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Marcia Rieke

Publications and source records attributed to Marcia Rieke.

At least 73 records · Page 4Linked to original sources
arXiv2024

The Cosmos in its Infancy: JADES Galaxy Candidates at z > 8 in GOODS-S and GOODS-N

We present a catalog of 717 candidate galaxies at $z > 8$ selected from 125 square arcminutes of NIRCam imaging as part of the JWST Advanced Deep Extragalactic Survey (JADES). We combine the full JADES imaging dataset with data from the JEMS and FRESCO JWST surveys along with extremely deep existing observations from HST/ACS for a final filter set that includes fifteen JWST/NIRCam filters and five HST/ACS filters. The high-redshift galaxy candidates were selected from their estimated photometric redshifts calculated using a template fitting approach, followed by visual inspection from seven independent reviewers. We explore these candidates in detail, highlighting interesting resolved or extended sources, sources with very red long-wavelength slopes, and our highest redshift candidates, which extend to $z_{phot} = 18$. We also investigate potential contamination by stellar objects, and do not find strong evidence from SED fitting that these faint high-redshift galaxy candidates are low-mass stars. Over 93\% of the sources are newly identified from our deep JADES imaging, including 31 new galaxy candidates at $z_{phot} > 12$. Using 42 sources in our sample with measured spectroscopic redshifts from NIRSpec and FRESCO, we find excellent agreement to our photometric redshift estimates, with no catastrophic outliers and an average difference of $\langle Δz = z_{phot}- z_{spec} \rangle= 0.26$. These sources comprise one of the most robust samples for probing the early buildup of galaxies within the first few hundred million years of the Universe's history.

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arXiv2024

JWST/NIRCam Imaging of Young Stellar Objects. I. Constraints on Planets Exterior to The Spiral Disk Around MWC 758

MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously-identified candidate companions have been identified -- one at the end the Southern spiral arm at ~0.6 arcsec, and one interior to the gap at ~0.1 arcsec. With JWST/NIRCam, we provide new images of the disk and constraints on planets exterior to ~1". We detect the two-armed spiral disk, a known background star, and a spatially resolved background galaxy, but no clear companions. The candidates that have been reported are at separations that are not probed by our data with sensitivity sufficient to detect them -- nevertheless, these observations place new limits on companions down to ~2 Jupiter-masses at ~150 au and ~0.5 Jupiter masses at ~600 au. Owing to the unprecedented sensitivity of JWST and youth of the target, these are among the deepest mass-detection limits yet obtained through direct imaging observations, and provide new insights into the system's dynamical nature.

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arXiv2024

JWST/NIRCam Imaging of Young Stellar Objects. II. Deep Constraints on Giant Planets and a Planet Candidate Outside of the Spiral Disk Around SAO 206462

We present JWST/NIRCam F187N, F200W, F405N and F410M direct imaging data of the disk surrounding SAO 206462. Previous images show a very structured disk, with a pair of spiral arms thought to be launched by one or more external perturbers. The spiral features are visible in three of the four filters, with the non-detection in F410M due to the large detector saturation radius. We detect with a signal-to-noise ratio of 4.4 a companion candidate (CC1) that, if on a coplanar circular orbit, would orbit SAO 206462 at a separation of $\sim300$ au, $2.25σ$ away from the predicted separation for the driver of the eastern spiral. According to the BEX models, CC1 has a mass of $M_\mathrm{CC1}=0.8\pm0.3~M_\mathrm{J}$. No other companion candidates were detected. At the location predicted by simulations of both spirals generated by a single massive companion, the NIRCam data exclude objects more massive than $\sim2.2~M_\mathrm{J}$ assuming the BEX evolutionary models. In terms of temperatures, the data are sensitive to objects with $T_{\text{eff}}\sim650-850$ K, when assuming planets emit like blackbodies ($R_\mathrm{p}$ between 1 and $3 R_\mathrm{J}$). From these results, we conclude that if the spirals are driven by gas giants, these must be either cold or embedded in circumplanetary material. In addition, the NIRCam data provide tight constraints on ongoing accretion processes. In the low extinction scenario we are sensitive to mass accretion rates of the order $\dot{M}\sim10^{-9} M_\mathrm{J}$ yr$^{-1}$. Thanks to the longer wavelengths used to search for emission lines, we reach unprecedented sensitivities to processes with $\dot{M}\sim10^{-7} M_\mathrm{J}$ yr$^{-1}$ even towards highly extincted environments ($A_\mathrm{V}\approx50$~mag).

