perez-Fournon, I.; Hernan-Caballero, Antonio; Castro-RodrIguez, Nieves; Lonsdale, C.; Surace, J.; Franceschini, A.; Wilkes, B. J.; Smith, H.

    2009-01-01

    We present submillimeter observations of the z= 3.653 quasar SDSS 160705+533558 together with data in the optical and infrared. The object is unusually bright in the far-IR and submillimeter with an IR luminosity of ∼10 14 L sun . We ascribe this luminosity to a combination of active galactic nucleus (AGN) and starburst emission, with the starburst forming stars at a rate of a few thousand solar masses per year. Submillimeter Array imaging observations with a resolution ∼1'' show that the submillimeter (850 μm) emission is extended on scales of 10- 35 kpc and is offset from the optical position by ∼10 kpc. This morphology is dissimilar to that found in submillimeter galaxies, which are generally unresolved or marginally resolved on arcsecond scales, or submillimeter-luminous AGNs where the AGN lies at the peak of the submillimeter or molecular emission. The simplest explanation is that the object is in the early stages of a merger between a gas-rich galaxy, which hosts the starburst, and a gas-poor AGN-host galaxy, which is responsible for the quasar emission. It is also possible that jet-induced star formation might contribute to the unusual morphology.

  2. Quasar Black Hole Mass Estimates from High-Ionization Lines: Breaking a Taboo?

    Directory of Open Access Journals (Sweden)

    Paola Marziani

    2017-09-01

    Full Text Available Can high ionization lines such as CIV λ 1549 provide useful virial broadening estimators for computing the mass of the supermassive black holes that power the quasar phenomenon? The question has been dismissed by several workers as a rhetorical one because blue-shifted, non-virial emission associated with gas outflows is often prominent in CIV λ 1549 line profiles. In this contribution, we first summarize the evidence suggesting that the FWHM of low-ionization lines like H β and MgII λ 2800 provide reliable virial broadening estimators over a broad range of luminosity. We confirm that the line widths of CIV λ 1549 is not immediately offering a virial broadening estimator equivalent to the width of low-ionization lines. However, capitalizing on the results of Coatman et al. (2016 and Sulentic et al. (2017, we suggest a correction to FWHM CIV λ 1549 for Eddington ratio and luminosity effects that, however, remains cumbersome to apply in practice. Intermediate ionization lines (IP ∼ 20–30 eV; AlIII λ 1860 and SiIII] λ 1892 may provide a better virial broadening estimator for high redshift quasars, but larger samples are needed to assess their reliability. Ultimately, they may be associated with the broad-line region radius estimated from the photoionization method introduced by Negrete et al. (2013 to obtain black hole mass estimates independent from scaling laws.

  3. A QUASAR CATALOG WITH SIMULTANEOUS UV, OPTICAL, AND X-RAY OBSERVATIONS BY SWIFT

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jian; Grupe, Dirk; Koch, Scott; Gelbord, Jonathan; Schneider, Donald P.; Gronwall, Caryl; Porterfield, Blair L. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Vanden Berk, Daniel; Wesolowski, Sarah, E-mail: jwu@astro.psu.edu [Department of Physics, Saint Vincent College, 300 Fraser Purchase Road, Latrobe, PA 15650 (United States)

    2012-08-01

    We have compiled a catalog of optically selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma-ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both Ultraviolet Optical Telescope (UVOT) and X-Ray Telescope (XRT) observations and 354 of which are detected by both instruments. The overall X-ray detection rate is {approx}60% which rises to {approx}85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution (SED) for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about {approx}0.3 dex to the quasar luminosity. We re-visit the {alpha}{sub ox}-L{sub 2500A} relation by selecting a clean sample with only Type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared with studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L{sub bol}/L{sub Edd} and {alpha}{sub UV}. We do not find significant correlations between {alpha}{sub x} and {alpha}{sub ox}, {alpha}{sub ox} and {alpha}{sub UV}, and {alpha}{sub x} and log L(0.3-10 keV). The correlations between {alpha}{sub UV} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub x}, {alpha}{sub ox} and {alpha}{sub UV}, L{sub bol}/L{sub Edd} and {alpha}{sub x}, and L{sub bol}/L{sub Edd} and {alpha}{sub ox} are stronger among low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

  4. A CHARACTERISTIC DIVISION BETWEEN THE FUELING OF QUASARS AND SEYFERTS: FIVE SIMPLE TESTS

    International Nuclear Information System (INIS)

    Hopkins, Philip F.; Hernquist, Lars

    2009-01-01

    Given the existence of the M BH -σ relation, models of self-regulated black hole (BH) growth require both a fuel supply and concomitant growth of the host bulge to deepen the central potential, or else the system will either starve or immediately self-regulate without any sustained activity. This leads to a generic prediction that the brightest quasars must be triggered in major mergers: a large fraction of the galaxy mass must be added/converted to new bulge mass and a galactic supply of gas must lose angular momentum in less than a dynamical time. Low-luminosity active galactic nuclei, in contrast, require little bulge growth and small gas supplies, and could be triggered in more common nonmerger events. This leads to the expectation of a characteristic transition to merger-induced fueling around the traditional quasar-Seyfert luminosity division (growth of BH masses above/below ∼10 7 M sun ). We compile and survey a number of observations in order to test several predictions of such a division, including (1) a transition to bulge-dominated hosts (which any major merger remnant, regardless of difficult-to-observe tidal features, should be). (2) A transition between 'pseudobulges' and 'classical' bulges hosting the remnant BHs: pseudobulges are formed in secular processes and minor mergers, whereas classical bulges are relics of major mergers. (3) An increase in the amplitude of small-scale clustering (increased halo occupation of small group environments) where mergers are more efficient. (4) Different redshift evolution, with gas-rich merger rates rising to redshifts z > 2 while secular processes are relatively constant in time. (5) An increasing prominence of post-starburst features in more luminous systems. Our compilation of observations in each of these areas provides tentative evidence for the predicted division around the Seyfert-quasar threshold, and we discuss how future observations can improve these constraints and, in combination with the tests

  5. The low-luminosity stellar mass function

    International Nuclear Information System (INIS)

    Kroupa, Pavel; Tout, C.A.; Gilmore, Gerard

    1990-01-01

    The stellar mass function for low-mass stars is constrained using the stellar luminosity function and the slope of the mass-luminosity relation. We investigate the range of mass functions for stars with absolute visual magnitude fainter than M V ≅ +5 which are consistent with both the local luminosity function and the rather poorly determined mass-absolute visual magnitude relation. Points of inflexion in the mass-luminosity relation exist because of the effects of H - , H 2 and of other molecules on the opacity and equation of state. The first two of these correspond to absolute magnitudes M V ≅ +7 and M V ≅ +12, respectively, at which structure is evident in the stellar luminosity function (a flattening and a maximum, respectively). Combining the mass-luminosity relation which shows these inflexion points with a peaked luminosity function, we test smooth mass functions in the mass range 0.9-0.1 the solar mass. (author)

  6. To High Luminosity and beyond!

    CERN Multimedia

    CERN Bulletin

    2015-01-01

    This week marks a major milestone for the High Luminosity LHC (HL-LHC - see here) project, as it moves from the design study to the machine construction phase. HL-LHC will extend the LHC’s discovery potential, increasing luminosity by a factor of 10 beyond the original design value and allowing the scientific community to study new phenomena.    Composer Domenico Vicinanza (left) directs the musical performance of sonified LHC data during a special Hi-Lumi event (see box). The green light was given during the 5th Joint HiLumi LHC-LARP annual meeting that took place at CERN from 26 to 30 October 2015. The meeting saw the participation of more than 230 experts from all over the world to discuss the results and achievements of the HiLumi LHC Design Study. During the week, these experts approved the first version of the HL-LHC Technical Design Report – the document that, following the Preliminary Design Report issued in 2014, describes in detail how the LHC upgrade progra...

  7. Black-hole masses of distant quasars

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2011-01-01

    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....

  8. Probing Extragalactic Planets Using Quasar Microlensing

    Science.gov (United States)

    Dai, Xinyu; Guerras, Eduardo

    2018-02-01

    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.

  9. Doppler interpretation of quasar red shifts.

    Science.gov (United States)

    Zapolsky, H S

    1966-08-05

    The hypothesis that the quasistellar sources (quasars) are local objects moving with velocities close to the speed of light is examined. Provided there is no observational cutoff on apparent bolometric magnitude for the quasars, the transverse Doppler effect leads to the expectation of fewer blue shifts than red shifts for an isotropic distribution of velocities. Such a distribution also yields a function N(z), the number of objects with red shift less than z which is not inconsistent with the present data. On the basis of two extreme assumptions concerning the origin of such rapidly moving sources, we computed curves of red shift plotted against magnitude. In particular, the curve obtained on the assumption that the quasars originated from an explosion in or nearby our own galaxy is in as good agreement with the observations as the curve of cosmological red shift plotted against magnitude.

  10. Quasars, companion galaxies and Poisson statistics

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    Arp has presented a sample of quasars lying close to the companion galaxies of bright spirals, from which he estimates a value of 10 -17 for the probability that the galaxies and quasars are sited independently on the celestial sphere; Browne, however, has found a simple fallacy in the statistics which accounts for about 10 of the 17 orders of magnitude. Here we draw attention to an obscure part of Arp's calculation which we have been unable to repeat; if it is carried out in what seems to be the most straightforward way, about five more orders may be accounted for. In consequence, it is not clear that the sample contains any evidence damaging to the popular notion that the redshifts of quasars indicate distance through the Hubble Law. (author)

  11. A Hungry Quasar Caught in the Act

    Science.gov (United States)

    2001-05-01

    The VLT Secures Spectacular Image of Distant Gravitational Interaction Summary A new image of a distant quasar (the luminous core of an "active" galaxy) shows that it is engaged in a gravitational battle with its neighbouring galaxies . It also provides information on how supermassive black holes present in the center of quasars are fed. Using the FORS2 multi-mode instrument at the ESO 8.2-m VLT KUEYEN telescope on Paranal (Chile), a team of German astronomers [1] obtained a spectacular image of the close and complex environment of the distant quasar "HE 1013-2136", located some 10 billion light-years away [2]. The remarkable structures revealed in this photo lend support to the hypothesis that quasar activity is connected to gravitational interaction between galaxies, already at this early epoch of the Universe (about 5 billion years after the Big Bang). PR Photo 20a/01 : A VLT image of the Quasar HE 1013-2136 . PR Photo 20b/01 : A sharpened version of the same image. Feeding the Black Hole "Quasars" (Quasi-Stellar Objects) were first discovered by Dutch-American astronomer Maarten Schmidt in 1963 as distant, energetic objects of star-like appearance. Since then, more than 15,000 quasars have been found and we now know that they are the luminous cores at the heart of distant galaxies. Such "Active Galactic Nuclei (AGN)" are thought to host Supermassive Black Holes of up to one billion solar masses at their centres. Black Holes represent the densest possible state of matter; if the Earth were to become one, it would measure no more than a few millimetres across. The Black Hole in a galaxy gobbles up the gas and dust of its host, a process that efficiently powers the luminous core that we observe as a point-like "quasar". A Black Hole must be continuously fed to remain active. During an active phase of typically 100 million years, the Black Hole in a quasar swallows material with a total weight of up to 10 solar masses every year. This may be predominantly in the

  12. Galaxy correlations at high redshift and the environment of quasars

    International Nuclear Information System (INIS)

    Phillipps, Steven

    1986-01-01

    In close line-of-sight pairs of quasars absorption lines may be seen in the spectrum of the further quasar at a redshift corresponding to that of the nearer quasar. This is indicative of the presence of an intervening galaxy belonging to the same cluster as the (galaxy containing the) nearer quasar. The likelihood of this occurring is calculated in terms of the galaxy correlation function and it is found that present results already suggest that quasars at redshifts above one must be associated with rich clusters. (author)

  13. A complete quasar sample at intermediate redshift

    International Nuclear Information System (INIS)

    Cristiani, S.; La Franca, F.; Barbieri, C.; Iovino, A.

    1991-01-01

    A search for intermediate-redshift quasars has been carried out with slitless spectroscopy in the central 21.07 deg 2 of the SA 94, where the existence of a large database of objects for which slit spectroscopy was already available provided a valuable opportunity of testing the properties of our selection technique. Fifty candidates have been observed with slit spectroscopy, confirming 34 quasars and two H II galaxies. The completeness of this survey as a function of magnitude and redshift has been analysed, and an effective area of 16.9 deg 2 has been evaluated. (author)

  14. IMPACT OF H{sub 2}-BASED STAR FORMATION MODEL ON THE z {>=} 6 LUMINOSITY FUNCTION AND THE IONIZING PHOTON BUDGET FOR REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Jaacks, Jason; Thompson, Robert [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154-4002 (United States); Nagamine, Kentaro, E-mail: jaacksj@physics.unlv.edu [Visiting Scientist. Kavli Institute for the Physics and Mathematics for the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8583, Japan. (Japan)

    2013-04-01

    We present the results of a numerical study examining the effect of an H{sub 2}-based star formation (SF) model on the rest-frame UV luminosity function and star formation rate function (SFRF) of z {>=} 6 galaxies, and the implications for reionization. Using cosmological hydrodynamical simulations outfitted with an H{sub 2}-SF model, we find good agreement with our previous results (non-H{sub 2} SF model) and observations at M{sub uv} {<=} -18. However, at M{sub uv} > -18, we find that the LF deviates from both our previous work and current observational extrapolations, producing significantly fewer low-luminosity galaxies and exhibiting additional turnover at the faint end. We constrain the redshift evolution of this turnover point using a modified Schechter function that includes additional terms to quantify the turnover magnitude (M{sub uv}{sup t}) and subsequent slope ({beta}). We find that M{sub uv}{sup t} evolves from M{sub uv}{sup t}=-17.33 (at z = 8) to -15.38 (z = 6), while {beta} becomes shallower by {Delta}{beta} = 0.22 during the same epoch. This occurs in an M{sub uv} range that will be observable by James Webb Space Telescope. By integrating the SFRF, we determine that even though the H{sub 2}-SF model significantly reduces the number density of low-luminosity galaxies at M{sub uv} > -18, it does not suppress the total SFR density enough to affect the capability of SF to maintain reionization.

  15. HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

    International Nuclear Information System (INIS)

    Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki; Kawamata, Ryota; Shimasaku, Kazuhiro; Oguri, Masamune

    2015-01-01

    We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functions with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ UV , at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ UV decrease trend can be reconciled with the large Thomson scattering optical depth, τ e , measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ UV decrease and the large τ e . It is possible that the ρ UV decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei

  16. HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Kawamata, Ryota; Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Oguri, Masamune, E-mail: ishigaki@icrr.u-tokyo.ac.jp [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-01-20

    We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functions with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ{sub UV}, at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ{sub UV} decrease trend can be reconciled with the large Thomson scattering optical depth, τ{sub e}, measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ{sub UV} decrease and the large τ {sub e}. It is possible that the ρ{sub UV} decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei.

  17. DES J0454-4448: discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Reed, S. L.; McMahon, R. G.; Banerji, M.; Becker, G. D.; Gonzalez-Solares, E.; Martini, P.; Ostrovski, F.; Rauch, M.; Abbott, T.; Abdalla, F. B.; Allam, S.; Benoit-Levy, A.; Bertin, E.; Buckley-Geer, E.; Burke, D.; Carnero Rosell, A.; da Costa, L. N.; D' Andrea, C.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Finley, D. A.; Fosalba, P.; Frieman, J.; Gruen, D.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marshall, J.; Merritt, K.; Miquel, R.; Mohr, J.; Nord, B.; Ogando, R.; Plazas, A.; Romer, K.; Roodman, A.; Rykoff, E.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla, I.; Smith, C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D.; Walker, A.; Wechsler, R. H.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = -26.5) quasar DES J0454-4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H I near zone size of 4.1+1.1-1.2 proper Mpc. The quasar was selected as an i-band drop out with i-z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i-z and z-Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.

  18. The hyperluminous infrared quasar 3C 318 and its implications for interpreting sub-mm detections of high-redshift radio galaxies

    OpenAIRE

    Willott, Chris J.; Rawlings, Steve; Jarvis, Matt J.

    1999-01-01

    We present near-infrared spectroscopy and imaging of the compact steep- spectrum radio source 3C 318 which shows it to be a quasar at redshift z=1.574 (the z=0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalogue (there is no evidence of strong gravitational lensing effects). Its bolometric luminosity greatly exceeds the 10^13 solar luminosity level above ...

  19. Using quasars as standard clocks for measuring cosmological redshift.

    Science.gov (United States)

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

    2012-06-08

    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.

  20. The rotating wind of the quasar PG 1700+518.

    Science.gov (United States)

    Young, S; Axon, D J; Robinson, A; Hough, J H; Smith, J E

    2007-11-01

    It is now widely accepted that most galaxies undergo an active phase, during which a central super-massive black hole generates vast radiant luminosities through the gravitational accretion of gas. Winds launched from a rotating accretion disk surrounding the black hole are thought to play a critical role, allowing the disk to shed angular momentum that would otherwise inhibit accretion. Such winds are capable of depositing large amounts of mechanical energy in the host galaxy and its environs, profoundly affecting its formation and evolution, and perhaps regulating the formation of large-scale cosmological structures in the early Universe. Although there are good theoretical grounds for believing that outflows from active galactic nuclei originate as disk winds, observational verification has proven elusive. Here we show that structures observed in polarized light across the broad Halpha emission line in the quasar PG 1700+518 originate close to the accretion disk in an electron scattering wind. The wind has large rotational motions (approximately 4,000 km s(-1)), providing direct observational evidence that outflows from active galactic nuclei are launched from the disks. Moreover, the wind rises nearly vertically from the disk, favouring launch mechanisms that impart an initial acceleration perpendicular to the disk plane.

