Knut Olsen
A5000458293- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Astrophysics and Cosmic Phenomena
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Scientific Computing and Data Management
- Pulsars and Gravitational Waves Research
- Distributed and Parallel Computing Systems
- Methane Hydrates and Related Phenomena
- Big Data and Business Intelligence
- Radio Astronomy Observations and Technology
- Space Exploration and Technology
- Historical Astronomy and Related Studies
- Research Data Management Practices
- Particle Accelerators and Free-Electron Lasers
- Calibration and Measurement Techniques
- Advanced Data Storage Technologies
- Scientific Research and Discoveries
Technical University of Denmark
2025
NSF’s NOIRLab
2019-2024
Community Science and Data Center
2020-2024
Campbell Collaboration
2023
Kitt Peak National Observatory
2011-2022
Optica
2008-2019
NOAA National Data Buoy Center
2019
Virginia Commonwealth University
2015
University of Colorado Denver
2015
University of Colorado System
2012
We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using IRAC MIPS instruments on board Spitzer Space Telescope in order to agents galaxy's evolution (SAGE), interstellar medium (ISM) stars LMC. The detection diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies dust processes ISM. SAGE's point source sensitivity enables complete census newly formed masses >3 solar that will determine current star formation rate...
The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish legacy of uniform multi-color photometry resolved stars for volume-limited sample nearby galaxies (D < 4 Mpc).The volume encompasses 69 in diverse environments, including close pairs, small & large groups, filaments, and truly isolated regions.The include nearly complete range morphological types spanning factor ∼ 10 luminosity star formation rate.The data consists images taken with the Advanced Camera Surveys...
We use moderate-resolution optical spectrophotometry and the new MARCS stellar atmosphere models to determine effective temperatures of 74 Galactic red supergiants (RSGs). The stars are mostly members OB associations or clusters with known distances, allowing a critical comparison modern evolutionary tracks. find we can achieve excellent matches between observations reddened model fluxes molecular transitions, although atomic lines Ca I λ4226 II H K found be unrealistically strong in models....
In an attempt to constrain evolutionary models of the asymptotic giant branch (AGB) phase at limit low masses and metallicities, we have examined luminosity functions number ratio between AGB red (RGB) stars from a sample resolved galaxies ACS Nearby Galaxy Survey Treasury (ANGST). This database provides HST optical photometry together with maps completeness, photometric errors, star formation histories for dozens within 4 Mpc. We select 12 characterized by predominantly metal-poor...
The Panchromatic Hubble Andromeda Treasury is an ongoing Space Telescope Multi-Cycle program to image ∼1/3 of M31's star-forming disk in six filters, spanning from the ultraviolet (UV) near-infrared (NIR). We use Wide Field Camera 3 (WFC3) and Advanced for Surveys (ACS) resolve galaxy into millions individual stars with projected radii 0 20 kpc. full survey will cover a contiguous 0.5 deg2area 828 orbits. Imaging being obtained F275W F336W filters on WFC3/UVIS camera, F475W F814W ACS/WFC,...
We present UBVRI photometry obtained from Mosaic images of M31 and M33 using the KPNO 4-m telescope. The survey covers 2.2 sq degrees M31, 0.8 M33, chosen so as to include all regions currently active in forming massive stars. catalog contains 371,781 146,622 stars respectively, where every star has a counterpart (at least) B, V, R. compare our previous studies. provide cross references confirmed members by spectroscopy, location these complete set color-magnitude diagrams. While follow-up...
We present ∼1000 new candidate Young Stellar Objects (YSOs) in the Large Magellanic Cloud selected from Spitzer Space Telescope data, as part of Surveying Agents a Galaxy's Evolution (SAGE) Legacy program. The YSOs, detected by their excess infrared (IR) emission, represent early stages evolution, still surrounded disks and/or infalling envelopes. Previously, fewer than 20 such YSOs were known. SAGE Point Source Catalog regions color–magnitude space least confused with other IR-bright...
We use the MARCS stellar atmosphere to derive physical properties of 36 red supergiants (RSGs) in LMC, and 39 RSGs SMC using moderate-resolution optical spectrophotometry (4000-9000A) broad-band colors (V-R, V-K). The results from dereddened V-R are good agreement with those derived spectrophotometry, but V-K give temperatures that 3-4% warmer for data, LMC Milky Way showing a smaller similar effect. conclude this discrepancy is due limitations 1D models. Our newly effective bolometric...
Characterizing the nature and spatial distribution of lensing objects that produce previously measured microlensing optical depth toward Large Magellanic Cloud (LMC) remains an open problem. We present appraisal ability SuperMACHO Project, a next-generation survey directed LMC, to discriminate between various proposed populations. consider two scenarios: by uniform foreground screen self-lensing LMC stars. have carried out extensive simulations, based upon data obtained during first year...
Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying Agents of a Galaxy's Evolution) survey Large Magellanic Cloud (LMC). IRAC and MIPS 24 μm epoch 1 data presented. These represent deepest, widest mid-infrared CMDs their kind ever produced in LMC. Combined with Two Micron All Sky Survey, used to delineate evolved stellar populations LMC, as well Galactic foreground extragalactic background populations. Some 32,000 stars brighter than tip red giant branch identified....
