We take advantage of gravitational lensing amplification by A1689 (z = 0.187) to undertake the first space-based census of emission line galaxies (ELGs) in the field of a massive lensing cluster. ...Forty-three ELGs are identified to a flux of i sub(775) = 27.3 via slitless grism spectroscopy. One ELG (at z = 0.7895) is very bright owing to lensing magnification by a factor of approximately 4.5. Several Balmer emission lines (ELs) detected from ground-based follow-up spectroscopy signal the onset of a major starburst for this low-mass galaxy (M sub(*) approximately 2 x 10 super(9) M sub(middot in circle)) with a high specific star formation rate ( approximately 20 Gyr super(-1)). From the blue ELs we measure a gas-phase oxygen abundance consistent with solar (12+log(O/H) = 8.8 + or - 0.2). We break the continuous line-emitting region of this giant arc into seven ~1 kpc bins (intrinsic size) and measure a variety of metallicity-dependent line ratios. A weak trend of increasing metal fraction is seen toward the dynamical center of the galaxy. Interestingly, the metal line ratios in a region offset from the center by ~1 kpc have a placement on the blue H II region excitation diagram with f(OIII)/f(H beta ) and f(NeIII)/f(H beta ) that can be fitted by an active galactic nucleus (AGN). This asymmetrical AGN-like behavior is interpreted as a product of shocks in the direction of the galaxy's extended tail, possibly instigated by a recent galaxy interaction.
ABSTRACT We report on our first set of spectroscopic Hubble Space Telescope observations of the candidate galaxy, which is strongly lensed by the MACSJ 0647.7+7015 galaxy cluster. The three lensed ...images are faint and we show that these early slitless grism observations are of sufficient depth to investigate whether this high-redshift candidate, identified by its strong photometric break at , could possibly be an emission line galaxy at a much lower redshift. While such an interloper would imply the existence of a rather peculiar object, we show here that such strong emission lines would clearly have been detected. Comparing realistic, two-dimensional simulations to these new observations, we would expect the necessary emission lines to be detected at , though we see no evidence for such lines in the dispersed data of any of the three lensed images. We therefore exclude that this object could be a low-redshift emission line interloper, which significantly increases the likelihood of this candidate being a bona fide galaxy.
Large surveys of galaxy clusters with the Hubble Space Telescope (HST) and Spitzer, including the Cluster Lensing And Supernova survey with Hubble and the Frontier Fields, have demonstrated the power ...of strong gravitational lensing to efficiently deliver large samples of high-redshift galaxies. We extend this strategy through a wider, shallower survey named RELICS, the Reionization Lensing Cluster Survey, described here. Our 188-orbit Hubble Treasury Program observed 41 clusters at 0.182 ≤ z ≤ 0.972 with Advanced Camera for Surveys (ACS) and WFC3/IR imaging spanning 0.4-1.7 m. We selected 21 of the most massive clusters known based on Planck PSZ2 estimates and 20 additional clusters based on observed or inferred lensing strength. RELICS observed 46 WFC3/IR pointings (∼200 arcmin2) each with two orbits divided among four filters (F105W, F125W, F140W, and F160W) and ACS imaging as needed to achieve single-orbit depth in each of three filters (F435W, F606W, and F814W). As previously reported by Salmon et al., we discovered over 300 z ∼ 6-10 candidates, including the brightest z ∼ 6 candidates known, and the most distant spatially resolved lensed arc known at z ∼ 10. Spitzer IRAC imaging (945 hr awarded, plus 100 archival, spanning 3.0-5.0 m) has crucially enabled us to distinguish z ∼ 10 candidates from z ∼ 2 interlopers. For each cluster, two HST observing epochs were staggered by about a month, enabling us to discover 11 supernovae, including 3 lensed supernovae, which we followed up with 20 orbits from our program. Reduced HST images, catalogs, and lens models are available on MAST, and reduced Spitzer images are available on IRSA.
