Rachana Bhatawdekar

We present the star formation and dust content properties for a sample of 646 galaxies at redshifts 3 < z < 7 as part of the JADES survey. Our analysis is based on measurements of the H α /H β Balmer decrement using medium resolution ( R ∼ 1000) spectroscopic observations with the JWST/NIRSpec microshutter assembly. Stellar masses and star formation rates (SFRs) are inferred with Prospector using deep multiband imaging. We utilize the Balmer decrement to measure dust-corrected H α -based SFRs, taking into account the subsolar metallicities observed in galaxies at high redshift. We confirm, with our large sample size, that the correlation between the Balmer decrement and stellar mass is already established out to z ∼ 7. We find that the relation between the Balmer decrement and stellar mass does not significantly evolve from the local Universe to z ∼ 7. We investigate the UV slope as a function of the Balmer optical depth and find that the best-fit correlation for our high redshift sample is specific SFR (sSFR) dependent and significantly different at high redshift when compared to galaxies at z ≈ 0 and z ≈ 2. For the highest sSFR galaxies in our sample, there is no significant correlation between the UV slope and Balmer optical depth. This is evidence that the UV slope should be used with great caution to correct for dust in high redshift galaxies.

Little red dots (LRDs) are compact, red sources discovered by JWST at high redshift ( z ≳ 4), marked by distinctive “V-shaped” spectral energy distributions (SEDs) and often interpreted as rapidly accreting active galactic nuclei (AGNs). Their true nature remains unclear though, and their evolutionary connection to their lower-redshift counterparts is still poorly constrained. Thus, we present WISEA J123635.56+621424.2 (here dubbed the Saguaro), a z = 2.0145 galaxy in GOODS-North, as a possible analog of high-redshift LRDs and a potential missing link in their evolutionary path toward lower-redshift systems. It features a compact LRD-like nucleus surrounded by a face-on spiral host. Its connections to LRDs include the following: (1) its nuclear spectrum shows a clear “V-shaped” SED, and (2) when redshifted to z = 7, surface brightness dimming makes the host undetectable, thus mimicking an LRD. This suggests that high-redshift LRDs may be embedded in extended hosts. To test this, we stack rest-frame UV images of 99 photometrically selected LRDs, revealing faint, diffuse emission. Stacking in redshift bins reveals mild radial growth, consistent with the expected galaxy size evolution. A simple analytic model confirms that surface brightness dimming alone can explain their compact appearance. Lastly, we show that the Saguaro is not unique by describing similar objects from the literature at z ≲ 3.5. Taken together, our results support a scenario in which LRDs may not be a distinct population, but could be the visible nuclei of galaxies undergoing a short-lived, (perhaps) AGN-dominated evolutionary phase, with their compact, red appearance driven largely by observational biases.

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.

The Euclid space telescope of the European Space Agency (ESA) is designed to provide sensitive and accurate measurements of weak gravitational lensing distortions over wide areas on the sky. Here, we present a weak gravitational lensing analysis of early Euclid observations obtained for the field around the massive galaxy cluster Abell 2390 as part of the Euclid Early Release Observations (ERO) programme. We conducted shape measurements for galaxies down to I _E ≲ 26.5 using three independent algorithms ( LensMC , KSB+ , and SourceXtractor++ ). Incorporating multi-band photometry from Euclid and Subaru/Suprime-Cam, we estimated photometric redshifts to preferentially select background sources from tomographic redshift bins, for which we calibrated the redshift distributions using the self-organising map approach and data from the Cosmic Evolution Survey (COSMOS). We quantified the residual cluster member contamination and corrected for it in bins of photometric redshift and magnitude using their source density profiles, including corrections for source obscuration and magnification. We reconstructed the cluster mass distribution and jointly fit the tangential reduced shear profiles of the different tomographic bins with spherical Navarro-Frenk-White profile predictions to constrain the cluster mass, finding consistent results for the three shape catalogues and good agreement with earlier measurements. As an important validation test, we compared these joint constraints to mass measurements obtained individually for the different tomographic bins, finding a good level of consistency. More detailed constraints on the cluster properties are presented in a companion paper, which additionally incorporates strong lensing measurements. Our analysis provides a first demonstration of the outstanding capabilities of Euclid for tomographic weak lensing measurements.

