WorldWideScience
1

Quality Factor for the Hadronic Calorimeter in High Luminosity Conditions  

CERN Document Server

The Tile Calorimeter (TileCal) is the central section of the hadronic calorimeter of ATLAS experiment and has about 10,000 eletronic channels. An Optimal Filter (OF) has been used to estimate the energy sampled by the calorimeter and applies a Quality Factor (QF) for signal acceptance. An approach using Matched Filter (MF) has also been pursued. In order to cope with the luminosity rising foreseen for LHC operation upgrade, different algorithms have been developed. Among them, the Constrained Optimal Filter (COF) is showing good capacity in handling such luminosity rise by using a deconvolution technique, which revocers physics signals from out of time pile up. When pile up noise is low, COF switches to MF estimator for optimal performance. Currently, the OF measure for signal acceptance is implemented through a chi-square test. At a low-muninosity scenario, such QF measure has been used as a way to describe how the acquired singal is compatible to the pulse shape pattern. However, at high-luminosity conditio...

Balabram, LE; The ATLAS collaboration; Filho, LM

2014-01-01

2

Quality Factor for the Hadronic Calorimeter in High Luminosity Conditions  

CERN Document Server

The Tile Calorimeter (TileCal) is the central section of the hadronic calorimeter of ATLAS experiment and has about 10,000 eletronic channels. An Optimal Filter (OF) has been used to estimate the energy sampled by the calorimeter and applies a Quality Factor (QF) for signal acceptance. An approach using Matched Filter (MF) has also been pursued. In order to cope with the luminosity rising foreseen for LHC operation upgrade, different algorithms have been developed. Currently, the OF measure for signal acceptance is implemented through a chi-square test. At a low luminosity scenario, such QF measure has been used as a way to describe how the acquired signal is compatible to the pulse shape pattern. However, at high-luminosity conditions, due to pile up, this QF acceptance is no longer possible when OF is employed, and the QF becomes a measure to indicate whether the reconstructed signal suffers or not from pile up. Methods are being developed in order to recover the superposed information, and the QF may be us...

Seixas, Jose; The ATLAS collaboration; Manhaes de Andrade Filho, Luciano; Sotto-Maior-Peralva, Bernardo

2014-01-01

3

Luminosity and Redshift Dependence of the Covering Factor of AGNs viewed with WISE and SDSS  

CERN Document Server

In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) (i) on the mid-infrared (MIR) luminosity and (ii) on the redshift. We constructed 12- and 22-micron luminosity functions (LFs) at 0.006 < z < 0.3 using the Wide-field Infrared Survey Explorer} (WISE) data. Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 micron and 25,721 galaxies at 22 micron for spectroscopic classification. We then identified 16,355 AGNs at 12 micron and 4,683 AGNs at 22 micron by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that (i) the CF decreased with increasing MIR luminosity, regardless of the choice of type 2 AGN classification criteria, and (ii) the CF did not change significantly ...

Toba, Yoshiki; Matsuhara, Hideo; Malkan, Matthew A; Gandhi, Poshak; Nakagawa, Takao; Isobe, Naoki; Shirahata, Mai; Oi, Nagisa; Ohyama, Youichi; Takita, Satoshi; Yamauchi, Chisato; Yano, Kenichi

2014-01-01

4

LORENTZ-FACTOR-ISOTROPIC-LUMINOSITY/ENERGY CORRELATIONS OF GAMMA-RAY BURSTS AND THEIR INTERPRETATION  

Energy Technology Data Exchange (ETDEWEB)

The bulk Lorentz factor of the gamma-ray burst (GRB) ejecta ({Gamma}{sub 0}) is a key parameter to understanding GRB physics. Liang et al. have discovered a correlation between {Gamma}{sub 0} and isotropic {gamma}-ray energy: {Gamma}{sub 0}{proportional_to}E{sup 0.25}{sub {gamma},iso,52}. By including more GRBs with updated data and more methods to derive {Gamma}{sub 0}, we confirm this correlation and obtain {Gamma}{sub 0} {approx_equal} 91E{sup 0.29}{sub {gamma},iso,52}. Evaluating the mean isotropic {gamma}-ray luminosities L{sub {gamma},iso} of the GRBs in the same sample, we discover an even tighter correlation {Gamma}{sub 0} {approx_equal} 249L{sup 0.30}{sub {gamma},iso,52}. We propose an interpretation to this later correlation. Invoking a neutrino-cooled hyperaccretion disk around a stellar mass black hole as the central engine of GRBs, we derive jet luminosity powered by neutrino annihilation and baryon loading from a neutrino-driven wind. Applying beaming correction, we finally derive {Gamma}{sub 0}{proportional_to}L{sup 0.22}{sub {gamma},iso}, which is consistent with the data. This suggests that the central engine of long GRBs is likely a stellar mass black hole surrounded by a hyper-accreting disk.

Lue Jing; Zou Yuanchuan; Lei Weihua; Wu Qingwen; Wang Dingxiong [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang Bing; Lue Houjun [Department of Physics and Astronomy, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 454002, Las Vegas, NV 89154-4002 (United States); Liang Enwei, E-mail: zouyc@hust.edu.cn, E-mail: leiwh@hust.edu.cn, E-mail: zhang@physics.unlv.edu [Department of Physics, Guangxi University, Nanning 530004 (China)

2012-05-20

5

The CO luminosity and CO-H2 conversion factor of diffuse ISM: does CO emission trace dense molecular gas?  

CERN Document Server

Aims: We wish to separate and quantify the CO luminosity and CO-H2 conversion factor applicable to diffuse but partially-molecular ISM when H2 and CO are present but C+ is the dominant form of gas-phase carbon. Methods: We discuss galactic lines of sight observed in \\HI, HCO+ and CO where CO emission is present but the intervening clouds are diffuse (locally \\AV\\ $\\la 1$ mag) with relatively small CO column densities $\\NCO \\la 2\\times10^{16}\\pcc$. We separate the atomic and molecular fractions statistically using \\EBV\\ as a gauge of the total gas column density and compare NH2 to the observed CO brightness. Results: Although there are H2-bearing regions where CO emission is too faint to be detected, the mean ratio of integrated CO brightness to NH2 for diffuse ISM does not differ from the usual value of 1\\K km/s of integrated CO brightness per $2\\times10^{20}$ H2 $\\pcc$ . Moreover, the luminosity of diffuse CO viewed perpendicular to the galactic plane is 2/3 that seen at the Solar galactic radius in surveys ...

Liszt, Harvey; Lucas, Robert

2010-01-01

6

Luminosity monitor  

International Nuclear Information System (INIS)

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

7

Light, Luminosity and the High Luminosity LHC  

CERN Multimedia

Short interview to Lucio Rossi, project leader of the High Luminosity LHC, about the concept of light in physics, light and luminosity in particle accelerators and the High Luminosity LHC project. On the occasion of International Year of Light 2015.

2015-01-01

8

RHIC LUMINOSITY UPGRADE PROGRAM  

Energy Technology Data Exchange (ETDEWEB)

The Relativistic Heavy Ion Collider (RHIC) operates with either ions or polarized protons. After increasing the heavy ion luminosity by two orders of magnitude since its commissioning in 2000, the current luminosity upgrade program aims for an increase by another factor of 4 by means of 3D stochastic cooling and a new 56 MHz SRF system. An Electron Beam Ion Source is being commissioned that will allow the use of uranium beams. Electron cooling is considered for collider operation below the current injection energy. For the polarized proton operation both luminosity and polarization are important. In addition to ongoing improvements in the AGS injector, the construction of a new high-intensity polarized source has started. In RHIC a number of upgrades are under way to increase the intensity and polarization transmission to 250 GeV beam energy. Electron lenses will be installed to partially compensate the head-on beam-beam effect.

Fischer, W.

2010-05-23

9

High Luminosity LHC Project Description  

CERN Document Server

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.

Apollinari, Giorgio; Rossi, Lucio

2014-01-01

10

Luminosity Measurement at ILC  

CERN Document Server

More than twenty institutes join the FCAL Collaboration in study of design of the very forward region of a detector for ILC and CLIC. Of particular importance is an accurate luminosity measurement to the level of 10-3, a requirement driven by the potential for precision physics at a future linear collider. In this paper, the method for luminosity measurement, requirements on luminometer and its integration in the forward region are presented. The impact of several effects contributing to the systematic uncertainty of luminosity measurement is given.

Bozovic-Jelisavcic, I; Bambade, P; Jovin, T; Pandurovic, M; Pawlik, B; Rimbault, C; Sadeh, I; Smiljanic, I

2010-01-01

11

Variations in solar luminosity  

International Nuclear Information System (INIS)

The roles of evolution and episodic mixing in determining the solar luminosity are discussed. The influence of perturbations in the convection zone on the luminosity is reviewed in detail, showing that the efficiency of convection has significant effects on both the luminosity and the radius. The amplitude of the change is strongly dependent on the time scale of the perturbation. In the superadiabatic zone and photosphere, the effects of local suppression of convection efficiency are visible in the form of sunspots. Empirical data on solar irradiance obtained from space-borne radiometers have demonstrated the effect of sunspots on irradiance and have led to the tentative conclusion that the flux blocked by the spots is stored for very long times. 210 references

12

properties and luminosity functions  

Directory of Open Access Journals (Sweden)

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.

Hektor Monteiro

2007-01-01

13

Luminosity enhancements at SLAC  

International Nuclear Information System (INIS)

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

14

Luminosity determination at the Tevatron  

OpenAIRE

In this paper we discuss the luminosity determination at the Tevatron. We discuss luminosity measurements by the machine as well as by using the luminosity detectors of the CDF and D0 experiments. We discuss the uncertainties of the measurements, the effort to maximize the initial and integrated luminosity, the challenges and the lessons learned.

Papadimitriou, Vaia

2011-01-01

15

Results From the DAFNE High Luminosity Test  

International Nuclear Information System (INIS)

The DAPHNE collider, based on a new collision scheme including Large Piwinsky angle and Crab-Waist, has been successfully commissioned and is presently delivering luminosity to the SIDDHARTA detector. Large crossing angle and Crab-Waist scheme proved to be effective in: (1) Increasing luminosity, now a factor 2.7 higher than in the past; and (2) controlling transverse beam blow-up due to the beam-beam. Work is in progress to reach the ultimate design luminosity goal 5.0 · 1032 cm-2s-1. The new collision scheme is the main design concept for a new project aimed at building a Super-B factory that is expected to achieve a luminosity of the order of 1036 cm-2 s-1 and it has been also taken into account to upgrade one of the LHC interaction regions.

16

Luminosity Measurement at COMPASS  

OpenAIRE

The measurement of absolutely normalized cross sections for high-energy scattering processes is an important reference for theoretical models. This paper discusses the first determination of the luminosity for data of the COMPASS experiment, which is the basis for such measurements. The resulting normalization is validated via the determination of the structure function $F_2$ from COMPASS data, which is compared to literature.

Collaboration, C. Ho?ppner For The Compass

2011-01-01

17

Increasing the Integrated Luminosity of SLHC by Luminosity Levelling via the Crossing Angle  

CERN Document Server

With an increase of luminosity by a factor of 10, the luminosity lifetime in an upgraded LHC would decrease from 15 hours to two to four hours, depending on the upgrade strategy. If the luminosity increase is achieved primarily by a stronger and more efficient focusing rather than a beam current increase, the luminosity lifetime is in the low bound of this range. We show in this paper that the "early separation" scheme and/or a crab crossing lend itself to a very efficient luminosity levelling. It can be used to counteract the faster luminosity decay and provide a constant luminosity over hours as well as a significant increase of integrated luminosity. This is achieved by adjusting the crossing angle rather than the b* function by means of a bump closed inside the experimental straight section, i.e. operationally simple. The initially large crossing angle reduces the beam-beam tune shift, allowing an increased beam current and higher performance with lower pile-up in the detector and lower energy deposition ...

Koutchouk, Jean-Pierre; Sterbini, G

2008-01-01

18

A luminosity model of RHIC gold runs  

Energy Technology Data Exchange (ETDEWEB)

In this note, we present a luminosity model for RHIC gold runs. The model is applied to the physics fills in 2007 run without cooling, and with the longitudinal cooling applied to one beam only. Having good comparison, the model is used to project a fill with the longitudinal cooling applied to both beams. Further development and possible applications of the model are discussed. To maximize the integrated luminosity, usually the higher beam intensity, smaller longitudinal and transverse emittance, and smaller {beta} are the directions to work on. In past 10 years, the RHIC gold runs have demonstrated a path toward this goal. Most recently, a successful commissioning of the bunched beam stochastic cooling, both longitudinal and transverse, has offered a chance of further RHIC luminosity improvement. With so many factors involved, a luminosity model would be useful to identify and project gains in the machine development. In this article, a preliminary model is proposed. In Section 2, several secondary factors, which are not yet included in the model, are identified based on the RHIC operation condition and experience in current runs. In Section 3, the RHIC beam store parameters used in the model are listed, and validated. In Section 4, the factors included in the model are discussed, and the luminosity model is presented. In Section 5, typical RHIC gold fills without cooling, and with partial cooling are used for comparison with the model. Then a projection of fills with more coolings is shown. In Section 6, further development of the model is discussed.

Zhang, S.Y.

2011-11-01

19

The Subdwarf Luminosity Function  

CERN Document Server

Using data from the Sloan Digital Sky Survey Early Data Release and SuperCOSMOS Sky Survey scans of POSS-I plates we identify a sample of 2600 subdwarfs using reduced proper motion methods and strict selection criteria. This forms one of the largest and most reliable samples of candidate subdwarfs known, and enables us to determine accurate luminosity functions along many different lines of sight. We derive the subdwarf luminosity function with unprecedented accuracy to M_V <= 13, finding good agreement with recent local estimates but discrepancy with results for the more distant spheroid. This provides further evidence that the inner and outer parts of the stellar halo cannot be described by a single density distribution. We also find that the form of the inner spheroid density profile within distances of 2.5 kpc is closely matched by a power law with an index of -3.15 +/- 0.3.

Digby, A P; Cooke, J A; Reid, I N; Cannon, R D; Digby, Andrew P.; Hambly, Nigel C.; Cooke, John A.; Cannon, Russell D.

2003-01-01

20

Hydrogen-Ion Potential of Antibiotics According to the Environment Factors Temperature and Luminosity / Potencial hidrogenionico de antimicrobianos, según los factores ambientales de temperatura y luminosidad / Potencial hidrogeniônico de antimicrobianos, segundo os fatores ambientais temperatura e luminosidade  

Scientific Electronic Library Online (English)

Full Text Available O objetivo deste estudo experimental foi medir o pH dos antibióticos de administração intravenosa ceftriaxona sódica, cloridrato de vancomicina, metronidazol, penicilina G potássica e sulfato de amicacina, após reconstituição com água destilada e diluição com NaCl 0,9%, ou soro glicosado 5%, conside [...] rando a influência da temperatura e luminosidade ambientais, assim como do tempo de exposição, no comportamento químico desses fármacos. Os resultados demonstraram variações que não ultrapassaram 1,0 valor de pH e que alguns antimicrobianos, eminentemente ácidos após a diluição, mantiveram esse comportamento em todas as situações estudadas, não sugerindo a influência de fatores ambientais no comportamento químico das soluções. Como alguns valores de pH encontrados podem contribuir para o desenvolvimento de flebite química e infiltração, é importante enfatizar para a prática clínica em saúde, a necessidade de conhecer as características das soluções de infusão intravenosa, considerando tipo de diluição e tempo de infusão. Abstract in spanish El objetivo de este estudio experimental fue medir el pH de los antibióticos de administración intravenosa ceftriaxona sódica, clorhidrato de vancomicina, metronidazol, penicilina G potásica y sulfato de amikacina, después de reconstitución con agua destilada y dilución con NaCl a 0,9%, o suero gluc [...] osado a 5%, considerando la influencia de la temperatura y luminosidad ambientales, así como el tiempo de exposición, en el comportamiento químico de esos fármacos. Los resultados demostraron variaciones que no ultrapasaron 1,0 (valor de pH) y que algunos antimicrobianos, eminentemente ácidos después de la dilución, mantuvieron ese comportamiento en todas las situaciones estudiadas, no sugiriendo la influencia de factores ambientales en el comportamiento químico de las soluciones. Considerando que algunos valores de pH encontrados pueden contribuir para el desarrollo de flebitis química e infiltración, es importante enfatizar que para la práctica clínica en salud, existe la necesidad de conocer las características de las soluciones de infusión intravenosa, considerando el tipo de dilución y el tiempo de infusión. Abstract in english The objective of this experimental study was to measure the pH of antibiotics administered by intravenous infusion - ceftriaxone sodium, vancomycin hydrochloride, metrodinazole, penicillin G potassium and amikacin sulfate - after reconstitution with sterile water and dilution with NaCl 0.9% or dextr [...] ose 5% in water, according to temperature and luminosity of the environment. The results showed that variation in the drugs' pH was less than 1.0 value and that some antibiotics remained acidic after dilution and maintained this chemical profile in all situations studied, suggesting that the studied environmental factors did not change the solutions' acid base characteristic. Some pH values measured characterize risk for the development of chemical phlebitis and infiltration, and it is important for clinical practice to emphasize the profile of intravenous solutions of antibiotics, considering method of dilution, and time to infusion.

Renata Maria Coelho, Crepaldi; Cíntia, Monteiro; Maria Angélica Sorgini, Peterlini; Mavilde da Luz Gonçalves, Pedreira.

2010-04-01

21

Hydrogen-Ion Potential of Antibiotics According to the Environment Factors Temperature and Luminosity Potencial hidrogenionico de antimicrobianos, según los factores ambientales de temperatura y luminosidad Potencial hidrogeniônico de antimicrobianos, segundo os fatores ambientais temperatura e luminosidade  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this experimental study was to measure the pH of antibiotics administered by intravenous infusion - ceftriaxone sodium, vancomycin hydrochloride, metrodinazole, penicillin G potassium and amikacin sulfate - after reconstitution with sterile water and dilution with NaCl 0.9% or dextrose 5% in water, according to temperature and luminosity of the environment. The results showed that variation in the drugs' pH was less than 1.0 value and that some antibiotics remained acidic after dilution and maintained this chemical profile in all situations studied, suggesting that the studied environmental factors did not change the solutions' acid base characteristic. Some pH values measured characterize risk for the development of chemical phlebitis and infiltration, and it is important for clinical practice to emphasize the profile of intravenous solutions of antibiotics, considering method of dilution, and time to infusion.El objetivo de este estudio experimental fue medir el pH de los antibióticos de administración intravenosa ceftriaxona sódica, clorhidrato de vancomicina, metronidazol, penicilina G potásica y sulfato de amikacina, después de reconstitución con agua destilada y dilución con NaCl a 0,9%, o suero glucosado a 5%, considerando la influencia de la temperatura y luminosidad ambientales, así como el tiempo de exposición, en el comportamiento químico de esos fármacos. Los resultados demostraron variaciones que no ultrapasaron 1,0 (valor de pH y que algunos antimicrobianos, eminentemente ácidos después de la dilución, mantuvieron ese comportamiento en todas las situaciones estudiadas, no sugiriendo la influencia de factores ambientales en el comportamiento químico de las soluciones. Considerando que algunos valores de pH encontrados pueden contribuir para el desarrollo de flebitis química e infiltración, es importante enfatizar que para la práctica clínica en salud, existe la necesidad de conocer las características de las soluciones de infusión intravenosa, considerando el tipo de dilución y el tiempo de infusión.O objetivo deste estudo experimental foi medir o pH dos antibióticos de administração intravenosa ceftriaxona sódica, cloridrato de vancomicina, metronidazol, penicilina G potássica e sulfato de amicacina, após reconstituição com água destilada e diluição com NaCl 0,9%, ou soro glicosado 5%, considerando a influência da temperatura e luminosidade ambientais, assim como do tempo de exposição, no comportamento químico desses fármacos. Os resultados demonstraram variações que não ultrapassaram 1,0 valor de pH e que alguns antimicrobianos, eminentemente ácidos após a diluição, mantiveram esse comportamento em todas as situações estudadas, não sugerindo a influência de fatores ambientais no comportamento químico das soluções. Como alguns valores de pH encontrados podem contribuir para o desenvolvimento de flebite química e infiltração, é importante enfatizar para a prática clínica em saúde, a necessidade de conhecer as características das soluções de infusão intravenosa, considerando tipo de diluição e tempo de infusão.

Renata Maria Coelho Crepaldi

2010-04-01

22

Luminosity Function of GRBs  

OpenAIRE

The luminosity function (LF) statistics applied to the BATSE GRBs (sources of GUSBAD catalog) is the theme approached in this work. The LF is a strong statistical tool to extract useful information from astrophysical samples, where the key point of this statistical analysis is in the detector sensitivity, where we have performed careful analysis. We applied the tool of the LF statistics to three GRB classes predicted by the Fireshell model. One of the main differences betwee...

Lemos, L. J. Rangel; Bianco, C.; Ruffini, R.; Malheiro, M.

2001-01-01

23

Supernova type I luminosity  

International Nuclear Information System (INIS)

The full time-dependent radiation spectrum of a supernova starts when the explosion shock wave reaches the surface of the presupernova envelope. An early radiation spectrum emitted by the expanded and cooling shock-ejected outer layers of an initially compact (R = 108 cm) type I supernova is derived. The relativistically ejected matter is presumably cosmic rays. The Doppler shifted and relativistically time contracted Planck radiation emitted from the expanding surface layers results in an emitted radiation associated with the cooling corresponding to an energy flux of 1.3 x 1043 t-1.05 ergs sec-1 with a spectrum I(h?) dh? = 1.5 x 1043 (h?)-0.92 ergs eV-1 and time behavior (h?)/sub eff/ = 108 t-0.61 eV. The optical luminosity from the shock is thus low congruent to 1040 ergs sec-1 and 1043 ergs total so that it would not be seen as a precursor to the main optical outburst occurring several days later. The x-ray luminosity (several x 1043 ergs in milliseconds) is observable but small compared to extended envelope models. The later optical light curve is then interpreted in terms of radioactive heating, ionization and excitation by 0.2 M/sub solar/ of 56Ni decaying via 56Co to 56Fe. Van Hise (1974) has already pointed out that the two optical decay constants are closely given by the respective radioactive decay constants multiplied by 3/4. This is interpreted as requiring efficiency to produce optical radiation, the Fe+blend, proportional to the (decay rate)/sup 1/3/. It is further noted that when the two optical decay rates are extrapolated to zero time, the intercepts agree with the predicted ratio of deposited energy from 56Ni ? 56Co, and from 56Co ? 56Fe when the appropriate fractional absorption of gamma rays and beta particles is included. The width and magnitude of the peak luminosity has already been calculated by Colgate and McKee

24

Luminosity function of GRBs  

CERN Document Server

The luminosity function (LF) statistics applied to the BATSE GRBs (sources of GUSBAD catalog) is the theme approached in this work. The LF is a strong statistical tool to extract useful information from astrophysical samples, where the key point of this statistical analysis is in the detector sensitivity, where we have performed careful analysis. We applied the tool of the LF statistics to three GRB classes predicted by the Fireshell model. One of the main differences between the Fireshell and Fireball models is the explanation of the GRB prompt emission, where the first claims that it is divided in two physical processes: 1) transparency of a optically thick Freshell producing the P-GRB emission and 2) interaction of a relativistic shell (composed by baryons electron-positron-photon) against the CBM (circumburst medium), producing the emission so-called extended afterglow peak (EAP). However, the Fireball model, the most quoted one, claims that the prompt emission is caused by interactions among several rela...

Lemos, L J Rangel; Ruffini, R; Malheiro, M

2013-01-01

25

High luminosity muon collider design  

Energy Technology Data Exchange (ETDEWEB)

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should be regarded as complementary. Parameters are given of 4 TeV high luminosity {mu}{sup +}{mu}{sup {minus}} collider, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders.

Palmer, R.; Gallardo, J.

1996-10-01

26

High luminosity muon collider design  

International Nuclear Information System (INIS)

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should be regarded as complementary. Parameters are given of 4 TeV high luminosity ?+?- collider, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders

27

Emittance preservation and luminosity tuning in future linear colliders  

OpenAIRE

The future International Linear Collider (ILC) and Compact Linear Collider (CLIC) are intended for precision measurements of phenomena discovered at the Large Hadron Collider (LHC) and also for the discovery of new physics. In order to offer optimal conditions for such experiments, the new colliders must produce very-high-luminosity collisions at energies in the TeV regime. Emittance growth caused by imperfections in the main linacs is one of the factors limiting the luminosity of CLIC and IL...

Eliasson, Peder

2008-01-01

28

Mass and luminosity function of the Pleiades  

International Nuclear Information System (INIS)

From a proper motion survey by Pels and photometric measurement of selected stars it was found that the Pleiades cluster extends till at least 4.60 from the centre, corresponding to 10 pc at a distance of 125 pc. It turns out that the luminosity function of the Pleiades is a function of the distance to the centre, the proportion of faint stars increasing with this distance. Because of this, the luminosity function as it was determined before flattened towards fainter stars, whereas for the total field with a diameter of 20 pc one finds a luminosity function that is still increasing at the faint end. Flare star observations in the Pleiades field show that the increase amounts to at least a factor 20 in the mass range 2 to 0.4 solar masses. Accurate proper motions of stars in the projected central field show a dispersion of velocities in the cluster of 700 m/sec. This could indicate a total mass of the Pleiades cluster of the order of 2000 solar masses. (Auth.)

29

LHC Luminosity and Energy Upgrade  

CERN Document Server

LHC upgrade studies are ongoing as part of the EU CARE-HHH and of the US-LARP programmes. The aim is a ten-fold increase of the LHC luminosity by the middle of next decade, a possible upgrade of the injector complex to inject at 1 TeV and, at a later stage, to raise the collider energy. The motivations for the LHC upgrade are discussed. An overview of beam dynamics and technological challenges is presented. Preferred scenarios to maximize the integrated luminosity and the physics reach are identified.

Scandale, Walter

2006-01-01

30

Technology of high luminosity detectors  

International Nuclear Information System (INIS)

The Workshop on Collider Detectors: Present Capabilities and Future Possibilities focused on the problems posed by high luminosity and high energy at hadron colliders. Four working groups considered problems in individual detector elements, tracking chambers, calorimeters, triggers and particle identification devices. A fifth group reviewed the general problems of detector systems. The working groups concluded that there are technical solutions for the problems of a luminosity of 1033 cm-2 sec-1. Everything is difficult and continued R and D is necessary to improve detectors

31

Free-free absorption effects on Eddington luminosity  

CERN Document Server

In standard treatments the Eddington luminosity is calculated by assuming that the electron-photon cross section is well described by the Thomson cross section which is gray (frequency independent). Here we discuss some consequence of the introduction of free-free opacity in the Eddington luminosity computation: in particular, due to the dependence of free-free emission on the square of the gas density, it follows that the associated absorption cross section increases linearly with the gas density, so that in high density environments Eddington luminosity is correspondingly reduced. We present a summary of an ongoing exploration of the parameter space of the problem, and we conclude that Eddington luminosity in high density environments can be lowered by a factor of ten or more, making it considerably easier for black holes to accelerate and eject ambient gas.

Ciotti, L

2003-01-01

32

Precision luminosity measurements at LHCb  

CERN Document Server

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...

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, Vladimir; 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

2014-01-01

33

High Luminosity Muon Collider Design  

OpenAIRE

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadrons and electron machines. They should be regarded as complementary. Parameters are given of a 4 TeV high luminosity muon-muon collider, and of a 0.5 TeV demonstration machine. We discuss the various systems in such muon collider.

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

1996-01-01

34

The luminosity function of quasars  

Science.gov (United States)

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 L1/4 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 zf 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.

Pei, Yichuan C.

1995-01-01

35

Sub-L* Galaxies at Redshifts z~4, 3, and 2: Their UV Luminosity Function and Luminosity Density  

CERN Document Server

We use very deep (R_lim=27) UGRI imaging to study the evolution of the faint end of the UV-selected galaxy luminosity function from z~4 to z~2. We find that the luminosity function evolves with time and that this evolution is differential with luminosity: the number of sub-L* galaxies increases from z~4 to z~3 by at least a factor of 2.3, while the bright end of the LF remains unchanged. Potential systematic biases restrict our ability to draw strong conclusions at lower redshifts, z~2, but we can say that the number density of sub-L* galaxies at z~2.2 is at least as high as it is at z~3. Turning to the UV luminosity density of the Universe, we find that the luminosity density starts dropping with increasing redshift already beginning at z=3 (earlier than recently thought - Steidel et al. 1999) and that this drop is dominated by the same sub-L* galaxies that dominate the evolution of the LF. This differential evolution of the luminosity function suggests that differentially comparing key diagnostics of dust, ...

Sawicki, M; Sawicki, Marcin; Thompson, David

2005-01-01

36

The Planetary Nebula Luminosity Function  

CERN Document Server

The [O III] 5007 planetary nebula luminosity function (PNLF) occupies an important place on the extragalactic distance ladder: it is the only standard candle that can be applied to all the large galaxies of the Local Supercluster. We review the method's precision, and use it to show that the distance scale defined by Cepheids and the Surface Brightness Fluctuation method is likely too large by ~ 7%. We also discuss some of the physics underlying the phenomenon, and present clues as why the technique is so resilient.

Ciardullo, R

2004-01-01

37

Unidentified IRAS sources: ultrahigh luminosity galaxies  

International Nuclear Information System (INIS)

Optical imaging and spectroscopy measurements were obtained for six of the high galactic latitude infrared sources reported by Houck, et al. (1984) from the IRAS survey to have no obvious optical counterparts on the POSS prints. All are identified with visually faint galaxies that have total luminosities in the range 5 x 10 to the 11th power stellar luminosity to 5 x 10 to the 12th power stellar luminosity. This luminosity emerges virtually entirely in the infrared. The origin of the luminosity, which is one to two orders of magnitude greater than that of normal galaxies, is not known at this time

38

Magnetic spectrograph with high luminosity  

International Nuclear Information System (INIS)

A magnetic spectrograph used to study nuclear reactions at low-energy incident particles is described. The spectrograph high luminosity intensity of 9x10-3 mm2 steradians makes it possible to obtain charged particle energy spectra for a relatively short time. Energy resolution as applied to protons (E/?E is about 600) is practically constant within the whole energy range of the spectrograph E max/E min is equal to 1.45. The luminosity is equal to 4.5x10-4 steradians. The main characteristics of the spectrograph are compared to those of two other ones used to study d,p reactions. The angular distribution of reaction products is ensured by the use of a system of magnets bending the particle beam incident on the target along the direction of registering. Selection of currents in the magnets assures the reaction product registration at any angle from 10 to 150 deg in a step of 10 deg. The magnet lay-out scheme is presented, spectra are shown for deuterons, alpha-particles and protons from the 27Al(d,p) 28Al reaction at the deuteron energy of 3.6 MeV obtained with the spectrograph described

39

Luminosity Dependence and Search Doppler  

Science.gov (United States)

The research supported by this grant covered two projects: (1) a study of the luminosity dependence of the properties of atoll sources; and (2) a search for Doppler shifts in the pulse arrival times of the anomalous pulsar 4U 0142+61. Following the discovery of kilohertz quasi-periodic oscillations (QPOS) in Sco X-1 studies of the X-ray properties of atoll sources have been dominated by searches for these QPOS, and the study of their dependence on other source properties, such as X-ray luminosity and spectral state. In the project supported by grant NAG5-3269 we have detected kHz QPOs for several atoll sources. The physical interpretation of these QPO is as yet unclear, but simple models (such as the Keplerian beat frequency model) can probably be excluded. The results of this research have been reported. We have studied the X-ray pulsations of the anomalous X-ray pulsar 4U 0142+61 using the Rossi XTE. A detailed search for Doppler shifts did not lead to a positive detection. The upper limits exclude almost all types of possible companion stars, except white dwarfs. However, the latter can be excluded since anomalous X-ray pulsars are very young objects. We therefore conclude that anomalous X-ray pulsars are single neutron stars.

VanParadijs, Johannes A.

1998-01-01

40

The Luminosity Dependence of Quasar Clustering  

CERN Document Server

We investigate the luminosity dependence of quasar clustering, inspired by numerical simulations of galaxy mergers that incorporate black hole growth. These simulations have motivated a new interpretation of the quasar luminosity function. In this picture, the bright end of the quasar luminosity function consists of quasars radiating nearly at their peak luminosities, while the faint end consists mainly of very similar sources, but at dimmer phases in their evolution. We combine this model with the statistics of dark matter halos that host quasar activity. We find that, since bright and faint quasars are mostly similar sources seen in different evolutionary stages, a broad range in quasar luminosities corresponds to only a narrow range in the masses of quasar host halos. On average, bright and faint quasars reside in similar host halos. Consequently, we argue that quasar clustering should depend only weakly on luminosity. This prediction is in qualitative agreement with recent measurements of the luminosity d...

Lidz, A; Cox, T J; Hernquist, L; Robertson, B; Lidz, Adam; Hopkins, Philip F.; Cox, Thomas J.; Hernquist, Lars; Robertson, Brant

2006-01-01

41

Determination of the Absolute Luminosity at the LHC  

CERN Document Server

For particle colliders, the most important performance parameters are the beam energy and the luminosity. High energies allow the particle physics experiments to study and observe new effects. The luminosity describes the ability of the collider to produce the required number of useful interactions or events. It is defined as the proportionality factor between the event rate, measured by the experiments, and the cross section of the observed event which describes its probability to occur. The absolute knowledge of the luminosity therefore allows for the experiments to measure the absolute cross sections. The Large Hadron Collider (LHC) was designed to produce proton proton collisions at a center of mass energy of 14 TeV. This energy would be the highest ever reached in a particle accelerator. The knowledge and understanding of particle physics at such high energy is based on simulations and theoretical predictions. As opposed to e+ e- colliders, for which the Bhabba scattering cross section can be accurately ...

White, Simon Mathieu; Puzo, P

2010-01-01

42

Prospects for the ATLAS upgrade for the high luminosity LHC  

CERN Document Server

The Large Hadron Collider (LHC) will continue to be the main infrastructure for experimental High Energy Physics. To maintain the physics potential of LHC, a series of upgrade will be required to increase the yearly integrated luminosity by a factor 10 compared to the original design value. ATLAS will need to correspondingly upgrade its detectors, triggers and data acquisition systems. The aim is to be able to maintain a high efficiency for Standard Model and Beyond Standard Model signals despite a much difficult environment caused by the increasing number of pileup from the high luminosity. This presentation will cover the prospects for the ATLAS upgrade for the high luminosity LHC and present the various planned detector upgrades and their effect on the performance.

Brenner, R; The ATLAS collaboration

2013-01-01

43

The Intrinsic Quasar Luminosity Function: Accounting for Accretion Disk Anisotropy  

Science.gov (United States)

Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ~2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

DiPompeo, M. A.; Myers, A. D.; Brotherton, M. S.; Runnoe, J. C.; Green, R. F.

2014-05-01

44

Operation of the LHC at High luminosity and High stored energy  

CERN Document Server

In 2011 the operation of the Large Hadron Collider LHC entered its first year of high luminosity production at a beam energy of 3.5 TeV. In the first months of 2011 the number of bunches was progressively increased to 1380, followed by a reduction of the transverse emittance, an increase of the bunch population and a reduction of the betatron function at the collision points. The performance improvements steps that were accumulated in 2011 eventually brought the peak luminosity to 3.6 × 1033cm?2s?1. The integrated luminosity delivered to each of the high luminosity experiments amounted to 5.6 fb?1, a factor of 5 above the initial target defined in 2010. The operational experience with high intensity and luminosity at the LHC will be presented, together with the issues that had to be tackled on the road to high intensity and luminosity.

Wenninger, J; Arduini, G; Assmann, R; Holzer, B; Holzer, EB; Kain, V; Lamont, M; Macpherson, A; Papotti, G; Pojer, M; Ponce, L; Redaelli, S; Solfaroli Camillocci, M; Uythoven, J; Venturini Delsolaro, W

2012-01-01

45

Luminosity of young Jupiters revisited. Massive cores make hot planets  

CERN Document Server

The intrinsic luminosity of young Jupiters is of high interest for planet formation theory. It is an observable quantity that is determined by important physical mechanisms during formation, namely the accretion shock structure, and even more fundamentally, the basic formation mechanism (core accretion or gravitational instability). We study the impact of the core mass on the post-formation entropy and luminosity of young giant planets forming via core accretion with a supercritical shock (cold accretion). For this, we conduct self-consistently coupled formation and evolution calculations of giant planets with masses between 1 and 12 Jovian masses and core masses between 20 and 120 Earth masses. We find that the post-formation luminosity of massive giant planets is very sensitive to the core mass. An increase of the core mass by a factor 6 results in an increase of the post-formation luminosity of a 10 Jovian mass planet by a factor 120. Due to this dependency, there is no single well defined post-formation l...

Mordasini, Christoph

2013-01-01

46

The LHCb Online Luminosity Monitoring and Control  

CERN Document Server

The LHCb experiment searches for New Physics by precision measurements in heavy flavour physics. The optimization of the data taking conditions relies on accurate monitoring of the instantaneous luminosity, and many physics measurements rely on accurate knowledge of the integrated luminosity. Most of the measurements have potential systematic effects associated with pileup and changing running conditions. To cope with these while aiming at maximising the collected luminosity, a control of the LHCb luminosity was put in operation. It consists of an automatic real-time feedback system controlled from the LHCb online system which communicates directly with an LHC application which in turn adjusts the beam overlap at the interaction point. It was proposed and tested in July 2010 and has been in routine operation during 2011-2012. As a result, LHCb has been operating at well over four times the design pileup, and 95% of the integrated luminosity has been recorded within 3% of the desired luminosity.

Jacobsson, R; Follin, F

2014-01-01

47

Luminosity spectrum reconstruction at linear colliders  

International Nuclear Information System (INIS)

A good knowledge of the luminosity spectrum is mandatory for many measurements at future e+e- colliders. As the beam-parameters determining the luminosity spectrum cannot be measured precisely, the luminosity spectrum has to be measured through a gauge process with the detector. The measured distributions, used to reconstruct the spectrum, depend on Initial State Radiation, cross-section, and Final State Radiation. To extract the basic luminosity spectrum, a parametric model of the luminosity spectrum is created, in this case the spectrum at the 3 TeV compact linear collider. The model is used within a reweighting technique to extract the luminosity spectrum from measured Bhabha event observables, taking all relevant effects into account. The centre-of-mass energy spectrum is reconstructed within 5 % over the full validity range of the model. The reconstructed spectrum does not result in a significant bias or systematic uncertainty in the exemplary physics benchmark process of smuon pair production. (orig.)

48

The D0 Run IIb luminosity measurement  

OpenAIRE

An assessment of the recorded integrated luminosity is presented for data collected with the D0 detector at the Fermilab Tevatron Collider from June 2006 to September 2011 (Run IIb). In addition, a measurement of the effective cross section for inelastic interactions, also referred to as the luminosity constant, is reported. This measurement incorporates new features that lead to a substantial improvement in the precision of the result. A luminosity constant of \\sigma_{LM} =...

Casey, Bck; Corcoran, M.; Devaughan, K.; Enari, Y.; Gallas, E.; Katsanos, I.; Linnemann, J.; Orduna, J.; Partridge, R.; Prewitt, M.; Schellman, H.; Snow, Gr; Verzocchi, M.

2013-01-01

49

Spatial and luminosity distributions of galactic satellites  

OpenAIRE

We investigate the luminosity functions (LFs) and projected number density profiles of galactic satellites around isolated primaries of different luminosities. We measure these quantities for model satellites placed into the Millennium and Millennium II dark matter simulations by the GALFORM semi-analytic galaxy formation model for different bins of primary galaxy magnitude and we investigate their dependence on satellite luminosity. We compare our model predictions to the d...

Guo, Quan; Cole, Shaun; Eke, Vincent; Frenk, Carlos; Helly, John

2013-01-01

50

Construction of luminosity function for galaxy clusters  

Science.gov (United States)

The luminosity function is an important quantity for analysis of large scale structure statistics, interpretation of galaxy counts (Lin & Kirshner 1996). We investigate the luminosity function of galaxy clusters. This is performed by counting the brightness of galaxies belonging to clusters in PF Catalogue. The obtained luminosity function is significantly different than that obtained both for optical and radiogalaxies (Machalski & Godowski 2000). The implications of this result for theories of galaxy formation are discussed as well.

God?owski, W?odzimierz; Popiela, Joanna; Bajan, Katarzyna; Biernacka, Monika; Flin, Piotr; Panko, Elena

2015-02-01

51

The AGN Contribution to Galaxy Merger Infrared Luminosities  

Science.gov (United States)

We investigate the contribution of AGN activity to the infrared luminosity of interacting galaxies by analyzing dust radiative transfer calculations of a hydrodynamically simulated merger, created with the code GADGET-2. We focus on emission in the mid-IR to far-IR wavelength ranges, and trace the luminosity density of an interacting gas-rich galaxy pair throughout its evolution. We find that the AGN contribution to IR luminosity is greatest during and immediately after coalescence of the galaxies' central black holes. This period lasts roughly 80 Myr, during which time the increased influx of gas to the center of the merger increases the total luminosity by a factor of a thousand or more due to both increased star formation rate (SFR) and black hole accretion. We compare different interstellar medium models used to describe sub-resolution gas and dust clouds in the radiative transfer calculations by studying the color evolution of our merger in the Herschel Space Observatory photometric filter bands, and compare the results to Herschel observations. We conclude that using infrared luminosity as a simple surrogate for SFR can overestimate the true rate, due to the contribution of AGN or other dust heating mechanisms. This conclusion has an especially significant impact in assessing the star formation activity in high-redshift galaxies for which luminosity (the best measured property) may not accurately measure the SFR, and in cases where the molecular gas content can differ from that of local systems. Further work will extend this analysis to simulations of mergers between late-type galaxies. This work was supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 1262851, by the Smithsonian Institution and by NASA grant NNX14AJ6IG.

Rosenthal, Lee; Hayward, Christopher C.; Smith, Howard; Ashby, Matthew; Hung, Chao-Ling; Martinez-Galarza, Rafael; Weiner, Aaron; Zezas, Andreas; Lanz, Lauranne

2015-01-01

52

Evolution of solar ultraviolet luminosity  

International Nuclear Information System (INIS)

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 104 times as much ultraviolet radiation (?<2000 A) than it does today. These results could impact our understanding of the photochemistry and escape of constituents of primordial planetary atmospheres

53

Factoring  

Science.gov (United States)

Test your factoring skills Factors and Multiples Jeopardy How much do you know about factoring and multiples? Play Jeopardy and find out! Prime Factoring Turkey Shoot Blast these turkeys using your factoring skills. Help the Professor Super save the planet by "cooking" the Giant Frozen Turkeys of Destruction. Math Lines 12 X-Factor Shoot the ball at the other factors to get a product of 12. You can also ...

Mr Clark

2012-10-31

54

HL-LHC: Integrated Luminosity and Availability  

CERN Document Server

The objective of LHC operation is to optimise the output for particle physics by maximising the integrated luminosity. An important constraint comes from the event pile–up for one bunch crossing that should not exceed 140 per bunch crossing. With bunches every 25 ns the luminosity for data taking of the experiments should therefore not exceed 5*10^34 s-1cm-2. For the optimisation of the integrated luminosity it is planned to design HL-LHC for much higher luminosity than acceptable for the experiments and to limit the initial luminosity by operating with larger beam size at the collision points. During the fill, the beam size will be slowly reduced to keep the luminosity constant (as already done in LHCb). The gain from luminosity levelling depends on the average length of the fills. Today, with the LHC operating at 4 TeV, most fills are terminated due to equipment failures, resulting in an average fill length of about 5 h. In this paper we discuss the expected integrated luminosity for HL-LHC as a function ...

Apollonio, A; Schmidt, R; Todd, B; Wagner, S; Wollmann, D; Zerlauth, M

2013-01-01

55

Overview of a high luminosity ?+?- collider  

International Nuclear Information System (INIS)

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should be regarded as complementary. Parameters are given of a 4 TeV high luminosity ?+?- collider, and of a 0.5 TeV lower luminosity demonstration machine. The authors discuss the various systems in such muon colliders

56

ISR Superconducting High-Luminosity (low beta ) insertion  

CERN Multimedia

The photograph shows two of the 8 Superconducting Quadrupoles installed in ISR intersection I8 with their helium supply flexible lines,vacuum equipment,power and signal cables. The increase of luminosity produced by this insertion was above a factor 7. On the right one can see part of Open-Axial-Field Magnet. The person on the left side is Stephan Pichler. See also photo 7702690 and its abstract.

1981-01-01

57

Luminosity Monitoring in ATLAS with MPX Detectors  

CERN Document Server

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.

The ATLAS collaboration

2013-01-01

58

Luminosity limits for funnels in thick accretion discs  

International Nuclear Information System (INIS)

A narrow, highly luminous funnel in a thick accretion disc is a common feature of many models for active galactic nuclei. The constraints on the luminosity imposed by the effects of radiation forces on the funnel are examined. The treatment allows properly for the irradiation of any part of the funnel by the rest, an important effect for this problem. It is found that the maximum luminosity of a funnel of small semi-angle phi is reduced below the Eddington limit Lsub(E) by a factor phi2 if the funnel is to be in strict equilibrium. Even with allowance for flow induced viscous stresses, the luminosity cannot exceed of the order of Lsub(E)phi. In contrast, current models have luminosities of the order of Lsub(E)/phi. It is shown that the resulting large unbalanced forces at the funnel surface cause a significant outflow of matter which should be incorporated in the model for consistency. These results do not depend on the detailed angular momentum distribution over the disc surface but only on the funnel geometry. (author)

59

Luminosity determination in $\\sqrt{s}$ = 7 TeV proton collisions using the LHCf Front Counter at LHC  

CERN Document Server

In the Large Hadron Collider forward (LHCf) experiment, the luminosity is determined with the counting rates of detectors called Front Counter. During the LHCf physics operation at ?s = 7 TeV in 2010, two series of calibration run in the conversion factors from the counting rate to the luminosity were carried out on 26th of April and 9th of May. Using the luminosities determined in the April and May scans with 5 % and 4 % accuracy, the conversion factors were determined with 5.0 % accuracy, providing the luminosity determination at the LHCf experiment with this accuracy.

Taki, K; Bonechi, L; Bongi, M; Castellini, G; D'Alessandro, R; Fukatsu, K; Haguenauer, M; Itow, Y; Kasahara, K; Mase, T; Kawade, K; Ricciarini, S; Macina, D; Masuda, K; Menjo, H; Mitsuka, G; Muraki, Y; Noda, K; Papini, P; Perrot, A L; Sako, T; Shimizu, Y; Suzuki, K; Suzuki, T; Tamura, T; Torii, S; Tricomi, A; Turner, W C

2012-01-01

60

Luminosity determination in ?s = 7 TeV proton collisions using the LHCf Front Counter at LHC  

International Nuclear Information System (INIS)

In the Large Hadron Collider forward (LHCf) experiment, the luminosity is determined with the counting rates of detectors called Front Counter. During the LHCf physics operation at ?s = 7 TeV in 2010, two series of calibration run in the conversion factors from the counting rate to the luminosity were carried out on 26th of April and 9th of May. Using the luminosities determined in the April and May scans with 5 % and 4 % accuracy, the conversion factors were determined with 5.0 % accuracy, providing the luminosity determination at the LHCf experiment with this accuracy.

61

THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82  

Energy Technology Data Exchange (ETDEWEB)

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{sub 1450} < -26) with Sloan Digital Sky Survey (SDSS) data covering {approx}6000 deg{sup 2}, then extend to lower luminosities (M{sub 1450} < -24) with newly discovered, faint z {approx} 5 quasars selected from 235 deg{sup 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 < z < 5.1 quasars that is highly complete, with 73 spectroscopic identifications out of 92 candidates. Our color selection method is also highly efficient: of the 73 spectra obtained, 71 are high-redshift quasars. These observations reach below the break in the luminosity function (M{sub 1450}{sup *}{approx}-27). The bright-end slope is steep ({beta} {approx}< -4), with a constraint of {beta} < -3.1 at 95% confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of {approx}2 greater decrease in the number density of luminous quasars (M{sub 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 {approx}30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

McGreer, Ian D.; Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Jiang Linhua [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Ross, Nicholas P.; White, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Schneider, Donald P.; Brandt, W. Niel [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); DeGraf, Colin [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Glikman, Eilat [Department of Physics and Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520-8121 (United States); Ge Jian [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Streblyanska, Alina, E-mail: imcgreer@as.arizona.edu [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)

2013-05-10

62

Luminosity determination at HERA-B  

International Nuclear Information System (INIS)

A detailed description of an original method used to measure the luminosity accumulated by the HERA-B experiment for a data sample taken during the 2002-2003 HERA running period is reported. We show that, with this method, a total luminosity measurement can be achieved with a typical precision, including overall systematic uncertainties, at a level of 5% or better. We also report evidence for the detection of ?-rays generated in the target and comment on the possible use of such delta rays to measure luminosity. (orig.)

63

Luminosity determination at HERA-B  

CERN Document Server

A detailed description of an original method used to measure the luminosity accumulated by the HERA-B experiment for a data sample taken during the 2002-2003 HERA running period is reported. We show that, with this method, a total luminosity measurement can be achieved with a typical precision, including overall systematic uncertainties, at a level of 5% or better. We also report evidence for the detection of delta-rays generated in the target and comment on the possible use of such delta rays to measure luminosity.

