Strong Lensing by Galaxies

Shajib, A. J.; Vernardos, G.; Collett, T. E.; Motta, V.; Sluse, D.; Williams, Liliya L. R.; Saha, P.; Birrer, S.; Spiniello, C.; Treu, T.

doi:10.48550/arxiv.2210.10790

Cited by 9 publications

(6 citation statements)

References 179 publications

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“…We selected a simple model for the simulations so that most effects are due to dynamical friction and not from simulation or model specifics. For the host galaxy, we selected an isothermal sphere model as the observed dynamical mass of galaxies that can be described by isothermal sphere-like distributions (Shajib et al 2022). The density decreases for the isothermal sphere with the radius as ρ ∝ r −2 , and all the locations have the same velocity dispersion σ.…”

Section: General Considerations and Initial Conditionsmentioning

confidence: 99%

Back to the present: A general treatment for the tidal field from the wake of dynamical friction

Kipper,

Tenjes,

Benito

et al. 2023

A&A

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Context. Dynamical friction can be a valuable tool for inferring dark matter properties that are difficult to constrain by other methods. Most applications of dynamical friction calculations are concerned with the long-term angular momentum loss and orbital decay of the perturber within its host. This, however, assumes knowledge of the unknown initial conditions of the system. Aims. We advance an alternative methodology to infer the host properties from the perturber’s shape distortions induced by the tides of the wake of dynamical friction, which we refer to as the tidal dynamical friction. Methods. As the shape distortions rely on the tidal field that has a predominantly local origin, we present a strategy to find the local wake by integrating the stellar orbits back in time along with the perturber, then removing the perturber’s potential and re-integrating them back to the present. This provides perturbed and unperturbed coordinates and hence a change in coordinates, density, and acceleration fields, which yields the back-reaction experienced by the perturber. Results. The method successfully recovers the tidal field of the wake based on a comparison with N-body simulations. We show that similar to the tidal field itself, the noise and randomness of the dynamical friction force due to the finite number of stars is also dominated by regions close to the perturber. Stars near the perturber influence it more but are smaller in number, causing a high variance in the acceleration field. These fluctuations are intrinsic to dynamical friction. We show that a stellar density of 0.0014 M⊙ kpc−3 yields an inherent variance of 10% to the dynamical friction. Conclusions. The current method extends the family of dynamical friction methods that allow for the inference of host properties from tidal forces of the wake. It can be applied to specific galaxies, such as Magellanic Clouds, with Gaia data.

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Section: General Considerations and Initial Conditionsmentioning

confidence: 99%

Back to the present: A general treatment for the tidal field from the wake of dynamical friction

Kipper,

Tenjes,

Benito

et al. 2023

A&A

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“…Strong gravitational lensing represents a significant category of celestial phenomena, occurring as light emitted by distant cosmic entities traverses regions occupied by supermassive objects such as galaxies, galaxy clusters, or black holes (Treu 2010;Kneib & Natarajan 2011;Meneghetti et al 2013;Birrer et al 2022;Shajib et al 2022;Treu et al 2022;Vegetti et al 2023;Lanusse 2018). Strong-lensing systems play a vital role in measuring mass distributions, confining cosmological parameters like the Hubble constant and dark energy density, and afford scientists the opportunity to investigate properties of remote celestial objects (Bradač et al 2002;Treu & Koopmans 2002;Auger et al 2010;Sonnenfeld et al 2015).…”

Section: Introductionmentioning

confidence: 99%

CSST Strong-lensing Preparation: A Framework for Detecting Strong Lenses in the Multicolor Imaging Survey by the China Survey Space Telescope (CSST)

Li,

Sun,

et al. 2024

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Strong gravitational lensing is a powerful tool for investigating dark matter and dark energy properties. With the advent of large-scale sky surveys, we can discover strong-lensing systems on an unprecedented scale, which requires efficient tools to extract them from billions of astronomical objects. The existing mainstream lens-finding tools are based on machine-learning algorithms and applied to cutout-centered galaxies. However, according to the design and survey strategy of optical surveys by the China Space Station Telescope (CSST), preparing cutouts with multiple bands requires considerable efforts. To overcome these challenges, we have developed a framework based on a hierarchical visual transformer with a sliding window technique to search for strong-lensing systems within entire images. Moreover, given that multicolor images of strong-lensing systems can provide insights into their physical characteristics, our framework is specifically crafted to identify strong-lensing systems in images with any number of channels. As evaluated using CSST mock data based on a semianalytic model named CosmoDC2, our framework achieves precision and recall rates of 0.98 and 0.90, respectively. To evaluate the effectiveness of our method in real observations, we have applied it to a subset of images from the DESI Legacy Imaging Surveys and media images from Euclid Early Release Observations. A total of 61 new strong-lensing system candidates are discovered by our method. However, we also identified false positives arising primarily from the simplified galaxy morphology assumptions within the simulation. This underscores the practical limitations of our approach while simultaneously highlighting potential avenues for future improvements.

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“…At high redshift, lensing galaxies can be difficult to detect due to limited spatial resolution, as well as their inherent faintness compared to the more luminous and potentially blended quasar images. Indeed, many systematic searches for dual quasars have turned up lensed quasars incidentally (see Shajib et al 2022, for a recent review). These systems are intriguing in their own right; cases of strong gravitational lensing have been used in recent decades to address cosmological questions including the value of the Hubble constant (Kochanek et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Varstrometry for Off-nucleus and Dual Subkiloparsec Active Galactic Nuclei (VODKA): Investigating the Nature of SDSS J0823+2418 at z = 1.81, A Likely Lensed Quasar

Gross,

Chen,

Foord

et al. 2023

ApJ

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Dual quasars at small physical separations are an important precursor phase of galaxy mergers, ultimately leading to the coalescence of the two supermassive black holes. Starting from a sample of dual and/or lensed quasar candidates discovered using astrometric jitter in Gaia data, we present a pilot case study of one of the most promising yet puzzling candidate dual quasars at cosmic noon (z ∼ 1.8). Using multiwavelength imaging and spectroscopy from X-ray to radio, we test whether the SDSS J0823+2418 system is two individual quasars in a bound pair at separation ∼0.″64, or instead a single quasar being gravitationally lensed by a foreground galaxy. We find consistent flux ratios (∼1.25−1.45) between the two sources in optical, near-IR (NIR), UV, and radio, and thus similar spectral energy distributions, suggesting a strong-lensing scenario. However, differences in the radio spectral index, as well as changing X-ray fluxes, hint at either a dual quasar with otherwise nearly identical properties or perhaps lensing-based time lag of ∼3 days paired with intrinsic variability. We find with lens mass modeling that the relative NIR positions and magnitudes of the two quasars and a marginally detected central galaxy are consistent with strong lensing. Archival Sloan Digital Sky Survey spectra likewise suggest a foreground absorber via Mg ii absorption lines. We conclude that SDSS J0823+2418 is likely a lensed quasar, and therefore that the VODKA sample contains a population of these lensed systems (perhaps as high as 50%) as well as dual quasars.

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Strong Lensing by Galaxies

Cited by 9 publications

References 179 publications

Back to the present: A general treatment for the tidal field from the wake of dynamical friction

Back to the present: A general treatment for the tidal field from the wake of dynamical friction

CSST Strong-lensing Preparation: A Framework for Detecting Strong Lenses in the Multicolor Imaging Survey by the China Survey Space Telescope (CSST)

Varstrometry for Off-nucleus and Dual Subkiloparsec Active Galactic Nuclei (VODKA): Investigating the Nature of SDSS J0823+2418 at z = 1.81, A Likely Lensed Quasar

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