  1. Apparent quasar disc sizes in the "bird's nest" paradigm

    Science.gov (United States)

    Abolmasov, P.

    2017-04-01

    Context. Quasar microlensing effects make it possible to measure the accretion disc sizes around distant supermassive black holes that are still well beyond the spatial resolution of contemporary instrumentation. The sizes measured with this technique appear inconsistent with the standard accretion disc model. Not only are the measured accretion disc sizes larger, but their dependence on wavelength is in most cases completely different from the predictions of the standard model. Aims: We suggest that these discrepancies may arise not from non-standard accretion disc structure or systematic errors, as it was proposed before, but rather from scattering and reprocession of the radiation of the disc. In particular, the matter falling from the gaseous torus and presumably feeding the accretion disc may at certain distances become ionized and produce an extended halo that is free from colour gradients. Methods: A simple analytical model is proposed assuming that a geometrically thick translucent inflow acts as a scattering mirror changing the apparent spatial properties of the disc. This inflow may be also identified with the broad line region or its inner parts. Results: Such a model is able to explain the basic properties of the apparent disc sizes, primarily their large values and their shallow dependence on wavelength. The only condition required is to scatter a significant portion of the luminosity of the disc. This can easily be fulfilled if the scattering inflow has a large geometrical thickness and clumpy structure.

  2. Integral luminosities of radio pulsars

    Science.gov (United States)

    Malov, I.; Malov, O.

    The integral radio luminosities L for 311 normal pulsars and for 27 ones with the rotation period Pfalls for fast ones. The mean values of K are -3.73 and -4.85 for normal and fast pulsars, respectively. There are no changes of L with the kinematic age T = z/V, where z is the pulsar height over the Galactic plane and V = 300 km/s is its mean velocity. The correlation between L and the rate of the rotation energy losses E is detected for both pulsar groups under consideration. It is shown that L= A E^(1/3) for the whole sample. The total number of pulsars in the Galaxy and their birth rate are in agreement with data on the rate of supernova explosions.

  3. Quasar Parallax: a Method for Determining Direct Geometrical Distances to Quasars

    OpenAIRE

    Elvis, Martin; Karovska, Margarita

    2002-01-01

    We describe a novel method to determine direct geometrical distances to quasars that can measure the cosmological constant, Lambda, with minimal assumptions. This method is equivalent to geometric parallax, with the `standard length' being the size of the quasar broad emission line region (BELR) as determined from the light travel time measurements of reverberation mapping. The effect of non-zero Lambda on angular diameter is large, 40% at z=2, so mapping angular diameter distances vs. redshi...

  4. Close companions to two high-redshift quasars

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-01

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

  5. The Associated Absorption Features in Quasar Spectra of the Sloan Digital Sky Survey. I. Mg II Absorption Doublets

    Science.gov (United States)

    Chen, Zhi-Fu; Huang, Wei-Rong; Pang, Ting-Ting; Huang, Hong-Yan; Pan, Da-Sheng; Yao, Min; Nong, Wei-Jing; Lu, Mei-Mei

    2018-03-01

    Using the SDSS spectra of quasars included in the DR7Q or DR12Q catalogs, we search for Mg II λλ2796, 2803 narrow absorption doublets in the spectra data around Mg II λ2798 emission lines. We obtain 17,316 Mg II doublets, within the redshift range of 0.3299 ≤ z abs ≤ 2.5663. We find that a velocity offset of υ r 6000 km s‑1. If associated Mg II absorbers are defined by υ r present at least one associated Mg II system with {W}{{r}}λ 2796≥slant 0.2 \\mathringA . The fraction of associated Mg II systems with high-velocity outflows correlates with the average luminosities of their central quasars, indicating a relationship between outflows and the quasar feedback power. The υ r distribution of the outflow Mg II absorbers is peaked at 1023 km s‑1, which is smaller than the corresponding value of the outflow C IV absorbers. The redshift number density evolution of absorbers (dn/dz) limited by υ r > ‑3000 km s‑1 differs from that of absorbers constrained by υ r > 2000 km s‑1. Absorbers limited by υ r > 2000 km s‑1 and higher values exhibit profiles similar to dn/dz. In addition, the dn/dz is smaller when absorbers are constrained with larger υ r . The distributions of equivalent widths, and the ratio of {W}rλ 2796/{W}rλ 2803, are the same for associated and intervening systems, and independent of quasar luminosity.

  6. Sunyaev–Zel’Dovich Signal from Quasar Hosts: Implications for Detection of Quasar Feedback

    International Nuclear Information System (INIS)

    Chowdhury, Dhruba Dutta; Chatterjee, Suchetana

    2017-01-01

    Several analytic and numerical studies have indicated that the interstellar medium of a quasar host galaxy heated by feedback can contribute to a substantial secondary signal in the cosmic microwave background (CMB) through the thermal Sunyaev–Zel’dovich (SZ) effect. Recently, many groups have tried to detect this signal by cross-correlating CMB maps with quasar catalogs. Using a self-similar model for the gas in the intra-cluster medium and a realistic halo occupation distribution (HOD) prescription for quasars, we estimate the level of SZ signal from gravitational heating of quasar hosts. The bias in the host halo signal estimation due to an unconstrained high mass HOD tail and yet unknown redshift dependence of the quasar HOD restricts us from drawing any robust conclusions at low redshift ( z < 1.5) from our analysis. However, at higher redshifts ( z > 2.5), we find an excess signal in recent observations than what is predicted from our model. The excess signal could be potentially generated from additional heating due to quasar feedback.

  7. Sunyaev–Zel’Dovich Signal from Quasar Hosts: Implications for Detection of Quasar Feedback

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Dhruba Dutta; Chatterjee, Suchetana, E-mail: dhruba.duttachowdhury@yale.edu [Department of Physics, Presidency University, Kolkata, 700073 (India)

    2017-04-10

    Several analytic and numerical studies have indicated that the interstellar medium of a quasar host galaxy heated by feedback can contribute to a substantial secondary signal in the cosmic microwave background (CMB) through the thermal Sunyaev–Zel’dovich (SZ) effect. Recently, many groups have tried to detect this signal by cross-correlating CMB maps with quasar catalogs. Using a self-similar model for the gas in the intra-cluster medium and a realistic halo occupation distribution (HOD) prescription for quasars, we estimate the level of SZ signal from gravitational heating of quasar hosts. The bias in the host halo signal estimation due to an unconstrained high mass HOD tail and yet unknown redshift dependence of the quasar HOD restricts us from drawing any robust conclusions at low redshift ( z < 1.5) from our analysis. However, at higher redshifts ( z > 2.5), we find an excess signal in recent observations than what is predicted from our model. The excess signal could be potentially generated from additional heating due to quasar feedback.

  8. Luminosity Measurements with the ATLAS Detector

    CERN Document Server

    Maettig, Stefan; Pauly, T

    For almost all measurements performed at the Large Hadron Collider (LHC) one crucial ingredient is the precise knowledge about the integrated luminosity. The determination and precision on the integrated luminosity has direct implications on any cross-section measurement, and its instantaneous measurement gives important feedback on the conditions at the experimental insertions and on the accelerator performance. ATLAS is one of the main experiments at the LHC. In order to provide an accurate and reliable luminosity determination, ATLAS uses a variety of different sub-detectors and algorithms that measure the luminosity simultaneously. One of these sub-detectors are the Beam Condition Monitors (BCM) that were designed to protect the ATLAS detector from potentially dangerous beam losses. Due to its fast readout and very clean signals this diamond detector is providing in addition since May 2011 the official ATLAS luminosity. This thesis describes the calibration and performance of the BCM as a luminosity detec...

  9. Quasar Elemental Abundances at High Redshifts

    DEFF Research Database (Denmark)

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

    2003-01-01

    the framework of the most recent photoionization models to estimate the metallicity of the gas associated with the high-z quasars. Standard photoionization parameters and the assumption of secondary nitrogen enrichment indicate an average abundance of Z/Z_sol = 4 to 5 in the line emitting gas. Assuming a time...

  10. Quasar Astrophysics with the Space Interferometry Mission

    Science.gov (United States)

    Unwin, Stephen; Wehrle, Ann; Meier, David; Jones, Dayton; Piner, Glenn

    2007-01-01

    Optical astrometry of quasars and active galaxies can provide key information on the spatial distribution and variability of emission in compact nuclei. The Space Interferometry Mission (SIM PlanetQuest) will have the sensitivity to measure a significant number of quasar positions at the microarcsecond level. SIM will be very sensitive to astrometric shifts for objects as faint as V = 19. A variety of AGN phenomena are expected to be visible to SIM on these scales, including time and spectral dependence in position offsets between accretion disk and jet emission. These represent unique data on the spatial distribution and time dependence of quasar emission. It will also probe the use of quasar nuclei as fundamental astrometric references. Comparisons between the time-dependent optical photocenter position and VLBI radio images will provide further insight into the jet emission mechanism. Observations will be tailored to each specific target and science question. SIM will be able to distinguish spatially between jet and accretion disk emission; and it can observe the cores of galaxies potentially harboring binary supermassive black holes resulting from mergers.

  11. Low resolution infrared spectra of quasars

    International Nuclear Information System (INIS)

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

    1980-01-01

    Low resolution spectra of a significant sample of quasars show that the Paschen α and Balmer line ratios do not agree with the radiative recombination case B result and vary widely within the quasars sampled. The range in Pα:Hβ ratios is a factor of approximately 6, while the range in Lyα:Hα ratios is a factor of approximately 5. For the Pα:Balmer series, the deviations from case B recombination are not consistent with reddening, but appear, within large dispersions, to be consistent with optical depth effects in the Balmer lines affecting the line ratios. The Lyα:Hα ratio is, however, correlated with the continuum spectral index, and can be explained as due to reddening affecting both the lines and continuum. Recent observational results based on a joint infrared/optical survey of the hydrogen line spectra of a significant number of the brightest low and high redshift quasars are summarised. This survey includes 12 quasars in the redshift range 0.07 1.5, where Hα and/or Hβ is redshifted into the 1.65μm or 2.2μm atmospheric windows. (Auth.)

  12. Quasar Mass Functions Across Cosmic Time

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2010-01-01

    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...

  13. Quasars, Seyfert galaxies and active galactic nuclei

    International Nuclear Information System (INIS)

    Osterbrock, D.E.

    1987-01-01

    This chapter is devoted to the spectroscopic methods for analyzing the observed plasma in the nuclei of quasars, Seyfert galazies, and active galactic nuclei. Both the narrow-line region and the broad-line region are discussed. Physical models are presented

  14. Cross-Correlations in Quasar Radio Emission

    Science.gov (United States)

    Nefedyev, Yuri; Panischev, Oleg; Demin, Sergey

    The main factors forming the complex evolution of the accretive astrophysical systems are nonlinearity, intermittency, nonstationarity and also collective phenomena. To discover the dynamic processes in these objects and to detain understanding their properties we need to use all the applicable analyzing methods. Here we use the Flicker-Noise Spectroscopy (FNS) as a phenomenological approach to analyzing and parameterizing the auto- and cross-correlations in time series of astrophysical objects dynamics. As an example we consider the quasar flux radio spectral density at frequencies 2.7 GHz and 8.1 GHz. Data have been observed by Dr. N. Tanizuka (Laboratory for Complex Systems Analysis, Osaka Prefecture University) in a period of 1979 to 1988 (3 309 days). According to mental habits quasar is a very energetic and distant active galactic nucleus containing a supermassive black hole by size 10-10,000 times the Schwarzschild radius. The quasar is powered by an accretion disc around the black hole. The accretion disc material layers, moving around the black hole, are under the influence of gravitational and frictional forces. It results in raising the high temperature and arising the resonant and collective phenomena reflected in quasar emission dynamics. Radio emission dynamics of the quasar 0215p015 is characterized by three quasi-periodic processes, which are prevalent in considering dynamics. By contrast the 1641p399's emission dynamics have not any distinguish processes. It means the presence of high intermittency in accretive modes. The second difference moment allows comparing the degree of manifesting of resonant and chaotic components in initial time series of the quasar radio emission. The comparative analysis shows the dominating of chaotic part of 1641p399's dynamics whereas the radio emission of 0215p015 has the predominance of resonant component. Analyzing the collective features of the quasar radio emission intensity demonstrates the significant

  15. Black hole mass estimates and emission-line properties of a sample of redshift z > 6.5 quasars

    Energy Technology Data Exchange (ETDEWEB)

    De Rosa, Gisella; Peterson, Bradley M.; Frank, Stephan [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Venemans, Bram P.; Decarli, Roberto; Walter, Fabian [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Gennaro, Mario [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Simcoe, Robert A. [MIT-Kavli Center for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Dietrich, Matthias [Department of Physics and Astronomy, Ohio University, Clippinger Lab 251B, Athens, OH 45701 (United States); McMahon, Richard G.; Hewett, Paul C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Mortlock, Daniel J. [Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ (United Kingdom); Simpson, Chris [Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom)

    2014-08-01

    We present the analysis of optical and near-infrared spectra of the only four z > 6.5 quasars known to date, discovered in the UKIDSS-LAS and VISTA-VIKING surveys. Our data set consists of new Very Large Telescope/X-Shooter and Magellan/FIRE observations. These are the best optical/NIR spectroscopic data that are likely to be obtained for the z > 6.5 sample using current 6-10 m facilities. We estimate the black hole (BH) mass, the Eddington ratio, and the Si IV/C IV, C III]/C IV, and Fe II/Mg II emission-line flux ratios. We perform spectral modeling using a procedure that allows us to derive a probability distribution for the continuum components and to obtain the quasar properties weighted upon the underlying distribution of continuum models. The z > 6.5 quasars show the same emission properties as their counterparts at lower redshifts. The z > 6.5 quasars host BHs with masses of ∼10{sup 9} M{sub ☉} that are accreting close to the Eddington luminosity ((log(L{sub Bol}/L{sub Edd})) = –0.4 ± 0.2), in agreement with what has been observed for a sample of 4.0 < z < 6.5 quasars. By comparing the Si IV/C IV and C III]/C IV flux ratios with the results obtained from luminosity-matched samples at z ∼ 6 and 2 ≤ z ≤ 4.5, we find no evidence of evolution of the line ratios with cosmic time. We compare the measured Fe II/Mg II flux ratios with those obtained for a sample of 4.0 < z < 6.4 sources. The two samples are analyzed using a consistent procedure. There is no evidence that the Fe II/Mg II flux ratio evolves between z = 7 and z = 4. Under the assumption that the Fe II/Mg II traces the Fe/Mg abundance ratio, this implies the presence of major episodes of chemical enrichment in the quasar hosts in the first ∼0.8 Gyr after the Big Bang.

  16. Luminosity monitoring and measurement at CDF

    International Nuclear Information System (INIS)

    Cronin-Hennessy, D.; Beretvas, A.; Derwent, P.F.

    2000-01-01

    Using two telescopes of beam-beam counters, CDF (Collider Detector at Fermilab) has measured the luminosity to an accuracy of 4.1% (3.6%) in run Ib (Ia). For run Ib (Ia) the average luminosity was 9.1(3.3)x10 30 cm -2 s -1 . For a typical data set the integrated luminosity was 86.47 (19.65) pb -1 in run Ib (Ia) resulting in a total integrated luminosity of 106.1±4.1 pb -1 . This paper shows how we have determined the accuracy of our results

  17. A Significantly off-center 56Ni Distribution for the Low-Luminosity Type Ia Supernova SN 2016brx from the 100IAS survey

    Science.gov (United States)

    Dong, Subo; Katz, Boaz; Kollmeier, Juna A.; Kushnir, Doron; Elias-Rosa, N.; Bose, Subhash; Morrell, Nidia; Prieto, J. L.; Chen, Ping; Kochanek, C. S.; Brandt, G. M.; Holoien, T. W.-S.; Gal-Yam, Avishay; Morales-Garoffolo, Antonia; Parker, Stuart; Phillips, M. M.; Piro, Anthony L.; Shappee, B. J.; Simon, Joshua D.; Stanek, K. Z.

    2018-06-01

    We present nebular-phase spectra of the Type Ia supernova (SN Ia) 2016brx, a member of the 1991bg-like subclass that lies at the faint end of the SN Ia luminosity function. Nebular spectra are available for only three other 1991bg-like SNe, and their Co line centers are all within ≲ 500 km/s of each other. In contrast, the nebular Co line center of SN 2016brx is blue-shifted by >1500 km/s compared to them and by ≈1200 km/s compared to the rest frame. This is a significant shift relative to the narrow nebular line velocity dispersion of ≲ 2000 km/s of these SNe. The large range of nebular line shifts implies that the 56Ni in the ejecta of SN 1991bg-like events is off-center by ˜1000 km/s rather than universally centrally confined as previously suggested. With the addition of SN 2016brx, the Co nebular line shapes of 1991bg-like objects appear to connect with the brighter SNe Ia that show double-peaked profiles, hinting at a continuous distribution of line profiles among SNe Ia. One class of models to produce both off-center and bi-modal 56Ni distributions is collisions of white dwarfs with unequal and equal masses.

  18. Evolution of solar ultraviolet luminosity

    International Nuclear Information System (INIS)

    Zahnle, K.J.; Walker, J.C.G.

