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SIRTF guaranteed time observers have specified field surveys to be carried out with IRAC with integration times per position ranging from 90 to over 10,000 seconds. This paper describes the plans for these surveys and their application to the study of galaxy formation and evolution.
The determination of the intergalactic photon densities from the FIR to the UV which is produced by stellar emission and dust reradiation at various redshifts can provide an independent measure of the star formation history of the universe. Using recent Spitzer and GALEX data in conjunction with other observational inputs, Stecker, Malkan and Scully have calculated the intergalactic photon density as a function of both energy and redshift for 0 < zeta < 6 for photon energies from 0.003 eV to the Lyman limit cutoff at 13.6 eV in a ACDM universe with Omega(sub Lambda) = 0.7 and Omega(sub m) = 0.3. Their results are based on backwards evolution models for galaxies which were developed by Malkan and Stecker previously. The calculated background SEDs at zeta = 0 are in good agreement with the present observational data and limits. The calculated intergalactic photon densities as a function of redshift were used to predict to extend the absorption of high energy 7-rays in intergalactic space from sources such as blazars and quasars, this absorption being produced by interactions the y-rays with the intergalactic FIR-UV photons having the calculated densities. The results are in excellent agreement with absorption features found in the low gamma-ray spectra of Mkn 421, Mkn 501 at, zeta = 0.03 and PKS
We calculate the intergalactic photon density as a function of both energy and redshift for 0<z<6 for photon energies from.003 eV to the Lyman limit cutoff at 13.6 eV in a (Omega)CDM universe with (Omega)(Lambda)=0.7 and (Omega)m=0.3. The basic features of our backward-evolution model for galaxies were developed in earlier papers by Malkan & Stecker. With a few improvements, we find that this evolutionary model gives predictions of new deep number counts from Spitzer, as well as a calculation of the spectral energy distribution of the diffuse infrared background, which are in good agreement with the data. We then use our calculated intergalactic photon densities to extend previous work on the absorption of high-energy Gamma-rays in intergalactic space owing to interactions with low-energy photons and the 2.7 K cosmic microwave background radiation. We calculate the optical depth of the universe, Tau , for Gamma-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from 0 to 5. We also give an analytic fit with numerical coefficients for approximating (E(Gamma), z). As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z=0.117 and compare it with the spectrum observed by the HESS air Cerenkov Gamma-ray telescope array.
Astronomical dust is observed in a variety of astrophysical environments and plays an important role in radiative processes and chemical evolution in the galaxy. Depending upon the environment, dust can be either carbon-rich or oxygen-rich (silicate grains). Both astronomical observations and ground-based data show that the optical properties of silicates can change dramatically with the crystallinity of the material, and recent laboratory research provides evidence that the optical properties of silicate dust vary as a function of temperature as well. Therefore, correct interpretation of a vast array of astronomical data relies on the understanding of the properties of silicate dust as functions of wavelength, temperature, and crystallinity. The OPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project addresses the need for high quality optical characterization of metal-enriched silicate condensates using a variety of techniques. A combination of both new and established experiments are used to measure the extinction, reflection, and emission properties of amorphous silicates across the infrared (near infrared to millimeter wavelengths), providing a comprehensive data set characterizing the optical parameters of dust samples. We present room temperature measurements and the experimental apparatus to be used to investigate and characterize additional metal-silicate materials.
I'll discuss several ways in which JWST will probe the cosmic history of accretion onto supermassive black holes, and the co-evolution of host galaxies. Key investigations include: 1) Measurements of redshift, luminosity, and AGN fraction for obscured AGN candidates identified by other missions. 2) Measurements of AGN hosts at all redshifts, including stellar masses, morphology, interactions, and star formation rates. 3) Measurements of stellar mass and black hole mass in AGN at high redshift, to chart the early history of black hole and galaxy growth.
We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approx.1000 all-sky) population of galaxies at high redshift (peaks at z = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 microns, yet are clearly detected at 12 and 22 microns. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (z > 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 microns, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 microns, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60 C120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) Stellar Luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.
