Abstract
We present an extinction map of the inner ∼15′ by 16′ of the Galactic center (GC) with map pixels measuring 5″ × 5″ using integrated light color measurements in the near- and mid-infrared. ...We use a variant of the Rayleigh–Jeans color excess (RJCE) method first described by Majewski et al. as the basis of our work, although we have approached our problem with a Bayesian mindset and dispensed with point-source photometry in favor of surface photometry, turning the challenge of the extremely crowded field at the GC into an advantage. Our results show that extinction at the GC is not inconsistent with a single power-law coefficient,
β
= 2.03 ± 0.06, and compare our results with those using the red clump (RC) point-source photometry method of extinction estimation. We find that our measurement of
β
and its apparent lack of spatial variation are in agreement with prior studies, despite the bimodal distribution of values in our extinction map at the GC with peaks at 5 and 7.5 mag. This bimodal nature of extinction is likely due to the infrared dark clouds that obscure portions of the inner GC field. We present our extinction law and map of the GC region using the point-source catalog of infrared sources compiled by DeWitt et al. The dereddening is limited by the error in the extinction measurement (typically 0.6 mag), which is affected by the size of our map pixels and is not fine-grained enough to separate out the multiple stellar populations present toward the GC.
ABSTRACT
We present results from end-to-end simulations of observations designed to constrain the rate of change in the expansion history of the Universe using the redshift drift of the Lyman-α ...forest absorption lines along the lines of sight towards bright quasars. For our simulations, we take Lyman-α forest lines extracted from Keck/HIRES spectra of bright quasars at z > 3, and compare the results from these real quasar spectra with mock spectra generated via Monte Carlo realizations. We use the results of these simulations to assess the potential for a dedicated observatory to detect redshift drift, and quantify the telescope and spectrograph requirements for these observations. Relative to Liske et al. (2008), two main refinements in the current work are inclusion of quasars from more recent catalogs and consideration of a realistic observing strategy for a dedicated redshift drift experiment that maximizes $\dot{v}/\sigma _{\dot{v}}$. We find that using a dedicated facility and our designed observing plan, the redshift drift can be detected at 3σ significance in 15 yr with a 25 m telescope, given a spectrograph with long-term stability with R = 50 000 and 25 per cent total system efficiency. To achieve this significance, the optimal number of targets is four quasars, with observing time weighted based upon $\dot{v}/\sigma _{\dot{v}}$ and object visibility. This optimized strategy leads to a 9 per cent decrease in the telescope diameter or a 6 per cent decrease in the required time to achieve the same S/N as for the idealized case of uniformly distributing time to the same quasars.
The future of space and ground based telescopes is intimately tied to technology and algorithm development surrounding wavefront sensing and control. Only with cutting edge developments and unusual ...ideas will we be able to build diffraction limited observatories on the ground that contend with earth-atmosphere, as well as space-based observatories that sense and control for optical aberrations and telescope jitter. There exist a variety of mathematical bases for decomposing wavefront images, including the zonal modal basis, Zernike polynomials, and Fourier modes. However, previous bases have neglected the most vital element of astronomical optics: our field is only as good as the people in it. In this paper we propose a new Many Headed Hydra Modal Basis (hydra heads) for wavefront decomposition, using physical representations of the Adaptive Optics community. We find that the first author makes the best wavefront decomposition, on the order of a correct reconstruction within \(\sim 1\%\) of the original turbulence image. We discuss engineering implications of the Many Headed Hydra Modal Basis, as applied to deformable mirror technology and within active and adaptive optics control loops. Finally, we explore predictive control avenues, by positing that the first author being the most effective wavefront predicts a successful future for them as a high contrast imaging scientist.
