Showing papers by "Tommaso Treu published in 2019"

Tensions between the early and late Universe

Abstract: A Kavli Institute for Theoretical Physics workshop in July 2019 directed attention to the Hubble constant discrepancy. New results showed that it does not appear to depend on the use of any one method, team or source. Proposed solutions focused on the pre-recombination era.

Tensions between the Early and the Late Universe

Abstract: The standard cosmological model successfully describes many observations from widely different epochs of the Universe, from primordial nucleosynthesis to the accelerating expansion of the present day. However, as the basic cosmological parameters of the model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. The workshop "Tensions between the Early and the Late Universe" was held at the Kavli Institute for Theoretical Physics on July 15-17 2019 (More details of the workshop (including on-line presentations) are given at the website: this https URL) to evaluate increasing evidence for these discrepancies, primarily in the value of the Hubble constant as well as ideas recently proposed to explain this tension. Multiple new observational results for the Hubble constant were presented in the time frame of the workshop using different probes: Cepheids, strong lensing time delays, tip of the red giant branch (TRGB), megamasers, Oxygen-rich Miras and surface brightness fluctuations (SBF) resulting in a set of six new ones in the last several months. Here we present the summary plot of the meeting that shows combining any three independent approaches to measure H$_0$ in the late universe yields tension with the early Universe values between 4.0$\sigma$ and 5.8$\sigma$. This shows that the discrepancy does not appear to be dependent on the use of any one method, team, or source. Theoretical ideas to explain the discrepancy focused on new physics in the decade of expansion preceding recombination as the most plausible. This is a brief summary of the workshop.

A single fast radio burst localized to a massive galaxy at cosmological distance

Abstract: Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.

H0LiCOW – IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant

Abstract: We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 We combine the relative time delay between the quasar images, Hubble Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias After unblinding, the inferred distances imply a Hubble constant H_0 = 688|$^{+54}_{-51}$| km s^−1 Mpc^−1, assuming a flat Λ cold dark matter cosmology with uniform prior on Ω_m in [005, 05] The precision of our cosmographic measurement with the doubly imaged quasar SDSS 1206+4332 is comparable with those of quadruply imaged quasars and opens the path to perform on selected doubles the same analysis as anticipated for quads Our analysis is based on a completely independent lensing code than our previous three H0LiCOW systems and the new measurement is fully consistent with those We provide the analysis scripts paired with the publicly available software to facilitate independent analysis (footnote with link to wwwh0licoworg) The consistency between blind measurements with independent codes provides an important sanity check on lens modelling systematics By combining the likelihoods of the four systems under the same prior, we obtain H_0 = 725|$^{+21}_{-23}$| km s^−1 Mpc^−1 This measurement is independent of the distance ladder and other cosmological probes

A SHARP view of H0LiCOW: H 0 from three time-delay gravitational lens systems with adaptive optics imaging

Abstract: We present the measurement of the Hubble Constant, $H_0$, with three strong gravitational lens systems. We describe a blind analysis of both PG1115+080 and HE0435-1223 as well as an extension of our previous analysis of RXJ1131-1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP AO effort, with Hubble Space Telescope (HST) imaging, velocity dispersion measurements, and a description of the line-of-sight mass distribution to build an accurate and precise lens mass model. This mass model is then combined with the COSMOGRAIL measured time delays in these systems to determine $H_{0}$. We do both an AO-only and an AO+HST analysis of the systems and find that AO and HST results are consistent. After unblinding, the AO-only analysis gives $H_{0}=82.8^{+9.4}_{-8.3}~\rm km\,s^{-1}\,Mpc^{-1}$ for PG1115+080, $H_{0}=70.1^{+5.3}_{-4.5}~\rm km\,s^{-1}\,Mpc^{-1}$ for HE0435-1223, and $H_{0}=77.0^{+4.0}_{-4.6}~\rm km\,s^{-1}\,Mpc^{-1}$ for RXJ1131-1231. The joint AO-only result for the three lenses is $H_{0}=75.6^{+3.2}_{-3.3}~\rm km\,s^{-1}\,Mpc^{-1}$. The joint result of the AO+HST analysis for the three lenses is $H_{0}=76.8^{+2.6}_{-2.6}~\rm km\,s^{-1}\,Mpc^{-1}$. All of the above results assume a flat $\Lambda$ cold dark matter cosmology with a uniform prior on $\Omega_{\textrm{m}}$ in [0.05, 0.5] and $H_{0}$ in [0, 150] $\rm km\,s^{-1}\,Mpc^{-1}$. This work is a collaboration of the SHARP and H0LiCOW teams, and shows that AO data can be used as the high-resolution imaging component in lens-based measurements of $H_0$. The full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper.