Abt, I; Agari, M; Albrecht, H; Aleksandrov, A; Amaral, V S; Amorim, A; Aplin, S J; Aushev, V; Bagaturia, Yu S; Balagura, V; Bargiotti, M; Barsukova, O; Bastos, J; Batista, J; Bauer, C; Bauer, T S; Belkov, A; Belkov, Ar; Belotelov, I; Bertin, A; Bobchenko, B; Böcker, M; Bogatyrev, A; Böhm, G; Brauer, M; Bruinsma, M; Bruschi, M; Buchholz, P; Buran, T; Carvalho, J; Conde, P; Cruse, C; Dam, M; Danielsen, K M; Danilov, M; De Castro, S; Deppe, H; Dong, X; Dreis, H B; Egorytchev, V; Ehret, K; Eisele, F; Emeliyanov, D; Essenov, S; Fabbri, L; Faccioli, P; Feuerstack-Raible, M; Flammer, J; Fominykh, B; Funcke, M; Garrido, L; Gellrich, A; Giacobbe, B; Glass, J; Goloubkov, D; Golubkov, Y; Golutvin, A; Golutvin, I A; Gorbounov, I; Gorisek, A; Gouchtchine, O; Goulart, D C; Gradl, S; Gradl, W; Grimaldi, F; Groth-Jensen, J; Guilitsky, Yu; Hansen, J D; Hernández, J M; Hofmann, W; Hohlmann, M; Hott, T; Hulsbergen, W; Husemann, U; Igonkina, O; Ispiryan, M; Jagla, T; Jiang, C; Kapitza, H; Karabekyan, S; Karpenko, N; Keller, S; Kessler, J; Khasanov, F; Kiryushin, Yu T; Kisel, I; Klinkby, E; Knöpfle, K T; Kolanoski, H; Korpar, S; Krauss, C; Kreuzer, P; Krizan, P; Krücker, D; Kupper, S; Kvaratskheliia, T; Lanyov, A; Lau, K; Lewendel, B; Lohse, T; Lomonosov, B; Männer, R; Mankel, R; Masciocchi, S; Massa, I; Matchikhilian, I; Medin, G; Medinnis, M; Mevius, M; Michetti, A; Mikhailov, Yu; Mizuk, R; Muresan, R; Zur Nedden, M; Negodaev, M; Nörenberg, M; Nowak, S; Núñez-Pardo de Vera, M T; Ouchrif, M; Ould-Saada, F; Padilla, C; Peralta, D; Pernack, R; Pestotnik, R; Petersen, B AA; Piccinini, M; Pleier, M A; Poli, M; Popov, V; Pose, D; Prystupa, S; Pugatch, V; Pylypchenko, Y; Pyrlik, J; Reeves, K; Ressing, D; Rick, H; Riu, I; Robmann, P; Rostovtseva, I; Rybnikov, V; Sánchez, F; Sbrizzi, A; Schmelling, M; Schmidt, B; Schreiner, A; Schröder, H; Schwanke, U; Schwartz, A J; Schwarz, A S; Schwenninger, B; Schwingenheuer, B; Sciacca, F; Semprini-Cesari, N; Shuvalov, S; Silva, L; Sozuer, L; Solunin, S; Somov, A; Somov, S; Spengler, J; Spighi, R; Spiridonov, A; Stanovnik, A; Staric, M; Stegmann, C; Subramanian, H S; Symalla, M; Tikhomirov, I; Titov, M; Tsakov, I; Uwer, U; Van Eldik, C; Vasilev, Yu; Villa, M; Vitale, A; Vukotic, I; Wahlberg, H; Walenta, A H; Walter, M; Wang, J J; Wegener, D; Werthenbach, U; Wolters, H; Wurth, R; Wurz, A; Xella, S M; Zaitsev, Yu; Zavertyaev, M; Zeuner, T; Zhelezov, A; Zheng, Z; Zimmermann, R; Zivko, T; Zoccoli, A

2007-01-01

64

The Environmental Dependence of the Luminosity-Size Relation for Galaxies  

CERN Document Server

We have examined the luminosity-size relationship as a function of environment for 12150 SDSS galaxies with precise visual classifications from the catalog of Nair & Abraham (2010a). Our analysis is subdivided into investigations of early-type galaxies and late-type galaxies. Early-type galaxies reveal a surprisingly tight luminosity-size relation. The dispersion in luminosity about the fiducial relation is only ~0.14 dex (0.35 mag), even though the sample contains galaxies which differ by a factor of almost 100 in luminosity. The dispersion about the luminosity-size relation is comparable to the dispersion about the fundamental plane, even though the luminosity-size relation is fundamentally simpler and computed using purely photometric parameters. The key contributors to the dispersion about the luminosity-size relation are found to be color and central concentration. Expanding our analysis to the full range of morphological types, we show that the slope, zero point, and scatter about the luminosity-siz...

Nair, Preethi B; Abraham, Roberto G

2010-01-01

65

SLC-2000: A luminosity upgrade for the SLC  

International Nuclear Information System (INIS)

The authors discuss a possible upgrade to the Stanford Linear Collider (SLC), whose objective is to increase the SLC luminosity by at least a factor 7, to an average Z production rate of more than 35,000 per week. The centerpiece of the upgrade is the installation of a new superconducting final doublet with a field gradient of 240 T/m, which will be placed at a distance of only 70 cm from the interaction point. In addition, several bending magnet in each final focus will be lengthened and two octupole correctors are added. A complementary upgrade of damping rings and bunch compressors will allow optimum use of the modified final focus and can deliver, or exceed, the targeted luminosity. The proposed upgrade will place the SLC physics program in a very competitive position, and will also enable it to pursue its pioneering role as the first and only linear collider

66

The D0 Run IIb luminosity measurement  

Energy Technology Data Exchange (ETDEWEB)

An assessment of the recorded integrated luminosity is presented for data collected with the D0 detector at the Fermilab Tevatron Collider from June 2006 to September 2011 (Run IIb). In addition, a measurement of the effective cross-section for inelastic interactions, also referred to as the luminosity constant, is reported. This measurement incorporates new features that lead to a substantial improvement in the precision of the result. A luminosity constant of ?{sub LM}=48.3±1.9±0.6mb is obtained, where the first uncertainty is due to the accuracy of the inelastic cross-section used by both CDF and D0, and the second uncertainty is due to D0 sources. The recorded luminosity for the highest E{sub T} jet trigger is L{sub rec}=9.2±0.4fb{sup ?1}, with a relative uncertainty of 4.3%.

Casey, B.C.K. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Corcoran, M. [Rice University, Houston, Texas 77005 (United States); DeVaughan, K. [University of Nebraska, Lincoln, Nebraska 68588 (United States); Enari, Y. [LPNHE, Universités Paris VI and VII, CNRS/IN2P3, Paris (France); Gallas, E. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Katsanos, I., E-mail: katsanos@fnal.gov [University of Nebraska, Lincoln, Nebraska 68588 (United States); Linnemann, J. [Michigan State University, East Lansing, Michigan 48824 (United States); Orduna, J. [Rice University, Houston, Texas 77005 (United States); Partridge, R. [Brown University, Providence, Rhode Island 02912 (United States); Prewitt, M. [Rice University, Houston, Texas 77005 (United States); Schellman, H. [Northwestern University, Evanston, Illinois 60208 (United States); Snow, G.R. [University of Nebraska, Lincoln, Nebraska 68588 (United States); Verzocchi, M. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

2013-01-11

67

The D0 Run IIb luminosity measurement  

International Nuclear Information System (INIS)

An assessment of the recorded integrated luminosity is presented for data collected with the D0 detector at the Fermilab Tevatron Collider from June 2006 to September 2011 (Run IIb). In addition, a measurement of the effective cross-section for inelastic interactions, also referred to as the luminosity constant, is reported. This measurement incorporates new features that lead to a substantial improvement in the precision of the result. A luminosity constant of ?LM=48.3±1.9±0.6mb is obtained, where the first uncertainty is due to the accuracy of the inelastic cross-section used by both CDF and D0, and the second uncertainty is due to D0 sources. The recorded luminosity for the highest ET jet trigger is Lrec=9.2±0.4fb?1, with a relative uncertainty of 4.3%.

68

LHC beam and luminosity lifetimes revisited  

CERN Document Server

The single beam lifetimes and luminosity lifetime during LHC Stable Beams in 2012 for a large number of fills are considered. The evolution of single beam lifetime through a given fill is obtained from fits to BCT data and from the combination of luminosity losses and calibrated beam loss to collimation. A breakdown of the single beam lifetime into principle components is performed allowing a quantitative picture of component lifetime evolution during Stable Beams. The situation before and after the octupole polarity change and concomitant increase in chromaticity in August 2012 are compared. The analysis is extended to the luminosity lifetime and an attempt to made to evaluate emittance growth from the luminous region size and luminosity evolution through the fill.

Lamont, M

2014-01-01

69

Luminosity and spectral evolution of QSOs  

CERN Document Server

We apply the observed spectral states of the Galactic black hole candidates (GBHCs) to the quasi-stellar object (QSO) luminosity evolution based on the correlation between luminosity and the spectrum, which is strongly supported by the similarities of emission mechanisms in GBHCs and QSOs. We derive the QSO luminosity evolution trends in the UV/optical and the X-ray energy bands and demonstrate that their trends are significantly affected by the spectral evolution. Each energy band shows distinct evolution properties. We test one of the widely discussed cosmological evolution scenarios of QSOs, in which QSOs evolve as a single long-lived population, and show that the resulting luminosity functions seen in different energy bands exhibit distinguishable and potentially observable evolution signatures in the X-ray energy bands.

Choi, Y Y; Yi, I S

1999-01-01

70

The D0 Run IIb Luminosity Measurement  

CERN Document Server

An assessment of the recorded integrated luminosity is presented for data collected with the D0 detector at the Fermilab Tevatron Collider from June 2006 to September 2011 (Run IIb). In addition, a measurement of the effective cross section for inelastic interactions, also referred to as the luminosity constant, is reported. This measurement incorporates new features that lead to a substantial improvement in the precision of the result. A luminosity constant of \\sigma_{LM} = 48.3\\pm1.9\\pm0.6 mb is obtained, where the first uncertainty is due to the accuracy of the inelastic cross section used by both CDF and D0, and the second uncertainty is due to D0 sources. The recorded luminosity for the highest E_T jet trigger is L_rec = 9.2 \\pm 0.4 fb^{-1}, with a relative uncertainty of 4.3%.

Casey, B C K; DeVaughan, K; Enari, Y; Gallas, E; Katsanos, I; Linnemann, J; Orduna, J; Partridge, R; Prewitt, M; Schellman, H; Snow, G R; Verzocchi, M

2014-01-01

71

Luminosity measurements with the ATLAS detector  

International Nuclear Information System (INIS)

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 detector in the years 2010 and 2011. The calibration was performed via so called van-der Meer (vdM-) scans. These scans allow to measure the convolved beam sizes in vertical and horizontal directions, which can be used, together with the precise knowledge of the beam intensities, to determine a luminosity calibration constant. Detailed evaluation of all possible error sources affecting this method including cross-checks amongst many different sub-detectors lead to a final ATLAS luminosity uncertainty for pp collisions at ?(s)=7 TeV of ?L/L=3.4% for 2010, and of ?L/L=2.2% for 2011.

72

THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE  

International Nuclear Information System (INIS)

We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22,301 i ?2, with confirmed spectroscopic redshifts between 2.2 i (z = 2.2) ? –24.5 and see a clear break in the QLF at all redshifts up to z = 3.5. A log-linear relation (in log ?* – M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2 < z < 3.5; across this interval the break luminosity increases by a factor of ?2.6 while ?* declines by a factor of ?8. At z ?< 2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of ''AGN downsizing'' is seen, in line with recent studies of the hard X-ray luminosity function. -ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities

73

A Luminosity Leveling Method for LHC Luminosity Upgrade using an Early Separation Scheme  

CERN Document Server

The very high luminosity foreseen for the LHC luminosity upgrade entails in all cases a significant luminosity decrease during a few hours run. We present in this note a new method of luminosity leveling, based on the on-line adjustment of the crossing angle, while keeping the optics unchanged. It is implemented using the D0 dipole of a possible Early Separation Scheme and an orbit corrector. The whole scheme is confined in the experimental drift space. It should be operationally simple as it avoids most complicated side effects that other leveling principles would produce.

Sterbini, G

2007-01-01

74

Dependence of Fanaroff-Riley break of radio galaxies on luminosity and redshift  

Science.gov (United States)

We investigate the dependence of the Fanaroff-Riley (FR) 1/2 dichotomy of radio galaxies on their luminosities and redshifts. Because of a very strong redshift-luminosity correlation (Malmquist bias) in a flux-limited sample, any redshift-dependent effect could appear as a luminosity-related effect and vice versa. A question could then arise—do all the morphological differences seen in the two classes (FR 1 and 2 types) of sources, usually attributed to the differences in their luminosities, could as well be primarily a redshift-dependent effect? A sharp break in luminosity, seen among the two classes, could after all reflect a sharp redshift dependence due to a rather critical ambient density value at some cosmic epoch. A doubt on these lines does not seem to have been raised in past and things have never been examined with this particular aspect in mind. We want to ascertain the customary prevalent view in the literature that the systematic differences in the two broad morphology types of FR 1 and 2 radio galaxies are indeed due to the differences in their luminosities, and not due to a change in redshift. Here we investigate the dependence of FR 1/2 dichotomy of radio galaxies on luminosity and redshift by using the 3CR sample, where the FR 1/2 dichotomy was first seen, supplemented by data from an additional sample (MRC), that goes about a factor of 5 or more deeper in flux-density than the original 3CR sample. This lets us compare sources with similar luminosities but at different redshifts as well as examine sources at similar redshifts but with different luminosities, thereby allowing us a successful separation of the otherwise two intricately entangled effects. We find that the morphology type is not directly related to redshift and the break between the two types of morphologies seems to depend only upon the radio luminosity.

Singal, Ashok K.; Rajpurohit, Kamlesh

2014-09-01

75

THE ENVIRONMENTAL DEPENDENCE OF THE LUMINOSITY--SIZE RELATION FOR GALAXIES  

International Nuclear Information System (INIS)

We have examined the luminosity-size relationship as a function of environment for 12,150 Sloan Digital Sky Survey galaxies with precise visual classifications from the catalog of Nair and Abraham. Our analysis is subdivided into investigations of early-type galaxies and late-type galaxies. Early-type galaxies reveal a surprisingly tight luminosity-size relation. The dispersion in luminosity about the fiducial relation is only ?0.14 dex (0.35 mag), even though the sample contains galaxies that differ by a factor of almost 100 in luminosity. The dispersion about the luminosity-size relation is comparable to the dispersion about the fundamental plane, even though the luminosity-size relation is fundamentally simpler and computed using purely photometric parameters. We attribute this to using a clean sample of elliptical galaxies and a large Petrosian size measure, implying that the fundamental plane may closely resemble a fundamental line, provided a different (and arguably better) size measurement is adopted. The key contributors to the dispersion about the luminosity-size relation are found to be color and central concentration expanding our analysis to the full range of morphological types, we show that the slope, zero point, and scatter about the luminosity-size relation are independent of environmental density. Our study thus indicates that whatever process is building galaxies is doing so in a way that preserves fundamental scaling laws even as the typical luminl scaling laws even as the typical luminosity of galaxies changes with environment. However, the distribution of galaxies along the luminosity-size relation is found to be strongly dependent on galaxy environment. This variation is in the sense that, at a given morphology, larger and more luminous galaxies are rarer in sparser environments. Our analysis of late-type galaxy morphologies reveals that scatter increases toward later Hubble types. Taken together, these results place strong constraints on conventional hierarchical models in which galaxies are built up in an essentially stochastic way.

76

Factorize  

Science.gov (United States)

This interactive applet allows a student to visually explore the concept of factors by creating different rectangular arrays for a number. The user constructs the array by clicking and dragging on a grid. The length and width of the array are factors of the number. A student can elect an option of a randomly selected number or the student selects his own number between 2 and 50. Exploration questions are included to promote student discovery of mathematical concepts with factors.

2000-01-01

77

Luminosity of serendipitous x-ray QSOs  

International Nuclear Information System (INIS)

We have identified the optical counterparts of 47 serendipitously discovered Einstein Observatory X-ray sources with previously unreported quasi-stellar objects. The mean ratio of X-ray to optical luminosity of this sample agrees reasonably well with that derived from X-ray observations of previously known QSOs. However, despite the fact that our limiting magnitude V = 18.5 should permit detection of typical QSOs (i.e., M/sub c/ = -26) to z = 0.9, the mean redshift of our sample is only z = 0.42 Thus the mean luminosity of these objects, M/sub c/ = -24, differs significantly from that of previous QSO surveys with similar optical thresholds. The existence of large numbers of these lower luminosity QSOs which are difficult to discover by previous selection techniques, provides observational confirmation of the steep luminosity function inferred indirectly from optical counts. However, possible explanations for the lack of higher luminosity QSOs in our sample prove even more interesting. If one accepts the global value of the X-ray to optical luminosity ratio proposed by Zamorani et al, and Ku, Helfand, and Lucy, then reconciliation of this ratio with our observations severely constrains the QSO space density and luminosity functions. Alternatively, the ''typical'' QSO-a radio quiet, high redshift (z>1), optically luminous but not superluminous (M/sub c/> or =-27) object-may not be a strong X-ray source. This inference is not in conflict with existing results from Einsteconflict with existing results from Einstein X-ray surveys of preselected QSOs, which also fail to detect such objects. The contribution of QSOs to the diffuse X-ray background radiation is therefore highly uncertain, but may be quite small. Current X-ray data probably do not place significant constraints on the optical number counts of faint QSOs

78

Luminosity evolution in gamma-ray bursts  

International Nuclear Information System (INIS)

We estimate the luminosity evolution and formation rate for over a 900 BATSE GRBs by using redshift and luminosity data calculated by Band, Norris, and Bonnell (Apj, 613 (2004) 484B) via the lag-luminosity correlation. By applying maximum likelihood techniques, we are able to infer the true distribution of the parent GRB population's luminosity function and density distributions in a way that accounts for detector selection effects. We find that after accounting for data truncation, there still exists a significant correlation between the average luminosity and redshift, indicating that distant GRBs are on average more luminous than nearby counterparts. This is consistent with previous studies showing strong source evolution and also recent observations of under luminous nearby GRBs. We find no evidence far beaming angle evolution in the current sample of GRBs with known redshift, suggesting that this increase in luminosity cannot be due to an evolution or the collimation of gamma-ray emission. The resulting luminosity function is well fit with a single power law of index L'-1.5, which is intermediate between the values predicted by the k = 2 power law and Gaussian structured jet models. We also find that the GRB comoving rate density rises steeply with a broad peak between 1 3. This rate density qualitatively matches the current estimates of the star formation rate at high redshifts, favoring a short lived mashigh redshifts, favoring a short lived massive star progenitor model, or a binary model with a short delay between the formation of the compact object and the eventual merger

79

Investigations of the Parameter Space for the LHC Luminosity Upgrade  

CERN Document Server

Increasing the LHC luminosity by a factor of ten is a major challenge, especially for the beam-beam long-range interactions and even more for the magnet technology and insertion layout. To help identifying consistent solutions in this multi-dimensional constrained space, a parametric model of an LHC insertion was prepared, based on the present LHC layout, i.e. ?quadrupole first? and small crossing angle. The model deals with the layout, beam optics, beam-beam effect, superconductor margin and peak heat deposition in the coils. The approach is simplified to obtain a large gain in the optimization time. This study puts in evidence, as critical for the luminosity upgrade, the following actions: enlarging significantly the quadrupole aperture, moving the insertion towards the interaction point, using the highest available critical field superconductors and complementing the insertion with an early separation scheme. The luminosity reach can then be extended to 2×1035 cm-2s-1 while 1×1035 can be obtained with si...

Koutchouk, Jean-Pierre

2006-01-01

80

ATLAS Upgrades Towards the High Luminosity LHC  

CERN Document Server

After successful LHC operation at the center-of-mass energy of 7 and 8 TeV in 2011 and 2012, plans are actively advancing for a series of upgrades, culminating roughly 10 years from now in the high luminosity LHC (HL-LHC) project, delivering of order five times the LHC nominal instantaneous luminosity along with luminosity levelling. The final goal is to extend the data set from about few hundred fb?1 expected for LHC running to 3000 fb?1 by around 2030. Current planning in ATLAS also has significant upgrades to the detector during the consolidation of the LHC to reach full LHC energy and further upgrades to accommodate running already beyond nominal luminosity this decade. The challenge of coping with HL-LHC instantaneous and integrated luminosity, along with the associated radiation levels, requires further major changes to the ATLAS detector. The designs are developing rapidly for an all-new inner-tracker, significant upgrades in the calorimeter and muon systems, as well as improved triggers and data a...

Cinca, D; The ATLAS collaboration

2014-01-01

81

Direct measurement of solar luminosity variation  

International Nuclear Information System (INIS)

Two rocket flights of an absolute pyrheliometer, separated by 30 months, indicate an increase in solar luminosity (solar constant) of 0.4 percent. The significance of this result is considered in light of the instrument performance during the rocket flights and of pre- and postflight intercomparisons with independently maintained pyrheliometers. There is a high probability that the measured difference is real. Additional observations are required to determine whether the difference results from random fluctuations in solar luminosity, a nonrandom change of short duration, or a sustained change that has climatological significance

82

Calculating luminosity for a coupled Tevatron lattice  

International Nuclear Information System (INIS)

The traditional formula for calculating luminosity assumes an uncoupled lattice and makes use of one-degree-of-freedom lattice functions, ?H and ?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

83

Luminosity of continuous beams with crossing angle  

International Nuclear Information System (INIS)

Since it appears difficult to reach a luminosity of even 1032 cm-2 sec-1 with (p, anti p) in a single ring if the number of events per bunch collision should not exceed unity, it seems appropriate to ask what could be done with two continuous beams in independent rings, ISR style. This subject was treated at some length in the first ICFA report by Keil and King, based on an optimization procedure developed earlier by Keil. In this note, a different approach is taken by considering the length of the interaction diamond and the luminosity to be of primary importance and relating the other parameters to them

84

Luminosity of continuous beams with crossing angle  

International Nuclear Information System (INIS)

Since it appears difficult to reach a luminosity of even 10/sup 32/ cm/sup -2/ sec/sup -1/ with (p, p-bar) in a single ring if the number of events per bunch collision should not exceed unity, it seems appropriate to ask what could be done with two continuous beams in independent rings, ISR style. This subject was treated at some length previously, based on an optimization procedure developed earlier. In this paper, a different approach is taken by considering the length of the interaction diamond and the luminosity to be of primary importance and relating the other parameters to them

85

X-ray spectral state is not correlated with luminosity in Holmberg II X-1  

CERN Document Server

The ultraluminous X-ray source (ULX) Holmberg II X-1 has been observed over 4 months in 2009/2010 by the Swift observatory. The source luminosity varied by a factor of up to 14, reaching a maximum 0.3-10 keV luminosity of ~3.0E40 erg/s. The spectral properties do not vary much over these 4 months, with only a slight monotonic increase of the hardness ratio with the count rate. This means that the erratic flaring activity of the source is not associated with spectral changes, as seen in other ULXs. Conversely, comparison with data obtained by Swift in 2006 shows a completely different picture: while at a luminosity also seen in the 2009/2010 data, the source appears with a hard spectrum. Thus, it appears that, as in Galactic black hole binaries, spectral states in this ULX are not determined only by the X-ray luminosity.

Grisé, Fabien; Feng, Hua; Kajava, Jari; Farrell, Sean; 10.1088/2041-8205/724/2/L148

2010-01-01

86

LOW CO LUMINOSITIES IN DWARF GALAXIES  

International Nuclear Information System (INIS)

We present maps of 12COJ = 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13'' angular resolution, ?250 pc at our average distance of D = 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarf galaxies outside the Local Group ranging from individual lines of sight, stacking over IR-bright regions of embedded star formation, and stacking over the entire galaxy. We detect five galaxies in CO with total CO luminosities of LCO2-1 = (3-28) × 106 K km s–1 pc2. The other 11 galaxies remain undetected in CO even in the stacked images and have LCO2-1 ?6 K km s–1 pc2. We combine our sample of dwarf galaxies with a large sample of spiral galaxies from the literature to study scaling relations of LCO with MB and metallicity. We find that dwarf galaxies with metallicities of Z ? 1/2-1/10 Z? have LCO of 2-4 orders of magnitude smaller than massive spiral galaxies and that their LCO per unit LB is 1-2 orders of magnitude smaller. A comparison with tracers of star formation (FUV and 24 ?m) shows that LCO per unit star formation rate (SFR) is 1-2 orders of magnitude smaller in dwarf galaxies. One possin dwarf galaxies. One possible interpretation is that dwarf galaxies form stars much more efficiently: we argue that the low LCO/SFR ratio is due to the fact that the CO-to-H2 conversion factor, ?CO, changes significantly in low-metallicity environments. Assuming that a constant H2 depletion time of ?dep = 1.8 Gyr holds in dwarf galaxies (as found for a large sample of nearby spirals) implies ?CO values for dwarf galaxies with Z ? 1/2-1/10 Z? that are more than one order of magnitude higher than those found in solar metallicity spiral galaxies. Such a significant increase of ?CO at low metallicity is consistent with previous studies, in particular those of Local Group dwarf galaxies that model dust emission to constrain H2 masses. Even though it is difficult to parameterize the dependence of ?CO on metallicity given the currently available data, the results suggest that CO is increasingly difficult to detect at lower metallicities. This has direct consequences for the detectability of star-forming galaxies at high redshift, which presumably have on average sub-solar metallicity.

87

Low CO Luminosities in Dwarf Galaxies  

Science.gov (United States)

We present maps of 12COJ = 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13'' angular resolution, ~250 pc at our average distance of D = 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarf galaxies outside the Local Group ranging from individual lines of sight, stacking over IR-bright regions of embedded star formation, and stacking over the entire galaxy. We detect five galaxies in CO with total CO luminosities of L CO 2-1 = (3-28) × 106 K km s-1 pc2. The other 11 galaxies remain undetected in CO even in the stacked images and have L CO 2-1 <~ (0.4-8) × 106 K km s-1 pc2. We combine our sample of dwarf galaxies with a large sample of spiral galaxies from the literature to study scaling relations of L CO with M B and metallicity. We find that dwarf galaxies with metallicities of Z ? 1/2-1/10 Z ? have L CO of 2-4 orders of magnitude smaller than massive spiral galaxies and that their L CO per unit L B is 1-2 orders of magnitude smaller. A comparison with tracers of star formation (FUV and 24 ?m) shows that L CO per unit star formation rate (SFR) is 1-2 orders of magnitude smaller in dwarf galaxies. One possible interpretation is that dwarf galaxies form stars much more efficiently: we argue that the low L CO/SFR ratio is due to the fact that the CO-to-H2 conversion factor, ?CO, changes significantly in low-metallicity environments. Assuming that a constant H2 depletion time of ?dep = 1.8 Gyr holds in dwarf galaxies (as found for a large sample of nearby spirals) implies ?CO values for dwarf galaxies with Z ? 1/2-1/10 Z ? that are more than one order of magnitude higher than those found in solar metallicity spiral galaxies. Such a significant increase of ?CO at low metallicity is consistent with previous studies, in particular those of Local Group dwarf galaxies that model dust emission to constrain H2 masses. Even though it is difficult to parameterize the dependence of ?CO on metallicity given the currently available data, the results suggest that CO is increasingly difficult to detect at lower metallicities. This has direct consequences for the detectability of star-forming galaxies at high redshift, which presumably have on average sub-solar metallicity.

Schruba, Andreas; Leroy, Adam K.; Walter, Fabian; Bigiel, Frank; Brinks, Elias; de Blok, W. J. G.; Kramer, Carsten; Rosolowsky, Erik; Sandstrom, Karin; Schuster, Karl; Usero, Antonio; Weiss, Axel; Wiesemeyer, Helmut

2012-06-01

88

Solar interior structure and luminosity variations  

International Nuclear Information System (INIS)

The assumptions of standard solar evolution theory are mentioned briefly, and the principle conclusions drawn from them are described. The result is a rationalization of the present luminosity and radius of the Sun. Because there is some uncertainty about the interior composition of the Sun, a range of models is apparantly acceptable. (orig./WL)

89

Jet spectrometer for SSC energies and luminosities  

International Nuclear Information System (INIS)

A limited solid angle (?theta = ?phi = +-0.8 radians) spectrometer designed to study high transverse momentum (p/sub T/) jets at SSC energies and luminosities are described. The reasoning for its overall size and the particular type of each detector component is explained. Trigger rates for two jet production, expected from QCD, as well as number of electronic channels are listed

90

KEKB B-Factory, the luminosity frontier  

International Nuclear Information System (INIS)

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)

91

Transformation of Galaxy Morphology and Luminosity Classes  

CERN Document Server

We present a unified picture on the evolution of galaxy luminosity and morphology. Galaxy morphology is found to depend critically on the local environment set up by the nearest neighbor galaxy in addition to luminosity and the large scale density. When a galaxy is located farther than the virial radius from its closest neighbor, the probability for the galaxy to have an early morphological type is an increasing function only of luminosity and the local density due to the nearest neighbor ($\\rho_1$). The tide produced by the nearest neighbor is thought to be responsible for the morphology transformation toward the early type at these separations. When the separation is less than the virial radius, i.e. when $\\rho_1 > \\rho_{\\rm virial}$, its morphology depends also on the neighbor's morphology and the large-scale background density over a few Mpc scales ($\\rho_{20}$) in addition to luminosity and $\\rho_1$. The early type probability keeps increasing as $\\rho_1$ increases if its neighbor is an early type. But t...

Park, Changbom; Choi, Yun-Young

2007-01-01

92

Luminosity function of high redshift quasars  

International Nuclear Information System (INIS)

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 (q0 = 1 and q0 = 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 rveys 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

93

How covariant is the galaxy luminosity function?  

CERN Document Server

We investigate the error properties of certain galaxy luminosity function (GLF) estimators. Using a cluster expansion of the density field, we show how, for both volume and flux limited samples, the GLF estimates are covariant. The covariance matrix can be decomposed into three pieces: a diagonal term arising from Poisson noise; a sample variance term arising from large-scale structure in the survey volume; an occupancy covariance term arising due to galaxies of different luminosities inhabiting the same cluster. To evaluate the theory one needs: the mass function and bias of clusters, and the conditional luminosity function (CLF). We use a semi-analytic model (SAM) galaxy catalogue from the Millennium run N-body simulation and the CLF of Yang et al. (2003) to explore these effects. The GLF estimates from the SAM and the CLF qualitatively reproduce results from the 2dFGRS. We also measure the luminosity dependence of clustering in the SAM and find reasonable agreement with 2dFGRS results for bright galaxies. ...

Smith, Robert E

2012-01-01

94

Luminosity Measurement at the Compact Linear Collider  

CERN Document Server

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...

Schwartz, Rina; Levy, Aharon

95

Luminosity Tuning at the Interaction Point  

CERN Document Server

Minimisation of the emittance in a linear collider is not enough to achieve optimal performance. For optimisation of the luminosity, tuning of collision parameters such as angle, offset, waist, etc. is needed, and a fast and reliable tuning signal is required. In this paper tuning knobs are presented, and their optimisation using beamstrahlung as a tuning signal is studied.

Eliasson, Peder; Schulte, Daniel; Tomás, R; Zimmermann, Frank

2006-01-01

96

Luminosity of initial breakdown in lightning  

Science.gov (United States)

Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG type (12 cases) or an IC type (3 cases) IB pulse in fast electric field change records. The E-change data for 217 flashes indicate that all CG and IC flashes have IB pulses. The luminosity bursts of 14 negative CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, linear segments visibly advance away from the first light burst for 55-200 µs, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial leaders or streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4-18 × 105 m s-1 over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 µs before the luminosity fades in about 100 µs, then this sequence may repeat several times. In several flashes, a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development.

Stolzenburg, M.; Marshall, T. C.; Karunarathne, S.; Karunarathna, N.; Vickers, L. E.; Warner, T. A.; Orville, R. E.; Betz, H.-D.

2013-04-01

97

Identifying the Low Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores  

CERN Document Server

We present a search for all embedded protostars with internal luminosities 4E-3 (d/140 pc)^2 solar luminosities, a factor of 25 better than the sensitivity of IRAS to such objects. We present selection criteria used to identify candidates from the Spitzer data and examine complementary data to decide whether each candidate is truly an embedded protostar. We find a tight correlation between the 70 micron flux and internal luminosity of a protostar, an empirical result based on observations and two-dimensional radiative transfer models of protostars. We identify 50 embedded protostars with Lint < 1 solar luminosities; 15 have Lint < 0.1 solar luminosities. The intrinsic distribution of source luminosities increases to lower luminosities. While we find sources down to the above sensitivity limit, indicating that the distribution may extend to luminosities lower than probed by these observations, we are able to rule out a continued rise in the distribution below 0.1 solar luminosities. Between 75-85% of co...

Dunham, Michael M; Evans, Neal J; Bourke, Tyler L; Huard, Tracy L; Myers, Philip C; Kauffmann, Jens

2008-01-01

98

Luminosity measurement method for the LHC: Event selection and absolute luminosity determination  

Energy Technology Data Exchange (ETDEWEB)

In our earlier papers Krasny et al. [1,2] have proposed a new luminosity measurement method which uses lepton pairs produced in peripheral collisions of the LHC beam particles, and identified the requirements for a new, specialized luminosity detector which is indispensable for their efficient on-line selection. In this paper we use the base-line detector model, with no precise timing capabilities, to evaluate the statistical and systematic accuracy of the method. We propose the complete event selection procedure and demonstrate that it allows to collect a sufficiently large sample of e{sup +}e{sup ?} pairs to achieve a better than 1% statistical accuracy of the luminosity measurement over less than one-month-long running time intervals. We argue that the absolute luminosity measurement systematic errors can be kept below 1%. The proposed method can be directly applied to the LHC running periods for which the machine instantaneous luminosity does not exceed the L=10{sup 33}s{sup ?1}cm{sup ?2} value. Two ways extending the method to the large pile-up periods corresponding to higher instantaneous luminosities are proposed.

Krasny, M.W., E-mail: krasny@lpnhep.in2p3.fr [LPNHE, Pierre and Marie Curie University, CNRS-IN2P3, Tour 33, RdC, 4, pl. Jussieu, 75005 Paris (France); Chwastowski, J. [Institute of Teleinformatics, Faculty of Physics, Mathematics and Computer Science, Cracow University of Technology, ul. Warszawska 24, 31-115 Kraków (Poland); Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland); Cyz, A.; S?owikowski, K. [Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland)

2013-11-21

99

Solar gravitational energy and luminosity variations  

CERN Document Server

Due to non-homogeneous mass distribution and non-uniform velocity rate inside the Sun, the solar outer shape is distorted in latitude. In this paper, we analyze the consequences of a temporal change in this figure on the luminosity. To do so, we use the Total Solar Irradiance (TSI) as an indicator of luminosity. Considering that most of the authors have explained the largest part of the TSI modulation with magnetic network (spots and faculae) but not the whole, we could set constraints on radius and effective temperature variations (dR, dT). However computations show that the amplitude of solar irradiance modulation is very sensitive to photospheric temperature variations. In order to understand discrepancies between our best fit and recent observations of Livingston et al. (2005), showing no effective surface temperature variation during the solar cycle, we investigated small effective temperature variation in irradiance modeling. We emphasized a phase-shift (correlated or anticorrelated radius and irradianc...

Fazel, Z; Lefebvre, S; Ajabshirizadeh, A; Pireaux, S; 10.1016/j.newst.2007.05.003

2009-01-01

100

Low-luminosity active galactic nuclei  

International Nuclear Information System (INIS)

The properties of low-luminosity active nuclei are summarized in an effort to determine the continuities which exist among classes of objects exhibiting nonstellar energy input. Questions are addressed which deal with the relations among the classes of active nuclei (low-ionization nuclei, weak Seyfert nuclei, composite objects and starbursts), their relation to star-forming nuclei, and how these objects differ from the high-luminosity classical Seyfert nuclei, radio galaxies and QSOs. It is suggested that starburst nuclei may evolve rapidly into compact configurations of collapsed remnants, which might further collapse into massive accretors. In contrast, some luminous active nuclei show surrounding star formation, indicating that nuclear activity may induce star formation in its environs. 129 references

101

LIGHT and LUMINOSITY, from Einstein to LHC  

CERN Document Server

After an introduction on the concept of light in physics, this talk will focus on CERN’s High Luminosity LHC project, aiming at extending the discovery potential of CERN’s flagship accelerator by increasing its “luminosity” (ie the number of particles that can be squeezed inside the accelerator to maximize the number of collisions). To achieve this objective, many new technologies are being developed at CERN and many collaborating institutes worldwide, especially in the field of superconductivity. Lucio Rossi, the main speaker, is the head of the HL-LHC project, based at CERN. Giorgio Apollinari, Director for the LHC Accelerator Research Program (LARP) will speak through a videoconference from Fermilab (USA). The event is webcast live and will be followed by Fermilab and other institutes in the USA.

CERN. Geneva; Prof. ROSSI, Lucio

2015-01-01

102

Luminosity measurements in ATLAS with MPX detectors  

International Nuclear Information System (INIS)

The ATLAS-MPX detectors are based on Medipix2 silicon devices designed by CERN for the detection of different types of radiation. These detectors are successfully operating in the ATLAS detector at 16 places and collect data independent of the ATLAS data-recording chain. Recently it has been recognized that these detectors are well suited for luminosity measurements. Results from these studies are presented.

103

Luminosity measurements in ATLAS with MPX detectors  

Energy Technology Data Exchange (ETDEWEB)

The ATLAS-MPX detectors are based on Medipix2 silicon devices designed by CERN for the detection of different types of radiation. These detectors are successfully operating in the ATLAS detector at 16 places and collect data independent of the ATLAS data-recording chain. Recently it has been recognized that these detectors are well suited for luminosity measurements. Results from these studies are presented.

Sopczak, Andre; Benes, Petr; Bergmann, Benedikt; Biskup, Bartolomej; Jakubek, Jan; Pospisil, Stanislav; Solc, Jaroslav; Sopko, Vit; Suk, Michal; Turecek, Daniel; Vykydal, Zdenek [IEAP CTU Prague (Czech Republic); Asbah, Nedaa; Leroy, Claude; Soueid, Paul [Universite de Montreal (Canada)

2013-07-01

104

Improved Photometric Redshifts with Surface Luminosity Priors  

CERN Document Server

We apply Bayesian statistics with prior probabilities of galaxy surface luminosity (SL) to improve photometric redshifts. We apply the method to a sample of 1266 galaxies with spectroscopic redshifts in the GOODS North and South fields at 0.1 0.2 is reduced from 15.0% to 10.4%, while the rms scatter of the fractional redshift error does not change much.

Xia, Lifang; Malhotra, Sangeeta; Rhoads, James; Grogin, Norman; Hathi, Nimish P; Windhorst, Rogier A; Pirzkal, Nor; Xu, Chun

2009-01-01

105

The Luminosity of Population III Star Clusters  

CERN Document Server

We analyze the time evolution of the luminosity of a cluster of Population III protostars formed in the early universe. We argue from the Jeans criterion that primordial gas can collapse to form a cluster of first stars that evolve relatively independently of one another (i.e., with negligible gravitational interaction). We model the collapse of individual protostellar clumps using 2+1D nonaxisymmetric numerical hydrodynamics simulations. Each collapse produces a protostar surrounded by a massive disk (i.e., $M_{\\rm disk} / M_{*} \\gtrsim 0.1$), whose evolution we follow for a further 30--40 kyr. Gravitational instabilities result in the fragmentation and the formation of gravitationally bound clumps within the disk. The accretion of these fragments by the host protostar produces accretion and luminosity bursts on the order of $10^6\\,\\LSun$. Within the cluster, we show that a simultaneity of such events across several protostellar cluster members can elevate the cluster luminosity to 5--10${\\times}$ greater th...

DeSouza, Alexander L

2015-01-01

106

Luminosity Evolution of Gamma-ray Pulsars  

CERN Document Server

We investigate the electrodynamic structure of a pulsar outer-magnetospheric particle accelerator and the resultant gamma-ray emission. By considering the condition for the accelerator to be self-sustained, we derive how the trans-magnetic-field thickness of the accelerator evolves with the pulsar age. It is found that the thickness is small but increases steadily if the neutron-star envelope is contaminated by sufficient light elements. For such a light element envelope, the gamma-ray luminosity of the accelerator is kept approximately constant as a function of age in the initial ten thousand years, forming the lower bound of the observed distribution of the gamma-ray luminosity of rotation-powered pulsars. If the envelope consists of only heavy elements, on the other hand, the thickness is greater but increases less rapidly than what a light element envelope has. For such a heavy element envelope, the gamma-ray luminosity decreases relatively rapidly, forming the upper bound of the observed distribution. Th...

Hirotani, Kouichi

2013-01-01

107

New Evidence for a Substellar Luminosity Problem  

Science.gov (United States)

HD 130948BC was the first field brown dwarf system to have both a dynamically measured mass and precise age constraint, from its solar-type host star, and it was unexpectedly ?2× more luminous than predicted by substellar evolutionary models. However, because of the difficulty in determining accurate stellar ages, even in this nearly ideal case of a young star where numerous age indicators agree, it has been unclear if the apparent over-luminosity could be due to an erroneous age for this unique system. If such large systematic errors actually exist in substellar evolutionary models it could have wide-ranging implications, from determinations of the initial mass function to the masses estimated for directly imaged planets. We present here a new dynamical mass for a pair of brown dwarfs that also have a well-determined age from their young, solar-type star. This first check on the substellar "luminosity problem" reveals a nearly identical systematic error as was previously observed. We compare predictions from commonly used evolutionary models and present possible explanations for this problem. There are little appreciated, large differences (?0.2 dex) in the predicted luminosity evolution of substellar objects which, along with the discrepancies of models compared to observations, currently limit our ability to characterize the fundamental properties of both brown dwarfs and directly imaged exoplanets.

Dupuy, Trent J.; Liu, M. C.; Ireland, M.

2014-01-01

108

The Luminosity Profiles of Brightest Cluster Galaxies  

CERN Document Server

(Abridged) 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 BCGs luminosity profiles: single and double component profiles. We found that double profile BCGs are brighter ~0.2 mag than single profile BCG. 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...

Donzelli, C J; Madrid, Juan P

2011-01-01

109

LOW CO LUMINOSITIES IN DWARF GALAXIES  

Energy Technology Data Exchange (ETDEWEB)

We present maps of {sup 12}COJ = 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13'' angular resolution, {approx}250 pc at our average distance of D = 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarf galaxies outside the Local Group ranging from individual lines of sight, stacking over IR-bright regions of embedded star formation, and stacking over the entire galaxy. We detect five galaxies in CO with total CO luminosities of L{sub CO2-1} = (3-28) Multiplication-Sign 10{sup 6} K km s{sup -1} pc{sup 2}. The other 11 galaxies remain undetected in CO even in the stacked images and have L{sub CO2-1} {approx}< (0.4-8) Multiplication-Sign 10{sup 6} K km s{sup -1} pc{sup 2}. We combine our sample of dwarf galaxies with a large sample of spiral galaxies from the literature to study scaling relations of L{sub CO} with M{sub B} and metallicity. We find that dwarf galaxies with metallicities of Z Almost-Equal-To 1/2-1/10 Z{sub Sun} have L{sub CO} of 2-4 orders of magnitude smaller than massive spiral galaxies and that their L{sub CO} per unit L{sub B} is 1-2 orders of magnitude smaller. A comparison with tracers of star formation (FUV and 24 {mu}m) shows that L{sub CO} per unit star formation rate (SFR) is 1-2 orders of magnitude smaller in dwarf galaxies. One possible interpretation is that dwarf galaxies form stars much more efficiently: we argue that the low L{sub CO}/SFR ratio is due to the fact that the CO-to-H{sub 2} conversion factor, {alpha}{sub CO}, changes significantly in low-metallicity environments. Assuming that a constant H{sub 2} depletion time of {tau}{sub dep} = 1.8 Gyr holds in dwarf galaxies (as found for a large sample of nearby spirals) implies {alpha}{sub CO} values for dwarf galaxies with Z Almost-Equal-To 1/2-1/10 Z{sub Sun} that are more than one order of magnitude higher than those found in solar metallicity spiral galaxies. Such a significant increase of {alpha}{sub CO} at low metallicity is consistent with previous studies, in particular those of Local Group dwarf galaxies that model dust emission to constrain H{sub 2} masses. Even though it is difficult to parameterize the dependence of {alpha}{sub CO} on metallicity given the currently available data, the results suggest that CO is increasingly difficult to detect at lower metallicities. This has direct consequences for the detectability of star-forming galaxies at high redshift, which presumably have on average sub-solar metallicity.

Schruba, Andreas; Walter, Fabian; Sandstrom, Karin [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Leroy, Adam K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Bigiel, Frank [Institut fuer Theoretische Astrophysik, Zentrum fuer Astronomie der Universitaet Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg (Germany); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); De Blok, W. J. G. [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Kramer, Carsten [IRAM, Avenida Divina Pastora 7, 18012 Granada (Spain); Rosolowsky, Erik [Department of Physics and Astronomy, University of British Columbia Okanagan, 3333 University Way, Kelowna, BC V1V 1V7 (Canada); Schuster, Karl [IRAM, 300 rue de la Piscine, 38406 St. Martin d' Heres (France); Usero, Antonio [Observatorio Astronomico Nacional, Alfonso XII, 3, 28014 Madrid (Spain); Weiss, Axel; Wiesemeyer, Helmut, E-mail: schruba@mpia.de [MPIfR, Auf dem Huegel 69, 53121 Bonn (Germany)

2012-06-15

110

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

Energy Technology Data Exchange (ETDEWEB)

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 {mu}m 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 {nu}L{sub {nu}}(7.8 {mu}m)/L(X) = -0.31 {+-} 0.35, and independent of classification determined from silicate emission or absorption. Dust luminosity scales closely with BHM, log {nu}L{sub {nu}}(7.8 {mu}m) = (37.2 {+-} 0.5) + 0.87 log BHM for luminosity in erg s{sup -1} and BHM in M{sub Sun }. The 100 most luminous type 1 quasars as measured in {nu}L{sub {nu}}(7.8 {mu}m) are found by comparing Sloan Digital Sky Survey (SDSS) optically discovered quasars with photometry at 22 {mu}m from the Wide-Field Infrared Survey Explorer (WISE), scaled to rest frame 7.8 {mu}m using an empirical template determined from IRS spectra. The most luminous SDSS/WISE quasars have the same maximum infrared luminosities for all 1.5 < z < 5, reaching total infrared luminosity L{sub IR} = 10{sup 14.4} L{sub Sun }. 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{sub bol} estimated from rest-frame optical or ultraviolet luminosities are compared to L{sub IR}. For the local AGN, the median log L{sub IR}/L{sub bol} = -0.35, consistent with a covering factor of 45% for the absorbing dust clouds. For the SDSS/WISE quasars, the median log L{sub IR}/L{sub bol} = 0.1, with extremes indicating that ultraviolet-derived L{sub bol} can be seriously underestimated even for type 1 quasars.

Weedman, Daniel; Sargsyan, Lusine; Houck, James; Barry, Donald [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Lebouteiller, Vianney, E-mail: dweedman@isc.astro.cornell.edu [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, DAPNIA/Service d' Astrophysique, Saclay, F-91191 Gif-sur-Yvette Cedex (France)

2012-12-20

111

THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE  

Energy Technology Data Exchange (ETDEWEB)

We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22,301 i {approx}< 21.8 quasars are selected over an area of 2236 deg{sup 2}, with confirmed spectroscopic redshifts between 2.2 < z < 3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. The completeness of the survey is derived through simulated quasar photometry, and this completeness estimate is checked using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar K-correction. We probe the faint end of the QLF to M{sub i} (z = 2.2) Almost-Equal-To -24.5 and see a clear break in the QLF at all redshifts up to z = 3.5. A log-linear relation (in log {Phi}* - M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2 < z < 3.5; across this interval the break luminosity increases by a factor of {approx}2.6 while {Phi}* declines by a factor of {approx}8. At z {approx}< 2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of ''AGN downsizing'' is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.

Ross, Nicholas P.; White, Martin; Bailey, Stephen [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); McGreer, Ian D. [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Palanque-Delabrouille, Nathalie; Yeche, Christophe [CEA, Centre de Saclay, IRFU, F-91191 Gif-sur-Yvette (France); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Shen, Yue; Swanson, Molly E. C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Aubourg, Eric [APC, University of Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cite (France); Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Bovy, Jo [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); DeGraf, Colin; Di Matteo, Tiziana, E-mail: npross@lbl.gov [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); and others

2013-08-10

112

A fast luminosity monitor system for PEP II  

Energy Technology Data Exchange (ETDEWEB)

The PEP II fast luminosity system provides a measurement of luminosity to the control system with a time constant of 0.3 s and fluctuations less than 0.1% for this interval, adequate for use in feedback systems. Continuous visual updates of luminosity are provided. The alignment of the positron beam at the collision point can also be monitored, and there is a visual display of the luminosity associated with each bunch pair in the machine, sampled approximately every 2 s.

Ecklund, Stan; Field, Clive E-mail: sargon@slac.stanford.edu; Mazaheri, Gholam

2001-05-01

113

A fast luminosity monitor system for PEP II  

International Nuclear Information System (INIS)

The PEP II fast luminosity system provides a measurement of luminosity to the control system with a time constant of 0.3 s and fluctuations less than 0.1% for this interval, adequate for use in feedback systems. Continuous visual updates of luminosity are provided. The alignment of the positron beam at the collision point can also be monitored, and there is a visual display of the luminosity associated with each bunch pair in the machine, sampled approximately every 2 s

114

Ideas for a high luminosity muon physics detector with complete particle identification  

International Nuclear Information System (INIS)

Modifications of the existing EMC-NA9 spectrometer at the SPS muon beam by using a Time Projection Chamber (TPC) as vertex-detector and Ring Mage Cerenkov (RICH) counters allow at least a factor 5 increase in luminosity and provide complete hadron identification. The compactness of the new detectors gives space for future 4? coverage for neutral particle detection. (orig.)

115

THE LUMINOSITY PROFILES OF BRIGHTEST CLUSTER GALAXIES  

International Nuclear Information System (INIS)

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 MR = -23.8 ± 0.6 mag for single profile BCGs and MR = -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 diffend double profile BCGs show different slopes: asingle = 3.29 ± 0.06 and adouble = 2.79 ± 0.08. Also, the logarithmic slope of the metric luminosity ? is higher in double profile BCGs (?double = 0.65 ± 0.12) than in single profile BCGs (?single = 0.59 ± 0.14). The mean isophote outer ellipticity (calculated at ? ? 24 mag arcsec-2) is higher in double profile BCGs (edouble = 0.30 ± 0.10) than in single profile BCGs (esingle = 0.26 ± 0.11). Similarly, the mean absolute value of inner minus outer ellipticity is also higher in double profile BCGs. From a subsample of 24 BCGs, we found strong evidence that extra-light at intermediate radii in double profile BCGs is related to the presence of a faint stellar envelope. Similarly, from another subsample of 12 BCGs we also found that extra-light is related to star formation. On the other hand, we did not find differences between these two BCG categories when we compared global cluster properties such as the BCG-projected position relative to the cluster X-ray center emission, X-ray luminosity, or BCG orientation with respect to the cluster position angle.

116

New evidence for galaxy luminosity evolution  

International Nuclear Information System (INIS)

Near-infrared photometry for 61 elliptical galaxies is used with previously published data to demonstrate that little or no color evolution is observed at infrared wavelengths, while galaxies near z = 1 are brighter than those at low redshift. Optically selected galaxies are compared with radio galaxies, and no differences in infrared properties are found. Evolution of a stellar population with an initial mass function similar to that observed in the solar neighborhood coupled with a value for q0 near 0.5 provides the best fit to the color and luminosity data

117

Galaxy luminosity function: a new analytic expression  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english We propose a new analytic approximation for the luminosity function of galaxies. The suggested expression behaves like the Schechter function at the faint end (f ~ La) but departs considerably at the bright end (L >> L*). We argue here that such a behavior may provide a better fit for the current ob [...] servational data than does the Schechter function. Its practical interest is stressed by considering roughly the data set provided by the Stromlo-APM redshift survey. Implications on the estimates of the matter density parameter from mass-to-light ratio are also briefly discussed.