    1982-01-01

    In view of the major role of the sun in defining the properties of planetary atmospheres, their evolution cannot be fully understood outside the context of an evolving sun. The ultraviolet radiation is especially interesting because of its strong interaction with planetary atmospheres. We use astronomical observation of stars that are analogous to the sun in order to reconstruct a tentative account of the evolution of solar UV luminosity. A wealth of evidence indicates that the young sun was a much more powerful source of energetic particles and radiation than it is today. While on the main sequence, solar activity has declined as an inverse power law of age (between t -5 and t/sup -1.2/) as a consequence of angular momentum loss to the solar wind. Recent IUE satellite observations of premain sequence stars suggest that before the sun reached the main sequence (at an age of about 50 m.y.), it may have emitted as much as 10 4 times as much ultraviolet radiation (γ<2000 A) than it does today. These results could impact our understanding of the photochemistry and escape of constituents of primordial planetary atmospheres

  19. Gravitationally Lensed Quasars in Gaia: II. Discovery of 24 Lensed Quasars

    Science.gov (United States)

    Lemon, Cameron A.; Auger, Matthew W.; McMahon, Richard G.; Ostrovski, Fernanda

    2018-04-01

    We report the discovery, spectroscopic confirmation and preliminary characterisation of 24 gravitationally lensed quasars identified using Gaia observations. Candidates were selected in the Pan-STARRS footprint with quasar-like WISE colours or as photometric quasars from SDSS, requiring either multiple detections in Gaia or a single Gaia detection near a morphological galaxy. The Pan-STARRS grizY images were modelled for the most promising candidates and 60 candidate systems were followed up with the William Herschel Telescope. 13 of the lenses were discovered as Gaia multiples and 10 as single Gaia detections near galaxies. We also discover 1 lens identified through a quasar emission line in an SDSS galaxy spectrum. The lenses have median image separation 2.13″ and the source redshifts range from 1.06 to 3.36. 4 systems are quadruply-imaged and 20 are doubly-imaged. Deep CFHT data reveal an Einstein ring in one double system. We also report 12 quasar pairs, 10 of which have components at the same redshift and require further follow-up to rule out the lensing hypothesis. We compare the properties of these lenses and other known lenses recovered by our search method to a complete sample of simulated lenses to show the lenses we are missing are mainly those with small separations and higher source redshifts. The initial Gaia data release only catalogues all images of ˜ 30% of known bright lensed quasars, however the improved completeness of Gaia data release 2 will help find all bright lensed quasars on the sky.

  20. The UDF05 Follow-up of the Hubble Ultra Deep Field. III. The Luminosity Function at z ~ 6

    Science.gov (United States)

    Su, Jian; Stiavelli, Massimo; Oesch, Pascal; Trenti, Michele; Bergeron, Eddie; Bradley, Larry; Carollo, Marcella; Dahlen, Tomas; Ferguson, Henry C.; Giavalisco, Mauro; Koekemoer, Anton; Lilly, Simon; Lucas, Ray A.; Mobasher, Bahram; Panagia, Nino; Pavlovsky, Cheryl

    2011-09-01

    In this paper, we present a derivation of the rest-frame 1400 Å luminosity function (LF) at redshift six from a new application of the maximum likelihood method by exploring the five deepest Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) fields, i.e., the Hubble Ultra Deep Field, two UDF05 fields, and two Great Observatories Origins Deep Survey fields. We work on the latest improved data products, which makes our results more robust than those of previous studies. We use unbinned data and thereby make optimal use of the information contained in the data set. We focus on the analysis to a magnitude limit where the completeness is larger than 50% to avoid possibly large errors in the faint end slope that are difficult to quantify. We also take into account scattering in and out of the dropout sample due to photometric errors by defining for each object a probability that it belongs to the dropout sample. We find the best-fit Schechter parameters to the z ~ 6 LF are α = 1.87 ± 0.14, M * = -20.25 ± 0.23, and phi* = 1.77+0.62 -0.49 × 10-3 Mpc-3. Such a steep slope suggests that galaxies, especially the faint ones, are possibly the main sources of ionizing photons in the universe at redshift six. We also combine results from all studies at z ~ 6 to reach an agreement in the 95% confidence level that -20.45 Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 10632 and 11563.

  1. Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6.

    Science.gov (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

    2017-05-24

    The existence of massive (10 11 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 10 9 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. Missing mass from low-luminosity stars

    International Nuclear Information System (INIS)

    Hawkins, M.R.S.

    1986-01-01

    Results from a deep photometric survey for low-luminosity stars show a turnup to the luminosity function at faint magnitudes, and reopen the possibility that the missing mass in the solar neighbourhood is made up of stars after all. (author)

  3. Luminosity Monitoring in ATLAS with MPX Detectors

    CERN Document Server

    AUTHOR|(CDS)2086061

    2013-01-01

    The ATLAS-MPX detectors are based on the Medipix2 silicon devices designed by CERN for the detection of multiple types of radiation. Sixteen such detectors were successfully operated in the ATLAS detector at the LHC and collected data independently of the ATLAS data-recording chain from 2008 to 2013. Each ATLAS-MPX detector provides separate measurements of the bunch-integrated LHC luminosity. An internal consistency for luminosity monitoring of about 2% was demonstrated. In addition, the MPX devices close to the beam are sensitive enough to provide relative-luminosity measurements during van der Meer calibration scans, in a low-luminosity regime that lies below the sensitivity of the ATLAS calorimeter-based bunch-integrating luminometers. Preliminary results from these luminosity studies are presented for 2012 data taken at $\\sqrt{s}=8$ TeV proton-proton collisions.

  4. Diversity of soft X-ray spectra in quasars

    International Nuclear Information System (INIS)

    Elvis, M.; Wilkes, B.J.; Tananbaum, H.

    1985-01-01

    Soft X-ray spectra for three quasars obtained with the Einstein Imaging Proportional Counter covering the 0.1-4.0 keV band are reported. Power-law fits to these spectra have best-fit energy indices of 1.2 +0.6 or -0.2, for the quasar NAB 0205 + 024, 0.6 +0.3 or -0.2 for the quasar B2 1028 + 313, and 2.2 + or -0.4 for the quasar PG 1211 + 143. None of the quasars shows any evidence for a column density of cold matter in excess of the galactic values. The derived spectra demonstrate that there is no single universal power law slope for quasar X-ray spectra. The implications of these results for the X-ray background, X-ray continuum emission mechanisms, and the production of the optical/UV emission lines are briefly discussed. 46 references

  5. On the periodicity in the distribution of quasar redshifts

    International Nuclear Information System (INIS)

    Kjaergaard, P.

    1978-01-01

    The periodicity in the distribution of quasar redshifts is explained in terms of selection effects. Special attention is drawn to a selection effect caused by the redshift dependent influence of the strong emission lines on the limiting magnitude for detecting quasars. This is especially important since the number of quasars increases with a large factor per magnitude. The limiting magnitude effect applies both to spectroscopic and to UV-excess surveys. It is shown that the redshift distribution of quasars selected by a combination of UV-excess information and agreement between radio and optical position is intermediate between the redshift distribution of the two groups of quasars selected by one of the two criteria. It is also shown that the distribution of redshifts for UV-excess selected quasars is very similar to the variation of the ultrsviolet excess as a function of redshift. This evidence indicates that strong selection effects are in play. (Auth.)

  6. Summary of the workshop on active galaxies and quasars

    International Nuclear Information System (INIS)

    Weistrop, D.

    1981-01-01

    The paper reports highlights of discussions carried out at the Tenth Texas Symposium on Relativistic Astrophysics concerning BL Lacertae objects and quasars and their relationship to active galactic nuclei. The discussions considered X-ray, optical and radio observations of active galaxies and quasars showing features which may be interpreted as jets or beams, and X-ray and VLBI observations of core-jet structures exhibiting apparent supraluminal expansion. Attention was also given to the properties of the energy source in the center of the active galaxies and quasars, the nature of quasar emission line regions, the production of the continuum in quasars and active galactic nuclei, and evidence for the association of quasars and BL Lac objects with galaxies

  7. BINARY QUASARS AT HIGH REDSHIFT. I. 24 NEW QUASAR PAIRS AT z ∼ 3-4

    International Nuclear Information System (INIS)

    Hennawi, Joseph F.; Myers, Adam D.; Shen, Yue; Strauss, Michael A.; Djorgovski, S. G.; Glikman, Eilat; Mahabal, Ashish; Fan Xiaohui; Martin, Crystal L.; Richards, Gordon T.; Schneider, Donald P.; Shankar, Francesco

    2010-01-01

    The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high-redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142 deg 2 of Sloan Digital Sky Survey imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high-redshift binaries (24 of them new discoveries) at redshifts 2.9 perpendicular perpendicular 3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is ∼50% complete. Our companion paper uses this knowledge to make the first measurement of the small-scale clustering (R -1 Mpc comoving) of high-redshift quasars. High-redshift binaries constitute exponentially rare coincidences of two extreme (M ∼> 10 9 M sun ) supermassive black holes. At z ∼ 4, there is about one close binary per 10 Gpc 3 , thus these could be the highest sigma peaks, the analogs of superclusters, in the early universe.

  8. The essential signature of a massive starburst in a distant quasar.

    Science.gov (United States)

    Solomon, P; Vanden Bout, P; Carilli, C; Guelin, M

    2003-12-11

    Observations of carbon monoxide emission in high-redshift (zeta > 2) galaxies indicate the presence of large amounts of molecular gas. Many of these galaxies contain an active galactic nucleus powered by accretion of gas onto a supermassive black hole, and a key question is whether their extremely high infrared luminosities result from the active galactic nucleus, from bursts of massive star formation (associated with the molecular gas), or both. In the Milky Way, high-mass stars form in the dense cores of interstellar molecular clouds, where gas densities are n(H2) > 10(5) cm(-3) (refs 1, 2). Recent surveys show that virtually all galactic sites of high-mass star formation have similarly high densities. The bulk of the cloud material traced by CO observations, however, is at a much lower density. For galaxies in the local Universe, the HCN molecule is an effective tracer of high-density molecular gas. Here we report observations of HCN emission from the infrared-luminous 'Cloverleaf' quasar (at a redshift zeta = 2.5579). The HCN line luminosity indicates the presence of 10 billion solar masses of very dense gas, an essential feature of an immense starburst, which contributes, together with the active galactic nucleus it harbours, to its high infrared luminosity.

  9. The Identification of Z-dropouts in Pan-STARRS1: Three Quasars at 6.5< z< 6.7

    Science.gov (United States)

    Venemans, B. P.; Bañados, E.; Decarli, R.; Farina, E. P.; Walter, F.; Chambers, K. C.; Fan, X.; Rix, H.-W.; Schlafly, E.; McMahon, R. G.; Simcoe, R.; Stern, D.; Burgett, W. S.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Magnier, E. A.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Waters, C.; AlSayyad, Y.; Banerji, M.; Chen, S. S.; González-Solares, E. A.; Greiner, J.; Mazzucchelli, C.; McGreer, I.; Miller, D. R.; Reed, S.; Sullivan, P. W.

    2015-03-01

    Luminous distant quasars are unique probes of the high-redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral hydrogen in the IGM makes quasars beyond a redshift of z≃ 6.5 very faint in the optical z band, thus locating quasars at higher redshifts requires large surveys that are sensitive above 1 micron. We report the discovery of three new z\\gt 6.5 quasars, corresponding to an age of the universe of \\lt 850 Myr, selected as z-band dropouts in the Pan-STARRS1 survey. This increases the number of known z\\gt 6.5 quasars from four to seven. The quasars have redshifts of z = 6.50, 6.52, and 6.66, and include the brightest z-dropout quasar reported to date, PSO J036.5078 + 03.0498 with {{M}1450}=-27.4. We obtained near-infrared spectroscopy for the quasars, and from the Mg ii line, we estimate that the central black holes have masses between 5 × 108 and 4 × 109 {{M}⊙ } and are accreting close to the Eddington limit ({{L}Bol}/{{L}Edd}=0.13-1.2). We investigate the ionized regions around the quasars and find near-zone radii of {{R}NZ}=1.5-5.2 proper Mpc, confirming the trend of decreasing near-zone sizes with increasing redshift found for quasars at 5.7\\lt z\\lt 6.4. By combining RNZ of the PS1 quasars with those of 5.7\\lt z\\lt 7.1 quasars in the literature, we derive a luminosity-corrected redshift evolution of {{R}NZ,corrected}=(7.2+/- 0.2)-(6.1+/- 0.7)× (z-6) Mpc. However, the large spread in RNZ in the new quasars implies a wide range in quasar ages and/or a large variation in the neutral hydrogen fraction along different lines of sight. Based in part on observations collected at the European Southern Observatory, Chile, programs 179.A-2010, 092.A-0150, 093.A-0863, and 093.A-0574, and at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). This paper

  10. Intrinsic variations of the double quasar 0957 + 56 AB

    International Nuclear Information System (INIS)

    Lloyd, C.

    1981-01-01

    Observations of the two components of the quasar 0957 + 56A and B are reported which show a variation of approximately 1 mag in both components and behaviour typical of intrinsically variable quasars with similar radio structure. It is argued that the near constancy of the magnitude difference between the components at several epochs, despite overall variations, favours all the variations being intrinsic to the quasar and also supports the hypothesis that the two images are produced by the gravitational lensing of a single distant quasar. (U.K.)

  11. An explanation of the mysterious quasars

    International Nuclear Information System (INIS)

    Borissov, O.

    1977-01-01

    The article presents details of a convincing new theory submitted by Russian scientists, concerning the physical nature of quasars. These were discovered in 1963 and for over ten years no satisfactory theory has been forthcoming to explain their seemingly incompatible properties or the associated phenomena. These very distant objects are believed to be sources of the most powerful electromagnetic emission. From the new theory expounded it is concluded that for the first time since their discovery a satisfactory explanation of their nature has been reached. From this it is hoped that the mechanism of energy generation by quasars may ultimately be understood and, though on a much reduced scale, contribute to the solution of energy problems on earth. (R.J.J.)

  12. Automated analysis of slitless spectra. II. Quasars

    International Nuclear Information System (INIS)

    Edwards, G.; Beauchemin, M.; Borra, F.

    1988-01-01

    Automated software have been developed to process slitless spectra. The software, described in a previous paper, automatically separates stars from extended objects and quasars from stars. This paper describes the quasar search techniques and discusses the results. The performance of the software is compared and calibrated with a plate taken in a region of SA 57 that has been extensively surveyed by others using a variety of techniques: the proposed automated software performs very well. It is found that an eye search of the same plate is less complete than the automated search: surveys that rely on eye searches suffer from incompleteness at least from a magnitude brighter than the plate limit. It is shown how the complete automated analysis of a plate and computer simulations are used to calibrate and understand the characteristics of the present data. 20 references

  13. Black hole accretion: the quasar powerhouse

    International Nuclear Information System (INIS)

    Anon.

    1983-01-01

    A program is described which calculates the effects of material falling into the curved space-time surrounding a rotation black hole. The authors have developed a two-dimensional, general-relativistic hydrodynamics code to simulate fluid flow in the gravitational field of a rotating black hole. Such calculations represent models that have been proposed for the energy sources of both quasars and jets from radiogalaxies. In each case, the black hole that powers the quasar or jet would have a mass of about 100 million times the mass of the sun. The black hole would be located in the center of a galaxy whose total mass is 1000 time greater than the black hole mass. (SC)

  14. 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)

    2013-12-01

    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.

  15. Do quasar ley lines really exist

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    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 earlier authors, 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. (author)

  16. Infrared observations of Seyfert galaxies and quasars

    International Nuclear Information System (INIS)

    Neugebauer, G.

    1978-01-01

    The infrared energy distributions of the Seyfert galaxies apparently contain three components: a galactic stellar component, a thermal component from heated dust, plus a nonthermal component. The appearance of the infrared energy distribution depends on which component dominates. There is also a correlation observed between the infrared energy distribution and the Khachikian Weedman class. Preliminary data on bright quasars are given. The infrared energy distributions generally increase into the infrared with a power law slope of approximately 1. In detail they differ from power laws with a significant fraction emitting most of their energy near 3μm. No differences in radio loud and radio quiet are obvious from the infrared energy distributions. The variability of the quasars in the infrared is generally correlated with the variability in the visible, although significant exceptions have been observed. (Auth.)

  17. Quasars in the Life of Astronomers

    Science.gov (United States)

    D'Onofrio, Mauro; Marziani, Paola; Sulentic, Jack W.; Collin, Suzy; Setti, Giancarlo; Gaskell, Martin; Wampler, Joe; Elvis, Martin; Pronik, Iraida; Pronik, Vladimir; Sergeev, Sergey; Volvach, Aleksander; Krolik, Julian; Netzer, Hagai; Cavaliere, Alfonso; Padovani, Paolo; Arp, Halton; Narlikar, Jayant

    We are approaching the 50th anniversary of the discovery of quasars. Those old enough to have been cognizant of astronomy in 1962-1963 can remember the sense of excitement connected with this finding. There was talk of a major new constituent of the universe. The excitement of the discovery was palpable even to one of us (the most senior of the editors) who was then a high school teenager.

  18. Star formation in active galaxies and quasars

    International Nuclear Information System (INIS)

    Heckman, T.M.

    1987-01-01

    I review the observational evidence for a causal or statistical link between star formation and active galactic nuclei. The chief difficulty is in quantitatively ascertaining the star formation rate in active galaxies: most of the readily observable manifestations of star formation superficially resemble those of an active nucleus. Careful multi-wavelength spatially-resolved observations demonstrate that many Seyfert galaxies are undergoing star formation. Our survey of CO emission from Seyferts (interpreted in conjunction IRAS data) suggests that type 2 Seyferts have unusually high rates of star formation, but type 1 Seyferts do not. Recent work also suggests that many powerful radio galaxies may be actively forming stars: radio galaxies with strong emission-lines often have blue colors and strong far-infrared emission. Determining the star formation rate in the host galaxies of quasars is especially difficult. Multi-color imaging and long-slit spectroscopy suggests that many of the host galaxies of radio-loud quasars are blue and a cold interstellar medium has been detected in some quasar hosts

  19. A quadruple quasar coincident with a giant Ly-alpha nebula and a protocluster at z=2

    Science.gov (United States)

    Vignali, Cristian

    2016-09-01

    We propose to observe the only known quadruple AGN system in the Universe, embedded in a giant Ly-alpha nebula at z 2. These active nuclei and the large number of Ly-alpha emitting galaxies at the same redshift are clear indications that this is one of the most overdense protoclusters known z 2. We request a 140 ks Chandra exposure to (a) define the basic X-ray properties of all the AGN and then their bolometric luminosities and Eddington ratios, and compare these with those of "isolated" quasars at similar redshifts/luminosities; (b) detect the hot gas emission in the protocluster. Chandra is unique for this investigation: the close (few arcsec) distance of some of the AGN needs high spatial resolution, and the extended emission requires low background contribution.

