ORCID Profile
0000-0002-8460-0390
Current Organisation
UCLA Division of Physical Sciences
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Astronomical and Space Sciences | Cosmology and Extragalactic Astronomy
Publisher: American Astronomical Society
Date: 07-2023
Abstract: The abundance of carbon relative to oxygen (C/O) is a promising probe of star formation history in the early universe, as the ratio changes with time due to production of these elements by different nucleosynthesis pathways. We present a measurement of log ( C / O ) = − 1.01 ± 0.12 (stat) ±0.15 (sys) in a z = 6.23 galaxy observed as part of the GLASS–JWST Early Release Science Program. Notably, we achieve good precision thanks to the detection of the rest-frame ultraviolet O iii ], C iii ], and C iv emission lines delivered by JWST/NIRSpec. The C/O abundance is ∼0.8 dex lower than the solar value and is consistent with the expected yield from core-collapse supernovae, indicating that longer-lived intermediate-mass stars have not fully contributed to carbon enrichment. This in turn implies rapid buildup of a young stellar population with age ≲100 Myr in a galaxy seen ∼900 Myr after the big bang. Our chemical abundance analysis is consistent with spectral energy distribution modeling of JWST/NIRCam photometric data, which indicates a current stellar mass log M * / M ☉ = 8.4 − 0.2 + 0.4 and specific star formation rate ≃20 Gyr −1 . These results showcase the value of chemical abundances and C/O in particular to study the earliest stages of galaxy assembly.
Publisher: American Astronomical Society
Date: 12-2022
Abstract: Wide Field Slitless Spectroscopy (WFSS) provides a powerful tool for detecting strong line emission in star-forming galaxies (SFGs) without the need for target preselection. As part of the GLASS-JWST Early Release Science (ERS) program, we leverage the near-infrared wavelength capabilities of NIRISS (1–2.2 μ m) to observe rest-optical emission lines out to z ∼ 3.4, to a depth and with a spatial resolution higher than ever before (H α to z 2.4 [O iii ]+H β to z 3.4). In this Letter we constrain the rest-frame [O III ] λ 5007 equivalent width (EW) distribution for a s le of 76 1 z 3.4 SFGs in the A2744 Hubble Frontier Field and determine an abundance fraction of extreme emission line galaxies with EW 750Å in our s le to be 12%. We determine a strong correlation between the measured H β and [O III ] λ 5007 EWs, supporting that the high [O III ] λ 5007 EW objects require massive stars in young stellar populations to generate the high-energy photons needed to doubly ionize oxygen. We extracted spectra for objects up to 2 mag fainter in the near-infrared than previous WFSS studies with the Hubble Space Telescope. Thus, this work clearly highlights the potential of JWST/NIRISS to provide high-quality WFSS data sets in crowded cluster environments.
Publisher: American Astronomical Society
Date: 21-04-2011
Publisher: Oxford University Press (OUP)
Date: 12-09-2019
Abstract: We present the measurement of the Hubble constant, H0, with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435−1223 as well as an extension of our previous analysis of RXJ 1131−1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP (Strong-lensing High Angular Resolution Programme) 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 H0. 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 PG 1115+080, $H_{0}=70.1^{+5.3}_{-4.5}~\\rm km\\, s^{-1}\\, Mpc^{-1}$ for HE 0435−1223, and $H_{0}=77.0^{+4.0}_{-4.6}~\\rm km\\, s^{-1}\\, Mpc^{-1}$ for RXJ 1131−1231. 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 these results assume a flat Λ cold dark matter cosmology with a uniform prior on Ωm in [0.05, 0.5] and H0 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 H0. The full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper.
Publisher: American Astronomical Society
Date: 12-11-2018
Publisher: American Astronomical Society
Date: 08-2022
Abstract: The GLASS-JWST Early Release Science (hereafter GLASS-JWST-ERS) Program will obtain and make publicly available the deepest extragalactic data of the ERS c aign. It is primarily designed to address two key science questions, namely, “what sources ionized the universe and when?” and “how do baryons cycle through galaxies?”, while also enabling a broad variety of first look scientific investigations. In primary mode, it will obtain NIRISS and NIRSpec spectroscopy of galaxies lensed by the foreground Hubble Frontier Field cluster, Abell 2744. In parallel, it will use NIRCam to observe two fields that are offset from the cluster center, where lensing magnification is negligible, and which can thus be effectively considered blank fields. In order to prepare the community for access to this unprecedented data, we describe the scientific rationale, the survey design (including target selection and observational setups), and present pre-commissioning estimates of the expected sensitivity. In addition, we describe the planned public releases of high-level data products, for use by the wider astronomical community.
Publisher: Oxford University Press (OUP)
Date: 06-05-2020
Abstract: The reionization of hydrogen is closely linked to the first structures in the Universe, so understanding the timeline of reionization promises to shed light on the nature of these early objects. In particular, transmission of Lyman alpha (Ly α) from galaxies through the intergalactic medium (IGM) is sensitive to neutral hydrogen in the IGM, so can be used to probe the reionization timeline. In this work, we implement an improved model of the galaxy UV luminosity to dark matter halo mass relation to infer the volume-averaged fraction of neutral hydrogen in the IGM from Ly α observations. Many models assume that UV-bright galaxies are hosted by massive dark matter haloes in overdense regions of the IGM, so reside in relatively large ionized regions. However, observations and N-body simulations indicate that scatter in the UV luminosity–halo mass relation is expected. Here, we model the scatter (though we assume the IGM topology is unaffected) and assess the impact on Ly α visibility during reionization. We show that UV luminosity–halo mass scatter reduces Ly α visibility compared to models without scatter, and that this is most significant for UV-bright galaxies. We then use our model with scatter to infer the neutral fraction, $\\overline{x}_{\\mathrm{ H}\\,{\\small I}}$, at z ∼ 7 using a s le of Lyman-break galaxies in legacy fields. We infer $\\overline{x}_{\\mathrm{ H}\\,{\\small I}} = 0.55_{-0.13}^{+0.11}$ with scatter, compared to $\\overline{x}_{\\mathrm{ H}\\,{\\small I}} = 0.59_{-0.14}^{+0.12}$ without scatter, a very slight decrease and consistent within the uncertainties. Finally, we place our results in the context of other constraints on the reionization timeline and discuss implications for future high-redshift galaxy studies.