J. S., Alcaniz; J. A. S., Lima.

2004-06-01

118

Spherical aberrations in the thermal-wave model for luminosity estimates in particle accelerators  

International Nuclear Information System (INIS)

An approach for estimating the luminosity in linear colliders in the presence of spherical aberrations is developed within the framework of the recently proposed thermal-wave model for relativistic-charged-particle-beam propagation. By taking into account a quadrupolelike lens with octupole deviations, the transverse beam motion is governed by a two-dimensional Schroedinger-like equation, with an anharmonic potential. To first order in perturbation theory and in the thin-lens approximation, we analytically find the transverse beam density, the spot size, and the luminosity reduction factor at the interaction point in terms of the initial conditions. Some numerical estimates are also given

119

High-energy gamma-ray afterglows from low-luminosity gamma-ray bursts  

OpenAIRE

The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs -- low-luminosity GRBs. The nature of the outflow responsible for them is not clear yet. Two scenarios have been suggested: one is the conventional relativistic outflow with initial Lorentz factor of order of $\\Gamma_0\\ga 10$ and the other is a trans-relativistic outflow with $\\Gamma_0\\si...

He, Hao-ning; Wang, Xiang-yu; Yu, Yun-wei; Meszaros, Peter

2009-01-01

120

60 micron luminosity evolution of rich clusters of galaxies  

International Nuclear Information System (INIS)

The average 60-micron flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination known of using the IRAS data base. The flux from this set of clusters has been compared to the 60-micron flux from a sample of nearby galaxy clusters. It is found that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the far-infrared emission from clusters over this redshift range. 38 refs

121

60 micron luminosity evolution of rich clusters of galaxies  

Energy Technology Data Exchange (ETDEWEB)

The average 60-micron flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination known of using the IRAS data base. The flux from this set of clusters has been compared to the 60-micron flux from a sample of nearby galaxy clusters. It is found that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the far-infrared emission from clusters over this redshift range. 38 refs.

Kelly, D.M.; Rieke, G.H. (Steward Observatory, Tucson, AZ (USA))

1990-10-01

122

Upgrade of RHIC Vacuum Systems for High Luminosity Operation  

CERN Document Server

With increasing ion beam intensity during recent RHIC operations, pressure rises of several decades were observed at most room temperature sections and at a few cold sections. The pressure rises are associated with electron multi-pacting, electron stimulated desorption and beam ion induced desorption and have been one of the major intensity and luminosity limiting factors for RHIC. Improvement of the warm sections has been carried out in the last few years. Extensive in-situ bakes, additional UHV pumping, anti-grazing ridges and beam tube solenoids have been implemented. Several hundred meters of NEG coated beam pipes have been installed and activated. Vacuum monitoring and interlock were enhanced to reduce premature beam aborts. Preliminary measures, such as pumping before cool down to reduce monolayer condensates, were also taken to suppress the pressure rises in the cold sections. The effectiveness of these measures in reducing the pressure rises during machine studies and during physics runs are discussed...

Hseuh Hsiao Chaun; Smart, Loralie; Todd, Robert J; Weiss, Daniel

2005-01-01

123

On the maximum luminosity in X-ray bursts  

Science.gov (United States)

A qualitative model is proposed which relates the burst behavior of 1608-52 observed by Murakami et al (1980) to the composition of the envelope in which the X-ray bursts occur. The model provides an explanation for the large scatter in the peak fluxes when the accretion rate is high. A flux would be transported outward at the top of the convective region which equals 1.5 to 2 times the Eddington limit appropriate to a helium-rich gas. Upon traversing the outer part of the accreted layer, which is not affected by the nuclear processes and is therefore hydrogen-rich, this flux is about a factor of 3 to 4 higher than the local value of the Eddington luminosity.

Van Paradijs, J.

1981-01-01

124

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

International Nuclear Information System (INIS)

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 ?m 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 ?L?(7.8 ?m)/L(X) = –0.31 ± 0.35, and independent of classification determined from silicate emission or absorption. Dust luminosity scales closely with BHM, log ?L?(7.8 ?m) = (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 ?L?(7.8 ?m) are found by comparing Sloan Digital Sky Survey (SDSS) optically discovered quasars with photometry at 22 ?m from the Wide-Field Infrared Survey Explorer (WISE), scaled to rest frame 7.8 ?m 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 = 1014.4 L?. Comparing with ub>. 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 Lbol estimated from rest-frame optical or ultraviolet luminosities are compared to LIR. For the local AGN, the median log LIR/Lbol = –0.35, consistent with a covering factor of 45% for the absorbing dust clouds. For the SDSS/WISE quasars, the median log LIR/Lbol = 0.1, with extremes indicating that ultraviolet-derived Lbol can be seriously underestimated even for type 1 quasars.

125

The Luminosity Function of QSO Host Galaxies  

CERN Document Server

Results from an HST imaging study of 71 QSO host galaxies are presented. The objects are selected to have redshifts less than 0.46 and total (nuclear and host) absolute visual magnitudes brighter than -23 (H_0=50 km/s/Mpc, q_0=0.5). We have investigated the composition of the sample with respect to host morphology and radio loudness, and have derived the QSO host galaxy luminosity function. The hosts are almost equally divided between radio-loud QSOs in ellipticals, radio-quiet QSOs in ellipticals, and radio-quiet QSOs in spirals. Radio-loud QSOs in spirals are extremely rare. Only two hosts went undetected. There are significant differences between some of the subclasses. Elliptical hosts are typically twice as luminous as spiral hosts, and the hosts of radio-loud QSOs are typically 2.5 times as luminous as those of radio-quiet QSOs. Subject to systematic uncertainties in normalization procedures, the luminosity function of low-redshift QSO hosts closely corresponds to the bright tail of the local normal gal...

Hamilton, T S; Turnshek, D A; Hamilton, Timothy S.; Casertano, Stefano; Turnshek, David A.

2002-01-01

126

Selected issues for the LHC luminosity upgrade  

CERN Document Server

The Large Hadron Collider started its operations on September 10th 2008. In a realistic forecast it is supposed to demonstrate (or confute) the existence of the Higgs boson for the year 2014. After this date the physics of rare events will be explored more in details and an upgrade of the luminosity can make an important difference in the program of experiments at CERN. This thesis proposes several ideas to increase the luminosity of ATLAS and CMS experiments and the acceptance of TOTEM experiment. The main ob ject of study is the Interaction Region, that consists in the set of magnets in charge to provide the ?nal beam focalization for the collisions. The Interaction Region is studied with the methods of beam optics and beam dynamics to design new layouts for the upgrade. These layouts are also explored from the point of view of integrability in the existing experiments developing the analysis of energy deposition and misalignment tolerances. This study was performed with the use of analytical methods for ...

Laface, Emanuele; Scandale, Walter

2008-01-01

127

Avoiding spurious breaks in binned luminosity functions  

CERN Document Server

We show that using either the method of Page & Carrera or the well-known $1/V_a$ method to construct the binned luminosity function (LF) of a flux limited sample of Active Galactic Nuclei (AGN) can produce an artificial flattening (or steepening in the case of negative evolution) of the binned LF for bins intersected by the flux cutoff of the sample. This effect is more pronounced for samples with steep and strongly evolving parent LFs but is still present even for non-evolving LFs. As a result of this distortion of the true LF, fitting a model LF to binned data may lead to errors in the estimation of the parameters and may even prompt the erroneous use of broken power law functions. We compute the expected positions of apparent breaks in the binned LF. We show that these spurious breaks in the binned LFs can be avoided if the binning is done in the flux--redshift plane instead of the typically used luminosity--redshift plane. Binning in the flux--redshift plane can be used in conjunction with the binning...

Cara, Mihai

2008-01-01

128

UV excess of quasars - Luminosity dependence  

International Nuclear Information System (INIS)

The transition from the near-infrared power law to the blue bump in quasar spectra is studied by analyzing the complete sample published by Neugebauer et al. (1987). It is found that the flattening of the continuum spectrum toward the UV increases with continuum luminosity; the spectral slope between 4200 A and 7500 A (in the quasar's rest frame) is strongly correlated with luminosity and redshift. Only part of this correlation can be attributed to contamination by starlight of the host galaxy. This result is modeled in terms of an accretion disk spectrum combined with a nonthermal power law. In order to fit the data, the Eddington ratio must be in the range L(opt)/L(E) approximately 0.003-0.03(epsilon/0.1) exp -1 (epsilon being the efficiency). This parameter range also yields inner disk temperatures of (30,000-200,000 K), in accordance with the temperatures inferred from the UV excess of quasars observed with the IUE. 21 references

129

Low EUV Luminosities Impinging on Protoplanetary Disks  

CERN Document Server

The amount of high-energy stellar radiation reaching the surface of protoplanetary disks is essential to determine their chemistry and physical evolution. Here, we use millimetric and centimetric radio data to constrain the EUV luminosity impinging on 14 disks around young (~2-10Myr) sun-like stars. For each object we identify the long-wavelength emission in excess to the dust thermal emission, attribute that to free-free disk emission, and thereby compute an upper limit to the EUV reaching the disk. We find upper limits lower than 10$^{42}$ photons/s for all sources without jets and lower than $5 \\times 10^{40}$ photons/s for the three older sources in our sample. These latter values are low for EUV-driven photoevaporation alone to clear out protoplanetary material in the timescale inferred by observations. In addition, our EUV upper limits are too low to reproduce the [NeII] 12.81 micron luminosities from three disks with slow [NeII]-detected winds. This indicates that the [NeII] line in these sources prima...

Pascucci, I; Gorti, U; Hollenbach, D; Hendler, N P; Brooks, K J; Contreras, Y

2014-01-01

130

LHC Report: A new luminosity record  

CERN Multimedia

After about one month of operation, the LHC has already accumulated an integrated luminosity of 28 pb-1, which corresponds to over 50% of the total delivered to the experiments in 2010. This impressive start to the LHC run in 2011 bodes well for the rest of year.   Following careful collimator set-up and validation, the first phase of beam commissioning 2011 has come to an end. The first stable beams were declared on Sunday 13 March with a moderate 3 bunches per beam and an initial luminosity of 1.6 × 1030 cm-2s-1. Machine protection tests continued during the following week as the commissioning team made absolutely sure that all critical systems (beam dumps, beam interlock system, etc.) were functioning properly. When these tests had finished, the way was opened to increased intensity and the LHC quickly moved through the first part of its planned, staged intensity increase. Fills with increasing numbers of bunches were delivered to the experiments, culminating in a fill with 200...

CERN Bulletin

2011-01-01

131

ROB performance in a high luminosity scenario  

CERN Document Server

The first layer of the CMS (Compact Muon Solenoid) DT (Drift Tube) readout system is built around the ROBs (Read Out Boards), which are responsible for the time measurement of the chamber signals to allow reconstruction of charged particle tracks with a resolution of 250 $\\mu m$ per cell. ROB boards have shown an excellent performance during LHC operation and are expected to continue their operation safely during all LHC Phase 1 up to 2022. Present LHC upgrades for Phase 2 foresee an increase of instantaneous luminosity up to $5 \\cdot 10^{34} ~ cm^{-2} \\cdot s^{-1}$ which will increase significantly the expected hit rate. Moreover, CMS is studying to increase the Level 1 Accept (\\emph{L1A}) latency of the trigger signal from 3.2 $\\mu s$ to 20 $\\mu s$ to allow including tracking subdetector information into the Level 1 trigger decision and also the \\emph{L1A} frequency from 100 kHz maximum to up to 1 MHz, in order to accommodate the increase of trigger rate due to the higher luminosity. ROB operation under suc...

Cela Ruiz, Jose Manuel

2014-01-01

132

Discovery of distant high luminosity infrared galaxies  

CERN Document Server

We have developed a method for selecting the most luminous galaxies detected by IRAS based on their extreme values of R, the ratio of 60 micron and B-band luminosity. These objects have optical counterparts that are close to or below the limits of Schmidt surveys. We have tested our method on a 1079 deg^2 region of sky, where we have selected a sample of IRAS sources with 60 micron flux densities greater than 0.2 Jy, corresponding to a redshift limit z~1 for objects with far-IR luminosities of 10^{13} L_sun. Optical identifications for these were obtained from the UK Schmidt Telescope plates, using the likelihood ratio method. Optical spectroscopy has been carried out to reliably identify and measure the redshifts of six objects with very faint optical counterparts, which are the only objects with R>100 in the sample. One object is a hyperluminous infrared galaxy (HyLIG) at z=0.834. Of the remaining, fainter objects, five are ultraluminous infrared galaxies (ULIGs) with a mean redshift of 0.45, higher than th...

Van der Werf, P P; Shaver, P A; Hawkins, M R S; Werf, Paul P. van der

1999-01-01

133

Low-luminosity AGN and Normal Galaxies  

CERN Document Server

Low-luminosity AGN (with X-ray luminosity < 1e42 ergs/s) far outnumber ordinary AGN, and are therefore perhaps more relevant to our understanding of AGN phenomena and the relationship between AGN and host galaxies. Many normal galaxies harbor LINER and starburst nuclei, which, together with LLAGN, are a class of ``low-activity'' galaxies that have a number of surprisingly similar X-ray characteristics, despite their heterogenous optical classification. This strongly supports the hypothesis of an AGN-starburst connection. Further, X-ray observations of normal galaxies without starburst or AGN-like activity in their nuclei offer opportunities to study populations of X-ray binaries, HII regions, and warm or hot ISM under different conditions than is often the case in the Milky Way. The results of recent X-ray observations of these types of galaxies are reviewed, and what we hope to learn about both nearby and high redshift galaxies of each type from observations with forthcoming and planned satellites is disc...

Ptak, A

2000-01-01

134

Key to the Mystery of Dark Energy: Corrected Relationship between Luminosity Distance and Redshift  

Directory of Open Access Journals (Sweden)

Full Text Available A new possible explanation to the luminosity distance (DL and redshift (Z measurements of type Ia supernovae (SNeIa is developed. Instead of modifying the theory of general relativity or the Friedmann equation of cosmology with an extra scalar ?eld or unknown energy component (e.g., dark energy, we re-examine the relationship between the luminosity distance and the cosmological redshift (DL Z. It is found that the DL Z relation previously applied to connect the cosmological model with the measured SNeIa data is only valid for nearby objects with Z ? 1. The luminosity distances of all distant SNela with Z ? 1 had been underestimated. The newly derived DL Z relation has an extra factor p 1 + Z, with which the cosmological model exactly explains all the SNeIa measurements without dark energy. This result indicates that our universe has not accelerated and does not need dark energy at all.

Zhang T. X.

2013-07-01

135

Impact of Energy and Luminosity upgrades at LHC on the Physics program of ATLAS  

CERN Document Server

The impact on the physics capabilities of the ATLAS detector of possible LHC upgrades is discussed. As a benchmark, an increase in the luminosity by a factor of ten is considered. For comparison, a doubling of the LHC energy is also explored. Both upgrades significantly enhance the physics capabilities of ATLAS. As measured in terms of the mass reach for new particles, the energy upgrade is more powerful. However, in cases where the effect of an upgrade is to increase the precision of measurements as a result of the larger data samples, the luminosity upgrade can be at least as powerful. The pile-up of minimum bias events at higher luminosity could limit the physics performance of ATLAS in areas where tagging of forward jets is needed.

Azuelos, Georges; Çakir, O; Elfgren, E; Gianotti, F; Hansen, J B; Hinchliffe, Ian; Hohlfeld, M; Jakobs, K; Leroy, C; Mehdiyev, R; Paige, Frank E; Polesello, G; Stenzel, H; Tapprogge, Stefan; Usubov, Z U; Vacavant, L

2002-01-01

136

Magnet Design of the 150 mm Aperture Low-? Quadrupoles for the High Luminosity LHC  

CERN Document Server

The High Luminosity LHC (HL-LHC) project is aimed at studying and implementing the necessary changes in the LHC to increase its luminosity by a factor five. Among the magnets that will be upgraded are the 16 superconducting low-? quadrupoles placed around the two high luminosity interaction regions (ATLAS and CMS experiments). In the current baseline scenario, these quadrupole magnets will have to generate a gradient of 140 T/m in a coil aperture of 150 mm. The resulting conductor peak field of more than 12 T will require the use of Nb3Sn superconducting coils. We present in this paper the HL-LHC low-? quadrupole design, based on the experience gathered by the US LARP program, and, in particular, we describe the support structure components to pre-load the coils, withstand the electro-magnetic forces, provide alignment and LHe containment, and integrate the cold mass in the LHC IRs.

Ferracin, P; Anerella, M; Borgnolutti, F; Bossert, R; Cheng, D; Dietderich, D R; Felice, H; Ghosh , A; Godeke, A; Izquierdo Bermudez, S; Fessia, P; Krave, S; Juchno, M; Perez, J C; Oberli, L; Sabbi, G; Todesco, E; Yu, M

2014-01-01

137

Effects of granular convection in the response of C I 5380 A to solar luminosity variations  

Science.gov (United States)

The response of the weak solar photospheric neutral carbon line at 5380.3 A to percolations of photospheric granulation and the five-minute solar oscillations is investigated in order to calibrate the sensitivity of the line to temporal variations in solar luminosity. Line strength variations and simultaneous continuum variations in two granular regions were observed at 30 sec intervals using a 25-cm coude spectrograph. The response of line equivalent width to continuum intensity variations is found to be essentially uniform at time scales ranging from 5 min to 2 hr independently of whether the variations arise from granular convection or velocity field oscillations. The extent to which line strength varies with luminosity (sensitivity) is observed to be significantly smaller than estimates based on models of the perturbed Harvard-Smithsonian Reference Atmosphere of Gingerich et al. (1970), and it is proposed that the structure of the solar granulation is a major factor determining local luminosity variations and line sensitivity.

Lindsey, C. A.; Landman, D. A.

1980-01-01

138

Superconducting Quadrupole Prototype for the ISR high luminosity (low beta) insertion  

CERN Multimedia

In colliders, smaller beam cross-section means higher luminosity. Beam-size being proportional to the square-root of the "beta function" value, a small beta means small beam size, hence high luminosity. In 1973 a study was launched on low-beta insertions using superconducting quadrupole magnets, which focus beams to very small sizes at the beam crossing points . In 1976 the first prototype of a superconducting quadrupole was tested. Here we see Theodor Tortschanoff with the prototype of 1.25 m magnetic length. Manufacture of 8 quadrupoles (4 of L=1.15 m, 4 of L=0.65 m) began at Alsthom in 1978. They were installed at intersection I8 of the ISR, enhancing luminosity there by a factor 7 until final low-beta operation in December 1983. For details see "Yellow Report" CERN 76-16. See also pictures 7702307, 7702308, 7702182,7510214X,7510217X.

1977-01-01

139

The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei  

CERN Document Server

We present an updated and revised analysis of the relationship between the Hbeta broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of 9 new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hbeta time lag, which is assumed to yield the average Hbeta BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of alpha = 0.533 (+0.035/-0.033), consistent ...

Bentz, Misty C; Grier, Catherine J; Barth, Aaron J; Peterson, Bradley M; Vestergaard, Marianne; Bennert, Vardha N; Canalizo, Gabriela; De Rosa, Gisella; Filippenko, Alexei V; Gates, Elinor L; Greene, Jenny E; Li, Weidong; Malkan, Matthew A; Pogge, Richard W; Stern, Daniel; Treu, Tommaso; Woo, Jong-Hak

2013-01-01

140

Operation of the Run IIB D0 Luminosity System and Determination of the Run IIB Luminosity Constant  

Energy Technology Data Exchange (ETDEWEB)

The luminosity system is an integral part of the D0 detector that must be properly maintained to provide accurate luminosity measurements for physics analysis. After the addition of a readout layer to the silicon vertex detector in 2006, it was necessary to re-calculate the effective inelastic cross section to which the luminosity monitor is sensitive. The preliminary analysis showed that the luminosity constant did not change with the addition of the extra layer of silicon. A full study of the revised luminosity constant including a complete analysis of systematic uncertainties has been completed. The luminosity constant was determined to be {sigma}{sub eff} = 48.3 {+-} 1.9 {+-} 0.6 mb, which reduces the D0 contribution to the luminosity measurement uncertainty by almost 3%.

Prewitt, Michelle Victoria; /Rice U.

2010-04-01

141

Operation of the Run IIB D0 Luminosity System and Determination of the Run IIB Luminosity Constant  

International Nuclear Information System (INIS)

The luminosity system is an integral part of the D0 detector that must be properly maintained to provide accurate luminosity measurements for physics analysis. After the addition of a readout layer to the silicon vertex detector in 2006, it was necessary to re-calculate the effective inelastic cross section to which the luminosity monitor is sensitive. The preliminary analysis showed that the luminosity constant did not change with the addition of the extra layer of silicon. A full study of the revised luminosity constant including a complete analysis of systematic uncertainties has been completed. The luminosity constant was determined to be ?eff = 48.3 ± 1.9 ± 0.6 mb, which reduces the D0 contribution to the luminosity measurement uncertainty by almost 3%.

142

Luminosity bias: from haloes to galaxies  

CERN Document Server

Large surveys of the local Universe have shown that galaxies with different intrinsic properties, such as colour, luminosity and morphological type display a range of clustering amplitudes. Galaxies are therefore not faithful tracers of the underlying matter distribution. This modulation of galaxy clustering, called bias, contains information about the physics behind galaxy formation. It is also a systematic to be overcome before the large-scale structure of the Universe can be used as a cosmological probe. Two types of approaches have been developed to model the clustering of galaxies. The first class is empirical and filters or weights the distribution of dark matter to reproduce the measured clustering. In the second approach an attempt is made to model the physics which governs fate of baryons in order to predict the number of galaxies in dark matter haloes. I will review the development of both approaches and summarize what we have learnt about galaxy bias.

Baugh, C M

2013-01-01

143

A New Analytic Galactic Luminosity Profile Function  

CERN Document Server

In 2010 Spergel introduced an alternative to the traditional Sersic form for galactic luminosity profiles based on modified Bessel functions of the second kind. His motivation was the desire for an accurate one-parameter profile form with a simple Fourier transform (in contrast to the Fourier transform of the Sersic profile which can't be written in closed form), but we have found that the Spergel profile almost universally makes integrals easier when it replaces the Sersic profile in the integrand. In the original paper on the subject Spergel noted that his profile seems to fit galaxies on average just as well as Sersic's. Here we make this observation quantitative by comparing the residuals from fitting Sersic and Spergel forms to data. We find that the Spergel profile actually fits better than the Sersic for a random sample of 16 galaxies.

Katz, Daniel; Lenthall, Matthew; Merousis, Alex; Sundaramurthy, Navin; Kim, Jeongki

2014-01-01

144

Composite luminosity function of cluster galaxies  

CERN Document Server

We constructed the composite Luminosity Function (LF) of cluster galaxies in the g,r and i bands from the photometry of a mixed (Abell and X-ray selected) sample of the cores of 65 clusters, ranging in redshift from 0.05 to 0.25. The composite LF has been obtained from complete samples of ~2200 galaxies in the magnitude range -23

Garilli, B; Andreon, S; Garilli, Bianca; Maccagni, Dario; Andreon, Stefano

1999-01-01

145

Identifying the Low-Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores  

Science.gov (United States)

We present the results of a search for all embedded protostars with internal luminosities =4×10-3(d/140 pc)2 Lsolar, a factor of 25 better than the sensitivity of the Infrared Astronomical Satellite (IRAS) to such objects. We present a set of selection criteria used to identify candidates from the Spitzer data and examine complementary data to decide whether each candidate is truly an embedded protostar. We find a tight correlation between the 70 ?m flux and internal luminosity of a protostar, an empirical result based on both observations and detailed two-dimensional radiative transfer models of protostars. We identify 50 embedded protostars with Lint<=1.0 Lsolar 15 have Lint<=0.1 Lsolar. The intrinsic distribution of source luminosities increases to lower luminosities. While we find sources down to the above sensitivity limit, indicating that the distribution may extend to luminosities lower than probed by these observations, we are able to rule out a continued rise in the distribution below Lint=0.1 Lsolar. Between 75% and 85% of cores classified as starless prior to being observed by Spitzer remain starless to our luminosity sensitivity; the remaining 15%-25% harbor low-luminosity, embedded protostars. We compile complete spectral energy distributions for all 50 objects and calculate standard evolutionary signatures (Lbol, Tbol, and Lbol/Lsmm) and argue that these objects are inconsistent with the simplest picture of star formation, wherein mass accretes from the core onto the protostar at a constant rate.

Dunham, Michael M.; Crapsi, Antonio; Evans, Neal J., II; Bourke, Tyler L.; Huard, Tracy L.; Myers, Philip C.; Kauffmann, Jens

2008-11-01

146

Constraining Physical Properties of Type IIn Supernovae through Rise Times and Peak Luminosities  

CERN Document Server

We investigate the diversity in the wind density, supernova ejecta energy, and ejecta mass in Type IIn supernovae based on their rise times and peak luminosities. We show that the wind density and supernova ejecta properties can be estimated independently if both the rise time and peak luminosity are observed. The peak luminosity is mostly determined by the supernova properties and the rise time can be used to estimate the wind density. We find that the ejecta energy of Type IIn supernovae needs to vary by factors of 0.2-5 from the average if their ejecta mass is similar. The diversity in the observed rise times indicates that their wind density varies by factors of 0.2-2 from the average. We show that Type IIn superluminous supernovae should have not only large wind density but also large ejecta energy and/or small ejecta mass to explain their large luminosities and the rise times at the same time. We also note that the shock breakout does not necessarily occur in the wind even if it is optically thick, exce...

Moriya, Takashi J

2014-01-01

147

Constraining Physical Properties of Type IIn Supernovae through Rise Times and Peak Luminosities  

Science.gov (United States)

We investigate the diversity in the wind density, supernova ejecta energy, and ejecta mass in Type IIn supernovae based on their rise times and peak luminosities. We show that the wind density and supernova ejecta properties can be estimated independently if both the rise time and peak luminosity are observed. The peak luminosity is mostly determined by the supernova properties and the rise time can be used to estimate the wind density. We find that the ejecta energies of Type IIn supernovae need to vary by factors of 0.2-5 from the average if their ejecta masses are similar. The diversity in the observed rise times indicates that their wind densities vary by factors of 0.2-2 from the average. We show that Type IIn superluminous supernovae should have not only large wind density but also large ejecta energy and/or small ejecta mass to explain their large luminosities and the rise times at the same time. We also note that shock breakout does not necessarily occur in the wind even if it is optically thick, except for the case of superluminous supernovae, and we analyze the observational data both with and without assuming that the shock breakout occurs in the dense wind of Type IIn supernovae.

Moriya, Takashi J.; Maeda, Keiichi

2014-08-01

148

Seeking the Epoch of Maximum Luminosity for Dusty Quasars  

CERN Document Server

Infrared luminosities vLv(7.8 um) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 ~ 3 with maximum luminosity vLv(7.8 um) >~ 10^{47} erg per s; luminosity functions show one quasar per cubic Gpc having vLv(7.8 um) > 10^{46.6} erg per s for all 2 5 magnitudes 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.

Vardanyan, Valeri; Sargsyan, Lusine

2014-01-01

149

The Morphological Type Dependence of K-band Luminosity Functions  

CERN Document Server

Differential 2.2um (K-band) luminosity functions are presented for a complete sample of 1570 nearby Vgsr < 3000 km/s, where Vgsr is the velocity measured with respect to the Galactic standard of rest), bright (K < 10 mag), galaxies segregated by visible morphology. The K-band luminosity function for late-type spirals follows a power law that rises towards low luminosities whereas the K-band luminosity functions for ellipticals, lenticulars and bulge-dominated spirals are peaked with a fall off at both high and low luminosities. However, each morphological type (E, S0, S0/a-Sab, Sb-Sbc, Sc-Scd) contributes approximately equally to the overall K-band luminosity density in the local universe, and by inference, the stellar mass density as well.

Devereux, Nick; Willner, S P; Ashby, M L N; Willmer, C N A

2009-01-01

150

Luminosity Functions of Gamma-Ray Burst Afterglows  

OpenAIRE

Aims: Use the standard fireball model to create virtual populations of gamma-ray burst afterglows and study their luminosity functions. Methods: We randomly vary the parameters of the standard fireball model to create virtual populations of afterglows. We use the luminosity of each burst at an observer's time of 1 day to create a luminosity function and compare our results with available observational data to assess the internal consistency of the standard fireball model. ...

Jo?hannesson, Guðlaugur; Bjo?rnsson, Gunnlaugur; Gudmundsson, Einar H.

2007-01-01

151

Luminosity Function of Faint Globular Clusters in M87  

OpenAIRE

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit \\textit{Hubble Space Telescope (HST)} WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between...

Waters, Christopher Z.; Zepf, Stephen E.; Lauer, Tod R.; Baltz, Edward A.; Silk, Joseph

2006-01-01

152

The low-luminosity end of the radius-luminosity relationship for active galactic nuclei  

DEFF Research Database (Denmark)

We present an updated and revised analysis of the relationship between the Hß broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hß time lag, which is assumed to yield the average Hß BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R BLR-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of , consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19 ± 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts. © 2013. The American Astronomical Society. All rights reserved.

Bentz, M.C.; Denney, K.D.

2013-01-01

153

X-ray luminosity functions of clusters of galaxies  

Energy Technology Data Exchange (ETDEWEB)

Clusters of galaxies must have a considerable intrinsic spread in their X-ray luminosities at given mass if they are formed bottom-up by direct gravitational instability. The distributions of luminosities at given mass take on the general form of a flat power law with a sharp upper cutoff, consistent with the recently obtained luminosity functions for Abell clusters of given richness classes. The quantitative features depend on the specific hierarchical cosmogony, with models including mass accretion after first collapse providing the best agreement. The same clustering mechanism, after integrating over mass, yields a steep overall luminosity function consistent with existing measurements. 31 refs.

Cavaliere, A.; Burg, R.; Giacconi, R. (Roma II Universita, Rome (Italy) Space Telescope Science Institute (USA) Johns Hopkins Univ., Baltimore, MD (USA))

1991-01-01

154

X-ray luminosity functions of clusters of galaxies  

Science.gov (United States)

Clusters of galaxies must have a considerable intrinsic spread in their X-ray luminosities at given mass if they are formed bottom-up by direct gravitational instability. The distributions of luminosities at given mass take on the general form of a flat power law with a sharp upper cutoff, consistent with the recently obtained luminosity functions for Abell clusters of given richness classes. The quantitative features depend on the specific hierarchical cosmogony, with models including mass accretion after first collapse providing the best agreement. The same clustering mechanism, after integrating over mass, yields a steep overall luminosity function consistent with existing measurements.

Cavaliere, A.; Burg, R.; Giacconi, R.

1991-01-01

155

The ATLAS Muon Trigger at high instantaneous luminosities  

International Nuclear Information System (INIS)

The ATLAS experiment at CERN's Large Hadron Collider (LHC) has taken data with colliding beams at instantaneous luminosities of 3.65 · 1033 cm?2 s?1. The LHC delivered an integrated luminosity of about 5fb?1 in the run period 2011, which required dedicated strategies to guard the highest physics output while reducing effectively the event rate. The Muon High Level Trigger has successfully adapted to the changing environment of the low luminosity running of LHC in 2010 to the luminosities encountered in 2011. The selection strategy has been optimized for the various physics analyses involving muons in the final state. This note reports about the performance of the muon trigger.

156

Does nest luminosity play a role in recognition of parasitic eggs in domed nests? A case study of the red bishop.  

Czech Academy of Sciences Publication Activity Database

Ro?. 101, ?. 12 (2014), s. 1009-1015. ISSN 0028-1042 Institutional support: RVO:68081766 Keywords : Brood parasitism * Domed nest * Egg discrimination * Light conditions * Nest luminosity Subject RIV: EG - Zoology Impact factor: 1.971, year: 2013

Honza, Marcel; Šulc, Michal; Cherry, M. I.

2014-01-01

157

Higher luminosities via alternative incident channels  

Energy Technology Data Exchange (ETDEWEB)

We show that PEP provides some unique opportunities for one and two photon physics with real photons as well as for QCD studies with internal targets. Photon beams would avoid the major limitation on the luminosity of present machines and could provide PEP an ideal b-physics factory producing the full range of J/sub c//sup PC/ and J/sub b//sup PC/ states that may not be observable otherwise as well as allow a whole new class of ''missing-mass'' experiments. These latter particles are the pseudo-Goldstone bosons and their supersymmetric counterparts. These and related possibilities like a single-pass, ''free electron laser'' facility or even synchrotron radiation beam lines all favor a mini-maxi configuration for the low-beta insertions in PEP. This allows more diverse experiments without excluding any ongoing experimental programs. Such possibilities have interesting implications for a number of proposed facilities including the SSC. Some systematic machine physics studies over a range of energies are suggested. 24 refs., 6 figs.

Spencer, J.E.

1985-04-01

158

Higher luminosities via alternative incident channels  

International Nuclear Information System (INIS)

We show that PEP provides some unique opportunities for one and two photon physics with real photons as well as for QCD studies with internal targets. Photon beams would avoid the major limitation on the luminosity of present machines and could provide PEP an ideal b-physics factory producing the full range of J/sub c//sup PC/ and J/sub b//sup PC/ states that may not be observable otherwise as well as allow a whole new class of ''missing-mass'' experiments. These latter particles are the pseudo-Goldstone bosons and their supersymmetric counterparts. These and related possibilities like a single-pass, ''free electron laser'' facility or even synchrotron radiation beam lines all favor a mini-maxi configuration for the low-beta insertions in PEP. This allows more diverse experiments without excluding any ongoing experimental programs. Such possibilities have interesting implications for a number of proposed facilities including the SSC. Some systematic machine physics studies over a range of energies are suggested. 24 refs., 6 figs

159

Low CO Luminosities in Dwarf Galaxies  

CERN Document Server

[Abridged] We present maps of CO 2-1 emission covering the entire star-forming disks of 16 nearby dwarf galaxies observed by the IRAM HERACLES survey. The data have 13 arcsec angular resolution, ~250 pc at our average distance of 4 Mpc, and sample the galaxies by 10-1000 resolution elements. We apply stacking techniques to perform the first sensitive search for CO emission in dwarfs outside the Local Group ranging from single lines-of-sight, stacked over IR-bright regions of embedded star formation, and stacked over the entire galaxy. We detect 5 dwarfs in CO with total luminosities of L_CO = 3-28 1e6 Kkmspc2. The other 11 dwarfs remain undetected in CO even in the stacked data and have L_CO < 0.4-8 1e6 Kkmspc2. We combine our sample of dwarfs with a large literature sample of spirals to study scaling relations of L_CO with M_B and metallicity. We find that dwarfs with metallicities of Z ~ 1/2-1/10 Z_sun have L_CO about 1e2-1e4x smaller than spirals and that their L_CO per unit L_B is 10-100x smaller. A co...

Schruba, Andreas; Walter, Fabian; Bigiel, Frank; Brinks, Elias; de Blok, W J G; Kramer, Carsten; Rosolowsky, Erik; Sandstrom, Karin; Schuster, Karl; Usero, Antonio; Weiss, Axel; Wiesemeyer, Helmut

2012-01-01

160

The Red Giant Branch Luminosity Function Bump  

CERN Document Server

We present observational estimates of the magnitude difference between the luminosity function RGB bump and the HB (Delta(bump-zahb)), and of star counts in the bump region (R_bump), for a sample of 54 Galactic globular clusters (GCs) observed by the HST. The large sample of stars resolved in each cluster, and the high photometric accuracy of the data allowed us to detect the bump also in a number of metal poor clusters. To reduce the photometric uncertainties, empirical values are compared with theoretical predictions obtained from a set of updated canonical stellar evolution models which have been transformed directly into the HST flight system. We found an overall qualitative agreement between theory and observations. Quantitative estimates of the confidence level are hampered by current uncertainties on the GCs metallicity scale, and by the strong dependence of Delta(bump-zahb) on the cluster metallicity. In case of the R_bump parameter, which is only weakly affected by the metallicity, we find a very goo...

Riello, M; Piotto, G; Recio-Blanco, A; De Angeli, F; Salaris, M; Pietrinferni, A; Bono, G; Zoccali, M

2003-01-01

161

The Black Hole Mass - Spheroid Luminosity relation  

CERN Document Server

The differing M_bh-Luminosity relations presented in McLure & Dunlop, Marconi & Hunt and Erwin et al. have been investigated. A number of issues have been identified and addressed in each of these studies, including but not limited to: the removal of a dependency on the Hubble constant; a correction for dust attenuation in the bulges of disc galaxies; the identification of lenticular galaxies previously treated as elliptical galaxies; and application of the same (Y|X) regression analysis. These adjustments result in relations which now predict similar black hole masses. The optimal K-band relation is log(M_bh/M_sun) = -0.37(+/-0.04)[M_K +24] + 8.29(+/-0.08), with a total (not intrinsic) scatter in log M_bh equal to 0.33 dex. This level of scatter is similar to the value of 0.34 dex from the M_bh-sigma relation of Tremaine et al. and compares favourably with the value of 0.31 dex from the M_bh-n relation of Graham & Driver. Using different photometric data, consistent relations in the B- and R-band...

Graham, Alister W

2007-01-01

162

The Luminosities of the Coldest Brown Dwarfs  

CERN Document Server

In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant planets of our own Solar System (at around 130K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures of in the range 1500-1000K). Distance measurements for these objects deliver absolute magnitudes that make critical tests of our understanding of very cool atmospheres. Here we report new distances for nine Y dwarfs and seven very-late T dwarfs. These reveal that Y dwarfs do indeed represent a continuation of the T dwarf sequence to both fainter luminosities and cooler temperatures. They also show that the coolest objects display a large range in absolute magnitude for a given photometric colour. The latest atmospheric models show good agreement with the majority of these ...

Tinney, C G; Kirkpatrick, J Davy; Cushing, Mike; Morley, Caroline V; Wright, Edward L

2014-01-01

163

ATLAS gets its own luminosity detector  

CERN Multimedia

During the winter shutdown, the ATLAS collaboration has completed the installation of ALFA, the detector system that aims at the LHC absolute luminosity at Point 1 analysing the elastic scattering of protons at small angles.   Upper and lower ALFA Roman Pots as installed in sector 8-1 of the LHC tunnel, 240 metres from the ATLAS Interaction Point. The detectors of the ALFA system are installed at ± 240 meters from the interaction point 1, on either side of the ATLAS detector. The whole system consists of four stations, two on each side of the interaction point. Each station is equipped with two Roman Pots; each pot – that is separated from the vacuum of the accelerator by a thin window but is connected with bellows to the beam-pipe – can be moved very close to the beam. “The Roman Pot technique has been used successfully in the past for the measurement of elastic scattering very close to the circulating beam,” says Patrick Fassn...

CERN Bulletin

2011-01-01

164

Intrinsic luminosities of the Jovian planets  

International Nuclear Information System (INIS)

We review available data and theories on the size and nature of interior power sources in the Jovian planets. Broad band infrared measurements indicate that Jupiter and Saturn have interior heat fluxes about 150 and 50 times larger, respectively, than the terrestrial value. While Neptune has a modest heat flux (approx.5 times terrestrial), it is clearly detected by earth-based measurements. Only Uranus seems to lack a detectable interior heat flow. Various models, ranging from simple cooling to gravitational layering to radioactivity, are discussed. Current evidence seems to favor a cooling model in which the escape of heat is regulated by the atmosphere. This model seems capable of explaining phenomena such as the uniformity of effective temperature over Jupiter's surface and the different emission rates of Uranus and Neptune. In such a model the heat radiated from the atmosphere may derived from depletion of a thermal reservoir in the interior, or it may derive from separation of chemical elements during formation of a core. Calculations indicate that in the earlier stages of cooling, Jupiter and Saturn may have more homogeneous abundances of hydrogen and helium and radiate energy derived from simple cooling. At a subsequent phase (which may be later than the present time), hydrogen and helium will separate and supply grativational energy. Either model is consistent with a hot, high-luminosity origin for the Jovian Planets

165

Galaxy luminosity function: evolution at high redshift  

Science.gov (United States)

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 (0.4tackle these problems. We present cluster galaxy luminosity 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.

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

2014-12-01

166

GALAXY CLUSTERING IN THE COMPLETED SDSS REDSHIFT SURVEY: THE DEPENDENCE ON COLOR AND LUMINOSITY  

International Nuclear Information System (INIS)

We measure the luminosity and color dependence of galaxy clustering in the largest-ever galaxy redshift survey, the main galaxy sample of the Sloan Digital Sky Survey Seventh Data Release. We focus on the projected correlation function wp (rp ) of volume-limited samples, extracted from the parent sample of ?700,000 galaxies over 8000 deg2, extending up to redshift of 0.25. We interpret our measurements using halo occupation distribution (HOD) modeling assuming a ?CDM cosmology (inflationary cold dark matter with a cosmological constant). The amplitude of wp (rp ) grows slowly with luminosity for L * and increases sharply at higher luminosities, with a large-scale bias factor b(> L) x (?8/0.8) = 1.06 + 0.21(L/L*)1.12, where L is the sample luminosity threshold. At fixed luminosity, redder galaxies exhibit a higher amplitude and steeper correlation function, a steady trend that runs through the 'blue cloud' and 'green valley' and continues across the 'red sequence'. The cross-correlation of red and blue galaxies is close to the geometric mean of their autocorrelations, dropping slightly below at rp -1 Mpc. The luminosity trends for the red and blue galaxy populations separately are strikingly different. Blue galaxies show a slow but steady increase of clustering strength with luminosity, with nearly constant shape of wp (rpnstant shape of wp (rp ). The large-scale clustering of red galaxies shows little luminosity dependence until a sharp increase at L > 4 L*, but the lowest luminosity red galaxies (0.04-0.25 L*) show very strong clustering on small scales (rp -1 Mpc). Most of the observed trends can be naturally understood within the ?CDM+HOD framework. The growth of wp (rp ) for higher luminosity galaxies reflects an overall shift in the mass scale of their host dark matter halos, in particular an increase in the minimum host halo mass Mmin. The mass at which a halo has, on average, one satellite galaxy brighter than L is M1 ? 17 Mmin(L) over most of the luminosity range, with a smaller ratio above L*. The growth and steepening of wp (rp ) for redder galaxies reflects the increasing fraction of galaxies that are satellite systems in high-mass halos instead of central systems in low-mass halos, a trend that is especially marked at low luminosities. Our extensive measurements, provided in tabular form, will allow detailed tests of theoretical models of galaxy formation, a firm grounding of semiempirical models of the galaxy population, and new constraints on cosmological parameters from combining real-space galaxy clustering with mass-sensitive statistics such as redshift-space distortions, cluster mass-to-light ratios, and galaxy-galaxy lensing.

167

Luminosities for collisions of intermediate bosons and other partons  

International Nuclear Information System (INIS)

Parton-parton luminosities (l/s) dpounds/d tau are presented for WW, WZ, ZZ, ?W, ?Z, ??, Wg, Wq, Zg, and Zq collisions. A comparison between the exact calculation and the calculation using our luminosities for Higgs boson production from WW fusion is also presented

168

The Radio and Gamma-Ray Luminosities of Blazars  

CERN Document Server

Based on the $\\gamma$-ray data of blazars in the third EGRET catalog and radio data at 5 GHz, we studied the correlation between the radio and $\\gamma$-ray luminosities using two statistical methods. The first method was the partial correlation analysis method, which indicates that there exist correlations between the radio and $\\gamma$-ray luminosities in both high and low states as well as in the average case. The second method involved a comparison of expected $\\gamma$-ray luminosity distribution with the observed data using the Kolmogorov-- Smirnov (KS) test. In the second method, we assumed that there is a correlation between the radio and $\\gamma$-ray luminosities and that the $\\gamma$-ray luminosity function is proportional to the radio luminosity function. The KS test indicates that the expected gamma-ray luminosity distributions are consistent with the observed data in a reasonable parameter range. Finally, we used different $\\gamma$-ray luminosity functions to estimate the possible 'observed' $\\gamm...

Zhang, L; Fan, J H

2001-01-01

169

The Satellite Luminosity Functions of Galaxies in SDSS  

CERN Document Server

We study the luminosity function of satellite galaxies around isolated primaries using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy samples. We select isolated primaries from the spectroscopic sample and search for potential satellites in the much deeper photometric sample. For primaries of similar luminosity to the Milky Way and M31, we are able to stack as many as $\\sim\

Guo, Quan; Eke, Vincent; Frenk, Carlos

2011-01-01

170

A Tale Twice Told: The Luminosity Profiles of the Sagittarius Tails  

OpenAIRE

The Sagittarius dwarf galaxy is the archetype of a tidally disrupting system. Both leading and trailing tails can be observed across at least 180 degrees of the sky and measurements of their luminosity density profiles have recently become available. Using numerical simulations, we explore the factors that control the appearance of such profiles. We use two possible models for the Sgr progenitor. The first is a one-component Plummer model, which may represent either a dark...

Niederste-ostholt, Martin; Belokurov, Vasily; Evans, Wyn

2012-01-01

171

The Luminosity Problem: Testing Theories of Star Formation  

CERN Document Server

Low-mass protostars are less luminous than expected. This luminosity problem is important because the observations appear to be inconsistent with some of the basic premises of star formation theory. Two possible solutions are that stars form slowly, which is supported by recent data, and/or that protostellar accretion is episodic; current data suggest that the latter accounts for less than half the missing luminosity. The solution to the luminosity problem bears directly on the fundamental problem of the time required to form a low-mass star. The protostellar mass and luminosity functions provide powerful tools both for addressing the luminosity problem and for testing theories of star formation. Results are presented for the collapse of singular isothermal spheres, for the collapse of turbulent cores, and for competitive accretion.

McKee, C F

2010-01-01

172

The white dwarf luminosity function. I. Statistical errors and alternatives  

CERN Document Server

Over the years, several methods have been proposed to compute galaxy luminosity functions, from the most simple ones -counting sample objects inside a given volume- to very sophisticated ones -like the C- method, the STY method or the Choloniewski method, among others. However, only the V/Vmax method is usually employed in computing the white dwarf luminosity function and other methods have not been applied so far to the observational sample of spectroscopically identified white dwarfs. Moreover, the statistical significance of the white dwarf luminosity function has also received little attention and a thorough study still remains to be done. In this paper we study, using a controlled synthetic sample of white dwarfs generated using a Monte Carlo simulator, which is the statistical significance of the white dwarf luminosity function and which are the expected biases. We also present a comparison between different estimators for computing the white dwarf luminosity function. We find that for sample sizes larg...

Geijo, E M; Isern, J; García-Berro, E

2006-01-01

173

Limitation on the luminosity of e+e- storage rings due to beamstrahlung  

CERN Document Server

Particle loss due to the emission of single energetic beamstrahlung photons in beam collisions is shown to impose a fundamental limit on storage-ring luminosities at energies greater than 2E~140 GeV for head-on collisions and 2E~40 GeV for crab-waist collisions. Above these threshold energies, the suppression factor due to beamstrahlung scales as 1/E^{4/3}, and for a fixed power of synchrotron radiation, the luminosity L is proportional to R/E^{13/3}, where R is the collider radius. For 2E > 150 GeV, both collision schemes have similar luminosity limits. The luminosities attainable at storage-ring and linear-collider (LC) 2E=240 GeV Higgs factories are comparable; at higher energies, LCs are preferable. This conference paper is based on my recent PRL publication [1], supplemented with additional comments on linac-ring e+e- colliders and ring e+e- colliders with charge compensation (four-beam collisions).

Telnov, V I

2013-01-01

174

GEM luminosity monitors for the OLYMPUS experiment to determine the effect of two-photon exchange  

Science.gov (United States)

The OLYMPUS experiment at DESY acquired its data in two distinct periods between 2012-2013 to measure the ratio of positron-proton and electron-proton elastic scattering cross sections. In light of those measurements, OLYMPUS will be able 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 separation and polarization transfer methods. In order to control the systematic uncertainties to the sub-percent level, the luminosities were monitored redundantly and with high precision. This was done 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. A total of nine GEM detectors were constructed for the OLYMPUS experiment. Within the scope of this thesis, every single step of construction, testing and installation of the GEM OLYMPUS luminosity monitors are explained in the hardware part of this thesis. Moreover, based on the analysis of the data taken with the GEM luminosity monitors at the OLYMPUS experiment, individual GEM detector performance and preliminary results on the positron/electron luminosity ratio measured with elastic scattering at forward angles are discussed in the analysis part of the thesis.

Ates, Ozgur

175

The X-ray luminosity function of AGN at z~3  

CERN Document Server

We combine Lyman-break colour selection with ultradeep (> 200 ks) Chandra X-ray imaging over a survey area of ~0.35 deg^2 to select high redshift AGN. Applying careful corrections for both the optical and X-ray selection functions, the data allow us to make the most accurate determination to date of the faint end of the X-ray luminosity function (XLF) at z~3. Our methodology recovers a number density of X-ray sources at this redshift which is at least as high as previous surveys, demonstrating that it is an effective way of selecting high z AGN. Comparing to results at z=1, we find no evidence that the faint slope of the XLF flattens at high z, but we do find significant (factor ~3.6) negative evolution of the space density of low luminosity AGN. Combining with bright end data from very wide surveys we also see marginal evidence for continued positive evolution of the characteristic break luminosity L*. Our data therefore support models of luminosity-dependent density evolution between z=1 and z=3. A sharp up...

Aird, James; Georgakakis, Antonis; Laird, Elise S; Steidel, Charles C; Sharon, Chelsea

2008-01-01

176

The Luminosities of the Coldest Brown Dwarfs  

Science.gov (United States)

In recent years, brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500 K and masses in the range of 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant planets of our own solar system (at around 130 K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures in the range of 1500-1000 K). Distance measurements for these objects deliver absolute magnitudes that make critical tests of our understanding of very cool atmospheres. Here we report new distances for nine Y dwarfs and seven very late T dwarfs. These reveal that Y dwarfs do indeed represent a continuation of the T-dwarf sequence to both fainter luminosities and cooler temperatures. They also show that the coolest objects display a large range in absolute magnitude for a given photometric color. The latest atmospheric models show good agreement with the majority of these Y-dwarf absolute magnitudes. This is also the case for WISE0855-0714, the coldest and closest brown dwarf to the Sun, which shows evidence for water ice clouds. However, there are also some outstanding exceptions, which suggest either binarity or the presence of condensate clouds. The former is readily testable with current adaptive optics facilities. The latter would mean that the range of cloudiness in Y dwarfs is substantial with most hosting almost no clouds—while others have dense clouds, making them prime targets for future variability observations to study cloud dynamics. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Tinney, C. G.; Faherty, Jacqueline K.; Kirkpatrick, J. Davy; Cushing, Mike; Morley, Caroline V.; Wright, Edward L.

2014-11-01

177

Evolution of Galaxy Luminosity Function Using Photometric Redshifts  

CERN Document Server

We examine the impact of using photometric redshifts for studying the evolution of both the global galaxy luminosity function (LF) and that for different galaxy types. To this end we compare LFs obtained using photometric redshifts from the CFHT Legacy Survey (CFHTLS) D1 field with those from the spectroscopic survey VIMOS VLT Deep Survey (VVDS) comprising ~4800 galaxies. We find that for z<2, in the interval of magnitudes considered by this survey, the LFs obtained using photometric and spectroscopic redshifts show a remarkable agreement. This good agreement led us to use all four Deep fields of CFHTLS comprising ~386000 galaxies to compute the LF of the combined fields and estimate directly the error in the parameters based on field-to-field variation. We find that the characteristic absolute magnitude M* of Schechter fits fades by ~0.7mag from z~1.8 to z~0.3, while the characteristic density phi* increases by a factor of ~4 in the same redshift bin. We use the galaxy classification provided by the templ...

