Željko Ivezić
A5054608563- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Distributed and Parallel Computing Systems
- History and Developments in Astronomy
- Planetary Science and Exploration
- Calibration and Measurement Techniques
- Remote Sensing in Agriculture
- Geophysics and Gravity Measurements
- Statistical and numerical algorithms
- Isotope Analysis in Ecology
- Solar and Space Plasma Dynamics
- CCD and CMOS Imaging Sensors
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Scientific Computing and Data Management
- Spectroscopy and Laser Applications
University of Washington
2015-2024
City University of Seattle
2018-2024
Seattle University
2004-2017
Large Synoptic Survey Telescope Corporation
2007-2015
University of Zagreb
1994-2013
Croatian Geological Survey
2012-2013
Konkoly Observatory
2013
Research Centre for Astronomy and Earth Sciences
2013
Center for Astrophysics Harvard & Smithsonian
2009-2012
Joint Institute for Nuclear Astrophysics
2012
We examine the properties of host galaxies 22,623 narrow-line AGN with 0.02
(Abridged) We describe here the most ambitious survey currently planned in optical, Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST have unique capability faint time domain. The design is driven four main themes: probing dark energy matter, taking an inventory Solar System, exploring transient optical sky, mapping Milky Way. wide-field ground-based system sited at Cerro Pach\'{o}n northern Chile. telescope 8.4 m...
Abstract The Astropy Project supports and fosters the development of open-source openly developed Python packages that provide commonly needed functionality to astronomical community. A key element is core package astropy , which serves as foundation for more specialized projects packages. In this article, we an overview organization project summarize features in package, recent major release, version 2.0. We then describe infrastructure designed facilitate support a broader ecosystem...
The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides 47 deg2 field of view and 8 s readout time, yielding more than an order magnitude improvement in speed relative to its predecessor survey, Factory. We describe design implementation observing system. ZTF data system at Infrared Processing Analysis Center near-real-time reduction identify moving varying objects. outline analysis...
We analyze the bivariate distribution, in color versus absolute magnitude (u-r vs. Mr), of a low-redshift sample galaxies from Sloan Digital Sky Survey (2400 deg2, 0.004 < z 0.08, -23.5 Mr -15.5). trace bimodality distribution luminous to faint by fitting double Gaussians functions separated bins. Color-magnitude (CM) relations are obtained for red and blue distributions (early- late-type, predominantly field, galaxies) without using any cut morphology. Instead, analysis is based on...
ABSTRACT The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic data from Baryon Oscillation Spectroscopic (BOSS). This ninth release (DR9) of SDSS project includes 535,995 new galaxy spectra (median z ∼ 0.52), 102,100 quasar 2.32), and 90,897 stellar spectra, along with presented in previous releases. These were obtained BOSS spectrograph taken between 2009 December 2011 July. In addition, parameters pipeline, which determines radial velocities, surface temperatures,...
Abridged: We estimate the distances to ~48 million stars detected by Sloan Digital Sky Survey and map their 3D number density distribution in 100 < D 20 kpc range over 6,500 deg^2 of sky. The data show strong evidence for a Galaxy consisting an oblate halo, disk component, localized overdensities with exponential parameters (bias-corrected assumed 35% binary fraction) H_1 = 300 pc, L_1 2600 H_2 900 L_2 3600 local normalization 12%. find halo be oblate, best-fit axis ratio c/a 0.64, r^{-2.8}...
The Sloan Extension for Galactic Understanding and Exploration (SEGUE) Survey obtained ≈240,000 moderate-resolution (R ∼ 1800) spectra from 3900 Å to 9000 of fainter Milky Way stars (14.0 < g 20.3) a wide variety spectral types, both main-sequence evolved objects, with the goal studying kinematics populations our Galaxy its halo. are clustered in 212 regions spaced over three quarters sky. Radial velocity accuracies at 18, degrading 20. For signal-to-noise ratio >10 per resolution element,...
We use Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) u, g, r, i, z photometry to study Milky Way halo substructure in the area around north Galactic cap. A simple color cut (g - r < 0.4) reveals tidal stream of Sagittarius dwarf spheroidal galaxy, as well a number other stellar structures field. Two branches (A and B) are clearly visible an RGB composite image created from three magnitude slices, there is also evidence for still more distant wrap behind branch. comparison these data...
Clumpy torus models with dusty clouds along radial equatorial rays successfully explain AGN infrared observations. The dust has standard Galactic composition, individual cloud optical depth τV ∼ 30–100 at visual. naturally the observed behavior of 10 μm silicate feature, in particular lack deep absorption features AGNs any type, and can reproduce weak emission feature tentatively detected type 2 QSOs. clouds' angular distribution must have a soft edge, e.g., Gaussian, should decrease as 1/r...
The properties of the host galaxies a well-defined sample 2215 radio-loud active galactic nuclei (AGN) with redshifts 0.03 < z 0.3, defined from Sloan Digital Sky Survey (SDSS), are investigated. These predominantly low radio-luminosity sources, 1.4-GHz luminosities in range 1023–1025 W Hz−1. fraction that AGN L1.4 GHz > 1023W Hz−1 is strong function stellar mass, rising nearly zero below mass 1010M⊙ to more than 30 per cent at masses 5 × 1011M⊙. In contrast integrated [Oiii] luminosity...
