Meredith Stone

Determining total infrared luminosities for very high-redshift galaxies is important to estimate the rate of star formation in heavily dust-embedded environments. It is also challenging because the most sensitive far-infrared observatory, Herschel, was limited in sensitivity and its deepest measurements are subject to confusion noise. Thus, these determinations largely depend on the Atacama Large Millimeter/submillimeter Array, observing in the millimeter and/or submillimeter wavelengths, which sample only the long-wavelength part of the spectral energy distributions (SEDs). Luminosities are conventionally estimated with modified blackbody fits to these measurements, but do not include the emission in the mid-infrared by warmer dust; there is evidence that this mid-infrared component may be relatively strong in very high-redshift galaxies compared with local ones. A correction factor must be applied to the modified blackbody luminosities to derive the total infrared luminosity. We study infrared SEDs using simulations tuned to galactic conditions typical of high- z galaxies. We find that the different behaviors of infrared SEDs are dominated by a single key physical parameter, the luminosity density. This allows us to estimate the corrections for the missing mid-infrared luminosity in a general way. We find that a factor of ∼1.6–1.7 (0.2 dex) is appropriate in most circumstances, with a larger factor of ∼1.75–1.85 (∼0.25 dex) up to 2 (0.3 dex) necessary for high-redshift ( z > 4) galaxies at the highest luminosities, >10 ¹² L _⊙ . These corrections are needed to estimate star formation rates based on total infrared luminosity.

Our understanding of the physical properties of star-forming galaxies during the Epoch of Reionization (EoR; at z > 6) suffers from degeneracies among the apparent properties of the stars, nebular gas, and dust. These degeneracies are most prominent with photometry, which has insufficient (1) spectral resolution and (2) rest-frame spectral coverage. We explore ways to break these degeneracies with a sample of N = 22 high-redshift star-forming galaxies at 7 < z _phot ≤ 9, using some of the deepest existing imaging from JWST/NIRCam and JWST/MIRI with JADES. Key to this study is the imaging from JWST/MIRI at 7.7 μ m, which provides coverage of the rest-frame I band at the observed redshifts. We infer stellar population properties and rest-frame colors using a variety of filter sets and star formation history (SFH) assumptions to explore the impact of these choices. Evaluating these quantities both with and without the 7.7 μ m data point shows that dense spectral coverage with JWST/NIRCam (eight or more filters, including at least one medium-band at λ _obs ≈ 4–5 μ m) can compensate for lacking the rest-frame I -band coverage for the vast majority (≈80%) of our sample. Furthermore, these galaxy properties are most consistently determined by assuming the delayed-tau SFH, which provides the smallest offsets and scatters around these offsets when including JWST/MIRI. Within extragalactic surveys like JADES and CEERS, our findings suggest that robust characterization of the stellar population properties and rest-frame colors for typical high-redshift star-forming galaxies (i.e., galaxies with M _UV ≈ −20 and β _UV ≈ −2) is possible with JWST/NIRCam alone at z ≈ 8.

JWST has discovered an early period of galaxy formation that was more vigorous than expected, which has challenged our understanding of the early Universe. In this work, we present the longest spectroscopic integration ever acquired by JWST/MIRI ( t _obs ≈ 51 hr). This spectrum covers the brightest rest-frame optical nebular emission lines for the luminous galaxy JADES-GS-z14-0 at z = 14.18. Most notably, we detect [O III ] λλ 4959, 5007 at ≈14 σ and H α at ≈4 σ with these ultradeep observations. These lines reveal that JADES-GS-z14-0 has low dust attenuation with a recent star formation rate of SFR ≈ 8 ± 2 M _⊙ yr ⁻¹ , star formation rate surface density of Σ _SFR ≈ 20 ± 5 M _⊙ yr ⁻¹ kpc ⁻² , and ionizing photon production efficiency of ξ _ion ≈ 10 ^25.3±0.1 Hz erg ⁻¹ . Using standard strong-line diagnostics, we infer a gas-phase oxygen abundance of log 10 ( O / H ) + 12 ≈ 7.5 ± 0.2 (≈6% Z _⊙ ), carbon-to-oxygen ratio of [C/O] ≈ −0.4 ± 0.2, ionization parameter of log 10 ( U ) ≳ − 2.4 , and density of n _H ≈ 690 ± 200 cm ⁻³ . Using detailed photoionization modeling, we instead derive log 10 ( O / H ) + 12 ≈ 8 . 5 − 0.4 + 0.4 (≈60% Z _⊙ ), log 10 ( U ) ≈ − 1 . 4 − 0.4 + 0.3 , and n H ≈ 54 0 − 320 + 520 cm − 3 . The inferred properties of JADES-GS-z14-0 are similar to those measured for similarly luminous galaxies at z > 10 with previous MIRI/Spectroscopy, such as GHZ2/GLASSz12, GN-z11, and MACS0647-JD1. These results suggest extreme ionization conditions and rapid metal enrichment less than 300 Myr after the Big Bang. Existing simulations are unable to reproduce the empirical and inferred properties of JADES-GS-z14-0. This work demonstrates an important step toward understanding the formation of the first stars and heavy elements in the Universe. Future work will focus on the detection of the rest-frame optical continuum and its interpretation for the stellar population properties of JADES-GS-z14-0.

