arXiv subjects

Tommaso Treu

Publications and source records attributed to Tommaso Treu.

At least 217 records · Page 12Linked to original sources

arXiv2019

Astro2020 Science White Paper: The Local Relics of of Supermassive Black Hole Seeds

We have compelling evidence for stellar-mass black holes (BHs) of ~5-80 M_sun that form through the death of massive stars. We also have compelling evidence for so-called supermassive BHs (10^5-10^10 M_sun) that are predominantly found in the centers of galaxies. We have very good reason to believe there must be BHs with masses in the gap between these ranges: the first ~10^9 M_sun BHs are observed only hundreds of millions of years after the Big Bang, and all theoretically viable paths to making supermassive BHs require a stage of "intermediate" mass. However, no BHs have yet been reliably detected in the 100-10}^5 M_sun mass range. Uncovering these intermediate-mass BHs of 10^3-10^5 M_sun is within reach in the coming decade. In this white paper we highlight the crucial role that 30-m class telescopes will play in dynamically detecting intermediate-mass black holes, should they exist.

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arXiv2019

Towards a high accuracy measurement of the local black hole occupation fraction in low mass galaxies

This document illustrates the feasibility of a few per cent level measurement of the local black hole occupation fraction in low mass galaxies through wide-field, high angular resolution X-ray imaging observations of local volume galaxies. The occupation fraction, particularly at the low end of the galaxy luminosity function, is a key benchmark for any model which aims to reproduce the formation and growth of super-massive black holes and their host galaxies. Our proposed measurement will complement orthogonal efforts that are planned in X-rays at high red-shifts, as well as in the local Universe with ground-based facilities.

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arXiv2019

Testing the Nature of Dark Matter with Extremely Large Telescopes

For nearly 40 years, dark matter has been widely assumed to be cold and collisionless. Cold dark matter models make fundamental predictions for the behavior of dark matter on small (<10 kpc) scales. These predictions include cuspy density profiles at the centers of dark matter halos and a halo mass function that increases as dN/dM ~ M^-1.9 down to very small masses. We suggest two observational programs relying on extremely large telescopes to critically test these predictions, and thus shed new light on the nature of dark matter. (1) Combining adaptive optics-enabled imaging with deep spectroscopy to measure the three-dimensional motions of stars within a sample of Local Group dwarf galaxies that are the cleanest dark matter laboratories known in the nearby universe. From these observations the inner slope of the dark matter density profile can be determined with an accuracy of 0.20 dex, enabling a central cusp to be distinguished from a core at 5 sigma significance. (2) Diffraction-limited AO imaging and integral field spectroscopy of gravitationally lensed galaxies and quasars to quantify the abundance of dark substructures in the halos of the lens galaxies and along the line of sight. Observations of 50 lensed arcs and 50 multiply-imaged quasars will be sufficient to measure the halo mass function over the range 10^7 < M < 10^10 Msun at cosmological scales, independent of the baryonic and stellar composition of those structures. These two observational probes provide complementary information about the small scale structure, with a joint self-consistent analysis mitigating limitations of either probe. This program will produce the strongest existing constraints on the properties of dark matter on small scales, allowing conclusive tests of alternative warm, fuzzy, and self-interacting dark matter models.

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arXiv2019

Measuring the Hubble Constant Near and Far in the Era of ELT's

Many of the fundamental physical constants in Physics, as a discipline, are measured to exquisite levels of precision. The fundamental constants that define Cosmology, however, are largely determined via a handful of independent techniques that are applied to even fewer datasets. The history of the measurement of the Hubble Constant (H0), which serves to anchor the expansion history of the Universe to its current value, is an exemplar of the difficulties of cosmological measurement; indeed, as we approach the centennial of its first measurement, the quest for H0 still consumes a great number of resources. In this white paper, we demonstrate how the approaching era of Extremely Large Telescopes (ELTs) will transform the astrophysical measure of H0 from the limited and few into a fundamentally new regime where (i) multiple, independent techniques are employed with modest use of large aperture facilities and (ii) 1% or better precision is readily attainable. This quantum leap in how we approach H0 is due to the unparalleled sensitivity and spatial resolution of ELT's and the ability to use integral field observations for simultaneous spectroscopy and photometry, which together permit both familiar and new techniques to effectively by-pass the conventional 'ladder' framework to minimize total uncertainty. Three independent techniques are discussed -- (i) standard candles via a two-step distance ladder applied to metal, poor stellar populations, (ii) standard clocks via gravitational lens cosmography, and (iii) standard sirens via gravitational wave sources -- each of which can reach 1% with relatively modest investment from 30-m class facilities.