We have used the Caltech Submillimeter Observatory (CSO) to follow-up a sample of Wide-field Infrared Survey Explorer (WISE) selected, hyperluminous galaxies, the so-called W1W2-dropout galaxies. This is a rare (approximately 1000 all-sky) population of galaxies at high redshift (peaks at zeta = 2-3), which are faint or undetected by WISE at 3.4 and 4.6 micrometers, yet are clearly detected at 12 and 22 micrometers. The optical spectra of most of these galaxies show significant active galactic nucleus activity. We observed 14 high-redshift (zeta greater than 1.7) W1W2-dropout galaxies with SHARC-II at 350-850 micrometers, with nine detections, and observed 18 with Bolocam at 1.1 mm, with five detections. Warm Spitzer follow-up of 25 targets at 3.6 and 4.5 micrometers, as well as optical spectra of 12 targets, are also presented in the paper. Combining WISE data with observations from warm Spitzer and CSO, we constructed their mid-IR to millimeter spectral energy distributions (SEDs). These SEDs have a consistent shape, showing significantly higher mid-IR to submillimeter ratios than other galaxy templates, suggesting a hotter dust temperature.We estimate their dust temperatures to be 60-120 K using a single-temperature model. Their infrared luminosities are well over 10(exp 13) solar luminosity. These SEDs are not well fitted with existing galaxy templates, suggesting they are a new population with very high luminosity and hot dust. They are likely among the most luminous galaxies in the universe.We argue that they are extreme cases of luminous, hot dust-obscured galaxies (DOGs), possibly representing a short evolutionary phase during galaxy merging and evolution. A better understanding of their long-wavelength properties needs ALMA as well as Herschel data.
The Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor is one of four large mission concept studies being developed by NASA for consideration in the 2020 Astrophysics Decadal Survey. LUVOIR will support a broad range of science objectives, including the direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of galaxy formation and evolution, the epoch of reionization, star and planet formation, and the remote sensing of Solar System bodies. The LUVOIR Science and Technology Definition Team (STDT) has tasked a Technology Working Group (TWG), with more than 60 members from NASA centers, academia, industry, and international partners, with identifying technologies that enable or enhance the LUVOIR science mission. The TWG has identified such technologies in the areas of Coronagraphy, Ultra-Stable Opto-mechanical Systems, Detectors, Coatings, Starshades, and Instrument Components, and has completed a detailed assessment of the state-of-the-art. We present here a summary of this technology assessment effort, as well as the current progress in defining a technology development plan to mature these technologies to the required technology readiness level (TRL).
In preparation for the 2020 Astrophysics Decadal Survey, NASA has commissioned the study of four large mission concepts, including the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor. The LUVOIR Science and Technology Definition Team (STDT) has identified a broad range of science objectives including the direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of galaxy formation and evolution, the epoch of reionization, star and planet formation, and the remote sensing of Solar System bodies. NASA’s Goddard Space Flight Center (GSFC) is providing the design and engineering support to develop executable and feasible mission concepts that are capable of the identified science objectives. We present an update on the first of two architectures being studied: a 15-meter-diameter segmented-aperture telescope with a suite of serviceable instruments operating over a range of wavelengths between 100 nm to 2.5 microns. Four instruments are being developed for this architecture: an optical / near-infrared coronagraph capable of 10(exp -10) contrast at inner working angles as small as 2 lambda/D; the LUVOIR UV Multi-object Spectrograph (LUMOS), which will provide low- and medium-resolution UV (100 – 400 nm) multi-object imaging spectroscopy in addition to far-UV imaging; the High Definition Imager (HDI), a high-resolution wide-field-of-view NUV-Optical-IR imager; and a UV spectro-polarimeter being contributed by Centre National d’Etudes Spatiales (CNES). A fifth instrument, a multi-resolution optical-NIR spectrograph, is planned as part of a second architecture to be studied in late 2017.
