5,563 research outputs found
NGC 7331: the Galaxy with the Multicomponent Central Region
We present the results of the spectral investigation of the regular Sb galaxy
NGC 7331 with the Multi-Pupil Field Spectrograph of the 6m telescope. The
absorption-line indices H-beta, Mgb, and are mapped to analyse the
properties of the stellar populations in the circumnuclear region of the
galaxy. The central part of the disk inside ~3" (200 pc) -- or a separate
circumnuclear stellar-gaseous disk as it is distinguished by decoupled fast
rotation of the ionized gas -- is very metal-rich, rather young, ~ 2 billion
years old, and its solar magnesium-to-iron ratio evidences for a very long
duration of the last episode of star formation there. However the gas
excitation mechanism now in this disk is shock-like. The star-like nucleus had
probably experienced a secondary star formation burst too: its age is 5 billion
years, much younger than the age of the circumnuclear bulge. But [Mg/Fe]=+0.3
and only solar global metallicity imply that the nuclear star formation burst
has been much shorter than that in the circumnuclear disk. The surrounding
bulge is rather old, 9--14 billion years old, and moderately metal-poor. The
rotation of the stars and gas within the circumnuclear disk is axisymmetric
though its rotation plane may be slightly inclined to the global plane of the
galaxy. Outside the circumnuclear disk the gas may experience non-circular
motions, and we argue that the low-contrast extended bulge of NGC 7331 is
triaxial.Comment: LATEX, 27 pages, + 15 Postscript figures. Accepted to Astronomical
Journal, July issu
Earth resources evaluation for New Mexico by LANDSAT-2
The author has identified the following significant results. The Middle Rio Grande project has not yet progressed to the point where mineral exploration sites can be chosen; however, there does appear to be some correlation between the known structure and mineral deposits and the LANDSAT lineament map. A circular feature identified in the southern Magdalena Mountains on LANDSAT-1 imagery agrees well with the location of a newly proposed caldron complex. Several recognized and unrecognized circular features were identified on imagery of the Mogollon-Datil volcanic field. A check of aeromagnetic maps for New Mexico found that the circular features on the LANDSAT imagery showed up as areas of generally high magnetic intensity
The Angular Momentum of Brightest Cluster Galaxies
Massive Brightest Cluster Galaxies (BCGs) are observed to have a range of angular momenta, suggesting a variety of merging historie
On local invariants of pure three-qubit states
We study invariants of three-qubit states under local unitary
transformations, i.e. functions on the space of entanglement types, which is
known to have dimension 6. We show that there is no set of six independent
polynomial invariants of degree less than or equal to 6, and find such a set
with maximum degree 8. We describe an intrinsic definition of a canonical state
on each orbit, and discuss the (non-polynomial) invariants associated with it.Comment: LateX, 13 pages. Minor typoes corrected. Published versio
Distributed Entanglement
Consider three qubits A, B, and C which may be entangled with each other. We
show that there is a trade-off between A's entanglement with B and its
entanglement with C. This relation is expressed in terms of a measure of
entanglement called the "tangle," which is related to the entanglement of
formation. Specifically, we show that the tangle between A and B, plus the
tangle between A and C, cannot be greater than the tangle between A and the
pair BC. This inequality is as strong as it could be, in the sense that for any
values of the tangles satisfying the corresponding equality, one can find a
quantum state consistent with those values. Further exploration of this result
leads to a definition of the "three-way tangle" of the system, which is
invariant under permutations of the qubits.Comment: 13 pages LaTeX; references added, derivation of Eq. (11) simplifie
Bipartite Mixed States of Infinite-Dimensional Systems are Generically Nonseparable
Given a bipartite quantum system represented by a tensor product of two
Hilbert spaces, we give an elementary argument showing that if either component
space is infinite-dimensional, then the set of nonseparable density operators
is trace-norm dense in the set of all density operators (and the separable
density operators nowhere dense). This result complements recent detailed
investigations of separability, which show that when both component Hilbert
spaces are finite-dimensional, there is a separable neighborhood (perhaps very
small for large dimensions) of the maximally mixed state.Comment: 5 pages, RevTe
Local symmetry properties of pure 3-qubit states
Entanglement types of pure states of 3 qubits are classified by means of
their stabilisers in the group of local unitary operations. It is shown that
the stabiliser is generically discrete, and that a larger stabiliser indicates
a stationary value for some local invariant. We describe all the exceptional
states with enlarged stabilisers.Comment: 32 pages, 5 encapsulated PostScript files for 3 figures. Published
version, with minor correction
Probing Electron-Capture Supernovae: X-Ray Binaries in Starbursts
Presenting population models of high-mass X-ray binaries (HMXBs) formed after
bursts of star formation, we investigate the effect of electron-capture
supernovae (ECS) of massive ONeMg white dwarfs and the hypothesis that ECS
events are associated with typically low supernova kicks imparted to the
nascent neutron stars. We identify an interesting ECS bump in the time
evolution of HMXB numbers; this bump is caused by significantly increased
production of wind-fed HMXBs 20-60 Myr post starburst. The amplitude and age
extent of the ECS bump depend on the strength of ECS kicks and the mass range
of ECS progenitors. We also find that ECS-HMXBs form through a specific
evolutionary channel that is expected to lead to binaries with Be donors in
wide orbits. These characteristics, along with their sensitivity to ECS
properties, provide us with an intriguing opportunity to probe ECS physics and
progenitors through studies of starbursts of different ages. Specifically, the
case of the Small Magellanic Cloud, with a significant observed population of
Be HMXBs and starburst activity 30-60 Myr ago, arises as a promising laboratory
for understanding the role of electron-capture supernovae in neutron star
formation.Comment: 5 pages, 3 figures, Published by ApJ in 07/0
C-GOALS II. Chandra Observations of the Lower Luminosity Sample of Nearby Luminous Infrared Galaxies in GOALS
We analyze Chandra X-ray observatory data for a sample of 63 luminous
infrared galaxies (LIRGs), sampling the lower-infrared luminosity range of the
Great Observatories All-Sky LIRG survey (GOALS), which includes the most
luminous infrared selected galaxies in the local universe. X-rays are detected
for 84 individual galaxies within the 63 systems, for which arcsecond
resolution X-ray images, fluxes, infrared and X-ray luminosities, spectra and
radial profiles are presented. Using X-ray and MIR selection criteria, we find
AGN in (315)% of the galaxy sample, compared to the (386)% previously
found for GOALS galaxies with higher infrared luminosities (C-GOALS I). Using
mid-infrared data, we find that (599)% of the X-ray selected AGN in the
full C-GOALS sample do not contribute significantly to the bolometric
luminosity of the host galaxy. Dual AGN are detected in two systems, implying a
dual AGN fraction in systems that contain at least one AGN of (2914)%,
compared to the (1110)% found for the C-GOALS I sample. Through analysis
of radial profiles, we derive that most sources, and almost all AGN, in the
sample are compact, with half of the soft X-ray emission generated within the
inner kpc. For most galaxies, the soft X-ray sizes of the sources are
comparable to those of the MIR emission. We also find that the hard X-ray
faintness previously reported for the bright C-GOALS I sources is also observed
in the brightest LIRGs within the sample, with
L.Comment: 24 pages, 13 figures, 11 tables, accepted for publication in A&
Are all noisy quantum states obtained from pure ones?
We ask what type of mixed quantum states can arise when a number of separated
parties start by sharing a pure quantum state and then this pure state becomes
contaminated by noise. We show that not all mixed states arise in this way.
This is even the case if the separated parties actively try to degrade their
initial pure state by arbitrary local actions and classical communication.Comment: 3 pages, no figure
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