Ramos, B H F; Benoist, C; da Costa, L N; Maia, M A G; Makler, M; Ogando, R L C; de Simoni, F; Mesquita, A A

2011-01-01

178

Peak luminosity correlated low-frequency oscillations in black holes  

Science.gov (United States)

Based on Rossi X-ray Timing Explorer (RXTE) observational data, we study the timing and spectral properties of some peculiar low-frequency (LF) quasi-periodic oscillations (QPOs), which have been found at the peak luminosity of the outburst of some transient black hole (BH) binaries: the 2005 outburst of GRO J1655-40, the 2003 outburst of H1743-322 and the 1998 outburst of XTE J1550-564. Appearing in the ultraluminous state, these QPOs from different sources show some common properties. The amplitude is very weak (less than 1 per cent) and the quality factor is larger than 6. Moreover, these QPOs (about several Hz) sometimes show up simultaneously with another QPO (about 10 Hz), but their frequencies are not harmonically related. We also find that the frequencies of these QPOs are inversely correlated with the mass of the BH, which implies that these QPOs might be correlated with the innermost stable circular orbit. The QPO frequency is also negative correlated with the inner disc radius among BHs. However, its frequency is too low to ascribe it to the Keperlian orbit frequency. Moreover, we discuss the physical origin of these QPOs and we suggest that they are not produced by the viscous variability of the inner disc either.

Li, Z. B.; Gao, H. Q.; Zhang, Z.; Zhang, S.; Qu, J. L.; Zhang, C. M.; Song, L. M.

2014-05-01

179

Hundreds of Milky Way Satellites? Luminosity Bias in the Satellite Luminosity Function  

CERN Document Server

We correct the observed Milky Way satellite luminosity function for luminosity bias using published completeness limits for the Sloan Digital Sky Survey DR5. Assuming that the spatial distribution of Milky Way satellites tracks the subhalos found in the Via Lactea LambdaCDM N-body simulation, we show that there should be between ~300 and ~600 satellites within 400 kpc of the Sun that are brighter than the faintest known dwarf galaxies, and that there may be as many as ~1000, depending on assumptions. By taking into account completeness limits, we show that the radial distribution of known Milky Way dwarfs is consistent with our assumption that the full satellite population tracks that of subhalos. These results alleviate the primary worries associated with the so-called "Missing Satellites Problem" in CDM. We show that future, deep wide-field surveys like SkyMapper, the Dark Energy Survey (DES), PanSTARRS, and the Large Synoptic Survey Telescope (LSST) will deliver a complete census of ultra-faint dwarf satel...

Tollerud, Erik J; Strigari, Louis E; Willman, Beth

2008-01-01

180

CONTRIBUTION OF THE ACCRETION DISK, HOT CORONA, AND OBSCURING TORUS TO THE LUMINOSITY OF SEYFERT GALAXIES: INTEGRAL AND SPITZER OBSERVATIONS  

International Nuclear Information System (INIS)

We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal-to-noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L15?m?L0.74±0.06HX. Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, LDisk, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, LCorona, with the LDisk/LCorona ratio varying by a factor of 2.1 around a mean value of 1.6. This ratio is a factor of ?2 smaller than for typical quasars producing the cosmic X-ray background. Therefore, over three orders of magnitude in luminosity, HX radiation carries a large, and roughly comparable, fraction of the bolometric output of AGNs. We estimate the cumulative bolometric luminosity density of local AGNs at ?(1-3) × 1040 AGNs at ?(1-3) × 1040 erg s–1 Mpc–3. Finally, the Compton temperature ranges between kTc ? 2 and ?6 keV for nearby AGNs, compared to kTc ? 2 keV for typical quasars, confirming that radiative heating of interstellar gas can play an important role in regulating SMBH growth.

181

Computation of the TEVATRON luminosity using measured machine parameters  

International Nuclear Information System (INIS)

In order to extract the cross section from a measured reaction rate an experimenter needs to know the incident flux. At a collider the flux is referred to as the luminosity L. The luminosity can be determined in an experiment by measuring the rate of a reaction with a known cross section. This paper describes an alternative calculation of the luminosity based on measurements made on the stored beam in the TEVATRON. The measurements necessary for the calculation, which must be made on each of the p and bar p bunches, are the intensity and the transverse and longitudinal extent of each of the bunches

182

High precision measurements of the luminosity at LEP  

International Nuclear Information System (INIS)

The art of the luminosity measurements at LEP is presented. First generation LEP detectors have measured the absolute luminosity with the precision of 0.3-0.5%. The most precise present detectors have reached the 0.07% precision and the 0.05% is not excluded in future. Center-of-mass energy dependent relative precision of the luminosity detectors and the use of the theoretical cross-section in the LEP experiments are also discussed. (author). 18 refs., 6 figs., 6 tabs

183

Simulation studies of tracking systems at very high luminosity  

International Nuclear Information System (INIS)

Detailed computer simulation studies of a tracking detector originally designed for high luminosity operation at the Superconducting Super Collider have been carried out. Detector simulation and track reconstruction techniques appropriate to the extremely high charged particle rates corresponding to luminosities of up to 1034 cm-2 s-1 are described. The detector performance is evaluated and compared to design requirements stemming from the physics goals of the SDC experiment. The results have implications for the design of tracking detectors at future high luminosity hadron colliders such as the Large Hadron Collider (LHC). (orig.)

184

Rad-hard Luminosity Monitoring for the LHC  

Energy Technology Data Exchange (ETDEWEB)

Luminosity measurements at the high luminosity points of the LHC are very challenging due to the extremely high radiation levels in the order of 180 MGy/yr. They have designed an ionization chamber that uses a flowing inorganic gas mixture and a combination of metals and ceramics. With such a choice, an additional challenge is achieving the necessary speed to be able to resolve bunch-by-bunch luminosity data. They present the design, analysis and experimental results of the early demonstration tests of this device.

Beche, J.F.; Byrd, J.M.; Chow, K.; Denes, P.; Ghiorso, W.; Matis,H.S.; Monroy, M.T.; Ratti, A.; de Santis, S.; Turner, W.C.; Bravin, E.; Manfredi, P.F.; Vandelli, W.

2007-06-24

185

Test Results of the Luminosity Monitors for the LHC  

Energy Technology Data Exchange (ETDEWEB)

The Luminosity Monitor for the LHC has been built at LBNL and will be operational in the LHC during the upcoming run. The device, a gas ionization chamber, is installed in the high luminosity regions (those dedicated to the ATLAS and CMS experiments) and capable to resolve bunch-by-bunch luminosity as well as survive extreme levels of radiation. During the experimental R&D phase of its design, a prototype of this detector has been tested extensively at the ALS, in RHIC as well as in the SPS. Results of these experiments are presented here.

Beche, J.F.; Byrd, J. M.; Doolittle, L.; Manfredi, P. F.; Matis, H. S.; Monroy, M.; Ratti, A.; Stezelberger, T.; Stiller, J.; Turner, W.; Yaver, H.; Drees, A.; Bravin, E.

2009-05-04

186

Rad-hard Luminosity Monitoring for the LHC  

International Nuclear Information System (INIS)

Luminosity measurements at the high luminosity points of the LHC are very challenging due to the extremely high radiation levels in the order of 180 MGy/yr. They have designed an ionization chamber that uses a flowing inorganic gas mixture and a combination of metals and ceramics. With such a choice, an additional challenge is achieving the necessary speed to be able to resolve bunch-by-bunch luminosity data. They present the design, analysis and experimental results of the early demonstration tests of this device

187

Test Results of the Luminosity Monitors for the LHC  

International Nuclear Information System (INIS)

The Luminosity Monitor for the LHC has been built at LBNL and will be operational in the LHC during the upcoming run. The device, a gas ionization chamber, is installed in the high luminosity regions (those dedicated to the ATLAS and CMS experiments) and capable to resolve bunch-by-bunch luminosity as well as survive extreme levels of radiation. During the experimental R and D phase of its design, a prototype of this detector has been tested extensively at the ALS, in RHIC as well as in the SPS. Results of these experiments are presented here.

188

MID-IR LUMINOSITIES AND UV/OPTICAL STAR FORMATION RATES AT z < 1.4  

International Nuclear Information System (INIS)

Ultraviolet (UV) nonionizing continuum and mid-infrared (IR) emission constitute the basis of two widely used star formation (SF) indicators at intermediate and high redshifts. We study 2430 galaxies with z 10-1012 Lsun). We show that the IR luminosity can be estimated from the UV and optical photometry to within a factor of 2, implying that most z IR>1011 Lsun, yet with little current SF. For them a reasonable amount of dust absorption of stellar light (but presumably higher than in nearby early-type galaxies) is sufficient to produce the observed levels of IR, which includes a large contribution from intermediate and old stellar populations. In our sample, which contains very few ultraluminous IR galaxies, optical and X-ray active galactic nuclei do not contribute on average more than ?50% to the mid-IR luminosity, and we see no evidence for a large population of 'IR excess' galaxies.

189

TESS - A high-luminosity high-resolution twin-etalon scanning spectrometer  

Science.gov (United States)

An analysis and the operation of a piezoelectric, twin-etalon scanned spectrometer (TESS) is reviewed. TESS provides high luminosity and large gain relative to the capabilities of single aperture Fabry-Perot spectrometers. Limiting factors are noted to exist in material inhomogeneities, the scanning scheme, field-of-view, etc. The luminosity gain, which allows measurement of faint sources with an arbitrary time resolution, occurs at the expense of the field-of-view. The angular spread of the last fringe (21 st) of the TESS spectrum is 3.4 deg. TESS angular coverage can be matched or limited, with respect to the source being observed, and is independent of the resolution.

Hernandez, G.; Mills, O. A.; Smith, J. L.

1981-11-01

190

A novel method for an absolute luminosity measurement at LHCb with beam-gas imaging  

International Nuclear Information System (INIS)

A novel technique to measure the absolute luminosity at the Large Hadron Collider (LHC) using beam-gas interactions has been successfully used in the LHCb experiment. A gas injection device (SMOG) has been installed in the LHCb experiment to increase the pressure around the interaction point during dedicated fills. The Beam-Gas Imaging method (BGI) has now the potential to surpass the accuracy of the commonly used *van der Meer scan* method (VDM). The technique has been used in 10 LHC fills during 2012 including and also provided a first luminosity measurement for proton-lead collisions. This talk presents the principles of the gas injection and the improvements reached with the increased pressure. Furthermore the gas injection increased the accuracy measurement of the so-called ghost charges and also intensities per bunch. Those uncertainties are becoming the dominating factor because the uncertainty on the total beam current have been reduced.

191

Gas dynamics in high-luminosity polarized 3He targets using diffusion and convection  

International Nuclear Information System (INIS)

The dynamics of the movement of gas is discussed for two-chambered polarized 3He target cells of the sort that have been used successfully for many electron-scattering experiments. A detailed analysis is presented showing that diffusion is a limiting factor in target performance, particularly as these targets are run at increasingly high luminosities. Measurements are presented on a new prototype polarized 3He target cell in which the movement of gas is due largely to convection instead of diffusion. Nuclear magnetic resonance tagging techniques have been used to visualize the gas flow, showing velocities along a cylindrically shaped target of between 5 and 80 cm/min. The new target design addresses one of the principle obstacles to running polarized 3He targets at substantially higher luminosities while simultaneously providing new flexibility in target geometry.

192

An upper limit on the luminosity of cosmological gamma-ray bursts  

International Nuclear Information System (INIS)

The Pioneer Venus Orbiter (PVO) log N-log P distribution follows a -3/2 power law for over a factor of 30 in intensity, which is inconsistent with Gamma-Ray Bursts from large redshifts. We develop log N-log P models suitable for cosmological gamma-ray bursts. The PVO data is best fit with a standard candle peak luminosity of 2x1050 erg/sec with 3x104 events/yr within a Hubble distance. However, non-cosmological models fit nearly as well (L0 much-lt 1050). A luminosity of 1052 erg/sec fits at a 3? level and is, therefore, a maximum upper limit allowed by the PVO data. This upper limit is roughly equal to other reported lower limits. The BATSE event rate combined with the PVO limits imply that evolution with epoch must be occurring

193

Operation of the ATLAS end-cap calorimeters at sLHC luminosities, an experimental study  

CERN Document Server

The expected increase of luminosity at sLHC by a factor of ten with respect to LHC luminosities has serious consequences for the signal reconstruction, radiation hardness requirements and operations of the ATLAS liquid argon calorimeters (EMEC, HEC, FCAL) in the endcap, respectively forward region. Small modules of each type of calorimeter have been built. The layout and the components used are very close to the ones used in the construction of the ATLAS calorimeter. The goal is to simulate in the high intensity proton beam at IHEP /Protvino the particle impact as expected for ATLAS in sLHC. Depending on the position in pseudorapidity |?|, each forward calorimeter has to cope with a different particle and energy flux. Placing absorber elements in-between the various small calorimeter modules, the particle and energy flux as expected in ATLAS later - given the variation due to |?| and longitudinal position - can be simulated very well.

Ferencei, J; The ATLAS collaboration

2009-01-01

194

A novel method for an absolute luminosity measurement at LHCb with beam-gas imaging  

Energy Technology Data Exchange (ETDEWEB)

A novel technique to measure the absolute luminosity at the Large Hadron Collider (LHC) using beam-gas interactions has been successfully used in the LHCb experiment. A gas injection device (SMOG) has been installed in the LHCb experiment to increase the pressure around the interaction point during dedicated fills. The Beam-Gas Imaging method (BGI) has now the potential to surpass the accuracy of the commonly used *van der Meer scan* method (VDM). The technique has been used in 10 LHC fills during 2012 including and also provided a first luminosity measurement for proton-lead collisions. This talk presents the principles of the gas injection and the improvements reached with the increased pressure. Furthermore the gas injection increased the accuracy measurement of the so-called ghost charges and also intensities per bunch. Those uncertainties are becoming the dominating factor because the uncertainty on the total beam current have been reduced.

Barschel, Colin [RWTH Aachen, III. Physikalisches Institut A (Germany)

2013-07-01

195

the D0 Luminosity Monitor operations and performance  

Energy Technology Data Exchange (ETDEWEB)

The D0 Luminosity Monitor (LM) plays a crucial role in D0 physics analyses by providing the normalization for many cross section measurements. The detector consists of two sets of 24 scintillator wedges read out with photomultiplier tubes. The detector is located in the forward regions surrounding the beam pipe, covering a pseudo-rapidity range of 2.7 < |{eta}| < 4.4. The LM is sensitive to a large fraction of the total inelastic cross section and measures the luminosity by counting the number of empty proton-antiproton bunch crossings, using Poisson statistics to extract the instantaneous luminosity. The techniques used to convert the measurements made by the LM into the assessed luminosity will be discussed, as well as the performance and operational details of the detector.

Prewitt, Michelle; /Rice U.

2011-09-01

196

The D0 Luminosity Monitor operations and performance  

International Nuclear Information System (INIS)

The D0 Luminosity Monitor (LM) plays a crucial role in D0 physics analyses by providing the normalization for many cross section measurements. The detector consists of two sets of 24 scintillator wedges read out with photomultiplier tubes. The detector is located in the forward regions surrounding the beam pipe, covering a pseudo-rapidity range of 2.7 < |?| < 4.4. The LM is sensitive to a large fraction of the total inelastic cross section and measures the luminosity by counting the number of empty proton-antiproton bunch crossings, using Poisson statistics to extract the instantaneous luminosity. The techniques used to convert the measurements made by the LM into the assessed luminosity will be discussed, as well as the performance and operational details of the detector.

197

The relation between bar formation, galaxy luminosity, and environment  

CERN Document Server

We derive the bar fraction in three different environments ranging from the field to Virgo and Coma clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of galaxy luminosity (and mass) in the field and Coma cluster are statistically significant, with Virgo being an intermediate case. We interpret this result as a variation of the effect of environment on bar formation depending on galaxy luminosity. We speculate that brighter disk galaxies are stable enough against interactions to keep their cold structure, thus, the interactions are able to trigger bar formation. For fainter galaxies the interactions become strong enough to heat up the disks inhibiting bar formation and even destroying the disks. Finally, we point out that the controversy regarding whether the bar fraction depends on...

Corsini, E M; Sanchez-Janssen, R; Aguerri, J A L; Zarattini, S

2013-01-01

198

Measurement of the absolute luminosity with the ALEPH detector  

Science.gov (United States)

We report on the absolute luminosity measurement performed with the ALEPH detector at LEP. The systematic errors of the measurements in 1990 are estimated to be 0.6% (experimental) and 0.3% (theoretical).

Decamp, D.; Deschizeaux, B.; Goy, C.; Lees, J.-P.; Minard, M.-N.; Alemany, R.; Crespo, J. M.; Delfino, M.; Fernandez, E.; Gaitan, V.; Garrido, Ll.; Mir, Ll. M.; Pacheco, A.; Catanesi, M. G.; Creanza, D.; de Palma, M.; Farilla, A.; Iaselli, G.; Maggi, G.; Maggi, M.; Natali, S.; Nuzzo, S.; Quattromini, M.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Gao, Y.; Hu, H.; Huang, D.; Huang, X.; Lin, J.; Lou, J.; Qiao, C.; Ruan, T.; Wang, T.; Xie, Y.; Xu, D.; Xu, R.; Zhang, J.; Zhao, W.; Atwood, W. B.; Bauerdick, L. A. T.; Bird, F.; Blucher, E.; Bonvicini, G.; Bossi, F.; Boudreau, J.; Brown, D.; Burnett, T. H.; Drevermann, H.; Forty, R. W.; Grab, C.; Hagelberg, R.; Haywood, S.; Hilgart, J.; Jost, B.; Kasemann, M.; Knobloch, J.; Lacourt, A.; Lançon, E.; Lehraus, I.; Lohse, T.; Lusiani, A.; Marchioro, A.; Martinez, M.; Mato, P.; Menary, S.; Minten, A.; Miotto, A.; Miquel, R.; Moser, H.-G.; Nash, J.; Palazzi, P.; Ranjard, F.; Redlinger, G.; Roth, A.; Rothberg, J.; Rotscheidt, H.; Saich, M.; Schlatter, D.; Schmelling, M.; Takashima, M.; Tejessy, W.; Wachsmuth, H.; Wasserbaech, S.; Wiedenmann, W.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Badaud, F.; Bardadin-Otwinowska, M.; Bencheikh, A. M.; El Fellous, R.; Falvard, A.; Gay, P.; Guicheney, C.; Harvey, J.; Henrard, P.; Jousset, J.; Michel, B.; Montret, J.-C.; Pallin, D.; Perret, P.; Proriol, J.; Prulhière, F.; Stimpfl, G.; Bertelsen, H.; Hansen, F.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Lindhal, A.; Møllerud, R.; Nilsson, B. S.; Petersen, G.; Efthymiopoulos, I.; Simopoulou, E.; Vayaki, A.; Badier, J.; Blondel, A.; Bonneaud, G.; Bourotte, J.; Braems, F.; Brient, J. C.; Fouque, G.; Gamess, A.; Guirlet, R.; Orteu, S.; Rosowsky, A.; Rougé, A.; Rumpf, M.; Tanaka, R.; Videau, H.; Candlin, D. J.; Veitch, E.; Moneta, L.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Ikeda, M.; Lannutti, J.; Levinthal, D.; Mermikides, M.; Sawyer, L.; Antonelli, A.; Baldini, R.; Bencivenni, G.; Bologna, G.; Campana, P.; Capon, G.; Cerutti, F.; Chiarella, V.; D'Ettorre-Piazzoli, B.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Picchi, P.; Zografou, P.; Altoon, B.; Boyle, O.; Halley, A. W.; Ten Have, I.; Hearns, J. L.; Lynch, J. G.; Morton, W. T.; Raine, C.; Scarr, J. M.; Smith, K.; Thompson, A. S.; Turnbull, R. M.; Brandl, B.; Braun, O.; Geiges, R.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Maumary, Y.; Putzer, A.; Rensch, B.; Stahl, A.; Tittel, K.; Wunsch, M.; Belk, A. T.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Cattaneo, M.; Dornan, P. J.; Dugeay, S.; Greene, A. M.; Hassard, J. F.; Lieske, N. M.; Patton, S. J.; Payne, D. G.; Phillips, M. J.; Sedgbeer, J. K.; Taylor, G.; Tomalin, I. R.; Wright, A. G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Finch, A. J.; Foster, F.; Hughes, G.; Keemer, N. R.; Nuttall, M.; Patel, A.; Rowlingson, B. S.; Sloan, T.; Snow, S. W.; Whelan, E. P.; Barczewski, T.; Kleinknecht, K.; Raab, J.; Renk, B.; Roehn, S.; Sander, H.-G.; Schmidt, H.; Steeg, F.; Walther, S. M.; Wolf, B.; Aubert, J.-J.; Benchouk, C.; Bernard, V.; Bonissent, A.; Carr, J.; Coyle, P.; Drinkard, J.; Etienne, F.; Papalexiou, S.; Payre, P.; Pietrzyk, B.; Qian, Z.; Rousseau, D.; Schwemling, P.; Talby, M.; Becker, H.; Blum, W.; Cattaneo, P.; Cowan, G.; Dehning, B.; Dietl, H.; Dydak, F.; Fernandez-Bosman, M.; Hansl-Kozanecka, T.; Jahn, A.; Kozanecki, W.; Lange, E.; Lauber, J.; Lütjens, G.; Lutz, G.; Männer, W.; Pan, Y.; Richter, R.; Schröder, J.; Schwarz, A. S.; Settles, R.; Stierlin, U.; Denis, R. St.; Thomas, J.; Wolf, G.; Bertin, V.; Boucrot, J.; Callot, O.; Chen, X.; Cordier, A.; Davier, M.; Ganis, G.; Grivaz, J.-F.; Heusse, Ph.; Janot, P.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Veillet, J.-J.; Videau, I.; Zhang, Z.; Zomer, F.; Abbaneo, D.; Amendolia, S. R.; Bagliesi, G.; Batignani, G.; Bosisio, L.; Bottigli, U.; Bradaschia, C.; Carpinelli, M.; Ciocci, M. A.; Dell'Orso, R.; Ferrante, I.; Fidecaro, F.; Foà, L.; Focardi, E.; Forti, F.; Gatto, C.; Giassi, A.; Giorgi, M. A.; Ligabue, F.; Mannelli, E. B.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Sanguinetti, G.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Vannini, C.; Venturi, A.; Verdini, P. G.; Walsh, J.; Carter, J. M.; Green, M. G.; March, P. V.; Medcalf, T.; Quazi, I. S.; Strong, J. A.; Thomas, R. M.; West, L. R.; Wildish, T.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Edwards, M.; Fisher, S. M.; Jones, T. J.; Norton, P. R.; Salmon, D. P.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Klopfenstein, C.; Locci, E.; Loucatos, S.; Monnier, E.; Perez, P.; Perlas, J. A.; Perrier, F.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.

1992-09-01

199

Performance of the Muon MWPC in high luminosity runs  

CERN Document Server

The LHCb detector was conceived to operate with an average luminosity of 2x10$^{32}$cm$^{-1}$s$^{-1}$. During the last year of the LHC run, the whole apparatus has shown to be able to perfectly acquire and manage data produced at a luminosity as high as 4x10$^{32}$cm$^{-2}$s$^{-1}$. In this condition, all subdetectors operated at average particle rates higher than the design ones and in particular the detectors equipping the Muon System had to sustain a particle rate as high as 100kHz/cm$^2$. In order to study the possibility of increasing the luminosity of operation several tests were performed. This paper reports detailed studies on the performance of the LHCb Muon System in runs with a luminosity between 4 x 10$^{32}$cm$^{-2}$s$^{-1}$ and 10$^{33}$ cm$^{-2}$s$^{-1}$.

Pinci, Davide

2013-01-01

200

Estimating the Prompt Electromagnetic Luminosity of a Black Hole Merger  

CERN Document Server

Although recent work in numerical relativity has made tremendous strides in quantifying the gravitational wave luminosity of black hole mergers, very little is known about the electromagnetic luminosity that might occur in immediate conjunction with these events. We show that whenever the heat deposited in the gas near a pair of merging black holes is proportional to its total mass, and the surface density of the gas in the immediate vicinity is greater than the (quite small) amount necessary to make it optically thick, the characteristic scale of the luminosity emitted in direct association with the merger is the Eddington luminosity independent of the gas mass. The duration of the photon signal is proportional to the gas mass, and is generally rather longer than the merger event. At somewhat larger distances, dissipation associated with realigning the gas orbits to the new spin orientation of the black hole can supplement dissipation of the energy gained from orbital adjustment to the mass lost in gravitati...

Krolik, Julian H

2009-01-01

201

The Intrinsic Quasar Luminosity Function: Accounting for Accretion Disk Anisotropy  

CERN Document Server

Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic --- in part due to its disk-like structure --- but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic l...

DiPompeo, M A; Brotherton, M S; Runnoe, J C; Green, R F

2014-01-01

202

The Radio and Gamma-Ray Luminosities of Blazars  

OpenAIRE

Based on the $\\gamma$-ray data of blazars in the third EGRET catalog and radio data at 5 GHz, we studied the correlation between the radio and $\\gamma$-ray luminosities using two statistical methods. The first method was the partial correlation analysis method, which indicates that there exist correlations between the radio and $\\gamma$-ray luminosities in both high and low states as well as in the average case. The second method involved a comparison of expected $\\gamma$-...

Zhang, L.; Cheng, K. S.; Fan, J. H.

2001-01-01

203

On the Luminosity Distance and the Hubble Constant  

Directory of Open Access Journals (Sweden)

Full Text Available By differentiating luminosity distance with respect to time using its standard formula we ?nd that the peculiar velocity is a time varying velocity of light. Therefore, a new de?nition of the luminosity distance is provided such that the peculiar velocity is equal to c. Using this de?nition a Hubble constant H0 = 67.3 km s?1 Mpc?1 is obtained from supernovae data.

Yuri Heymann

2013-07-01

204

A relationship between structure and luminosity for extragalactic radio sources  

International Nuclear Information System (INIS)

For a sample of identified extragalactic radio sources with double structure, a strong relation is found between the luminosity at 178 MHz and the fraction of the flux density originating in 'hot spots'. For a sample of unidentified sources the fraction originating in 'hot spots' is very similar to that for the identified sources of high luminosity, and a detailed comparison suggests that the unidentified sources are mostly at redshifts z > 0.5. (author)

205

The Intrinsic Quasar Luminosity Function: Accounting for Accretion Disk Anisotropy  

OpenAIRE

Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic --- in part due to its di...

Dipompeo, M. A.; Myers, A. D.; Brotherton, M. S.; Runnoe, J. C.; Green, R. F.

2014-01-01

206

The white dwarf luminosity function – I. Statistical errors and alternatives  

OpenAIRE

The white dwarf luminosity function is an important tool for the study of the solar neighbourhood, since it allows the determination of the age of the Galactic disc. Over the years, several methods have been proposed to compute galaxy luminosity functions, from the most simple ones – counting sample objects inside a given volume – to very sophisticated ones – like the C- method, the STY method or the Choloniewski method, among others. However, only the 1/Vmax method is usually employed ...

Geijo, Enrique M.; Torres Gil, Santiago; Isern Vilaboy, Jordi; Garci?a-berro Montilla, Enrique

2005-01-01

207

A new universal photon energy-luminosity relationship for GRBs  

International Nuclear Information System (INIS)

We define a new characteristic photon energy for the Band function, Ewz, and describe a new way of estimating the peak luminosity of the prompt emission from GRBs, Liso, which is not dependent on the time binning. We show that Ewz and Liso are correlated for all bursts, long and short. The new photon energy-luminosity relationship gives us a strong indication that the underlying process responsible for the prompt GRB emission is thermal

208

Mass and luminosity evolution of young stellar objects  

OpenAIRE

A model of protostar mass and luminosity evolution in clusters gives new estimates of cluster age, protostar birthrate, accretion rate and mean accretion time. The model assumes constant protostar birthrate, core-clump accretion, and equally likely accretion stopping. Its parameters are set to reproduce the initial mass function, and to match protostar luminosity distributions in nearby star-forming regions. It obtains cluster ages and birthrates from the observed numbers of...

Myers, Philip C.

2012-01-01

209

Evolution of the cluster X-ray luminosity function  

DEFF Research Database (Denmark)

We report measurements of the cluster X-ray luminosity function out to z = 0.8 based on the final sample of 201 galaxy systems from the 160 Square Degree ROSAT Cluster Survey. There is little evidence for any measurable change in cluster abundance out to z similar to 0.6 at luminosities of less than a few times 10(44) h(50)(-2) ergs s(-1) (0.5 - 2.0 keV). However, for 0.6 luminosities above 10(44) h(50)(-2) ergs s(-1), the observed volume densities are significantly lower than those of the present-day population. We quantify this cluster deficit using integrated number counts and a maximum likelihood analysis of the observed luminosity-redshift distribution fit with a model luminosity function. The negative evolution signal is more than 3 sigma regardless of the adopted local luminosity function or cosmological framework. Our results and those from several other surveys independently confirm the presence of evolution. Whereas the bulk of the cluster population does not evolve, the most luminousand presumably most massive structures evolve appreciably between z = 0.8 and the present. Interpreted in the context of hierarchical structure formation, we are probing sufficiently large mass aggregations at sufficiently early times in cosmological history, when the universe has yet to assemble these clusters to present-day volume densities.

Mullis, C.R.; Vikhlinin, A.

2004-01-01

210

Luminosity function and jet structure of Gamma Ray Bursts  

CERN Document Server

The structure of Gamma Ray Burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per unit solid angle within the jet aperture, or it could instead be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1e46-1e48 erg/s) and high (i.e. with L > 1e50 erg/s) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1e48-1e50} erg/s). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the ...

Pescalli, A; Salafia, O S; Ghisellini, G; Nappo, F; Salvaterra, R

2014-01-01

211

Colors and luminosities of stars with spots  

Science.gov (United States)

Theoretical zero-age main sequence models from 0.2 to 1.9 solar masses have been made for stars with large sunspot-like spots, and their black body UBVRIJK colors calculated. The effect of spots is different on long and short time scales (compared with the thermal time scale of the convection zone) and differs between mainly convective and mainly radiative stars. During a short term increase in spot area the stars always become redder in all color indices, but the long term change can be either to the blue or the red, depending on stellar mass and the color index used. The anomalies in color diagrams predicted for Hyades stars are much smaller than those discussed by Campbell (1984), unless a spot coverage factor close to unity is assumed. It is suggested that these color anomalies may reflect the brightening in short wavelength bands due to chromospheric emission rather than the effect of spots themselves.

Spruit, H. C.; Weiss, A.

1986-09-01

212

The Radius-Luminosity Relationship for Active Galactic Nuclei : The Effect of Host-Galaxy Starlight on Luminosity Measurements  

DEFF Research Database (Denmark)

We have obtained high resolution images of the central regions of 14 reverberation-mapped active galactic nuclei (AGN) using the Hubble Space Telescope Advanced Camera for Surveys High Resolution Camera to account for host-galaxy starlight contamination of measured AGN luminosities. We measure the host-galaxy starlight contribution to the continuum luminosity at 5100 A through the typical ground-based slit position and geometry used in the reverberation-mapping campaigns. We find that removing the starlight contribution results in a significant correction to the luminosity of each AGN, both for lower luminosity sources, as expected, but also for the higher luminosity sources such as the PG quasars. After accounting for the host galaxy starlight, we revisit the well-known broad-line region radius--luminosity relationship for nearby AGN. We find the power-law slope of the relationship for the H beta line to be 0.518 +/- 0.039, shallower than previously reported and consistent with the slope of 0.5 expected fromthe naive theoretical assumption that all AGN have, on average, the same ionizing spectrum and the same ionization parameter and gas density in the H beta line-emitting region.

Bentz, Misty C.; Peterson, Bradley M.

2006-01-01

213

Energy Deposition Patterns in the LHC Inner Triplet and Their Impact on the Phase II Luminosity Upgrade  

CERN Document Server

Recent studies show that the energy deposition for the LHC Phase I luminosity upgrade, aiming at a peak luminosity 2.5×10**34 cm**-2s**-1, can be handled by appropriate shielding. The Phase II upgrade aims at a further increase of peak luminosity by a factor 4, possibly using Nb3Sn quadrupoles. This paper describes how the main features of the triplet layout, such as quadrupole lengths, gaps between magnets, and aperture, affect the energy deposition in the insertion. We demonstrate how the energy deposition patterns depend on the triplet lay-out. An additional variable which is taken into account is the choice of conductor, i.e. solutions with Nb-Ti and Nb3Sn are compared. Nb3Sn technology gives possibilities for increasing the magnet apertures and space for new shielding solutions. Our studies give an indication on the possibility of managing energy deposition for the Phase II upgrade.

Wildner, E; Cerutti, F; Ferrari, A; Mereghetti, A; Todesco, E

2010-01-01

214

On the Radio and Optical Luminosity Evolution of Quasars  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-05-20

215

A luminosity measurement at LEP using the L3 detector  

International Nuclear Information System (INIS)

To perform high precision measurements at particle colliders it is crucial to know the exact intensity of the colliding beams. In particle physics this quantity is generally referred to as the luminosity. The determination of the luminosity in one of the experiments (L3) is the topic of this thesis. The implementation and the use of a silicon strip detector in L3, will be described in detail. In chapter one the most important parameters measured at LEP are discussed, preceded by a short introduction to the Standard Model. The process generally used for luminosity measurements in electron positron colliders is small angle Bhabha scattering. This process is discussed at the end of chapter one. In chapter two the characteristics of the collider and the L3 experiment are given. Together with the signature of the small angle Bhabha scattering, these experimental conditions determine the specifications for the design of the luminosity monitor. The general features of silicon strip detectors for their application in high energy physics are presented in chapter three. Some special attention is given to the behaviour of the sensors used for the tracking detector in the luminosity monitor. The more specific design details of the luminosity monitor are constricted to chapter four. In chapter five the conversion from detector signals into ccordinates relevant for the analysis is explained. The selection of the small angle Bhabha scattering events and the subsequent determination of the luminosity, are presented in chapter six. Systematic uncertainties are carefully studied. Important for a good understanding of the Bhabha selection are the events where a photon is produced in the scattering process. These events are separately studied. In chapter seven a comparison is presented between the radiative events observed in the data and their modelling in the Bhlumi Monte Carlo programme. (orig.)

216

The critical accretion luminosity for magnetized neutron stars  

Science.gov (United States)

The accretion flow around X-ray pulsars with a strong magnetic field is funnelled by the field to relatively small regions close to the magnetic poles of the neutron star (NS), the hotspots. During strong outbursts regularly observed from some X-ray pulsars, the X-ray luminosity can be so high that the emerging radiation is able to stop the accreting matter above the surface via radiation-dominated shock, and the accretion column begins to rise. This border luminosity is usually called the `critical luminosity'. Here we calculate the critical luminosity as a function of the NS magnetic field strength B using the exact Compton scattering cross-section in a strong magnetic field. Influence of the resonant scattering and photon polarization is taken into account for the first time. We show that the critical luminosity is not a monotonic function of the B-field. It reaches a minimum of a few 1036 erg s-1 when the cyclotron energy is about 10 keV and a considerable amount of photons from a hotspot have energy close to the cyclotron resonance. For small B, this luminosity is about 1037 erg s-1, nearly independent of the parameters. It grows for the B-field in excess of 1012 G because of the drop in the effective cross-section of interaction below the cyclotron energy. We investigate how different types of the accretion flow and geometries of the accretion channel affect the results and demonstrate that the general behaviour of the critical luminosity on the B-field is very robust. The obtained results are shown to be in good agreement with the available observational data and provide a necessary ground for the interpretation of upcoming high-quality data from the currently operating and planned X-ray telescopes.

Mushtukov, Alexander A.; Suleimanov, Valery F.; Tsygankov, Sergey S.; Poutanen, Juri

2015-02-01

217

Contribution of the accretion disk, hot corona, and obscuring torus to the luminosity of Seyfert galaxies: INTEGRAL and Spitzer observations  

CERN Document Server

We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spizter mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal to noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L_MIR L_HX^(0.74+/-0.06). Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, L_D, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, L_C, with the L_D/L_C ratio varying by a factor of 2.1 around a mea...

Sazonov, S; Goulding, A D; Hickox, R C; Gorjian, V; Werner, M W; Churazov, E; Krivonos, R; Revnivtsev, M; Sunyaev, R; Jones, C; Murray, S S; Vikhlinin, A; Fabian, A C; Forman, W R

2012-01-01

218

The Luminosity Function at z ~ 8 from 97 Y-band Dropouts: Inferences about Reionization  

Science.gov (United States)

We present the largest search to date for Y-band dropout galaxies (z ~ 8 Lyman break galaxies, LBGs) based on 350 arcmin2 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 arcmin2 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 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^\\star = -20.15^{+0.29}_{-0.38}, a faint-end slope of \\alpha = -1.87^{+0.26}_{-0.26}, and a number density of log _{10} \\phi ^\\star [{Mpc}^{-3}] = -3.24^{+0.25}_{-0.24}. Integrated down to M = -17.7, this luminosity function yields a luminosity density log _{10} \\epsilon [erg\\, s^{-1\\, Hz^{-1}\\, Mpc^{-3}}] = 25.52^{+0.05}_{-0.05}. Our luminosity function analysis is consistent with previously published determinations within 1?. 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 escape fraction we show that the UV luminosity density from galaxy samples down to M = -17.7 can ionize only 10%-50% of the neutral hydrogen at z ~ 8. Full reionization would require extending the luminosity function down to M = -15. The data are consistent with a substantial fraction of neutral hydrogen at z > 7, in agreement with recent suggestions based on deep spectroscopy of z ~ 8 LBGs.

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

2014-05-01

219

The Dependence of Type Ia Supernova Luminosities on their Host Galaxies  

CERN Document Server

(Abridged) Precision cosmology with Type Ia supernovae (SNe Ia) makes use of the fact that SN Ia luminosities depend on their light-curve shapes and colours. Using Supernova Legacy Survey (SNLS) and other data, we show that there is an additional dependence on the global characteristics of their host galaxies: events of the same light-curve shape and colour are, on average, 0.08mag (~4.0sigma) brighter in massive host galaxies (presumably metal-rich) and galaxies with low specific star-formation rates (sSFR). SNe Ia in galaxies with a low sSFR also have a smaller slope ("beta") between their luminosities and colours with ~2.7sigma significance, and a smaller scatter on SN Ia Hubble diagrams (at 95% confidence), though the significance of these effects is dependent on the reddest SNe. SN Ia colours are similar between low-mass and high-mass hosts, leading us to interpret their luminosity differences as an intrinsic property of the SNe and not of some external factor such as dust. If the host stellar mass is in...

Sullivan, M; Howell, D A; Neill, J D; Astier, P; Balland, C; Basa, S; Carlberg, R G; Fouchez, D; Guy, J; Hardin, D; Hook, I M; Pain, R; Palanque-Delabrouille, N; Perrett, K M; Pritchet, C J; Regnault, N; Rich, J; Ruhlmann-Kleider, V; Baumont, S; Hsiao, E; Kronborg, T; Lidman, C; Perlmutter, S; Walker, E S

2010-01-01

220

Low-luminosity X-ray sources and the Galactic ridge X-ray emission  

CERN Document Server

Using the XMM-Newton Slew Survey, we construct a hard-band selected sample of low-luminosity Galactic X-ray sources. Two source populations are represented, namely coronally-active stars and binaries (ASBs) and cataclysmic variables (CVs), with X-ray luminosities collectively spanning the range 10^(28-34) erg/s (2-10 keV). We derive the 2-10 keV X-ray luminosity function (XLF) and volume emissivity of each population. Scaled to the local stellar mass density, the latter is found to be 1.08 +/- 0.16 x 10^28 erg/s/M and 2.5 +/- 0.6 x 10^27 erg/s/M, for the ASBs and CVs respectively, which in total is a factor 2 higher than previous estimates. We employ the new XLFs to predict the X-ray source counts on the Galactic plane at l = 28.5 deg and show that the result is consistent with current observational constraints. The X-ray emission of faint, unresolved ASBs and CVs can account for a substantial fraction of the Galactic ridge X-ray emission (GRXE). We discuss a model in which roughly 80 per cent of the 6-10 keV...

Warwick, R S

2014-01-01

221

Mid-infrared properties of nearby low-luminosity AGN at high angular resolution  

CERN Document Server

High spatial resolution mid-infrared (MIR) 12 \\mum continuum imaging of low-luminosity active galactic nuclei (LLAGN) obtained by VLT/VISIR is presented. The goal of this investigation is to determine if the nuclear MIR emission of LLAGN is consistent with the existence of a dusty obscuring torus. A sample of 17 nearby LLAGN was selected and combined with archival VISIR data of 9 additional LLAGN with available X-ray measurements. Of the 17 observed LLAGN, 7 are detected, while upper limits are derived for the 10 non-detections. All detections except NGC 3125 appear point-like on a spatial scale of \\sim 0.35". The detections do not significantly deviate from the known MIR-X-ray correlation but extend it by a factor of \\sim 10 down to luminosities < 10^41 erg/s with a narrow scatter. The latter is dominated by the uncertainties in the X-ray luminosity. Interestingly, a similar correlation with comparable slope but with a normalization differing by \\sim 2.6 orders of magnitude has been found for local starbu...

Asmus, D; Smette, A; Hönig, S F; Duschl, W J

2011-01-01

222

ATLAS Phase II for the High Luminosity Upgrade  

CERN Document Server

After successful LHC operation at the center-of-mass energy of 7 and 8 TeV in 2011 and 2012, plans are actively advancing for a series of upgrades, culminating roughly 10 years from now in the high luminosity LHC (HL-LHC) project, delivering of order five times the LHC nominal instantaneous luminosity along with luminosity levelling. The final goal is to extend the data set from about few hundred fb-1 expected for LHC running to 3000 fb-1 by around 2030. Current planning in ATLAS also has significant upgrades to the detector during the consolidation of the LHC to reach full LHC energy and further upgrades to accommodate running already beyond nominal luminosity this decade. The challenge of coping with HL-LHC instantaneous and integrated luminosity, along with the associated radiation levels, requires further major changes to the ATLAS detector. The designs are developing rapidly for an all-new inner-tracker, significant upgrades in the calorimeter and muon systems, as well as improved triggers and data acqui...

Huffman, B T; The ATLAS collaboration

2013-01-01

223

The HerMES SPIRE submillimeter local luminosity function  

CERN Document Server

Local luminosity functions are fundamental benchmarks for high-redshift galaxy formation and evolution studies as well as for models describing these processes. Determining the local luminosity function in the submillimeter range can help to better constrain in particular the bolometric luminosity density in the local Universe, and Herschel offers the first opportunity to do so in an unbiased way by imaging large sky areas at several submillimeter wavelengths. We present the first Herschel measurement of the submillimeter 0luminosity function and infrared bolometric (8-1000 $\\mu$m) local luminosity density based on SPIRE data from the HerMES Herschel Key Program over 14.7 deg^2. Flux measurements in the three SPIRE channels at 250, 350 and 500 \\mum are combined with Spitzer photometry and archival data. We fit the observed optical-to-submillimeter spectral energy distribution of SPIRE sources and use the 1/V_{max} estimator to provide the first constraints on the monochromatic 250, 350 and ...

Vaccari, M; Franceschini, A; Altieri, B; Amblard, A; Arumugam, V; Auld, R; Aussel, H; Babbedge, T; Blain, A; Bock, J; Boselli, A; Buat, V; Burgarella, D; Castro-Rodriguez, N; Cava, A; Chanial, P; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dwek, E; Dye, S; Eales, S; Elbaz, D; Farrah, D; Fox, M; Gear, W; Glenn, J; Solares, E A Gonzalez; Griffin, M; Halpern, M; Hatziminaoglou, E; Huang, J; Ibar, E; Isaak, K; Ivison, R J; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Mortier, A M J; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Page, M J; Panuzzo, P; Papageorgiou, A; Pearson, C P; Perez-Fournon, I; Pohlen, M; Rawlings, J I; Raymond, G; Rigopoulou, D; Rizzo, D; Rodighiero, G; Roseboom, I G; Rowan-Robinson, M; Portal, M Sanchez; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Symeonidis, M; Trichas, M; Tugwell, K E; Valiante, E; Valtchanov, I; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

2010-01-01

224

Very high-luminosity infrared galaxies - are they very young?  

International Nuclear Information System (INIS)

It is proposed that most of the very high-luminosity IRAS galaxies, those which emit greater than or equal to 10 to the 12th solar luminosities nearly all in the far infrared out to 100 microns, are very young systems with ages less than or equal to 10 to the 9th years. The luminosity comes largely from stars with masses near 100 solar masses which evolve rapidly, ejecting much of their mass as elements heavier than hydrogen. The gas ejected condenses into dust in circumstellar shells. The prototype star in the Galaxy which shows all of these attributes is Eta Car. It is shown that total masses of order 10 to the 7th-10 to the 8th solar masses condensed into such stars can produce the observed luminosities, and that 10-100 generations of such stars will produce enough dust (about 10 to the 8th solar masses) to explain the observed infrared luminosities. If this hypothesis is correct the composition of gas and dust may well be highly anomalous, and there should be no old stars with ages about 10 to the 10th years present. Initial star formation is probably triggered by interactions with close companion galaxies. 40 references

225

Blue Stragglers in Low-Luminosity Star Clusters  

CERN Document Server

We examine the blue straggler populations of 13 low-luminosity (M_V_t >~ -6) globular clusters and 2 old open clusters. These clusters test blue straggler formation in environments intermediate between higher luminosity (and usually higher density) clusters and the Galactic field. The anti-correlation between the relative frequency of blue stragglers (F_BSS = N_BSS / N_HB) and cluster luminosity continues to the lowest luminosity clusters, which have frequencies meeting or exceeding that of field stars. In addition we find that the anti-correlation between straggler frequency and central density disappears for clusters with density less than about 300 L_V,sun pc^-3, although this appears to be an artifact of the correlation between cluster luminosity and central density. We argue on observational (wide, eccentric binaries containing blue stragglers in M67, and the existence of very bright stragglers in most of the clusters in our sample) and theoretical grounds that stellar collisions still produce a signific...

Sandquist, E L

2005-01-01

226

The critical accretion luminosity for magnetized neutron stars  

CERN Document Server

The accretion flow around X-ray pulsars with a strong magnetic field is funnelled by the field to relatively small regions close to the magnetic poles of the neutron star (NS), the hotspots. During strong outbursts regularly observed from some X-ray pulsars, the X-ray luminosity can be so high, that the emerging radiation is able to stop the accreting matter above the surface via radiation-dominated shock, and the accretion column begins to rise. This border luminosity is usually called the "critical luminosity". Here we calculate the critical luminosity as a function of the NS magnetic field strength $B$ using exact Compton scattering cross section in strong magnetic field. Influence of the resonant scattering and photon polarization is taken into account for the first time. We show that the critical luminosity is not a monotonic function of the B-field. It reaches a minimum of a few 10^{36} erg s^{-1} when the cyclotron energy is about 10 keV and a considerable amount of photons from a hotspot have energy c...

Mushtukov, Alexander A; Tsygankov, Sergey S; Poutanen, Juri

2014-01-01

227

A statistical study of the luminosity gap in galaxy groups  

CERN Document Server

The luminosity gap between the two brightest members of galaxy groups and clusters is thought to offer a strong test for the models of galaxy formation and evolution. This study focuses on the statistics of the luminosity gap in galaxy groups, in particular fossil groups, e.g. large luminosity gap, in an analogy with the same in a cosmological simulation. We use spectroscopic legacy data of seventh data release (DR7) of SDSS, to extract a volume limited sample of galaxy groups utilizing modified friends-of-friends (mFoF) algorithm. Attention is paid to galaxy groups with the brightest group galaxy (BGG) more luminous than \\Mr = -22. An initial sample of 620 groups in which 109 optical fossil groups, where the luminosity gap exceeds 2 magnitude, were identified. We compare the statistics of the luminosity gap in galaxy groups at low mass range from the SDSS with the same in the Millennium simulations where galaxies are modeled semi-analytically. We show that the BGGs residing in galaxy groups with large lumino...

Tavasoli, Saeed; Koohpaee, Ali; Rahmani, Hadi; Ghanbari, Jamshid

2010-01-01

228

An early separation scheme for the LHC luminosity upgrade  

CERN Document Server

The present document is organized in five chapters. In the first chapter the framework of the study is described, developing the motivations, the goals and the requirements for the LHC Luminosity Upgrade. We analyze the need for the crossing angle and its impact on the peak luminosity of the collider. After having introduced the Early Separation Scheme, we explain how it may overcome some limitations of the present machine. We compare the nominal LHC crossing scheme with the proposed one underlining its potential in terms of performance and its issues with respect to the integration in the detectors. An analysis of the integrated magnetic field required is given. In the second chapter we introduce one of the most powerful aspect of the scheme: the luminosity leveling. After the description of the physical model adopted, we compare the results of its analytical and numerical solutions. All the potential improvement due to the Early Separation Scheme are shown on the luminosity plane (peak luminosity versus int...

Sterbini, G

2010-01-01

229

An Early Separation Scheme for the LHC Luminosity Upgrade  

CERN Document Server

In this thesis we evaluate the potential of the Early Separation Scheme for the Luminosity Upgrade of the Large Hadron Collider (LHC). The main goal of the Early Separation Scheme is to reduce the crossing angle between the proton beams at the collision point in order to increase the luminosity performance of the machine and to alleviate, at the same time, the detrimental effects due to the electromagnetic interaction between the beams. The Early Separation Scheme consists of four dipoles for each of the two high luminosity Interaction Points of the LHC, corresponding to the ATLAS and CMS detectors. Two dipoles out of the four, the so-called D0 dipoles, have to be integrated in the experimental cavern. We show that, working in synergy with an increased beam current and with a stronger final focusing system, the Early Separation Scheme can provide an integrated luminosity of 3000 fb^(?1) over a period of 6.5 ? 7 years with a leveled luminosity of 5.5 10^34 cm^(?2) s^(?1). These figures are possible tha...

