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1

The Lorentz factor distribution and luminosity function of relativistic jets in AGNs  

CERN Multimedia

The observed apparent velocities and luminosities of the relativistic jets in AGNs are significantly different from their intrinsic values due to strong special relativistic effects. We adopt the maximum likelihood method to determine simultaneously the intrinsic luminosity function and the Lorentz factor distribution of a sample of AGNs. The values of the best estimated parameters are consistent with the previous results, but with much better accuracy. In previous study, it was assumed that the shape of the observed luminosity function of Fanaroff-Riley type II radio galaxies is the same with the intrinsic luminosity function of radio loud quasars. Our results prove the validity of this assumption. We also find that low and high redshift groups divided by z=0.1 are likely to be from different parent populations.

Liu, Yuan

2007-01-01

2

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

International Nuclear Information System (INIS)

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

1991-01-01

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 GRBS and Their Interpretation  

CERN Document Server

The bulk Lorentz factor of the gamma-ray burst (GRB) ejecta (Gamma_0) is a key parameter to understand the GRB physics. Liang et al. have discovered a correlation between Gamma_0 and isotropic gamma-ray energy: Gamma_0\\proptoE_{gamma,iso,52}^{0.25}. By including more GRBs with updated data and more methods to derive Gamma_0, we confirm this correlation and obtain Gamma_0~118E_{gamma,iso,52}^{0.26}. Evaluating the mean isotropic gamma-ray luminosities L_{gamma,iso} of the GRBs in the same sample, we discover an even tighter correlation Gamma_0~264 L_{gamma,iso,52}^{0.27}. 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_0\\proptoL_{gamma,iso}^{0.22}, which is well consistent with the data. This suggests that the central engine of long GRBs...

Lv, Jing; Lei, Wei-Hua; Zhang, Bing; Wu, Qing-Wen; Wang, Ding-Xiong; Liang, En-Wei; Lv, Hou-Jun

2011-01-01

5

Luminosity and Redshift Dependence of the Covering Factor of Active Galactic Nuclei viewed with WISE and Sloan Digital Sky Survey  

Science.gov (United States)

In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 ?m luminosity functions (LFs) at 0.006 dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z <= 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.

Toba, Y.; Oyabu, S.; Matsuhara, H.; Malkan, M. A.; Gandhi, P.; Nakagawa, T.; Isobe, N.; Shirahata, M.; Oi, N.; Ohyama, Y.; Takita, S.; Yamauchi, C.; Yano, K.

2014-06-01

6

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

Science.gov (United States)

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 ? 1 mag) with relatively small CO column densities NCO ? 2 × 1016 cm-2. We separate the atomic and molecular fractions statistically using EB-V as a gauge of the total gas column density and compare N_H_2 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 N_H_2 for diffuse ISM does not differ from the usual value of 1K km s-1 of integrated CO brightness per 2 × 1020 H2 cm-2. Moreover, the luminosity of diffuse CO viewed perpendicular to the galactic plane is 2/3 that seen at the Solar galactic radius in surveys of CO emission near the galactic plane. Conclusions: Commonality of the CO-H2 conversion factors in diffuse and dark clouds can be understood from considerations of radiative transfer and CO chemistry. There is unavoidable confusion between CO emission from diffuse and dark gas and misattribution of CO emission from diffuse to dark or giant molecular clouds. The character of the ISM is different from what has been believed if CO and H2 that have been attributed to molecular clouds on the verge of star formation are actually in more tenuous, gravitationally-unbound diffuse gas. Appendix E is only available in electronic form at http://www.aanda.org

Liszt, H. S.; Pety, J.; Lucas, R.

2010-07-01

7

Notes on luminosity variation at ISABELLE  

International Nuclear Information System (INIS)

In the present ISABELLE design, the luminosity at each insertion will be the same, unless special efforts are taken to get a low-? insertion or reduced crossing angle. These can only change the luminosity by factors of 2 to 4 from insertion to insertion. An estimation of the range of desired luminosities is given

1977-07-29

8

OLYMPUS luminosity monitoring  

International Nuclear Information System (INIS)

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

2012-03-19

9

Luminosities of radio Pulsars  

CERN Document Server

Luminosity is an intrinsic property of radio pulsars related to the properties of the magnetospheric plasma and the beam geometry, and inversely proportional to the observing frequency. In traditional models, luminosity has been considered as a function of the spin parameters of pulsars. On the other hand, parameter independent models like power law and lognormal have been also used to fit the observed luminosities. Some of the older studies on pulsar luminosities neglected observational biases, but all of the recent studies tried to model observational effects as accurately as possible. Luminosities of pulsars in globular clusters and in the Galactic disk have been studied separately. Older studies concluded that these two categories of pulsars have different luminosity distributions, but the most recent study concluded that those are the same. This article reviews all significant works on pulsar luminosities and discusses open questions.

Bagchi, Manjari

2013-01-01

10

Luminosity Function of GRBs  

CERN Document Server

We attempt to constrain the luminosity function of Gamma Ray Bursts (GRBs) from the observed number count--flux relation and the afterglow redshift data. We assume three classes of luminosity functions for our analysis: (a) Log-normal distribution, (b) Schechter distribution, and (c) Scale-free distribution. We assume several models of the evolution of the GRB population for each luminosity function. Our analysis shows that: (a) log-normal is the only luminosity function that is compatible with both the observations. This result is independent of the GRB evolution model, (b) for log-normal function, the average photon luminosity $L_0$ and the width of the luminosity function $\\sigma$ that are compatible with both the observations fall in the range: $10^{55} sec^{-1} \\la L_0 \\la 10^{56} sec^{-1}$ and $2 \\la \\sigma \\la 3$, (c) the agreement of observations with other luminosity functions requires the GRB population to evolve more strongly than the evolution of the star-formation rate of the universe.

Sethi, S; Sethi, Shiv

2001-01-01

11

Luminosities of proton--antiproton colliding beams  

International Nuclear Information System (INIS)

A comparison is given of the luminosities achievable with the proton-antiproton collision schemes proposed by CERN and by Fermilab. Estimates have been made by both CERN and Fermilab groups but these estimates have not been made with a consistent set of assumptions. A comparison of the potential performance of the two schemes at present is therefore not possible. A realistic assessment of the many details entering is needed, and a deep understanding of the factors contributing to the luminosity may lead to improvements which in turn could result in increased luminosity. Using the antiproton schemes proposed, it is found that the luminosity at 1000 GeV/c of the Fermilab Doubler as a antip-p collider is 3.4 x 10"2"9 and the luminosity of the SPS at 270 GeV/c as a anti p-p collider is 1.0 x 10"3"0

1978-03-31

12

Crab Cavity Voltage and Luminosity Calculation  

CERN Multimedia

The luminosity is a very important parameter for an accelerator, because it describes the interaction rate per unit cross section. One of the goals of the designer is to improve as much as possible the luminosity, but there are factors which can affect and reduce it. The crossing angle is a scheme which mitigates the effect of the long-range beam-beam interaction on the accelerator, but also reduces the luminosity. One possible solution to keep low the long-range beam-beam effects, but improve the luminosity is the Crab Cavity (CC). The CC is a superconducting RF cavity operated in a transverse dipole mode, which provides a transverse kick on the beam particles that varies with the longitudinal position along the bunch. The kick produces a rotation of the bunch at the collision point so as to achieve an effective head-on collision and, therefore, restores the luminosity otherwise lost by the crossing angle.

Yee, B

2010-01-01

13

Luminosities of AGB Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The prevailing evidence suggests that most large-amplitude AGB variables follow the period luminosity (PL) relation that has been established for Miras in the LMC and galactic globular clusters. Hipparcos observations indicate that most Miras in the solar neighbourhood are consistent with such a relation. There are two groups of stars with luminosities that are apparently greater than the PL relation would predict: (1) in the LMC and SMC there are large amplitude variables, ...

Whitelock, Patricia

2002-01-01

14

SDC at high luminosity  

International Nuclear Information System (INIS)

Why is it prudent to plan for a luminosity (L) of >1034/(cm2sec) from the beginning? First, the SSC is easily capable of attaining high luminosity. In comparison, for bar pp machines such as the Tevatron, increases in L are difficult. Second, after early runs at design luminosity, the only simple upgrade to a general purpose detector is an increase in luminosity. Third, and most important, the only known model independent physics goal of SSC is in the electroweak sector; the ZZ scattering amplitude reaches the unitarity bound for ?s ? 3 TeV. In order to reach this mass range, and assure that some new physics is found, high luminosity running is needed. Since high luminosity running is desirable and easily attainable, it is inevitable. Therefore, one should build the ''hooks'' for upgrades to high L into the SDC from the beginning. The experience of CDF is that if this is not done, upgrades can be painful. Specifically, if possible, SDC should make sure that the chosen technologies allow high L operation. The time to plan for the whole useful lifetime of SDC is from the beginning. 9 refs., 6 figs

1990-04-23

15

A Luminosity Calorimeter for CLIC  

CERN Document Server

For the relative precision of the luminosity measurement at CLIC, a preliminary target value of 1% is being assumed. This may be accomplished by constructing a finely granulated calorimeter, which will measure Bhabha scattering at small angles. In order to achieve the design goal, the geometrical parameters of the calorimeter need to be defined. Several factors influence the design of the calorimeter; chief among these is the need to minimize the error on the luminosity measurement while avoiding the intense beam background at small angles. In this study the geometrical parameters are optimized for the best performance of the calorimeter. In addition, the suppression of physics background to Bhabha scattering is investigated and a set of selection cuts is introduced.

Abramowicz, H; Kananov, S; Levy, A; Sadeh, I

2009-01-01

16

Luminosities of AGB Variables  

CERN Document Server

The prevailing evidence suggests that most large-amplitude AGB variables follow the period luminosity (PL) relation that has been established for Miras in the LMC and galactic globular clusters. Hipparcos observations indicate that most Miras in the solar neighbourhood are consistent with such a relation. There are two groups of stars with luminosities that are apparently greater than the PL relation would predict: (1) in the LMC and SMC there are large amplitude variables, with long periods, P> 420 days, which are probably undergoing hot bottom burning, but which are very clearly more luminous than the PL relation (these are visually bright and are likely to be among the first stars discovered in more distant intermediate age populations); (2) in the solar neighbourhood there are short period, P<235 days, red stars which are probably more luminous than the PL relation. Similar short-period red stars, with high luminosities, have not been identified in the Magellanic Clouds.

Whitelock, P A

2002-01-01

17

Luminosity measurements at hadron colliders  

Energy Technology Data Exchange (ETDEWEB)

In this paper we discuss luminosity measurements at Tevatron and HERA as well as plans for luminosity measurements at LHC. We discuss luminosity measurements using the luminosity detectors of the experiments as well as measurements by the machine. We address uncertainties of the measurements, challenges and lessons learned.

Papadimitriou, Vaia; /Fermilab

2008-04-01

18

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

1984-03-15

19

Luminosity enhancements at SLAC  

Energy Technology Data Exchange (ETDEWEB)

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.

Coward, D.H.

1984-04-01

20

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.

2009-04-15

 
 
 
 
21

Results From the DAFNE High Luminosity Test  

Energy Technology Data Exchange (ETDEWEB)

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 {center_dot} 10{sup 32} cm{sup -2}s{sup -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 10{sup 36} cm{sup -2} s{sup -1} and it has been also taken into account to upgrade one of the LHC interaction regions.

Milardi, C.; Alesini, D.; Biagini, M.E.; Boni, R.; Boscolo, M.; Bossi, F.; Buonomo, B.; Clozza, A.; Delle Monache, G.; Demma, T.; Di Pasquale, E.; Di Pirro, G.; Drago, A.; Gallo, A.; Ghigo, A.; Guiducci, S.; Ligi, C.; Marcellini, F.; Mazzitelli, G.; Murtas, F.; Pellegrino, L.; /Frascati /Novosibirsk, IYF /CERN /INFN, Cosenza /INFN, Rome /KEK, Tsukuba /Orsay, LAL /Rome U. /Pisa U. /INFN, Pisa /INFN, Rome3 /SLAC

2012-04-11

22

The MICE luminosity monitor  

Science.gov (United States)

The MICE experiment will provide the first measurement of ionisation cooling, a technique suitable for reducing the transverse emittance of a tertiary muon beam in a future neutrino factory accelerator facility. MICE is presently in the final stages of commissioning its beam line. The MICE luminosity monitor has proved an invaluable tool throughout this process, providing independent measurements of particle rate from the MICE target, normalisation for beam line detectors and verification of simulation codes.

Dobbs, A.; Forrest, D.; Soler, F. J. P.

2013-02-01

23

SLHC: The LHC luminosity upgrade  

International Nuclear Information System (INIS)

The LHC will provide unprecedented sensitivity to Standard Model and beyond the Standard Model Physics. However, some important Standard Model measurements as well as a wide part of the spectrum of particles predicted by many promising theoretical models of New Physics are likely beyond the LHC reach. For such observations, a factor-of-ten increase in LHC statistics will have a major impact. A luminosity upgrade is therefore planned for the LHC. The SLHC as well as offering the possibility to increase the Physics potential will create an extreme operating environment for the detectors, particularly the tracking devices. An increase in the number of minimum bias events per beam crossing by at least an order of magnitude beyond the levels envisioned for LHC design luminosity creates the need to handle much higher occupancies and for the innermost layers unprecedented levels of radiation. This will require a fully upgraded tracking system giving a higher granularity, while trying not to exceed the material budget and power levels of the current trackers. The much higher rate of interactions may also push the limits of the Level-1 trigger system. Efforts have already begun to address these issues. This paper presents the possible Physics reaches at SLHC and the current understanding of what systems will need to be upgraded.

2008-10-21

24

STS atmospheric luminosities  

Science.gov (United States)

During the STS-8 space shuttle mission special photographic and TV operations were carried out to record the properties of the spacecraft induced luminosities. One of these luminous phenomena is the quiescent vehicle glow which was photographed during the STS-8 mission with an image intensified photographic camera, with and without an objective grating. During the latter part of the mission the altitude of the shuttle was relatively low (120 n.m. = 222 km) and unprecedentedly high intensity of the glow was observed. The crew reported that the glow was easily visible to the naked eye. The proper orientation of the shuttle with respect to the velocity vector and the objective grating permitted the exposure of good objective spectrum of the glow in the visible region. From the results it is clear that the spectrum appears to be a continuum as observed by the image intensifier objective grating camera. Qualitative examination of the data shows that there is very tail little glow ion the wavelength range of 4300 to about 5000 angstroms. Above 5000 angstroms the glow becomes stronger towards the red and then it falls off towards higher wavelength and of the spectrum presumably because of the responsivity of the device.

Mende, S. B.

1984-01-01

25

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 SciELO Brazil | Language: English Abstract in portuguese 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.

26

Luminosity lifetime in the Tevatron  

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-06-09

27

Low-Luminosity Seyfert Nuclei  

CERN Multimedia

We describe a new sample of Seyfert nuclei discovered during the course of an optical spectroscopic survey of nearby galaxies. The majority of the objects, many recognized for the first time, have luminosities much lower than those of classical Seyferts and populate the faint end of the AGN luminosity function. A significant fraction of the nuclei emit broad H-alpha emission qualitatively similar to the broad lines seen in classical Seyfert 1 nuclei and QSOs.

Ho, L C; Sargent, W L W; Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W.

1996-01-01

28

Fast luminosity monitor at LEP  

Energy Technology Data Exchange (ETDEWEB)

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

Bini, C. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); De Pedis, D. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); De Zorzi, G. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); Diambrini-Palazzi, G. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); Di Cosimo, G. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); Di Domenico, A. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); Gauzzi, P. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy)); Zanello, D. (Dipartimento di Fisica, Universita ' ' La Sapienza' ' , Roma and INFN Sezione di, Roma (Italy))

1994-09-15

29

Luminosity measurement in H1  

International Nuclear Information System (INIS)

At HERA, luminosity is determined on-line and bunch by bunch by measuring the Bremsstrahlung spectrum from e-p collisions. The Hl collaboration has built a completely new luminosity system in order to sustain the harsh running conditions after the fourfold luminosity increase. Namely, the higher synchrotron radiation doses and the increased event pile-up have governed the design of the two major components, a radiation resistant quartz-fibre electro-magnetic calorimeter, and a fast read-out electronic with on-line energy histogram loading at a rate of 500 kHz. The group was in charge of the electronic and the on-line data analysis of the new luminosity system. In this thesis, I present analysis tools and methods to improve the precision of the luminosity measurement. The energy scale and acceptance calculation methods set out in this thesis permit these values to be determined every four minutes, to an accuracy of 0.5 parts per thousand for the energy scale and 2 parts per thousand for the acceptance. From these results, the degree of accuracy obtained on the luminosity measurement is between 6.5 and 9.5 parts per thousand. These results are currently undergoing validation, with the aim of becoming the standard H1 method. I also studied quasi-elastic Compton events to cross-check the luminosity measurement using the 2003- 2004 and 2005 data. Indeed, this process has a well calculable cross section and a clear experimental signature. The leptonic final state consists of a coplanar e-gamma system, both observable in the central H1 detector. (author)

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 10"3"3 cm"-"2 sec"-"1. Everything is difficult and continued R and D is necessary to improve detectors

1983-08-11

31

Physics potential of precision measurements of the LHC luminosity  

CERN Document Server

The uncertainty in the determination of the LHC luminosity is rapidly becoming a limiting factor for the analysis and interpretation of many important LHC processes. In this talk first of all we discuss the theoretical accuracy of total cross sections and examine in which cases the luminosity error is or will be dominant. We then review the impact of LHC data in PDF determinations, with enphasis on the effects of the luminosity uncertainty. We explore the requirements for the accuracy of the 2011 luminosity determination from the point of view of standard candle cross section and other important processes. Finally we discuss what we can learn from the accurate measurement of cross section ratios at different center of mass energies for processes like W, ttbar and dijet production.

CERN. Geneva

2012-01-01

32

The [O II] lambda 3727 Luminosity Function at z ~ 1  

CERN Document Server

We measure the evolution of the [O II] lambda 3727 luminosity function at 0.75 < z < 1.45 using high-resolution spectroscopy of ~ 14,000 galaxies observed by the DEEP2 galaxy redshift survey. We find that brighter than L([O II])=10^{42} erg s^{-1} the luminosity function is well-represented by a power law dN/dL \\propto L^{\\alpha} with slope \\alpha ~ -3. The number density of [O II]-emitting galaxies above this luminosity declines by a factor of \\gtrsim 2.5 between z ~ 1.35 and z ~ 0.84. In the limit of no density evolution, the characteristic [O II] luminosity, defined as the luminosity where the space density equals 10^{-3.5} dex^{-1} Mpc^{-3}, declines by a factor of ~ 1.7 over the same redshift interval. These results imply a ~ 25% per Gyr decrease in the amount of star formation in galaxies during this epoch. Integrating the observed [O II] luminosity function assuming a faint-end power-law slope of -1.3 +/- 0.2, we derive the integrated star formation rate density in four redshift bins centered aro...

Zhu, Guangtun; Blanton, Michael R

2008-01-01

33

Luminosity monitors at the LHC  

CERN Document Server

We study the theoretical accuracy of various methods that have been proposed to measure the luminosity of the LHC pp collider, as well as for Run II of the Tevatron p barp collider. In particular we consider methods based on (i) the total and forward elastic data, (ii) lepton-pair production and (iii) W and Z production.

Khoze, V A; Orava, Risto; Ryskin, M G

2001-01-01

34

Luminosity monitor studies for TESLA.  

Science.gov (United States)

The feasibility of a luminosity monitor based on a radiative Bhabha detector is investigated n the context of the TESLA linear collider. Another option based on low energy e(sup +)e(sup -) pair calorimetry is also discussed. In order to monitor the beam p...

O. Napoly D. Schulte

1997-01-01

35

Luminosity enhancement of trioxane fuels  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a trioxane-based solid fuel having improved flame luminosity comprising trioxane and 0.1 to about 5 wt. % based on the fuel of a sodium salt wherein the sodium salt has a specific gravity of less than 2.00 and the salt is mixed within the trioxane-based solid fuel.

Forschirm, A.

1988-03-22

36

Upsilon spectroscopy at high luminosities  

International Nuclear Information System (INIS)

This report discusses the advantages of high luminosity running on the bb-bar system as a test of QCD and the quark-antiquark forces. The author limits himself to the cases of 1,000 pb/sup -1//year and 10,000 pb/sup -1//year, and what physics goals can be achieved at these integrated luminosity levels. A summary of theoretical spectroscopic predictions is presented, together with a detailed evaluation of the decays 3/sup 3/S-> ??1/sup 1/P/sub 1/->???1/sup 1/S/sub o/ and 1/sup 3/S/sub 1/->?1/sup 1/S/sub o/. A brief discussion of other possible 'exotic' spectrosocpy is given

1982-07-16

37

Galaxy Luminosity Function in Groups  

CERN Document Server

We compute the luminosity function of galaxies in groups. The data consists in two samples of groups of galaxies selected in distance and redshift space comprising a total number of 66 groups. The assignment of galaxies to the groups were derived from the Edinburgh-Durham Southern Galaxy Catalog, considering a limiting apparent magnitude $m_{lim}=19.4$. We find a flat faint end of the mean galaxy luminosity function in groups in contrast to the mean galaxy LF in clusters where a large relative number of faint galaxies is present. We find that a Schechter function with parameters $M^{*}\\simeq -19.6\\pm 0.2,$ $\\alpha \\simeq -1.0\\pm $ 0.2 provides a satisfactory fit to the galaxy LF of our total sample of groups in the range of absolute magnitudes $-22

Muriel, H; Lambas, D G; Muriel, Hernán; Valotto, Carlos A.; Lambas, Diego G.

1998-01-01

38

Converting Halpha luminosities into SFRs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Star-formation rates (SFRs) of galaxies are commonly calculated by converting the measured Halpha luminosities (L_Halpha) into current SFRs. This conversion is based on a constant initial mass function (IMF) independent of the total SFR. As recently recognised the maximum stellar mass in a star cluster is limited by the embedded total cluster mass and, in addition, the maximum embedded star cluster mass is constrained by the current SFR. The combination of these two relation...

Pflamm-altenburg, Jan; Weidner, Carsten; Kroupa, Pavel

2007-01-01

39

Symmetric Moeller/Bhabha Luminosity Monitor  

Energy Technology Data Exchange (ETDEWEB)

Recent determinations of the proton electric to magnetic elastic form factor ratio from polarization transfer measurements at Jefferson Lab indicate an discrepancy with the elastic form factor ratio obtained using the Rosenbluth separation technique in unpolarized cross section measurements. This discrepancy has been explained as the effect of two-photon exchange in the calculation of the elastic electron-proton scattering cross section. The OLYMPUS experiment at DESY has been proposed to measure the ratio of positron-proton and electron-proton elastic scattering cross sections to quantify the effect of two-photon exchange to a percent level. In order to control the systematic uncertainties to the percent level the Symmetric Moeller/Bhabha Luminosity Monitor was proposed. The design and aspected performance will be presented.

Perez Benito, Roberto [Helmholtz-Institut Mainz, Johannes Gutenberg-Universitaet, Johann-Joachim-Becher-Weg 45, 55128 Mainz (Germany); Collaboration: OLYMPUS-Collaboration

2011-07-01

40

Symmetric Moeller/Bhabha Luminosity Monitor  

International Nuclear Information System (INIS)

Recent determinations of the proton electric to magnetic elastic form factor ratio from polarization transfer measurements at Jefferson Lab indicate an discrepancy with the elastic form factor ratio obtained using the Rosenbluth separation technique in unpolarized cross section measurements. This discrepancy has been explained as the effect of two-photon exchange in the calculation of the elastic electron-proton scattering cross section. The OLYMPUS experiment at DESY has been proposed to measure the ratio of positron-proton and electron-proton elastic scattering cross sections to quantify the effect of two-photon exchange to a percent level. In order to control the systematic uncertainties to the percent level the Symmetric Moeller/Bhabha Luminosity Monitor was proposed. The design and aspected performance will be presented.

2011-03-21

 
 
 
 
41

Evolution of the luminosity function of quasars  

International Nuclear Information System (INIS)

We show that the evolution of the luminosity of quasars cannot be excluded from the observational data. The observed evolution of the luminosity function may be interpreted as luminosity evolution as well as density evolution. Approximating the luminosity evolution by a single parameter exponential law, we show how to determine the evolution parameter by use of a limiting volume analysis. We apply the method to some useable complete samples and we present a brief discussion of the results. (orig.)

1976-11-01

42

Precision luminosity measurement at ILC  

CERN Document Server

In these proceedings a novel approach to deal with the beam-induced effects in luminosity measurement is presented. Based on the relativistic kinematics of the collision frame of the Bhabha process, the beam-beam related uncertainties can be reduced to the permille level independently of a precision with which the beam parameters are known. Specific event selection combined with the corrective methods we introduce, leads to the systematic uncertainty from the beam-induced effects to be at a few permille level in the peak region above the 80% of the nominal centre-of-mass energies at ILC.

Bozovic-Jelisavcic, I; Pandurovic, M; Smiljanic, I

2014-01-01

43

The low-luminosity stellar mass function  

International Nuclear Information System (INIS)

The stellar mass function for low-mass stars is constrained using the stellar luminosity function and the slope of the mass-luminosity relation. We investigate the range of mass functions for stars with absolute visual magnitude fainter than MV ? +5 which are consistent with both the local luminosity function and the rather poorly determined mass-absolute visual magnitude relation. Points of inflexion in the mass-luminosity relation exist because of the effects of H-, H2 and of other molecules on the opacity and equation of state. The first two of these correspond to absolute magnitudes MV ? +7 and MV? +12, respectively, at which structure is evident in the stellar luminosity function (a flattening and a maximum, respectively). Combining the mass-luminosity relation which shows these inflexion points with a peaked luminosity function, we test smooth mass functions in the mass range 0.9-0.1 the solar mass. (author)

1990-05-01

44

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

45

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

46

Implications of Lag-Luminosity Relationship for Unified GRB Paradigms  

CERN Document Server

Spectral lags are deduced for 1437 long GRBs with peak fluxes extending to near the BATSE trigger threshold. The lags are modeled to approximate the observed distribution in the peak flux-lag plane, realizing a noise-free representation. Assuming a two-branch lag-luminosity relationship, the lags are self- consistently corrected for cosmological effects to yield distributions in luminosity, distance, and redshift. The results have several consequences for GRB populations -- including a possible nearby subpopulation of low-luminosity, long-lag GRBs -- and for unified gamma-ray/afterglow scenarios which would account for afterglow break times and gamma-ray spectral evolution in terms of jet opening angle, viewing angle, or a profiled jet with variable Lorentz factor.

Norris, J P

2002-01-01

47

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

48

The satellite luminosity functions of galaxies in Sloan Digital Sky Survey  

Science.gov (United States)

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 ˜20 000 galaxy systems to obtain robust statistical results. We derive the satellite luminosity function extending almost 8 mag fainter than the primary galaxy. We also determine how the satellite luminosity function varies with the luminosity, colour and concentration of the primary. We find that, in the mean, isolated primaries of comparable luminosity to the Milky Way and M31 contain about a factor of 2 fewer satellites brighter than MV=-14 than the average of the Milky Way and M31.

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

2011-10-01

49

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

50

Luminosity calibration from elastic scattering  

CERN Document Server

The absolute luminosity of the LHC at the ATLAS interaction point will be calibrated by the measurement of the t-distribution of elastic pp-scattering in the Coulomb-Nuclear interference region. The ALFA detector housed in Roman Pots located 240m away from IP1 is designed to approach the beam at mm distance and to measure elastic pp-scattering at micro-radian scattering angles. This measurement will be performed with dedicated runs using a special beam optics with high beta* and parallel-to-point focusing in order to access the Coulomb regime. In this note the expected performance of this method, evaluated with a simulation of the experimental set-up, is presented.

Stenzel, H

2006-01-01

51

Luminosity monitoring and calibration of BLM  

Science.gov (United States)

The BEPCII Luminosity Monitor (BLM) monitors relative luminosity per bunch. The counting rates of gamma photons, which are proportional to the luminosities from the BLM at the center of mass system energy of the ? (3770) resonance, are obtained with a statistical error of 0.01% and a systematic error of 4.1%. Absolute luminosities are also determined by the BESIII End-cap Electro-Magnetic Calorimeter (EEMC) using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%. The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03 (×1026 cm-2·count-1). With the calibration constant, the counting rates of the BLM can be scaled up to absolute luminosities.

Xue, Zhen; Xu, Zi-Zong; Wang, Xiao-Lian; Hu, Tao; Wang, Zhi-Yong; Fu, Cheng-Dong; Yan, Wen-Biao; Lü, Jun-Guang; Zhou, Li; Cai, Xiao; Yu, Bo-Xiang; Fang, Jian; Sun, Xi-Lei; Shi, Feng; Wang, Zhi-Gang; An, Zheng-Hua; Sun, Li-Jun; Liu, Hong-Bang; Zhang, Ai-Wu; Wang, Xiao-Dong

2011-01-01

52

Luminosity monitoring and calibration of BLM  

International Nuclear Information System (INIS)

The BEPC Luminosity Monitor (BLM) monitors relative luminosity per bunch.The counting rates of gamma photons,which are proportional to the luminosities from the BLM at the center of mass system energy of the ?(3770) resonance, are obtained with a statistical error of 0.01% and a systematic error of 4.1%. Absolute luminosities are also determined by the BES End-cap Electro-Magnetic Calorimeter (EEMC) using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%. The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03 ( x 1026 cm-2·count-1). With the calibration constant, the counting rates of the BLM can be scaled up to absolute luminosities. (authors)

2011-01-01

53

Luminosity Spectrum Reconstruction at Linear Colliders  

CERN Document Server

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 (CLIC). 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.

Poss, Stéphane

2013-01-01

54

Differential Luminosity Measurement using Bhabha Events  

CERN Document Server

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 CLIC. The model is used in 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.

Poss, Stephane

2013-01-01

55

The luminosity function of cluster pulsars  

CERN Document Server

We study luminosities of millisecond pulsars in globular clusters by fitting the observed luminosity distribution with single and double power laws. We use simulations to model the observed distribution as the brighter part of some parent distribution for Terzan 5 and try to find a model which simultaneously agrees with the observed diffuse radio flux, total predicted number of pulsars and observed luminosity distribution. We find that wide ranges of parameters for log-normal and power-law distributions give such good models. No clear difference between the luminosity distributions of millisecond pulsars in globular clusters and normal disk pulsars was seen.

Bagchi, Manjari

2010-01-01

56

ZEUS Luminosity Photon Calorimeter Linearity Measurement  

International Nuclear Information System (INIS)

Report presents the test results of the linearity measurement of the Luminosity Photon Calorimeter readout electronics. Nonlinearity of the preamplifiers, amplifiers, 140 meters long analog signal transmission, integrators and FADC have been measured and analyzed. This allows making data correction and results in increased luminosity measurement precision for off-line processing. (author)

2007-01-01

57

The QSO variability-luminosity-redshift relation  

CERN Document Server

The relationship between variability, luminosity and redshift in the South Galactic Pole QSO sample is examined in an effort to disentangle the effects of luminosity and redshift in the amplitude of the optical variations. The anticorrelation between variability and luminosity found by other authors is confirmed. Our analysis also supports claims that variability increases with redshift, most likely due to an anticorrelation between variability and wavelength. In particular, our parametric fits show that the QSO variability-wavelength relation is consistent with that observed in low-luminosity nearby active galactic nuclei. The results are used to constrain Poissonian-type models. We find that if QSO variability results from a random superposition of pulses, then the individual events must have B-band energies between $\\sim 10^{50}$ and a few times $10^{51}$ erg and time-scales of $\\sim 2$ yr. Generalized Poissonian models in which the pulse energy and lifetime scale with luminosity are also discussed.

Fernandes, R C; Terlevich, R J

1996-01-01

58

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.

Sopczak, Andre

2014-01-01

59

z~1 Lya Emitters I. The Luminosity Function  

CERN Document Server

We construct a flux-limited sample of 135 candidate z~1 Lya emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data using a new data cube search method. These LAEs have luminosities comparable to those at high redshifts and lie within a 7 Gyr gap present in existing LAE samples. We use archival and newly obtained optical spectra to verify the UV redshifts of these LAEs. We use the combination of the GALEX UV spectra, optical spectra, and X-ray imaging data to estimate the active galactic nucleus (AGN) fraction and its dependence on Lya luminosity. We remove the AGNs and compute the luminosity function (LF) from 60 z~1 LAE galaxies. We find that the best fit LF implies a luminosity density increase by a factor of ~1.5 from z~0.3 to z~1 and ~20 from z~1 to z~2. We find a z~1 volumetric Lya escape fraction of 0.7+/-0.4%.

Wold, Isak G B; Cowie, Lennox L

2014-01-01

60

Reverberation Mapping of High-Luminosity Quasars: First Results  

CERN Multimedia

Reverberation mapping of nearby active galactic nuclei has led to estimates of broad-line-region (BLR) sizes and central-object masses for some 37 objects to date. However, successful reverberation mapping has yet to be performed for quasars of either high luminosity (above L_opt~10^{46} erg/s) or high redshift (z>0.3). Over the past six years, we have carried out, at the Hobby-Eberly Telescope, rest-frame-ultraviolet spectrophotometric monitoring of a sample of six quasars at redshifts z=2.2--3.2, with luminosities of L_opt~10^{46.4}--10^{47.6} erg/s, an order of magnitude greater than those of previously mapped quasars. The six quasars, together with an additional five having similar redshift and luminosity properties, were monitored photometrically at the Wise Observatory during the past decade. All 11 quasars monitored show significant continuum variations of order 10%--70%. This is about a factor of two smaller variability than for lower luminosity quasars monitored over the same rest-frame period. In th...

Kaspi, S; Maoz, D; Netzer, H; Schneider, D P; Shemmer, O; Kaspi, Shai; Maoz, Dan; Netzer, Hagai; Schneider, Donald P.; Shemmer, Ohad

2006-01-01

 
 
 
 
61

Optical luminosity function of quasars and low-luminosity active galactic nuclei  

Energy Technology Data Exchange (ETDEWEB)

The optical luminosity function derived from quasars with M(B) less than -23 is extended to include the nuclear luminosities of Seyfert 1 galaxies. The model is fitted to the (total) luminosity data for active galaxies from a complete flux-limited survey. A good fit is obtained with dN/dL varying inversely as L exp -1.2, matching onto the steeper quasar luminosity function near M(B) = -22. Using a luminosity evolution model derived from quasar data, this feature compares well with the results from faint quasar surveys. 26 references.

Marshall, H.L.

