Miss Rachel Anderson (STScI)
Cosmic rays are a known problem in infrared astronomy, causing both loss of data and data accuracy. The problem becomes even more extreme when considering data from a high radiation environment such as in orbit around Earth, or outside the Earth's magnetic field altogether, unprotected, as is the case for the James Webb Space Telescope (JWST). For JWST, all the instruments employ non-destructive reads, i.e. ramps. To find the best method to correct for this disturbance we study three cosmic ray detection methods: a 2-point difference method, a deviation from the fit method, and a y-intercept method. These methods are applied to simulated non-destructive read ramps with varying combinations of slope, number of frames, number of cosmic rays, cosmic ray frame number, and cosmic ray strength. We show that the 2-point difference method is the fastest, optimal detection method in the photon-dominated regime and the y-intercept method is the optimal detection method in the read noise-dominated regime.
Jay Anderson (STScI)
I will present an scenario for observing the Galactic center with NIRCam. Issues that must be dealt with are: how to observe the center without saturating too many star and how to accomplish a deep-and-wide mosaic where we get as much exposure time on the center, but also have good coverage of the surrounding field. Recent images with HST's WFC3/IR camera and ground-based adaptive-optics images from Keck give us a sense of what JWST will see.
Dr. Daniel Batcheldor (Florida Institute of Technology)
A fundamental legacy of HST has been the direct detection of supermassive black holes (SMBHs) lurking at the centers of galaxies. Furthermore, these SMBHs seem to be intricately linked to the galaxy in which they reside. Such observations have fueled a wealth of theoretical studies aimed at understanding the role of SMBHs in galaxy formation and evolution. However, there still remain a number of critical questions. For example, the impact of SMBH mergers, the consistency of mass measurement techniques, and the potential for a population of galaxies and SMBHs that have yet to reach a steady state. Consequently, a key science goal of JWST - understanding the assembly of galaxies - will require a more complete picture of SMBHs. How JWST may be able to achieve this, and the likely consequences for our understanding of SMBH and galaxy co-evolution, will be discussed.
Dr. Tracy Beck (Space Telescope Science Insitute)
The James Webb Space Telescope will provide unprecedented views of the formation of planetary systems around young stars through the study of their primordial circumstellar gas and dust disks. Spectral imaging observations with JWST will push our knowledge of these proto-planetary disks to fainter limits. This will allow us to: understand the disks in very young embedded protostars, reveal disk structure in low mass stars and brown dwarfs, and use high contrast to understand faint gas phase species in evolving disks. In this poster, we highlight some exciting prospects for using JWST NIRSpec and MIRI spectral imaging of circumstellar disks around young stars to reveal the formation sites of future planetary systems.
Valentina Calvi (Padova University)
We studied the contribution of undetected galaxies in the Hubble Ultra Deep Field using the ACS data for the NICP12 field in the i775 and z850 band. Running SExtractor we detected all the visible galaxies and created a mask to cover them. Applying the Fast Fourier Transform we got the power spectrum for each ACS image. The difference between the i775-power spectrum and z850-power spectrum points out the contribution of the undetectable galaxies at z~6. Monte Carlo simulations of galaxies with characteristics similar to those of the faintest galaxies of the field show the random variability of the power spectrum and permit us to estimate the number of faint galaxies at z~6.
Dr. Christine Chen (STScI)
STScI has released prototype Exposure Time Calculators (ETC), limited web-based tools to estimate the Signal-to-Noise Ratios (SNRs) expected for an astronomical source given target and sky background brightnesses, detector performance, and assumed exposure times. For MIRI, the prototype ETCs currently estimate the performance requirements with an accuracy of 20% for observations of point sources in Imaging and Medium Resolution Spectroscopy (MRS) modes. Currently, these calculations are optimized for observations of faint objects. We discuss (1) the requirements for MIRI throughputs and (2) the principal sources of sky backgrounds at 5 - 25 micron (zodiacal light and telescope and sunshield thermal emission). We show example SNR estimates using the MIRI Imaging and MRS ETCs.