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arXiv2023

JADES: Carbon enrichment 350 Myr after the Big Bang in a gas-rich galaxy

Finding the emergence of the first generation of metals in the early Universe, and identifying their origin, are some of the most important goals of modern astrophysics. We present deep JWST/NIRSpec spectroscopy of GS-z12, a galaxy at z=12.5, in which we report the detection of C III]$λλ$1907,1909 nebular emission. This is the most distant detection of a metal transition and the most distant redshift determination via emission lines. In addition, we report tentative detections of [O II]$λλ$3726,3729 and [Ne III]$λ$3869, and possibly O III]$λλ$1661,1666. By using the accurate redshift from C III], we can model the Ly$α$ drop to reliably measure an absorbing column density of hydrogen of $N_{HI} \approx 10^{22}$ cm$^{-2}$ - too high for an IGM origin and implying abundant ISM in GS-z12 or CGM around it. We infer a lower limit for the neutral gas mass of about $10^7$ MSun which, compared with a stellar mass of $\approx4 \times 10^7$ MSun inferred from the continuum fitting, implies a gas fraction higher than about 0.1-0.5. We derive a solar or even super-solar carbon-to-oxygen ratio, tentatively [C/O]>0.15. This is higher than the C/O measured in galaxies discovered by JWST at z=6-9, and higher than the C/O arising from Type-II supernovae enrichment, while AGB stars cannot contribute to carbon enrichment at these early epochs and low metallicities. Such a high C/O in a galaxy observed 350 Myr after the Big Bang may be explained by the yields of extremely metal poor stars, and may even be the heritage of the first generation of supernovae from Population III progenitors.

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arXiv2023

JADES: Using NIRCam Photometry to Investigate the Dependence of Stellar Mass Inferences on the IMF in the Early Universe

The detection of numerous and relatively bright galaxies at redshifts z > 9 has prompted new investigations into the star-forming properties of high-redshift galaxies. Using local forms of the initial mass function (IMF) to estimate stellar masses of these galaxies from their light output leads to galaxy masses that are at the limit allowed for the state of the LambdaCDM Universe at their redshift. We explore how varying the IMF assumed in studies of galaxies in the early universe changes the inferred values for the stellar masses of these galaxies. We infer galaxy properties with the SED fitting code Prospector using varying IMF parameterizations for a sample of 102 galaxies from the JWST Advanced Deep Extragalactic Survey (JADES) spectroscopically confirmed to be at z > 6.7, with additional photometry from the JWST Extragalactic Medium Band Survey (JEMS) for twenty-one galaxies. We demonstrate that models with stellar masses reduced by a factor of three or more do not affect the modeled spectral energy distribution (SED).

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arXiv2023

Searching for Planets Orbiting Fomalhaut with JWST/NIRCam

We report observations with the JWST/NIRCam coronagraph of the Fomalhaut system. This nearby A star hosts a complex debris disk system discovered by the IRAS satellite. Observations in F444W and F356W filters using the round 430R mask achieve a contrast ratio of ~ 4 x 10-7 at 1'' and ~ 4 x 10-8 outside of 3''. These observations reach a sensitivity limit <1 MJup across most of the disk region. Consistent with the hypothesis that Fomalhaut b is not a massive planet but is a dust cloud from a planetesimal collision, we do not detect it in either F356W or F444W (the latter band where a Jovian-sized planet should be bright). We have reliably detected 10 sources in and around Fomalhaut and its debris disk, all but one of which are coincident with Keck or HST sources seen in earlier coronagraphic imaging; we show them to be background objects, including the "Great Dust Cloud" identified in MIRI data. However, one of the objects, located at the edge of the inner dust disk seen in the MIRI images, has no obvious counterpart in imaging at earlier epochs and has a relatively red [F356W]-[F444W]>0.7 mag (Vega) color. Whether this object is a background galaxy, brown dwarf, or a Jovian mass planet in the Fomalhaut system will be determined by an approved Cycle 2 follow-up program. Finally, we set upper limits to any scattered light from the outer ring, placing a weak limit on the dust albedo at F356W and F444W.

astro-ph.EP↗
arXiv2023

JADES: Discovery of extremely high equivalent width Lyman-alpha emission from a faint galaxy within an ionized bubble at z=7.3