1987-09-01

62

Beam-beam interactions and luminosity considerations in RHIC  

International Nuclear Information System (INIS)

This paper reports on the performance of the RHIC machine which is largely determined by the intrabeam scattering process. However, beam-beam interactions due to both nuclear scattering and intrinsic Coulomb excitation of the heavy ions will result in beam loss and luminosity reductions. The transverse electric field, responsible for Coulomb excitation is multiplied by a Lorentz Gamma factor at relativistic energies. For 197Au beams in RHIC (Lab. Frame) this factor is 108. Once Coulomb excitation has occurred, the nucleus may fragment or emit a proton, and thus be lost from the beam. Estimates of the beam lifetime is presented, based on perturbative calculations for the Coulomb excitation process. In addition, di-lepton production from the enormous transverse electric field is discussed and related to the more general luminosity questions

1988-06-07

63

Galaxy correlations and the luminosity function  

Energy Technology Data Exchange (ETDEWEB)

Given the simple assumption that any excess of correlated galaxies seen close on the sky to a galaxy of known distance are also at the same distance, a galaxy luminosity function can be determined from the variation in excess number with magnitude. Averaged over many 'centre' galaxies this luminosity function has good statistical accuracy at the faint end compared to the usual direct estimation from magnitude-limited surveys since the latter necessarily contain few intrinsically faint objects. The form of the luminosity function found from recent redshift surveys is confirmed.

Phillipps, S.; Shanks, T.

1987-07-01

64

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.)

2007-01-01

65

Luminosity determination at HERA-B  

Energy Technology Data Exchange (ETDEWEB)

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. (orig.)

Abt, I. [Max-Planck-Institut fuer Physik, Muenchen (Germany); Adams, M. [Dortmund Univ. (Germany). Inst. fuer Physik; Agari, M. [Max-Planck-Institut fuer Kernphysik, Heidelberg (DE)] (and others)

2007-05-15

66

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

67

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

68

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

69

Single Bremsstrahlung luminosity measurements at DAPHINE  

Energy Technology Data Exchange (ETDEWEB)

At DAPHINE luminosity measurements are performed by detecting the photons from single Bremsstrahlung at the two interaction points. Set up and measurement method are presented with special emphasis on background subtraction schemes, error evaluation and machine related issues.

Mazzitelli, G.; Sannibale, F. E-mail: fsannibale@lbl.govfernando.sannibale@lnf.inf.it; Cervelli, F.; Lomtadze, T.; Serio, M.; Vignola, G

2002-07-01

70

Single Bremsstrahlung luminosity measurements at DAPHINE  

International Nuclear Information System (INIS)

At DAPHINE luminosity measurements are performed by detecting the photons from single Bremsstrahlung at the two interaction points. Set up and measurement method are presented with special emphasis on background subtraction schemes, error evaluation and machine related issues

2002-07-01

71

A Flexible Method of Estimating Luminosity Functions  

CERN Document Server

We describe a Bayesian approach to estimating luminosity functions. We derive the likelihood function and posterior probability distribution for the luminosity function, given the observed data, and we compare the Bayesian approach with maximum-likelihood by simulating sources from a Schechter function. For our simulations confidence intervals derived from bootstrapping the maximum-likelihood estimate can be too narrow, while confidence intervals derived from the Bayesian approach are valid. We develop our statistical approach for a flexible model where the luminosity function is modeled as a mixture of Gaussian functions. Statistical inference is performed using Markov chain Monte Carlo (MCMC) methods, and we describe a Metropolis-Hastings algorithm to perform the MCMC. The MCMC simulates random draws from the probability distribution of the luminosity function parameters, given the data, and we use a simulated data set to show how these random draws may be used to estimate the probability distribution for t...

Kelly, Brandon C; Vestergaard, Marianne

2008-01-01

72

Simulations of luminosity monitor for PANDA experiment  

International Nuclear Information System (INIS)

The Panda experiment at the future GSI facility FAIR (Facility of Antiprotons Research) is designed to address broad physics programs in hadron physics using the antiproton beam. The physics program includes, among other things, the study of charmonium spectrum and open charm states with high precision and search of exotic hybrids and glueballs in the charmonium mass region. While in some measurements, such as, the resonance scans to determine the resonance widths and mass, only a relative measurement of luminosity may be sufficient, the measurement of the time integrated luminosity at the interaction point is essential in most of the cases to determine the cross section for physical processes. A luminosity monitor based on Si-strip detectors is planned for the PANDA experiment. In the present work, initial simulation studies that have been started at NPD, BARC on the design and optimization of the Si-strip based luminosity monitor for the PANDA experiment have been reported

2011-12-01

73

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

74

Online Luminosity Optimization at the LHC  

CERN Multimedia

The online luminosity control of the LHC experiments consists of an automatic slow real-time feedback system controlled by a specific experiment software that communicates directly with an LHC application.

Follin, F; Jacobsson, R

2014-01-01

75

Luminosity increasing in the PETRA storage ring  

International Nuclear Information System (INIS)

To improve the beam luminosity of PETRA storage ring, introduced are sections with the minimal #betta#-function value of the focusing quadrupoles. The sections are intended for compressing the beam in four regions of interaction. The beam lifetime has not shortened, other parameters have remained the same, whereas the luminosity has in-- creased three times. The solution found allowed one to completely exclude the compensating coils and install new quadrupoles

1982-01-01

76

Detectors for absolute luminosity measurement at DAFNE  

Energy Technology Data Exchange (ETDEWEB)

Since the second half of year 2007, the Frascati {Phi}- factory DAFNE has been running with an upgraded interaction region in order to test the crabbed waist collision scheme. The aim is to reach a large improvement of the specific luminosity of the accelerator. We describe the various detectors realized to have a reliable and fast absolute luminosity measurement, the on-line analysis in order to get rid of the machine background contribution, and the performances of the system.

Valente, P., E-mail: paolo.valente@roma1.infn.i [INFN Roma, Rome (Italy); Boscolo, M.; Bossi, F.; Buonomo, B.; Mazzitelli, G.; Murtas, F.; Sensolini, G.; Raimondi, P. [INFN LNF, Frascati (Italy); Arnaud, N.; Breton, D.; Burmistrov, L.; Stocchi, A.; Variola, A.; Viaud, B. [LAL, Orsay (France); Branchini, P. [INFN Roma Tre, Rome (Italy); Schioppa, M. [INFN Cosenza, Rende (Italy)

2010-05-21

77

Detectors for absolute luminosity measurement at DAFNE  

International Nuclear Information System (INIS)

Since the second half of year 2007, the Frascati ?- factory DAFNE has been running with an upgraded interaction region in order to test the crabbed waist collision scheme. The aim is to reach a large improvement of the specific luminosity of the accelerator. We describe the various detectors realized to have a reliable and fast absolute luminosity measurement, the on-line analysis in order to get rid of the machine background contribution, and the performances of the system.

2010-05-11

78

Detectors for absolute luminosity measurement at DAFNE  

Science.gov (United States)

Since the second half of year 2007, the Frascati ?- factory DAFNE has been running with an upgraded interaction region in order to test the crabbed waist collision scheme. The aim is to reach a large improvement of the specific luminosity of the accelerator. We describe the various detectors realized to have a reliable and fast absolute luminosity measurement, the on-line analysis in order to get rid of the machine background contribution, and the performances of the system.

Valente, P.; Boscolo, M.; Bossi, F.; Buonomo, B.; Mazzitelli, G.; Murtas, F.; Sensolini, G.; Raimondi, P.; Arnaud, N.; Breton, D.; Burmistrov, L.; Stocchi, A.; Variola, A.; Viaud, B.; Branchini, P.; Schioppa, M.

2010-05-01

79

Luminosity Measurement at PEP-N  

CERN Document Server

The PEP-N experiment requires a fast on-line luminosity monitor of modest accuracy plus an off-line method of determining integrated luminosity with accuracy of 0.01 for each pb$^{-1}$. We propose the PEP-2 monitor, based on observing single bremsstrahlung at zero degrees to the positron direction at collision for the former and the use of Bhabha scatters at polar angles $>$.03 radians for the latter requirement.

Mandelkern, M A

2001-01-01

80

Extension of OB star winds to lower luminosities  

Energy Technology Data Exchange (ETDEWEB)

Mass loss rates derived for a number of early-to-mid B main-sequence stars have been compared with extrapolations of recently derived empirical correlations between M and stellar parameters for luminous OB stars. Although there is sufficient scatter within the sample of B star mass loss rates to obscure any correlations that may exist within this group, the order of magnitude of the rates for these stars is consistent with a simple dependence on luminosity over the range from Of to mid-B, and is not consistent with previously derived correlations involving a dependence on mass or radius. This implies that luminosity is the dominant factor in driving the mass loss through the range of spectral types from mid-B main sequence to Of. It appears that the winds in Be stars may represent a straightforward extension of the OB star wind phenomenon to lower luminosities, although the internal scatter allows the possibility that factors other than L may have some influence on M for the B main-sequence stars. There appears to be no significant difference between B and Be stars in terms of their wind characteristics.

Snow, T.P. Jr.

1982-02-01

 
 
 
 
81

Luminosity-Dependent Quasar Lifetimes: Reconciling the Optical and X-ray Quasar Luminosity Functions  

CERN Document Server

We consider implications of our new model of quasar lifetimes and light curves for the quasar luminosity function (LF) at different frequencies and redshifts. In our picture, quasars evolve rapidly and the lifetime depends on both their instantaneous and peak luminosities. The bright end of the LF traces the peak intrinsic quasar activity, but the faint end consists of quasars which are either undergoing exponential growth to much larger masses and luminosities, or are in sub-Eddington quiescent states going into or coming out of a period of peak activity. The 'break' in the observed LF corresponds directly to the maximum in the intrinsic distribution of peak luminosities, which falls off at both brighter and fainter luminosities. We study this model using simulations of galaxy mergers which successfully reproduce a wide range of observed quasar phenomena, including the observed column density distribution. By combining quasar lifetimes and the distribution of maximum quasar luminosities determined from the o...

Hopkins, P F; Cox, T J; Matteo, T D; Robertson, B; Springel, V; Hopkins, Philip F.; Hernquist, Lars; Cox, Thomas J.; Matteo, Tiziana Di; Robertson, Brant; Springel, Volker

2005-01-01

82

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

1996-08-26

83

SLC-2000: A luminosity upgrade for the SLC  

International Nuclear Information System (INIS)

We 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 magnets 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. (author)

1996-11-15

84

On the variation of galaxy correlations with luminosity  

Energy Technology Data Exchange (ETDEWEB)

A method if presented for investigating, in a direct way, the possible variation of galaxy clustering with luminosity, namely the counts of excess galaxies projected near galaxies of known distance. Large variations in either slope or amplitude of the galaxy correlation function are ruled out by the present data. In particular no evidence is found that bright galaxies have a steeper correlation function slope than faint galaxies (the expectation from many 'biased' galaxy formation theories) although the statistical uncertainty for our available sample is too large to allow a definite rejection of this possibility. The data are also consistent with there being no difference in the amplitude of the clustering of bright and faint galaxies, although in this case current uncertainty in the luminosity function would allow up to a factor approx. 2 variation.

Phillipps, S.; Shanks, T.

1987-12-15

85

Hipparcos period-luminosity relations for Miras and semiregular variables  

CERN Multimedia

We present period-luminosity diagrams for nearby Miras and semiregulars, selecting stars with parallaxes better than 20 per cent and well-determined periods. Using K-band magnitudes, we find two well-defined P-L sequences, one corresponding to the standard Mira P-L relation and the second shifted to shorter periods by a factor of about 1.9. The second sequence only contains semiregular variables, while the Mira sequence contains both Miras and semiregulars. Several semiregular stars show double periods in agreement with both relations. The Whitelock evolutionary track is shown to fit the data, indicating that the semiregulars are Mira progenitors. The transition between the two sequences may correspond to a change in pulsation mode or to a change in the stellar structure. Large amplitude pulsations leading to classical Mira classification occur mainly near the tip of the local AGB luminosity function.

Bedding, T R

1998-01-01

86

HIPPARCOS Period-Luminosity Relations for Mira and Semiregular variables  

Science.gov (United States)

We present period-luminosity (P-L) diagrams for nearby Mira and semiregular variables, selecting stars with parallaxes better than 20% and well-determined periods. Using K-band magnitudes, we find two well-defined P-L sequences, one corresponding to the standard Mira P-L relation and the second shifted to shorter periods by a factor of about 1.9. The second sequence contains only semiregular variables, while the Mira sequence contains both Mira and semiregular variables. Several semiregular stars show double periods that are in agreement with both relations. The Whitelock evolutionary track is shown to fit the data, indicating that the semiregular variables are Mira progenitors. The transition between the two sequences may correspond to a change in the pulsation mode or to a change in the stellar structure. Large-amplitude pulsations that lead to the classical Mira classification occur mainly near the tip of the local asymptotic giant branch luminosity function.

Bedding, Timothy R.; Zijlstra, Albert A.

1998-10-01

87

The line continuum luminosity ratio in AGN: Or on the Baldwin Effect  

Science.gov (United States)

The luminosity dependence of the equivalent width of CIV in active galaxies, the "Baldwin" effect, is shown to be a consequence of a luminosity dependent ionization parameter. This law also agrees with the lack of a "Baldwin" effect in Ly alpha or other hydrogen lines. A fit to the available data gives a weak indication that the mean covering factor decreases with increasing luminosity, consistent with the inference from X-ray observations. The effects of continuum shape and density on various line ratios of interest are discussed.

Mushotzky, R.; Ferland, F. J.

1983-01-01

88

Line continuum luminosity ratio in AGN: or on the Baldwin Effect  

International Nuclear Information System (INIS)

The luminosity dependence of the equivalent width of CIV in active galaxies, the Baldwin effect, is shown to be a consequence of a luminosity dependent ionization parameter. This law also agrees with the lack of a Baldwin effect in Ly alpha or other hydrogen lines. A fit to the available data gives a weak indication that the mean covering factor decreases with increasing luminosity, consistent with the inference from X-ray observations. The effects of continuum shape and density on various line ratios of interest are discussed

1983-01-01

89

The line continuum luminosity ratio in active galactic nuclei - or, on the 'Baldwin effect'  

Science.gov (United States)

The luminosity dependence of the equivalent width of CIV in active galaxies, the 'Baldwin' effect, is shown to be a consequence of a luminosity dependent ionization parameter. This law also agrees with the lack of a 'Baldwin' effect in Ly alpha or other hydrogen lines. A fit to the available data gives a weak indication that the mean covering factor decreases with increasing luminosity, consistent with the inference from X-ray observations. The effects of continuum shape and density on various line ratios of interest are discussed. Previously announced in STAR as N83-35975

Mushotzky, R.; Ferland, G. J.

1984-01-01

90

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 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.

2010-05-20

91

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 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

1982-02-01

92

Ly? luminosity functions at redshift z ? 4.5  

Science.gov (United States)

We present a spectroscopically confirmed sample of Lyman ? emitting galaxies (LAEs) at z ˜ 4.5 in the Extended Chandra Deep Field-South (ECDFS), which we combine with a sample of z ˜ 4.5 LAEs from previous narrow-band surveys from the Large Area Lyman Alpha (LALA) survey to build a unified Ly? luminosity function. We spectroscopically observed 64 candidate LAEs in the ECDFS, confirming 46 objects as z ˜ 4.5 LAEs based on single-line detections with no continuum emission bluewards of the line, resulting in a Ly? confirmation rate of ˜70 per cent. We did not detect significant flux from neither the C IV ?1549 Å emission line nor the He II ?1640 Å emission line in individual LAE spectra. These lines were also undetected in a co-added spectrum, with the co-added line ratio of He II to Ly? constraining the Population III star formation rate (SFR) to be LAE was detected in both the X-ray and radio, while the other objects remained undetected, even when stacked. The Ly? luminosity functions in our two deepest narrow-band filters in the ECDFS differ at greater than 2? significance, and the product L*?* differs by a factor of >3. Similar luminosity function differences have been used to infer evolution in the neutral gas fraction in the intergalactic medium at z > 6, yet here the difference is likely due to cosmic variance, given that the two samples are from adjoining line-of-sight volumes. Combining our new sample of LAEs with those from previous LALA narrow-band surveys at z = 4.5, we obtain one of the best measured Ly? luminosity functions to date, with our sample of over 200 spectroscopically confirmed Ly? galaxies yielding log10(L*) = 42.83 ± 0.06 (erg s-1) and log10(?*) = -3.48 ± 0.09 (Mpc-3). We compare our new luminosity function to others from the literature to study the evolution of the Ly? luminosity density at 0 < z < 7. We find tentative evidence for evolution in the product L*?*, which approximately tracks the cosmic SFR density, but since field-to-field and survey-to-survey variations are in some cases as large as the possible evolution, some caution is needed in interpreting this trend.

Zheng, Zhen-Ya; Finkelstein, Steven L.; Finkelstein, Keely; Tilvi, Vithal; Rhoads, James E.; Malhotra, Sangeeta; Wang, Jun-Xian; Miller, Neal; Hibon, Pascale; Xia, Lifang

2013-06-01

93

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

94

The Optical Luminosity Function of Virialized Systems  

Science.gov (United States)

We determine the optical luminosity function of virialized systems over the full range of density enhancements, from single galaxies to clusters of galaxies. The analysis is based on galaxy systems identified from the Nearby Optical Galaxy (NOG) sample, which is the largest all-sky catalog of objectively identified bound objects presently available. We find that the B-band luminosity function of systems is insensitive to the choice of group-finding algorithms and is well described, over the absolute magnitude range -24.5Lpl, with Lpl=8.5×1010 h-275 Lsolar, corresponding to Ms-5 log h75=-21.85. The characteristic luminosity of virialized systems, Lpl, is ~3 times that (L*gal) of the NOG galaxies. Our results show that half of the luminosity of the universe is generated in systems with Ls30L*gal. We find a significant environmental dependence in the luminosity function of systems, in the sense that overdense regions, as measured on scales of 5 h-1 Mpc, preferentially host brighter, and presumably more massive, virialized systems.

Marinoni, Christian; Hudson, Michael J.; Giuricin, Giuliano

2002-04-01

95

The stellar mass function at low luminosities  

International Nuclear Information System (INIS)

The author has combined the most recent studies of the stellar luminosity function to derive the mass function for stars in the mass range 1.0 > M/M solar mass > 0.08. The analysis shows the importance of using bolometric magnitudes in investigations of cool, late-type stars. The well established 'Wielen dip' at Msub(V) approx. = + 7 carries over into the bolometric function, which peaks at Msub(bol) approx. = + 9.5. However evidence is found for a second minimum at Msub(bol) approx. = + 12.5 and a subsequent rise to fainter luminosities. The stellar mass-luminosity relation is poorly defined at these luminosities, but the continuity of the HR diagram provides a strong argument that none of the isolated low-luminosity stars found to date are brown dwarfs. Under this interpretation, the observed mass density locally is approx. 0.09 M solar mass pc"-"3 and the missing mass remains unfound. (author)

1987-04-15

96

What Shapes the Luminosity Function of Galaxies?  

CERN Multimedia

We investigate the physical mechanisms that shape the luminosity function of galaxies in hierarchical clustering models. Beginning with the mass function of dark matter halos in the $\\Lambda$CDM cosmology, we show, in incremental steps, how gas cooling, photoionization at high redshift, feedback processes, galaxy merging and thermal conduction affect the shape of the luminosity function. We consider three processes whereby supernovae and stellar wind energy can affect the forming galaxy: (1) the reheating of cold disk gas to the halo temperature; (2) expansion of the hot, diffuse halo gas; (3) complete expulsion of cold disk gas from the halo. We demonstrate that while feedback of form (1) is able to flatten the faint end of the galaxy luminosity function, this process alone does not produce the sharp cut-off observed at large luminosities. Feedback of form (2) is also unable to solve the problem at the bright end of the luminosity function. The relative paucity of very bright galaxies can only be explained i...

Benson, A J; Frenk, C S; Lacey, C G; Baugh, C M; Cole, S

2003-01-01

97

Spatial and luminosity distributions of galactic satellites  

Science.gov (United States)

We investigate the luminosity functions and projected number density profiles of galactic satellites around isolated primaries of different luminosity. 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 data of Guo et al. from the Sloan Digital Sky Survey Data Release 8 (SDSS DR8). First, we use a mock light-cone catalogue to verify that the method we used to count satellites in the SDSS DR8 is unbiased. We find that the radial distributions of model satellites can be fitted by a Navarro-Frenk-White profile similar to those around comparable primary galaxies in the SDSS DR8, with only slight differences at low luminosities and small projected radii. However, when splitting the satellites by colour, the model and SDSS satellite systems no longer resemble one another, with many red model satellites in contrast to the dominant blue fraction at similar luminosity in the SDSS. The few model blue satellites are also significantly less centrally concentrated in the halo of their stacked primary than their SDSS counterparts. We discuss how these discrepancies may reflect inadequacies in the treatment of the processes that determine the star formation histories of small galaxies in the model.

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

2013-09-01

98

EU supports the LHC high-luminosity study  

CERN Multimedia

The design collision energy and luminosity of the LHC are already at record numbers, making the machine one of the most complex scientific instruments ever built. However, to extend its discovery potential even further, a major upgrade of the LHC will be required around 2020. This will increase its average luminosity by a factor of 5 to 10 beyond its design value. Fifteen worldwide institutions and the European Union are supporting the initial design phase of the project through the HiLumi LHC programme, whose kick-off meeting will take place on 16-18 November.   The CERN team that has successfully built and tested the Short Magnet Coil – a small 40 cm long magnet capable of producing a 12.5 T magnetic field. The upgrade of the LHC will require about 10 years of design, construction and implementation. The new machine configuration will be called “High Luminosity LHC” (HL-LHC). The similarly named “HiLumi LHC” is the EU programme that supports...

CERN Bulletin

2011-01-01

99

Using Spectral Flux Ratios to Standardize SN Ia Luminosities  

CERN Document Server

We present a new method to standardize Type Ia supernova (SN Ia) luminosities to ~<0.13 magnitudes using flux ratios from a single flux-calibrated spectrum per SN. Using Nearby Supernova Factory spectrophotomery of 58 SNe Ia, we performed an unbiased search for flux ratios which correlate with SN Ia luminosity. After developing the method and selecting the best ratios from a training sample, we verified the results on a separate validation sample and with data from the literature. We identified multiple flux ratios whose correlations with luminosity are stronger than those of light curve shape and color, previously identified spectral feature ratios, or equivalent width measurements. In particular, the flux ratio R(642/443) = F(642 nm) / F(443 nm) has a correlation of 0.95 with SN Ia absolute magnitudes. Using this single ratio as a correction factor produces a Hubble diagram with a residual scatter standard deviation of 0.125 +- 0.011 mag, compared with 0.161 +- 0.015 mag when fit with the SALT2 light cur...

Bailey, S; Antilogus, P; Aragon, C; Baltay, C; Bongard, S; Buton, C; Childress, M; Chotard, N; Copin, Y; Gangler, E; Loken, S; Nugent, P; Pain, R; Pécontal, E; Pereira, R; Perlmutter, S; Rabinowitz, D; Rigaudier, G; Runge, K; Scalzo, R; Smadja, G; Swift, H; Tao, C; Thomas, R C; Wu, C

2009-01-01

100

The DA?NE luminosity monitor  

International Nuclear Information System (INIS)

DA?NE, the Frascati ?-factory, is an e+/e- collider with 2 interaction points (IPs). The center of mass energy is 1020 MeV and the design luminosity 4.2x1030 cm-2 s-1 in single bunch mode and 5x1032 cm-2 s-1 in multibunch mode. Between the possible electromagnetic reactions at the interaction point, single bremsstrahlung (SB) has been selected for the luminosity measurement. The SB high counting rate allows real-time monitoring, which is very useful during machine tune-up and moreover the narrow peak of the SB angular distribution makes the counting rate almost independent from the beam position at the IP. A description of the experimental set-up, calibration results and luminosity measurements is presented

1998-12-10

 
 
 
 
101

Energy and luminosity limits of hadron supercolliders  

International Nuclear Information System (INIS)

Extending the frontiers of experimental high energy physics in a manner that maximizes discovery potential requires the building accelerators of ever higher particle energies and luminosities. Both hadron and e+e- colliders have been proposed for this role. Based on a self-consistent computational model, this paper explores the features of hadron supercolliders beyond the SSC. The application of the presently available accelerator technologies embodied in the designs of the LHC and SSC to an ELOISATRON operating at 100 TeV per beam would yield a collider with a luminosity of 1034 cm-2 s-1. Even higher energies and luminosities are clearly possible. The paper concludes with an examination of the ultimate potential of synchrontron-based colliders to explore PeV energies

1993-05-17

102

Title: Measuring Luminosity Dependent Quasar Clustering  

Science.gov (United States)

Whether luminous quasars reside in dark matter halos of the same mass and accrete at different rates, or, live in haloes of different masses, and accretion is near the Eddington limit, is still an open question. Here, we present measurements of the luminosity-dependence of quasar clustering, using data from the SDSS, 2SLAQ QSO and the new SDSS-III: BOSS Quasar surveys, allowing us to span 4 magnitudes in luminosity, at a given redshift. Using a cross-correlation technique, we measure the clustering of 3100 0.5luminosity, black-hole mass and Eddington ratio of the quasar sample.

Kirkpatrick, Jessica

2012-01-01

103

Intrinsic ?-ray luminosity, black hole mass, jet and accretion in Fermi blazars  

Science.gov (United States)

We have analysed a large sample of clean blazars detected by Fermi Large Area Telescope (LAT). Using the literature and calculation, we obtained intrinsic ?-ray luminosity excluding beaming effect, black hole mass, broad-line luminosity (used as a proxy for disc luminosity), jet kinetic power from `cavity' power and bulk Lorentz factor for parsec-scale radio emission, and studied the distributions of these parameters and relations between them. Our main results are as follows. (i) After excluding beaming effect and redshift effect, intrinsic ?-ray luminosity with broad-line luminosity, black hole mass and Eddington ratio have significant correlations. Our results confirm the physical distinction between BL Lacs and FSRQs. (ii) The correlation between broad-line luminosity and jet power is significant which supports that jet power has a close link with accretion. Jet power depends on both the Eddington ratio and black hole mass. We also obtain logLBLR ˜ (0.98 ± 0.07)logPjet for all blazars, which is consistent with the theoretical predicted coefficient. These results support that jets are powered by energy extraction from both accretion and black hole spin (i.e. not by accretion only). (iii) For almost all BL Lacs, Pjet > Ldisc; for most of FSRQs, Pjet < Ldisc. The `jet-dominance' (parametrized as P_jet/L_disc) is mainly controlled by the bolometric luminosity. Finally, the radiative efficiency of ?-ray and properties of TeV blazars detected by Fermi LAT were discussed.

Xiong, D. R.; Zhang, X.

2014-07-01

104

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 < 2.5 are discussed and the apparent magnitude distribution for quasars in that range is compared to that of UVX-selected quasars. A separate sample of blue continuum objects is defined by examining the spectral continuum for confirmed quasars. The surface density of the blue objects compared to that of high redshift quasars in the same survey indicates the high redshift quasars comprise about 20% of the blue continuum objects. The completion limits of the new surveys are examined in detail to establish the best sample for the study of the luminosity function. The luminosity function of high redshift quasars is determined assuming cosmological redshifts, #betta# = 0, and H/sub o/ = 75 km s"-_1 Mpc"-_1 for each of two cosmologies (q"0 = 1 and q"0 = 0). For either cosmology, the function exhibits a steep increase with magnitude at high luminosities and a gentler increase at intermediate luminosities. Data from the new surveys indicate a possible turnover at the faint end of the distribution. Total volume densities of quasars are computed for each of three extrapolations of the trend of the data to low luminosities. These densities are compared to those of active galaxies and field galaxies

1982-01-01

105

The Local Luminosity Function at 25 Microns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The local luminosity function at 25 $\\mu$m provides the basis for interpreting the results of deep mid-infrared surveys planned or in progress with space astrophysics missions including ISO, WIRE and SIRTF. We have selected a sample of 1458 galaxies from the IRAS Faint Source Survey with a flux density limit of 250 mJy at 25 $\\mu$m. The local luminosity function is derived using both parametric and non-parametric maximum-likelihood techniques, and the classical $1/V_{max}$ e...

Shupe, David L.; Fang, Fan; Hacking, Perry B.; Huchra, John P.

1998-01-01

106

Offline Software for the PANDA Luminosity Detector  

Science.gov (United States)

In 2018 data taking for hadronphysics facility PANDA is planned to commence. It will be build at the antiproton accelerator HESR, which itself is a part of the FAIR complex (GSI, Darmstadt, Germany). The luminosity at PANDA will be measured by a dedicated sub-detector, which will register scattered antiproton tracks from pp elastic scattering. From a software point of view, the Luminosity Detector is a tracking system. Therefore the most of its offline software parts are typical for a track reconstruction. The basic concept and Monte Carlo based performance studies of each reconstruction step is presented in this paper.

Karavdina, A.; Denig, A.; Feldbauer, F.; Jasinski, P.; Leithoff, H.; Michel, M.; Motzko, C.; Pflüger, S.; Weber, T.; Fritsch, M.

2014-06-01

107

High precision scrapers for ISR luminosity measurements  

International Nuclear Information System (INIS)

Two intersections of the CERN ISR were recently equipped with beam scrapers. Controlled by computer, they permit the vertical profile of the circulating current intensity to be plotted automatically, so that the position of the center of a beam can then be determined to within 10 microns. This was used to calibrate the beam displacements used in the standard ''Van der Meer'' type luminosity measurements. The particle density profiles allow a direct evaluation of the luminosity. A description of the mechanism and the computer control system are given, and some results are discussed. (auth)

1975-06-01

108

High precision scrapers for ISR luminosity measurements  

CERN Document Server

Two intersections of the CERN ISR have recently been equipped with beam scrapers. Controlled by computer, they permit the vertical profile of the circulating current intensity to be plotted automatically, so that the position of the centre of a beam can then be determined to within 10 microns. This has been used to calibrate the beam displacements used in the standard 'Van der Meer' type luminosity measurements while the particle density profiles allow a direct evaluation of the luminosity. A description of the mechanism and the computer control system is given and some results are discussed. (9 refs).

Potter, K M

1975-01-01

109

Beam-beam effects and generalized luminosity  

International Nuclear Information System (INIS)

The assumption is made that before an NLC is approved, a prototype will be necessary that demonstrates the feasibility of a general purpose linear collider capable of rvec e± rvec e±, rvec ? rvec e and rvec ? rvec ? incident channels. At an upgraded SLC, such channels could provide new physics over a range of energies upwards of a few GeV. Effects that limit the luminosity of a GLC are discussed together with their possible mitigations. The expected luminosities in the different channels are then predicted in a consistent way for ?see = 0.5 TeV

1995-08-03

110

New luminosity component in 3C 48  

Energy Technology Data Exchange (ETDEWEB)

The infrared emission from the quasar 3C48 has a luminosity L approximately 5 x 10 to the 12th power solar luminosity and dominates the power output of the quasar system. It is shown that the infrared emission, unlike that of most radio loud quasars, is most likely not an extension of the radio emission of the quasar. It is argued that the infrared emission in 3C48 is probably thermal radiation arising in a highly luminous galaxy surrounding the quasar. 20 references.

Neugebauer, G.; Soifer, B.T.; Miley, G.K.

1985-08-01

111

The SDSS-III Baryon Oscillation Spectroscopic Survey: The Quasar Luminosity Function from Data Release Nine  

Science.gov (United States)

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 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. 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.; McGreer, Ian D.; White, Martin; Richards, Gordon T.; Myers, Adam D.; Palanque-Delabrouille, Nathalie; Strauss, Michael A.; Anderson, Scott F.; Shen, Yue; Brandt, W. N.; Yèche, Christophe; Swanson, Molly E. C.; Aubourg, Éric; Bailey, Stephen; Bizyaev, Dmitry; Bovy, Jo; Brewington, Howard; Brinkmann, J.; DeGraf, Colin; Di Matteo, Tiziana; Ebelke, Garrett; Fan, Xiaohui; Ge, Jian; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum, Rachel; Maraston, Claudia; Muna, Demitri; Oravetz, Daniel; Pan, Kaike; Pâris, Isabelle; Petitjean, Patrick; Schawinski, Kevin; Schlegel, David J.; Schneider, Donald P.; Silverman, John D.; Simmons, Audrey; Snedden, Stephanie; Streblyanska, Alina; Suzuki, Nao; Weinberg, David H.; York, Donald

2013-08-01

112

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. 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

2013-08-10

113

Academic Training - LHC luminosity upgrade: detector challenges  

CERN Multimedia

ACADEMIC TRAINING LECTURE SERIES 13, 14, 15, March, from 11:00 to 12:00 - 16 March from 10:00 to 12:00 Main Auditorium, bldg. 500 on 14, 15 March, Council Room on 13, 16 March LHC luminosity upgrade: detector challenges A. De Roeck / CERN-PH, D. Bortoletto / Purdue Univ. USA, R. Wigmans / Texas, Tech Univ. USA, W. Riegler / CERN-PH, W. Smith / Wisconsin Univ. USA The upgrade of the LHC machine towards higher luminosity (1035 cm-2s-1) has been studied over the last few years. These studies have investigated scenarios to achieve the increase in peak luminosity by an order of magnitude, as well as the physics potential of such an upgrade and the impact of a machine upgrade on the LHC DETECTORS. This series of lectures will cover the following topics: Physics motivation and machine scenarios for an order of magnitude increase in the LHC peak luminosity (lecture 1) Detector challenges including overview of ideas for R&D programs by the LHC experiments: tracking and calorimetry, other new detector ...

Françoise Benz

2006-01-01

114

Spatial and luminosity distributions of galactic satellites  

CERN Document Server

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 data of Guo et al. from the Sloan Digital Sky Survey Data Release 8 (SDSS DR8). First, we use a mock light-cone catalogue to verify that the method we used to count satellites in the SDSS DR8 is unbiased. We find that the radial distributions of model satellites are similar to those around comparable primary galaxies in the SDSS DR8, with only slight differences at low luminosities and small projected radii. However, when splitting the satellites by colour, the model and SDSS satellite systems no longer resemble one another, with many red m...

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

2013-01-01

115

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

116

Absolute luminosity determination for the ATLAS experiment  

CERN Document Server

ATLAS is one of the four big experiments at the Large Hadron Collider (LHC). In order to accurately measure cross sections, the precise knowledge of the integrated luminosity is a prerequisite. The relative luminosity is measured with various detectors and algorithms. The purpose of the algorithms is to convert raw rates measured by a detector into a quantity which is proportional to the luminosity. In this work, three algorithms linked to the two main ATLAS luminosity detectors are absolutely calibrated: BCMH_EventOR, BCMV_EventOR, and LUCID_EventOR. The determination of the calibration constants is based on Van der Meer (VdM) scans, which were carried out in July and November 2012. The statistical errors of this method are negligible and the precision is limited by systematic uncertainties. The different uncertainty sources are quantitatively estimated. The overall uncertainty on the calibration constants is estimated to be 5.40% for the July VdM scans and 2.50% for the November VdM scans. The November cali...

