94 research outputs found
Secondary homotopy groups
Secondary homotopy groups supplement the structure of classical homotopy
groups. They yield a track functor on the track category of pointed spaces
compatible with fiber sequences, suspensions and loop spaces. They also yield
algebraic models of homotopy types with homotopy groups concentrated in two
consecutive dimensions.Comment: We added further commets and references to make the paper more easily
readabl
SMS-Builder: An adaptive software tool for building systematic mapping studies
A Systematic Mapping Study is an instrument frequently used to carry out a search process, identification,
and classification of studies in different fields. Researchers in front of this type of process have
a challenge while managing the data about these studies. This paper presents a software tool that
has been created to help those who need to build a systematic mapping study. In addition, this work
follows the evidence-based software engineering approach and extends it through a software tool by
including different ways of adapting this process
Affine convex body semigroups
In this paper we present a new kind of semigroups called convex body
semigroups which are generated by convex bodies of R^k. They generalize to
arbitrary dimension the concept of proportionally modular numerical semigroup
of [7]. Several properties of these semigroups are proven. Affine convex body
semigroups obtained from circles and polygons of R^2 are characterized. The
algorithms for computing minimal system of generators of these semigroups are
given. We provide the implementation of some of them
An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources
We have studied the stellar and interstellar environments of two luminous
X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain
insight into their nature. Archival Hubble Space Telescope images were used to
identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and
to make photometric measurements of the local stellar populations of these and
the luminous source IC 10 X-1. We obtained high-dispersion spectroscopic
observations of the nebulae around these seven sources to search for He II
lambda-4686 emission and to estimate the expansion velocities and kinetic
energies of these nebulae. Our observations did not detect nebular He II
emission from any source, with the exception of LMC X-1; this is either because
we missed the He III regions or because the nebulae are too diffuse to produce
He II surface brightnesses that lie within our detection limit. We compare the
observed ionization and kinematics of the supershells around the ULXs Ho IX X-1
and NGC 1313 X-2 with the energy feedback expected from the underlying stellar
population to assess whether additional energy contributions from the ULXs are
needed. In both cases, we find insufficient UV fluxes or mechanical energies
from the stellar population; thus these ULXs may be partially responsible for
the ionization and energetics of their supershells. All seven sources we
studied are in young stellar environments and six of them have optical
counterparts with masses >~7 M_sun; thus, these sources are most likely
high-mass X-ray binaries.Comment: 30 pages, 9 figures. Numerous minor revisions, primarily to more
accurately cite earlier work by Pakull and Mirioni, and to correct
typographical errors. Removed a misleading sentence in the Introduction (re:
X-ray photoionization by ULXs). Accepted for publication in The Astrophysical
Journal. Figures have been reduced in resolution for space requirements;
full-resolution figures may be requested by email to [email protected]
An Optical Study of Stellar and Interstellar Environments of Seven Luminous and Ultraluminous X-Ray Sources
We have studied the stellar and interstellar environments of two luminous
X-ray sources and five ultraluminous X-ray sources (ULXs) in order to gain
insight into their nature. Archival Hubble Space Telescope images were used to
identify the optical counterparts of the ULXs Ho IX X-1 and NGC 1313 X-2, and
to make photometric measurements of the local stellar populations of these and
the luminous source IC 10 X-1. We obtained high-dispersion spectroscopic
observations of the nebulae around these seven sources to search for He II
lambda-4686 emission and to estimate the expansion velocities and kinetic
energies of these nebulae. Our observations did not detect nebular He II
emission from any source, with the exception of LMC X-1; this is either because
we missed the He III regions or because the nebulae are too diffuse to produce
He II surface brightnesses that lie within our detection limit. We compare the
observed ionization and kinematics of the supershells around the ULXs Ho IX X-1
and NGC 1313 X-2 with the energy feedback expected from the underlying stellar
population to assess whether additional energy contributions from the ULXs are
needed. In both cases, we find insufficient UV fluxes or mechanical energies
from the stellar population; thus these ULXs may be partially responsible for
the ionization and energetics of their supershells. All seven sources we
studied are in young stellar environments and six of them have optical
counterparts with masses >~7 M_sun; thus, these sources are most likely
high-mass X-ray binaries.Comment: 30 pages, 9 figures. Numerous minor revisions, primarily to more
accurately cite earlier work by Pakull and Mirioni, and to correct
typographical errors. Removed a misleading sentence in the Introduction (re:
X-ray photoionization by ULXs). Accepted for publication in The Astrophysical
Journal. Figures have been reduced in resolution for space requirements;
full-resolution figures may be requested by email to [email protected]
Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10
Infrared observations from the Spitzer Space Telescope archive are used to
study the dust component of the interstellar medium in the IC~10 irregular
galaxy. Dust distribution in the galaxy is compared to the distributions of
H and [SII] emission, neutral hydrogen and CO clouds, and ionizing
radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH)
in the galaxy is shown to be highly non-uniform with the mass fraction of these
particles in the total dust mass reaching 4%. PAHs tend to avoid bright HII
regions and correlate well with atomic and molecular gas. This pattern suggests
that PAHs form in the dense interstellar gas. We propose that the significant
decrease of the PAH abundance at low metallicity is observed not only globally
(at the level of entire galaxies), but also locally (at least, at the level of
individual HII regions). We compare the distribution of the PAH mass fraction
to the distribution of high-velocity features, that we have detected earlier in
wings of H and SII lines, over the entire available galaxy area. No
conclusive evidence for shock destruction of PAHs in the IC~10 galaxy could be
found.Comment: Accepted for publication in Astronomy Report
Gas Emission Spectrum in the Irr Galaxy IC 10
Spectroscopic long-slit observations of the dwarf Irr galaxy IC 10 were
conducted at the 6-m Special Astrophysical Observatory telescope with the
SCORPIO focal reducer. The ionized-gas emission spectra in the regions of
intense current star formation were obtained for a large number of regions in
IC 10. The relative abundances of oxygen, N+, and S+ in about twenty HII
regions and in the synchrotron superbubble were estimated. We found that the
galaxy-averaged oxygen abundance is 12 + log(O/H) = 8.17 +- 0.35 and the
metallicity is Z = 0.18 +- 0.14 Z_sun. Our abundances estimated from the strong
emission lines are found to be more reliable than those obtained by comparing
diagnostic diagrams with photoionization models.Comment: Abridged; accepted in Astronomy Letter
Synchrotron superbubble in the galaxy IC10: the ionized gas structure, kinematics, and emission spectrum
We have investigated the structure, kinematics, and emission spectrum of the
ionized gas in the synchrotron superbubble in the irregular galaxy IC 10 based
on observations with the 6-m Special Astrophysical Observatory telescope with
the SCORPIO focal reducer in three modes: direct imaging in the
[SII](6717+6731)A lines, long-slit spectroscopy, and spectroscopy with a
scanning Fabry--Perot interferometer. We have identified a bright (in the [SII]
lines) filamentary optical shell and determined its expansion velocity, mass,
and kinetic energy. The nature of the object is discussed.Comment: 12 pages, 9 EPS figure
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