The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is one of four mission concepts being studied by NASA for the 2020 Decadal Survey in Astronomy and Astrophysics. LUVOIR will be capable of a broad range of science, including: direct imaging and characterization of a wide range of exoplanets and the search for biosignatures on Earth-like planets around sun-like stars; studying galaxy formation and evolution; investigating star and planet formation; and remote sensing of bodies within the Solar System. Enabling a mission as ambitious as LUVOIR requires an array of technologies, such as ultra-stable structures and optics, precision metrology and wavefront sensing, high-contrast imaging techniques, large-format detectors with very low noise, and high-throughput ultraviolet instrumentation. Critically, a systems-level approach must be taken to developing these technologies, guided by architecture studies to place each technology in the appropriate system context.In this poster, we describe LUVOIR's technology needs, as well as current efforts that are actively developing these technologies. We will discuss recent advancements in: measuring picometer-level displacements of optical and structural elements; sub-milli-kelvin thermal sensing and control; non-contact vibration isolation for pointing and dynamic stability; coronagraph design for achieving 10-10 contrast on a segmented system; high-speed metrology for optical system alignment; low-order and out-of-band wavefront sensing for maintaining high-contrast images; low-noise detectors across the ultraviolet, optical, and near infrared bands; broadband coatings with high-reflectivity below Ly. We will also describe a systems approach to coordinating the development of these technologies to achieve the necessary maturity for a LUVOIR mission start in the next decade.
The Large Ultraviolet/Optical/Infrared (LUVOIR) Surveyor is one of four large strategic mission concept studies commissioned by NASA for the 2020 Decadal Survey in Astronomy and Astrophysics. Slated for launch to the second Lagrange point (L2) in the mid-to-late 2030s, LUVOIR seeks to directly image habitable exoplanets around sun-like stars, characterize their atmospheric and surface composition, and search for biosignatures, as well as study a large array of astrophysics goals including galaxy formation and evolution. Two observatory architectures are currently being considered which bound the trade-off between cost, risk, and scientific return: a 15-meter diameter segmented aperture primary mirror in a three-mirror anastigmat configuration, and an 8-meter diameter unobscured segmented aperture design. To achieve its science objectives, both architectures require milli-Kelvin level thermal stability over the optics, structural components, and interfaces to attain picometer wavefront RMS stability. A 270 Kelvin operational temperature was chosen to balance the ability to perform science in the near-infrared band and the desire to maintain the structure at a temperature with favorable material properties and lower contamination accumulation. This paper will focus on the system-level thermal designs of both LUVOIR observatory architectures. It will detail the various thermal control methods used in each of the major components - the optical telescope assembly, the spacecraft bus, the sunshade, and the suite of accompanying instruments - as well as provide a comprehensive overview of the analysis and justification for each design decision. It will additionally discuss any critical thermal challenges faced by the engineering team should either architecture be prioritized by the Astro2020 Decadal Survey process to proceed as the next large strategic mission for development.
The Large Ultraviolet/Optical/Infrared (LUVOIR) Surveyor is one of four large strategic mission concept studies commissioned by NASA for the 2020 Decadal Survey in Astronomy and Astrophysics. Slated for launch to the second Lagrange point (L2) in the mid-to-late 2030s, LUVOIR seeks to directly image habitable exoplanets around sun-like stars, characterize their atmospheric and surface composition, and search for biosignatures, as well as study a large array of astrophysics goals including galaxy formation and evolution. Two observatory architectures are currently being considered which bound the trade-off between cost, risk, and scientific return: a 15-meter diameter segmented aperture primary mirror in a three-mirror anastigmat configuration, and an 8-meter diameter unobscured segmented aperture design. To achieve its science objectives, both architectures require milli-Kelvin level thermal stability over the optics, structural components, and interfaces to attain picometer wavefront RMS stability. A 270 Kelvin operational temperature was chosen to balance the ability to perform science in the near-infrared band and the desire to maintain the structure at a temperature with favorable material properties and lower contamination accumulation. This paper will focus on the system-level thermal designs of both LUVOIR observatory architectures. It will detail the various thermal control methods used in each of the major components - the optical telescope assembly, the spacecraft bus, the sunshade, and the suite of accompanying instruments - as well as provide a comprehensive overview of the analysis and justification for each design decision. It will additionally discuss any critical thermal challenges faced by the engineering team should either architecture be prioritized by the Astro2020 Decadal Survey process to proceed as the next large strategic mission for development.
Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2- to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget.