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arXiv2019

UV Diagnostics of Galaxies from the Peak of Star-Formation to the Epoch of Reionization

The rest-frame UV emission from massive stars contains a wealth of information about the physical nature and conditions of star formation in galaxies. Using studies of the rest-frame UV, the past decade has witnessed the beginning of knowledge about the existence and properties of galaxies during the first few billion years after the Big Bang. This period of history corresponds to the formation of the first stars, the rapid formation of galaxy stellar populations, the reionization of the IGM, the production and dissemination of heavy elements, and the formation of the first black holes. Massive stars in these galaxies drive all of these events, and their light dominates the spectral energy distributions of galaxies. As we look to the 2020s, fundamental questions remain about the nature of these stellar populations and their evolution, from just before the peak of the cosmic star formation density (z~3), up to the epoch of reionization (z > 6). This next decade will provide transformative gains both in our ability to identify star-forming galaxies and accreting supermassive black holes at these early epochs with imaging surveys in the rest-frame UV (e.g., LSST, WFIRST). Ground-based, rest-frame UV spectroscopy on >20 m-class telescopes (e.g., GMT/TMT) offers the ability to investigate the astrophysical conditions in galaxies at the earliest cosmic times. This includes studies of the evolution in galaxy stellar populations, gas ionization (temperature, pressure), metallicity, and interstellar (and circumgalactic) gas kinematics and covering fractions. In this white paper, we describe the scientific prospects and the requirements for research in this area.

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arXiv2019

The First Luminous Quasars and Their Host Galaxies

The discovery of luminous quasars at redshifts up to 7.5 demonstrates the existence of several billion M_sun supermassive black holes (SMBHs) less than a billion years after the Big Bang. They are accompanied by intense star formation in their host galaxies, pinpointing sites of massive galaxy assembly in the early universe, while their absorption spectra reveal an increasing neutral intergalactic medium (IGM) at the epoch of reionization. Extrapolating from the rapid evolution of the quasar density at z=5-7, we expect that there is only one luminous quasar powered by a billion M_sun SMBH in the entire observable universe at z~9. In the next decade, new wide-field, deep near-infrared (NIR) sky surveys will push the redshift frontier to the first luminous quasars at z~9-10; the combination with new deep X-ray surveys will probe fainter quasar populations that trace earlier phases of SMBH growth. The identification of these record-breaking quasars, and the measurements of their BH masses and accretion properties require sensitive spectroscopic observations with next generation of ground-based and space telescopes at NIR wavelengths. High-resolution integral-field spectroscopy at NIR, and observations at millimeter and radio wavelengths, will together provide a panchromatic view of the quasar host galaxies and their galactic environment at cosmic dawn, connecting SMBH growth with the rise of the earliest massive galaxies. Systematic surveys and multiwavelength follow-up observations of the earliest luminous quasars will strongly constrain the seeding and growth of the first SMBHs in the universe, and provide the best lines of sight to study the history of reionization.

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arXiv2019

Inferences on the Timeline of Reionization at z~8 From the KMOS Lens-Amplified Spectroscopic Survey

Detections and non-detections of Lyman alpha (Ly$α$) emission from $z>6$ galaxies ($<1$ Gyr after the Big Bang) can be used to measure the timeline of cosmic reionization. Of key interest to measuring reionization's mid-stages, but also increasing observational challenge, are observations at z > 7, where Ly$α$ redshifts to near infra-red wavelengths. Here we present a search for z > 7.2 Ly$α$ emission in 53 intrinsically faint Lyman Break Galaxy candidates, gravitationally lensed by massive galaxy clusters, in the KMOS Lens-Amplified Spectroscopic Survey (KLASS). With integration times of ~7-10 hours, we detect no Ly$α$ emission with S/N>5 in our sample. We determine our observations to be 80% complete for 5$σ$ spatially and spectrally unresolved emission lines with integrated line flux $>5.7\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$. We define a photometrically selected sub-sample of 29 targets at $z=7.9\pm0.6$, with a median 5$σ$ Ly$α$ EW limit of 58A. We perform a Bayesian inference of the average intergalactic medium (IGM) neutral hydrogen fraction using their spectra. Our inference accounts for the wavelength sensitivity and incomplete redshift coverage of our observations, and the photometric redshift probability distribution of each target. These observations, combined with samples from the literature, enable us to place a lower limit on the average IGM neutral hydrogen fraction of $> 0.76 \; (68\%), \; > 0.46 \; (95\%)$ at z ~ 8, providing further evidence of rapid reionization at z~6-8. We show that this is consistent with reionization history models extending the galaxy luminosity function to $M_\textrm{UV} \lesssim -12$, with low ionizing photon escape fractions, $f_\textrm{esc} \lesssim 15\%$.

