The James Webb Space Telescope Mission

JWST was designed to address four science themes, which trace cosmic history from the Big Bang to planets conducive to life. The End of the Dark Ages: First Light and Reionization theme seeks to identify the first luminous sources to form and to determine the ionization history of the early universe. The Assembly of Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The Birth of Stars and Protoplanetary Systems theme seeks to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The Planetary Systems and the Origins of Life theme seeks to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems.

Observing time on JWST has been allocated by three methods: Guaranteed Time Observations (GTO), General Observers (GO) time, and Director’s Discretionary (DD) time. The GTO time consists of 4020 hours of JWST observations over the first three years, allocated to the four instrument teams and other scientists on the Science Working Group. The DD time consists of 10% of the time available for the lifetime of the mission. The GO time is the remainder.

The GTO allocations are listed in Table 2. Changes from the original allocations are due to programs shared between the GTOs and to changes in the overheads that occurred after the selected observations were specified prior to the Cycle 1 Call For Proposals. The GTO scientists chose to allocate the majority of the GTO time in Cycle 1, leaving just 196.1 hours of observation time for Cycles 2 and 3. The table shows the amount of time executed as of 2022 September 30. Further updates are available from https://www.stsci.edu/cgi-bin/get-jwst-gto-time.

The DD time is allocated by the Director of JWST’s Science and Operations Center (SOC), located at the Space Telescope Science Institute. In 2018, following a recommendation by the JSTAC, Director Ken Sembach allocated up to 525 hours of Cycle 1 DD time to the DD-Early Release Science Program. The DD-ERS program was designed and implemented by Janice Lee, Jennifer Lotz and Neill Reid. It consists of 13 peer-review selected programs designed to demonstrate JWST’s capabilities and provide open-access data to the community early in the mission. The DD-ERS programs were intended to be conducted within the first 3 to 5 months of Cycle 1; Table 3 lists the programs.

Observing time on JWST is allocated by wall-clock time; all overheads are included in the time allocated. Overheads that are determined by the observing sequence, such as slews or mechanism movements, are accounted by the planning software. Overheads that are independent of the specific observations, such as the calibration program or station-keeping maneuvers, are accounted by a percentage of time applied to each program.

The Cycle 1 GO program allocated approximately 6000 hours. Between the GTO, DD and GO programs, the total number of hours in Cycle 1 exceeds 1 year (8760 hours) by about 25%. The field of regard of JWST is about 40% of the sky at any given time. There will need to be enough targets within the field of regard at the end of Cycle 1 to efficiently schedule the observations, and the extra 25% tail will ensure a smooth transition from the end of Cycle 1 to the beginning of Cycle 2. The remaining allocated Cycle 1 observations will be conducted during the early months of Cycle 2, and there will be a similar transition from Cycle 2 to Cycle 3.

III.1 Director’s Discretionary Early Release Observation programs

The DD-ERS program consists of 13 programs ranging from the early Universe to our Solar System. Collectively the programs use most of the JWST instrument modes; the data taken have no exclusive access period so that prior to writing Cycle 2 observing proposals, the scientific community were able to obtain JWST data from the archive that is relevant to their proposals. In this section we describe the DD-ERS programs, and report on those that had early scientific results that were published or submitted by 2022 September 30.

III.1.1 DD-ERS 1288; PDRs4All: Radiative Feedback from Massive Stars

Massive stars produce intense winds and radiation which ionizes and heats the surrounding molecular cloud material, affecting future star formation in the cloud. These interactions create Photo-Dissociation Regions (PDRs), which dominate the infrared spectra of star-forming galaxies and drive the evolution of star formation from interstellar matter. PDRs4All consists of NIRCam and MIRI imaging and MIRI MRS and NIRSpec IFU spectroscopy of PDRs in the Orion Bar.