Inferences on the timeline of reionization at z ∼ 8 from the KMOS Lens-Amplified Spectroscopic Survey

Abstract: Author(s): Mason, CA; Fontana, A; Treu, T; Schmidt, KB; Hoag, A; Abramson, L; Amorin, R; Bradac, M; Guaita, L; Jones, T; Henry, A; Malkan, MA; Pentericci, L; Trenti, M; Vanzella, E | Abstract: Detections and non-detections of Lyman alpha (Lyα) emission from z g 6 galaxies (l1 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 g 7, where Lyα redshifts to near infra-red wavelengths. Here we present a search for z g 7.2 Lyα 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 h, we detect no Lyα emission with signal-to-noise ratio (S/N) g 5 in our sample. We determine our observations to be 80 per cent complete for 5σ spatially and spectrally unresolved emission lines with integrated line flux g5.7 × 10−18 erg s−1 cm−2. We define a photometrically selected sub-sample of 29 targets at z = 7.9 ± 0.6, with a median 5σ Lyα EW limit of 58 A. 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 g 0.76 (68 per cent), g 0.46 (95 per cent) 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 MUV −12, with low ionizing photon escape fractions, fesc 15 per cent.

TDCOSMO. I. An exploration of systematic uncertainties in the inference of $H_0$ from time-delay cosmography

Abstract: Time-delay cosmography of lensed quasars has achieved 2.4% precision on the measurement of the Hubble constant, $H_0$. As part of an ongoing effort to uncover and control systematic uncertainties, we investigate three potential sources: 1- stellar kinematics, 2- line-of-sight effects, and 3- the deflector mass model. To meet this goal in a quantitative way, we reproduced the H0LiCOW/SHARP/STRIDES (hereafter TDCOSMO) procedures on a set of real and simulated data, and we find the following. First, stellar kinematics cannot be a dominant source of error or bias since we find that a systematic change of 10% of measured velocity dispersion leads to only a 0.7% shift on $H_0$ from the seven lenses analyzed by TDCOSMO. Second, we find no bias to arise from incorrect estimation of the line-of-sight effects. Third, we show that elliptical composite (stars + dark matter halo), power-law, and cored power-law mass profiles have the flexibility to yield a broad range in $H_0$ values. However, the TDCOSMO procedures that model the data with both composite and power-law mass profiles are informative. If the models agree, as we observe in real systems owing to the "bulge-halo" conspiracy, $H_0$ is recovered precisely and accurately by both models. If the two models disagree, as in the case of some pathological models illustrated here, the TDCOSMO procedure either discriminates between them through the goodness of fit, or it accounts for the discrepancy in the final error bars provided by the analysis. This conclusion is consistent with a reanalysis of six of the TDCOSMO (real) lenses: the composite model yields $74.0^{+1.7}_{-1.8}$ $km.s^{-1}.Mpc^{-1}$, while the power-law model yields $H_0=74.2^{+1.6}_{-1.6}$ $km.s^{-1}.Mpc^{-1}$. In conclusion, we find no evidence of bias or errors larger than the current statistical uncertainties reported by TDCOSMO.

Constraining the Neutral Fraction of Hydrogen in the IGM at Redshift 7.5

Abstract: We present a large spectroscopic campaign with Keck/Multi-Object Spectrometer for InfraRed Exploration (MOSFIRE) targeting Lyα emission (Lyα) 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 Lyα equivalent-width limits. During the campaign, we targeted 70 LBG candidates with the MOSFIRE Y band, selected photometrically to cover Lyα over the range 7 < z 5 emission lines in two of these galaxies and find that they are likely Lyα 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, xH I, in the IGM during reionization to be xH I =0.88+0.05-0.10 at z = 7.6 ±0.6. Our result is consistent with a late and rapid reionization scenario inferred by Planck.

