13,284 research outputs found
Sagittarius: The Nearest Dwarf Galaxy
We have discovered a new Galactic satellite galaxy in the constellation of
Sagittarius. The Sagittarius dwarf galaxy is the nearest galaxy known, subtends
an angle of degrees on the sky, lies at a distance of 24 \kpc from the
Sun, \sim 16 \kpc from the centre of the Milky Way. Itis comparable in size
and luminosity to the largest dwarf spheroidal, has a well populated red
horizontal branch with a blue HB extension; a substantial carbon star
population; and a strong intermediate age stellar component with evidence of a
metallicity spread. Isodensity maps show it to be markedly elongated along a
direction pointing towards the Galactic centre and suggest that it has been
tidally distorted. The close proximity to the Galactic centre, the
morphological appearance and the radial velocity of 140 km/s indicate that this
system must have undergone at most very few close orbital encounters with the
Milky Way. It is currently undergoing strong tidal disruption prior to being
integrated into the Galaxy. Probably all of the four globular clusters, M54,
Arp 2, Ter 7 and Ter 8, are associated with the Sagittarius dwarf galaxy, and
will probably share the fate of their progenitor.Comment: MNRAS in press, 22pp uuencoded PS file, 26 printed figures available
on request from [email protected]
Self-Dual Yang-Mills and Vector-Spinor Fields, Nilpotent Fermionic Symmetry, and Supersymmetric Integrable Systems
We present a system of a self-dual Yang-Mills field and a self-dual
vector-spinor field with nilpotent fermionic symmetry (but not supersymmetry)
in 2+2 dimensions, that generates supersymmetric integrable systems in lower
dimensions. Our field content is (A_\mu{}^I, \psi_\mu{}^I, \chi^{I J}), where I
and J are the adjoint indices of arbitrary gauge group. The \chi^{I J} is a
Stueckelberg field for consistency. The system has local nilpotent fermionic
symmetry with the algebra \{N_\alpha{}^I, N_\beta{}^J \} = 0. This system
generates supersymmetric Kadomtsev-Petviashvili equations in D=2+1, and
supersymmetric Korteweg-de Vries equations in D=1+1 after appropriate
dimensional reductions. We also show that a similar self-dual system in seven
dimensions generates self-dual system in four dimensions. Based on our results
we conjecture that lower-dimensional supersymmetric integral models can be
generated by non-supersymmetric self-dual systems in higher dimensions only
with nilpotent fermionic symmetries.Comment: 15 pages, no figure
Generalized coherent states are unique Bell states of quantum systems with Lie group symmetries
We consider quantum systems, whose dynamical symmetry groups are semisimple
Lie groups, which can be split or decay into two subsystems of the same
symmetry. We prove that the only states of such a system that factorize upon
splitting are the generalized coherent states. Since Bell's inequality is never
violated by the direct product state, when the system prepared in the
generalized coherent state is split, no quantum correlations are created.
Therefore, the generalized coherent states are the unique Bell states, i.e.,
the pure quantum states preserving the fundamental classical property of
satisfying Bell's inequality upon splitting.Comment: 4 pages, REVTeX, amssymb style. More information on
http://www.technion.ac.il/~brif/science.htm
Caring for Transgender patients in the ICU: Current insights for equitable care
There is ever more focus on issues surrounding Transgender/Trans people and their healthcare needs, and while there is a dearth of evidence related to Intensive Care, this paper aims to address considerations for ICU nurses when caring for Trans patients. These include both the overall approach to person-centred care for Trans patients as well as the physiological considerations that necessitate nursing interventions
Ethical considerations for the nursing care of transgender patients in the intensive care unit
There is more discussion than ever surrounding the health and care needs of Transgender communities. However, there is limited research on the care of Transgender patients in the Intensive Care Unit which can contribute to knowledge gaps, inconsistencies and uncertainties surrounding health care practices. This article is not intended to address all of the specific needs of Transgender patients in ICU, but to explore the ethical considerations for caring for a Transgender woman in the ICU. In doing so, this article will explore some specific considerations around gender affirming care, challenging discrimination, physiological changes, and systems change to enhance car
Authentic allyship for gender minorities
The visibility and discussion on the rights and needs of Trans and Non-Binary communities in relation to healthcare have seen growing prominence in recent years. Despite an overall improvement in access to legal protections, civil rights, and in many jurisdictions specialist provision of healthcare for gender minorities, there remain poorer health outcomes in many areas and ongoing experiences of discrimination and transphobia. In this article, we set out the prerogative for nurses to step up as authentic allies for Trans and Non Binary people and put forward strategies to enhance the experience of gender minorities in healthcare through practice, education, and systems change
The mass of dwarf spheroidal galaxies and the missing satellite problem
We present the results from a suite of N-body simulations of the tidal
stripping of two-component dwarf galaxies comprising some stars and dark
matter. We show that recent kinematic data from the local group dwarf
spheroidal (dSph) galaxies suggests that dSph galaxies must be sufficiently
massive (M) that tidal stripping is of little
importance for the stars. We discuss the implications of these massive dSph
galaxies for cosmology and galaxy formation.Comment: 4 pages, 1 figure, to appear in the proceedings of the IAUC198
"Near-Field Cosmology with Dwarf Elliptical Galaxies", H. Jerjen & B.
