#large scale structure

Record-Breaking 3D Map Of The Universe Reveals Some Big Surprises

“The Universe is not curved on the largest scales, but is spatially flat to 499 parts in 500: the tightest constraint ever. The Universe not only needs dark energy, but it makes up 70% of the Universe and is perfectly consistent with a cosmological constant. Of the other 30%, 25% is dark matter and just 5% is normal matter, with the Universe expanding at 68.2 km/s/Mpc. This is based on over 2 million galaxies observed from nearby to in excess of 19 billion light-years away, corresponding to more than 11 billion years of cosmic history.

In the coming years, the Dark Energy Spectroscopic Instrument (DESI) will take us to tens of millions of galaxies, with even greater advances coming with the launch of ESA's Euclid, NASA's WFIRST, and the NSF's ground-based Vera Rubin Observatory. There are now three major players in the quest to measure the expansion of the Universe: the Cosmic Microwave Background, the cosmic distance ladder, and the imprint of acoustic oscillations in the Universe’s large-scale structure. The first and third methods agree with each other, but not with the second. Until we figure out why, along with the puzzles of dark matter and dark energy, this will remain one of the most compelling mysteries about the very nature of our cosmos.”

More than 2 million galaxies have been exquisitely measured, corresponding to distances of more than 19 billion light-years and lookback times that take us 80% of the way back to the Big Bang itself. In many ways, it’s the most comprehensive map of the structure in the Universe ever constructed.

What Was It Like When The Cosmic Web Took Shape?

“Although the seeds necessary for cosmic structure were planted in the very earliest stages of the Universe, it takes time and the right resources for those seeds to grow to fruition. The seeds for small-scale structure germinate first, as the gravitational force propagates at the speed of light, growing overdense regions into the earliest star clusters after only a few tens of millions of years. As time goes on, the seeds for galaxy-scale structure grow too, taking hundreds of millions of years to bring about galaxies within the Universe.

But galaxy clusters, growing from the same magnitude seeds on larger distance scales, take billions of years. By time the Universe is 7.8 billion years old, the accelerated expansion has taken over, explaining why there are no larger bound structures than galaxy clusters. The cosmic web is no longer growing as it once was, but is primarily being torn apart by dark energy. Enjoy what we have while we have it; the Universe will never be this structured again!”

When we look out at the Universe today, we find stars bound together in enormous collections known as galaxies, and galaxies clumped together into groups and clusters, which themselves appear to be connected by filaments of matter. This cosmic web took many billions of years to form, though, and the smaller-scale structure formed far earlier in the Universe than the large-scale structure. While it took only tens of millions of years for stars and hundreds of millions for galaxies, it took billions of years for galaxy clusters, and anything you’ve heard about ‘superclusters’ is a mere phantasm.

Finding all the matter in the cosmos — even the invisible stuff

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“Weak Lensing” Helps Astronomers Map the Mass of the Universe By making galaxies a little bit brighter, it points the way to elusive galaxies and lets us detect that most mysterious of substances: dark matter

For Smithsonian Magazine:

In ordinary visible…

Fundamental Issues of the Standard Cosmological Model

The Planck Satellite measurement have increased the accuracy of cosmological observations to a level which allows to constrain cosmological models with unprecedented precision. The aim of this workshop is to discuss the implications of these recent results combined with other (i.e. Planck, but also WMAP, galaxy surveys, SNIa data…) on models that aim at describing the primordial epochs and the…

Simulating the first realistic cosmic web

Un gruppo di ricercatori guidati da Mark Vogelsberger dell’Harvard-Smithsonian Center for Astrophysics, in collaborazione con l’Heidelberg Institute for Theoretical Studies in Germania, hanno realizzato la prima mappa virtuale, alquanto realistica, dell’Universo utilizzando una simulazione numerica denominata “Illustris“. Il modello ha permesso di ricreare uno spazio cubico di lato pari a 350…