Anders, Gabriel; Pauly, Thilo

117

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

118

Calibration of GRB Luminosity Relations with Cosmography  

CERN Multimedia

For the use of Gamma-Ray Bursts (GRBs) to probe cosmology in a cosmology-independent way, a new method has been proposed to obtain luminosity distances of GRBs by interpolating directly from the Hubble diagram of SNe Ia, and then calibrating GRB relations at high redshift. In this paper, following the basic assumption in the interpolation method that objects at the same redshift should have the same luminosity distance, we propose another approach to calibrate GRB luminosity relations with cosmographic fitting directly from SN Ia data. In cosmography, there is a well-known fitting formula which can reflect the Hubble relation between luminosity distance and redshift with cosmographic parameters which can be fitted from observation data. Using the Cosmographic fitting results from the Union set of SNe Ia, we calibrate five GRB relations using GRB sample at $z\\leq1.4$ and deduce distance moduli of GRBs at $1.4< z \\leq 6.6$ by generalizing above calibrated relations at high redshift. Finally, we constrain the...

Gao, He; Zhu, Zong-Hong

2010-01-01

119

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 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

120

Luminosity-Dependent Quasar Lifetimes: A New Interpretation of the Quasar Luminosity Function  

CERN Document Server

We propose a new interpretation of the quasar luminosity function (LF), derived from physically motivated models of quasar lifetimes and light curves. In our picture, quasars evolve rapidly and their lifetime depends on both their instantaneous and peak luminosities. We study this model using simulations of galaxy mergers that successfully reproduce a wide range of observed quasar phenomena. With lifetimes inferred from the simulations, we deconvolve the observed quasar LF from the distribution of peak luminosities, and show that they differ qualitatively, unlike for the simple models of quasar lifetimes used previously. We find that the bright end of the LF traces the intrinsic peak quasar activity, but that the faint end consists of quasars which are either undergoing exponential growth to much larger masses and higher luminosities, or are in sub-Eddington quiescent states going into or coming out of a period of peak activity. The 'break' in the LF corresponds directly to the maximum in the intrinsic distri...

Hopkins, P F; Cox, T J; Matteo, T D; Robertson, B; Springel, V; Hopkins, Philip F.; Hernquist, Lars; Cox, Thomas J.; Matteo, Tiziana Di; Robertson, Brant; Springel, Volker

2005-01-01

 
 
 
 
121

Intrinsic $\\gamma$-ray luminosity, black hole mass, jet and accretion in Fermi blazars  

CERN Document Server

We have analyzed a large sample of clean blazars detected by Fermi Large Area Telescope (LAT). Using literature and calculation, we obtained intrinsic $\\gamma$-ray luminosity excluding beaming effect, black hole mass, broad-line luminosity (used as a proxy for disk luminosity), jet kinetic power from "cavity" power and bulk Lorentz factor for parsec-scale radio emission, and studied the distributions of these parameters and relations between them. Our main results are as follows. (i) After excluding beaming effect and redshift effect, intrinsic $\\gamma$-ray luminosity with broad line luminosity, black hole mass and Eddington ratio have significant correlations. Our results confirm the physical distinction between BL Lacs and FSRQs. (ii) The correlation between broad line luminosity and jet power is significant which supports that jet power has a close link with accretion. Jet power depends on both the Eddington ratio and black hole mass. We also obtain $LogL_{\\rm BLR}\\sim(0.98\\pm0.07)Log P_{\\rm jet}$ for all ...

Xiong, Dingrong

2014-01-01

122

The cross-correlation between galaxies of different luminosities and Colors  

CERN Document Server

We study the cross-correlation between galaxies of different luminosities and colors, using a sample selected from the SDSS Dr 4. Galaxies are divided into 6 samples according to luminosity, and each of these samples is divided into red and blue subsamples. Projected auto-correlation and cross-correlation is estimated for these subsample. At projected separations r_p > 1\\mpch, all correlation functions are roughly parallel, although the correlation amplitude depends systematically on luminosity and color. On r_p 1\\mpch for each subsample using its auto-correlation function and cross-correlation functions. The relative bias factors obtained from different methods are similar. For blue galaxies the luminosity-dependence of the relative bias is strong over the luminosity range probed (-23.0luminosities below L^*. To examine whether a significant stochastic/nonlinear component exists in the bias relation, we study the...

Wang, Y; Mo, H J; Van den Bosch, F C; Wang, Yu; Yang, Xiaohu; Bosch, Frank C. van den

2007-01-01

123

Galaxy luminosity function and environmental dependencies  

International Nuclear Information System (INIS)

The observational data base for the Nearby Galaxies Atlas (Tully and Fisher, 1987) and Nearby Galaxies Catalog (Tully, 1988) is analyzed statistically, with a focus on three problems related to the galactic luminosity function (GLF). Sample data are presented in tables and graphs; the GLF is formulated as M(asterisk) = -20.18 + 1.25(1 + alpha) + 5log h(75); and alpha = -1.0 is recommended. An expression for the degree of incompleteness in the catalog is then derived as a function of galaxy distance, and the correlation between galactic morphology and the local density function is explored. It is shown that gas-poor, early-type, and gas-rich galaxies tend to appear in regions of high, intermediate, and low density, respectively. Within the gas-rich subset, however, morphology and luminosity are found to be poorly correlated with density. 20 references

1988-01-01

124

Wet drift chambers for precise luminosity  

Energy Technology Data Exchange (ETDEWEB)

A set of high-precision compact drift chambers has been a vital component of the OPAL luminosity monitor since the start of data-taking at LEP. They were augmented in 1992 by the addition of Small Angle Reference Chambers with a very similar design to the original chamber. The performance of the chambers is reviewed, highlighting both the importance of using polyalkylene glycol (Breox) to maintain a uniform and parallel electric field and the construction techniques used to sustain the required field strength. We describe some of the operating problems, with their solutions, and show how the chambers have been used in achieving a systematic error of 0.41% on the luminosity measurement. ((orig.))

Anderson, B.E. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Kennedy, B.W. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Ahmet, K. (Department of Physics, Birkbeck College, Malet Street, London WC1E 7VV (United Kingdom)); Attree, D.J. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Barraclough, G.A. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Cresswell, M.J. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Hayes, D.A. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)); Miller, D.J. (Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kin

1994-09-01

125

Molecular gas in intermediate luminosity IRAS galaxies  

Science.gov (United States)

Single dish CO (J = 1-0) measurements are reported for 29 galaxies of intermediate IR lumionosity in the IRAS Bright Galaxy sample, at distances in the range 20-40 Mpc. Most of the galaxies were mapped at 3-7 points with a 55 arcsec beam. The total H2 masses, assuming a standard Galactic CO-to-H2 conversion ratio, lie in the range of 500 million to 20 billion solar masses. The mean ratio of L(FIR)/M(H2) for this intermediate luminosity sample is approximately three times that found for Virgo spirals and approximately one-third of that found for a sample of higher-luminosity IRAS Bright Galaxies.

Tinney, C. G.; Scoville, N. Z.; Sanders, D. B.; Soifer, B. T.

1990-01-01

126

Molecular gas in intermediate luminosity IRAS galaxies  

Energy Technology Data Exchange (ETDEWEB)

Single dish CO (J = 1-0) measurements are reported for 29 galaxies of intermediate IR lumionosity in the IRAS Bright Galaxy sample, at distances in the range 20-40 Mpc. Most of the galaxies were mapped at 3-7 points with a 55 arcsec beam. The total H2 masses, assuming a standard Galactic CO-to-H2 conversion ratio, lie in the range of 500 million to 20 billion solar masses. The mean ratio of L(FIR)/M(H2) for this intermediate luminosity sample is approximately three times that found for Virgo spirals and approximately one-third of that found for a sample of higher-luminosity IRAS Bright Galaxies. 26 refs.

Tinney, C.G.; Scoville, N.Z.; Sanders, D.B.; Soifer, B.T. (California Institute of Technology, Pasadena (USA))

1990-10-01

127

LHC operation at higher energy and luminosity  

CERN Multimedia

The Large Hadron Collider (LHC) at CERN (Geneva) was commissioned and operated in the years 2009-2013 up to a beam energy of 4 TeV. A peak luminosity of 0.77 · 1034 cm?2s?1 was reached and an integrated luminosity of around 29 fb?1 was delivered to both ATLAS and CMS. This performance allowed the discovery of a scalar boson. The LHC is presently in a shutdown phase dedicated to consolidation and maintenance that will allow the restart of beam operation in early 2015 at an increased beam energy of 6.5 to 7TeV. Maximum acceptable pileup, effectiveness of electron-cloud scrubbing, and fast loss events are some of the issues that will shape the choice of operational parameters, cycle setup, and the commissioning strategy. The baseline choices and options for the restart after the shutdown are presented. In addition the roadmap for future performance upgrades is sketched.

Papotti, G

2013-01-01

128

Shedding Light on the Galaxy Luminosity Function  

CERN Document Server

From as early as the 1930s, astronomers have tried to quantify the statistical nature of the evolution and large-scale structure of galaxies by studying their luminosity distribution as a function of redshift - known as the galaxy luminosity function (LF). Accurately constructing the LF remains a popular and yet tricky pursuit in modern observational cosmology where the presence of observational selection effects due to e.g. detection thresholds in apparent magnitude, colour, surface brightness or some combination thereof can render any given galaxy survey incomplete and thus introduce bias into the LF. Over the last seventy years there have been numerous sophisticated statistical approaches devised to tackle these issues; all have advantages -- but not one is perfect. This review takes a broad historical look at the key statistical tools that have been developed over this period, discussing their relative merits and highlighting any significant extensions and modifications. In addition, the more generalised ...

Johnston, Russell

2011-01-01

129

Evolution of QSO and QSG luminosities  

International Nuclear Information System (INIS)

The dependences of the magnitude m0 of the statistically brightest QSOs and QSGs on their lg z (z is a red shift) are constructed. The slope of the diagram for QSOs is 2.2. The GSGs' magnitude drops quickly to approximately 17sup(m) at z approximately equal to 0.3 and remains nearly onstant at larger z. The differences in m0 (lg z) for QSOs and QSGs reach approximately 1.sup(m)5 at z approximately equal to 0.3, and, as is shown, cannot be accounted for by the detection selection. The dependence m0 (lg z) is explained by the decrease at z > 0.3 of the QSOs' luminosities by 0sup(m).46 and of the QSCs' luminosities by 0sup(m).70 at a time jnterval of 109 years

1983-01-01

130

Evolution of QSG and QSG luminosities  

International Nuclear Information System (INIS)

The dependences of the magnitude m0 of the statistically brightest QSOs and QSGs on their lg z (z is a red shift) are constructed. The slope of the diagram for QSOs is 2.2. The GSGs' magnitude drops quickly to approximately 17sup(m) at z approximately equal to 0.3 and remains nearly onstant at larger z. The differences in m0 (lg z) for QSOs and QSGs reach approximately 1.sup(m)5 at z approximately equal to 0.3, and, as is shown, cannot be accounted for by the detection selection. The dependence m0 (lg z) is explained by the decrease at z > 0.3 of the QSOs' luminosities by 0sup(m).46 and of the QSCs luminosities by 0sup(m).70 at a time jnterval of 109 years

1983-01-01

131

Alternative high luminosity LHC matching section layout  

CERN Document Server

In the framework of the HL-LHC Upgrade project possible variants for the layout of the LHC matching section located in the high luminosity insertions are investigated. This layout is optimized to reduce the demand on the voltage of the crab cavities, it also improves the optics squeeze-ability, both in ATS [1] and non-ATS mode. Moreover the injection and transitions to collision optics are also discussed.

Dalena, B; Chancé, A; De Maria, R

2014-01-01

132

The Luminosity Profiles of Brightest Cluster Galaxies  

CERN Multimedia

(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

133

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

134

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

135

Luminosity Lifetime at the LHC in 2012 Proton Physics  

CERN Document Server

In 2012, the LHC was operated at 4 TeV at top energy with beam parameters that allowed exceeding a peak instantaneous luminosity of 7500 µb^-1 s^-1 and a total of 23 fb^-1 integrated luminosity in the ATLAS and CMS experiments. This paper elaborates on the evolution of the LHC luminosity and luminosity lifetime during proton physics fills and through the year 2012. Bunch to bunch differences and the impact of different machine settings are highlighted.

Hostettler, M

2013-01-01

136

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

137

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

138

Relation between the X-ray and Optical Luminosities in Binary Systems with Accreting Nonmagnetic White Dwarfs  

CERN Document Server

We investigate the relation between the optical (g-band) and X-ray (0.5-10 keV) luminosities of accreting nonmagnetic white dwarfs. According to the present-day counts of the populations of star systems in our Galaxy, these systems have the highest space density among the close binary systems with white dwarfs. We show that the dependence of the optical luminosity of accreting white dwarfs on their X-ray luminosity forms a fairly narrow one-parameter curve. The typical half-width of this curve does not exceed 0.2-0.3 dex in optical and X-ray luminosities, which is essentially consistent with the amplitude of the aperiodic flux variability for these objects. At X-ray luminosities Lx~1e32 erg/sec or lower, the optical g-band luminosity of the accretion flow is shown to be related to its X-ray luminosity by a factor ~2-3. At even lower X-ray luminosities (Lx~1e30 erg/sec), the contribution from the photosphere of the white dwarf begins to dominate in the optical spectrum of the binary system and its optical brig...

Revnivtsev, M G; Suleimanov, V F

2014-01-01

139

Variations of Core Luminosity and Solar Neutrino Fluxes  

CERN Document Server

In a Dynamic Solar Model (DSM) the temperature dependences of the pp cycle neutrinos will be different from the ones determined by solar model calculations with the luminosity constraint. Instead of the usual neutrino fluxes pp ~ T^{-1/2}, Be ~ T^8, B ~ T^{18}, we determined by the nuclear reaction rates formulas pp ~ T^{4.2}, Be ~ T^{-1/2}, B ~ T^{13.5}, for $\\tau < 10^2$ years. These latter relations have high significance at estimating the uncertainties of the solar central temperatures without assuming the luminosity constraint. Although the purely astrophysical solutions seem to be ruled out, this is not the case for a model in which astrophysical effects are included besides the neutrino oscillations. Therefore a combined, DSM+MSW model is suggested to calculate the observed solar neutrino fluxes. The combined SSM+MSW fits to the rates+spectra+D/N changes give a bad fit to the total rates, indicating the need to include the astrophysical factors besides the MSW effect. The DSM suggest that the core d...

Grandpierre, A

2002-01-01

140

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 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.

2011-08-01

 
 
 
 
141

Deriving Kinetic Luminosity Functions from the Low-Frequency Radio Luminosity Functions of FRII Sources  

Science.gov (United States)

FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions (RLF) and fit them to the observed low-frequency radio data that cover redshifts up to z 2, which gives us the most plausible distributions of FRIIs' fundamental properties. Moreover, based on these RLFs, we obtain the kinetic luminosity functions of these powerful sources.

Kapinska, Anna D.; Uttley, P.; Kaiser, C. R.

2010-02-01

142

New luminosity component in 3c 48  

Energy Technology Data Exchange (ETDEWEB)

The infrared emission from the quasar 3C 48 has a luminosity Lroughly-equal5 x 10/sup 12/L/sub sun/ and dominates the power output of the quasar system. It is shown that the infrared emission, unlike that of most radio-loud quasars, is most likely not an extension of the radio emission of the quasar. It is argued that the infrared emission in 3C 48 is probably thermal radiation arising in a highly luminous galaxy surrounding the quasar.

Neugebauer, G.; Soifer, B.T.; Miley, G.K.

1985-08-15

143

Temperature, luminosity, and spectrum of kapteyn's star  

International Nuclear Information System (INIS)

The spectrum of Kapteyn's star has been observed in the blue and red regions with an objective prism. There is no obvious weakening of the atomic lines, but the TiO bands are weak for the atomic-line strength, while the bands of MgH and CaH are greatly enhanced relative to their strength in normal early M dwarfs. Although the metal abundance of Kapteyn's star cannot be determined from the present data, its TiO and CaH band strengths are found to be fairly reliable indicators of its temperature and luminosity, respectively

1976-04-01

144

Luminosity Profiles of Resolved Young Massive Clusters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Young massive clusters (YMCs) differ markedly from old globular clusters in featuring extended, rather than tidally truncated, envelopes. Their projected- luminosity profiles are well fit by Elson-Fall-Freeman (EFF) models with core radii of 0.3 pc < r_c < 8 pc and power-law envelopes of negative exponent 2 < gamma < 3.8. These envelopes form within the first few 10^6 yr and last ~10^8 to 10^9.5 yr, depending on the environment. Many young massive clusters show clumpy substr...

Schweizer, Francois

2004-01-01

145

CORRELATION BETWEEN GROUP LOCAL DENSITY AND GROUP LUMINOSITY  

International Nuclear Information System (INIS)

In this study, we investigate the correlation between group local number density and total luminosity of groups. In four volume-limited group catalogs, we can conclude that groups with high luminosity exist preferentially in high-density regions, while groups with low luminosity are located preferentially in low-density regions, and that in a volume-limited group sample with absolute magnitude limit Mr = –18, the correlation between group local number density and total luminosity of groups is the weakest. These results basically are consistent with the environmental dependence of galaxy luminosity.

2012-11-10

146

Elastic scattering, total cross section and luminosity measurements at ATLAS  

CERN Document Server

The ATLAS strategy to monitor and measure the absolute LHC luminosity will be reviewed. The absolute luminosity will be extracted from the measurement of the t-distribution of the elastic pp scattering in the CNI region, as performed during dedicated runs with specific beam optics. A luminosity monitor to be precisely calibrated during the elastic scattering parametrization will also be working in high-luminosity running conditions, where it will provide online luminosity values for both beam monitoring and data analysis. The detector designs, installation plans and expected performances will also be reported.

Sbarra, C

2007-01-01

147

The Mid-Infrared Color-Luminosity Relation and the Local 12 micron Luminosity Function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have established a model to systematically estimate the contribution of the mid-infrared emission features between 3 and 11.6 micron to the IRAS in-band fluxes, using the results of ISO PHT-S observation of 16 galaxies by Lu et al. (1997). The model is used to estimate more properly the k-corrections for calculating the restframe 12 and 25 micron fluxes and luminosities of IRAS galaxies. We have studied the 12-25 micron color-luminosity relation for a sample of galaxies s...

Fang, Fan; Shupe, David L.; Xu, Cong; Hacking, Perry B.

1998-01-01

148

Remarks on the differential luminosity in the weak disruption and the transition region  

International Nuclear Information System (INIS)

The time dependence of the different enhancement factors of the luminosity, in the region of weak disruption, has been discussed here, for the first time, and the corresponding time integral has been explicitly discussed upon. For the case of stronger disruption (transition region), the existing numerical results from various research works, has been checked analytically with the help of a square distribution

1993-05-17

149

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.)

1983-02-10

150

Selected issues for the LHC luminosity upgrade  

International Nuclear Information System (INIS)

The Large Hadron Collider started its operations on September 10. 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 object of study is the Interaction Region, that consists in the set of magnets in charge to provide the final 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 the general considerations and numerical methods for the parameters optimization. (author)

2008-01-01

151

Jet Cleansing: Pileup Removal at High Luminosity  

CERN Document Server

One of the greatest impediments to extracting useful information from high luminosity hadron-collider data is radiation from secondary collisions (i.e. pileup) which can overlap with that of the primary interaction. In this paper we introduce a simple jet-substructure technique termed cleansing which can consistently correct for large amounts of pileup in an observable independent way. Cleansing works at the subjet level, combining tracker and calorimeter-based data to reconstruct the pileup-free primary interaction. The technique can be used on its own, with various degrees of sophistication, or in concert with jet grooming. We apply cleansing to both kinematic and jet shape reconstruction, finding in all cases a marked improvement over previous methods both in the correlation of the cleansed data with uncontaminated results and in measures like S/rt(B). Cleansing should improve the sensitivity of new-physics searches at high luminosity and could also aid in the comparison of precision QCD calculations to co...

Krohn, David; Schwartz, Matthew D; Wang, Lian-Tao

2013-01-01

152

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

153

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

154

Globular cluster luminosity function as distance indicator  

CERN Document Server

Globular clusters are among the first objects used to establish the distance scale of the Universe. In the 1970-ies it has been recognized that the differential magnitude distribution of old globular clusters is very similar in different galaxies presenting a peak at M_V ~ -7.5. This peak magnitude of the so-called Globular Cluster Luminosity Function has been then established as a secondary distance indicator. The intrinsic accuracy of the method has been estimated to be of the order of ~0.2 mag, competitive with other distance determination methods. Lately the study of the Globular Cluster Systems has been used more as a tool for galaxy formation and evolution, and less so for distance determinations. Nevertheless, the collection of homogeneous and large datasets with the ACS on board HST presented new insights on the usefulness of the Globular Cluster Luminosity Function as distance indicator. I discuss here recent results based on observational and theoretical studies, which show that this distance indica...

Rejkuba, M

2012-01-01

155

Prospects for indirect luminosity measurements at LHCb  

CERN Document Server

We summarise the prospects for indirect luminosity measurements at LHCb. Two candidate processes have been identified for such measurements: electroweak boson production and elastic dimuon production via two photon fusion. The cross-section for W and Z production at LHCb has been calculated at NNLO with an uncertainty of $\\sim$ 4\\%, where the dominant theoretical error is due to the uncertainty on the parton distribution functions (PDFs). Using the first 16.5 pb$^{-1}$ of data, a very clean sample of 833 Z bosons and a larger, but less clean, sample of W bosons have been recorded at LHCb. Using the currently available sample of W$^{+}$ (Z) events an integrated luminosity measurement with an uncertainty of $\\sim$5\\% ($\\sim$6\\%) could be made. Once 150 pb$^{-1}$ of data has been collected a measurement using a high purity Z sample could be performed that would have an uncertainty of 4\\%. Cross-section predictions for elastic dimuon production via two photon fusion have been performed...

Anderson, Jonathan

2011-01-01

156

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

1987-01-01

157

The Luminosity Function of QSO Host Galaxies  

CERN Multimedia

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

158

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

159

The Abundance of Low-luminosity Lyman alpha Emitters at High Redshift  

CERN Document Server

We derive the luminosity function of high-redshift Lyman alpha emitting sources from a deep, blind, spectroscopic survey that utilized strong-lensing magnification by intermediate-redshift clusters of galaxies. We observed carefully selected regions near 9 clusters, consistent with magnification factors generally greater than 10 for the redshift range 4.5L) proportional to L^-1 over 10^41 to 10^42.5 erg/s. When combined with the results of other surveys, limited at higher luminosities, our results suggest evidence for the suppression of star formation in low-mass halos, as predicted in popular models of galaxy formation.

Santos, M R; Kneib, J P; Richard, J; Kuijken, K; Santos, Michael R.; Ellis, Richard S.; Kneib, Jean-Paul; Richard, Johan; Kuijken, Konrad

2004-01-01

160

Luminosity-dependent unification of active galactic nuclei and the X-ray Baldwin effect  

Science.gov (United States)

The existence of an anti-correlation between the equivalent width (EW) of the narrow core of the iron K? line and the luminosity of the continuum (i.e., the X-ray Baldwin effect) in type I active galactic nuclei has been confirmed in recent years by several studies carried out with XMM-Newton, Chandra and Suzaku. However, no general consensus on the origin of this trend has been reached so far. Several works have proposed the decrease of the covering factor of the molecular torus with the luminosity (in the framework of the luminosity-dependent unification models) as a possible explanation for the X-ray Baldwin effect. Using the fraction of obscured sources measured by recent X-ray and infrared (IR) surveys as a proxy of the half-opening angle of the torus and recent Monte Carlo simulations of the X-ray radiation reprocessed by a structure with a spherical-toroidal geometry, we test the hypothesis that the X-ray Baldwin effect is related to the decrease of the half-opening angle of the torus with the luminosity. Simulating the spectra of an unabsorbed population with a luminosity-dependent covering factor of the torus as predicted by recent X-ray surveys, we find that this mechanism is able to explain the observed X-ray Baldwin effect. Fitting the simulated data with a log-linear L2-10 keV - EW relation, we found that in the Seyfert regime (L2-10 keV ? 1044.2 erg s-1) luminosity-dependent unification produces a slope consistent with the observations for average values of the equatorial column densities of the torus of log NHT ? 23.2, and can reproduce both the slope and the intercept for log NHT ? 23.2. Lower values of NHT are obtained assuming the decrease of the covering factor of the torus with the luminosity extrapolated from IR observations (22.9 ? log NHT ? 23). In the quasar regime (L 2-10 keV > 1044.2 erg s-1), a decrease of the covering factor of the torus with the luminosity slower than that observed in the Seyfert regime (as found by recent hard X-ray surveys) is able to reproduce the observations for 23.2 ? log NHT ? 24.2.

Ricci, C.; Paltani, S.; Awaki, H.; Petrucci, P.-O.; Ueda, Y.; Brightman, M.

2013-05-01

 
 
 
 
161

UPGRADE OF RHIC VACUUM SYSTEMS FOR HIGH LUMINOSITY OPERATION.  

Energy Technology Data Exchange (ETDEWEB)

With increasing ion beam intensity during recent RHIC operations, rapid pressure rises of several decades were observed at most warm 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 and anti-grazing ridges have been implemented. Several hundred meters of NEG coated beam pipes have been installed and activated. Vacuum monitoring and logging were enhanced. Preventive 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 and summarized.

HSEUH, H.C.; MAPES, M.; SMART, L.A.; TODD, R.; WEISS, D.

2005-05-16

162

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

163

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

164

The Galaxy Luminosity Function and Luminosity Density at Redshift z=0.1  

CERN Document Server

Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS) we measure the galaxy luminosity density at z=0.1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their restframe shape at z=0.1. We denote the bands {0.1}{u}, {0.1}{g}, {0.1}{r}, {0.1}{i}, {0.1}{z}, with \\lambda_{eff} = [3216, 4240, 5595, 6792, 8111] Angstroms respectively. We use a maximum likelihood method which allows for a general form for the shape of the luminosity function, simple luminosity and number evolution, incorporates flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z=0.1 in absolute AB magnitudes in a Mpc^3 of [-14.10 \\pm 0.15, -15.18 \\pm 0.03, -15.90 \\pm 0.03, -16.24 \\pm 0.03, -16.56 \\pm 0.02] in [{0.1}{u}, {0.1}{g}, {0.1}{r}, {0.1}{i}, {0.1}{z}], respectively, using \\Omega_0 =0.3, \\Omega_\\Lambda=0.7, and h=1, and using Petrosian magnitudes. Similar results are obtained using Sersic model magnitudes, suggesting tha...

Blanton, M R; Brinkmann, J; Connolly, A J; Csabai, I; Bahcall, Neta A; Fukugita, M; Loveday, J; Meiksin, A; Munn, J A; Nichol, R C; Okamura, S; Quinn, T; Schneider, D P; Shimasaku, K; Strauss, M A; Tegmark, M; Vogeley, M S; Weinberg, D H; Blanton, Michael R.; Hogg, David W.; Connolly, Andrew J.; Csabai, Istvan; Bahcall, Neta A.; Fukugita, Masataka; Loveday, Jon; Meiksin, Avery; Munn, Jeffrey A.; Okamura, Sadanori; Quinn, Thomas; Schneider, Donald P.; Shimasaku, Kazuhiro; Strauss, Michael A.; Tegmark, Max; Vogeley, Michael S.; Weinberg, David H.

2003-01-01

165

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

166

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

167

Impact of energy and luminosity upgrades at LHC on the physics programme of ATLAS  

International Nuclear Information System (INIS)

The impact of possible LHC upgrades on the physics capabilities of the ATLAS detector is discussed. As a benchmark, an increase in the luminosity by a factor of 10 is considered. For comparison, the doubling of the LHC energy is also explored. Both upgrades significantly enhance the physics capabilities of ATLAS. 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 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. (author)

2002-09-01

168

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

2013-01-01

169

ATLAS Tile Calorimeter Readout Electronics Upgrade Program for the High Luminosity LHC  

CERN Document Server

The Tile Calorimeter (TileCal) is the hadronic calorimeter covering the most central region of the ATLAS experiment at LHC. The TileCal readout consists of about 10000 channels. The ATLAS upgrade program is divided in three phases: The Phase 0 occurs during 2013-2014 and prepares the LHC to reach peak luminosities of 1034 cm2s-1; Phase 1, foreseen for 2018-1019, prepares the LHC for peak luminosity up to 2-3 x 1034 cm2s-1, corresponding to 55 to 80 interactions per bunch-crossing with 25 ns bunch interval; and Phase 2 is foreseen for 2022-2023, whereafter the peak luminosity will reach 5-7 x 1034 cm2s-1 (HL-LHC). With luminosity leveling, the average luminosity will increase with a factor 10. The main TileCal upgrade is focused on the HL-LHC period. The upgrade aims at replacing the majority of the on- and off-detector electronics so that all calorimeter signals are directly digitized and sent to the off-detector electronics in the counting room. All new electronics must be able to cope with the increased rad...

Cerqueira, A S; The ATLAS collaboration

2013-01-01

170

The GRB luminosity function in the internal shock model confronted to observations  

CERN Multimedia

We compute the expected luminosity function of GRBs in the context of the internal shock model. We assume that GRB central engines generate relativistic outflows characterized by the respective distributions of injected kinetic power Edot and contrast in Lorentz factor Kappa = Gamma_max/Gamma_min. We find that if the distribution of contrast extends down to values close to unity (i.e. if both highly variable and smooth outflows can exist) the luminosity function has two branches. At high luminosity it follows the distribution of Edot while at low luminosity it is close to a power law of slope -0.5. We then examine if existing data can constrain the luminosity function. Using the log N - log P curve, the Ep distribution of bright BATSE bursts and the XRF/GRB ratio obtained by HETE2 we show that single and broken power-laws can provide equally good fits of these data. Present observations are therefore unable to favor one form of the other. However when a broken power-law is adopted they clearly indicate a low ...

Zitouni, H; Mochkovitch, R; Zerguini, T H

2010-01-01

171

The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z=0 to z=3  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the evolution of the rest-frame optical luminosity density, of the integrated rest-frame optical color, and of the stellar mass density for a sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity density in the rest-frame U, B, and V-bands and found that the luminosity density increases by a factor of 1.9+-0.4, 2.9+-0.6, and 4.9+-1.0 in the V, B, and U rest-frame bands respectively between a redshift of 0.1 and 3.2. We derived the luminosity ...

Rudnick, Gregory; Rix, Hans-walter; Franx, Marijn; Labbe, Ivo; Blanton, Michael; Daddi, Emanuele; Schreiber, Natascha M. Foerster; Moorwood, Alan; Rottgering, Huub; Trujillo, Ignacio; Wel, Arjen; Werf, Paul; Dokkum, Pieter G.; Starkenburg, Lottie

2003-01-01

172

Semiconductor detectors for high-luminosity environments  

CERN Document Server

As the final touches are being put to the LHC detectors, the race is on to perfect technologies which could be used to confront the challenges of the ultra-high luminosities of the SLHC and International Linear Collider (ILC). These challenges include ever more hostile radiation environments, short signal shaping times and increasing emphasis on the highest possible granularity combined with the lowest possible mass. In the semiconductor detector field, dedicated studies have identified many mechanisms behind radiation damage and pointed the way towards the use of new techniques such as MCz silicon and p-type sensors. In the most extreme environments, completely new approaches, such as the use of diamond or 3D sensor detectors, will be essential. Pixel technology, which has been successfully employed to build large-scale vertex detection systems for the LHC, will be pushed towards higher density, lower mass and greater integration, to satisfy in particular the ILC requirements. We review the highlights of the...

Collins, P

2007-01-01

173

Disruption and luminosity of flat beams  

International Nuclear Information System (INIS)

It has been suggested (ref.1) that high energy linear colliders might operate with non-round beam profiles, i.e. with different sigma/sub x/ and sigma/sub y/, described by an aspect ratio R = sigma/sub y/sigma/sub x/. The advantage of flat beams is the expectation, that ''beamstrahlung'', i.e., beam-beam synchrotron radiation is reduced with increasing R. The reason for this reduction comes from the fact that for constant bunch area and therefore constant luminosity the mean physical distance between the particles increases with R. When the physical distances are larger, the electromagnetic fields and therefore particle acceleration and radiation decrease. This would be of particular importance for very large linear colliders (VLC), where beamstrahlung may consume an appreciable fraction of the incident energy. The underlying assumption is that the emittance quality can be preserved in the deformed bunch. 4 refs., 3 figs., 3 tabs

1985-01-01

174

On Coupled Stellar Luminosity and Gravitation  

Science.gov (United States)

We derive a analytic nonperturbative solution to the coupled field equations of general relativity and electrodynamics, for a star of initial mass Mo and lifetime-averaged luminosity L. We carry out our solution in familiar spherical coordinates, including an off-diagonal term in the metric tensor to allow for "frame dragging” caused by the radial flux of light. We then show how our metric can be transformed into a diagonal one; and how the "photon dust” electomagnetic stress tensor assumed by early investigators of this problem forms an approximation to our solution. We also estimate the magnitude of some of the small effects inferred by this model of radial frame dragging. We thank The Catalysts, an SNU science alumni organization, for its support.

Neuenschwander, Dwight E.; McCully, C. V.

2008-09-01

175

Luminosity bias: from haloes to galaxies  

CERN Multimedia

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

176

The luminosity function in NGC 2023  

International Nuclear Information System (INIS)

Sellgren (1983) has shown that the young stellar cluster within the molecular cloud associated with the reflection nebula NGC 2023 has a luminosity function consistent with the Salpeter IMF for stars brighter than K = 12 mag. Extrapolation predicts that approximately 50 additional stars brighter than K = 15 mag, arguably of spectral types G through K, should be present. However, images of the cluster using a sensitive two-dimensional IR array reveal no additional cluster members, which suggests that either no low-mass stars have formed or that they are still heavily shrouded in molecular 'cocoons' left over from the star formation process. A straightforward experimental resolution of the alternatives is proposed. 22 refs

1990-01-01

177

Measurement of the Luminosity by the ATLAS Experiment  

CERN Multimedia

The luminosity is a fundamental parameter of a particle collider. The success of physics programme of ATLAS experiment depends on the precise determination of the luminosity. Several detectors have been used during the 2010-2011 data taking for the measurement of the luminosity and for monitoring its evolution as a function of time. The absolute calibration is performed using dedicated beam-separation scans which allows the determination of the luminosity without prior knowledge of the detector efficiency and inelastic pp cross section. Based on this method ATLAS has determined the luminosity with an uncertainty of 3.7%. A summary of the luminosity calibration methods and results are presented in this poster.