Binggeli (eds.). Comments welcom
The tidal stripping of satellites
We present an improved analytic calculation for the tidal radius of
satellites and test our results against N-body simulations.
The tidal radius in general depends upon four factors: the potential of the
host galaxy, the potential of the satellite, the orbit of the satellite and
{\it the orbit of the star within the satellite}. We demonstrate that this last
point is critical and suggest using {\it three tidal radii} to cover the range
of orbits of stars within the satellite. In this way we show explicitly that
prograde star orbits will be more easily stripped than radial orbits; while
radial orbits are more easily stripped than retrograde ones. This result has
previously been established by several authors numerically, but can now be
understood analytically. For point mass, power-law (which includes the
isothermal sphere), and a restricted class of split power law potentials our
solution is fully analytic. For more general potentials, we provide an equation
which may be rapidly solved numerically. Over short times (\simlt 1-2 Gyrs
satellite orbit), we find excellent agreement between our analytic and
numerical models. Over longer times, star orbits within the satellite are
transformed by the tidal field of the host galaxy. In a Hubble time, this
causes a convergence of the three limiting tidal radii towards the prograde
stripping radius. Beyond the prograde stripping radius, the velocity dispersion
will be tangentially anisotropic.Comment: 10 pages, 5 figures. Final version accepted for publication in MNRAS.
Some new fully analytic tidal radii have been added for power law density
profiles (including the isothermal sphere) and some split power law
The Absence of Extra-Tidal Structure in the Sculptor Dwarf Spheroidal Galaxy
The results of a wide-field survey of the Sculptor dwarf spheroidal galaxy
are presented. Our aims were to obtain an accurate map of the outer structure
of Sculptor, and to determine the level of interaction between this system and
the Galaxy. Photometry was obtained in two colours down to the magnitude limits
of V=20 and I=19, covering a 3.1 times 3.1 square deg area centred on Sculptor.
The resulting colour-magnitude data were used as a mask to select candidate
horizontal branch and red giant branch stars for this system. Previous work has
shown that the red horizontal branch (HB) stars are more concentrated than the
blue HB stars. We have determined the radial distributions of these two
populations and show that the overall Sculptor density profile is well
described by a two component model based on a combination of these radial
distributions. Additionally, spectra of the Ca ii triplet region were obtained
for over 700 candidate red giant stars over the 10 square deg region using the
2dF instrument on the Anglo-Australian Telescope. These spectra were used to
remove foreground Galactic stars based on radial velocity and Ca ii triplet
strength. The final list of Sculptor members contained 148 stars, seven of
which are located beyond the nominal tidal radius. Both the photometric and
spectroscopic datasets indicate no significant extra-tidal structure. These
results support at most a mild level of interaction between this system and the
Galaxy, and we have measured an upper mass limit for extra-tidal material to be
2.3 +/- 0.6% of the Sculptor luminous mass. This lack of tidal interaction
indicates that previous velocity dispersion measurements (and hence the amount
of dark matter detected) in this system are not strongly influenced by the
Galactic tidal field.Comment: 53 pages, 23 figures. Accepted for publication in the Astronomical
Journal. Some figures are reduced in size, and a full version is available
at: ftp://ftp.mso.anu.edu.au/pub/coleman/sculptor.pd
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