A5005808635- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- History and Developments in Astronomy
- Astro and Planetary Science
- Radio Astronomy Observations and Technology
- Scientific Computing and Data Management
- Pulsars and Gravitational Waves Research
- Advanced Adaptive Filtering Techniques
- Economic Growth and Productivity
- Computational Physics and Python Applications
- Remote Sensing in Agriculture
- Impact of Light on Environment and Health
- Solar and Space Plasma Dynamics
- Semiconductor Lasers and Optical Devices
- Particle Detector Development and Performance
- Occupational and Professional Licensing Regulation
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Cell Image Analysis Techniques
University of Washington
2014-2023
City University of Seattle
2020-2023
Seattle University
2007-2017
Large Synoptic Survey Telescope Corporation
2015
The University of Texas at Austin
2005-2010
We analyze the global structure of 34 late-type, edge-on, undisturbed, disk galaxies spanning a wide range mass. measure structural parameters for using two-dimensional least-squares fitting to our R-band photometry. The fits require both thick and thin adequately fit data. disks have larger scale heights longer lengths than embedded by factors ∼2 ∼1.25, respectively. observed agree well with properties derived from star counts in Milky Way resolved stellar populations nearby galaxies. find...
The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field, ground-based survey system that will image the sky in six optical bands from 320 to 1050 nm, uniformly covering approximately $18,000$deg$^2$ of over 800 times. LSST currently under construction on Cerro Pachón Chile, and expected enter operations 2022. Once operational, explore wide range astrophysical questions, discovering "killer" asteroids examining nature Dark Energy. generate average 15 TB data per night,...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
Vera C. Rubin Observatory is a ground-based astronomical facility under construction, joint project of the National Science Foundation and U.S. Department Energy, designed to conduct multi-purpose 10-year optical survey southern hemisphere sky: Legacy Survey Space Time. Significant flexibility in strategy remains within constraints imposed by core science goals probing dark energy matter, cataloging Solar System, exploring transient sky, mapping Milky Way. The survey's massive data...
The Vera C. Rubin Observatory is expected to start the Legacy Survey of Space and Time (LSST) in early mid-2025. This multi-band wide-field synoptic survey will transform our view solar system, with discovery monitoring over 5 million small bodies.The final strategy chosen for LSST has direct implications on discoverability characterization system minor planets passing interstellar objects. Creating an inventory one four main science drivers. observing cadence a complex optimization problem...
We find that disk galaxies show a sharp, mass-dependent transition in the structure of their dusty ISM. Dust lanes are generic feature massive disks with V_rot>120km/s, but completely absent V_rot<120km/s. The reflects an increase scale height cold ISM low mass galaxies, driven by larger turbulent velocities supporting gas layer, rather than sharp drops surface density. identify V_rot=120km/s onset gravitational instabilities high galaxies. lead to fragmentation and collapse along...
We present an analysis of the data produced by MaNGA prototype run (P-MaNGA), aiming to test how radial gradients in recent star formation histories, as indicated 4000 Å break (Dn(4000)), Hδ absorption (EW(HδA)), and Hα emission (EW(Hα)) indices, can be useful for understanding disk growth cessation local galaxies. classify 12 galaxies observed on two P-MaNGA plates either centrally quiescent (CQ) or star-forming (CSF), according whether Dn(4000) measured central spaxel each datacube exceeds...
We present the survey design, data reduction, and spectral fitting pipeline for VIRUS-P Exploration of Nearby Galaxies (VENGA). VENGA is an integral field spectroscopic survey, which maps disks 30 nearby spiral galaxies. Targets span a wide range in Hubble type, star formation activity, morphology, inclination. The data-cubes have 5.6'' FWHM spatial resolution, ~5A sample 3600A-6800A range, cover large areas typically sampling galaxies out to ~0.7 R_25. These can be used produce 2D rate,...
In this paper we present and characterize a nearest-neighbors color-matching photometric redshift estimator that features direct relationship between the precision accuracy of input magnitudes output redshifts. This aspect makes our an ideal tool for evaluating impact changes to LSST survey parameters affect measurement errors photometry, which is main motivation work (i.e., it not intended provide "best" redshifts data). We show how will improve with time over 10-year confirm nominal...
Abstract We report studies on the mitigation of optical effects bright low-Earth-orbit (LEO) satellites Vera C. Rubin Observatory and its Legacy Survey Space Time (LSST). These include options for pointing telescope to avoid satellites, laboratory investigations trails LSST camera sensors, algorithms correcting image artifacts caused by trails, experiments darkening SpaceX Starlink ground-based follow-up observations. The original v0.9 are g ∼ 4.5 mag, initial experiment “DarkSat” is 6.1...
The discovery of the electromagnetic counterpart to binary neutron star merger GW170817 has opened era gravitational-wave multi-messenger astronomy. Rapid identification optical/infrared kilonova enabled a precise localization source, which paved way deep multi-wavelength follow-up and its myriad related science results. Fully exploiting this new territory exploration requires acquisition data from samples mergers other gravitational wave sources. After GW170817, frontier is now map...
