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galaxy clusters

This tag is associated with 31 posts

Dark in the Lightness

New results from stacked weak lensing measurements of over a hundred thousand galaxies show that, on large scales, light from stars appears to trace the dark matter distribution of the Universe remarkably well.

Circling problems with our model of the Universe: what can groups of galaxies tell us about Lambda CDM?

Measurements of the circular velocities in groups of galaxies can test whether our current cosmology is correct.

An example showing a model SED fit to observation

What came before clusters? Protoclusters

A galaxy cluster in the act of forming reveals some interesting details about the lives of galaxies.

Cartography of the Local Cosmos

Astronomers map out the local universe in a way that is both intuitive and fascinating, marking the birth of the new science of “Cosmography”.

Ram pressure stripping: a classic paper

A classic 1972 paper by Jim Gunn and J. Richard Gott, III describing the growth of clusters from primordial density perturbations and, most famously, the importance of ram pressure stripping in explaining the observed lack of spiral galaxies towards the center of clusters.

Simulations of Dark matter core formation

The Top 12 of 2012

What were astronomers reading and talking about in their research last year? Check out figures from the top 12 most-cited astronomy papers from 2012 (so far) and find out what researchers were up to and why!

Gravitational Lensing in the Canary Islands

I recently attended a two-week crash course in the “Astrophysical Applications of Gravitational Lensing”. In this post, I overview a few of the ways astronomers employ lensing to study the Universe, from extrasolar planets to distant quasars and large-scale structure.

Observing the Velocity Anisotropy of Cluster Galaxies

Title: Spatial Anisotropy of Galaxy Kinematics in Sloan Digital Sky Survey Galaxy Clusters First Author: Skielboe, A. Galaxy clusters are beautifully simple, but also fantastically complicated structures. For many years, astronomers have treated these systems as spherical cows, but simulations and observations have repeatedly shown that clusters exhibit triaxial rather than spherical shapes with nice […]

Mixing up gas in the wake of a strangled satellite

Most simulations to date have implied that satellite galaxies traveling through galaxy clusters are stripped of gas for future star formation in a process known as “strangulation”. In contrast, the authors of this paper suggest that satellite galaxies may not be as cut off as some might think: instead, their simulations show that the cooler, stripped gas from the corona will mix with the surrounding intra-cluster medium and remain near the original galaxy as a potential new source of star-forming fuel.

Strands in the Cosmic Web

Throughout much of the 20th century, it was an open question in astronomy as to what the universe looked like on the largest observable scales. Were galaxies and galaxy clusters distributed uniformly throughout space, or was there a pattern? Thanks to galaxy surveys we know that, on large scales, the matter distribution of the universe is clumpy instead of smooth. Through these surveys we observe directly the distribution of luminous matter like stars, gas, and galaxies. However, luminous matter comprises only a small fraction of the matter in the universe (17%), the rest is dark matter which interacts via gravity but does not absorb and emit electromagnetic radiation like normal matter. Theoretical simulations of dark matter cosmologies firmly predict that there is a dark matter backbone to the cosmic web, with filaments of dark matter stretching between clusters of galaxies, though has not yet been a robust detection of a dark matter filament, until now.

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