A5069727845- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Geomagnetism and Paleomagnetism Studies
- Historical Astronomy and Related Studies
- Astrophysics and Cosmic Phenomena
- Statistical and numerical algorithms
- Calibration and Measurement Techniques
- High-pressure geophysics and materials
- Pulsars and Gravitational Waves Research
- Solidification and crystal growth phenomena
- Material Science and Thermodynamics
- Solar and Space Plasma Dynamics
- Space Exploration and Technology
University of Cambridge
2016-2025
Institute of Astronomy
2009-2025
Flatiron Institute
2018-2023
Flatiron Health (United States)
2018-2023
Bridge University
2005-2022
Universitat de Barcelona
2022
Science Oxford
2002-2018
Max Planck Institute for Astrophysics
2008
Center for Theoretical Physics
2004
Lomonosov Moscow State University
2003
This paper describes the Seventh Data Release of Sloan Digital Sky Survey (SDSS), marking completion original goals SDSS and end phase known as SDSS-II. It includes 11,663 deg2 imaging data, with most ∼2000 increment over previous data release lying in regions low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. survey also repeat on a 120° long, 25 wide stripe along celestial equator Southern Cap, some covered by many 90 individual runs. We...
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...
Using a large sample of Main Sequence stars with 7-D measurements supplied by Gaia and SDSS, we study the kinematic properties local (within ~10 kpc from Sun) stellar halo. We demonstrate that halo's velocity ellipsoid evolves strongly metallicity. At low [Fe/H] end, orbital anisotropy (the amount motion in radial direction compared to tangential one) is mildly 0.2<beta<0.4. However, for [Fe/H]>-1.7 measure extreme values beta~0.9. Across metallicity range considered, i.e. -3<[Fe/H]<-1, spin...
We present five new satellites of the Milky Way discovered in Sloan Digital Sky Survey (SDSS) imaging data, four which were followed up with either Subaru or Isaac Newton Telescopes. They include probable dwarf galaxies—one each constellations Coma Berenices, Canes Venatici, Leo, and Hercules—together one unusually extended globular cluster, Segue 1. provide distances, absolute magnitudes, half-light radii, color-magnitude diagrams for all satellites. The morphological features are generally...
This paper describes the Fifth Data Release (DR5) of Sloan Digital Sky Survey (SDSS). DR5 includes all survey quality data taken through June 2005 and represents completion SDSS-I project (whose successor, SDSS-II will continue mid-2008). It five-band photometric for 217 million objects selected over 8000 square degrees, 1,048,960 spectra galaxies, quasars, stars from 5713 degrees that imaging data. These numbers represent a roughly 20% increment those Fourth Release; previous releases are...
We present ∼47,000 periodic variables found during the analysis of 5.4 million variable star candidates within a 20,000 deg2 region covered by Catalina Surveys Data Release-1 (CSDR1). Combining these with type ab RR Lyrae from our previous work, we produce an online catalog containing periods, amplitudes, and classifications for ∼61,000 variables. By cross-matching those prior surveys, find that >90% ∼8000 known in survey are recovered. For sources, excellent agreement between values...
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....
Abstract The Gaia Sausage is the major accretion event that built stellar halo of Milky Way galaxy. Here, we provide dynamical and chemical evidence for a second substantial episode, distinct from Sausage. Sequoia Event provided bulk high-energy retrograde stars in halo, as well recently discovered globular cluster FSR 1758. There are up to six further clusters, including ω Centauri, many substructures Myeong et al., associated with progenitor dwarf galaxy, named Sequoia. mass galaxy ∼5 × 10...
In this Letter, we announce the discovery of a new satellite Milky Way in constellation Bootes at distance 60 kpc. It was found systematic search for stellar overdensities North Galactic Cap using Sloan Digital Sky Survey Data Release 5 (SDSS DR5). The color-magnitude diagram shows well-defined turn-off, red giant branch, and extended horizontal branch. Its absolute magnitude is -5.8, which makes it one faintest galaxies known. half-light radius 220 pc. isodensity contours are elongated have...
We have used the publicly released Dark Energy Survey (DES) data to hunt for new satellites of Milky Way (MW) in southern hemisphere. Our search yielded a large number promising candidates. In this paper, we announce discovery nine unambiguous ultra-faint objects, whose authenticity can be established with DES alone. Based on morphological properties, three are dwarf galaxies, one which is located at very outskirts MW, distance 380 kpc. The remaining six objects sizes and luminosities...
In this Letter, we announce the discovery of a new dwarf satellite Milky Way, located in constellation Canes Venatici. It was found as stellar overdensity north Galactic cap using Sloan Digital Sky Survey Data Release 5 (SDSS DR5). The satellite's color-magnitude diagram shows well-defined red giant branch well horizontal branch. As judged from tip branch, it lies at distance ~220 kpc. Based on SDSS data, estimate an absolute magnitude MV ~ -7.9, central surface brightness μ0, V 28 mag...
ABSTRACT For stars with unresolved companions, motions of the centre light and that mass decouple, causing a single-source astrometric model to perform poorly. We show such can be easily detected reduced χ2 statistic, or renormalized unit weight error (RUWE), provided as part Gaia DR2. convert RUWE into amplitude image centroid wobble, which, if scaled by source distance, is proportional physical separation between companions (for periods up several years). test this idea on sample known...