We present a large spectroscopic survey with JWST’s Mid-Infrared Instrument Low Resolution Spectrometer (LRS) targeting 37 infrared-bright galaxies between z = 0.65–2.46 with infrared luminosities log L IR / L ⊙ > 11.5 and log M * / M ⊙ = 10 − 11.5 . Targets were taken from a Spitzer 24 μ m selected sample with archival spectroscopy from the Infrared Spectrograph (IRS) and include a mix of star-forming galaxies and dust-obscured active galactic nuclei. By combining IRS with the increased sensitivity of LRS, we expand the range of spectral features observed between 5 and 30 μ m for every galaxy in our sample. In this paper, we outline the sample selection, reduction of the JWST data, extraction of the 1D spectra, and polycyclic aromatic hydrocarbon (PAH) feature measurements from λ _rest = 3.3–11.3 μ m. In the JWST spectra, we detect PAH emission features at 3.3–5.3 μ m, as well as Paschen and Brackett lines. The 3.3 μ m feature can be as bright as 1% of the 8–1000 μ m infrared luminosity and exhibits a tight correlation with the dust-obscured star formation rate. We detect absorption features from CO gas, CO ₂ ice, H ₂ O ice, and aliphatic dust. From the joint JWST and Spitzer analysis, we find that the 11.3/3.3 μ m PAH ratios are on average three times higher than that of local luminous infrared galaxies. This is interpreted as evidence that the PAH grains are larger at z ∼ 1–2. The size distribution may be affected by coagulation of grains due to high gas densities and low temperatures. These conditions are supported by the observation of strong water ice absorption at 3.05 μ m and can lower stellar radiative feedback because large PAHs transmit less energy per photon into the interstellar medium.

We present an overview of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES), an ambitious program of infrared imaging and spectroscopy in the GOODS-S and GOODS-N deep fields, designed to study galaxy evolution from high redshift to cosmic noon. JADES uses about 770 hr of Cycle 1 guaranteed time largely from the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) instrument teams. In GOODS-S, in and around the Hubble Ultra Deep Field and Chandra Deep Field South, JADES produces a deep imaging region of ∼42 arcmin ² with over 100 hr of exposure time spread over nine NIRCam filters, including two medium-band filters. This is extended at medium depth in GOODS-S and GOODS-N with NIRCam imaging of ∼167 arcmin ² , averaging 25 hr of exposure over 8–10 filters. In both fields, we conduct extensive NIRSpec multiobject spectroscopy, including two deep pointings of 55 hr exposure time, 14 medium pointings of ∼12 hr, and 15 shallower pointings of ∼4 hr, targeting over 5000 Hubble Space Telescope– and JWST-detected faint sources with five low-, medium-, and high-resolution dispersers covering 0.6–5.3 μ m. Finally, JADES extends redward via coordinated parallels with the JWST Mid-Infrared Instrument, featuring ∼10 arcmin ² with 43 hr of exposure at 7.7 μ m and thrice that area with 1.4–6.8 hr of exposure at 12.8 and 15 μ m. For nearly 30 yr, the GOODS-S and GOODS-N fields have been developed as the premier deep fields on the sky; JADES is now providing a compelling start on JWST's legacy in these fields.

We evaluate the underlying assumptions for the identification of active galactic nuclei (AGNs) through near- and mid-infrared photometry and spectral energy distribution (SED) fitting out to z ∼ 3. For massive galaxies, log( M ) ≥ 9.5, our high-resolution spectra of the rest optical range generally confirm the results of SED fitting, which relies primarily on excesses above the stellar emission between 1 and 6 μ m to identify AGN. However, the method is undermined if the redshift used for the SED fitting is incorrect. Low-mass galaxies, log( M ) < 9.5, can contain relatively warm dust that emits in the 4–6 μ m range. We show that the potential contamination of AGN samples by purely star-forming low-mass galaxies can be avoided by the use of the infrared properties of Haro 11 as a limiting star-forming SED template. However, relatively few star-forming galaxies emit as strongly in the 3–6 μ m range as this template, so this could result in missing some obscured AGNs to avoid a minor contamination. Including the behavior of the galaxies at rest λ ∼ 13.5 μ m can mitigate this problem and yield more complete samples of bona fide AGN. JWST/MIRI supports this approach out to z ≲ 0.6.

