We conduct a comprehensive study on dropout galaxy candidates at z∼9−17 using the JWST/NIRCam images taken by the ERO, ERS, and GO programs. We carefully apply a secure photo-z selection criterion and conventional color criteria with confirmations of the ERO, ERS, and GO NIRSpec spectroscopic redshifts. Using the first 90 arcmin2 data, we obtain a total of ~20 dropout galaxies at z∼9−17, including two candidates at zphot=16-17 with the latest NIRCam calibration. We derive the UV luminosity functions at z∼9−17, and confirm that our UV luminosity functions at z∼9 and 12 agree with those determined by previous studies. The cosmic SFR density decreases from z∼9 to 12, and perhaps to 17, but the densities at z∼12−17 are higher than the constant star formation efficiency model. Interestingly, there are six bright candidates at z∼11−17 with MUV<−19.5. Because a majority of them show no signatures of AGNs in their morphologies, the high cosmic SFR densities and the existence of these UV-bright galaxies are explained by no suppression of star-formation by the UV background radiation at the pre-reionization epoch or an efficient UV radiation production by a top-heavy IMF possibly with Population III-like star formation. In this talk, I will also present the latest results from new NIRCam datasets including a lensing field to probe the faint end of the luminosity function calibrated with NIRSpec spectroscopic data obtained so far.
The emergence of the first galaxies had a profound effect on the Universe, beginning its last major phase-transition, the Epoch of Reionization. Finding and characterizing early objects has thus far proved challenging owing to their rarity and apparent faintness. The arrival of JWST’s infrared capabilities thus opens a new window to study early galaxy evolution. In this talk I will summarize the GLASS-JWST ERS survey and the first z>8 results from spectro-photometric analyses using NIRISS and NIRCam over the Abell 2744 cluster. We showcase the power of JWST to peer deep into Reionization, when most intergalactic hydrogen is neutral, by confirming two lensed galaxies via their Lyman Breaks with NIRISS, placing them at redshifts z~8. The absence of emission line indicators (e.g., Lyα, NV, HeII), blue UV slopes (< −1.7) and moderate absolute magnitudes (MUV~ −20 AB) suggest these objects are young, dust-poor, and representative of general z~8 populations that have thus far been missed.
At higher redshifts, we further report the discovery of two unusually luminous (MUV~ −21) galaxy candidates at z>10, via analyses of multi-band NIRCam imaging in parallel fields. The discovery challenges the expected number density of galaxies in such volumes. Exploiting JWST-ALMA synergy, we spectroscopically verify the most distant NIRCam candidate via [OIII] 88 micron emission with ALMA, revealing a 5.5σ emission line at z=12.117 and a dust-/metal-poor system in the early universe.
I will present the recent discovery of a significant number of new candidate high-redshift (z > 6.5) galaxies in the early Universe using the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) GTO survey, as well the most up-to-date public surveys, such as now completed CEERS survey. This is currently the largest JWST investigation of its kind to date, with over 100 square arcmins spanning 6 fields to some of the greatest depths reachable thus far. I will present the details of our z>6.5 sample of more than 160 galaxies, including many new candidates between 12<z<20, significantly increasing the number of galaxies known at this epoch. My talk will describe how our robust sample at the highest redshifts is found, present the first robust UV luminosity function at z > 10 based on these galaxies, and show preliminary results studying the first stellar mass and star forming properties of a statistical sample at these redshifts. I will conclude with the implications of our results for the theoretical ideas behind galaxy formation as well as what our novel results imply about reionization.
JWST has ushered in a great new golden age of astronomy, opening the possibility of discovering and characterising primordial galaxies deep within the epoch of reionisation (EoR). In these early days of JWST, it is therefore imperative to establish the feasibility and best practices for identifying true high-redshift systems. In this talk I will therefore share JWST’s early glimpse of EoR galaxies in the SMACS 0723, GLASS and CEERS fields, for which both NIRCam photometry and NIRSpec spectroscopy are available. I will discuss how effective SED fitting and colour selections are at identifying EoR galaxies from NIRCam photometry alone. Furthermore, I will highlight the physical properties of these galaxies, demonstrating that the four SMACS0723 galaxies all sit at the extreme ends of theoretical predictions from numerical simulations. Indeed, these EoR galaxies exhibit similar properties to intensely star-forming dwarf galaxies in the local Universe, indicating that such “extreme” conditions are likely the norm, rather than the exception, in the EoR. Additionally, I will introduce a set of photometric and spectroscopic diagnostics that I have developed to identify potential first galaxy candidates, i.e. chemically pristine Population III galaxies in the EoR. Utilising the most comprehensive JWST dataset thus far (by combining public data with proprietary PEARLS GTO data), I will reveal whether any convincing Pop III candidates have been identified from the early Webb data. Finally, I hope to close by highlighting both the discovery and the properties of the first passive galaxies emerging at cosmic dawn.
Within the MIRI European Consortium (MIRI-EC) guaranteed time observations (GTO), 60 hours of telescope time will be invested on MIRI imaging in the F560W filter of a single pointing centered on the Hubble Ultra Deep Field (HUDF). Parallell observations will be obtained with NIRCAM (~40 hours, imaging) and NIRISS (20 hours slitless spectroscopy) targeting two other areas within GOODS-S with available HST imaging. The observations are scheduled for December 2022. We will describe observational strategy and the science goals, and report on the first scientific results.
The first images from the JWST show a huge number of z>12 galaxies, breaking the previous record held by the Hubble Space Telescope. But are these galaxies at extremely high redshift expected ? To try to answer this question, one can combine both imaging and spectroscopic data from JWST and HST to study the stellar populations within the first billion years of the Universe. Several conclusions arise from these studies : (i) star formation is expected at z>15 and (ii) in one JWST pointing we estimate that ~33% of the galaxies at z>8 show mature stellar population formed at z>12.
I will review the JADES GTO survey spectroscopy of z>6 galaxies in the GOODS fields (including the HUDF).
We have spectroscopically confirmed many galaxies within the epoch of reionization selected through the Lyman break technique, in many cases detecting strong emission lines and allowing us to infer the ISM conditions.
In particular, we determine a spectroscopic redshift of z=10.6 for GN-z11 (the brightest Lyman break at z~11 in GOODS-North) which unexpectedly shows Lyman-alpha in emission, and some rarely-seen lines of nitrogen.