Gabaldon, C

2011-01-01

178

The Morphological Type Dependence of K-band Luminosity Functions  

Science.gov (United States)

Differential 2.2 ?m (K-band) luminosity functions are presented for a complete sample of 1570 nearby (Vgsr ? 3000 km s-1, 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, N.; Hriljac, P.; Willner, S. P.; Ashby, M. L. N.; Willmer, C. N. A.

2009-12-01

179

The luminosity of serendipitous X-ray QSOs  

Science.gov (United States)

The optical counterparts of 47 X-ray sources with previously unreported quasi-stellar objects are identified. The mean ratio of X-ray to optical luminosity of the sample agrees with that derived from X-ray observations of previously known QSOs, although the mean redshift of the sample is z=0.42, and thus the main luminosity of the objects (Mv=24) differs significantly from that of previous QSO surveys with similar optical thresholds. The steep luminosity function inferred indirectly from optical counts is confirmed. Reconciliation of the observed QSO luminosity function with optically and radio-selected QSO samples requires one of two significant stipulations. Either the space and luminosity distributions of QSOs become quite well specified, or the X-ray luminosity of the typical QSO falls short of that inferred by Zamorani et al. (1981).

Margon, B.; Chanan, G. A.; Downes, R. A.

1982-01-01

180

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

 
 
 
 
181

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

182

Implications of Lag-Luminosity Relationship for Unified GRB Paradigms  

Science.gov (United States)

Spectral lags (tau(sub lag)) are deduced for 1437 long (T(sub 90) greater than 2 s) BATSE gamma-ray bursts (GRBs) with peak flux F(sub p) greater than 0.25 photons cm(sup -2)/s, near to the BATSE trigger threshold. The lags are modeled to approximate the observed distribution in the F(sub p)-T(sub lag) plane, realizing a noise-free representation. Assuming a two-branch lag-luminosity relationship, the lags are self-consistently corrected for cosmological effects to yield distributions in luminosity, distance, and redshift. The results have several consequences for GRB populations and for unified gamma-ray/afterglow scenarios which would account for afterglow break times and gamma-ray spectral evolution in terms of jet opening angle, viewing angle, or a profiled jet with variable Lorentz factor: A component of the burst sample is identified - those with few, wide pulses, lags of a few tenths to several seconds, and soft spectra - whose Log[N]-Log[F(sub p)] distribution approximates a -3/2 power-law, suggesting homogeneity and thus relatively nearby sources. The proportion of these long-lag bursts increases from negligible among bright BATSE bursts to approx. 50% at trigger threshold. Bursts with very long lags, approx. 1-2 less than tau(sub lag) (S) less than 10, show a tendency to concentrate near the Supergalactic Plane with a quadrupole moment of approx. -0.10 +/- 0.04. GRB 980425 (SN 1998bw) is a member of this subsample of approx. 90 bursts with estimated distances less than 100 Mpc. The frequency of the observed ultra-low luminosity bursts is approx. 1/4 that of SNe Ib/c within the same volume. If truly nearby, the core-collapse events associated with these GRBs might produce gravitational radiation detectable by LIGO-II. Such nearby bursts might also help explain flattening of the cosmic ray spectrum at ultra-high energies, as observed by AGASA.

Norris, J. P.; White, Nicholas E. (Technical Monitor)

2002-01-01

183

Modeling Luminosity-Dependent Galaxy Clustering Through Cosmic Time  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We employ high-resolution dissipationless simulations of the concordance LCDM cosmology to model the observed luminosity dependence and evolution of galaxy clustering through most of the age of the universe, from z~5 to z~0. We use a simple, non-parametric model which monotonically relates galaxy luminosities to the maximum circular velocity of dark matter halos (V_max) by preserving the observed galaxy luminosity function in order to match the halos in simulations with obse...

Conroy, Charlie; Wechsler, Risa H.; Kravtsov, Andrey V.

2005-01-01

184

Standardization of CDF and D OE reported luminosities  

International Nuclear Information System (INIS)

During FNAL collider store 5094, CDF- and D OE modified the computation of their reported luminosities to utilize a standardized world average inelastic cross-section. The changes made at each experiment and in the Accelerator Division are detailed below. A net decrease was expected and was observed for the reported instantaneous luminosity from each experiment. These changes affect the estimates of instantaneous and integrated luminosities reported to the Accelerator Division for the purposes of operational coordination

1994-01-01

185

First measurements of HERA luminosity by ZEUS lumi monitor  

International Nuclear Information System (INIS)

The first measurement of the HERA collider luminosity by the ZEUS luminosity monitor is reported. The measurement was performed for collisions of 26.6 GeV electrons with 480 GeV protons. Over 4 weeks of HERA operation in November 1991 the measured luminosity has increased from ? 7 x 1026 cm-2 x s-1 to ? 2 x 1028 cm-2 x s-1 as a result of increasing beam currents and improved machine tuning. (orig.)

1992-01-01

186

Luminosity issues in 2009 100 GeV polarized proton run  

International Nuclear Information System (INIS)

Several luminosity issues are reviewed. Questions remain, which are stated for further investigation. Some suggestions are made for possible luminosity improvement. There are several factors affecting the luminosity in 2009 100 GeV polarized proton run: (1) The highest bunch intensity at RHIC early store (1.5 hour after accramp in this note) in 2009 is 1.25 x 1011 protons. In 2008 run, it was 1.42 x 1011 protons, which gives rise to 30% higher luminosity if other conditions are the same. Yellow ramp efficiency is identified as one of the main problem. Meanwhile, the beam-beam induced loss in about 1 hour into collision accounts actually no less than the ramp. (2) The typical transverse emittance at early store is 13 ?(micro)m for bunch intensity of 1011 protons, but it is 17 ?(micro) for 1.25 x 1011 protons. The increase of the emittance implies a 30% difference in luminosity if other conditions are the same. The emittance growth with electron cloud below instability threshold may be partially responsible. Meanwhile, the Booster scraping may also be relevant. (3) The luminosity lifetime in 2009 run is significantly lower than that in 2005, 2006, and 2008 runs. At the beam-beam parameter of 0.01, the typical average luminosity lifetime in early store is 10 hours in 2009, and it is 15 hours in previous runs. Given 8 hours of store time, this implies more than 20% of the difference in integrated luminosity. The 0.7 m betastar adopted in 2009 might be relevant, but the evidence is not fully convincing. On the other hand, the continuing RF voltage ramp in store may be of concern. (4) In the last month of the run, the polarization at RHIC early store is declined from 60% to 55%, a 30% reduction in p4 factor. It is noted that the Booster scraping is reduced in order to increase bunch intensity at RHIC, and the source polarization is also declined at the same time. Questions regarding these issues are discussed, and some suggestions are made.

2009-01-01

187

Precision measurement of the luminosity in the ATLAS experiment.  

CERN Multimedia

A precision luminosity measurement is of critical importance for the ATLAS physics program, both for searches for new physics as well as for precision measurements of Standard Model cross-sections. The calibration of the luminosity is based on so-called van der Meer scans. The calibration determines the convolved beam sizes in the vertical and horizontal directions, and together with the precise knowledge of the beam current a luminosity calibration can be determined. Based on this analysis ATLAS has determined the luminosity with a total uncertainty of only 3.7% for the 2011 data at sqrt{s}=7 TeV.

Hedberg, V; The ATLAS collaboration

2011-01-01

188

The H II region luminosity function of the Milky Way  

Energy Technology Data Exchange (ETDEWEB)

Published radio surveys of H-II regions in the Milky Way are used to derive the radio continuum and equivalent H-alpha luminosity function for the Galaxy. It is found that the Galactic luminosity function can be fitted by a power-law function N(L) proportional to L exp -2.3 + or - 0.5. The luminosity function and the physical properties of the H-II regions are consistent with a Hubble type intermediate between Sb and Sc, based on comparisons with external galaxies. The qualitative resemblance of the Galactic luminosity function with the mass function of Galactic giant molecular clouds is also discussed. 20 refs.

Smith, T.R.; Kennicutt, R.C. Jr. (Washington Univ., Seattle (USA); Steward Observatory, Tucson, AZ (USA))

1989-07-01

189

Luminosity Measurement Using Cherenkov Integrating Detector (LUCID) in ATLAS  

CERN Document Server

LUCID (LUminosity measurement using Cherenkov Integrating Detector) is a Cherenkov counter designed to monitor the luminosity in the ATLAS experiment. Since the final accuracy of the measurement of some crucial physical quantities in the LHC program will depend on the precision of the luminosity measurement, it is mandatory to push the latter to its best. This in turn implies the need to monitor the beam conditions. In this paper an overview of LUCID is given. After a description of the detector, an insight into the luminosity measurement strategy in ATLAS is given, as well as a description of the calibration strategy of LUCID.

Caforio, D

2008-01-01

190

Pure luminosity evolution hypothesis for QSOs from luminosity functions to synthetic catalogues  

CERN Document Server

This paper describes the simulation of realistic Monte-Carlo extragalactic catalogues, aimed at comparing the behaviour of cosmological tests versus input parameters. QSO catalogues are built on a Luminosity Function derived from data through suitable computation of individual maximum volumes in complete (but magnitude- and redshift-limited) samples requiring neither of redshift nor of apparent magnitude histogram. The values of the evolution parameter are derived for various cosmologies, corresponding to =1/2 in the sample of 400 Ultra-Violet Excess (UVX) QSOs (Boyle et al 1990). The various luminosity functions are compared, both for the whole sample and in redshift bins. An evolution characteristic time is defined and computed, depending strongly on the cosmology, but practically constant when expressed in terms of the age of the Universe. Algorithms are given for producing unbiased or biased catalogues based on the null hypothesis that the objects are uniformly distributed in volume but suffer Pure Lumino...

Mathez, G; Mellier, Y; Bonnet, H; Lachièze-Rey, M

1995-01-01

191

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

Science.gov (United States)

We present an updated and revised analysis of the relationship between the H? 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 H? time lag, which is assumed to yield the average H? 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 ? = 0.533^{+0.035}_{-0.033}, 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.

Bentz, Misty C.; Denney, K.; Grier, C.; Barth, A. J.; Peterson, B. M.; Vestergaard, M.

2014-01-01

192

THE LOW-LUMINOSITY END OF THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI  

Energy Technology Data Exchange (ETDEWEB)

We present an updated and revised analysis of the relationship between the H{beta} 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 H{beta} time lag, which is assumed to yield the average H{beta} 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{sub BLR}-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of {alpha}= 0.533{sup +0.035}{sub -0.033}, 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{sub BLR}-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.

Bentz, Misty C. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States); Denney, Kelly D.; Vestergaard, Marianne [Dark Cosmology Center, Niels Bohr Institute, Juliane Maries Vej 30, DK-2100 Copenhagen O (Denmark); Grier, Catherine J.; Peterson, Bradley M.; De Rosa, Gisella; Pogge, Richard W. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Barth, Aaron J. [Department of Physics and Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697 (United States); Bennert, Vardha N. [Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 (United States); Canalizo, Gabriela [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); Filippenko, Alexei V.; Li Weidong [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Gates, Elinor L. [University of California Observatories/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Peyton Hall - Ivy Lane, Princeton, NJ 08544 (United States); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Treu, Tommaso [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Woo, Jong-Hak, E-mail: bentz@chara.gsu.edu [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul (Korea, Republic of)

2013-04-20

193

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

194

THE LUMINOSITIES OF PROTOSTARS IN THE SPITZER c2d AND GOULD BELT LEGACY CLOUDS  

International Nuclear Information System (INIS)

Motivated by the long-standing 'luminosity problem' in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate Lbol for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 L? to 69 L?, and has a mean and median of 4.3 L? and 1.3 L?, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (Lbol ??) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 ?m bol underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35%-40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased data set should aid such future work.

2013-04-01

195

Multiwavelength Characteristics of Period-Luminosity Relations  

CERN Multimedia

We present a physically motivated explanation for the observed, monotonic increase in slope, and the simultaneous (and also monotonic) decrease in the width/scatter of the Leavitt Law (the Cepheid Period-Luminosity (PL) relation) as one systematically moves from the blue and visual into the near and mid-infared. We calibrate the wavelength-dependent, surface-brightness sensitivities to temperature using the observed slopes of PL relations from the optical through the mid-infrared, and test the calibration by comparing the theoretical predictions with direct observations of the wavelength dependence of the scatter in the Large Magellanic Cloud Cepheid PL relation. In doing so we find the slope of the Period-Radius (PR) relation is c = 0.724 +/- 0.006. Investigating the effect of differential reddening suggests that this value may be overestimated by as much as 10%; however the same slope of the PR relation fits the (very much unreddened) Cepheids in IC1613, albeit with lower precision. The discussion given is ...

Madore, Barry F

2011-01-01

196

GRB Variability-Luminosity Correlation Confirmed  

CERN Document Server

Recently, Guidorzi et al. (2005) expanded the size of the sample of GRBs for which variabilities and peak luminosities have been measured, from 11 to 32. They confirm the existence of a correlation, but find a dramatically different relationship between L and V than had originally been found. We find that this is the result of improper statistical methodology. When we fit a model to the data that accommodates both statistical variance (in two dimensions) and sample variance, we find that L ~ V^3.4(+0.9,-0.6) with a sample variance of sigma_logV = 0.20(+0.04,-0.04), which is consistent with the original finding of Reichart et al. (2001) -- L ~ V^3.3(+1.1,-0.9) with a sample variance of sigma_logV = 0.18(+0.07,-0.05) -- and inconsistent with the finding of Guidorzi et al. (2005): L ~ V^1.3(+0.8,-0.4) with sample variance assumed to be zero.

Reichart, D E; Reichart, Daniel E.; Nysewander, Melissa C.

2005-01-01

197

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

1985-04-05

198

AGN Black Hole Masses and Bolometric Luminosities  

CERN Document Server

Black hole mass, along with mass accretion rate, is a fundamental property of active galactic nuclei. Black hole mass sets an approximate upper limit to AGN energetics via the Eddington limit. We collect and compare all AGN black hole mass estimates from the literature; these 177 masses are mostly based on the virial assumption for the broad emission lines, with the broad-line region size determined from either reverberation mapping or optical luminosity. We introduce 200 additional black hole mass estimates based on properties of the host galaxy bulges, using either the observed stellar velocity dispersion or using the fundamental plane relation to infer $\\sigma$; these methods assume that AGN hosts are normal galaxies. We compare 36 cases for which black hole mass has been generated by different methods and find, for individual objects, a scatter as high as a couple of orders of magnitude. The less direct the method, the larger the discrepancy with other estimates, probably due to the large scatter in the u...

Urry, C M; Urry, Jong-Hak Woo & C. Megan

2002-01-01

199

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

200

The IR Luminosity Functions of Rich Clusters  

CERN Multimedia

We present MIPS observations of the cluster A3266. About 100 spectroscopic cluster members have been detected at 24 micron. The IR luminosity function in A3266 is very similar to that in the Coma cluster down to the detection limit L_IR~10^43 ergs/s, suggesting a universal form of the bright end IR LF for local rich clusters with M~10^15 M_sun. The shape of the bright end of the A3266-Coma composite IR LF is not significantly different from that of nearby field galaxies, but the fraction of IR-bright galaxies (SFR > 0.2M_sun/yr) in both clusters increases with cluster-centric radius. The decrease of the blue galaxy fraction toward the high density cores only accounts for part of the trend; the fraction of red galaxies with moderate SFRs (0.2 < SFR < 1 M_sun/yr) also decreases with increasing galaxy density. These results suggest that for the IR bright galaxies, nearby rich clusters are distinguished from the field by a lower star-forming galaxy fraction, but not by a change in L*_IR. The composite IR LF...

Bai, Lei; Rieke, Marcia J; Christlein, Daniel; Zabludoff, Ann I

2008-01-01

 
 
 
 
201

The Black Hole Mass - Spheroid Luminosity relation  

CERN Multimedia

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

202

Aerogel Cherenkov detectors for the luminosity measurement at HERA  

Energy Technology Data Exchange (ETDEWEB)

Construction of the Cherenkov detectors using the silica aerogel SP-30 (Matsushita) and fast photomultipliers is described. Application of these detectors for the luminosity measurement in the ZEUS experiment at HERA is then presented. The HERA luminosity is measured using high rate, high-energy bremsstrahlung photons, and the Cherenkov detectors are designed for achieving the required resolution of the photon energy measurement.

Chwastowski, Janusz E-mail: janusz@chall.ifj.edu.pl; Figiel, Jan. E-mail: figiel@chall.ifj.edu.pl; Kotarba, Andrzej E-mail: kotarba@chall.ifj.edu.pl; Olkiewicz, Krystyna E-mail: olki@chall.ifj.edu.pl; Suszycki, Leszek E-mail: suszycki@chall.ifj.edu.pl

2003-05-21

203

Aerogel Cherenkov detectors for the luminosity measurement at HERA  

International Nuclear Information System (INIS)

Construction of the Cherenkov detectors using the silica aerogel SP-30 (Matsushita) and fast photomultipliers is described. Application of these detectors for the luminosity measurement in the ZEUS experiment at HERA is then presented. The HERA luminosity is measured using high rate, high-energy bremsstrahlung photons, and the Cherenkov detectors are designed for achieving the required resolution of the photon energy measurement

2003-05-21

204

Absorbers for the high luminosity insertions of the LHC.  

Science.gov (United States)

At design luminosity and inelastic cross section (sigma)(sub pp) = 80mb there are 8 (times) 10(sup 8) inelastic collisions per second at the high luminosity interaction points IP1 and IP5 of the LHC. These interactions give rise to (approximately) 0.9 kW ...

W. C. Turner E. H. Hoyer N. V. Mokhov

1998-01-01

205

What is L*?: Anatomy of the Galaxy Luminosity Function  

CERN Document Server

Using the empirical relations between the central galaxy luminosity and the halo mass, and between the total galaxy luminosity in a halo and the halo mass, we construct the galaxy luminosity function (LF). To the luminosity of the central galaxy in a halo of a given mass we assign log-normal scatter with a mean calibrated against the observations. In halos where the total galaxy luminosity exceeds that of the central galaxy, satellite galaxies are distributed as a power-law in luminosity. Combined with the halo mass function, this description reproduces the observed characteristics of the galaxy LF, including a shape consistent with the Schechter function. When all galaxies are included, regardless of the environment or the Hubble type, the Schechter L* is the luminosity scale above which the central galaxy luminosity-halo mass relation flattens; L* corresponds to ~10^{13}Msun on the halo mass scale. In surveys where central galaxies in massive clusters are neglected, either by design or because of the cosmic...

Cooray, A R; Cooray, Asantha; Milosavljevic, Milos

2005-01-01

206

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

207

Cosmological parameters and evolution of the galaxy luminosity function  

Science.gov (United States)

The relationship between the observed distribution of discrete sources of a flux limited sample, the luminosity function of these sources, and the cosmological model is discussed. It is stressed that some assumptions about the form and evolution of the luminosity function must be made in order to determine the cosmological parameters from the observed distribution of sources. Presented is a method to test the validity of these assumptions using the observations. It is shown how, using higher moments of the observed distribution, one can determine, independently of the cosmological model, all parameters of the luminosity function except those describing evolution of the density and the luminosity of the luminosity function. These methods are applied to the sample of approximately 1000 galaxies recently used by Loh and Spillar to determine a value of the cosmological density parameter Omega approx = 1. It is shown that the assumptions made by Loh and Spillar about the luminosity function are inconsistent with the data, and that a self-consistent treatment of the data indicates a lower value of Omega approx = 0.2 and a flatter luminosity function. It should be noted, however, that incompleteness in the sample could cause a flattening of the luminosity function and lower the calculated value of Omega and that uncertainty in the values of these parameters due to random fluctuations is large.

Caditz, David; Petrosian, Vahe

1988-01-01

208

Luminosity and Beam Spot Determination Using the ATLAS Detector  

CERN Multimedia

We present the algorithms and results of the reconstruction of the luminous region (also known as beam spot) and measurement of the luminosity in the ATLAS experiment during the first LHC run at energies between sqrt(s) = 900 GeV (in 2009) and sqrt(s) = 7 TeV (in 2010). The LHC luminosity is determined in real time approximately once per second using a number of detectors and algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. These results are displayed in the ATLAS control room and archived every two minutes; a single "preferred" measurement is reported to the LHC. During offline analysis, additional luminosity algorithms are studied and are compared to online results to further constrain systematic uncertainties on the measurement. Relative luminosities between detectors and methods agree to within a few per cent. Determination of the absolute luminosity using Monte Carlo calibrations is limited by a ~20% systematic uncertainty from the modeling of diffrac...

Miller, D W; The ATLAS collaboration

2010-01-01

209

Upgrade of the D0 luminosity monitor readout system  

Energy Technology Data Exchange (ETDEWEB)

We describe upgrades to the readout system for the D0 Luminosity Monitor. The D0 Luminosity Monitor consists of plastic scintillation detectors with fine-mesh photomultiplier readout that cover the pseudorapidity range 2.7 < |{eta}| < 4.4. The detector is designed to provide a precise measurement of the rate for non-diffractive inelastic collisions that is used to calculate the TeVatron luminosity at D0. The new readout system is based on custom VME electronics that make precise time-of-flight and charge measurements for each luminosity counter. These measurements are used to identify beam crossings with non-diffractive interactions by requiring in-time hits in both the forward and backward luminosity counters. We have also significantly increased signal/noise for the photomultiplier signals by developing a new front-end preamplifier and improving the grounding scheme.

Anderson, John; Bridges, Lloyd; Casey, Brendan; Enari, Yuji; Green, Johnny; Johnson, Marvin; Kwarciany, Rick; Miao, Chyi-Chiang; Partridge, Richard; Yoo, Hwi Dong; Wang,; /Brown U. /Fermilab

2006-12-01

210

ATLAS Future Plans: Upgrade and the Physics with High Luminosity  

CERN Document Server

ATLAS is planning a series of detector upgrades to cope with increasing instantaneous luminosity and multiple interactions per crossing to ensure that acceptance to new physics and precision measurements are preserved. During the next several years, LHC is expected to collide protons on protons at a center of mass energy up to 14 TeV with luminosities reaching 1 to 2 x 1034 cm^-2 s^-1, accumulating ~100 fb^-1 per year following a Phase 1 Upgrade (2018). The detector upgrades focus on precision tracking and improved trigger capabilities to sustain higher rates. Subsequently, the LHC plans calls for a five-fold increase in instantaneous luminosity, thereby increasing the delivered luminosity to ~3000 fb^-1 by 2030. The increased luminosity will significantly increase the physics reach of ATLAS building on the recent discovery of the Higgs-like boson. The planned detector upgrades and the impact on the ATLAS physics program will be discussed.

Rajagopalan, Srini; The ATLAS collaboration

2012-01-01

211

Simulation of the LHC BRAN luminosity monitor for high luminosity interaction regions  

Energy Technology Data Exchange (ETDEWEB)

The BRAN (Beam RAte of Neutrals) detector monitors the collision rates in the high luminosity interaction regions of LHC (ATLAS and CMS). This Argon gas ionization detector measures the forward neutral particles from collisions at the interaction point. To predict and improve the understanding of the detector's performance, we produced a detailed model of the detector and its surroundings in Fluka. In this paper, we present the model and results of our simulations including the detectors estimated response to interactions for beam energies of 3.5, 5, and 7 TeV.

Miyamoto, R.; Matis, H.; Ratti, A.; Stiller, J.; White, S.M.

2010-05-23

212

Simulation of the LHC BRAN luminosity monitor for high luminosity interaction regions  

International Nuclear Information System (INIS)

The BRAN (Beam RAte of Neutrals) detector monitors the collision rates in the high luminosity interaction regions of LHC (ATLAS and CMS). This Argon gas ionization detector measures the forward neutral particles from collisions at the interaction point. To predict and improve the understanding of the detector's performance, we produced a detailed model of the detector and its surroundings in Fluka. In this paper, we present the model and results of our simulations including the detectors estimated response to interactions for beam energies of 3.5, 5, and 7 TeV.

2010-05-23

213

Simulation of the LHC BRAN Luminosity Monitor for High Luminosity Interaction Regions  

CERN Document Server

The BRAN (Beam RAte of Neutrals) detector monitors the collision rates in the high luminosity interaction regions of LHC (ATLAS and CMS). This Argon gas ionization detector measures the forward neutral particles from collisions at the interaction point. To predict and improve the understanding of the detector’s performance, we produced a detailed model of the detector and its surroundings in Fluka. In this paper, we present the model and results of our simulations including the detectors estimated response to interactions for beam energies of 3.5, 5, and 7 TeV

Stiller, Johannes; Ratti, Alessandro; Turner, William; Miyamoto, Ryoichi; White, Simon

2010-01-01

214

Towards a new LHC interaction region design for a luminosity upgrade  

Energy Technology Data Exchange (ETDEWEB)

After the LHC operates for several years at nominal parameters, it will be necessary to upgrade it for higher luminosity. Replacing the low-{beta} insertions with a higher performance design based on advanced superconducting magnets is one of the most straightforward steps in this direction. Preliminary studies show that, with magnet technology that is expected to be developed by early in the next decade, a factor of 2 to 5 reduction in {beta}* could be achieved with new insertions, as part of an upgrade aimed at a factor of 10 luminosity increase. In this paper we survey several possible second generation LHC interaction regions designs, which address the expected limitations on LHC performance imposed by the baseline insertions.

James Strait et al.

2003-05-29

215

GALACTIC ULTRACOMPACT X-RAY BINARIES: EMPIRICAL LUMINOSITIES  

Energy Technology Data Exchange (ETDEWEB)

Ultracompact X-ray binaries (UCXBs) are thought to have relatively simple binary evolution post-contact, leading to clear predictions of their luminosity function. We test these predictions by studying the long-term behavior of known UCXBs in our Galaxy, principally using data from the MAXI All-Sky Survey and the Galactic bulge scans with RXTE's Proportional Counter Array instrument. Strong luminosity variations are common (and well documented) among persistent UCXBs, which requires an explanation other than the disk instability mechanism. We measure the luminosity function of known UCXBs in the Milky Way, which extends to lower luminosities than some proposed theoretical luminosity functions of UCXBs. The difference between field and globular cluster (GC) X-ray luminosity functions in other galaxies cannot be explained by an increased fraction of UCXBs in GCs. Instead, our measured luminosity function suggests that UCXBs only make up a small fraction of the X-ray binaries above a few Multiplication-Sign 10{sup 36} erg s{sup -1} in both old field populations and GCs.

Cartwright, T. F.; Engel, M. C.; Heinke, C. O.; Sivakoff, G. R.; Berger, J. J.; Gladstone, J. C.; Ivanova, N., E-mail: heinke@ualberta.ca [Physics Department, 4-183 CCIS, University of Alberta, Edmonton, AB T6G 2E1 (Canada)

2013-05-10

216

Description of a high rate luminosity monitor installed at CESR  

International Nuclear Information System (INIS)

In response to a need for a fast, direct measure of luminosity for the purpose of machine optimization, a high rate luminosity monitor has been constructed for CESR. The interaction regions at CESR employ a standard minibeta lattice in which the inner quadrupoles are vertically focussing. Bhabha scattered particles are horizontally defocussed upon traversing these quadrupoles. A beam pipe constricted in the horizontal plane was constructed to detect these high event rate particles. This paper is a description of the luminosity, background, and accidental rates observed with various detector schemes. These results are compared with calculations. Stability and beam steering sensitivies are also explored

1985-10-01

217

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

2007-06-25

218

Reverberation Mapping of High-Redshift, High-Luminosity Quasars  

CERN Multimedia

We present preliminary results from a reverberation mapping program to measure the Broad Line Region size in high-redshift, high-luminosity quasars. The observations are carried out at the Hobby-Eberly Telescope and at the Wise Observatory. The data cover 8 yr of photometric monitoring of 11 quasars, and 2.5 yr of spectrophotometric monitoring of 7 of these sources. Thus far we detected continuum variations but no line variations. We find that the continua of the high-luminosity quasars have smaller variability amplitudes and longer variability timescales compared with low-luminosity AGNs.

Kaspi, S; Maoz, D; Shemmer, O; Brandt, W N; Schneider, D P; Kaspi, Shai; Netzer, Hagai; Maoz, Dan; Shemmer, Ohad; Schneider, Donald P.

2002-01-01

219

Precision luminosity measurement with the OPAL silicon-tungsten calorimeters  

CERN Multimedia

A preliminary, high precision measurement of the luminosity of the LEP colliding beams for the LEP I data recorded between 1993 and 1995 with the OPAL experiment is presented, the measurement is based on the OPAL Silicon-Tungten luminosity monitor, which detects electrons from small-angle Bhabha scattering at angles between approximately 25 and 58 mrad. The overall experimental uncertainty on the measured luminosity is 3.3*10/sup -4/. Such uncertainty contributes negligibly to the uncertainty on the OPAL cross section measurements near the Z /sup 0/ resonance. (3 refs).

Arcelli, S

1999-01-01

220

Prospects for the high luminosity LHC (ATLAS and CMS)  

CERN Document Server

This presentation reviews the different physic topics which could be accessible with the High-Luminosity LHC program (HL-LHC) with the ATLAS and CMS detectors. An integrated luminosity of 3000 fb-1 at 14 TeV is expected and detectors will have to adapt to severe data-taking conditions. The Higgs boson coupling to fermions/bosons will be measured with precisions reaching the percent level. Expections on Higgs self coupling and vector-vector boson scattering are also reachable with this luminosity. The direct search of heavy resonances or SUSY particles will reach the TeV scale.

Jezequel, S; The ATLAS collaboration

2013-01-01

 
 
 
 
221

Luminosity Optimization With Offset, Crossing Angle, and Distortion  

Energy Technology Data Exchange (ETDEWEB)

In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In this paper, we study the luminosity loss and then the optimization required to partially cancel the luminosity loss both analytically and with direct simulation.

Wu, Juhao; Raubenheimer, T.O.; /SLAC

2005-06-15

222

First measurements of HERA luminosity by ZEUS lumi monitor  

Energy Technology Data Exchange (ETDEWEB)

The first measurement of the HERA collider luminosity by the ZEUS luminosity monitor is reported. The measurement was performed for collisions of 26.6 GeV electrons with 480 GeV protons. Over 4 weeks of HERA operation in November 1991 the measured luminosity has increased from {approx equal} 7 x 10{sup 26} cm{sup -2} x s{sup -1} to {approx equal} 2 x 10{sup 28} cm{sup -2} x s{sup -1} as a result of increasing beam currents and improved machine tuning. (orig.).

Andruszkow, J.; Chwastowski, J.; Daniluk, W.; Dwurazny, A.; Eskreys, A.; Halik, J.; Jurkiewicz, P.; Jakubowski, Z.; Kotarba, A.; Machowski, B.; Niziol, B.; Oliwa, K.; Piotrzkowski, K.; Wierba, W.; Zachara, M.; Zawiejski, L. (Inst. of Nuclear Physics, Krakow (Poland)); Eskreys, K.; Etgens, G.; Kisielewska, D.; Kulka, J.; Suszycki, L. (Academy of Mining and Metallurgy, Krakow (Poland). Inst. of Nuclear Physics and Te

1992-05-01

223

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

224

The White Dwarf Luminosity Function from SDSS Imaging Data  

CERN Document Server

A sample of white dwarfs is selected from SDSS DR3 imaging data using their reduced proper motions, based on improved proper motions from SDSS plus USNO-B combined data. Numerous SDSS and followup spectra (Kilic et al. 2005) are used to quantify completeness and contamination of the sample; kinematic models are used to understand and correct for velocity-dependent selection biases. A luminosity function is constructed covering the range 7 < M_bol < 16, and its sensitivity to various assumptions and selection limits is discussed. The white dwarf luminosity function based on 6000 stars is remarkably smooth, and rises nearly monotonically to M_bol = 15.3. It then drops abruptly, although the small number of low-luminosity stars in the sample and their unknown atmospheric composition prevent quantitative conclusions about this decline. Stars are identified that may have high tangential velocities, and a preliminary luminosity function is constructed for them.

Harris, H C; Kilic, M; Liebert, J; Williams, K A; Von Hippel, T; Levine, S E; Monet, D G; Eisenstein, D J; Kleinman, S J; Metcalfe, T S; Nitta, A; Winget, D E; Brinkmann, J; Fukugita, M; Knapp, G R; Lupton, R H; Smith, J A; Schneider, D P; Harris, Hugh C.; Munn, Jeffrey A.; Kilic, Mukremin; Liebert, James; Williams, Kurtis A.; Hippel, Ted von; Levine, Stephen E.; Monet, David G.; Eisenstein, Daniel J.; Nitta, Atsuko; Fukugita, Masataka; Lupton, Robert H.; Schneider, Donald P.

2005-01-01

225

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

226

When teaching: Out with magnitudes, in with monochromatic luminosities!  

CERN Multimedia

The goal of this document is to illustrate that teaching the concepts of magnitudes is a needless complication in introductory astronomy courses, and that use of monochromatic luminosities, rather than arbitrarily defined magnitudes, leads to a large gain in transparency. This illustration is done through three examples: the Hertzsprung-Russell diagram, the cosmic distance ladder, and interstellar reddening. I provide conversion equations from the magnitude-based to the luminosity-based system; a brief discussion; and a reference to sample lecture notes. I suggest that we, astronomers in the 21st century, abolish magnitudes and instead use (apparent) monochromatic luminosities in non-specialist teaching. Given the large gain in transparency I further propose that we seriously consider using (apparent) monochromatic luminosities also in research papers, bringing optical astronomy in line with astronomy at other wavelengths. Comments are welcome.

Verbunt, Frank

2008-01-01

227

The Kinematics of the Lag-Luminosity Relationship  

Energy Technology Data Exchange (ETDEWEB)

Herein I review the argument that kinematics, i.e. relativistic motions of the emitting source in gamma-ray bursts (GRBs), are the cause of the lag-luminosity relationship observed in bursts with known redshifts.

Salmonson, J D

2004-03-17

228

Practical and foreseeable limitations in usable luminosity for the collider  

International Nuclear Information System (INIS)

The present situation and possible short-term improvements of the panti p collider are discussed. A long-term plan, aiming at an increase in luminosity by an order of magnitude is then described. (orig.)