Publisher: Oxford University Press (OUP)
Date: 21-01-2010
Publisher: Oxford University Press (OUP)
Date: 23-12-2022
Abstract: The JWST has discovered a surprising abundance of bright galaxy candidates in the very early universe (≤500 Myr after the Big Bang), calling into question current galaxy formation models. Spectroscopy is needed to confirm the primeval nature of these candidates, as well as to understand how the first galaxies form stars and grow. Here we present deep spectroscopic and continuum ALMA observations towards GHZ2/GLASS-z12, one of the brightest and most robust candidates at z & 10, identified in the GLASS-JWST Early Release Science Program. We detect a 5.8σ line, offset 0${_{.}^{\\prime\\prime}}$5 from the JWST position of GHZ2/GLASS-z12, that associating it with the [O iii] 88 $\\mu {\\rm m}$ transition, implies a spectroscopic redshift of z = 12.117 ± 0.001. We verify the detection using extensive statistical tests. The oxygen line luminosity places GHZ2/GLASS-z12 above the [O iii]-SFR relation for metal-poor galaxies, implying an enhancement of [O iii] emission in this system while the JWST-observed emission is likely a lower-metallicity region. The lack of dust emission seen by these observations is consistent with the blue UV slope observed by JWST, which suggest little dust attenuation in galaxies at this early epoch. Further observations will unambiguously confirm the redshift and shed light on the origins of the wide and offset line and physical properties of this early galaxy. This work illustrates the synergy between JWST and ALMA, and paves the way for future spectroscopic surveys of z & 10 galaxy candidates.
Publisher: American Astronomical Society
Date: 04-2023
Abstract: We present the spectroscopic confirmation of a protocluster at z = 7.88 behind the galaxy cluster Abell 2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a projected radius of 60 kpc. Although the galaxies reside in an overdensity around ≳20× greater than a random volume, they do not show strong Ly α emission. We place 2 σ upper limits on the rest-frame equivalent width –28 Å. Based on the tight upper limits to the Ly α emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be x HI 0.45 (68% C i ). Using an empirical M UV – M halo relation for in idual galaxies, we estimate that the total halo mass of the system is ≳4 × 10 11 M ⊙ . Likewise, the line-of-sight velocity dispersion is estimated to be 1100 ± 200 km s −1 . Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be ∼2 × 10 15 M ⊙ , comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at hr total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.
Publisher: American Astronomical Society
Date: 14-10-2020
Publisher: American Astronomical Society
Date: 12-2022
Abstract: We investigate the blue and optical rest-frame sizes ( λ ≃ 2300–4000 Å) of three compact star-forming regions in a galaxy at z = 4 strongly lensed (×30, ×45, and ×100) by the Hubble Frontier Field galaxy cluster A2744 using GLASS-ERS James Webb Space Telescope (JWST)/NIRISS imaging at 1.15 μ m, 1.50 μ m, and 2.0 μ m with a point-spread function ≲0.″1. In particular, the Balmer break is probed in detail for all multiply imaged sources of the system. With ages of a few tens of Myr, stellar masses in the range (0.7–4.0) ×10 6 M ⊙ and optical/ultraviolet effective radii spanning the interval 3 R eff 20 pc, such objects are currently the highest-redshift (spectroscopically confirmed) gravitationally bound young massive star clusters (YMCs), with stellar mass surface densities resembling those of local globular clusters. Optical (4000 Å, JWST-based) and ultraviolet (1600 Å, Hubble Space Telescope–based) sizes are fully compatible. The contribution to the ultraviolet underlying continuum emission (1600 Å) is ∼30%, which decreases by a factor of 2 in the optical for two of the YMCs (∼4000 Å rest-frame), reflecting the young ages ( Myr) inferred from the spectral energy distribution fitting and supported by the presence of high-ionization lines secured with the Very Large Telescope/MUSE. Such bursty forming regions enhance the specific star formation rate of the galaxy, which is ≃10 Gyr −1 . This galaxy would be among the extreme analogs observed in the local universe having a high star formation rate surface density and a high occurrence of massive stellar clusters in formation.
Publisher: American Astronomical Society
Date: 04-2023
Abstract: We present a first look at the reddest 2–5 μ m sources found in deep images from the GLASS Early Release Science program. We undertake a general search, i.e., not looking for any particular spectral signatures, for sources detected only in bands redder than is reachable with the Hubble Space Telescope, and which would likely not have been identified in pre-JWST surveys. We search for sources down to AB ∼27 (corresponding to σ detection threshold) in any of the F200W to F444W filters, with a magnitude excess relative to F090W to F150W bands. Fainter than F444W we find 56 such sources of which 37 have reasonably constrained spectral energy distributions to which we can fit photometric redshifts. We find the majority of this population (∼65%) as 2 z 6 star-forming low-attenuation galaxies that are faint at rest-frame ultraviolet-optical wavelengths, have stellar masses 10 8.5 –10 9.5 M ⊙ , and have observed fluxes at μ m boosted by a combination of the Balmer break and emission lines. The typical implied rest equivalent widths are ∼200 Å with some extreme objects up to ∼1000 Å. This is in contrast with brighter magnitudes where the red sources tend to be z 3 quiescent galaxies and dusty star-forming objects. Our general selection criteria for red sources allow us to independently identify other phenomena as erse as extremely low-mass (∼10 8 M ⊙ ) quiescent galaxies at z 1, recovering recently identified z 11 galaxies and a very cool brown dwarf.