We report the discovery of a remarkable Ly$α$ emitting galaxy at z = 7.2782, JADES-GS-z7-LA, with EW$_0$(Ly$α$) $= 388.0 \pm 88.8$Åand UV magnitude -17.0. The spectroscopic redshift is confirmed via rest-frame optical lines [O II], H$β$ and [O III] in its JWST/NIRSpec Micro-Shutter Assembly (MSA) spectrum. The Ly$α$ line is detected in both lower resolution PRISM as well as medium resolution G140M grating spectra. The LSF-deconvolved Ly$α$ FWHM in the grating is $383.9 \pm 56.2$ km/s and the Ly$α$ velocity offset compared to the systemic redshift is $113.3 \pm 80.0$ km/s, indicative of very little neutral gas or dust within the galaxy. We estimate the Ly$α$ escape fraction to be >70%. JADES-GS-z7-LA has a O32 ratio of $11.1 \pm 2.2$ and a R23 ratio of $11.2 \pm 2.6$, consistent with low metallicity and high ionization parameters. Deep NIRCam imaging also revealed a close companion source (separated by 0.23"), which exhibits similar photometry to that of JADES-GS-z7-LA, with a photometric excess in the F410M NIRCam image consistent with [O III]+H$β$ emission at the same redshift. The spectral energy distribution of JADES-GS-z7-LA indicates a "bursty" star formation history, with a low stellar mass of $\approx 10^7$ $M_\odot$. Assuming that the Ly$α$ transmission through the intergalactic medium is the same as its measured escape fraction, an ionized region of size > 1.5 pMpc is needed to explain the high Ly$α$ EW and low velocity offset compared to systemic seen in JADES-GS-z7-LA. Owing to its UV-faintness, we show that it is incapable of single-handedly ionizing a region large enough to explain its Ly$α$ emission. Therefore, we suggest that JADES-GS-z7-LA (and possibly the companion source) may be a part of a larger overdensity, presenting direct evidence of overlapping ionized bubbles at $z>7$.

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arXiv2023

JADES: Insights on the low-mass end of the mass--metallicity--star-formation rate relation at $3 < z < 10$ from deep JWST/NIRSpec spectroscopy

We analyse the gas-phase metallicity properties of a sample of low stellar mass (log M*/M_sun <= 9) galaxies at 3 < z < 10, observed with JWST/NIRSpec as part of the JADES programme in its deep GOODS-S tier. By combining this sample with more massive galaxies at similar redshifts from other programmes, we study the scaling relations between stellar mass, oxygen abundance (O/H), and star-formation rate (SFR) for 146 galaxies, spanning across three orders of magnitude in stellar mass and out to the epoch of early galaxy assembly. We find evidence for a shallower slope at the low-mass-end of the mass-metallicity relation (MZR), with 12 + log(O/H) = (7.72+-0.02) + (0.17+-0.03) log(M* / 10^8 M_sun), in good agreement with the MZR probed by local analogues of high-redshift systems like 'Green Pea' and 'Blueberry' galaxies. The inferred slope is well matched by models including 'momentum-driven' SNe winds, suggesting that feedback mechanisms in dwarf galaxies (and at high-z) might be different from those in place at higher masses. The evolution in the normalisation is observed to be relatively mild compared to previous determinations of the MZR at z~3 (~ 0.1 - 0.2 dex across the explored mass regime). We observe a deviation from the local fundamental metallicity relation (FMR) for our sample at high redshift, especially at z > 6, with galaxies significantly less enriched (with a median offset in log(O/H) of ~ 0.5 dex, significant at ~ 5 sigma) than predicted given their M* and SFR. These observations are consistent with an enhanced stochasticity in the star-formation history, and/or with an increased efficiency in metal removals by outflows, prompting us to reconsider the nature of the relationship between M*, O/H, and SFR in the early Universe.

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arXiv2023

Minor merger growth in action: JWST detects faint blue companions around massive quiescent galaxies at 0.5 < z < 3

Minor mergers are thought to drive the structural evolution of massive quiescent galaxies; however, existing HST imaging is primarily sensitive to stellar mass ratios >1:10. Here, we report the discovery of a large population of low-mass companions within 35 kpc of known logM*/Msun > 10.5 quiescent galaxies at 0.5 < z < 3. While massive companions like those identified by HST are rare, JWST imaging from JADES reveals that the average massive quiescent galaxy hosts ~5 nearby companions with stellar mass ratios <1:10. Despite a median stellar mass ratio of just 1:900, these tiny companions are so numerous that they represent at least 30\% of the total mass being added to quiescent galaxies via minor mergers. While relatively massive companions have colors similar to their hosts, companions with mass ratios <1:10 typically have bluer colors and lower mass-to-light ratios than their host galaxies at similar radii. The accretion of these tiny companions is likely to drive evolution in the color gradients and stellar population properties of the host galaxies. Our results suggest that the well-established ``minor merger growth" model for quiescent galaxies extends down to very low mass ratios of <1:100, and demonstrates the power of JWST to constrain both the spatially-resolved properties of massive galaxies and the properties of low-mass companions beyond the local universe.