1983-05-01

229

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

2008-05-22

230

Luminosity jumps in pre-main-sequence stars  

Energy Technology Data Exchange (ETDEWEB)

Thermal relaxation in young stars is discussed, showing how luminosity jumps occur in those of sufficient mass. The essential character of the thermal relaxation process is shown to be internal heat transfer accompanied by nonhomologous contraction. A simple model of this heat transfer is used, in conjunction with a series of stellar atmospheric calculations, to provide a crude determination of the luminosity jump in a five solar mass star. The observational relevance of this phenomenon is discussed. 30 refs.

Stahler, S.W. (MIT, Cambridge, MA (USA))

1989-12-01

231

The rate and luminosity function of Short GRBs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We compare the luminosity function and rate inferred from the BATSE short hard bursts (SHBs) peak flux distribution with the redshift and luminosity distributions of SHBs observed by Swift/HETE II. The Swift/HETE II SHB sample is incompatible with SHB population that follows the star formation rate. However, it is compatible with a distribution of delay times after the SFR. This would be the case if SHBs are associated with binary neutron star mergers. The implied SHB rates ...

Piran, Tsvi; Guetta, Dafne

2006-01-01

232

Redshifts and Luminosities for 112 Gamma Ray Bursts  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two different luminosity indicators have recently been proposed for Gamma Ray Bursts that use gamma-ray observations alone. They relate the burst luminosity (L) with the time lag between peaks in hard and soft energies, and the spikiness or variability of the burst's light curve (V). These relations are currently justified and calibrated with only 6 or 7 bursts with known red shifts. We have examined BATSE data for the lag and V for 112 bursts. (1) A strong correlation betwe...

Schaefer, Bradley E.; Deng, Ming; Band, David L.

2001-01-01

233

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

234

Using luminosity data as a proxy for economic statistics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A pervasive issue in social and environmental research has been how to improve the quality of socioeconomic data in developing countries. Given the shortcomings of standard sources, the present study examines luminosity (measures of nighttime lights visible from space) as a proxy for standard measures of output (gross domestic product). We compare output and luminosity at the country level and at the 1° latitude × 1° longitude grid-cell level for the period 1992–2008. We find that lumino...

Chen, Xi; Nordhaus, William D.

2011-01-01

235

The Planetary Nebula Luminosity Function at the Dawn of Gaia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The [O III] 5007 Planetary Nebula Luminosity Function (PNLF) is an excellent extragalactic standard candle. In theory, the PNLF method should not work at all, since the luminosities of the brightest planetary nebulae (PNe) should be highly sensitive to the age of their host stellar population. Yet the method appears robust, as it consistently produces < 10% distances to galaxies of all Hubble types, from the earliest ellipticals to the latest-type spirals and irregulars. It ...

Ciardullo, Robin

2012-01-01

236

The luminosity function of Swift long gamma-ray bursts  

CERN Multimedia

The formation rate of long gamma-ray bursts (GRBs) could follow the cosmic star formation rate (SFR) incorporating with cosmic metallicity evolution. Therefore, the luminosity function (LF) of GRBs can in principle be explored by modeling the redshift-luminosity distributions of {\\it Swift} observed GRBs. For an assumed LF form as $\\Phi_z(L)\\propto e^{-L_p/L}\\left({L/L_p}\\right)^{-\

Cao, Xiao-Feng; Cheng, K S; Zheng, Xiao-Ping

2011-01-01

237

ERL-Ring Type High Luminosity Charm Factory  

International Nuclear Information System (INIS)

A high luminosity energy recovery linac-ring type electron-positron collider serving as super charm factory is proposed. It is shown that the design luminosity L=1035 cm-2s-1 and more can be achieved for center of mass energy ?s=3.77 GeV. The physics potential of this machine in investigation for charmed particles properties is briefly discussed.

2011-01-01

238

An early separation scheme for the LHC luminosity upgrade  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Sterbini, Guido

2010-01-01

239

Luminosity Dependence in the Fundamental Plane Projections of Elliptical Galaxies  

CERN Multimedia

We analyze the fundamental plane projections of elliptical galaxies as a function of luminosity, using a sample of approximately 80,000 galaxies drawn from Data Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). We exclude brightest cluster galaxies (BCGs) from our sample because of a problem with the default pipeline sky subtraction for BCGs. The observables we consider are effective radius (R_o), velocity dispersion (sigma), dynamical mass (M_dyn ~ R_o sigma^2), effective density (sigma^2/R_o^2), and effective surface brightness (mu_o). With the exception of the L-M_dyn correlation, we find evidence of variations in the slope of the fundamental plane projections with luminosity. In particular, the radius-luminosity and Faber-Jackson relations are steeper at high luminosity relative to low luminosity, and the more luminous ellipticals become progressively less dense and have lower surface brightnesses than lower luminosity ellipticals. These variations can be understood as arising from differing formati...

Desroches, L B; Ma, C P; West, A A; Desroches, Louis-Benoit; Quataert, Eliot; Ma, Chung-Pei; West, Andrew A.

2006-01-01

240

The luminosity function of diverse satellite galaxy systems  

CERN Multimedia

The high-resolution, SPH galaxies of the McMaster Unbiased Galaxy Survey (MUGS) are used to examine the satellite systems of sixteen model host galaxies. Each galaxy has a different mass, angular momentum and merger history that yield a rich set of satellite luminosity functions. With new observations of distant satellite systems, we can compare these luminosity functions to satellite systems beyond the Local Group. We find that the luminosity functions of our simulations compare well to observations when the luminosity functions are scaled according to host mass. We use the recently-found relationship between dwarf satellites and host mass in distant satellite systems (Trentham & Tully 2009) to normalize a theoretical, complete luminosity function for the Milky Way (Koposov et al. 2008). The luminosity function of satellites, expressed as a function of the host mass, is given by dN/dM_V= 3.5 x M_host^(0.91) x 10^(0.1 x M_V-10.2), where host mass is given in M_sun. The mass of a host galaxy can be used to...

Nickerson, S; Couchman, H M P; Bailin, J; Wadsley, J

2012-01-01

 
 
 
 
241

The Luminosity and Color Dependence of the Galaxy Correlation Function  

CERN Document Server

We study the luminosity and color dependence of the galaxy 2-point correlation function in the Sloan Digital Sky Survey, starting from a sample of 200,000 galaxies over 2500 deg^2. We concentrate on the projected correlation function w(r_p), which is directly related to the real space \\xi(r). The amplitude of w(r_p) grows continuously with luminosity, rising more steeply above the characteristic luminosity L_*. Redder galaxies exhibit a higher amplitude and steeper correlation function at all luminosities. The correlation amplitude of blue galaxies increases continuously with luminosity, but the luminosity dependence for red galaxies is less regular, with bright red galaxies more strongly clustered at large scales and faint red galaxies more strongly clustered at small scales. We interpret these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters. For most samples, an HOD model with two adjustable parameters fits the w(r_p) data better than a power-law, explain...

Zehavi, I; Weinberg, D H; Frieman, J A; Berlind, Andreas A; Blanton, M R; Scoccimarro, R; Sheth, R K; Strauss, M A; Kayo, I; Suto, Y; Fukugita, M; Nakamura, O; Bahcall, Neta A; Brinkmann, J; Gunn, J E; Hennessy, G S; Ivezic, Z; Knapp, G R; Loveday, J; Meiksin, A; Schlegel, D J; Schneider, D P; Szapudi, I; Tegmark, M; Vogeley, M S; York, D G

2004-01-01

242

The local radio luminosity function of galaxies at 843 MHz  

International Nuclear Information System (INIS)

Following a previous investigation of the radio luminosity function, two samples of galaxies have been observed with the Molonglo Observatory Synthesis Telescope at 843 MHz. These comprise 176 E and SO galaxies, and 21 galaxies with delta <= -45"0. The resulting local radio luminosity function (LRLF) has been extended to radio powers of approx. 10"1"8 WHz"-"1 sr"-"1. At such low luminosities, the irregular galaxies apparently begin to dominate the LRLF. Spirals on the other hand, continue to be confined to radio powers in the range 10sup(19-22) W Hz"-"1 sr"-"1. E and SO galaxies appear unimportant to the LRLF at low radio luminosities but behave like similar standard candles above powers of approx. 10sub(22.5) WHz"-"1 sr"-"1. The most massive SO galaxies appear similar to radio ellipticals, but at lower optical luminosities comparable to those of spirals. In addition SO galaxies resemble early-type spirals closely both in their detection rate and correlation between radio and optical luminosities. (author)

1987-03-15

243

The Luminosities of Protostars in the Spitzer c2d and Gould Belt Legacy Clouds  

CERN Multimedia

Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate Lbol for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 Lsun - 69 Lsun, and has a mean and median of 4.3 Lsun and 1.3 Lsun, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (Lbol < 0.5 Lsun) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 um < wavelength < 850 um) and have Lbol underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source...

Dunham, Michael M; Allen, Lori E; Evans, Neal J; Broekhoven-Fiene, Hannah; Chapman, Nicholas L; Cieza, Lucas A; Gutermuth, Robert A; Harvey, Paul M; Hatchell, Jennifer; Huard, Tracy L; Kirk, Jason M; Matthews, Brenda C; Merin, Bruno; Miller, Jennifer F; Peterson, Dawn E; Spezzi, Loredana

2013-01-01

244

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

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.

2009-07-20

245

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

246

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

CERN Multimedia

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

Dolph, P A M; Averett, T; Kelleher, A; Mooney, K E; Nelyubin, V; Tobias, W A; Wojsekhowski, B; Cates, G D

2011-01-01

247

THE LUMINOSITIES OF PROTOSTARS IN THE SPITZER c2d AND GOULD BELT LEGACY CLOUDS  

Energy Technology Data Exchange (ETDEWEB)

Motivated by the long-standing 'luminosity problem' in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate L{sub bol} for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 L{sub Sun} to 69 L{sub Sun }, and has a mean and median of 4.3 L{sub Sun} and 1.3 L{sub Sun }, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (L{sub bol} {approx}< 0.5 L{sub Sun }) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 {mu}m <{lambda} < 850 {mu}m) and have L{sub bol} underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35%-40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased data set should aid such future work.

Dunham, Michael M.; Arce, Hector G. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Allen, Lori E. [National Optical Astronomy Observatories, Tucson, AZ (United States); Evans II, Neal J.; Harvey, Paul M. [Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States); Broekhoven-Fiene, Hannah; Matthews, Brenda C. [Herzberg Institute, National Research Council of Canada, 5071 W. Saanich Road, Victoria, BC V9E 2E7 (Canada); Chapman, Nicholas L. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, IL 60208 (United States); Cieza, Lucas A. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Hatchell, Jennifer [Astrophysics Group, Physics, University of Exeter, Exeter EX4 4QL (United Kingdom); Huard, Tracy L.; Miller, Jennifer F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Kirk, Jason M. [School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Merin, Bruno [Herschel Science Centre, ESAC-ESA, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Peterson, Dawn E. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Spezzi, Loredana, E-mail: michael.dunham@yale.edu [European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany)

2013-04-15

248

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

CERN Multimedia

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 from...

Bentz, M C; Peterson, B M; Pogge, R W; Vestergaard, M; Bentz, Misty C.; Onken, Christopher A.; Peterson, Bradley M.; Pogge, Richard W.; Vestergaard, Marianne

2006-01-01

249

A luminosity measurement at LEP using the L3 detector  

Energy Technology Data Exchange (ETDEWEB)

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.).

Koffeman, E.N.

1996-06-25

250

MAGNITUDE GAP STATISTICS AND THE CONDITIONAL LUMINOSITY FUNCTION  

International Nuclear Information System (INIS)

In a recent preprint, Hearin et al. (H12) suggest that the halo mass-richness calibration of clusters can be improved by using the difference in the magnitude of the brightest and the second brightest galaxy (magnitude gap) as an additional observable. They claim that their results are at odds with the results from Paranjape and Sheth (PS12) who show that the magnitude distribution of the brightest and second brightest galaxies can be explained based on order statistics of luminosities randomly sampled from the total galaxy luminosity function. We find that a conditional luminosity function (CLF) for galaxies which varies with halo mass, in a manner which is consistent with existing observations, naturally leads to a magnitude gap distribution which changes as a function of halo mass at fixed richness, in qualitative agreement with H12. We show that, in general, the luminosity distribution of the brightest and the second brightest galaxy depends upon whether the luminosities of galaxies are drawn from the CLF or the global luminosity function. However, we also show that the difference between the two cases is small enough to evade detection in the small sample investigated by PS12. This shows that the luminosity distribution is not the appropriate statistic to distinguish between the two cases, given the small sample size. We argue in favor of the CLF (and therefore H12) based upon its consistency with other independent observations, such as the kinematics of satellite galaxies, the abundance and clustering of galaxies, and the galaxy-galaxy lensing signal from the Sloan Digital Sky Survey.

2012-12-20

251

Magnitude Gap Statistics and the Conditional Luminosity Function  

Science.gov (United States)

In a recent preprint, Hearin et al. (H12) suggest that the halo mass-richness calibration of clusters can be improved by using the difference in the magnitude of the brightest and the second brightest galaxy (magnitude gap) as an additional observable. They claim that their results are at odds with the results from Paranjape & Sheth (PS12) who show that the magnitude distribution of the brightest and second brightest galaxies can be explained based on order statistics of luminosities randomly sampled from the total galaxy luminosity function. We find that a conditional luminosity function (CLF) for galaxies which varies with halo mass, in a manner which is consistent with existing observations, naturally leads to a magnitude gap distribution which changes as a function of halo mass at fixed richness, in qualitative agreement with H12. We show that, in general, the luminosity distribution of the brightest and the second brightest galaxy depends upon whether the luminosities of galaxies are drawn from the CLF or the global luminosity function. However, we also show that the difference between the two cases is small enough to evade detection in the small sample investigated by PS12. This shows that the luminosity distribution is not the appropriate statistic to distinguish between the two cases, given the small sample size. We argue in favor of the CLF (and therefore H12) based upon its consistency with other independent observations, such as the kinematics of satellite galaxies, the abundance and clustering of galaxies, and the galaxy-galaxy lensing signal from the Sloan Digital Sky Survey.

More, Surhud

2012-12-01

252

The Luminosity Function of Galaxies in Compact Groups  

CERN Document Server

From R-band images of 39 Hickson compact groups (HCGs), we use galaxy counts to determine a luminosity function extending to M_R=-14.0, approximately two magnitudes deeper than previous compact group luminosity functions. We find that a single Schechter function is a poor fit to the data, so we fit a composite function consisting of separate Schechter functions for the bright and faint galaxies. The bright end is best fit with M^*=-21.6 and alpha=-0.52 and the faint end with M^*=-16.1 and alpha=-1.17. The decreasing bright end slope implies a deficit of intermediate luminosity galaxies in our sample of HCGs and the faint end slope is slightly steeper than that reported for earlier HCG luminosity functions. Furthermore, luminosity functions of subsets of our sample reveal more substantial dwarf populations for groups with x-ray halos, groups with tidal dwarf candidates, and groups with a dominant elliptical or lenticular galaxy. Collectively, these results support the hypothesis that within compact groups, the...

Hunsberger, S D; Zaritsky, D; Hunsberger, Sally D.; Charlton, Jane C.; Zaritsky, Dennis

1998-01-01

253

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

254

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

255

Modeling Luminosity-Dependent Galaxy Clustering Through Cosmic Time  

CERN Document Server

We employ high-resolution dissipationless simulations of the concordance LambdaCDM cosmology to model the observed luminosity dependence and evolution of galaxy clustering through most of the age of the universe, from z~5 to z~0. We use a simple, non-parametric model which monotonically relates galaxy luminosities to the maximum circular velocity of dark matter halos (V_max) by preserving the observed galaxy luminosity function in order to match the halos in simulations with observed galaxies. The novel feature of the model is the use of the maximum circular velocity at the time of accretion, V_max,acc, for subhalos, the halos located within virial regions of larger halos. We argue that for subhalos in dissipationless simulations, V_max,acc reflects the luminosity and stellar mass of the associated galaxies better than the circular velocity at the epoch of observation, V_max,now. The simulations and our model L-V_max relation predict the shape, amplitude, and luminosity dependence of the two-point correlation...

Conroy, C; Kravtsov, A V; Conroy, Charlie; Wechsler, Risa H.; Kravtsov, Andrey V.

2005-01-01

256

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

257

Magnitude Gap Statistics and the Conditional Luminosity Function  

CERN Document Server

In a recent preprint, Hearin et al. (2012,H12) suggest that the halo mass-richness calibration of clusters can be improved by using the difference in the magnitude of the brightest and the second brightest galaxy (magnitude gap) as an additional observable. They claim that their results are at odds with the results from Paranjape & Sheth (2012, PS12) who show that the magnitude distribution of the brightest and second brightest galaxies can be explained based on order statistics of luminosities randomly sampled from the total galaxy luminosity function. We find that a conditional luminosity function (CLF) for galaxies which varies with halo mass, in a manner which is consistent with existing observations, naturally leads to a magnitude gap distribution which changes as a function of halo mass at fixed richness, in qualitative agreement with H12. We show that, in general, the luminosity distribution of the brightest and the second brightest galaxy depends upon whether the luminosities of galaxies are drawn...

More, Surhud

2012-01-01

258

An X-ray luminosity analysis for FRIs and FRIIs  

Science.gov (United States)

Radio galaxies are divided into two groups according to their luminosities at 178 MHz, namely Fanaroff-Riley type Is (FRIs) and Fanaroff-Riley type IIs (FRIIs) with FRIs showing lower radio luminosities than FRIIs. In this paper, the X-ray data are compiled for 183 radio galaxies (61 FRIs and 122 FRIIs), from the available literature, for the analysis of the X-ray properties. The 1 keV X-ray luminosities are calculated and discussed for the two groups, and an averaged X-ray luminosity of log L {X/1 keV} = 41.30±2.51 erg·s-1·keV-1 is found for FRIs, which is lower than that for FRIIs, log L {X/1 keV} = 43.39±3.06 erg·s-1·keV-1. A Kolmogorov-Smirnov (K-S) test indicates that the probability for the X-ray luminosity distributions of the two groups to be from the same parent distribution is 1.44×10-10. We also discuss the origin and the mechanism of the X-ray emission for FRIs and FRIIs.

Zhang, Chunling; Fan, Junhui

2009-09-01

259

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

260

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

 
 
 
 
261

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

262

The Ks-band Luminosity and Stellar Mass Functions of Galaxies in z~1 Clusters  

CERN Document Server

We present the near-infrared (Ks-band) luminosity function of galaxies in two z~1 cluster candidates, 3C336 and Q1335+28. A third cluster, 3C289, was observed but found to be contaminated by a foreground system. Our wide field imaging data reach to Ks=20.5 (5sigma), corresponding to ~M*+2.7 with respect to the passive evolution. The near-infrared luminosity traces the stellar mass of a galaxy due to its small sensitivity to the recent star formation history. Thus the luminosity function can be transformed to the stellar mass function of galaxies using the $J-K$ colours with only a small correction (factor>1) in the cluster core, it seems that the galaxy formation processes (both star formation and mass assembly) are strongly accerelated in dense environments and has been largely completed by z=1. We investigate whether the epoch of mass assembly of massive cluster galaxies is earlier than that predicted by the hierarchical galaxy formation models. These models predict the increase of characteristic mass by mo...

Kodama, T; Kodama, Tadayuki

2003-01-01

263

Truncation of the Inner Accretion Disk around a Black Hole at Low Luminosity  

CERN Document Server

Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Measurements of the location of the inner edge (Rin) can be made using iron emission lines that arise due to fluorescence of iron in the disk, and these indicate that Rin is very close to the black hole at high and moderate luminosities (near 1% of the Eddington luminosity, Ledd). Here, we report on X-ray observations of the black hole GX 339-4 in the hard state by Suzaku and the Rossi X-ray Timing Explorer (RXTE) that extend iron line studies to 0.14% Ledd and show that Rin increases by a factor of >27 over the value found when GX 339-4 was bright. The exact value of Rin depends on the inclination of the inner disk (i), and we derive 90% confidence limits of Rin > 35 Rg at i = 0 degrees and Rin > 175 Rg at i = 30 degrees. This provides...

Tomsick, John A; Corbel, Stephane; Kaaret, Philip; Kalemci, Emrah; Migliari, Simone

2009-01-01

264

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

CERN Multimedia

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

265

Luminosity-dependent unification of Active Galactic Nuclei and the X-ray Baldwin effect  

CERN Document Server

The existence of an anti-correlation between the equivalent width (EW) of the narrow core of the iron Kalpha line and the luminosity of the continuum (i.e. the X-ray Baldwin effect) in type-I active galactic nuclei has been confirmed over the last years by several studies carried out with XMM-Newton, Chandra and Suzaku. However, so far no general consensus on the origin of this trend has been reached. Several works have proposed the decrease of the covering factor of the molecular torus with the luminosity (in the framework of the luminosity-dependent unification models) as a possible explanation for the X-ray Baldwin effect. Using the fraction of obscured sources measured by recent X-ray and IR surveys as a proxy of the half-opening angle of the torus, and the recent Monte-Carlo simulations of the X-ray radiation reprocessed by a structure with a spherical-toroidal geometry by Ikeda et al. (2009) and Brightman & Nandra (2011), we test the hypothesis that the X-ray Baldwin effect is related to the decreas...

Ricci, Claudio; Awaki, Hisamitsu; Petrucci, Pierre-Olivier; Ueda, Yoshihiro; Brightman, Murray

2013-01-01

266

Can photo-ionization explain the decreasing fraction of X-ray obscured AGN with luminosity?  

CERN Document Server

Chandra and XMM surveys show that the fraction of obscured AGN decreases rapidly with increasing luminosity. Although this is usually explained by assuming that the covering factor of the central engine is much smaller at luminous QSOs, the exact origin of this effect remains unknown. We perform toy simulations to test whether photo-ionisation of the obscuring screen in the presence of a strong radiation field can reproduce this effect. In particular, we create X-ray spectral simulations using a warm absorber model assuming a range of input column densities and ionization parameters. We fit instead the simulated spectra with a simple cold absorption power-law model that is the standard practice in X-ray surveys. We find that the fraction of absorbed AGN should fall with luminosity as $L^{-0.16\\pm0.03}$ in rough agreement with the observations. Furthermore, this apparent decrease in the obscuring material is consistent with the dependence of the FeK$\\alpha$ narrow-line equivalent width on luminosity, ie. the X...

Akylas, A

2008-01-01

267

The rest-frame optical luminosity functions of galaxies at 2  

CERN Document Server

[ABRIDGED] We present the rest-frame optical (B, V, and R-band) luminosity functions (LFs) of galaxies at 22 are consistent with those in the local LFs. The characteristic magnitudes are significantly brighter than the local values, while the measured values for Phi_star are a factor of ~5 smaller with respect to the local values. By integrating the LFs, we estimate the number and luminosity densities. We present for the first time the LF of Distant Red Galaxies (DRGs; defined here as z>2 sources with observed J-K>2.3). While DRGs and non-DRGs are characterized by similar LFs at the bright end, the faint-end slope of the non-DRG LF is much steeper than that of DRGs. Comparing the rest-frame V-band LF of non-DRGs to that inferred for Lyman break galaxies by Shapley et al. (2001), we find a significantly less steep faint-end slope. The contribution of DRGs to the global densities is 14%-25% in number and 22%-33% in luminosity. From the rest-frame U-V colors and stellar population synthesis models, we estimate t...

Marchesini, D; Quadri, R; Rudnick, G; Franx, M; Lira, P; Wuyts, S; Gawiser, E; Christlein, D; Toft, S; Marchesini, Danilo; Dokkum, Pieter van; Quadri, Ryan; Rudnick, Gregory; Franx, Marijn; Lira, Paulina; Wuyts, Stijn; Gawiser, Eric; Christlein, Daniel; Toft, Sune

2006-01-01

268

High luminosity interaction region design for collisions with detector solenoid  

CERN Document Server

An innovatory interaction region has been recently conceived and realized on the Frascati DA{\\Phi}NE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evolved towards enhanced beam focusing at the interaction point with large horizontal crossing angle, thanks to a new compensation mechanism for the beam-beam resonances. The novel configuration has been tested with a small detector without solenoidal field yielding a remarkable improvement in terms of peak as well as integrated luminosity. The high luminosity interaction region has now been modified to host a large detector with a strong solenoidal field which significantly perturbs the beam optics introducing new design challenges in terms of interaction region optics design, beam transverse coupling control and beam stay clear requirements

Milardi, C; Raimondi, P; Sensolini, G; Sgamma, F

2010-01-01

269

HIGH LUMINOSITY INTERACTION REGION DESIGN FOR COLLISIONS WITH DETECTOR SOLENOID  

CERN Document Server

An innovatory interaction region has been recently conceived and realized on the Frascati DANE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evolved towards enhanced beam focusing at the interaction point with large horizontal crossing angle, thanks to a new compensation mechanism for the beam-beam resonances. The novel configuration has been tested with a small detector without solenoidal field yielding a remarkable improvement in terms of peak as well as integrated luminosity. The high luminosity interaction region has now been modified to host a large detector with a strong solenoidal field which significantly perturbs the beam optics introducing new design challenges in terms of interaction region optics design, beam transverse coupling control and beam stay clear requirements.

Milardi, C; Raimondi, P; Sensolini, G; Sgamma, F

2010-01-01

270

The Correlation Between Galaxy HI Linewidths and K' Luminosities  

CERN Document Server

The relationship between galaxy luminosities and rotation rates is studied with total luminosities in the K' band. Extinction problems are essentially eliminated at this band centered at 2.1 micron. A template luminosity-linewidth relation is derived based on 65 galaxies drawn from two magnitude-limited cluster samples. The zero-point is determined using 4 galaxies with accurately known distances. The calibration is applied to give the distance to the Pisces Cluster (60 Mpc) at a redshift in the CMB frame of 4771 km/s. The resultant value of the Hubble Constant is 81 km/s/Mpc. The largest sources of uncertainty arises from the small number of zero-point calibrators at this time at K' and present application to only one cluster.

Rothberg, B; Tully, R B; Witchalls, P L

1999-01-01

271

Modeling Large Populations: Steep Luminosity Functions and Redshift Distribution Artifacts  

Science.gov (United States)

The luminosity function (LF) of distant objects and its redshift dependence are important quantities in understanding the physics of the population studied and its cosmological evolution. We show that popular forms of cosmological evolution (power law and exponential dependence) used to model the redshift dependence of the observed luminosity functions can lead to unrealistic low redshift spikes in the model redshift distributions in the case ofsteep (power law index mask these artifacts. We favor the solution in which the LF becomes shallower at lower luminosities but for samples in which the break in the LF cannot be detected, using special forms of the evolution function may be a viable option. We suggest that it is important to always compare the model and observed redshift distributions even when the other distributions seem to be in agreement.

Cara, Mihai; Perlman, E. S.

2010-01-01

272

Resolving the Luminosity Problem in Low-Mass Star Formation  

CERN Document Server

We determine the observational signatures of protostellar cores by coupling two-dimensional radiative transfer calculations with numerical hydrodynamical simulations that predict accretion rates that both decline with time and feature short-term variability and episodic bursts caused by disk gravitational instability and fragmentation. We calculate the radiative transfer of the collapsing cores throughout the full duration of the collapse, using as inputs the core, disk, and protostellar masses, radii, and mass accretion rates predicted by the hydrodynamical simulations. From the resulting spectral energy distributions, we calculate standard observational signatures (bolometric luminosity, bolometric temperature, ratio of bolometric to submillimeter luminosity) to directly compare to observations. We show that the accretion process predicted by these models reproduces the full spread of observed protostars in both Lbol - Tbol and Lbol - core mass space, including very low luminosity objects, provides a reason...

Dunham, Michael M

2011-01-01

273

ATLAS Future Plans: Upgrade and the Physics with High Luminosity  

CERN Document Server

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 $\\rm 5x10^{34}\\ cm^{-2}s^{-1}$. 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; The ATLAS collaboration

2013-01-01

274

Luminosity function of faint galaxies with ultraviolet continuum  

International Nuclear Information System (INIS)

The spatial density of faint galaxies with ultraviolet continuum in the Second Survey of the Byurakan Astrophysical Observatory is determined. The luminosity function of galaxies with ultraviolet continuum can be extended to objects fainter by 1-1.5 magnitudes. The spatial density of such galaxies in the interval of luminosities -16 /sup m/ .5 to -21 /sup m/ .5 is on the average 0.08 of the total density of field galaxies in the same interval of absolute magnitudes. The spatial density of low-luminosity galaxies with ultraviolet continuum is very high. In the interval from -12 /sup m/ .5 to -15 /sup m/ .5 it is 0.23 Mpc-3

1985-05-01

275

On the Radio and Optical Luminosity Evolution of Quasars  

CERN Document Server

We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness, 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...

Singal, J; Lawrence, A; Stawarz, L

2011-01-01

276

Analysis of Luminosity Data in BaBar  

International Nuclear Information System (INIS)

Luminosity is a value describing the number of interactions between particles when their respective beams collide. The BaBar (B and B-bar) ambient database and the Oracle server contain archived measurements of instantaneous luminosity from two separate detectors. It is important to understand these data to describe the performance of the B-Factory. Extracting these data, the more reliable PEP-II (Positron Electron Two) luminosity detector can be calibrated to the data collected by the more accurate BaBar L3 (Level 3) detector. Using the ROOT programming language and standard BaBar tools for data extraction, graphs and statistics are generated. Some logistical errors contained in the logbook are also corrected. These programs help aid in understanding both what is happening within the B-Factory, as well as the correlations between the interrelationship of detector data and the information recorded in the logbook

2004-01-01

277

Mass and luminosity evolution of young stellar objects  

CERN Document Server

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 protostars and pre-main sequence (PMS) stars, and from the modal value of the protostar luminosity. In 31 embedded clusters and complexes the global cluster age is 1-3 Myr, matching available estimates based on optical spectroscopy and evolutionary tracks. This method of age estimation is simpler than optical spectroscopy, and is more useful for young embedded clusters where optical spectrocopy is not possible. In the youngest clusters, the protostar fraction decreases outward from the densest gas, indicating that the local star-forming a...

Myers, Philip C

2012-01-01

278

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

1996-11-04

279

Report of the Working Group on High Luminosities at LEP  

International Nuclear Information System (INIS)

The availability of an order-of-magnitude increase in the luminosity of LEP (CERN's Large Electron-Positron Collider) can dramatically increase its physics output. With the help of a pretzel scheme, it should be possible to increase the peak luminosity beyond 1032 cm-2 s-1 at the Z energy and to significantly increase the luminosity around the W-pari threshold. This report spells out the physics possibilities opened up by the availability of several 107Z events. The three domains of physics that benefit mostly from this abundance are very accurate measurements of Standard Model parameters, rare decays of the Z, and the physics of fermion-antifermion states such as B physics. The possibilities and implications for the machine and the experiments are presented. The physics possibilities are explored and compared with those at other accelerators. (orig.)

1991-01-01

280

Determination of the Luminosity by the LHC Experiments  

International Nuclear Information System (INIS)

The high resolution of the LHCb vertex detector allows for precise measurements of vertex positions of beam-gas and beam-beam interactions. From these measurements beam parameters such as width and position can be inferred. A novel method will be presented for determining the absolute luminosity at the LHC using these directly measured beam parameters, in combination with beam intensity information provided by the accelerator. Results will be shown for both the 2009 and 2010 run, and prospects for the ultimate precision of this method will be discussed. A forward look will also be given to alternative methods of luminosity determination which with data samples of ?1 fb-1 will offer the possibility of ?1% level precision. These include measurements of the production rate of elastic two photon dimuon production, and studies based on W and Z production in the forward region. In addition, luminosity measurements at ATLAS and CMS will also be discussed. (author)

2010-07-22

 
 
 
 
281

Global luminosity function of the Fornax dwarf elliptical galaxy  

International Nuclear Information System (INIS)

UK Schmidt plates in B and V are used to obtain the global luminosity function for the Fornax dwarf elliptical galaxy. Both functions are shown to provide evidence of structure in the giant branch. The results indicate that the old population of Fornax is similar to that of such moderately metal-poor clusters as M5 and M13, and they demonstrate the existence of a significant excess population of very bright stars over that seen in pure old systems. Theoretical luminosity functions of various ages and helium abundances are not found to provide good fits to the observed luminosity functions, suggesting that Fornax has had a star-formation history more complex than the two-burst models considered. 51 references

1987-01-01

282

The observational consequences of an intrinsic burst luminosity distribution  

International Nuclear Information System (INIS)

The Galactic monoluminosity gamma burst models of Jennings and White (1980) are generalized to encompass intrinsic burst luminosity distributions. LogN-LogS is markedly affected by distributions moderately peaked toward low luminosity and of dynamic range greater than about 0.01. Spherical or 'Halo' distributions, which are unacceptable for monoluminosity sources, are, together with Disk distributions, compatible with LogN-LogS observations when an intrinsic variation in burst luminosity is introduced. The generalized models are used in predicting source angular distributions versus LogS. It is found that neither Disk nor Halo geometries can reconcile the present LogN-LogS and angular position observations. The significance of this is analyzed

1982-01-01

283

The jets and disc of SS 433 at super-Eddington luminosities  

Science.gov (United States)

We examine the jets and the disc of SS 433 at super-Eddington luminosities with by time-dependent two-dimensional radiation hydrodynamical calculations, assuming an ?-model for the viscosity. One-dimensional supercritical accretion disc models with mass loss or advection are used as the initial configurations of the disc. As a result, from the initial advective disc models with ? = 0.001 and 0.1, we obtain total luminosities ~2.5 × 1040 and 2.0 × 1040ergs-1. The total mass-outflow rates are ~4 × 10-5 and 10-4Msolaryr-1, and the rates of the relativistic axial outflows in a small half opening angle of ~1° are about 10-6Msolaryr-1: the values are generally consistent with the corresponding observed rates of the wind and the jets, respectively. From the initial models with mass loss but without advection, we obtain total mass-outflow and axial outflow rates smaller than or comparable to the observed rates of the wind and the jets, respectively, depending on ?. In the advective disc model with ? = 0.1, the initially radiation-pressure-dominant, optically thick disc evolves to a gas-pressure-dominated, optically thin state in the inner region of the disc, and the inner disc is unstable. Consequently, we find remarkable modulations of the disc luminosity and the accretion rate through the inner edge. These modulations manifest themselves as recurrent hot blobs with high temperatures and low densities at the disc plane, which develop outwards and upwards and produce quasi-periodic oscillations (QPOs) of the total luminosity with an amplitude of a factor of ~2 and quasi-periods of ~10-25 s. This may explain the massive jet ejection and the QPO phenomena observed in SS 433.

Okuda, T.; Lipunova, G. V.; Molteni, D.