The goal of this paper is to present the results a preliminary analysis extended infrared (IR) emission by dust in interstellar medium (ISM) Large Magellanic Cloud (LMC). We combine Spitzer Surveying Agents Galaxy Evolution (SAGE) and Infrared Astronomical Satellite (IRAS) data correlate with gas tracers H i, CO, Hα. global as well detailed modeling spectral energy distribution (SED) few selected regions. Extended associated neutral, molecular, diffuse ionized phases ISM detected at all IR...
The Small Magellanic Cloud (SMC) provides a unique laboratory for the study of lifecycle dust given its low metallicity (~1/5 solar) and relative proximity (~60 kpc). This motivated SAGE-SMC (Surveying Agents Galaxy Evolution in Tidally-Stripped, Low Metallicity Cloud) Spitzer Legacy program with specific goals studying amount type present interstellar medium, sources winds evolved stars, how much is consumed star formation. mapped full SMC (30 sq. deg.) including Body, Wing, Tail 7 bands...
We describe a search for Hα emission-line stars in M31, M33, and seven dwarfs or near the Local Group (IC 10, NGC 6822, WLM, Sextans B, A, Pegasus, Phoenix dwarf) using interference filter imaging with KPNO CTIO 4 m telescopes Mosaic cameras. The survey is aimed primarily at identifying new luminous blue variables (LBVs) from their spectroscopic similarity to known LBVs, avoiding bias toward photometric variability, which may require centuries manifest itself if LBVs go through long...
We have obtained UBVRI images with the Kitt Peak and Cerro Tololo 4-m telescopes Mosaic cameras of seven dwarfs in (or near) Local Group, all which known evidence recent star formation: IC10, NGC 6822, WLM, Sextans B, A, Pegasus,and Phoenix. construct color-magnitude diagrams (CMDs) these systems, as well neighboring regions that can be used to evaluate degree foreground contamination by stars Milky Way. Inter-comparison CMDs those M31, M33, LMC, SMC permits us determine improved reddening...
We have combined deep photometry in the B, V and I bands from CTIO/MOSAIC of Sculptor dwarf spheroidal galaxy, going down to oldest main sequence turn-offs, with spectroscopic metallicity distributions red giant branch stars. This allows us obtain most detailed complete star formation history date, as well an accurate timescale for chemical enrichment. The shows that is dominated by old (>10 Gyr), metal-poor stars, but younger, more metal-rich populations are also present. Using histories...
We examine the nuclear morphology, kinematics, and stellar populations in nearby S0 galaxy NGC 404 using a combination of adaptive optics assisted near-IR integral-field spectroscopy, optical Hubble Space Telescope imaging. These observations enable study nucleus at level detail possible only nearest galaxies. The surface brightness profile suggests presence three components: bulge, star cluster (NSC), central light excess within radii < 3 pc. components have distinct kinematics with modest...
We present an analysis of the stellar kinematics Large Magellanic Cloud based on ~5900 new and existing velocities massive red supergiants, oxygen-rich carbon-rich AGB stars, other giants. After correcting line-of-sight for LMC's space motion accounting asymmetric drift in population, we derive a rotation curve that is consistent with all tracers used, as well published HI data. The amplitude v_0=87+/-5 km s^-1 beyond radius R_0=2.4+/-0.1 kpc, has position angle kinematic line nodes...
We report the discovery of two ultra-faint satellites in vicinity Large Magellanic Cloud (LMC) data from Satellites Survey (MagLiteS). Situated 18$^{\circ}$ ($\sim 20$ kpc) LMC and separated each other by only $18^\prime$, Carina~II III form an intriguing pair. By simultaneously modeling spatial color-magnitude stellar distributions, we find that both Carina~III are likely dwarf galaxies, although this is less clear for Carina~III. There fact several obvious differences between satellites....
We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within data from ongoing Survey Magellanic Stellar History conducted with Dark Energy Camera on Blanco 4 m Telescope. The satellite is compact ( ± 11 pc) and faint 0.3), but well realm galaxies. stellar distribution II in color–magnitude diagram well-described by metal-poor () old (13 Gyr) isochrone shows distinct blue horizontal branch, some possible red clump stars, stars that are suggestive stragglers. At...
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...
Abstract We present the second public data release (DR2) from DECam Local Volume Exploration survey (DELVE). DELVE DR2 combines new observations with archival Dark Energy Survey, Legacy and other community programs. consists of ∼160,000 exposures that cover >21,000 deg 2 high-Galactic-latitude (∣ b ∣ > 10°) sky in four broadband optical/near-infrared filters ( g , r i z ). provides point-source automatic aperture photometry for ∼2.5 billion astronomical sources a median 5 σ depth =...
We present analysis of the proper-motion (PM) field red clump stars in Large Magellanic Cloud (LMC) disk using Gaia Early Data Release 3 catalog. Using a kinematic model based on old with 3D velocity measurements, we construct residual PM by subtracting center-of-mass motion and internal rotation components. The reveals asymmetric patterns, including larger PMs southern disk. Comparisons between observed those five numerical simulations an LMC analog that is subject to tidal fields Milky Way...
We report the discovery of six ultra-faint Milky Way satellites discovered through matched-filter searches conducted using Dark Energy Camera (DECam) data processed as part second release DECam Local Volume Exploration (DELVE) survey. Leveraging deep Gemini/GMOS-N imaging (for four candidates) well follow-up two candidates), we characterize morphologies and stellar populations these systems. find that candidates all share faint absolute magnitudes ($M_{V} \geq -3.2$ mag) old, metal-poor...