Quantum well infrared photodetectors (QWIPs) are attractive for use in astronomy because they offer good sensitivity, are very stable, are easily manufactured in large sizes, and have (comparatively) ...warm operating temperatures. We describe an astronomical camera based on an 8.5 μm QWIP array which was built at the Jet Propulsion Laboratory and is operated at the Palomar 5-m telescope. We highlight some science results obtained with this instrument, then discuss the prospects for QWIP arrays in future NASA astronomy missions.
Sagittarius A* (Sgr A*), the roughly 4 million solar mass black hole at the center of our galaxy, is arguably the best natural test-bed for supermassive black hole accretion models. Its close ...proximity allows for detailed observations to be made across the electromagnetic spectrum that provide strong, multi-scale constraints on analytic and numerical calculations. These include exciting new event horizon scale results that directly probe the strong field regime for the first time. Spanning roughly 7 orders of magnitude in radius, the accretion system begins at ~ parsec scales where a large population of Wolf-Rayet (WR) stars interact via powerful stellar winds. A fraction of the wind material accretes to the event horizon scales, heating up and radiating on the way down to provide the observed multi-wavelength emission. Detailed modeling of this process requires 3D numerical simulations spanning as large of a dynamical range as possible. The goal of this thesis has been to improve the predictive power of such simulations applied to Sgr A* by limiting the number of free parameters that they contain. This is done by incorporating more theoretical and observational knowledge into the calculations, for example, what collisionless physics tells us about how electrons/ions are heated in a turbulent medium and the properties of the winds of the WR stars. The resulting simulations have shown excellent agreement with a wide range of observational constraints and could have major implications for how the accretion flow around Sgr A* is modeled in the future. The techniques presented here are also applicable to other low luminosity AGN and X-ray binaries.
The Near-Earth Object Surveyor Mission Mainzer, A. K.; Masiero, J. R.; Abell, Paul A. ...
The planetary science journal,
12/2023, Letnik:
4, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Abstract
The Near-Earth Object (NEO) Surveyor mission is a NASA Observatory designed to discover and characterize asteroids and comets. The mission’s primary objective is to find the majority of ...objects large enough to cause severe regional impact damage (>140 m in effective spherical diameter) within its 5 yr baseline survey. Operating at the Sun–Earth L1 Lagrange point, the mission will survey to within 45° of the Sun in an effort to find objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard reliably. Over the course of its survey, NEO Surveyor will discover ∼200,000–300,000 new NEOs down to sizes as small as ∼10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century.
Galaxy and occupies perhaps a quarter of the volume of the Galactic disk. Decoding the spectrum of the Galactic diffuse ionizing field is of fundamental interest. This can be done via direct ...measurements of ionization fractions of various elements. Based on current physical models for the WIM we predicted that mid-IR fine structure lines of Ne, Ar and S would be within the grasp of the Mid-Infrared Imager-Medium Resolution Spectrometer (MIRI-MRS), an Integral Field Unit (IFU) spectrograph, aboard the James Webb Space Telescope (JWST). Motivated thus we analyzed a pair of commissioning data sets and detected NeII 12.81 \(\mu\)m, SIII 18.71 \(\mu\)m and possibly SIV 10.51 \(\mu\)m. The inferred emission measure for these detections is about 10 \({\rm cm^{-6} pc}\), typical of the WIM. These detections are broadly consistent with expectations of physical models for the WIM. The current detections are limited by uncorrected fringing (and to a lesser extent by baseline variations). In due course, we expect, as with other IFUs, the calibration pipeline to deliver photon-noise-limited spectra. The detections reported here bode well for the study of the WIM. Along most lines-of-sight hour-long MIRI-MRS observations should detect line emission from the WIM. When combined with optical observations by modern IFUs with high spectral resolution on large ground-based telescopes, the ionization fraction and temperature of neon and sulfur can be robustly inferred. Separately, the ionization of helium in the WIM can be probed by NIRspec. Finally, joint JWST and optical IFU studies will open up a new cottage industry of studying the WIM on arcsecond scales.
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