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Blobrana


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RE: large scale structures
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Cosmos Symmetry suggests universe spun an axis

University of Michigan scientists have argued a long-held assumption that the universe has mirror symmetry, like a basketball.
They have suggested that the shape of the Big Bang might be more complicated than previously thought, and that the early universe spun about an axis.
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Blobrana


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SAURON Project
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Title: The SAURON Project - XIX. Optical and near-infrared scaling relations of nearby elliptical, lenticular and Sa galaxies
Authors: J. Falcón-Barroso, G. van de Ven, R.F. Peletier, M. Bureau, H. Jeong, R. Bacon, M. Cappellari, R.L. Davies, P.T. de Zeeuw, E. Emsellem, D. Krajnovi, H. Kuntschner, R.M. McDermid, M. Sarzi, K.L. Shapiro, R.C.E. van den Bosch, G. van der Wolk, A. Weijmans, S. Yi

We present ground-based MDM V-band and Spitzer/IRAC 3.6um-band photometric observations of the 72 representative galaxies of the SAURON Survey. In combination with the SAURON stellar velocity dispersion measured within an effective radius (se), this allows us to explore the location of our galaxies in the main scaling relations. We investigate the dependence of these relations on our recent kinematical classification of early-type galaxies (i.e. Slow/Fast Rotators) and the stellar populations. Slow Rotator and Fast Rotator E/S0 galaxies do not populate distinct locations in the scaling relations, although Slow Rotators display a smaller intrinsic scatter. Surprisingly, extremely young objects do not display the bluest (V-[3.6]) colours in our sample, as is usually the case in optical colours. This can be understood in the context of the large contribution of TP-AGB stars to the infrared, even for young populations, resulting in a very tight (V-[3.6]) - se relation that in turn allows us to define a strong correlation between metallicity and velocity dispersion. Many Sa galaxies appear to follow the Fundamental Plane defined by E/S0 galaxies. Galaxies that appear offset from the relations correspond mostly to objects with extremely young populations, with signs of on-going, extended star formation. We correct for this effect in the Fundamental Plane, by replacing luminosity with stellar mass using an estimate of the stellar mass-to-light ratio, so that all galaxies are part of a tight, single relation. The new estimated coefficients are consistent in both photometric bands and suggest that differences in stellar populations account for about half of the observed tilt with respect to the virial prediction. After these corrections, the Slow Rotator family shows almost no intrinsic scatter around the best-fit Fundamental Plane.

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Blobrana


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Large scale structures
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Astronomers reveal a cosmic 'axis of evil'

Astronomers are puzzled by the announcement that the masses of the largest objects in the Universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on 'Scaling Relations of Galaxy Clusters' organised by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.
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Blobrana


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Largest cosmic structures 'too big' for theories
 
Space is festooned with vast "hyperclusters" of galaxies, a new cosmic map suggests. It could mean that gravity or dark energy - or perhaps something completely unknown - is behaving very strangely indeed.
We know that the universe was smooth just after its birth. Measurements of the cosmic microwave background radiation (CMB), the light emitted 370,000 light years after the big bang, reveal only very slight variations in density from place to place. Gravity then took hold and amplified these variations into today's galaxies and galaxy clusters, which in turn are arranged into big strings and knots called superclusters, with relatively empty voids in between.
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Blobrana


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Physicist Michael Longo Discovers an Apparent Cosmic Parity Violation

Does our universe have mirror symmetry? That is the question Professor Michael Longo of the Michigan Physics Department asked. The answer could perhaps be found by studying the rotation directions of spiral galaxies.
Physicists and astronomers have always assumed that the Universe has this symmetry. To test this, Professor Longo and his team of five undergraduates used data from the Sloan Digital Sky Survey to study the rotation directions of spiral galaxies. The mirror image of a counter-clockwise rotating galaxy, like the example, would have clockwise rotation. An excess of one type over the other would be evidence for a breakdown of mirror symmetry, or, in physics speak, a "parity violation" on cosmic scales.
Professor Longo and his team, after studying tens of thousands of spiral galaxies, found an excess of left-handed spirals in the part of the sky toward the north pole of our galaxy, the Milky Way. The excess is small, about 7%. However, Professor Longo estimates the chance that the excess could be a cosmic accident is something like one in a million. The effect extended out to distances over 600 million light years. Our galaxy also rotates in the same sense.

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Blobrana


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The Planck space telescope has identified some of the largest structures ever seen in the Universe.
These are clusters of galaxies that are gravitationally bound to each other and which measure tens of millions of light-years across.
Astronomers say the Planck observatory has made more than 20 detections that are brand new to science.
The European Space Agency telescope has also confirmed the existence of a further 169 galaxy clusters.