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arXiv2019

Sub-Eddington super-massive black hole activity in Fornax early type galaxies

We characterize the incidence and intensity of low-level super-massive black hole activity within the Fornax cluster, through X-ray observations of the nuclei of 29 quiescent early-type galaxies. Using the \textit{Chandra X-ray Telescope}, we target 17 galaxies from the HST Fornax Cluster Survey, down to a uniform (3$σ$) limiting X-ray luminosity threshold of $5\cdot10^{38}$ergs$^{-1}$, which we combine with deeper, archival observations for an additional 12 galaxies. A nuclear X-ray point-source is detected in 11 out of 29 targets. After accounting for the low mass X-ray binary contamination to the nuclear X-ray signal, the X-ray active fraction is measured at $26.6\% \pm 9.6\%$. The results from this analysis are compared to similar investigations targeting quiescent early types in the Virgo cluster, as well as the field. After correcting for the different mass distributions, the measured Fornax active fraction is less than the field fraction, at more than 3$σ$, confirming that the funneling of gas to the nuclear regions of cluster members is inhibited compared to those galaxies in the field. At the same time, we find no statistically significant difference between Fornax and Virgo galaxies, with only marginal evidence for a lower active fraction in Fornax (1 $σ$); if real, owing to Fornax's higher galaxy number density, this could indicate that galaxy-galaxy interactions are more effective at gas removal than galaxy-gas effects.

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arXiv2019

Constraining the neutral fraction of hydrogen in the IGM at redshift 7.5

We present a large spectroscopic campaign with Keck/MOSFIRE targeting Lyman-alpha emission (Ly$α$) from intrinsically faint Lyman-break Galaxies (LBGs) behind 12 efficient galaxy cluster lenses. Gravitational lensing allows us to probe the more abundant faint galaxy population to sensitive Ly$α$ equivalent width limits. During the campaign we targeted 70 LBG candidates with MOSFIRE Y-band, selected photometrically to cover Ly$α$ over the range $7 5$ emission lines in 2 of these galaxies and find that they are likely Ly$α$ at $z=7.148\pm0.001$ and $z=7.161\pm0.001$. We present new lens models for 4 of the galaxy clusters, using our previously published lens models for the remaining clusters to determine the magnification factors for the source galaxies. Using a Bayesian framework that employs large scale reionization simulations of the intergalactic medium (IGM) as well as realistic properties of the interstellar medium and circumgalactic medium, we infer the volume-averaged neutral hydrogen fraction, $\overline{x}_{\mathrm{HI}}$, in the IGM during reionization to be $\overline{x}_{\mathrm{HI}}=0.88^{+0.05}_{-0.10}$ at $z=7.6\pm0.6$. Our result is consistent with a late and rapid reionization scenario inferred by Planck.

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arXiv2018

Mass and Light of Abell 370: A Strong and Weak Lensing Analysis

We present a new gravitational lens model of the Hubble Frontier Fields cluster Abell 370 ($z = 0.375$) using imaging and spectroscopy from Hubble Space Telescope and ground-based spectroscopy. We combine constraints from a catalog of 1344 weakly lensed galaxies and 39 multiply-imaged sources comprised of 114 multiple images, including a system of multiply-imaged candidates at $z=7.93 \pm 0.02$, to obtain a best-fit mass distribution using the cluster lens modeling code Strong and Weak Lensing United. As the only analysis of A370 using strong and weak lensing constraints from Hubble Frontier Fields data, our method provides an independent check on assumptions in other methods on the mass distribution. Convergence, shear, and magnification maps are made publicly available through the HFF website. We find that the model we produce is similar to models produced by other groups, with some exceptions due to the differences in lensing code methodology. In an effort to study how our total projected mass distribution traces light, we measure the stellar mass density distribution using Spitzer/Infrared Array Camera imaging. Comparing our total mass density to our stellar mass density in a radius of 0.3 Mpc, we find a mean projected stellar to total mass ratio of $\langle f* \rangle = 0.011 \pm 0.003$ (stat.) using the diet Salpeter initial mass function. This value is in general agreement with independent measurements of $\langle f* \rangle$ in clusters of similar total mass and redshift.