We present results of the HST Advanced Camera for Surveys spectroscopic ground-based redshift survey in the field of A1689. We measure 98 redshifts, increasing the number of spectroscopically ...confirmed objects sixfold. We present two spectra from this catalog of the Sextet Arcs, images that arise from a strongly lensed Lyman break galaxy (LBG) at a redshift of z = 3.038. Gravitational lensing by the cluster magnifies its flux by a factor of similar to 16 and produces six separate images with a total r-band magnitude of unk = 21.7. The two spectra, each of which represents emission from different regions of the LBG, show H I and interstellar metal absorption lines at the systemic redshift. Significant variations are seen in the Ly alpha profile across a single galaxy, ranging from strong absorption to a combination of emission plus absorption. A spectrum of a third image close to the brightest arc shows Ly alpha emission at the same redshift as the LBG, arising from either another spatially distinct region of the galaxy or from a companion galaxy close to the LBG. Taken as a group, the Ly alpha equivalent width in these three spectra decreases with Increasing equivalent width of the strongest interstellar absorption lines. We discuss how these variations can be used to understand the physical conditions in the LBG. Intrinsically, this LBG is faint, similar to 0.1L*, and is forming stars at a modest rate, similar to 4 M unk yr super(-1). We also detect absorption-line systems toward the Sextet Arcs at z = 2.873 and z = 2.534. The latter system is seen across two of our spectra.
We present high-resolution ultraviolet spectra of absorption-line systems towards the low-z quasi-stellar object (QSO) HS 0624+6907 (zQSO= 0.3700). Coupled with ground-based imaging and spectroscopic ...galaxy redshifts, we find evidence that many of these absorbers do not arise in galaxy haloes but rather are truly intergalactic gas clouds distributed within large-scale structures, and moreover, the gas is cool (T < 105 K) and has relatively high metallicity (Z > 0.9 Z⊙). Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) data reveal a dramatic cluster of 13 H i Lyman α (Lyα) lines within a 1000 km s−1 interval at zabs= 0.0635. We find 10 galaxies at this redshift with impact parameters ranging from ρ= 135 h−170 kpc to 1.37 h−170 Mpc. The velocities and velocity spread of the Lyα lines in this complex are unlikely to arise in the individual haloes of the nearby galaxies; instead, we attribute the absorption to intragroup medium gas, possibly from a large-scale filament viewed along its long axis. Contrary to theoretical expectations, this gas is not the shock-heated warm-hot intergalactic medium (WHIM); the width of the Lyα lines all indicate a gas temperature T≪ 105 K, and metal lines detected in the Lyα complex also favour photoionized, cool gas. No O vi absorption lines are evident, which is consistent with photoionization models. Remarkably, the metallicity is near-solar, M/H=−0.05 ± 0.4 (2σ uncertainty), yet the nearest galaxy which might pollute the intergalactic medium is at least 135 h−170 kpc away. Tidal stripping from nearby galaxies appears to be the most likely origin of this highly enriched, cool gas. More than six Abell galaxy clusters are found within 4° of the sight line suggesting that the QSO line of sight passes near a node in the cosmic web. At z≈ 0.077, we find absorption systems as well as galaxies at the redshift of the nearby clusters Abell 564 and Abell 559. We conclude that the sight line pierces a filament of gas and galaxies feeding into these clusters. The absorber at zabs= 0.075 73 associated with Abell 564/559 also has a high metallicity with C/H > −0.6, but again the closest galaxy is relatively far from the sight line (ρ= 293 h−170 kpc). The Doppler parameters and H i column densities of the Lyα lines observed along the entire sight line are consistent with those measured towards other low-z QSOs, including a number of broad (b > 40 km s−1) Lyα lines.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
We have selected a sample of 11 massive clusters of galaxies observed by the Hubble Space Telescope in order to study the impact of the dynamical state on the intracluster light (ICL) fraction, the ...ratio of total integrated ICL to the total galaxy member light. With the exception of the Bullet cluster, the sample is drawn from the Cluster Lensing and Supernova Survey and the Frontier Fields program, containing five relaxed and six merging clusters. The ICL fraction is calculated in three optical filters using the CHEFs ICL estimator, a robust and accurate algorithm free of a priori assumptions. We find that the ICL fraction in the three bands is, on average, higher for the merging clusters, ranging between ∼7% and 23%, compared with the ∼2%-11% found for the relaxed systems. We observe a nearly constant value (within the error bars) in the ICL fraction of the regular clusters at the three wavelengths considered, which would indicate that the colors of the ICL and the cluster galaxies are, on average, coincident and, thus, so are their stellar populations. However, we find a higher ICL fraction in the F606W filter for the merging clusters, consistent with an excess of lower-metallicity/younger stars in the ICL, which could have migrated violently from the outskirts of the infalling galaxies during the merger event.