Is every strong lens model unhappy in its own way? Uniform modelling of a sample of 13 quadruply+ imaged quasars

Abstract: Strong-gravitational lens systems with quadruply imaged quasars (quads) are unique probes to address several fundamental problems in cosmology and astrophysics. Although they are intrinsically very rare, ongoing and planned wide-field deep-sky surveys are set to discover thousands of such systems in the next decade. It is thus paramount to devise a general framework to model strong-lens systems to cope with this large influx without being limited by expert investigator time. We propose such a general modelling framework (implemented with the publicly available software lenstronomy) and apply it to uniformly model three-band Hubble Space Telescope Wide Field Camera 3 images of 13 quads. This is the largest uniformly modelled sample of quads to date and paves the way for a variety of studies. To illustrate the scientific content of the sample, we investigate the alignment between the mass and light distribution in the deflectors. The position angles of these distributions are well-aligned, except when there is strong external shear. However, we find no correlation between the ellipticity of the light and mass distributions. We also show that the observed flux-ratios between the images depart significantly from the predictions of simple smooth models. The departures are strongest in the bluest band, consistent with microlensing being the dominant cause in addition to millilensing. Future papers will exploit this rich data set in combination with ground-based spectroscopy and time delays to determine quantities such as the Hubble constant, the free streaming length of dark matter, and the normalization of the initial stellar mass function.

Probing dark matter structure down to 107 solar masses: flux ratio statistics in gravitational lenses with line-of-sight haloes

Abstract: Strong lensing provides a powerful means of investigating the nature of dark matter as it probes dark matter structure on sub-galactic scales. We present an extension of a forward modeling framework that uses flux ratios from quadruply imaged quasars (quads) to measure the shape and amplitude of the halo mass function, including line of sight (LOS) halos and main deflector subhalos. We apply this machinery to 50 mock lenses --- roughly the number of known quads --- with warm dark matter (WDM) mass functions exhibiting free-streaming cutoffs parameterized by the half-mode mass $m_{\rm{hm}}$. Assuming cold dark matter (CDM), we forecast bounds on $m_{\rm{hm}}$ and the corresponding thermal relic particle masses over a range of tidal destruction severity, assuming a particular WDM mass function and mass-concentration relation. With significant tidal destruction, at $2 \sigma$ we constrain $m_{\rm{hm}} 10^{7.7} M_{\odot}$ over CDM with relative likelihoods of 22:1 and 8:1 with flux uncertainties of $2\%$ and $6\%$, respectively. These bounds improve over those obtained by modeling only main deflector subhalos because LOS objects produce additional flux perturbations, especially for high redshift systems. These results indicate that $\sim 50$ quads can conclusively differentiate between warm and cold dark matter.

Cosmic dissonance: new physics or systematics behind a short sound horizon?

Abstract: Persistent tension between low-redshift observations and the Cosmic Microwave Background radiation (CMB), in terms of two fundamental distance scales set by the sound horizon $r_d$ and the Hubble constant $H_0$, suggests new physics beyond the Standard Model or residual systematics. We examine recently updated distance calibrations from Cepheids, gravitational lensing time-delay observations, and the Tip of the Red Giant Branch. Calibrating the Baryon Acoustic Oscillations (BAO) and Type Ia supernovae with combinations of the distance indicators, we obtain a joint and self-consistent measurement of $H_0$ and $r_d$ at low redshift, independent of cosmological models and CMB inference. In an attempt to alleviate the tension between late-time and CMB-based measurements, we consider four extensions of the standard $\Lambda$CDM model. The sound horizon from our different measurements is $r_d=(137\pm3^{stat.}\pm2^{syst.})$~Mpc. Depending on the adopted distance indicators, the $combined$ tension in $H_0$ and $r_d$ ranges between 2.3 and 5.1 $\sigma$. We find that modifications of $\Lambda$CDM that change the physics after recombination fail to solve the problem, for the reason that they only resolve the tension in $H_0$, while the tension in $r_d$ remains unchanged. Pre-recombination extensions (with early dark energy or the effective number of neutrinos $\rm{N}_{\rm{eff}}=3.24 \pm 0.16$) are allowed by the data, unless the calibration from Cepheids is included. Results from time-delay lenses are consistent with those from distance-ladder calibrations and point to a discrepancy between absolute distance scales measured from the CMB (assuming the standard cosmological model) and late-time observations. New proposals to resolve this tension should be examined with respect to reconciling not only the Hubble constant but also the sound horizon derived from the CMB and other cosmological probes.

The mass relations between supermassive black holes and their host galaxies at 1<z<2 with HST-WFC3

Abstract: Correlations between the mass of a supermassive black hole and the properties of its host galaxy (e.g., total stellar mass (M*), luminosity (Lhost)) suggest an evolutionary connection. A powerful test of a co-evolution scenario is to measure the relations MBH-Lhost and MBH-M* at high redshift and compare with local estimates. For this purpose, we acquired HST imaging with WFC3 of 32 X-ray-selected broad-line AGN at 1.2

A single fast radio burst localized to a massive galaxy at cosmological distance

Abstract: Fast Radio Bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Non-repeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single pulse FRB 180924 to a position 4 kpc from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.

Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum

Abstract: We model the ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 obtained with the Hubble Space Telescope during the 6 month reverberation mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Lyα and C iv, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Lyα and C iv have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show a delayed response to continuum variations corresponding to recombination in gas with a density of ~105 cm−3. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in ~2012 corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.

COSMOGRAIL. XVIII. time delays of the quadruply lensed quasar WFI2033-4723

Abstract: We present new measurements of the time delays of WFI2033−4723. The data sets used in this work include 14 years of data taken at the 1.2 m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3 m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2 m telescope. The time delays measured from these different data sets, all taken in the R -band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in days (2.1% precision), days (5.6%) and days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2 m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033−4723. Our time-delay measurements are not precise enough to conclude that microlensing time delay is present or absent from the data. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033−4723.

COSMOGRAIL XVIII: time delays of the quadruply lensed quasar WFI2033-4723

Abstract: We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2m telescope. The time delays measured from these different data sets, all taken in the R-band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in Dt_AB = 36.2-0.8+0.7 days (2.1% precision), Dt_AC = -23.3-1.4+1.2 days (5.6%) and Dt_BC = -59.4-1.3+1.3 days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033-4723. There is however no strong indication in our measurements that microlensing time delay is neither present nor absent. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.

Searching for Highly Magnified Stars at Cosmological Distances: Discovery of a Redshift 0.94 Blue Supergiant in Archival Images of the Galaxy Cluster MACS J0416.1-2403

Abstract: This work was supported in part by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and JSPS KAKENHI grants JP15H05892 and JP18K03693. R.J.F. is supported in part by NSF grant AST1518052, the Gordon & Betty Moore Foundation, the HeisingSimons Foundation, and by a fellowship from the David and Lucile Packard Foundation. Analysis of highly magnified stars at the University of Minnesota by P.L.K is supported in part by NSF grant AST-1908823. P.L.K., A.V.F., and T.T. acknowledge generous financial assistance from NASA/HST grants GO-14922 and GO-14872 from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Additional support for A.V.F. was provided by the Christopher R. Redlich Fund, the TABASGO Foundation, and the Miller Institute for Basic Research inScience (U.C. Berkeley). J.M.D. acknowledges the support of projects AYA2015-64508-P (MINECO/FEDER, UE), funded by the Ministerio de Economia y Competitividad. J.H. was supported by a VILLUM FONDEN Investigator grant (project No. 16599). This work utilizes gravitational lensing models produced by PIs Bradac Natarajan, & Kneib (CATS); Merten & Zitrin; Sharon, Williams, Keeton, Bernstein, and Diego; and the GLAFIC group. This lens modeling was partially funded by the HST Frontier Fields program conducted by STScI. The lens models were obtained from the Mikulski Archive for Space Telescopes (MAST).

Discovery of Strongly Inverted Metallicity Gradients in Dwarf Galaxies at z ̃ 2

Abstract: Author(s): Wang, X; Jones, TA; Treu, T; Hirtenstein, J; Brammer, GB; Daddi, E; Meng, XL; Morishita, T; Abramson, LE; Henry, AL; Peng, YJ; Schmidt, KB; Sharon, K; Trenti, M; Vulcani, B | Abstract: We report the first measurements with sub-kiloparsec spatial resolution of strongly inverted gas-phase metallicity gradients in two dwarf galaxies at z ∼ 2. The galaxies have stellar masses ∼109 , specific star formation rate ∼20 Gyr-1, and global metallicity (1/4 solar), assuming the strong-line calibrations of [O iii]/Hβ and [O ii]/Hβ from Maiolino et al. Their radial metallicity gradients are measured to be highly inverted, i.e., 0.122 ± 0.008 and 0.111 ± 0.017 dex kpc-1, which is hitherto unseen at such small masses in similar redshift ranges. From the Hubble Space Telescope observations of the source nebular emission and stellar continuum, we present two-dimensional spatial maps of star formation rate surface density, stellar population age, and gas fraction, which show that our galaxies are currently undergoing rapid mass assembly via disk inside-out growth. More importantly, using a simple chemical evolution model, we find that the gas fractions for different metallicity regions cannot be explained by pure gas accretion. Our spatially resolved analysis based on a more advanced gas regulator model results in a spatial map of net gaseous outflows, triggered by active central starbursts, that potentially play a significant role in shaping the spatial distribution of metallicity by effectively transporting stellar nucleosynthesis yields outwards. The relation between wind mass loading factors and stellar surface densities measured in different regions of our galaxies shows that a single type of wind mechanism, driven by either energy or momentum conservation, cannot explain the entire galaxy. These sources present a unique constraint on the effects of gas flows on the early phase of disk growth from the perspective of spatially resolved chemical evolution within individual systems.

