On the Probability Distribution of Cosmological Microlensing Optical Depths

Wyithe, J. Stuart B.; Turner, Edwin L.

doi:10.1086/338426

Cited by 21 publications

(36 citation statements)

References 32 publications

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“…1 show the optical depth as a funciton of redshift for chosen cosmological parameters (densities). Recently, Wyithe & Turner (2002a) considered probability distributions for the cases when lensing objects are concentrated in galaxies. The authors found that about 1% of high-redshift sources (z ∼ 3) are microlensed by stars at any time.…”

Section: Cosmological Distribution Of Microlensesmentioning

confidence: 99%

“…Multiple imaged sources dominate the stellar microlensing statistics. However, if CDM halos are composed of compact objects, Wyithe & Turner (2002a) concluded that the microlensing rate should be = 21 the authors found that the probability that a quasar could show a variability larger than m B = 0.5 due to microlensing by stars is about 2 × 10 −3 (the cosmological density of stars is assumed to be equal to Ω * = 0.005). 90% of these events are in multiple-imaged systems.…”

Section: Cosmological Distribution Of Microlensesmentioning

confidence: 99%

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On the contribution of microlensing to X-ray variability of high-redshifted QSOs

Popovic

Jovanović

2004

A&A

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Abstract. We consider a contribution of microlensing to the X-ray variability of high-redshifted QSOs. Such an effect could be caused by stellar mass objects (SMO) located in a bulge or/and in a halo of this quasar as well as at cosmological distances between an observer and a quasar. Here, we not consider microlensing caused by deflectors in our Galaxy since it is wellknown from recent MACHO, EROS and OGLE observations that the corresponding optical depth for the Galactic halo and the Galactic bulge is lower than 10 −6 . Cosmologically distributed gravitational microlenses could be localized in galaxies (or even in bulge or halo of gravitational macrolenses) or could be distributed in a uniform way. We have analyzed both cases of such distributions. As a result of our analysis, we obtained that the optical depth for microlensing caused by stellar mass objects is usually small for quasar bulge and quasar halo gravitational microlens distributions (τ ∼ 10 −4 ). On the other hand, the optical depth for gravitational microlensing caused by cosmologically distributed deflectors could be significant and could reach 10 −2 −0.1 at z ∼ 2. This means that cosmologically distributed deflectors may contribute significantlly to the X-ray variability of high-redshifted QSOs (z > 2). Considering that the upper limit of the optical depth (τ ∼ 0.1) corresponds to the case where dark matter forms cosmologically distributed deflectors, observations of the X-ray variations of unlensed QSOs can be used for the estimation of the dark matter fraction of microlenses.

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Section: Cosmological Distribution Of Microlensesmentioning

confidence: 99%

Section: Cosmological Distribution Of Microlensesmentioning

confidence: 99%

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

Popovic

Jovanović

2004

A&A

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“…In this section we expand on the discussion in Wyithe & Loeb (2002) and calculate the a posteriori probability for the magnification of a known quasar in the high-redshift samples. If a quasar is observed with a magnification of l obs , then it is intrinsically fainter by a factor of l obs and therefore more abundant by a factor of ðL=l obs Þ= l obs ðLÞ ½ f g .…”

Section: Magnification Of Observed Sourcesmentioning

confidence: 99%

Gravitational Lensing of the Sloan Digital Sky Survey High‐Redshift Quasars

Wyithe

Loeb

2002

ApJ

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We predict the effects of gravitational lensing on the color-selected flux-limited samples of z s $ 4:3 and z s e5:8 quasars, recently published by the Sloan Digital Sky Survey (SDSS). Our main findings are the following: (1) The lensing probability should be 1-2 orders of magnitude higher than for conventional surveys. The expected fraction of multiply imaged quasars is highly sensitive to redshift and the uncertain slope of the bright end of the luminosity function, h . For h ¼ 2:58 (3.43) we find that at z s $ 4:3 and i Ã < 20:0 the fraction is $4% (13%), while at z s $ 6 and z Ã < 20:2 the fraction is $7% (30%). (2) The distribution of magnifications is heavily skewed; sources having the redshift and luminosity of the SDSS z s e5:8 quasars acquire median magnifications of medðl obs Þ $ 1:1 1:3 and mean magnifications of hl obs i $ 5 50. Estimates of the quasar luminosity density at high redshift must therefore filter out gravitationally lensed sources. (3) The flux in the Gunn-Peterson trough of the highest redshift (z s ¼ 6:28) quasar is known to be f < 3 Â 10 À19 ergs s À1 cm À2 Å À1 . Should this quasar be multiply imaged, we estimate a 40% chance that light from the lens galaxy would have contaminated the same part of the quasar spectrum with a higher flux. Hence, spectroscopic studies of the epoch of reionization need to account for the possibility that a lens galaxy, which boosts the quasar flux, also contaminates the Gunn-Peterson trough. (4) Microlensing by stars should result in $ 1 3 of multiply imaged quasars in the z s e5:8 catalog varying by more than 0.5 mag over the next decade. The median emission-line equivalent width of multiply imaged quasars would be lowered by $20% with respect to the intrinsic value because of differential magnification of the continuum and emission-line regions.