Dr. Nicola Da Rio (STScI)
The James Webb Space Telescope, thanks to its extreme resolution and sensitivity in the infrared, will guarantee an unprecedented breakthrough for the study of young stellar clusters, specifically in the very-low mass range and substellar regime. We present a detailed study of such science cases with NIRCAM, based on synthetic photometry and JWST exposure time calculations. We prove the feasibility of detecting and fully characterizing brown dwarf members of young populations in the Magellanic Clouds. This type of studies, critical for our understanding of star formation processes and the substellar IMF at low metallicity, are not possible with current astronomical facilities, and will be a prerogative of JWST. We also outline the optimal choice of NIRCAM filters and observational layout to efficiently derive memberships, stellar parameters, individual extinctions and possible circumstellar disk presence for young BDs in the LMC. Finally, we investigate an observational imaging survey with NIRCAM to detect and fully characterize young, free-floating, giant gas planets in the Orion Nebula Cluster, the closest site of active star formation. With the ability of detecting such objects down to 1Mjup, this study will improve our understanding of the IMF in the planetary mass range.
Dr. Steven Finkelstein (Texas A&M University)
We will present the current state of our knowledge of the physical properties of high-redshift galaxies, including their uncertainties. Briefly, only the stellar mass can be reasonably constrained in individual galaxies at z > 7, with the stellar population age, dust content and star-formation history remaining essentially unconstrained. We will examine how near-infrared and mid-infrared imaging with JWST will reduce these uncertainties, and comment on how this will improve our understanding of galaxy evolution at high redshift.
Prof. K. E. Saavik Ford (BMCC-CUNY/AMNH)
Non-redundant masking is a technique for turning a single-dish, filled aperture telescope (e.g. JWST) into a multi-aperture interferometer. The benefits of doing so include an improvement in angular resolution and contrast of the telescope; however, one penalty is an increase in the complexity of the data collected. The PSF of the telescope becomes difficult to interpret by eye. However, interferometric data reduction techniques pioneered in the radio can readily be applied to JWST interferometric data and should permit mapping of the sort routinely carried out by radio interferometers. We will discuss the techniques for recovering image maps and their application to simulated JWST data. We will also present some of the implications of these results for studies of extragalactic sources with JWST.
Dr. Scott Friedman (STScI)
Observers will use the Astronomer's Proposal Tool (APT) to plan their observations with JWST, just as they have done with HST. For JWST, however, a series of templates, specific to each instrument, will greatly assist the specification of the observations and help avoid errors. We present descriptions of the observing templates for the MIRI instrument, including the choices astronomers must make to properly define the observing parameters of their science program.
Karl Gordon (STScI)
The Mid-Infrared Instrument (MIRI) calibration plan describes the steps to reduce MIRI data from raw ramps to fully calibrated images and spectra. The MIRI calibration plan is split into 3 stages. The first stage converts the raw ramps into slope measurements. The second stage calibrates the slope images. The third stage mosaics images, creates spectral cubes, and extracts spectra. The plans for all four different instrument channels - imaging, coronagraphy, low-resolution spectroscopy, and mid-resolution integral field unit (IFU) spectroscopy - will be shown.
Dr. Sara Heap (NASA/GSFC)
According to Davé (2011), galaxies in their birth phase are star-forming galaxies whose: • halo mass is less than ~109 M☉ • SF rate is regulated by photo-ionization of newly formed massive stars Studies of local galaxies in their birth phase find that such galaxies have a low stellar mass, very low metallicities, and have converted only a small fraction of their H I envelope to stars. These galaxies are Ly α absorbers, because the H I envelope (Ncol(HI)>1020 cm-2) smothers any galactic Ly α emission. Because of their low metallicity, the stellar winds are too weak to drive an outflow. We used the local galaxy, I Zw 18 (D~14 Mpc), as a template for high-redshift galaxies in their birth phase. We find that JWST can detect z=8.2 star-forming galaxies in 105 s in MSA/prism surveys if their restframe far-UV fluxes are at least 10 times that of I Zw 18. Whether these brighter galaxies are still in the birth phase is an open issue.
Dr. Dean Hines (STScI)
The Mid-Infrared Instrument (MIRI) to be flown onboard the James Webb Space Telescope (JWST) provides direct and coronagraphic imaging, and integral field spectroscopic measurements over the wavelength range 5 - 28 µm. We present an overview of the instrument and the current status of its construction.