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We present the first search for z ≥ 7, continuum-confirmed Lyman break sources with NIRISS/WFS spectroscopy over the Abell 2744 Frontier Fields cluster, as part of the GLASS-JWST-ERS survey. With ∼15 hr of preimaging and multiangle grism exposures in the F115W, F150W, and F200W filters, we describe the general data handling (i.e., reduction, cleaning, modeling, and extraction processes) and analysis for the GLASS-JWST survey. We showcase the power of JWST to peer deep into reionization, when most intergalactic hydrogen is neutral, by confirming two galaxies at z = 8.04 ± 0.15 and z = 7.90 ± 0.13 by means of their Lyman breaks. Fainter continuum spectra are observed in both the F150W and F200W bands, indicative of blue (−1.69 and −1.33) UV slopes and moderately bright absolute magnitudes (−20.37 and −19.68 mag). We do not detect strong Ly α in either galaxy, but do observe tentative (∼2.7–3.8 σ ) He ii λ 1640 Å, O iii ] λλ 1661,1666 Å, and N iii ] λλ 1747,1749 Å line emission in one, suggestive of low-metallicity, star-forming systems with possible nonthermal contributions. These novel observations provide a first look at the extraordinary potential of JWST/NIRISS for confirming representative s les of bright z ≥ 7 sources in the absence of strong emission lines, and gain unprecedented insight into their contributions toward cosmic reionization.
Publisher: American Astronomical Society
Date: 07-2023
Abstract: We present a new high-precision, JWST-based, strong-lensing model for the galaxy cluster Abell 2744 at z = 0.3072. By combining the deep, high-resolution JWST imaging from the Grism Lens Amplified Survey from Space–JWST and Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization programs and a Director’s Discretionary Time program, with newly obtained Very Large Telescope/Multi Unit Spectroscopic Explorer (MUSE) data, we identify 32 multiple images from 11 background sources lensed by two external subclusters at distances of ∼160″ from the main cluster. The new MUSE observations enable the first spectroscopic confirmation of a multiple-image system in the external clumps. Moreover, the reanalysis of the spectrophotometric archival and JWST data yields 27 additional multiple images in the main cluster. The new lens model is constrained by 149 multiple images (∼66% more than in our previous model) covering an extended redshift range between 1.03 and 9.76. The subhalo mass component of the cluster includes 177 member galaxies down to m F160W = 21, of which 163 are spectroscopically confirmed. Internal velocity dispersions are measured for 85 members. The new lens model is characterized by a remarkably low scatter between the predicted and observed positions of the multiple images (0.″43). This precision is unprecedented given the large multiple-image s le, the complexity of the cluster mass distribution, and the large modeled area. The improved precision and resolution of the cluster total mass distribution provides a robust magnification map over a ∼30 arcmin 2 area, which is critical for inferring the intrinsic physical properties of the highly magnified, high- z sources. The lens model and the new MUSE redshift catalog are released with this publication.
Publisher: American Astronomical Society
Date: 2023
Abstract: We exploit James Webb Space Telescope (JWST) NIRCam observations from the GLASS-JWST-Early Release Science program to investigate galaxy stellar masses at z 7. We first show that JWST observations reduce the uncertainties on the stellar mass by a factor of at least 5–10, when compared with the highest-quality data sets available to date. We then study the UV mass-to-light ratio, finding that galaxies exhibit a a two orders of magnitude range of M / L UV values for a given luminosity, indicative of a broad variety of physical conditions and star formation histories. As a consequence, previous estimates of the cosmic stellar-mass density—based on an average correlation between UV luminosity and stellar mass—can be biased by as much as a factor of ∼6. Our first exploration demonstrates that JWST represents a new era in our understanding of stellar masses at z 7 and, therefore, of the growth of galaxies prior to cosmic reionization.
Publisher: American Astronomical Society
Date: 10-04-2017
Publisher: American Astronomical Society
Date: 16-12-2016
Publisher: American Astronomical Society
Date: 29-06-2018
Publisher: American Astronomical Society
Date: 30-11-2015
Publisher: SPIE
Date: 26-07-2016
DOI: 10.1117/12.2233182
Publisher: American Astronomical Society
Date: 04-2023
Abstract: We use the GLASS-JWST Early Release Science NIRCam parallel observations to provide a first view of the UV continuum properties of NIRCam/F444W selected galaxies at 4 z 7. By combining multiwavelength NIRCam observations, we constrain the UV continuum slope for a s le of 401 galaxies with stringent quality controls. We find that % of the galaxies are blue star-forming galaxies with very low levels of dust ( Av β ∼ 0.01 ± 0.33). We find no statistically significant correlation for UV slope with redshift or UV magnitude. However, we find that in general galaxies at higher redshifts and fainter UV magnitudes have steeper UV slopes. We find a statistically significant correlation for UV slope with stellar mass, with galaxies with higher stellar mass showing shallower UV slopes. In idual fits to some of our galaxies reach the bluest UV slopes of β ∼ −3.1 allowed by stellar population models used in this analysis. Therefore, it is likely that stellar population models with a higher amount of Lyman continuum leakage, active galactic nucleus effects, and/or Population III contributions are required to accurately reproduce the rest-UV and optical properties of some of our bluest galaxies. This dust-free early view confirms that our current cosmological understanding of gradual mass + dust buildup of galaxies with cosmic time is largely accurate to describe the ∼0.7–1.5 Gyr age window of the universe. The abundance of a large population of UV faint dust-poor systems may point to a dominance of low-mass galaxies at z 6 playing a vital role in cosmic reionization.