  20. Luminosity performance reach after LS1

    International Nuclear Information System (INIS)

    Herr, W.

    2012-01-01

    Based on past experience (2010/2011), in particular expected limitations from beam-beam effects, and taking into account the expected beam quality from the LHC injectors, the peak and integrated luminosity at top energy is discussed for different scenarios (e.g. bunch spacing, beta*). In particular it will be shown which are the key parameters to reach the nominal luminosity and it is also shown that peak luminosities two times larger than nominal (or higher) are possible. Possible test in 2012 are discussed

  1. Luminosity Measurements at LHCb for Run II

    CERN Multimedia

    Coombs, George

    2018-01-01

    A precise measurement of the luminosity is a necessary component of many physics analyses, especially cross-section measurements. At LHCb two different direct measurement methods are used to determine the luminosity: the “van der Meer scan” (VDM) and the “Beam Gas Imaging” (BGI) methods. A combined result from these two methods gave a precision of less than 2% for Run I and efforts are ongoing to provide a similar result for Run II. Fixed target luminosity is determined with an indirect method based on the single electron scattering cross-section.

  2. The performance of the CDF luminosity monitor

    CERN Document Server

    Acosta, D; Konigsberg, J; Korytov, A; Mitselmakher, G; Necula, V; Nomerotski, A; Pronko, A; Sukhanov, A; Safonov, A; Tsybychev, D; Wang, S M; Wong, M

    2002-01-01

    We describe the initial performance of the detector used for the luminosity measurement in the CDF experiment in Run II at the Tevatron. The detector consists of low-mass gaseous Cherenkov counters with high light yield (approx 100 photoelectrons) and monitors the process of inelastic pp-bar scattering. It allows for several methods of precise luminosity measurements at peak instantaneous luminosities of 2x10 sup 3 sup 2 cm sup - sup 2 s sup - sup 1 , corresponding to an average of six pp-bar interactions per bunch crossing.

  3. REVERBERATION AND PHOTOIONIZATION ESTIMATES OF THE BROAD-LINE REGION RADIUS IN LOW-z QUASARS

    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: cnegrete@inaoep.mx, E-mail: deborah@astro.unam.mx, E-mail: paola.marziani@oapd.inaf.it, E-mail: sulentic@iaa.es [Instituto de Astrofisica de Andalucia, E-18008 Granada (Spain)

    2013-07-01

    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. Interstellar scintillation as the origin of the rapid radio variability of the quasar J1819+3845.

    Science.gov (United States)

    Dennett-Thorpe, J; de Bruyn, A G

    2002-01-03

    The liberation of gravitational energy as matter falls onto a supermassive black hole at the centre of a galaxy is believed to explain the high luminosity of quasars. The variability of this emission from quasars and other types of active galactic nuclei can provide information on the size of the emitting regions and the physical process of fuelling the black hole. Some active galactic nuclei are variable at optical (and shorter) wavelengths, and display radio outbursts over years and decades. These active galactic nuclei often also show faster intraday variability at radio wavelengths. The origin of this rapid variability has been extensively debated, but a correlation between optical and radio variations in some sources suggests that both are intrinsic. This would, however, require radiation brightness temperatures that seem physically implausible, leading to the suggestion that the rapid variations are caused by scattering of the emission by the interstellar medium inside our Galaxy. Here we show that the rapid variations in the extreme case of quasar J1819+3845 (ref. 10) indeed arise from interstellar scintillation. The transverse velocity of the scattering material reveals the presence of plasma with a surprisingly high velocity close to the Solar System.

  5. X-RAY AND MULTIWAVELENGTH INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT LOW REDSHIFT

    Energy Technology Data Exchange (ETDEWEB)

    Wu Jianfeng; Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Diamond-Stanic, Aleksandar M. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92903 (United States); Hall, Patrick B. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3 (Canada); Plotkin, Richard M. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Shemmer, Ohad, E-mail: jfwu@astro.psu.edu [Department of Physics, University of North Texas, Denton, TX 76203 (United States)

    2012-03-01

    We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of {approx}> 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization 'shielding gas' covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our

  6. X-RAY AND MULTIWAVELENGTH INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT LOW REDSHIFT

    International Nuclear Information System (INIS)

    Wu Jianfeng; Brandt, W. N.; Schneider, Donald P.; Anderson, Scott F.; Diamond-Stanic, Aleksandar M.; Hall, Patrick B.; Plotkin, Richard M.; Shemmer, Ohad

    2012-01-01

    We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightness for our low-redshift weak-line quasar (WLQ) candidates is significantly different from that of typical radio-quiet quasars, having an excess of X-ray weak sources, but it is consistent with that of high-redshift WLQs. Over half of the low-redshift WLQ candidates are X-ray weak by a factor of ∼> 5, compared to a typical SDSS quasar with similar UV/optical luminosity. These X-ray weak sources generally show similar UV emission-line properties to those of the X-ray weak quasar PHL 1811 (weak and blueshifted high-ionization lines, weak semiforbidden lines, and strong UV Fe emission); they may belong to the notable class of PHL 1811 analogs. The average X-ray spectrum of these sources is somewhat harder than that of typical radio-quiet quasars. Several other low-redshift WLQ candidates have normal ratios of X-ray-to-optical/UV flux, and their average X-ray spectral properties are also similar to those of typical radio-quiet quasars. The X-ray weak and X-ray normal WLQ candidates may belong to the same subset of quasars having high-ionization 'shielding gas' covering most of the wind-dominated broad emission-line region, but be viewed at different inclinations. The mid-infrared-to-X-ray spectral energy distributions (SEDs) of these sources are generally consistent with those of typical SDSS quasars, showing that they are not likely to be BL Lac objects with relativistically boosted continua and diluted emission lines. The mid-infrared-to-UV SEDs of most radio-quiet weak-featured AGNs without sensitive X-ray coverage (34 objects) are also consistent with those of typical SDSS quasars. However, one source in our X

  7. Gas-rich galaxy pair unveiled in the lensed quasar 0957+561

    Science.gov (United States)

    Planesas; Martin-Pintado; Neri; Colina

    1999-12-24

    Molecular gas in the host galaxy of the lensed quasar 0957+561 (QSO 0957+561) at the redshift of 1.41 has been detected in the carbon monoxide (CO) line. This detection shows the extended nature of the molecular gas distribution in the host galaxy and the pronounced lensing effects due to the differentially magnified CO luminosity at different velocities. The estimated mass of molecular gas is about 4 x 10(9) solar masses, a molecular gas mass typical of a spiral galaxy like the Milky Way. A second, weaker component of CO is interpreted as arising from a close companion galaxy that is rich in molecular gas and has remained undetected so far. Its estimated molecular gas mass is 1.4 x 10(9) solar masses, and its velocity relative to the main galaxy is 660 kilometers per second. The ability to probe the molecular gas distribution and kinematics of galaxies associated with high-redshift lensed quasars can be used to improve the determination of the Hubble constant H(0).

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

    International Nuclear Information System (INIS)

    Shemmer, Ohad; Trakhtenbrot, Benny; Netzer, Hagai; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Lira, Paulina; Plotkin, Richard M.; Richards, Gordon T.; Strauss, Michael A.

    2010-01-01

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

  9. A Photo-Ionization Method for Black Hole Mass Estimation in Quasars

    Directory of Open Access Journals (Sweden)

    Marziani Paola

    2011-09-01

    Full Text Available Determining the masses of the central compact object believed to power all active galactic nuclei is relevant to our understanding of their evolution and of their inner workings. Keys to present-day mass estimates are: (1 the assumption of line broadening due to virial motion of the emitting gas, (2 an estimate of the distance of broad-line emitting gas from the central compact object, and (3 a measure of the AGN luminosity. We discuss the merits and the limitations of an alternative method based on estimates of physical conditions in the broad line emitting region derived from an appropriate multi-component analysis of emission line profiles. This ‘photo-ionization method’, applied to UV intermediate-ionization lines appears to be promising for at least a sizable population of high-z quasars.

  10. Fluctuations of quasars and other astronomical sources: final report on New Research Initiatives Program W-210

    International Nuclear Information System (INIS)

    Terrell, J.

    1978-01-01

    New Research Initiatives Program W-210 produced a number of scientific results, publications, colloquia, and talks. Investigations under this program dealt with power spectra of fluctuating light sources, the apparent expansion rates of astronomical sources exploding at relativistic speed, the limits on fluctuation rates of such expanding (and nonexpanding) light sources, and related matters. Probably the most important result was a study of the time history of such an exploding light source, which showed that a widely held belief that unusually rapid fluctuations of light output would be produced in this case is not correct. This result has an important bearing on the interpretation of the redshifts of quasars and BL Lac objects, indicating that cosmological distance is very difficult to reconcile with the observations of rapid variations of luminosity. These results, and the power-spectrum results, are also of considerable interest in the study of astronomical x-ray sources. A list of publications is included

  11. The formation of galaxies and quasars in a texture-seeded cold dark matter cosmogony

    International Nuclear Information System (INIS)

    Gooding, A.K.; Turok, N.; Spergel, D.N.

    1991-01-01

    The nonGaussian perturbations produced by global texture lead to the early formation of stars, quasars, and galaxies. Growth of the density fluctuation in cold dark matter induced by the unwinding of a texture 'knot' is calculated and the evolution of the mass multiplicity function in this galaxy formation model is determined. By z of about 50, about 3 percent of the mass of the universe has formed nonlinear objects of mass greater than 10 to the 6th solar masses - these objects may have reionized the universe. Most objects larger than 10 to the 12th solar masses form by z about 2-3, consistent with the observed epoch of QSO formation. Today, about 35 percent of the mass of the universe is in bound objects of mass greater than 10 to the 12th solar masses. It is found that the slope and the amplitude of the multiplicity function is consistent with the observed galaxy luminosity function. 24 refs

  12. Multiwavelength search and studies of active galaxies and quasars

    Science.gov (United States)

    Mickaelian, Areg M.

    2017-12-01

    The Byurakan Astrophysical Observatory (BAO) has always been one of the centres for surveys and studies of active galaxies. Here we review our search and studies of active galaxies during last 30 years using various wavelength ranges, as well as some recent related works. These projects since late 1980s were focused on multiwavelength search and studies of AGN and Starbursts (SB). 1103 blue stellar objects (BSOs) on the basis of their UV-excess were selected using Markarian Survey (First Byurakan Survey, FBS) plates and Markarian's criteria used for the galaxies. Among many blue stars, QSOs and Seyfert galaxies were found by follow-up observations. 1577 IRAS point sources were optically identified using FBS low-dispersion spectra and many AGN, SB and high-luminosity IR galaxies (LIRG/ULIRG) were discovered. 32 extremely high IR/opt flux ratio galaxies were studies with Spitzer. 2791 ROSAT FSC sources were optically identified using Hamburg Quasar Survey (HQS) low-dispersion spectra and many AGN were discovered by follow-up observations. Fine analysis of emission line spectra was carried out using spectral line decomposition software to establish true profiles and calculate physical parameters for the emitting regions, as well as to study the spectral variability of these objects. X-ray and radio selection criteria were used to find new AGN and variable objects for further studies. We have estimated AGN content of X-ray sources as 52.9%. We have also combined IRAS PSC and FSC catalogs and compiled its extragalactic sample, which allowed us to estimate AGN content among IR sources as 23.7%. Multiwavelength approach allowed revealing many new AGN and SB and obtaining a number of interesting relations using their observational characteristics and physical properties.

  13. INVESTIGATING THE COMPLEX X-RAY SPECTRUM OF A BROAD-LINE 2MASS RED QUASAR: XMM-NEWTON OBSERVATION OF FTM 0830+3759

    International Nuclear Information System (INIS)

    Piconcelli, Enrico; Nicastro, Fabrizio; Fiore, Fabrizio; Vignali, Cristian; Bianchi, Stefano; Miniutti, Giovanni

    2010-01-01

    We report results from a 50 ks XMM-Newton observation of the dust-reddened broad-line quasar FTM 0830+3759 (z = 0.413) selected from the Faint Images of the Radio Sky at Twenty cm/Two Micron All Sky Survey red quasar survey. For this active galactic nucleus (AGN), a very short 9 ks Chandra exposure had suggested a feature-rich X-ray spectrum and Hubble Space Telescope images revealed a very disturbed host galaxy morphology. Contrary to classical, optically selected quasars, the X-ray properties of red (i.e., with J - K s > 1.7 and R - K s > 4.0) broad-line quasars are still quite unexplored, although there is a growing consensus that, due to moderate obscuration, these objects can offer a unique view of spectral components typically swamped by the AGN light in normal, blue quasars. The XMM-Newton observation discussed here has definitely confirmed the complexity of the X-ray spectrum revealing the presence of a cold (or mildly ionized) absorber with N H ∼ 10 22 cm -2 along the line of sight to the nucleus and a Compton reflection component accompanied by an intense Fe Kα emission line in this quasar with a L 2-10 k eV ∼ 5 x 10 44 erg s -1 . A soft-excess component is also required by the data. The match between the column density derived by our spectral analysis and that expected on the basis of reddening due to the dust suggests the possibility that both absorptions occur in the same medium. FTM 0830+3759 is characterized by an extinction/absorption-corrected X-ray-to-optical flux ratio α ox = -2.3, which is steeper than expected on the basis of its UV luminosity. These findings indicate that the X-ray properties of FTM 0830+3759 differ from those typically observed for optically selected broad-line quasars with comparable hard X-ray luminosity.

  14. Online luminosity measurement at BES III

    International Nuclear Information System (INIS)

    Song Wenbo; Fu Chengdong; Mo Xiaohu; He Kanglin; Zhu Kejun; Li Fei; Zhao Shujun

    2010-01-01

    As a crucial parameter of both accelerator and detector, the realization of online luminosity measurement is of great importance. Several methods of luminosity measurement are recapitulated and the emphasis is laid on the algorithm of using e + e - and γγ final states. Taking into account the status at the beginning of the joint commissioning of detector and accelerator, the information from end cap electromagnetic calorimeter is used to select the good event. With the help of online Event filter, the luminosity is calculated and the monitoring of online cross section of hadron is realized. The preliminary results indicate that the online luminosity measurement is stable and its role for machine tuning and monitoring of the overall running status is indispensable. (authors)

  15. COMPLETE IONIZATION OF THE NEUTRAL GAS: WHY THERE ARE SO FEW DETECTIONS OF 21 cm HYDROGEN IN HIGH-REDSHIFT RADIO GALAXIES AND QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Curran, S. J. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Whiting, M. T., E-mail: sjc@physics.usyd.edu.au [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

    2012-11-10

    From the first published z {approx}> 3 survey of 21 cm absorption within the hosts of radio galaxies and quasars, Curran et al. found an apparent dearth of cool neutral gas at high redshift. From a detailed analysis of the photometry, each object is found to have a {lambda} = 1216 A continuum luminosity in excess of L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}, a critical value above which 21 cm has never been detected at any redshift. At these wavelengths, and below, hydrogen is excited above the ground state so that it cannot absorb in 21 cm. In order to apply the equation of photoionization equilibrium, we demonstrate that this critical value also applies to the ionizing ({lambda} {<=} 912 A) radiation. We use this to show, for a variety of gas density distributions, that upon placing a quasar within a galaxy of gas, there is always an ultraviolet luminosity above which all of the large-scale atomic gas is ionized. While in this state, the hydrogen cannot be detected or engage in star formation. Applying the mean ionizing photon rate of all of the sources searched, we find, using canonical values for the gas density and recombination rate coefficient, that the observed critical luminosity gives a scale length (3 kpc) similar that of the neutral hydrogen (H I) in the Milky Way, a large spiral galaxy. Thus, this simple yet physically motivated model can explain the critical luminosity (L {sub 912} {approx} L {sub 1216} {approx} 10{sup 23} W Hz{sup -1}), above which neutral gas is not detected. This indicates that the non-detection of 21 cm absorption is not due to the sensitivity limits of current radio telescopes, but rather that the lines of sight to the quasars, and probably the bulk of the host galaxies, are devoid of neutral gas.

  16. Ultra-compact structure in radio quasars as a cosmological probe: a revised study of the interaction between cosmic dark sectors

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Xiaogang; Biesiada, Marek; Cao, Shuo; Qi, Jingzhao; Zhu, Zong-Hong, E-mail: zhengxg2012@mail.bnu.edu.cn, E-mail: marek.biesiada@us.edu.pl, E-mail: caoshuo@bnu.edu.cn, E-mail: 11132016039@bnu.edu.cn, E-mail: zhuzh@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    2017-10-01

    A new compilation of 012 angular-size/redshift data for compact radio quasars from very-long-baseline interferometry (VLBI) surveys motivates us to revisit the interaction between dark energy and dark matter with these probes reaching high redshifts z ∼ 3.0. In this paper, we investigate observational constraints on different phenomenological interacting dark energy (IDE) models with the intermediate-luminosity radio quasars acting as individual standard rulers, combined with the newest BAO and CMB observation from Planck results acting as statistical rulers. The results obtained from the MCMC method and other statistical methods including figure of Merit and Information Criteria show that: (1) Compared with the current standard candle data and standard clock data, the intermediate-luminosity radio quasar standard rulers , probing much higher redshifts, could provide comparable constraints on different IDE scenarios. (2) The strong degeneracies between the interaction term and Hubble constant may contribute to alleviate the tension of H {sub 0} between the recent Planck and HST measurements. (3) Concerning the ranking of competing dark energy models, IDE with more free parameters are substantially penalized by the BIC criterion, which agrees very well with the previous results derived from other cosmological probes.