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“…Several authors have studied possible micro-lensing where γ-ray intensity gets enhanced in a well predicted way over several days [19]. Because of the systematic surveying of GLAST-LAT over many years, we will also observe several strong lensing events in the temporal coordinate where a similar light curve (eg.…”

Section: Lensing In Time Domainmentioning

confidence: 94%

Future GeV γ-ray Missions and New Discovery Potential

Kamae¹

2005

AIP Conference Proceedings

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Abstract. Future GeV γ-ray missions, efforts to improve the diffuse γ-ray emission modeling, and possible exploitation of temporal variability for source characterization are reviewed. GLAST-LAT with its improved point-spread-function is expected to attain mCrab sensitivity, facilitate identification of γ-ray sources with those in other wavelength, and discover new source classes. However these new sources are likely to suffer from the Galactic diffuse background and/or the source confusion. Accurate modeling of the background will be essential to enhance discovery potential for Galactic sources and full exploitation of temporal variability will allow source identification even in highly confusing environment. GALPROP by Strong and Moskalenko provides a platform on which models and measurements on the cosmic ray, ISM and radiation field can be combined in a consistent way. An up-to-date high-energy pp interaction modeling has reduced the "GeV Excess" in the diffuse γ-ray spectrum significantly. Updating GALPROP with this interaction modeling as well as with other improvements will be needed before GLAST goes to orbit. The new temporal domain will be fully explored by GLAST-LAT as a new way to identify and characterize AGNs at cosmological distance. A FEW MILLI-CRAB SENSITIVITY FROM 100KEV TO 100TEVBefore the first decade of the 21st century closes, we will be able to map the entire sky in γ-ray from 100keV to 100TeV at sensitivity around a few to 10 milli-Crab. On the ground are 3 Air Cherenkov Telescopes (ACT: Cangaroo, HESS and Magic) operational, covering the highest 3 decades in the energy range above. Veritas is expected to join the three in 2005. In space is Integral covering the energy range from 100keV to 10MeV at a few to a few 100mCrab sensitivity. In a year Astro-E2 Hard X-ray Detector will join to cover between 10 and 500keV. The energy range from sub-GeV to hundreds of GeV will soon be covered by AGILE and GLAST-Large Area Telescope (LAT) of which GLAST-LAT will reach sensitivity around mCrab. The differential sensitivity of these instruments is plotted in Fig.1 together with popular multi-wavelength sources [1].The instruments described above are or will be operated in the pointing mode except for GLAST whose observation time will be mostly in the survey mode. The observation times assumed in making the curves in Fig.1 are: 100ks (3σ) for Astro-E2 HXD; 1Ms (3σ) for Integral IBIS (ISGRI and PICsIT); 50hrs (5σ) for ACT's; 1Ms (5σ) for AGILE; 1 yr (5σ) for GLAST-LAT. EGRET sensitivity (3σ) has been calculated by the author on the paper by de Jager et al. of the Crab nebula (total 300hrs) [2]. The AGILE and GLAST sensitivities are based on Monte Carlo simulation and to be considered as preliminary. The source fluxes shown in Fig.1 have been calculated on observational data except for Cas A where a model prediction has been used to interpolate between hard X-ray observations and a TeV γ-ray

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On the Probability Distribution of Cosmological Microlensing Optical Depths

Cited by 21 publications

References 32 publications

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

Gravitational Lensing of the Sloan Digital Sky Survey High‐Redshift Quasars

Future GeV γ-ray Missions and New Discovery Potential

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