Publisher: American Astronomical Society
Date: 05-2023
Abstract: We report the detection of a high density of redshift z ≈ 10 galaxies behind the foreground cluster A2744, selected from imaging data obtained recently with NIRCam on board JWST by three programs—GLASS-JWST, UNCOVER, and DDT#2756. To ensure robust estimates of the lensing magnification μ , we use an improved version of our model that exploits the first epoch of NIRCam images and newly obtained MUSE spectra and avoids regions with μ 5 where the uncertainty may be higher. We detect seven bright z ≈ 10 galaxies with demagnified rest frame −22 ≲ M UV ≲ −19 mag, over an area of ∼37 arcmin 2 . Taking into account photometric incompleteness and the effects of lensing on luminosity and cosmological volume, we find that the density of z ≈ 10 galaxies in the field is about 10× (3×) larger than the average at M UV ≈ −21 ( −20) mag reported so far. The density is even higher when considering only the GLASS-JWST data, which are the deepest and the least affected by magnification and incompleteness. The GLASS-JWST field contains five out of seven galaxies, distributed along an apparent filamentary structure of 2 Mpc in projected length, and includes a close pair of candidates with M UV −20 mag having a projected separation of only 16 kpc. These findings suggest the presence of a z ≈ 10 overdensity in the field. In addition to providing excellent targets for efficient spectroscopic follow-up observations, our study confirms the high density of bright galaxies observed in early JWST observations but calls for multiple surveys along independent lines of sight to achieve an unbiased estimate of their average density and a first estimate of their clustering.
Publisher: American Astronomical Society
Date: 04-2023
Abstract: The JWST observations of high-redshift galaxies are used to measure their star formation histories—the buildup of stellar mass in the earliest galaxies. Here we use a novel analysis program, SEDz*, to compare near-IR spectral energy distributions for galaxies with redshifts 5 z 7 to combinations of stellar population templates evolved from z = 12. We exploit NIRCam imaging in seven wide bands covering 1–5 μ m taken in the context of the GLASS-JWST-ERS program and use SEDz* to solve for well-constrained star formation histories for 24 exemplary galaxies. In this first look, we find a variety of histories, from long, continuous star formation over 5 z 12 to short but intense starbursts, sometimes repeating, and, most commonly, contiguous mass buildup lasting ∼0.5 Myr, possibly the seeds of today’s typical M * galaxies.
Publisher: American Astronomical Society
Date: 09-08-2016
Publisher: Oxford University Press (OUP)
Date: 04-06-2018
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We present the first rest-frame optical size–luminosity relation of galaxies at z 7, using the NIRCam imaging data obtained by the GLASS James Webb Space Telescope Early Release Science (GLASS-JWST-ERS) program, providing the deepest extragalactic data of the ERS c aign. Our s le consists of 19 photometrically selected bright galaxies with m F444W ≤ 27.8 at 7 z 9 and m F444W 28.2 at z ∼ 9−15. We measure the size of the galaxies in five bands, from rest-frame optical (∼4800 Å) to the UV (∼1600 Å) based on the Sérsic model, and analyse the size–luminosity relation as a function of wavelength. Remarkably, the data quality of the NIRCam imaging is sufficient to probe the half-light radius r e down to ∼100 pc at z 7. Given the limited s le size and magnitude range, we first fix the slope to that observed for larger s les in rest-frame UV using Hubble Space Telescope s les. The median size r 0 at the reference luminosity M = −21 decreases slightly from rest-frame optical (600 ± 80 pc) to UV (450 ± 130 pc). We then refit the size–luminosity relation allowing the slope to vary. The slope is consistent with β ∼ 0.2 for all bands except F150W, where we find a marginally steeper slope of β = 0.53 ± 0.15. The steep UV slope is mainly driven by the smallest and faintest galaxies. If confirmed by larger s les, it implies that the UV size–luminosity relation breaks toward the faint end, as suggested by lensing studies.
Publisher: American Astronomical Society
Date: 07-11-2016
Publisher: SPIE
Date: 28-07-2014
DOI: 10.1117/12.2055599
Publisher: American Astronomical Society
Date: 2023
Abstract: We present the serendipitous discovery of a late T-type brown dwarf candidate in JWST NIRCam observations of the Early Release Science Abell 2744 parallel field. The discovery was enabled by the sensitivity of JWST at 4 μ m wavelengths and the panchromatic 0.9–4.5 μ m coverage of the spectral energy distribution. The unresolved point source has magnitudes F115W = 27.95 ± 0.15 and F444W = 25.84 ± 0.01 (AB), and its F115W−F444W and F356W−F444W colors match those expected for other known T dwarfs. We can exclude it as a reddened background star, high redshift quasar, or a very high redshift galaxy. Comparison with stellar atmospheric models indicates a temperature of T eff ≈ 650 K and surface gravity log g ≈ 5.25 , implying a mass of 0.03 M ⊙ and age of 5 Gyr. We estimate the distance of this candidate to be 570–720 pc in a direction perpendicular to the Galactic plane, making it a likely thick disk or halo brown dwarf. These observations underscore the power of JWST to probe the very low-mass end of the substellar mass function in the Galactic thick disk and halo.
Publisher: American Astronomical Society
Date: 24-11-2014
Publisher: American Astronomical Society
Date: 06-09-2019
Publisher: American Astronomical Society
Date: 07-2023
Abstract: We present images and a multiwavelength photometric catalog based on all of the JWST NIRCam observations obtained to date in the region of the Abell 2744 galaxy cluster. These data come from three different programs, namely, the GLASS-JWST Early Release Science Program, UNCOVER, and the Director’s Discretionary Time program 2756. The observed area in the NIRCam wide-band filters—covering the central and extended regions of the cluster, as well as new parallel fields—is 46.5 arcmin 2 in total. All images in eight bands (F090W, F115W, F150W, F200W, F277W, F356W, F410M, and F444W) have been reduced adopting the latest calibration and reference files available. Data reduction has been performed using an augmented version of the official JWST pipeline, with improvements aimed at removing or mitigating defects in the raw images and improving the background subtraction and photometric accuracy. We obtain an F444W-detected multiband catalog, including all NIRCam and available Hubble Space Telescope data, adopting forced-aperture photometry on point-spread-function-matched images. The catalog is intended to enable early scientific investigations and is optimized for the study of faint galaxies it contains 24,389 sources, with a 5 σ limiting magnitude in the F444W band ranging from 28.5 AB to 30.5 AB, as a result of the varying exposure times of the surveys that observed the field. We publicly release the reduced NIRCam images, associated multiwavelength catalog, and the code adopted for 1/ f noise removal with the aim of aiding users in familiarizing themselves with JWST NIRCam data and identifying suitable targets for follow-up observations.