  17. Luminosity Optimization Feedback in the SLC

    International Nuclear Information System (INIS)

    1999-01-01

    The luminosity optimization at the SLC has been limited by the precision with which one can measure the micron size beams at the Interaction Point. Ten independent tuning parameters must be adjusted. An automated application has been used to scan each parameter over a significant range and set the minimum beam size as measured with a beam-beam deflection scan. Measurement errors limited the accuracy of this procedure and degraded the resulting luminosity. A new luminosity optimization feedback system has been developed using novel dithering techniques to maximize the luminosity with respect to the 10 parameters, which are adjusted one at a time. Control devices are perturbed around nominal setpoints, while the averaged readout of a digitized luminosity monitor measurement is accumulated for each setting. Results are averaged over many pulses to achieve high precision and then fitted to determine the optimal setting. The dithering itself causes a small loss in luminosity, but the improved optimization is expected to significantly enhance the performance of the SLC. Commissioning results are reported

  18. NuSTAR J033202-2746.8: direct constraints on the Compton reflection in a heavily obscured quasar at z ≈ 2

    DEFF Research Database (Denmark)

    Del Moro, A.; Mullaney, J. R.; Alexander, D. M.

    2014-01-01

    We report Nuclear Spectroscopic Telescope Array (NuSTAR) observations of NuSTAR J033202-2746.8, a heavily obscured, radio-loud quasar detected in the Extended Chandra Deep Field-South, the deepest layer of the NuSTAR extragalactic survey (∼400 ks, at its deepest). NuSTAR J033202-2746.8 is reliably......-2746.8, indicating that this source is a heavily obscured quasar (NH = 5.6+−0.80.9 × 1023 cm−2) with luminosity L10-40 keV ≈ 6.4 × 1044 erg s−1. Although existing optical and near-infrared (near-IR) data, as well as follow-up spectroscopy with the Keck and VLT telescopes, failed to provide a secure redshift......-Newton data alone. The measured reflection fraction is higher than the R∼0 typically observed in bright radio-loud quasars such as NuSTAR J033202-2746.8, which has L1.4 GHz≈1027 W Hz−1. Constraining the spectral shape of active galactic nuclei (AGNs), including bright quasars, is very important...

  19. The Hunt for Red Quasars: Luminous Obscured Black Hole Growth Unveiled in the Stripe 82 X-Ray Survey

    Science.gov (United States)

    LaMassa, Stephanie M.; Glikman, Eilat; Brusa, Marcella; Rigby, Jane R.; Tasnim Ananna, Tonima; Stern, Daniel; Lira, Paulina; Urry, C. Megan; Salvato, Mara; Alexandroff, Rachael; Allevato, Viola; Cardamone, Carolin; Civano, Francesca; Coppi, Paolo; Farrah, Duncan; Komossa, S.; Lanzuisi, Giorgio; Marchesi, Stefano; Richards, Gordon; Trakhtenbrot, Benny; Treister, Ezequiel

    2017-10-01

    We present results of a ground-based near-infrared campaign with Palomar TripleSpec, Keck NIRSPEC, and Gemini GNIRS to target two samples of reddened active galactic nucleus (AGN) candidates from the 31 deg2 Stripe 82 X-ray survey. One sample, which is ˜89% complete to Kprogram, and is selected to have red R - K colors (> 4, Vega). The fainter sample (K> 17, Vega) represents a pilot program to follow-up four sources from a parent sample of 34 that are not detected in the single-epoch SDSS catalog and have WISE quasar colors. All 12 sources are broad-line AGNs (at least one permitted emission line has an FWHM exceeding 1300 km s-1) and span a redshift range 0.59 0.5), and a greater percentage have high X-ray luminosities ({L}{{X},{full}}> {10}44 erg s-1). Such outflows and high luminosities may be consistent with the paradigm that reddened broad-line AGNs represent a transitory phase in AGN evolution as described by the major merger model for black hole growth. Results from our pilot program demonstrate proof of concept that our selection technique is successful in discovering reddened quasars at z> 1 missed by optical surveys.

  20. Quasar evolution: not a deficit at low redshifts

    International Nuclear Information System (INIS)

    Avni, Y.; Schiller, N.

    1983-01-01

    We consider the recent suggestion of Hawkins and Stewart that complete quasar samples can be interpreted in terms of a (real or apparent) deficit of quasars at low redshifts. By using a larger sample and a more efficient method of analysis, we rule out this interpretation

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

    NARCIS (Netherlands)

    Vestergaard, M; Wilkes, BJ; Barthel, PD

    2000-01-01

    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

  2. Statistical studies on quasars and active nuclei of galaxies

    International Nuclear Information System (INIS)

    Stasinska, G.

    1987-01-01

    A catalogue of optical, radio and X-ray properties of quasars and other active galactic nuclei, now in elaboration, is presented. This catalogue may serve as a data base for statistical studies. As an example, we give some preliminary results concerning the determination of the quasar masses [fr

  3. High-redshift SDSS Quasars with Weak Emission Lines

    DEFF Research Database (Denmark)

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

    2009-01-01

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

  4. Performance of the Pixel Luminosity Telescope for Luminosity Measurement at CMS during Run 2

    CERN Document Server

    CMS Collaboration

    2017-01-01

    The Pixel Luminosity Telescope (PLT) is a dedicated system for luminosity measurement at the CMS experiment using silicon pixel sensors arranged into "telescopes", each consisting of three planes. It was installed during LS1 at the beginning of 2015 and has been providing online and offline luminosity measurements throughout Run 2. The online bunch-by-bunch luminosity measurement employs the "fast-or" capability of the pixel readout chip (PSI46) to identify events where a hit is registered in all three sensors in a telescope corresponding primarily to tracks originating from the interaction point. In addition, the full pixel information is read out at a lower rate, allowing for the calculation of corrections to the online luminosity from effects such as the miscounting of tracks not originating from the interaction point and detector efficiency. In this talk, we will present results from 2016 running and preliminary 2017 results, including commissioning and operational history, luminosity calibration using Va...

  5. Performance of the Pixel Luminosity Telescope for Luminosity Measurement at CMS during Run2

    CERN Document Server

    Lujan, Paul Joseph

    2017-01-01

    The Pixel Luminosity Telescope (PLT) is a dedicated system for luminosity measurement at the CMS experiment using silicon pixel sensors arranged into telescopes, each consisting of three sensor planes. It was installed in CMS at the beginning of 2015 and has been providing online and offline luminosity measurements throughout Run 2 of the LHC. The online bunch-by-bunch luminosity measurement employs the fast-or capability of the pixel readout chip to identify events where a hit is registered in all three sensors in a telescope, corresponding primarily to tracks originating from the interaction point. In addition, the full pixel information is read out at a lower rate, allowing for the calculation of corrections to the online luminosity from effects such as the miscounting of tracks not originating from the interaction point and detector efficiency. This paper presents results from the 2016 running of the PLT, including commissioning and operational history, luminosity calibration using Van der Meer scans, and...

  6. Close Companions to Two High-redshift Quasars

    Science.gov (United States)

    McGreer, Ian D.; Fan, Xiaohui; Strauss, Michael A.; Haiman, Zoltàn; Richards, Gordon T.; Jiang, Linhua; Bian, Fuyan; Schneider, Donald P.

    2014-10-01

    We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS Stripe 82 region. The initial MMT slit spectroscopy shows excess Lyα emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i AB = 23.6) located 2'' (12 kpc projected) from the quasar with strong Lyα emission (EW0 ≈ 100 Å) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ~ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y AB = 25) at a separation of 0.''9. The red i 775 - Y 105 color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short. Based in part 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 programs #12184 and #12493. Observations were also made with the LBT and MMT.

  7. The clustering of quasars from an objective-prism survey

    International Nuclear Information System (INIS)

    Webster, A.

    1982-01-01

    The positions and redshifts of 108 quasars from the Cerro Tololo objective-prism survey are subjected to Fourier Power Spectrum Analysis in a search for clustering in their spatial distribution. It is found that, on the whole, these quasars are not clustered but are scattered in space independently at random. The sole exception is a group of four quasars at z = 0.37 which has a low probability of being a chance event and which, with a size of about 100 Mpc, may therefore be the largest known structure in the Universe. The conclusions disagree with Arp's analysis of this catalogue: his 'clouds of quasars' ejected by certain low-redshift galaxies, for example, are attributable to sensitivity variations among the different plates of the survey. It is shown that analysis of deeper surveys is likely to show up quasar clusters even at high redshift, and could therefore provide a useful new cosmological probe. (author)

  8. Operational results from the LHC luminosity monitors

    Energy Technology Data Exchange (ETDEWEB)

    Miyamoto, R.; Ratti, A.; Matis, H.S.; Stezelberger, T.; Turner, W.C.; Yaver, H.; Bravin, E.

    2011-03-28

    The luminosity monitors for the high luminosity regions in the LHC have been operating to monitor and optimize the luminosity since 2009. The device is a gas ionization chamber inside the neutral particle absorber 140 m from the interaction point and monitors showers produced by high energy neutral particles from the collisions. It has the ability to resolve the bunch-by-bunch luminosity as well as to survive the extreme level of radiation in the nominal LHC operation. We present operational results of the device during proton and lead ion operations in 2010 and make comparisons with measurements of experiments. The Large Hadron Collider (LHC) at CERN can accelerate proton and lead ion beams to 7 TeV and 547 TeV and produce collisions of these particles. Luminosity measures performance of the LHC and is particularly important for experiments in high luminosity interaction points (IPs), ATLAS (IP1) and CMS (IP5). To monitor and optimize the luminosities of these IPs, BRAN (Beam RAte Neutral) detectors [1, 2] have been installed and operating since the beginning of the 2009 operation [3]. A neutral particle absorber (TAN) protects the D2 separation dipole from high energy forward neutral particles produced in the collisions [4]. These neutral particles produce electromagnetic and hadronic showers inside the TAN and their energy flux is proportional to the collision rate and hence to the luminosity. The BRAN detector is an Argon gas ionization chamber installed inside the TANs on both sides of the IP1 and IP5 and monitors the relative changes in the luminosity by detecting the ionization due to these showers. When the number of collisions per bunch crossing (multiplicity) is small, the shower rate inside the TAN is also proportional to the luminosity. Hence, the detector is designed to operate by measuring either the shower rate (counting mode for low and intermediate luminosities) or the average shower flux (pulse height mode for high luminosities). The detector is

  9. Ultraviolet spectropolarimetry of high-redshift quasars with the Hubble Space Telescope

    Science.gov (United States)

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

    1995-01-01

    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

  10. Data mining for gravitationally lensed quasars

    Science.gov (United States)

    Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.

    2015-04-01

    Gravitationally lensed quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target-selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine-learning techniques and demonstrate that a two-step strategy can be highly effective. In the first step, we use catalogue-level information (griz+WISE magnitudes, second moments) to pre-select targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (gradient-boosted trees), to form a final set of candidates. The results from this procedure can be used to further refine the simpler SQLS algorithms, with a twofold (or threefold) gain in purity and the same (or 80 per cent) completeness at target-selection stage, or a purity of 70 per cent and a completeness of 60 per cent after the candidate-selection step. Simpler photometric searches in griz+WISE based on colour cuts would provide samples with 7 per cent purity or less. Our technique is extremely fast, as a list of candidates can be obtained from a Stage III experiment (e.g. DES catalogue/data base) in a few CPU hours. The techniques are easily extendable to Stage IV experiments like LSST with the addition of time domain information.

  11. SDSS QUASARS IN THE WISE PRELIMINARY DATA RELEASE AND QUASAR CANDIDATE SELECTION WITH OPTICAL/INFRARED COLORS

    International Nuclear Information System (INIS)

    Wu Xuebing; Hao Guoqiang; Jia Zhendong; Zhang Yanxia; Peng Nanbo

    2012-01-01

    We present a catalog of 37,842 quasars in the Sloan Digital Sky Survey (SDSS) Data Release 7, which have counterparts within 6'' in the Wide-field Infrared Survey Explorer (WISE) Preliminary Data Release. The overall WISE detection rate of the SDSS quasars is 86.7%, and it decreases to less than 50.0% when the quasar magnitude is fainter than i = 20.5. We derive the median color-redshift relations based on this SDSS-WISE quasar sample and apply them to estimate the photometric redshifts of the SDSS-WISE quasars. We find that by adding the WISE W1- and W2-band data to the SDSS photometry we can increase the photometric redshift reliability, defined as the percentage of sources with photometric and spectroscopic redshift difference less than 0.2, from 70.3% to 77.2%. We also obtain the samples of WISE-detected normal and late-type stars with SDSS spectroscopy, and present a criterion in the z – W1 versus g – z color-color diagram, z – W1 > 0.66(g – z) + 2.01, to separate quasars from stars. With this criterion we can recover 98.6% of 3089 radio-detected SDSS-WISE quasars with redshifts less than four and overcome the difficulty in selecting quasars with redshifts between 2.2 and 3 from SDSS photometric data alone. We also suggest another criterion involving the WISE color only, W1 – W2 > 0.57, to efficiently separate quasars with redshifts less than 3.2 from stars. In addition, we compile a catalog of 5614 SDSS quasars detected by both WISE and UKIDSS surveys and present their color-redshift relations in the optical and infrared bands. By using the SDSS ugriz, UKIDSS, YJHK, and WISE W1- and W2-band photometric data, we can efficiently select quasar candidates and increase the photometric redshift reliability up to 87.0%. We discuss the implications of our results on the future quasar surveys. An updated SDSS-WISE quasar catalog consisting of 101,853 quasars with the recently released WISE all-sky data is also provided.

  12. Optical images of quasars and radio galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hutchings, J.B.; Johnson, I.; Pyke, R.

    1988-04-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references.

  13. Optical images of quasars and radio galaxies

    International Nuclear Information System (INIS)

    Hutchings, J.B.; Johnson, I.; Pyke, R.

    1988-01-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references

  14. Optical images of quasars and radio galaxies

    Science.gov (United States)

    Hutchings, J. B.; Johnson, I.; Pyke, R.

    1988-04-01

    Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions.

  15. MPX detectors as LHC luminosity monitor

    Energy Technology Data Exchange (ETDEWEB)

    Sopczak, Andre; Ali, Babar; Bergmann, Benedikt; Caforio, Davide; Heijne, Erik; Pospisil, Stanislav; Seifert, Frank; Solc, Jaroslav; Suk, Michal; Turecek, Daniel [IEAP CTU in Prague (Czech Republic); Ashba, Nedaa; Leroy, Claude; Soueid, Paul [University of Montreal (Canada); Bekhouche, Khaled [Biskra University (Algeria); Campbell, Michael; Nessi, Marzio [CERN (Switzerland); Lipniacka, Anna [Bergen University (Norway)

    2016-07-01

    A network of 16 Medipix-2 (MPX) silicon pixel devices was installed in the ATLAS detector cavern at CERN. It was designed to measure the composition and spectral characteristics of the radiation field in the ATLAS experiment and its surroundings. This study demonstrates that the MPX network can also be used as a self-sufficient luminosity monitoring system. The MPX detectors collect data independently of the ATLAS data-recording chain, and thus they provide independent measurements of the bunch-integrated ATLAS/LHC luminosity. In particular, the MPX detectors located close enough to the primary interaction point are used to perform van der Meer calibration scans with high precision. Results from the luminosity monitoring are presented for 2012 data taken at √(s) =8 TeV proton-proton collisions. The characteristics of the LHC luminosity reduction rate are studied and the effects of beam-beam (burn-off) and beam-gas (single bunch) interactions are evaluated. The systematic variations observed in the MPX luminosity measurements are below 0.3% for one minute intervals.

  16. The Gaseous Environments of Quasars: Outflows, Feedback & Cold Mode Accretion

    Science.gov (United States)

    Chen, Chen; Hamann, Fred

    2018-06-01

    The early stages of massive galaxy evolution can involve galaxy-scale outflows driven by a starburst or a central quasar and cold-mode accretion (infall) that adds to the mass buildup in the galaxies. I will describe three related studies that use quasar absorption lines to measure outflows, infall, and the general gaseous environments of quasars across a range of spatial scales. The three studies are: 1) High-resolution spectroscopy with Keck-HIRES and VLT-UVES to study associated absorption lines (AALs) that have redshifts greater than the emission redshifts indicating infall and/or rich multi-component AAL complexes that might be interstellar clouds in the host galaxies that have been shredded and dispersed by a fast unseen quasar-driven wind. The data provide strong constraints on the gas kinematics, spatial structure, column densities, metallicities, and energetics. 2) A complete inventory of high-velocity CIV 1548,1550 mini-BAL outflows in quasars using high-resolution high signal-to-noise spectra in the public VLT-UVES and Keck-HIRES archives. This sensitive mini-BAL survey fills an important niche between previous work on narrow absorption lines (NALs) and the much-studied broad absorption lines (BALs) to build a more complete picture of quasar outflows. I will report of the mini-BAL statistics, the diversity of lines detected, and some tests for correlations with the quasar properties. We find, for example, that mini-BALs at v > 4000 km/s in at least 10% of 511 quasars studied, including 1% at v > 0.1 c. Finally, 3) Use the much larger database of NALs measured in 262,449 BOSS quasars by York et al. (in prep.) to study their potential relationships to the quasars and, specifically, their origins in quasar outflows. This involves primarily comparisons of the incidence and properties of NALs at different velocity shifts to other measured properties of the quasars such as BAL outflows, emission line characteristics, radio-loudness, and red colors. We find

  17. The period-luminosity relation for Cepheids

    International Nuclear Information System (INIS)

    Brodie, J.P.

