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 per cent 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 modelling, (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 modelling. In cosmological models with one-parameter extension to flat Lambda cold dark matter, we expect to measure H-0 to <3.5 per cent in most models, spatial curvature Omega(k) to 0.004, w to 0.14 and the effective number of neutrino species to 0.2 (1s uncertainties) when combined with current cosmic microwave background (CMB) experiments. These are, respectively, a factor of similar to 15, similar to 2 and similar to 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.

/pdf/h0licow-i-h0-lenses-in-cosmograil-s-wellspring-program-wnein8zeuu.pdf

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

ERC grant "Cosmic Dawn"; DFG [1573]; National Aeronautics and Space Administration through the Planetary Science Division of the NASA Science Mission Directorate [NNX08AR22G]; National Science Foundation [AST-1238877]; ESO Telescopes at the La Silla Paranal Observatory [092.A-0339(A), 092.A-0150(A), 092.A-0150(B), 093.A-0863(A), 095.A-9001(A), 095.A-0375(A), 095.A-0535(A), 095.A-0535(B), 096.A-0420(A), 096.A-9001(A), 097.A-9001(A), 097.A-0094(A), 097.A-0094(B)]; Leibniz Prize (DFG grant) [HA 1850/28-1]; W. M. Keck Foundation; NFS [AST-1109915]; NSF Telescope System Instrumentation Program (TSIP); Ohio Board of Regents; Ohio State University Office of Research; NSF [AST-9987045]; INSU/CNRS (France); MPG (Germany); IGN (Spain); National Aeronautics and Space Administration

/pdf/physical-properties-of-15-quasars-at-z-6-5-2ok2e14840.pdf

Physical Properties of 15 Quasars at z ≳ 6.5

We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range z{sub d} = 0.2-0.8, while the lensed sources are at z{sub s} = 1-3.5. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lenses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile, γ' (ρ(r)∝r{sup -γ{sup '}}), on stellar mass, size, and redshift. We find that two parameters are sufficient to determine γ' with less than 6% residual scatter. At fixed redshift, γ' depends solely on the surface stellar mass density ∂γ'/∂Σ{sub *} = 0.38 ± 0.07, i.e., galaxies with denser stars also have steeper slopes. At fixed M{sub *} and R{sub eff}, γ' depends on redshift, in the sense that galaxies at a lower redshift have steepermore » slopes (∂γ'/∂z = –0.31 ± 0.10). However, the mean redshift evolution of γ' for an individual galaxy is consistent with zero dγ'/dz = –0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ' on z, M{sub *},R{sub eff} with the evolution of the R{sub eff}-M{sub *} taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work.« less

https://iopscience.iop.org/article/10.1088/0004-637X/777/2/98/pdf

The SL2S Galaxy-scale Lens Sample. IV. The Dependence of the Total Mass Density Profile of Early-type Galaxies on Redshift, Stellar Mass, and Size

The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here, we present spectra covering the wavelength ranges 0.35-0.55 ?m and 0.72-1.03 ?m for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-to-noise ratio is 200 ??1 out to 1 ?m, which is sufficient to measure gravity-sensitive features for individual galaxies and to determine how they depend on other properties of the galaxies. Combining the new data with previously obtained spectra for globular clusters in M31 and the most massive elliptical galaxies in the Virgo cluster, we find that the dwarf-sensitive Na I ?8183, 8195 doublet and the FeH ?9916 Wing-Ford band increase systematically with velocity dispersion, while the giant-sensitive Ca II ?8498, 8542, 8662 triplet decreases with dispersion. These trends are consistent with a varying IMF, such that galaxies with deeper potential wells have more dwarf-enriched mass functions. In a companion paper, we use a comprehensive stellar population synthesis model to demonstrate that IMF effects can be separated from age and abundance variations and quantify the IMF variation among early-type galaxies.

The Stellar Initial Mass Function in Early-type Galaxies from Absorption Line Spectroscopy. I. Data and Empirical Trends

I present and summarize a software package ("LPipe") for completely automated, end-to-end reduction of both bright and faint sources with the Low-Resolution Imaging Spectrometer (LRIS) at Keck Observatory. It supports all gratings, grisms, and dichroics, and also reduces imaging observations, although it does not include multislit or polarimetric reduction capabilities at present. It is suitable for on-the-fly quicklook reductions at the telescope, for large-scale reductions of archival data-sets, and (in many cases) for science-quality post-run reductions of PI data. To demonstrate its capabilities the pipeline is run in fully-automated mode on all LRIS longslit data in the Keck Observatory Archive acquired during the 12-month period between August 2016 and July 2017. The reduced spectra (of 675 single-object targets, totaling ~200 hours of on-source integration time in each camera), and the pipeline itself, are made publicly available to the community.

/pdf/fully-automated-reduction-of-longslit-spectroscopy-with-the-12vg1pialf.pdf

Fully Automated Reduction of Longslit Spectroscopy with the Low Resolution Imaging Spectrometer at the Keck Observatory

A mosaic of two 2k x 4k fully depleted, high resistivity CCD
 detectors was installed in the red channel of the Low Resolution
 Imaging Spectrograph for the Keck-I Telescope in June, 2009 replacing
 a monolithic Tektronix/SITe 2k x 2k CCD. These CCDs were fabricated
 at Lawrence Berkeley National Laboratory (LBNL) and packaged and
 characterized by UCO/Lick Observatory. Major goals of the detector
 upgrade were increased throughput and reduced interference fringing
 at wavelengths beyond 800 nm, as well as improvements in the
 maintainability and serviceability of the instrument. We report on
 the main features of the design, the results of optimizing detector
 performance during integration and testing, as well as the
 throughput, sensitivity and performance of the instrument as
 characterized during commissioning.

The low-resolution imaging spectrograph red channel CCD upgrade: fully depleted, high-resistivity CCDs for Keck

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The low-resolution imaging spectrograph red channel CCD upgrade: fully depleted, high-resistivity CCDs for Keck