We present a large spectroscopic campaign with Keck/Multi-Object Spectrometer for InfraRed Exploration (MOSFIRE) targeting Ly emission (Ly ) 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 equivalent-width limits. During the campaign, we targeted 70 LBG candidates with the MOSFIRE Y band, selected photometrically to cover Ly over the range 7 < z < 8.2. We detect signal-to-noise ratio > 5 emission lines in two of these galaxies and find that they are likely Ly at z = 7.148 0.001 and z = 7.161 0.001. We present new lens models for four 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, , in the IGM during reionization to be at z = 7.6 0.6. Our result is consistent with a late and rapid reionization scenario inferred by Planck.
ABSTRACT We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of 10 massive clusters ...of galaxies at redshift z = 0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 (WFC3) yields near-infrared spectra of the cluster cores covering the wavelength range 0.81-1.69 m through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACS J0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all of the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than We provide a catalog of 139 emission-line-based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative). In addition to the data itself, we also release software tools that are helpful to navigate the data.
Amorphous silicon is a promising high-capacity anode material for the next generation of lithium-ion batteries. However, the enormous volume expansion of the active material during lithiation up to ...400% (V/V 0) is held responsible for capacity fading during cycling. In this study we measured continuously the volume modifications taking place during galvanostatic lithiation of amorphous silicon thin film electrodes by in-operando neutron reflectometry experiments. The results indicate (after initial effects) a linear increase in volume as a function of lithiation time and lithium content independent of current density and initial film thickness. The experimental results are in agreement with recent atomistic calculations.
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IJS, KILJ, NUK, PNG, UL, UM
ABSTRACT
We search the five CANDELS fields (COSMOS, EGS, GOODS-North, GOODS-South, and UDS) for passively evolving a.k.a. ‘red and dead’ massive galaxies in the first 2 Gyr after the big bang, ...integrating and updating the work on GOODS-South presented in a previous paper. We perform SED-fitting on photometric data, with top-hat star-formation histories to model an early and abrupt quenching, and using a probabilistic approach to select only robust candidates. Using libraries without (with) spectral lines emission, starting from a total of more than 20 000 z > 3 sources we end up with 102 (40) candidates, including one at z = 6.7. This implies a minimal number density of 1.73 ± 0.17 × 10−5 (6.69 ± 1.08 × 10−6) Mpc−3 for 3 < z < 5; applying a correction factor to account for incompleteness yields 2.30 ± 0.20 × 10−5. We compare these values with those from five recent hydrodynamical cosmological simulations, finding a reasonable agreement at z < 4; tensions arise at earlier epochs. Finally, we use the star-formation histories from the best-fitting models to estimate the contribution of the high-redshift passive galaxies to the global star formation rate density during their phase of activity, finding that they account for ∼5–10 per cent of the total star formation at 3 < z < 8, despite being only $\sim 0.5{{\ \rm per\ cent}}$ of the total in number. The resulting picture is that early and strong star formation activity, building massive galaxies on short time-scales and followed by a quick and abrupt quenching, is a rare but crucial phenomenon in the early Universe: the evolution of the cosmos must be heavily influenced by the short but powerful activity of these pristine monsters.
We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S . This evidence includes feedback process ...understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density (PDF) for S given all the evidence, including tests of robustness to difficult‐to‐quantify uncertainties and different priors. The 66% range is 2.6‐3.9 K for our Baseline calculation, and remains within 2.3‐4.5 K under the robustness tests; corresponding 5‐95% ranges are 2.3‐4.7 K, bounded by 2.0‐5.7 K (although such high‐confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent, and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S , in particular using comprehensive models and process understanding to address limitations in the traditional forcing‐feedback paradigm for interpreting past changes.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We present a full data analysis of the pure-parallel Hubble Space Telescope (HST) imaging observations in the Brightest of Reionizing Galaxies Survey (BoRGz9) in Cycle 22. The medium-deep exposures ...with five HST/WFC3IR+UVIS filter bands from 79 independent sightlines (∼370 arcmin2) provide the least biased determination of number density for z 9 bright galaxies against cosmic variance. After a strict two-step selection for candidate galaxies, including dropout color and photometric redshift analyses, and revision of previous BoRG candidates, we identify one source at z ∼ 10 and two sources at z ∼ 9. The z ∼ 10 candidate shows evidence of line-of-sight lens magnification ( ∼ 1.5), yet it appears surprisingly luminous ( mag), making it one of the brightest candidates at known (∼0.3 mag brighter than the z = 8.68 galaxy EGSY8p7, spectroscopically confirmed by Zitrin and collaborators). For z ∼ 9 candidates, we include previous data points at fainter magnitudes and find that the data are well fitted by a Schechter luminosity function with , mag, and Mpc−3 mag−1, for the first time without fixing any parameters. The inferred cosmic star formation rate density is consistent with unaccelerated evolution from lower redshift.