    1980-01-01

    Numerical simulations of the empirical determination of the period-luminosity-colour relation for classical Cepheids are presented. In this study the quantitative effects of random errors, reddening, sample size and the presence of both colour and period cut-offs (imposed by the finite extent of the instability strip) on the observational redetermination of the original relation are evaluated. Both random errors in the photometry and correlated errors in the reddening corrections are shown to have systematic effects. Especially sensitive to these errors is the colour coefficient in the period-luminosity-colour relation, where the ratio of the error to the width of the instability strip is the determining factor. With present observations only broad confidence limits can be placed on present knowledge of the intrinsic period-luminosity-colour relation and/or its variations from galaxy to galaxy. (author)

  18. Correlation function of the luminosity distances

    Energy Technology Data Exchange (ETDEWEB)

    Biern, Sang Gyu; Yoo, Jaiyul, E-mail: sgbiern@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich, Winterthurerstrasse 190, CH-8057, Zürich (Switzerland)

    2017-09-01

    We present the correlation function of the luminosity distances in a flat ΛCDM universe. Decomposing the luminosity distance fluctuation into the velocity, the gravitational potential, and the lensing contributions in linear perturbation theory, we study their individual contributions to the correlation function. The lensing contribution is important at large redshift ( z ∼> 0.5) but only for small angular separation (θ ∼< 3°), while the velocity contribution dominates over the other contributions at low redshift or at larger separation. However, the gravitational potential contribution is always subdominant at all scale, if the correct gauge-invariant expression is used. The correlation function of the luminosity distances depends significantly on the matter content, especially for the lensing contribution, thus providing a novel tool of estimating cosmological parameters.

  19. The BRAN luminosity detectors for the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Matis, H.S.; Placidi, M.; Ratti, A.; Turner, W.C. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Bravin, E. [CERN, 1211 Geneva 23 (Switzerland); Miyamoto, R. [European Spallation Source, ESS AB, P.O. Box 176, SE-221 00 Lund (Sweden)

    2017-03-11

    This paper describes the several phases which led, from the conceptual design, prototyping, construction and tests with beam, to the installation and operation of the BRAN (Beam RAte of Neutrals) relative luminosity monitors for the LHC. The detectors have been operating since 2009 to contribute, optimize and maintain the accelerator performance in the two high luminosity interaction regions (IR), the IR1 (ATLAS) and the IR5 (CMS). The devices are gas ionization chambers installed inside a neutral particle absorber 140 m away from the Interaction Points in IR1 and IR5 and monitor the energy deposited by electromagnetic showers produced by high-energy neutral particles from the collisions. The detectors have the capability to resolve the bunch-by-bunch luminosity at the 40 MHz bunch rate, as well as to survive the extreme level of radiation during the nominal LHC operation. The devices have operated since the early commissioning phase of the accelerator over a broad range of luminosities reaching 1.4×10{sup 34} cm{sup −2} s{sup −1} with a peak pileup of 45 events per bunch crossing. Even though the nominal design luminosity of the LHC has been exceeded, the BRAN is operating well. After describing how the BRAN can be used to monitor the luminosity of the collider, we discuss the technical choices that led to its construction and the different tests performed prior to the installation in two IRs of the LHC. Performance simulations are presented together with operational results obtained during p-p operations, including runs at 40 MHz bunch rate, Pb-Pb operations and p-Pb operations.

  20. A gravitationally lensed quasar discovered in OGLE

    Science.gov (United States)

    Kostrzewa-Rutkowska, Zuzanna; Kozłowski, Szymon; Lemon, Cameron; Anguita, T.; Greiner, J.; Auger, M. W.; Wyrzykowski, Ł.; Apostolovski, Y.; Bolmer, J.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Poleski, R.; Pietrukowicz, P.; Skowron, J.; Mróz, P.; Ulaczyk, K.; Pawlak, M.

    2018-05-01

    We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the ˜670deg2 area encompassing the Magellanic Clouds. The source was selected as one of ˜60 `red W1 - W2' mid-infrared objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made `the other way around', meaning we first measured the time delay between the two lensed quasar images of -132 Technology Telescope spectra. The spectral energy distribution (SED) fitting with the fixed source redshift provided the estimate of the lensing galaxy redshift of z ≈ 0.9 ± 0.2 (90 per cent CL), while its type is more likely to be elliptical (the SED-inferred and lens-model stellar mass is more likely present in ellipticals) than spiral (preferred redshift by the lens model).

  1. Powering the High-Luminosity Triplets

    Science.gov (United States)

    Ballarino, A.; Burnet, J. P.

    The powering of the magnets in the LHC High-Luminosity Triplets requires production and transfer of more than 150 kA of DC current. High precision power converters will be adopted, and novel High Temperature Superconducting (HTS) current leads and MgB2 based transfer lines will provide the electrical link between the power converters and the magnets. This chapter gives an overview of the systems conceived in the framework of the LHC High-Luminosity upgrade for feeding the superconducting magnet circuits. The focus is on requirements, challenges and novel developments.

  2. Calculating luminosity for a coupled Tevatron lattice

    International Nuclear Information System (INIS)

    Holt, J.A.; Martens, M.A.; Michelotti, L.; Goderre, G.

    1995-05-01

    The traditional formula for calculating luminosity assumes an uncoupled lattice and makes use of one-degree-of-freedom lattice functions, β H and β v , for relating transverse beam widths to emittances. Strong coupling requires changing this approach. It is simplest to employ directly the linear normal form coordinates of the one turn map. An equilibrium distribution in phase space is expressed as a function of the Jacobian's eigenvectors and beam size parameters or emittances. Using the equilibrium distributions an expression for the luminosity was derived and applied to the Tevatron lattice, which was coupled due to a quadrupole roll

  3. Luminosity Targets for FCC-hh

    CERN Document Server

    Zimmermann, F.; Buffat, X.; Schulte, D.

    2016-01-01

    We discuss the choice of target values for the peak and integrated luminosity of a future high-energy frontier circular hadron collider (FCC-hh). We review the arguments on the physics reach of a hadron collider. Next we show that accelerator constraints will limit the beam current and the turnaround time. Taking these limits into account, we derive an expression for the ultimate integrated luminosity per year, depending on a possible pile-up limit imposed by the physics experiments. We finally benchmark our result against the planned two phases of FCC-hh [1, 2, 3

  4. Further Rehabilitating CIV-based Black Hole Mass Estimates in Quasars

    Science.gov (United States)

    Brotherton, Michael S.; Runnoe, Jessie C.; Shang, Zhaohui; Varju, Melinda

    2016-06-01

    Virial black hole masses are routinely estimated for high-redshift quasars using the C IV lambda 1549 emission line using single-epoch spectra that provide a gas velocity and a continuum luminosity. Such masses are very uncertain, however, especially because C IV likely possesses a non-virial component that varies with the Eddington ratio. We have previously used the 1400 feature, a blend of S i IV and O IV] emission that does not suffer the problems of C IV, to rehabilitate C IV-based mases by providing a correction term. The C IV profile itself, however, provides enough information to correct the black hole masses and remove the effects of the non-virial component. We use Mg II-based black hole masses to calibrate and test a new C IV-based black hole mass formula using only C IV and continuum measurements superior to existing formulations, as well as to test for additional dependencies on luminosity.

  5. A DEEP XMM-NEWTON OBSERVATION OF THE QUASAR 3C 287

    International Nuclear Information System (INIS)

    Salvesen, G.; Miller, J. M.; Cackett, E.; Siemiginowska, A.

    2009-01-01

    We report on an XMM-Newton observation of the z = 1.055 quasar and Gigahertz Peaked Spectrum (GPS) source 3C 287. Our 62.3 ks observation provides an exceptional X-ray view of a prominent member of this important subclass of active galactic nuclei (AGNs). The X-ray spectra of 3C 287 are consistent with a simple absorbed power law with a spectral index of Γ = 1.72 ± 0.02. Our fits imply a bolometric luminosity of L = 5.8 ± 0.2 x 10 45 erg s -1 over the 0.3-10.0 keV band; this gives a mass lower limit of M BHmin ≥ 4.6 x 10 7 M sun assuming X-rays contribute 10% of the bolometric luminosity and radiation at the Eddington limit. Iron emission lines are common in the X-ray spectra of many AGNs, but the observed spectra appear to rule out strong emission lines in 3C 287. The simple power-law spectrum and the absence of strong emission lines may support a picture where our line of sight intersects a relativistic jet. Milliarcsecond radio imaging of 3C 287 appears to support this interpretation. We discuss our results in the context of different AGNs subclasses and the possibility that GPS sources harbor newly formed black hole jets.

  6. Nustar Reveals an Intrinsically X-ray Weak Broad Absorption Line Quasar in the Ultraluminous Infrared Galaxy Markarian 231

    Science.gov (United States)

    Teng, Stacy H.; Brandt. W. N.; Harrison, F. A.; Luo, B.; Alexander, D. M.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.; hide

    2014-01-01

    We present high-energy (3-30 keV) NuSTAR observations of the nearest quasar, the ultraluminous infrared galaxy (ULIRG) Markarian 231 (Mrk 231), supplemented with new and simultaneous low-energy (0.5-8 keV) data from Chandra. The source was detected, though at much fainter levels than previously reported, likely due to contamination in the large apertures of previous non-focusing hard X-ray telescopes. The full band (0.5-30 keV) X-ray spectrum suggests the active galactic nucleus (AGN) in Mrk 231 is absorbed by a patchy and Compton-thin N(sub H) approx. 1.2(sup +0.3) sub-0.3) x 10(exp 23) / sq cm) column. The intrinsic X-ray luminosity L(sub 0.5-30 Kev) approx. 1.0 x 10(exp 43) erg /s) is extremely weak relative to the bolometric luminosity where the 2-10 keV to bolometric luminosity ratio is approx. 0.03% compared to the typical values of 2-15%. Additionally, Mrk 231 has a low X-ray-to-optical power law slope alpha(sub 0X) approx. -1.7. It is a local example of a low-ionization broad absorption line (LoBAL) quasar that is intrinsically X-ray weak. The weak ionizing continuum may explain the lack of mid-infrared [O IV], [Ne V], and [Ne VI] fine-structure emission lines which are present in sources with otherwise similar AGN properties. We argue that the intrinsic X-ray weakness may be a result of the super-Eddington accretion occurring in the nucleus of this ULIRG, and may also be naturally related to the powerful wind event seen in Mrk 231, a merger remnant escaping from its dusty cocoon.

  7. The luminosity of galactic components and morphological segregation

    International Nuclear Information System (INIS)

    Solanes, J. M.; Salvador-Sole, E.; Sanroma, M.

    1989-01-01

    The luminosities of the bulge and disk components of disk galaxies are analyzed, and the possible correlation of these luminosities with morphological type and local density is explored. Galaxies of different types are found to be located in distinct bands in the bulge-to-disk luminosity ratio vs total luminosity diagram, allowing the determination of the typical bulge luminosity function of disk galaxies of different types from their respective total luminosity functions, along with a better characterization of morphological segregation among disk galaxies. No evidence for any bulge luminosity segregation is found, and disks appear to be less luminous with increasing local density. 33 refs

  8. The Hyperluminous Infrared Quasar 3C 318 and Its Implications for Interpreting Sub-MM Detections of High-Redshift Radio Galaxies

    Science.gov (United States)

    Willott, Chris J.; Rawlings, Steve; Jarvis, Matt J.

    1999-01-01

    We present near-infrared spectroscopy and imaging of the compact steep-spectrum radio source 3C 318 which shows it to be a quasar at redshift z = 1.574 (the z = 0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalogue (there is no evidence of strong gravitational lensing effects). Its bolometric luminosity greatly exceeds the 10(exp 13) solar luminosity level above which an object is said to be hyperluminous. Its spectral energy distribution (SED) requires that the quasar heats the dust responsible for the FIR flux, as is believed to be the case in other hyperluminous galaxies, and contributes (at the greater than 10% level) to the heating of the CIA dust responsible for the sub-mm emission. We cannot determine whether a starburst makes an important contribution to the heating of the coolest dust, so evidence for a high star-formation rate is circumstantial being based on the high dust, and hence gas, C-1 mass required by its sub-mm detection. We show that the current sub-mm and FIR data available for the highest-redshift radio galaxies are consistent with SEDs similar to that of 3C 318. This indicates that at least some of this population may be detected in the sub-mm because of dust heated by the quasar nucleus, and that interpreting sub-mm detection as evidence for very high (approx. less than 1000 solar mass/yr) star-formation rates may not always be valid. We show that the 3C318 quasar is slightly reddened (A(sub v) approx. = 0.5), the most likely cause of which is SMC-type dust in the host galaxy. If very distant radio galaxies are reddened in a similar way then we show that only slightly greater amounts of dust could obscure the quasars in these sources. We speculate that the low fraction of quasars amongst the very high redshift (z approx. greater than 3) objects in low-frequency radio-selected samples is the result of

  9. THE EXTENDED HIGH A ( V ) QUASAR SURVEY: SEARCHING FOR DUSTY ABSORBERS TOWARD MID-INFRARED-SELECTED QUASARS

    Energy Technology Data Exchange (ETDEWEB)

    Krogager, J.-K.; Noterdaeme, P. [Institut d’Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France); Fynbo, J. P. U.; Heintz, K. E.; Vestergaard, M. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Geier, S. [Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Ledoux, C. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Møller, P. [European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching bei München (Germany); Venemans, B. P. [Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2016-11-20

    We present the results of a new spectroscopic survey for dusty intervening absorption systems, particularly damped Ly α absorbers (DLAs), toward reddened quasars. The candidate quasars are selected from mid-infrared photometry from the Wide-field Infrared Survey Explorer combined with optical and near-infrared photometry. Out of 1073 candidates, we secure low-resolution spectra for 108 using the Nordic Optical Telescope on La Palma, Spain. Based on the spectra, we are able to classify 100 of the 108 targets as quasars. A large fraction (50%) is observed to have broad absorption lines (BALs). Moreover, we find six quasars with strange breaks in their spectra, which are not consistent with regular dust reddening. Using template fitting, we infer the amount of reddening along each line of sight ranging from A ( V ) ≈ 0.1 to 1.2 mag (assuming a Small Magellanic Cloud extinction curve). In four cases, the reddening is consistent with dust exhibiting the 2175 Å feature caused by an intervening absorber, and for two of these, an Mg ii absorption system is observed at the best-fit absorption redshift. In the rest of the cases, the reddening is most likely intrinsic to the quasar. We observe no evidence for dusty DLAs in this survey. However, the large fraction of BAL quasars hampers the detection of absorption systems. Out of the 50 non-BAL quasars, only 28 have sufficiently high redshift to detect Ly α in absorption.

  10. KEKB B-Factory, the luminosity frontier

    International Nuclear Information System (INIS)

    Oide, Katsunobu

    2009-01-01

    The experiment at the KEKB B-Factory, as well as PEP-II, brought the final blow on the 2008 Nobel Prize in Physics for the Kobayashi-Maskawa theory. A few key issues will be described on the design and performance of KEKB to make the world's highest luminosity possible. (author)

  11. Luminosity Measurement at the Compact Linear Collider

    CERN Document Server

    Schwartz, Rina; Levy, Aharon

    The compact linear collider (CLIC) is a proposed high energy accelera- tor, planned to collide electrons with positrons at a maximal center-of-mass energy of 3 TeV, and a peak luminosity of 5.9·1034 cm−2s−1. Complementary to the large hadron collider, CLIC is to provide high precision measurements of both known and new physics processes. The required relative precision of luminosity measurement at the CLIC is 10−2. The measurement will be done by the luminosity calorimeter (Lumi- Cal), designed to measure the rate of low angles Bhabha scattering events, a process with well-known cross-section from electroweak theory. Beam-beam effects, which are of unprecedented intensity at the CLIC, influence the lumi- nosity spectrum shape and create a significant amount of background charge deposits in the LumiCal, thus setting a challenge on the requirement for precision. The ability of the LumiCal to provide accurate luminosity mea- surement depends on its ability to perform accurate energy reconstruction of Bhab...

  12. RHIC Proton Luminosity and Polarization Improvement

    International Nuclear Information System (INIS)

    Zhang, S. Y.

    2014-01-01

    The RHIC proton beam polarization can be improved by raising the Booster scraping, which also helps to reduce the RHIC transverse emittance, and therefore to improve the luminosity. By doing this, the beam-beam effect would be enhanced. Currently, the RHIC working point is constrained between 2/3 and 7/10, the 2/3 resonance would affect intensity and luminosity lifetime, and the working point close to 7/10 would enhance polarization decay in store. Run 2013 shows that average polarization decay is merely 1.8% in 8 hours, and most fills have the luminosity lifetime better than 14 hours, which is not a problem. Therefore, even without beam-beam correction, there is room to improve for RHIC polarization and luminosity. The key to push the Booster scraping is to raise the Booster input intensity; for that, two approaches can be used. The first is to extend the LINAC tank 9 pulse width, which has been successfully applied in run 2006. The second is to raise the source temperature, which has been successfully applied in run 2006 and run 2012.

  13. Academic Training - LHC luminosity upgrade: detector challenges

    CERN Multimedia

    Françoise Benz

    2006-01-01

    ACADEMIC TRAINING LECTURE SERIES 13, 14, 15, March, from 11:00 to 12:00 - 16 March from 10:00 to 12:00 Main Auditorium, bldg. 500 on 14, 15 March, Council Room on 13, 16 March LHC luminosity upgrade: detector challenges A. De Roeck / CERN-PH, D. Bortoletto / Purdue Univ. USA, R. Wigmans / Texas, Tech Univ. USA, W. Riegler / CERN-PH, W. Smith / Wisconsin Univ. USA The upgrade of the LHC machine towards higher luminosity (1035 cm-2s-1) has been studied over the last few years. These studies have investigated scenarios to achieve the increase in peak luminosity by an order of magnitude, as well as the physics potential of such an upgrade and the impact of a machine upgrade on the LHC DETECTORS. This series of lectures will cover the following topics: Physics motivation and machine scenarios for an order of magnitude increase in the LHC peak luminosity (lecture 1) Detector challenges including overview of ideas for R&D programs by the LHC experiments: tracking and calorimetry, other new detector ...