We report an investigation of the deep JWST survey in the SMACS0723 cluster, analysing NIRCam and MIRI images. We search for sources in the F444W band that are undetected in the F200W catalogues. We characterise the main properties of these sources via detailed SED modelling that account for a wide set of parameters and star formation histories, after a careful determination of their photometry. Among a robust sample of 20 candidates, we identify a mixed population of very red sources. We highlight the identification of candidate evolved systems, with stellar masses M*~10^(9-11)Msun at 8<z<13 characterized by unexpectedly important dust content at those epochs (Av up to ~5.8mag), challenging current model predictions. We further identify an extremely red source (F200W-F440W~7mag) that can be reproduced only by the spectrum of a passive, quenched galaxy of M*~10^11.8Msun at z~5, filled of dust (Av~5mag).
The sources of ionizing photons to reionize the early Universe set the initial conditions for subsequent galaxy formation and evolution. However, direct empirical constraints on the number of ionizing photons emitted by the first galaxies have been challenging to estimate. Here, we present the first glimpse into the total number of ionizing photons emitted by a sample of redshift 6-9 star-forming galaxies observed with the MSA on JWST/NIRSpec. This 22 hour integration of a single pointing in the GOODS-North field reveals deep rest-frame near ultraviolet and optical features that trace the intrinsic production and escape of ionizing photons from bright galaxies within the epoch of reionization. In particular, these observations cover the faint Mg II emission lines, which are sensitive to the neutral gas opacity, and consequently the ionizing escape fraction, within these galaxies. Additionally, Balmer emission lines provide estimates for the intrinsic production of ionizing photons. Combined these two quantities estimate the total number of ionizing photons emitted by galaxies within the epoch of reionization into the circum-galactic medium. These new JWST observations will provide empirical constraints for what may have driven cosmic reionization and demonstrate the capabilities of the JWST/NIRSpec to achieve deep restframe optical observations during the epoch of reionization.
The James Webb Space Telescope (JWST) was built to reveal the earliest moments of cosmic history and the faintest objects driving reionization. This goal drove the design of the Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) Cycle 1 Treasury program. The UNCOVER survey includes a first epoch of ultradeep imaging (~30AB without lensing, and down to ~32AB with extreme magnification) covering ~24 sq. arcmin on and around the well-studied Abell 2744 galaxy cluster at z=0.308, expected in late October/early November 2022. Within Cycle 1 (July 2023), the program will follow-up ~500 background JWST-identified galaxies with extremely deep (up to ~20 hours, to ~29AB) low-resolution spectroscopy with the NIRSpec/PRISM. These high S/N continuum spectra will yield secure redshifts for nearly all targets but will also uncover the physical nature of these galaxies. Our program also includes NIRISS and NIRCam parallel imaging to expand the deep imaging footprint to ~45 sq. arcmin. In this talk, we will present our first results, highlighting unparalleled resolved and ultradeep 2-4 micron imaging of known and previously unknown objects in the field. We will also give an overview of public data releases including early imaging mosaics and photometric catalogs.
JWST has expanded our cosmic horizon to the first few hundred million years after the Big Bang (redshift > 10), enabling us to observe the build up of the first galaxies and understand how they reionized intergalactic hydrogen in the first billion years. Excitingly, an excess of luminous galaxy candidates at z>10 has been discovered in early JWST data, which exceeds theoretical predictions. I will discuss how the new JWST observations test theoretical models and possible solutions. I will also discuss efforts to constrain how the first galaxies reionized the universe, both by using new JWST data from the GLASS ERS program to measure the ionizing photon output of high redshift galaxies, and by constraints on the ionization state of the IGM from Lyman-alpha spectroscopy.
Over the past decade, a wealth of imaging data have revealed that the brightest reionization-era galaxies often exhibit young ages and strong nebular line emission, hinting at high ionizing efficiency among early galaxies. However, Spitzer/IRAC’s limited sensitivity has long hindered efforts to study the fainter, more numerous z>6 population often thought largely responsible for reionization. In this talk, we present a study of the star-forming and ionizing properties of >100 UV-faint (Muv ~ -19.5) z~6.5-8 galaxies utilizing CEERS NIRCam data. We find that the observed rest-UV+optical SEDs are typically dominated by light from young, low-mass stellar populations with morphologies reflecting very active star formation and galaxy assembly. Folding in previous results of much brighter z~7-8 galaxies, we find evidence for a strong increase in sSFRs towards lower luminosities, implying a more dominant contribution from OB stars to the emergent light. We discuss implications for ionizing efficiency, arguing that faint reionization-era galaxies likely produce 2-3x more ionizing photons than originally expected while perhaps simultaneously being efficient leakers. Despite the much larger sSFRs towards fainter UV luminosities, we find little increase in the equivalent widths of [OIII]+H-beta. We discuss how, if confirmed, this may indicate the emergence of extremely metal poor galaxies among the UV-faint z~7-8 population, though high ionizing photon escape fractions or bursty star formation histories can also weaken the nebular lines in a subset of the galaxies.
Understanding the ionizing properties of galaxies in the epoch of reionization has been at the forefront of galaxy evolution studies ever since such systems were first identified.
Campaigns using HST have demonstrated that galaxies in this era typically have blue UV slopes, suggesting they host populations of young, low metallicity stars, which are capable of significant ionizing radiation production. In this talk I will present UV slopes of z>7 derived using NIRCam imaging from the CEERS and JADES programs, demonstrating improved constraints owing to the sensitivity of JWST, and large samples that are now available at these redshifts. Among this population, a sample of galaxies with extremely blue UV slopes (beta~-3) have emerged, whose SEDs are challenging to describe with standard models and assumptions. We discuss the escape of ionizing radiation as a prominent solution, as it facilitates the reduction of nebular continuum, revealing the intrinsically blue stellar continuum. We present the sample of extremely blue UV slopes that are robustly identified in JWST imaging, and discuss the implications for the escape of ionizing radiation among the z>7 galaxy population. Further insights into the stellar populations and ionizing properties of galaxies are provided by JWST spectroscopy at lower redshift. We present early results utilizing spectroscopic measurements of Halpha combined with the UV continuum to uncover the properties and ubiquity of recent star formation at z~5. Finally, we discuss their implied ionizing properties of these sources, and insight gained for the ionizing properties of reionization-era systems.
We present the early results from the EIGER survey (Emission-line galaxies and Intergalactic Gas in the Epoch of Reionization), a 116-hr NIRCam wide-field slitless spectroscopy (WFSS) campaign in the fields of six high-redshift quasars. The program is complemented by deep optical-NIR spectroscopy of the quasars and observations with MUSE, KCWI, ALMA, and HST.