The Zwicky Transient Facility (ZTF), a public-private enterprise, is new time domain survey employing dedicated camera on the Palomar 48-inch Schmidt telescope with 47 deg$^2$ field of view and 8 second readout time. It well positioned in development astronomy, offering operations at 10% scale style Large Synoptic Survey Telescope (LSST) single 1-m class telescope. public surveys will cover observable northern sky every three nights g r filters visible Galactic plane night r. Alerts...
According to unified schemes of Active Galactic Nuclei (AGN), the central engine is surrounded by dusty, optically thick clouds in a toroidal structure. We have recently developed formalism that for first time takes proper account clumpy nature AGN torus. now provide detailed report our findings two-paper series. Here we present general radiative transfer media and construct its building blocks problem -- source functions individual dusty heated radiation field. show fundamental difference...
Using effective temperature and metallicity derived from SDSS spectra for ~60,000 F G type main sequence stars (0.2
The Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with unique combination of high angular resolution ($\approx$2.5"), sensitivity (a 1$\sigma$ goal 70 $\mu$Jy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2-4 GHz). first observations began September 2017, observing for will finish 2024. VLASS use approximately 5500 hours on Karl G. Jansky (VLA) to cover whole visible VLA (Declination $>-40^{\circ}$), total...
The structure and kinematics of the recognized stellar components Milky Way are explored, based on well-determined atmospheric parameters kinematic quantities for 32360 "calibration stars" from Sloan Digital Sky Survey (SDSS) its first extension, SDSS-II, which included sub-survey Extension Galactic Understanding Exploration (SEGUE). Full space motions a sub-sample 16,920 stars, exploring local volume within 4 kpc Sun, used to derive velocity ellipsoids inner- outer-halo Galaxy, as well...
We discuss measurements of the properties ∼13,000 asteroids detected in 500 deg2 sky Sloan Digital Sky Survey (SDSS) commissioning data. The moving objects are magnitude range 14 < r* 21.5, with a baseline ∼5 minutes, resulting typical velocity errors ∼3%. Extensive tests show that sample is at least 98% complete, contamination rate less than 3%. find size distribution resembles broken power law, independent heliocentric distance: D-2.3 for 0.4 km ≲ D 5 km, and D-4 40 km. As consequence this...
Unified schemes of active galactic nuclei require an obscuring dusty torus around the central source, giving rise to a Seyfert 1 line spectrum for pole-on viewing and 2 characteristics in edge-on sources. Although observed IR is broad agreement with this scheme, behavior 10 μm silicate feature width far-IR emission peak remained serious problems all previous modeling efforts. We show that these find natural explanation if dust contained approximately five clouds along radial rays through...
Abstract We summarize the Sloan Digital Sky Survey data acquisition and processing steps, describe runQA , a pipeline designed for automated quality assessment. In particular, we show how position of stellar locus in color‐color diagrams can be used to estimate accuracy photometric zeropoint calibration better than 0.01 mag 0.03 deg 2 patches. Using this method, that typical errors SDSS imaging are not larger ∼0.01 g r i bands, 0.02 z band, u band (root‐mean‐scatter offsets). (© 2004...
The Sloan Digital Sky Survey (SDSS) and Two Micron All (2MASS) are rich resources for studying stellar astrophysics the structure formation history of Galaxy. As new surveys instruments adopt similar filter sets, it is increasingly important to understand properties ugrizJHKs locus, both inform studies "normal" main-sequence stars enable robust searches point sources with unusual colors. Using a sample ∼600,000 detected by SDSS 2MASS, we tabulate position width locus as function g - i color,...
We have used data from the Sloan Digital Sky Survey (SDSS) Data Release 5 to explore overall structure and substructure of stellar halo Milky Way using about 4 million color-selected main sequence turn-off stars. fit oblate triaxial broken power-law models data, found a `best-fit' oblateness 0.5~100pc, after accounting for (known) contribution Poisson uncertainties. The fractional RMS deviation actual distribution any smooth, parameterized model is >~40%: hence, highly structured....
An extensive sample of M, L and T dwarfs identified in the Sloan Digital Sky Survey (SDSS) has been compiled. The 718 includes 677 new objects (629 M dwarfs, 48 dwarfs) together with 41 that have previously published. All some published ones optical spectra obtained either SDSS spectrographs or Apache Point Observatory 3.5m ARC telescope. Spectral types colors are available for all objects; approximately 35% also near-infrared magnitudes measured by 2MASS on Mauna Kea system. We use this to...
We present evidence for a ring of stars in the plane Milky Way, extending at least from l = 180° to 227° with turnoff magnitude g ~ 19.5; could encircle Galaxy. infer that low Galactic latitude structure is fairly constant distance R 18 ± 2 kpc center above and has 20 region sampled below plane. The includes 500 Sloan Digital Sky Survey spectroscopic radial velocities within 30° velocity dispersion associated this found be 27 km s-1 (l, b) (198°, - 27°), 22 (225°, 28°), 30 (188°, 24°),...
We model the time variability of ∼9000 spectroscopically confirmed quasars in SDSS Stripe 82 as a damped random walk (DRW). Using 2.7 million photometric measurements collected over 10 yr, we confirm results Kelly et al. and Kozłowski that this can explain quasar light curves at an impressive fidelity level (0.01–0.02 mag). The DRW provides simple, fast (O(N) for N data points), powerful statistical description by characteristic timescale (τ) asymptotic rms on long timescales (SF∞). searched...