A5025870120- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Cosmology and Gravitation Theories
- vaccines and immunoinformatics approaches
- Phase Equilibria and Thermodynamics
- Impact of Light on Environment and Health
- Radio Astronomy Observations and Technology
- Spaceflight effects on biology
- Plant Virus Research Studies
- RNA Interference and Gene Delivery
- Adaptive optics and wavefront sensing
- Scientific Computing and Data Management
- Fluid Dynamics Simulations and Interactions
- Pulsars and Gravitational Waves Research
- T-cell and B-cell Immunology
- Monoclonal and Polyclonal Antibodies Research
- Immune Cell Function and Interaction
ETH Zurich
2015-2019
University of Zurich
2010-2015
Instituto de Física Teórica
2013
University of Washington
2008-2012
University of Central Lancashire
2008-2010
McMaster University
2008-2010
California Institute of Technology
2010
Institute for Advanced Study
2008
Stars in disks of spiral galaxies are usually assumed to remain roughly at their birth radii. This assumption is built into decades modelling the evolution stellar populations our own Galaxy and external systems. We present results from self-consistent high-resolution $N$-body + Smooth Particle Hydrodynamics simulations disk formation, which stars migrate across significant galactocentric distances due resonant scattering with transient arms, while preserving circular orbits. investigate...
We have performed a high mass and force resolution simulation of an idealized galaxy forming from dissipational collapse gas embedded in spherical dark matter halo. The includes star formation effects stellar feedback. In our disk forms with surface density profile consisting inner exponential breaking to steeper outer exponential. break early on persists throughout the evolution, moving outward as more is able cool add disk. parameters are excellent agreement observations. corresponds rapid...
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r<20 and proper-motion measurements derived from SDSS POSS astrometry, including ~170,000 radial-velocity the spectroscopic survey. Distances to are determined photometric parallax relation, covering distance range ~100 pc 10 kpc over quarter sky at high Galactic latitudes (|b|>20 degrees). find that in region defined by 1 <Z< 5 3 <R< 13 kpc, rotational velocity for disk smoothly decreases, all three...
Within a cosmological hydrodynamical simulation, we form disc galaxy with sub- components which can be assigned to thin stellar disc, thick disk, and low mass halo via chemical decomposition. The populations so selected are distinct in their ages, kinematics, metallicities. Thin stars young (<6.6 Gyr), possess velocity dispersion ({\sigma}U,V,W = 41, 31, 25 km/s), high [Fe/H], [O/Fe]. old (6.6<age<9.8 Gyrs), lag the by \sim21 km/s, higher 49, 44, 35 relatively [Fe/H] component comprises less...
Using high resolution, fully cosmological smoothed particle hydrodynamical simulations of dwarf galaxies in a Lambda cold dark matter Universe, we show how redshift gas outflows can modify the baryon angular momentum distribution and allow pure disc to form. We outline galactic preferentially remove low material due combination (a) star formation peaking at shallow potentials, an epoch when accreted has relatively momentum, (b) existence extended reservoir outer provide for prolonged SF...
The separation of the Milky Way disk into a thin and thick component is supported by differences in spatial, kinematic metallicity distributions their stars. These have led to view that formed early via cataclysmic event constitutes fossil evidence hierarchical growth Way. We show here, using N-body simulations, how double-exponential vertical structure, with stellar populations displaying similar dichotomies can arise purely through internal evolution. In this picture, stars migrate...
Within a fully cosmological hydrodynamical simulation, we form galaxy which rotates at 140 km s−1, and it is characterized by two loose spiral arms bar, indicative of Hubble-type SBc/d galaxy. We show that our simulated has no classical bulge, with pure disc profile z = 1, well after the major merging activity ended. A long-lived bar subsequently forms, resulting in formation secularly formed 'pseudo-'bulge, final bulge-to-total light ratio 0.21. majority gas loses angular momentum falls to...
Abstract The architecture of mouse and human antibody repertoires is defined by the sequence similarity networks clones that compose them. major principles define have remained largely unknown. Here, we establish a high-performance computing platform to construct large-scale from comprehensive murine repertoire sequencing datasets (>100,000 unique sequences). Leveraging network-based statistical framework, identify three fundamental architecture: reproducibility, robustness redundancy....
We seek to understand the origin of radial migration in spiral galaxies by analyzing detail structure and evolution an idealized, isolated galactic disk. To redistribution stars, we characterize time-evolution properties spirals that spontaneously form Our models unambiguously show such disks, single are unlikely, but a number transient patterns may coexist However, also while amplitude, at any given time disk favors certain pattern speeds. Using several runs with different numerical...
We analyse the structure and chemical enrichment of a Milky Way-like galaxy with stellar mass 2 10^{10} M_sun, formed in cosmological hydrodynamical simulation. It is disk-dominated flat rotation curve, has disk scale length similar to Way's, but velocity dispersion that ~50% higher. Examining stars narrow [Fe/H] [\alpha/Fe] abundance ranges, we find remarkable qualitative agreement between this simulation observations: a) The old lie thickened distribution short length, while young form...