Cosmin Ilie (University of Michigan)
We propose two mechanisms that could explain the growth of Dark Stars to become supermassive (SMDS) of one to ten million solar masses. The growth continues as long as dark matter heating persists, since dark stars are large and cool and do not emit enough ionizing photons to prevent further accretion of baryons onto the star. The dark matter may be provided by two mechanisms: (1) gravitational attraction of dark matter particles on a variety of orbits not previously considered, and (2) capture of WIMPs due to elastic scattering. Once the dark matter fuel is exhausted, the SMDS becomes a heavy main sequence star. These stars eventually collapse to form massive black holes that may provide seeds for supermassive black holes in the Universe. SMDS are very bright, with luminosities exceeding 1e9 solar luminosities. The launch of the JWST opens up the possibility of detecting Dark Stars. Using various dropout redshift selection functions we show that JWST could detect SMDS in a typical deep field survey. Specifically, at z~10 there could be several million solar mass SMDS detected with an exposure time of ten thousand seconds. However the detection of more massive SMDS is relatively slim at z~10. This apparent paradox, that the brighter DS is less detectable can be explained by the following: at a given redshift, the formation rate of DM halos hosting the lower mass DS is higher by about one order of magnitude, therefore those objects are much more abundant. However if one uses the F150W and F200W of NIRCam even the ten million solar mass SMDS have a significant chance of being observed as a dropout at z~12, whereas million solar mass supermassive dark stars at z~12 could show up in large numbers in a JWST ultra deep field survey as an F150W dropout. At z~15 one million solar mass SMDS could still be easily detected as F200W band dropouts in a JWST survey, but for more massive SMDS this occurrence is relatively unlikely. Therefore, we conclude that the most promising technique to use in searching for SMDS would be to look for them as F150W dropouts. We show that their colours in the various filters where JWST could detect them are different from those of high redshift PopIII galaxies and this test could be used as a confirmation of the detection of a SMDS.
Patrick Ingraham (Université de Montréal)
The Tunable Filter Imager (TFI) is one of the four scientific instruments aboard the James Webb Space Telescope (JWST). TFI features a low-order Fabry-Perot etalon enabling imaging spectroscopy at an average resolution of 100. TFI also includes a coronagraph and is an advantageous design for high-contrast imaging applications involving spectral differential imaging (SDI), a technique widely used by current and future high contrast imaging instruments. In order to determine TFI's on-sky performance, we perform a Fresnel propagation of the telescope and instrument using the measured wavefront error maps of TFI's optical elements and the theoretical wavefront error maps of the optical telescope assembly. Using this simulation, we determine that SDI offers an improvement in contrast ranging from a factor of ~7 to ~100 depending on the instrument's configuration. We present the companion detection capability using both the coronagraphic and non-coronagraphic modes of TFI. These results will be used in the planning of future high-contrast observations with TFI.
Wayne Kinzel (CSC/STScI)
The James Webb Space Telescope (JWST) will be a large infrared space observatory in orbit about the Sun-Earth second Lagrange Point. The Astronomer’s Proposal Tool (APT) developed for the Hubble Space Telescope is being expanded to provide the observer’s observation specification interface to JWST. APT will use specialized Observation Templates that support the observatory’s basic science activities such as imaging, spectroscopy, and coronography. The Observer will have the ability to specify complex observations, including mosaics and cluster targets, using the “Observation” concept. Each Observation will contain one or more Visits where each Visit contains a set of exposures that can be obtained using one Guide Star. This poster will explain the Observation Template, Observation, Visit, and target specification concepts and will detail the hard observation constraints imposed by the JWST orbit, the sunshield, and Guide Star availability. It will also explain the possible limitations on Observation and Visit size and durations.
Dr. Jennifer Lotz (STScI)
The detection of the first galaxies and understanding the evolution of those galaxies during the first half of cosmic time are primary JWST science mission goals. We present a test NIRCam observing program of the Chandra Deep Field South designed to detect Lyman-break galaxies at z > 8. Simultaneous deep imaging in both the short-wavelength and long-wavelength NIRCam channels allows us to detect both the Lyman break and 4000A break for high redshift galaxies. JWST/NIRCam's high spatial resolution imaging will resolve rest-frame optical structures at < 0.5 - 1 kpc out to z ~ 10. The long total integration times required for z~10 detections are mostly easily scheduled with multi-epoch observations, enabling high-redshift transit searches. We discuss the strategies for dither and mosaic patterns, guide star acquisition, and observational cadence.
