Can I easily crash STATCALC?

Browne, T. J.; Williams, Roy G.

doi:10.1007/978-1-349-08152-3_15

Cited by 69 publications

(108 citation statements)

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“…J0958+2958 has two compact radio sources separated by 8 arcsec, but these objects are distinct quasars with redshifts of 2.064 and 2.744, ruling out this system as a gravitational lens (Lehár et al 2001). J0935+0719 has a series of radio observations indicating that it might be a gravitational lens in which the source is a compact symmetric object, and is mentioned as the candidate J0935+073 in Browne et al (2003). We find that the flux density ratio is 19:1 at 5, 8.5 and 22 GHz, supporting the lensing interpretation.…”

Section: S U Rv E Y a N D O B S E Rvat I O N Ssupporting

confidence: 67%

“…At 3 mas resolution substructure is seen only in the brighter, more magnified image. All but one of the CLASS candidates with multiple compact components in VLBA maps were confirmed as lenses (Browne et al 2003). The exception, B0827+525, had significantly different spectra for the two components and is likely to be a binary quasar .…”

Section: Discussionmentioning

confidence: 92%

“…The size of the emitting region is larger in the radio than in optical or X-ray (Koopmans & de Bruyn 2000), making the image brightnesses less susceptible to microlensing, while central images are strongly affected by dust absorption and confusion in the optical regime but not in the radio frequency range 5-40 GHz (Winn et al 2004). The largest sample of radio-loud lenses has been provided by CLASS (Myers et al 2003;Browne et al 2003), which found 22 instances of a bright radio source lensed by a foreground galaxy. E-mail: edward.boyce@manchester.ac.uk (ERB) A crucial step in CLASS was the rejection of double sources with a flux density ratio >10:1 (Myers et al 2003) after the initial 8.4-GHz VLA snapshot.…”

Section: Introductionmentioning

confidence: 99%

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J0316+4328: a probable ‘asymmetric double’ lens

Boyce

Myers

Browne

et al. 2007

Monthly Notices of the Royal Astronomical Society: Letters

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We report a probable gravitational lens J0316+4328, one of 19 candidate asymmetric double lenses (two images at a high flux density ratio) from CLASS. Observations with the Very Large Array (VLA), MERLIN and the Very Long Baseline Array (VLBA) imply that J0316+4328 is a lens with high confidence. It has two images separated by 0.40 arcsec, with 6‐GHz flux densities of 62 mJy and 3.2 mJy. The flux density ratio of ∼19 (constant over the frequency range 6–22 GHz) is the largest for any two‐image gravitational lens. High‐resolution optical imaging and deeper VLBI maps should confirm the lensing interpretation and provide inputs to detailed lens models. The unique configuration will give strong constraints on the lens galaxy's mass profile.

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Section: S U Rv E Y a N D O B S E Rvat I O N Ssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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J0316+4328: a probable ‘asymmetric double’ lens

Boyce

Myers

Browne

et al. 2007

Monthly Notices of the Royal Astronomical Society: Letters

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“…Both in optical surveys such as Sloan Lens ACS Survey (SLACS) (Bolton et al 2006) and in radio surveys such as Jordrell Bank‐VLA Astrometric Survey (JVAS) or Cosmic Lens All Sky Survey (CLASS) (King et al 1999; Browne et al 2003), early‐type lenses dominate over late‐types since the lensing cross‐section scales as the fourth power of velocity dispersion but only linearly with number density. Roughly one in every 1000 distant sources has detectable multiple images, although this depends on the source population in question – due to factors such as their luminosity function and characteristic size – and on how lens systems are detected – through, for example, the angular resolution and sensitivity of the search.…”

Section: Introductionmentioning

confidence: 99%

“…Roughly one in every 1000 distant sources has detectable multiple images, although this depends on the source population in question – due to factors such as their luminosity function and characteristic size – and on how lens systems are detected – through, for example, the angular resolution and sensitivity of the search. For example, Browne et al (2003) found that roughly one in 700 distant flat spectrum radio sources is multiply imaged, down to an image separation of 0.3 arcsec.…”

Section: Introductionmentioning

confidence: 99%

Probing galactic dark matter in dense environments: on the strong lensing efficiency of galaxies in rich clusters

King¹

2007

Monthly Notices of the Royal Astronomical Society

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The recent detection by Limousin et al. of five new strong lensing events dominated by galaxy cluster members in Abell 1689, and outside the critical regime of the cluster itself, offers a way to obtain constraints on the cluster mass distribution in a region inaccessible to standard lensing analysis. In addition, modelling such systems will provide another window on the dark matter haloes of galaxies in very dense environments. Here, it is shown that the boost in image separation due to the external shear and convergence from a smooth cluster component means that more numerous, less massive galaxies have the potential to create multiple images with detectable separations, relative to isolated field galaxies. This comes in addition to a potential increase in their lensing (source plane) cross‐section. To gain insight into the factors involved and as a precursor to a numerical study using N‐body simulations, a simple analytic model of a cluster at z= 0.3 lensing background galaxies at z= 2 is considered here. The fiducial model has cluster members with isothermal density profiles and luminosities L, distributed in a Schechter function (faint‐end slope ν=−1.25), related to their velocity dispersions σ via the Faber–Jackson scaling L∝σ4. Just outside the critical regime of the cluster, the scale of galaxy‐dominated image separations is significantly increased. Folding in the fact that less massive galaxies present a lower lensing cross‐section, and that the cross‐section can itself be enhanced in an external field leads to a factor of a few times more detected events relative to field galaxies. These values will be higher closer to the critical curve. Given that the events in Abell 1689 were detected over a very small region of the cluster where ACS data were available, this motivates the search for such events in other clusters.

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Strong lensing constraints on the velocity dispersion and density profile of elliptical galaxies

Davis

Huterer

Krauss

2003

Monthly Notices RAS

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We use the statistics of strong gravitational lensing from the Cosmic Lens All‐Sky Survey to impose constraints on the velocity dispersion and density profile of elliptical galaxies. This approach differs from much recent work, where the luminosity function, velocity dispersion and density profile have been typically assumed in order to constrain cosmological parameters. It is indeed remarkable that observational cosmology has reached the point where we can consider using cosmology to constrain astrophysics, rather than vice versa. We use two different observables to obtain our constraints: total optical depth and angular distributions of lensing events. In spite of the relatively poor statistics and the uncertain identification of lenses in the survey, we obtain interesting constraints on the velocity dispersion and density profiles of elliptical galaxies. For example, assuming the singular isothermal sphere density profile and marginalizing over other relevant parameters, we find 168 ≤σ*≤ 200 km s−1 (68 per cent confidence level), and 158 ≤σ*≤ 220 km s−1 (95 per cent confidence level). Furthermore, if we instead assume a generalized Navarro–Frenk–White density profile and marginalize over other parameters, the slope of the profile is constrained to be 1.50 ≤β≤ 2.00 (95 per cent confidence level). We also constrain the concentration parameter as a function of the density profile slope in these models. These results are essentially independent of the exact knowledge of cosmology. We briefly discuss the possible impact on these constraints of allowing the galaxy luminosity function to evolve with redshift, and also possible useful future directions for exploration.

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Can I easily crash STATCALC?

Cited by 69 publications

References 0 publications

J0316+4328: a probable ‘asymmetric double’ lens

J0316+4328: a probable ‘asymmetric double’ lens

Probing galactic dark matter in dense environments: on the strong lensing efficiency of galaxies in rich clusters

Strong lensing constraints on the velocity dispersion and density profile of elliptical galaxies

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