First data in the field of z=6.33 hyperluminous quasar J0100+2802 yielded a sample of >110 confirmed [OIII]5008-emitting galaxies over z=5.3-7. These galaxies typically have very high [OIII] EWs (rest-frame ~1000A), low metallicities (~0.1 solar), and often exhibit
complex morphologies, unlike what is observed locally. Correlating the [OIII]-emitter sample to the quasar’s Lyman-alpha forest data enabled us to determine the dominant sources of the ionizing radiation at different epochs. We discovered three strong overdensities, respectively, within the quasar near zone (z=6.19), around the quasar itself (z=6.33), and in the background (z=6.78). These are likely progenitors of massive structures in the present day universe. We also characterized the earliest supermassive blackhole triggering this most luminous quasar and its host galaxy, and identified ~17 galaxies that are likely to host the known metal-absorption systems over 4<z<6.3, unveiling the physical processes in the circumgalactic media of the varying ionization conditions. Our presentation will also include further results from the upcoming observations in three more quasar fields scheduled in December–January.
Understanding the role of first galaxies in the Reionization of the Universe needs a synergy between theory and observations. Here we present our effort on JWST forecasts, using a large sample of galaxies extracted from the FirstLight simulations, we show the diversity of [OIII] emitters at the end of the reionization epoch (EoR). We find a 1 dex range in the equivalent width of the [OIII] line, even among galaxies with similar UV properties. This is driven by a factor 40 variation in the specific star-formation rate (sSFR). Variations in nebular metallicity and ionization parameter lead to a scatter in the equivalent widths at a fixed sSFR. This also drives large variations in the spatial extent of the line-emitting regions. These results allow us to make predictions for approved JWST Cycle 1-GO program on a complete sample of LAEs/LBGs at redshifts above 6 identified as [OIII]88um emitters with ALMA. (Alvarez-Marquez et al. 2021). The comparison between simulations and JWST multi-wavelength imaging and spectroscopy, in conjunction with ancillary ALMA data, will provide key insights on the early stellar mass and galaxy assembly in the EoR, and the relevance of [OIII] emitters in the reionization of the universe.
The Wide-Field Slitless Spectroscopic (WFSS) mode of JWST/NIRCam is becoming a game changer for the study of the high-redshift Universe. The in-flight spectroscopic sensitivity of this mode is 20-40% higher than the pre-launch prediction, and it started to unveil the rest-frame optical emission lines (e.g., [OIII] 5007 and Halpha) of z>6 galaxies even with the shallow (10~20-min integration) commissioning data taken in April 2022. In our two recent works, we discovered four [OIII]+Halpha line emitters at z>6 using the flux-calibration data of NIRCam/WFSS. In the [OIII]/Hbeta-[NII]/Halpha BPT diagram, these sources occupy the same parameter space as that of z~2 star-forming galaxies, indicating that they have been enriched rapidly to sub-solar metallicities (~0.6 Zsun), similar to galaxies with comparable stellar masses at much lower redshifts. We also obtained the first direct measurement of the [OIII] λ5007 and Halpha luminosity functions (LFs) at z>6. We found substantial brightening of the [OIII] λ5007 line LF from z=3 to 6, while little redshift evolution of the Halpha line LF from z=2 to 6. Both LFs are under-predicted at z∼6 by a factor of ~10 in certain cosmological simulations. Our studies suggest an enhanced ionizing photon production rate and the ubiquity of strong Halpha and [OIII] line emitters in the early Universe, both of which will be further uncovered in the era of JWST.
Exploring the formation of the first galaxies in the early Universe requires the use of innovative instruments and tools beyond our current facilities. The James Webb Space Telescope (JWST) has arrived to revolutionize our understanding of the early Universe, and will open a window into the almost uncharted Epoch of Reionization (EoR). This talk will present the early results of the medium-size GO1 JWST program (#1840) titled “ALMA [OIII]88um Emitters: Signpost of Early Stellar Buildup and Reionization in the Universe''. It combines NIRCam imaging and NIRSpec high-resolution integral-field spectroscopy (IFS) for a large sample (12) of LAEs/LBGs at redshifts between 6 to 8.4 identified as [OIII]88um emitters with ALMA. The combination of JWST and ALMA will establish for galaxies in the EoR: i) the age and mass of the stellar population, ii) the structure of the stellar population and ionized gas nebula, and iii) the physical conditions, kinematics and ionization status of the ISM. At the time of the conference, we expect to hold 4/12 galaxies with NIRSpec IFS observations, and 10/12 galaxies with NIRCam imaging observations.
Over the last few years, low-resolution infrared observations have revealed a population of optically-dark galaxies undetected with HST, the so-called HST-dark galaxies. We know that these galaxies are likely to be massive and at z>3. However, due to the limited photometry in infrared wavelengths, the true nature of these galaxies has remained elusive. For the first time, the JWST is providing data that allows us to characterise these galaxies.
In this talk, I will present the results of 33 HST-dark sources selected based on their red colours across 1.6 to 4.4 microns with NIRCam imaging from the Early Release Science Program CEERS. These galaxies are generally heavily dust-obscured, massive, star-forming sources at z~2-8. Our analysis shows the unique power of JWST to reveal this previously missing galaxy population and to provide a more complete census of galaxies at z=2-8 based on rest-frame optical imaging. Interestingly, HST-dark galaxies present a considerable contribution to the obscured star formation red density at z~7, already in the Epoch of Reionization.
I will also present the first spectra of HST-dark galaxies with NIRSpec observations to show for the first time their spectroscopic redshifts from my program 'Quiescent or dusty? Unveiling the nature of extremely red galaxies at z>3'.
We use JWST data from the CEERS survey in the Extended Groth Strip, jointly with HST observations from AEGIS and CANDELS, to select and study in detail near-infrared faint, mid-infrared bright galaxies, previously known as HST-dark sources. These datasets allow to address the problem of characterizing this type of galaxies with the innovative approach of using spatially resolved optical-to-mid-IR spectral energy distributions to estimate photometric redshifts and stellar populations properties in 2 dimensions. We anticipate that this methodology will be very valuable for JWST-based studies of galaxy evolution. We find that the red color limit implies a selection of dusty and quiescent galaxies with masses log(M/M_sun)=9-11 and redshifts between z=2.5 and z=7. Among the galaxies in our sample, we find a dozen systems dominated by evolved stellar populations at redshifts as high as z=5, more precisely, in a post-starburst stage. Their star formation histories started beyond z=20 and they could have formed masses as high as 10^10 M_sun by z=10-15 (in one or several progenitors), implying a very efficient star formation in the Universe at very early cosmic epochs, consonant with the large number of very high-z (z>10) galaxies found with the first (relatively shallow) JWST datasets.
