The launch of the James Webb Space Telescope (JWST) marks a pivotal moment for precise atmospheric characterization of Y dwarfs, the coldest brown dwarf spectral type. In this study, we leverage moderate spectral resolution observations (R $\sim$ 2700) with the G395H grating of the Near-Infrared Spectrograph (NIRSpec) onboard of JWST to characterize the nearby (9.9 pc) Y dwarf WISEPA J182831.08+265037.8 (WISE 1828). With the NIRSpec G395H 2.88-5.12 $\mathrm{\mu}$m spectrum, we measure the abundances of CO, CO$_2$, CH$_4$, H$_2$S, NH$_3$, and H$_2$O, which are the major carbon, nitrogen, oxygen, and sulfur bearing species in the atmosphere. Based on the retrieved volume mixing ratios with the atmospheric retrieval framework CHIMERA, we report that the C/O ratio is $0.45 \pm 0.01$, close to the solar C/O value of 0.55, and the metallicity to be +0.30 $\pm$ 0.02 dex. Comparison between the retrieval results with the forward modeling results suggests that the model bias for C/O and metallicity could be as high as 0.03 and 0.97 dex respectively. We also report a lower limit of the $^{12}$CO/$^{13}$CO ratio of $>40 $, being consistent with the nominal solar value of 90. Our results highlight the potential of JWST in measuring the C/O ratios down to percent-level precision and characterizing isotopologues of cold planetary atmospheres similar to WISE 1828.

The SALTUS Probe mission will provide a powerful far-infrared (far-IR) pointed space observatory to explore our cosmic origins and the possibility of life elsewhere. The observatory employs an innovative deployable 14-m aperture, with a sunshield that will radiatively cool the off-axis primary to <45K. This cooled primary reflector works in tandem with cryogenic coherent and incoherent instruments that span the 34 to 660 micron far-IR range at both high and moderate spectral resolutions.

MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are likely companion-driven, and two previously identified candidate companions have been identified—one at the end the Southern spiral arm at ∼0.″6, and one interior to the gap at ∼0.″1. With JWST/NIRCam, we provide new images of the disk and constraints on planets exterior to ∼1″. We detect the two-armed spiral disk, a known background star, and a spatially resolved background galaxy, but no clear companions. The candidates that have been reported are at separations that are not probed by our data with sensitivity sufficient to detect them−nevertheless, these observations place new limits on companions down to ∼2 M _Jup at ∼150 au and ∼0.5 M _Jup at ≳600 au. Owing to the unprecedented sensitivity of JWST and youth of the target, these are among the deepest mass-detection limits yet obtained through direct imaging observations, and provide new insights into the system’s dynamical nature.

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

The Single Aperture Large Telescope for Universe Studies (SALTUS) is a far-infrared space mission concept with unprecedented spatial and spectral resolution. SALTUS consists of a 14-m inflatable primary, providing 16x the sensitivity and 4x the angular resolution of Herschel, and two cryogenic detectors spanning a wavelength range of 34 to 660 mu m and spectral resolving power of 300-10(7). Spectroscopic observations in the far-infrared offer many unique windows into the processes of star and planet formation. These include observations of low-energy water transitions, the H-2 mass tracer HD, many CHONS constraining molecules such as NH3 and H2S, and emission lines from the phonon modes of molecular ices. Observing these species will allow us to build a statistical sample of protoplanetary disk masses, characterize the water snowline, identify Kuiper Belt-like debris rings around other stars, and trace the evolution of CHONS from prestellar cores, through to protoplanetary disks and debris disks. We detail several key star and planet formation science goals achievable with SALTUS.

The Near Infrared Camera for the James Webb Space Telescope is delivering the imagery that astronomers have hoped for ever since JWST was proposed back in the 1990s. In the Commissioning Period that extended from right after launch to early July 2022 NIRCam has been subjected to a number of performance tests and operational checks. The camera is exceeding pre-launch expectations in virtually all areas with very few surprises discovered in flight. NIRCam also delivered the imagery needed by the Wavefront Sensing Team for use in aligning the telescope mirror segments (\citealt{Acton_etal2022}, \citealt{McElwain_etal2022}).