2009-10-01

284

MODELING THE RED SEQUENCE: HIERARCHICAL GROWTH YET SLOW LUMINOSITY EVOLUTION  

International Nuclear Information System (INIS)

We explore the effects of mergers on the evolution of massive early-type galaxies by modeling the evolution of their stellar populations in a hierarchical context. We investigate how a realistic red sequence population set up by z ? 1 evolves under different assumptions for the merger and star formation histories, comparing changes in color, luminosity, and mass. The purely passive fading of existing red sequence galaxies, with no further mergers or star formation, results in dramatic changes at the bright end of the luminosity function and color-magnitude relation. Without mergers there is too much evolution in luminosity at a fixed space density compared to observations. The change in color and magnitude at a fixed mass resembles that of a passively evolving population that formed relatively recently, at z ? 2. Mergers among the red sequence population ('dry mergers') occurring after z = 1 build up mass, counteracting the fading of the existing stellar populations to give smaller changes in both color and luminosity for massive galaxies. By allowing some galaxies to migrate from the blue cloud onto the red sequence after z = 1 through gas-rich mergers, younger stellar populations are added to the red sequence. This manifestation of the progenitor bias increases the scatter in age and results in even smaller changes in color and luminosity between z = 1 and z = 0 at a fixed mass. The resultant evolution appears much slower, resembling the passive evolution of a population that formed at high redshift (z ? 3-5), and is in closer agreement with observations. We conclude that measurements of the luminosity and color evolution alone are not sufficient to distinguish between the purely passive evolution of an old population and cosmologically motivated hierarchical growth, although these scenarios have very different implications for the mass growth of early-type galaxies over the last half of cosmic history.

2012-07-01

285

Development and Commissioning of the CMS Luminosity Readout System  

CERN Document Server

We discuss the development and commissioning of a luminosity monitor. It is based on hardware that provides realtime histograms of data from the forward hadronic calorimeters in CMS. Measuring the total energy deposition and occupancy in these detectors allows us to calculate the relative instantaneous luminosity of the collider on a bunch by bunch basis, which is useful for machine diagnostics. Once calibrated with measurements from the LHC we will be able to make the first proton-proton inelastic cross-section measurement. Further information on the calculations themselves can be found in [1]. This paper discusses the readout hardware design and implementation.

Jones, J

2007-01-01

286

Luminosity dependence of the quasar clustering from SDSS NBCKDE catalogue  

International Nuclear Information System (INIS)

We study the clustering of quasars from the SDSS NBCKDE catalogue of photometrically selected quasar candidates (SDSS DR6). Dividing our sample with 0.8phot<2.2 onto three luminosity bins we have found no evidence for luminosity dependence of the quasar clustering. It is consistent with the models of the quasar formation, in which bring and faint quasars are assumed to be similar sources, hosted by dark matter halos of similar masses, but observed at different stages of their evolution

2012-11-21

287

The ATLAS and CMS Plans for the LHC Luminosity Upgrade  

CERN Document Server

In January 2007 the CERN director general announced the plan for the staged upgrade of the LHC luminosity. The plan foresees a phase 1 upgrade reaching a peak luminosity of $3 \\times 10^{34}$ cm$^{-2}$s$^{-1}$ followed by phase reaching up to $ 10^{35}$ cm$^{-2}$s$^{-1}$. We discuss the physics potential and the experimental challenges of an upgraded LHC running. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are also discussed.

Bortoletto, Daniela

2008-01-01

288

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 approximately 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

1980-06-01

289

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

290

The Evolution of the Optical and Near-Infrared Galaxy Luminosity Functions and Luminosity Densities to z~2  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using Hubble Space Telescope and ground-based U through K- band photometry from the Great Observatories Origins Deep Survey (GOODS), we measure the evolution of the luminosity function and luminosity density in the rest-frame optical (UBR) to z ~ 2, bridging the poorly explored ``redshift desert'' between z~1 and z~2. We also use deep near-infrared observations to measure the evolution in the rest-frame J-band to z~1. Compared to local measurements from the SDSS, we find a b...

Dahlen, Tomas; Mobasher, Bahram; Somerville, Rachel S.; Moustakas, Leonidas A.; Dickinson, Mark; Ferguson, Henry C.; Giavalisco, Mauro

2005-01-01

291

Luminosity Variations Along Bunch Trains in PEP-II  

Energy Technology Data Exchange (ETDEWEB)

In the spring of 2005 after a long shut-down, the luminosity of the B-Factory PEP-II decreased along the bunch trains by about 25-30%. There were many reasons studied which could have caused this performance degradation, like a bigger phase transient due to an additional RF station in the Low-Energy-Ring (LER), bad initial vacuum, electron cloud, chromaticity, steering, dispersion in cavities, beam optics, etc. The initial specific luminosity of 4.2 sloped down to 3.2 and even 2.8 for a long train (typical: 130 of 144), later in the run with higher currents and shorter trains (65 of 72) the numbers were more like 3.2 down to 2.6. Finally after steering the interaction region for an unrelated reason (overheated BPM buttons) and the consequential lower luminosity for two weeks, the luminosity slope problem was mysteriously gone. Several parameters got changed and there is still some discussion about which one finally fixed the problem. Among others, likely candidates are: the LER betatron function in x at the interaction point got reduced, making the LER x stronger, dispersion reduction in the cavities, and finding and fixing a partially shorted magnet.

Decker, F.J.; Boyes, M.; Colocho, W.S.; Novokhatski, A.; Sullivan, M.K.; Turner, J.L.; Weathersby, S.P.; Wienands, U.; Yocky, G.; /SLAC

2007-05-18

292

Calorimeters for absolute luminosity at upgraded DA?NE  

International Nuclear Information System (INIS)

This paper describes the LUMI project which aims at providing fast, reliable and absolute luminosity measurements at the modified DA?NE interaction point in Frascati for testing the new 'crabbed waist' scheme. We present a description of the experimental setup (two luminometers, LUMI1 and LUMI2), the simulation framework developed for this project and summarize the results and performances.

2009-04-01

293

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

CERN Multimedia

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

294

Indicators of Intrinsic AGN Luminosity: a Multi-Wavelength Approach  

CERN Multimedia

We consider five indicators for intrinsic AGN luminosity: the luminosities of the [OIII]$\\lambda$5007 line, the [OIV]25.89$\\mu$m line, the mid-infrared (MIR) continuum emission by the torus, and the radio and hard X-ray (E $>$ 10keV) continuum emission. We compare these different proxies using two complete samples of low-redshift type 2 AGN selected in a homogeneous way based on different indicators: an optically selected [OIII] sample and a mid-infrared selected 12$\\mu$m sample. We examine the correlations between all five different proxies, and find better agreement for the [OIV], MIR, and [OIII] luminosities than for the hard X-ray and radio luminosities. Next, we compare the ratios of the fluxes of the different proxies to their values in unobscured Type 1 AGN. The agreement is best for the ratio of the [OIV] and MIR fluxes, while the ratios of the hard X-ray to [OIII], [OIV], and MIR fluxes are systematically low by about an order-of-magnitude in the Type 2 AGN, indicating that hard X-ray selected sample...

LaMassa, Stephanie M; Ptak, Andrew; Martins, Lucimara; Wild, Vivienne; Sonnentrucker, Paule; Tremonti, Christy

2010-01-01

295

Absorbers for the high luminosity insertions of the LHC  

International Nuclear Information System (INIS)

At design luminosity and inelastic cross section ?pp = 80mb there are 8 x 108 inelastic collisions per second at the high luminosity interaction points IP1 and IP5 of the LHC. These interactions give rise to ? 0.9 kW of power in collision products leaving an IP in each direction. The inelastic collision power carried off by neutrals, mostly neutrons and photons, in each direction and intercepted by neutral absorbers (TAN) has been estimated with the MARS13 code to be 210W. Similarly the collision power escaping the beam tube and incident on the front face of the inner triplet quadrupole absorber (TAS) has been estimated to be ? 270W, mostly carried by charged pions and photons. Special purpose absorbers must intercept this power to prevent quenching the inner triplet quadrupoles (Q1 to Q3) and the twin aperture magnets outside the second beam separation dipole D2. Because of the high incident flux of collision products near zero degrees the absorbers are natural places to consider for the location of radiation hard gas ionization detectors which could be used for: (1) measurement of luminosity, (2) measurement of the beam transverse dimensions at the IP and (3) feedback control of the colliding beam centers at the IP's to maximize luminosity. The following sections describe: (1) the conceptual design of the absorbers, (2) the radiation deposition and activation calculations and (3) the possibilities for instrumentation

1998-06-22

296

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

297

Calorimeters for absolute luminosity at upgraded DAphiNE  

Science.gov (United States)

This paper describes the LUMI project which aims at providing fast, reliable and absolute luminosity measurements at the modified DAphiNE interaction point in Frascati for testing the new "crabbed waist" scheme. We present a description of the experimental setup (two luminometers, LUMI1 and LUMI2), the simulation framework developped for this project and summarize the results and performances.

Romano, V.; Schioppa, M.; Bossi, F.; Buonomo, B.; Mazzitelli, G.; Murtas, F.; Raimondi, P.; Arnaud, N.; Breton, D.; Roudeau, P.; Stocchi, A.; Variola, A.; Viaud, B.; Valente, P.; Branchini, P.

2009-04-01

298

LINERs as Low-Luminosity Active Galactic Nuclei  

CERN Multimedia

Many nearby galaxies contain optical signatures of nuclear activity in the form of LINER nuclei. LINERs may be the weakest and most common manifestation of the quasar phenomenon. The physical origin of this class of objects, however, has been ambiguous. I draw upon a number of recent observations to argue that a significant fraction of LINERs are low-luminosity active galactic nuclei.

Ho, L C

1998-01-01

299

Optimization of Integrated Luminosity of the Fermilab Tevatron Collider  

CERN Multimedia

We present the strategy which has been used recently to optimize integrated luminosity at the Fermilab Tevatron proton-antiproton collider. We use a relatively simple model where we keep the proton intensity fixed, use parameters from fits to the luminosity decay of recent stores as a function of initial antiproton intensity (stash size), and vary the stash size to optimize the integrated luminosity per week. The model assumes a fixed rate of antiproton production, that a store is terminated as soon as the target stash size for the next store is reached, and that the only downtime is due to store turn-around time. An optimal range of stash sizes is predicted. Since the start of Tevatron operations based on this procedure, we have seen an improvement of approximately 35% in integrated luminosity. Other recent operational improvements have been achieved by decreasing the shot-setup time and by reducing beam-beam effects by making the proton and antiproton brightnesses more compatible, for example by scraping pr...

Convery, M E

2009-01-01

300

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

 
 
 
 
301

Rotation Velocities of Two Low Luminosity Field Galaxies  

CERN Document Server

We present H-alpha rotation curves of two low luminosity field galaxies with r-band absolute magnitudes M_r=-13.9^{+0.8}_{-0.5} and M_r=-14.7^{+0.3}_{-0.2} (for h=0.7; the large error bars reflect distance uncertainties). Most previously studied galaxies in this luminosity range are members of groups defined by brighter galaxies, but these two systems, selected from Blanton et al.'s (2004) sample of low luminosity galaxies in the Sloan Digital Sky Survey (SDSS), appear to have no bright companions. The measured rotation speeds at the outer extent of the H-alpha rotation curves, 34.8+/-3.8 km/s and 30.9+/-7.2 km/s, are larger than the values of 16.0^{+6.1}_{-5.4} km/s and 20.9^{+6.2}_{-5.2} km/s predicted by extrapolating the inverse Tully-Fisher relation of luminous SDSS galaxies to these faint luminosities. However, a previous HI measurement of the first galaxy shows that it has a gas mass similar to its stellar mass, and the total baryonic mass is consistent with that predicted by McGaugh et al.'s (2000) "b...

Pizagno, J; Weinberg, D H; Bahcall, Neta A; Brinkmann, J; Pizagno, James; Blanton, Michael R.; Weinberg, David H.; Bahcall, Neta A.; Brinkmann, Jon

2004-01-01

302

Physics of a high-luminosity Tau-Charm Factory  

International Nuclear Information System (INIS)

This paper highlights the physics capabilities of a Tau-Charm Factory; i.e., high luminosity (?10"3"3cm"-"2s"-"1) e"+e"- collider operating in the center-of-mass energy range of 3-5 GeV, with a high-precision, general-purpose detector. Recent developments in ? and charm physics are emphasized

1992-09-08

303

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

304

Theoretical analysis of luminosity drop in red giant branch evolution  

International Nuclear Information System (INIS)

Recent evolutionary computations of stars in the globular clusters show that the star ascending up the red giant branch decreases its luminosity temporarily when the outward advancing hydrogen-burning shell passes over the discontinuity in the chemical compositions, which is the trace of maximum inward penetration of the convective envelope in the previous subgiant stage. To understand the physical circumstance of this luminosity drop, the semi-analytical approach using the classical red giant model was applied. The difference of the present analysis from those with usual models of the red giant is that the gradient and the discontinuity in the hydrogen profile, which were usually neglected in the classical red giant model, in the region into which the hydrogen-burning shell advances were taken into account explicitly. It was found that the luminosity would always drop at the critical stage, the stage when the hydrogen-burning shell just passes over the discontinuity. It was also pointed out that the luminosity drop depends on the time step chosen for constructing the stellar evolutionary models and computations with crude time step would fail to catch up this phenomenon. (orig.)

1981-01-01

305

Optimization of Integrated Luminosity of the Fermilab Tevatron Collider  

International Nuclear Information System (INIS)

We present the strategy which has been used recently to optimize integrated luminosity at the Fermilab Tevatron proton-antiproton collider. We use a relatively simple model where we keep the proton intensity fixed, use parameters from fits to the luminosity decay of recent stores as a function of initial antiproton intensity (stash size), and vary the stash size to optimize the integrated luminosity per week. The model assumes a fixed rate of antiproton production, that a store is terminated as soon as the target stash size for the next store is reached, and that the only downtime is due to store turn-around time. An optimal range of stash sizes is predicted. Since the start of Tevatron operations based on this procedure, we have seen an improvement of approximately 35% in integrated luminosity. Other recent operational improvements have been achieved by decreasing the shot-setup time and by reducing beam-beam effects by making the proton and antiproton brightnesses more compatible, for example by scraping protons to smaller emittances

2009-07-26

306

ATLAS CNI Experiment Total Cross Sections and Luminosity  

CERN Document Server

The absolute luminosity measurement will be performed for the ATLAS detector at LHC during dedicated runs with a precision of a few percents using elastic scattering at very low momentum transfer. The principle of the measurement, the experimental requirements and the last detector performances found in a 2008 test-beam are presented in this article.

Heller, M

2009-01-01

307

Are Most Low-Luminosity AGN Really Obscured?  

CERN Multimedia

At low Eddington ratio (mdot), two effects make it harder to detect AGN given some selection criteria. First, they may transition to a radiatively inefficient state, changing SED shape and dramatically decreasing in optical/IR luminosity. Second, even with fixed accretion physics, AGN are diluted/less luminous relative to their hosts; the magnitude of this depends on host properties and so on luminosity and redshift. These effects lead to differences in observed AGN samples, even at fixed bolometric luminosity and after correction for obscuration. The true Eddington ratio distribution may depend strongly on luminosity, but this will be seen only in surveys robust to dilution and radiative inefficiency (X-ray or narrow-line samples); selection effects imply that AGN in optical samples will have uniformly high mdot. This also implies that different selection methods yield systems with different hosts: the clustering of faint optical/IR sources will be weaker than that of X-ray sources, and optical/IR Seyferts w...

Hopkins, Philip F; Quataert, Eliot; Hernquist, Lars

2009-01-01

308

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

309

LHC Report: Boost in bunches brings record luminosity  

CERN Multimedia

Having hit a luminosity of around 8.4x1032 cm-2 s-1 with 768 bunches per beam, the LHC went into a 5-day machine development (MD) program on Wednesday 4 May. Operators are now working on increasing the number of particle bunches in the machine towards a 2011 maximum of around 1380 bunches. The team is already hitting major milestones, recording another record-breaking peak luminosity on Monday 23 May.   Former LHC Project Leader Lyn Evans (to the right) and Laurette Ponce, the engineer-in-charge when the recent luminosity record was achieved. The MD periods improve our understanding of the machine, with the aim of increasing its short- and long-term performance. This one also included tests of the machine’s configurations for special physics runs and a future high luminosity LHC. It was an intense program and overall it went very well, with most measurements carried out successfully. Highlights included: commissioning a dedicated machine setup for TOTEM and ALFA; succe...

2011-01-01

310

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

311

High Luminosity Issues for DAPhNE Upgrade  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We give an overview of presentations and discussions during the Accelerator Working Group Session dedicated to High Luminosity Issues for a future upgrade of the Frascati e+e- Phi-Factory DAPhNE at the Workshop "e+e- in the 1-2 GeV range: Physics and Accelerator Prospects" held at Alghero (Italy) on 10-13 September 2003.

Ruggiero, F.; Zobov, M.

2004-01-01

312

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.

2010-04-10

313

Machine constraints for experiments in an intermediate luminosity interaction region  

International Nuclear Information System (INIS)

We summarize existing information about the luminosity as a function of clear space between the interaction point and the front of the final-focus triplet, and about the minimum beam pipe dimensions (stay-clear dimensions) in the region. 7 refs., 4 figs., 1 tab

1989-01-01

314

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

315

DISK GALAXIES WITH BROKEN LUMINOSITY PROFILES FROM COSMOLOGICAL SIMULATIONS  

International Nuclear Information System (INIS)

We present smoothed particle hydrodynamics cosmological simulations of the formation of three disk galaxies with a detailed treatment of chemical evolution and cooling. The resulting galaxies have properties compatible with observations: relatively high disk-to-total ratios, thin stellar disks, and good agreement with the Tully-Fisher and the luminosity-size relations. They present a break in the luminosity profile at 3.0 ± 0.5 disk scale lengths while showing an exponential mass profile without any apparent breaks, which is in line with recent observational results. Since the stellar mass profile is exponential, only differences in the stellar populations can be the cause of the luminosity break. Although we find a cutoff for the star formation rate (SFR) imposed by a density threshold in our star formation model, it does not coincide with the luminosity break and is located at 4.3 ± 0.4 disk scale lengths, with star formation going on between both radii. The color profiles and the age profiles are 'U-shaped', with the minimum for both profiles located approximately at the break radius. The SFR to stellar mass ratio increases until the break, explaining the coincidence of the break with the minimum of the age profile. Beyond the break, we find a steep decline in the gas density and, consequently, a decline in the SFR and redder colors. We show that most stars (64%-78%) in the outer disk originate in the inner disk and afterward migrate there. Such stellar migrations are likely the main origin of the U-shaped age profile and, therefore, of the luminosity break.

2009-11-10

316

Constraints on Accretion Disk Physics in Low Luminosity Radio Galaxies  

Science.gov (United States)

It is currently believed that essentially all galaxies harbor a massive black hole in their nuclei. If this is true, then it becomes hard to understand why we do not see the luminosity released by the inevitable accretion of the galaxy ISM onto the black hole in all galaxies. The differences in AGN output between the two classes of narrow-line radio galaxies (FRI and FRII) may hold the vital clue. High radio luminosity FRIIs generally show strong high-excitation narrow lines and are believed to be the obscured counterparts of radio loud quasars. Low radio luminosity FRIs by contrast have weaker, low-ionization lines and low ratios of optical to radio luminosities. A large difference in accretion rate and radiative efficiency between FRI and FRIIs would explain the difference in the optical properties and also provide a new unification between different classes of active galaxies in which the dominant parameter is accretion rate. Spitzer IRAC and MIPS observations already exist for most of a well defined sample of FRIs. However, the previously observed objects are the 'famous' ones, e.g., M87, M84, NGC315, 3C264, 3C31. Thus, the existing datasets are highly selected. Here we propose a very small request to complete the sample. We propose IRAC observations in all 4 bands, and MIPS photometry at 24 and 70 microns of 8, and 7 sources, respectively, for a total request of 1.7 hrs. These observations will complete the sample at very little cost in observing time. The large amount of existing complmentary data at multiple wavebands will greatly enhance the legacy value of the proposed observations. By completing the sample, the proposed IRAC and MIPS observations will produce a well defined and very well studied sample of nearby low luminosity radio galaxies. We will use the completed sample to investigate the properties of the accretion disk radiation, and the circumnuclear obscuring material.

Baum, Stefi; Noel-Storr, Jacob; O'Dea, Christopher

2008-03-01

317

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 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

318

Linear size-extended radio luminosity ( D- P E ) correlation in BL Lacertae objects: evidence for large scale beaming?  

Science.gov (United States)

In this paper, we use the distributions of projected linear size ( D), core- ( P C ) and extended- ( P E ) radio luminosities, to investigate a consequence of relativistic beaming and radio source orientation scenario for low-luminosity extragalactic radio sources. In this scenario, BL Lacertae objects (BL Lacs) are believed to be Fanaroff-Riley type I (FR I) radio galaxies, but with radio axes aligned close to the line of sight. At this orientation, the core emission is greatly enhanced by relativistic Doppler boosting and linear size foreshortened due to geometrical projection. A simple outcome of this scenario is that the extended luminosity is expected to be orientation invariant, but a D- P C correlation is envisaged. Results show that both the relative core dominance ( R) and linear size are strongly correlated with extended luminosity ( r? 0.7). Using the R-distribution and R- P E anti-correlation, we show that the difference in radio core-dominance between FR I radio galaxies and X-ray selected BL Lacs can be accounted for by a bulk Lorentz factor ?˜5-13 and viewing angle ?˜5-15?, which can be understood in terms of the scenario, with relativistic beaming persisting at largest scales.

Odo, F. C.; Ubachukwu, A. A.

2013-10-01

319

Mass-loss rates and luminosity functions of dust-enshrouded AGB stars and red supergiants in the LMC  

CERN Multimedia

A radiative transfer code is used to model the spectral energy distributions of 57 mass-losing Asymptotic Giant Branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC) for which ISO spectroscopic and photometric data are available. As a result we derive mass-loss rates and bolometric luminosities. A gap in the luminosity distribution around M_bol = -7.5 mag separates AGB stars from RSGs. The luminosity distributions of optically bright carbon stars, dust-enshrouded carbon stars and dust-enshrouded M-type stars have only little overlap, suggesting that the dust-enshrouded AGB stars are at the very tip of the AGB and will not evolve significantly in luminosity before mass loss ends their AGB evolution. Derived mass-loss rates span a range from Mdot about 10^-7 to 10^-3 M_sun/yr. More luminous and cooler stars are found to reach higher mass-loss rates. The highest mass-loss rates exceed the classical limit set by the momentum of the stellar radiation field, L/c, by a factor of a few due...

Van Loon, J T; De Koter, A; Trams, N R; Waters, L B F M; Zijlstra, A A; Whitelock, P A; Loup, C; Loon, Jacco Th. van; Trams, Norman R.; Zijlstra, Albert A.; Whitelock, Patricia A.; Loup, Cecile

1999-01-01

320

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

 
 
 
 
321

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

322

Relativistic effects on the observed AGN luminosity distribution  

CERN Multimedia

Recently Zhang (2005) has proposed a model to account for the well established effect that the fraction of type-II AGNs is anti-correlated with the observed X-ray luminosity; the model consists of an X-ray emitting accretion disk coaligned to the dusty torus within the standard AGN unification model. In this paper the model is refined by including relativistic effects of the observed X-ray radiations from the vicinity of the supermassive black hole in an AGN. The relativistic corrections improve the combined fitting results of the observed luminosity distribution and the type-II AGN fraction, though the improvement is not significant. The type-II AGN fraction prefers non- or mildly spinning black hole cases and rules out the extremely spinning case.

Liu, Y; Zhang, X L; Liu, Yuan; Zhang, Shuang Nan; Zhang, Xiao Ling

2006-01-01

323

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

324

Luminosity variations in several parallel auroral arcs before auroral breakup  

Directory of Open Access Journals (Sweden)

Full Text Available Variation of the luminosity in two parallel auroral arcs before auroral breakup has been studied by using digitised TV-data with high temporal and spatial resolution. The intervals when a new arc appears near already existing one were chosen for analysis. It is shown, for all cases, that the appearance of a new arc is accompanied by fading or disappearance of another arc. We have named these events out-of-phase events, OP. Another type of luminosity variation is characterised by almost simultaneous enhancement of intensity in the both arcs (in-phase event, IP. The characteristic time of IP events is 10–20 s, whereas OP events last about one minute. Sometimes out-of-phase events begin as IP events. The possible mechanisms for OP and IP events are discussed.

V. Safargaleev

325

Metallicity effects on synthetic Cepheid Period-Luminosity relations  

CERN Document Server

On the basis of new theoretical results useful predictions concerning the Period-Luminosity (PLR) and Period-Luminosity-Color (PLCR) relations both for optical and infrared magnitudes are presented. It is shown that, following the dependence of the instability strip on metallicity, there is a non negligible dependence of the PLRs and PLCRs on the metallicity of the pulsating stars, mainly for optical bands. In particular theoretical results predict a dependence of the PLR on metals which is reversed with respect to current empirical evaluations. To give a possible explanation for this discrepancy the typical observational procedures used to estimate extragalactic distances through Cepheid PLRs are here tested, with the aim of disentangling, if possible, the reddening and metallicity effects. To this purpose, synthetic PLRs for different metallicities were produced and treated as typical observational samples.

Musella, I

1999-01-01

326

On the kinematic deconvolution of the local neighbourhood luminosity function  

CERN Multimedia

A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three r\\'egimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane parallel models and the epicyclic model. This more realistic model is taylored to account for local neighbourhood density and velocity distribution. The first model is fully investigated both analytically and via means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated via a 5D+2D non-parametric inversion technique where positivity of the underlying luminosity function is explicitely accounted for. It is argued that its future application to d...

Pichon, C

2002-01-01

327

Relativistic Cosmology Number Counts and the Luminosity Function  

CERN Document Server

This paper aims to connect the theory of relativistic cosmology number counts with the astronomical data, practice, and theory behind the galaxy luminosity function (LF). We treat galaxies as the building blocks of the Universe, but ignore most aspects of their internal structures by considering them as point sources. However, we do consider general morphological types in order to use data from galaxy redshift surveys, where some kind of morphological classification is adopted. We start with a general relativistic treatment for a general spacetime, and then link the derived expressions with the LF definition adopted in observational cosmology. Then equations for differential number counts, the related relativistic density per source, and observed and total relativistic energy densities of the universe, and other related quantities are written in terms of the luminosity and selection functions. As an example of how these theoretical/observational relationships can be used, we apply them to test the LF paramete...

Ribeiro, M B; Ribeiro, Marcelo B.; Stoeger, William R.

2003-01-01

328

The origin of the infrared luminosity in Centaurus A  

Science.gov (United States)

The origin of the infrared luminosity in Centaurus A is studied using new tracking and data acquisition techniques which yield diffraction-limited profiles at both 50 and 100 microns. Ninety percent of the 100 micron flux is found to originate in a source which extends 5 kpc along the optical dust lane that bisects the galaxy; the remaining 10 percent comes from an unresolved source coincident with the active radio nucleus. The extended 100 micron emission profile is fully consistent with a uniform disk of thermally radiating particles; when combined with results of previous studies at shorter wavelengths, these measurements indicate that nearly all of the infrared luminosity is produced by thermally emitting grains which are heated by massive young stars distributed throughout the optically thick dust lane.

Joy, Marshall; Lester, Daniel F.; Harvey, Paul M.; Ellis, H. Benton

1988-01-01

329

An Independent Derivation of the Oxford Jet Kinetic Luminosity Formula  

CERN Document Server

This letter presents a theoretical derivation of an estimate for a radio source jet kinetic luminosity. The expression yields jet powers that are quantitatively similar to a more sophisticated empirical relation published by the Willott, Blundell and Rawlings at Oxford. The formula allows one to estimate the jet kinetic luminosity from the measurement of the optically thin radio lobe emission in quasars and radio galaxies. Motivated by recent X-ray observation, the derivation assumes that most of the energy in the lobes is in plasma thermal energy with a negligible contribution from magnetic energy (not equipartition). The close agreement of the two independent expressions makes the veracity of these estimates seem very plausible.

Punsly, B

2005-01-01

330

Calorimeters for absolute luminosity at upgraded DAphiNE  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the LUMI project which aims at providing fast, reliable and absolute luminosity measurements at the modified DAphiNE interaction point in Frascati for testing the new 'crabbed waist' scheme. We present a description of the experimental setup (two luminometers, LUMI1 and LUMI2), the simulation framework developed for this project and summarize the results and performances.

Romano, V; Schioppa, M [Universita della Calabria, Cosenza (Italy); Bossi, F; Buonomo, B; Mazzitelli, G; Murtas, F; Raimondi, P [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Arnaud, N; Breton, D; Roudeau, P; Stocchi, A; Variola, A; Viaud, B [LAL, Orsay (France); Valente, P [INFN Roma ' La Sapienza' , Roma (Italy); Branchini, P, E-mail: Paolo.Branchini@roma3.infn.i [Sez. INFN Roma Tre, Roma (Italy)

2009-04-01

331

The beam-gas method for luminosity measurement at LHCb  

CERN Multimedia

The high resolution of the LHCb vertex detector makes it possible to perform precise measurements of the vertex positions of beam-gas and beam-beam interactions. With these measurements beam parameters such as width and position can be measured. A novel method for determining the absolute luminosity at the LHC using the directly measured beam parameters is presented. The data taken in 2009 is used to illustrate the procedure.

Hopchev, Plamen

2010-01-01

332

THE SIZE-LUMINOSITY DISTRIBUTIONS OF LYMAN-BREAK GALAXIES  

Science.gov (United States)

Lyman-break galaxies (LBGs) comprise the largest sample of star-forming galaxies at z>3 and are crucial to our understanding of galaxy formation and evolution. Their luminosity functions allow us to calculate the cosmic star formation history, and their sizes also provide valuable information about the angular momentum content of the galaxies and dark matter halos. However, due to surface brightness dimming effects, galaxies at high redshifts are especially susceptible to selection effects; it is important to understand the selection effects before we can draw conclusions from the statistics of LBG properties. In this work we will investigate the size--luminosity distribution of LBGs between 3 and 6 with careful modeling of selection effects and measurement errors of size and magnitude. Our modeling is more careful than previous studies because it is performed in the two-dimensional size--magnitude space. The results of this work show that (1) the effective radii of star-forming galaxies likely evolve as H(z)^{-2/3} at a fixed luminosity, (2) the widths of the LBG size distribution are larger than expected from the spin parameter distribution of dark matter halos, and (3) the size--luminosity relation slopes of LBGs are similar to those for late-type disk galaxies in the local universe. These results favor the disk formation theory put forward by Fall & Efstathiou (1980) if the majority of LBGs are disks, but more observational evidence is needed to confirm the kinematical structure of LBGs as well as to explain the widths of the size distribution.

Huang, Kuang-Han; CANDELS Collaboration

2014-01-01

333

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

334

Constraints on the Spatial Distribution and Luminosity function of GRBs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The distance scale to gamma ray bursts has been a subject of scientific debate for almost thirty years. Up to the discovery of afterglows only indirect methods could be used to constrain the distance scale to this objects. I review some of these results, and show the current limits on the spatial distribution and luminosity function of GRBs. The results obtained with different methods indicate that gamma-ray bursts lie at the typical redshifts $z_{ave}$ between 1 and 2, howe...

Bulik, Tomasz

1999-01-01

335

Luminosity limits on white dwarfs in a Galactic shroud  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We place observational constraints on a recently proposed Galactic population, dubbed the shroud (Gyuk & Gates 1999, Gates & Gyuk 2001). The shroud would be a very thick Galactic disk of low luminosity objects, most likely old white dwarfs, proposed to explain the optical depth seen in microlensing surveys towards the Magellanic clouds. The shroud is a simple alternative to the lenses being distributed in a classical, near-spherical dark halo; the advantage of the shroud is ...

Holopainen, Janne; Flynn, Chris

2004-01-01

336

The Luminosities and Diameters of Mira Variables from Hipparcos Parallaxes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hipparcos trigonometrical parallaxes of Mira-type variables have been combined with ground-based angular diameter measurements to derive linear diameters. Of eight stars with ground-based data, six have diameters indicating overtone pulsation whilst two, both with periods over 400 day, are pulsating in the fundamental. Hipparcos parallaxes of 11 Miras have been combined with extensive infrared photometry to determine the zero-point of the Mira period-luminosity relation. ...

Whitelock, P. A.; Leeuwen, F.; Feast, M. W.

1997-01-01

337

RESOLVING THE LUMINOSITY PROBLEM IN LOW-MASS STAR FORMATION  

Energy Technology Data Exchange (ETDEWEB)

We determine the observational signatures of protostellar cores by coupling two-dimensional radiative transfer calculations with numerical hydrodynamical simulations that predict accretion rates that both decline with time and feature short-term variability and episodic bursts caused by disk gravitational instability and fragmentation. We calculate the radiative transfer of the collapsing cores throughout the full duration of the collapse, using as inputs the core, disk, protostellar masses, radii, and mass accretion rates predicted by the hydrodynamical simulations. From the resulting spectral energy distributions, we calculate standard observational signatures (L{sub bol}, T{sub bol}, L{sub bol}/L{sub smm}) to directly compare to observations. We show that the accretion process predicted by these models reproduces the full spread of observed protostars in both L{sub bol}-T{sub bol} and L{sub bol}-M{sub core} space, including very low luminosity objects, provides a reasonable match to the observed protostellar luminosity distribution, and resolves the long-standing luminosity problem. These models predict an embedded phase duration shorter than recent observationally determined estimates (0.12 Myr versus 0.44 Myr), and a fraction of total time spent in Stage 0 of 23%, consistent with the range of values determined by observations. On average, the models spend 1.3% of their total time in accretion bursts, during which 5.3% of the final stellar mass accretes, with maximum values being 11.8% and 35.5% for the total time and accreted stellar mass, respectively. Time-averaged models that filter out the accretion variability and bursts do not provide as good of a match to the observed luminosity problem, suggesting that the bursts are required.

Dunham, Michael M. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States); Vorobyov, Eduard I., E-mail: michael.dunham@yale.edu, E-mail: eduard.vorobiev@univie.ac.at [Institute of Astronomy, University of Vienna, Vienna 1180 (Austria)

2012-03-01

338

ATLAS Inner Tracker Upgrade Simulation for High-Luminosity LHC  

CERN Document Server

Design of new ATLAS Inner Tracker for the High-Luminosity LHC Upgrade is based on detailed simulation of layout geometries. It should satisfy challenging operation and performance requirements: tracks and vertices reconstruction in presence of up to 200 collisions in an event, high radiation doses and up to 12 years of operation. Advanced studies of the existing layout and plans for development of new ones will be presented.

Burdin, S; The ATLAS collaboration; Hayward, H; Styles, N

2013-01-01

339

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

1997-10-20

340

Electron-cloud effects in high-luminosity colliders  

Energy Technology Data Exchange (ETDEWEB)

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.