Sterbini, G; Rivkin, L

2009-01-01

230

The Luminosity Function of Galaxies in SDSS Commissioning Data  

CERN Document Server

During commissioning observations, the Sloan Digital Sky Survey (SDSS) has produced one of the largest existing galaxy redshift samples selected from CCD images. Using 11,275 galaxies complete to r^* = 17.6 over 140 square degrees, we compute the luminosity function of galaxies in the r^* band over a range -23 < M < -16 (for h=1). The result is well-described by a Schechter function with parameters phi_* = 0.0146 +/- 0.0012 h^3 Mpc^{-3}, M_* = -20.83 +/- 0.03, and alpha = -1.20 +/- 0.03. The implied luminosity density in r^* is j = (2.6 +/- 0.3) x 10^8 h L_sun Mpc^{-3}. The surface brightness selection threshold has a negligible impact for M < -18. We measure the luminosity function in the u^*, g^*, i^*, and z^* bands as well; the slope at low luminosities ranges from alpha=-1.35 to alpha=-1.2. We measure the bivariate distribution of r^* luminosity with half-light surface brightness, intrinsic color, and morphology. High surface brightness, red, highly concentrated galaxies are on average more lumin...

Blanton, M R; Eisenstein, D J; Loveday, J; Strauss, M A; Subba-Rao, M; Weinberg, D H; Anderson, J E; Annis, J; Bahcall, Neta A; Bernardi, M; Brinkmann, J; Brunner, R J; Burles, S M; Carey, L D; Castander, F J; Connolly, A J; Csabai, I; Doi, M; Finkbeiner, D; Friedman, S; Frieman, Joshua A; Fukugita, M; Gunn, J E; Hennessy, G S; Hindsley, R B; Ichikawa, T; Ivezic, Z; Kent, S; Knapp, G R; Lamb, D Q; French-Leger, R; Long, D C; Lupton, R H; McKay, T A; Meiksin, A; Merelli, A; Munn, J A; Narayanan, V K; Newcomb, M; Nichol, R C; Okamura, S; Owen, R; Pier, J R; Pope, A C; Postman, M; Quinn, M; Rockosi, C M; Schlegel, D J; Schneider, D P; Shimasaku, K; Siegmund, W A; Smee, S; Snir, Y; Stoughton, C; Stubbs, C; Szalay, A S; Szokoly, G P; Thakar, A R; Tremonti, C A; Tucker, D L; Uomoto, A; Vanden Berk, Daniel E; Vogeley, M S; Waddell, P; Yanny, B; Yasuda, N; York, D G

2001-01-01

231

Performance evaluation and optimization of the luminosity detector ALFA  

CERN Document Server

The startup of the LHC (Large Hadron Collider) has initialized a new era in particle physics. The standard model of particle physics has for the last 40 years with tremendous success described all measurements with phenomenal precision. The experiments at the LHC will test the standard model in a new energy regime. To normalize the measurements and understand the potential discoveries of the LHC experiments it is often crucial to know the interaction rate - the absolute luminosity. The ATLAS (A Toroidal LHC ApparatuS) detector will measure luminosity by numerous methods. But for most of the methods only the relative luminosity is measured with good precision. The absolute scale has to be provided from elsewhere. Therefore ATLAS plans to measure the flux of protons scattered under very small angles as this flux relates directly and with good precision to the absolute luminosity. This will be done by the ALFA (Absolute Luminosity For ATLAS) detector. The detectors will be positioned about 240 m from the interac...

Jakobsen, Sune; Grafström, P; Joram, C

2010-01-01

232

LHCb: LHCb Muon System Performance at High Luminosity  

CERN Multimedia

The LHCb detector was conceived to operate with an average Luminosity of $2 \\times 10^{32}$ cm$^{-2}$ s$^{-1}$. During the last year of LHC run, the whole apparatus has shown to be able to perfectly acquire and manage data produced at a Luminosity as high as $4 \\times 10^{32}$ cm$^{-2}$ s$^{-1}$. In these conditions, all sub-detectors operated at average particle rates higher than the design ones and in particular the Multi-Wire Proportional Chambers equipping the Muon System had to sustain a particle rate as high as 250 kHz/cm$^{2}$. In order to study the possibility of increasing the Luminosity of operation of the whole experiment several tests were performed. The effective beam Luminosity at the interaction point of LHCb was increased in several steps up to $10^{33}$ cm$^{-2}$ s$^{-1}$ and in each step the behavior of all the detectors in the Muon System was recorded. The data analysis has allowed to study the performance of the Muon System as a function of the LHC Luminosity and the results are r...

Pinci, D

2013-01-01

233

ATLAS Future Plans: Upgrade and the Physics with High Luminosity  

Directory of Open Access Journals (Sweden)

Full Text Available The ATLAS experiment is planning a series of detector upgrades to cope with the planned increases in instantaneous luminosity and multiple interactions per crossing to maintain its physics capabilities. During the coming decade, the Large Hadron Collider will collide protons on protons at a center of mass energy up to 14 TeV with luminosities steadily increasing in a phased approach to over 5 × 1034 cm?2s?1. The resulting large data sets will significantly enhance the physics reach of the ATLAS detector building on the recent discovery of the Higgs-like boson. The planned detector upgrades being designed to cope with the increasing luminosity and its impact on the ATLAS physics program will be discussed.

Rajagopalan S.

2013-05-01

234

The global luminosity function of the Fornax dwarf elliptical galaxy  

Science.gov (United States)

The global luminosity function for the Fornax dwarf elliptical galaxy has been determined from UK Schmidt plates in B and V. The functions do not extend below the horizontal-branch (HB) peak, and thus provide information on only the bright giants. Both functions show evidence of structure in the giant branch. Comparisons are made with luminosity functions (LFs) of globular clusters covering a range in metallicity similar to that found in the Fornax system. These comparisons indicate the old population of Fornax is similar to that of such moderately metal-poor clusters as M5 and M13. They also demonstrate vividly the existence of a significant excess population of very bright stars over that seen in pure old systems. Comparisons are also made with theoretical luminosity functions of various ages and helium abundances.

Eskridge, Paul B.

1987-12-01

235

An Early Beam Separation Scheme for the LHC Luminosity Upgrade  

CERN Document Server

The high nominal luminosity of the LHC requires a large number of bunches spaced by about 7.5 m. To prevent more than one head-on collision in each interaction region, a crossing angle of 0.285 mrad is necessary. A side effect of this crossing angle is the increase of the effective transverse beam cross-section, thereby decreasing the luminosity by some 16%. For the LHC luminosity upgrade, depending on the focusing scenarios, this loss significantly increases and largely offsets the potential gain of a stronger focusing. In this paper we analyze a strategy to circumvent this difficulty, based on an early beam separation using small dipoles placed at a few meters from the interaction point. From the beam dynamics point of view, the essential constraint is to control the long-range beamâ??beam interactions in a scenario where the normalized beam separation is not constant.

Koutchouk, Jean-Pierre

2006-01-01

236

Cosmicflows-2: I-band Luminosity - HI Linewidth Calibration  

CERN Document Server

In order to measure distances with minimal systematics using the correlation between galaxy luminosities and rotation rates it is necessary to adhere to a strict and tested recipe. We now derive a measure of rotation from a new characterization of the width of a neutral Hydrogen line profile. Additionally, new photometry and zero point calibration data are available. Particularly the introduction of a new linewidth parameter necessitates the reconstruction and absolute calibration of the luminosity-linewidth template. The slope of the new template is set by 267 galaxies in 13 clusters. The zero point is set by 36 galaxies with Cepheid or Tip of the Red Giant Branch distances. Tentatively, we determine H0 = 75 km s-1 Mpc-1. Distances determined using the luminosity-linewidth calibration will contribute to the distance compendium Cosmicflows-2.

Tully, R Brent

2012-01-01

237

High luminosity ?+ ?- collider: Report of a feasibility study  

International Nuclear Information System (INIS)

Parameters are given of 4 TeV and 0.5 TeV (c-of-m) high luminosity ?+?- colliders, and of a 0.5 TeV lower luminosity demonstration machine. We discuss the various systems in such muon colliders, starting from the proton accelerator needed to generate the muons and proceeding through muon cooling, acceleration and storage in a collider ring. Detector background, polarization, and nonstandard operating conditions are analyzed. Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadron and electron machines. They should thus be regarded as complementary. We briefly mention the luminosity requirements of hadrons and lepton machines and their high-energy-physics advantages and disadvantages in reference to their effective center of mass energy. Finally, we present an R ampersand D plan to determine whether such machines are practical

238

Physics potential of ATLAS detector with high luminosity  

CERN Document Server

The ATLAS experiment is designed to exploit the full physics discovery potential in the TeV energy region opened up by the Large Hadron Collider at a center of mass energy of 14 TeV with very high luminosities ($10^{34}-10^{35} \\ cm^{-2} s^{-1}$). We present some examples of ATLAS physics reach at the LHC based on the detail simulations of the ATLAS detector's response for a selection of electroweak, extra-dimension, and new strong force physics processes. The examples were chosen to demonstrate the great discovery potential of the ATLAS experiment at high and very high luminosities, as well as for their intrinsic physics interest. We also present that the high luminosities of the LHC will allow to perform high precision measurements with the ATLAS experiment to search for deviations from the predictions of the Standard Model which signal its breakdown.

Zhou Bing

2004-01-01

239

Luminosity Coincident with Initial Breakdown Pulses in Lightning  

Science.gov (United States)

Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG-type (12 cases) or IC-type (3 cases) IB pulse in fast electric field change records. Some of these IB pulses have a coincident VLF/LF (LINET) or a VHF (LDAR2) radiation source. The luminosity bursts of 14 CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, streamer-type linear segments visibly advance away from the first light burst for 55-200 ?s, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4 to 18 x 10^5 m/s over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 ?s before the luminosity fades in about 100 ?s, then this sequence may repeat several times. In several of the flashes a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development. In this presentation we will show examples of the IB luminosity and coincident electromagnetic data.

Stolzenburg, M.; Marshall, T.; Karunarathne, S.; Karunarathna, N.; Vickers, L.; Warner, T. A.; Orville, R. E.; Betz, H.

2012-12-01

240

A Deep Multicolor Survey; 5, The M Dwarf Luminosity Function  

CERN Document Server

We present a study of M dwarfs discovered in a large area, multicolor survey. We employ a combination of morphological and color criteria to select M dwarfs to a limiting magnitude in V of 22, the deepest such ground-based survey for M dwarfs to date. We solve for the vertical disk stellar density law and use the resulting parameters to derive the M dwarf luminosity and mass functions from this sample. We find the stellar luminosity function peaks at M_V = 12 and declines thereafter. Our derived mass function for stars with M M > 0.1 M_sun.

Martini, P; Martini, Paul; Osmer, Patrick S.

1998-01-01

241

A Deep Multicolor Survey V: The M Dwarf Luminosity Function  

OpenAIRE

We present a study of M dwarfs discovered in a large area, multicolor survey. We employ a combination of morphological and color criteria to select M dwarfs to a limiting magnitude in V of 22, the deepest such ground-based survey for M dwarfs to date. We solve for the vertical disk stellar density law and use the resulting parameters to derive the M dwarf luminosity and mass functions from this sample. We find the stellar luminosity function peaks at M_V = 12 and declines th...

Martini, Paul; Osmer, Patrick S.

1998-01-01

242

The x-ray luminosity-redshift relationship of quasars  

Science.gov (United States)

Chronometric cosmology provides an excellent fit for the phenomenological x-ray luminosity-redshift relationship for 49 quasars observed by the Einstein satellite. Analysis of the data on the basis of the Friedmann cosmology leads to a correlation of absolute x-ray luminosity with redshift of >0.8, which is increased to ?1 in the bright envelope. Although the trend might be ascribed a priori to an observational magnitude bias, it persists after nonparametric, maximum-likelihood removal of this bias. PMID:16592826

Segal, I. E.; Segal, W.

1980-01-01

243

The Relation Between the Globular Cluster Mass and Luminosity Functions  

OpenAIRE

The relation between the globular cluster luminosity function (GCLF, dN/d log L) and globular cluster mass function (GCMF, dN/d logM) is considered. Due to low-mass star depletion, dissolving GCs have mass-to-light (M/L) ratios that are lower than expected from their metallicities. This has been shown to lead to an M/L ratio that increases with GC mass and luminosity. We model the GCLF and GCMF and show that the power law slopes inherently differ (1.0 versus 0.7, respectivel...

Kruijssen, J. M. D.; Portegies Zwart, S. F.

2009-01-01

244

On the Interpretation of the Globular Cluster Luminosity Function  

OpenAIRE

The conversion of the globular cluster luminosity function (GCLF, dN/dlogL) to the globular cluster mass function (GCMF, dN/dlogM) is addressed. Dissolving globular clusters (GCs) become preferentially depleted in low-mass stars, which have a high mass-to-light ratio. This has been shown to result in a mass-to-light ratio (M/L) that increases with GC luminosity or mass, because more massive GCs have lost a smaller fraction of their stars than low-mass GCs. Using GC models, w...

Kruijssen, J. M. Diederik; Zwart, Simon F. Portegies

2009-01-01

245

LUCID, the Luminosity Monitor for ATLAS - A Status Report  

CERN Document Server

In addition to the main ATLAS detector, three smaller systems are being built to provide good coverage in the very forward region . These are closely connected to the luminosity determination in ATLAS, but are also foreseen to study forward physics. If ordered according to their distance from the ATLAS interaction point, the first system is LUCID the main luminosity monitor of ATLAS located at a distance of 17 m from the interaction point. This detector is now nearing the end of construction at CERN. The LUCID detector and its status with regards to construction, testing and installation are described in this document.

Pinfold, James

2008-01-01

246

The Nuclear Infrared Emission of Low-Luminosity AGN  

CERN Document Server

We have obtained high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs) and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGN; L_bol < 5 x 10^42 erg/s). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGN, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGN have not yet been well-determined. In these proceedings we summarise the results for the LLAGN at the relatively high-luminosity, high-Eddington ratio end of the sample. Strong, compact nuclear sources are visible in the MIR images of these objects, with luminosities consistent with or slightly in execss of that predicted by the standard MIR/X-ray relation. Their broadband nuclear SEDs are diverse; some resemble typical Seyfert nuclei, while others possess less of a well-defined...

Mason, R E; Packham, C; Alonso-Herrero, A; Levenson, N A; Radomski, J; Almeida, C Ramos; Colina, L; Elitzur, M; Aretxaga, I; Roche, P F; Oi, N

2012-01-01

247

Workshop on Physics at the High-Luminosity LHC  

CERN Document Server

Workshop dedicated to the proton-proton physics programme of the High-Luminosity phase of the LHC. The meeting will be driven by dedicated talks, followed by ample time for discussion. It will provide a dedicated open forum, to continue and expand the work initiated during the Aix-les-Bains ECFA 2013 and 2014 HL-LHC workshops.

2015-01-01

248

TOTAL INFRARED LUMINOSITY ESTIMATION OF RESOLVED AND UNRESOLVED GALAXIES  

International Nuclear Information System (INIS)

The total infrared (TIR) luminosity from galaxies can be used to examine both star formation and dust physics. We provide here new relations to estimate the TIR luminosity from various Spitzer bands, in particular from the 8 ?m and 24 ?m bands. To do so, we use data for 45'' subregions within a subsample of nearby face-on spiral galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) that have known oxygen abundances as well as integrated galaxy data from the SINGS, the Local Volume Legacy survey (LVL), and Engelbracht et al. samples. Taking into account the oxygen abundances of the subregions, the star formation rate intensity, and the relative emission of the polycyclic aromatic hydrocarbons at 8 ?m, the warm dust at 24 ?m, and the cold dust at 70 ?m and 160 ?m, we derive new relations to estimate the TIR luminosity from just one or two of the Spitzer bands. We also show that the metallicity and the star formation intensity must be taken into account when estimating the TIR luminosity from two wave bands, especially when data longward of 24 ?m are not available.

249

Accretion disk coronae in high-luminosity systems  

Science.gov (United States)

We present the results of self-consistent models of Compton-heated accretion disk coronae. The models are calculated using a new method for computing monochromatic radiative transfer n two dimensions. The method splits the radiation into direct and scattered components. The direct radiation is computed by calculating the optical depth along rays, while transfer of the scattered radiation is approximated by flux-limited diffusion. The resulting code agrees with more accurate treatments to within 50%, and is highly efficient, making it practical for use in large hydrodynamic simulations. The coronal models are used to confirm the results of earlier work, and to extend it to higher luminosities. In contrast to earlier work, which found the outer disks to be shadowed by the inner corona at high luminosities, we find our results to form an almost continuous extension of the models at lower luminosities. This is due to the presence of multiply scattered radiation, which acts to partially offset the loss of direct radiation from the central source. Although the analytic methods derived at lower luminosities cannot be used to derive the coronal structure for L/L(sub Edd) approx. greater than 0.1, the results of the models are amenable to semiempirical fits. We also discuss possible observational consequences of the results for coronal veiling and line fluorescence from the disk.

Murray, Stephen D.; Castor, John I.; Klein, Richard I.; Mckee, Christopher F.

1994-01-01

250

Attaining high luminosity in linear e+e- colliders  

International Nuclear Information System (INIS)

The attainment of high luminosity in linear colliders is a complex problem because of the interdependence of the critical parameters. For instance, changing the number of particles per bunch affects the damping ring design and thus the emittance; it affects the wakefields in the linac and thus the momentum spread; the momentum spread affects the final focus design and thus the final ?*; but the emittance change also affects the final focus design; and all these come together to determine the luminosity, disruption and beamstrahlung at the intersection. Changing the bunch length, or almost any other parameter, has a similar chain reaction. Dealing with this problem by simple scaling laws is very difficult because one does not know which parameter is going to be critical, and thus which should be held constant. One can only maximize the luminosity by a process of search and iteration. The process can be facilitated with the aid of a computer program. Examples can then be optimized for maximum luminosity, and compared to the optimized solutions with different approaches. This paper discusses these approaches

251

Direct Oxygen Abundances for Low Luminosity LVL Galaxies  

CERN Document Server

We present MMT spectroscopic observations of HII regions in 42 low luminosity galaxies in the LVL. For 31 galaxies, we measured the temperature sensitive [O III] line at a strength of 4 sigma or greater, and thus determine direct oxygen abundances. Our results provide the first direct estimates of oxygen abundance for 19 galaxies. Oxygen abundances were compared to B-band and 4.5 micron luminosities and stellar masses in order to characterize the luminosity-metallicity (L-Z) and mass-metallicity (M-Z) relationships at low-luminosity. We present and analyze a "Combined Select" sample composed of 38 objects (drawn from our parent sample and the literature) with direct oxygen abundances and reliable distance determinations (TRGB or Ceph). Consistent with previous studies, the B-band and 4.5 micron L-Z relationships were found to be 12+log(O/H)=(6.27+/-0.21)+(-0.11+/-0.01)M_B and 12+log(O/H)=(6.10+/-0.21)+(-0.10+/-0.01)M_[4.5] (sigma=0.15 and 0.14). For this sample, we derive a M-Z relationship of 12+log(O/H)=(5....

Berg, Danielle A; Marble, Andrew R; van Zee, Liese; Engelbracht, Charles W; Lee, Janice C; Kennicutt, Robert C; Jr.,; Calzetti, Daniela; Dale, Daniel A; Johnson, Benjamin D

2012-01-01

252

A new record peak luminosity for the LHC  

CERN Multimedia

Two weeks of dedicated machine development paid off last weekend when the LHC ran for physics with three nominal intensity (?1011 protons) bunches in each beam.   This brought a new record peak luminosity of around 8×1029 cm-2 s-1, and allowed the LHC to double the integrated luminosity delivered to the experiments since 30 March from 16 to 32 inverse nanobarns over the weekend. After a few more fills in this configuration, the number of bunches will be raised to six per beam, which will in turn allow the peak luminosity to break the 1030 cm-2 s-1 barrier for the first time, well on the way to achieving the 2010 objective of 1032 cm-2 s-1. This peak luminosity goal requires 800 nominal bunches per beam squeezed to a beta of 3.5 metres. The plan for 2011 is to run the LHC in this configuration over about 10 months, thus achieving the objective of recording one inverse femtobarn of data in total. The machine development period also allowed the TOTEM detectors to be set up with 45...

CERN Bulletin

2010-01-01

253

A Single Bremsstrahlung Monitor to Measure Luminosity at LEP  

CERN Multimedia

The luminosity, the beam divergence and the longitudinal polarization can be measured at an interaction point of LEP by dectecting the energy, the angular distribution and the circular polarization of the single bremsstrahlung photons (SB) emitted at very forward angle. The luminosity can be measured by this met than by the conventional method of detecting small angle Bhabha scattering. The bunch to bunch relative luminosity can be monitored at a few per mil level in few minutes. Absolute values of the luminosity and of the polarization can be measured with a precision of the order of 1\\%. \\\\ \\\\ The apparatus to detect SB photons consists of a low Z absorber and of an EM calorimeter made of lead and scintillating fibres. Both the total energy and the space distribution of the SB photons are measured. This apparatus has been designed and built at the Department of Physics and INFN Section of the University of Rome ``La Sapienza''. Later on, together with suitable monocrystal converters, it may be used also for...

2002-01-01

254

The Luminosity Function and Mass Function in the Galactic Bulge  

CERN Document Server

We present deep photometry obtained with the Hubble Space Telescope (HST) in a field in Baade's Window in the Galactic bulge. We derive a luminosity function down to I ~ 24.3, or V ~ 27.5, corresponding to M ~ 0.3 Msun. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We derive a mass function using both an empirical local mass-luminosity relation and a mass-luminosity relation from recent stellar model calculations, allowing for the presence of binaries and photometric errors. The mass function has a power law form with dN/dM proportional to M^{-2.2} for M >~ 0.7 Msun. However, we find strong evidence for a break in the mass function slope around 0.5-0.7 Msun, with a significantly shallower slope at lower masses. The value of the slope for the low masses depends on the assumed binary fraction and the accuracy of our completeness correction. This mass function should directly reflect the initial mass function.

Holtzmann, J A; Baum, W A; Grillmair, C J; Groth, E J; Light, R M; Lynds, R; O'Neil, E J; Holtzman, Jon A.; Watson, Alan M.; Baum, William A.; Grillmair, Carl J.; Groth, Edward J.; Light, Robert M.; Lynds, Roger; Neil, Earl J. O'

1998-01-01

255

Her X-1: the positive cyclotron line energy / luminosity correlation  

CERN Document Server

Studies of some bright, super-Eddington transient pulsars show a negative correlation between the energy of the cyclotron resonance scattering feature (CRSF) and the bolometric luminosity. For Her X-1, using repeated RXTE observations during 1996-2005, the inverse dependence was found: the energy of the cyclotron line increases as the luminosity increases. The X-ray flux measured by the RXTE/ASM (2-10 keV) has been assumed to represent the luminosity - more precisely: the maximum X-ray flux reached during the respective 35 d Main-On. Here, we question whether the ASM flux is really an accurate measure of the bolometric luminosity of the source. We redetermined the energy of the cyclotron line and performed spectral fits using the combined data from the PCA (3.5-60 keV) and HEXTE (20-75 keV) instruments on RXTE of the same 35 d cycles as used in the original work to determine the bolometric flux from those spectra. We confirm the result of the original analysis that the cyclotron line energy changes by ~7% for...

Vasco, D; Staubert, R

2011-01-01

256

Review of mini beta luminosities in PETRA at different energies  

International Nuclear Information System (INIS)

The mini beta operation with PETRA started in March 1981. Since that time many data were taken at 17, 11 and 7 GeV. The maximum luminosities, tune shifts, limitations etc. are summarized and compared in this note. (orig./HSI)

257

Luminosity Function of Faint Globular Clusters in M87  

International Nuclear Information System (INIS)

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit Hubble Space Telescope (HST) WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rate of mass loss is consistent with standard evaporation models, and not with the much higher rates proposed by some recent studies of very young cluster systems. We also find that the mass-size relation has very little slope, indicating that there is almost no increase in the size of a cluster with increasing mass

258

Luminosity Function of Faint Globular Clusters in M87  

Energy Technology Data Exchange (ETDEWEB)

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit Hubble Space Telescope (HST) WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rate of mass loss is consistent with standard evaporation models, and not with the much higher rates proposed by some recent studies of very young cluster systems. We also find that the mass-size relation has very little slope, indicating that there is almost no increase in the size of a cluster with increasing mass.

Waters, Christopher Z.; Zepf, Stephen E.; /Michigan State U.; Lauer, Tod R.; /NOAO, Tucson; Baltz, Edward A.; /KIPAC, Menlo Park; Silk, Joseph; /Oxford U.

2006-07-14

259

Luminosity Function of Faint Globular Clusters in M87  

CERN Document Server

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit \\textit{Hubble Space Telescope (HST)} WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rat...

Waters, C Z; Lauer, T R; Baltz, E A; Silk, J; Waters, Christopher Z.; Zepf, Stephen E.; Lauer, Tod R.; Baltz, Edward A.; Silk, Joseph

2006-01-01

260

Luminosity Tuning Bumps in the CLIC Main Linac  

CERN Document Server

Preservation of beam emittance in the CLIC main linac is a challenging task. This requires not only beam-based alignment of the beam line components but also the use of emittance tuning bumps. In this paper the potential use of luminosity tuning bumps is explored and compared to emittance tuning bumps.

Eliasson, Peder

2005-01-01

261

AGN BLR structure, luminosity and mass from combined reverberation mapping and optical interferometry observations  

Science.gov (United States)

Unveiling the structure of the Broad-Line Region (BLR) of AGN is critical to understand the quasar phenomenon. Detail study of the geometry and kinematic of these objects can answer the basic questions about the central BH mass, accretion mechanism and rate, growth and evolution history. Observing the response of the BLR clouds to continuum variations, Reverberation Mapping (RM) provides size-luminosity and mass-luminosity relations for QSOs and Sy1 AGNs with the goal to use these objects as standard candles and mass tags. However, the RM size can receive different interpretations depending on the assumed geometry and the corresponding mass depends on an unknown geometrical factor as well on the possible confusion between local and global velocity dispersion. From RM alone, the scatter around the mean mass is as large as a factor 3. Though BLRs are expected to be much smaller than the current spatial resolution of large optical interferometers (OI), we show that differential interferometry with AMBER, GRAVITY and successors can measure the size and constrain the geometry and kinematics on a large sample of QSOs and Sy1 AGNs. AMBER and GRAVITY (K_ 10:5) could be easily extended up to K= 13 by an external coherencer or by advanced "ncoherent" data processing. Future VLTI instrument could reach K~ 15. This opens a large AGN BLR program intended to obtain a very accurate calibration of mass, luminosity and distance measurements from RM data which will allow using many QSOs as standard candles and mass tags to study the general evolution of mass accretion in the Universe. This program is analyzed with our BLR model allowing predicting and interpreting RM and OI measures together and illustrated with the results of our observations of 3C273 with the VLTI.

Rakshit, Suvendu; Petrov, Romain G.

2014-07-01

262

Precision luminosity measurement at LHCb with beam-gas imaging  

International Nuclear Information System (INIS)

The luminosity is the physical quantity which relates the cross-section to the production rate in collider experiments. The cross-section being the particle physics observable of interest, a precise determination of the luminosity is required. This work presents the absolute luminosity calibration results performed at the Large Hadron Collider beauty (LHCb) experiment at CERN using a novel method based on beam-gas interactions with data acquired at a center of mass energy ?(s)=8 TeV and ?(s)=2.76 TeV. Reconstructed beam-gas interaction vertices in LHCb are used to measure the beam profiles, thus making it possible to determine the beams overlap integral. An important element of this work was to install and use a neon gas injection system to increase the beam-gas interaction rate. The precision reached with the beam-gas imaging method relies on the two-dimensional beam shape determination developed in this work. For such precision, the interaction vertex resolution is an important ingredient. Therefore, a new method has been developed using all reconstructed vertices in order to improve the understanding of the vertex resolution. In addition to the overlap integral, the knowledge of the colliding bunch populations is required to measure the luminosity. The determination of the bunch populations relies on LHC instruments to measure the bunch population fractions and the total beam intensity. Studies performed as part of this work resulted in a reduction of the bunch current normalization uncertainty from ±2.7% to ±0.2% and making it possible to achieve precision luminosity measurements at all LHC experiments. Furthermore, information on beam-gas interactions not originating from nominally filled bunches was analyzed to determine the charge fraction not participating in bunch collisions. The knowledge of this fraction is required to correct the total beam intensity. The reference cross-section of pp interactions with at least two tracks in the vertex detector was measured with the beam-gas imaging method. The result is ?Track=60.6±0.9 mb at a center-of-mass energy of ?(s)=8 TeV. The same measurement performed at ?(s)=2.76 TeV results in a cross-section of ?Track=52.7±1.2 mb. The luminosity measurement at ?(s)=8 TeV presented here, with an uncertainty of 1.4%, is to date the most precise luminosity calibration performed at the LHC and at any other bunched-beam proton collider.

263

DIRECT OXYGEN ABUNDANCES FOR LOW-LUMINOSITY LVL GALAXIES  

International Nuclear Information System (INIS)

We present MMT spectroscopic observations of H II regions in 42 low luminosity galaxies in the Spitzer Local Volume Legacy survey. For 31 of the 42 galaxies in our sample, we were able to measure the temperature sensitive [O III] ?4363 line at a strength of 4? or greater, and thus determine oxygen abundances using the 'direct' method. Our results provide the first 'direct' estimates of oxygen abundance for 19 of these galaxies. 'Direct' oxygen abundances were compared to B-band luminosities, 4.5 ?m luminosities, and stellar masses in order to characterize the luminosity-metallicity and mass-metallicity relationships at low luminosity. We present and analyze a 'Combined Select' sample composed of 38 objects (drawn from a sub-set of our parent sample and the literature) with 'direct' oxygen abundances and reliable distance determinations (based on the tip of the red giant branch or Cepheid variables). Consistent with previous studies, the B band and 4.5 ?m luminosity-metallicity relationships for the 38 objects were found to be 12 + log(O/H) = (6.27 ± 0.21) + (– 0.11 ± 0.01)MB and 12 + log(O/H) = (6.10 ± 0.21) + (– 0.10 ± 0.01)M[4.5] with dispersions of ? = 0.15 and 0.14, respectively. The slopes of the optical and near-IR L-Z relationships have been reported to be different for galaxies with luminosities greater than that of the LMC. However, the similarity of the slopes of the optical and near-IR L-Z relationships for our sample probtionships for our sample probably reflects little influence by dust extinction in the low luminosity galaxies. For this sample, we derive a mass-metallicity relationship of 12 + log(O/H) = (5.61 ± 0.24) + (0.29 ± 0.03)log (M*), which agrees with previous studies; however, the dispersion (? = 0.15) is not significantly lower than that of the L-Z relationships. Because of the low dispersions in these relationships, if an accurate distance is available, the luminosity of a low luminosity galaxy is often a better indicator of metallicity than that derived using certain 'strong-line' methods, so significant departures from the L-Z relationships may indicate that caution is prudent in such cases. With these new 'direct' metallicities we also revisit the 70/160 ?m color metallicity relationship. Additionally, we examine N/O abundance trends with respect to oxygen abundance and B – V color. We find a positive correlation between N/O ratio and B – V color for 0.05 ?< B – V ?< 0.75: log (N/O) = (1.18 ± 0.9) × (B – V) + (– 1.92 ± 0.08), with a dispersion of ? = 0.14, which is in agreement with previous studies.

264

DIRECT OXYGEN ABUNDANCES FOR LOW-LUMINOSITY LVL GALAXIES  

Energy Technology Data Exchange (ETDEWEB)

We present MMT spectroscopic observations of H II regions in 42 low luminosity galaxies in the Spitzer Local Volume Legacy survey. For 31 of the 42 galaxies in our sample, we were able to measure the temperature sensitive [O III] {lambda}4363 line at a strength of 4{sigma} or greater, and thus determine oxygen abundances using the 'direct' method. Our results provide the first 'direct' estimates of oxygen abundance for 19 of these galaxies. 'Direct' oxygen abundances were compared to B-band luminosities, 4.5 {mu}m luminosities, and stellar masses in order to characterize the luminosity-metallicity and mass-metallicity relationships at low luminosity. We present and analyze a 'Combined Select' sample composed of 38 objects (drawn from a sub-set of our parent sample and the literature) with 'direct' oxygen abundances and reliable distance determinations (based on the tip of the red giant branch or Cepheid variables). Consistent with previous studies, the B band and 4.5 {mu}m luminosity-metallicity relationships for the 38 objects were found to be 12 + log(O/H) = (6.27 {+-} 0.21) + (- 0.11 {+-} 0.01)M{sub B} and 12 + log(O/H) = (6.10 {+-} 0.21) + (- 0.10 {+-} 0.01)M{sub [4.5]} with dispersions of {sigma} = 0.15 and 0.14, respectively. The slopes of the optical and near-IR L-Z relationships have been reported to be different for galaxies with luminosities greater than that of the LMC. However, the similarity of the slopes of the optical and near-IR L-Z relationships for our sample probably reflects little influence by dust extinction in the low luminosity galaxies. For this sample, we derive a mass-metallicity relationship of 12 + log(O/H) = (5.61 {+-} 0.24) + (0.29 {+-} 0.03)log (M{sub *}), which agrees with previous studies; however, the dispersion ({sigma} = 0.15) is not significantly lower than that of the L-Z relationships. Because of the low dispersions in these relationships, if an accurate distance is available, the luminosity of a low luminosity galaxy is often a better indicator of metallicity than that derived using certain 'strong-line' methods, so significant departures from the L-Z relationships may indicate that caution is prudent in such cases. With these new 'direct' metallicities we also revisit the 70/160 {mu}m color metallicity relationship. Additionally, we examine N/O abundance trends with respect to oxygen abundance and B - V color. We find a positive correlation between N/O ratio and B - V color for 0.05 {approx}< B - V {approx}< 0.75: log (N/O) = (1.18 {+-} 0.9) Multiplication-Sign (B - V) + (- 1.92 {+-} 0.08), with a dispersion of {sigma} = 0.14, which is in agreement with previous studies.

Berg, Danielle A.; Skillman, Evan D. [Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Marble, Andrew R.; Engelbracht, Charles W. [Steward Observatory, University of Arizona, 933 N Cherry Ave., Tucson, AZ 85721 (United States); Van Zee, Liese [Astronomy Department, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States); Lee, Janice C. [STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Kennicutt, Robert C. Jr. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Calzetti, Daniela [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Dale, Daniel A. [Department of Physics and Astronomy, University of Wyoming, 1000 E. University, Laramie, WY 82071 (United States); Johnson, Benjamin D., E-mail: berg@astro.umn.edu, E-mail: skillman@astro.umn.edu, E-mail: cengelbracht@as.arizona.edu, E-mail: amarble@nso.edu, E-mail: vanzee@astro.indiana.edu, E-mail: jlee@stsci.edu, E-mail: calzetti@astro.umass.edu, E-mail: ddale@uwyo.edu, E-mail: johnson@iap.fr [Institut d' Astrophysique de Paris, UMR 7095, 98 bis Bvd Arago, 75014 Paris (France)

2012-08-01

265

Mid-infrared properties of nearby low-luminosity AGN at high angular resolution  

Science.gov (United States)

We present high spatial resolution mid-infrared (MIR) 12 ?m continuum imaging of low-luminosity active galactic nuclei (LLAGN) obtained with VLT/VISIR. Our goal is to determine whether the nuclear MIR emission of LLAGN is consistent with the existence of a dusty obscuring torus, the key component of the unification model for AGN. Based on available hard X-ray luminosities and the previously known tight correlation between the hard X-ray and 12 ?m luminosities, we selected a sample of 17 nearby LLAGN without available VISIR N-band photometry. Combined with archival VISIR data of 9 additional LLAGN with available X-ray measurements, the dataset represents the bulk of southern LLAGN currently detectable from the ground in the MIR. Of the 17 observed LLAGN, 7 are detected, while upper limits are derived for the 10 non-detections. This increases the total number of AGN detected with VLT/VISIR to more than 50. All detections except NGC 3125 appear point-like on a spatial scale of ~0.35?. The detections do not significantly deviate from the known MIR-X-ray correlation but exceed it by a factor of ~10 down to luminosities VISIR data with lower spatial resolution data from Spitzer/IRS and IRAS. By using a scaled starburst template spectral energy distribution and the polycyclic aromatic hydrocarbon (PAH) 11.3 ?m emission line, we were able to restrict the maximum nuclear star-formation contamination of the VISIR photometry to ?30% for 75% of the LLAGN. Exceptions are NGC 1097 and NGC 1566, which may possess unresolved strong PAH emission. Furthermore, the MIR-X-ray luminosity ratio is unchanged over more than 4 orders of magnitude in accretion rate within the uncertainties. These results are consistent with the existence of the dusty torus in all observed LLAGN, although a jet or accretion disk as origin of the MIR emission cannot be excluded. Finally, because the MIR-X-ray correlation holds for all LLAGN and Seyferts, this is a very useful empirical tool for converting between the MIR and X-ray powers of these nuclei. Based the ESO observing programs 083.B-0536 and 086.B-0349.Appendices are available in electronic form at http://www.aanda.org

Asmus, D.; Gandhi, P.; Smette, A.; Hönig, S. F.; Duschl, W. J.

2011-12-01

266

CONTRIBUTION OF THE ACCRETION DISK, HOT CORONA, AND OBSCURING TORUS TO THE LUMINOSITY OF SEYFERT GALAXIES: INTEGRAL AND SPITZER OBSERVATIONS  

Energy Technology Data Exchange (ETDEWEB)

We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal-to-noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L{sub 15{mu}m}{proportional_to}L{sup 0.74{+-}0.06}{sub HX}. Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, L{sub Disk}, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, L{sub Corona}, with the L{sub Disk}/L{sub Corona} ratio varying by a factor of 2.1 around a mean value of 1.6. This ratio is a factor of {approx}2 smaller than for typical quasars producing the cosmic X-ray background. Therefore, over three orders of magnitude in luminosity, HX radiation carries a large, and roughly comparable, fraction of the bolometric output of AGNs. We estimate the cumulative bolometric luminosity density of local AGNs at {approx}(1-3) Multiplication-Sign 10{sup 40} erg s{sup -1} Mpc{sup -3}. Finally, the Compton temperature ranges between kT{sub c} Almost-Equal-To 2 and Almost-Equal-To 6 keV for nearby AGNs, compared to kT{sub c} Almost-Equal-To 2 keV for typical quasars, confirming that radiative heating of interstellar gas can play an important role in regulating SMBH growth.

Sazonov, S.; Churazov, E.; Krivonos, R.; Revnivtsev, M.; Sunyaev, R.; Vikhlinin, A. [Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, Moscow 117997 (Russian Federation); Willner, S. P.; Goulding, A. D.; Jones, C.; Murray, S. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Gorjian, V.; Werner, M. W. [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Forman, W. R. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)

2012-10-01

267

A new model of galaxy formation: How sensitive are predicted galaxy luminosities to the choice of SPS model?  

CERN Document Server

We present a new release of the GALFORM semi-analytical model of galaxy formation and evolution, which exploits a Millennium Simulation-class N-body run performed with the WMAP7 cosmology. We use this new model to study the impact of the choice of stellar population synthesis (SPS) model on the predicted evolution of the galaxy luminosity function. The semi-analytical model is run using seven different SPS models. In each case we obtain the rest-frame luminosity function in the far-ultra-violet, optical and near-infrared (NIR) wavelength ranges. We find that both the predicted rest-frame ultra-violet and optical luminosity function are insensitive to the choice of SPS model. However, we find that the predicted evolution of the rest-frame NIR luminosity function depends strongly on the treatment of the thermally pulsating asymptotic giant branch (TP-AGB) stellar phase in the SPS models, with differences larger than a factor of 2 for model galaxies brighter than K(AB)-5logh<-22 (about L* for 0 < z < 1....

V.,; Lacey, C G; Baugh, C M; Lagos, C D P; Helly, J; Campbell, D J R

2013-01-01

268

Fast Polycrystalline-CdTe Detectors for LHC Luminosity Measurements  

CERN Document Server

Beam diagnostics in future high-energy accelerators will require long lived instrumentation in highly hostile radiation environments. A research program aiming at individuating new solutions and testing them under extreme operational conditions has been launched at CERN in the framework of developments for the LHC instrumentation. Its outcome might be used in future accelerator projects, in industry or in physics applications. The detectors which will be adopted for the LHC luminosity monitoring and optimization will be installed close to or inside copper absorbers specifically designed for radiation protection of the accelerator magnetic elements in the interaction regions. These detectors will have to withstand extreme radiation levels and their long-term operation has to be assured without requiring human intervention. Polycrystalline-CdTe detectors have demonstrated their radiation hardness against extreme doses of X-ray exposure in the LEP collider and are considered as good candidates for LHC luminosity...

Rossa, E; Placidi, Massimo; Schmickler, Hermann; Brambilla, A; Mongellaz, F; Verger, L; Cindro, V; Mikuz, M; Moritz, P

2002-01-01

269

LHC Luminosity and energy upgrade A Feasibility Study  

CERN Document Server

We discuss a possible staged upgrade of the LHC and of its injectors, with a view to increasing the luminosity from the nominal 10**34 cm**-2s**-1 to 10**35 cm**-2s**-1 in each of the two high-luminosity experiments. We also consider possible scenarios for an upgrade to a proton beam energy of about 14 TeV. Starting from beam dynamics considerations and fundamental limitations of the hardware subsystems, we derive realistic requirements for the major components, such as superconducting magnets, cryogenic and RF systems, beam dump and vacuum. We also discuss a novel approach to the optimization of the collider performance, compatible with the beam-beam limit for high intensity proton bunches or long "super-bunches", and sketch a new design of the interaction regions, including an alternative beam crossing scheme. Finally we identify further studies required for an LHC performance upgrade and propose an R&D programme

Brüning, Oliver Sim; Garoby, R; Gröbner, Oswald; Herr, Werner; Linnecar, Trevor Paul R; Ostojic, R; Potter, K; Rossi, L; Ruggiero, F; Schindl, Karlheinz; Stevenson, Graham Roger; Tavian, L; Taylor, T; Tsesmelis, E; Weisse, E; Zimmermann, Frank

2002-01-01

270

Maximum Likelihood Random Galaxy Catalogues and Luminosity Function Estimation  

CERN Document Server

We present a new algorithm to generate a random (unclustered) version of an observational galaxy redshift catalogue. It takes into account both galaxy evolution and the perturbing effects of large scale structure. The key to the algorithm is a new maximum likelihood (ML) method for jointly estimating both the luminosity function (LF) and the overdensity as a function of redshift. The random catalogue algorithm then works by cloning each galaxy in the original catalogue, with the number of clones determined by the ML solution. Each of these cloned galaxies is then assigned a random redshift uniformly distributed over the accessible survey volume, taking account of the survey magnitude limit(s) and, optionally, both luminosity and number density evolution. The resulting random catalogues, which can be employed in traditional estimates of galaxy clustering, make fuller use of the information available in the original catalogue and hence are superior to simply fitting a functional form to the observed redshift di...

Cole, Shaun

2011-01-01

271

Offline software for the luminosity detector at PANDA  

International Nuclear Information System (INIS)

The precise determination of the luminosity is crucial for the PANDA experiment which will be built at the new antiproton accelerator HESR (FAIR, Darmstadt, Germany). For this measurement elastic antiproton-proton scattering can be used. In the range of very small momentum transfer this process can be calculated exactly from QED. Therefore we are going to perform measurements at very small momentum transfer (and thus very small scattering angle). The current design for the detector has four planes (10/20 cm in between). It is located outside the magnetic field, 11 m behind the interaction point. Our reconstruction software includes standard parts as hit reconstruction, track finding and track fitting and specific procedures for luminosity extraction and background treatment. Beside these algorithms we developed a software alignment procedure based on reconstructed tracks by using the Millipede algorithm. In this talk an overview of the basic concept and Monte Carlo based performance studies is presented.

272

LUMINOUS SATELLITES. II. SPATIAL DISTRIBUTION, LUMINOSITY FUNCTION, AND COSMIC EVOLUTION  

International Nuclear Information System (INIS)

We infer the normalization and the radial and angular distributions of the number density of satellites of massive galaxies (log10[M*h/M?] > 10.5) between redshifts 0.1 and 0.8 as a function of host stellar mass, redshift, morphology, and satellite luminosity. Exploiting the depth and resolution of the COSMOS Hubble Space Telescope images, we detect satellites up to 8 mag fainter than the host galaxies and as close as 0.3 (1.4) arcsec (kpc). Describing the number density profile of satellite galaxies to be a projected power law such that P(R)?R?p, we find ?p = –1.1 ± 0.3. We find no dependency of ?p on host stellar mass, redshift, morphology, or satellite luminosity. Satellites of early-type hosts have angular distributions that are more flattened than the host light profile and are aligned with its major axis. No significant average alignment is detected for satellites of late-type hosts. The number of satellites within a fixed magnitude contrast from a host galaxy is dependent on its stellar mass, with more massive galaxies hosting significantly more satellites. Furthermore, high-mass late-type hosts have significantly fewer satellites than early-type galaxies of the same stellar mass, possibly indicating that they reside in more massive halos. No significant evolution in the number of satellites per host is detected. The cumulative luminosity function of satellites is qualitativeion of satellites is qualitatively in good agreement with that predicted using SubHalo Abundance Matching techniques. However, there are significant residual discrepancies in the absolute normalization, suggesting that properties other than the host galaxy luminosity or stellar mass determine the number of satellites.

273

The two period-luminosity relations for population I Cepheids  

Science.gov (United States)

We summarize the evidence that most Population I Cepheids with periods less than approximately 8 days pulsate in the first overtone mode. Fundamental model and first overtone pulsators must follow different period-luminosity (P - L) relations. We demonstrate these different relations for different stellar systems, especially for the calibrating Cepheids in clusters and for Cepheids in the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), M31, and IC 4182.

Bohm-Vitense, Erika

1994-01-01

274

Electron-cloud effects in high-luminosity colliders  

International Nuclear Information System (INIS)

Electron-cloud instabilities are expected to be important in most high-luminosity double-ring colliders. In this report, the author describes a few parameter regimes and some critical parameter dependences of this type of instability, and illustrate these with simulation results for the PEP-II and KEK B factories, the LHC, the VLHC, and DAPHNE. In addition, the author studies the possibility and the potential impact of an electron cloud in the interaction region

275

Close stars and accretion in Low Luminosity Active Galactic Nuclei  

OpenAIRE

Quasar accretion disks are believed to form stars by self-gravity. Low Luminosity Active Galactic Nuclei (LLAGN) are much dimmer galactic centers, and are often believed to be quasars that ran out of gaseous fuel. LLAGN accretion disks should thus co-exist with thousands to millions of stars or proto-stars left from the previous stronger accretion activity. In principle, these stars may produce several important effects: (i) contribute to the optical/UV spectra of some LLAGN...

Nayakshin, Sergei

2004-01-01

276

LHC abort gap cleaning studies during luminosity operation  

CERN Document Server

The presence of significant intensities of un-bunched beam is a potentially serious issue in the LHC. Procedures using damper kickers for cleaning both the Abort Gap (AG) and the buckets targeted for injection, are currently in operation at flat bottom. Recent observations of relatively high population of the AG during physics runs brought up the need for AG cleaning during luminosity operation. In this paper the results of experimental studies performed in October 2011 are presented.

Bartmann, W; Bracco, C; Bravin, E; Goddard, B; Höfle, W; Jacquet, D; Jeff, A; Kain, V; Meddahi, M; Roncarolo, F; Uythoven, J; Valuch, D; Gianfelice-Wendt, E

2012-01-01

277

SDSS Galaxy Clustering: Luminosity & Colour Dependence and Stochasticity  

OpenAIRE

Differences in clustering properties between galaxy subpopulations complicate the cosmological interpretation of the galaxy power spectrum, but can also provide insights about the physics underlying galaxy formation. To study the nature of this relative clustering, we perform a counts-in-cells analysis of galaxies in the Sloan Digital Sky Survey (SDSS) in which we measure the relative bias between pairs of galaxy subsamples of different luminosities and colours. We use a gen...

Swanson, Molly E. C.; Tegmark, Max; Blanton, Michael; Zehavi, Idit

2007-01-01

278

The optical alignment system for luminosity detector at ILC  

CERN Document Server

The possibility to use semi-transparent silicon detectors to measure the displacement detector luminosity LumiCal, planned for the future linear accelerator ILC / CLIC, was studied using an optical laser system based on these detectors. Preliminary results of measurements were achieved using the prototype of this system provided in the displacement measurement values of the X and Y directions with an accuracy of a few microns.

Banas, E; Kielar, E; Kotula, J; Krupa, B; Moszczynski, A; Oliwa, K; Pawlik, B; Wierba, W; Zawiejski, L

2015-01-01

279

Prospects for physics at high luminosity with CMS  

OpenAIRE

The precision measurements of the properties of the recently discovered Higgs-like boson will be central to the future LHC physics program. In parallel the search for New Physics beyond the SM will continue. Higher luminosity will extend the mass reach and allow sensitive searches for possible subtle signatures for new physics. In this paper we review the potential sensitivity of CMS to a selection of relevant future physics scenarios accessible with the LHC upgrades and a correspondingly upg...

Varela João

2013-01-01

280

LHC Abort Gap Cleaning Studies During Luminosity Operation  

Energy Technology Data Exchange (ETDEWEB)

The presence of significant intensities of un-bunched beam is a potentially serious issue in the LHC. Procedures using damper kickers for cleaning both the Abort Gap (AG) and the buckets targeted for injection, are currently in operation at flat bottom. Recent observations of relatively high population of the AG during physics runs brought up the need for AG cleaning during luminosity operation. In this paper the results of experimental studies performed in October 2011 are presented.

Gianfelice-Wendt, E.; /Fermilab; Bartmann, W.; Boccardi, A.; Bracco, C.; Bravin, E.; Goddard, B.; Hofle, W.; Jacquet, D.; Jeff, A.; Kain, V.; Meddahi, M.; /CERN

2012-05-11

281

Determinationm of Effective Temperatures and Luminosities of Rotating Stars  

CERN Document Server

Spectral energy distributions for models of arbitrarily rotating stars are computed using two dimensional rotating stellar models, NLTE plane parallel model atmospheres, and a code to integrate the appropriately weighted intensities over the visible surface of the stellar disk. The spectral energy distributions depend on the inclination angle between the observer and the rotation axis of the model. We use these curves to deduce what one would infer the model's luminosity and effective temperature to be assuming the object was nonrotating.

Gillich, A; Lovekin, C; Short, I; Toque, N

2008-01-01

282

Determinationm of Effective Temperatures and Luminosities of Rotating Stars  

OpenAIRE

Spectral energy distributions for models of arbitrarily rotating stars are computed using two dimensional rotating stellar models, NLTE plane parallel model atmospheres, and a code to integrate the appropriately weighted intensities over the visible surface of the stellar disk. The spectral energy distributions depend on the inclination angle between the observer and the rotation axis of the model. We use these curves to deduce what one would infer the model's luminosity and...

Gillich, A.; Deupree, R.; Lovekin, C.; Short, I.; Toque, N.