  14. Recent improvements in luminosity at PEP

    International Nuclear Information System (INIS)

    Helm, R.; Allen, M.; Chao, A.

    1983-03-01

    We will describe improvements which have led to new records for peak and average luminosity at PEP. Comparison of recent results with several earlier lattice and optical modifications shows rather good correlation with the predictions of a beam-beam simulation program

  15. MPX Detectors as LHC Luminosity Monitor

    CERN Document Server

    Sopczak, Andre; Asbah, Nedaa; Bergmann, Benedikt; Bekhouche, Khaled; Caforio, Davide; Campbell, Michael; Heijne, Erik; Leroy, Claude; Lipniacka, Anna; Nessi, Marzio; Pospisil, Stanislav; Seifert, Frank; Solc, Jaroslav; Soueid, Paul; Suk, Michal; Turecek, Daniel; Vykydal, Zdenek

    2015-01-01

    A network of 16 Medipix-2 (MPX) silicon pixel devices was installed in the ATLAS detector cavern at CERN. It was designed to measure the composition and spectral characteristics of the radiation field in the ATLAS experiment and its surroundings. This study demonstrates that the MPX network can also be used as a self-sufficient luminosity monitoring system. The MPX detectors collect data independently of the ATLAS data-recording chain, and thus they provide independent measurements of the bunch-integrated ATLAS/LHC luminosity. In particular, the MPX detectors located close enough to the primary interaction point are used to perform van der Meer calibration scans with high precision. Results from the luminosity monitoring are presented for 2012 data taken at sqrt(s) = 8 TeV proton-proton collisions. The characteristics of the LHC luminosity reduction rate are studied and the effects of beam-beam (burn-off) and beam-gas (single bunch) interactions are evaluated. The systematic variations observed in the MPX lum...

  16. Luminosity Variations in Post-AGB Stars

    Science.gov (United States)

    Mesler, Robert; Henson, G.

    2007-12-01

    Although much is known about AGB stars and planetary nebulae, relatively little is known about the phase of a star's life in which it transitions between those two states. We have measured the variations in luminosity of a sample of known Post-AGB stars (as well as several candidates) relative to nearby, non-variable stars in order to compare them with theoretical models. The typical behavior of the observed variations is described and an attempt is made to discern whether any periodicity might be present. Luminosity variations were found to be on the order of a few hundredths to a few tenths of a magnitude for the stars that were surveyed, with occasional fluctuations of up to a magnitude. This agrees with current models of Post-AGB stars. Each star fell into one of three categories, which were termed groups 1, 2, and 3. Group 1 stars showed long term, non-periodic luminosity variations on the scale of weeks or longer and were most likely to display some sort of short term, coherent luminosity oscillation (each of which lasted for only a few cycles). Group 2 stars showed erratic, short-term magnitude variations occurring on scales of several days. Group 3 stars showed little or no variation in magnitude. Of the 27 Post-AGB stars that were sampled, five fell into group 1, fifteen fell into group 2, and seven fell into group 3. The luminosity variations tended to be color-independent, and occurred on timescales ranging nearly continuously from a few days to more than a year. No clear periodic behavior was found in any star in our sample. This project was funded by a partnership between the National Science Foundation (NSF AST-0552798), Research Experiences for Undergraduates (REU), and the Department of Defense (DoD) ASSURE (Awards to Stimulate and Support Undergraduate Research Experiences) programs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ishibashi, Wako, E-mail: wako.ishibashi@physik.uzh.ch [Physik-Institut, University of Zurich, Zürich (Switzerland)

    2017-10-17

    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.

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

    Indian Academy of Sciences (India)

    retical arguments together with some numerical evidence. The evolution of the orbits is studied, as mass is transported from the disk to the nucleus. ... galaxies and non-axially symmetric quasar models (see Papadopoulos & Caranicolas.

  19. The Doppler Effect: A Consideration of Quasar Redshifts.

    Science.gov (United States)

    Gordon, Kurtiss J.

    1980-01-01

    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)

  20. Probing the dark energy with quasar clustering.

    Science.gov (United States)

    Calvão, M O; de Mello Neto, J R T; Waga, I

    2002-03-04

    We show through Monte Carlo simulations that the Alcock-Paczyński test, as applied to quasar clustering, is a powerful tool to probe the cosmological density and equation of state parameters Omega(m0), Omega(x0), and w. By taking into account the effect of peculiar velocities upon the correlation function we obtain for the Two-Degree Field QSO Redshift Survey the predicted confidence contours for the cosmological constant (w = -1) and spatially flat (Omega(m0)+Omega(x0) = 1) cases. For w = -1, the test is especially sensitive to the difference Omega(m0)-Omega(Lambda0), thus being ideal to combine with cosmic microwave background results. For the flat case, it is competitive with future supernova and galaxy number count tests, besides being complementary to them.

  1. Discovery and spectrophotometry of high-redshift quasars

    International Nuclear Information System (INIS)

    MacAlpine, G.M.; Feldman, F.R.

    1982-01-01

    We report on the discovery and spectrophotometry of 30 new high-redshift quasars, which were detected using the Curtis Schmidt technique. We also discuss new follow-up spectrophotometry for 23 quasar candidates from University of Michigan Lists I--IV. Our program sample contains eight quasars with z>3, at least five objects exhibiting broad absorption troughs, and a pair of quasars which are 1' apart on the sky and nearly identical in redshift, at z near 2.13. The redshift distribution for the majority of quasars in UM List IV suggests that most of the single-line quasar candidates in the UM List have low to moderate redshifts, with the reported line often being Mg II lambda2798 or C III] lambda1909. For 17 high-redshift quasars where lambda912 at the emission-line redshift could be examined, we did not find any definite Lyman limit cutoffs. Although three objects show a decline of the continuum within 100 A of lambda912, we do not believe them to be unambiguous examples for emission-line clouds situated in the line of sight. When our O I lambda1304 measurements are combined with the data of others to yield a composite spectrum, we obtain O I lambda1304/lambda8446 = 1.35. This suggests reddening with E/sub B/-Vroughly-equal0.23. Finally, our data exhibit a correlation between Lyα emission line velocity widths and redshift. The higher z quasars in the sample tend to have narrower lines, due, at least in part, to bias in the detection technique

  2. Optical constancy of the quasar 1928+738

    International Nuclear Information System (INIS)

    Corso, G.J.; Harris, R.W.; Fox, R.; Schultz, J.

    1990-01-01

    It has been suggested that the low-red shift quasar 1928 + 738 be utilized in the establishment of an extragalactic reference frame. We have observed the quasar in blue light during an interval of 137 days and found it essentially constant, varying by no more than about I 0.15 magnitude from its average value. Slowly varying long-term changes are not ruled out and others are encouraged to monitor this source in the future. (author)

  3. Effective collision strengths of quasar ultraviolet emission lines

    International Nuclear Information System (INIS)

    Osterbrock, D.E.; Wallace, R.K.

    1977-01-01

    The best available published collision strengths for excitation of permitted and semiforbidden emission lines of abundant ions observed or expected in quasars have been collected and averaged over Maxwellian velocity distributions. For a few ions for which calculations are not available, extrapolation along isoelectronic sequences or in principal quantum number n was used to estimate values. These collision strengths were used to correct differentially published photoionization models of quasars, and the corrected models compared with published observational data

  4. Quasar Winds as Dust Factories at High Redshift

    OpenAIRE

    Elvis, Martin; Marengo, Massimo; Karovska, Margarita

    2003-01-01

    Winds from AGN and quasars will form large amounts of dust, as the cool gas in these winds passes through the (pressure, temperature) region where dust is formed in AGB stars. Conditions in the gas are benign to dust at these radii. As a result quasar winds may be a major source of dust at high redshifts, obviating a difficulty with current observations, and requiring far less dust to exist at early epochs.

  5. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    International Nuclear Information System (INIS)

    Scaringi, Simone; Knigge, Christian; Cottis, Christopher E.; Goad, Michael R.

    2008-01-01

    We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

  6. One millimeter continuum observations of high redshift quasars

    International Nuclear Information System (INIS)

    Ennis, D.J.; Soifer, B.T.

    1981-01-01

    Upper limits to the one-millimeter continuum flux densities of the high redshift quasars B2 1225 + 31, Ton 490, and PHL 957 are presented. The upper limit to the power observed from these quasars at 1 mm is, on the average, one half of the observed power in the continuum at L-alpha. These observations are used to constrain the temperature of a hypothetical dust shell which reddens the quasar line and continuum emission by an extinction optical depth sufficient to account for the anomalously low L-alpha/H-alpha emission line ratio observed in each of these quasars. For the quasars studied, dust shell temperatures between 25 K and 50 to 95 K are prohibited by the present data. A dust shell at a temperature within this span reradiating all the power absorbed from the quasar ultraviolet continuum would produce a one-millimeter flux density greater than the measured upper limit. The average radius of the model dust shell cannot be between 70 kpc and 1 Mpc

  7. Circum-Galactic Medium in the Halo of Quasars

    Directory of Open Access Journals (Sweden)

    Riccardo Ottolina

    2017-12-01

    Full Text Available The properties of circum-galactic gas in the halo of quasar host galaxies are investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along the line of sight close to quasars. We used optical spectroscopy of closely aligned pairs of quasars (projected distance ≤ 200 kpc, but at very different redshift obtained at the VLT and Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of quasars at z ~1. Absorption systems of EW ≥0.3 associated with the foreground quasars are revealed up to 200 kpc from the centre of the host galaxy, showing that the structure of the absorbing gas is patchy with a covering fraction quickly decreasing beyond 100 kpc. In this contribution we use optical and near-IR images obtained at VLT to investigate the relations between the properties of the circum-galactic medium of the host galaxies and of the large scale galaxy environments of the foreground quasars.

  8. An astrophysics data program investigation of a synoptic study of quasar continua

    Science.gov (United States)

    Elvis, Martin

    1991-01-01

    A summary of the program is presented. The major product of the program, an atlas of quasar energy distributions, is presented in the appendices along with papers written as a result of this research. The topics covered in the papers include: (1) accurate galactic N(sub h) values toward quasars and active galactic nuclei (AGN); (2) weak bump quasars; (3) millimeter measurements of hard x ray selected active galaxies- implications for the nature of the continuous spectrum; (3) persistence and change in the soft x ray spectrum of the quasar PG1211+143; (4) the soft x ray excess in einstein quasar spectra; and (5) EXOSAT x ray spectra of quasars.

  9. X-ray Spectral Survey of WGACAT Quasars, II: Optical and Radio Properties of Quasars with Low Energy X-ray Cut-offs

    OpenAIRE

    Elvis, Martin; Fiore, Fabrizio; Giommi, Paolo; Padovani, Paolo

    1997-01-01

    We have selected quasars with X-ray colors suggestive of a low energy cut-off, from the ROSAT PSPC pointed archive. We examine the radio and optical properties of these 13 quasars. Five out of the seven quasars with good optical spectra show associated optical absorption lines, with two having high delta-v candidate systems. Two other cut-off quasars show reddening associated with the quasar. We conclude that absorption is highly likely to be the cause of the X-ray cut-offs, and that the abso...

  10. Robust Tracking at the High Luminosity LHC

    CERN Document Server

    Woods, Natasha Lee; The ATLAS collaboration

    2018-01-01

    The High Luminosity LHC (HL-LHC) aims to increase the LHC data-set by an order of magnitude in order to increase its potential for discoveries. Starting from the middle of 2026, the HL-LHC is expected to reach the peak instantaneous luminosity of 7.5×10^34cm^-2s^-1 which corresponds to about 200 inelastic proton-proton collisions per beam crossing. To cope with the large radiation doses and high pileup, the current ATLAS Inner Detector will be replaced with a new all-silicon Inner Tracker. In this talk the expected performance of tracking and vertexing with the HL-LHC tracker is presented. Comparison is made to the performance with the Run2 detector. Ongoing developments of the track reconstruction for the HL-LHC are also discussed.

  11. Recent luminosity improvements at the SLC

    International Nuclear Information System (INIS)

    Raimondi, P.; Usher, T.; Akre, R.

    1998-07-01

    The luminosity of the SLAC Linear Collider (SLC) has been increased by more than a factor of three during the 1997--98 run. Improved alignment and emittance tuning techniques throughout the accelerator resulted in minimal emittance growth from the damping rings to the final focus. In particular, a revised strategy for wakefield cancellation using precision beam size measurements at the entrance of the final focus proved effective for optimizing emittance. The final focus lattice was modified to provide stronger demagnification near the interaction point and to remove residual higher-order aberrations. Beam sizes as small as 1.5 by 0.65 microns were achieved at full beam intensity of 4 10 10 particles per pulse. With these parameters, the mutual focusing of the beams in collision becomes significant, resulting in a further increase in the luminosity. Recorded SLD event rates confirmed the theoretical calculations of the disruption enhancement which was typically 50 to 100%

  12. High luminosity muon scattering at FNAL

    International Nuclear Information System (INIS)

    Bazizi, K.; Conrad, J.; Fang, G.; Erdmann, M.; Geesaman, D.; Jackson, H.; Guyot, C.; Virchaux, M.; Holmgren, H.; Malensek, A.; Melanson, H.; Morfin, J.; Schellman, H.; Nickerson, R.

    1990-02-01

    The charge of this group was to evaluate the physics that can be done with a high luminosity μ scattering experiment at FNAL using the upgraded Tevatron muon beam, and consider the apparatus required. In this report, the physics that can be accomplished with a high luminosity μ scattering experiment is evaluated. The CERN and FNAL μ beams are compared in the context of such an experiment. The expected muon flux with the upgraded machine is estimated. Two possible detectors are compared: the air-core toroid experiment proposed by Guyot et al., and an upgraded version of the E665 double-diode apparatus now in place at FNAL. The relative costs of the detectors are considered. A list of detailed questions that need to be answered regarding the double-diode experiment has be compiled. 2 refs., 10 figs., 2 tabs

  13. Wet drift chambers for precise luminosity

    International Nuclear Information System (INIS)

    Anderson, B.E.; Kennedy, B.W.; Ahmet, K.; Attree, D.J.; Barraclough, G.A.; Cresswell, M.J.; Hayes, D.A.; Miller, D.J.; Selby, C.; Sherwood, P.

    1994-01-01

    A set of high-precision compact drift chambers has been a vital component of the OPAL luminosity monitor since the start of data-taking at LEP. They were augmented in 1992 by the addition of Small Angle Reference Chambers with a very similar design to the original chamber. The performance of the chambers is reviewed, highlighting both the importance of using polyalkylene glycol (Breox) to maintain a uniform and parallel electric field and the construction techniques used to sustain the required field strength. We describe some of the operating problems, with their solutions, and show how the chambers have been used in achieving a systematic error of 0.41% on the luminosity measurement. ((orig.))

  14. Luminosity with more bunches in PEP

    International Nuclear Information System (INIS)

    Corbett, W.J.

    1990-12-01

    The near term accelerator physics program for PEP includes experiments in a collider mode with up to 9 bunches in each beam. In this memo, luminosity data from the 3 x 3 configuration is first used to calculate vertical beam size, emittance and tune shift as a function of current. The data is then used to extrapolate to the case with either 6 x 6 or 9 x 9 bunches colliding in PEP. Vertical emittance growth from the separated bunch optics and dispersion at the IP are included in the calculations. The conclusion is that given a 90 mA current drive limitation in PEP, operating with 6 x 6 bunches yields the maximum luminosity. 9 refs., 6 figs

  15. Classical Cepheid luminosities from binary companions

    International Nuclear Information System (INIS)

    Evans, N.R.

    1991-01-01

    Luminosities for the classical Cepheids Eta Aql, W Sgr, and SU Cas are determined from IUE spectra of their binary companions. Spectral types of the companions are determined from the spectra by comparison with the spectra of standard stars. The absolute magnitude inferred from these spectral types is used to determine the absolute magnitude of the Cepheid, either directly or from the magnitude difference between the two stars. For the temperature range of the companions (A0 V), distinctions of a quarter of a spectral subclass can be made in the comparison between the companions and standard stars. The absolute magnitudes for Eta Aql and W Sgr agree well with the period-luminosity-color relation of Feast and Walker (1987). Random errors are estimated to be 0.3 mag. SU Cas, however, is overluminous for pulsation in the fundamental mode, implying that it is pulsating in an overtone. 58 refs

  16. High Luminosity LHC Studies with ATLAS

    CERN Document Server

    Duncan, Anna Kathryn; The ATLAS collaboration

    2017-01-01

    The High-Luminosity LHC aims to provide a total integrated luminosity of 3000fb$^{-1}$ from proton-proton collisions at $\\sqrt{s}$ = 14 TeV over the course of $\\sim$ 10 years, reaching instantaneous luminosities of up to L = 7.5 $\\times$ 1034cm$^{-2}s$^{-1}$, corresponding to an average of 200 inelastic p-p collisions per bunch crossing ($\\mu$ = 200). Fast simulation studies have been carried out to evaluate the prospects of various benchmark physics analyses to be performed using the upgraded ATLAS detector with the full HL-LHC dataset. The performance of the upgrade has been estimated in full simulation studies, assuming expected HL-LHC conditions. This talk will focus on the results of physics prospects studies for benchmark analyses involving in particular boosted hadronic objects (e.g. ttbar resonances, HH resonances), and on results of Jet/EtMiss studies of jet performance and pileup mitigation techniques that will be critical in HL-LHC analyses.