Publisher: American Astronomical Society
Date: 09-2008
DOI: 10.1086/589989
Publisher: American Astronomical Society
Date: 05-2023
Abstract: We present a rest-frame optical morphological analysis of galaxies observed with the NIRCam imager on the James Webb Space Telescope (JWST) as part of the GLASS-JWST Early Release Science program. We select 388 sources at redshifts 0.8 z 5.4 and use the seven 0.9–5 μ m NIRCam filters to generate rest-frame gri composite color images, and conduct visual morphological classification. Compared to Hubble Space Telescope (HST)–based work we find a higher incidence of disks and bulges than expected at z 1.5, revealed by rest-frame optical imaging. We detect 123 clear disks (58 at z 1.5) of which 76 have bulges. No evolution of bulge fraction with redshift is evident: 61% at z 2 ( N = 110) versus 60% at z ≥ 2 ( N = 13). A stellar mass dependence is evident, with bulges visible in 80% of all disk galaxies with mass 9.5 M ⊙ ( N = 41) but only 52% at M 10 9.5 M ⊙ ( N = 82). We supplement visual morphologies with nonparametric measurements of Gini and asymmetry coefficients in the rest-frame i band. Our sources are more asymmetric than local galaxies, with slightly higher Gini values. When compared to high- z rest-frame ultraviolet measurements with HST, JWST shows more regular morphological types such as disks, bulges, and spiral arms at z 1.5, with smoother (i.e., lower Gini) and more symmetrical light distributions.
Publisher: American Astronomical Society
Date: 05-2023
Abstract: We combine JWST/NIRCam imaging and MUSE data to characterize the properties of galaxies in different environmental conditions in the cluster Abell2744 ( z = 0.3064) and in its immediate surroundings. We investigate how galaxy colors, morphology, and star-forming fractions depend on wavelength and on different parameterizations of environment. Our most striking result is the discovery of a “red excess” population in F200W−F444W colors in both the cluster regions and the field. These galaxies have normal F115W−F150W colors but are up to 0.8 mag redder than red sequence galaxies in F200W−F444W. They also have rather blue rest-frame B − V colors. Galaxies in the field and at the cluster virial radius are overall characterized by redder colors, but galaxies with the largest color deviations are found in the field and in the cluster core. Several results suggest that mechanisms taking place in these regions might be more effective in producing these colors. Looking at their morphology, many cluster galaxies show signatures consistent with ram pressure stripping, while field galaxies have features resembling interactions and mergers. Our hypothesis is that these galaxies are characterized by dust-enshrouded star formation: a JWST/NIRSpec spectrum for one of the galaxies is dominated by a strong PAH at 3.3 μ m, suggestive of dust-obscured star formation. Larger spectroscopic s les are needed to understand whether the color excess is due exclusively to dust-obscured star formation, as well as the role of environment in triggering it.
Publisher: American Astronomical Society
Date: 17-03-2017
Publisher: American Astronomical Society
Date: 2023
Abstract: Star-forming galaxies can exhibit strong morphological differences between the rest-frame far-UV and optical, reflecting inhomogeneities in star formation and dust attenuation. We exploit deep, high-resolution, NIRCAM seven-band observations to take a first look at the morphology of galaxies in the epoch of reionization ( z 7), and its variation in the rest-frame wavelength range between Ly α and 6000–4000 Å, at z = 7–12. We find no dramatic variations in morphology with wavelength—of the kind that would have overturned anything we have learned from the Hubble Space Telescope. No significant trends between morphology and wavelengths are detected using standard quantitative morphology statistics. We detect signatures of mergers/interactions in 4/19 galaxies. Our results are consistent with a scenario in which Lyman-break galaxies—observed when the universe is only 400–800 Myr old—are growing via a combination of rapid, galaxy-scale star formation supplemented by the accretion of star-forming clumps and interactions.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 09-08-2019
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 in idual 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.
Publisher: American Astronomical Society
Date: 05-02-2016
Publisher: American Astronomical Society
Date: 09-07-2018
Publisher: Oxford University Press (OUP)
Date: 14-01-2023
Abstract: Despite the success of galaxy-scale strong gravitational lens studies with Hubble-quality imaging, a number of well-studied strong lenses remains small. As a result, robust comparisons of the lens models to theoretical predictions are difficult. This motivates our application of automated Bayesian lens modelling methods to observations from public data releases of overlapping large ground-based imaging and spectroscopic surveys: Kilo-Degree Survey (KiDS) and Galaxy and Mass Assembly (GAMA), respectively. We use the open-source lens modelling software pyautolens to perform our analysis. We demonstrate the feasibility of strong lens modelling with large-survey data at lower resolution as a complementary avenue to studies that utilize more time-consuming and expensive observations of in idual lenses at higher resolution. We discuss advantages and challenges, with special consideration given to determining background source redshifts from single-aperture spectra and to disentangling foreground lens and background source light. High uncertainties in the best-fitting parameters for the models due to the limits of optical resolution in ground-based observatories and the small s le size can be improved with future study. We give broadly applicable recommendations for future efforts, and with proper application, this approach could yield measurements in the quantities needed for robust statistical inference.