Zimmermann, F.

1998-01-01

 
 
 
 
341

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

342

Enhanced luminosity of young stellar objects in cometary globules  

Science.gov (United States)

In this study we investigated the effects of external trigger on the characteristics of young stellar objects (YSOs) associated with cometary globules (CGs). We made optical spectroscopy of stars associated with star-forming CGs. We find that the masses of the most massive stars associated with CGs are correlated with the masses of the parent cloud but they are systematically larger than expected for clouds of similar mass from the relation M max-star=0.33 M {cl/0.43} given by Larson (Mon. Not. R. Astron. Soc. 200:159, 1982). We have also estimated the luminosities of the IRAS sources found associated with CGs as a function of cloud mass and then compared them with those of the IRAS sources found associated with isolated opacity class 6 clouds (isolated and relatively away from large star forming regions). We find that the luminosities of IRAS sources associated with CGs are larger than those of the opacity class 6 clouds. These findings support results from recent simulations in which it was shown that the Radiation Driven Implosion (RDI) process, believed to be responsible for the cometary morphology and star formation, can increase the luminosity 1 2 orders of magnitudes higher than those of protostars formed without external triggering due to an increase in accretion rates. Thus implying that the massive stars can have profound influence on the star formation in clouds located in their vicinity.

Maheswar, G.; Bhatt, H. C.

2008-06-01

343

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

344

Status of the luminosity monitor for the PANDA experiment  

International Nuclear Information System (INIS)

A good luminosity monitoring is crucial for the PANDA experiment at the planned antiproton accelerator HESR (FAIR, Darmstadt, Germany). For the measurement of the luminosity one can use the elastic antiproton-proton scattering at extreme forward angles. This exploits the fact that the elastic scattering in the range of very small momentum transfer (and thus very small scattering angle) can be calculated exactly from QED. At larger scattering angles the hadronic component of the elastic scattering dominates and this has to be taken from measurements. Unfortunately there are no or only a few data with large uncertainties available in the momentum range we need for PANDA. The current design for the luminosity monitor are four planes of eight double-sided silicon microstrip detectors with trapezoidal shape. The detector itself has an angular acceptance from 3 to 8 mrad and good spatial resolution due to using sensors with high resolution (50 ?m pitch). An overview of the basic concept and Monte Carlo based performance studies within the PANDARoot framework are presented.

2011-03-21

345

Total Infrared Luminosity Estimation of Resolved and Unresolved Galaxies  

CERN Document Server

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 micron and 24 micron bands. To do so, we use 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. (2008) 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 micron, the warm dust at 24 micron and the cold dust at 70 micron and 160 micron 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 lumin...

Boquien, M; Calzetti, D; Dale, D; Engelbracht, C; Kennicutt, R; Lee, J C; van Zee, L; Moustakas, J

2010-01-01

346

The GRB variability/peak luminosity correlation: new results  

International Nuclear Information System (INIS)

We test the correlation between time variability and isotropic-equivalent peak luminosity found by Reichart et al. (ApJ, 552 (2001) 57) using a set of 26 Gamma-Ray Bursts (GRBs) with known redshift. We confirm the correlation, thought with a larger spread around the best-fit power-law obtained by Reichart et al. which in turn does not provide an acceptable description any longer. In addiction, we find no evidence for correlation between variability and beaming-corrected peak luminosity for a subset of 14 GRBs whose beaming angles have been taken from Ghirlanda et al. (ApJ, 616 (2004) 331). Finally, we investigate the possible connection for some GRBs between the location in the variability/peak luminosity space and some afterglow properties, such as the detectability in the optical band, by adding some GRBs whose redshifts, unknown from direct measurements, have been derived assuming the Amati at al. (AeA, 390 (2002) 81) relationship

2005-01-01

347

The Black Hole Mass - Galaxy Luminosity Relationship for SDSS Quasars  

CERN Multimedia

We investigate the relationship between the mass of the central supermassive black hole, M_bh, and the host galaxy luminosity, L_gal, in a sample of quasars from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H + K features in the composite spectra. We evaluate the evolution in the M_bh - L_gal relationship by examining the redshift dependence of Delta log M_bh, the offset in black hole mass from the local black hole - bulge relationship. There is little systematic trend in Delta log M_bh out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, sigma_*, we find agreement of our derived host luminosities with the locally-observed Faber-Jackson relati...

Salviander, S; Bonning, E W

2014-01-01

348

Order statistics of the early-type galaxy luminosity function  

CERN Multimedia

We apply order statistics (OS) to the bright end ($M_r < -22$) of the luminosity distribution of early-type galaxies spectroscopically identified in the SDSS DR7 catalog. We calculate the typical OS quantities of this distribution numerically, measuring the expectation value and variance of the $k^{th}$ most luminous galaxy in a sample with cardinality $N$ over a large ensemble of such samples. From these statistical quantities we explain why and in what limit the $k^{th}$ most luminous galaxies can be used as standard candles for cosmological studies. Since our sample contains all bright galaxies including the brightest cluster galaxies (BCG), based on OS we argue that BCGs can be considered as statistical extremes of a well-established Schechter luminosity distribution when galaxies are binned by redshift and not cluster-by-cluster. We presume that the reason behind this might be that luminous red ellipticals in galaxy clusters are \\em not random \\em samples of an overall luminosity distribution but bias...

Dobos, Laszlo

2011-01-01

349

Probing the Low-Luminosity XLF in Normal Elliptical Galaxies  

CERN Multimedia

We present the first low luminosity (LX > 5 - 10 1036 erg s-1) X-ray luminosity functions (XLFs) of low-mass X-ray binaries (LMXBs) determined for two typical old elliptical galaxies, NGC 3379 and NGC 4278. Because both galaxies contain little diffuse emission from hot ISM and no recent significant star formation (hence no high-mass X-ray binary contamination), they provide two of the best homogeneous sample of LMXBs. With 110 and 140 ks Chandra ACIS S3 exposures, we detect 59 and 112 LMXBs within the D25 ellipse of NGC 3379 and NGC 4278, respectively. The resulting XLFs are well represented by a single power-law with a slope (in a differential form) of 1.9 0.1. In NGC 4278, we can exclude the break at LX ~ 5 x 1037 erg s-1 that was recently suggested to be a general feature of LMXB XLFs. In NGC 3379 instead we find a localized excess over the power law XLF at ~4 x 1037 erg s-1, but with a marginal significance of ~1.6s. Because of the small number of luminous sources, we cannot constrain the high luminosity ...

Kim, D W; Kalogera, V; King, A R; Pellegrini, S; Trinchieri, G; Zepf, S E; Zezas, A L; Angelini, L; Davies, R L; Gallagher, J S

2006-01-01

350

Modeling the red sequence: Hierarchical growth yet slow luminosity evolution  

CERN Multimedia

We explore the effects of mergers on the evolution of massive early-type galaxies by modeling the evolution of their stellar populations in a hierarchical context. We investigate how a realistic red sequence population set up by z~1 evolves under different assumptions for the merger and star formation histories, comparing changes in color, luminosity and mass. The purely passive fading of existing red sequence galaxies, with no further mergers or star formation, results in dramatic changes at the bright end of the luminosity function and color-magnitude relation. Without mergers there is too much evolution in luminosity at a fixed space density compared to observations. The change in color and magnitude at a fixed mass resemble that of a passively evolving population that formed relatively recently, at z~2. Mergers amongst the red sequence population ("dry mergers") occurring after z=1 build up mass, counteracting the fading of the existing stellar populations to give smaller changes in both color and luminos...

Skelton, Rosalind E; Somerville, Rachel S

2011-01-01

351

Lyman Alpha Constraints on Very Low Luminosity AGN  

CERN Multimedia

Recent surveys have detected Lya emission from z=4.5-6.5 at luminosities as low as 10^41 erg/s. There is good evidence that low numbers of AGN are among observed faint Lya emitters. Combining these observations with an empirical relation between the intrinsic Lya and B-band luminosities of AGN, we obtain an upper limit on the number density of AGN with absolute magnitudes M_B=[-16,-19] at z=4.5-6.5. These AGN are up to two orders of magnitude fainter than those discovered in the Chandra Deep Field, resulting in the faintest observational constraints to date at these redshifts. At z=4.5, the powerlaw slope of the very faint end of the luminosity function of AGN is shallower than the slope observed at lower redshifts, beta -20 is lower than expected from the M_BH-sigma relation by one-two orders of magnitude. Extrapolating from reverberation-mapping studies suggests that these black holes would have M_BH=10^6-10^7 Msun. To facilitate the identification of AGN among observed Lya emitters, we derive observational...

Dijkstra, M; Dijkstra, Mark; Wyithe, Stuart

2006-01-01

352

Effect of pyrene addition on the luminosity of methane flames  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses a study of enhancing the luminosity and hence the heat transfer from methane-air and methane-oxygen flames which is of importance in many processing applications. A kinetic analysis of soot formation by precursors addition shows that particle growth dominates oxidation for molecules larger than C{sub 16} scale hydrocarbons. For normal stoichiometric methane-air or methane-oxygen combustion, only one percent of the methane is converted to acetylene through pyrolysis and only 10% of the acetylene formed (0.1% of the initial methane) grows to particles size of pyrene. Preheating to 1,500 K can increase the production of acetylene and the molecular clusters of C{sub 16}H{sub 10} size to about 0.03%. However, by adding pyrene directly to the methane flame it is suggested that enhancement of soot generation and luminosity can be directly accomplished. The modeling of methane flames with pyrene addition is presented together with experimental verification of the predictions for soot and luminosity enhancement.

Fridman, A.A.; Nestor, S.A.; Saveiliev, A.V.; Zelepouga, S.A.; Kennedy, L.A.

1997-07-01

353

Height distribution of luminosity of molecular nitrogen bands in aurorae  

International Nuclear Information System (INIS)

In rocket experiments performed on Keis island during the winter season of 1972-1973 by means of spectrophotometers intensities of auroral luminosity in the 3000-8000 A spectral range have been measured. The paper deals with the analysis of height distribution of luminosity of the first negative band N_2"+(0-0)lambda 3914 A and second positive band N_2 (0-0)lambda 3371 A of molecular nitrogen in rocket experiments on 13 December 1972. 01.01 UT. and 10 January 1973, 18.34.UT. It is shown that relation volume emission velocities eta (3914)/eta(3371) at heights below 130 km can more than twice exceed the value calculated under the condition of collision interaction of precipitating electron flux with upper atmosphere. Such relatuion values can be satisfactorily explained with regard to collisionless processes in the ionosphere which are developed in bright auroral forms. By the data on auroral luminosity spectral distributions of secondary electron fluxes at different heights are plotted. It is shown that at collective interactions the N_2"+ lambda 3914 A by secondary electron flux can attain approximately 70%. It is shown that at the turbulent layer boundary (120 km) cobcentration growth of secondary electrons occurs

1972-12-13

354

MASS AND LUMINOSITY EVOLUTION OF YOUNG STELLAR OBJECTS  

Energy Technology Data Exchange (ETDEWEB)

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 protostars and pre-main sequence (PMS) stars, and from the modal value of the protostar luminosity. In 31 embedded clusters and complexes, the global cluster age is 1-3 Myr, matching available estimates based on optical spectroscopy (OS) and evolutionary tracks. This method of age estimation is simpler than OS and is more useful for young embedded clusters where optical spectroscopy is not possible. In the youngest clusters, the protostar fraction decreases outward from the densest gas, indicating that the local star-forming age increases outward from a few 0.1 Myr in small protostar-dominated zones to a few Myr in large PMS-dominated zones.

Myers, Philip C., E-mail: pmyers@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2012-06-10

355

Infrared Luminosity Functions of AKARI-SDSS Galaxies  

CERN Document Server

By cross-correlating AKARI infrared (IR) sources with the SDSS galaxies, we identified 2357 infrared galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial FIR bands (9, 18, 65, 90, 140, and 160um) in accurately measuring galaxy SED across the peak of the dust emission at ~100um. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (L_IR) of individual galaxies more accurately. Using this L_IR, we constructed luminosity functions of infrared galaxies at a median redshift of z=0.031, with 4 times larger sample than previous work. The LF agrees well with that at z=0.0082 (RBGS), showing smooth and continuous evolution toward higher redshift LFs measured in the AKARI NEP deep field. The derived local cosmic IR luminosity density is Omega_IR=3.8x10^8 LsunMpc^-3. We separate galaxies into AGN, star-forming, and composite by using the [NII]/Ha vs [OIII]/Hb line ratios. The fraction of AGN show...

Goto, Tomotsugu; Malkan, Matthew; Takagi, Toshinobu; Inami, Hanae; Pearson, Chris; Wada, Takehiko; Matsuhara, Hideo; Yamauchi, Chisato; Takeuchi, Tsutomu T; Nakagawa, Takao; Oyabu, Shinki; Ishihara, Daisuke; Sanders, David B; Floc'h, Emeric Le; Lee, Hyung Mok; Jeong, Woong-Seob; Serjeant, Stephen; Sedgwick, Chris

2011-01-01

356

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 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.

2013-05-10

357

Luminosity limits on white dwarfs in a Galactic shroud  

CERN Document Server

We place observational constraints on a recently proposed Galactic population, dubbed the shroud (Gyuk & Gates 1999, Gates & Gyuk 2001). The shroud would be a very thick Galactic disk of low luminosity objects, most likely old white dwarfs, proposed to explain the optical depth seen in microlensing surveys towards the Magellanic clouds. The shroud is a simple alternative to the lenses being distributed in a classical, near-spherical dark halo; the advantage of the shroud is that it would compose only a fraction of a dark halo's total mass. In this paper, we argue that stars of the Galactic shroud would be detectable in the recent proper motion survey of Oppenheimer et al. (2001) if their absolute luminosities were brighter than M_R_59F = 19.4 or approximately M_V = 18.6. We adopt a range of simple models of the shroud's kinematics and morphology, and the colours and luminosities of its white dwarfs; via Monte-Carlo simulations, we predict the numbers expected in the Oppenheimer et al. survey, which wo...

Holopainen, J; Holopainen, Janne; Flynn, Chris

2004-01-01

358

Theoretical Models of Multi-waveband QSO Luminosity Functions  

CERN Multimedia

Cosmological evolution of the QSO luminosity functions (LFs) xat NIR/optical/X-ray bands for $1.3 \\ltsim z \\ltsim 3.5$ is investigated based on the realistic QSO spectra. The accretion-disk theory predicts that although QSO luminosities only depend on mass-accretion rate, $\\Mdot$, QSO spectra have a dependence on black-hole mass, $M_{BH}$, as well. The smaller $M_{BH}$ is and/or the larger $\\Mdot$ is, the harder becomes the QSO NIR/optical/UV spectrum. We model disk spectra which can reproduce these features and calculated LFs for redshift $z \\sim 3$ with the assumption of new-born QSOs being shining at the Eddington luminosity. The main results are: (i) the observed LFs at optical and X-rays can be simultaneously reproduced. (ii) LFs at optical and X-ray bands are not sensitive to $M_{BH}$, while LFs at NIR bands are; about one order of magnitude difference is expected in volume number densities at $L_{I, J} \\sim 10^{46} \\rm{erg s^{-1}}$ between the case that all QSOs would have the same spectral shape as th...

Hosokawa, T; Kawaguchi, T; Yoshikawa, K; Umemura, M

2001-01-01

359

Cosmological simulations of black hole growth: AGN luminosities and downsizing  

CERN Document Server

In this study, we present a detailed, statistical analysis of black hole (BH) growth and the evolution of active galactic nuclei (AGN) using cosmological hydrodynamic simulations run down to z=0. The simulations self-consistently follow radiative cooling, star formation, metal enrichment, BH growth and associated feedback processes from both supernovae typeII/Ia and AGN. We consider two simulation runs, one with a large co-moving volume of (128 Mpc/h)^3 and one with a smaller volume of (48 Mpc/h)^3 but with a higher mass resolution. Consistently with previous results, our simulations are in reasonably good agreement with BH properties of the local Universe. Furthermore, they can successfully reproduce the evolution of the bolometric AGN luminosity function for both the low- and the high-luminosity end up to z=2.5. The smaller but higher resolution run can match the observational data of the low bolometric luminosity end even up to z=4-5. We also perform a direct comparison with the observed soft and hard X-ra...

Michaela, Hirschmann; Alexandro, Saro; Stefano, Borgani; Andreas, Burkert

2013-01-01

360

Gamma-ray luminosity function of BL Lac objects  

Science.gov (United States)

The gamma-ray luminosity function (GLF) of BL Lac objects is constructed by using a sample of BL Lac objects with redshifts selected from the Second LAT AGN catalog. The GLFs of BL Lacs in the frame of the pure density evolution (PDE), the pure luminosity evolution (PLE), and the luminosity-dependent density (LDDE) models are determined by using the Markov Chain Monte Carlo (MCMC) technique, respectively. Our results suggest that the PDE model can give best description for BL Lac GLF based on the combination of constraints of model parameters and good fits to the observed data of Fermi-Large Area Telescope (LAT) BL Lacs, but other two models (PLE and LDDE) cannot be excluded. Based on our constructed GLFs, the contribution to the extragalactic diffuse gamma-ray background (EGRB) from BL Lacs is estimated, and ˜1-5 per cent of the EGRB in the 0.1-100 GeV band is found to come from unresolved BL Lacs (including the cascade emission). In addition, it is found that the BL Lac GLF is very different from flat spectrum radio quasar GLF and then the contribution of blazars to the EGRB should be estimated separately.

Zeng, Houdun; Yan, Dahai; Zhang, Li

2014-06-01

 
 
 
 
361

The ISO 170um Luminosity Function of Galaxies  

CERN Document Server

We constructed a local luminosity function (LF) of galaxies using a flux-limited sample (S_170 > 0.195Jy) of 55 galaxies at z < 0.3 taken from the ISO FIRBACK survey at 170um. The overall shape of the 170-um LF is found to be different from that of the total 60-um LF (Takeuchi et al. 2003): the bright end of the LF declines more steeply than that of the 60-um LF. This behavior is quantitatively similar to the LF of the cool subsample of the IRAS PSCz galaxies. We also estimated the strength of the evolution of the LF by assuming the pure luminosity evolution (PLE): L(z) \\propto (1+z)^Q. We obtained Q=5.0^{+2.5}_{-0.5} which is similar to the value obtained by recent Spitzer observations, in spite of the limited sample size. Then, integrating over the 170-um LF, we obtained the local luminosity density at 170um, \\rho_L(170um). A direct integration of the LF gives \\rho_L(170um) = 1.1 \\times 10^8 h Lsun Mpc^{-3}, whilst if we assume a strong PLE with Q=5, the value is 5.2 \\times 10^7 h Lsun Mpc^{-3}. This is ...

Takeuchi, T T; Dole, H; Dennefeld, M; Lagache, G; Puget, J L; Takeuchi, Tsutomu T.; Ishii, Takako T.; Dole, Herve; Dennefeld, Michel; Lagache, Guilaine; Puget, Jean-Loup

2005-01-01

362

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

363

Parallax and Luminosity Measurements of an L Subdwarf  

CERN Document Server

We present the first parallax and luminosity measurements for an L subdwarf, the sdL7 2MASS J05325346+8246465. Observations conducted over three years by the USNO infrared astrometry program yield an astrometric distance of 26.7+/-1.2 pc and a proper motion of 2.6241+/-0.0018"/yr. Combined with broadband spectral and photometric measurements, we determine a luminosity of log(Lbol/Lsun) = -4.24+/-0.06 and Teff = 1730+/-90 K (the latter assuming an age of 5-10 Gyr), comparable to mid-type L field dwarfs. Comparison of the luminosity of 2MASS J05325346+8246465 to theoretical evolutionary models indicates that its mass is just below the sustained hydrogen burning limit, and is therefore a brown dwarf. Its kinematics indicate a ~110 Myr, retrograde Galactic orbit which is both eccentric (3 <~ R <~ 8.5 kpc) and extends well away from the plane (Delta_Z = +/-2 kpc), consistent with membership in the inner halo population. The relatively bright J-band magnitude of 2MASS J05325346+8246465 implies significantly r...

Burgasser, Adam J; Lépine, Sébastien; Munn, Jeffrey A; Luginbuhl, Christian B; Henden, Arne A; Guetter, Harry H; Canzian, Blaise C

2007-01-01

364

Evolution of the cluster X-ray luminosity function from the WARPS survey  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The evolution of the X-ray luminosity function of clusters of galaxies has been measured to z=0.85 using over 150 X-ray selected clusters found in the WARPS survey. We find no evidence for evolution of the luminosity function at any luminosity or redshift. The observations constrain the evolution of the space density of moderate luminosity clusters to be very small, and much less than predicted by most models of the growth of structure with Omega=1.

Jones, L. R.; Ebeling, H.; Scharf, C.; Perlman, E.; Horner, D.; Fairley, B.; Wegner, G.; Malkan, M.

2000-01-01

365

The galaxy cluster X-ray luminosity-gravitational mass relation in the light of the WMAP 3rd year data  

Science.gov (United States)

Context: .The 3rd year WMAP results mark a shift in best fit values of cosmological parameters compared to the 1st year data and the concordance cosmological model. Aims: .We test the consistency of the new results with previous constraints on cosmological parameters from the HIFLUGCS galaxy cluster sample and the impact of this shift on the X-ray luminosity-gravitational mass relation. Methods: .The measured X-ray luminosity function combined with the observed luminosity-mass relation are compared to mass functions predicted for given cosmological parameter values. Results: .The luminosity function and luminosity-mass relation derived previously from HIFLUGCS are in perfect agreement with mass functions predicted using the best fit parameter values from the 3rd year WMAP data (?_m=0.238, ?_8=0.74) and inconsistent with the concordance cosmological model (?_m=0.3, ?_8=0.9), assuming a flat Universe. Trying to force consistency with the concordance model requires artificially decreasing the normalization of the luminosity-mass relation by a factor of 2. Conclusions: .The shift in best fit values for ?m and ?8 has a significant impact on predictions of cluster abundances. The new WMAP results are now in perfect agreement with previous results on the ?_m-?8 relation determined from the mass function of HIFLUGCS clusters and other X-ray cluster samples (the "low cluster normalization"). We conclude that - unless the true values of ?m and ?8 differ significantly from the 3rd year WMAP results - the luminosity-mass relation is well described by their previous determination from X-ray observations of clusters, with a conservative upper limit on the bias factor of 1.5. These conclusions are currently being tested directly in a complete follow-up program of all HIFLUGCS clusters with Chandra and XMM-Newton.

Reiprich, T. H.

2006-07-01

366

The space density and X-ray luminosity function of non-magnetic cataclysmic variables  

Science.gov (United States)

We combine two complete, X-ray flux-limited surveys, the ROSAT Bright Survey (RBS) and the ROSAT North Ecliptic Pole (NEP) survey, to measure the space density (?) and X-ray luminosity function (?) of non-magnetic cataclysmic variables (CVs). The combined survey has a flux limit of FX? 1.1 × 10-12 erg cm-2 s-1 over most of its solid angle of just over ?, but is as deep as ?10-14 erg cm-2 s-1 over a small area. The CV sample that we construct from these two surveys contains 20 non-magnetic systems. We carefully include all sources of statistical error in calculating ? and ? by using Monte Carlo simulations; the most important uncertainty proves to be the often large errors in distances estimates. If we assume that the 20 CVs in the combined RBS and NEP survey sample are representative of the intrinsic population, the space density of non-magnetic CVs is ?. We discuss the difficulty in measuring ? in some detail - in order to account for biases in the measurement, we have to adopt a functional form for ?. Assuming that the X-ray luminosity function of non-magnetic CVs is a truncated power law, we constrain the power-law index to -0.80 ± 0.05. It seems likely that the two surveys have failed to detect a large, faint population of short-period CVs, and that the true space density may well be a factor of 2 or 3 larger than what we have measured; this is possible, even if we only allow for undetected CVs to have X-ray luminosities in the narrow range 28.7 log(LX/erg s-1) < 29.7. However, ? as high as 2 × 10-4 pc-3 would require that the majority of CVs has X-ray luminosities below LX= 4 × 1028 erg s-1 in the 0.5-2.0 keV band.

Pretorius, Magaretha L.; Knigge, Christian

2012-01-01

367

The Low CO Luminosity of Three Extremely Metal-Poor Star-Forming Galaxies  

Science.gov (United States)

We present sensitive observations in the CO J = 1 ? 0 emission line of the metal-poor dwarf irregular galaxies Sextans A, Sextans B, and Leo P, all obtained with the CARMA interferometer. While no confirmed detections of CO emission were found, the proximity of the three systems allows us to place very stringent upper limits on the CO luminosity in metal poor galaxies. We find the CO luminosities to be LCO pc2 for Leo P, LCO pc2 for Sextans B, and LCO pc2 for Sextans A. These are among the most sensitive CO upper limits in metal poor galaxies to date. Comparing the star formation rate to our CO upper limit provides evidence that either the CO to H2 conversion factor increases sharply as metallicity decreases, or stars are forming in these three galaxies very efficiently, requiring little molecular hydrogen. The Cornell ALFALFA team is supported by NSF AST-1107390 and by the Brinson Foundation. The Undergraduate ALFALFA Team is supported by NSF grant AST-1211005. JMC is supported by NSF grant AST-1211683.

Molter, Edward; Warren, S. R.; Bolatto, A. D.; Cannon, J. M.; Adams, E. A.; Elson, E. C.; Giovanelli, R.; Haynes, M. P.; McQuinn, K. B.; Rhode, K. L.; Salzer, J. J.; Skillman, E. D.

2014-01-01

368

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

369

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

370

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

371

Constraining the Redshift z=6 Quasar Luminosity Function Using Gravitational Lensing  

CERN Multimedia

Recent discoveries by the Sloan Digital Sky Survey (SDSS) of four bright redshift z=6 quasars could constrain the mechanism by which the supermassive black holes powering these sources are assembled. Here we compute the probability that the fluxes of the quasars are strongly amplified by gravitational lensing, and therefore the likelihood that the black hole masses are overestimated when they are inferred assuming Eddington luminosities. The poorly-constrained shape of the intrinsic quasar luminosity function (LF) at redshift z=6 results in a large range of possible lensing probabilities. If the LF is either steep, or extends to faint magnitudes, the probability for amplification by a factor of ten ore more (and with only one image detectable by SDSS) can reach essentially 100 percent. We show that future observations, in particular, either of the current four quasars at the high angular resolution provided by the Hubble Space Telescope, or of an increased sample of about twenty redshift six quasars at the cu...

Comerford, J M; Schaye, J; Comerford, Julia M.; Haiman, Zoltan; Schaye, Joop

2002-01-01

372

The radio luminosity distribution of pulsars in 47 Tucanae  

CERN Document Server

We have used the Australia Telescope Compact Array to seek the integrated radio flux from all the pulsars in the core of the globular cluster 47 Tucanae. We have detected an extended region of radio emission and have calibrated its flux against the flux distribution of the known pulsars in the cluster. We find the total 20-cm radio flux from the cluster's pulsars to be S = 2.0 +/- 0.3 mJy. This implies the lower limit to the radio luminosity distribution to be L_1400 = 0.4 mJy kpc^2 and the size of the observable pulsar population to be N < 30.

McConnell, D; Connors, T; Ables, J G

2004-01-01

373

The luminosity monitor of the HERMES experiment at DESY  

CERN Document Server

A detector is described which measures the luminosity of the HERMES experiment at DESY. It is based on the coincident detection of electron-positron and photon pairs, or electron pairs, originating from the interaction of the beam positrons, or electrons, with the electrons of the atomic gas target. It consists of two calorimeters with radiation hard NaBi(WO sub 4) sub 2 crystals. Properties of the monitor, investigated in an electron test beam, and its performance in the experiment are presented.

Benisch, T; Devitsin, E G; Kozlov, V; Potashov, S Yu; Rith, K; Terkulov, A R; Weiskopf, C

2001-01-01

374

Sky luminosity for Rio de Janeiro City - Brazil  

International Nuclear Information System (INIS)

This paper presents sky luminosity data for Rio de Janeiro City, useful to be used in daylighting design in architecture. The data are presented as monthly graphics that correlate sunshine-hours with the frequency of occurrence during the day of a specific type of sky, that would present one of five defined characteristics (among clear and overcast sky). These results were derived from the knowledge of daily solar radiation and sunshine-hours data, for every day for a twelve year period. (author). 10 refs, 13 figs, 16 tabs

1995-01-01

375

Low-luminosity X-ray sources in Omega Centauri  

Energy Technology Data Exchange (ETDEWEB)

UBV observations of three X-ray sources in Omega Cen (sources A, D, and E of Hertz and Grindlay, 1983), obtained with a CCD detector on the 4-m telescope at CTIO in February and August 1985, are reported. The results are presented in images, graphs, and tables and characterized in detail. No optical cataclysmic variable candidates are found down to V = 24.5 mag, corresponding to M(V) = 10.6 in the cluster. It is inferred that these low-luminosity sources, located outside the globular cluster, may be superposed unrelated objects rather than close mass-exchange binaries. 35 references.

Margon, B.; Bolte, M.

1987-10-01

376

The Luminosity Function for L > L* Galaxies at z > 3  

CERN Document Server

Through use of multiband (U, B, R, I) photometry we have isolated high redshift (3.0 L* luminosity function for z = 3-5 galaxies obtained by a photometric redshift analysis of the Hubble Deep Field (HDF) by Gwyn & Hartwick (1996). Our results at R ~ 23 are more consistent with the photometric redshift analysis of the faint HDF galaxies by Sawicki & Yee (1996), but our present upper limits at the brightest magnitudes (R < 21.5, M(R) < -24) allow more generous volume densities of these super-L* galaxies.

Bershady, M A; Koo, D C; Kron, Richard G; Munn, J A; Bershady, Matthew A.; Majewski, Steven R.; Koo, David C.; Kron, Richard G.; Munn, Jeffrey A.

1997-01-01

377

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

378

The source of luminosity at the Galactic Centre  

International Nuclear Information System (INIS)

New infrared spectroscopic data from the central parsec of the Galactic Centre show that the black hole believed to account for the non-thermal radio source Sgr A*, and already known to be an insignificant source of luminosity, is also not obviously associated with the broad-line gas. We find that the components of the IRS 16 complex and a nearby source 8 arcsec south-east of IRS 16 have 2 ?m spectra which are similar to young luminous stars found in significant numbers in the Magellanic Clouds. The new source has an infrared spectral type of WN9/Ofpe, and may be unique in the Galaxy. (author)

1990-06-15

379

The source of luminosity at the Galactic Centre  

Energy Technology Data Exchange (ETDEWEB)

New infrared spectroscopic data from the central parsec of the Galactic Centre show that the black hole believed to account for the non-thermal radio source Sgr A*, and already known to be an insignificant source of luminosity, is also not obviously associated with the broad-line gas. We find that the components of the IRS 16 complex and a nearby source 8 arcsec south-east of IRS 16 have 2 {mu}m spectra which are similar to young luminous stars found in significant numbers in the Magellanic Clouds. The new source has an infrared spectral type of WN9/Ofpe, and may be unique in the Galaxy. (author).

Allen, D.A. (Anglo-Australian Observatory, Epping (Australia)); Hyland, A.R. (Mount Stromlo and Siding Spring Observatories, Weston (Australia)); Hillier, D.J. (Center for Astrophysics, Cambridge, MA (USA))

1990-06-15

380

Autofib Redshift Survey - I. Evolution of the Galaxy Luminosity Function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a detailed determination of the restframe B-band galaxy luminosity function (LF) as a function of redshift and star formation activity from z=0 to z=0.75. The dataset used for this purpose is a combined sample of over 1700 redshifts spanning a wide range in apparent magnitude, 11.5

Ellis, Richard S.; Colless, Matthew; Broadhurst, Tom; Heyl, Jeremy; Glazebrook, Karl

1995-01-01

 
 
 
 
381

Reverberation Mapping of High-Luminosity Quasars: First Results  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reverberation mapping of nearby active galactic nuclei has led to estimates of broad-line-region (BLR) sizes and central-object masses for some 37 objects to date. However, successful reverberation mapping has yet to be performed for quasars of either high luminosity (above L_opt~10^{46} erg/s) or high redshift (z>0.3). Over the past six years, we have carried out, at the Hobby-Eberly Telescope, rest-frame-ultraviolet spectrophotometric monitoring of a sample of six quasars ...

Kaspi, Shai; Brandt, W. N.; Maoz, Dan; Netzer, Hagai; Schneider, Donald P.; Shemmer, Ohad

2006-01-01

382

Globular Clusters and the Mira Period-Luminosity Relation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A globular cluster distance scale based on Hipparcos parallaxes of subdwarfs has been used to derive estimates of M_K for cluster Miras, including one in the SMC globular cluster NGC121. These lead to a zero-point of the Mira infrared period-luminosity relation, PL(K), in good agreement with that derived from Hipparcos parallaxes of nearby field Miras. The mean of these two estimates together with data on LMC Miras yields an LMC distance modulus of 18.60 +/- 0.10 in evident ...

Feast, Michael; Whitelock, Patricia; Menzies, John

2001-01-01

383

AGB Variables and the Mira Period-Luminosity Relation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Published data for large amplitude asymptotic giant branch variables in the Large Magellanic Cloud are re-analysed to establish the constants for an infrared (K) period-luminosity relation of the form: Mk=rho[log P-2.38] + delta. A slope of rho=-3.51+/-0.20 and a zero point of delta=-7.15+/-0.06 are found for oxygen-rich Miras (if a distance modulus of 18.39+/-0.05 is used for the LMC). Assuming this slope is applicable to Galactic Miras we discuss the zero-point for these s...

Whitelock, Patricia A.; Feast, Michael W.; Leeuwen, Floor

2008-01-01

384

NGC4258 a jet-dominated low-luminosity AGN?  

CERN Multimedia

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

385

Evolution of the 1.4 GHz Radio Luminosity Function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The results of an optical and infrared investigation of a complete sub-sample of the Leiden-Berkeley Deep Survey (flux > 1 mJy at 1.4 GHz) are presented. Optical counterparts have been identified for 69 of the 73 sources in the two Hercules fields, and redshifts obtained for 49 of them. Photometric redshifts are computed from the g,r,i,K data for the remaining 21 sources. This complete sample is compared with the radio luminosity functions (RLFs) of Dunlop and Peacock (1990)...

Waddington, Ian

1999-01-01

386

Development of internal jet targets for high-luminosity experiments  

International Nuclear Information System (INIS)

We report on recent developments of the internal supersonic gas jet target at IUCF. The emphasis has been on hydrogen jets that can be used as targets of similar 1016 atoms/cm2 thickness in high-luminosity experiments. A method of scanning jets with an ionizing 1 keV electron beam has been employed in order to study jet formation as a function of nozzle geometry and temperature. We summarize our results, obtained by scanning H2 jets from 23 different nozzles, most of them made from glass capillaries. The present setup of the jet target in the Cooler storage ring is described. (orig.)

