2,749 research outputs found
Simultaneous Iliacus and Psoas Muscle Variations
Dissection of a 98-year-old female cadaver identified three previously unrecorded simultaneous variations in the iliac region. A variant iliacus muscle originated in the iliac fossa and then split at the insertion point of the lesser trochanter to blend with the psoas major and vastus medialis muscles. Two variant psoas muscles were found located medial and lateral to the psoas major muscle. The position of the psoas muscle variations resulted in an altered course of the typical path of both the femoral and obturator nerves. The current findings and clinical significance are discussed
Glenohumeral Joint Dissection: A New Protocol
Objectives: The glenohumeral joint, as a component of the shoulder girdle, is one of the most frequently injured joints of the upper extremity. Typical dissection of the glenohumeral joint does not allow an intracapsular view without sacrificing the joint capsule and surrounding structures.
Methods: A dissection method is presented which reveals the internal capsule of the glenohumeral joint, the glenoid labrum, the proximal insertion of the long head of the biceps tendon, and glenohumeral joint surfaces while preserving the posterior aspect of the capsule and surrounding supportive muscles and tendons of the joint.
Results: The novel dissection technique allowed for preservation of glenohumeral joint structures and consideration or reexamination of the relationships and structures. Conclusion: The authors present an alternative protocol for dissection of the glenohumeral joint that minimizes destruction of the surrounding structures while allowing visualization of the internal capsule and maintains the relationships of the surrounding supporting structures of the pectoral girdle that may be used for study at a later time.
Conclusion: The authors present an alternative protocol for dissection of the glenohumeral joint that minimizes destruction of the surrounding structures while allowing visualization of the internal capsule and maintains the relationships of the surrounding supporting structures of the pectoral girdle that may be used for study at a later time
The X-Ray Concentration-Virial Mass Relation
We present the concentration (c)-virial mass (M) relation of 39 galaxy
systems ranging in mass from individual early-type galaxies up to the most
massive galaxy clusters, (0.06-20) x 10^{14} M_sun. We selected for analysis
the most relaxed systems possessing the highest quality data currently
available in the Chandra and XMM public data archives. A power-law model fitted
to the X-ray c-M relation requires at high significance (6.6 sigma) that c
decreases with increasing M, which is a general feature of CDM models. The
median and scatter of the c-M relation produced by the flat, concordance LCDM
model (Omega_m=0.3, sigma_8=0.9) agrees with the X-ray data provided the sample
is comprised of the most relaxed, early forming systems, which is consistent
with our selection criteria. Holding the rest of the cosmological parameters
fixed to those in the concordance model the c-M relation requires 0.76< sigma_8
<1.07 (99% conf.), assuming a 10% upward bias in the concentrations for early
forming systems. The tilted, low-sigma_8 model suggested by a new WMAP analysis
is rejected at 99.99% confidence, but a model with the same tilt and
normalization can be reconciled with the X-ray data by increasing the dark
energy equation of state parameter to w ~ -0.8. When imposing the additional
constraint of the tight relation between sigma_8 and Omega_m from studies of
cluster abundances, the X-ray c-M relation excludes (>99% conf.) both open CDM
models and flat CDM models with Omega_m ~1. This result provides novel evidence
for a flat, low-Omega_m universe with dark energy using observations only in
the local (z << 1) universe. Possible systematic errors in the X-ray mass
measurements of a magnitude ~10% suggested by CDM simulations do not change our
conclusions.Comment: Accepted for Publication in ApJ; 13 pages, 4 figures; minor
clarifications and updates; correlation coefficients corrected in Table 1
(correct values were used in the analysis in previous versions); conclusions
unchange
Large scatter in X-ray emission among elliptical galaxies: correlations with mass of host halo
The enormous range of X-ray luminosities among elliptical galaxies with similar optical luminosities can be attributed to large scatter and systematic variations in the dark halo mass determined from X-ray observations. The mean halo mass decreases sharply with both the X-ray and K-band luminosities. Smaller halos contain less diffuse hot gas and have lower X-ray luminosities. In addition the hot gas in low mass halos is more easily depleted by supernova-driven outflows, further lowering the X-ray luminosity
The Absence of Adiabatic Contraction of the Radial Dark Matter Profile in the Galaxy Cluster A2589
We present an X-ray analysis of the radial mass profile of the radio-quiet
galaxy cluster A2589 between 0.015-0.25 r_vir using an XMM-Newton observation.
