13 research outputs found
The Evolutionary Status of Clusters of Galaxies at z ~ 1
Combined HST, X-ray, and ground-based optical studies show that clusters of
galaxies are largely "in place" by , an epoch when the Universe was
less than half its present age. High resolution images show that elliptical,
S0, and spiral galaxies are present in clusters at redshifts up to . Analysis of the CMDs suggest that the cluster ellipticals formed their
stars several Gyr earlier, near redshift 3. The morphology--density relation is
well established at , with star-forming spirals and irregulars residing
mostly in the outer parts of the clusters and E/S0s concentrated in dense
clumps. The intracluster medium has already reached the metallicity of
present-day clusters. The distributions of the hot gas and early-type galaxies
are similar in clusters, indicating both have largely virialized in
the deepest potentials wells. In spite of the many similarities between
and present-day clusters, there are significant differences. The
morphologies revealed by the hot gas, and particularly the early-type galaxies,
are elongated rather than spherical. We appear to be observing the clusters at
an epoch when the sub-clusters and groups are still assembling into a single
regular cluster. Support for this picture comes from CL0152 where the gas
appears to be lagging behind the luminous and dark mass in two merging
sub-components. Moreover, the luminosity difference between the first and
second brightest cluster galaxies at is smaller than in 93% of
present-day Abell clusters, which suggests that considerable luminosity
evolution through merging has occurred since that epoch. Evolution is also seen
in the bolometric X-ray luminosity function.Comment: 18 pages, 12 figures, to appear in Penetrating Bars through Masks of
Cosmic Dust: the Hubble Tuing Fork Strikes a New Note, eds. D.L. Block, K.C.
Freeman, I. Puerari & R. Groess. Figures degraded to meet astroph size limit;
a version with higher resolution figures may be downloaded from:
http://acs.pha.jhu.edu/~jpb/z1clusters/ford_clusters.pd
Fundamental Strings, Holography, and Nonlinear Superconformal Algebras
We discuss aspects of holography in the AdS_3 \times S^p near string geometry
of a collection of straight fundamental heterotic strings. We use anomalies and
symmetries to determine general features of the dual CFT. The symmetries
suggest the appearance of nonlinear superconformal algebras, and we show how
these arise in the framework of holographic renormalization methods. The
nonlinear algebras imply intricate formulas for the central charge, and we show
that in the bulk these correspond to an infinite series of quantum gravity
corrections. We also makes some comments on the worldsheet sigma-model for
strings on AdS_3\times S^2, which is the holographic dual geometry of parallel
heterotic strings in five dimensions.Comment: 25 page
Increased cardiovascular risk in rats with primary renal dysfunction; mediating role for vascular endothelial function
Primary chronic kidney disease is associated with high cardiovascular risk. However, the exact mechanisms behind this cardiorenal interaction remain unclear. We investigated the interaction between heart and kidneys in novel animal model for cardiorenal interaction. Normal Wistar rats and Munich Wistar Fromter rats, spontaneously developing renal dysfunction, were subjected to experimental myocardial infarction to induce cardiac dysfunction (CD) and combined cardiorenal dysfunction (CRD), respectively (N = 5–10). Twelve weeks later, cardiac- and renal parameters were evaluated. Cardiac, but not renal dysfunction was exaggerated in CRD. Accelerated cardiac dysfunction in CRD was indicated by decreased cardiac output (CD 109 ± 10 vs. CRD 79 ± 8 ml/min), diastolic dysfunction (E/e′) (CD 26 ± 2 vs. CRD 50 ± 5) and left ventricular overload (LVEDP CD 10.8 ± 2.8 vs. CRD 21.6 ± 1.7 mmHg). Congestion in CRD was confirmed by increased lung and atrial weights, as well as exaggerated right ventricular hypertrophy. Absence of accelerated renal dysfunction, measured by increased proteinuria, was supported by absence of additional focal glomerulosclerosis or further decline of renal blood flow in CRD. Only advanced peripheral endothelial dysfunction, as found in CRD, appeared to correlate with both renal and cardiac dysfunction parameters. Thus, proteinuric rats with myocardial infarction showed accelerated cardiac but not renal dysfunction. As parameters mimic the cardiorenal syndrome, these rats may provide a clinically relevant model to study increased cardiovascular risk due to renal dysfunction. Peripheral endothelial dysfunction was the only parameter that correlated with both renal and cardiac dysfunction, which may indicate a mediating role in cardiorenal interaction
Excursions into the Evolution of Early-Type Galaxies in Clusters
Recent observations have revealed that early-type galaxies (ETG) in clusters
comprise an old galaxy population that is evolving passively. We review some
recent observations from the ground and from HST that show that ETG have
undergone a significant amount of luminosity evolution. This evolution is
traced by two projections of the fundamental plane (FP): the size-magnitude
relation (SMR) and the color-magnitude relation (CMR). We will briefly discuss
the relevance of all these results in the context of the universality of the
IMF.Comment: 10 pages, 2 figures, to appear in the proccedings of "New Quests in
Stellar Astrophysics: The Link Between Stars and Cosmology, Chavez et al. ed
Early assembly of the most massive galaxies
The current consensus is that galaxies begin as small density fluctuations in
the early Universe and grow by in situ star formation and hierarchical merging.
Stars begin to form relatively quickly in sub-galactic sized building blocks
called haloes which are subsequently assembled into galaxies. However, exactly
when this assembly takes place is a matter of some debate. Here we report that
the stellar masses of brightest cluster galaxies, which are the most luminous
objects emitting stellar light, some 9 billion years ago are not significantly
different from their stellar masses today. Brightest cluster galaxies are
almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than
90% of their final stellar mass by this time. Our data conflict with the most
recent galaxy formation models based on the largest simulations of dark matter
halo development. These models predict protracted formation of brightest
cluster galaxies over a Hubble time, with only 22% of the stellar mass
assembled at the epoch probed by our sample. Our findings suggest a new picture
in which brightest cluster galaxies experience an early period of rapid growth
rather than prolonged hierarchical assembly.Comment: Published in Nature 2nd April 2009. This astro ph version includes
main text and supplementary material combine
Globular cluster systems and galaxy formation
Globular clusters are compact, gravitationally bound systems of up to a
million stars. The GCs in the Milky Way contain some of the oldest stars known,
and provide important clues to the early formation and continuing evolution of
our Galaxy. More generally, GCs are associated with galaxies of all types and
masses, from low-mass dwarf galaxies to the most massive early-type galaxies
which lie in the centres of massive galaxy clusters. GC systems show several
properties which connect tightly with properties of their host galaxies. For
example, the total mass of GCs in a system scales linearly with the dark matter
halo mass of its host galaxy. Numerical simulations are at the point of being
able to resolve globular cluster formation within a cosmological framework.
Therefore, GCs link a range of scales, from the physics of star formation in
turbulent gas clouds, to the large-scale properties of galaxies and their dark
matter. In this Chapter we review some of the basic observational approaches
for GC systems, some of their key observational properties, and describe how
GCs provide important clues to the formation of their parent galaxies.Comment: 32 pages, 6 figures. Accepted for publication in the book "Reviews in
Frontiers of Modern Astrophysics: From Space Debris to Cosmology" (eds
Kabath, Jones and Skarka; publisher Springer Nature) funded by the European
Union Erasmus+ Strategic Partnership grant "Per Aspera Ad Astra Simul"
2017-1-CZ01-KA203-03556