Dr. Barry McKernan (BMCC-CUNY/AMNH)
Non-redundant masking (NRM) is a technique for turning a single-dish, filled aperture telescope (e.g. JWST) into a multi-aperture interferometer. Ground-based NRM and radio interferometers can extract source information from an analysis of closed triangles and quads of apertures (so-called closure variable analysis). We discuss the application of closure variable analysis to simulated JWST-TFI observations of extended sources, in particular extragalactic objects such as AGN and quasars. We discuss the stability and statistical significance of our results for a range of contrast ratios.
Mr. Hugo Messias (CAAUL)
The last decade has seen the appearance of various MIR color criteria for the selection of AGN candidates. Mainly using IRAC (Spitzer) observations, they are effective at lower redshifts (z<~2). However, at z>3, where JWST is expected to play a major discovery role, the current MIR AGN selection criteria become degenerate, failing to distinguish AGN emission from that due to star-formation. In this talk I will present a new set of MIR AGN-selection criteria particularly suited for JWST observations and effective to the highest redshifts (z~7). Present-day science applications (compton-thick AGN, high-z radio galaxies, ...) will also be discussed.
Dr. Marshall Perrin (STScI)
Three of JWST's instruments will include coronagraphic capabilities for high contrast science, particularly direct imaging of exoplanets. Each instrument has chosen a different coronagraphic architecture: band-limited masks for NIRCam, classical Lyot coronagraphs for TFI, and quadrant phase masks plus a classical Lyot for MIRI. Each of these presents its own particular set of challenges for data acquisition and reduction, and offers unique scientific capabilities in terms of accessible spectral coverage and parameter space of detectable planets. Optimizing observing strategies will require high fidelity models of JWST wavefront quality and instrumental performance. We present a summary of the available coronagraphic modes with NIRCam, MIRI, and TFI, and show initial simulation results from a new software package, WebbPSF, developed to allow consistent modeling of imaging performance across JWST's full instrument suite.
Dr. John Pye (University of Leicester)
We present simulations of deep, extragalactic surveys that might be conducted by MIRI, based on results from an instrument simulator software package developed at the University of Leicester.
Dr. John Pye (University of Leicester)
We present the University of Leicester activities in the design and development of MIRI. These include: mechanical engineering systems lead for the MIRI European Consortium; design and development of the Primary Structure; support of the functional and performance testing of the instrument. We show some of the results from the structural verification of the hardware and via CAD modelling.
Dr. Jane Rigby (NASA/GSFC)
I'll present JWST's sensitivity numbers for photometry, low-resolution (R~100) spectroscopy, and medium-resolution (R~1000-3000) spectroscopy, and make apples-to-apples comparisons to current observatories (Hubble, Spitzer, VLT, Keck, Gemini). I'll also present "rules of thumb" (e.g. time to detect H alpha for the LMC at z=3). The poster will help astronomers visualize JWST's capabilities, and how JWST will advance their own science.
Dr. Paola Rodriguez Hidalgo (Pennsylvania State University)
Quasar absorption lines, such as MgII absorption lines, allow the study of the gas in galaxies and their halos, helping us understand their kinematics and chemical composition. In particular, the ratio of the rest-frame equivalent widths Wr of FeII to MgII provides information about the relative abundance of Fe to Mg, which can be used as a star formation history clock because Fe is mostly produced in Type Ia supernovae, occurring approximately 1 Gyr after the massive core supernovae start polluting the galactic gas with Mg. Star forming galaxies are also expected to show special signatures in the kinematic properties of the observed absorption systems. We present a study of the evolution of several classes of MgII, and their correspondent FeII and MgI, over a large fraction of cosmic history: 2.3 to 8.7 Gyrs of the age of the Universe. Our sample consists of 87 strong W_r(2796)>0.3 A MgII absorbers, with redshifts 0.3<z<2.5, measured in 81 quasar spectra obtained from the Very Large Telescope (VLT) / Ultraviolet and Visual Echelle Spectrograph (UVES) archives of high-resolution spectra (R~45,000). We compare our findings to those presented in Narayanan et al. (2007) of a sample of 100 weak (Wr(2796)<0.3 A) found in the same quasar spectra as our study. At low redshift, we find an absence of very strong MgII absorbers with small ratio of equivalent widths of FeII to MgII, while at higher redshifts absorbers with smaller Wr(FeII)/Wr(MgII) are present. On the case of the weak MgII absorbers, there is also and absence, but it occurs at high redshifts and large ratios of Wr(FeII)/Wr(MgII). No particular trend is found on the strong MgII absorbers. We find that the main effect driving the evolution of very strong MgII systems is the difference between the kinematic profiles at low and high redshift. At high redshift, we observe that, among the very strong MgII absorbers, all of the systems with small ratios of Wr(FeII)/Wr(MgII) show non-saturated profiles with relative large velocity spreads. This type of profile is not present at low redshift. These systems could be a correspondence of the previously found sub-DLA systems, also found to have larger velocity spreads in average, and possibly linked to superwinds in star forming galaxies. The small ratios of Wr(FeII)/Wr(MgII) could be due to lower abundance of FeII at high redshifts, which could indicate early stages in the star formation of these galaxies. Unfortunately, saturation in most of the MgII profiles prevent us from being able to account for the factor that ionization and alpha-enhancement/depletion have on the chemical abundance of these systems.