Publisher: American Astronomical Society
Date: 10-03-2017
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We report the first gas-phase metallicity map of a distant galaxy measured with the James Webb Space Telescope (JWST). We use the NIRISS slitless spectroscopy acquired by the GLASS Early Release Science program to spatially resolve the rest-frame optical nebular emission lines in a gravitationally lensed galaxy at z = 3.06 behind the A2744 galaxy cluster. This galaxy (dubbed GLASS-Zgrad1) has stellar mass ∼10 8.6 M ⊙ , instantaneous star formation rate ∼8.6 M ⊙ yr −1 (both corrected for lensing magnification), and global metallicity one-fourth solar. From its emission-line maps ([O iii ], H β , H γ , [Ne iii ], and [O ii ]), we derive its spatial distribution of gas-phase metallicity using a well-established forward-modeling Bayesian inference method. The exquisite resolution and sensitivity of JWST/NIRISS, combined with lensing magnification, enable us to resolve this z ∼ 3 dwarf galaxy in ≳50 resolution elements with sufficient signal, an analysis hitherto not possible. We find that the radial metallicity gradient of GLASS-Zgrad1 is strongly inverted (i.e., positive): Δ log ( O / H ) / Δ r = 0.165 ± 0.023 dex kpc −1 . This measurement is robust at ≳ 4 − σ confidence level against known systematics. This positive gradient may be due to tidal torques induced by a massive nearby (∼15 kpc projected) galaxy, which can cause inflows of metal-poor gas into the central regions of GLASS-Zgrad1. These first results showcase the power of JWST wide-field slitless spectroscopic modes to resolve the mass assembly and chemical enrichment of low-mass galaxies in and beyond the peak epoch of cosmic star formation ( z ≳ 2). Reaching masses ≲ 10 9 M ⊙ at these redshifts is especially valuable to constrain the effects of galactic feedback and environment and is possible only with JWST’s new capabilities.
Publisher: American Astronomical Society
Date: 05-06-2019
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We present the results of a first search for galaxy candidates at z ∼ 9–15 on deep seven-band NIRCam imaging acquired as part of the GLASS-James Webb Space Telescope (JWST) Early Release Science Program on a flanking field of the Frontier Fields cluster A2744. Candidates are selected via two different renditions of the Lyman-break technique, isolating objects at z ∼ 9–11, and z ∼ 9–15, respectively, supplemented by photometric redshifts obtained with two independent codes. We find five color-selected candidates at z 9, plus one additional candidate with photometric redshift z phot ≥ 9. In particular, we identify two bright candidates at M UV ≃ −21 that are unambiguously placed at z ≃ 10.6 and z ≃ 12.2, respectively. The total number of galaxies discovered at z 9 is in line with the predictions of a nonevolving luminosity function. The two bright ones at z 10 are unexpected given the survey volume, although cosmic variance and small number statistics limits general conclusions. This first search demonstrates the unique power of JWST to discover galaxies at the high-redshift frontier. The candidates are ideal targets for spectroscopic follow-up in Cycle-2.
Publisher: American Astronomical Society
Date: 07-2023
Abstract: Ly α emission is possibly the best indirect diagnostic of Lyman continuum (LyC) escape since the conditions that favor the escape of Ly α photons are often the same that allow for the escape of LyC photons. In this work, we present the rest-frame UV–optical spectral characteristics of 11 Ly α emitting galaxies at 3 z 6—the redshift range that optimizes between intergalactic medium attenuation effects and temporal proximity to the epoch of reionization. From a combined analysis of JWST/NIRSpec and MUSE data, we present the Ly α escape fraction and study its correlation with other physical properties of galaxies that might facilitate Ly α escape. We find that our galaxies have low masses (80% of the s le with log 10 M ⋆ 9.5 M ⊙ ), compact sizes (median R e ∼ 0.7 kpc), low dust content, moderate [O iii ]/[O ii ] flux ratios (mean ∼ 6.8 ± 1.2), and moderate Ly α escape fractions (mean f esc Ly α ∼ 0.11). Our s le shows characteristics that are broadly consistent with low-redshift galaxies with Ly α emission, which are termed as “analogs” of the high-redshift population. We predict the LyC escape fraction in our s le to be low (0.03–0.07), although larger s les in the postreionization epoch are needed to confirm these trends.
Publisher: American Astronomical Society
Date: 2023
Abstract: We present the first James Webb Space Telescope/NIRCam-led determination of 7 z 9 galaxy properties based on broadband imaging from 0.8 to 5 μ m as part of the GLASS-JWST Early Release Science program. This is the deepest data set acquired at these wavelengths to date, with an angular resolution ≲0.″14. We robustly identify 13 galaxies with signal-to-noise ratio ≳ 8 in F444W from 8 arcmin 2 of data at m AB ≤ 28 from a combination of dropout and photometric redshift selection. From simulated data modeling, we estimate the dropout s le purity to be ≳90%. We find that the number density of these F444W-selected sources is broadly consistent with expectations from the UV luminosity function determined from Hubble Space Telescope data. We characterize galaxy physical properties using a Bayesian spectral energy distribution fitting method, finding a median stellar mass of 10 8.5 M ⊙ and age 140 Myr, indicating they started ionizing their surroundings at redshift z 9.5. Their star formation main sequence is consistent with predictions from simulations. Lastly, we introduce an analytical framework to constrain main-sequence evolution at z 7 based on galaxy ages and basic assumptions, through which we find results consistent with expectations from cosmological simulations. While this work only gives a glimpse of the properties of typical galaxies that are thought to drive the reionization of the universe, it clearly shows the potential of JWST to unveil unprecedented details of galaxy formation in the first billion years.