The Wide-Field Infrared Explorer (WIRE) is a cryogenically-cooled spaceborne telescope designed to study the evolution of starburst galaxies...We describe the design and implementation of the simulator, with particular emphasis on the generation of point-spread functions. The simulator is written in C for use on Unix workstations, and we assess its performance. Sample raw and combined images are displayed, and the image processing steps are outlined. The uses of the simulator to verify that mission requirements are met, to optimize observing strategy, and to test data analysis techniques are also described.
JWST - launched December 25, 2021 - is poised to change the way we understand the universe, and we are already making some groundbreaking discoveries in just the first several months of operations. I will discuss the engineering milestones that made the mission possible, as well as the over-arching scientific themes/goals of the telescope: first galaxies around the time of cosmic reionization, galaxy assembly and evolution, the birth of stars & protoplanetary systems, and study of planets (both within the solar system and exoplanets). I will also discuss specific scientific programs approved for Cycle 1, as well as early results from the mission.
ABSTRACT In this paper, we present data from 72 low-redshift, hard X-ray selected active galactic nucleus (AGN) taken from the Swift–BAT 58 month catalogue. We utilize spectral energy distribution fitting to the optical to infrared photometry in order to estimate host galaxy properties. We compare this observational sample to a volume- and flux-matched sample of AGN from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations in order to verify how accurately the simulations can reproduce observed AGN host galaxy properties. After correcting for the known +0.2 dex offset in the SFRs between EAGLE and previous observations, we find agreement in the star formation rate (SFR) and X-ray luminosity distributions; however, we find that the stellar masses in EAGLE are 0.2–0.4 dex greater than the observational sample, which consequently leads to lower specific star formation rates (sSFRs). We compare these results to our previous study at high redshift, finding agreement in both the observations and simulations, whereby the widths of sSFR distributions are similar (∼0.4–0.6 dex) and the median of the SFR distributions lie below the star-forming main sequence by ∼0.3–0.5 dex across all samples. We also use EAGLE to select a sample of AGN host galaxies at high and low redshift and follow their characteristic evolution from z = 8 to z = 0. We find similar behaviour between these two samples, whereby star formation is quenched when the black hole goes through its phase of most rapid growth. Utilizing EAGLE we find that 23 per cent of AGN selected at z ∼ 0 are also AGN at high redshift, and that their host galaxies are among the most massive objects in the simulation. Overall, we find EAGLE reproduces the observations well, with some minor inconsistencies (∼0.2 dex in stellar masses and ∼0.4 dex in sSFRs).
T Coronae Borealis (TCrB) is a recurrent nova with recorded outbursts in 1866 and 1946 and possible outbursts in 1217 and 1787. It is predicted to explode again in 2025 or 2026 based on multiple observational studies. The system consists of a massive ( M wd ≳ 1.35 M ⊙ ) white dwarf (WD) and a red giant (M3–M4 III). We have performed 1D hydrodynamic simulations with NOVA to predict the behavior of the next outburst. These simulations consist of a range of mass accretion rates onto ∼1.35 M ⊙ WDs, designed to bound the conditions necessary to achieve ignition of an explosion after an ≈80 yr interoutburst period. We have used both carbon–oxygen and oxygen–neon initial compositions, in order to include the possible ejecta abundances to be measured in the observations of the next outburst. As the WD in the TCrB system is observed to be massive, theoretical predictions reported here imply that the WD is growing in mass as a consequence of the thermonuclear runaway. Therefore, the secular evolution of the WD may allow it to approach the Chandrasekhar limit and either explode as a Type Ia supernova or undergo accretion-induced collapse, depending on its underlying composition. We have followed the evolution of just the WD, after removing the ejected matter from the surface layers. Our intent is to illuminate the mystery of the unique, second maximum in the two well-observed outbursts and we have found conditions that bracket the predictions.
The authors present numerical experiments on dynamical friction in pairs of elliptical galaxies of unequal mass. They confirm that the self-gravity of the response is not important and show the drastic effect of the deformability of the companion which reduces the decay time by more than a factor of 2. Almost the same amount of orbital energy is dissipated within the satellite as within the large galaxy. Finally, the authors discuss the importance of distant encounters for the dynamical evolution of systems of galaxies.