ABSTRACT
The deep, wide-area (∼800–900 arcmin
2
) near-infrared/WFC3/IR +
Spitzer
/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of ...high-redshift UV luminosity functions. However, the lack of
Hubble Space Telescope
(
HST
) 1.05
μ
m observations over the CANDELS fields has made it difficult to identify
z
∼ 9–10 sources robustly, since such data are needed to confirm the presence of an abrupt Lyman break at 1.2
μ
m. Here, we report on the successful identification of many such
z
∼ 9–10 sources from a new
HST
program (z9-CANDELS) that targets the highest-probability
z
∼ 9–10 galaxy candidates with observations at 1.05
μ
m, to search for a robust Lyman-break at 1.2
μ
m. The potential
z
∼ 9–10 candidates were preselected from the full
HST
,
Spitzer
/IRAC S-CANDELS observations, and the deepest-available ground-based optical+near-infrared observations (CFHTLS-DEEP+HUGS+UltraVISTA+ZFOURGE). We identified 15 credible
z
∼ 9–10 galaxies over the CANDELS fields. Nine of these galaxies lie at
z
∼ 9 and five are new identifications. Our targeted follow-up strategy has proven to be very efficient in making use of scarce
HST
time to secure a reliable sample of
z
∼ 9–10 galaxies. Through extensive simulations, we replicate the selection process for our sample (both the preselection and follow-up) and use it to improve current estimates for the volume density of bright
z
∼ 9 and
z
∼ 10 galaxies. The volume densities we find are 5
and
lower, respectively, than those found at
z
∼ 8. When compared with the best-fit evolution (i.e.,
) in the UV luminosity densities from
z
∼ 8 to
z
∼ 4 integrated to
(−20 mag), these luminosity densities are
and
lower, respectively, than the extrapolated trends. Our new results are broadly consistent with the “accelerated evolution” scenario at
z
> 8, consistent with that seen in many models.
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 report on five compact, extremely young (<10 Myr) and blue (βUV < −2.5, Fλ = λβ) objects observed with VLT/Multi Unit Spectroscopic Explorer at redshifts 3.1169 and 3.235, in addition to ...three objects at z = 6.145. These sources are strongly magnified (3–40 times) by the Hubble Frontier Field galaxy clusters MACS J0416 and AS1063. Their delensed half-light radii (Re) are between 16 and 140 pc, the stellar masses are ≃1–20 × 106 M⊙, the magnitudes are mUV = 28.8–31.4 (−17 < MUV < −15) and specific star formation rates can be as large as ∼800 Gyr−1. Remarkably, the inferred physical properties of two objects are similar to those expected in some globular cluster formation scenarios, representing the best candidate proto-GCs discovered so far. Rest-frame optical high-dispersion spectroscopy of one of them at z = 3.1169 yields a velocity dispersion σv ≃ 20 km s−1, implying a dynamical mass dominated by the stellar mass. Another object at z = 6.145, with delensed MUV ≃ −15.3 (mUV ≃ 31.4), shows a stellar mass and a star formation rate surface density consistent with the values expected from popular GC formation scenarios. An additional star-forming region at z = 6.145, with delensed mUV ≃ 32, a stellar mass of 0.5 × 106 M⊙ and a star formation rate of 0.06 M⊙ yr−1 is also identified. These objects currently represent the faintest spectroscopically confirmed star-forming systems at z > 3, elusive even in the deepest blank fields. We discuss how proto-GCs might contribute to the ionization budget of the Universe and augment Lyα visibility during reionization. This work underlines the crucial role of JWST in characterizing the rest-frame optical and near-infrared properties of such low-luminosity high-z objects.
A variety of organisms have evolved mechanisms to detect and respond to light, in which the response is mediated by protein structural changes after photon absorption. The initial step is often the ...photoisomerization of a conjugated chromophore. Isomerization occurs on ultrafast time scales and is substantially influenced by the chromophore environment. Here we identify structural changes associated with the earliest steps in the trans-to-cis isomerization of the chromophore in photoactive yellow protein. Femtosecond hard x-ray pulses emitted by the Linac Coherent Light Source were used to conduct time-resolved serial femtosecond crystallography on photoactive yellow protein microcrystals over a time range from 100 femtoseconds to 3 picoseconds to determine the structural dynamics of the photoisomerization reaction.
