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H0LiCOW V. New COSMOGRAIL time delays of HE0435-1223: $H_0$ to 3.8% precision from strong lensing in a flat $Λ$CDM model

V. Bonvin, F. Courbin, S. H. Suyu, P. J. Marshall, C. E. Rusu, D. Sluse, M. Tewes, K. C. Wong, T. Collett, C. D. Fassnacht, T. Treu, M. W. Auger, S. Hilbert, L. V. E. Koopmans, G. Meylan, N. Rumbaugh, A. Sonnenfeld, C. Spiniello

TL;DR

This work reports a new, blind measurement of the Hubble constant $H_0$ from strong lens time delays using HE 0435$-$1223, and combines it with two prior lenses to form the Time Delay Strong Lensing (TDSL) probe. By integrating long-duration COSMOGRAIL light curves with detailed lens and line-of-sight modeling, the authors extract a robust time-delay distance and propagate it through a suite of cosmological models, both within and beyond flat $\Lambda$CDM. When combined with Planck, BAO, and JLA data, TDSL helps break degeneracies and yields precise constraints on $H_0$, curvature, neutrino properties, and dark-energy equation of state, with occasional mild tensions suggesting potential new physics or systematics. The results demonstrate that time-delay cosmography is a mature, independent tool for cosmology, with ongoing potential to reach sub-percent precision as the sample of lenses grows and mass modeling improves.

Abstract

We present a new measurement of the Hubble Constant H0 and other cosmological parameters based on the joint analysis of three multiply-imaged quasar systems with measured gravitational time delays. First, we measure the time delay of HE0435-1223 from 13-year light curves obtained as part of the COSMOGRAIL project. Companion papers detail the modeling of the main deflectors and line of sight effects, and how these data are combined to determine the time-delay distance of HE 0435-1223. Crucially, the measurements are carried out blindly with respect to cosmological parameters in order to avoid confirmation bias. We then combine the time-delay distance of HE0435-1223 with previous measurements from systems B1608+656 and RXJ1131-1231 to create a Time Delay Strong Lensing probe (TDSL). In flat $Λ$CDM with free matter and energy density, we find $H_0$ = 71.9 +2.4 -3.0 km/s/Mpc and $Ω_Λ$ = 0.62 +0.24 -0.35 . This measurement is completely independent of, and in agreement with, the local distance ladder measurements of H0. We explore more general cosmological models combining TDSL with other probes, illustrating its power to break degeneracies inherent to other methods. The TDSL and Planck joint constraints are $H_0$ = 69.2 +1.4 -2.2 km/s/Mpc, $Ω_Λ$ = 0.70 +0.01 -0.01 and $Ω_k$ = 0.003 +0.004 -0.006 in open $Λ$CDM and $H_0$ = 79.0 +4.4 -4.2 km/s/Mpc, $Ω_{de}$ = 0.77 +0.02 -0.03 and $w$ = -1.38 +0.14 -0.16 in flat $w$CDM. Combined with Planck and Baryon Acoustic Oscillation data, when relaxing the constraints on the numbers of relativistic species we find $N_{eff}$ = 3.34 +0.21 -0.21 and when relaxing the total mass of neutrinos we find 0.182 eV. In an open $w$CDM in combination with Planck and CMB lensing we find $H_0$ = 77.9 +5.0 -4.2 km/s/Mpc, $Ω_{de}$ = 0.77 +0.03 -0.03, $Ω_k$ = -0.003 +0.004 -0.004 and $w$ = -1.37 +0.18 -0.23.

H0LiCOW V. New COSMOGRAIL time delays of HE0435-1223: $H_0$ to 3.8% precision from strong lensing in a flat $Λ$CDM model

TL;DR

This work reports a new, blind measurement of the Hubble constant from strong lens time delays using HE 04351223, and combines it with two prior lenses to form the Time Delay Strong Lensing (TDSL) probe. By integrating long-duration COSMOGRAIL light curves with detailed lens and line-of-sight modeling, the authors extract a robust time-delay distance and propagate it through a suite of cosmological models, both within and beyond flat CDM. When combined with Planck, BAO, and JLA data, TDSL helps break degeneracies and yields precise constraints on , curvature, neutrino properties, and dark-energy equation of state, with occasional mild tensions suggesting potential new physics or systematics. The results demonstrate that time-delay cosmography is a mature, independent tool for cosmology, with ongoing potential to reach sub-percent precision as the sample of lenses grows and mass modeling improves.

