Category Archives: Astronomy


very exciting … in a few hours I’ll be presenting the SWIFT simulation code and its advanced features at the big International SuperComputing mega-conference. If you’re there maybe I’ll see you at the Intel stand??

more details here…

The multiverse and the nature of dark energy

Multiverse3In my recent papers (lead by Jaime Salcido  and Luke Barnes), we used the simulation code to explore the multiverse! Specifically, we examined how the abundance of dark energy (or more technically, the zero point energy of empty space) affected the ability of a universe to form stars and galaxies. Because of the realism of the computer universe generated in the Eagle project, we have a great deal of faith in our predictions for other Universes.

We expected to find that the abundance of Dark Energy in our universe was close to the upper limit for the abundant formation of stars, but our results show that this is far from true!  Universes with much much larger Dark Energy contributions would still be inhabited by viable observers. This places the multiverse hypothesis on rocky ground, and suggests that we should focus our attention on improving the physical explanation for dark energy.

Our work has been written up in The Conversation, and that is a good place to find out more.

The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

I’ve just submitted a new paper to MNRAS, the professional journal of astronomy… its all about black holes and how they bring star formation in galaxies to an end, creating two distinct galaxy types and making the Universe look the way it is. Far from being exotic predictions of Einsteins General Relativity, it seems that black holes play a fundamental role in shaping the observable universe.


Here’s the paper’s abstract, click to get a link to the paper… Continue reading The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

LDSS at the Las Campanas Observatory

It’s amazing. I’m at the Las Campanas Observatory, using the LDSS (low Dispersion Survey) spectrograph. A triumph of North East engineering, she was built in Durham University in 1991 by a team of “real” engineers,  including John Webster. It was one of the first instruments to allow astronomer to survey the distant Universe and to see galaxies when the Universe was only a fraction of its present age.

In 2001, John and I moved LDSS to its new home at the incredible 6.5m Magellan Clay telescope. The instrument has evolved for strength to strength, using its solid engineering as a plot form for the latest technological developments in optics and, most recently, its CCD detector. LDSS is still at the leading edge of cosmology.

Now, here I am looking for some of the faintest galaxies in the Universe. Our new ‘Deep Depletion’ detector lets us find galaxies at even higher redshift, and clever electronics allow us to detect lower mass galaxies than ever before, revealing the secrets of how galaxies, and the nuclear elements they contain (such as the carbon and oxygen that we are made of) have been created over the history of time.


EAGLE takes off

The first EAGLE paper is now available on the astro-ph archive. It will tell you everything you wanted to know about the project (and more probably more!).  Most importantly, it sets out the project philosophy and shows just how much the simulated universe looks like the real one.


This plot counts the numbers of galaxies of different masses. It compares the main Eagle simulation (the dark blue line) to previous work (the other lines) and observational data (the fray points)… you’re meant to see that EAGLE fits the data really well – it captures both the flat part (similar numbers of galaxies with masses to our Milky Way galaxy and with mass 10 times smaller), and the exponential break at higher masses (galaxies much larger than our own are incredibly rare). EAGLE is a huge step forward compared to previous work. There are many more comparisons like this in the paper.

Here’s the paper’s abstract…. Continue reading EAGLE takes off

Cosmic Own Goal

gas imageOne of the very exciting things about the Eagle project is that it is possible to pick out interesting objects, and then re-simulate the volume around them at higher resolution giving a much better view of what’s going on and letting us find even the smallest galaxies.

So what are the smallest galaxies? Surely galaxies can be as small as you want? Well – no. There’s a limit to the smallest size of galaxies, and Till Sawala has just written an exciting paper demonstrating why.

The science paper is available here…

but we’ve also issued a press realease with some very cool pictures. The full pictures are here…

Here’s the story ….

Continue reading Cosmic Own Goal

EAGLE in the News

Images from our EAGLE simulations appeared on the BBC’s Newsnight program last night. Journalist Rebecca Morelle used them to explain the concept of Dark Matter: the exotic and invisible matter that makes up most of the mass of the Universe. The images contrast the universe as we see it (from looking at starlight) to the way it would appear if it were possible to see the Dark Matter.


Follow the on-line story at the BBC’s news website.

If you would like to explore more of the Universe, download our app “Cosmic Universe” from the apple store.