We present novel 3D multi-scale SPH simulations of gas-rich galaxy mergers between the most massive galaxies at $z \sim 8 - 10$, designed to scrutinize direct collapse formation scenario for black hole seeds proposed in \citet{mayer+10}. The achieve a resolution 0.1 pc, and include both metallicity-dependent optically-thin cooling model thermal balance high optical depth. consider different formulations hydrodynamical equations, including metal diffusion. When two merging cores collide, gas...
We present new Hubble Space Telescope (HST) observations of NGC 300 taken as part the Advanced Camera for Surveys Nearby Galaxy Survey Treasury (ANGST). Individual stars are resolved in these images down to an absolute magnitude MF814W = 1.0 (below red clump). determine star formation history galaxy six radial bins by comparing our observed color–magnitude diagrams (CMDs) with synthetic CMDs based on theoretical isochrones. find that stellar disk out 5.4 kpc is primarily old, contrast...
We analyzed the radial surface brightness profile of spiral galaxy NGC 7793 using HST/ACS images from GHOSTS survey and a new HST/WFC3 image across disk break. used photometry resolved stars to select distinct populations covering wide range stellar ages. found breaks in profiles all at 280" (~5.1 kpc). Beyond this break, become steeper for younger populations. This same trend is seen numerical simulations where outer formed almost entirely by migration. also that older extend significantly...
We present evidence that isolated growing discs, subject to internal spiral perturbations, thicken due both heating \emph{and} radial migration. show this by demonstrating the thickness and vertical velocity dispersions of coeval stars depend on their age as well change in radii. While disc thickens processes, we find induces only a minor amount flaring. further demonstrate consequences such thickening structural properties stellar populations they qualitatively agree with recent studies...
Galaxy formation models and simulations rely on various feedback mechanisms to reproduce the observed baryonic scaling relations galaxy morphologies. Although dwarf giant elliptical properties can be explained using from supernova active galactic nuclei, Milky Way-sized galaxies still represent a challenge current theories of formation. In this paper, we explore possible role stellar radiation in regulating main disk such as our own Way. We have performed suite cosmological same $\sim10^{12}...
The role of gas in the mass assembly at nuclei galaxies is still subject to some uncertainty. Stellar nuclear discs bridge gap between large-scale galaxy and central massive objects that reside there. Using a high resolution simulation forming out cooling settling into disc, we study formation properties discs. Gas, driven centre by bar, settles rotating star-forming disc (ND). This ND thinner, younger, kinematically cooler, more metal-rich than surrounding bar. elliptical orthogonal complex...
We simulate an equal-mass merger of two Milky Way-size galaxy discs with moderate gas fractions at parsec-scale resolution including a new model for radiative cooling and heating in multiphase medium, as well star formation feedback from supernovae. The initially have 2.6 × 106 M⊙ supermassive black hole (SMBH) embedded their centres. As the completes galactic cores merge, SMBHs form pair separation few hundred pc that gradually decays. Due to stochastic nature system immediately following...
We study the orbital properties of stars in four (published) simulations thick disks formed by: i) accretion from disrupted satellites, ii) heating a pre-existing thin disk by minor merger, iii) radial migration and iv) gas rich mergers. find that distribution eccentricities are predicted to be different for each model: prominent peak at low eccentricity is expected heating, gas-rich merging scenarios, while broader shifted towards higher values model. These differences can traced back...
We present a detailed analysis of disc galaxy forming in high-resolution fully cosmological simulation to investigate the nature outer regions discs and their relevance for formation process. Specifically, we focus on phenomenon misaligned components find that warp is consequence misalignment between inner surrounding hot gaseous halo. As infalling cold gas sinks toward centre galaxy, it strongly torqued by By time fresh reaches central disc-forming region its angular momentum completely...
Models of the Sagittarius Stream have consistently found that Milky Way disc is oriented such its short axis along intermediate triaxial dark matter halo. We attempt to build models galaxies in an `intermediate-axis orientation'. do this with three models. In first two cases we simply rigidly grow a halo ends up perpendicular global axis. also coax form intermediate-axis orientation by producing gas+dark system gas angular momentum about all fail produce systems which remain stellar aligned...
We present near-infrared integral field spectroscopy of the central kiloparsec 17 nearby luminous and ultra-luminous infrared galaxies undergoing major mergers. These observations were taken with OSIRIS assisted by Keck I II Adaptive Optics systems, providing spatial resolutions a few tens parsecs. The resulting kinematic maps reveal gas disks in at least 16 out 19 nuclei stellar 11 observed these galaxy merger systems. In our late-stages mergers, are young (stellar ages $<30$ Myr) likely...
The center of our disk galaxy, the Milky Way, is dominated by a boxy/peanut-shaped bulge. Numerous studies bulge based on stellar photometry have concluded that stars are exclusively old. perceived lack young in strongly constrains its likely formation scenarios, providing evidence unique population formed early and separately from disk. However, recent individual using microlensing technique reported they span range ages, emphasizing may not be monolithic structure. In this Letter we...
ABSTRACT Recent analysis of the SDSS-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 12 stellar catalog has revealed that Milky Way’s (MW) metallicity distribution function (MDF) changes shape as a radius, transitioning from being negatively skewed at small Galactocentric radii to positively large radii. Using high-resolution, N -body+SPH simulation, we show changing skewness arises radial migration—metal-rich stars form in inner disk and subsequently migrate...