A Determination of H0 with the CLASS Gravitational Lens B1608+656. III. A Significant Improvement in the Precision of the Time Delay Measurements

By C. Fassnacht, E. Xanthopoulos, Leon V. E. Koopmans, D. Rusin. 2002

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The gravitational lens CLASS B1608+656 is the only four-image lens system for which all three independent time delays have been measured. This makes the system an excellent candidate for a high-quality determination of H0 at cosmological distances. However, the original measurements of the time delays had large (12%-20%) uncertainties, due to the low level of variability of the background source during the monitoring campaign. In this paper, we present results from two additional VLA monitoring campaigns. In contrast to the ~5% variations seen during the first season of monitoring, the source flux density changed by 25%-30% in each of the subsequent two seasons. We analyzed the combined data set from all three seasons of monitoring to improve significantly the precision of the time delay measurements; the delays are consistent with those found in the original measurements, but the uncertainties have decreased by factors of 2-3. We combined the delays with revised isothermal mass models to derive a measurement of H0. Depending on the positions of the galaxy centroids, which vary by up to 0.″1 in Hubble Space Telescope (HST) images obtained with different filters, we obtain H0 = 61-65 km s-1 Mpc-1, for (ΩM, ΩΛ) = (0.3, 0.7). The value of H0 decreases by 6% if (ΩM, ΩΛ) = (1.0, 0.0). The formal uncertainties on H0 due to the time-delay measurements are ±1 (±2) km s-1 Mpc-1 for the 1 σ (2 σ) confidence limits. Thus, the systematic uncertainties due to the lens model, which are on the order of ±15 km s-1 Mpc-1, now dominate the error budget for this system. In order to improve the measurement of H0 with this lens, new models that incorporate the constraints provided by stellar dynamics and the optical/infrared Einstein ring seen in HST images must be developed.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fa13e402f1361546b83f4d537f3f90102f6a8e81

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Citations in the corpus

Gravitational lensing (2010, result): “[123]), but lens models constructed upon a large number of constraints yield values which are very well in agreement with other determinations.”
DISSECTING THE GRAVITATIONAL LENS B1608+656. II. PRECISION MEASUREMENTS OF THE HUBBLE CONSTANT, SPATIAL CURVATURE, AND THE DARK ENERGY EQUATION OF STATE (2009, methodology): “This system is special in that the three relative time delays between the four images were measured accurately with errors of only a few percent: ∆tAB = 31.5 +2.0 −1.0 days, ∆tCB = 36.0 +1.5 −1.5 days, and ∆tDB = 77.0 +2.0 −1.0 days (Fassnacht et al. 1999, 2002).”
The Cosmic Lens All-Sky Survey - II. Gravitational lens candidate selection and follow-up (2002, methodology): “Time delays between the four radio images have been determined with VLA monitoring observations by Fassnacht et al. (1999b,2002) (see Table 5).”
TDCOSMO IV: Hierarchical time-delay cosmography -- joint inference of the Hubble constant and galaxy density profiles (2020, methodology): “The first problem has been solved by high cadence and high precision photometric monitoring, often with dedicated telescopes (e.g., Fassnacht et al. 2002; Tewes et al. 2013; Courbin et al. 2018).”
The Cosmic Lens All-Sky Survey - I. Source selection and observations (2002, methodology): “The CLASS group has successfully monitored the quadruple lens CLASS B1608+656 (Fassnacht et al. 1999b; Koopmans & Fassnacht 1999, Fassnacht et al. 2002), and all three independent time delays between the four components have been measured.”
H0LiCOW - V. New COSMOGRAIL time delays of HE 0435-1223: H0 to 3.8 per cent precision from strong lensing in a flat ΛCDM model (2016, background): “B1608+656, monitored in radio band with the VLA (Fassnacht et al. 2002), and RXJ1131−1231, monitored by COSMOGRAIL in the visible (Tewes et al. 2013b), have already shown promising results, with relative precisions on the time-delay distance of 5% and 6.6% respectively (Suyu et al. 2010, 2014).”
Time delay cosmography (2016, background): “Monitoring of the CLASS lens B1608 + 656 in the radio with the Very Large Array enabled the breakthrough time delay measurements of Fassnacht et al. (2002).”
Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys (2010, methodology): “Measuring time delays requires dense sampling: we assume that a cadence of <10 d and a season length of ≥3 months are the minimum needed to allow time-delay estimation, based on results of previous lens monitoring campaigns (e.g. Fassnacht et al. 2002).”
H0LiCOW – I. H0 Lenses in COSMOGRAIL's wellspring: program overview (2016, methodology): “Using three seasons of monitoring of B1608+656, especially the third season which showed significant variability that repeated in all four quasar images, Fassnacht et al. (2002) measured all three relative time delays between the four quasar images with uncertainties of a few percent.”
TWO ACCURATE TIME-DELAY DISTANCES FROM STRONG LENSING: IMPLICATIONS FOR COSMOLOGY (2012, background): “Modern light curves have much higher photometric precision, sampling, and duration (Fassnacht et al. 2002; Courbin et al. 2011) compared to the early pioneering light curves (e.g., Lehar et al. 1992).”
H0LiCOW - IV. Lens mass model of HE 0435-1223 and blind measurement of its time-delay distance for cosmology (2016, background): “…Lenses (COSMOGRAIL; Courbin et al. 2005; Eigenbrod et al. 2005; Bonvin et al. 2016b) project and from Very Large Array (VLA) monitoring (Fassnacht et al. 2002), a photometric and spectroscopic survey to characterize the LOS mass distribution to estimate κext in these systems, and…”
An alternative to the cosmological 'concordance model' (2003, background): “However Koopmans et al. (2003) have recently obtained H0 = 75 +7 −6 km/s/Mpc from a detailed reanalysis of the system B1608+656, significantly higher than their previous estimate of 59 ± 2 km/s/Mpc for this system (Fassnacht et al. 2002).”
Tests for Substructure in Gravitational Lenses (2003, background): “We examined the optical depth function using the four- (or more) image radio lenses with fluxes measured at 5 GHz and either 8 or 15 GHz (MG 0414+0534: Katz et al. 1997; B0712+472: Jackson et al. 1998; B1359+154: Myers et al. 1999; B1422+231: Patnaik & Narasimha 2001; B1555+375: Marlow et al. 1999b;”
H0LiCOW – XIII. A 2.4 per cent measurement of H0 from lensed quasars: 5.3σ tension between early- and late-Universe probes (2019, methodology): “…of GRAvItational Lenses (COSMOGRAIL; Courbin et al. 2005; Eigenbrod et al. 2005; Bonvin et al. 2018) project and radio-wavelength monitoring (Fassnacht et al. 2002), deep Hubble Space Telescope (HST), and/or ground-based adaptive optics (AO) imaging (H0LiCOW I, IX; Chen et al. 2016, 2019),…”