4 research outputs found
Closely-Spaced Object Classification Using MuyGPyS
Accurately detecting rendezvous and proximity operations (RPO) is crucial for
understanding how objects are behaving in the space domain. However, detecting
closely-spaced objects (CSO) is challenging for ground-based optical space
domain awareness (SDA) algorithms as two objects close together along the
line-of-sight can appear blended as a single object within the point-spread
function (PSF) of the optical system. Traditional machine learning methods can
be useful for differentiating between singular objects and closely-spaced
objects, but many methods require large training sample sizes or high
signal-to-noise conditions. The quality and quantity of realistic data make
probabilistic classification methods a superior approach, as they are better
suited to handle these data inadequacies. We present CSO classification results
using the Gaussian process python package, MuyGPyS, and examine classification
accuracy as a function of angular separation and magnitude difference between
the simulated satellites. This orbit-independent analysis is done on highly
accurate simulated SDA images that emulate realistic ground-based
commercial-of-the-shelf (COTS) optical sensor observations of CSOs. We find
that MuyGPyS outperforms traditional machine learning methods, especially under
more challenging circumstances.Comment: Accepted to the 2023 Advanced Maui Optical and Space Surveillance
Technologies Conference (AMOS
Disentangling the Black Hole Mass Spectrum with Photometric Microlensing Surveys
From the formation mechanisms of stars and compact objects to nuclear
physics, modern astronomy frequently leverages surveys to understand
populations of objects to answer fundamental questions. The population of dark
and isolated compact objects in the Galaxy contains critical information
related to many of these topics, but is only practically accessible via
gravitational microlensing. However, photometric microlensing observables are
degenerate for different types of lenses, and one can seldom classify an event
as involving either a compact object or stellar lens on its own. To address
this difficulty, we apply a Bayesian framework that treats lens type
probabilistically and jointly with a lens population model. This method allows
lens population characteristics to be inferred despite intrinsic uncertainty in
the lens-class of any single event. We investigate this method's effectiveness
on a simulated ground-based photometric survey in the context of characterizing
a hypothetical population of primordial black holes (PBHs) with an average mass
of . On simulated data, our method outperforms current black hole
(BH) lens identification pipelines and characterizes different subpopulations
of lenses while jointly constraining the PBH contribution to dark matter to
\%. Key to robust inference, our method can marginalize over
population model uncertainty. We find the lower mass cutoff for stellar origin
BHs, a key observable in understanding the BH mass gap, particularly difficult
to infer in our simulations. This work lays the foundation for cutting-edge PBH
abundance constraints to be extracted from current photometric microlensing
surveys.Comment: 31 pages, 18 figures, submitted to AA
A Reanalysis of Public Galactic Bulge Gravitational Microlensing Events from OGLE-III and IV
Modern surveys of gravitational microlensing events have progressed to
detecting thousands per year. Surveys are capable of probing Galactic
structure, stellar evolution, lens populations, black hole physics, and the
nature of dark matter. One of the key avenues for doing this is studying the
microlensing Einstein radius crossing time distribution (). However,
systematics in individual light curves as well as over-simplistic modeling can
lead to biased results. To address this, we developed a model to simultaneously
handle the microlensing parallax due to Earth's motion, systematic instrumental
effects, and unlensed stellar variability with a Gaussian Process model. We
used light curves for nearly 10,000 OGLE-III and IV Milky Way bulge
microlensing events and fit each with our model. We also developed a forward
model approach to infer the timescale distribution by forward modeling from the
data rather than using point estimates from individual events. We find that
modeling the variability in the baseline removes a source of significant bias
in individual events, and previous analyses over-estimated the number of long
timescale ( days) events due to their over simplistic models ignoring
parallax effects and stellar variability. We use our fits to identify hundreds
of events that are likely black holes.Comment: Submitted version, in review, 33 pages, 18 figures, MCMC posterior
samples available by publisher after acceptanc
The Complete Calibration of the Color–Redshift Relation (C3R2) Survey: Analysis and Data Release 2
The Complete Calibration of the Color-Redshift Relation (C3R2) survey is a multi-institution, multi-instrument survey that aims to map the empirical relation of galaxy color to redshift to i ~ 24.5 (AB), thereby providing a firm foundation for weak lensing cosmology with the Stage IV dark energy missions Euclid and WFIRST. Here we present 3171 new spectroscopic redshifts obtained in the 2016B and 2017A semesters with a combination of DEIMOS, LRIS, and MOSFIRE on the Keck telescopes.13 The observations come from all of the Keck partners: Caltech, NASA, the University of Hawaii, and the University of California. Combined with the 1283 redshifts published in DR1, the C3R2 survey has now obtained and published 4454 high-quality galaxy redshifts. We discuss updates to the survey design and provide a catalog of photometric and spectroscopic data. Initial tests of the calibration method performance are given, indicating that the sample, once completed and combined with extensive data collected by other spectroscopic surveys, should allow us to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for WFIRST. We use the full spectroscopic sample to demonstrate that galaxy brightness is weakly correlated with redshift once a galaxy is localized in the Euclid or WFIRST color space, with potentially important implications for the spectroscopy needed to calibrate redshifts for faint WFIRST and LSST sources