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arXiv2023

Carbonaceous dust grains seen in the first billion years of cosmic time

Large dust reservoirs (up to $\sim 10^8 \, \mathrm{M_\odot}$) have been detected in galaxies out to redshift $z \sim 8$, when the age of the universe was only about 600 Myr. Generating significant amounts of dust within such a short timescale has proven challenging for theories of dust formation and has prompted the revision of the modelling of potential sites of dust production such as the atmospheres of asymptotic giant branch (AGB) stars in low-metallicity environments, supernovae (SNe) ejecta, and the accelerated growth of grains in the interstellar medium (ISM). However, degeneracies between different evolutionary pathways remain when the total dust mass of galaxies is the only available observable. Here we report observations of the $2175 \, \mathring{\rm A}$ dust attenuation feature, well known in the Milky Way (MW) and galaxies at $z \lesssim 3$, in the near-infrared spectra of galaxies up to $z \sim 7$, corresponding to the first billion years of cosmic time. The relatively short timescale implied for the formation of carbonaceous grains giving rise to this feature suggests a rapid production process, likely in Wolf-Rayet (WR) stars or SN ejecta.

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arXiv2023

JADES: Probing interstellar medium conditions at $z\sim5.5-9.5$ with ultra-deep JWST/NIRSpec spectroscopy

We present emission line ratios from a sample of 26 Lyman break galaxies from $z\sim5.5-9.5$ with $-17.0 5.5$ spectra. We find that the emission line ratios exhibited by these $z\sim5.5-9.5$ galaxies occupy clearly distinct regions of line-ratio space compared to typical z~0-3 galaxies, instead being more consistent with extreme populations of lower-redshift galaxies. This is best illustrated by the [OIII]/[OII] ratio, tracing interstellar medium (ISM) ionisation, in which we observe more than half of our sample to have [OIII]/[OII]>10. Our high signal-to-noise spectra reveal more than an order of magnitude of scatter in line ratios such as [OII]/H$β$ and [OIII]/[OII], indicating significant diversity in the ISM conditions within the sample. We find no convincing detections of [NII] in our sample, either in individual galaxies, or a stack of all G395M/F290LP spectra. The emission line ratios observed in our sample are generally consistent with galaxies with extremely high ionisation parameters (log $U\sim-1.5$), and a range of metallicities spanning from $\sim0.1\times Z_\odot$ to higher than $\sim0.3\times Z_\odot$, suggesting we are probing low-metallicity systems undergoing periods of rapid star-formation, driving strong radiation fields. These results highlight the value of deep observations in constraining the properties of individual galaxies, and hence probing diversity within galaxy population.

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arXiv2023

The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope -- I. Instrument Overview and in-Flight Performance

The Near-Infrared Imager and Slitless Spectrograph (NIRISS) is the science module of the Canadian-built Fine Guidance Sensor (FGS) onboard the James Webb Space Telescope (JWST). NIRISS has four observing modes: 1) broadband imaging featuring seven of the eight NIRCam broadband filters, 2) wide-field slitless spectroscopy (WFSS) at a resolving power of $\sim$150 between 0.8 and 2.2 $μ$m, 3) single-object cross-dispersed slitless spectroscopy (SOSS) enabling simultaneous wavelength coverage between 0.6 and 2.8 $μ$m at R$\sim$700, a mode optimized for exoplanet spectroscopy of relatively bright ($J<6.3$) stars and 4) aperture masking interferometry (AMI) between 2.8 and 4.8 $μ$m enabling high-contrast ($\sim10^{-3}-10^{-4}$) imaging at angular separations between 70 and 400 milliarcsec for relatively bright ($M<8$) sources. This paper presents an overview of the NIRISS instrument, its design, its scientific capabilities, and a summary of in-flight performance. NIRISS shows significantly better response shortward of $\sim2.5\,μ$m resulting in 10-40% sensitivity improvement for broadband and low-resolution spectroscopy compared to pre-flight predictions. Two time-series observations performed during instrument commissioning in the SOSS mode yield very stable spectro-photometry performance within $\sim$10% of the expected noise. The first space-based companion detection of the tight binary star AB Dor AC through AMI was demonstrated.