ABSTRACT We present a model using both strong and weak gravitational lensing of the galaxy cluster MACS J0416.1-2403, constrained using spectroscopy from the Grism Lens-Amplified Survey from Space ...(GLASS) and Hubble Frontier Fields (HFF) imaging data. We search for emission lines in known multiply imaged sources in the GLASS spectra, obtaining secure spectroscopic redshifts of 30 multiple images belonging to 15 distinct source galaxies. The GLASS spectra provide the first spectroscopic measurements for five of the source galaxies. The weak lensing signal is acquired from 884 galaxies in the F606W HFF image. By combining the weak lensing constraints with 15 multiple image systems with spectroscopic redshifts and nine multiple image systems with photometric redshifts, we reconstruct the gravitational potential of the cluster on an adaptive grid. The resulting map of total mass density is compared with a map of stellar mass density obtained from the deep Spitzer Frontier Fields imaging data to study the relative distribution of stellar and total mass in the cluster. We find that the projected stellar mass to total mass ratio, f⋆, varies considerably with the stellar surface mass density. The mean projected stellar mass to total mass ratio is (stat.), but with a systematic error as large as 0.004-0.005, dominated by the choice of the initial mass function. We find agreement with several recent measurements of f⋆ in massive cluster environments. The lensing maps of convergence, shear, and magnification are made available to the broader community in the standard HFF format.
Abstract The Lyman alpha (Ly α) line of Hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km s−1 compared to the systemic redshift. This ...large offset hampers follow-up surveys, galaxy pair statistics, and correlations with quasar absorption lines when only Ly α is available. We propose diagnostics that can be used to recover the systemic redshift directly from the properties of the Ly α line profile. We use spectroscopic observations of Ly α emitters for which a precise measurement of the systemic redshift is available. Our sample contains 13 sources detected between z ≈ 3 and z ≈ 6 as part of various multi-unit spectroscopic explorer guaranteed time observations. We also include a compilation of spectroscopic Ly α data from the literature spanning a wide redshift range (z ≈ 0–8). First, restricting our analysis to double-peaked Ly α spectra, we find a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, $V_{\rm peak}^{\rm red}$, and the separation of the peaks. Secondly, we find a correlation between $V_{\rm peak}^{\rm red}$ and the full width at half-maximum of the Ly α line. Fitting formulas to estimate systemic redshifts of galaxies with an accuracy of ≤100 km s−1, when only the Ly α emission line is available, are given for the two methods.
ABSTRACT We present a strong and weak lensing reconstruction of the massive cluster Abell 2744, the first cluster for which deep Hubble Frontier Fields (HFF) images and spectroscopy from the Grism ...Lens-Amplified Survey from Space (GLASS) are available. By performing a targeted search for emission lines in multiply imaged sources using the GLASS spectra, we obtain five high-confidence spectroscopic redshifts and two tentative ones. We confirm one strongly lensed system by detecting the same emission lines in all three multiple images. We also search for additional line emitters blindly and use the full GLASS spectroscopic catalog to test reliability of photometric redshifts for faint line emitters. We see a reasonable agreement between our photometric and spectroscopic redshift measurements, when including nebular emission in photometric redshift estimations. We introduce a stringent procedure to identify only secure multiple image sets based on colors, morphology, and spectroscopy. By combining 7 multiple image systems with secure spectroscopic redshifts (at 5 distinct redshift planes) with 18 multiple image systems with secure photometric redshifts, we reconstruct the gravitational potential of the cluster pixellated on an adaptive grid, using a total of 72 images. The resulting mass map is compared with a stellar mass map obtained from the deep Spitzer Frontier Fields data to study the relative distribution of stars and dark matter in the cluster. We find that the stellar to total mass ratio varies substantially across the cluster field, suggesting that stars do not trace exactly the total mass in this interacting system. The maps of convergence, shear, and magnification are made available in the standard HFF format.
Abstract
We present 36 spectroscopically confirmed intrinsically UV-faint Ly
α
-emitting galaxies from follow-up observations with Keck/DEep Imaging Multi-Object Spectrograph of gravitationally ...lensed high-redshift candidates. Candidates were selected to be between 5 ≲
z
≲ 7 from photometric data using Hubble Space Telescope and Spitzer imaging surveys. We performed an integrated photometric redshift probability cut >1% between 5 <
z
< 7 to construct a sample of 198 high-redshift objects. Our sample spans intrinsic UV luminosities from a few
L
* down to 0.001
L
*. We identified 19 high-confidence detections and 17 likely detections of Ly
α
. We divided our sample into lower-redshift (
z
∼ 5.5) and higher-redshift (
z
∼ 6.5) bins and ran Monte Carlo trials, incorporating the strengths of the Ly
α
emission and the photometric redshifts of the nondetections. Considering only objects where Ly
α
could be detected at EW(Ly
α
) > 25 Å at 3
σ
at the fiducial depth of our survey, and only those galaxies with EW(Ly
α
) > 25 Å, and only objects with
m
AB
< 26.8, we found the Ly
α
emitter (LAE) fraction to be flat or modestly increase from 0.26 ± 0.04 to 0.30 ± 0.04. These values are consistent with a rising LAE fraction with redshift out to
z
∼ 6, but at
z
∼ 6.5, there is some tension between our results and results from surveys at intrinsically brighter luminosities. We conclude that intrinsically fainter galaxies have Ly
α
emission, and there is a steep drop in the LAE fraction from our high-redshift sample at
z
∼ 6.5 and from similar galaxies at
z
∼ 7.5. This likely indicates we are witnessing the tail end of the epoch of reionization, as such a drop is not expected due to changes of intrinsic galaxy properties between these redshifts.
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