Massive Dead Galaxies at z ̃ 2 with HST Grism Spectroscopy. I. Star Formation Histories and Metallicity Enrichment

Abstract: Author(s): Morishita, T; Abramson, LE; Treu, T; Brammer, GB; Jones, T; Kelly, P; Stiavelli, M; Trenti, M; Vulcani, B; Wang, X | Abstract: Observations have revealed massive (log M∗/Mo ≳ 11) galaxies that were already dead when the universe was only ∼2 Gyr. Given the short time before these galaxies were quenched, their past histories and quenching mechanism(s) are of particular interest. In this paper, we study star formation histories (SFHs) of 24 massive galaxies at 1.6 l z l 2.5. A deep slitless spectroscopy and imaging data set collected from multiple Hubble Space Telescope surveys allows robust determination of their spectral energy distributions and SFHs with no functional assumption on their forms. We find that most of our massive galaxies had formed g50% of their extant masses by ∼1.5 Gyr before the time of observed redshifts, with a trend where more massive galaxies form earlier. Their stellar-phase metallicities are already compatible with those of local early-type galaxies, with a median value of log Z∗/Zo = 0.25 and scatter of ∼0.15 dex. In combination with the reconstructed SFHs, we reveal their rapid metallicity evolution from z ∼ 5.5 to ∼2.2 at a rate of ∼0.2 dex Gyr-1 in Z∗/Zo. Interestingly, the inferred stellar-phase metallicities are, when compared at half-mass time, ∼0.25 dex higher than observed gas-phase metallicities of star-forming galaxies. While systematic uncertainties remain, this may imply that these quenched galaxies have continued low-level star formation, rather than abruptly terminating their star formation activity, and kept enhancing their metallicity until recently.

Astrometric requirements for strong lensing time-delay cosmography

Abstract: The time delay between the arrival of photons of multiple images of time variable sources can be used to constrain absolute distances in the Universe (Refsdal 1964), and in turn obtain a direct estimate of the Hubble constant and other cosmological parameters. To convert the time delay into distances, it is well known that the gravitational potential of the main deflector and the contribution of the matter along the line-of-sight need to be known to a sufficient level of precision. In this paper, we discuss a new astrometric requirement that is becoming important as time-delay cosmography improves in precision and accuracy with larger samples, and better data and modelling techniques. We derive an analytic expression for the propagation of astrometric uncertainties on the multiple image positions into the inference of the Hubble constant and derive requirements depending on image separation and relative time delay. We note that this requirement applies equally to the image position measurements and to the accuracy of the model in reproducing them. To illustrate the requirement, we discuss some example lensing configurations and highlight that, especially for time delays of order 10 days or shorter, the relative astrometric requirement is of order milli-arcseconds, setting a tight requirement on both measurements and models. With current optical infrared technology, astrometric uncertainties may be the dominant limitation for strong lensing cosmography in the small image-separation regime when high-precision time-delays become accessible.

Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum

Abstract: We model the ultraviolet spectra of the Seyfert 1 galaxy NGC~5548 obtained with the Hubble Space Telescope during the 6-month reverberation-mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly$\alpha$ and C IV, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly$\alpha$ and C IV have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show delayed response to continuum variations corresponding to recombination in gas with a density of $\sim 10^5~\rm cm^{-3}$. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in $\sim\,2012$ corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.