Early results from JWST suggest that Epoch of Reionization (EoR) galaxies produce copious ionizing photons, which, if they escape efficiently, could cause reionization to occur too early. We study this problem using JWST imaging and prism spectroscopy for 412 galaxies at 4.5 < z < 9.0. We fit these data simultaneously with stellar population and nebular emission models that include a parameter for the fraction of ionizing photons that escape the galaxy, f _esc . We find that the ionization production efficiency, ξ _ion = Q ( H ₀ )/ L _UV , increases with redshift and decreasing UV luminosity, but shows significant scatter, σ ( log ξ ion ∣ z , M UV ) ≃ 0.3 dex. The inferred escape fractions averaged over the population are low, ranging from〈 f _esc 〉 ≃ 2.6% ± 1.4% at 6 < z < 9 to 6.5% ± 2.2% at 4.5 < z < 6, with weak or no indication of evolution with redshift. This implies that in our models most of the ionizing photons need to be absorbed to account for the nebular emission. We compute the impact of our results on reionization, including the distributions for ξ _ion and f _esc , and the evolution and uncertainty of the UV luminosity function. Considering galaxies brighter than M _UV < −16 mag would produce an intergalactic medium hydrogen-ionized fraction of x _e = 0.5 at 5.3 < z < 5.8, possibly too late compared to constraints from from quasi-stellar object (QSO) sight lines. Including fainter galaxies, M _UV < −14 mag, we obtain x _e = 0.5 at 6.0 < z < 8.1, fully consistent with QSO and cosmic microwave background data. This implies that EoR galaxies produce plenty of ionizing photons, but that these do not efficiently escape. This may be a result of high gas column densities combined with burstier star formation histories, which limit the time massive stars are able to clear channels through the gas for ionizing photons to escape.

We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M _* > 10 ¹⁰ M _⊙ over 0.5 < z < 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii ( R _e ) of the galaxies at rest-frame 0.3, 0.5, and 1 μ m. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μ m than they are at 0.3 μ m (0.5 μ m). Regardless of wavelengths, the R _e of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M _* = 10 ¹⁰ –10 ^10.6 M _⊙ , the evolution follows R _e ∝ (1 + z ) ^−1.1 , whereas it becomes steeper, following R _e ∝ (1 + z ) ^−1.7 , for higher-mass quiescent galaxies with M _* > 10 ^10.6 M _⊙ . To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between R _e and the formation redshift ( z _form ) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with R e ∝ ( 1 + z form ) − 1 , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between R _e and z _form depends on stellar age. Older quiescent galaxies have a steeper relationship between R _e and z _form than that expected from the progenitor effect alone, suggesting that mergers and/or post-quenching continuous gas accretion drive additional size growth in very massive systems. We find that the z > 3 quiescent galaxies in our sample are very compact, with mass surface densities Σ _e ≳ 10 ¹⁰ M _⊙ kpc ⁻² , and their R _e are possibly even smaller than anticipated from the size evolution measured for lower-redshift quiescent galaxies. Finally, we take a close look at the structure of GS-9209, one of the earliest confirmed massive quiescent galaxies at z _spec ∼ 4.7. From UV to NIR, GS-9209 becomes increasingly compact, and its light profile becomes more spheroidal, showing that the color gradient is already present in this earliest massive quiescent galaxy.