Abstract

We present a new measurement of the Hubble Constant H0 and other cosmological parameters based on the joint analysis of three multiply-imaged quasar systems with measured gravitational time delays. First, we measure the time delay of HE0435-1223 from 13-year light curves obtained as part of the COSMOGRAIL project. Companion papers detail the modeling of the main deflectors and line of sight effects, and how these data are combined to determine the time-delay distance of HE 0435-1223. Crucially, the measurements are carried out blindly with respect to cosmological parameters in order to avoid confirmation bias. We then combine the time-delay distance of HE0435-1223 with previous measurements from systems B1608+656 and RXJ1131-1231 to create a Time Delay Strong Lensing probe (TDSL). In flat CDM with free matter and energy density, we find = 71.9 +2.4 -3.0 km/s/Mpc and = 0.62 +0.24 -0.35 . This measurement is completely independent of, and in agreement with, the local distance ladder measurements of H0. We explore more general cosmological models combining TDSL with other probes, illustrating its power to break degeneracies inherent to other methods. The TDSL and Planck joint constraints are = 69.2 +1.4 -2.2 km/s/Mpc, = 0.70 +0.01 -0.01 and = 0.003 +0.004 -0.006 in open CDM and = 79.0 +4.4 -4.2 km/s/Mpc, = 0.77 +0.02 -0.03 and = -1.38 +0.14 -0.16 in flat CDM. Combined with Planck and Baryon Acoustic Oscillation data, when relaxing the constraints on the numbers of relativistic species we find = 3.34 +0.21 -0.21 and when relaxing the total mass of neutrinos we find 0.182 eV. In an open CDM in combination with Planck and CMB lensing we find = 77.9 +5.0 -4.2 km/s/Mpc, = 0.77 +0.03 -0.03, = -0.003 +0.004 -0.004 and = -1.37 +0.18 -0.23.

Paper Structure

This paper contains 23 sections, 6 equations, 7 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Photometric monitoring data
  3. Data reduction
  4. On the importance of long light curves
  5. Time-delay measurement
  6. Application to the data
  7. Robustness checks
  8. Time delays of HE 0435$-$1223
  9. Time-delay distance
  10. Principles of the measurement
  11. Determination of the external convergence
  12. Spectroscopy of the field
  13. Weighted galaxy number counts
  14. Mass modeling
  15. Blinding methodology and unblinded results
  16. ...and 8 more sections

Figures (7)

  • Figure 1: Part of the field of view of EulerCAM installed on the Swiss 1.2m telescope around the quasar HE 0435$-$1223. This image is a combination of 100 exposures of 360s each, for a total exposure time of 10 hours. The stars used to build a PSF model for each EulerCAM exposure are circled and labeled PSF1 to PSF7 in red, and the stars used for the photometric calibrations are circled and labeled N1 to N8 in green. The insert in the bottom left shows the single, 360s exposure of the lens, for reference. Note that photometric and spectroscopic redshifts are available for many galaxies in the field of view (see H0LiCOW Paper II and H0LiCOW Paper III for details).
  • Figure 2: From top to bottom: Light curves for the four lensed images of the quasar HE 0435$-$1223. The relative shifts in magnitude are chosen to ease visualization, and do not influence the time-delay measurements. The second panel shows a model of the intrinsic variations of the quasar (black) and the 4 curves for the extrinsic variations in each quasar image using the free-knot spline technique (color code). The vertical ticks indicate the position of the spline knots. The residuals of the fits for each light curve is shown in the next panel. Finally, the bottom panel displays the journal of the observations for HE 0435$-$1223 for the 5 telescopes or cameras used to gather the data over 13 years (see column "$\#$obs" of Table \ref{['tab:monitoring']}), where each point represents one monitoring night. The light curves will be made publicly available on the CDS and COSMOGRAIL websites once the paper is accepted for publication.
  • Figure 3: Time delays for the 6 pairs of quasar images, as indicated in top left corner of each panel. In each panel, we show the time delay measurement along with the 1$\sigma$ error bar using our two best curve-shifting techniques, and we compare with the measurement of Courbin2011. We also show the result of measurements carried out with the free-knot spline technique and regression difference technique when splitting the data in 3 continuous chunks of 4 or 5 years each. All cosmological results in this work use the time delay measurements from the free-knot splines (larger blue symbols on the figure).
  • Figure 4: Marginalized posterior probability distributions for $H_0$ in the ${\rm U}H_0$, ${\rm U \Lambda CDM}$, ${\rm U{\it w}CDM}$ and ${\rm Uo}\Lambda {\rm CDM}$ cosmologies using the constraints from the three strong lenses B1608$+$656, RXJ1131$-$1231 and HE 0435$-$1223. The overlaid histograms present the distributions for each individual strong lens (ignoring the other two datasets), and the solid black line corresponds to the distribution resulting from the joint inference from all three datasets (TDSL). The quoted values of $H_0$ in the top-left corner of each panel are the median, 16th and 84th percentiles.
  • Figure 5: Comparison of the three strong lenses in the ${\rm U \Lambda CDM}$ (top), ${\rm U{\it w}CDM}$ (middle) and ${\rm Uo}\Lambda {\rm CDM}$ (bottom) cosmologies. The colored overlays delimit the 95% credible region for B1608$+$656, RXJ1131$-$1231 and HE 0435$-$1223. The solid and dashed black lines draw the contours of the 68.3% and 95% credible regions, respectively, for the combination of the three lenses.
  • ...and 2 more figures