H0LiCOW – X. Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI 2033−4723

Abstract: Swiss National Science FoundationSwiss National Science Foundation (SNSF); European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programmeEuropean Research Council (ERC) [787886]; World Premier International Research Center Initiative (WPI Initiative), MEXT, JapanMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Packard FoundationThe David & Lucile Packard Foundation; NSFNational Science Foundation (NSF) [AST-1450141, AST-1312329]; Max Planck Society through the Max Planck Research Group; EACOA Fellowship - East Asia Core Observatories Association, Academia Sinica Institute of Astronomy and Astrophysics; National Astronomical Observatory of JapanNational Institutes of Natural Sciences (NINS) - Japan; National Astronomical Observatories of the Chinese Academy of Sciences; Korea Astronomy and Space Science Institute; DFG cluster of excellence 'Origin and Structure of the Universe'German Research Foundation (DFG); NASA through STSCI grant [HSTGO-15320]; U.S. Department of EnergyUnited States Department of Energy (DOE) [DE-AC02-76SF00515]; NWO-VICI career grant [639.043.308]; European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) [091.A-0642(A), 074.A-0302(A), 60.A-9306(A), 097.A-0454(A), 090.A-0531(A)]; U.S. Department of EnergyUnited States Department of Energy (DOE); U.S. National Science FoundationNational Science Foundation (NSF); Ministry of Science and Education of SpainMinistry of Education and Science, Spain; Science and Technology Facilities Council of the United KingdomScience & Technology Facilities Council (STFC); Higher Education Funding Council for EnglandHigher Education Funding Council for England; National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign; Kavli Institute of Cosmological Physics at the University of Chicago; Center for Cosmology and Astro-Particle Physics at the Ohio State UniversityOhio State University; Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University; Financiadora de Estudos e ProjetosCiencia Tecnologia e Inovacao (FINEP); Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro; Conselho Nacional de Desenvolvimento Cientifico e TecnologicoNational Council for Scientific and Technological Development (CNPq); Ministerio da Ciencia, Tecnologia e Inovacao; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG); Argonne National LaboratoryUnited States Department of Energy (DOE)University of Chicago; University of California at Santa Cruz; University of CambridgeUniversity of Cambridge; Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid; University of ChicagoUniversity of Chicago; University College London; DES-Brazil Consortium; University of Edinburgh; Eidgenossische Technische Hochschule (ETH) ZurichETH Zurich; Fermi National Accelerator LaboratoryUnited States Department of Energy (DOE)University of Chicago; University of Illinois at Urbana-Champaign; Institut de Ciencies de l'Espai (IEEC/CSIC); Institut de Fisica d'Altes Energies; Lawrence Berkeley National LaboratoryUnited States Department of Energy (DOE); Ludwig-Maximilians Universitat Munchen; associated Excellence Cluster Universe; University of MichiganUniversity of Michigan System; National Optical Astronomy ObservatoryNational Science Foundation (NSF)NSF - Directorate for Mathematical & Physical Sciences (MPS); University of Nottingham; Ohio State UniversityOhio State University; University of Pennsylvania; University of Portsmouth; SLAC National Accelerator Laboratory; Stanford UniversityStanford University; University of Sussex; Texas AM University; OzDES Membership Consortium; National Science FoundationNational Science Foundation (NSF) [AST-1138766, AST-1536171]; MINECO [AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV-20160597, MDM-2015-0509]; ERDF funds from the European Union; CERCA program of the Generalitat de Catalunya; European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013); ERCEuropean Research Council (ERC) [240672, 291329, 306478]; Brazilian Instituto Nacional de Ciencia e Tecnologia (INCT) e-Universe (CNPq)National Council for Scientific and Technological Development (CNPq) [465376/2014-2]; U.S. Department of Energy, Office of Science, Office of High Energy PhysicsUnited States Department of Energy (DOE) [DE-AC02-07CH11359]; NASANational Aeronautics & Space Administration (NASA) [NAS 5-26555]; NASA through Space Telescope Science InstituteSpace Telescope Science Institute [12889]; National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA); National Science FoundationNational Science Foundation (NSF)

Constraining Lyman-alpha spatial offsets at 3 < z < 5.5 from VANDELS slit spectroscopy

Abstract: Author(s): Hoag, A; Treu, T; Pentericci, L; Amorin, R; Bolzonella, M; Bradac, M; Castellano, M; Cullen, F; Fynbo, JPU; Garilli, B; Guaita, L; Hathi, N; Henry, A; Jones, T; Mason, C; McLeod, D; McLure, R; Morishita, T; Pozzetti, L; Schaerer, D; Schmidt, KB; Talia, M; Thomas, R | Abstract: We constrain the distribution of spatially offset Lyman-alpha emission (Ly α) relative to rest-frame ultraviolet emission in ∼300 high redshift (3 l z l 5.5) Lyman-break galaxies (LBGs) exhibiting Ly α emission from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep Survey and Chandra Deep Field South fields (≈0.2 deg2 total). Because slit spectroscopy only provides one spatial dimension, we use Bayesian inference to recover the underlying two-dimensional Ly α spatial offset distribution. We model the distribution using a two-dimensional circular Gaussian, defined by a single parameter σr,Ly α, the standard deviation expressed in polar coordinates. Over the entire redshift range of our sample (3 l z l 5.5), we find σr,Ly α = 1.70+0.09-0.08 kpc (68 per cent conf.), corresponding to ∼0′.25 at 〈z〉 = 4.5. We also find that σr,Ly α decreases significantly with redshift. Because Ly α spatial offsets can cause slit losses, the decrease in σr,Ly α with redshift can partially explain the increase in the fraction of Ly α emitters observed in the literature over this same interval, although uncertainties are still too large to reach a strong conclusion. If σr,Ly α continues to decrease into the reionization epoch, then the decrease in Ly α transmission from galaxies observed during this epoch might require an even higher neutral hydrogen fraction than what is currently inferred. Conversely, if spatial offsets increase with the increasing opacity of the intergalactic medium, slit losses may explain some of the drop in Ly α transmission observed at z g 6. Spatially resolved observations of Ly α and UV continuum at 6 l z l8 are needed to settle the issue.