We present a high signal-to-noise spectrum of a bright galaxy at image in 14 hr of integration on VLT FORS2. This galaxy is extremely bright, image, and is strongly lensed by the foreground massive ...galaxy cluster A1689. Stellar continuum is seen longward of the Ly alpha emission line at image7100 Aa, while intergalactic H i produces strong absorption shortward of Ly alpha . Two transmission spikes at image6800 and image7040 Aa are also visible, along with other structures at shorter wavelengths. Although this star-forming is galaxy fainter than a QSO, the absence of a strong central ultraviolet flux source in it enables a measurement of the H i flux transmission in the intergalactic medium (IGM) in the vicinity of a high- redshift object. We find that the effective H i optical depth of the IGM is remarkably high within a large 14 Mpc (physical) region surrounding the galaxy compared to that seen toward QSOs at similar redshifts. Evidently, this high-redshift galaxy is located in a region of space where the amount of H i is much larger than that seen at similar epochs in the diffuse IGM. We argue that observations of high-redshift galaxies like this one provide unique insights into the nascent stages of baryonic large-scale structures that evolve into the filamentary cosmic web of galaxies and clusters of galaxies observed in the current universe.
Using Hubble Space Telescope/Space Telescope Imaging Spectrograph G140M spectroscopy, we investigate an absorption-line system at z = 0.07489 in the spectrum of the quasi-stellar object PG 1543+489 ...(zQSO = 0.401). The sightline passes within = 66 kpc of an edge-on disk galaxy at a similar redshift, but the galaxy belongs to a group with four other galaxies within = 160 kpc. We detect H i log N(H i/cm−2) = 19.12 0.04 as well as N i, Mg ii, Si ii, and Si iii, from which we measure a gas-phase abundance of N/H = −1.0 0.1. Photoionization models indicate that the nitrogen-to-silicon relative abundance is solar, yet magnesium is underabundant by a factor of 2. We also report spatially resolved emission-line spectroscopy of the nearby galaxy, and we extract its rotation curve. The galaxy's metallicity is 8× higher than N/H in the absorber, and interestingly, the absorber velocities suggest that the gas at = 66 kpc is corotating with the galaxy's stellar disk, possibly with an inflow component. These characteristics could indicate that this sub-damped Ly absorber system arises in a "cold-accretion" flow. However, the absorber abundance patterns are peculiar. We hypothesize that the gas was ejected from its galaxy of origin (or perhaps is a result of tidal debris from interactions between the group galaxies) with a solar nitrogen abundance, but that subsequently mixed with (and was diluted by) gas in the circumgalactic medium or group. If the gas is bound to the nearby galaxy, this system may be an example of the gas "recycling" predicted by theoretical galaxy simulations. Our hypothesis is testable with future observations.
Abstract
The massive galaxy cluster El Gordo (
z
= 0.87) imprints multitudes of gravitationally lensed arcs onto James Webb Space Telescope Near-Infrared Camera (NIRCam) images. Eight bands of NIRCam ...imaging were obtained in the “Prime Extragalactic Areas for Reionization and Lensing Science” (“PEARLS”) program. Point-spread function–matched photometry across Hubble Space Telescope and NIRCam filters supplies new photometric redshifts. A new light-traces-mass lens model based on 56 image multiplicities identifies the two mass peaks and yields a mass estimate within 500 kpc of (7.0 ± 0.30) × 10
14
M
⊙
. A search for substructure in the 140 cluster members with spectroscopic redshifts confirms the two main mass components. The southeastern mass peak that contains the brightest cluster galaxy is more tightly bound than the northwestern one. The virial mass within 1.7 Mpc is (5.1 ± 0.60)×10
14
M
⊙
, lower than the lensing mass. A significant transverse velocity component could mean the virial mass is underestimated. We contribute one new member to the previously known
z
= 4.32 galaxy group. Intrinsic (delensed) positions of the five secure group members span a physical extent of ∼60 kpc. 13 additional candidates selected by spectroscopic/photometric constraints are small and faint, with a mean intrinsic luminosity ∼2.2 mag fainter than
L
*
. NIRCam imaging admits a fairly wide range of brightnesses and morphologies for the group members, suggesting a more diverse galaxy population in this galaxy overdensity.
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