  17. The AGN Luminosity Fraction in Galaxy Mergers

    Science.gov (United States)

    Dietrich, Jeremy; Weiner, Aaron; Ashby, Matthew; Martinez-Galarza, Juan Rafael; Smith, Howard Alan

    2017-01-01

    Galaxy mergers are key events in galaxy evolution, generally triggering massive starbursts and AGNs. However, in these chaotic systems, it is not yet known what fraction each of these two mechanisms contributes to the total luminosity. Here we measure and model spectral energy distributions (SEDs) using the Code for Investigating Galaxy Emission (CIGALE) in up to 33 broad bands from the UV to the far-IR for 23 IR-luminous galaxies to estimate the fraction of the bolometric IR luminosity that can be attributed to the AGN. The galaxies are split nearly evenly into two subsamples: late-stage mergers, found in the IRAS Revised Bright Galaxy Sample or Faint Source Catalog, and early-stage mergers found in the Spitzer Interacting Galaxy Sample. We find that the AGN contribution to the total IR luminosity varies greatly from system to system, from 0% up to ~90%, but is substantially greater in the later-stage and brighter mergers. This is consistent with what is known about galaxy evolution and the triggering of AGNs.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851, and by the Smithsonian Institution.

  18. K0 finding efficiencies in increasing luminosities

    International Nuclear Information System (INIS)

    Hassard, J.F.; Margetides S.

    1993-01-01

    In early LHC running it is anticipated that experiments will obtain luminosities of 10 32 cm -2 sec -1 , during which typically only one interaction per event will be obtained. But at higher luminosities, necessary for any Higgs and myriad other searches, experiments will have to deal with up to 50 distinct primary processes. Most will be minimum bias, and easily distinguished in terms of trigger. They can still, of course, confuse analysis of high P T events. When it comes to B events, the confusion even from minimum bias events becomes more acute, since B events are not open-quotes high P T close quotes in this environment. The need for vertex discrimination, particularly in z, is well understood; however, a collateral effect - the increasing difficulty in finding tracks at all - has received little attention. The authors show the distribution of the K 0 in the Pythia process B → J/ψK 0 in the space γ vs. η. Confusion in reconstructing the K 0 is acute for many reasons, not the least of which is the way their pions are boosted forward, and even out of acceptance. Extra luminosity merely increases the problems in finding K 0 's, so it must not be assumed that 10 33 cm -2 sec -1 is ten times better than 10 32 cm -2 sec -1

  19. Bayesian Multiscale Analysis of X-Ray Jet Features in High Redshift Quasars

    Science.gov (United States)

    McKeough, Kathryn; Siemiginowska, A.; Kashyap, V.; Stein, N.

    2014-01-01

    X-ray emission of powerful quasar jets may be a result of the inverse Compton (IC) process in which the Cosmic Microwave Background (CMB) photons gain energy by interactions with the jet’s relativistic electrons. However, there is no definite evidence that IC/CMB process is responsible for the observed X-ray emission of large scale jets. A step toward understanding the X-ray emission process is to study the Radio and X-ray morphologies of the jet. We implement a sophisticated Bayesian image analysis program, Low-count Image Reconstruction and Analysis (LIRA) (Esch et al. 2004; Conners & van Dyk 2007), to analyze jet features in 11 Chandra images of high redshift quasars (z ~ 2 - 4.8). Out of the 36 regions where knots are visible in the radio jets, nine showed detectable X-ray emission. We measured the ratios of the X-ray and radio luminosities of the detected features and found that they are consistent with the CMB radiation relationship. We derived a range of the bulk lorentz factor (Γ) for detected jet features under the CMB jet emission model. There is no discernible trend of Γ with redshift within the sample. The efficiency of the X-ray emission between the detected jet feature and the corresponding quasar also shows no correlation with redshift. This work is supported in part by the National Science Foundation REU and the Department of Defense ASSURE programs under NSF Grant no.1262851 and by the Smithsonian Institution, and by NASA Contract NAS8-39073 to the Chandra X-ray Center (CXC). This research has made use of data obtained from the Chandra Data Archive and Chandra Source Catalog, and software provided by the CXC in the application packages CIAO, ChIPS, and Sherpa. We thank Teddy Cheung for providing the VLA radio images. Connors, A., & van Dyk, D. A. 2007, Statistical Challenges in Modern Astronomy IV, 371, 101 Esch, D. N., Connors, A., Karovska, M., & van Dyk, D. A. 2004, ApJ, 610, 1213

  20. CORRELATIONS OF QUASAR OPTICAL SPECTRA WITH RADIO MORPHOLOGY

    International Nuclear Information System (INIS)

    Kimball, Amy E.; Ivezic, Zeljko; Wiita, Paul J.; Schneider, Donald P.

    2011-01-01

    Using the largest homogeneous quasar sample with high-quality optical spectra and robust radio morphology classifications assembled to date, we investigate relationships between radio and optical properties with unprecedented statistical power. The sample consists of 4714 radio quasars from FIRST with S 20 ≥ 2 mJy and with spectra from the Sloan Digital Sky Survey (SDSS). Radio morphology classes include core-only (core), core-lobe (lobe), core-jet (jet), lobe-core-lobe (triple), and double-lobe. Electronic tables of the quasar samples, along with spectral composites for individual morphology classes, are made available. We examine the optical colors of these subsamples and find that radio quasars with core emission unresolved by FIRST (on ∼5'' scale) have a redder color distribution than radio-quiet quasars (S 20 ∼ I ) are correlated, which supports the hypothesis that both parameters are indicative of line-of-sight orientation. We investigate spectral line equivalent widths (EWs) as a function of R and R I , including the O [III] narrow line doublet and the C IV λ1549 and Mg II λ2799 broad lines. We find that the rest EWs of the broad lines correlate positively with R I at the 4σ-8σ level. However, we find no strong dependence of EW on R, in contrast to previously published results. A possible interpretation of these results is that EWs of quasar emission lines increase as the line-of-sight angle to the radio-jet axis decreases. These results are in stark contrast to commonly accepted orientation-based theories, which suggest that continuum emission should increase as the angle to the radio-jet axis decreases, resulting in smaller EWs of emission lines (assumed isotropic). Finally, we observe the Baldwin effect in our sample and find that it does not depend strongly on quasar radio morphology.

  1. A Wealth of Dust Grains in Quasar Winds

    Science.gov (United States)

    2007-01-01

    [figure removed for brevity, see original site] Click on image for larger poster version This plot of data captured by NASA's Spitzer Space Telescope reveals dust entrained in the winds rushing away from a quasar, or growing black hole. The quasar, called PG2112+059, is located deep inside a galaxy 8 billion light-years away. Astronomers believe the dust might have been forged in the winds, which would help explain where dust in the very early universe came from. The data were captured by Spitzer's infrared spectrograph, an instrument that splits apart light from the quasar into a spectrum that reveals telltale signs of different minerals. Each type of mineral, or dust grain, has a unique signature, as can be seen in the graph, or spectrum, above. The strongest features are from the mineral amorphous olivine, or glass (purple); the mineral forsterite found in sand (blue); and the mineral corundum found in rubies (light blue). The detection of forsterite and corundum is highly unusual in galaxies without quasars. Therefore, their presence is a key clue that these grains might have been created in the quasar winds and not by dying stars as they are in our Milky Way galaxy. Forsterite is destroyed quickly in normal galaxies by radiation, so it must be continually produced to be detected by Spitzer. Corundum is hard, and provides a seed that softer, more common minerals usually cover up. As a result, corundum is usually not seen in spectra of galaxies. Since Spitzer did detect the mineral, it is probably forming in a clumpy environment, which is expected in quasar winds. All together, the signatures of the unusual minerals in this spectrum point towards dust grains forming in the winds blowing away from quasars.

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

    CERN Document Server

    Marziani, Paola; Sulentic, Jack

    2012-01-01

    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 ...

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

    International Nuclear Information System (INIS)

    Hainline, Kevin N.; Hickox, Ryan C.; Greene, Jenny E.; Myers, Adam D.; Zakamska, Nadia L.; Liu, Guilin; Liu, Xin

    2014-01-01

    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 –15 erg s –1 cm –2 arcsec –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 8 μm /erg s –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.

  4. On the distinction between density and luminosity evolution

    International Nuclear Information System (INIS)

    Bahcall, J.N.

    1977-01-01

    It is shown that the assumptions of pure density evolution and pure luminosity evolution lead to observable differences in the distribution of sources for all convergent luminosity functions. The proof given is valid for sources with an arbitrary number of intrinisic luminosities (e.g., optical, infrared, and radio) and also holds in the special cases of mixed evolution that are considered. (author)

  5. High-resolution observations of quasars from the Parkes +- 40 sample

    International Nuclear Information System (INIS)

    Booth, R.S.; Spencer, R.E.; Stannard, D.; Baath, L.B.

    1979-01-01

    VLBI observations of 20 compact quasars have been made between Jodrell Bank and Onsala at a frequency of 1666 MHz. Twelve of the quasars have inverted or peaked spectra at centimetre wavelengths and these are all unresolved, having angular diameters of < 0.015 arcsec. Two out of five quasars with overall flat spectra are partially resolved on this scale size, as are three steep-spectrum quasars. (author)

  6. Planetary Nebulae in the Solar Neighbourhood: Statistics, Distance Scale and Luminosity Function

    Science.gov (United States)

    Frew, David J.

    2008-07-01

    An accurate census of the nearest planetary nebulae (PNe) is needed for calculations of the total number, space density, scale height, and birth rate of PNe in the Galaxy, to understand the dynamics of an evolving nebula and its relationship to the cooling history of the central star, and also to provide an unbiased sample to investigate the frequency of binary central stars and their role in the formation and shaping of these objects. This study presents the most refined volume-limited survey of PNe known to date. Integrated H-alpha fluxes for over 400 mostly evolved PNe are presented, based primarily on data from the Southern H-alpha Sky Survey Atlas (SHASSA) and the Virginia Tech Spectral-Line Survey (VTSS). Aperture photometry on the digital images was performed to extract H-alpha+[NII] fluxes. The [NII] contribution was then de-convolved using literature data, new data from slit spectra, or spectrophotometric data from the Wisconsin H-Alpha Mapper (WHAM) also obtained as part of this project. Comparison with previous work shows that the flux scale presented here has no significant zero-point error. The H-alpha fluxes are used to determine new Zanstra temperatures for those PNe with accurate central star photometry, calculating surface-brightness distances for each PN in the sample, and in conjunction with accurate [OIII] fluxes, new absolute PN magnitudes for delineating the faint end of the PN luminosity function. A spectroscopic survey of a range of MASH PNe is also presented. New emission-line intensities for 60 PNe are given, including a preliminary discussion of the chemical abundances of this sample. New distances have been determined for a large number of PNe, by either critically examining the literature, or by deriving new extinction and kinematic distances where suitable. For all PNe not amenable to these approaches, distances were estimated from a new H-alpha surface brightness-radius (SB-r) relation. The Hα SB-r relation covers >6 dex in SB, and

  7. THE LUMINOSITY PROFILES OF BRIGHTEST CLUSTER GALAXIES

    International Nuclear Information System (INIS)

    Donzelli, C. J.; Muriel, H.; Madrid, J. P.

    2011-01-01

    We have derived detailed R-band luminosity profiles and structural parameters for a total of 430 brightest cluster galaxies (BCGs), down to a limiting surface brightness of 24.5 mag arcsec -2 . Light profiles were initially fitted with a Sersic's R 1/n model, but we found that 205 (∼48%) BCGs require a double component model to accurately match their light profiles. The best fit for these 205 galaxies is an inner Sersic model, with indices n ∼ 1-7, plus an outer exponential component. Thus, we establish the existence of two categories of the BCG luminosity profiles: single and double component profiles. We found that double profile BCGs are brighter (∼0.2 mag) than single profile BCGs. In fact, the Kolmogorov-Smirnov test applied to these subsamples indicates that they have different total magnitude distributions, with mean values M R = -23.8 ± 0.6 mag for single profile BCGs and M R = -24.0 ± 0.5 mag for double profile BCGs. We find that partial luminosities for both subsamples are indistinguishable up to r = 15 kpc, while for r > 20 kpc the luminosities we obtain are on average 0.2 mag brighter for double profile BCGs. This result indicates that extra-light for double profile BCGs does not come from the inner region but from the outer regions of these galaxies. The best-fit slope of the Kormendy relation for the whole sample is a = 3.13 ± 0.04. However, when fitted separately, single and double profile BCGs show different slopes: a single = 3.29 ± 0.06 and a double = 2.79 ± 0.08. Also, the logarithmic slope of the metric luminosity α is higher in double profile BCGs (α double = 0.65 ± 0.12) than in single profile BCGs (α single = 0.59 ± 0.14). The mean isophote outer ellipticity (calculated at μ ∼ 24 mag arcsec -2 ) is higher in double profile BCGs (e double = 0.30 ± 0.10) than in single profile BCGs (e single = 0.26 ± 0.11). Similarly, the mean absolute value of inner minus outer ellipticity is also higher in double profile BCGs. From a

  8. 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.

    2009-01-01

    We present mass functions of distant actively accreting supermassive black holes residing in luminous quasars discovered in the Large Bright Quasar Survey, the Bright Quasar Survey, and the Fall Equatorial Stripe of the Sloan Digital Sky Survey (SDSS). The quasars cover a wide range of redshifts (0...... 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......, and discussion of these mass functions will be made with other existing black hole mass functions, notably that based on the SDSS DR3 quasar catalog. We present the relationships used to estimate the black hole mass based on the MgII emission line; the relations are calibrated to the Hbeta and CIV relations...

  9. Serendipitous discovery of quadruply imaged quasars: two diamonds

    Science.gov (United States)

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

    2018-05-01

    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 multicomponent 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.

  10. QUASAR PG1115+080 AND GRAVITATIONAL LENS

    Science.gov (United States)

    2002-01-01

    Left: The light from the single quasar PG 1115+080 is split and distorted in this infrared image. PG 1115+080 is at a distance of about 8 billion light years in the constellation Leo, and it is viewed through an elliptical galaxy lens at a distance of 3 billion light years. The NICMOS frame is taken at a wavelength of 1.6 microns and it shows the four images of the quasar (the two on the left are nearly merging) surrounding the galaxy that causes the light to be lensed. The quasar is a variable light source and the light in each image travels a different path to reach the Earth. The time delay of the variations allows the distance scale to be measured directly. The linear streaks on the image are diffraction artifacts in the NICMOS instrument (NASA/Space Telescope Science Institute). Right: In this NICMOS image, the four quasar images and the lens galaxy have been subtracted, revealing a nearly complete ring of infrared light. This ring is the stretched and amplified starlight of the galaxy that contains the quasar, some 8 billion light years away. (NASA/Space Telescope Science Institute). Credit: Christopher D. Impey (University of Arizona)

  11. HIGH-REDSHIFT SDSS QUASARS WITH WEAK EMISSION LINES

    International Nuclear Information System (INIS)

    Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Jiang Linhua; Kim, J. Serena; Schmidt, Gary D.; Smith, Paul S.; Vestergaard, Marianne; Young, Jason E.; Brandt, W. N.; Shemmer, Ohad; Gibson, Robert R.; Schneider, Donald P.; Strauss, Michael A.; Shen Yue; Anderson, Scott F.; Carilli, Christopher L.; Richards, Gordon T.

    2009-01-01

    We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z > 4. These weak emission-line quasars (WLQs) constitute a prominent tail of the Lyα + N v equivalent width distribution, and we compare them to quasars with more typical emission-line properties and to low-redshift active galactic nuclei with weak/absent emission lines, namely BL Lac objects. We find that WLQs exhibit hot (T ∼ 1000 K) thermal dust emission and have rest-frame 0.1-5 μm spectral energy distributions that are quite similar to those of normal quasars. The variability, polarization, and radio properties of WLQs are also different from those of BL Lacs, making continuum boosting by a relativistic jet an unlikely physical interpretation. The most probable scenario for WLQs involves broad-line region properties that are physically distinct from those of normal quasars.

  12. IRAS observations of radio-quiet and radio-loud quasars

    Science.gov (United States)

    Neugebauer, G.; Soifer, B. T.; Miley, G.; Habing, H. J.; Young, E.; Low, F. J.; Beichman, C. A.; Clegg, P. E.; Harris, S.; Rowan-Robinson, M.

    1984-01-01

    Observations from 12 to 100 microns are presented of two radio-quiet and three radio-loud quasars. Over this wavelength range, all five have grossly similar continuum energy distributions. The continua of the radio-loud quasars are consistent with synchrotron radiation. There is an indication, however, of excess 100 micron emission in the two radio-quiet quasars.

  13. CORNELL: Bunch trains provide higher luminosity

    International Nuclear Information System (INIS)

    Anon.

    1995-01-01

    The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10 32 cm -2 s -1 . In the bid to increase reaction rate for any particular process, this luminosity is pushed as high as possible. Once all other luminosityincreasing cards have been played, the only practical way of making a large gain in luminosity is to increase the frequency of bunch-bunch collisions by increasing the number of bunches stored in the ring. However this is not without its own problems: • If the two beams travel the same orbit, the n bunches in one beam collide with the n bunches of the other at 2n points around the ring, and the resulting cumulative nonlinear beam-beam effect (tune shift) severely limits the luminosity attainable at any interaction point. • The destabilizing wakefield effects of bunches on each other increase as the number of bunches increases and the spacing between them decreases. • The synchrotron radiation emitted by the beams becomes a severe problem as the total beam current is raised: to overcome these effects means supplying radiofrequency power to maintain the beam energy, carrying away heat from the vacuum chamber walls, pumping out desorbed gases, and controlling Xray backgrounds in the experiment. In 1979, CESR was designed to run with a single bunch of electrons and a single bunch of positrons circulating on the same orbit and colliding head-on at two diametrically opposite points in the ring, where the CLEO and CUSB experiments were then located. Ideally one could store multiple bunches and solve the multiple collision point problem by using separate rings for the two beams, as in the CERN ISR proton-proton collider and in the original DORIS two-ring configuration at DESY, Hamburg, making the two beams intersect only at the experiments. A less expensive version of this two-ring scheme was accomplished at CESR in

  14. CORNELL: Bunch trains provide higher luminosity

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1995-09-15

    The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10{sup 32} cm{sup -