Publisher: American Astronomical Society
Date: 11-09-2017
Publisher: American Astronomical Society
Date: 02-2017
Publisher: American Astronomical Society
Date: 16-09-2015
Publisher: American Astronomical Society
Date: 14-10-2015
Publisher: Oxford University Press (OUP)
Date: 06-07-2020
Abstract: We present results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS), an ESO Very Large Telescope (VLT) large program using gravitational lensing to study the spatially resolved kinematics of 44 star-forming galaxies at 0.6 & z & 2.3 with a stellar mass of 8.1 & log(M⋆/M⊙) & 11.0. These galaxies are located behind six galaxy clusters selected from the Hubble Space Telescope Grism Lens-Amplified Survey from Space (GLASS). We find that the majority of the galaxies show a rotating disc, but most of the rotation-dominated galaxies only have a low υ rot/σ0 ratio (median of υrot/σ0 ∼ 2.5). We explore the Tully–Fisher relation by adopting the circular velocity, $V_{\\mathrm{ circ}}=(\\upsilon _{\\mathrm{ rot}}^2+3.4\\sigma _0^2)^{1/2}$, to account for pressure support. We find that our s le follows a Tully–Fisher relation with a positive zero-point offset of +0.18 dex compared to the local relation, consistent with more gas-rich galaxies that still have to convert most of their gas into stars. We find a strong correlation between the velocity dispersion and stellar mass in the KLASS s le. When combining our data to other surveys from the literature, we see an increase of the velocity dispersion with stellar mass at all redshift. We obtain an increase of υrot/σ0 with stellar mass at 0.5 & z & 1.0. This could indicate that massive galaxies settle into regular rotating discs before the low-mass galaxies. For higher redshift (z & 1), we find a weak increase or flat trend. We find no clear trend between the rest-frame UV clumpiness and the velocity dispersion and υrot/σ0. This could suggest that the kinematic properties of galaxies evolve after the clumps formed in the galaxy disc or that the clumps can form in different physical conditions.
Publisher: Oxford University Press (OUP)
Date: 27-04-2022
Abstract: Strongly lensed quasars can provide measurements of the Hubble constant (H0) independent of any other methods. One of the key ingredients is exquisite high-resolution imaging data, such as Hubble Space Telescope (HST) imaging and adaptive-optics (AO) imaging from ground-based telescopes, which provide strong constraints on the mass distribution of the lensing galaxy. In this work, we expand on the previous analysis of three time-delay lenses with AO imaging (RX J1131−1231, HE 0435−1223, and PG 1115+080), and perform a joint analysis of J0924+0219 by using AO imaging from the Keck telescope, obtained as part of the Strong lensing at High Angular Resolution Program (SHARP) AO effort, with HST imaging to constrain the mass distribution of the lensing galaxy. Under the assumption of a flat Λ cold dark matter (ΛCDM) model with fixed Ωm = 0.3, we show that by marginalizing over two different kinds of mass models (power-law and composite models) and their transformed mass profiles via a mass-sheet transformation, we obtain $\\Delta t_{\\rm BA}=6.89\\substack{+0.8\\\\-0.7}\\, h^{-1}\\hat{\\sigma }_{v}^{2}$ d, $\\Delta t_{\\rm CA}=10.7\\substack{+1.6\\\\-1.2}\\, h^{-1}\\hat{\\sigma }_{v}^{2}$ d, and $\\Delta t_{\\rm DA}=7.70\\substack{+1.0\\\\-0.9}\\, h^{-1}\\hat{\\sigma }_{v}^{2}$ d, where $h=H_{0}/100\\,\\rm km\\, s^{-1}\\, Mpc^{-1}$ is the dimensionless Hubble constant and $\\hat{\\sigma }_{v}=\\sigma ^{\\rm ob}_{v}/(280\\,\\rm km\\, s^{-1})$ is the scaled dimensionless velocity dispersion. Future measurements of time delays with 10 per cent uncertainty and velocity dispersion with 5 per cent uncertainty would yield a H0 constraint of ∼15 per cent precision.
Publisher: EDP Sciences
Date: 04-2023
DOI: 10.1051/0004-6361/202345866
Abstract: The escape fraction of Lyman-continuum (LyC) photons ( f esc ) is a key parameter for determining the sources of cosmic reionization at z ≥ 6. At these redshifts, owing to the opacity of the intergalactic medium, the LyC emission cannot be measured directly. However, LyC leakers during the epoch of reionization could be identified using indirect indicators that have been extensively tested at low and intermediate redshifts. These include a high [O III ]/[O II ] flux ratio, high star-formation surface density, and compact sizes. In this work, we present observations of 29 4.5 ≤ z ≤ 8 gravitationally lensed galaxies in the Abell 2744 cluster field. From a combined analysis of JWST-NIRSpec and NIRCam data, we accurately derived their physical and spectroscopic properties: our galaxies have low masses (log( M ⋆ )∼8.5), blue UV spectral slopes ( β ∼ −2.1), compact sizes ( r e ∼ 0.3 − 0.5 kpc), and high [O III ]/[O II ] flux ratios. We confirm that these properties are similar to those characterizing low-redshift LyC leakers. Indirectly inferring the fraction of escaping ionizing photons, we find that more than 80% of our galaxies have predicted f esc values larger than 0.05, indicating that they would be considered leakers. The average predicted f esc value of our s le is 0.12, suggesting that similar galaxies at z ≥ 6 have provided a substantial contribution to cosmic reionization.