Recent studies have shown that galaxies at cosmic noon are redder in the center and bluer in the outskirts, mirroring results in the local universe. However, investigating the physical causes is impossible with HST photometry, which traces the rest-frame optical. Longer wavelengths are needed. In this talk I will present recent results investigating the causes of color gradients in the early universe using JWST. We use NIRCam images from the CEERS survey to construct resolved spatially-resolved rest-frame U-V vs. V-J color-color diagrams for a sample of 54 galaxies at z~2. We model the light profiles using imcascade, a Bayesian implementation of the Multi-Gaussian expansion technique which flexibly represents galaxy profiles using a series of Gaussians. We find star-forming galaxies generally have red centers and blue outskirts in both U-V and V-J colors implying strong central dust attenuation with a smaller fraction showing gradients in star-formation. In quiescent galaxies we find a diversity of U-V and V-J color profiles, with roughly one-third showing star-formation in their center. These results showcase the potential of JWST to study the resolved stellar populations of galaxies at cosmic noon.
We report the discovery of a galaxy protocluster at z = 5.4 in the GOODS-S field using JWST/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide field slitless spectroscopy from FRESCO. Potential protocluster members were identified using HST+JWST photometry spanning wavelengths of 0.4-5.0 microns. These data provide accurate and well-constrained photometric redshifts down to apparent AB magnitudes of 29-30 by tracing the Balmer alpha excess in the F410M filter relative to the F444W filter. Potential protocluster members were spectroscopically confirmed using JWST slitless spectroscopy over wavelengths of 3.9-5.0 microns through a targeted emission line search for Balmer alpha around the best-fit photometric redshift. We verified 43 galaxies residing in an overdensity around ~10 times that of a random volume in addition to 53 galaxies residing in the field at z = 5.2-5.5. Stellar populations for these 96 galaxies were inferred from the photometry and used to construct the star-forming main sequence, where protocluster members appeared more massive and evolved when compared to their field galaxy counterparts. We estimate the total halo mass of this large-scale structure to be 12.5 < log10(Mhalo/Mstar) < 13.5 using an empirical stellar mass to halo mass relation, although this is likely an underestimate based on our selection criteria and assumptions. Our discovery demonstrates the power of JWST at constraining dark matter halo assembly and galaxy formation at very early cosmic times.
I present an overview of the 200 hours GTO program CANUCS. Using imaging and spectroscopy of lensing clusters and flanking fields from all three near-IR instruments on JWST, CANUCS enables a diverse set of studies probing galaxy evolution from the earliest epochs through to redshift 0.4. I will describe the data collected so far and some of the early science results.
One of the most puzzling discoveries of the decade is that substantial populations of massive galaxies ceased forming stars as early as two billion years after the Big Bang (i.e. by z = 3). These are likely some of the first galaxies in the Universe, yet we have failed to understand how they form and evolve. In order to piece the evolutionary puzzle together, we must capture massive galaxies at all phases of their evolution, from gas-rich star formers to post-starbursts to fully quiescent systems. Due to the rarity and diversity of the massive galaxy population at z > 3, such an endeavor requires a combination of wide-field observations from the UV to millimeter. In this talk, I will present a first look on the JWST-derived stellar properties of massive, gas-rich star forming galaxies at z > 3 detected in the Ex-MORA 2mm Survey -- the largest ever ALMA blank-field survey. Ex-MORA was designed to capture massive z > 3 galaxies that are too dust obscured to be detected in most pre-JWST UV/optical surveys. I will also present a preliminary sample of massive post-starburst and quiescent galaxies at z > 3 selected via a new technique using data from incoming Cycle 1 JWST wide-field surveys. Finally, I will discuss ongoing and future plans for leveraging these two samples to generate a robust census on massive galaxy evolution during the first 2 Gyr of the Universe.
The first images taken with the James Webb Space Telescope (JWST) are unveiling galaxies in the distant universe and enabling detailed studies of their properties. In this talk, I will present some of the first results on how our understanding of the growth of galaxy structure in the universe has changed based on these first images. We have conducted a comprehensive analysis of the evolution of the morphological and structural properties of a large sample of galaxies at z=3-9 using the NIRCam images at 1-5 microns taken as part of the Cosmic Evolution Early Release Science (CEERS) Survey. Our team conducted a set of visual classifications, with each galaxy in the sample classified by three different individuals. We also measured quantitative parametric and non-parametric morphologies using the publicly available codes Galfit, Galapagos-2/GalfitM, and statmorph across all seven NIRCam filters. Using these measurements, I will present the morphologies of these high redshift galaxies, their structural properties, and the fraction of each type as a function of redshift. I will also compare their morphologies to what we knew based on Hubble imaging, and discuss the implication of these results for galaxy evolution. Finally, I will also highlight some early results on galaxy morphologies from PRIMER and COSMOS-Web observations.
We present an analysis of the evolution of the morphological and structural properties of a sample of high-redshift galaxies using the early-release JWST CEERS NIRCam observations. Our sample consists of 382 galaxies at z > 4 that overlap with the CANDELS EGS catalog, detected in four CEERS pointings with seven NIRCam filters. We perform two-dimensional, simultaneous, multi-band model fitting to investigate the overall morphological properties of the galaxies in their rest-frame optical wavelengths to quantify the global properties of the galaxies, as well as subcomponents such as bulges, disks, nuclei, bars, and spiral arms. We compare and contrast the results derived from three fitting codes: standard GALFIT, GALFITM, and a newly developed version GALFITS. We study the error budget of the derived structural parameters using realistic mock images, taking into account systematic uncertainties due to the choice of fitting method, the point-spread function, and cosmological dimming and resolution effects. We discuss the physical implications of the results in the context of the evolution of the Hubble sequence and its connection to the galaxy population at cosmic noon.
TEMPLATES is a JWST Early Release science program to study four extremely bright gravitationally lensed galaxies with NIRSpec IFU spectra, MIRI IFU spectra, and MIRI and NIRCam imaging. I will summarize early science results from the TEMPLATES program, including large morphological differences among different tracers of star formation (PAHs, far-IR, Paschen alpha), and early results on the metallicity and ionization conditions. I will also summarize what high-level data products (reduction notebooks and science-ready data products) we are preparing for the community, and lessons learned about planning integral field spectroscopy with JWST.