We present an extinction map of the inner \(\sim\)\SI{15}{\arcminute} by {16}{\arcminute} of the Galactic Center (GC) with map `pixels' measuring \SI{5}{\arcsecond} \(\times\) \SI{5}{\arcsecond} ...using integrated light color measurements in the near- and mid-infrared. We use a variant of the Rayleigh-Jeans Color Excess (RJCE) method first described by Majewski et al. (2011) as the basis of our work, although we have approached our problem with a Bayesian mindset and dispensed with point-source photometry in favor of surface photometry, turning the challenge of the extremely crowded field at the GC into an advantage. Our results show that extinction at the GC is not inconsistent with a single power law coefficient, \(\beta=2.03\pm0.06\), and compare our results with those using the Red Clump (RC) point-source photometry method of extinction estimation. We find that our measurement of \(\beta\) and its apparent lack of spatial variation are in agreement with prior studies, despite the bimodal distribution of values in our extinction map at the GC with peaks at \num{5} and \SI{7.5}{mag}. This bimodal nature of extinction is likely due to the InfraRed Dark Clouds that obscure portions of the inner GC field. We present our extinction law and map and de-reddened NIR CMDs and color-color diagram of the GC region using the point-source catalog of IR sources compiled by DeWitt et al. (2010). The de-reddening is limited by the error in the extinction measurement (typically \SI{0.6}{mag}), which is affected by the size of our map pixels and is not fine-grained enough to separate out the multiple stellar populations present toward the GC.
We present end-to-end simulations of SCALES, the third generation thermal-infrared diffraction limited imager and low/med-resolution integral field spectrograph (IFS) being designed for Keck. The 2-5 ...micron sensitivity of SCALES enables detection and characterization of a wide variety of exoplanets, including exoplanets detected through long-baseline astrometry, radial-velocity planets on wide orbits, accreting protoplanets in nearby star-forming regions, and reflected-light planets around the nearest stars. The simulation goal is to generate high-fidelity mock data to assess the scientific capabilities of the SCALES instrument at current and future design stages. The simulation processes arbitrary-resolution input intensity fields with a proposed observation pattern into an entire mock dataset of raw detector read-out lenslet-based IFS frames with calibrations and metadata, which are then reduced by the IFS data reduction pipeline to be analyzed by the user.
We present the design and lab performance of a prototype lenslet-slicer hybrid integral field spectrograph (IFS), validating the concept for use in future instruments like SCALES/PSI-Red. By imaging ...extrasolar planets with IFS, it is possible to measure their chemical compositions, temperatures and masses. Many exoplanet-focused instruments use a lenslet IFS to make datacubes with spatial and spectral information used to extract spectral information of imaged exoplanets. Lenslet IFS architecture results in very short spectra and thus low spectral resolution. Slicer IFSs can obtain higher spectral resolution but at the cost of increased optical aberrations that propagate through the down-stream spectrograph and degrade the spatial information we can extract. We have designed a lenslet/slicer hybrid that combines the minimal aberrations of the lenslet IFS with the high spectral resolution of the slicer IFS. The slicer output f/\# matches the lenslet f/\# requiring only additional gratings.
We present the innovative macro-slicer optical and opto-mechanical designs for the third-generation Mid-resolution InfraReD Astronomical Spectrograph (MIRADAS) instrument for the 10.4m Gran ...Telescopio Canarias (GTC) in the 1-2.5 \(\mu\)m bandpass. MIRADAS uses up to 12 cryogenic, fully steerable probes to select simultaneous targets in a 5 arcminute field of view. The spectrograph module is a cross-dispersed echelle spectrograph. The macro-slicer is effectively a stack of six advanced image slicer Integral Field Units (IFUs) such as FRIDA or FISICA, and like other IFUs designed and built at the University of Florida by our group, uses a `bolt-and-go' approach to minimize the difficulty in alignment and maximize robustness. Like other advanced image slicer IFUs, there are three sets of mirrors that work together to geometrically rearrange the loosely packed inputs from the probe arms into a tightly packed pseudo-slit. The macro-slicer also passively keeps the spectral resolution of MIRADAS fixed at \(R>20,000\) in seeing from 1.2 arcseconds down to 0.4 arcseconds, (typical observing conditions at GTC).
SCALES for Keck: Optical Design Kupke, Renate; R Deno Stelter; Hasan, Amirul ...
arXiv (Cornell University),
08/2022
Paper, Journal Article
Odprti dostop
SCALES is a high-contrast, infrared coronagraphic imager and integral field spectrograph (IFS) to be deployed behind the W.M. Keck Observatory adaptive optics system. A reflective optical design ...allows diffraction-limited imaging over a large wavelength range (1.0 - 5.0 microns). A microlens array-based IFS coupled with a lenslet reformatter ("slenslit") allow spectroscopy at both low (R = 35 - 250) and moderate (R = 2000 - 6500) spectral resolutions. The large wavelength range, diffraction-limited performance, high contrast coronagraphy and cryogenic operation present a unique optical design challenge. We present the full SCALES optical design, including performance modeling and analysis and manufacturing.
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