Publisher: Oxford University Press (OUP)
Date: 03-09-2018
Publisher: Springer Science and Business Media LLC
Date: 10-04-2017
Publisher: American Astronomical Society
Date: 07-03-2017
Publisher: American Astronomical Society
Date: 30-11-2018
Publisher: American Astronomical Society
Date: 15-09-2020
Publisher: American Astronomical Society
Date: 10-2023
Publisher: American Astronomical Society
Date: 27-01-2016
Publisher: Oxford University Press (OUP)
Date: 03-02-2020
Abstract: We present a catalogue of 22 755 objects with slitless, optical, Hubble Space Telescope (HST) spectroscopy from the Grism Lens-Amplified Survey from Space (GLASS). The data cover ∼220 sq. arcmin to 7-orbit (∼10 ks) depth in 20 parallel pointings of the Advanced Camera for Survey’s G800L grism. The fields are located 6 arcmin away from 10 massive galaxy clusters in the HFF and CLASH footprints. 13 of the fields have ancillary HST imaging from these or other programs to facilitate a large number of applications, from studying metal distributions at z ∼ 0.5, to quasars at z ∼ 4, to the star formation histories of hundreds of galaxies in between. The spectroscopic catalogue has a median redshift of 〈z〉 = 0.60 with a median uncertainty of $\\Delta z / (1+z)\\lesssim 2{{\\ \\rm per\\ cent}}$ at $F814\\mathit{ W}\\lesssim 23$ AB. Robust continuum detections reach a magnitude fainter. The 5 σ limiting line flux is $f_{\\rm lim}\\approx 5\\times 10^{-17}\\rm ~erg~s^{-1}~cm^{-2}$ and half of all sources have 50 per cent of pixels contaminated at ≲1 per cent. All sources have 1D and 2D spectra, line fluxes/uncertainties and identifications, redshift probability distributions, spectral models, and derived narrow-band emission-line maps from the Grism Redshift and Line Analysis tool (grizli). We provide other basic s le characterizations, show data ex les, and describe sources and potential investigations of interest. All data and products will be available online along with software to facilitate their use.
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We present the reduced images and multiwavelength catalog of the first JWST NIRCam extragalactic observations from the GLASS Early Release Science Program, obtained as coordinated parallels of the NIRISS observations of the Abell 2744 cluster. Images in seven bands (F090W, F115W, F150W, F200W, F277W, F356W, and F444W) have been reduced using an augmented version of the official JWST pipeline we discuss the procedures adopted to remove or mitigate defects in the raw images. We obtain a multiband catalog by means of forced aperture photometry on point-spread function (PSF)-matched images at the position of F444W-detected sources. The catalog is intended to enable early scientific investigations, and it is optimized for faint galaxies it contains 6368 sources, with limiting magnitude 29.7 at 5 σ in F444W. We release both images and catalog in order to allow the community to become familiar with the JWST NIRCam data and evaluate their merit and limitations given the current level of knowledge of the instrument.
Publisher: Cambridge University Press (CUP)
Date: 11-2019
DOI: 10.1017/S1743921319002734
Abstract: We study star formation and metallicity enrichment histories of 24 massive galaxies at 1.6 z 2.5. Deep slitless spectroscopy + imaging data set collected from multiple HST surveys allows robust determination of their SEDs. Our new SED modeling with no functional assumptions on star formation histories revels that 1. most of the s le galaxies have already formed % of their extant masses ∼1.5 Gyr before the time of observed redshifts, with a trend where more massive galaxies form earlier, 2. most of our galaxies already have stellar metallicities compatible with those of local early-type galaxies, and 3. inferred metallicities are on average ∼ 0.25 dex higher than observed gas-phase metallicities of star forming galaxies at the time of their formation. Continuation of low-level star formation, rather than abrupt termination of star forming activity, may explain the observed gap of metallicities.
Publisher: American Astronomical Society
Date: 2023
Abstract: How passive galaxies form, and the physical mechanisms which prevent star formation over long timescales, are some of the most outstanding questions in understanding galaxy evolution. The properties of quiescent galaxies over cosmic time provide crucial information to identify the quenching mechanisms. Passive galaxies have been confirmed and studied out to z ∼ 4, but all of these studies have been limited to massive systems (mostly with log ( M star / M ⊙ ) 10.8 ). Using JWST-NIRISS grism slitless spectroscopic data from the GLASS-JWST Early Release Science program, we present spectroscopic confirmation of two quiescent galaxies at z spec = 2.650 − 0.006 + 0.004 and z spec = 2.433 − 0.016 + 0.032 (3 σ errors) with stellar masses of log ( M star / M ⊙ ) = 10.59 − 0.05 + 0.11 and log ( M star / M ⊙ ) = 10.07 − 0.03 + 0.06 (corrected for magnification factors of μ = 2.0 and μ = 2.1, respectively). The latter represents the first spectroscopic confirmation of the existence of low-mass quiescent galaxies at cosmic noon, showcasing the power of JWST to identify and characterize this enigmatic population.
Publisher: American Astronomical Society
Date: 26-03-2019
Publisher: American Astronomical Society
Date: 19-03-2018
Publisher: American Astronomical Society
Date: 03-06-2016
Publisher: American Astronomical Society
Date: 10-02-2014
Publisher: American Astronomical Society
Date: 08-2008
DOI: 10.1086/589327
Publisher: American Astronomical Society
Date: 11-04-2016
Publisher: American Astronomical Society
Date: 02-2021
Abstract: In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM c aign by recovering velocity–delay maps for the prominent broad emission lines (Ly α , C iv , He ii , and H β ) in the spectrum of NGC 5548. These are the most detailed velocity–delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He ii response inside 5–10 lt-day has a broad single-peaked velocity profile. The Ly α , C iv , and H β responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s −1 in the 10–20 lt-day delay range. An incomplete ellipse in the velocity–delay plane is evident in H β . We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at R = 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay τ = ( R / c ) ( 1 − sin i ) ≈ 5 days gives the inclination i ≈ 45°. The inferred black hole mass is M BH ≈ 7 × 10 7 M ⊙ . In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the “BLR Holiday” identified in previous work. Moreover, a helical “Barber-Pole” pattern, with stripes moving from red to blue across the C iv and Ly α line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.
Publisher: American Astronomical Society
Date: 20-08-2019
Location: United States of America
Start Date: 2014
End Date: 03-2017
Amount: $346,000.00
Funder: Australian Research Council
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