Mr. Claes-Erik Rydberg (Stockholm)
Population III.1 stars are postulated to exist at approximately z=10-30. According to current research population III.1 stars are expected to be extremely massive (around 100 solar masses) or exist in smaller clusters, but still massive (around 10 solar masses). Here, we derive the surface number densitites and apparent AB-magnitudes for 10-300 Msolar population III.1 stars in various JWST filters at z=10-30. Our calculations are based on realistic stellar atmospheres and take into account the potential flux contribution from the surrounding HII region. The gravitational magnification boost achieved when pointing JWST through a foreground galaxy cluster is also considered. Using this machinery, we derive the conditions required for JWST to be able to detect population III stars in isolation. The results is displayed in the poster.
Mr. Claes-Erik Rydberg (Stockholm)
The James Webb Space Telescope (JWST) may be able to test the theoretical prediction that the first, chemically pristine stars (population III) formed with high characteristic masses. Small population III galaxies may offer the best prospects of directly detecting such stars. Here, we present Yggdrasil, a new spectral synthesis code geared towards the first galaxies. Using this model, we explore the imaging detection limits for population III galaxies and investigate the prospects of identifying population III galaxy candidates based on JWST broadband color criteria. We predict that JWST may be able to detect population III galaxies with stellar population masses as low as 10^5 Msolar at z = 10 in ultra deep exposures. Over limited redshift intervals, it should moreover be possible to robustly select population III galaxy candidates either with or without significant nebular emission based on their colors. In the case of population III galaxies dominated by nebular emission, this holds for stellar initial mass function ranging from very top-heavy to those more reminiscent of galaxies in the local Universe.
Dr. Kailash Sahu (STScI)
Observation scenarios for two exoplanet science projects, which are likely to be of top-priority for JWST, are outlined. These test case observations are explored in detail to check if the current capabilities with NIRCam are adequate to carry out these observations. We find that, in order to keep the data volume within limits, it must be possible to operate single detectors (hereafter referred to as Single Chip Arrays, or SCAs) in the short wavelength (SW) and long wavelength (LW) channels, both in subarray and full-frame modes. The on-board averaging capability from 2 to 16 frames in powers of 2 is also crucial in keeping the data volume within limits. Further investigations are needed to find if additional subarrays will help in grism observations of bright stars in the LW channel. The use of weak lenses will greatly help in achieving sigh signal-to-noise for explanet transit studies.
Dr. Benjamin Sargent (Space Telescope Science Institute)
We are conducting studies of evolved star mass loss in the Large Magellanic Cloud (LMC) using Spitzer Space Telescope mid-infrared photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Legacy program. Combined with optical and near-infrared photometry from other catalogs, we have assembled spectral energy distributions (SEDs) for more than 25,000 evolved stars in the LMC. To determine the mass loss from these stars and probe their dust formation, we model their SEDs using the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS). For simplicity, we assume spherical symmetry, but 2Dust does have the capability to model general axisymmetric circumstellar dust shell geometries. GRAMS includes over 80,000 models of both Oxygen-rich and Carbon-rich evolved stars, for ranges of different parameters, including stellar effective temperature and luminosity, dust shell inner radius, dust shell optical depth, etc. We discuss possible extensions of our 2Dust GRAMS modeling of the SAGE evolved stars dataset by means of obtaining mid-infrared photometry and spectroscopy of such stars using MIRI on James Webb Space Telescope. By understanding the origins of dust around evolved stars, we may learn more about the life cycle of dust and other matter in the LMC; e.g., its residence in the interstellar medium, its time spent in molecular clouds, and its incorporation in protoplanetary disks to form new generations of planetary systems. This, in turn, should be of benefit in learning about the life cycle of matter in other galaxies, including our own.