III.1.2 DD-ERS 1309; IceAge: Chemical Evolution of Ices During Star Formation

Icy grain mantles hold volatile elements and pre-biotic complex organic molecules in star-forming regions. IceAge will use NIRSpec and MIRI spectroscopy and NIRCam wide-field slitless spectroscopy to study ice chemistry in a representative low-mass star-forming region at several stages: pre-stellar core, Class 0 protostar, Class I protostar and protoplanetary disk. The program will map the spatial distribution of ices to 20 to 50 AU. If the organic molecules survive protostellar infall intact, then the molecular cloud could provide the precursors of biomolecules to the planetary systems that form within it, which could mean that life is a common outcome of star and planetary system formation.

III.1.3 DD-ERS 1324; Through the looking GLASS: a JWST exploration of galaxy formation and evolution from cosmic dawn to present day

Gravitational lensing by a Frontier Field cluster allows JWST to reach intrinsically faint galaxies in the epoch of reionization. GLASS will observe Abell 2744 with NIRSpec multi-object spectroscopy and NIRISS wide-field slitless spectroscopy, and will also create a parallel deep field with NIRCam imaging. The parallel field will contain the deepest extragalactic data of the DD-ERS program; the spectroscopy will also be the deepest DD-ERS data obtained in those modes.

GLASS will identify galaxies within the epoch of reionization and measure Lyα velocities and morphologies, rest-frame UV and optical emission line fluxes and UV/optical photometry and sizes. The program will map metallicity, dust and star-formation rate for galaxies spanning log M⋆∼6 to 10 at z>2, when disks and bulges emerged and feedback was most active. The GLASS NIRISS observations will map systems at z<3.5 and log M⋆≳6. The higher resolution NIRSpec observations will spectrally resolve key diagnostic lines which are blended at the lower resolution of the grism spectra. NIRSpec will also reach beyond z≳4 galaxies.

The NIRCam parallel observations will cover ∼18arcmin² in two regions. They will use 7 broadband filters from F090W to F444W, and will reach 5σ limits of 29.2 to 29.7 AB magnitudes (according to the pre-launch exposure time calculator.)

The GLASS team has published a series of papers with initial results, and other groups have also used these public data. The GLASS team papers include: (1) lensed galaxies at z>7, (2) photometry and catalogs, (3) galaxies at z>9, (4) metallicity in low-mass galaxies at z∼3, (5) the size-luminosity relation at z>7, (6) measurements of rest-frame optical lines, (7) globular clusters at z∼4, (8) the detection of a lensed star at z=2.65, (9) spectra of low-mass galaxies at z≳2, (10) measurements of the rest-frame UV at 7<z<9, (11) masses and M/L at z>7, (12) the morphology of high-z galaxies, (13) faint cold brown dwarfs, (14) a morphological atlas at 1<z<5, (15) faint high-z sources are intrinsically blue, (16) UV slopes at 4<z<7, and (17) star-formation histories at 5<z<7.

Other results from the GLASS observations include a lensing model of Abell 2722 and two studies using ALMA data of z>12 candidates.

III.1.4 DD-ERS 1328; A JWST Study of the Starburst-AGN Connection in Merging LIRGs

Luminous Infrared Galaxies (LIRGs) are some of the most active regions of star formation in the Universe. The connection between starbusts and Active Galactic Nuclei (AGN), and the role of galaxy merging in feeding both the star formation and supermassive black hole growth, has implications for both feedback and the star-formation history of the Universe. Program 1328 [72, e.g.,] will obtain NIRSpec and MIRI IFU spectroscopy, along with NIRCam and MIRI imaging, of active galaxies taken from the Great Observatories All-Sky LIRG Survey [1, GOALS].

