Interpreting microlensing signal in QSO 2237+0305: Stars or planets?

Gil-Merino, R.; Lewis, Geraint F.

doi:10.1051/0004-6361:200500128

Cited by 4 publications

(3 citation statements)

References 34 publications

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“…In addition to providing information about the global mass structure of the galaxy (Schneider et al 1988;Kent & Falco 1988;Mihov 2001;Trott & Webster 2002), it has also been used to study the properties of stars, or compact objects, in the lensing galaxy through microlensing (e.g. Gil-Merino & Lewis 2005), and the structure of the broad-line region of the lensed quasar (Wayth et al 2005;Vakulik et al 2007;Eigenbrod et al 2008b). Previously published spectra of 2237+0305 have either concentrated on studying the quasar spectrum, or only presented a small wavelength range for the galaxy spectrum.…”

Section: Introductionmentioning

confidence: 99%

Stars and dark matter in the spiral gravitational lens 2237+0305

Trott

Treu

Koopmans³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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We construct a mass model for the spiral lens galaxy 2237+0305, at redshift z_l=0.04, based on gravitational-lensing constraints, HI rotation, and new stellar-kinematic information, based on data taken with the ESI spectrograph on the 10m Keck-II Telescope. High resolution rotation curves and velocity dispersion profiles along two perpendicular directions, close to the major and minor axes of the lens galaxy, were obtained by fitting the Mgb-Fe absorption line region. The stellar rotation curve rises slowly and flattens at r~1.5" (~1.1 kpc). The velocity dispersion profile is approximately flat. A combination of photometric, kinematic and lensing information is used to construct a mass model for the four major mass components of the system -- the dark matter halo, disc, bulge, and bar. The best-fitting solution has a dark matter halo with a logarithmic inner density slope of gamma=0.9+/-0.3 for rho_DM propto r^-gamma, a bulge with M/L_B=6.6+/-0.3 Upsilon_odot, and a disc with M/L_B =1.2+/-0.3 Upsilon_odot, in agreement with measurements of late-type spirals. The bulge dominates support in the inner regions where the multiple images are located and is therefore tightly constrained by the observations. The disc is sub-maximal and contributes 45+/-11 per cent of the rotational support of the galaxy at 2.2r_d. The halo mass is (2.0+/-0.6) x 10^12 M_odot, and the stellar to virial mass ratio is 7.0+/-2.3 per cent, consistent with typical galaxies of the same mass.Comment: 14 pages, 6 figures, MNRAS, in pres

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Section: Introductionmentioning

confidence: 99%

Stars and dark matter in the spiral gravitational lens 2237+0305

Trott

Treu

Koopmans³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…The variability of the light-curve of a lensed object induced by the discretization of the mass distribution of the lens galaxy in stars or other compact objects (gravitational microlensing, Chang & Refsdal 1979;Young 1981;Paczynski 1986;Kayser, Refsdal & Stabell 1986;Schneider & Weiss 1987;Irwin et al 1989;Witt 1990;Wambsganss 2001;Gil-Merino & Lewis 2005) offers a promising way of studying the unresolved source of the continuum of QSOs. Other characteristic regions of QSOs and AGN, such as the broad line region (BLR) and the narrow line region (NLR), were considered too large (Rees 1984) to be significantly affected by the microlensing effect (Nemiroff 1988;Schneider & Wambsganss 1990).…”

Section: Introductionmentioning

confidence: 99%

Microlensing of a Biconical Broad‐Line Region

Abajas

Mediavilla

Muñoz

et al. 2007

ApJ

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The influence of microlensing in the profiles of the emission lines generated in a biconical geometry is discussed. Microlensing amplification in this anisotropic model is not directly related to the bicone's intrinsic size but depends on the orientation of the bicone axis and on the cone aperture. The orientation of the projected bicone with respect to the shear of the magnification pattern can induce very interesting effects, like the quasi-periodic enhancements of the red/blue part of the emission line profile or the lack of correlation between the broad line region (BLR) and continuum light curves of QSOs. The emission line profiles of a BLR moving in a high caustic concentration exhibit sharp features that are well defined in wavelength. These features (spikes) correspond to the scanning of the kinematics of the BLR by the caustic clusters. The biconical model can qualitatively reproduce with a transversal (with respect to the shear) movement of the BLR, the recurrent blue-wing enhancement detected in the emission line profile of the A image of the quasar lensed system SDSS J1004+4112. The probability of observing this repetitive event is almost a 2% for a fraction of matter in stars of a 5%. This result would make plausible the detection of the spectral variability in SDSS J1004+4112 under the hypothesis of microlensing of a bicone.

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“…At this point, however, this remains a speculative possibility. As it has been noted widely, the effects of many lenses combine in a highly nonlinear fashion and the role of the individual lenses even in the simplest phenomenology is nontrivial (see e.g., Gil-Merino & Lewis 2005). While one could expect that the approach of decomposing the star field into lattices outlined in the previous paragraph might fare better than the simplistic approach of seeing the star field as the combination of individual stars (since it takes care of some of the nonlinear effects), no compelling argument can yet be made that this is the case.…”

Section: External Shearmentioning

confidence: 99%

Gravitational lensing by point masses on regular grid points

2007

Monthly Notices of the Royal Astronomical Society

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It is shown that gravitational lensing by point masses arranged in an infinitely extended regular lattice can be studied analytically using the Weierstrass functions. In particular, we draw the critical curves and the caustic networks for the lenses arranged in regular-polygonal -- square, equilateral triangle, regular hexagon -- grids. From this, the mean number of positive parity images as a function of the average optical depth is derived and compared to the case of the infinitely extended field of randomly distributed lenses. We find that the high degree of the symmetry in the lattice arrangement leads to a significant bias towards canceling of the shear caused by the neighboring lenses on a given lens position and lensing behaviour that is qualitatively distinct from the random star field. We also discuss some possible connections to more realistic lensing scenarios.Comment: to appear in Monthly Notices of RAS, including 17 figs, 1 appendix. High-res figs and F95 code used available upon reques

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Interpreting microlensing signal in QSO 2237+0305: Stars or planets?

Cited by 4 publications

References 34 publications

Stars and dark matter in the spiral gravitational lens 2237+0305

Stars and dark matter in the spiral gravitational lens 2237+0305

Microlensing of a Biconical Broad‐Line Region

Gravitational lensing by point masses on regular grid points

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