The ionizing spectral energy distributions (SEDs) of young stellar populations are a key ingredient in studies of galactic star formation histories, feedback, and nebular emission. While observations indicate that galaxies’ ionizing spectra become significantly harder at low metallicity, current stellar population models struggle to reproduce the observed high-ionization emission lines. Observationally, constraining the ionizing spectral shape with UV+optical emission lines is difficult, given uncertainties due to attenuation, underlying stellar spectral features, relative abundances, and radiative transfer effects.
I will present the first results from an exciting JWST Cycle 1 program using MIRI/MRS spectroscopy to measure a suite of nebular emission lines with ionization potentials of 22-97 eV that will constrain the ionizing spectral shape of low-metallicity, extreme emission-line galaxies. Additionally, the spatially resolved emission-line data will map the ionization structure of different star-forming knots and trace the propagation and escape of ionizing radiation.
Using JWST ERO and GTO JADES data, I will present new results on the growth histories of early galaxies. Specifically, I will discuss the stellar population properties of F115W dropouts, with the focus on stellar masses, star-formation rates, and star-formation histories of galaxies at redshift z>9. I use those measurements then to discuss the mode of early star formation, such as star-formation surface densities and integrated star-formation efficiency by looking at the stellar-to-halo mass relation. For galaxies where we have constraints on the gas-phase metallicity, I will discuss how star-bursting galaxies can have very different gas-phase metallicities due to internal and external mechanisms that drive the star-burst. I will highlight that there are clear indications for pristine gas inflow that can drive very concentrated star formation.
How do bulges form in high-redshift galaxies? What are the differences in age, star-formation rate, and stellar mass between bulges and discs? What are the nature of high-redshift bulges — classical or pseudo — and how do they compare to bulges of local galaxies? I will address these questions using the JADES survey, the most extensive extragalactic survey with JWST. I will present new results from bulge-disc decompositions of >20k galaxies, using a new photometry and morphology tool called Forcepho. I will briefly highlight the technical limitations of bulge-disc decompositions including effects of PSF (size of galaxy vs FWHM of PSF), redshift and luminosity. I will then focus on the SED-fitting obtained with Prospector to investigate the stellar masses, the star-formation rates and stellar ages of the bulges and discs in order to assess their growth rates, thereby presenting constraints on in-situ and ex-situ bulge formation mechanisms.
Ratios of rest-frame optical emission lines provide one of our most powerful and well-studied tools for studying conditions in the interstellar medium (ISM) of galaxies.
While such studies have long been conducted for large samples of low- and intermediate-redshift galaxies, until recently, probing the early epochs of galaxy assembly at redshifts beyond z > 6 in this way was simply not possible.
However, the advent of JWST/NIRSpec has changed this landscape, enabling unprecedented new insights into the ISM properties of galaxies within the first 1 Gyr of galaxy assembly.
Early observations of star-forming galaxies in this epoch have already found extreme line ratios suggesting that the ISM conditions may differ significantly different to those in lower-redshift galaxies.
In this talk, I will present an initial census of emission line ratios for z~6-9 galaxies from the JADES survey. These results include our "Deep" tier - the deepest spectroscopic observations scheduled for Cycle 1. I will discuss what this census already reveals about the conditions in the ionized ISM, and the sources powering this emission.
These initial findings will be critical for refining models of the high-redshift ISM which in turn will be important for adequately interpreting the deluge of z>6 emission line measurements that will be delivered by JWST over the coming years.
The unprecedented infrared capabilities, high sensitivity, and high angular resolution of JWST compared to its predecessors open a new window to study properties of ISM dust grains across redshifts: from high-resolution resolved observations of dust emission in the local Universe to the first view of obscured star formation in individually detected typical and low mass galaxies at cosmic noon (z~1-3), and dust attenuation properties in rest-frame UV emission of galaxies in the reionization era. I this talk, I will review preliminary results on the properties of dust across redshifts from three different JWST cycle 1 surveys: 1) how the PAH emission varies with UV absorption and stellar population properties in resolved regions of local galaxies (PHANGS survey), 2) dissecting dust emission from AGN and star formation activity in the mid-IR and studying obscured star formation fraction down to an order of magnitude lower stellar masses than has ever been possible (multi-band MIRI US-GTO survey), and 3) dissecting properties of dust grains by observing dust attenuation in the rest-frame UV spectra of galaxies at z~4-7 (JADES survey).
Interstellar dust captures a significant fraction of elements heavier than helium in the solid state and is an indispensable component both in theory and observations of galaxy evolution. Dust emission is generally the primary coolant of the interstellar medium (ISM) and facilitates the gravitational collapse and fragmentation of gas clouds from which stars form, while altering the emission spectrum of galaxies from ultraviolet (UV) to far-infrared wavelengths through the reprocessing of starlight. However, the astrophysical origin of various types of dust grains remains an open question, especially in the early Universe. In this talk, I will present direct evidence for the presence of carbonaceous grains from the detection of the broad UV absorption feature around 2175 Å in deep JWST/NIRSpec spectra of galaxies up to the first billion years of cosmic time, at a redshift of z ~ 7. This dust attenuation feature has previously only been observed spectroscopically in older, more evolved galaxies at redshifts of z < 3. The carbonaceous grains giving rise to this feature are often thought to be produced on timescales of hundreds of millions of years by asymptotic giant branch (AGB) stars, while our results suggest a more rapid evolutionary scenario for the growth of dust grains.
We aim to characterise the physical processes of the galaxies responsible for reionising the Universe. Through the analysis of spatially resolved Lyman alpha and H-alpha emission we trace the regions where ionising photons are produced and where they are attenuated, while measuring the properties of the galaxies.
Our sample consists of ~20 Lyman alpha emitters at z~5.4-6.6, all of which have certain spectroscopic redshifts from MUSE. The NIRCam Medium Band Survey provides us with F182M and F210M images to constrain the rest-frame UV continuum, and thus, reduce dust attenuation uncertainties in SED fitting. In addition, we use F430M, F460M and F480M to measure H-alpha, in combination with Cloudy models to disentangle the contribution of [NII] emission in our measurements.
We provide direct constraints on the ionising photon production efficiency in these galaxies, and provide a framework to expand this work to larger samples.