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arXiv2018

The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad-Line Region

We present models of the H$β$-emitting broad-line region (BLR) in seven Seyfert 1 galaxies from the Lick AGN (Active Galactic Nucleus) Monitoring Project 2011 sample, drawing inferences on the BLR structure and dynamics as well as the mass of the central supermassive black hole. We find that the BLR is generally a thick disk, viewed close to face-on, with preferential emission back toward the ionizing source. The dynamics in our sample range from near-circular elliptical orbits to inflowing or outflowing trajectories. We measure black hole masses of $\log_{10}(M_{\rm BH}/M_\odot) = 6.48^{+0.21}_{-0.18}$ for PG 1310$-$108, $7.50^{+0.25}_{-0.18}$ for Mrk 50, $7.46^{+0.15}_{-0.21}$ for Mrk 141, $7.58^{+0.08}_{-0.08}$ for Mrk 279, $7.11^{+0.20}_{-0.17}$ for Mrk 1511, $6.65^{+0.27}_{-0.15}$ for NGC 4593, and $6.94^{+0.14}_{-0.14}$ for Zw 229$-$015. We use these black hole mass measurements along with cross-correlation time lags and line widths to recover the scale factor $f$ used in traditional reverberation mapping measurements. Combining our results with other studies that use this modeling technique, bringing our sample size to 16, we calculate a scale factor that can be used for measuring black hole masses in other reverberation mapping campaigns. When using the root-mean-square (rms) spectrum and using the line dispersion to measure the line width, we find $\log_{10}(f_{{\rm rms},σ})_{\rm pred} = 0.57 \pm 0.19$. Finally, we search for correlations between $f$ and other AGN and BLR parameters and find marginal evidence that $f$ is correlated with $M_{\rm BH}$ and the BLR inclination angle, but no significant evidence of a correlation with the AGN luminosity or Eddington ratio.

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arXiv2018

Evidence for radial variations in the stellar mass-to-light ratio of massive galaxies from weak and strong lensing

The Initial Mass Function (IMF) for massive galaxies can be constrained by combining stellar dynamics with strong gravitational lensing. However, this method is limited by degeneracies between the density profile of dark matter and the stellar mass-to-light ratio. In this work we reduce this degeneracy by combining weak lensing together with strong lensing and stellar kinematics. Our analysis is based on two galaxy samples: 45 strong lenses from the SLACS survey and 1,700 massive quiescent galaxies from the SDSS main spectroscopic sample with weak lensing measurements from the Hyper Suprime-Cam survey. We use a Bayesian hierarchical approach to jointly model all three observables. We fit the data with models of varying complexity and show that a model with a radial gradient in the stellar mass-to-light ratio is required to simultaneously describe both galaxy samples. This result is driven by a subset of strong lenses with very steep total density profile, that cannot be fitted by models with no gradient. Our measurements are unable to determine whether $M_*/L$ gradients are due to variations in stellar population parameters at fixed IMF, or to gradients in the IMF itself. The inclusion of $M_*/L$ gradients decreases dramatically the inferred IMF normalisation, compared to previous lensing-based studies, with the exact value depending on the assumed dark matter profile. The main effect of strong lensing selection is to shift the stellar mass distribution towards the high mass end, while the halo mass and stellar IMF distribution at fixed stellar mass are not significantly affected.

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arXiv2018

Constraining the microlensing effect on time delays with new time-delay prediction model in $H_{0}$ measurements