astro-ph.IM↗
arXiv2023

JWST NIRCam+NIRSpec: Interstellar medium and stellar populations of young galaxies with rising star formation and evolving gas reservoirs

We present an interstellar medium and stellar population analysis of three spectroscopically confirmed $z>7$ galaxies in the ERO JWST NIRCam and JWST NIRSpec data of the SMACS J0723.3-7327 cluster. We use the Bayesian spectral energy distribution (SED) fitting code \texttt{Prospector} with a flexible star-formation history (SFH), a variable dust attenuation law, and a self-consistent model of nebular emission (continuum and emission lines). Importantly, we self-consistently fit both the emission line fluxes from JWST NIRSpec and the broad-band photometry from JWST NIRCam, taking into account slit-loss effects. We find that these three $z=7.6-8.5$ galaxies ($M_{\star}\approx10^{8}~M_{\odot}$) are young with rising SFHs and mass-weighted ages of $3-4$ Myr, though we find indications for underlying older stellar populations. The inferred gas-phase metallicities broadly agree with the direct metallicity estimates from the auroral lines. The galaxy with the lowest gas-phase metallicity ($\mathrm{Z}_{\rm gas}=0.06~\mathrm{Z}_{\odot}$) has a steeply rising SFH, is very compact ($<0.2~\mathrm{kpc}$) and has a high star-formation rate surface density ($Σ_{\rm SFR}\approx22~\mathrm{M}_{\odot}~\mathrm{yr}^{-1}~\mathrm{kpc}^{-2}$), consistent with rapid gas accretion. The two other objects with higher gas-phase metallicity show more complex multi-component morphologies on kpc scales, indicating that their recent increase in star-formation rate is driven by mergers or internal, gravitational instabilities. We discuss effects of assuming different SFH priors or only fitting the photometric data. Our analysis highlights the strength and importance of combining JWST imaging and spectroscopy for fully assessing the nature of galaxies at the earliest epochs.

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arXiv2023

JADES Imaging of GN-z11: Revealing the Morphology and Environment of a Luminous Galaxy 430 Myr After the Big Bang

We present JWST NIRCam 9-band near-infrared imaging of the luminous $z=10.6$ galaxy GN-z11 from the JWST Advanced Deep Extragalactic Survey (JADES) of the GOODS-N field. We find a spectral energy distribution (SED) entirely consistent with the expected form of a high-redshift galaxy: a clear blue continuum from 1.5 to 4 microns with a complete dropout in F115W. The core of GN-z11 is extremely compact in JWST imaging. We analyze the image with a two-component model, using a point source and a Sérsic profile that fits to a half-light radius of 200 pc and an index $n=0.9$. We find a low-surface brightness haze about $0.4''$ to the northeast of the galaxy, which is most likely a foreground object but might be a more extended component of GN-z11. At a spectroscopic redshift of 10.60 (Bunker et al. 2023), the comparison of the NIRCam F410M and F444W images spans the Balmer jump. From population synthesis modeling, here assuming no light from an active galactic nucleus, we reproduce the SED of GN-z11, finding a stellar mass of $\sim$$10^{9}~M_{\odot}$, a star-formation rate of $\sim$$20~M_{\odot}~\mathrm{yr}^{-1}$ and a young stellar age of $\sim$$20~\mathrm{Myr}$. As massive galaxies at high redshift are likely to be highly clustered, we search for faint neighbors of GN-z11, finding 9 galaxies out to $\sim$5 comoving Mpc transverse with photometric redshifts consistent with $z=10.6$, and a 10$^{\rm th}$ more tentative dropout only $3''$ away. This is consistent with GN-z11 being hosted by a massive dark-matter halo ($\approx8\times10^{10}~M_{\odot}$), though lower halo masses cannot be ruled out.

