Galaxy clusters magnify background objects through strong gravitational lensing. Typical magnifications for lensed galaxies are factors of a few but can also be as high as tens or hundreds, ...stretching galaxies into giant arcs
. Individual stars can attain even higher magnifications given fortuitous alignment with the lensing cluster. Recently, several individual stars at redshifts between approximately 1 and 1.5 have been discovered, magnified by factors of thousands, temporarily boosted by microlensing
. Here we report observations of a more distant and persistent magnified star at a redshift of 6.2 ± 0.1, 900 million years after the Big Bang. This star is magnified by a factor of thousands by the foreground galaxy cluster lens WHL0137-08 (redshift 0.566), as estimated by four independent lens models. Unlike previous lensed stars, the magnification and observed brightness (AB magnitude, 27.2) have remained roughly constant over 3.5 years of imaging and follow-up. The delensed absolute UV magnitude, -10 ± 2, is consistent with a star of mass greater than 50 times the mass of the Sun. Confirmation and spectral classification are forthcoming from approved observations with the James Webb Space Telescope.
Abstract We present a new sample of 158 galaxies at redshift z > 7.5 selected from deep James Webb Space Telescope (JWST) NIRCam imaging of five widely separated sight lines in the CANUCS survey. ...Two-thirds of the pointings and 80% of the galaxies are covered by 12–14 NIRCam filters, including seven to nine medium bands, providing accurate photometric redshifts and robustness against low-redshift interlopers. A sample of 28 galaxies at z > 7.5 with spectroscopic redshifts shows a low systematic offset and scatter in the difference between photometric and spectroscopic redshifts. We derive the galaxy UV luminosity function at redshifts 8–12, finding a slightly higher normalization than previously seen with the Hubble Space Telescope at redshifts 8–10. We observe a steeper decline in the galaxy space density from z = 8 to 12 than found by most JWST Cycle 1 studies. In particular, we find only eight galaxies at z > 10 and none at z > 12.5, with no z > 10 galaxies brighter than F277W AB = 28 or M UV = −20 in our unmasked, delensed survey area of 53.4 arcmin 2 . We attribute the lack of bright z > 10 galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in the galaxy density along different sight lines. The evolution in the CANUCS luminosity function between z = 8 and 12 is comparable to that predicted by simulations that assume a standard star formation efficiency without invoking any special adjustments.
The gravitational potential of clusters of galaxies acts as a cosmic telescope allowing us to find and study galaxies at fainter limits than otherwise possible and thus probe closer to the epoch of ...formation of the first galaxies. We use the Bullet cluster 1E0657 - 56 (z = 0.296) as a case study, because its high mass and merging configuration makes it one of the most efficient cosmic telescopes we know. We develop a new algorithm to reconstruct the gravitational potential of the Bullet cluster based on a non-uniform adaptive grid, combining strong and weak gravitational lensing data derived from deep Hubble Space Telescope/Advanced Camera for Surveys F606W-F775W-F850LP and ground-based imaging. We exploit this improved mass map to study z ~ 5-6 Lyman break galaxies (LBGs), which we detect as dropouts. One of the LBGs is multiply imaged, providing a geometric confirmation of its high redshift, and is used to further improve our mass model. We quantify the uncertainties in the magnification map reconstruction in the intrinsic source luminosity, and in the volume surveyed, and show that they are negligible compared to sample variance when determining the luminosity function of high-redshift galaxies. With shallower and comparable magnitude limits to Hubble Ultra Deep Field (HUDF) and Great Observatories Origins Deep Survey (GOODS), the Bullet cluster observations, after correcting for magnification, probe deeper into the luminosity function of the high-redshift galaxies than GOODS and only slightly shallower than HUDF. We conclude that accurately focused cosmic telescopes are the most efficient way to sample the bright end of the luminosity function of high-redshift galaxies and-in case they are multiply imaged-confirm their redshifts.
Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift universe, magnifying distant and faint background galaxies. Reliable strong-lensing (SL) ...models are crucial for determining the intrinsic properties of distant, magnified sources and for constructing their luminosity function. We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9−40.7, two massive galaxy clusters imaged with the Hubble Space Telescope, in the framework of the Reionization Lensing Cluster Survey (RELICS). We use the light-traces-mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters. Our SL analysis reveals that both clusters have particularly large Einstein radii (θE > 30″ for a source redshift of zs = 2), providing fairly large areas with high magnifications, useful for high-redshift galaxy searches (∼2 arcmin2 with > 5 to ∼1 arcmin2 with > 10, similar to a typical Hubble Frontier Fields cluster). We also find that MACS J0308.9+2645 hosts a promising, apparently bright (J ∼ 23.2-24.6 AB), multiply imaged high-redshift candidate at z ∼ 6.4. These images are among the brightest high-redshift candidates found in RELICS. Our mass models, including magnification maps, are made publicly available for the community through the Mikulski Archive for Space Telescopes.
We present a strong lensing analysis of four massive galaxy clusters imaged with the Hubble Space Telescope in the Reionization Lensing Cluster Survey. We use a light-traces-mass technique to uncover ...sets of multiple images and constrain the mass distribution of the clusters. These mass models are the first published for Abell S295 and MACS J0159.8-0849 and are improvements over previous models for Abell 697 and MACS J0025.4-1222. Our analysis for MACS J0025.4-1222 and Abell S295 shows a bimodal mass distribution supporting the merger scenarios proposed for these clusters. The updated model for MACS J0025.4-1222 suggests a substantially smaller critical area than previously estimated. For MACS J0159.8-0849 and Abell 697, we find a single peak and relatively regular morphology revealing fairly relaxed clusters. Despite being less prominent lenses, three of these clusters seem to have lensing strengths, i.e., cumulative area above certain magnification, similar to those of the Hubble Frontier Fields clusters (e.g., A( > 5) ∼ 1-3 arcmin2, A( > 10) ∼ 0.5-1.5 arcmin2), which in part can be attributed to their merging configurations. We make our lens models publicly available through the Mikulski Archive for Space Telescopes. Finally, using Gemini-N/GMOS spectroscopic observations, we detect a single emission line from a high-redshift J125 25.7 galaxy candidate lensed by Abell 697. While we cannot rule out a lower-redshift solution, we interpret the line as Ly at z = 5.800 0.001, in agreement with its photometric redshift and dropout nature. Within this scenario, we measure a Ly rest-frame equivalent width of 52 22 and an observed Gaussian width of 117 15 km s−1.
Strong gravitational lensing (SL) is a powerful means of mapping the distribution of dark matter. In this work, we perform an SL analysis of the prominent X-ray cluster RXJ0152.7-1357 (z = 0.83, also ...known as CL0152.7-1357) in Hubble Space Telescope images, taken in the framework of the Reionization Lensing Cluster Survey (RELICS). On top of a previously known z = 3.93 galaxy multiply imaged by RXJ0152.7-1357, for which we identify an additional multiple image, guided by a light-traces-mass approach, we identify seven new sets of multiply imaged background sources lensed by this cluster, spanning the redshift range 1.79-3.93. A total of 25 multiple images are seen over a small area of ∼0.4 arcmin2, allowing us to put relatively high-resolution constraints on the inner matter distribution. Although modestly massive, the high degree of substructure, together with its very elongated shape, makes RXJ0152.7-1357 a very efficient lens for its size. This cluster also comprises the third-largest sample of z ∼ 6-7 candidates in the RELICS survey. Finally, we present a comparison of our resulting mass distribution and magnification estimates with those from a Lenstool model. These models are made publicly available through the Mikulski Archive for Space Telescopes.
Abstract
We present measurements of stellar populations properties of a
z
= 9.1 gravitationally lensed galaxy MACS1149-JD1 using deep James Webb Space Telescope NIRISS slitless spectroscopy as well ...as NIRISS and NIRCam imaging from the CAnadian NIRISS Unbiased Cluster Survey (CANUCS). The galaxy is split into four components. Three magnified (
μ
∼ 11) star-forming components are unresolved, giving intrinsic sizes of <25 pc. In addition, the underlying extended component contains the bulk of the stellar mass, formed the majority of its stars ∼50 Myr earlier than the other three components, and is not the site of the most active star formation currently. The NIRISS and NIRCam resolved photometry does not confirm a strong Balmer break previously seen in Spitzer. The NIRISS grism spectrum has been extracted for the entire galaxy and shows a clear continuum and Lyman break, with no Ly
α
detected.