I will discuss the emerging picture on the chemical properties of high-redshift galaxies, mainly leveraging early data from the joint NIRCam-NIRSpec GTO Survey JADES. Deep spectroscopic observations of tens of galaxies with emission line detections up to z~10 allows us to characterise the evolution of the metallicity scaling relations across the cosmic time, shedding light onto the processes driving galaxy assembly in the early Universe. In the same framework, I will also introduce the 'MARTA' Survey, a 'very deep' (up to ~36 hours on source in G140M/F100LP + 7 hours in G235H/F170LP) Cycle 1 NIRSpec programme (scheduled in May 2023) aimed at robustly measuring the metallicity in z~2-3 galaxies with the Te method via the detection of auroral lines, and hence at performing a self-consistent recalibration of the main oxygen abundance indicators for the high-z Universe.
I will discuss several key results from ERS and JWST Cycle 1 programs aimed at understanding the ionizing radiation field, ionized ISM, and dust contents and bolometric star-formation rates of high-redshift galaxies. First, I will present an analysis of JWST/FRESCO data to probe the slope of the relationship between [OIII] equivalent width and mass for EOR galaxies and the identification of very low-metallicity galaxies. Second, I will discuss JWST/ERS (and forthcoming JWST/AURORA and LyC22) data that can be used to assess the physical conditions in low-mass galaxies at z~2-7 and explore the connection between gas density and ionization parameter. Third, I will present preliminary results from FRESCO on the nebular dust reddening and bolometric SFRs of galaxies at z~1.5-3.0 based on combining ground-based Balmer line measurements with Paschen lines detected with JWST. Finally (and time permitting), I will show how JWST/LyC22 can be used to extend existing analyses probing the correlations between Lyman Continuum escape and indirect proxies for such escape.
Understanding the evolution of the interstellar medium across cosmic time is one of the key open issues in modern astrophysics where JWST is set to make substantial progress. One of the most exciting aspects of the JWST ERO observations was the detection of the faint auroral line [O III]λ4363 in three z>7 galaxies, allowing for the first time, direct method constraints on the metallicity of reionization epoch galaxies. However, perhaps the most striking spectral feature of these observations was the curiously high [O III]λ4363/[O III]λ5007 (RO3) ratio of 0.055 (when dust-corrected) for S04590 at z=8.50, which is unlike anything seen in the local Universe. This implies either extremely high electron temperatures, ~30,000 K or gas densities >10,000 cm^-3, or excessive recombination from OIV. I will discuss how physics such as the inclusion of high-mass X-ray binaries or a high cosmic-ray background in addition to a young, low-metallicity stellar population can provide the heating necessary to explain the observed high RO3 while remaining consistent with other observed line ratios. Furthermore, I will show that such high temperatures can bias metallicity measurements low, which can have a substantial impact on how we chart the metallicity evolution of the Universe. Our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the Epoch of Reionization.
We present JWST/NIRSpec Integral Field Spectrograph rest-frame optical data of the compact z=5.55 galaxy GS_3073. Its prominent broad components in several hydrogen and helium lines (while absent in the forbidden lines), and the detection of a large equivalent width of He II4686, EW(He II)~20 Angstrom, unambiguously identify it as an active galactic nucleus (AGN). We measure a gas-phase metallicity of Z_gas/Z_sun~0.21, lower than what has been inferred for both more luminous AGN at similar redshift and lower redshift AGN. We empirically show that classical emission line ratio diagnostic diagrams cannot be used to distinguish between the primary ionisation source (AGN or star formation) for such low-metallicity systems, whereas different diagnostic diagrams involving He II4686 prove very useful, independent of metallicity. We measure the central black hole mass to be log(M_BH/M_sun)~8.20. While this places GS_3073 at the lower end of known high-redshift black hole masses, it still appears to be over-massive compared to its host galaxy properties. We detect an outflow with projected velocity ≥700 km/s and an ionised gas mass outflow rate of about 100 M_sun/yr, suggesting that GS_3073 is able to enrich the intergalactic medium with metals one billion years after the Big Bang. We discuss our findings in the context of other recent JWST results on high-z AGN.
A broad census of the quasar population at z ~ 6 is now feasible with the identification of 162 low-luminosity quasars from the Subaru High-z Exploration of Low-Luminosity Quasars program (SHELLQs; e.g., Matsuoka et al. 2022). With the inclusion of those at higher luminosity, we can now begin to establish the black hole mass function, Eddington rate distribution, and connection with their host galaxies. On their hosts, ALMA has clearly demonstrated that low-luminosity quasars have plentiful molecular gas reservoirs and reside in typical star forming galaxies (Izumi et al. 2019). However, no telescope to date has detected the starlight from their host galaxies. For this purpose, we were awarded JWST observations of 12 low-luminosity quasars in Cycle 1 using NIRCAM plus NIRSPEC to measure their black hole masses. Here, we present the first JWST observations, analysis, and knowledge on optimizing the decomposition of quasar and host galaxy emission applicable to most JWST quasar programs.
Studying the host galaxies of high-redshift quasars provides vital insights into the early growth of supermassive black holes and the black hole—galaxy connection. JWST has launched a new era in this field, providing the opportunity to observe the stellar components of these host galaxies for the first time, due to its exquisite spatial resolution and infrared spectral capabilities. I will summarize the latest results from two JWST programs searching for these quasar host galaxies. With NIRCam we are performing detailed quasar subtraction on two quasars to detect the stellar continuum from their host galaxies for the first time; I will present results from the first quasar to be observed, SDSS J0129-0035 at z=5.8. In the NIRSpec Galaxy Assembly IFS GTO program we are observing six z>6 quasars with the NIRSpec IFU, with both high-resolution spectroscopy to study the key optical diagnostic lines, and at low-resolution to detect the host continuum. I will present our latest results, including the first reliable M_BH/M_dyn ratios at high-z, and a wide range of host properties, for example their interstellar medium structure and kinematics, star formation rates, and excitation mechanisms. Overall, I will summarize our latest results and outline the plans for the rest of our upcoming Cycle 1 observations.
TBC
BEAGLE is a Bayesian SED-fitting code which allows an efficient exploration of a variety of physical parameters affecting the spectra of galaxies. We have recently updated BEAGLE to also include models of the nebular emission from the Narrow-Line Regions (NLR) in Active Galactic Nuclei (AGNs). This new version of the code is therefore able to interpret the mixed emission-line signatures of AGNs and star-forming regions.