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arXiv2023

First Sample of H$α$+[O III] $λ$5007 Line Emitters at $z > 6$ Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line Luminosity Functions

We present a sample of four emission-line galaxies at $z=6.11-6.35$ that were serendipitously discovered using the commissioning data for the JWST/NIRCam wide-field slitless spectroscopy (WFSS) mode. One of them (at $z=6.11$) has been reported previously while the others are new discoveries. These sources are selected by the secure detections of both [O III] $λ$5007 and H$α$ lines with other fainter lines tentatively detected in some cases (e.g., [O II] $λ$3727, [O III] $λ$4959). In the [O III]/H$β$ - [N II]/H$α$ Baldwin-Phillips-Terlevich diagram, these galaxies occupy the same parameter space as that of $z\sim2$ star-forming galaxies, indicating that they have been enriched rapidly to sub-solar metallicities ($\sim$0.4 $Z_{\odot}$), similar to galaxies with comparable stellar masses at much lower redshifts. The detection of strong H$α$ lines suggests a higher ionizing photon production efficiency within galaxies in the early Universe. We find brightening of the [O III] $λ$5007 line luminosity function (LF) from $z=3$ to 6, and weak or no redshift evolution of the H$α$ line LF from $z=2$ to 6. Both LFs are under-predicted at $z\sim6$ by a factor of $\sim$10 in certain cosmological simulations. This further indicates a global Ly$α$ photon escape fraction of 7-10% at $z\sim6$, slightly lower than previous estimates through the comparison of the UV-derived star-formation rate density and Ly$α$ luminosity density. Our sample recovers $66^{+128}_{-44}$% of $z=6.0-6.6$ galaxies in the survey volume with stellar masses greater than $5\times10^8$ $M_{\odot}$, suggesting the ubiquity of strong H$α$ and [O III] line emitters in the Epoch of Reionization, which will be further uncovered in the era of JWST.

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arXiv2023

JADES NIRSpec Spectroscopy of GN-z11: Lyman-$α$ emission and possible enhanced nitrogen abundance in a $z=10.60$ luminous galaxy

We present JADES JWST/NIRSpec spectroscopy of GN-z11, the most luminous candidate $z>10$ Lyman break galaxy in the GOODS-North field with $M_{UV}=-21.5$. We derive a redshift of $z=10.603$ (lower than previous determinations) based on multiple emission lines in our low and medium resolution spectra over $0.8-5.3 μ$m. We significantly detect the continuum and measure a blue rest-UV spectral slope of $β=-2.4$. Remarkably, we see spatially-extended Lyman-$α$ in emission (despite the highly-neutral IGM expected at this early epoch), offset 555 km s$^{-1}$ redward of the systemic redshift. From our measurements of collisionally-excited lines of both low- and high-ionization (including [O II]$\lambda3727$, [Ne III]$λ3869$ and C III]$\lambda1909$) we infer a high ionization parameter ($\log U\sim -2$). We detect the rarely-seen N IV]$\lambda1486$ and N III]$\lambda1748$ lines in both our low and medium resolution spectra, with other high ionization lines seen in the low resolution spectrum such as He II (blended with O III]) and C IV (with a possible P-Cygni profile). Based on the observed rest-UV line ratios, we cannot conclusively rule out photoionization from AGN, although the high C III]/He II and N III]/He II ratios are compatible with a star-formation explanation. If the observed emission lines are powered by star formation, then the strong N III]$\lambda1748$ observed may imply an unusually high $N/O$ abundance. Balmer emission lines (H$γ$, H$δ$) are also detected, and if powered by star formation rather than an AGN we infer a star formation rate of $\sim 20-30 M_{\odot} yr^{-1}$ (depending on the IMF) and low dust attenuation. Our NIRSpec spectroscopy confirms that GN-z11 is a remarkable galaxy with extreme properties seen 430 Myr after the Big Bang.

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arXiv2023

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.

astro-ph.IM↗
arXiv2023

Spectroscopic confirmation of four metal-poor galaxies at z=10.3-13.2

Finding and characterising the first galaxies that illuminated the early Universe at cosmic dawn is pivotal to understand the physical conditions and the processes that led to the formation of the first stars. In the first few months of operations, imaging from the James Webb Space Telescope (JWST) have been used to identify tens of candidates of galaxies at redshift (z) greater than 10, less than 450 million years after the Big Bang. However, none of these candidates has yet been confirmed spectroscopically, leaving open the possibility that they are actually low-redshift interlopers. Here we present spectroscopic confirmation and analysis of four galaxies unambiguously detected at redshift 10.3<z<13.2, previously selected from NIRCam imaging. The spectra reveal that these primeval galaxies are extremely metal poor, have masses between 10^7 and a few times 10^8 solar masses, and young ages. The damping wings that shape the continuum close to the Lyman edge are consistent with a fully neutral intergalactic medium at this epoch. These findings demonstrate the rapid emergence of the first generations of galaxies at cosmic dawn.

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