Towards the Automatic Estimation of Time Delays of Gravitational Lenses

Hirv, A.; Olspert, N.; Pelt, J.

doi:10.1515/astro-2017-0273

Cited by 9 publications

(7 citation statements)

References 34 publications

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“…Monitoring in the optical requires a long baseline or high photometric precision to overcome systematic variations due to microlensing by stars in the lensing galaxy that could be mistaken as the background source intrinsic variability (e.g., Tewes et al 2013b;Sluse & Tewes 2014). Curve-shifting methods have been developed to measure the time delays from the light curves (e.g., Press et al 1992;Pelt et al 1996;Fassnacht et al 2002;Harva & Raychaudhury 2008;Hirv et al 2011;Morgan et al 2008;Tewes et al 2013a;Hojjati et al 2013). A recent time-delay challenge showed that some of the methods can recover accurately the time delays in a blind test (Dobler et al 2015;Liao et al 2015), particularly the methods we use from the COSMOGRAIL collaboration (e.g., Tewes et al 2013a;Bonvin et al 2016).…”

Section: Observational Requirements Of the Time-delay Methodsmentioning

confidence: 99%

H0LiCOW – I. H0 Lenses in COSMOGRAIL's Wellspring: program overview

Suyu

Bonvin

Courbin

et al. 2017

Monthly Notices of the Royal Astronomical Society

363

356

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Strong gravitational lens systems with time delays between the multiple images allow measurements of time-delay distances, which are primarily sensitive to the Hubble constant that is key to probing dark energy, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. We present H0LiCOW (H 0 Lenses in COSMOGRAIL's Wellspring), a program that aims to measure H 0 with < 3.5% uncertainty from five lens systems (B1608+656, RXJ1131−1231, HE 0435−1223, WFI2033−4723 and HE 1104−1805). We have been acquiring (1) time delays through COSMOGRAIL and Very Large Array monitoring, (2) high-resolution Hubble Space Telescope imaging for the lens mass modeling, (3) wide-field imaging and spectroscopy to characterize the lens environment, and (4) moderate-resolution spectroscopy to obtain the stellar velocity dispersion of the lenses for mass modeling. In cosmological models with one-parameter extension to flat ΛCDM, we expect to measure H 0 to < 3.5% in most models, spatial curvature Ω k to 0.004, w to 0.14, and the effective number of neutrino species to 0.2 (1σ uncertainties) when combined with current CMB experiments. These are, respectively, a factor of ∼ 15, ∼ 2, and ∼ 1.5 tighter than CMB alone. Our data set will further enable us to study the stellar initial mass function of the lens galaxies, and the co-evolution of supermassive black holes and their host galaxies. This program will provide a foundation for extracting cosmological distances from the hundreds of time-delay lenses that are expected to be discovered in current and future surveys.

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Section: Observational Requirements Of the Time-delay Methodsmentioning

confidence: 99%

H0LiCOW – I. H0 Lenses in COSMOGRAIL's Wellspring: program overview

Suyu

Bonvin

Courbin

et al. 2017

Monthly Notices of the Royal Astronomical Society

363

356

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“…A broad range of curve-shifting algorithms have been developed in the past to measure time delays between light curves (e.g. Press et al 1992;Pelt et al 1994;Kelly et al 2009;Hirv et al 2011;Hojjati et al 2013;Hojjati & Linder 2014;Aghamousa & Shafieloo 2015). Efficient algorithms must be robust against photometric noise, coarse temporal sampling, season gaps and must also take into account the presence of microlensing caused by moving stars in the lensing galaxy.…”

Section: Time-delay Measurementsmentioning

confidence: 99%

Cosmograil

Millon

Courbin

Bonvin

et al. 2020

A&A

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We present the results of 15 years of monitoring lensed quasars, which was conducted by the COSMOGRAIL programme at the Leonhard Euler 1.2 m Swiss Telescope. The decade-long light curves of 23 lensed systems are presented for the first time. We complement our data set with other monitoring data available in the literature to measure the time delays in 18 systems, among which nine reach a relative precision better than 15% for at least one time delay. To achieve this, we developed an automated version of the curve-shifting toolbox PyCS to ensure robust estimation of the time delay in the presence of microlensing, while accounting for the errors due to the imperfect representation of microlensing. We also re-analysed the previously published time delays of RX J1131−1231 and HE 0435−1223, by adding six and two new seasons of monitoring, respectively, and confirming the previous time-delay measurements. When the time delay measurement is possible, we corrected the light curves of the lensed images from their time delay and present the difference curves to highlight the microlensing signal contained in the data. To date, this is the largest sample of decade-long lens monitoring data, which is useful to measure H0 and the size of quasar accretion discs with microlensing as well as to study quasar variability.

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“…Unevenly spaced data resulting from, for example, weather and/or observing time allocation, are a challenge for light-curve analysis. A number of techniques have been specially developed to utilize these multiple light curves of mirage images with unevenly sampled data (Edelson & Krolik 1988;Press et al 1992;Burud et al 2001;Pelt et al 1998;Pindor 2005;Scargle 1982;Roberts et al 1987;Geiger & Schneider 1996;Gürkan et al 2014;Hirv et al 2011).…”

Section: Time Delay Measurementmentioning

confidence: 99%

Resolving the High-Energy Universe With Strong Gravitational Lensing: The Case of PKS 1830–211

Barnacka

Geller

Dell’Antonio

et al. 2015

ApJ

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Gravitational lensing is a potentially powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission from distance sources and produce time delays between mirage images. Gravitationally-induced time delays depend on the position of the emitting regions in the source plane. The Fermi/LAT telescope continuously monitors the entire sky and detects gamma-ray flares, including those from gravitationally-lensed blazars. Therefore, temporal resolution at gamma-ray energies can be used to measure these time delays, which, in turn, can be used to resolve the origin of the gamma-ray flares spatially. We provide a guide to the application and Monte Carlo simulation of three techniques for analyzing these unresolved light curves: the Autocorrelation Function, the Double Power Spectrum, and the Maximum Peak Method. We apply these methods to derive time delays from the gamma-ray light curve of the gravitationally-lensed blazar PKS 1830-211. The result of temporal analysis combined with the properties of the lens from radio observations yield an improvement in spatial resolution at gamma-ray energies by a factor of 10000. We analyze four active periods. For two of these periods, the emission is consistent with origination from the core and for the other two, the data suggest that the emission region is displaced from the core by more that ∼ 1.5 kpc. For the core emission, the gamma-ray time delays, 23 ± 0.5 days and 19.7 ± 1.2 days, are consistent with the radio time delay 26 +4 −5 days.

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Towards the Automatic Estimation of Time Delays of Gravitational Lenses

Cited by 9 publications

References 34 publications

H0LiCOW – I. H0 Lenses in COSMOGRAIL's Wellspring: program overview

H0LiCOW – I. H0 Lenses in COSMOGRAIL's Wellspring: program overview

Cosmograil

Resolving the High-Energy Universe With Strong Gravitational Lensing: The Case of PKS 1830–211

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