Initial results from GOALS-JWST include detection of an AGN-driven outflow from the nucleus of NGC 7469 using mid-IR spectroscopy, and a map of the Polycyclic Aromatic Hydrocarbon (PAH), molecular gas emission, and ionization states in the object. NIRCam and MIRI imaging of NGC 7469 show star-forming regions consistent with young (<5 Myr) stellar populations, showing an age bimodality in the star-forming regions of the ring. GOALS-JWST observations of the merger VV114 resolved its double nuclei and showed that the south-western core had AGN-like colors while the north-eastern core was a starburst. About half of the mid-IR emission in the object was diffuse, including PAH emission. Observations of the merging galaxy IIZw096 showed that between 40 at 70 percent of the IR bolometric luminosity came from a single region smaller than 175 pc in radius.

III.1.5 DD-ERS 1334; The Resolved Stellar Populations Early Release Science Program

The Resolved Stellar Populations DD-ERS program will observe the globular cluster M92, the ultra-faint dwarf Draco II and the star-forming dwarf WLM to measure the sub-Solar mass stellar initial mass function (IMF), extinction maps, evolved stars, proper motions and globular clusters. The program will use NIRCam imaging with NIRISS imaging in parallel, both using the F090W and F150W filters, with either wide or medium-band filters in the long-wavelength NIRCam channel. The program will also develop point-spread-function-fitting software specific to NIRCam and NIRISS for evaluating crowded stellar populations.

Early results from Program 1334 include color-magnitude diagrams of M92, reaching almost to the bottom of the M92 main sequence (∼0.1M⊙), and finding white dwarf candidate members of M92 in the brightest portion of the white dwarf cooling sequence.

III.1.6 DD-ERS 1335; Q-3D: Imaging Spectroscopy of Quasar Hosts with JWST Analyzed with a Powerful New PSF Decomposition and Spectral Analysis Package

The Q-3D program uses NIRSpec and MIRI IFU observations of luminous quasars as templates to develop a PSF decomposition and spectral analysis packages, separating the bright central quasar from the host galaxy extended emission. The program will measure the stellar, gas and dust components to determine the impact of luminous quasars on their hosts. It will observe three systems: F2M1106, XID2028 and SDSSJ1652.

III.1.7 DD-ERS 1345; The Cosmic Evolution Early Release Science (CEERS) Survey

The statistical study of galaxy formation and evolution through deep-field observations with Hubble, Spitzer, Chandra and many other facilities has a rich history, including the Hubble Deep Field, the Great Observatories Origins Deep Survey, the Hubble Ultra-Deep Field, The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey [54, 69, CANDELS,], the Frontier Fields and many others. The CEERS survey will image 100 arcmin² within the CANDELS Extended Groth Strip field with NIRCam and MIRI. The program will obtain NIRSpec MSA and NIRCam WFSS spectroscopy of objects detected in the imaging. The science goals of CEERS includes finding galaxies at z>9 and constraining their nature and abundance, obtaining spectra of galaxies at z>3, including candidates at z>6, and characterizing the MIR emission from galaxies to study dust-obscured star formation and supermassive black hole growth.

Early results from the CEERS data include the discovery of candidate galaxies at z>8 [39, 92, 130, 97, e.g.,], studies of galaxies at 3<z<7, including quiescent galaxies, AGN host galaxies, star-forming clumps, and sources detected at other wavelengths [23, e.g.,].

III.1.8 DD-ERS 1349; Establishing Extreme Dynamic Range with JWST: Decoding Smoke Signals in the Glare of a Wolf-Rayet Binary

Colliding-wind Wolf-Rayet (WR) binaries efficiently produce dust, and are important sources for the production of dust in galaxy evolution. WR DustERS will observe two carbon-rich WR systems; WR-140 is the archetypal colliding-wind binary, while WR-137 is a known periodic dust-maker. The program will obtain the first resolved mid-infrared spectrum of the dust around a carbon-rich WR star, using MIRI IFU and imaging. They will develop PSF-subtraction techniques for observing faint extended emission around bright sources in IFU datasets. The observations of WR-137 will be done with NIRISS AMI mode to detect the faint dust spiral around the bright central source.

