257 research outputs found
Dust formation in Milky Way-like galaxies
We introduce a dust model for cosmological simulations implemented in the moving-mesh code arepo and present a suite of cosmological hydrodynamical zoom-in simulations to study dust formation within galactic haloes. Our model accounts for the stellar production of dust, accretion of gas-phase metals on to existing grains, destruction of dust through local supernova activity, and dust driven by winds from star-forming regions. We find that accurate stellar and active galactic nuclei feedback is needed to reproduce the observed dust–metallicity relation and that dust growth largely dominates dust destruction. Our simulations predict a dust content of the interstellar medium which is consistent with observed scaling relations at z = 0, including scalings between dust-to-gas ratio and metallicity, dust mass and gas mass, dust-to-gas ratio and stellar mass, and dust-to-stellar mass ratio and gas fraction. We find that roughly two-thirds of dust at z = 0 originated from Type II supernovae, with the contribution from asymptotic giant branch stars below 20 per cent for z ≳ 5. While our suite of Milky Way-sized galaxies forms dust in good agreement with a number of key observables, it predicts a high dust-to-metal ratio in the circumgalactic medium, which motivates a more realistic treatment of thermal sputtering of grains and dust cooling channels.United States. Department of Energy (DE-FG02-97ER25308
Simulating galactic dust grain evolution on a moving mesh
Interstellar dust is an important component of the galactic ecosystem,
playing a key role in multiple galaxy formation processes. We present a novel
numerical framework for the dynamics and size evolution of dust grains
implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological
galaxy formation simulations. We employ a particle-based method for dust
subject to dynamical forces including drag and gravity. The drag force is
implemented using a second-order semi-implicit integrator and validated using
several dust-hydrodynamical test problems. Each dust particle has a grain size
distribution, describing the local abundance of grains of different sizes. The
grain size distribution is discretised with a second-order piecewise linear
method and evolves in time according to various dust physical processes,
including accretion, sputtering, shattering, and coagulation. We present a
novel scheme for stochastically forming dust during stellar evolution and new
methods for sub-cycling of dust physics time-steps. Using this model, we
simulate an isolated disc galaxy to study the impact of dust physical processes
that shape the interstellar grain size distribution. We demonstrate, for
example, how dust shattering shifts the grain size distribution to smaller
sizes resulting in a significant rise of radiation extinction from optical to
near-ultraviolet wavelengths. Our framework for simulating dust and gas
mixtures can readily be extended to account for other dynamical processes
relevant in galaxy formation, like magnetohydrodynamics, radiation pressure,
and thermo-chemical processes.Comment: 38 pages, 27 figures, accepted by MNRAS, with movies available at
http://www.mit.edu/~ryanmck/#researc
AREPO-RT: Radiation hydrodynamics on a moving mesh
We introduce AREPO-RT, a novel radiation hydrodynamic (RHD) solver for the
unstructured moving-mesh code AREPO. Our method solves the moment-based
radiative transfer equations using the M1 closure relation. We achieve second
order convergence by using a slope limited linear spatial extrapolation and a
first order time prediction step to obtain the values of the primitive
variables on both sides of the cell interface. A Harten-Lax-Van Leer flux
function, suitably modified for moving meshes, is then used to solve the
Riemann problem at the interface. The implementation is fully conservative and
compatible with the individual timestepping scheme of AREPO. It incorporates
atomic Hydrogen (H) and Helium (He) thermochemistry, which is used to couple
the ultra-violet (UV) radiation field to the gas. Additionally, infrared
radiation is coupled to the gas under the assumption of local thermodynamic
equilibrium between the gas and the dust. We successfully apply our code to a
large number of test problems, including applications such as the expansion of
regions, radiation pressure driven outflows and the levitation
of optically thick layer of gas by trapped IR radiation. The new implementation
is suitable for studying various important astrophysical phenomena, such as the
effect of radiative feedback in driving galactic scale outflows, radiation
driven dusty winds in high redshift quasars, or simulating the reionisation
history of the Universe in a self consistent manner.Comment: v2, accepted for publication in MNRAS, changed to a Strang split
scheme to achieve second order convergenc
Dust in and around galaxies: dust in cluster environments and its impact on gas cooling
Simulating the dust content of galaxies and their surrounding gas is
challenging due to the wide range of physical processes affecting the dust
evolution. Here we present cosmological hydrodynamical simulations of a cluster
of galaxies, , including a
novel dust model for the moving mesh code {\sc Arepo}. This model includes dust