Dr. Jonathan Seale (STScI)
Because of its close proximity, location out of the plan of the Galaxy, and face-on viewing orientation, the Large Magellanic Cloud has become one of the most popular laboratories for studying the process of star formation, perhaps second to only the Milky Way. Studies of our own galaxy suffer from a number of observational constraints, namely confusion along the line-of-sight and the inability to observe the Galaxy in its entirety. Conversely, by being able to observe the entire LMC at a favorable orientation and close distance, the LMC provides us with a unique statistical opportunity to study star formation on both galactic and single star system scales. It wasn't until the launch of the Spitzer Space Telescope, with its superior spatial resolution, that individual sites of massive star formation could be resolved in the LMC. And now JWST is the next step forward in LMC star formation studies - it will be able to further resolve young stellar clusters to reveal the multiplicity of young stellar systems, and will have the sensitivity to detect the lower mass objects that may be the key to understanding the temporal choreography within a star formation region.
Dr. Anand Sivaramakrishnan (STScI)
Non-redundant masking (NRM) on JWST-TFI more than doubles the resolution of the full aperture, while sidestepping speckle noise that plague direct diffraction-limited moderate and high contrast imaging. Ground-based NRM is rapidly gaining ground, with observations well beyond Hubble's angular resolution and a 5-sigma point source contrast approaching 8 magnitudes. TFI's sparse aperture mask operating between 3.8 and 5 microns in JWST's Tunable Filter Imager (TFI) will enable science complementary to JWST coronagraphs as well as future 30-m class ground-based telescopes. We show that TFI's NRM will open up a search space between ~75 and 500 mas, with point source contrast of ~10 magnitudes, as shown by our models of an observation of an M=7.5 star, simulating the observing techniques and data calibration methods being developed by the JWST Aperture Masking (JAM) team. Stars as bright as M ~3 will be observable with TFI's NRM, meshing with Gemini's GPI and ESO's SPHERE, with the additional ability of observing fainter targets. We also show how TFI's NRM will be able to probe the structure of dusty tori around active galactic nuclei (AGNs), provide 1 to a few mas astrometry of the galactic center's stars at 5um, and substantially mitigate JWST mission risk associated with JWST's active primary mirrors' wavefront sensing.
George Sonneborn (NASA/GSFC)
We present initial results of a study of abundance and mass loss properties of O-type stars based on theoretical near-IR spectra computed with state-of-the-art stellar atmosphere models. The James Webb Space Telescope (JWST) will be a powerful tool to obtain high signal-to-noise ratio near-IR (1-5 micron) spectra of massive stars in different environments of local galaxies. Our goal is to analyze model near-IR spectra corresponding to those expected from NIRspec on JWST in order to map the wind properties and surface composition across the parameter range of O stars and to determine projected rotational velocities. As a massive star evolves, internal coupling, related mixing, and mass loss impact its intrinsic rotation rate. These three parameters form an intricate loop, where enhanced rotation leads to more mixing which in turn changes the mass loss rate, the latter thus affecting the rotation rate. Since the effects of rotation are expected to be much more pronounced at low metallicity, we pay special attention to models for massive stars in the the Small Magellanic Cloud (SMC). This galaxy provides a unique opportunity to probe stellar evolution, and the feedback of massive stars on galactic evolution in conditions similar to the epoch of maximal star formation.
Dr. Amber Straughn (NASA/GSFC)
While the primary purpose of the NIRCam grism is to assist with the coarse phasing of JWST, we present here some prospects of doing science with the grism, In particular, recent work with the HST WFC3 near-infrared grisms (0.8-1.6 microns) has pushed the study of faint emission line galaxies to redshifts z~2, enabling detailed study of star-forming properties of these galaxies with extremely faint continuum magnitudes. The NIRCam grism offers slitless spectroscopic capabilities at 2.4-5 microns at resolution R~2000, allowing study of emission-line galaxies at higher redshift. I will discuss some of these unique capabilities the NIRCam grism will have for extragalactic studies.