High-contrast imaging of debris disk systems permits us to assess the composition and size distribution of circumstellar dust, to probe recent dynamical histories, and to directly detect and characterize embedded exoplanets. Observations of these systems in the infrared beyond 2–3 μ m promise access to both extremely favorable planet contrasts and numerous scattered-light spectral features—but have typically been inhibited by the brightness of the sky at these wavelengths. We present coronagraphy of the AU Microscopii (AU Mic) system using JWST’s Near Infrared Camera (NIRCam) in two filters spanning 3–5 μ m. These data provide the first images of the system’s famous debris disk at these wavelengths and permit additional constraints on its properties and morphology. Conducting a deep search for companions in these data, we do not identify any compelling candidates. However, with sensitivity sufficient to recover planets as small as ∼0.1 Jupiter masses beyond ∼2″ (∼20 au) with 5 σ confidence, these data place significant constraints on any massive companions that might still remain at large separations and provide additional context for the compact, multiplanet system orbiting very close-in. The observations presented here highlight NIRCam’s unique capabilities for probing similar disks in this largely unexplored wavelength range, and they provide the deepest direct imaging constraints on wide-orbit giant planets in this very well-studied benchmark system.

Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a space-based, MIDEX-class mission concept that employs a 17-meter diameter inflatable aperture with cryogenic heterodyne receivers, enabling high sensitivity and high spectral resolution (resolving power ≥106) observations at terahertz frequencies. OASIS science is targeting submillimeter and far-infrared transitions of H2O and its isotopologues, as well as deuterated molecular hydrogen (HD) and other molecular species from 660 to 80 μm, which are inaccessible to ground-based telescopes due to the opacity of Earth’s atmosphere. OASIS will have <20x the collecting area and ~5x the angular resolution of Herschel, and it complements the shorter wavelength capabilities of the James Webb Space Telescope. With its large collecting area and suite of terahertz heterodyne receivers, OASIS will have the sensitivity to follow the water trail from galaxies to oceans, as well as directly measure gas mass in a wide variety of astrophysical objects from observations of the ground-state HD line. OASIS will operate in a Sun-Earth L1 halo orbit that enables observations of large numbers of galaxies, protoplanetary systems, and solar system objects during the course of its 1-year baseline mission. OASIS embraces an overarching science theme of “following water from galaxies, through protostellar systems, to oceans.” This theme resonates with the NASA Astrophysics Roadmap and the 2010 Astrophysics Decadal Survey, and it is also highly complementary to the proposed Origins Space Telescope’s objectives.

We describe the design and performance of the near-infrared (1.51-1.70 mu m), fiber-fed, multi-object (300 fibers), high resolution (R = lambda/Delta lambda similar to 22,500) spectrograph built for the Apache Point Observatory Galactic Evolution Experiment (APOGEE). APOGEE is a survey of similar to 10(5) red giant stars that systematically sampled all Milky Way populations (bulge, disk, and halo) to study the Galaxy's chemical and kinematical history. It was part of the Sloan Digital Sky Survey III (SDSS-III) from 2011 to 2014 using the 2.5 m Sloan Foundation Telescope at Apache Point Observatory, New Mexico. The APOGEE-2 survey is now using the spectrograph as part of SDSS-IV, as well as a second spectrograph, a close copy of the first, operating at the 2.5 m du Pont Telescope at Las Campanas Observatory in Chile. Although several fiber-fed, multi-object, high resolution spectrographs have been built for visual wavelength spectroscopy, the APOGEE spectrograph is one of the first such instruments built for observations in the near-infrared. The instrument's successful development was enabled by several key innovations, including a "gang connector" to allow simultaneous connections of 300 fibers; hermetically sealed feedthroughs to allow fibers to pass through the cryostat wall continuously; the first cryogenically deployed mosaic volume phase holographic grating; and a large refractive camera that includes mono-crystalline silicon and fused silica elements with diameters as large as similar to 400 mm. This paper contains a comprehensive description of all aspects of the instrument including the fiber system, optics and opto-mechanics, detector arrays, mechanics and cryogenics, instrument control, calibration system, optical performance and stability, lessons learned, and design changes for the second instrument.

We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2. The Trumpler 14/Carina I region is in the western part of the Carina Nebula Complex (CNC), which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 μ m transition of [C ii ] with a spatial resolution of 48″ and a velocity resolution of 0.17 km s −1 . The observations cover a 0.°25 by 0.°28 area with central position l = 297.°34, b = −0.°60. The kinematics show that bright [C ii ] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region (PDR) and ionization front of each molecular cloud. Along seven lines of sight (LOSs) that traverse Tr 14 into the dark ridge to the southwest, we find that the [C ii ] luminosity from the H ii region is 3.7 times that from the PDR. In the same LOS, we find in the PDRs an average ratio of 1 : 4.1 : 5.6 for the mass in atomic gas : dark CO gas : molecular gas traced by CO. Comparing multiple gas tracers, including H i 21 cm, [C ii ], CO, and radio recombination lines, we find that the H ii regions of the CNC are well described as H ii regions with one side freely expanding toward us, consistent with the Champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20–30 Myr.