Evolution of the Stellar Mass–Metallicity Relation. II. Constraints on Galactic Outflows from the Mg Abundances of Quiescent Galaxies

Abstract: We present the stellar mass–[Fe/H] and mass–[Mg/H] relation of quiescent galaxies in two galaxy clusters at z ~ 0.39 and z ~ 0.54. We derive the age, [Fe/H], and [Mg/Fe] for each individual galaxy using a full-spectrum fitting technique. By comparing with the relations for z ~ 0 Sloan Digital Sky Survey galaxies, we confirm our previous finding that the mass–[Fe/H] relation evolves with redshift. The mass–[Fe/H] relation at higher redshift has lower normalization and possibly steeper slope. However, based on our sample, the mass–[Mg/H] relation does not evolve over the observed redshift range. We use a simple analytic chemical evolution model to constrain the average outflow that these galaxies experience over their lifetime, via the calculation of mass-loading factor. We find that the average mass-loading factor η is a power-law function of galaxy stellar mass, η ∝ M*^(−0.21±0.09). The measured mass-loading factors are consistent with the results of other observational methods for outflow measurements and with the predictions where outflow is caused by star formation feedback in turbulent disks.

Hubble Frontier Field photometric catalogues of Abell 370 and RXC J2248.7-4431: multiwavelength photometry, photometric redshifts, and stellar properties

Abstract: This paper presents multiwavelength photometric catalogues of the last two Hubble Frontier Fields (HFF), the massive galaxy clusters Abell 370 and RXC J2248.7-4431. The photometry ranges from imaging performed on the Hubble Space Telescope (HST) to ground based Very Large Telescope (VLT) and Spitzer/IRAC, in collaboration with the ASTRODEEP team, and using the ASTRODEEP pipeline. While the main purpose of this paper is to release the catalogues, we also perform, as a proof of concept, a brief analysis of z > 6 objects selected using drop-out method, as well as spectroscopically confirmed sources and multiple images in both clusters. While dropout methods yield a sample of high-z galaxies, the addition of longer wavelength data reveals that as expected the samples have substantial contamination at the ~30-45% level by dusty galaxies at lower redshifts. Furthermore, we show that spectroscopic redshifts are still required to unambiguously determine redshifts of multiply imaged systems. Finally, the now publicly available ASTRODEEP catalogues were combined for all HFFs and used to explore stellar properties of a large sample of 20,000 galaxies across a large photometric redshift range. The powerful magnification provided by the HFF clusters allows us an exploration of the properties of galaxies with intrinsic stellar masses as low as $M_* \gtrsim 10^7M_{\odot}$ and intrinsic star formation rates $\mbox{SFRs}\sim 0.1\mbox{-}1M_\odot/\mbox yr$ at z > 6.

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

Abstract: We present a large spectroscopic campaign with Keck/MOSFIRE targeting Lyman-alpha emission (Ly$\alpha$) 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$\alpha$ equivalent width limits. During the campaign we targeted 70 LBG candidates with MOSFIRE Y-band, selected photometrically to cover Ly$\alpha$ over the range $7 5$ emission lines in 2 of these galaxies and find that they are likely Ly$\alpha$ 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.

Searching for Highly Magnified Stars at Cosmological Distances: Discovery of a Redshift 0.94 Blue Supergiant in Archival Images of the Galaxy Cluster MACS J0416.1-2403.

