3,085 research outputs found
A comprehensive radial velocity error budget for next generation Doppler spectrometers
We describe a detailed radial velocity error budget for the NASA-NSF Extreme
Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet
Investigations with Doppler spectroscopy). Such an instrument performance
budget is a necessity for both identifying the variety of noise sources
currently limiting Doppler measurements, and estimating the achievable
performance of next generation exoplanet hunting Doppler spectrometers. For
these instruments, no single source of instrumental error is expected to set
the overall measurement floor. Rather, the overall instrumental measurement
precision is set by the contribution of many individual error sources. We use a
combination of numerical simulations, educated estimates based on published
materials, extrapolations of physical models, results from laboratory
measurements of spectroscopic subsystems, and informed upper limits for a
variety of error sources to identify likely sources of systematic error and
construct our global instrument performance error budget. While natively
focused on the performance of the NEID instrument, this modular performance
budget is immediately adaptable to a number of current and future instruments.
Such an approach is an important step in charting a path towards improving
Doppler measurement precisions to the levels necessary for discovering
Earth-like planets.Comment: 20 pages, 12 figures, published in Proc. of SPIE Astronomical
Telescopes + Instrumentation 201
Review of subjective measures of human response to aircraft noise
The development of aircraft noise rating scales and indexes is reviewed up to the present time. Single event scales, multiple event indexes, and their interrelation with each other, are considered. Research requirements for further refinement and development of aircraft noise rating quantification factors are discussed
PSFs of coadded images
We provide a detailed exploration of the connection between choice of
coaddition schemes and the point-spread function (PSF) of the resulting coadded
images. In particular, we investigate what properties of the coaddition
algorithm lead to the final coadded image having a well-defined PSF. The key
elements of this discussion are as follows:
1. We provide an illustration of how linear coaddition schemes can produce a
coadd that lacks a well-defined PSF even for relatively simple scenarios and
choices of weight functions.
2. We provide a more formal demonstration of the fact that a linear coadd
only has a well-defined PSF in the case that either (a) each input image has
the same PSF or (b) the coadd is produced with weights that are independent of
the signal.
3. We discuss some reasons that two plausible nonlinear coaddition algorithms
(median and clipped-mean) fail to produce a consistent PSF profile for stars.
4. We demonstrate that all nonlinear coaddition procedures fail to produce a
well-defined PSF for extended objects.
In the end, we conclude that, for any purpose where a well-defined PSF is
desired, one should use a linear coaddition scheme with weights that do not
correlate with the signal and are approximately uniform across typical objects
of interest.Comment: 13 pages, 4 figures; pedagogical article for submission to the Open
Journal of Astrophysic
A Catalog of Cool Dwarf Targets for the Transiting Exoplanet Survey Satellite
We present a catalog of cool dwarf targets (, ) and their stellar properties for the upcoming Transiting Exoplanet
Survey Satellite (TESS), for the purpose of determining which cool dwarfs
should be observed using two-minute observations. TESS has the opportunity to
search tens of thousands of nearby, cool, late K and M-type dwarfs for
transiting exoplanets, an order of magnitude more than current or previous
transiting exoplanet surveys, such as {\it Kepler}, K2 and ground-based
programs. This necessitates a new approach to choosing cool dwarf targets. Cool
dwarfs were chosen by collating parallax and proper motion catalogs from the
literature and subjecting them to a variety of selection criteria. We calculate
stellar parameters and TESS magnitudes using the best possible relations from
the literature while maintaining uniformity of methods for the sake of
reproducibility. We estimate the expected planet yield from TESS observations
using statistical results from the Kepler Mission, and use these results to
choose the best targets for two-minute observations, optimizing for small
planets for which masses can conceivably be measured using follow up Doppler
spectroscopy by current and future Doppler spectrometers. The catalog is
incorporated into the TESS Input Catalog and TESS Candidate Target List until a
more complete and accurate cool dwarf catalog identified by ESA's Gaia Mission
can be incorporated.Comment: Accepted to The Astronomical Journal. For the full catalog, please
contact the corresponding autho
H0LiCOW X: Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI2033-4723
Galaxies and galaxy groups located along the line of sight towards
gravitationally lensed quasars produce high-order perturbations of the
gravitational potential at the lens position. When these perturbation are too
large, they can induce a systematic error on of a few-percent if the lens
system is used for cosmological inference and the perturbers are not explicitly
accounted for in the lens model. In this work, we present a detailed
characterization of the environment of the lens system WFI2033-4723 (, = 0.6575), one of the core targets of the H0LICOW
project for which we present cosmological inferences in a companion paper (Rusu
et al. 2019). We use the Gemini and ESO-Very Large telescopes to measure the
spectroscopic redshifts of the brightest galaxies towards the lens, and use the
ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the
lens ( km/s) and of several nearby
galaxies. In addition, we measure photometric redshifts and stellar masses of
all galaxies down to mag, mainly based on Dark Energy Survey imaging
(DR1). Our new catalog, complemented with literature data, more than doubles
the number of known galaxy spectroscopic redshifts in the direct vicinity of
the lens, expanding to 116 (64) the number of spectroscopic redshifts for
galaxies separated by less than 3 arcmin (2 arcmin) from the lens. Using the
flexion-shift as a measure of the amplitude of the gravitational perturbation,
we identify 2 galaxy groups and 3 galaxies that require specific attention in
the lens models. The ESO MUSE data enable us to measure the
velocity-dispersions of three of these galaxies. These results are essential
for the cosmological inference analysis presented in Rusu et al. (2019).Comment: Matches the version accepted for publication by MNRAS. Note that this
paper previously appeared as H0LICOW X
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