A5005936672- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Carcinogens and Genotoxicity Assessment
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Numerical methods for differential equations
- Fluid Dynamics Simulations and Interactions
- Dark Matter and Cosmic Phenomena
- Occupational and environmental lung diseases
- Chemical Reactions and Isotopes
- Enzyme function and inhibition
- Quantum chaos and dynamical systems
- Analytical Chemistry and Chromatography
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
Heidelberg University
2021-2025
University of Leicester
2015-2024
Stuttgart Observatory
2020-2022
Ludwig-Maximilians-Universität München
2019-2022
Max Planck Institute for Astronomy
1999-2004
American Institute of Physics
2003
Leibniz Institute for Astrophysics Potsdam
2003
Health First
2003
Heidelberg University
2002
Max Planck Society
2001
The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere collect spectra ≈106 galaxies, 100,000 quasars, 30,000 stars, serendipity targets. In 2001 June, SDSS released to general astronomical community its early data release, roughly 462 deg2 including almost 14 million detected objects 54,008 follow-up spectra. were collected in drift-scan mode five bandpasses (u, g, r, i, z); our 95% completeness...
We re-examine the stellar kinematics of Solar neighbourhood in terms velocity Sun with respect to local standard rest. show that classical determination its component V_sun direction Galactic rotation via Stroemberg's relation is undermined by metallicity gradient disc, which introduces a correlation between colour group stars and radial gradients properties. Comparing chemodynamical model accounts for these effects, we obtain (U,V,W)_sun = (11.1 +/- 0.74, 12.24 0.47, 7.25 +/-0.37) km/s,...
(shortened) From a kinematically unbiased subsample of the Hipparcos catalogue we have redetermined as function colour kinematics main-sequence stars. The stars' mean heliocentric velocity nicely follows asymmetric drift relation, except for stars blueward B-V=0.1. Extrapolating to zero dispersion yields Sun w.r.t. LSR in km/s: U_0=10.00+/-0.36 (radially inwards), V_0=5.23+/-0.62 (in direction galactic rotation), and W_0=7.17+/-0.38 (vertically upwards). A plot vs. beautifully shows...
We present the first data release of Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity) up one million stars using Six Degree Field multiobject spectrograph on 1.2 m UK Schmidt Telescope Anglo-Australian Observatory. The RAVE program started in 2003, obtaining medium-resolution spectra (median R = 7500) Ca-triplet region (8410-8795 Å) for southern hemisphere drawn from...
The numerical convergence of smoothed particle hydrodynamics (SPH) can be severely restricted by random force errors induced disorder, especially in shear flows, which are ubiquitous astrophysics. increase the number NH neighbours when switching to more extended smoothing kernels at fixed resolution (using an appropriate definition for SPH scale) is insufficient combat these errors. Consequently, trading better necessary, but traditional this option limited pairing (or clumping) instability....
A family of spherical potential–density pairs is presented. The densities are proportional to r–4 at large radii and diverge in the centre as r–γ with |$0\leq \gamma \lt 3$|. models Jaffe Hernquist included special cases. gravitational potential analytical for all γ. For specific values γ, most intrinsic projected properties, such distribution function, surface density velocity dispersion, can be expressed terms elementary functions. comparison de Vaucouleurs R1/4-profile shows that model γ...
We report new constraints on the local escape speed of our Galaxy. Our analysis is based a sample high velocity stars from RAVE survey and two previously published datasets. use cosmological simulations disk galaxy formation to motivate assumptions shape distribution, allowing for significantly more precise measurement compared previous studies. find that lies within range $498\kms < \ve 608 \kms$ (90 per cent confidence), with median likelihood $544\kms$. The fact $\ve^2$ greater than...
A parametrized model of the mass distribution within Milky Way is fitted to available observational constraints. The most important single parameter ratio scalelength Rd* stellar disc R0. and bulge dominate vc(R) at R≲R0 only for Rd,*/R0≲0.3. Since knowledge we have halo derives from studies like present one, allow it contribute density all radii. When allowed this freedom, however, causes changes in assumptions relating R ≪ R0 affect profoundly structure best-fitting ≫ For example, changing...