JWST has started its scientific journey and is delivering already several observations of different ERS programs. After checking the capabilities of the tool in a paper that explored the recovery of parameters in synthetic galaxy spectra, we are now ready to apply it to these first observations. We have selected, in particular, the various ongoing ERS programs and we will fit them with BEAGLE-AGN. No other tool can simultaneously constrain the stellar, nebular and NLR physical properties of galaxy spectra. We will therefore show unique analysis of the physical properties of the narrow-line and star-forming regions.
The luminous high redshift radio galaxy, TN J1338-1942 (z=4.11), is one of the most powerful radio sources known in the early Universe and is known to reside at heart of a significant over density of galaxies, making it a unique laboratory for studying both AGN feedback in action and the earliest stages of proto-cluster formation. I will present the first analyses of JWST NIRCam observations obtained as part of the ``Prime Extragalactic Areas for Reionization and Lensing Science'' (PEARLS) project. Our observations were designed to probe the key rest-frame optical continuum and emission line features at this redshift and enable detailed resolved spectral energy distribution modelling. Confirming previous observations, we find that TN J1338-1942 is one of the most massive galaxies at this epoch (M ~ 10^11 Ms), with powerful AGN jets that are driving radiative shocks and extensive recent star-formation. With the SFR attributed to the jet-triggered starburst conservatively estimated as >500 Ms/yr, the extraordinary scale of the jet-triggered star-formation activity highlights the potentially important but poorly understood role of positive AGN feedback in the earliest stages of massive galaxy formation.
Quasars are among the most active sources emerging in the early Universe (z > 6). Their host galaxies have stellar masses and star formation rates orders of magnitude higher than what is observed in typical galaxies at the same redshifts. Investigating these sources is thus necessary if we want to unveil how the first massive galaxies formed.
Here we present the first rest-frame optical spectrum of a z = 6.23 quasar obtained with the JWST/NIRSpec IFU. As shown by previous ALMA and HST data, the quasar presents two companion galaxies and lies within a prominent Ly-alpha halo. The NIRSpec data provide us with: 1) the rest-frame optical spectrum of the quasar, detected at superb S/N, that we can use to characterize the quasar phenomenology (black hole mass, accretion rate, outflows); 2) a map of the ionized gas in the system, and its complex velocity structure, that enables a detailed study of the dynamics within this system; 3) a chart of the photoionization conditions in the gas, that enables to shed light on the physics of the ISM (metallicity, hardness of the ionization field, powering source, etc); 4) a map of the halo seen in Halpha, that reveals resonance scattering as the main mechanism powering the Ly-alpha halo. These data offer a pristine insight on the assembly and early growth of the first massive galaxies and black holes.
Galaxy evolution studies have revealed that most galaxies follow a tight main sequence between their stellar mass and star formation rate (SFR), which evolves with redshift. But in addition to these ‘normal’ galaxies, there have been numerous detections of galaxies with exceptionally high SFRs for their given redshift and stellar mass. These ‘starburst’ galaxies are not representative of the underlying galaxy population, but they present a unique mystery: what causes their high levels of star formation? Early theories pointed to major mergers that introduce gas and induce shocks, but the detection of regularly rotating starburst galaxies at high redshift suggests that secular accretion may be more dominant. One such starburst galaxy (HFLS3, z~6.3) has been very well studied, revealing a multiple-component system within ~3”: a z~2 gravitational lens, two HST-detected sources, and a primary z~6.34 source that is a gas-rich (~10^11Msol), dusty (M_dust~10^9Msol) starburst galaxy (SFR~2900Msol/year). But these observations were at best marginally resolved, and further observations are required. Recently, we have observed the HFLS3 field with JWST NIRSpec-IFU (G395H/290LP; PID 1264). Initial results from this observation show multiple line detections for three sources at z~6.4 (Ha, [NII], [OIII]5007,4949, Hb) and a refined redshift for the lensing galaxy (z=3.48). In this presentation, I will present the current morpho-kinematic constraints on this complex field that are now made possible with the high-quality NIRSpec data.
The process of mass assembly in young galaxies is still poorly understood. Contrary to theoretical expectations, the first deep images from JWST have revealed a surprising number of high-redshift galaxies with disk-like morphologies. Measurements of the galaxy kinematics are crucial to confirm whether these galaxies are truly rotating disks, and to understand the evolution of these systems. Only JWST NIRSpec offers the sensitivity, resolution, and statistical power that are necessary to tackle these questions. In this talk, I will present the first results on the dynamical properties of the ionised gas in high-redshift galaxies from the first JADES spectroscopic observations. With a wealth of data still to come, I will discuss the prospects of using the multi-object spectroscopy mode of NIRSpec, enabled by the micro-shutter assembly, to perform statistical studies of (spatially-resolved) galaxy kinematics at high redshifts.
JWST/NIRSpec observations have been able to obtain spectroscopic confirmations for massive quiescent galaxies in the z>3 Universe. These galaxies were photometrically selected as massive (>2E10M_sol) bright (K~21-24) z~3-4 quiescent galaxy candidates from existing Hubble and ground-based K band observations. While 12 out of the 24 galaxies were spectroscopically confirmed by deep Keck/MOSFIRE observations, confirming the redshift or quiescence nature of the remaining 12 candidates were not possible from deep Keck/MOSFIRE and VLT/XSHOOTER observations.
With JWST GO observations from NIRSpec CLEAR/PRISM we are able to cover the 0.6-5 micron window of these 12 quiescent galaxy candidates to constrain there redshift and overall SED shape. At the time of writing observations of 8 quiescent candidates have been obtained over the UDS field, and rest of the program is scheduled to be completed in December 2022. In my talk I will show how the analysis of the first results suggest that these galaxies to be ~10E11M_sol quiescent galaxies and discuss their AGN nature. I will also show that the SFH contained through joint spectrophotometric fitting suggest a rapid buildup of stellar mass which may have implication for z>6 star-formation efficiencies and hierarchical galaxy growth scenarios. Since the program would be completed by March, I would also be able to discuss the “real” abundance of massive quiescent galaxies in the z>3 Universe as uncovered by JWST.
Despite many years of effort and detailed observations, even as of 2022 it is still not clear how or why galaxies quench their star formation. However, two clear channels of quenching have emerged: the low mass galaxies tend to quench via their environments, whilst the high mass galaxies are (probably, maybe) quenched by their AGN. Interestingly, the highest redshift (z>2) quiescent galaxies appear to predominantly be massive, and exhibit signs of ongoing or recent AGN activity, hinting that environmental quenching has yet to occur at such early times.