ABSTRACT We present the first results and design from the redshift z ∼ 9-10 Brightest of the Reionizing Galaxies Hubble Space Telescope survey BoRGz9-10, aimed at searching for intrinsically luminous ...unlensed galaxies during the first 700 Myr after the Big Bang. BoRGz9-10 is the continuation of a multi-year pure-parallel near-IR and optical imaging campaign with the Wide Field Camera 3. The ongoing survey uses five filters, optimized for detecting the most distant objects and offering continuous wavelength coverage from λ = 0.35 m to λ = 1.7 m. We analyze the initial ∼130 arcmin2 of area over 28 independent lines of sight (∼25% of the total planned) to search for galaxies using a combination of Lyman-break and photometric redshift selections. From an effective comoving volume of (5-25) × 105 Mpc3 for magnitudes brighter than in the -band respectively, we find five galaxy candidates at 8.3-10 detected at high confidence ( ), including a source at 8.4 with ( ), which, if confirmed, would be the brightest galaxy identified at such early times ( ). In addition, BoRGz9-10 data yield four galaxies with . These new Lyman-break galaxies with are ideal targets for follow-up observations from ground and space-based observatories to help investigate the complex interplay between dark matter growth, galaxy assembly, and reionization.
We present VLT/X-Shooter and MUSE spectroscopy of a faint F814W = 28.60 + or - 0.33 (M sub(UV)=-17.0, low-mass (<, ~10 super(7)M sub(middo t in circle)), and compact (R sub(eff)= 62 pc) freshly ...star-forming galaxy at z= 3.1169 magnified (16x) by the Hubble Frontier Fields galaxy cluster Abell S1063. Gravitational lensing allows for a significant jump toward low-luminosity regimes, in moderately high-resolution spectroscopy (R= lambda /dlambda ~ 3000-7400). We measured C IV lambda 1548, 1550, He II lambda 1640, O IIIlambda 1661,1666, C IIIlambdalambda 1907,1909, Hbeta, OIIIlambdalambda 4959,5007 emission lines with <, ~ 50 km s super(-1) and (de-lensed) fluxes spanning the interval 1.0 x 10 super(-19)-2 x 10 super(-18) erg s super(-1) cm super(-2) at signal-to-noise ratio (S/N) = 4-30. The double-peaked Lyalpha emission with Deltanured - blue) = 280 (+ or -7) km s super(-1) and de-lensed fluxes 2.4 sub((blue)) 8.5 sub((red)) x 10 super(-18) erg s super(-1) cm super(-2)(S/N = 38 sub((blue)) 110 sub((red))) indicate a low column density of neutral hydrogen gas consistent with a highly ionized interstellar medium as also inferred from the large OIIIlambda 5007/ OIIlambda 3727 > 10 ratio. We detect C IV lambda 1548,1550 resonant doublet in emission, each component with FWHM <, ~ 45 km s super(-1) and redshifted by +51(+ or -10) km s super(-1) relative to the systemic redshift. We interpret this as nebular emission tracing an expanding optically thin interstellar medium. Both C IV lambda 1548,1550 and He II lambda 1640 suggest the presence of hot and massive stars (with a possible faint active galactic nucleus). The ultraviolet slope is remarkably blue, beta =-2.95 + or - 0.20 (F sub(lambda)= lambda super(beta)), consistent with a dust-free and young <, ~20 Myr galaxy. Line ratios suggest an oxygen abundance 12 + log(O/H) < 7.8. We are witnessing an early episode of star formation in which a relatively low N sub(H I) and negligible dust attenuation might favor a leakage of ionizing radiation. This galaxy currently represents a unique low-luminosity reference object for future studies of the reionization epoch with the James Webb Space Telescope.
We examine the massive colliding cluster El Gordo, one of the most massive clusters at high redshift. We use a free-form lensing reconstruction method that avoids making assumptions about the mass ...distribution. We use data from the RELICS program and identify new multiply lensed system candidates. The new set of constraints and free-form method provide a new independent mass estimate of this intriguing colliding cluster. Our results are found to be consistent with earlier parametric models, indirectly confirming the assumptions made in earlier work. By fitting a double gNFW profile to the lens model and extrapolating to the virial radius, we infer a total mass for the cluster of M . We estimate the uncertainty in the mass due to errors in the photometric redshifts and discuss the uncertainty in the inferred virial mass due to the extrapolation from the lens model. We also find in our lens map a mass overdensity corresponding to the large cometary tail of hot gas, reinforcing its interpretation as a large tidal feature predicted by hydrodynamical simulations that mimic El Gordo. Finally, we discuss the observed relation between the plasma and the mass map, finding that the peak in the projected mass map may be associated with a large concentration of colder gas exhibiting possible star formation. El Gordo is one of the first clusters that will be observed with JWST, which is expected to unveil new high-redshift lensed galaxies around this interesting cluster and provide a more accurate estimation of its mass.
