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MACS0647–JD is a triply lensed z ∼ 11 galaxy originally discovered with the Hubble Space Telescope. The three lensed images are magnified by factors of ∼8, 5, and 2 to AB mag 25.1, 25.6, and 26.6 at 3.5 μm. The brightest is over a magnitude brighter than other galaxies recently discovered at similar redshifts z > 10 with JWST. Here, we report new JWST imaging that clearly resolves MACS0647–JD as having two components that are either merging galaxies or stellar complexes within a single galaxy. The brighter larger component “A” is intrinsically very blue (β ∼ −2.6 ± 0.1), likely due to very recent star formation and no dust, and is spatially extended with an effective radius ∼70 ± 24 pc. The smaller component “B” (r ∼ 20 − 5 + 8 pc) appears redder (β ∼ −2 ± 0.2), likely because it is older (100–200 Myr) with mild dust extinction (A V ∼ 0.1 mag). With an estimated stellar mass ratio of roughly 2:1 and physical projected separation ∼400 pc, we may be witnessing a galaxy merger 430 million years after the Big Bang. We identify galaxies with similar colors in a high-redshift simulation, finding their star formation histories to be dissimilar, which is also suggested by the spectral energy distribution fitting, suggesting they formed further apart. We also identify a candidate companion galaxy “C” ∼3 kpc away, likely destined to merge with A and B. Upcoming JWST Near Infrared Spectrograph observations planned for 2023 January will deliver spectroscopic redshifts and more physical properties for these tiny magnified distant galaxies observed in the early universe.

In this paper, we study the effects of a recent drop in star formation rate (SFR) on the spectra of epoch of reionization (EoR) galaxies, and the resulting degeneracy with the spectral features produced by extreme Lyman continuum leakage. In order to study these effects in the wavelength range relevant for the upcoming James Webb Space Telescope (JWST), we utilize synthetic spectra of simulated EoR galaxies from cosmological simulations together with synthetic spectra of partially quenched mock galaxies. We find that rapid declines in the SFR of EoR galaxies could seriously affect the applicability of methods that utilize the equivalent width of Balmer lines and the ultraviolet spectral slope to assess the escape fraction of EoR galaxies. In order to determine if the aforementioned degeneracy can be avoided by using the overall shape of the spectrum, we generate mock NIRCam observations and utilize a classification algorithm to identify galaxies that have undergone quenching. We find that while there are problematic cases, JWST/NIRCam or NIRSpec should be able to reliably identify galaxies with redshifts z ∼ 7 that have experienced a significant decrease in the SFR (by a factor 10-100) in the past 50-100 Myr with a success rate 85%. We also find that uncertainties in the dust-reddening effects on EoR galaxies significantly affect the performance of the results of the classification algorithm. We argue that studies that aim to characterize the dust extinction law most representative in the EoR would be extremely useful.

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Background The indocyanine green retention rate at 15 min (ICGR15) is a gold standard parameter of liver function when deciding on the extent of hepatectomy. However, ICGR15 is influenced by several hepatic conditions. To evaluate auxiliary preoperative liver functional reserve, we examined the clinical significance of modified parameters by blood tests and technetium-99m galactosyl human serum albumin (99mTc-GSA) scintigraphy. Methods We measured liver function parameters, including the hepatic uptake ratio (LHL15) and the blood pool clearance index (HH15) of 99mTc-GSA and their modified formulae [LHL/HH15, LHL minus HH15, and converted ICGR15 (cICGR15) from a preliminary study] in 229 patients, including 18 with biliary obstruction. Results The mean values of LHL15/HH15, LHL minus HH15, and cICGR15 were 1.646 ± 0.295, 0.347 ± 0.116, and 13.2 ± 5.3%, respectively. These parameters correlated significantly with other liver functions measured by blood tests except for the bilirubin level (P < 0.05) although the actual ICGR15 level correlated positively with the bilirubin level. The difference of ICGR15 (ICGR15 minus cICGR15) in patients with biliary obstruction tended to be higher in comparison with that in patients without biliary obstruction (P = 0.044). Values of LHL/HH15, LHL minus HH15, and the cICGR15 were not significantly associated with postoperative complications. Conclusion The modified parameters of 99mTc-GSA were useful for evaluating hepatic function in patients with high bilirubinemia due to biliary obstruction. However, it remains difficult to establish a more reliable parameter as a standard hepatic function test instead of ICGR15.