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1. TDCOSMO: II. Six new time delays in lensed quasars from high-cadence monitoring at the MPIA 2.2 m telescope

   https://doi.org/10.1051/0004-6361/202038698  

   Millon, M. ; Courbin, F. ; Bonvin, V. ; Buckley-Geer, E. ; Fassnacht, C. D. ; Frieman, J. ; Marshall, P. J. ; Suyu, S. H. ; Treu, T. ; Anguita, T. ; et al ( October 2020 , Astronomy & Astrophysics)

   null (Ed.)

   We present six new time-delay measurements obtained from R c -band monitoring data acquired at the Max Planck Institute for Astrophysics (MPIA) 2.2 m telescope at La Silla observatory between October 2016 and February 2020. The lensed quasars HE 0047−1756, WG 0214−2105, DES 0407−5006, 2M 1134−2103, PSJ 1606−2333, and DES 2325−5229 were observed almost daily at high signal-to-noise ratio to obtain high-quality light curves where we can record fast and small-amplitude variations of the quasars. We measured time delays between all pairs of multiple images with only one or two seasons of monitoring with the exception of the time delays relative to image D of PSJ 1606−2333. The most precise estimate was obtained for the delay between image A and image B of DES 0407−5006, where τ AB = −128.4 −3.8 +3.5 d (2.8% precision) including systematics due to extrinsic variability in the light curves. For HE 0047−1756, we combined our high-cadence data with measurements from decade-long light curves from previous COSMOGRAIL campaigns, and reach a precision of 0.9 d on the final measurement. The present work demonstrates the feasibility of measuring time delays in lensed quasars in only one or two seasons, provided high signal-to-noise ratio data are obtained at a cadence close to daily. 

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2. Accretion Disk Size and Updated Time-delay Measurements in the Gravitationally Lensed Quasar SDSS J165043.44+425149.3

   https://doi.org/10.3847/1538-4357/ad3069  

   Rivera, A. B. ; Morgan, C. W. ; Florence, S. M. ; Kniezewski, K. ; Millon, M. ; Courbin, F. ; Dahm, S. E. ; Vrba, F. J. ; Tilleman, T. M. ; Cornachione, M. A. ; et al ( March 2024 , The Astrophysical Journal)

   We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of$\mathrm{\Delta }{t}_{\mathrm{AB}}=-{55.1}_{-3.7}^{+4.0}$days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk atλ_rest= 2420 Å, finding a half-light radius of log(r_1/2/cm) =${16.19}_{-0.58}^{+0.38}$assuming a 60° inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mgiiline in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system’s supermassive black hole, findingM_BH= 2.47 × 10⁹M_⊙. We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of theM_BHscale, is fully consistent with the existing quasar accretion disk size–black hole mass relation.

    

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3. TDCOSMO: V. Strategies for precise and accurate measurements of the Hubble constant with strong lensing

   https://doi.org/10.1051/0004-6361/202039179  

   Birrer, Simon ; Treu, Tommaso ( May 2021 , Astronomy & Astrophysics)

   null (Ed.)

   Strong lensing time delays can measure the Hubble constant H 0 independently of any other probe. Assuming commonly used forms for the radial mass density profile of the lenses, a 2% precision has been achieved with seven Time-Delay Cosmography (TDCOSMO) lenses, in tension with the H 0 from the cosmic microwave background. However, without assumptions on the radial mass density profile – and relying exclusively on stellar kinematics to break the mass-sheet degeneracy – the precision drops to 8% with the current data obtained using the seven TDCOSMO lenses, which is insufficient to resolve the H 0 tension. With the addition of external information from 33 Sloan Lens ACS (SLACS) lenses, the precision improves to 5% if the deflectors of TDCOSMO and SLACS lenses are drawn from the same population. We investigate the prospect of improving the precision of time-delay cosmography without relying on mass profile assumptions to break the mass-sheet degeneracy. Our forecasts are based on a previously published hierarchical framework. With existing samples and technology, 3.3% precision on H 0 can be reached by adding spatially resolved kinematics of the seven TDCOSMO lenses. The precision improves to 2.5% with the further addition of kinematics for 50 nontime-delay lenses from SLACS and the Strong Lensing Legacy Survey. Expanding the samples to 40 time-delay and 200 nontime-delay lenses will improve the precision to 1.5% and 1.2%, respectively. Time-delay cosmography can reach sufficient precision to resolve the Hubble tension at 3–5 σ , without assumptions on the radial mass profile of lens galaxies. By obtaining this precision with and without external datasets, we will test the consistency of the samples and enable further improvements based on even larger future samples of time-delay and nontime-delay lenses (e.g., from the Rubin , Euclid , and Roman Observatories). 

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4. JWST Photometric Time-delay and Magnification Measurements for the Triply Imaged Type Ia “SN H0pe” at z = 1.78

   https://doi.org/10.3847/1538-4357/ad3c43  

   Pierel, J_D_R ; Frye, B_L ; Pascale, M. ; Caminha, G_B ; Chen, W. ; Dhawan, S. ; Gilman, D. ; Grayling, M. ; Huber, S. ; Kelly, P. ; et al ( May 2024 , The Astrophysical Journal)

   Supernova (SN) SN H0pe is a gravitationally lensed, triply imaged, Type Ia SN (SN Ia) discovered in James Webb Space Telescope imaging of the PLCK G165.7+67.0 cluster of galaxies. Well-observed multiply imaged SNe provide a rare opportunity to constrain the Hubble constant (H₀), by measuring the relative time delay between the images and modeling the foreground mass distribution. SN H0pe is located atz= 1.783 and is the first SN Ia with sufficient light-curve sampling and long enough time delays for anH₀inference. Here we present photometric time-delay measurements and SN properties of SN H0pe. Using JWST/NIRCam photometry, we measure time delays of Δt_ab=$-{116.6}_{-9.3}^{+10.8}$observer-frame days and Δt_cb=$-{48.6}_{-4.0}^{+3.6}$observer-frame days relative to the last image to arrive (image 2b; all uncertainties are 1σ), which corresponds to a ∼5.6% uncertainty contribution forH₀assuming 70 km s⁻¹Mpc⁻¹. We also constrain the absolute magnification of each image toμ_a=${4.3}_{-1.8}^{+1.6}$,μ_b=${7.6}_{-2.6}^{+3.6}$,μ_c=${6.4}_{-1.5}^{+1.6}$by comparing the observed peak near-IR magnitude of SN H0pe to the nonlensed population of SNe Ia.

    

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5. STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408−5354

   https://doi.org/10.1093/mnras/staa828  

   Shajib, A J ; Birrer, S ; Treu, T ; Agnello, A ; Buckley-Geer, E J ; Chan, J H ; Christensen, L ; Lemon, C ; Lin, H ; Millon, M ; et al ( June 2020 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present a blind time-delay cosmographic analysis for the lens system DES J0408−5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the ‘effective’ time-delay distance corresponding to the redshifts of the deflector and the lensed quasar $D_{\Delta t}^{\rm eff}=$$3382_{-115}^{+146}$ Mpc and the angular diameter distance to the deflector Dd = $1711_{-280}^{+376}$ Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H0= $74.2_{-3.0}^{+2.7}$ km s−1 Mpc−1 assuming a flat ΛCDM cosmology and a uniform prior for Ωm as $\Omega _{\rm m} \sim \mathcal {U}(0.05, 0.5)$. This measurement gives the most precise constraint on H0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement. 

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