Except for a ~16 kpc shift of the X-ray center of the R=45-60 kpc annulus,
A2589 possesses a remarkably symmetrical X-ray image and is therefore an
exceptional candidate for precision studies of its mass profile by applying
hydrostatic equilibrium. The total gravitating matter profile is well described
by the NFW model (fractional residuals <~10%) with c_vir=6.1 +/- 0.3 and M_vir
= 3.3 +/- 0.3 x 10^{14} M_sun (r_vir = 1.74 +/- 0.05 Mpc) in excellent
agreement with LCDM. When the mass of the hot ICM is subtracted from the
gravitating matter profile, the NFW model fitted to the resulting dark matter
(DM) profile produces essentially the same result. However, if a component
accounting for the stellar mass (M_*) of the cD galaxy is included, then the
NFW fit to the DM profile is substantially degraded in the central r ~50 kpc
for reasonable M_*/L_V. Modifying the NFW DM halo by adiabatic contraction
arising from the early condensation of stellar baryons in the cD galaxy further
degrades the fit. The fit is improved substantially with a Sersic-like model
recently suggested by high resolution N-body simulations but with an inverse
Sersic index, alpha ~0.5, a factor of ~3 higher than predicted. We argue that
neither random turbulent motions nor magnetic fields can provide sufficient
non-thermal pressure support to reconcile the XMM mass profile with adiabatic
contraction of a CDM halo assuming reasonable M_*/L_V. Our results support the
scenario where, at least for galaxy clusters, processes during halo formation
counteract adiabatic contraction so that the total gravitating mass in the core
approximately follows the NFW profile.Comment: 15 pages, 11 figures, accepted for publication in ApJ. Minor changes
to match published versio
Serendipitous XMM-Newton discovery of a cluster of galaxies at z=0.28
We report the discovery of a galaxy cluster serendipitously detected as an
extended X-ray source in an offset observation of the group NGC 5044. The
cluster redshift, z=0.281, determined from the optical spectrum of the
brightest cluster galaxy, agrees with that inferred from the X-ray spectrum
using the Fe K alpha complex of the hot ICM (z=0.27 +/- 0.01). Based on the 50
ks XMM observation, we find that within a radius of 383 kpc the cluster has an
unabsorbed X-ray flux, f_X (0.5-2 keV) = 3.34 (+0.08, -0.13) x 10^{-13}
erg/cm^2/s, a bolometric X-ray luminosity, L_X = 2.21 (+0.34, -0.19) x 10^{44}
erg/s, kT = 3.57 +/- 0.12 keV, and metallicity, 0.60 +/- 0.09 solar. The
cluster obeys the scaling relations for L_X and T observed at intermediate
redshift. The mass derived from an isothermal NFW model fit is, M_vir = 3.89
+/- 0.35 x 10^{14} solar masses, with a concentration parameter, c = 6.7 +/-
0.4, consistent with the range of values expected in the concordance
cosmological model for relaxed clusters. The optical properties suggest this
could be a ``fossil cluster''.Comment: 5 pages, 4 colour figures, accepted for publication in Ap
Probing the Dark Matter and Gas Fraction in Relaxed Galaxy Groups with X-ray observations from Chandra and XMM
We present radial mass profiles within 0.3 r_vir for 16 relaxed galaxy
groups-poor clusters (kT range 1-3 keV) selected for optimal mass constraints
from the Chandra and XMM data archives. After accounting for the mass of hot
gas, the resulting mass profiles are described well by a two-component model
consisting of dark matter (DM), represented by an NFW model, and stars from the
central galaxy. The stellar component is required only for 8 systems, for which
reasonable stellar mass-to-light ratios (M/L_K) are obtained, assuming a Kroupa
IMF. Modifying the NFW dark matter halo by adiabatic contraction does not
improve the fit and yields systematically lower M/L_K. In contrast to previous
results for massive clusters, we find that the NFW concentration parameter
(c_vir) for groups decreases with increasing M_vir and is inconsistent with no
variation at the 3 sigma level. The normalization and slope of the c_vir-M_vir