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Blobrana


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Cl0016+16 supercluster
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Title: A GALEX/Spitzer survey of the Cl0016+16 supercluster at z=0.55: acceleration of the onset of star-formation in satellite groups
Authors: J. E. Geach (McGill), R. S. Ellis (Caltech), Ian Smail (Durham), T. D. Rawle (Steward), S. M. Moran (JHU)

We present the results of a panoramic (15 Mpc-scale) survey of the Cl0016+16 supercluster (z=0.55) using Spitzer Space Telescope MIPS 24um and Galaxy Evolution Explorer near-UV (2500A; NUV) imaging. The supercluster regions probed are characterised by several dense nodes connected by a pronounced intermediate-density filamentary structure. We have studied the mid-IR and NUV properties of potential cluster members within a Dz=0.1 photometric redshift slice, compared to an identical blank field selection. We have two main findings: (a) the star-formation rates of individual star-forming galaxies throughout the cluster are not significantly different to identically selected field galaxies, and (b) the cluster harbours pockets of 'accelerated' activity where galaxies have an enhanced probability of undergoing star formation. This observation could be explained in a simple model of 'pre-processing' of galaxies during cluster infall: galaxies in satellite groups have an increased chance of having star-formation triggered via gravitational tidal interactions compared to their counterparts in the field, but there is no environmental mechanism boosting the individual star-formation rates of galaxies. We estimate a lower-limit for the total star-formation rate of galaxies in the supercluster as ~850 Msun/yr (field corrected). If this rate is maintained over the typical infall time of a few Gyr, then the infall population could contribute ~1-2x10^12 Msun of stellar mass to the structure.

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Blobrana


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Title: The most massive objects in the Universe
Authors: Daniel E. Holz, Saul Perlmutter
(Version v2)

We calculate the most massive object in the Universe, finding it to be a cluster of galaxies with total mass M_200=3.8e15 solar masses at z=0.22, with the 1 sigma marginalised regions being 3.3e15 solar masses <4.4e15 solar masses and 0.12<0.36. We restrict ourselves to self-gravitating bound objects, and base our results on halo mass functions derived from N-body simulations. Since we consider the very highest mass objects, the number of candidates is expected to be small, and therefore each candidate can be extensively observed and characterised. If objects are found with excessively large masses, or insufficient objects are found near the maximum expected mass, this would be a strong indication of the failure of LambdaCDM. The expected range of the highest masses is very sensitive to redshift, providing an additional evolutionary probe of LambdaCDM. We find that the three most massive clusters in the recent SPT 178 deg² catalogue match predictions, while XMMU J2235.3--2557 is roughly 3 sigma inconsistent with LambdaCDM. We discuss Abell 2163 and Abell 370 as candidates for the most massive cluster in the Universe, although uncertainties in their masses preclude definitive comparisons with theory. Our findings motivate further observations of the highest mass end of the mass function. Future surveys will explore larger volumes, and the most massive object in the Universe may be identified within the next decade. The mass distribution of the largest objects in the Universe is a potentially powerful test of LambdaCDM, probing non-Gaussianity and the behaviour of gravity on large scales.

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Blobrana


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Title: Tracing the Filamentary Structure of the Galaxy Distribution at z~0.8
Authors: Ena Choi, Nicholas A. Bond, Michael A. Strauss, Alison L. Coil, Marc Davis, Christopher N. A. Willmer

We study filamentary structure in the galaxy distribution at z ~ 0.8 using data from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Redshift Survey and its evolution to z ~ 0.1 using data from the Sloan Digital Sky Survey (SDSS). We trace individual filaments for both surveys using the Smoothed Hessian Major Axis Filament Finder, an algorithm which employs the Hessian matrix of the galaxy density field to trace the filamentary structures in the distribution of galaxies. We extract 33 subsamples from the SDSS data with a geometry similar to that of DEEP2. We find that the filament length distribution has not significantly changed since z ~ 0.8, as predicted in a previous study using a \Lamda CDM cosmological N-body simulation. However, the filament width distribution, which is sensitive to the non-linear growth of structure, broadens and shifts to smaller widths for smoothing length scales of 5-10 Mpc/h from z ~ 0.8 to z ~ 0.1, in accord with N-body simulations.

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Blobrana


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For astronomers who study the large-scale structure of the universe, dwarf galaxies have proven quite vexing. Because the leading model of cosmology has been unable to account for their relative lack of substance. Now scientists writing in the journal Nature show that the current model can actually generate dwarf galaxies just fine. You just need to look at the stars.
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-- Edited by Blobrana on Friday 15th of January 2010 08:01:06 PM

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