Photometric variations in the Q2237 + 0305 system - First detection of a microlensing event

Irwin, M. J.; Webster, R. L.; Hewett, Paul C.; Corrigan, R. T.; Jędrzejewski, R.

doi:10.1086/115272

Cited by 262 publications

(203 citation statements)

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“…For example, in the case of the redshift corresponding to the famous Einstein Cross QSO 2237+0305 where the optical depth is smaller than for other two redshifts. One could say that it is natural that the discovery of X-ray microlensing was made for this quasar, since the Einstein Cross QSO 2237+0305 is the most "popular" object to search for microlensing, because the first cosmological microlensing phenomenon was found by Irwin et al (1989) in this object and several groups have been monitoring the quasar QSO 2237+0305 to find evidence for microlensing. Microlensing has been suggested for the quasar MG J0414+0534 (Angonin-Willaime et al 1999) and for the quasar QSO H1413+117 (Remy et al 1996;Ostensen et al 1997;Turnshek et al 1997;Chae et al 2001).…”

Section: Discussionmentioning

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: Discussionmentioning

confidence: 99%

“…First evidence of quasar microlensing was found by Irwin et al (1989). Now there is a number of known gravitational lens systems (Claeskens & Surdej 2002;Browne et al 2003) and some of them show evidence for microlensing (Wambsganss 2001a).…”

Section: Microlensing Of Gravitationally Lensed Objectsmentioning

confidence: 99%

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

Popovic

Jovanović

2004

A&A

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“…This phenomenon was subsequently observed in the quadruple gravitational lens Q2237]0305 (Irwin et al 1989 ;Corrigan et al 1991). The idea that most quasar variability results from microlensing due to cosmologically distributed compact objects has since been championed by Hawkins (1993).…”

Section: Introductionmentioning

confidence: 89%

On the Probability Distribution of Cosmological Microlensing Optical Depths

Wyithe¹,

Turner²

2002

ApJ

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It is conventional to calculate the probability of microlensing for a cosmologically distant source based on the Press-Gunn approximation that the lensing objects are uniformly and randomly distributed in the intervening space with a constant comoving density. We here investigate more realistic cosmological microlensing statistics by considering the strong spatial clustering of likely lensing objects with each other in galaxies and their association with the clumps of dark matter that make up the massive halos of galaxies. Both cases in which microlensing objects are distributed like the observed starlight in galaxies and ones in which the extended massive halos themselves are also composed of compact massive objects capable of acting as microlenses are investigated. The distribution of microlensing optical depth i along randomly chosen sight lines is calculated, as is the conditional distribution of i along sight lines near one that is strongly microlensed. Illustrative magniÐcation biases are also considered. These distributions allow us to calculate both the probability that a high-redshift source will be microlensed in the various scenarios and the likely local i (averaged over nearby sight lines) at which such microlensing events will occur. Our overall result is that the Press-Gunn approximation is a useful order-of-magnitude approximation if the massive halos of galaxies are made of dark compact objects, but that it fails badly and can be qualitatively misleading in the more likely case in which only the ordinary stellar populations of galaxies are the dominant source of cosmological microlensing events. In particular, we Ðnd that microlensing by stars is limited to of the order of 1% of high-redshift sources at any one time. Furthermore, even though only a small fraction of high-redshift sources are multiply imaged (by galaxies), it is these sources that are most likely to be microlensed by stars. Consequently, microlensing by stars is usually observed at i near 1 where the simple isolated point mass lens approximation is not appropriate. However, if cold dark matter halos are composed of condensed objects, then more than 10% of high-redshift sources are microlensed at any given time. The vast majority of these sources are not multiply imaged, and have i smaller than 0.01.

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“…This cosmic mirage, also named "Einstein cross" because of its shape, consists of a z s = 1.695 quasar gravitationally lensed into four images separated by about 1.5 and arranged in a crosslike pattern around a bright z l = 0.0394 barred, Sab lensing galaxy (Yee 1988). This system is known to show microlensing-induced temporal and spectral variations (Irwin et al 1989;Lewis et al 1996, and references therein). In addition, Sluse et al (2011) and O'Dowd et al (2011) have detected differential microlensing through the velocity structure of the high-ionization carbon line.…”

Section: Introductionmentioning

confidence: 99%

The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

Braibant

Hutsemékers

Sluse

et al. 2016

A&A

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We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high-and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization Hα line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high-and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high-and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of Hα favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations.

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Photometric variations in the Q2237 + 0305 system - First detection of a microlensing event

Cited by 262 publications

References 0 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

On the Probability Distribution of Cosmological Microlensing Optical Depths

The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

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