2008-01-01

283

Photometric Redshifts and Luminosity Functions from the SPITZER SWIRE Survey  

Science.gov (United States)

This Thesis presents a study of galaxies and quasars from the viewpoint of their optical and infrared properties. Rather than focusing in on individual objects, the general characteristics of extragalactic sources are explored by classifying them as one of a small set of generic `types'. This template-fitting approach opens up a wealth of possible applications, from deriving redshifts to tracing the distribution and evolution of different galaxy populations in both space and time. The investigations carried out in this Thesis have been conducted in the context of, and building on, the field of infrared astronomy and the most important phenomenological and physical properties of galaxies at these wavelengths, in concert with their perhaps more familiar optical properties. More precisely, this Thesis develops a photometric redshift technique that derives redshifts and dust extinction for both galaxies and quasars. This is first applied to optical data and then extended to incorporate infrared data as well. Following on from the recent successful launch and ongoing operation of the SPITZER infrared space observatory, this Thesis utilises data from the SWIRE extragalactic survey which combines SPITZER and ground-based observations in six extragalactic fields. As well as reducing ground-based optical photometry to produce band-merged source catalogues this Thesis uses the optical-infrared catalogues to derive redshifts and then applies an infrared template-fitting technique to the mid- to far-infrared emission of these sources in order to derive luminosities. The large-scale nature of the SWIRE survey then allows luminosity functions to be constructed in a number of SPITZER wavebands, which are an important probe of galaxy evolution and star formation. Evolution of both the galaxy and quasar luminosity functions is seen with redshift, such that there are more high-luminosity sources to higher redshift. There is then a drop in space densities at redshifts of 1.5 to 2 for galaxies, and 3 to 4 for quasars, indicating the likely onset of main activity.

Babbedge, T. S. R.

2004-11-01

284

Low-luminosity X-ray sources and the Galactic ridge X-ray emission  

Science.gov (United States)

Using the XMM-Newton slew survey, we construct a hard-band selected sample of low-luminosity Galactic X-ray sources. Two source populations are represented, namely coronally active stars and binaries (ASBs) and cataclysmic variables (CVs), with X-ray luminosities collectively spanning the range 1028-34 erg s-1 (2-10 keV). We derive the 2-10 keV X-ray luminosity function (XLF) and volume emissivity of each population. Scaled to the local stellar mass density, the latter is found to be 1.08 ± 0.16 × 1028 and 2.5 ± 0.6 × 10^{27} {erg s}^{-1} M_{{?}}^{-1}, for the ASBs and CVs, respectively, which in total is a factor of 2 higher than previous estimates. We employ the new XLFs to predict the X-ray source counts on the Galactic plane at l = 28.5° and show that the result is consistent with current observational constraints. The X-ray emission of faint, unresolved ASBs and CVs can account for a substantial fraction of the Galactic ridge X-ray emission (GRXE). We discuss a model in which ˜80 per cent of the 6-10 keV GRXE intensity is produced in this way, with the remainder attributable to X-ray scattering in the interstellar medium and/or young Galactic source populations. Much of the hard X-ray emission attributed to the ASBs is likely to be produced during flaring episodes.

Warwick, R. S.

2014-11-01

285

Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?  

Science.gov (United States)

Our group has demonstrated that massive clusters, acting as powerful cosmic lenses, can constrain the abundance and properties of low-luminosity star-forming sources beyond z 6; such sources are thought to be responsible for ending cosmic reionization. The large magnification possible in the critical regions of well-constrained clusters brings sources into view that lie at or beyond the limits of conventional exposures such as the UDF. We have shown that the combination of HST and Spitzer is particularly effective in delivering the physical properties of these distant sources, constraining their mass, age and past star formation history. Indirectly, we therefore gain a valuable glimpse to yet earlier epochs. Recognizing the result {and limitations} of blank field surveys, we propose a systematic search through 10 lensing clusters with ACS/F814W and WFC3/[F110W+F160W] {in conjunction with existing deep IRAC data}. Our goal is to measure with great accuracy the luminosity function at z 7 over a range of at least 3 magnitude, based on the identification of about 50 lensed galaxies at 6.5luminosities and, by virtue of the WFC3/IRAC combination, to higher redshift. Thanks to the lensing amplification spectroscopic follow-up will be possible and make our findings the most robust prior to the era of JWST and the ELTs.

Kneib, Jean-Paul

2009-07-01

286

An upgraded ATLAS Central Trigger for post-2014 LHC luminosities  

International Nuclear Information System (INIS)

In early 2012, the Large Hadron Collider (LHC) reached instantaneous luminosities of 6.7·1033 cm?2s?1 and produced events with up to 40 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS trigger in order to reduce the collision rate of up to 40 MHz when operating with design parameters to a manageable event storage rate of about 400 Hz without discarding those events considered interesting. The Level-1 trigger is the first rate-reducing step in the ATLAS trigger and primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS detectors. After 2014, the LHC will run at a centre of mass energy of up to 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 1034 cm?2s?1. With higher luminosities, the required number and complexity of Level-1 triggers will increase in order to satisfy the physics goals of ATLAS while keeping the total Level-1 rates at a maximum of 100 kHz. To provide this added functionality, the Central Trigger Processor will be upgraded during the planned LHC shutdown that begins in 2013.

287

Luminosity Evolution of Rotation-powered Gamma-ray Pulsars  

CERN Document Server

We investigate the electrodynamic structure of a pulsar outer-magnetospheric particle accelerator and the resultant gamma-ray emission. By considering the condition for the accelerator to be self-sustained, we derive how the trans-magnetic-field thickness of the accelerator evolves with the pulsar age. It is found that the thickness is small but increases steadily if the neutron-star envelope is contaminated by sufficient light elements. For such a light element envelope, the gamma-ray luminosity of the accelerator is kept approximately constant as a function of age in the initial ten thousand years, forming the lower bound of the observed distribution of the gamma-ray luminosity of rotation-powered pulsars. If the envelope consists of only heavy elements, on the other hand, the thickness is greater but increases less rapidly than what a light element envelope has. For such a heavy element envelope, the gamma-ray luminosity decreases relatively rapidly, forming the upper bound of the observed distribution. Th...

Hirotani, Kouichi

2013-01-01

288

Precision luminosity measurement at LHCb with beam-gas imaging  

CERN Document Server

The luminosity is the physical quantity which relates the cross-section to the production rate in collider experiments. The cross-section being the particle physics observable of interest, a precise determination of the luminosity is required. This work presents the absolute luminosity calibration results performed at the Large Hadron Collider beauty (LHCb) experiment at CERN using a novel method based on beam-gas interactions with data acquired at a center of mass energy $\\sqrt{s}=8$ TeV and $\\sqrt{s}=2.76$ TeV. Reconstructed beam-gas interaction vertices in LHCb are used to measure the beam profiles, thus making it possible to determine the beams overlap integral. An important element of this work was to install and use a neon gas injection system to increase the beam-gas interaction rate. The precision reached with the beam-gas imaging method relies on the two-dimensional beam shape determination developed in this work. For such precision, the interaction vertex resolution is an important ingredient. There...

Barschel, Colin

289

THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82  

International Nuclear Information System (INIS)

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 (M1450 2, then extend to lower luminosities (M1450 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 (? ?1450 < –26) from z = 5 to< –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.

290

Luminosity Functions of Young Clusters: Modeling the Substellar Mass Regime  

CERN Document Server

We predict near-infrared luminosity functions of young (5 Myr to 1 Gyr) star clusters by combining evolutionary models of very low-mass ($1 M_J$ to $0.15 M_{odot}$) dwarfs with empirical bolometric corrections. We identify several characteristic features in our results. These can be attributed to three causes: (1) deuterium burning in the most massive substellar objects; (2) methane absorption in bodies with $T_{eff}$ less than 1300 K, the temperature of the L/T transition; and (3) the formation of dust clouds and the rainout of dust at roughly the same effective temperature as methane formation. Accurate reconstruction of the substellar mass function from luminosity function observations requires that these phenomena are taken into account. At present, few observational studies extend to sufficient sensitivities to allow detection of these effects. However, the luminosity function of the young open cluster IC 2391 shows a clear peak at $M_I sim 14$ which we attribute to the result of deuterium burning in sub...

Allen, P R; Körner, D W; Reid, I N

2003-01-01

291

An Improved Black Hole Mass - Bulge Luminosity Relationship for AGNs  

CERN Document Server

Two effects have substantially increased the scatter in the AGN black hole mass - host galaxy bulge luminosity relationship derived from SDSS spectra. The first is that at a fixed black hole mass, the SDSS spectrum depends strongly on redshift because an SDSS fiber sees a larger fraction of the total light of more distant galaxies. The second is that at a given redshift, the fraction of host-galaxy light in the fiber increases with decreasing galaxy luminosity. We illustrate the latter effect using the Kormendy et al. (2009) light profiles of Virgo ellipticals. With allowance for the two effects, we obtain a black hole mass - bulge luminosity relationship for AGNs which has a scatter of only +/- 0.23 dex in mass. This is less than the scatter found for inactive galaxies, and is consistent with the measuring errors. We show that there is a correspondingly tight linear relationship between the fraction of host galaxy light in AGN spectra and the Eddington ratio. This linearity implies that at a given black hole...

Gaskell, C Martin

2009-01-01

292

Galactic distribution, production rate and evolution of pulsar luminosity  

International Nuclear Information System (INIS)

The radial distribution of pulsars in the Galaxy is investigated. It is shown that this distribution has a circular structure with the average width 7-8 kpc. The surface density distribution of pulsars inside the circle reaches maximum at R=5.2+-0.4 kpc and then decreases rapidly, showing a small gradient in the direction to the galactic centre. The total number of pulsars with the luminosity 3x102629 erg/s is estimated and their production rate in the Galaxy is obtained, ?sub(p)0.027+-0.009 yr-1 or one pulsar in 37sub(-9)sup(+18) yrs. This value is the upper limit. The evolution of pulsar luminosity with the age is investigated and it is obtained that L=csub(2)tsup(-?) where c2=(4.3+-3.9)x1035 and ?=(1.3+-0.09), t is in yrs L - in erg/s. Proceeding from this law, the true age of pulsars with the luminosity L>=3x1026 erg/s is estimated to be equal to t=(3.6+-0.4)x106 yr. This value well agrees to the estimations of ''kinematic'' and the mean characteristic age determined from young pulsars

293

PREDICTIONS OF QUASAR CLUSTERING: REDSHIFT, LUMINOSITY, AND SELECTION DEPENDENCE  

International Nuclear Information System (INIS)

We show that current clustering observations of quasars and luminous active galactic nuclei (AGNs) can be explained by a merger model augmented by feedback from outflows. Using numerical simulations large enough to study clustering out to 25 comoving h -1 Mpc, we calculate correlation functions, biases, and correlation lengths as a function of AGN redshift and optical and X-ray luminosity. At optical wavelengths, our results match a wide range of current observations and generate predictions for future data sets. We reproduce the weak luminosity dependence of clustering over the currently well-measured range and predict a much stronger dependence at higher luminosities. The increase in the amplitude of binary quasar clustering observed in the Sloan Digital Sky Survey (SDSS) is also reproduced and is predicted to occur at higher redshift, an effect that is due to the one-halo term in the correlation function. On the other hand, our results do not match the rapid evolution of the correlation length observed in the SDSS at z ? 3, a discrepancy that is at least partially due to differences in the scales probed by our simulation versus this survey. In fact, we show that changing the distances sampled from our simulations can produce changes as large as 40% in the fitted correlation lengths. Finally, in the X-ray, our simulations produce correlation lengths similar to that observed in the Chandra Deep Field (CDF) North, but not the significantly larger correlatut not the significantly larger correlation length observed in the CDF-South.

294

An analytic method to compute star cluster luminosity statistics  

Science.gov (United States)

The luminosity distribution of the brightest star clusters in a population of galaxies encodes critical pieces of information about how clusters form, evolve and disperse, and whether and how these processes depend on the large-scale galactic environment. However, extracting constraints on models from these data is challenging, in part because comparisons between theory and observation have traditionally required computationally intensive Monte Carlo methods to generate mock data that can be compared to observations. We introduce a new method that circumvents this limitation by allowing analytic computation of cluster order statistics, i.e. the luminosity distribution of the Nth most luminous cluster in a population. Our method is flexible and requires few assumptions, allowing for parametrized variations in the initial cluster mass function and its upper and lower cutoffs, variations in the cluster age distribution, stellar evolution and dust extinction, as well as observational uncertainties in both the properties of star clusters and their underlying host galaxies. The method is fast enough to make it feasible for the first time to use Markov chain Monte Carlo methods to search parameter space to find best-fitting values for the parameters describing cluster formation and disruption, and to obtain rigorous confidence intervals on the inferred values. We implement our method in a software package called the Cluster Luminosity Order-Statistic Code, which we have made publicly available.

da Silva, Robert L.; Krumholz, Mark R.; Fumagalli, Michele; Fall, S. Michael

2014-03-01

295

LHC Luminosity Upgrade Protecting Insertion Region Magnets from Collision Debris  

CERN Document Server

The Large Hadron Collider built at CERN now enters a starting-up phase where the present design luminosity up to 1034 cm-2 s-1 will be reached after the running in phase. A possible upgrading of the machine to luminosity up to 10^35 cm^-2 s^-1 requires a new insertion region design, and will be implemented in essentially two phases. The energy from collision debris is deposited in the insertion regions and in particular in the superconducting magnet coils with a possible risk of quench. We describe here how to protect the interaction region magnets against this irradiation to keep the energy deposition below critical values estimated for safe operation. The constraint is to keep the absorber size as small as possible to leave most of the magnet aperture available for the beam. This can be done by choosing a suitable material and design minimizing the load on the cryogenic system. Here we will describe design proposals for the phase I upgrade lay-out, i.e. luminosity up to 2.5 10^34 cm^-2 s^-1.

Wildner, E; Ferrari, A; Mauri, M; Mereghetti, A

2008-01-01

296

The luminosity-metallicity relation for bulges of spiral galaxies  

CERN Document Server

Optical integrated spectra of bulges have been obtained for 28 spiral galaxies. By applying an appropriate aperture size for each galaxy, the unavoidable contamination of disk starlight has been carefully minimized and set to \\sim 1/7 of the total stellar light. The sample covers a wide range in bulge luminosity and morphology. The Mg_2 index shows a tight correlation with the bulge intrinsic luminosity, similar - and extended at fainter magnitudes - to the relationship known for ellipticals. Other features such as CaIIK, CN, G-band, and TiO show similar trend with the bulge luminosity. On the contrary, the Fe5270 and Fe5335 iron lines show a constant equivalent width - within some dispersion - for all bulges. A simple application of a stellar population synthesis model suggests that magnesium should be most enhanced with respect to iron in the brightest bulges. Concerning the structural parameters, bulges do occupy the same region in the fundamental plane as ellipticals. In conclusion, the present study favo...

Jablonka, P; Arimoto, N

1996-01-01

297

QSO Narrow [OIII] Line Width and Host Galaxy Luminosity  

CERN Document Server

Galaxy bulge luminosity L, black hole mass (Mbh), and stellar velocity dispersion (sigma_*) increase together in a way suggesting a close evolutionary relationship. Measurements of the Mbh-sigma_* relationship as a function of cosmic time may shed light on the origin of this relationship. Direct measurements of sigma_* at high redshift are difficult, and the width of the narrow emission lines of AGN has been proposed as a surrogate. We investigate the utility of using sigma_[OIII] for sigma_* by examining host galaxy magnitudes and [OIII] line widths for low redshift QSOs. For radio-quiet QSOs, sigma_[OIII] is consistent in the mean with the value of sigma_* predicted by the Faber-Jackson relation. For our limited range of host luminosity, scatter obscures the expected increase of sigma_[OIII] with host luminosity. However, for a sample of AGN covering a wide range of measured or inferred sigma_*, there is a clear increase of sigma_[OIII] with sigma_*. Radio-loud QSOs on average have sigma_* smaller by ~0.1 d...

Bonning, E W; Salviander, S; McLure, R J

2005-01-01

298

Studies of the high luminosity quasar, PDS 456  

CERN Document Server

X-ray and multi-wavelength observations of the most luminous known local (z<0.3) AGN, the recently discovered radio-quiet quasar PDS 456, are presented. The spectral energy distribution shows that PDS 456 has a bolometric luminosity of 1e47 erg/s, peaking in the UV. The X-ray spectrum obtained by ASCA and RXTE shows considerable complexity. The most striking feature observed is a deep, highly-ionised, iron K edge (8.7 keV, rest-frame), originating via reprocessing from highly ionised material, possibly the inner accretion disk. PDS 456 was found to be remarkably variable for its luminosity; in one flare the X-ray flux doubled in just about 15 ksec. If confirmed this would be an unprecedented event in a high-luminosity source, with a light-crossing time corresponding to about 2RS. The implications are that either flaring occurs within the very central regions, or else that PDS 456 is a super-Eddington or relativistically beamed system.

Reeves, J; Vaughan, S; Law-Green, D; Ward, M; Simpson, C; Pounds, K; Edelson, R

2000-01-01

299

Luminosity measurement method for the LHC: The detector requirement studies  

Energy Technology Data Exchange (ETDEWEB)

In our earlier paper [1] we have proposed a new luminosity measurement method for the LHC collider. It is based on the detection of lepton pairs produced in the peripheral collisions of the LHC beam particles and allows to reach better than 1% accuracy of the theoretical control of the event rate. In order to implement this method a new, specialized luminosity detector must be incorporated within the fiducial volume of one of the existing LHC detectors. In this paper the requirement studies for such a detector are presented. They are driven, almost exclusively, by its capacity to identify, within the level 1 trigger latency of the host detector, the bunch crossings with exclusive, coplanar pairs of opposite charge particles. It is shown that a tracking detector with the azimuthal hit resolution of 2 mrad allows us to reduce the rate of background events to the requisite O(1kHz) level while retaining a sufficiently large fraction of the signal events for the precise luminosity measurement.

Krasny, M.W., E-mail: Mieczyslaw.Krasny@cern.ch [LPNHE, Pierre and Marie Curie University, CNRS-IN2P3, Tour 33, RdC, 4, pl. Jussieu, 75005 Paris (France); Chwastowski, J. [Institute of Teleinformatics, Faculty of Physics, Mathematics and Computer Science, Cracow University of Technology, ul. Warszawska 24, 31-115 Kraków (Poland); Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland); Cyz, A.; S?owikowski, K. [Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland)

2013-11-21

300

High Luminosity Large Hadron Collider A description for the European Strategy Preparatory Group  

CERN Document Server

The Large Hadron Collider (LHC) is the largest scientific instrument ever built. It has been exploring the new energy frontier since 2009, gathering a global user community of 7,000 scientists. It will remain the most powerful accelerator in the world for at least two decades, and its full exploitation is the highest priority in the European Strategy for Particle Physics, adopted by the CERN Council and integrated into the ESFRI Roadmap. To extend its discovery potential, the LHC will need a major upgrade around 2020 to increase its luminosity (rate of collisions) by a factor of 10 beyond its design value. As a highly complex and optimized machine, such an upgrade of the LHC must be carefully studied and requires about 10 years to implement. The novel machine configuration, called High Luminosity LHC (HL-LHC), will rely on a number of key innovative technologies, representing exceptional technological challenges, such as cutting-edge 13 tesla superconducting magnets, very compact and ultra-precise superconduc...

Rossi, L

2012-01-01

301

Double galaxies: redshift measurements, error analysis, and mean mass/luminosity ratio  

International Nuclear Information System (INIS)

New radial-velocity measurements are presented for 44 double systems drawn from the author's Catalog of Isolated Pairs of Galaxies and not covered by previous spectroscopic surveys. The absolute errors in the redshifts measured on the 6-m telescope spectrograms are estimated by comparison of data for 75 galaxies common to the Catalog and the sample of White et al. The ratio k = sigma/sub e//sigma/sub i/ of the external (absolute) and internal errors in the measured redshift increases from 1.0 to 2.1 as one passes from galaxies with strong emission lines to absorption-line objects. The factor k is smaller for the redshift differential between pair components than for individual redshift measurements. From the k-dependence of the sample moments of the orbital-mass/luminosity ratio, an overall average k = 1.4 is deduced, yielding for 490 pairs a mean mass/luminosity ratio f = (7.6 +- 0.9)f/sub sun/

302

Looking below the floor: constraints on the AGN radio luminosity functions at low power  

Science.gov (United States)

We constrain the behaviour of the radio luminosity function (RLF) of two classes of active galactic nuclei (AGN) namely AGN of low radio power (LRP) and BL Lac objects. The extrapolation of the observed steep RLFs to low power predicts a space density of such objects that exceeds that of the sources that can harbour them and this requires a break to a shallower slope. For LRP AGN, we obtain Pbr, LRP ? 1020.5 W Hz- 1 at 1.4 GHz to limit their density to be smaller than that of elliptical galaxies with black hole masses MBH > 107.5 M?. By combining this value with the limit derived by the observations the break must occur at Pbr, LRP ˜ 1020.5-1021.5 W Hz- 1. For BL Lacs, we find Pbr, BLLAC ? 1023.3 W Hz- 1 otherwise they would outnumber the density of weak-lined and compact radio sources, while the observations indicate Pbr, BLLAC ? 1024.5 W Hz- 1. In the framework of the AGN unified model, a low luminosity break in the RLF of LRP AGN must correspond to a break in the RLF of BL Lacs. The ratio between Pbr, LRP and Pbr, BLLAC is ˜103, as expected for a jet Doppler factor of ˜10.

Capetti, Alessandro; Raiteri, Claudia M.

2015-04-01

303

Upgraded Readout Electronics for the ATLAS Liquid Argon Calorimeters at the High Luminosity LHC  

CERN Document Server

The ATLAS Liquid Argon (LAr) calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics is summing analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up noise expected during the High Luminosity phases of LHC will be increased by factors of 3 to 7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background ejection rates. For the first upgrade phase cite{pahse1loi} in 2018, new LAr Trigger Digitizer Boards (LTDB) are being designed to receive higher granularity signals, digitize them on detector and send them via fast optical links to a new digital processing system (DPS). The DPS applies a digital filtering and id...

Andeen, T; The ATLAS collaboration

2012-01-01

304

PHOTOMETRIC PROPERTIES AND LUMINOSITY FUNCTION OF NEARBY MASSIVE EARLY-TYPE GALAXIES  

International Nuclear Information System (INIS)

We perform photometric analyses of a bright early-type galaxy sample with 2949 galaxies (Mr r –2 and 1% of the sky brightness are on average 0.16 mag, 0.20 mag, and 0.26 mag brighter than the SDSS Petrosian values, respectively. In the first case, the underestimations are caused by overestimations in the sky background by the SDSS PHOTO algorithm, while the latter two are also due to deeper photometry. Similarly, the typical half-light radii (r50) measured by the SDSS algorithm are smaller than our measurements. As a result, the bright end of the r-band luminosity function is found to decline more slowly than previous works. Our measured luminosity densities at the bright end are more than one order of magnitude higher than those of Blanton et al., and the stellar mass densities at M* ? 5 × 1011 M? and M* ? 1012 M? are a few tenths and a factor of a few higher than those of Bernardi et al. These results may significantly alleviate the tension in the assembly of massion in the assembly of massive galaxies between observations and predictions of the hierarchical structure formation model

305

The Host Galaxies of High-Luminosity Obscured Quasars at z~2.5  

Science.gov (United States)

Active Galactic Nuclei play a key role in the evolution of galaxies.However, very little is known about the host galaxies of the mostluminous quasars at z 2.5, the epoch when massive black hole growthpeaked. The brightness of the quasar itself, which can easilyoutshine a galaxy by a large factor, makes it very difficult to studyemission from extended gas or stars in the host galaxy. We propose toimage extended emission from the host galaxies of a unique sample ofsix optically extincted {Type II} luminous quasars with z 2.5, withWFC3/F160W in the rest-frame optical longward of 4000A and ACS/F814Win the rest-frame near-ultraviolet. These objects are selected fromthe spectroscopic database of the SDSS/Baryon OscillationSpectroscopic Survey to have strong, narrow emission lines and weakcontinua. Because the central engines are obscured, we are able toimage their low surface brightness hosts. With these images, we willquantify the luminosity, morphology, and dynamical state of the hostgalaxies, and search for extended scattered light from the obscuredcentral engine. Our proposed HST observations will be the firstcomprehensive study of both host galaxy light and scattered light inhigh-luminosity quasars at the epoch of maximum black hole growth, andwill give insights into the relationship between host galaxies andblack holes during this important, and yet largely unexplored period.

Strauss, Michael

2012-10-01

306

GRB 120422A: A Low-luminosity Gamma-ray Burst Driven by Central Engine  

CERN Document Server

GRB 120422A is a low-luminosity Gamma-ray burst (GRB) associated with a bright supernova, which distinguishes itself by its relatively short T90 ~ 5 s and an energetic X-ray tail. We analyze the Swift BAT and XRT data and discuss the physical implications. We show that the early steep decline in the X-ray light curve can be interpreted as the curvature tail of a late emission episode around 58-86 s, with a curved instantaneous spectrum at the end of the emission episode. Together with the main activity in the first ~ 20 s and the weak emission from 40 s to 60 s, the prompt emission is variable, which points towards a central engine origin, in contrast to the shock breakout origin as invoked to interpret some other nearby low-luminosity supernova GRBs. The curvature effect interpretation and interpreting the early shallow decay as the coasting external forward shock emission in a wind medium both give a constraint on the bulk Lorentz factor \\Gamma to be around several. Comparing the properties of GRB 120422A a...

Zhang, Bin-Bin; Shen, Rong-Feng; Xu, Dong; Zhang, Fu-Wen; Wei, Da-Ming; Burrows, David N; Zhang, Bing

2012-01-01

307

Upgraded readout electronics for the ATLAS LAr Calorimeter at the High Luminosity LHC  

CERN Document Server

The ATLAS Liquid Argon (LAr) calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics is summing analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up noise expected during the High Luminosity phases of LHC will be increased by factors of 3 to 7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background ejection rates. For the first upgrade phase [1] in 2018, new digital tower builder boards (sTBB) are being designed to receive higher granularity signals, digitize them on detector and send them via fast optical links to a new digital processing system (DPS). The DPS applies a digital filtering and identifies sig...

Andeen, T; The ATLAS collaboration

2012-01-01

308

LUMINOSITY FUNCTIONS OF TYPE Ia SUPERNOVAE AND THEIR HOST GALAXIES FROM THE SLOAN DIGITAL SKY SURVEY  

International Nuclear Information System (INIS)

The sample of 137 low-redshift type Ia supernovae (SNe Ia) with 0.05 ? z ? 0.3 obtained from the Sloan Digital Sky Survey (SDSS)-II supernova survey for the southern equatorial stripe of 300 deg2 is used to derive the luminosity functions (LFs) of SNe Ia and of their host galaxies in the g, r, i passbands. We show that the LF of SNe Ia host galaxies matches well with that of galaxies in the general field, suggesting that the occurrence of SNe Ia does not favor a particular type of galaxy but is predominantly proportional to the luminosity of galaxies. The evidence is weak that the SNe rate varies with the color of host galaxies. The only evidence that points to possible correlation between the SN rate and star formation activity is that the SN rate in late-type galaxies is higher than that in early-type galaxies by 31% ± 35%. In our low-redshift sample, the component of type Ia SN rate that is proportional to star formation activity is not evident in the integrated SN rate, while our observation is compatible with the current two-component models. The sample contains eight SNe Ia whose host galaxies were not identified, but it is shown that their occurrence is consistent with them occurring in low-luminous galaxies beyond the survey. The LF of SNe Ia is approximately Gaussian with the full width at half-maximum being a factor of ? = 0.24 mag or 1.67 in luminosity. The Gaussian distribution becomes tighter if the ratio of extinction to reddening, RV , is lower than the characteristic value for the Milky Way and if luminosity is corrected for the light-curve shape. The average color excess is ?0.07 mag, which is significantly smaller than reddening expected for field galaxies. This color excess does not vary with the distance of the SNe from the center of the host galaxy to 15 kpc. This suggests that the major part of the color excess appears to be either intrinsic or reddening that arises in the immediate environment of SNe, rather than interstellar reddening in host galaxies, and most of SNe Ia take place in a relatively dust-free environment.

309

The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei from Reverberation Mapping and Hubble Space Telescope Imaging  

DEFF Research Database (Denmark)

We investigate the relationship between black hole mass and bulge luminosity for AGNs with reverberation-based black hole mass measurements and bulge luminosities from two-dimensional decompositions of Hubble Space Telescope host galaxy images. We find that the slope of the relationship for AGNs is 0.76-0.85 with an uncertainty of ~0.1, somewhat shallower than the M_BH \\propto L^{1.0+/-0.1} relationship that has been fit to nearby quiescent galaxies with dynamical black hole mass measurements. This is somewhat perplexing, as the AGN black hole masses include an overall scaling factor that brings the AGN M_BH-sigma relationship into agreement with that of quiescent galaxies. We discuss biases that may be inherent to the AGN and quiescent galaxy samples and could cause the apparent inconsistency in the forms of their M_BH-L_bulge relationships.

Bentz, Misty C.; Peterson, Bradley M.

2008-01-01

310

LUMINOSITIES OF BARRED AND UNBARRED S0 GALAXIES  

International Nuclear Information System (INIS)

Lenticular galaxies with MB < –21.5 are almost exclusively unbarred, whereas both barred and unbarred objects occur at fainter luminosity levels. This effect is observed both for objects classified in blue light, and for those that were classified in the infrared. This result suggests that the most luminous (massive) S0 galaxies find it difficult to form bars. As a result, the mean luminosity of unbarred lenticular galaxies in both B and IR light is observed to be ?0.4 mag brighter than that of barred lenticulars. A small contribution to the observed luminosity difference that is found between SA0 and SB0 galaxies may also be due to the fact that there is an asymmetry between the effects of small classification errors on SA0 and SB0 galaxies. An elliptical (E) galaxy might be misclassified as a lenticular (S0) or an S0 as an E. However, an E will never be misclassified as an SB0, nor will an SB0 ever be called an E. This asymmetry is important because E galaxies are typically twice as luminous as S0 galaxies. The present results suggest that the evolution of luminous lenticular galaxies may be closely linked to that of elliptical galaxies, whereas fainter lenticulars might be more closely associated with ram-pressure stripped spiral galaxies. Finally, it is pointed out that fine details of the galaxy formation process might account for some of the differences between the classifications of the same galaxy by individual competent morphologists.ual competent morphologists.

311

The luminosity-size relation of galaxies to z=1?  

OpenAIRE

We use the Hubble Ultra Deep Field (UDF) to study the galaxy luminosity-size (M-Re) distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability we identify bias-free regions in the M-Re plane for a series of volume-limited samples. We also investigate the colour-log(n) distribution of these galaxies and further subdivide our data by structural type to separately study compact and diffuse objects. By comparison to ...

Cameron, E.; Driver, S. P.

2007-01-01

312

Hipparcos Luminosities for Giants with Non-Solar Abundances  

Science.gov (United States)

Philip C. Keenan is currently reclassifying giants of spectral types G5-K2 in an attempt to answer the following questions: (1) Do the non-solar abundance groups contain stars belonging to the clump, which in normal stars lies about one magnitude below the main ridge of giants? (2) If so, how do the mean magnitudes of the clump stars compare with those of normal giants? The available samples will not always permit these questions to be answered. For example, there are no S stars bright enough to have Hipparcos parallaxes that define their luminosities well.

Newsom, G. H.; Keenan, P. C.

313

A New Frequency-Luminosity Relation for Long GRBs?  

CERN Document Server

We have studied power density spectra (PDS) of 206 long Gamma-Ray Bursts (GRBs). We fitted the PDS with a simple power-law and extracted the exponent of the power-law (alpha) and the noise-crossing threshold frequency (f_th). We find that the distribution of the extracted alpha peaks around -1.4 and that of f_th around 1 Hz. In addition, based on a sub-set of 58 bursts with known redshifts, we show that the redshift-corrected threshold frequency is positively correlated with the isotropic peak luminosity. The correlation coefficient is 0.57 +/- 0.03.

Ukwatta, T N; Morris, D C; MacLachlan, G; Parke, W C; Maximon, L C; Eskandarian, A; Gehrels, N; Norris, J P; Shenoy, A

2010-01-01

314

HERA LUMINOSITY UPGRADE SUPERCONDUCTING MAGNET PRODUCTION AT BNL.  

Energy Technology Data Exchange (ETDEWEB)

Production of two types of superconducting multi-function magnets, needed for the HEX4 Luminosity Upgrade is underway at BNL. Coil winding is now completed and cryostat assembly is in progress. Magnet type GO and type GG cold masses have been satisfactorily cold tested in vertical dewars and the first fully assembled GO magnet system has been horizontally cold tested and shipped to DESY. Warm measurements confirm that the coils meet challenging harmonic content targets. In this paper we discuss GO and GG magnet design and construction solutions, field harmonic measurements and quench test results.

PARKER,B.; ANERELLA,M.; ESCALLIER,J.; GHOSH,A.; JAIN,A.; MARONE,A.; MURATORE,J.; PRODELL,A.; THOMPSON,P.; WANDERER,P.; WU,K.C.

2000-09-17

315

NGC4258 a jet-dominated low-luminosity AGN?  

CERN Document Server

Low-luminosity AGNs (LLAGNs) are a very important class of sources since they occupy a significant fraction of local galaxies. Their spectra differ significantly from the canonical luminous AGNs, most notably by the absence of the ``big blue bump''. In the present paper, taking a typical LLAGN--NGC4258--as an example, we investigate the origin of their spectral emission. The observational data of NGC4258 is extremely abundant, including water maser emission, putting very strict constraints to its theoretical models. The infrared (IR) spectrum is well described by a steep power-law form $f_{\

Yuan, F; Falcke, H; Biermann, P L; Yuan, Feng; Markoff, Sera; Falcke, Heino; Biermann, Peter L.

2002-01-01

316

Prospects for physics at high luminosity with CMS  

Directory of Open Access Journals (Sweden)

Full Text Available The precision measurements of the properties of the recently discovered Higgs-like boson will be central to the future LHC physics program. In parallel the search for New Physics beyond the SM will continue. Higher luminosity will extend the mass reach and allow sensitive searches for possible subtle signatures for new physics. In this paper we review the potential sensitivity of CMS to a selection of relevant future physics scenarios accessible with the LHC upgrades and a correspondingly upgraded CMS detector.

Varela João

2013-05-01

317

Radiation environment and shielding for a high luminosity collider detector  

International Nuclear Information System (INIS)

Detectors now under design for use in the proposed high energy high luminosity colliders must deal with unprecedented radiation levels. We have performed a comprehensive study for the GEM detector at the SSC to determine the best way to shield critical detector components from excessive radiation, with special attention paid to the low energy neutrons and photons. We have used several detailed Monte-Carlo simulations to calculate the particle fluxes in the detector. We describe these methods and demonstrate that two orders of magnitude reduction in the neutron and photon fluxes can be obtained with appropriate shielding of critical forward regions such as the low beta quadrupoles and the forward calorimeter

318

MgII Line Variability of High Luminosity Quasars  

OpenAIRE

We monitored five high-luminosity quasars with lambda L_{3000A} > 10^45 erg s^-1 at 0.4 < z < 0.6 to measure flux variability of the MgII 2798 line and explore feasibility of reverberation mapping using MgII. Over the two year monitoring program, imaging data were obtained with the A Noble Double-Imaging Camera on the 1.3-m telescope at the Cerro Tololo Inter-American Observatory (CTIO), while spectroscopic data were obtained at the same night with the R-C spectrograph on th...

Woo, Jong-hak

2008-01-01

319

The Evolving Faint-End of the Luminosity Function  

OpenAIRE

We investigate the evolution of the faint-end slope of the luminosity function, $\\alpha$, using semi-analytical modeling of galaxy formation. In agreement with observations, we find that the slope can be fitted well by $\\alpha (z) =a+b z$, with a=-1.13 and b=-0.1. The main driver for the evolution in $\\alpha$ is the evolution in the underlying dark matter mass function. Sub-L_* galaxies reside in dark matter halos that occupy a different part of the mass function. At high re...

Khochfar, S.; Silk, J.; Windhorst, R. A.; Ryan Jr, R. E.

2007-01-01

320

RESULTS FROM LUMINOSITY SCANS DURING THE RHIC 2000 RUN  

International Nuclear Information System (INIS)

During the year 2000 run a total of eight beam scans (Vernier Scans) were performed at various interaction points (IF) at RHIC. During a Vernier Scan the experimental collision rates are recorded while the beams are stepwise scanned across each other. Vernier Scans yield transverse beam sizes as well as maximum luminosity and thus the absolute cross section, which with the limited data from the 2000 run we measured to be ? = 8.9 ± 0.3 barn at (?sNN) = 130 GeV. Also, Vernier Scans permit performance studies of the beam orbit control and local coupling

321

On Schmidt's Vm estimator and other estimators of luminosity functions  

Science.gov (United States)

Schmidt's (1968) estimator, sometimes used to calculate the luminosity function from a complete sample of observed objects, can be generalized naively to the case in which the maximum distance for detection is a function of the direction. Though unbiased, this estimator then does not have minimum variance and, in some cases, is inferior to the classical estimator. The classical estimator, however, is biased when the magnitude boxes are not infinitesimal. A generalization of Schmidt's estimator is proposed which is unbiased and usually superior to both Schmidt's and the classical estimator. Variance formulas and numerical examples are given. The results can be used in combining several catalogs.

Felten, J. E.

1976-01-01

322

Preliminary study of a high luminosity e+ e- storage ring at a C.M. energy of 5 GeV  

International Nuclear Information System (INIS)

The design of a facility for the study of tau-charm interactions, with 5 GeV C.M. energy and a luminosity of 1033/sqcm.s is investigated. The performances of some known storage rings are underlined. The influence of the emittances, space charge and collision rate limit, and the design constraints of the micro beta quadrupoles are discussed. Design examples and considerations of the sloping parts are included. The analysis shows that the round beam scheme saves a factor 2 on the stored current for a given luminosity, is very demanding in terms of tolerances for superconducting quadrupoles and requires one crossing point

323

Tolman's Luminosity-Distance, Poincare's Light-Distance and Cayley-Klein's Hyperbolic Distance  

CERN Document Server

We deduce Tolman's formula of luminosity-distance in Cosmology from Poincare's definition of light-distance with Lorentz Transformation (LT).In Minkowskian metric, if distance is proper time (as it is often argued) then light-distance must be also the shortest distance, like proper duration (unlike Einstein's longest length within rest system). By introducing Poincare's proper light-distance in Einstein's basic synchronization we deduce a dilated distance between observer and receding mirror (with relativistic Doppler factor). Such a distance corresponds not to an Euclidean distance (Einstein's rigid rod) but to an Hyperbolic distance (Cayley-Klein) with a Lobatchevskian Horizon. From a basic proportionality hyperbolic distance-velocity, we deduce the law of Hubble. By following Penrose's Lobatchevskian representation of LT, we transform Special Relativity (SR) into an Hyperbolic Cosmological Relativity (HCR). by using only the LT but the whole LT. In Hyperbolic Rotation motion (basic active LT or Einstein's ...

Pierseaux, Yves

2009-01-01

324

Observational evidence for a correlation between peak-luminosities and beaming in GRBs  

CERN Document Server

We calculate the unseen-but-true GRB-event rate from a current flux-limited sample of 33 GRBs with individually measured redshifts. We consider a GRB-event rate which is proportional to the star-formation rate, in view of the GRB-SNe association in SN1998bw and GRB030329. By fitting a log-normal distribution of GRB peak-luminosities, we find a ratio of about 450 for the true-to-observed GRB-event rates. This provides an independent derivation of the GRB-beaming factor of about 500 obtained by Frail et al. (2001) from sources with standard GRB-energies. We discuss applications to GRB980425.

Van Putten, M H P M; Putten, Maurice H.P.M. van; Regimbau, Tania

2003-01-01

325

Luminosity limit due to the beam-beam interactions with or without crossing angle  

International Nuclear Information System (INIS)

In recent high luminosity colliders, the finite crossing angle scheme becomes popular to gain the luminosity with multibunch or long bunch operation. Success of the KEKB factory showed that the finite crossing angle scheme has no problem achieving beam-beam parameters up to 0.05. We have studied the beam-beam interactions with and without crossing angle toward higher luminosity. We discuss how the crossing angle affects the beam-beam parameter and luminosity in the present KEKB using computer simulations. The simulations showed that crab cavities, which realize the head-on collision effectively, can be expected to double the luminosity

326

Structure and Luminosity of Neutrino-cooled Accretion Disks  

Science.gov (United States)

Neutrino-cooled hyperaccretion disks around stellar-mass black holes are plausible candidates for the central engines of gamma-ray bursts. We calculate the one-dimensional structure and the annihilation luminosity of such disks. The neutrino optical depth is of crucial importance in determining the neutrino cooling rate and is in turn dependent on the electron fraction, the free nucleon fraction, and the electron degeneracy, for a given density and temperature of the disk matter. We construct a bridging formula for the electron fraction that works for various neutrino optical depths and give exact definitions for the free proton fraction and free neutron fraction. We show that the electron degeneracy has important effects, in the sense that it increases the absorption optical depth for neutrinos and, along with the neutronization processes favored by high temperature, causes the electron fraction to drop below 0.1 in the inner region of the disk. The resulting neutrino annihilation luminosity is considerably reduced in comparison with that obtained in previous works in which the electron degeneracy was not considered and the electron fraction was simply taken to be 0.5, but it is still likely to be adequate for gamma-ray bursts, and it is ejected mainly from the inner region of the disk with an anisotropic distribution.

Liu, Tong; Gu, Wei-Min; Xue, Li; Lu, Ju-Fu

2007-06-01

327

The z=5 Quasar Luminosity Function from SDSS Stripe 82  

CERN Document Server

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<-26) with Sloan Digital Sky Survey (SDSS) data covering ~6000 deg^2, then extend to lower luminosities (M_1450<-24) with newly discovered, faint z~5 quasars selected from 235 deg^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 (BOSS), and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7

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

2012-01-01

328

An Upgraded ATLAS Central Trigger for 2014 LHC Luminosities  

CERN Document Server

During 2011, the LHC reached instantaneous luminosities of 4*10^33 cm^-1*s^-1 and produced events with up to 24 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of ~400Hz and, at the same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75kHz and a decision latency of less than 2.5us. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS sub-detectors. In 2014, the LHC will run at a center of mass energy of 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10^34 cm^-1*s^-1. With h...

Kaneda, M; The ATLAS collaboration

2012-01-01

329

An Upgraded ATLAS Central Trigger for 2014 Luminosities  

CERN Document Server

During 2011, the LHC reached instantaneous luminosities of 4*10^33 cm-2*s-1 and produced events with up to 24 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of ~400Hz and, at the same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75kHz and a decision latency of less than 2.5us. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS detectors. In 2014, the LHC will run at a center of mass energy of 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10^34 cm^-2*s^-1. With higher ...

Anders, G; The ATLAS collaboration; Bertelsen, H; Childers, T; Dam, M; Dobson, E; Ellis, N; Farthouat, P; Gabaldon, C; Gorini, B; Haas, S; Kaneda, M; Maettig, S; Messina, A; Pauly, T; Pöttgen, R; Spiwoks, R; Wengler, T; Xella, S

2012-01-01

330

An Upgraded ATLAS Central Trigger for 2014 LHC Luminosities  

CERN Document Server

During 2011, the LHC reached instantaneous luminosities of 4*10^33 cm-2*s-1 and produced events with up to 24 interactions per colliding proton bunch. Thisplaces stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of ~400Hz and, atthe same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75kHz and adecision latency of less than 2.5us. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom builtVME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS subdetectors. In 2014, the LHC will run at a center of mass energy of 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10^34 cm^-2*s^-1. With higher l...

Kaneda, M; The ATLAS collaboration

2012-01-01

331

An upgraded ATLAS Central Trigger for post-2014 LHC luminosities  

CERN Document Server

During 2011, the LHC reached instantaneous luminosities of 6.7 · 10^33 cm?2s?1 and produced events with up to 40 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS trigger in order to reduce the 40 MHz collision rate to a manageable event storage rate of 400 Hz without discarding those events considered interesting. The Level-1 trigger is the first rate-reducing step in the ATLAS trigger, with an output rate of 75 kHz and a decision latency of less than 2.5 ? s. It is primarily composed of the Calorimeter Trigger, Muon Trigger, and the Central Trigger Processor which are implemented in custom built VME electronics. The Central Trigger Processor collects trigger information from all Level-1 systems and produces a Level-1 trigger decision that initiates the readout of all ATLAS detectors. After 2014, the LHC will run at a center of mass energy of up to 14 TeV, compared to the current 8 TeV, and the luminosity will exceed 10^34 cm?2s?1. Wit...

Anders, G; The ATLAS collaboration; Bertelsen, H; Childers, T; Dam, M; Dobson, E; Ellis, N; Farthouat, P; Gabaldon, C; Gorini, B; Haas, S; Kaneda, M; Maettig, S; Messina, A; Ohm, C; Pauly, T; Poettgen, R; Spiwoks, R; Wengler, T; Xella, S

2012-01-01

332

Luminosity functions of LMXBs in different stellar environments  

CERN Document Server

Based on the archival data of Chandra observations of nearby galaxies we study different sub-populations of low-mass X-ray binaries -- dynamically formed systems in globular clusters, in the nucleus of M31 and (presumably primordial) X-ray binaries in the fields of galaxies. Our aim is to produce accurate luminosity distributions of X-ray binaries in different environments, suitable for quantitative comparison with each other and with the output of population synthesis calculations. Our sample includes seven nearby galaxies (M31, Maffei1, Centaurus A, M81, NGC 3379, NGC 4697 and NGC 4278) and the Milky Way, which together provide relatively uniform coverage down to the luminosity limit of e35 erg/s. In total we have detected 185 LMXBs associated with globular clusters, 35 X-ray sources in the nucleus of M31 and 998 field sources of which ~ 365 are expected to be background AGN. We combine these data, taking a special care of accurate incompleteness correction and removal of CXB contamination, and produce lumi...

Zhang, Zhongli; Voss, Rasmus; Sivakoff, Gregory R; Kraft, Ralph P; Brassington, Nicola J; Kundu, Arunav; Jordán, Andrés; Sarazin, Craig

2011-01-01

333

Radio Variability Survey of Very Low Luminosity Protostars  

CERN Document Server

Ten very low luminosity objects were observed multiple times in the 8.5 GHz continuum in search of protostellar magnetic activities. A radio outburst of IRAM 04191+1522 IRS was detected, and the variability timescale was about 20 days or shorter. The results of this survey and archival observations suggest that IRAM 04191+1522 IRS is in active states about half the time. Archival data show that L1014 IRS and L1148 IRS were detectable previously and suggest that at least 20%-30% of very low luminosity protostars are radio variables. Considering the variability timescale and flux level of IRAM 04191+1522 IRS and the previous detection of the circular polarization of L1014 IRS, the radio outbursts of these protostars are probably caused by magnetic flares. However, IRAM 04191+1522 IRS is too young and small to develop an internal convective dynamo. If the detected radio emission is indeed coming from magnetic flares, the discovery implies that the flares may be caused by the fossil magnetic fields of interstella...

Choi, Minho; Kang, Miju

2014-01-01

334

LHC Report: spring cleaning over, bunches of luminosity  

CERN Multimedia

Scrubbing was completed on Wednesday 13 April. The run had seen over 1000 bunches per beam successfully circulating at 450 GeV. Measurements showed that electron cloud activity in the cold regions had been suppressed. A decrease of vacuum activity in the warm regions demonstrated that the cleaning had also achieved the required results there. As discussed in the last Bulletin, the scrubbing was performed with high intensity bunches with 50 nanosecond spacing. Given the potential luminosity performance with this spacing (more bunches, higher bunch intensity from the injectors) and in the light of the results of the scrubbing run, the decision was taken to continue the 2011 physics run with this bunch spacing.   A few issues with 50 nanosecond spacing had to be resolved when standard operations for luminosity production resumed. Once things had been tidied up, stable beams were provided for the experiments, firstly with 228 bunches per beam and then with 336 bunches per beam. The 336 bunch fill that w...

CERN Bulletin

2011-01-01

335

An Upgraded ATLAS Central Trigger for 2015 LHC Luminosities  

CERN Document Server

The LHC collides protons at a rate of 40 MHz and each collision produces ?1.5~MB of data from the ATLAS detector. The ATLAS trigger system is implemented in three levels and selects only the most interesting collision events to reduce the event storage rate to about 400 Hz. The first level is implemented in custom electronics and reduces the input rate to ?75 kHz with a decision latency of ?2.5 us. It is also responsible for initiating the read-out of data from all the sub-detectors in ATLAS. Based primarily on information from calorimeters and muon trigger detectors, the Central Trigger Processor (CTP) produces the Level-­1 trigger decision. After a very successful first run, the LHC is now being upgraded to operate with increased luminosity and a center-of-mass energy of up to 14 TeV. To cope with the higher luminosities, the Level-1 trigger system will have to perform a more refined selection in order to not lose interesting physics data while keeping the total Level-1 rate below 100~kHz. In this pr...

Ohm, C; The ATLAS collaboration

2014-01-01

336

An upgraded ATLAS Central Trigger for 2015 LHC luminosities  

CERN Document Server

The LHC collides protons at a rate of 40 MHz and each collision produces $\\sim$1.5~MB of data from the ATLAS detector. The ATLAS trigger system is implemented in three levels and selects only the most interesting collision events to reduce the event storage rate to about 400 Hz. The first level is implemented in custom electronics and reduces the input rate to $\\sim$75 kHz with a decision latency of $\\sim$2.5 us. It is also responsible for initiating the read-out of data from all the sub-detectors in ATLAS. Based primarily on information from calorimeters and muon trigger detectors, the Central Trigger Processor (CTP) produces the Level-­1 trigger decision. After a very successful first run, the LHC is now being upgraded to operate with increased luminosity and a center-of-mass energy of up to 14 TeV. To cope with the higher luminosities, the Level-1 trigger system will have to perform a more refined selection in order to not lose interesting physics data while keeping the total Level-1 rate below 100~kHz. I...

Ohm, C

2014-01-01

337

High luminosity electron-hadron collider eRHIC  

Energy Technology Data Exchange (ETDEWEB)

We present the design of a future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan on adding 20 (potentially 30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 10{sup 34} cm{sup -2} s{sup -1} can be achieved in eRHIC using the low-beta interaction region with a 10 mrad crab crossing. We report on the progress of important eRHIC R&D such as the high-current polarized electron source, the coherent electron cooling, ERL test facility and the compact magnets for recirculation passes. A natural staging scenario of step-by-step increases of the electron beam energy by building-up of eRHIC's SRF linacs is presented.

Ptitsyn, V.; Aschenauer, E.; Bai, M.; Beebe-Wang, J.; Belomestnykh, S.; Ben-Zvi, I.; Blaskiewicz, M..; Calaga, R.; Chang, X.; Fedotov, A.; Gassner, D.; Hammons, L.; Hahn, H.; Hammons, L.; He, P.; Hao, Y.; Jackson, W.; Jain, A.; Johnson, E.C.; Kayran, D.; Kewisch, J.; Litvinenko, V.N.; Luo, Y.; Mahler, G.; McIntyre, G.; Meng, W.; Minty, M.; Parker, B.; Pikin, A.; Rao, T.; Roser, T.; Skaritka, J.; Sheehy, B.; Skaritka, J.; Tepikian, S.; Than, Y.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J.; Wang, G.; Webb, S.; Wu, Q.; Xu, W.; Pozdeyev, E.; Tsentalovich, E.