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a joint project between NASA and the German Aerospace Center DLR to provide infrared and sub-millimeter observing capabilities to the worldwide astronomical community. With a wide range of instruments that cover both imaging and spectroscopy, SOFIA has produced unique scientific results that could not be obtained with a ground-based facility. In the coming decade, SOFIA will be a critical complement to the other major facilities for astronomical research, the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA) by filling in the otherwise unobservable wavelength range of 30–300 μm. SOFIA provides a wide range of instrumentation, and this paper will describe some of the new capabilities in heterodyne spectroscopy, direct detection spectroscopy, and polarimetry.

Department of Physics and Astronomy, University of California, Riverside, CA 92521 Department of Physics and Astronomy, University of California, Davis, CA 92616 School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, OH 43210 Observatories of the Carnegie Institute of Washington, Pasadena, CA 91101, USA Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 Space Telescope Science Institute, Baltimore, MD 21218 Department of Astronomy, University of Washington, Seattle, WA 98195-1580 Department of Astronomy, University of Massachusetts, Amherst, MA 01003 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom Research School of Astronomy & Astrophysics, The Australian National University, ACT 2611, Australia Association of Universities for Research in Astronomy, Washington, DC 20005 Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 NASA–Goddard Space Flight Center, Greenbelt, MD 20771 Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, Via Gobetti 101, 40129 Bologna, Italy National Optical Astronomy Observatories, Tucson, AZ 85726-6732 Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom NASA–Jet Propulsion Laboratory, Pasadena, CA 91109 Cerro Tololo Inter-American Observatory, La Serena, Chile NASA–Ames Research Center, Moffett Field, CA 94035

We present a Monte Carlo simulation designed to predict the vertical velocity dispersion of brown dwarfs in the Milky Way. We show that since these stars are constantly cooling, the velocity dispersion has a noticeable trend with the spectral type. With realistic assumptions for the initial mass function, star formation history, and the cooling models, we show that the velocity dispersion is roughly consistent with what is observed for M dwarfs, decreases to cooler spectral types, and increases again for the coolest types in our study (∼T9). We predict a minimum in the velocity dispersions for L/T transition objects, however, the detailed properties of the minimum predominately depend on the star formation history. Since this trend is due to brown dwarf cooling, we expect that the velocity dispersion as a function of spectral type should deviate from the constancy around the hydrogen-burning limit. We convert from velocity dispersion to vertical scale height using standard disk models and present similar trends in disk thickness as a function of spectral type. We suggest that future, wide-field photometric and/or spectroscopic missions may collect sizable samples of distant ( kpc) dwarfs that span the hydrogen-burning limit. As such, we speculate that such observations may provide a unique way of constraining the average spectral type of hydrogen burning.

We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (∼6–10 Myr old), relatively nearby (800 pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24 μm. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from ∼0.1 to ∼10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ∼1 to ∼18 Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24 μm excesses ([8] – [24] ≥ 1.5) increases from (8.4 ± 1.3)% at ∼3 Myr to (46 ± 5)% at ∼10 Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.

Large parts of the IR spectrum are inaccessible in observations made from ground-based telescopes because of absorption by water vapor in the atmosphere.1 For this reason, the Stratospheric Observatory for IR Astronomy (SOFIA)— a joint project between NASA and the German Aerospace Center (DLR)—was designed and has been operational since 2010.2 The observatory consists of a gyro-stabilized telescope (with an effective diameter of 2.5m), mounted within a Boeing 747SP (special performance) aircraft (see Figure 1) that flies at altitudes as high as 45,000 feet (13.7km). At such altitudes, the atmospheric water vapor overburden typically has a column depth of less than 10 m, which is 20–100 times lower than at good terrestrial sites. Indeed, the average atmospheric transmission is 80% or more across SOFIA’s wide wavelength range (0.3 m to 1.6mm), as shown in Figure 2. Although some strong water absorption lines remain in the spectra, high-quality spectroscopy and broadband photometry can be achieved between the telluric (i.e., atmospheric) lines. SOFIA has thus become a key facility for several astronomy investigations, e.g., for studying regions of star formation, observing objects obscured by interstellar dust, and making time-critical measurements of transient events. SOFIA also presents several other advantages compared with ground-based or space-based (e.g., the European Space Agency’s Herschel Space Observatory) IR observatories. For example, unlike space telescopes, SOFIA can be upgraded continually and can be used as a test bed (with conditions similar to those encountered during space flights) for stateof-the-art and high-risk technologies. SOFIA also serves as an excellent ‘training ground’ for a new generation of instrumentalists and experimental astronomers. In addition, the observatory provides the opportunity—via flight participation—for Figure 1. Top: Photograph of the Boeing 747 special performance aircraft that houses the Stratospheric Observatory for Infrared Astronomy (SOFIA). This image was obtained from a chase airplane, during a door-open test flight in 2010. Bottom: SOFIA’s 2.5m-diameter primary mirror. The aft ramp, which minimizes circulating wind (caused by airflow over the open cavity), is shown on the right. (Images courtesy of NASA.)