Dr. Jason Tumlinson (STScI)
JWST's Near-Infrared Spectrograph will incorporate a MEMS-based Microshutter Array (MSA) that covers a 3.4x3.4 arcmin field with 249,660 individually configurable shutters (0.2" x 0.5"). NIRSpec is thus ideally suited to performing MOS observations in sky regions with very dense fields of sources. I will present a study of this new capability that applies NIRSpec to observations of the globular cluster Omega Cen and the Galactic bulge, where there is 1 star for every 2-5 shutters on the MSA. Both regions are suitable for NIRSpec observations provided that the user is satisfied by a statistical sampling of stars in the region. I will also describe some simple observing strategies that will improve the quality and dynamic range of these measurements, and the tradeoffs involved in employing them. (Comment: I would like to get some exposure for this potentially very important but still underappreciated use of NIRSpec. So I'd prefer a short talk, 10-15 min would be fine, to reach potential users. I will submit a poster even if a talk slot is available, so that I can show this use case as a full MSA on the sky).
Jeff Valenti (STScI)
JWST will image and characterize exoplanets. This poster summarizes the relevant capabilities and discovery space of the four science instruments (NIRCam, NIRSpec, MIRI, and TFI). Operational issues that may affect scientific yield include field of regard, roll constraints, event-driven operations, target acquisition precision, target drift, pointing transients, thermal stability, electronic stability, bad pixels, intra-pixel sensitivity, and persistence. I will solicit feedback from the community on what can be done now to maximize data quality and scientific impact of exoplanet observations.
Dr. Michael Werner (JPL)
The Spitzer Space Telescope, even in its current warm mission phase operating only at 3.6 and 4.5um, is an important scientific precursor to JWST. In May the Spitzer Science Center announced the selection of 10 Exploration Science projects, totaling 7500 hours of observing time, which will be carried out by Spitzer in the next two years. These projects span the scientific landscape from brown dwarfs to distant galaxies and clusters and touch on many of the major scientific themes of JWST. This presentation will summarize this scientific program and highlight a few specific investigations of particular relevance to JWST.
Prof. Rogier Windhorst (Arizona State University)
We first briefly review the instrumental and natural confusion limits for JWST,which apply to unresolved or resolved objects, resp. For deep JWST surveys with ~0.08" FWHM resolution, the natural confusion limit may become as important for the definition of faint object samples as the survey surface brightness (SB) limit, which is already visible in the deepest HST images. This does, however, not mean that the deepest JWST are fundamentally limited by natural confusion. Instead, hierarchical simulations suggest that faint objects (AB>29 mag) imaged by JWST will be mostly unresolved at 0.08" FWHM, and instrumental confusion doesn't set in until AB>33.5 mag, a limit which even JWST will not reach. Does this therefore mean that the confusion limit is irrelevant for JWST? In Wyithe et al. (2011, Nature, 469, 181), we showed that gravitational lensing will lead to a correlation between the sky positions of high redshift candidates and foreground galaxies at z=1--2. Yan et al. (2010 and this Conf) presented evidence for this correlation among a sample of dropout candidates at z~8-10. By extrapolating the evolution of the galaxy LF-slope and L^* to z>8, we suggest that gravitational lensing may dominate the observed properties of galaxies at z>10 discovered by JWST. The observed surface density of galaxies at z~12-15 will likely be boosted by an order of magnitude, and most z>12-15 galaxies may well be part of a multiply-imaged system, located <~ 1" from a brighter foreground galaxy at z=1--2. This means that deep JWST surveys of the First Light epoch at z>10 may be limited by "gravitational" confusion, where a good part of the First Light "forest" may be gravitationally amplified by the foreground galaxy "trees". Gravitational lensing bias will therefore need to be carefully considered and corrected for in First Light studies with JWST. The exquisite resolution and sensitivity of JWST --- together with a new generation of object finding algorithms --- will be essential to properly address this issue at z>8--10.
Haojing Yan (CCAPP, Ohio State University)
We present our revised analysis of the candidate galaxies at z~8-10 found in the full set of the HUDF09 data. About ~30% of these candidates are found to be close to bright foreground galaxies and/or galaxy groups, which suggests that a significant fraction of galaxies at z~8-10 that we can detect could be gravitationally lensed. This also suggests that, even at the depth of the HUDF, we could still only be probing the bright-end of their LF. All this is consistent with the results of Wyithe et al. (2011) and Yan et al. (2010), and will have important implications to our understanding of the star formation processes in the reionization epoch. JWST will be able to reveal a more comprehensive picture if its observations are designed carefully.