JWST observations of quasars in the Epoch of Reionization have revealed that many lie in host galaxies that are severely undermassive relative to the supermassive black holes. It is unclear how these systems will evolve to the tight local relation between stellar mass and black hole mass. We search for companions around the z = 7.08 quasar ULAS J1120+0641 using JWST/NIRCam narrow-, medium-, and wide-band photometry to identify [O III ] emitters at the quasar redshift, and explore the potential for growth of the host galaxy through future mergers. We find 22 sources near the quasar’s redshift across our two 4.4 arcmin ² fields, indicating that the environment of ULAS J1120+0641 is strongly overdense in z ∼ 7.1 galaxies relative to the field. We estimate the potential future mass budget of the quasar host galaxy by summing the current stellar and gas masses of the quasar host and surrounding galaxies, and correcting for incompleteness and selection effects. With no further black hole growth, ULAS J1120+0641 is unlikely to reach an M _BH / M _* ratio less than ∼2.5% at z = 0, still much higher than typical for local galaxies. However, such systems—a quiescent black hole in a low-luminosity galaxy—may have escaped detection locally if they are sufficiently distant.

We analyze 99 photometrically selected Little Red Dots (LRDs) at z ≈ 4–8 in the GOODS fields, leveraging ultradeep JADES NIRCam short-wavelength (SW) data. Among the 99 selected LRDs, we examine the morphology of 30. The remaining 69 appear predominantly compact, with sizes ≲400 pc and no extended components even in stacked SW images. However, their unresolved nature may partly reflect current depth limitations, which could prevent the detection of faint diffuse components. Among the 30 morphologically analyzed LRDs, 50% show multiple associated components, while the rest exhibit highly asymmetric structures, despite appearing as single sources. This diversity in rest-frame UV morphologies may point to interactions or strong internal feedback. We find median stellar masses of log 10 ( M ⋆ / M ⊙ ) = 9.0 7 − 0.08 + 0.11 for pure stellar models with A V ≈ 1.1 6 − 0.21 + 0.11 mag, and log 10 ( M ⋆ / M ⊙ ) = 9.6 7 − 0.27 + 0.17 for models including active galactic nuclei (AGNs) with A V ≈ 2.7 4 − 0.71 + 0.55 mag, in line with recent studies suggesting higher masses and dust content for AGN-fitted LRDs. NIRSpec spectra are available for 15 sources, six of which are also in the morphological sample. Broad Hα is detected in 40% (FWHM = 1200–2900 km s⁻¹), and one source shows broad Hβ emission. Emission line ratios indicate a composite nature, consistent with both AGN and stellar processes. Altogether, these results suggest that LRDs are a mixed population, and their rest-frame UV morphology reflects this complexity. Morphological studies of larger samples could provide a new way to understand what drives their properties and evolution.

We explore the accretion rates of supermassive black holes (SMBHs) in late-stage galaxy mergers by observing three ultraluminous infrared galaxies (ULIRGs), IRAS 14378-3651, IRAS 17208-0014 and IRAS 23365+3604, using the JWST/MIRI Medium Resolution Spectrometer and JWST/NIRSpec integral field unit. In all three cases, we fail to detect [Ne vi] λ7.65 μm, a robust active galactic nuclei (AGN) tracer lying in a low-opacity interstellar window, nor do we detect any other lines that might indicate AGNs. The only detected high-excitation emission line, [Mg iv] (λ4.488 μm), arises from shocks associated with supernovae. Our new, deep flux limits on AGN tracers in the near- and mid-infrared indicate that the nuclear obscuration of any purported AGNs in our sample is isotropic, i.e., the far-infrared luminosities of these galaxies are unlikely to be driven by escaping AGN power. This allows us to show that the Eddington ratios of their SMBHs are low. We then assemble an unbiased sample of 19 ULIRGs (from the IRAS Bright Galaxy Sample with L(TIR) ≥ 10¹² L _⊙) in late-stage mergers and show that their dynamically measured black hole masses are consistent with the values from scaling from their stellar masses. On this basis, we show that the Eddington ratios of any AGNs in 15 of these galaxies are also very low, ≲10%. This indicates that any black holes are in a relatively quiescent state. That is, high levels of accretion are found in only a minority of late-merger-phase ULIRGs.