Time-delay strong lensing provides a unique way to directly measure the Hubble constant ($H_{0}$). The precision of the $H_{0}$ measurement depends on the uncertainties in the time-delay measurements, the mass distribution of the main deflector(s), and the mass distribution along the line of sight. Tie and Kochanek (2018) have proposed a new microlensing effect on time delays based on differential magnification of the coherent accretion disc variability of the lensed quasar. If real, this effect could significantly broaden the uncertainty on the time delay measurements by up to $30\%$ for lens systems such as PG1115+080, which have relatively short time delays and monitoring over several different epochs. In this paper we develop a new technique that uses the time-delay ratios and simulated microlensing maps within a Bayesian framework in order to limit the allowed combinations of microlensing delays and thus to lessen the uncertainties due to the proposed effect. We show that, under the assumption of Tie and Kochanek (2018), the uncertainty on the time-delay distance ($D_{Δt}$, which is proportional to 1/$H_{0}$) of short time-delay ($\sim18$ days) lens, PG1115+080, increases from $\sim7\%$ to $\sim10\%$ by simultaneously fitting the three time-delay measurements from the three different datasets across twenty years, while in the case of long time-delay ($\sim90$ days) lens, the microlensing effect on time delays is negligible as the uncertainty on $D_{Δt}$ of RXJ1131-1231 only increases from $\sim2.5\%$ to $\sim2.6\%$.

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arXiv2018

Probing the nature of dark matter by forward modeling flux ratios in strong gravitational lenses

The free streaming length of dark matter particles determines the abundance of structure on sub-galactic scales. We present a statistical technique, amendable to any parameterization of subhalo density profile and mass function, to probe dark matter on these scales with quadrupole image lenses. We consider a warm dark matter particle with a mass function characterized by a normalization and free streaming scale $m_{\rm{hm}}$. We forecast bounds on dark matter warmth for 120-180 lenses, attainable with future surveys, at typical lens (source) redshifts of 0.5 (1.5) in early-type galaxies with velocity dispersions of 220-270 km/sec. We demonstrate that limits on $m_{\rm{hm}}$ deteriorate rapidly with increasing uncertainty in image fluxes, underscoring the importance of precise measurements and accurate lens models. For our forecasts, we assume the deflectors in the lens sample do not exhibit complex morphologies, so we neglect systematic errors in their modeling. Omitting the additional signal from line of sight halos, our constraints underestimate the true power of the method. Assuming cold dark matter, for a low normalization, corresponding the destruction of all subhalos within the host scale radius, we forecast $2σ$ bounds on $m_{\rm{hm}}$ (thermal relic mass) of $10^{7.5} \ (5.0)$, $10^{8} \ (3.6)$, and $10^{8.5} \ (2.7) \ M_{\odot} \left(\rm{keV}\right)$ for flux errors of $2\%$, $4\%$, and $8\%$. With a higher normalization, these constraints improve to $10^{7.2} \ (6.6)$, $10^{7.5} \ (5.3) $, and $10^{7.8} \ (4.3) \ M_{\odot} \left(\rm{keV}\right)$ with 120 systems. We are also able to measure the normalization of the mass function, which has implications for baryonic feedback models and tidal stripping.

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arXiv2018

Studying the [OIII]$λ$5007A emission-line width in a sample of $\sim$80 local active galaxies: A surrogate for $σ_{\star}$?

For a sample of $\sim$80 local ($0.02 \leq z \leq 0.1$) Seyfert-1 galaxies with high-quality long-slit Keck spectra and spatially-resolved stellar-velocity dispersion ($σ_{\star}$) measurements, we study the profile of the [OIII]$λ$5007A emission line to test the validity of using its width as a surrogate for $σ_{\star}$. Such an approach has often been used in the literature, since it is difficult to measure $σ_{\star}$ for type-1 active galactic nuclei (AGNs) due to the AGN continuum outshining the stellar-absorption lines. Fitting the [OIII] line with a single Gaussian or Gauss-Hermite polynomials overestimates $σ_{\star}$ by 50-100%. When line asymmetries from non-gravitational gas motion are excluded in a double Gaussian fit, the average ratio between the core [OIII] width ($σ_{\rm {[OIII],D}}$) and $σ_{\star}$ is $\sim$1, but with individual data points off by up to a factor of two. The resulting black-hole-mass-$σ_{\rm {[OIII],D}}$ relation scatters around that of quiescent galaxies and reverberation-mapped AGNs. However, a direct comparison between $σ_{\star}$ and $σ_{\rm {[OIII],D}}$ shows no close correlation, only that both quantities have the same range, average and standard deviation, probably because they feel the same gravitational potential. The large scatter is likely due to the fact that line profiles are a luminosity-weighted average, dependent on the light distribution and underlying kinematic field. Within the range probed by our sample (80-260 km s$^{-1}$), our results strongly caution against the use of [OIII] width as a surrogate for $σ_{\star}$ on an individual basis. Even though our sample consists of radio-quiet AGNs, FIRST radio-detected objects have, on average, a $\sim$10% larger [OIII] core width.

