3,798 research outputs found
Dissecting the spiral galaxy M83: mid-infrared emission and comparison with other tracers of star formation
We present a detailed mid-infrared study of the nearby, face-on spiral galaxy
M83 based on ISOCAM data. M83 is a unique case study, since a wide variety of
MIR broad-band filters as well as spectra, covering the wavelength range of 4
to 18\mu m, were observed and are presented here. Emission maxima trace the
nuclear and bulge area, star-formation regions at the end of the bar, as well
as the inner spiral arms. The fainter outer spiral arms and interarm regions
are also evident in the MIR map. Spectral imaging of the central 3'x3' (4 kpc x
4 kpc) field allows us to investigate five regions of different environments.
The various MIR components (very small grains, polycyclic aromatic hydrocarbon
(PAH) molecules, ionic lines) are analyzed for different regions throughout the
galaxy. In the total 4\mu m to 18\mu m wavelength range, the PAHs dominate the
luminosity, contributing between 60% in the nuclear and bulge regions and 90%
in the less active, interarm regions. Throughout the galaxy, the underlying
continuum emission from the small grains is always a smaller contribution in
the total MIR wavelength regime, peaking in the nuclear and bulge components.
The implications of using broad-band filters only to characterize the
mid-infrared emission of galaxies, a commonly used ISOCAM observation mode, are
discussed. We present the first quantitative analysis of new H-alpha and 6cm
VLA+Effelsberg radio continuum maps of M83. The distribution of the MIR
emission is compared with that of the CO, HI, R band, H-alpha and 6cm radio. A
striking correlation is found between the intensities in the two mid-infrared
filter bands and the 6cm radio continuum. To explain the tight
mid-infrared-radio correlation we propose the anchoring of magnetic field lines
in the photoionized shells of gas clouds.Comment: 22 pages, 15 figures. Accepted for publication in A&
Systems, Apparatuses, and Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures
Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life
Effect of random disorder and spin frustration on the reentrant spin glass phase and ferromagnetic phase in stage-2 Cu_{0.93}Co_{0.07}Cl_{2} graphite intercalation compound near the multicritical point
Stage-2 CuCoCl graphite intercalation compound
magnetically behaves like a reentrant ferromagnet near the multicritical point
(). It undergoes two magnetic phase transitions at
( K) and ( K). The static
and dynamic nature of the ferromagnetic and reentrant spin glass phase has been
studied using DC and AC magnetic susceptibility. Characteristic memory
phenomena of the DC susceptibility are observed at and . The
nonlinear AC susceptibility has a positive local maximum at
, and a negative local minimum at . The relaxation time
between and shows a critical slowing down: with and sec. The
influence of the random disorder on the critical behavior above is
clearly observed: , , and . The
exponent of is far from that of 3D Heisenberg model.Comment: 15 pages, 16 figures, submitted to Phys. Rev.
Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures
Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life
Self-Renormalization of the Classical Quasilocal Energy
Pointlike objects cause many of the divergences that afflict physical
theories. For instance, the gravitational binding energy of a point particle in
Newtonian mechanics is infinite. In general relativity, the analog of a point
particle is a black hole and the notion of binding energy must be replaced by
quasilocal energy. The quasilocal energy (QLE) derived by York, and elaborated
by Brown and York, is finite outside the horizon but it was not considered how
to evaluate it inside the horizon. We present a prescription for finding the
QLE inside a horizon, and show that it is finite at the singularity for a
variety of types of black hole. The energy is typically concentrated just
inside the horizon, not at the central singularity.Comment: 7 pages, 4 figure
Progress report of the third Generation ECR ion source fabrication
Recent progress in the construction of the 3rd Generation ECR ion source at the 88" cyclotron in Berkeley is reported. Test results of a full scale prototype superconducting magnet structure, which has been described in the last ECR Ion Source Workshop, lead to an improved coil design for the 3rd Generation ECR ion source. Solenoids of the new design have been fabricated and exceeded the design field values without quench. The new sextupole coils are currently being wound and will be tested this summer. This magnet structure consists of three solenoids and six race track coils with iron poles forming the sextupole. It is described in the report along with the structural support and coil winding specifications. The coils are designed to generate a 4T axial mirror field at injection and 3T at extraction and a radial sextupole field of 2.4 T at the plasma chamber wall. The high axial magnetic field of the 3rd Generation ECR ion source influences ion beam extraction considerably and we have initiated simulations of the extraction and beam transport system in order to enhance transmission through the injection beam line of the 88" cyclotron
Molecular depletion times and the CO-to-H2 conversion factor in metal-poor galaxies
Tracing molecular hydrogen content with carbon monoxide in low-metallicity
galaxies has been exceedingly difficult. Here we present a new effort, with
IRAM 30-m observations of 12CO(1-0) of a sample of 8 dwarf galaxies having
oxygen abundances ranging from 12+logO/H=7.7 to 8.4. CO emission is detected in
all galaxies, including the most metal-poor galaxy of our sample (0.1 Zsun); to
our knowledge this is the largest number of 12CO(1-0) detections ever reported
for galaxies with 12+logO/H<=8 (0.2 Zsun) outside the Local Group. We calculate
stellar masses (Mstar) and star-formation rates (SFRs), and analyze our results
by combining our observations with galaxy samples from the literature.
Extending previous results for a correlation of the molecular gas depletion
time, tau(dep), with Mstar and specific SFR (sSFR), we find a variation in
tau(dep) of a factor of 200 or more (from <50 Myr to 10 Gyr) over a spread of
1000 in sSFR and Mstar. We exploit the variation of tau(dep) to constrain the
CO-to-H2 mass conversion factor alpha(CO) at low metallicity, and assuming a
power-law variation find alpha(CO) \propto (Z/Zsun)^1.9, similar to results
based on dust continuum measurements compared with gas mass. By including HI
measurements, we show that the fraction of total gas mass relative to the
baryonic mass is higher in galaxies that are metal poor, of low mass, and of
high sSFR. Finally, comparisons of the data with star-formation models of the
molecular gas phases suggest that, at metallicities Z/Zsun<=0.2, there are some
discrepancies with model predictions.Comment: 18 pages, 15 figures, accepted for publication in A&
Classifying the unknown: discovering novel gravitational-wave detector glitches using similarity learning
The observation of gravitational waves from compact binary coalescences by
LIGO and Virgo has begun a new era in astronomy. A critical challenge in making
detections is determining whether loud transient features in the data are
caused by gravitational waves or by instrumental or environmental sources. The
citizen-science project \emph{Gravity Spy} has been demonstrated as an
efficient infrastructure for classifying known types of noise transients
(glitches) through a combination of data analysis performed by both citizen
volunteers and machine learning. We present the next iteration of this project,
using similarity indices to empower citizen scientists to create large data
sets of unknown transients, which can then be used to facilitate supervised
machine-learning characterization. This new evolution aims to alleviate a
persistent challenge that plagues both citizen-science and instrumental
detector work: the ability to build large samples of relatively rare events.
Using two families of transient noise that appeared unexpectedly during LIGO's
second observing run (O2), we demonstrate the impact that the similarity
indices could have had on finding these new glitch types in the Gravity Spy
program
Scaling Law and Aging Phenomena in the Random Energy Model
We study the effect of temperature shift on aging phenomena in the Random
Energy Model (REM). From calculation on the correlation function and simulation
on the Zero-Field-Cooled magnetization, we find that the REM satisfies a
scaling relation even if temperature is shifted. Furthermore, this scaling
property naturally leads to results obtained in experiment and the droplet
theory.Comment: 8 pages, 7 figures, to be submitted to J. Phys. Soc. Jp
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