Hydrodynamic modeling of the inner Galaxy suggests that radius outer Lindblad resonance (OLR) Galactic bar lies in vicinity Sun. How does this affect distribution function parts a barred disk, and can we identify any effect velocity actually observed solar neighborhood? To answer these questions, detailed simulations distribution, f(v), an exponential stellar disk with nearly flat rotation curve rotating central have been performed. For model resembling old OLR causes distinct feature f(v)...
We report the discovery of two well-defined tidal tails emerging from sparse remote globular cluster Palomar 5. These stretch out symmetrically to both sides in direction constant Galactic latitude and subtend an angle 26 on sky. The have been detected commissioning data Sloan Digital Sky Survey, providing deep five-color photometry a 25-wide band along equator. stars make up substantial part (~) current total population magnitude interval 19.5 ≤ i* 22.0. This reveals that is subject heavy...
In smooth-particle hydrodynamics (SPH), artificial viscosity is necessary for the correct treatment of shocks, but often generates unwanted dissipation away from shocks. We present a novel method controlling amount viscosity, which uses total time derivative velocity divergence as shock indicator and aims at completely eliminating subject new scheme to numerous tests find that works least well any previous technique in strong-shock regime, becomes virtually inviscid while still maintaining...
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...
A parameterized model of the mass distribution within Milky Way is fitted to available observational constraints. The most important single parameter ratio scale length R_d* stellar disk R0. and bulge dominate v_c(R) at R<R0 only for R_d*/R0< 0.3. Since knowledge we have halo derives from studies like present one, allow it contribute density all radii. When allowed this freedom, however, causes changes in assumptions relating R << R0 affect profoundly structure best-fitting >> For example,...
We present an analysis of the asymmetries in population Galactic M-giant stars 2MASS All Sky catalogue. Several large-scale are detected, most significant which is a strong elliptical-shaped stellar over-density, close to plane at (l=240, b=-8), constellation Canis Major. A small grouping globular clusters (NGC 1851, NGC 1904, 2298, and 2808), coincident position radial velocity, surround this structure, as do number open clusters. The over-density similar that core Sagittarius dwarf galaxy....
Using wide-field photometric data from the Sloan Digital Sky Survey (SDSS), we recently showed that Galactic globular cluster Palomar 5 is in process of being tidally disrupted. Its tidal tails were initially detected a 25 wide band along celestial equator. A new analysis SDSS for larger field now reveals Pal have much spatial extent and can be traced over an arc 10° on sky, corresponding to projected length 4 kpc at distance cluster. The tail trails behind motion fades into angular 65...
The velocity distribution f(v) of nearby stars is estimated, via a maximum likelihood algorithm, from the positions and tangential velocities kinematically unbiased sample 14,369 observed by Hipparcos satellite. f shows rich structure in radial azimuthal motions, vR vφ, but not vertical velocity, vz: there are four prominent many smaller maxima, which correspond to well-known moving groups. While samples early-type dominated these also up about quarter red main-sequence associated with them....
We present the second data release of Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity, surface gravity, rotational velocity) up one million stars using 6 dF multi-object spectrograph on 1.2 m UK Schmidt Telescope Anglo-Australian Observatory (AAO). The RAVE program started in 2003, obtaining medium resolution spectra (median R = 7500) Ca-triplet region (8410–8795 Å) for southern...
The tidal tails of the globular cluster Palomar 5 are analyzed over a 41 deg2 area Sloan Digital Sky Survey photometric catalogs. matched filter algorithm provides maximum possible signal-to-noise detection stars measured background, and expected actual effectiveness technique in context this data set is discussed. stellar background examined some detail for systematic variation as function Galactic position order to assess its effect on efficiency. Of total number Pal detected, 45% out...
Non-axisymmetric components, such as spirals and central bars, play a major role in shaping galactic discs. An important aspect of the disc secular evolution driven by these perturbers is radial migration stars. It has been suggested recently that can populate thick-disc component from inner-disc stars with high vertical energies. Since this never demonstrated simulations, we study detail effect on velocity dispersion thickness, separating simulated into migrators non-migrators. We apply...
Non-axisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as Hercules stream. Assuming that is caused by effects of Outer Lindblad Resonance bar, we model analytically its properties a function position Galaxy dependence on bar's pattern speed orientation. Using data from RAVE survey find azimuthal velocity structure decreases Galactocentric radius, manner consistent with our analytical model. This allows us to obtain new estimates parameters Milky Way's...