We present kinematic measurements of the thick and thin disks in two edge-on galaxies. have derived stellar rotation curves at above galaxies' midplanes using Ca II triplet features measured with GMOS spectrograph on Gemini North. In one galaxy, FGC 1415, kinematics plane show clear that lags midplane by ~20-50%, similar to behavior seen Milky Way. However, second 227, are quite different. The is extremely slow, showing <25% speed stars midplane. decompose observed into a superposition...
We present kinematic measurements of thin and thick disk components in a sample nine edge-on galaxies. extract stellar ionized gas rotation curves at above the galaxies' midplanes using Ca II triplet absorption features H-alpha emission lines measured with GMOS spectrographs on Gemini North South. For higher mass galaxies sample, we fail to detect differences between kinematics. In lower galaxies, there is wide range behavior including disks substantial lag one counter-rotating disk. compare...
We have measured Lick index equivalent widths to derive luminosity weighted stellar ages and metallicities for thin- thick-disk-dominated regions of nine edge-on disk galaxies with the ARC 3.5 m telescope at Apache Point Observatory. In all cases, thick disks are confirmed be old populations, typical between 4 10 Gyr. The thin uniformly younger than disks, show strong radial age gradients, outer being 1 do not detect any significant metallicity differences or α-element enhancement in...
We use SDSS photometry of 73 million stars to simultaneously obtain best-fit main-sequence stellar energy distribution (SED) and amount dust extinction along the line sight towards each star. Using a subsample 23 with 2MASS photometry, whose addition enables more robust results, we show that alone is sufficient break degeneracies between intrinsic color when shape curve fixed. When using both ratio total selective absorption, $R_V$, can be determined an uncertainty about 0.1 for most in...
The LSST will, over a 10-year period, produce multi-color, multi-epoch survey of more than 18000 square degrees the southern sky. It will generate multi-petabyte archive images and catalogs astrophysical sources from which wide variety high-precision statistical studies can be undertaken. To accomplish these goals, project has developed suite modeling simulation tools for use in validating that design as-delivered components system yield data products with required properties. In this paper...
We use the Mitchell Spectrograph (formerly VIRUS-P) to observe 12 nearby disk galaxies. successfully measure ages in outer six systems. In three cases (NGC 2684, NGC 6155, and 7437), we find that a downward break surface brightness profile corresponds with change dominant stellar population interior being dominated by active star formation exterior having older populations are best fit histories decline time. The observed increase average beyond is similar theoretical models predict breaks...
We describe the Metrics Analysis Framework (MAF), an open-source python framework developed to provide a user-friendly, customizable, easily-extensible set of tools for analyzing data sets. MAF is part Large Synoptic Survey Telescope (LSST) Simulations effort. Its initial goal tool evaluate LSST Operations Simulation (OpSim) simulated surveys help understand effects telescope scheduling on survey performance, however can be applied much wider range datasets. The building blocks are...
In May 2019 SpaceX launched its first batch of 60 Starlink communication satellites, which surprised astronomers and laypeople with their appearance in the night sky. Astronomers have only now, a little over year later, accumulated enough observations constellation satellites like those being by OneWeb, run computer simulations likely impact when fully deployed, to thoroughly understand magnitude complexity problem. This research informed discussion at Satellite Constellations 1 (SATCON1)...
We present a study of the kinematics extraplanar ionized gas around several dozen galaxies observed by Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. considered sample 67 edge-on out more than 1400 extragalactic targets MaNGA, in which we found 25 (or 37%) with regular lagging rotation curve large distances from galactic midplane. model $H\alpha$ emission velocity fields galaxies, taking projection effects and simple for dust extinction into account. show that vertical...
The disc of galaxies is made the superposition a thin and thick disc. Star formation hosted in discs contributes to their growth. Thick are formed old stars. mechanisms under discussion. might have either at high redshift on short timescale or been built slowly over Hubble-Lemaître time. They may an internal external origin. Here we adopt galactic archaeology approach study ESO 533-4, i.e. kinematics stellar populations this galaxy detail. 533-4 Southern, nearby, almost bulgeless galaxy. We...
Abstract We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial constellations in low-Earth orbit on Vera C. Rubin Observatory Legacy Survey Space and Time (LSST). simulate orbits currently planned Starlink OneWeb (∼40,000 satellites) test how effectively an upgraded scheduler algorithm can avoid them, assess overall survey is affected. Given reasonably accurate forecast, we find it possible adjust some satellites. Overall, sacrificing 10% LSST...
Like the majority of spiral galaxies, NGC 6155 exhibits an exponential surface brightness profile that steepens significantly at large radii. Using VIRUS-P IFU spectrograph, we have gathered spatially resolved spectra system. Modifying GANDALF spectral fitting routine for use on complex stellar populations found in spirals, find average ages increase beyond break radius. This result is good agreement with recent simulations predict outskirts disk galaxies are populated through migration....
We have generated accurate V and I template light curves using a combination of Fourier decomposition principal component analysis for large sample Cepheid curves. Unlike previous studies, we include short-period Cepheids stars pulsating in the first overtone mode our analysis. Extensive Monte Carlo simulations show that templates can be used to precisely measure magnitudes periods, even cases where there are few observational epochs. These ideal characterizing serendipitously discovered...