1995-08-01

387

High Luminosity LHC matching section layout vs crab cavity voltage  

CERN Multimedia

In the framework of the HiLumi-LHC project we present a new possible variant for the layout of the LHC matching section located in the high luminosity insertions. This layout is optimized to reduce the demand on the voltage of the crab cavities, while substantially improving the optics squeeze-ability, both in ATS [1] and non-ATS mode. This new layout will be described in details together with its performance figures in terms of mechanical acceptance, chromatic properties and optics flexibility.

Dalena, B; Chance, A; De Maria, R; Fartoukh, S

2013-01-01

388

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

389

GRB Formation Rates inferred from the Spectral Peak Energy - Luminosity Relation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the GRB formation rate based on the relation between the spectral peak energy ($E_{p}$) and the isotropic luminosity. The $E_{p}$--luminosity relation covers the energy range of 50 -- 2000 keV and the luminosity range of $10^{50}$--$10^{54} erg/s, respectively. We find that the relation is considerably tighter than similar relations suggested previously. Using $E_{p}$--luminosity relation, we estimate the luminosity and the redshift of 684 GRBs with the unknow...

Yonetoku, D.; Murakami, T.; Nakamura, T.; Yamazaki, R.; Inoue, A. K.; Ioka, K.

2003-01-01

390

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

CERN Document Server

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; Pogge, Richard W; Vestergaard, Marianne

2008-01-01

391

The GRB luminosity function: prediction of the internal shock model and comparison to observations  

International Nuclear Information System (INIS)

We compute the expected GRB luminosity function in the internal shock model. We find that if the population of GRB central engines produces all kind of relativistic outflows, from very smooth to highly variable, the luminosity function has to branchs: at low luminosity, the distribution is dominated by low efficiency GRBs and is close to a power law of slope -0.5, whereas at high luminosity, the luminosity function follows the distribution of injected kinetic power. Using Monte Carlo simulations and several observational constrains (BATSE logN-logP diagram, peak energy distribution of bright BATSE bursts, fraction of XRFs in the HETE2 sample), we show that it is currently impossible to distinguish between a single power law or a broken power law luminosity function. However, when the second case is considered, the low-luminosity slope is found to be -0.6±0.2, which is compatible with the prediction of the internal shock model

2008-05-22

392

The cosmological evolution and luminosity function of X-ray selected active galactic nuclei  

Science.gov (United States)

The cosmological evolution and the X-ray luminosity function of X-ray selected active galactic nuclei (AGNs) are derived and discussed. The sample used consists of 31 AGNs extracted from a fully identified sample of X-ray sources from the Einstein Observatory Medium Sensitivity Survey and is therefore exclusively defined by its X-ray properties. The distribution in space is found to be strongly nonuniform. The amount of cosmological evolution required by the X-ray data is derived in the framework of pure luminosity evolution and is found to be smaller than the amount determined from optically selected samples. The X-ray luminosity function is derived. It can be satisfactorily represented by a single power law only over a limited range of absolute luminosities. Evidence that the luminosity function flattens at low luminosity or steepens at high luminosity, or both, is presented and discussed.

Maccacaro, T.; Gioia, I. M.; Avni, Y.; Giommi, P.; Griffiths, R. E.; Liebert, J.; Stocke, J.; Danziger, J.

1983-01-01

393

Cosmological evolution and luminosity function of x-ray selected active galactic nuclei  

International Nuclear Information System (INIS)

The cosmological evolution and the X-ray luminosity function of X-ray selected active galactic nuclei (AGNs) are derived and discussed.The sample used consists of 31 AGNs extracted from a fully identified sample of X-ray sources from the Einstein Observatory Medium Sensitivity Survey and is therefore exclusively defined by its X-ray properties. The distribution in space is found to be strongly nonuniform. The amount of cosmological evolution required by the X-ray data is derived in the framework of pure luminosity evolution and is found to be smaller than the amount determined from optically selected samples. The X-ray luminosity function is derived. It can be satisfactorily represented by a single power law only over a limited range of absolute luminosities. Evidence that the luminosity function flattens at low luminosity or steepens at high luminosity, or both, is presented and discussed

1983-03-15

394

Low-luminosity active galactic nuclei: are they UV faint and radio loud?  

Science.gov (United States)

Low-luminosity active galactic nuclei (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, ultraviolet (UV) and X-ray wavelengths, for a sample of 13 nearby galaxies with low-ionization nuclear emission-line region (LINER) nuclei. I show that, contrary to common wisdom, low-luminosity LINERs have significant non-stellar UV flux, and UV/X-ray luminosity ratios similar, on average, to those of Seyfert 1 nuclei ~104 times more luminous. The ?ox index that quantifies this ratio is in the range between -0.8 and -1.4, and is below the extrapolation to low luminosities of the relation between ?ox and UV luminosity observed at higher luminosities. In terms of radio loudness, most of the LINERs are indeed radio loud (or sometimes even `super radio loud') based on their radio/UV luminosity ratios, when compared to the most luminous quasars. However, the entire distribution of radio loudness has been shown to shift to higher radio/UV ratios at low AGN luminosities. In the context of this global shift, some LINERs (the majority) can be considered radio quiet, and some (from among those with black hole masses >~108.5Msolar) are radio loud. The SEDs of these low-luminosity (~1040ergs-1) AGNs are thus quite similar to those of Seyferts up to luminosities of ~1044ergs-1, and there is no evidence for a sharp change in the SED at the lowest luminosities. Thin AGN accretion discs may therefore persist at low accretion rates, in analogy to some recent findings for Galactic stellar-mass accreting black holes.

Maoz, Dan

2007-06-01

395

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

396

A primer on detectors in high luminosity environment  

International Nuclear Information System (INIS)

The following remarks are relevant to the problem of balancing luminosity versus energy in new HEP construction. In a previous study, it was stated that the only experiment that would succeed at a luminosity of 10/sup 33/cm/sup -2/sec/sup -1/ was one in which the apparatus was shielded from the collision region by massive quantity of steel. In 1981, this opinion was confirmed by an authority in the field. It may be instructive to review the progress of collider detectors over the past decade. In 1973, the time resolution or, better, the integrating time of tracking detectors was --100 ns. In 1982, this time has remained the same since PWC's are still the fastest tracking devices available. The fundamental limit is the saturated drift velocity of electrons in gases. Better resolution and three dimensional properties have led to the choice of drift chambers and TPC's which have considerably longer integration times. A new characteristic of 1982 detectors is the increasing pervasiveness of calorimeters which have become indispensable devices for measurement of electromagnetic and hadronic energy, especially at momenta where magnetic measurements become imprecise. Calorimeters, because of their innate geometric dimensions set by the nuclear mean free path and their distance from the interaction point have integration times of --200-1000 ns. Of course this is the present state of the art which depends on the properties of BBQ, gas chambers, liquid argon, lead glass, etc

1982-07-16

397

Modelling ISO Galaxy Counts with Luminosity and Merger Rate Evolution  

CERN Document Server

We model galaxy evolution in the 6.75 and 15 micron passbands of the ISO satellite, by combining models of galaxy evolution at optical wavelengths (which are consistent with the optical galaxy counts) with observed spectral energy distributions in the infra-red. Our model is consistent with the local 12 micron galaxy luminosity, if 3.5 per cent of spirals at z=0 are in interacting pairs with mid-infra-red luminosities enhanced by major starbursts. Source counts from deep ISO surveys exceed non-evolving predictions but are more consistent with our evolving model. The steep number count of 6.75 micron sources appears to be explained primarily by evolving early-type galaxies, whereas at 15 microns the main contributors are star-forming spirals and starbursting interacting/merging galaxies. The 31 per cent of 15 micron sources which are visibly interacting galaxies have high mid-infra-red/optical flux ratios indicating major starbursts combined with dust extinction. The numbers and high mean redshift of these sou...

Roche, N; Roche, Nathan; Eales, Steve

1998-01-01

398

Metallicity and Far-Infrared Luminosity of High Redshift Quasars  

CERN Multimedia

We present the results of an exploratory study of broad line region (BLR) metallicity in 34 2.2 < z < 4.6 quasars with far-infrared (FIR) luminosities (L_FIR) from 10^13.4 to 10^12.1 L_\\odot . Quasar samples sorted by L_FIR might represent an evolutionary sequence if the star formation rates (SFRs) in quasar hosts generally diminish across quasar lifetimes. We use rest-frame ultraviolet spectra from the Sloan Digital Sky Survey to construct three composite spectra sorted by L_FIR, corresponding to average SFRs of 4980, 2130 and 340 M_\\odot yr^-1 after correcting for a nominal quasar FIR contribution. The measured N V {\\lambda} 1240/C IV {\\lambda} 1550 and Si IV {\\lambda} 1397+O IV] {\\lambda} 1402/C IV {\\lambda} 1550 emission line ratios indicate super-solar BLR metallicities in all three composites, with no evidence for a trend with the star formation rate. The formal derived metallicities, Z ~ 5-9 Z_\\odot , are similar to those derived for the BLRs of other quasars at similar redshifts and luminosities...

Simon, Leah E

2010-01-01

399

Designing the ATLAS trigger menu for high luminosities  

CERN Document Server

Poster on the ATLAS trigger menu for CHEP 2012. The ATLAS trigger system consists of three sub-levels, hardware-based Level 1, software-based Level 2 and Event Filter. The DAQ system imposes severe limits on the trigger output rates at each level. The trigger decisions are made based on the “Trigger Menu”, a list of event-signature-specific trigger chains/signatures with full coverage of not only all ATLAS physics analyses with high efficiencies but also all detector calibrations and monitoring, while reducing the rate from the 20 MHz collision rate to a recording rate of around 400 Hz. After the successful commissioning of the Trigger Menu in 2010 and 2011 at luminosities from 10^27 cm-2 s-1 to 5x10^33 cm-2 s-1, we designed the 2012 menu for the up-coming high luminosity (~10^34 cm-2 s-1) and high pile-up (~35 interactions/crossing) environment and successfully deployed it in April.

Nakahama, Y; The ATLAS collaboration

2012-01-01

400

Absolute luminosity measurements with the LHCb detector at the LHC  

CERN Document Server

Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic ``van der Meer scan'' method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overall precision of 3.5\\% in the absolute lumi...

Aaij, R; Adinolfi, M; Adrover, C; Affolder, A; Ajaltouni, Z; Albrecht, J; Alessio, F; Alexander, M; Alkhazov, G; Alvarez Cartelle, P; Alves, A A; Amato, S; Amhis, Y; Anderson, J; Appleby, R B; Aquines Gutierrez, O; Archilli, F; Arrabito, L; Artamonov, A; Artuso, M; Aslanides, E; Auriemma, G; Bachmann, S; Back, J J; Bailey, D S; Balagura, V; Baldini, W; Barlow, R J; Barschel, C; Barsuk, S; Barter, W; Bates, A; Bauer, C; Bauer, Th; Bay, A; Bediaga, I; Belous, K; Belyaev, I; Ben-Haim, E; Benayoun, M; Bencivenni, G; Benson, S; Benton, J; Bernet, R; Bettler, M-O; van Beuzekom, M; Bien, A; Bifani, S; Bizzeti, A; Bjørnstad, P M; Blake, T; Blanc, F; Blanks, C; Blouw, J; Blusk, S; Bobrov, A; Bocci, V; Bondar, A; Bondar, N; Bonivento, W; Borghi, S; Borgia, A; Bowcock, T J V; Bozzi, C; Brambach, T; van den Brand, J; Bressieux, J; Brett, D; Brisbane, S; Britsch, M; Britton, T; Brook, N H; Brown, H; Büchler-Germann, A; Burducea, I; Bursche, A; Buytaert, J; Cadeddu, S; Caicedo Carvajal, J M; Callot, O; Calvi, M; Calvo Gomez, M; Camboni, A; Campana, P; Carbone, A; Carboni, G; Cardinale, R; Cardini, A; Carson, L; Carvalho Akiba, K; Casse, G; Cattaneo, M; Charles, M; Charpentier, Ph; Chiapolini, N; Ciba, K; Cid Vidal, X; Ciezarek, G; Clarke, P E L; Clemencic, M; Cliff, H V; Closier, J; Coca, C; Coco, V; Cogan, J; Collins, P; Constantin, F; Conti, G; Contu, A; Cook, A; Coombes, M; Corti, G; Cowan, G A; Currie, R; D'Almagne, B; D'Ambrosio, C; David, P; De Bonis, I; De Capua, S; De Cian, M; De Lorenzi, F; De Miranda, J M; De Paula, L; De Simone, P; Decamp, D; Deckenhoff, M; Degaudenzi, H; Deissenroth, M; Del Buono, L; Deplano, C; Deschamps, O; Dettori, F; Dickens, J; Dijkstra, H; Diniz Batista, P; Donleavy, S; Dordei, F; Dosil Suárez, A; Dossett, D; Dovbnya, A; Dupertuis, F; Dzhelyadin, R; Eames, C; Easo, S; Egede, U; Egorychev, V; Eidelman, S; van Eijk, D; Eisele, F; Eisenhardt, S; Ekelhof, R; Eklund, L; Elsasser, Ch; d'Enterria, D G; Esperante Pereira, D; Estève, L; Falabella, A; Fanchini, E; Färber, C; Fardell, G; Farinelli, C; Farry, S; Fave, V; Fernandez Albor, V; Ferro-Luzzi, M; Filippov, S; Fitzpatrick, C; Fontana, M; Fontanelli, F; Forty, R; Frank, M; Frei, C; Frosini, M; Furcas, S; Gallas Torreira, A; Galli, D; Gandelman, M; Gandini, P; Gao, Y; Garnier, J-C; Garofoli, J; Garra Tico, J; Garrido, L; Gaspar, C; Gauvin, N; Gersabeck, M; Gershon, T; Ghez, Ph; Gibson, V; Gligorov, V V; Göbel, C; Golubkov, D; Golutvin, A; Gomes, A; Gordon, H; Grabalosa Gándara, M; Graciani Diaz, R; Granado Cardoso, L A; Graugés, E; Graziani, G; Grecu, A; Gregson, S; Gui, B; Gushchin, E; Guz, Yu; Gys, T; Haefeli, G; Haen, C; Haines, S C; Hampson, T; Hansmann-Menzemer, S; Harji, R; Harnew, N; Harrison, J; Harrison, P F; He, J; Heijne, V; Hennessy, K; Henrard, P; Hernando Morata, J A; van Herwijnen, E; Hicks, E; Hofmann, W; Holubyev, K; Hopchev, P; Hulsbergen, W; Hunt, P; Huse, T; Huston, R S; Hutchcroft, D; Hynds, D; Iakovenko, V; Ilten, P; Imong, J; Jacobsson, R; Jaeger, A; Jahjah Hussein, M; Jans, E; Jansen, F; Jaton, P; Jean-Marie, B; Jing, F; John, M; Johnson, D; Jones, C R; Jost, B; Kandybei, S; Karacson, M; Karbach, T M; Keaveney, J; Kerzel, U; Ketel, T; Keune, A; Khanji, B; Kim, Y M; Knecht, M; Koblitz, S; Koppenburg, P; Kozlinskiy, A; Kravchuk, L; Kreplin, K; Kreps, M; Krocker, G; Krokovny, P; Kruse, F; Kruzelecki, K; Kucharczyk, M; Kukulak, S; Kumar, R; Kvaratskheliya, T; La Thi, V N; Lacarrere, D; Lafferty, G; Lai, A; Lambert, D; Lambert, R W; Lanciotti, E; Lanfranchi, G; Langenbruch, C; Latham, T; Le Gac, R; van Leerdam, J; Lees, J-P; Lefèvre, R; Leflat, A; Lefrançois, J; Leroy, O; Lesiak, T; Li, L; Li Gioi, L; Lieng, M; Liles, M; Lindner, R; Linn, C; Liu, B; Liu, G; Lopes, J H; Lopez Asamar, E; Lopez-March, N; Luisier, J; Machefert, F; Machikhiliyan, I V; Maciuc, F; Maev, O; Magnin, J; Malde, S; Mamunur, R M D; Manca, G; Mancinelli, G; Mangiafave, N; Marconi, U; Märki, R; Marks, J; Martellotti, G; Martens, A; Martin, L; Martín Sánchez, A; Martinez Santos, D; Massafferri, A; Matev, R; Mathe, Z; Matteuzzi, C; Matveev, M; Maurice, E; Maynard, B; Mazurov, A; McGregor, G; McNulty, R; Mclean, C; Meissner, M; Merk, M; Merkel, J; Messi, R; Miglioranzi, S; Milanes, D A; Minard, M-N; Monteil, S; Moran, D; Morawski, P; Mountain, R; Mous, I; Muheim, F; Müller, K; Muresan, R; Muryn, B; Musy, M; Mylroie-Smith, J; Naik, P; Nakada, T; Nandakumar, R; Nardulli, J; Nasteva, I; Nedos, M; Needham, M; Neufeld, N; Nguyen-Mau, C; Nicol, M; Nies, S; Niess, V; Nikitin, N; Oblakowska-Mucha, A; Obraztsov, V; Oggero, S; Ogilvy, S; Okhrimenko, O; Oldeman, R; Orlandea, M; Otalora Goicochea, J M; Owen, P; Pal, B; Palacios, J; Palutan, M; Panman, J; Papanestis, A; Pappagallo, M; Parkes, C; Parkinson, C J; Passaleva, G; Patel, G D; Patel, M; Paterson, S K; Patrick, G N; Patrignani, C; Pavel-Nicorescu, C

2012-01-01

 
 
 
 
401

The luminosities of type II Cepheids and RR Lyrae variables  

CERN Document Server

Recent work on the luminosities of type II Cepheids (CephIIs) and RR Lyrae variables is reviewed.In the near infrared (JHKs) the CephIIs in globular clusters show a narrow, linear, period-luminosity relation over their whole period range (about 1 to 100 days). The CephIIs in the general field of the LMC follow this relation for periods shorter than about 20 days. At longer period (the region of the RV Tau stars), the LMC field stars have a significant scatter and in the mean are more luminous than the PL relation. The OGLEIII optical data for the LMC field variables show similar trends. Infrared colours of stars in the RV Tau period range show marked mean differences between three groupings; the Galactic field, the LMC field, and globular clusters. In the case of the Galactic field, at least, this may be strongly influenced by selection effects. In the period range about 4 to 20 days (the W Vir range) there are stars lying above the PL relation which may be recognized by their light curves and are all likely ...

Feast, Michael

2009-01-01

402

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

403

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

404

Bar fraction in lenticular galaxies: dependence on luminosity and environment  

CERN Document Server

We present a study of bars in lenticular galaxies based on a sample of 371 galaxies from the SDSS-DR 7 and 2MASS in optical and near-infrared bands, respectively. We found a bar in 15% of the lenticular galaxies in our sample, which is consistent with recent studies. The barred galaxy fraction shows a luminosity dependence, with faint lenticular galaxies (MK > -24.5, total absolute magnitude in K band) having a larger fraction of bars than bright lenticular galaxies (MK < -24.5). A similar trend is seen when Mr = -21.5, the total absolute magnitude in SDSS r band is used to divide the sample into faint and bright lenticular galaxies. We find that faint galaxies in clusters show a higher bar fraction than their counterparts in the field. This suggests that the formation of bars in lenticular galaxies not only depends on the total luminosity of galaxy but also on the environment of the host galaxy.

Barway, Sudhanshu; Kembhavi, Ajit K

2010-01-01

405

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

406

The CLASS BL Lac sample: The Radio Luminosity Function  

CERN Document Server

This paper presents a new sample of BL Lac objects selected from a deep (30 mJy) radio survey of flat spectrum radio sources (the CLASS blazar survey, henceforth CBS). The sample is one of the largest well defined samples in the low power regime with a total of 130 sources of which 55 satisfy the 'classical' optical BL Lac selection criteria, and the rest have indistinguishable radio properties. The primary goal of this study is to establish the Radio Luminosity Function (RLF) on firm statistical ground at low radio luminosities where previous samples have not been able to investigate. The gain of taking a peek at lower powers is the possibility to search for the flattening of the LF which is a feature predicted by the beaming model but which has remained elusive to observational confirmation. In this study we extend for the first time the BL Lac RLF down to very low radio powers ~10^22 W/Hz, ie, two orders of magnitude below the RLF currently available in the literature. In the process we confirm the importa...

Marcha, M J M

2013-01-01

407

Luminosity Optimization for a Higher-Energy LHC  

CERN Document Server

A Higher-Energy Large Hadron Collider (HE-LHC) is an option to further push the energy frontier of particle physics beyond the present LHC. A beam energy of 16.5 TeV would require 20 T dipole magnets in the existing LHC tunnel, which should be compared with 7 TeV and 8.33 T for the nominal LHC. Since the synchrotron radiation power increases with the fourth power of the energy, radiation damping becomes significant for the HE-LHC. It calls for transverse and longitudinal emittance control vis-a-vis beam-beam interaction and Landau damping. The heat load from synchrotron radiation, gas scattering, and electron cloud also increases with respect to the LHC. In this paper we discuss the proposed HE-LHC beam parameters; the time evolution of luminosity, beam-beam tune shifts, and emittances during an HE-LHC store; the expected heat load; and luminosity optimization schemes for both round and flat beams.

Dominguez, O

2011-01-01

408

Biases in the Quasar Mass-Luminosity Plane  

CERN Document Server

We report that the reported sub-Eddington boundary in the quasar mass-luminosity plane (a departure from the Eddington luminosity limit for the highest quasar black hole masses at a given redshift) is an artifact due to biases in black hole mass measurements. The sub-Eddington boundary was initially found by Steinhardt & Elvis (2010a) using the FWHM-based black hole mass catalogue of Shen et al. (2008). However, the significance of the boundary is reduced when the FWHM-based mass-scaling relationship is recalibrated following Wang et al. (2009) and using the most updated reverberation mapping estimates of black hole masses. Furthermore, this boundary is not seen using mass estimates based on the line dispersion of the same quasars' MgII emission lines. Thus, the initial report of the sub-Eddington boundary was due to biases in estimating masses using the FWHM of a fit of one or two Gaussians to quasar MgII emission lines. We provide evidence that using the line dispersion of the MgII line produces less bi...

Rafiee, Alireza

2010-01-01

409

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

410

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

411

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

412

Metallicity effects on synthetic Cepheid Period-Luminosity relations  

Science.gov (United States)

On the basis of new theoretical results (Bono, Marconi & Stellingwerf, 1998, hereafter BMS; Bono, Caputo, Castellani & Marconi, 1998, hereafter BCCM) useful predictions concerning the Period-Luminosity (PLR) and Period-Luminosity-Color (PLCR) relations both for optical and infrared magnitudes are presented. It is shown that, following the dependence of the instability strip on metallicity, there is a non negligible dependence of the PLRs and PLCRs on the metallicity of the pulsating stars, mainly for optical bands. In particular theoretical results predict a dependence of the PLR on metals which is reversed with respect to current empirical evaluations (see for instance Gould 1994, Sasselov et al. 1997, Kennicutt et al. 1998, hereafter K98). To give a possible explanation for this discrepancy the typical observational procedures used to estimate extragalactic distances through Cepheid PLRs are here tested, with the aim of disentangling, if possible, the reddening and metallicity effects. To this purpose, synthetic PLRs for different metallicities were produced and treated as typical observational samples.

Musella, I.

413

The Luminosities and Diameters of Mira Variables from Hipparcos Parallaxes  

CERN Multimedia

Hipparcos trigonometrical parallaxes of Mira-type variables have been combined with ground-based angular diameter measurements to derive linear diameters. Of eight stars with ground-based data, six have diameters indicating overtone pulsation whilst two, both with periods over 400 day, are pulsating in the fundamental. Hipparcos parallaxes of 11 Miras have been combined with extensive infrared photometry to determine the zero-point of the Mira period-luminosity relation. Adopting the relation at K (2.2 micron), since this is less likely to be subject to abundance effects than that at Mbol, leads to a distance modulus for the LMC of 18.6 mag with a uncertainty of slightly less than 0.2 mag. A brief discussion is given of the preliminary analysis of the parallaxes of a much larger sample of Miras. Some consideration is given to possible problems in interpreting the Hipparcos data which arise because of the physical characteristics of the Mira variables. Finally the apparent low-luminosity of the carbon Mira, R ...

Whitelock, P A; Van Leeuwen, F W; Feast, M W

1997-01-01

414

AGB Variables and the Mira Period-Luminosity Relation  

CERN Document Server

Published data for large amplitude asymptotic giant branch variables in the Large Magellanic Cloud are re-analysed to establish the constants for an infrared (K) period-luminosity relation of the form: Mk=rho[log P-2.38] + delta. A slope of rho=-3.51+/-0.20 and a zero point of delta=-7.15+/-0.06 are found for oxygen-rich Miras (if a distance modulus of 18.39+/-0.05 is used for the LMC). Assuming this slope is applicable to Galactic Miras we discuss the zero-point for these stars using the revised Hipparcos parallaxes together with published VLBI parallaxes for OH Masers and Miras in Globular Clusters. These result in a mean zero-point of delta=-7.25+/-0.07 for O-rich Galactic Miras. The zero-point for Miras in the Galactic Bulge is not significantly different from this value. Carbon-rich stars are also discussed and provide results that are consistent with the above numbers, but with higher uncertainties. Within the uncertainties there is no evidence for a significant difference between the period-luminosity ...

Whitelock, Patricia A; van Leeuwen, Floor

2008-01-01

415

TURBULENT CELLS IN STARS: FLUCTUATIONS IN KINETIC ENERGY AND LUMINOSITY  

International Nuclear Information System (INIS)

Three-dimensional (3D) hydrodynamic simulations of shell oxygen burning exhibit bursty, recurrent fluctuations in turbulent kinetic energy. These are shown to be due to a general instability of the convective cell, requiring only a localized source of heating or cooling. Such fluctuations are shown to be suppressed in simulations of stellar evolution which use the mixing-length theory. Quantitatively similar behavior occurs in the model of a convective roll (cell) of Lorenz, which is known to have a strange attractor that gives rise to chaotic fluctuations in time of velocity and, as we show, luminosity. Study of simulations suggests that the behavior of a Lorenz convective roll may resemble that of a cell in convective flow. We examine some implications of this simplest approximation and suggest paths for improvement. Using the Lorenz model as representative of a convective cell, a multiple-cell model of a convective layer gives total luminosity fluctuations which are suggestive of irregular variables (red giants and supergiants), and of the long secondary period feature in semiregular asymptotic giant branch variables. This '?-mechanism' is a new source for stellar variability, which is inherently nonlinear (unseen in linear stability analysis), and one closely related to intermittency in turbulence. It was already implicit in the 3D global simulations of Woodward et al. This fluctuating behavior is seen in extended two-dimensional simulations of CNeOSi burning shells, and may cause instability which leads to eruptions in progenitors of core-collapse supernovae prior to collapse.

2011-11-01

416

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

417

HERA+LC based ?p collider: Luminosity and physics  

International Nuclear Information System (INIS)

We discuss the possibility of constructing a Linac-Ring type ep collider and a ?p collider based on it at DESY, namely the HERA+LC proposal. Using the parameters of the proton ring of HERA and those of the proposed linear e+e- collider (LC), we expect a luminosity of L?p=(1-2)x1031 cm-2 s-1 due to reasonable improvement of the proton beam. In a ?p collider, high energy ? beam is produced by the Compton backscattering of laser photons off electron beam from linear accelerator. In the case of opposite choice of laser photon and electron beam helicities, the luminosity of ?p collisions still exceeds 1031 cm-2 s-1 up to a distance of 12 m between the conversion region and the collision point. We examine the physics research program for the HERA+LC ?p collider proposal. Search for the supersymmetric partners, leptoquark production as well as heavy quark investigation are considered in detail. The capacity of HERA+LC surpasses that of HERA and is comparable with LC. Polarization facilities of the gamma and proton beams, and the clearer background compared to the hadron colliders are stated as additional advantages of the proposed ?p collider. (orig.)

1995-01-01

418

Upper limits to the annihilation radiation luminosity of Centaurus A  

International Nuclear Information System (INIS)

A high-resolution observation of the active nucleus galaxy Centaurus A (NGC 5128) was made by the GSFC Low Energy ?-ray Spectrometer (LEGS) during a balloon flight on 1981 November 19. The measured spectrum between 70 and 500 keV is well represented by a power law of the form 1.05 x 10-4 (E/100 keV)-1 59 ph cm-2 s-1 with no breaks or line features observed. The 98% confidence (2sigma) flux upper limit for a narrow (-4 ph cm-2 s-1 Using this upper limit, the ratio of the narrow-line annihilation radiation luminosity to the intergral > 511 keV luminosity is estimated to be < 0.09 (2sigma upper limit). This is compared with the measured value for our galactic center in the Fall of 1979 of 0.10-0.13, indicating a difference in the emission regions in the nuclei of the two galaxies. 16 references, 1 figure

1983-01-06

419

Pure luminosity evolution models for faint field galaxy samples  

CERN Document Server

We have examined a set of pure luminosity evolution (PLE) models in order to explore up to what extent the rapidly increasing observational constraints from faint galaxy samples can be understood in this simple framework. We find that a PLE model, in which galaxies evolve mildly in time even in the rest frame UV, can reproduce most of the observed properties of faint galaxies assuming an open (\\Omega\\sim0) universe. In particular, such a model is able to fit reasonably well the number counts in the U,~b_j,~r_f,~I, and K bands, as well as the colour and redshift distributions derived from most of the existing samples. The most significant discrepancy between the predictions of this model and the data is the z distribution of faint K-selected galaxies. Significantly worse fits are obtained with PLE models for the theoretically attractive value of \\Omega = 1, although a simple number luminosity evolution model with a significant amount of merger events fits the data also in this cosmology.

Pozzetti, L

1996-01-01

420

The Luminosity Profile and Structural Parameters of the Andromeda Galaxy  

CERN Document Server

We have constructed an extended composite luminosity profile for the Andromeda galaxy, M31, and have decomposed it into three basic luminous structural components: a bulge, a disk and a halo. The dust-free Spitzer/IRAC imaging and extended spatial coverage of ground-based optical imaging and deep star counts allow us to map M31's structure from its center to 22 kpc along the major axis. We apply different decomposition methods for the 1D luminosity profiles and 2D images. These include non-linear least-squares and Bayesian Monte-Carlo Markov-chain analyses. The basic photometric model for M31 has a Sersic bulge with shape index n = 2.2 +/- 0.3 and effective radius R_e = 1.0 +/- 0.2 kpc, a dust-free exponential disk of scale length R_d = 5.3 +/- 0.5 kpc; the parameter errors reflect the range between various decomposition methods. The bulge parameter, n, is rather insensitive to bandpass effects and its value suggests a first rapid formation via mergers followed by secular growth from the disk. The M31 halo ha...

Courteau, Stephane; McDonald, Michael; Guhathakurta, Puragra; Gilbert, Karoline M; Zhu, Yucong; Beaton, Rachael Lynn; Majewski, Steven R

2011-01-01

 
 
 
 
421

The metric of the cosmos from luminosity and age data  

Science.gov (United States)

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; Hellaby, Charles; Alfedeel, Alnadhief H. A.

2011-09-01

422

Luminosity and tune shift in e+e- storage rings  

International Nuclear Information System (INIS)

Luminosity and tune shift have been the subject of numerous papers and talks since the invention of electron-positron storage rings. This paper derives an equation for luminosity and one for the linear tune shift based upon two simple assumptions. The first assumption is that the storage ring be designed such that the linear tune shifts in the two transverse planes, x and y, are equal; i.e., that ?nu/sub x/ = ?nu/sub y/. The second assumption is that the maximum acceptable disruption angle, ?/sub D/, of the colliding beams is approximately equal to the ''natural'' beam spread, ?/sub B/, of the stored colliding beams at the interaction point. First derived is the results for round beams having transverse gaussian distribution functions and then extend the derivation to beams having elliptical cross sections. Then compared are theoretical results with the observed results in several operating machines and with the ''design'' parameters of three new machines; namely KEK, BEPC, and LEP

1987-01-26

423

Gamma-Ray Luminosity Function of Blazars and the Cosmic Gamma-Ray Background: Evidence for the Luminosity Dependent Density Evolution  

CERN Document Server

We present a comprehensive study for the gamma-ray luminosity function (GLF) of blazars and their contribution to the extragalactic diffuse gamma-ray background (EGRB). Radio and gamma-ray luminosity correlation is introduced to take into account the radio detectability which is important for the blazar identification. Previous studies considered only pure luminosity evolution (PLE) or pure density evolution, but we introduce the luminosity dependent density evolution (LDDE) model, which is favored from the evolution of X-ray luminosity function (XLF) of AGNs. The model parameters are constrained by likelihood analyses about the observed redshift and gamma-ray flux distributions of the EGRET blazars. We find that the LDDE model gives a better fit to the observed distributions than the PLE model, indicating that the LDDE model is also appropriate for gamma-ray blazars, and that the jet activity is universally correlated with the accretion history of AGNs. The normalization between the GLF and XLF is consistent...

Narumoto, T; Narumoto, Takuro; Totani, Tomonori

2006-01-01

424

LUMINOSITY-METALLICITY RELATIONS FOR BLUE COMPACT DWARF GALAXIES IN THE OPTICAL AND NEAR-INFRARED  

International Nuclear Information System (INIS)

In this paper, we present systematic studies on the B-, R- and Ks -band luminosity-metallicity (L-Z) relations for a set of metal-poor, blue compact dwarf galaxies (BCDs). Metallicity is derived by using both the empirical N2 and the direct Te methods. Our work reconciles contradictory results obtained by different authors and shows that the L-Z relationship does also hold for BCDs. The empirical N2-based slope of the L-Z relation, for each photometric band, is consistent with the Te -based one. We confirm that the slope of the L-Z relation is shallower in the near-infrared than that in the optical. Our investigations on the correlations between the LB -Z relation residuals and different galactic parameters show that the star formation activities could be a cause of the large scatter in the optical L-Z relationships, whereas the internal absorption might be another possible contributing factor.

2010-02-10

425

The Non-Parametric Model for Linking Galaxy Luminosity with Halo/Subhalo Mass  

CERN Document Server

We present a non-parametric, empirically based, model for associating galaxy luminosities with halo/subhalo masses, based on a self-consistent treatment of subhalo mass loss and the subhalo mass function. We find that, at high mass, the mass-luminosity relation is almost independent of the actual luminosity function considered, when luminosity is scaled by the characteristic luminosity L*. Additionally, the shape of the total halo