2011-03-28

338

A two-mode planetary nebula luminosity function  

CERN Document Server

We propose a new Planetary Nebula Luminosity Function (PNLF) that includes two populations in the distribution. Our PNLF is a direct extension of the canonical function proposed by Jacoby et al. (1987), in order to avoid problems related with the histogram construction, it is cast in terms of cumulative functions. We are interested in recovering the shape of the faint part of the PNLF in a consistent manner, for galaxies with and without a dip in their PN luminosity functions. The parameters for the two mode PNLF are obtained with a genetic algorithm, which obtains a best fit to the PNLF varying all of the parameters simultaneously in a broad parameter space. We explore a sample of 9 galaxies with various Hubble types and construct their PNLF. All of the irregular galaxies, except one, are found to be consistent with a two-mode population, while the situation is less clear for ellipticals and spirals.For the case of NGC\\, 6822, we show that the two-mode PNLF is consistent with previous studies of the star for...

Rodríguez-González, A; Esquivel, A; Raga, A C; Stasi?ska, G; Peña, M; Mayya, D

2014-01-01

339

Galactic distribution, birthrate, and luminosity evolution of pulsars  

International Nuclear Information System (INIS)

Galactic pulsars are distributed in a ring about 7--8 kpc across, on the average. The pulsar surface density within the ring rises outward from the galactic center, peaks at R = 5.2 +- 0.4 kpc, and then falls off rapidly. The total number of pulsars whose luminosity L = (0.3--300) x 1027 erg/sec is estimated; their birthrate ?/sub p/ = 0.027 +- 0.009 yr-1, or one pulsar every 37+18/sub -/9 yr. This ?/sub p/ value is an upper limit, corresponding to a minimum value of the orientation coefficient (f = 1/9). Pulsar luminosity evolves with age as L = c2t/sup -mu/, where c2 = (4.3 +- 3.9) x 1035, ? = 1.34 +- 0.09 (t in yr, L in erg/sec). For pulsars with L> or =3 x 1026 erg/sec this law yields a true age t/sub p/ = (3.6 +- 0.4) x 106 yr, in good accord with kinematic and spindown ages estimated for young pulsars

340

The dynamical state of galaxy groups and their luminosity content  

CERN Document Server

We analyse the dependence of the luminosity function of galaxies in groups (LF) on group dynamical state. We use the Gaussianity of the velocity distribution of galaxy members as a measurement of the dynamical equilibrium of groups identified in the SDSS Data Release 7 by Zandivarez & Martinez. We apply the Anderson-Darling goodness-of-fit test to distinguish between groups according to whether they have Gaussian or Non-Gaussian velocity distributions, i.e., whether they are relaxed or not. For these two subsamples, we compute the $^{0.1}r-$band LF as a function of group virial mass and group total luminosity. For massive groups, ${\\mathcal M}>5 \\times 10^{13} \\ M_{\\odot} \\ h^{-1}$, we find statistically significant differences between the LF of the two subsamples: the LF of groups that have Gaussian velocity distributions have a brighter characteristic absolute magnitude ($\\sim0.3$ mag) and a steeper faint end slope ($\\sim0.25$). We detect a similar effect when comparing the LF of bright ($M^{group}_{^{0...

Martinez, Hector J

2011-01-01

341

The U-band Galaxy Luminosity Function of Nearby Clusters  

CERN Document Server

Despite the great potential of the U-band galaxy luminosity function (GLF) to constrain the history of star formation in clusters, to clarify the question of variations of the GLF across filter bands, to provide a baseline for comparisons to high-redshift studies of the cluster GLF, and to estimate the contribution of bound systems of galaxies to the extragalactic near-UV background, determinations have so far been hampered by the generally low efficiency of detectors in the U-band and by the difficulty of constructing both deep and wide surveys. In this paper, we present U-band GLFs of three nearby, rich clusters to a limit of M_U=-17.5 (M*_U+2). Our analysis is based on a combination of separate spectroscopic and R-band and U-band photometric surveys. For this purpose, we have developed a new maximum-likelihood algorithm for calculating the luminosity function that is particularly useful for reconstructing the galaxy distribution function in multi-dimensional spaces (e.g., the number of galaxies as a simult...

Christlein, D; Zabludoff, A I

2004-01-01

342

Topological and Central Trigger Processor for 2014 LHC luminosities  

CERN Document Server

The ATLAS experiment is located at the European Center for Nuclear Research (CERN) in Switzerland. It is designed to observe phenomena that involve highly massive particles produced in the collisions at the Large Hadron Collider (LHC): the world’s largest and highest-energy particle accelerator. Event triggering and Data Acquisition is one of the extraordinary challenges faced by the detectors at the high luminosity LHC collider. During 2011, the LHC reached instantaneous luminosities of 4 10^33 cm?1 s?1 and produced events with up to 24 interactions per colliding proton bunch. This places stringent operational and physical requirements on the ATLAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of 400Hz and, at the same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75kHz and decision latency of less than 2.5 micro seconds. It is primarily composed of the Calori...

Simioni, E; The ATLAS collaboration; Bauss, B; Berge, D; Buscher, V; Childers, T; Degele, R; Dobson, E; Ebling, A; Ellis, N; Farthouat, P; Gabaldon, C; Gorini, B; Haas, S; Ji, W; Kaneda, M; Mattig, S; Messina, A; Meyer, C; Moritz, S; Pauly, T; Pottgen, R; Schafer, U; Spiwoks, R; Tapprogge, S; Wengler, T; Wenzel, V

2012-01-01

343

Topological and Central Trigger Processor for 2014 LHC luminosities  

CERN Document Server

The ATLAS experiment is located at the European Center for Nu- clear Research (CERN) in Switzerland. It is designed to observe phe- nomena that involve highly massive particles produced in the collisions at the Large Hadron Collider (LHC): the world’s largest and highest-energy particle accelerator. Event triggering and Data Acquisition is one of the extraordinary challenges faced by the detectors at the high luminosity LHC collider. During 2011, the LHC reached instantaneous luminosities of 4×10^33 cm?1 s?1 and produced events with up to 24 interactions per colliding proton bunch. This places stringent operational and physical requirements on the AT- LAS Trigger in order to reduce the 40MHz collision rate to a manageable event storage rate of 400Hz and, at the same time, selecting those events considered interesting. The Level-1 Trigger is the first rate-reducing step in the ATLAS Trigger, with an output rate of 75kHz and decision latency of less than 2.5?s. It is primarily composed of the Calorimete...

Simioni, E; The ATLAS collaboration; Bauss, B; Berge, D; B\\"{u}scher, V; Childers, T; Degele, R; Dobson, E; Ebling, A; Ellis, N; Farthouat, P; Gabaldon, C; Gorini, B; Haas, S; Ji, W; Kaneda, M; M\\"{a}ttig, S; Messina, A; Meyer, C; Moritz, S; Pauly, T; Pottgen, R; Sch\\"{a}fer, U; Spiwoks, R; Tapprogge, S; Wengler, T; Wenzel, V

2012-01-01

344

Progress toward a high-energy, high-luminosity ?+-?- collider  

Science.gov (United States)

In the past two years, considerable progress has been made in development of the ?+-?- collider concept. This collider concept could permit exploration of elementary particle physics at energy frontiers beyond the reach of currently existing and proposed electron and hadron colliders. As a benchmark prototype, we present a candidate design for a high-energy high-luminosity ?+-?- collider, with Ecm=4 TeV, L=3×1034 cm-2 s-1, based on existing technical capabilities. The design uses a rapid-cycling medium-energy proton synchrotron, producing proton beam pulses which are focused onto two ?-producing targets, with two ?-decay transport lines producing ?+'s and ?-'s. The ?'s are collected, rf-rotated, cooled and compressed into a recirculating linac for acceleration, and then transferred into a storage ring collider. The keys to high luminosity are maximal ? collection and cooling, and innovations with these goals are presented. Possible variations and improvements are discussed. Recent progress in collider concept development is summarized, and future plans for collider development are discussed.

Neuffer, David V.; Palmer, Robert B.

1996-01-01

345

Luminosity determination at ANKE with different reference reactions  

International Nuclear Information System (INIS)

A high precision measurement on the mass of the eta meson was the main objective of the COSY proposal Nr. 187. In detail the meson production reaction dp ? 3HeX has been studied with X being the eta meson identified by the missing mass technique. However, parallel to the already very successfully performed eta mass determination, the obtained data also allow for studies on total and differential cross sections for the reaction dp ? 3He? close to threshold as well as for a study of the ABC-effect in the channel dp ? 3He?+?-. For this purpose a careful data normalization and luminosity determination is required. While dp-elastic scattering is commonly used as reference reaction for the luminosity determination at ANKE, an independent normalization channel is of high interest as cross reference. Therefore, the 3He?0 final state is analyzed in parallel and the results are compared to the dp-elastic scattering data. The method and recent results are presented.

346

SDSS Galaxy Clustering: Luminosity & Color Dependence and Stochasticity  

CERN Document Server

Differences in clustering properties between galaxy subpopulations complicate the cosmological interpretation of the galaxy power spectrum, but can also provide insights about the physics underlying galaxy formation. To study the nature of this relative clustering, we perform a counts-in-cells analysis of galaxies in the Sloan Digital Sky Survey (SDSS) in which we measure the relative bias between pairs of galaxy subsamples of different luminosities and colors. We use a generalized chi-squared test to determine if the relative bias between each pair of subsamples is consistent with the simplest deterministic linear bias model, and we also use a maximum likelihood technique to further understand the nature of the relative bias between each pair. We find that the simple, deterministic model is a good fit for the luminosity-dependent bias on scales above about 5 Mpc/h, which is good news for using magnitude-limited surveys for cosmology. However, the color-dependent bias shows evidence for stochasticity and/or n...

Swanson, M E C; Blanton, M; Zehavi, I; Swanson, Molly E.C.; Tegmark, Max; Blanton, Michael; Zehavi, Idit

2007-01-01

347

Optical variability properties of high luminosity AGN classes  

CERN Document Server

We present the results of a comparative study of the intra-night optical variability (INOV) characteristics of radio-loud and radio-quiet quasars, which involves a systematic intra-night optical monitoring of seven sets of high luminosity AGNs covering the redshift range {it z} $simeq 0.2$ to {it z} $simeq 2.2$. The sample, matched in the optical luminosity -- redshift (M$_B$ -- z) plane, consists of seven radio-quiet quasars (RQQs), eight radio lobe-dominated quasars (LDQs), six radio core-dominated quasars (CDQs) and five BL Lac objects (BLs). Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to detect INOV with amplitudes as low as 1%. Present observations cover a total of 113 nights (720 hours) with only a single quasar monitored as continuously as possible on a night. Considering cases of only unambiguous detections of INOV we have estimated duty cycles (DCs) of 17%, 12%, 20% and 72% respectively for RQQs, LDQs, CDQs, and BLs. The low amplitude and low DC of INOV sh...

Stalin, C S; Wiita, P J; Sagar, Ram; Wiita, Paul J.

2003-01-01

348

The metric of the cosmos from luminosity and age data  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the algorithm for determining the Lemaître-Tolman model that best fits given datasets for maximum stellar ages, and SNIa luminosities, both as functions of redshift. It then applies it to current cosmological data. Special attention must be given to the handling of the origin, and the region of the maximum diameter distances. As with a previous combination of datasets (galaxy number counts and luminosity distances versus redshift), there are relationships that must hold at the region of the maximum diameter distance, which are unlikely to be obeyed exactly by real data. We show how to make corrections that enable a self-consistent solution to be found. We address the questions of the best way to approximate discrete data with smooth functions, and how to estimate the uncertainties of the output — the 3 free functions that determine a specific Lemaître-Tolman metric. While current data does not permit any confidence in our results, we show that the method works well, and reasonable Lemaître-Tolman models do fit with or without a cosmological constant.

Bolejko, Krzysztof [Astrophysics Department, University of Oxford, 1 Keble Road, Oxford OX1 3RH (United Kingdom); Hellaby, Charles; Alfedeel, Alnadhief H.A., E-mail: Krzysztof.Bolejko@astro.ox.ac.uk, E-mail: Charles.Hellaby@uct.ac.za, E-mail: Alnadhief.Alfedeel@uct.ac.za [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa)

2011-09-01

349

The metric of the cosmos from luminosity and age data  

International Nuclear Information System (INIS)

This paper presents the algorithm for determining the Lemaître-Tolman model that best fits given datasets for maximum stellar ages, and SNIa luminosities, both as functions of redshift. It then applies it to current cosmological data. Special attention must be given to the handling of the origin, and the region of the maximum diameter distances. As with a previous combination of datasets (galaxy number counts and luminosity distances versus redshift), there are relationships that must hold at the region of the maximum diameter distance, which are unlikely to be obeyed exactly by real data. We show how to make corrections that enable a self-consistent solution to be found. We address the questions of the best way to approximate discrete data with smooth functions, and how to estimate the uncertainties of the output — the 3 free functions that determine a specific Lemaître-Tolman metric. While current data does not permit any confidence in our results, we show that the method works well, and reasonable Lemaître-Tolman models do fit with or without a cosmological constant

350

Cosmological Evolution Models for QSO/AGN Luminosity Functions Effects of Spectrum-Luminosity Correlation and Massive Black Hole Remnants  

CERN Document Server

We investigate a large number of cosmological evolution models for QSOs and Active Galactic Nuclei (AGN). We introduce a spectrum-luminosity correlation as a new input parameter and adopt the estimated mass function (MF) of massive black holes in centers of nearby galactic nuclei as a constraint to distinguish among different QSO/AGN models. We explore three basic types of phenomenological scenarios; (i) Models with multiple short-lived ($\\sim$ a few $10^{6-8}$ yrs) populations, (ii) Models with a single long-lived ($\\sim 10^9$ yr) QSO population, and (iii) Models with recurrent QSO/AGN activities which are driven by long-term variabilities of the disk instability type. In each model, we derive the expected theoretical luminosity function (LF) and the MF of black holes which grow through mass accretion. We assess the plausibility of each model based on whether each model's LF and MF are compatible with the observed data. We find that the best fits to the observed LFs are obtained in the model with multiple sh...

Choi, Y Y; Yi, I; Choi, Yun-Young; Yang, Jongmann; Yi, Insu

2000-01-01

351

Bolometric luminosity black hole growth time and slim accretion discs in active galactic nuclei  

Science.gov (United States)

We investigate the accretion rate, bolometric luminosity, black hole (BH) growth time and BH spin in a large active galactic nucleus (AGN) sample under the assumption that all such objects are powered via thin or slim accretion discs (ADs). We use direct estimates of the mass accretion rate, dot{M}, to show that many currently used values of Lbol and L/LEdd are either underestimated or overestimated because they are based on bolometric correction factors that are adjusted to the properties of moderately accreting AGNs and do not take into account the correct combination of BH mass, spin and accretion rate. The consistent application of AD physics to our sample of Sloan Digital Sky Survey (SDSS) AGNs leads to the following findings. (1) Even the most conservative assumption about the radiative efficiency of fast-accreting BHs shows that many of these sources must contain slim ADs. We illustrate this by estimating the fraction of such objects at various redshifts. (2) Many previously estimated BH growth times are inconsistent with the AD theory. In particular, the growth times of the fastest accreting BHs were overestimated in the past by large factors with important consequences to AGN evolution. (3) Currently used bolometric correction factors for low accretion rate very massive SDSS BHs are inconsistent with the AD theory. Applying the AD set of assumptions to such objects, combined with standard photoionization calculations of broad emission lines, leads to the conclusion that many such objects must contain fast-spinning BHs.

Netzer, Hagai; Trakhtenbrot, Benny

2014-02-01

352

Galaxy clustering and projected density profiles as traced by satellites in photometric surveys: Methodology and luminosity dependence  

CERN Document Server

We develop a new method which measures the projected density distribution w_p(r_p)n of photometric galaxies surrounding a set of spectroscopically-identified galaxies, and simultaneously the projected cross-correlation function w_p(r_p) between the two populations. In this method we are able to divide the photometric galaxies into luminosity intervals even when redshift information is unavailable, enabling us to measure w_p(r_p)n and w_p(r_p) as a function of not only the luminosity of the spectroscopic galaxy, but also that of the photometric galaxy. We have applied our method to data from the Sloan Digital Sky Survey (SDSS) including a sample of 10^5 luminous red galaxies (LRGs) at z~0.4 and a sample of about half a million galaxies at z~0.1, both of which are cross-correlated with a deep photometric sample drawn from the SDSS. On large scales, the relative bias factor measured from w_p(r_p) for LRGs at z~0.4 depends on luminosity in a manner similar to what is found for galaxies at z~0.1, which are usually...

Wang, Wenting; Li, Cheng; Okumura, Teppei; Han, Jiaxin

2010-01-01

353

The distribution in luminosity of OB stars and evolutionary timescales  

International Nuclear Information System (INIS)

The authors have obtained the observed fraction of supergiant (luminosity classes I and II), giant (III) and dwarf (IV-V) stars of spectral types B2 and earlier. The stellar sample used was formed with all the stars with bidimensional spectral classification listed in the Catalogue of Galactic O stars by Cruz-Gonzalez et al. (1974) , and unpublished compilation of BO and BO.5 stars by J. F. Rayo, and the B1-B2 stars listed by Morgan et at. (1955). The results are listed together with the total number of stars considered in each spectral interval. A prominent conclusion is drawn from the table: The fractions remain approximately constant all over the spectral range considered. (Auth.)

354

Redshift drift and luminosity distance in VSL cosmology  

CERN Document Server

We derive a redshift drift formula within the framework of varying speed of light (VSL) theory using the specific ansatz for the variability of $c(t) = c_0 a^n(t)$. We show that negative values of the parameter $n$, which corresponds to diminishing value of the speed of light during the evolution of the universe, effectively rescales dust matter to become little negative pressure matter and the cosmological constant to became phantom. Positive values of $n$ (growing $c(t)$) make VSL model to become more like Cold Dark Matter (CDM) model. We also present the luminosity distance formula for the VSL theory which involves higher order characteristics of expansion such as jerk and snap which can test the impact of varying speed of light $c$ onto the kinematics of the universe.

Balcerzak, Adam

2014-01-01

355

An Upgraded ATLAS Central Trigger for 2015 Luminosities  

CERN Document Server

The Central Trigger Processor (CTP) is the core unit of the first of three levels that constitute the ATLAS trigger system. Based on information from calorimeter and muon trigger processors as well as from some additional systems it produces the level-1 trigger decision and prompts the read-out of the sub-detectors. The increase in luminosity at the LHC has pushed the CTP operation to its design limits. In order to still satisfy the physics goals of the experiment after the shutdown of the LHC of 2013/2014 the CTP will be upgraded during this period. This article discusses the current Central Trigger Processor, the motivation for the upgrade, and the changes foreseen to meet the requirements of the post-2014 physics runs at the LHC.

Poettgen, R; The ATLAS collaboration

2013-01-01

356

Kinematic corrections to the averaged luminosity distance in inhomogeneous universes  

CERN Document Server

The redshift surfaces within inhomogeneous universes are shifted by the matter peculiar velocities. The arising average corrections to the luminosity distance are calculated relativistically in several Swiss-cheese models with mass compensated Lemaitre-Tolman-Bondi voids. These kinematic corrections are different from weak lensing effects and can be much bigger close to the observer. The statistical averaging over all directions is performed by tracing numerically light rays propagating through a random void lattice. The probability of a supernova emision from a comoving volume is assumed proportional to the rest mass in it. The average corrections to the distance modulus can be significant for redshifts smaller than 0.02 for small voids (radius 30 Mpc) and redshifts smaller than 0.1 for big voids (radius 300 Mpc), yet not large enough to substitute for dark energy. The corrections decay inversely proportional to the distance from the observer. In addition, there is a random cancelation of corrections between...

Kostov, Valentin

2010-01-01

357

The Metallicity Dependence of the Cepheid Period-Luminosity Relation  

CERN Document Server

We have assessed the influence of the stellar iron content on the Cepheid Period-Luminosity (PL) relation by relating the V band residuals from the Freedman et al (2001) PL relation to [Fe/H] for 68 Galactic and Magellanic Cloud Cepheids. The iron abundances were measured from FEROS and UVES high-resolution and high signal-to-noise optical spectra. Our data indicate that the stars become fainter as metallicity increases, until a plateau or turnover point is reached at about solar metallicity. This behavior appears at odds both with the PL relation being independent from iron abundance and with Cepheids becoming monotonically brighter as metallicity increases (e.g. Kennicutt et al 1998, Sakai et al 2004).

Romaniello, M; Primas, F; Groenewegen, M; Bono, G; François, P

2004-01-01

358

CMS in the high luminosity era of the LHC  

CERN Document Server

In this presentation, the presentations and discussions of the workshop are summarized. LHC and CMS progress in physics thus far are covered along with the status of the Higgs and related new physics searches. The absence of new physics in any searches has created some stir in the theoretical community, emphasizing the need for greater input from the experimental side. Lessons for the near term are considered, followed by a look forward to potential future High Luminosity and High Energy eras of operation for the LHC. The potential new physics landscape to be explored remains fairly broad as presented in many talks at the workshop. Properties of a Higgs at 125–126 GeV could be studied in these future periods. In the Higgs sector the key items to be measured are delineated and related back to the needs of CMS upgrades. The opportunities and challenges are both very great.

Incandela, J

2013-01-01

359

Masses, radii, temperatures, luminosities and surface compositions of white dwarfs  

Science.gov (United States)

The masses, radii, temperature, luminosities and compositions of white dwarf stars are discussed, with particular emphasis on those areas in which considerable work remains to be done. It is pointed out that radii for stars of known parallax are available, together with masses and their variance. Consideration is then given to the difficulties involved in the determination of the temperatures of the hottest stars and helium stars by means of Stromgren or multichannel photometry, and it is noted that the frequency of binaries among the hottest degenerates seems too high to be due to chance. Results of IUE observations of the UV spectra of three DA and one DO star are discussed, with attention given to the similarities between UV-derived and ground-based determinations of temperatures and surface gravities. The metal abundances of hydrogen and helium degenerate stars are finally considered, and spectral classes and abundances of the helium atmosphere degenerates are tabulated.

Greenstein, J. L.

1979-01-01

360

Robust Constraint of Luminosity Function Evolution Through MCMC Sampling  

CERN Document Server

We present a new galaxy survey simulation package, which combines the power of Markov Chain Monte Carlo (MCMC) sampling with a robust and adaptable model of galaxy evolution. The aim of this code is to aid in the characterization and study of new and existing galaxy surveys. In this paper we briefly describe the MCMC implementation and the survey simulation methodology and associated tools. A test case of this full suite was to constrain the evolution of the IR Luminosity Function (LF) based on the HerMES (Herschel SPIRE) survey of the Spitzer First Look Survey field. The initial results are consistent with previous studies, but our more general approach should be of wider benefi?t to the community.

Kurinsky, Noah

2014-01-01

361

On the accretion luminosity of isolated neutron stars  

CERN Document Server

The accretion process onto a magnetized isolated neutron star, which captures material from the interstellar medium, is discussed. The evolutionary track of such a star can be presented as a sequence of four states: ejector, supersonic propeller, subsonic propeller, and steady accretor. I show that subsonic propeller - accretor transition does not occur as long as the magnetic field of the star is strong enough to control the accretion flow in the stellar vicinity. During the subsonic propeller state the accretion rate onto the stellar surface is limited to the rate of plasma diffusion into its magnetosphere. The diffusion rate is at least three orders of magnitude smaller than the maximum possible mass capture rate by the star. Therefore, the expected accretion luminosity of magnetized isolated neutron stars is at least three orders of magnitude smaller than that previously evaluated.

Ikhsanov, N R

2003-01-01

362

Low-luminosity Seyfert nuclei in nearby galaxies  

Energy Technology Data Exchange (ETDEWEB)

Broad H..cap alpha.. emission lines have been detected in the nuclei of many bright galaxies such as M81 and M87. These lines are similar to, but much weaker than, those seen in type 1 Seyfert nuclei and QSOs. If massive black holes are responsible for the broad lines and the immense luminosities of classical AGNs, continuity arguments suggest that they also produce the features observed at lower levels in the relatively ''normal'' galaxies studied here, especially since the intensity ratios of the narrow emission lines are like those expected from gas photoionized by dilute nonstellar (e.g., power-law) radiation. The possible presence of massive black holes in nearby galaxies is consistent with the conclusion that the nucleus of our own Milky Way may harbor such an object.

Filippenko, A.V.; Sargent, W.L.W.

1987-04-15

363

Low-luminosity Seyfert nuclei in nearby galaxies  

International Nuclear Information System (INIS)

Broad H? emission lines have been detected in the nuclei of many bright galaxies such as M81 and M87. These lines are similar to, but much weaker than, those seen in type 1 Seyfert nuclei and QSOs. If massive black holes are responsible for the broad lines and the immense luminosities of classical AGNs, continuity arguments suggest that they also produce the features observed at lower levels in the relatively ''normal'' galaxies studied here, especially since the intensity ratios of the narrow emission lines are like those expected from gas photoionized by dilute nonstellar (e.g., power-law) radiation. The possible presence of massive black holes in nearby galaxies is consistent with the conclusion that the nucleus of our own Milky Way may harbor such an object

364

130 mm Aperture Quadrupoles for the LHC Luminosity Upgrade  

CERN Document Server

Several studies for the LHC luminosity upgrade pointed out the need for low-beta quadrupoles with apertures larger than the present baseline (70 mm). In this paper we focus on the design issues of a 130 mm aperture quadrupole. We first consider the Nb-Ti option, presenting a magnetic design with the LHC dipole and quadrupole cables. We study the electromagnetic forces and we discuss the field quality constraints. For the Nb3Sn option, we sketch three designs, two based on the LARP 10 mm width cable, and one on a larger cable with the same strand. The issue of the stress induced by the e.m. forces, which is critical for the Nb3Sn, is discussed using both scaling laws and finite element models.

Todesco, E; Mailfert, A

2007-01-01

365

Properties of the Molecular Cores of Low Luminosity Objects  

Science.gov (United States)

We present a survey toward 16 low luminosity objects (LLOs with an internal luminosity, Lint, lower than 0.2 L?) with N2H+ (1–0), N2H+ (3–2), N2D+ (3–2), HCO+ (3–2), and HCN (3–2) using the Arizona Radio Observatory Kitt Peak 12 m Telescope and Submillimeter Telescope. Our goal is to probe the nature of these faint protostars which are believed to be either very low mass or extremely young protostars. We find that the N2D+/N2H+ column density ratios of LLOs are similar to those of typical starless cores and Class 0 objects. The N2D+/N2H+ column density ratios are relatively high (>0.05) for LLOs with kinetic temperatures less than 10 K in our sample. The distribution of N2H+ (1–0) line widths spreads between that of starless cores and young Class 0 objects. If we use the line width as a dynamic evolutionary indicator, LLOs are likely young Class 0 protostellar sources. We further use the optically thick tracers, HCO+ (3–2) and HCN (3–2), to probe the infall signatures of our targets. We derive the asymmetry parameters from both lines and estimate the infall velocities by fitting the HCO+ (3–2) spectra with two-layer models. As a result, we identify eight infall candidates based on the infall velocities and seven candidates have infall signatures supported by asymmetry parameters from at least one of HCO+ (3–2) and HCN (3–2).

Hsieh, Tien-Hao; Lai, Shih-Ping; Belloche, Arnaud; Wyrowski, Friedrich; Hung, Chao-Ling

2015-04-01

366

The Origin of Intermediate-Luminosity Red Transients  

Science.gov (United States)

Intermediate-luminosity red transients (ILRTs) are a new class of optical transients. They have maximum luminosities between novae and SNe, and outbursts lasting several months, becoming cool, dusty, and extremely red as the eruptions proceed. A prototype is V838 Mon, which illuminated a spectacular light echo. Their outbursts may be due to catastrophic stellar collisions and mergers. This is demonstrably true for V1309 Sco, which was a contact binary before its eruption and is now a single star. However, it is not yet clear whether all ILRTs are due to mergers.I propose WFC3 imaging of 3 ILRTs: (1) V4332 Sgr, which erupted in the Galactic bulge in 1994, is now a 19th-mag, very red remnant. Based on a high degree of linear polarization in ground-based measurements, it has been proposed that it is surrounded and obscured by a dusty, edge-on envelope, ejected during a stellar merger. If so, V4332 Sgr ought to display a dark lane at HST imaging resolution. (2) M31 RV is an ILRT that occurred in the bulge of M31 in 1988. HST images of the site taken between 1999 and 2010 failed to reveal a credible remnant of this event. However, models of expanding dusty envelopes predict that eventually, as the optical depth diminishes, the remnant should brighten. The passage of 5 years since the last HST observation of the field justifies another attempt to identify the putative merged binary. (3) CK Vul, the bright "nova" of 1670, is a candidate ILRT because of its red color and an outburst light curve resembling that of V838 Mon. A faint bipolar nebula lies at the site of CK Vul, but no credible remnant star has been found in ground-based images. HST resolution may reveal it.

Bond, Howard

2014-10-01

367

VARIABILITY-SELECTED LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI IN THE 4 Ms CHANDRA DEEP FIELD-SOUTH  

International Nuclear Information System (INIS)

The 4 Ms Chandra Deep Field-South (CDF-S) and other deep X-ray surveys have been highly effective at selecting active galactic nuclei (AGNs). However, cosmologically distant low-luminosity AGNs (LLAGNs) have remained a challenge to identify due to significant contribution from the host galaxy. We identify long-term X-ray variability (?month-years, observed frame) in 20 of 92 CDF-S galaxies spanning redshifts z ? 0.08-1.02 that do not meet other AGN selection criteria. We show that the observed variability cannot be explained by X-ray binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole (SMBH). The variable galaxies are not heavily obscured in general, with a stacked effective power-law photon index of ?stack ? 1.93 ± 0.13, and are therefore likely LLAGNs. The LLAGNs tend to lie a factor of ?6-80 below the extrapolated linear variability-luminosity relation measured for luminous AGNs. This may be explained by their lower accretion rates. Variability-independent black hole mass and accretion-rate estimates for variable galaxies show that they sample a significantly different black hole mass-accretion-rate space, with masses a factor of 2.4 lower and accretion rates a factor of 22.5 lower than variable luminous AGNs at the same redshift. We find that an empirical model based on a universal broken power-law power spectral density function, where the break frequency depe, where the break frequency depends on SMBH mass and accretion rate, roughly reproduces the shape, but not the normalization, of the variability-luminosity trends measured for variable galaxies and more luminous AGNs.

368

Variability Selected Low-Luminosity Active Galactic Nuclei in the 4 Ms Chandra Deep Field-South  

Science.gov (United States)

The 4 Ms Chandra Deep Field-South (CDF-S) and other deep X-ray surveys have been highly effective at selecting active galactic nuclei (AGN). However, cosmologically distant low-luminosity AGN (LLAGN) have remained a challenge to identify due to significant contribution from the host galaxy. We identify long-term X ray variability (approx. month years, observed frame) in 20 of 92 CDF-S galaxies spanning redshifts approx equals 00.8 - 1.02 that do not meet other AGN selection criteria. We show that the observed variability cannot be explained by X-ray binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole. The variable galaxies are not heavily obscured in general, with a stacked effective power-law photon index of Gamma(sub Stack) approx equals 1.93 +/- 0.13, and arc therefore likely LLAGN. The LLAGN tend to lie it factor of approx equal 6-89 below the extrapolated linear variability-luminosity relation measured for luminous AGN. This may he explained by their lower accretion rates. Variability-independent black-hole mass and accretion-rate estimates for variable galaxies show that they sample a significantly different black hole mass-accretion-rate space, with masses a factor of 2.4 lower and accretion rates a factor of 22.5 lower than variable luminous AGNs at the same redshift. We find that an empirical model based on a universal broken power-law power spectral density function, where the break frequency depends on SMBH mass and accretion rate, roughly reproduces the shape, but not the normalization, of the variability-luminosity trends measured for variable galaxies and more luminous AGNs.

Young, M.; Brandt, W. N.; Xue, Y. Q.; Paolillo, D. M.; Alexander, F. E.; Bauer, F. E.; Lehmer, B. D.; Luo, B.; Shemmer, O.; Schneider, D. P.; Vignail, C.

2012-01-01

369

PHOTOMETRIC PROPERTIES AND LUMINOSITY FUNCTION OF NEARBY MASSIVE EARLY-TYPE GALAXIES  

Energy Technology Data Exchange (ETDEWEB)

We perform photometric analyses of a bright early-type galaxy sample with 2949 galaxies (M{sub r} < -22.5 mag) in the redshift range of 0.05-0.15, drawn from the Sloan Digital Sky Survey (SDSS) DR7 with morphological classification from Galaxy Zoo 1. We measure the Petrosian and isophotal magnitudes, as well as the corresponding half-light radius for each galaxy. We find that for the brightest galaxies (M{sub r} < -23 mag), our Petrosian magnitudes and isophotal magnitudes to 25 mag arcsec{sup -2} and 1% of the sky brightness are on average 0.16 mag, 0.20 mag, and 0.26 mag brighter than the SDSS Petrosian values, respectively. In the first case, the underestimations are caused by overestimations in the sky background by the SDSS PHOTO algorithm, while the latter two are also due to deeper photometry. Similarly, the typical half-light radii (r{sub 50}) measured by the SDSS algorithm are smaller than our measurements. As a result, the bright end of the r-band luminosity function is found to decline more slowly than previous works. Our measured luminosity densities at the bright end are more than one order of magnitude higher than those of Blanton et al., and the stellar mass densities at M{sub *} {approx} 5 Multiplication-Sign 10{sup 11} M{sub Sun} and M{sub *} {approx} 10{sup 12} M{sub Sun} are a few tenths and a factor of a few higher than those of Bernardi et al. These results may significantly alleviate the tension in the assembly of massive galaxies between observations and predictions of the hierarchical structure formation model.

He, Y. Q. [University of Chinese Academy of Sciences, Beijing 100049 (China); Xia, X. Y.; Hao, C. N. [Tianjin Astrophysics Center, Tianjin Normal University, Tianjin 300387 (China); Jing, Y. P. [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Mao, S. [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Li, Cheng, E-mail: xyxia@bao.ac.cn [Partner Group of the Max Planck Institute for Astrophysics at the Shanghai Astronomical Observatory and Key Laboratory for Research in Galaxies and Cosmology of Chinese Academy of Sciences, Nandan Road 80, Shanghai 200030 (China)

2013-08-10

370

Upgraded Readout Electronics for the ATLAS Liquid Argon Calorimeters at the High Luminosity LHC  

Science.gov (United States)

The ATLAS liquid-argon calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics sum analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up background expected during the high luminosity phases of the LHC will be increased by factors of 3 to 7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background rejection rates. For the first upgrade phase in 2018, new Liquid Argon Trigger Digitizer Boards are being designed to receive higher granularity signals, digitize them on detector and send them via fast optical links to a new, off-detector digital processing system. The digital processing system applies digital filtering and identifies significant energy depositions. The refined trigger primitives are then transmitted to the first level trigger system to extract improved trigger signatures. The general concept of the upgraded liquid-argon calorimeter readout together with the various electronics components to be developed for such a complex system is presented. The research activities and architectural studies undertaken by the ATLAS Liquid Argon Calorimeter Group are described, particularly details of the on-going design of mixed-signal front-end electronics, of radiation tolerant optical-links, and of the high-speed off-detector digital processing system.

Andeen, Timothy R.; ATLAS Liquid Argon Calorimeter Group

2012-12-01

371

Upgraded Readout Electronics for the ATLAS Liquid Argon Calorimeters at the High Luminosity LHC  

International Nuclear Information System (INIS)

The ATLAS liquid-argon calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics sum analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up background expected during the high luminosity phases of the LHC will be increased by factors of 3 to 7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background rejection rates. For the first upgrade phase in 2018, new Liquid Argon Trigger Digitizer Boards are being designed to receive higher granularity signals, digitize them on detector and send them via fast optical links to a new, off-detector digital processing system. The digital processing system applies digital filtering and identifies significant energy depositions. The refined trigger primitives are then transmitted to the first level trigger system to extract improved trigger signatures. The general concept of the upgraded liquid-argon calorimeter readout together with the various electronics components to be developed for such a complex system is presented. The research activities and architectural studies undertaken by the ATLAS Liquid Argon Calorimeter Group are describLiquid Argon Calorimeter Group are described, particularly details of the on-going design of mixed-signal front-end electronics, of radiation tolerant optical-links, and of the high-speed off-detector digital processing system.

372

Measurement of the luminosity in the ZEUS experiment at HERA II  

Energy Technology Data Exchange (ETDEWEB)

The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung off protons. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.

Adamczyk, L. [AGH University of Science and Technology, Cracow (Poland); Andruszkow, J. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Bold, T. [AGH University of Science and Technology, Cracow (Poland); Borzemski, P. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Buettner, C.; Caldwell, A. [Max-Planck-Institut fuer Physik, München (Germany); Chwastowski, J.; Daniluk, W. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Drugakov, V. [Deutsches Elektronen Synchrotron, Hamburg (Germany); NCPHEP, Minsk (Belarus); Eskreys, A.; Figiel, J.; Galas, A.; Gil, M. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Helbich, M. [Columbia University, New York (United States); Januschek, F. [Deutsches Elektronen Synchrotron, Hamburg (Germany); Jurkiewicz, P. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Kisielewska, D. [AGH University of Science and Technology, Cracow (Poland); Klein, U. [Deutsches Elektronen Synchrotron, Hamburg (Germany); Kotarba, A. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow (Poland); Lohmann, W., E-mail: wolfgang.lohmann@desy.de [Deutsches Elektronen Synchrotron, Hamburg (Germany); Brandenburgische Technische Universität, Cottbus (Germany); and others

2014-04-21

373

Measurement of the luminosity in the ZEUS experiment at HERA II  

Energy Technology Data Exchange (ETDEWEB)

The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.

Adamczyk, L.; Bold, T. [AGH Univ. of Science and Technology, Cracow (Poland); Andruszkow, J. [Polish Academy of Sciences, Cracow (Poland). Inst. of Nuclear Physics] [and others

2013-06-15

374

On the core-mass-shell-luminosity relation for shell-burning stars  

International Nuclear Information System (INIS)

Core-mass-shell-luminosity relations for several types of shell-burning star have been calculated using simultaneous differential equations derived from simple homology approximations. The principal objective of obtaining a mass-luminosity relation for helium giants was achieved. This relation gives substantially higher luminosities than the equivalent relation for H-shell stars with core masses greater than 1 solar mass. The algorithm for calculating mass-luminosity relations in this fashion was investigated in detail. Most of the assumptions regarding the physics in the shell do not play a critical role in determining the core-mass-shell-luminosity relation. The behaviour of the core-mass-core-radius relation for a growing degenerate core as a single unique function of mass and growth rate needs to be defined before a single core-mass-shell-luminosity relation for all H-shell stars can be obtained directly from the homology approximations. (author)

375

Measurement of the luminosity in the ZEUS experiment at HERA II  

International Nuclear Information System (INIS)

The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung off protons. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported

376

Galaxy UV-luminosity Function and Reionisation Constraints on Axion Dark Matter  

OpenAIRE

If the dark matter (DM) were composed of axions, then structure formation in the Universe would be suppressed below the axion Jeans scale. Using an analytic model for the halo mass function of a mixed dark matter model with axions and CDM, combined with the abundance-matching technique, we construct the UV luminosity function. Axions suppress high-$z$ galaxy formation and the UV-luminosity function is truncated at a faintest limiting magnitude. From the UV-luminosity functio...

Bozek, Brandon; Marsh, David J. E.; Silk, Joseph; Wyse, Rosemary F. G.

2014-01-01

377

Correlation between radio luminosities with its richness, structure and content of galaxy clusters  

International Nuclear Information System (INIS)

The correlations between radio luminosities at 102,5 MHz and richness, structure and content of 140 nearby Abell clusters ofgalaxies are studied. It is shown that the shape of the luminosity function correlates with these properties of clusters in the range of moderate radio luminosities (?1025-1027 WxHz-1). The significance of the correlations found for a search of possible ways of origin and of evolution of radio galaxies in clusters is briefly discussed

378

Testing Fundamental Particle Physics with the Galactic White Dwarf Luminosity Function  

OpenAIRE

Recent determinations of the white dwarf luminosity function (WDLF) from very large surveys have extended our knowledge of the WDLF to very high luminosities. It has been shown that the shape of the luminosity function of white dwarfs (WDLF) is a powerful tool to test the possible properties and existence of fundamental weakly interacting subelectronvolt particles. This, together with the availability of new full evolutionary white dwarf models that are reliable at high lumi...

Bertolami, Marcelo M. Miller; Melendez, Brenda E.; Althaus, Leandro G.; Isern, Jordi

2014-01-01

379

Measuring Lensing Magnification of Quasars by Large Scale Structure using the Variability-Luminosity Relation  

OpenAIRE

We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a...

Bauer, Anne H.; Seitz, Stella; Jerke, Jonathan; Scalzo, Richard; Rabinowitz, David; Ellman, Nancy; Baltay, Charles

2011-01-01

380

A composite HII region luminosity function in H alpha of unprecedented statistical weight  

CERN Document Server

Context. Statistical properties of HII region populations in disk galaxies yield important clues to the physics of massive star formation. Aims. We present a set of HII region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. Methods. HII region luminosity functions are derived for individual galaxies which, after photometric calibration, are summed to form a total luminosity function comprising 17,797 HII regions from 53 galaxies. Results. The total luminosity function, above its lower limit of completeness, is clearly best fitted by a double power law with a significantly steeper slope for the high luminosity portion of the function. This change of slope has been reported in the literature for individual galaxies, and occurs at a luminosity of log L = 38.6\\pm0.1 (L in erg/s) which has been termed the Stromgren luminosity. A steep fall off in the luminosity function above log L = 40 is also noted, and is related to an...

Bradley, T R; Beckman, J E; Folkes, S L

2006-01-01

381

Low-Luminosity Active Galactic Nuclei: Are They UV-Faint and Radio Loud?  

CERN Document Server

Low-luminosity AGNs are perceived to be radio loud and devoid of a ``big blue bump'', indicating a transition from a radiatively efficient, geometrically thin, accretion disc in high-luminosity AGNs, to a geometrically thick, radiatively inefficient accretion flow at low luminosities and accretion rates. I revisit the issue of the spectral energy distributions (SEDs) of low-luminosity AGNs using recently published, high-angular-resolution data at radio, UV, and X-ray wavelengths, for a sample of 13 nearby galaxies with LINER nuclei. I show that, contrary to common wisdom, low-luminosity AGNs have significant nonstellar UV flux, and UV/X-ray luminosity ratios similar, on average, to those of Seyfert 1 nuclei ~10^4 times more luminous. The alpha_ox index that quantifies this ratio is in the range between -0.8 to -1.4, and is below the extrapolation to low luminosities of the relation between alpha_ ox and UV luminosity observed at higher luminosities. In terms of radio loudness, most of the LINERs are indeed ra...

Maoz, D

2007-01-01

382

The Luminosity function of Narrow-Line Seyfert galaxies based on SDSS DR7 data  

CERN Document Server

We present measurements of AGN type 1 luminosity function in the forbidden line [OIII]5007\\AA using data from SDSS DR7. A special attention is paid to NLSy1. A new approach in calculating the luminosity function is present. We also account for the large-scale structure variations of the Universe density. The results obtained are compared with ones from the literature. A prediction of X-ray luminosity function based on our results shows an agreement with observations. One of our preliminary conclusions is that NLSy1 seems to occupy a more narrow range in the nuclear luminosity than BLSy1, but the average values are within errors.

Ermash, Andrey

2013-01-01

383

Cosmic Evolution of Black Holes and Spheroids. IV. The BH Mass - Spheroid Luminosity Relation  

OpenAIRE

From high-resolution images of 23 Seyfert-1 galaxies at z=0.36 and z=0.57 obtained with the Near Infrared Camera and Multi-Object Spectrometer on board the Hubble Space Telescope (HST), we determine host-galaxy morphology, nuclear luminosity, total host-galaxy luminosity and spheroid luminosity. Keck spectroscopy is used to estimate black hole mass (M_BH). We study the cosmic evolution of the M_BH-spheroid luminosity (L_sph) relation. In combination with our previous work, t...

Bennert, Vardha Nicola; Treu, Tommaso; Woo, Jong-hak; Malkan, Matthew A.; Bris, Alexandre Le; Auger, Matthew W.; Gallagher, Sarah; Blandford, Roger D.

2009-01-01

384

THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. I. TESTING FWHM-BASED VIRIAL BLACK HOLE MASSES  

International Nuclear Information System (INIS)

We jointly constrain the luminosity function (LF) and black hole mass function (BHMF) of broad-line quasars with forward Bayesian modeling in the quasar mass-luminosity plane, based on a homogeneous sample of ?58, 000 Sloan Digital Sky Survey (SDSS) Data Release 7 quasars at z ? 0.3-5. We take into account the selection effect of the sample flux limit; more importantly, we deal with the statistical scatter between true BH masses and FWHM-based single-epoch virial mass estimates, as well as potential luminosity-dependent biases of these mass estimates. The LF is tightly constrained in the regime sampled by SDSS and makes reasonable predictions when extrapolated to ?3 mag fainter. Downsizing is seen in the model LF. On the other hand, we find it difficult to constrain the BHMF to within a factor of a few at z ?> 0.7 (with Mg II and C IV-based virial BH masses). This is mainly driven by the unknown luminosity-dependent bias of these mass estimators and its degeneracy with other model parameters, and secondly driven by the fact that SDSS quasars only sample the tip of the active BH population at high redshift. Nevertheless, the most likely models favor a positive luminosity-dependent bias for Mg II and possibly for C IV, such that at fixed true BH mass, objects with higher-than-average luminosities have overestimated FWHM-based virial masses. There is tentative evidence that downsizing also manifests itself in the active BHMF, and the BH mass density in broad-line the BH mass density in broad-line quasars contributes an insignificant amount to the total BH mass density at all times. Within our model uncertainties, we do not find a strong BH mass dependence of the mean Eddington ratio, but there is evidence that the mean Eddington ratio (at fixed BH mass) increases with redshift.

385

The HELLAS2XMM Survey. VII. The Hard X-Ray Luminosity Function of AGNs up to z = 4: More Absorbed AGNs at Low Luminosities and High Redshifts  

Science.gov (United States)

We have determined the cosmological evolution of the density of active galactic nuclei (AGNs) and of their NH distribution as a function of the unabsorbed 2-10 keV luminosity up to redshift 4. We used the HELLAS2XMM sample combined with other published catalogs, yielding a total of 508 AGNs. Our best fit is obtained with a luminosity-dependent density evolution (LDDE) model where low-luminosity (LX~1043 ergs s-1) AGNs peak at z~0.7, while high-luminosity AGNs (LX>1045 ergs s-1) peak at z~2.0. A pure luminosity evolution model (PLE) can instead be rejected. There is evidence that the fraction of absorbed (NH>1022 cm-2) AGNs decreases with the intrinsic X-ray luminosity and increases with the redshift. Our best-fit solution provides a good fit to the observed counts, the cosmic X-ray background, and to the observed fraction of absorbed AGNs as a function of the flux in the 10-15 ergs cm-2 s-11044 ergs s-1) AGNs have a density of 267 deg-2 at fluxes S2-10>10-15 ergs cm-2 s-1. Using these results, we estimate a density of supermassive black holes in the local universe of ?BH=3.2 h270×105 Msolar Mpc-3, which is consistent with the recent measurements of the black hole mass function in the local galaxies.

La Franca, F.; Fiore, F.; Comastri, A.; Perola, G. C.; Sacchi, N.; Brusa, M.; Cocchia, F.; Feruglio, C.; Matt, G.; Vignali, C.; Carangelo, N.; Ciliegi, P.; Lamastra, A.; Maiolino, R.; Mignoli, M.; Molendi, S.; Puccetti, S.

2005-12-01

386

The HELLAS2XMM survey. VII. The hard X-ray luminosity function of AGN up to z=4: more absorbed AGN at low luminosities and high redshifts  

CERN Document Server

We have determined the cosmological evolution of the density of AGN and of their Nh distribution as a function of the un-absorbed 2-10 keV luminosity up to redshift 4. We used the HELLAS2XMM sample combined with other published catalogs, yielding a total of 508 AGN. Our best fit is obtained with a luminosity-dependent density evolution (LDDE) model where low luminosity (Lx~10^43 erg s^-1) AGN peak at z~0.7, while high luminosity AGN (Lx>10^45 erg s^-1) peak at z~2.0. A pure luminosity evolution model (PLE) can instead be rejected. There is evidence that the fraction of absorbed (Nh>10^22 cm^-2) AGN decreases with the intrinsic X-ray luminosity, and increases with the redshift. Our best fit solution provides a good fit to the observed counts, the cosmic X-ray background, and to the observed fraction of absorbed AGN as a function of the flux in the 10^-1510^44 erg s^-1) AGN have a density of 267 deg^-2 at fluxes S(2-10)>10^-15 erg s^-1 cm^-2. Using these results, we estimate a density of supermassive black hole...

La Franca, F; Comastri, A; Perola, G C; Sacchi, N; Brusa, M; Cocchia, F; Feruglio, C; Matt, G; Vignali, C; Carangelo, N; Ciliegi, P; Lamastra, A; Maiolino, R; Mignoli, M; Molendi, S; Puccetti, S

2005-01-01

387

Low Energy Neutrinos, Neutrino Luminosity of the Sun and LENS  

International Nuclear Information System (INIS)

The LENS detector is designed to be a real time spectrometer sensitive to the sub-MeV part of the solar neutrino spectrum, including pp-neutrinos which dominate the solar neutrino flux. The objective of LENS is to measure the Neutrino Luminosity of the sun with high precision, which will allow a test of current standard and nonstandard neutrino flavor conversion models along with the solar model in a single experiment, and might open doors to new physics. In addition, the Gamow-energy shift in the pp-neutrino spectrum could be measured, directly probing the temperature profile of pp fusion in the solar core, thus bringing solar neutrino physics full circle to its original astrophysical objective, i.e. the study of the sun. The experimental tool used is tagged capture of ?e's on 115In via charged current interaction. Tremendous progress has been achieved in the detector design, In liquid scintillator chemistry and background rejection study. A novel design for a liquid scintillator detector, the 'Scintillation Lattice Chamber' will provide 3-dimensional spatial resolution in a large mass of liquid scintillator. The feasibility of LENS with less than 200t of scintillator has been established

388

Measuring the Neutrino Luminosity of the Sun - LENS and MINILENS  

International Nuclear Information System (INIS)

The LENS detector will be a real time spectrometer sensitive to the sub-MeV part of the solar neutrino spectrum, including pp-neutrinos which dominate the solar neutrino fiux. LENS will measure the Neutrino-inferred Luminosity of the sun with high precision, which will allow a test of current standard and nonstandard neutrino flavor conversion models along with the solar model in a single experiment, and might open doors to new physics. In addition, the Gamow-energy shift in the pp-neutrino spectrum could be measured, directly probing the temperature profile of pp fusion in the solar core, thus bringing solar neutrino physics back to its original astrophysical objective, i.e. the study of the sun. The experimental tool used is tagged capture of ?e's on 115In via charged current interaction. Tremendous progress has been achieved in the detector design, In liquid scintillator chemistry and background rejection study. A novel design for a liquid scintillator detector, the ''Scintillation Lattice Chamber'' will provide 3-dimensional spatial resolution in a large mass of liquid scintillator. The feasibility of LENS with less than 200t of scintillator has been established

389

The Luminosity-size Relation of Galaxies to z=1?  