relation are consistent with the standard LambdaCDM cosmological model with
sigma_8 = 0.9. The small intrinsic scatter measured about the c_vir-M_vir
relation implies the groups represent preferentially relaxed, early forming
systems. The mean gas fraction (f =0.05 +/- 0.01) of the groups measured within
an overdensity Delta=2500 is lower than for hot, massive clusters, but the
fractional scatter (sigma_f/f=0.2) for groups is larger, implying a greater
impact of feedback processes on groups, as expected.Comment: Accepted for Publication in ApJ; 30 pages, 9 figures. No changes from
previous versio
A Chandra View of Dark Matter in Early-Type Galaxies
We present a Chandra study of mass profiles in 7 elliptical galaxies, of
which 3 have galaxy-scale and 4 group-scale halos demarcated at 1E13Msun. These
represent the best available data for nearby objects with comparable X-ray
luminosities. We measure ~flat mass-to-light (M/L) profiles within an optical
half-light radius (Reff), rising by an order of magnitude at ~10Reff, which
confirms the presence of dark matter (DM). The data indicate hydrostatic
equilibrium, which is also supported by agreement with studies of stellar
kinematics in elliptical galaxies. The data are well-fitted by a model
comprising an NFW DM profile and a baryonic component following the optical
light. The distribution of DM halo concentration parameters (c) versus Mvir
agrees with LCDM predictions and our observations of bright groups.
Concentrations are slightly higher than expected, which is most likely a
selection effect. Omitting the stellar mass drastically increases c, possibly
explaining large concentrations found by some past observers. The stellar M/LK
agree with population synthesis models, assuming a Kroupa IMF. Allowing
adiabatic compression (AC) of the DM halo by baryons made M/L more discrepant,
casting some doubt on AC. Our best-fitting models imply total baryon fractions
\~0.04--0.09, consistent with models of galaxy formation incorporating strong
feedback. The groups exhibit positive temperature gradients, consistent with
the "Universal" profiles found in other groups and clusters, whereas the
galaxies have negative gradients, suggesting a change in the evolutionary
history of the systems around Mvir=1E13 Msun.Comment: 22 pages and 6 figures. Accepted for publication in the Astrophysical
Journal. Minor changes to match published version. Expanded galaxy/group
discussion. Results unchange
X-ray Isophotes in a Rapidly Rotating Elliptical Galaxy: Evidence of Inflowing Gas
We describe two-dimensional gasdynamical computations of the X-ray emitting
gas in the rotating elliptical galaxy NGC 4649 that indicate an inflow of about
one solar mass per year at every radius. Such a large instantaneous inflow
cannot have persisted over a Hubble time. The central constant-entropy
temperature peak recently observed in the innermost 150 parsecs is explained by
compressive heating as gas flows toward the central massive black hole. Since
the cooling time of this gas is only a few million years, NGC 4649 provides the
most acutely concentrated known example of the cooling flow problem in which
the time-integrated apparent mass that has flowed into the galactic core
exceeds the total mass observed there. This paradox can be resolved by
intermittent outflows of energy or mass driven by accretion energy released
near the black hole. Inflowing gas is also required at intermediate kpc radii
to explain the ellipticity of X-ray isophotes due to spin-up by mass ejected by
stars that rotate with the galaxy and to explain local density and temperature
profiles. We provide evidence that many luminous elliptical galaxies undergo
similar inflow spin-up. A small turbulent viscosity is required in NGC 4649 to
avoid forming large X-ray luminous disks that are not observed, but the
turbulent pressure is small and does not interfere with mass determinations
that assume hydrostatic equilibrium.Comment: 21 pages, 9 figures, accepted for publication by Ap
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