1,184 research outputs found
Assessing modulation of the actin cytoskeleton in differing macrophage phenotypes :relevance to macrophage invasion, protease profile, and foam cell formation, during the progression of cardiovascular pathologies.
Fronteras, Año 6 no. 6
Contenido: Editorial por Jorge Morello.
Ambiente y Ecología en un país joven agroexportador: Argentina por Jorge Morello y Andrea Rodríguez.
Un indicador de sustentabilidad para las unidades administrativas de una región por Silvia D. Matteucci.
Procesos de transformación en las áreas de borde agropecuario, cambio climático y efectos de las nuevas demandas productivas por Walter A. Pengue y Jorge Morello.
Región y estudios regionales. Consideraciones desde los diferentes enfoques de la Geografía por Claudia A. Baxendale.
Metodología para la clasificación de ambientes en el Sistema Nacional de Áreas Protegidas, Argentina por Morello, J.; A.F. Rodriguez; M.E. Silva; N. Mendoza y S.D. Matteucci.
Los sin dato. Una propuesta para pensar, mejorar y ejecutar por Silvia D. Matteucci.
Áreas de potencial conflicto entre usos del suelo: identificación mediante el uso de Sistemas de Información Geográfica (Primera Parte: descripción metodológica) por Gustavo D. Buzai y Claudia A. Baxendale.
Actividades. Nuevo Libro “Crecimiento urbano y sus consecuencias sobre el entorno rural”. El caso de la ecorregión pampeana.
Publicaciones del GEPAMA (2006-2007)
Where does galactic dust come from?
Here we investigate the origin of the dust mass (Mdust) observed in the Milky Way (MW) and of dust scaling relations found in a sample of local galaxies from the DGS and KINGFISH surveys. To this aim, we model dust production from Asymptotic Giant Branch (AGB) stars and supernovae (SNe) in simulated galaxies forming along the assembly of aMW-like halo in a well-resolved cosmic volume of 4 cMpc using the GAMESH pipeline. We explore the impact of different sets of metallicity and mass-dependent AGB and SN dust yields on the predicted Mdust. Our results show that models accounting for grain destruction by the SN reverse shock predict a total dust mass in the MW, that is a factor of ~4 less than observed, and cannot reproduce the observed galaxy-scale relations between dust and stellar masses, and dust-togas ratios and metallicity, with a smaller discrepancy in galaxies with low metallicity (12 + log(O/H) < 7.5) and low stellar masses (Mstar < 107 M⊙). In agreement with previous studies, we suggest that competing processes in the interstellar medium must be at play to explain the observed trends. Our result reinforces this conclusion by showing that it holds independently of the adopted AGB and SN dust yields
Where does galactic dust come from?
Here we investigate the origin of the dust mass (Mdust) observed in the Milky
Way (MW) and of dust scaling relations found in a sample of local galaxies from
the DGS and KINGFISH surveys. To this aim, we model dust production from
Asymptotic Giant Branch (AGB) stars and supernovae (SNe) in simulated galaxies
forming along the assembly of a Milky Way-like halo in a well resolved cosmic
volume of 4cMpc using the GAMESH pipeline. We explore the impact of different
sets of metallicity and mass-dependent AGB and SN dust yields on the predicted
Mdust. Our results show that models accounting for grain destruction by the SN
reverse shock predict a total dust mass in the MW that is a factor of ~4 lower
than observed, and can not reproduce the observed galaxy-scale relations
between dust and stellar masses, and dust-to-gas ratios and metallicity, with a
smaller discrepancy in galaxies with low metallicity (12 + log(O/H) < 7.5) and
low stellar masses (Mstar < 10^7 Msun). In agreement with previous studies, we
suggest that competing processes in the interstellar medium must be at play to
explain the observed trends. Our result reinforces this conclusion by showing
that it holds independently of the adopted AGB and SN dust yields.Comment: 6 pages, 4 figures. Accepted version for publication in MNRA
Numerical Simulations of Supernova Dust Destruction. II. Metal-Enriched Ejecta Knots
Following our previous work, we investigate through hydrodynamic simulations
the destruction of newly-formed dust grains by sputtering in the reverse shocks
of supernova remnants. Using an idealized setup of a planar shock impacting a
dense, spherical clump, we implant a population of Lagrangian particles into
the clump to represent a distribution of dust grains in size and composition.
We vary the relative velocity between the reverse shock and ejecta clump to
explore the effects of shock-heating and cloud compression. Because supernova
ejecta will be metal-enriched, we consider gas metallicities from Z/Zsun = 1 to
100 and their influence on cooling properties of the cloud and the thermal
sputtering rates of embedded dust grains. We post-process the simulation output
to calculate grain sputtering for a variety of species and size distributions.
In the metallicity regime considered in this paper, the balance between
increased radiative cooling and increased grain erosion depends on the impact
velocity of the reverse shock. For slow shocks (velocity less than or equal to
3000 km/s), the amount of dust destruction is comparable across metallicities,
or in some cases is decreased with increased metallicity. For higher shock
velocities (velocity greater than or equal to 5000 km/s), an increase in
metallicity from Z/Zsun = 10 to 100 can lead to an additional 24% destruction
of the initial dust mass. While the total dust destruction varies widely across
grain species and simulation parameters, our most extreme cases result in
complete destruction for some grain species and only 44% dust mass survival for
the most robust species. These survival rates are important in understanding
how early supernovae contribute to the observed dust masses in high-redshift
galaxies.Comment: 10 pages, 6 figures, 2 tables, changes made to the text and figures
as suggested by the anonymous referee, accepted by the Astrophysical Journa
The origin of the most iron-poor star
We investigate the origin of carbon-enhanced metal-poor (CEMP) stars starting
from the recently discovered star SMSS J031300 (Keller et al.
2014). We show that the elemental abundances observed on the surface of SMSS
J031300 can be well fit by the yields of faint, metal free, supernovae. Using
properly calibrated faint supernova explosion models, we study, for the first
time, the formation of dust grains in such carbon-rich, iron-poor supernova
ejecta. Calculations are performed assuming both unmixed and uniformly mixed
ejecta and taking into account the partial destruction by the supernova reverse
shock. We find that, due to the paucity of refractory elements beside carbon,
amorphous carbon is the only grain species to form, with carbon condensation
efficiencies that range between (0.15-0.84), resulting in dust yields in the
range (0.025-2.25)M. We follow the collapse and fragmentation of a
star forming cloud enriched by the products of these faint supernova explosions
and we explore the role played by fine structure line cooling and dust cooling.
We show that even if grain growth during the collapse has a minor effect of the
dust-to-gas ratio, due to C depletion into CO molecules at an early stage of
the collapse, the formation of CEMP low-mass stars, such as SMSS J031300, could
be triggered by dust cooling and fragmentation. A comparison between model
predictions and observations of a sample of C-normal and C-rich metal-poor
stars supports the idea that a single common pathway may be responsible for the
formation of the first low-mass stars.Comment: 14 pages, 8 figures, accepted for publication in ApJ. Rephrased
sentence in section 5 to avoid text overlap with arXiv:1307.2239 in their
model descriptio
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