production, growth, supernova-shock-driven destruction, ion-collision-driven
thermal sputtering, and high temperature dust cooling through far infrared
re-radiation of collisionally deposited electron energies. Adopting a rather
low thermal sputtering rate, we find, consistent with observations, a
present-day overall dust-to-gas ratio of , a total dust
mass of , and a dust mass fraction of . The typical thermal sputtering timescales within are around , and increase towards the outer
parts of the cluster to at a cluster-centric distance of
. The condensation of gas phase metals into dust grains reduces
high temperature metal-line cooling, but also leads to additional dust infrared
cooling. The additional infrared cooling changes the overall cooling rate in
the outer parts of the cluster, beyond , by factors of a
few. This results in noticeable changes of the entropy, temperature, and
density profiles of cluster gas once dust formation is included. The emitted
dust infrared emission due to dust cooling is consistent with observational
constraints.Comment: 14 pages, 10 figures. MNRAS accepte
Dust formation in Milky Way-like galaxies
We introduce a dust model for cosmological simulations implemented in the moving-mesh code AREPO and present a suite of cosmological hydrodynamical zoom-in simulations to study dust formation within galactic haloes. Our model accounts for the stellar production of dust, accretion of gas-phase metals on to existing grains, destruction of dust through local supernova activity, and dust driven by winds from star-forming regions. We find that accurate stellar and active galactic nuclei feedback is needed to reproduce the observed dust–metallicity relation and that dust growth largely dominates dust destruction. Our simulations predict a dust content of the interstellar medium which is consistent with observed scaling relations at z = 0, including scalings between dust-to-gas ratio and metallicity, dust mass and gas mass, dust-to-gas ratio and stellar mass, and dust-to-stellar mass ratio and gas fraction. We find that roughly two-thirds of dust at z = 0 originated from Type II supernovae, with the contribution from asymptotic giant branch stars below 20 per cent for z ≳ 5. While our suite of Milky Way-sized galaxies forms dust in good agreement with a number of key observables, it predicts a high dust-to-metal ratio in the circumgalactic medium, which motivates a more realistic treatment of thermal sputtering of grains and dust cooling channels
An analysis of the evolving comoving number density of galaxies in hydrodynamical simulations
The cumulative comoving number-density of galaxies as a function of stellar
mass or central velocity dispersion is commonly used to link galaxy populations
across different epochs. By assuming that galaxies preserve their
number-density in time, one can infer the evolution of their properties, such
as masses, sizes, and morphologies. However, this assumption does not hold in
the presence of galaxy mergers or when rank ordering is broken owing to
variable stellar growth rates. We present an analysis of the evolving comoving
number density of galaxy populations found in the Illustris cosmological
hydrodynamical simulation focused on the redshift range . Our
primary results are as follows: 1) The inferred average stellar mass evolution
obtained via a constant comoving number density assumption is systematically
biased compared to the merger tree results at the factor of 2(4) level
when tracking galaxies from redshift out to redshift ; 2) The
median number density evolution for galaxy populations tracked forward in time
is shallower than for galaxy populations tracked backward in time; 3) A similar
evolution in the median number density of tracked galaxy populations is found
regardless of whether number density is assigned via stellar mass, stellar
velocity dispersion, or dark matter halo mass; 4) Explicit tracking reveals a
large diversity in galaxies' assembly histories that cannot be captured by
constant number-density analyses; 5) The significant scatter in galaxy linking
methods is only marginally reduced by considering a number of additional
physical and observable galaxy properties as realized in our simulation. We
provide fits for the forward and backward median evolution in stellar mass and
number density and discuss implications of our analysis for interpreting
multi-epoch galaxy property observations.Comment: 18 pages, 11 figures, submitted to MNRAS, comments welcom
Salvage along the Red River: The Red Cox (3LA18) Site and its Place on the Caddo Landscape
The Red Cox (3LA18) site is located in Lafayette County, Arkansas along the Red River. As recounted in his weekly report of April 9, 1975, Dr. Frank Schambach received word that the site was being directly impacted by land leveling machinery. Salvage efforts collected the remains from the floor of a burned Caddo farmstead structure. Remains include ceramic sherds, carbonized corn kernels, acorn nutmeat and nutshells, burned wood fragments, and bits of daub. In this paper, we present the results of a recent analysis of the materials and situate the farmstead within the Red River landscape during a period shortly after Haley (ca. A.D. 1200 - 1400) phase and into the early part of the Belcher (ca. A.D. 1400 - 1700) phase
- …