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arXiv2018

Mass Modeling of Frontier Fields Cluster MACS J1149.5+2223 Using Strong and Weak Lensing

We present a gravitational lensing model of MACS J1149.5+2223 using ultra-deep Hubble Frontier Fields imaging data and spectroscopic redshifts from HST grism and VLT/MUSE spectroscopic data. We create total mass maps using 38 multiple images (13 sources) and 608 weak lensing galaxies, as well as 100 multiple images of 31 star-forming regions in the galaxy that hosts Supernova Refsdal. We find good agreement with a range of recent models within the HST field of view. We present a map of the ratio of projected stellar mass to total mass ($f_{\star}$), and find that the stellar mass fraction for this cluster peaks on the primary BCG. Averaging within a radius of 0.3 Mpc, we obtain a value of $\langle f_{\star} \rangle = 0.012^{+0.004}_{-0.003}$, consistent with other recent results for this ratio in cluster environments, though with a large global error (up to $δf_{\star} = 0.005$) primarily due to the choice of an IMF. We compare values of $f_{\star}$ and measures of star formation efficiency for this cluster to other Hubble Frontier Fields clusters studied in the literature, finding that MACS1149 has a higher stellar mass fraction than these other clusters, but a star formation efficiency typical of massive clusters.

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arXiv2018

Calibration and Limitations of the Mg II line-based Black Hole Masses

We present the single-epoch black hole mass (M$_{\rm BH}$) calibrations based on the rest-frame UV and optical measurements of Mg II 2798Å and H$β$ 4861Å lines and AGN continuum, using a sample of 52 moderate-luminosity AGNs at z$\sim$0.4 and z$\sim$0.6 with high-quality Keck spectra. We combine this sample with a large number of luminous AGNs from the Sloan Digital Sky Survey to increase the dynamic range for a better comparison of UV and optical velocity and luminosity measurements. With respect to the reference M$_{\rm BH}$ based on the line dispersion of H$β$ and continuum luminosity at 5100Å, we calibrate the UV and optical mass estimators, by determining the best-fit values of the coefficients in the mass equation. By investigating whether the UV estimators show systematic trend with Eddington ratio, FWHM of H$β$, the Fe II strength, and the UV/optical slope, we find no significant bias except for the slope. By fitting the systematic difference of Mg II-based and H$β$-based masses with the L$_{3000}$/L$_{5100}$ ratio, we provide a correction term as a function of the spectral index as $Δ$C = 0.24 (1+$α_λ$) + 0.17, which can be added to the Mg II-based mass estimators if the spectral slope can be well determined. The derived UV mass estimators typically show $>$$\sim$0.2 dex intrinsic scatter with respect to H$β$-based M$_{\rm BH}$, suggesting that the UV-based mass has an additional uncertainty of $\sim$0.2 dex, even if high quality rest-frame UV spectra are available.

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arXiv2018

Improving time-delay cosmography with spatially resolved kinematics

Strongly gravitational lensed quasars can be used to measure the so-called time-delay distance $D_{Δt}$, and thus the Hubble constant $H_0$ and other cosmological parameters. Stellar kinematics of the deflector galaxy play an essential role in this measurement by: (i) helping break the mass-sheet degeneracy; (ii) determining in principle the angular diameter distance $D_{\rm d}$ to the deflector and thus further improving the cosmological constraints. In this paper we simulate observations of lensed quasars with integral field spectrographs and show that spatially resolved kinematics of the deflector enable further progress by helping break the mass-anisotropy degeneracy. Furthermore, we use our simulations to obtain realistic error estimates with current/upcoming instruments like OSIRIS on Keck and NIRSPEC on the James Webb Space Telescope for both distances (typically $\sim6$ per cent on $D_{Δt}$ and $\sim10$ per cent on $D_{\rm d}$). We use the error estimates to compute cosmological forecasts for the sample of nine lenses that currently have well measured time delays and deep Hubble Space Telescope images and for a sample of 40 lenses that is projected to be available in a few years through follow-up of candidates found in ongoing wide field surveys. We find that $H_0$ can be measured with 2 per cent (1 per cent) precision from nine (40) lenses in a flat $Λ$cold dark matter cosmology. We study several other cosmological models beyond the flat $Λ$cold dark matter model and find that time-delay lenses with spatially resolved kinematics can greatly improve the precision of the cosmological parameters measured by cosmic microwave background data.

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