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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1988

The reionization of unshocked ejecta in SN 1006

The validity of carbon-deflagration models white dwarf models for type Ia supernovae is investigated by examining whether most of the iron in the center of SN 1006 exists in forms other than Fe II, such as iron grains or other ionic stages of iron, as the models require. The possible ways in which iron can be hidden in SN 1006 are reviewed, and an argument on observational grounds is made against any appreciable fraction of iron in grains or Fe I. Various mechanisms for ionizing unshocked iron beyond Fe II are discussed; the most probable mechanism for ionizing the iron appears to be photoionization by UV and X-ray emission from reverse-shocked ejecta. A detailed model for this reverse-shcok photoionization mechanism is described.

Hamilton, Andrew J. S.↗
NASA NTRS2011

RATIR: Reionization and Transients Infra-Red Camera. A New Instrument to Identify High Red-Shift GRBs

We are currently constructing the cryogenic infrared portion of the RATIR instrument at NASA's Goddard Space Flight Center (GSFC) in collaboration with University of California, Berkeley (UCB) and The University of Mexico (UNAM). The infrared instrument will consist of two 2048x2048 Hawaii 2RG detectors, one on axis and one off axis using diachronic. The detectors will be operated using state-of-the-art Teledyne SIDECAR (System Image, Digitizing, Enhancing, Controlling, And Retrieving) ASICs (Application- Specific Integrated Circuits) similar to NIRSpec on JWST. The visible portion of the instrument is currently being developed at UCB consisting of two CCD imagining cameras. Once completed, the two sections will be integrated into the RATIR instrument. Mounted on a dedicated, fully-automated 1.5-m telescope, the instrument will provide rapid (<10 min) identification of VHR GRBs allowing high-resolution spectroscopic follow-up observations with large aperture telescopes possible. The hosting Observatorio Astronomico Nacional of the Universidad Nacional Autonoma de Mexico (UNAM), located on the Sierra de San Pedro Martir in Baja California, Mexico, provides great seeing (-1 aresec), good weather, dark skies, and significant sky coverage so that RATIR will detect a significant number of Swift afterglows. While not all GRBs will be at high red shifts, the resulting light curves, combined with X-ray/UV observations, will address several open questions, including the nature of both "dark GRBs" and the GRB emission mechanism.

Rapchun, David A.↗
NASA NTRS2011

Inflation, Reionization, and All That: The Primordial Inflation Explorer

The Primordial Inflation Explorer is an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. PIXIE uses an innovative optical design to achieve background-limited sensitivity in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 micron wavelength). The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r less than l0^{-3) at 5 standard deviations. The rich PIXIE data set will also constrain physical processes ranging from Big Bang cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy. I describe the PIXIE instrument and mission architecture needed to detect the inflationary signature using only 4 semiconductor bolometers.

Kogut, Alan J.↗
NASA NTRS2012

Inflation, Reionization, and All That: The Primordial Inflation Explorer

The Primordial Inflation Explorer is an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. PIXIE uses an innovative optical design to achieve background-limited sensitivity in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 micron wavelength). The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r < 10(exp -3) at 5 standard deviations. The rich PIXIE data set will also constrain physical processes ranging from Big Bang cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy. I describe the PIXIE instrument and mission architecture needed to detect the inflationary signature using only 4 semiconductor bolometers.

Kogut, Alan J.↗
NASA NTRS2015

Reconstructing Emission from Pre-Reionization Sources with Cosmic Infrared Background Fluctuation Measurements by the JWST

We present new methodology to use cosmic infrared background (CIB) fluctuations to probe sources at 10 less than or approx. equal to z less than or approx. equal to 30 from a James Webb Space Telescope (JWST) NIRCam configuration that will isolate known galaxies to 28 AB mag at 0.55 m. At present significant mutually consistent source-subtracted CIB fluctuations have been identified in the Spitzer and AKARI data at 25 m, but we demonstrate internal inconsistencies at shorter wavelengths in the recent CIBER data. We evaluate CIB contributions from remaining galaxies and show that the bulk of the high-z sources will be in the confusion noise of the NIRCam beam, requiring CIB studies. The accurate measurement of the angular spectrum of the fluctuations and probing the dependence of its clustering component on the remaining shot noise power would discriminate between the various currently proposed models for their origin and probe the flux distribution of its sources. We show that the contribution to CIB fluctuations from remaining galaxies is large at visible wavelengths for the current instruments precluding probing the putative Lyman-break of the CIB fluctuations. We demonstrate that with the proposed JWST configuration such measurements will enable probing the Lyman-break. We develop a Lyman-break tomography method to use the NIRCam wavelength coverage to identify or constrain, via the adjacent two-band subtraction, the history of emissions over 10 less than or approx. equal to z less than or approx. equal to 30 as the universe comes out of the Dark Ages. We apply the proposed tomography to the current SpitzerIRAC measurements at 3.6 and 4.5 m, to find that it already leads to interestingly low upper limit on emissions at z greater than or approx. equal to 30.

NIRCam beam↗
NASA NTRS2019

Lyα Galaxies in the Epoch of Reionization (LAGER): Spectroscopic Confirmation of Two Redshift ~7.0 Galaxies

We spectroscopically confirmed two narrowband-selected redshift 7.0 Lyα galaxies and studied their rest-frame UV spectra. The Lyα and other UV nebular lines are very useful to confirm the galactic redshifts and diagnose the different mechanisms driving the ionizing emission. We observed two narrowband-selected z = 7.0 Lyα candidates in the LAGER Chandra Deep Field South (CDFS) field with IMACS at the Magellan telescope and confirmed they are Lyα emitters at z = 6.924 and 6.931. In one galaxy, we also obtained deep near-infrared (NIR) spectroscopy, which yields non-detections of the high-ionization UV nebular lines. We measured the upper limits of the ratios of C iv λ1548/Lyα, He ii λ1640/Lyα, O iii]λ1660/Lyα, and C iii]λ1909/Lyα from the NIR spectra. These upper limits imply that the ionizing emission in this galaxy is dominated by normal star formation instead of an active galactic nucleus.

Yang, Huan↗