Abstract: Individual highly magnified stars have been recently discovered at lookback times of more than half the age of the Universe, in lensed galaxies that straddle the critical curves of massive galaxy clusters. Having confirmed their detectability, it is now important to carry out systematic searches for them in order to establish their frequency, and in turn learn about the statistical properties of high-redshift stars and of the granularity of matter in the foreground deflector. Here we report the discovery of a highly magnified star at redshift $z = 0.94$ in a strongly lensed arc behind a Hubble Frontier Field galaxy cluster, MACS J0416.1-2403, discovered as part of a systematic archival search. The bright transient (dubbed "Warhol") was discovered in Hubble Space Telescope data taken on 2014 September 15 and 16. This single image faded over a period of two weeks, and observations taken on 2014 September 1 show that the duration of the microlensing event was at most four weeks in total. The light curve may also exhibit slow changes over a period of years consistent with the level of microlensing expected from stars responsible for the intracluster light (ICL) of the cluster. Optical and infrared observations taken near peak brightness can be fit by a stellar spectrum with moderate host-galaxy extinction. A blue supergiant matches the measured spectral energy distribution near peak, implying a temporary magnification of at least several thousand. While the spectrum of an O-type star would also fit the transient's spectral energy distribution, extremely luminous O-type stars are much less common than blue supergiants. The short timescale of the event and the estimated effective temperature indicate that the lensed source is an extremely magnified star.

Where Do Quasar Hosts Lie with Respect to the Size–Mass Relation of Galaxies?

Abstract: The evolution of the galaxy size - stellar mass (Mstellar) relation has been a puzzle for over a decade. High redshift galaxies are significantly more compact than galaxies observed today, at an equivalent mass, but how much of this apparent growth is driven by progenitor bias, minor mergers, secular processes, or feedback from AGN is unclear. To help disentangle the physical mechanisms at work by addressing the latter, we study the galaxy size - Mstellar relation of 32 carefully-selected broad-line AGN hosts at 1.2 0.1). Using HST with multi-band photometry and state-of-the-art modeling techniques, we measure half-light radii while accounting for uncertainties from subtracting bright central point sources. We find AGN hosts to have sizes ranging from 1 to 6 kpc at Mstellar ~ 0.3 - 1 x 10^11 Msun. Thus, many hosts have intermediate sizes as compared to equal-mass star-forming and quiescent galaxies. While inconsistent with the idea that AGN feedback may induce an increase in galaxy sizes, this finding is consistent with hypotheses in which AGNs preferentially occur in systems with prior concentrated gas reservoirs, or are involved in secular compaction processes perhaps responsible for simultaneously building bulges and shutting down star formation. If driven by minor mergers, which do not grow central black holes as fast as they do bulge-like stellar structures, such a process would explain both the galaxy size - mass relation observed here and the evolution in the black hole, bulge mass relation described in a companion paper.

The OSIRIS Lens-amplified Survey (OLAS). I. Dynamical Effects of Stellar Feedback in Low-mass Galaxies at z ∼ 2

Abstract: Author(s): Hirtenstein, J; Jones, T; Wang, X; Wetzel, A; El-Badry, K; Hoag, A; Treu, T; Bradac, M; Morishita, T | Abstract: We introduce the OSIRIS Lens-Amplified Survey (OLAS), a kinematic survey of gravitationally lensed galaxies at cosmic noon taken with Keck adaptive optics. In this paper, we present spatially resolved spectroscopy and nebular emission kinematic maps for 17 star-forming galaxies with stellar masses 8 l log(M ∗/M o) l 9.8 and redshifts 1.2 l z l 2.3. OLAS is designed to probe the stellar mass (M ∗) and specific star formation rate (sSFR) range where simulations suggest that stellar feedback is most effective at driving gaseous outflows that create galaxy-wide potential fluctuations, which can generate dark matter cores. We compare our kinematic data with the trend among sSFR, M ∗, and Hα velocity dispersion, σ, from the Feedback In Realistic Environments (FIRE) simulations. Our observations reveal a correlation between sSFR and σ at fixed M ∗ that is similar to the trend predicted by simulations: feedback from star formation drives star-forming gas and newly formed stars into more dispersion-dominated orbits. The observed magnitude of this effect is in good agreement with the FIRE simulations, in which feedback alters the central density profiles of low-mass galaxies, converting dark matter cusps into cores over time. Our data support the scenario that stellar feedback drives gaseous outflows and potential fluctuations, which in turn drive dark matter core formation in dwarf galaxies.

The First Luminous Quasars and Their Host Galaxies

Abstract: High-Redshift quasars probe the growth of early supermassive black holes (SMBHs) in the universe. In the next decade, new observations will push the frontier to the first luminous quasars at z > 9, probe fainter quasar populations that trace earlier phases of BH growth, and connect SMBH growth with the rise of the earliest massive galaxies.