ABSTRACT We report on a $\rm {CII}_{158\mu \rm {m}}$ search using the Atacama Large Millimeter/submillimeter Array (ALMA) on three lensed, confirmed Ly α emitting galaxies at z ∼ 7. Our targets are ...ultraviolet (UV) faint systems with stellar masses on the order of M* ∼ 109 M⊙. We detect a single C ii line emission (4σ) from the brightest (L ∼ 2.4 × 1010L⊙) galaxy in our sample, MACS0454-1251. We determine a systemic redshift (zC ii = 6.3151 ± 0.0005) for MACS0454-1251 and measure a Ly α velocity offset of $\Delta v \approx 300 \pm 70 \rm {km\, s}^{-1}$. The remaining two galaxies we detect no C ii but provide 3σ upper limits on their C ii line luminosities which we use to investigate the $L_{\textrm {CII}} - \rm {SFR}$ relation. Overall our single C ii detection shows agreement with the relation for local dwarf galaxies. Our C ii deficient galaxies could potentially be exhibiting low metallicities (Z < Z⊙). Another possible explanation for weaker C ii emission could be strong feedback from star formation disrupting molecular clouds. We do not detect continuum emission in any of the sources, placing upper limits on their dust masses. Assuming a single dust temperature of $T_{d}=35 \rm {K}$ dust masses (Mdust) range from <4.8 × 107 M⊙ to 2.3 × 108 M⊙. Collectively, our results suggest faint reionization era sources could be metal poor and/or could have strong feedback suppressing C ii emission.
ABSTRACT We report the detection of Ly emission at ∼9538 in the Keck/DEIMOS and Hubble Space Telescope WFC3 G102 grism data from a triply imaged galaxy at z = 6.846 0.001 behind galaxy cluster MACS ...J2129.4−0741. Combining the emission line wavelength with broadband photometry, line ratio upper limits, and lens modeling, we rule out the scenario that this emission line is O ii at z = 1.57. After accounting for magnification, we calculate the weighted average of the intrinsic Ly luminosity to be ∼ 1.3 × 10 42 erg s − 1 and Ly equivalent width to be 74 15 . Its intrinsic UV absolute magnitude at 1600 is −18.6 0.2 mag and stellar mass ( 1.5 0.3 ) × 10 7 M , making it one of the faintest (intrinsic L UV ∼ 0.14 L UV * ) galaxies with Ly detection at z ∼ 7 to date. Its stellar mass is in the typical range for the galaxies thought to dominate the reionization photon budget at z 7 ; the inferred Ly escape fraction is high ( 10 %), which could be common for sub-L* z 7 galaxies with Ly emission. This galaxy offers a glimpse of the galaxy population that is thought to drive reionization, and it shows that gravitational lensing is an important avenue for probing the sub-L* galaxy population.
Abstract
We present results of C
ii
158
μ
m emission line observations, and report the spectroscopic redshift confirmation of a strongly lensed (
μ
∼ 20) star-forming galaxy, MACS0308-zD1 at
z
= ...6.2078 ± 0.0002. The C
ii
emission line is detected with a signal-to-noise ratio >6 within the rest-frame UV-bright clump of the lensed galaxy (zD1.1) and exhibits multiple velocity components; the narrow C
ii
has a velocity full width half maximum (FWHM) of 110 ± 20 km s
−1
, while broader C
ii
is seen with an FWHM of 230 ± 50 km s
−1
. The broader C
ii
component is blueshifted (−80 ± 20 km s
−1
) with respect to the narrow C
ii
component, and has a morphology that extends beyond the UV-bright clump. We find that, while the narrow C
ii
emission is most likely associated with zD1.1, the broader component is possibly associated with a physically distinct gas component from zD1.1 (e.g., outflowing or inflowing gas). Based on the nondetection of
λ
158
μ
m
dust continuum, we find that MACS0308-zD1's star formation activity occurs in a dust-free environment indicated by a strong upper limit of infrared luminosity ≲9 × 10
8
L
⊙
. Targeting this strongly lensed faint galaxy for follow-up Atacama Large Millimeter/submillimeter Array and JWST observations will be crucial to characterize the details of typical galaxy growth in the early Universe.
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