MIRI imaging of WR-140 detected 17 nested dust shells, which formed at each periastron 7.93 years apart over the past 130 years. Understanding the chemical properties and spectral signatures of dust formed by binaries like WR-140 is important given their potential role as dust sources in the inter-stellar medium. MIRI spectroscopy of the second dust shell confirmed the survival of carbonaceous dust grains seen as PAH features, and are consistent with a composition of carbon-rich aromatic compounds in a hydrogen-poor environment. Since this carbonaceous dust has lasted for at least 130 years in the harsh radiation environment of the central binary system, it could be a possible early and potentially dominant source of organic compounds and dust in the ISM of our galaxy.

III.1.9 DD-ERS 1355 - TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star formation

Objects that are magnified by gravitational lensing can be observed with greater intrinsic spatial resolution and higher sensitivity. TEMPLATES will obtain NIRSpec and MIRI IFU spectroscopy and imaging of 4 gravitationally-lensed galaxies selected at 1<z<4. The program will spatially resolve star formation structures in an extinction-robust manner, mapping Hα, Paα and 3.3μm PAH features within the galaxies. The selected targets are the brightest and best-characterized lensed systems known.

III.1.10 DD-ERS 1364 - Nuclear Dynamics of a Nearby Seyfert with NIRSpec Integral Field Spectroscopy

Measuring the mass of a super-massive black hole in a galaxy can be done with dynamical measurements or with reverberation mapping. It is important to connect dynamical measurements, primarily done on local quiescent galaxies, to reverberation mapping of more distant active galaxies. Program 1364 will use NIRSpec IFU observations of NGC 4151 to directly measure the mass of the central black hole and compare to previous reverberation mapping measurements of the same object. The program will measure kinematic maps of the stars and gas, intensity maps of the gas and stellar dynamical models of the galaxy.

III.1.11 DD-ERS 1366: The Transiting Exoplanet Community Early Release Science Program

Transiting exoplanets will allow JWST to measure atmospheric compositions, structures and dynamics in unprecedented detail. Program 1366 will use time-series observations in all four instruments to observe WASP-39b in transit, a MIR phase curve of WASP-43b, and a secondary eclipse of WASP-18b.

Early results include the first clear detection of CO2 at 4.3μm in an exoplanet, WASP-39b. The observations were made with the NIRSpec bright object time sequence mode and the 1.6” x 1.6” fixed slit aperture. A total of 21,500 integrations over 8.23 hours included the 2.8 hour transit duration.

III.1.12 DD-ERS 1373: ERS observations of the Jovian System as a demonstration of JWST’s capabilities for Solar System science

JWST enables Solar System observations with moving-target tracking and several modes optimized for bright targets. The pre-launch moving-target tracking requirement was 30 mas/sec, but the telescope managed to track the Double Asteroid Redirection Test (DART) impact on P/Didymos on 2022 September 26 at a rate of 105 mas/sec. Program 1373 is an in-depth study of the Jovian system to characterize Jupiter’s cloud layers, winds, composition, auroral activity and temperature structure; to map Io and Ganymede, and to characterize Jupiter’s ring structure. The program uses all four instruments.

III.1.13 DD-ERS 1386: High Contrast Imaging of Exoplanets and Exoplanetary Systems

The direct characterization of exoplanets with JWST will enable mid-infrared coronagraphy and detailed spectroscopy for the first time. Program 1386 will use all four instruments to characterize two exoplanets and a circumstellar disk in the NIR and MIR. Early results include NIRCam and MIRI coronagraphic imaging of the super-Jupiter exoplanet HIP 65426b from 2μm to 16μm, the first direct detection of an exoplanet at wavelengths longer than 5μm. The observations are fit by a mass of 7.4±1.1 MJup. presented the highest fidelity spectrum to date of a planetary-mass object, VHS 1256 b, which is a <20MJup, widely separated, young brown dwarf companion. Water, methane, carbon monoxide, carbon dioxide, sodium and potassium were observed in the JWST spectra, indicating disequilibrium chemistry and clouds. They made a direct detection of silicate clouds for the first time in a planetary-mass companion.