Science.gov (United States)

We use the Hubble Ultra Deep Field (UDF) to study the galaxy luminosity-size (M-R_e) distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability we identify bias-free regions in the M-R_e plane for a series of volume-limited samples. We also investigate the colour-log(n) distribution of these galaxies and further subdivide our data by structural type to separately study compact and diffuse objects. By comparison to the nearby Millennium Galaxy Catalogue, we present tentative evidence for evolution of diffuse, disk-like galaxies with redshift---both in mean surface brightness and the slope of the M-R_e relation. In contrast we find no evidence of structural evolution in the compact galaxy M-R_e relation over this redshift range, although there is a suggestion of colour evolution. We also highlight the importance of considering surface brightness dependent measurement biases in addition to incompleteness biases. In particular, the increasing, systematic under-estimation of Kron fluxes towards low surface brightnesses may cause diffuse, yet luminous, systems to be mistaken for faint, compact objects.

Cameron, E.; Driver, S. P.

2007-12-01

390

The luminosity-size relation of galaxies to z=1?  

CERN Document Server

We use the Hubble Ultra Deep Field (UDF) to study the galaxy luminosity-size (M-Re) distribution. With a careful analysis of selection effects due to both detection completeness and measurement reliability we identify bias-free regions in the M-Re plane for a series of volume-limited samples. We also investigate the colour-log(n) distribution of these galaxies and further subdivide our data by structural type to separately study compact and diffuse objects. By comparison to the nearby Millennium Galaxy Catalogue, we present tenative evidence for evolution of diffuse, disk-like galaxies with redshift -- both in mean surface brightness and the slope of the M-Re relation. In contrast we find no evidence of structural evolution in the compact galaxy M-Re relation over this redshift range, although there is a suggestion of colour evolution. We also highlight the importance of considering surface brightness dependent measurement biases in addition to incompleteness biases. In particular, the increasing, systematic ...

Cameron, E

2007-01-01

391

Estimating Luminosity Function Constraints from High-Redshift Galaxy Surveys  

Science.gov (United States)

The installation of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) will revolutionize the study of high-redshift galaxy populations. Initial observations of the HST Ultra Deep Field (UDF) have yielded multiple z >~ 7 dropout candidates. Supplemented by the GOODS Early Release Science (ERS) and further UDF pointings, these data will provide crucial information about the most distant known galaxies. However, achieving tight constraints on the z ~ 7 galaxy luminosity function (LF) will require even more ambitious photometric surveys. Using a Fisher matrix approach to fully account for Poisson and cosmic sample variance, as well as covariances in the data, we estimate the uncertainties on LF parameters achieved by surveys of a given area and depth. Applying this method to WFC3 z ~ 7 dropout galaxy samples, we forecast the LF parameter uncertainties for a variety of model surveys. We demonstrate that performing a wide area (~1 deg2) survey to H AB ~ 27 depth or increasing the UDF depth to H AB ~ 30 provides excellent constraints on the high-z LF when combined with the existing Ultradeep Field Guest Observation and GOODS ERS data. We also show that the shape of the matter power spectrum may limit the possible gain of splitting wide area (gsim0.5 deg2) high-redshift surveys into multiple fields to probe statistically independent regions; the increased rms density fluctuations in smaller volumes mostly offset the improved variance gained from independent samples.

Robertson, Brant E.

2010-04-01

392

ATLAS ALFA-measuring absolute luminosity with scintillating fibres  

International Nuclear Information System (INIS)

ALFA is a high-precision scintillating fibre tracking detector under construction for the absolute determination of the LHC luminosity at the ATLAS interaction point. This detector, mounted in so-called Roman Pots, will track protons elastically scattered under ?rad angles at IP1.In total there are four pairs of vertically arranged detector modules which approach the LHC beam axis to mm distance. Each detector module consists of ten layers of two times 64 scintillating fibres each (U and V planes). The fibres are coupled to 64 channels Multi-Anodes PhotoMultipliers Tubes read out by compact front-end electronics. Each detector module is complemented by so-called overlap detectors: Three layers of two times 30 scintillating fibres which will be used to measure the relative positioning of two vertically arranged main detectors. The total number of channels is about 15000. Conventional plastic scintillator tiles are mounted in front of the fibre detectors and will serve as trigger counter. The extremely restricted space inside the pots makes the coupling to the read out devices very challenging. Several technologies have been tested in a beam at DESY and a cosmic-ray setup at CERN. A possible upgrade of the photo detection could consist in the replacement of the PMT by Geiger-mode avalanche photodiodes. Preliminary tests are being performed comparing the performance of these devices with the ones of the PMTs.

393

The Luminosity Function of Low-Redshift Abell Galaxy Clusters  

CERN Document Server

We present the results from a survey of 57 low-redshift Abell galaxy clusters to study the radial dependence of the luminosity function (LF). The dynamical radius of each cluster, r200, was estimated from the photometric measurement of cluster richness, Bgc. The shape of the LFs are found to correlate with radius such that the faint-end slope, alpha, is generally steeper on the cluster outskirts. The sum of two Schechter functions provides a more adequate fit to the composite LFs than a single Schechter function. LFs based on the selection of red and blue galaxies are bimodal in appearance. The red LFs are generally flat for -22 -18. The blue LFs contain a larger contribution from faint galaxies than the red LFs. The blue LFs have a rising faint-end component (alpha ~ -1.7) for M_Rc > -21, with a weaker dependence on radius than the red LFs. The dispersion of M* was determined to be 0.31 mag, which is comparable to the median measurement uncertainty of 0.38 mag. This suggests that the bright-end of the LF is...

Barkhouse, Wayne A; López-Cruz, Omar

2007-01-01

394

EVN observations of low-luminosity flat-spectrum AGNs  

CERN Document Server

We present and discuss the results of VLBI (EVN) observations of three low-luminosity (P(5 GHz)<10^25 W/Hz) Broad Emission Line AGNs carefully selected from a sample of flat spectrum radio sources (CLASS). Based on the total and the extended radio power at 5 GHz and at 1.4 GHz respectively, these objects should be technically classified as radio-quiet AGN and thus the origin of their radio emission is not clearly understood. The VLBI observations presented in this paper have revealed compact radio cores which imply a lower limit on the brightness temperature of about 3X10^8 K. This result rules out a thermal origin for the radio emission and strongly suggests an emission mechanism similar to that observed in more powerful radio-loud AGNs. Since, by definition, the three objects show a flat (or inverted) radio spectrum between 1.4 GHz and 8.4 GHz, the observed radio emission could be relativistically beamed. Multi-epoch VLBI observations can confirm this possibility in two years time.

Caccianiga, A; Thean, A; Dennett-Thorpe, J

2001-01-01

395

On the perturbation of the luminosity distance by peculiar motions  

CERN Document Server

We consider some aspects of the perturbation to the luminosity distance $d(z)$ that are of relevance for SN1a cosmology and for future peculiar velocity surveys at non-negligible redshifts. 1) Previous work has shown that the correction to the lowest order perturbation $\\delta d / d = -\\delta v / c z$ has the peculiar characteristic that it appears to depend on the absolute state of motion of sources, rather than on their motion relative to that of the observer. The resolution of this apparent violation of the equivalence principle is that it is necessary to allow for evolution of the velocities with time, and also, when considering perturbations on the scale of the observer-source separation, to include the gravitational redshift effect. We provide an expression for $\\delta d / d$ that provides a physically consistent way to compute the impact of peculiar motions for SN1a cosmology and peculiar velocity surveys. 2) We then calculate the perturbation to the redshift as a function of source flux density, which...

Kaiser, Nick

2014-01-01

396

On the luminosity distance and the epoch of acceleration  

CERN Document Server

Standard cosmological models based on general relativity (GR) with dark energy predict that the Universe underwent a transition from decelerating to accelerating expansion at a moderate redshift $z_{acc} \\sim 0.7$. Clearly, it is of great interest to directly measure this transition in a model-independent way, without the assumption that GR is the correct theory of gravity. We explore to what extent supernova (SN) luminosity distance measurements provide evidence for such a transition: we show that, contrary to intuition, the well-known "turnover" in the SN distance residuals $\\Delta\\mu$ relative to an empty (Milne) model does not give firm evidence for such a transition within the redshift range spanned by SN data. The observed turnover in that diagram is predominantly due to the negative curvature in the Milne model, {\\em not} the deceleration predicted by $\\Lambda$CDM and relatives. We show that there are several advantages in plotting distance residuals against a flat, non-accelerating model $(w = -1/3)$,...

Sutherland, Will

2015-01-01

397

On the luminosity distance and the epoch of acceleration  

Science.gov (United States)

Standard cosmological models based on general relativity (GR) with dark energy predict that the Universe underwent a transition from decelerating to accelerating expansion at a moderate redshift zacc ˜ 0.7. Clearly, it is of great interest to directly measure this transition in a model-independent way, without the assumption that GR is the correct theory of gravity. We explore to what extent supernova (SN) luminosity distance measurements provide evidence for such a transition: we show that, contrary to intuition, the well-known `turnover' in the SN distance residuals ?? relative to an empty (Milne) model does not give firm evidence for such a transition within the redshift range spanned by SN data. The observed turnover in that diagram is predominantly due to the negative curvature in the Milne model, not the deceleration predicted by ? cold dark matter and relatives. We show that there are several advantages in plotting distance residuals against a flat, non-accelerating model (w = -1/3), and also remapping the z-axis to u = ln (1 + z); we outline a number of useful and intuitive properties of this presentation. We conclude that there are significant complementarities between SNe and baryon acoustic oscillations (BAOs): SNe offer high precision at low redshifts and give good constraints on the net amount of acceleration since z ˜ 0.7, but are weak at constraining zacc; while radial BAO measurements are probably superior for placing direct constraints on zacc.

Sutherland, Will; Rothnie, Paul

2015-02-01

398

Jet and disk luminosities in tidal disruption events  

CERN Document Server

Tidal disruption events (TDE) in which a star is devoured by a massive black hole at a galac- tic center pose a challenge to our understanding of accretion processes. Within a month the accretion rate reaches super-Eddington levels. It then drops gradually over a time scale of a year to sub-Eddington regimes. The initially geometrically thick disk becomes a thin one and eventually an ADAF at very low accretion rates. As such, TDEs explore the whole range of accretion rates and configurations. A challenging question is what the corresponding light curves of these events are. We explore numerically the disk luminosity and the conditions within the inner region of the disk using a fully general relativistic slim disk model. Those conditions determine the magnitude of the magnetic field that engulfs the black hole and this, in turn, determines the Blandford-Znajek jet power. We estimate this power in two different ways and show that they are self-consistent. We find, as expected earlier from analytic argu- ments ...

Piran, Tsvi; Tchekhovskoy, Alexander

2015-01-01

399

Close stars and accretion in Low Luminosity Active Galactic Nuclei  

CERN Document Server

Quasar accretion disks are believed to form stars by self-gravity. Low Luminosity Active Galactic Nuclei (LLAGN) are much dimmer galactic centers, and are often believed to be quasars that ran out of gaseous fuel. LLAGN accretion disks should thus co-exist with thousands to millions of stars or proto-stars left from the previous stronger accretion activity. In principle, these stars may produce several important effects: (i) contribute to the optical/UV spectra of some LLAGN; (ii) reprocessing of the stellar radiation in the dusty disks could dominate the LLAGN infra-red spectra; (iii) deplete the (accretion) gas disk much faster than it can accrete onto the supper-massive black hole (SMBH); (iv) stars, individually or in groups, may slow down and modulate the accretion flow significantly due to their inertia. In this way they may produce the LLAGN cut-off disks; (v) alternatively, frequent enough stellar collisions and resulting stellar disruptions could keep the inner disk empty. Here we explore these ideas...

Nayakshin, S

2004-01-01

400

The LMC stellar complexes in luminosity slices. Star formation indicators  

Science.gov (United States)

An approach towards the investigation of the star formation mechanisms in galaxies can be achieved through the search of stellar complexes and the determination of their properties. A method has been developed for the detection of stellar complexes and the derivation of their fundamental properties in the LMC. Photographic plates taken with the 1.2m U.K. Schmidt Telescope have been digitized by the APM and SuperCosmos machines to produce homogeneous data for extended regions. Star counts have been performed for extended areas in selected luminosity slices and colours (U, HeII, R filters). Isodensity contours have been used to identify the various structures with enhanced stellar number density (3sigma above the mean background density). About 50 large stellar groupings have been revealed showing: 1) hierarchical structure, where the smallest are found within the large ones. 2) their size distribution has peaks at 250+/-50 pc (aggregates) and 600+/-50 pc (complexes), there are also a few cases with size 1200+/-50 pc (supercomplexes). 3) there is evidence that at the fainter magnitudes these structures are aligned to a general trend whereas at the most bright end (B1, O spectral types) they become more clumpy and symmetrical in shape. The relationship between the above complexes' properties and the various scenarios of star formation are discussed.

Maragoudaki, F.; Kontizas, M.; Kontizas, E.; Dapergolas, A.; Morgan, D. H.

1998-10-01

401

A two-mode planetary nebula luminosity function  

Science.gov (United States)

Context. We propose a new planetary nebula luminosity function (PNLF) that includes two populations in the distribution. Our PNLF is a direct extension of the canonical function proposed by Jacoby et al. (1987), in order to avoid problems related with the histogram construction, it is cast in terms of cumulative functions. Aims: We are interested in recovering the shape of the faint part of the PNLF in a consistent manner, for galaxies with and without a dip in their PNLFs. Methods: The parameters for the two-mode PNLF are obtained with a genetic algorithm, which obtains a best fit to the PNLF varying all of the parameters simultaneously in a broad parameter space. Results: We explore a sample of nine galaxies with various Hubble types and construct their PNLF. All of the irregular galaxies, except one, are found to be consistent with a two-mode population, while the situation is less clear for ellipticals and spirals.For the case of NGC 6822, we show that the two-mode PNLF is consistent with previous studies of the star formation history within that galaxy. Our results support two episodes of star formation, in which the second episode is significantly stronger.

Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A.; Raga, A. C.; Stasi?ska, G.; Peña, M.; Mayya, Y. D.

2015-03-01

402

Bivariate Galaxy Luminosity Functions in the Sloan Digital Sky Survey  

CERN Document Server

Bivariate luminosity functions (LFs) are computed for galaxies in the Sloan Digital Sky Survey Data Release 3 for a range of galaxy properties, including morphological type assigned by an artificial neural network, inverse concentration index, surface brightness (bivariate brightness distribution), eClass spectral type, reference frame colours, S\\'ersic index, absolute Petrosian 90\\% radius, stellar mass and galaxy environment. Several of the parameters are used in this way for the first time. In particular, the sample of 25,915 galaxies classified by Hubble type at the resolution E, S0, Sa ... Sd represents the largest such set in an LF by an order of magnitude. The morphological sample is flux limited to galaxies with $r<15.9$ while the other bivariate LFs use $r<17.6$ samples with a median redshift of $z \\sim 0.1$. A wealth of detail is seen, with clear variation between the LFs according to absolute magnitude and the second parameter. They are consistent with a early type, bright, concentrated, red ...

Ball, N M; Brunner, R J; Baldry, I K; Brinkmann, J; Ball, Nicholas M; Loveday, Jon; Brunner, Robert J; Baldry, Ivan K; Brinkmann, Jon

2005-01-01

403

ESTIMATING LUMINOSITY FUNCTION CONSTRAINTS FROM HIGH-REDSHIFT GALAXY SURVEYS  

International Nuclear Information System (INIS)

The installation of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) will revolutionize the study of high-redshift galaxy populations. Initial observations of the HST Ultra Deep Field (UDF) have yielded multiple z ?> 7 dropout candidates. Supplemented by the GOODS Early Release Science (ERS) and further UDF pointings, these data will provide crucial information about the most distant known galaxies. However, achieving tight constraints on the z ? 7 galaxy luminosity function (LF) will require even more ambitious photometric surveys. Using a Fisher matrix approach to fully account for Poisson and cosmic sample variance, as well as covariances in the data, we estimate the uncertainties on LF parameters achieved by surveys of a given area and depth. Applying this method to WFC3 z ? 7 dropout galaxy samples, we forecast the LF parameter uncertainties for a variety of model surveys. We demonstrate that performing a wide area (?1 deg2) survey to HAB ? 27 depth or increasing the UDF depth to HAB ? 30 provides excellent constraints on the high-z LF when combined with the existing Ultradeep Field Guest Observation and GOODS ERS data. We also show that the shape of the matter power spectrum may limit the possible gain of splitting wide area (?>0.5 deg2) high-redshift surveys into multiple fields to probe statistically independent regions; the increased rms density fluctuations in smaller volumes mostly s in smaller volumes mostly offset the improved variance gained from independent samples.

404

Estimating Luminosity Function Constraints from High-Redshift Galaxy Surveys  

CERN Document Server

The installation of the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) will revolutionize the study of high-redshift galaxy populations. Initial observations of the HST Ultra Deep Field (UDF) have yielded multiple z>~7 dropout candidates. Supplemented by the Great Observatory Origins Deep Survey (GOODS) Early Release Science (ERS) and further UDF pointings, these data will provide crucial information about the most distant known galaxies. However, achieving tight constraints on the z~7 galaxy luminosity function (LF) will require even more ambitious photometric surveys. Using a Fisher matrix approach to fully account for Poisson and cosmic sample variance, as well as covariances in the data, we estimate the uncertainties on LF parameters achieved by surveys of a given area and depth. Applying this method to WFC3 z~7 dropout galaxy samples, we forecast the LF parameter uncertainties for a variety of model surveys. We demonstrate that performing a wide area (~1 deg^2) survey to H_AB~27 depth or ...

Robertson, Brant E

2010-01-01

405

Jet-Driven Disk Accretion in Low Luminosity AGN?  

CERN Document Server

We explore an accretion model for low luminosity AGN (LLAGN) that attributes the low radiative output to a low mass accretion rate rather than a low radiative efficiency. In this model, electrons are assumed to drain energy from the ions as a result of collisionless plasma microinstabilities. Consequently, the accreting gas collapses to form a geometrically thin disk at small radii and is able to cool before reaching the black hole. The accretion disk is not a standard disk, however, because the radial disk structure is modified by a magnetic torque which drives a jet and which is primarily responsible for angular momentum transport. We also include relativistic effects. We apply this model to the well known LLAGN M87 and calculate the combined disk-jet steady-state broadband spectrum. A comparison between predicted and observed spectra indicates that M87 may be a maximally spinning black hole accreting at a rate of 10^{-3} solar masses per year. This is about 6 orders of magnitude below the Eddington rate fo...

Jolley, Erin J D

2007-01-01

406

Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions  

CERN Document Server

Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fit over a range of more than ten magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue-plus-red sample, require double power-law Schechter functions to fit a dip in their LF faintward of the characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disk galaxies. We measure evolution of the galaxy LF over the redshift range 0.002 < z &...

Loveday, J; Baldry, I K; Driver, S P; Hopkins, A M; Peacock, J A; Bamford, S P; Liske, J; Bland-Hawthorn, J; Brough, S; Brown, M J I; Cameron, E; Conselice, C J; Croom, S M; Frenk, C S; Gunawardhana, M; Hill, D T; Jones, D H; Kelvin, L S; Kuijken, K; Nichol, R C; Parkinson, H R; Phillipps, S; Pimbblet, K A; Popescu, C C; Prescott, M; Robotham, A S G; Sharp, R G; Sutherland, W J; Taylor, E N; Thomas, D; Tuffs, R J; van Kampen, E; Wijesinghe, D

2011-01-01

407

LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS  

Energy Technology Data Exchange (ETDEWEB)

We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Using protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity functions to those predicted by models and find that our observed luminosity functions are best matched by models that invoke competitive accretion, although we do not find strong agreement between the high-mass SF clouds and any of the models.

Kryukova, E.; Megeath, S. T.; Allen, T. S. [Department of Physics and Astronomy, University of Toledo, Toledo, OH (United States); Gutermuth, R. A. [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Pipher, J. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Allen, L. E. [National Optical Astronomy Observatories, Tucson, AZ (United States); Myers, P. C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Muzerolle, J. [Space Telescope Science Institute, Baltimore, MD (United States)

2012-08-15

408

The 2dF Galaxy Redshift Survey: the number and luminosity density of galaxies  

Science.gov (United States)

We present the bivariate brightness distribution (BBD) for the 2dF Galaxy Redshift Survey (2dFGRS) based on a preliminary subsample of 45000 galaxies. The BBD is an extension of the galaxy luminosity function, incorporating surface brightness information. It allows the measurement of the local luminosity density, jB, and of the galaxy luminosity and surface brightness distributions, while accounting for surface brightness selection biases. The recovered 2dFGRS BBD shows a strong luminosity-surface brightness relation MB~(2.4+/-0.51.5)?e], providing a new constraint for galaxy formation models. In terms of the number density, we find that the peak of the galaxy population lies at MB>=-16.0mag. Within the well-defined selection limits (-24luminosity density is dominated by conventional giant galaxies (i.e., 90 per cent of the luminosity density is contained within -22.5luminosity-density peak lies away from the selection boundaries, implying that the 2dFGRS is complete in terms of sampling the local luminosity density, and that luminous low surface brightness galaxies are rare. The final value we derive for the local luminosity density, inclusive of surface brightness corrections, is jB=2.49+/- 0.20×108h100LsolarMpc- 3. Representative Schechter function parameters are M*=-19.75+/-0.05, ?*=2.02+/-0.02×10-2 and ?=-1.09+/-0.03. Finally, we note that extending the conventional methodology to incorporate surface brightness selection effects has resulted in an increase in the luminosity density of ~37 per cent. Hence surface brightness selection effects would appear to explain much of the discrepancy between previous estimates of the local luminosity density.

Cross, Nicholas; Driver, Simon P.; Couch, Warrick; Baugh, Carlton M.; Bland-Hawthorn, Joss; Bridges, Terry; Cannon, Russell; Cole, Shaun; Colless, Matthew; Collins, Chris; Dalton, Gavin; Deeley, Kathryn; De Propris, Roberto; Efstathiou, George; Ellis, Richard S.; Frenk, Carlos S.; Glazebrook, Karl; Jackson, Carole; Lahav, Ofer; Lewis, Ian; Lumsden, Stuart; Maddox, Steve; Madgwick, Darren; Moody, Stephen; Norberg, Peder; Peacock, John A.; Peterson, Bruce A.; Price, Ian; Seaborne, Mark; Sutherland, Will; Tadros, Helen; Taylor, Keith

2001-07-01

409

THE DISK EVAPORATION MODEL FOR THE SPECTRAL FEATURES OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI  

International Nuclear Information System (INIS)

Observations show that the accretion flows in low-luminosity active galactic nuclei probably have a two-component structure with an inner, hot, optically thin, advection-dominated accretion flow (ADAF) and an outer, truncated, cool, optically thick accretion disk. As shown by Taam et al., the truncation radius as a function of mass accretion rate is strongly affected by including the magnetic field within the framework of disk evaporation model, i.e., an increase in the magnetic field results in a smaller truncation radius of the accretion disk. In this work, we calculate the emergent spectrum of an inner ADAF + an outer truncated accretion disk around a supermassive black hole based on the prediction by Taam et al.. It is found that an increase in the magnetic field from ? = 0.8 to ? = 0.5 (with magnetic pressure pm = B 2/8? = (1 – ?)ptot, ptot = pgas + pm) results in a factor of ?8.7 increase in the luminosity from the truncated accretion disk. Meanwhile, results of the peak emission of the truncated accretion disk shift toward a a factor of ?5 higher frequency. We found that the equipartition of gas pressure to magnetic pressure, i.e., ? = 0.5, failed to explain the observed anti-correlation between L2-10keV/LEdd and the bolometric correction ?2-10keV (with ?2-10keV = Lbol/L2-10keV). The emergent spectra for larger values of ? = 0.8 or ? = 0.95 can explain the observed L2-10keV/LEdd-?2-10keV correlation. We argue that in the disk evaporation model, the electrons in the corona are assumed to be heated only by a transfer of energy from the ions to electrons via Coulomb collisions, which is reasonable for accretion with a lower mass accretion rate. Coulomb heating is the dominated heating mechanism for the electrons only if the magnetic field is strongly sub-equipartition, which is roughly consistent with observations

410

THE DISK EVAPORATION MODEL FOR THE SPECTRAL FEATURES OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI  

Energy Technology Data Exchange (ETDEWEB)

Observations show that the accretion flows in low-luminosity active galactic nuclei probably have a two-component structure with an inner, hot, optically thin, advection-dominated accretion flow (ADAF) and an outer, truncated, cool, optically thick accretion disk. As shown by Taam et al., the truncation radius as a function of mass accretion rate is strongly affected by including the magnetic field within the framework of disk evaporation model, i.e., an increase in the magnetic field results in a smaller truncation radius of the accretion disk. In this work, we calculate the emergent spectrum of an inner ADAF + an outer truncated accretion disk around a supermassive black hole based on the prediction by Taam et al.. It is found that an increase in the magnetic field from ? = 0.8 to ? = 0.5 (with magnetic pressure p{sub m} = B {sup 2}/8? = (1 – ?)p{sub tot}, p{sub tot} = p{sub gas} + p{sub m}) results in a factor of ?8.7 increase in the luminosity from the truncated accretion disk. Meanwhile, results of the peak emission of the truncated accretion disk shift toward a a factor of ?5 higher frequency. We found that the equipartition of gas pressure to magnetic pressure, i.e., ? = 0.5, failed to explain the observed anti-correlation between L{sub 2-10{sub keV}}/L{sub Edd} and the bolometric correction ?{sub 2-10{sub keV}} (with ?{sub 2-10{sub keV}} = L{sub bol}/L{sub 2-10{sub keV}}). The emergent spectra for larger values of ? = 0.8 or ? = 0.95 can explain the observed L{sub 2-10{sub keV}}/L{sub Edd}-?{sub 2-10{sub keV}} correlation. We argue that in the disk evaporation model, the electrons in the corona are assumed to be heated only by a transfer of energy from the ions to electrons via Coulomb collisions, which is reasonable for accretion with a lower mass accretion rate. Coulomb heating is the dominated heating mechanism for the electrons only if the magnetic field is strongly sub-equipartition, which is roughly consistent with observations.

Qiao, Erlin; Liu, B. F. [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Panessa, Francesca [INAF-Istituto di Astrofisica e Planetologia Spaziali di Roma (IAPS), Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Liu, J. Y., E-mail: qiaoel@nao.cas.cn [Yunnan Observatories, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China)

2013-11-10

411

Calculation of integrated luminosity for beams stored in the Tevatron collider  

Energy Technology Data Exchange (ETDEWEB)

A model for calculating the integrated luminosity of beams stored in the Tevatron collider will be presented. The model determines the instantaneous luminosity by calculating the overlap integral of bunched beams passing through the interaction region. The calculation accounts for the variation in beam size due to the beta functions and also for effects due to finite longitudinal emittance and non-zero dispersion in the interaction region. The integrated luminosity is calculated for the beams as they evolve due to processes including collisions and intrabeam scattering. The model has been applied to both the extant and upgraded Tevatron collider, but is not limited to them. The original motivation for developing the computer model was to determine the reduction in luminosity due to beams with non-zero longitudinal emittances. There are two effects: the transverse beam size is increased where the dispersion is non-zero; the finite length of the beam bunch combined with an increasing /beta/ function results in an increased transverse beam size at the ends of the bunch. The derivation of a sufficiently useful analytic expression for the luminosity proved to be intractable. Instead, a numerical integration computer program was developed to calculate the luminosity in the presence of a finite longitudinal emittance. The program was then expanded into a model which allows the luminosity to vary due to changes in emittances and reduction in bunch intensities. At that point, it was not difficult to calculate the integrated luminosity. 5 refs., 2 figs., 4 tabs.

Finley, D.A.

1989-03-20

412

Calculation of integrated luminosity for beams stored in the Tevatron collider  

International Nuclear Information System (INIS)

A model for calculating the integrated luminosity of beams stored in the Tevatron collider will be presented. The model determines the instantaneous luminosity by calculating the overlap integral of bunched beams passing through the interaction region. The calculation accounts for the variation in beam size due to the beta functions and also for effects due to finite longitudinal emittance and non-zero dispersion in the interaction region. The integrated luminosity is calculated for the beams as they evolve due to processes including collisions and intrabeam scattering. The model has been applied to both the extant and upgraded Tevatron collider, but is not limited to them. The original motivation for developing the computer model was to determine the reduction in luminosity due to beams with non-zero longitudinal emittances. There are two effects: the transverse beam size is increased where the dispersion is non-zero; the finite length of the beam bunch combined with an increasing ? function results in an increased transverse beam size at the ends of the bunch. The derivation of a sufficiently useful analytic expression for the luminosity proved to be intractable. Instead, a numerical integration computer program was developed to calculate the luminosity in the presence of a finite longitudinal emittance. The program was then expanded into a model which allows the luminosity to vary due to changes in emittances and reduction in bunch intensities. At that point, it was not difficult to calculate the integrated luminosity. 5 refs., 2 figs., 4 tabs

413

A precise measurement of luminosity by TOPAZ forward calorimeter at TRISTAN  

International Nuclear Information System (INIS)

A precise measurement of luminosity with the TOPAZ forward calorimeter at TRISTAN by tagging small angle Bhabha events has been started. By using experimental data collected in 1990 the systematic errors of the measured luminosity were estimated in detail. After an intensive study, total systematic error was estimated to be at most 1.6%. (author)

414

The luminosities of the brightest cluster galaxies and brightest satellites in SDSS groups  

CERN Document Server

We show that the distribution of luminosities of Brightest Cluster Galaxies, in two SDSS-based group catalogs, suggests that BCG luminosities are just the statistical extremes of the group galaxy luminosity function. This latter happens to be very well approximated by the all-galaxy luminosity function (restricted to Mr<-19.9), provided one uses a parametrization of this function that is accurate at the bright end. Since extreme value statistics are explicitly a function of the number of draws, the consistency of BCG luminosities with extreme value statistics is most clearly seen if one is careful to perform the test at fixed group richness N. Tests at, e.g., fixed total group luminosity Ltot, will generally be biased and may lead to erroneous conclusions. A similar analysis of the luminosity distribution of the Brightest Satellite Galaxies suggests that they are best thought of as being the second brightest pick from the same luminosity distribution of which BCGs are the brightest. I.e., BSGs are not the ...

Paranjape, Aseem

2011-01-01

415

Electron-electron luminosity in the Next Linear Collider -- a preliminary study  

International Nuclear Information System (INIS)

In this paper, the authors discuss some operational aspects of electron-electron collisions at the Next Linear Collider (NLC) and estimate the luminosity attainable in such a machine. They also consider the use of two future technologies which could simplify the operation and improve the luminosity in an e-e- collider: polarized rf guns and plasma lenses

416

A statistical method for luminosity monitoring in high energy collider experiments  

CERN Document Server

A statistical method which uses a combination of two subdetectors to monitor the luminosity in high energy interactions is presented. To illustrate its performance, this method was applied to random triggered minimum bias data collected in the commissioning period of the HERA-B experiment in spring 2000. It is found that luminosity estimates with an intrinsic systematic error of 3% can be obtained.

Bastos, J; Schmelling, M

2006-01-01

417

Relating Galaxy Cluster X-Ray Luminosities to Gravitational Masses in Wide Angle Surveys  

OpenAIRE

It is shown that galaxy cluster surveys selecting clusters by their X-ray luminosity effectively select by cluster mass. It is shown that a selection based solely on Abell galaxy richness is less efficient in terms of mass. Furthermore the empirical X-ray luminosity - gravitational mass relation and its scatter is quantified and the relation is compared to predicted relations.

Reiprich, Thomas H.; Boehringer, Hans

2000-01-01

418

Optimisation of average luminosity in pp and /SUP p/ p colliders  

International Nuclear Information System (INIS)

Algorithms are presented for the optimisation of the luminosity in pp and /SUP p/ p colliders. Their average luminosity is lower than the peak luminosity because the transverse dimensions of the beams increase due to intra-beam scattering, and the beam currents decay due to the collisions with the rest gas and the opposite beam. Assuming that the /SUP p/ are produced during the collision time links the /SUP p/ production rate to the maximum /SUP p/ current. Either the average luminosity or the average number of collisions with exactly one beam-beam event are optimised. The free parameters are the collision time, the initial luminosity, and the density of the beams. Numerical solutions are based on the parameters of the /SUP p/ p option of the Large Hadron Collider (LHC) and on the /SUP p/ production rate of the /SUP p/ source (ACOL) at CERN. Approximate analytical solutions are also presented

419

Galaxy luminosity function and Tully-Fisher relation: reconciled through rotation-curve studies  

CERN Document Server

The relation between galaxy luminosity L and halo virial velocity v_vir required to fit the galaxy luminosity function differs from the observed Tully-Fisher relation between L and disc speed v_rot. Hence the problem of reproducing the galaxy luminosity function and the Tully-Fisher relation simultaneously has plagued semianalytic models since their inception. Here we study the relation between v_rot and v_vir by fitting observational average rotation curves of disc galaxies binned in luminosity. We show that the v_rot - v_vir relation that we obtain in this way can fully account for this seeming inconsistency. Therefore, the reconciliation of the luminosity function with the Tully-Fisher relation rests on the complex dependence of v_rot on v_vir, which arises because the ratio of stellar mass to dark matter mass is a strong function of halo mass.

Cattaneo, Andrea; Papastergis, Emmanouil

2014-01-01

420

Leaving the ISCO: the inner edge of a black-hole accretion disk at various luminosities  

CERN Document Server

The "radiation inner edge" of an accretion disk is defined as the inner boundary of the region from which most of the luminosity emerges. Similarly, the "reflection edge" is the smallest radius capable of producing a significant X-ray reflection of the fluorescent iron line. For black hole accretion disks with very sub-Eddington luminosities these and all other "inner edges" locate at ISCO. Thus, in this case, one may rightly consider ISCO as the unique inner edge of the black hole accretion disk. However, even for moderate luminosities, there is no such unique inner edge as differently defined edges locate at different places. Several of them are significantly closer to the black hole than ISCO. The differences grow with the increasing luminosity. For nearly Eddington luminosities, they are so huge that the notion of the inner edge losses all practical significance.

Abramowicz, Marek A; Kato, Shoji; Lasota, Jean-Pierre; Rozanska, Agata; Sadowski, Aleksander

2010-01-01

421

Study on high rate MRPC for high luminosity experiments  

Science.gov (United States)

Multi-gap Resistive Plate Chambers (MRPC) has been used to construct time-of-flight system in the field of nuclear and particle physics, due to their high-precision timing properties, high efficiency, reliability and coverage of large area. With the increase of accelerator luminosity, MRPCs have to withstand particle fluxes up to several tens of kHz/cm2 in view of the next generation physics experiments, such as the SIS-100/300 at FAIR-CBM, SoLID at JLab and NICA at JINR. But the MRPC assembled with float glass has very low rate capability not exceeding some hundreds of Hz/cm2. Two possible solutions for increasing rate capability, one is to reduce the bulk resistivity of glass and the other is to reduce the electrode thickness. Tsinghua University has done R&D on high rate MRPC for many years. A special low resistive glass with bulk resistivity around 1010?.cm was developed. We also studied the rate capability changes with glass thickness. In this paper we describe the performance of low resistive glass and two kinds of high rate MRPC (Pad readout and Strip readout) tested by deuterium beams. The results show that the tolerable particle flux can reach 70 kHz/cm2. In the mean time, MRPCs assembled with three thickness (0.7 mm, 0.5 mm and 0.35 mm) of float glass were also tested with deuteron beams, the results show that the three detectors can afford particle rate up to 500 Hz/cm2, 0.75 kHz/cm2 and 3 kHz/cm2, respectively.

Wang, Y.; Huang, X.; Lv, P.; Zhu, W.; Shi, L.; Xie, B.; Cheng, J.; Li, Y.

2014-08-01

422

PAIR PRODUCTION IN LOW-LUMINOSITY GALACTIC NUCLEI  

International Nuclear Information System (INIS)

Electron-positron pairs may be produced near accreting black holes by a variety of physical processes, and the resulting pair plasma may be accelerated and collimated into a relativistic jet. Here, we use a self-consistent dynamical and radiative model to investigate pair production by ?? collisions in weakly radiative accretion flows around a black hole of mass M and accretion rate M-dot . Our flow model is drawn from general relativistic magnetohydrodynamic simulations, and our radiation field is computed by a Monte Carlo transport scheme assuming the electron distribution function is thermal. We argue that the pair production rate scales as r-6M-1 M-dot6. We confirm this numerically and calibrate the scaling relation. This relation is self-consistent in a wedge in M, M-dot parameter space. If M-dot is too low the implied pair density over the poles of the black hole is below the Goldreich-Julian density and ?? pair production is relatively unimportant; if M-dot is too high the models are radiatively efficient. We also argue that for a power-law spectrum the pair production rate should scale with the observables LX ? X-ray luminosity and M as L2X M-4. We confirm this numerically and argue that this relation likely holds even for radiatively efficient flows. The pair production rates are sensitive to black hole spin and to the ion-electron temperature ratio which are fixed in this exple ratio which are fixed in this exploratory calculation. We finish with a brief discussion of the implications for Sgr A* and M87.

423

Pair Production in Low-luminosity Galactic Nuclei  

Science.gov (United States)

Electron-positron pairs may be produced near accreting black holes by a variety of physical processes, and the resulting pair plasma may be accelerated and collimated into a relativistic jet. Here, we use a self-consistent dynamical and radiative model to investigate pair production by ?? collisions in weakly radiative accretion flows around a black hole of mass M and accretion rate \\dot{M}. Our flow model is drawn from general relativistic magnetohydrodynamic simulations, and our radiation field is computed by a Monte Carlo transport scheme assuming the electron distribution function is thermal. We argue that the pair production rate scales as r^{-6} M^{-1} \\dot{M}^{6}. We confirm this numerically and calibrate the scaling relation. This relation is self-consistent in a wedge in M, \\dot{M} parameter space. If \\dot{M} is too low the implied pair density over the poles of the black hole is below the Goldreich-Julian density and ?? pair production is relatively unimportant; if \\dot{M} is too high the models are radiatively efficient. We also argue that for a power-law spectrum the pair production rate should scale with the observables LX ? X-ray luminosity and M as L 2 X M -4. We confirm this numerically and argue that this relation likely holds even for radiatively efficient flows. The pair production rates are sensitive to black hole spin and to the ion-electron temperature ratio which are fixed in this exploratory calculation. We finish with a brief discussion of the implications for Sgr A* and M87.

Mo?cibrodzka, M.; Gammie, C. F.; Dolence, J. C.; Shiokawa, H.

2011-07-01

424

The low-luminosity active galactic nucleus in the centre of the Galaxy  

Science.gov (United States)

The observations of far-infrared line and continuum spectra throughout the Galactic Centre and in some regions of the disc are analysed in order to determine the physical conditions (densities, shock velocities, radiation parameters etc.) and the relative abundances of some elements (C, N and O). Consistent model calculations of the line and continuum spectra show that, although the radiation from the stars dominates, an active galactic nucleus (AGN) is clearly present, with a radiation maximum in the Sgr A* region. The models account for the coupled effect of photoionization and shocks. The flux, similar to that found in low-luminosity AGNs, is lower by a factor of ˜100 than that of AGN. Gas densities in the downstream line emission region range between 100 and 3000 cm-3, the shock velocities between 50 and 300 km s-1. Densities of ˜5 × 106 cm-3, close to the Sgr A* black hole, lead to self-absorption of free-free radiation in the radio frequency range, while X-ray data are explained by shock velocities of ˜3000 km s-1. A magnetic field of ˜10 -4 G shows relatively small fluctuations throughout the Galactic Centre. The dust-to-gas ratios range between 3 × 10-15 and ?10-13 by number. Lower values are found far from the centre, suggesting that N and O, which are depleted from the gaseous phase, are included into molecules rather than trapped into grains.

Contini, M.

2011-12-01

425

Characterization of new ATLAS pixel Front-End prototype for upgraded luminosity  

International Nuclear Information System (INIS)

Around the year 2012, a first upgrade to the Large Hadron Collider (LHC) is scheduled which should enhance the luminosity by a factor 2-3. To cope with the increased hit rate, the Front-End of the ATLAS innermost pixel detector layer needs to be replaced. A new Front-End chip, called FE-I4, is presently under development in several laboratories around the world. FE-I4 is designed to cope with the higher hit rate and has an enhanced radiation tolerance. In the process of developing FE-I4, an intermediate test chip (FEI4-proto1) has been designed and produced in a 130 nm technology. Several independent blocks are implemented on this chip. The main block is an array of 61 by 14 pixel cells with associated configuration logic, bias circuits and DACs as needed for the new ATLAS pixel FE. To test this chip, a test setup consisting of two PCBs has been developed. The first PCB carries the FEI4-proto1 and routes the designated signals and supply voltages to the chip. The second PCB is a master FPGA board to control the FE, with a USB interface to connect to a PC and provide a user friendly interface. The hardware, software and firmware were developed in Bonn. Using this setup, the behavior and the characteristics of the new blocks were tested to feedback the designers of the FE-I4 and optimize the new chip

426

A Tale Twice Told: The Luminosity Profiles of the Sagittarius Tails  

CERN Document Server

The Sagittarius dwarf galaxy is the archetype of a tidally disrupting system. Both leading and trailing tails can be observed across at least 180 degrees of the sky and measurements of their luminosity density profiles have recently become available. Using numerical simulations, we explore the factors that control the appearance of such profiles. We use two possible models for the Sgr progenitor. The first is a one-component Plummer model, which may represent either a dark matter free progenitor, or one in which pre-existing dark matter has already been largely stripped. The second is a two-component model in which the stars are represented by a Hernquist sphere embedded in a cosmologically modish Navarro-Frenk-White dark halo. Disruption of the models in the Milky Way galaxy provides us with two tellings of the tale of the formation of the Sgr stream. The initial disintegration of the baryons proceeds more slowly for the two-component models because of the protective cocoon of dark matter. Once this has been...

Niederste-Ostholt, Martin; Evans, Wyn

2012-01-01

427

The BH mass of nearby QSOs: a comparison of the bulge luminosity and virial methods  

CERN Document Server

We report on the analysis of the photometric and spectroscopic properties of a sample of 29 low redshift (z<0.6) QSOs for which both HST WFPC2 images and ultraviolet HST FOS spectra are available. For each object we measure the R band absolute magnitude of the host galaxy, the CIV (1550A) line width and the 1350A continuum luminosity. From these quantities we can estimate the black hole (BH) mass through the M(BH)-L(bulge) relation for inactive galaxies, and from the virial method based on the kinematics of the regions emitting the broad lines. The comparison of the masses derived from the two methods yields information on the geometry of the gas emitting regions bound to the massive BH. The cumulative distribution of the line widths is consistent with that produced by matter laying in planes with inclinations uniformly distributed between 10 and 50 deg, which corresponds to a geometrical factor f=1.3. Our results are compared with those of the literature and discussed within the unified model of AGN.

Labita, M; Falomo, R; Uslenghi, M; Labita, Marzia; Treves, Aldo; Falomo, Renato; Uslenghi, Michela

2006-01-01

428

Bolometric luminosity black-hole growth time and slim accretion discs in active galactic nuclei  

CERN Document Server

We investigate the accretion rate, bolometric luminosity, black hole (BH) growth time and BH spin in a large AGN sample under the assumption that all such objects are powered via thin or slim accretion discs (ADs). We use direct estimates of the mass accretion rate, Mdot, to show that many currently used values of Lbol and Ledd are either under estimated or over estimated because they are based on bolometric correction factors that are adjusted to the properties of moderately accreting active galactic nuclei (AGN) and do not take into account the correct combination of BH mass, spin and accretion rate. The consistent application of AD physics to our sample of Sloan Digital Sky Survey (SDSS) AGN leads to the following findings: 1. Even the most conservative assumption about the radiative efficiency of fast accreting BHs shows that many of these sources must contain slim ADs. We illustrate this by estimating the fraction of such objects at various redshifts. 2. Many previously estimated BH growth times are inco...

Netzer, Hagai

2013-01-01

429

HIGH-ENERGY GAMMA-RAY AFTERGLOWS FROM LOW-LUMINOSITY GAMMA-RAY BURSTS  

International Nuclear Information System (INIS)

The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs-LL-GRBs. The nature of the outflow responsible for them is not yet clear. Two scenarios have been suggested: one is the conventional relativistic outflow with initial Lorentz factor of order of ?0 ?> 10 and the other is a trans-relativistic outflow with ?0 ? 1-2. Here, we compare the high-energy gamma-ray afterglow emission from these two different models, taking into account both synchrotron self-inverse Compton (SSC) scattering and the external inverse Compton scattering due to photons from the cooling supernova or hypernova envelope (SNIC). We find that the conventional relativistic outflow model predicts a relatively high gamma-ray flux from SSC at early times (4 s for typical parameters) with a rapidly decaying light curve, while in the trans-relativistic outflow model, one would expect a much flatter light curve of high-energy gamma-ray emission at early times, which could be dominated by both the SSC emission and the SNIC emission, depending on the properties of the underlying supernova and the shock parameter ?e and ?B. The Fermi Gamma-ray Space Telescope should be able to distinguish between the two models in the future.

430

INFRARED LUMINOSITIES AND DUST PROPERTIES OF z ? 2 DUST-OBSCURED GALAXIES  

International Nuclear Information System (INIS)

We present SHARC-II 350 ?m imaging of twelve 24 ?m bright (F24?m > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Booetes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 ?m imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 ?m flux density. The 350 ?m upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: Tdust > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of ?3 x 108 Msun. In comparison to other dusty z ? 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 x 1013 Lsun versus 6 x 1012 Lsun for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus ?30 K) and lower inferred dust masses (3 x 108 Msun versus 3 x 109 Msun). Wide-field Herschel and Submillimeter ld Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 ?m bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z ? 2 involves a submillimeter bright, cold-dust, and star-formation-dominated phase followed by a 24 ?m bright, warm-dust and AGN-dominated phase.

431

The European Large Area ISO Survey IV the preliminary 90 micron luminosity function  

CERN Document Server

We present the luminosity function of 90um selected galaxies from the European Large Area ISO Survey (ELAIS), extending to z=0.3. Their luminosities are in the range 10^9 = 100mJy database, we found optical, 15um or 1.4GHz identifications for 24 (65%). We have obtained 2dF and UK Schmidt FLAIR spectroscopy of 89% of IDs to rigid multivariate flux limits. We construct a luminosity function assuming (a) our spectroscopic subset is an unbiased sparse sample, and (b) there are no galaxies which would not be represented in our spectroscopic sample at {\\it any} redshift. We argue that we can be confident of both assumptions. We find the luminosity function is well-described by the local 100um luminosity function of Rowan-Robinson, Helou & Walker (1987). {\\it Assuming} this local normalisation, we derive luminosity evolution of (1+z)^{2.45\\pm0.85} (95% confidence). We argue that star formation dominates the bolometric luminosities of these galaxies and we derive comoving star formation rates in broad agreement w...

Serjeant, S; Oliver, S; Surace, C; Heraudeau, P; Linden-Voernle, M J D; Gruppioni, C; La Franca, F; Rigopoulou, D; Morel, T; Crockett, H; Sumner, T J; Rowan-Robinson, M; Graham, M

2000-01-01

432

Gamma-ray luminosity function of gamma-ray bright AGNs  

International Nuclear Information System (INIS)

Detection of ?-ray emissions from a class of active galactic nuclei (viz blazars), has been one of the important findings from the Compton Gamma-Ray Observatory (CGRO). However, their ?-ray luminosity function has not been well determined. Few attempts have been made in earlier works, where BL Lacs and Flat Spectrum Radio Quasars (FSRQs) have been considered as a single source class. In this paper, we investigated the evolution and ?-ray luminosity function of FSRQs and BL Lacs separately. Our investigation indicates no evolution for BL Lacs, however FSRQs show significant evolution. Pure luminosity evolution is assumed for FSRQs and exponential and power law evolution models are examined. Due to the small number of sources, the low luminosity end index of the luminosity function for FSRQs is constrained with an upper limit. BL Lac luminosity function shows no signature of break. As a consistency check, the model source distributions derived from these luminosity functions show no significant departure from the observed source distributions. (research papers)

433

The lag and duration-luminosity relations of gamma-ray burst pulses  

CERN Document Server

Relations linking the temporal or/and spectral properties of the prompt emission of gamma-ray bursts (hereafter GRBs) to the absolute luminosity are of great importance as they both constrain the radiation mechanisms and represent potential distance indicators. Here we discuss two such relations: the lag-luminosity relation and the newly discovered duration-luminosity relation of GRB pulses. We aim to extend our previous work on the origin of spectral lags, using the duration-luminosity relation recently discovered by Hakkila et al. to connect lags and luminosity. We also present a way to test this relation which has originally been established with a limited sample of only 12 pulses. We relate lags to the spectral evolution and shape of the pulses with a linear expansion of the pulse properties around maximum. We then couple this first result to the duration-luminosity relation to obtain the lag-luminosity and lag-duration relations. We finally use a Monte-Carlo method to generate a population of synthetic G...

Boci, S; Mochkovitch, R

2011-01-01

434

Cosmic Evolution of Black Holes and Spheroids. IV. The BH Mass - Spheroid Luminosity Relation  

CERN Document Server

From high-resolution images of 23 Seyfert-1 galaxies at z=0.36 and z=0.57 obtained with the Near Infrared Camera and Multi-Object Spectrometer on board the Hubble Space Telescope (HST), we determine host-galaxy morphology, nuclear luminosity, total host-galaxy luminosity and spheroid luminosity. Keck spectroscopy is used to estimate black hole mass (M_BH). We study the cosmic evolution of the M_BH-spheroid luminosity (L_sph) relation. In combination with our previous work, totaling 40 Seyfert-1 galaxies, the covered range in BH mass is substantially increased, allowing us to determine for the first time intrinsic scatter and correct evolutionary trends for selection effects. We re-analyze archival HST images of 19 local reverberation-mapped active galaxies to match the procedure adopted at intermediate redshift. Correcting spheroid luminosity for passive luminosity evolution and taking into account selection effects, we determine that at fixed present-day V-band spheroid luminosity, M_BH/L_sph \\propto (1+z)^(...

Bennert, Vardha Nicola; Woo, Jong-Hak; Malkan, Matthew A; Le Bris, Alexandre; Auger, Matthew W; Gallagher, Sarah; Blandford, Roger D

2009-01-01