1,323 research outputs found
Supernova dust for the extinction law in a young infrared galaxy at z = 1
We apply the supernova(SN) extinction curves to reproduce the observed
properties of SST J1604+4304 which is a young infrared (IR) galaxy at z = 1.
The SN extinction curves used in this work were obtained from models of unmixed
ejecta of type II supernovae(SNe II) for the Salpeter initial mass function
(IMF) with a mass range from 8 to 30 M_sun or 8 to 40 M_sun.
The effect of dust distributions on the attenuation of starlight is
investigated by performing the chi-square fitting method against various dust
distributions. These are the commonly used uniform dust screen, the clumpy dust
screen, and the internal dust geometry. We add to these geometries three
scattering properties, namely, no-scattering, isotropic scattering, and
forward-only scattering. Judging from the chi-square values, we find that the
uniform screen models with any scattering property provide good approximations
to the real dust geometry. Internal dust is inefficient to attenuate starlight
and thus cannot be the dominant source of the extinction.
We show that the SN extinction curves reproduce the data of SST J1604+4304
comparable to or better than the Calzetti extinction curve. The Milky Way
extinction curve is not in satisfactory agreement with the data unless several
dusty clumps are in the line of sight. This trend may be explained by the
abundance of SN-origin dust in these galaxies; SN dust is the most abundant in
the young IR galaxy at z = 1, abundant in local starbursts, and less abundant
in the Galaxy. If dust in SST J1604+4304 is dominated by SN dust, the dust
production rate is about 0.1 M_sun per SN.Comment: 12 pages, 8 figures, 1 tabl
Aggregation of SiC-X Grains in Supernova Ejecta
We present a model for the formation of silicon carbide aggregates within the
expanding and cooling supernova remnant. Many SiC-X grains have been found to
be aggregates of smaller crystals which are isotopically homogenous. The
initial condensation of SiC in the ejecta occurs within a interior dense shell
of material which is created by a reverse shock which rebounds from the
core-envelope interface. A subsequent reverse shock accelerates the grains
forward, but the gas drag from the ejecta on the rapidly moving particles
limits their travel distance. By observing the effects of gas drag on the
travel distance of grains, we propose that supernova grain aggregates form from
material that condensed in a highly localized region, which satisfies the
observational evidence of isotopic homogeneity in SiC-X grains.Comment: 9 pages, 5 figures, To be published in the Astrophysical Journa
Construction of Highly Accurate Models of Rotating Neutron Stars: Comparison of Three Different Numerical Schemes
We conduct a direct comparison of three different representative numerical codes for constructing models of rapidly rotating neutron stars in general relativity. Our aim is to evaluate the accuracy of the codes and to investigate how the accuracy is affected by the choice of interpolation, domain of integration and equation of state. In all three codes, the same physical parameters, equations of state and interpolation method are used. We construct 25 selected models for polytropic equations of state and 22 models with realistic neutron star matter equations of state. The three codes agree well with each other (typical agreement is better than 0.1% to 0.01%) for most models, except for the extreme assumption of uniform density stars. We conclude that the codes can be used for the construction of highly accurate initial data configurations for polytropes of index N > 0.5 (which typically correspond to realistic neutron stars), when the domain of integration includes all space and for realistic equations with no phase transitions. With the exception of the uniform density case, the obtained values of physical parameters for the models considered in this paper can be regarded as ``standard'' and we display them in detail for all models
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