Not so! We present a sample of low mass, z~2 quiescent galaxies (including one galaxy at z~3.3) observed with the CANUCS survey. In this talk I will discuss results of their broad and narrow band SED fitting, grism redshift fitting, morphologies, star formation histories and environment, in order to build a comprehensive picture of low mass quenching at high redshift, and answer the crucial question: what killed these galaxies’ star formation?
Ground-based observations have identified and confirmed the existence of a potentially numerous population of massive quiescent galaxies up to z~4, a hard limit set by the atmosphere and previous technology. JWST held the promise to break this ceiling, look farther, and deeper to catch the earliest quenching galaxies. The first months of observations kept this promise and offer a spectacular new view on the first quiescent galaxies in the universe. In this talk, I will present the results of an analysis combining data from 11 fields with public JWST observations covering a total of ~150 sq.arcmin. By applying classical UVJ and new color selection optimized to identify recently quenched galaxies, we charted the population of quiescent objects at z>3 irrespectively of their masses. We retrieve number densities of massive objects in slight excess, but consistent with previous estimates. However, we found substantial field-to-field variations, implying a significant effect of cosmic variance and the presence of overdensities traced by red quiescent objects at z>3 - the possible mature progenitors of modern clusters. We will also introduce an intriguing population of low-mass quiescent galaxies that eluded pre-JWST analyses, potentially defying simple mass-quenching mechanisms in our evolutionary models.
What physical processes regulate star formation in dense environments? Understanding why galaxy evolution is environment dependent is one of the key questions of current astrophysics. The advent of JWST has opened many new pathways to answer these questions, opening an unprecedented view on the NIR wavelengths. Exploiting the deep observations taken in the context of the GLASS-JWST-ERS program (PI Treu) that targeted the massive cluster A2744 at z=0.3 — a key epoch as clusters are in a fast mass-growing phase —, I will show how galaxies are influenced by the cluster environment. Using NIRISS data, I will show the spatially resolved Paschen beta properties of ram pressure stripped galaxies and therefore characterise star formation typically hidden at optical wavelengths and quantify the presence of dust. Using NIRSpec data, I will show the NIR spectrum of a post stardust galaxy, providing a better timing to the quenching event. Using NIRCAM data that observed galaxies at different clustercentric distances, I will show how their morphology and star forming properties depend on their position within the cluster and their local environment. These first results will showcase the potentiality of JWST in understanding galaxy evolution in massive systems.
Directly observing the first quiescent galaxies - i.e. galaxies with no or negligible star formation activity at the epoch of observation - and determining the causes which quenched them (perhaps temporarily), is of utmost importance to constrain models of galaxy formation and transformation. To date, quiescent galaxies have been identified out to z<5; and are all found to be massive (M⋆ > 1010 M⊙). I will present the discovery of a of a quiescent, post-starburst galaxy at z=7.3 from the JWST JADES GTO survey. This galaxy exhibits a Ly drop, a Balmer break and complete absence of any emission lines. Its SFH consists of a short and intense burst terminating only 10-40 Myr before the time of observation. Crucially, this galaxy has a stellar mass of only 4–6×108 M⊙. This is a significantly lower stellar mass than any known high-redshift quiescent galaxy (redshifts 3<z<5), yet it is much larger than the maximum mass of reionization-quenched dwarf galaxies in simulations. Further, there are indications for the galaxy having low stellar metallicity [M/H] ≈ -2. This suggests that likely different physical mechanisms were dominantly responsible for quenching this galaxy. This galaxy lies in a pivotal mass range between ‘bursty’ and stable SFHs, and in which feedback from a primordial black hole or star formation might drive powerful outflows leading to (temporary) quiescence. The discovery of this galaxy calls for a detailed theoretical and numerical investigation of galaxy quenching at z>5 in the Epoch of Reionization.
JWST enables to study massive galaxies at redshifts 2-3, directly during the epoch when they became quiescent. We report JWST/NIRSpec IFS observations of a massive, post-starburst galaxy at redshift 3. This X-ray AGN has been previously identified as an obscured starburst. NIRSpec reveals spectacularly deep Balmer absorption features and low-equivalent-width Balmer emission, consistent with the post-starburst interpretation; non detection in the sub-mm rules out a large gas mass and therefore heavily obscured star formation. We detect exceptionally broad and bright OIII and NII; the emission-line ratios rule out star formation as the main source of ionisation; instead, we propose shocks or type-2 AGN as powering the emission lines, consistent with the X-ray interpretation. We detect fast outflows in both the warm ionised gas and in the neutral gas, evidence of ongoing ejective feedback. Finally, we measured spatially resolved stellar kinematics -- to our knowledge, the most distant measurement to date. The stellar rotation-to-dispersion ratio is high, therefore feedback was not sufficiently strong to destroy the stellar disc, a fact that constrains theoretical feedback models.
We analyze a collection of compact red objects around a remarkable z=1.38 galaxy ("The Sparkler") being strongly lensed by the SMACS 0723 cluster. Data from NIRISS and NIRCam were combined to allow us to probe the star-formation history of these "sparkles" in detail. We find them to be both red and quiescent - ideal candidates for globular clusters which formed at z>7. This discovery opens up the possibility of studying the growth of galaxies and their parent halos through investigation of quiescent globular cluster populations at higher redshifts than thought possible before JWST. The CANUCS Cycle 1 GTO program will look at five strong-lensing cluster fields with NIRISS, NIRCam & NIRSpec (four to be observed before March 2023), and will extend this dataset, allowing us to search for other galaxies with similar characteristics.
Passive galaxies are excellent sites to test galaxy formation models from parsec to gigaparsec scales via constraining the shape of the initial mass function at early times and tracing the hierarchical growth of dark matter haloes in ΛCDM. Due to the growing number of near-infrared imaging surveys and followup spectroscopic campaigns, we have detected robust passive candidates at z < 5 and constrained their key physical properties and star formation histories. This work has been limited to the brightest (Ks < 23 AB), most massive objects (M* > 10^10.5 M_\odot). We present JWST/NIRSpec PRISM spectra for a sample of 6 faint (F200W > 25 AB), low-mass passive galaxies at 3 < z < 6, identified behind the MACS0647 cluster. They have rest-frame colors typical of quiescent and post-starburst galaxies and lie ~0.5 - 1 dex below the star-forming main sequence at these redshifts. The strong lensing in the foreground cluster provides a unique opportunity to begin to uncover and study passive galaxies in the lowest mass regimes (M* ~ 10^8.5 - 9.5 solar masses). We confirm, for the first time, the existence of this population at these redshifts and explore their implications for quenching timescales and mechanisms in the early Universe.