ABSTRACT We analyze the spatial distribution of dusty young stellar objects (YSOs) identified in the Spitzer Survey of the Orion Molecular clouds, augmenting these data with Chandra X-ray observations to correct for incompleteness in dense clustered regions. We also devise a scheme to correct for spatially varying incompleteness when X-ray data are not available. The local surface densities of the YSOs range from 1 pc −2 to over 10,000 pc −2 , with protostars tending to be in higher density regions. This range of densities is similar to other surveyed molecular clouds with clusters, but broader than clouds without clusters. By identifying clusters and groups as continuous regions with surface densities ≥10 pc −2 , we find that 59% of the YSOs are in the largest cluster, the Orion Nebula Cluster (ONC), while 13% of the YSOs are found in a distributed population. A lower fraction of protostars in the distributed population is evidence that it is somewhat older than the groups and clusters. An examination of the structural properties of the clusters and groups shows that the peak surface densities of the clusters increase approximately linearly with the number of members. Furthermore, all clusters with more than 70 members exhibit asymmetric and/or highly elongated structures. The ONC becomes azimuthally symmetric in the inner 0.1 pc, suggesting that the cluster is only ∼2 Myr in age. We find that the star formation efficiency (SFE) of the Orion B cloud is unusually low, and that the SFEs of individual groups and clusters are an order of magnitude higher than those of the clouds. Finally, we discuss the relationship between the young low mass stars in the Orion clouds and the Orion OB 1 association, and we determine upper limits to the fraction of disks that may be affected by UV radiation from OB stars or dynamical interactions in dense, clustered regions.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is the world's largest airborne observatory, featuring a 2.5 meter effective aperture telescope housed in the aft section of a Boeing 747SP aircraft. SOFIA's current instrument suite includes: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), a 5-40 mu m dual band imager/grism spectrometer developed at Cornell University; HIPO (High-speed Imaging Photometer for Occultations), a 0.3-1.1 mu m imager built by Lowell Observatory; GREAT (German Receiver for Astronomy at Terahertz Frequencies), a multichannel heterodyne spectrometer from 60-240 mu m, developed by a consortium led by the Max Planck Institute for Radio Astronomy; FLITECAM (First Light Infrared Test Experiment CAMera), a 1-5 mu m wide-field imager/grism spectrometer developed at UCLA; FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), a 42-200 mu m IFU grating spectrograph completed by University Stuttgart; and EXES (Echelon-Cross-Echelle Spectrograph), a 5-28 mu m highresolution spectrometer designed at the University of Texas and being completed by UC Davis and NASA Ames Research Center. HAWC+(High-resolution Airborne Wideband Camera) is a 50-240 mu m imager that was originally developed at the University of Chicago as a first-generation instrument (HAWC), and is being upgraded at JPL to add polarimetry and new detectors developed at Goddard Space Flight Center (GSFC). SOFIA will continually update its instrument suite with new instrumentation, technology demonstration experiments and upgrades to the existing instrument suite. This paper details the current instrument capabilities and status, as well as the plans for future instrumentation.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) has recently concluded a set of engineering flights for Observatory performance evaluation. These in-flight opportunities are viewed as a first comprehensive assessment of the Observatory's performance and are used to guide future development activities, as well as to identify additional Observatory upgrades. Pointing stability was evaluated, including the image motion due to rigid-body and flexible-body telescope modes as well as possible aero-optical image motion. We report on recent improvements in pointing stability by using an active mass damper system installed on the telescope. Measurements and characterization of the shear layer and cavity seeing, as well as image quality evaluation as a function of wavelength have also been performed. Additional tests targeted basic Observatory capabilities and requirements, including pointing accuracy, chopper evaluation and imager sensitivity. This paper reports on the data collected during these flights and presents current SOFIA Observatory performance and characterization.