Figure 2 - available via license: Creative Commons Attribution 4.0 International
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Three-color images of Maisie's Galaxy. The left image is a composite of HST/ACS F606W and F814W in blue, F115W and F150W in green, and F200W in red. This shows the galaxy candidate as red due to the very high redshift resulting in no detected flux in the filters assigned to the blue and green colors. The right image shows an approximated "true" rest-UV color image, composed entirely of the long-wavelength channel filters F277W in blue, F356W in green, F410M+F444W in red). As we discuss further in §4, intrinsically this galaxy is quite blue. The scale bar corresponds to 1 (physical) kpc assuming z = 14 at a scale of 0.3 per kpc.
Source publication
We report the discovery of a candidate galaxy with a photo-z of z~14 in the first epoch of JWST NIRCam imaging from the Cosmic Evolution Early Release Science (CEERS) Survey. We searched for z>12 sources using photo-z's based primarily on the expected Lyman-alpha breaks. Following conservative vetting criteria, we identify a robust source at z_phot...
Context in source publication
Context 1
... The properties of this galaxy are summarized in Table 1, and we list its photometry in Table 2. Figure 1 shows cutouts of this candidate galaxy in the NIRCam bands, while Figure 2 shows two color composites. Figure 3 shows the observed spectral energy distribution of our candidate with photometric redshift fits. ...
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We present JWST/NIRSpec prism spectroscopy of MACS0647-JD, the triply-lensed $z \sim 11$ candidate discovered in HST imaging and spatially resolved by JWST imaging into two components A and B. Spectroscopy of component A yields a spectroscopic redshift $z=10.17$ based on 7 detected emission lines: CIII] $\lambda\lambda$1907,1909, [OII] $\lambda$372...
Citations
... Our results may furthermore explain the under-prediction of observed H 2 column densities by models 31 and the shift of the H/H 2 transition closer to the ionization front in resolved PDRs 32 . Additionally, our work brings one possibility to solve the contradiction between the possible discovery of James Webb telescope ultra-high-redshift galaxies on one hand 33 , and on the other, the redshift limit above which stars could not have formed, obtained by crossing the efficiency of H 2 formation against dust temperature and the dust temperature dependence against the redshift 21,34-36 with a minimum temperature ultimately defined by the CMB. The warmer CMB of high-redshift galaxies is observed in the (sub-)millimetre dust continuum and the line emission as it provides an additional source of heating 37,38 . ...
The microphysics of molecular hydrogen formation has an influence on galactic-scale star-formation rates over cosmic time. H2 is the cooling agent needed to initiate the cloud collapse regulating the star-formation efficiency. H2 formation is inefficient in the gas phase under typical interstellar conditions, requiring dust grain surfaces to act as catalysts. Small carbonaceous grains with sizes from roughly 4 to 100–200 Å, including polycyclic aromatic hydrocarbons (PAHs), have been shown to increase the H2 formation rates due to their large surface-to-volume ratios. H2 formation rates on PAHs were previously thought to reduce above temperatures of 50 K and H atom recombination was believed to be highly efficient only below 20 K. Until now, both laboratory experiments and theoretical modelling have suggested that H2 cannot form on grains with temperatures above 100 K. Here we report evidence, through direct laboratory measurements, of the highly efficient formation of H2 at temperatures up to 250 K on carbonaceous surfaces mimicking interstellar dust. By pushing their formation towards warmer temperatures, the H2 molecules could start contributing substantially to the cooling of warmer gas (temperatures of roughly 50–250 K). This will have a marked impact on our understanding of H2 formation in nearby galaxies and its efficiency in high-redshift galaxies where the Cosmic Microwave Background already pushes dust temperatures to more than 20 K.
We have conducted a search for z ≃ 7 Lyman break galaxies over 8.2 square degrees of near-infrared imaging from the VISTA Deep Extragalactic Observations (VIDEO) survey in the XMM-Newton - Large Scale Structure (XMM-LSS) and the Extended Chandra Deep Field South (ECDF-S) fields. Candidate galaxies were selected from a full photometric redshift analysis down to a Y + J depth of 25.3 (5σ), utilizing deep auxiliary optical and Spitzer/IRAC data to remove brown dwarf and red interloper galaxy contaminants. Our final sample consists of 28 candidate galaxies at 6.5 ≤ z ≤ 7.5 with −23.5 ≤ MUV ≤ −21.6. We derive stellar masses of 9.1 ≤ log10(M⋆/M⊙) ≤ 10.9 for the sample, suggesting that these candidates represent some of the most massive galaxies known at this epoch. We measure the rest-frame UV luminosity function (LF) at z ≃ 7, confirming previous findings of a gradual decline in number density at the bright-end (MUV < −22) that is well described by a double-power law (DPL). We show that quasar contamination in this magnitude range is expected to be minimal, in contrast to conclusions from recent pure-parallel Hubble studies. Our results are up to a factor of ten lower than previous determinations from optical-only ground-based studies at MUV ≲ −23. We find that the inclusion of YJHKs photometry is vital for removing brown-dwarf contaminants, and z ≃ 7 samples based on red-optical data alone could be highly contaminated (≳ 50 per cent). In comparison with other robust z > 5 samples, our results further support little evolution in the very bright-end of the rest-frame UV LF from z = 5–10, potentially signalling a lack of mass quenching and/or dust obscuration in the most massive galaxies in the first Gyr.
The distribution of dark matter halo masses can be accurately predicted in the lambda cold dark matter (ΛCDM) cosmology. The presence of a single massive halo or galaxy at a particular redshift, assuming some baryon and stellar fraction for the latter, can therefore be used to test the underlying cosmological model. A number of recent measurements of very large galaxy stellar masses at high redshift (z > 8) motivate an investigation into whether any of these objects are in tension with ΛCDM. We use extreme value statistics to generate confidence regions in the mass–redshift plane for the most extreme mass haloes and galaxies. Tests against numerical models show no tension, neither in their dark matter halo masses nor their galaxy stellar masses. However, we find tentative >3σ tension with recent observational determinations of galaxy masses at high redshift from both Hubble Space Telescope and James Webb Space Telescope, despite using conservative estimates for the stellar fraction (f⋆ ∼ 1). Either these galaxies are in tension with ΛCDM, or there are unaccounted for uncertainties in their stellar mass or redshift estimates.