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 present a spectroscopic search for broad H α emitters at z ≈ 3.7–6.5 in the GOODS-N field, utilizing JWST/NIRCam slitless spectroscopy from FRESCO and CONGRESS, complemented by JADES imaging. We identify 19 broad H α emitters with FWHM > 1000 km s ⁻¹ at z ≈ 4–5.5, including nine new sources. The broad H α luminosity function derived from our sample is consistent with those of other JWST-selected broad-line active galactic nuclei (AGN) reported in the literature. The black hole masses and AGN bolometric luminosities inferred from the broad H α components indicate that most sources are accreting at ∼10% of the Eddington limit. We derive their host stellar masses via spectral energy distribution (SED) fitting and find higher M _BH / M _* ratios relative to the local M _BH – M _* relations, consistent with previous studies. We find that 42% of the sample do not satisfy the widely used color selection criteria for little red dots (LRDs), with the majority of these sources lacking the characteristic steep rest-optical red slope, indicating that the LRD selection is highly incomplete when selecting AGN galaxies. A comparison of the average SEDs between our sample and LRDs selected in the same field reveals that the steep red slopes observed in some LRDs are likely due to line-boosting effects as previously suggested. Furthermore, we find that 68% of color-selected LRDs with H α detections in the NIRCam/grism spectra do not exhibit broad-line features. While the limited sensitivity of the grism spectra may hinder the detection of broad-line components in faint sources, our findings still highlight the enigmatic nature of the LRD population.

We present an analysis of rest-frame UV continuum slopes, β , using a sample of 1011 galaxies at 6.5 < z < 13 from the EPOCHS photometric sample collated from the GTO PEARLS and public ERS/GTO/GO (JADES, CEERS, NGDEEP, GLASS) JWST/NIRCam imaging across 178.9 arcmin 2 of unmasked blank sky. We correct our UV slopes for the photometric error coupling bias using 200,000 power-law spectral energy distributions for each β = {−1, −1.5, −2, −2.5, −3} in each field, finding biases as large as Δ β ≃ −0.55 for the lowest signal-to-noise ratio galaxies in our sample. Additionally, we simulate the impact of rest-UV line emission (including Ly α ) and damped Ly α systems on our measured β , finding biases as large as 0.5–0.6 for the most extreme systems. We find a decreasing trend with redshift of β = −1.51 ± 0.08 − (0.097 ± 0.010) × z , with potential evidence for Population III stars or top-heavy initial mass functions in a subsample of 68 β + σ _β < −2.8 galaxies. At z ≃ 11.5, we measure an extremely blue β ( M _UV = −19) = −2.73 ± 0.06, deviating from simulations, indicative of low-metallicity galaxies with nonzero Lyman continuum escape fractions f _esc,LyC ≳ 0 and minimal dust content. The observed steepening of d β / d log 10 ( M ⋆ / M ⊙ ) from 0.22 ± 0.02 at z ≃ 7 to 0.81 ± 0.13 at z ≃ 11.5 implies that dust produced in core-collapse supernovae at early times may be ejected via outflows from low-mass galaxies. We also observe a flatter d β / d M _UV = 0.03 ± 0.02 at z ≃ 7 and a shallower d β / d log 10 ( M ⋆ / M ⊙ ) at z < 11 than seen by the Hubble Space Telescope, unveiling a new population of low-mass, faint galaxies reddened by dust produced in the stellar winds of asymptotic giant branch stars or carbon-rich Wolf–Rayet binaries.

We summarize the properties and initial data release of the JADES Origins Field (JOF), the longest single pointing yet imaged with the James Webb Space Telescope (JWST). This field falls within the GOODS-S region about 8′ southwest of the Hubble Ultra Deep Field (HUDF), where it was formed initially in Cycle 1 as a parallel field of HUDF spectroscopic observations within the JWST Advanced Deep Extragalactic Survey (JADES). This imaging was greatly extended in Cycle 2 program 3215, which observed the JOF for 5 days in six medium-band filters, seeking robust candidates for z > 15 galaxies. This program also includes ultradeep parallel NIRSpec spectroscopy (up to 91 hr on source, summing over the dispersion modes) on the HUDF. Cycle 3 observations from program 4540 added 20 hr of NIRCam slitless spectroscopy and F070W imaging to the JOF. With these three campaigns, the JOF was observed for 380 open-shutter hours with NIRCam using 15 imaging filters and two grism bandpasses. Further, parts of the JOF have deep 43 hr MIRI observations in F770W. Taken together, the JOF is one of the most compelling deep fields available with JWST and a powerful window into the early Universe. This paper presents the second data release from JADES, featuring the imaging and catalogs from the year 1 JOF observations.