In a companion paper by Koposov et al., RR Lyrae from \textit{Gaia} Data Release 2 are used to demonstrate that stars in the Orphan stream have velocity vectors significantly misaligned with track, suggesting it has received large gravitational perturbation satellite of Milky Way. We argue such mismatch cannot arise due any realistic static Way potential and then explore perturbative effects Large Magellanic Cloud (LMC). find LMC can produce precisely observed motion-track we therefore use...
We introduce a new maximum-likelihood method to model the density profile of blue horizontal branch and straggler stars apply it Sloan Digital Sky Survey Data Release 8 photometric catalogue. There are large number (∼20 000) these tracers available over an impressive 14 000 deg2 in both Northern Southern Galactic hemispheres, they provide robust measurement shape Milky Way stellar halo. After masking out vicinity Virgo overdensity Sagittarius stream, data consistent with smooth, oblate halo...
We present analysis of 12,227 type-ab RR Lyraes (RRLs) found among the 200 million public light curves in Catalina Surveys Data Release 1. These stars span largest volume Milky Way ever surveyed with RRLs, covering ∼20,000 deg2 sky (0° < α 360°, −22° δ 65°) to heliocentric distances up 60 kpc. Each RRLs is observed between and 419 times over a six-year period. Using period finding Fourier fitting techniques we determine periods apparent magnitudes for each source. find that are generally...
Using a large sample of bright nearby stars with accurate Gaia Data Release 2 astrometry and auxiliary spectroscopy we map out the properties principle Galactic components such as "thin" "thick" discs halo. We show that in Solar neighborhood, there exists population metal-rich ([Fe/H]>-0.7) on highly eccentric orbits. By studying evolution elemental abundances, kinematics stellar ages plane azimuthal velocity v_phi metallicity [Fe/H], demonstrate this halo-like component, which dub...
Motivated by recent observations of the Sagittarius stream, we devise a rapid algorithm to generate faithful representations centroids stellar tidal streams formed in disruption progenitor an arbitrary mass potential. Our method works releasing swarms test particles at Lagrange points around satellite and subsequently evolving them combined potential host progenitor. We stress that action progenitor's gravity is crucial making look almost indistinguishable from N-body realizations, as indeed...
We announce the discovery of Crater 2 dwarf galaxy, identified in imaging data VST ATLAS survey. Given its half-light radius ~1100 pc, is fourth largest Milky Way, surpassed only by LMC, SMC and Sgr dwarf. With a total luminosity $M_V\approx-8$, this satellite galaxy also one lowest surface brightness dwarfs. Falling under nominal detection boundary 30 mag arcsec$^{-2}$, it compares nebulosity to recently discovered Tuc IV UMa II. located ~120 kpc from Sun appears be aligned 3-D with...
Abstract The Gaia Sausage is an elongated structure in velocity space discovered by Belokurov et al. using the kinematics of metal-rich halo stars. They showed that it could be created a massive dwarf galaxy (∼5 × 10 ) on strongly radial orbit merged with Milky Way at redshift z ≲ 3. This merger would also have brought globular clusters (GCs). We seek evidence for associated Globular Clusters (GCs) analyzing 91 GCs action Data Release 2 catalog, complemented Hubble Space Telescope proper...
We assemble a catalogue of candidate Sagittarius stream members with 5d and 6d phase-space information, using astrometric data from Gaia DR2, distances estimated RR Lyrae stars, line-of-sight velocities various spectroscopic surveys. find clear misalignment between the track direction reflex-corrected proper motions in leading arm stream, which we interpret as signature time-dependent perturbation gravitational potential. A likely cause this is recent passage most massive Milky Way satellite...
We report the discovery of a Milky Way satellite in constellation Antlia. The Antlia 2 dwarf galaxy is located behind Galactic disc at latitude $b\sim 11^{\circ}$ and spans $1.26$ degrees, which corresponds to $\sim2.9$ kpc its distance 130 kpc. While similar spatial extent Large Magellanic Cloud, orders magnitude fainter $M_V=-9$ mag, making it by far lowest surface brightness system known (at $\sim31.9$ mag/arcsec$^2$), $\sim100$ times more diffuse than so-called ultra galaxies. was...
We use accurate estimates of aluminium abundance provided as part the APOGEE Data Release 17 and Gaia Early 3 astrometry to select a highly pure sample stars with metallicity $-1.5\lesssim {\rm [Fe/H]}\lesssim 0.5$ born in-situ in Milky Way proper. show that low-metallicity ([Fe/H]$\lesssim -1.3$) component we dub Aurora is kinematically hot an approximately isotropic velocity ellipsoid modest net rotation. exhibit large scatter number element ratios. The median tangential increases sharply...
WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for William Herschel Telescope, will see first light in late 2022. WEAVE comprises a 2-degree field-of-view prime-focus corrector system, nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and single large IFU. These systems feed dual-beam spectrograph covering wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges $R\sim20\,000$. After summarising...