Abstract
Gravitational lensing by clusters of galaxies offers a powerful probe of their structure and mass distribution. Several research groups have developed techniques independently to achieve ...this goal. While these methods have all provided remarkably high-precision mass maps, particularly with exquisite imaging data from the Hubble Space Telescope (HST), the reconstructions themselves have never been directly compared. In this paper, we present for the first time a detailed comparison of methodologies for fidelity, accuracy and precision. For this collaborative exercise, the lens modelling community was provided simulated cluster images that mimic the depth and resolution of the ongoing HST Frontier Fields. The results of the submitted reconstructions with the un-blinded true mass profile of these two clusters are presented here. Parametric, free-form and hybrid techniques have been deployed by the participating groups and we detail the strengths and trade-offs in accuracy and systematics that arise for each methodology. We note in conclusion that several properties of the lensing clusters are recovered equally well by most of the lensing techniques compared in this study. For example, the reconstruction of azimuthally averaged density and mass profiles by both parametric and free-form methods matches the input models at the level of ∼10 per cent. Parametric techniques are generally better at recovering the 2D maps of the convergence and of the magnification. For the best-performing algorithms, the accuracy in the magnification estimate is ∼10 per cent at μtrue = 3 and it degrades to ∼30 per cent at μtrue ∼ 10.
Abstract
To extend the search for quasars in the epoch of reionization beyond the tip of the luminosity function, we explore point-source candidates at redshift
z
∼ 8 in SuperBoRG, a compilation of ...∼0.4 deg
2
archival medium-deep (
m
F160
W
∼ 26.5 ABmag, 5
σ
) parallel infrared (IR) images taken with the Hubble Space Telescope (HST). Initial candidates are selected by using the Lyman-break technique. We then carefully analyze source morphology, and robustly identify three point sources at
z
∼ 8. Photometric redshift analysis reveals that they are preferentially fit by extragalactic templates, and we conclude that they are unlikely to be low-
z
interlopers, including brown dwarfs. A clear IRAC ch2 flux excess is seen in one of the point sources, which is expected if the source has strong H
β
+O
iii
emission with a rest-frame equivalent width of ∼3000 Å. Deep spectroscopic data taken with Keck/MOSFIRE, however, do not reveal Ly
α
emission from the object. In combination with the estimated H
β
+O
iii
equivalent width, we place an upper limit on its Ly
α
escape fraction of
. We estimate the number density of these point sources as ∼1 × 10
−6
Mpc
−3
mag
−1
at
M
UV
∼ −23 mag. The final interpretation of our results remains inconclusive: extrapolation from low-
z
studies of
faint
quasars suggests that ≳100× survey volume may be required to find one of this luminosity. The James Webb Space Telescope will be able to conclusively determine the nature of our luminous point-source candidates, while the Roman Space Telescope will probe ∼200 times the area of the sky with the same observing time considered in this HST study.
We present a detailed strong-lensing, weak-lensing and X-ray analysis of Abell 2744 (z= 0.308), one of the most actively merging galaxy clusters known. It appears to have unleashed 'dark', 'ghost', ...'bullet' and 'stripped' substructures, each ∼1014 M⊙. The phenomenology is complex and will present a challenge for numerical simulations to reproduce. With new, multiband Hubble Space Telescope (HST) imaging, we identify 34 strongly lensed images of 11 galaxies around the massive Southern 'core'. Combining this with weak-lensing data from HST, VLT and Subaru, we produce the most detailed mass map of this cluster to date. We also perform an independent analysis of archival Chandra X-ray imaging. Our analyses support a recent claim that the Southern core and Northwestern substructure are post-merger and exhibit morphology similar to the Bullet Cluster viewed from an angle. From the separation between X-ray emitting gas and lensing mass in the Southern core, we derive a new and independent constraint on the self-interaction cross-section of dark matter particles σ/m < 3 ± 1 cm2 g−1. In the Northwestern substructure, the gas, dark matter and galaxy components have become separated by much larger distances. Most curiously, the 'ghost' clump (primarily gas) leads the 'dark' clump (primarily dark matter) by more than 150 kpc. We propose an enhanced 'ram-pressure slingshot' scenario which may have yielded this reversal of components with such a large separation, but needs further confirmation by follow-up observations and numerical simulations. A secondary merger involves a second 'bullet' clump in the North and an extremely 'stripped' clump to the West. The latter appears to exhibit the largest separation between dark matter and X-ray emitting baryons detected to date in our sky.
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