galaxy formation and evolution


A 3D printed universe in your hand

3D-printing technology has been used to create everything from iPad stands to guitars to lawnmowers and cars. Now a physicist at the University of California, Riverside is using the technology to understand the universe – its structure, the evolution of cosmic structures within it, and galaxy formation.

“These problems in cosmology are very difficult to visualize, even using computer graphics,” said Miguel Aragón-Calvo, a visiting assistant researcher in the Department of Physics and Astronomy.  “By 3D-printing them I am able to interact directly with the models and ‘see’ the problem at once.  In some cases this results in ‘eureka’ moments.”

Recently, Aragón-Calvo was trying to develop an automated method to identify and track the cosmic web across time in computer simulations. By 3D-printing a simpler 2D simulation and assigning the third dimension to time he realized that this was in fact the solution to his problem.

“Tridimensional cosmic structures can be easily identified and tracked as four-dimensional objects where time is taken as another spatial variable,” he said.  “Even though I had visualized the cosmic web many times before in the computer screen, the solution only became obvious once I held the model in my hand.”

Watch the video about it here


Astronomers today (28 June) released spectacular new infrared images of the distant universe, providing the deepest view ever obtained over a large area of sky. The team, led by Prof. Omar Almaini of the University of Nottingham, present their results at the National Astronomy Meeting [] at the same university.

The final data release from the Ultra-Deep Survey (UDS) maps an area four times the size of the full Moon to unprecedented depth. Over 250,000 galaxies have been detected, including several hundred observed within the first billion years after the Big Bang. Astronomers around the world will use the new images to study the early stages of galaxy formation and evolution.

The release of the final UDS images represents the culmination of a project that began taking data in 2005. The scientists used the United Kingdom Infrared Telescope (UKIRT) on Hawaii to observe the same patch of sky repeatedly, building up more than 1,000 hours of exposure time. Observing in the infrared is vital for studying the distant universe, as ordinary starlight is “redshifted” to longer wavelengths due to the cosmological expansion of the universe.

Because of the finite speed of light, the most distant galaxies are also observed very far back in time.

“With the UDS we can study distant galaxies in large numbers, and observe how they evolved at different stages in the history of the universe. We see most of the galaxies in our image as they were billions of years before the Earth was formed,” said Almaini.

The UDS is the deepest of 5 projects, collectively known as the UKIRT Infrared Deep Sky Survey (UKIDSS).

Earlier releases of data from the UDS have already produced a wide range of scientific advances, including studies of the earliest galaxies in the first billion years after the Big Bang, measurements of the build-up of galaxies through cosmic time, and studies of the large-scale distribution of galaxies to weigh the mysterious ‘dark matter’ that pervades the cosmos. The added depth from the new release is expected to produce many new breakthroughs.

“We are particularly keen to understand the dramatic transformation that many massive galaxies underwent around 10 billion years ago,” said Dr. William Hartley, a postdoctoral researcher at University College London. “At that time many galaxies appear to have abruptly stopped forming stars, and they also changed shape to form spheroidal-looking galaxies. We still don’t fully understand why this happens. With our new UDS images we expect to find large numbers of these galaxies, caught in the act of transformation, so we can study them in detail to solve this important puzzle.”

Installing the first of 18 flight mirrors onto the James Webb Space Telescope at NASA’s Goddard Space Flight Center in Greenbelt, Maryland this week. 

“The James Webb Space Telescope will be the premier astronomical observatory of the next decade,” said John Grunsfeld, astronaut and associate administrator of the Science Mission Directorate at NASA Headquarters in Washington. “This first-mirror installation milestone symbolizes all the new and specialized technology that was developed to enable the observatory to study the first stars and galaxies, examine the formation stellar systems and planetary formation, provide answers to the evolution of our own solar system, and make the next big steps in the search for life beyond Earth on exoplanets.”

The birth of monsters

Just counting the number of galaxies in a patch of sky provides a way to test astronomers’ theories of galaxy formation and evolution. However, such a simple task becomes increasingly hard as astronomers attempt to count the more distant and fainter galaxies. It is further complicated by the fact that the brightest and easiest galaxies to observe – the most massive galaxies in the Universe – are rarer the further astronomers peer into the Universe’s past, whilst the more numerous less bright galaxies are even more difficult to find.

A team of astronomers, led by Karina Caputi of the Kapteyn Astronomical Institute at the University of Groningen, has now unearthed many distant galaxies that had escaped earlier scrutiny. They used images from the UltraVISTA (http://ultravista.​org/​) survey, one of six projects using VISTA to survey the sky at near-infrared wavelengths, and made a census of faint galaxies when the age of the Universe was between just 0.75 and 2.1 billion years old.

UltraVISTA has been imaging the same patch of sky, nearly four times the size of a full Moon, since December 2009. This is the largest patch of sky ever imaged to these depths at infrared wavelengths. The team combined these UltraVISTA observations with those from the NASA Spitzer Space Telescope, which probes the cosmos at even longer, mid-infrared wavelengths [1].

“We uncovered 574 new massive galaxies – the largest sample of such hidden galaxies in the early Universe ever assembled,” explains Karina Caputi. “Studying them allows us to answer a simple but important question: when did the first massive galaxies appear?”

Imaging the cosmos at near-infrared wavelengths allowed the astronomers to see objects that are both obscured by dust, and extremely distant [2], created when the Universe was just an infant.

The team discovered an explosion in the numbers of these galaxies in a very short amount of time. A large fraction of the massive galaxies [3] we now see around us in the nearby Universe were already formed just three billion years after the Big Bang.

“We found no evidence of these massive galaxies earlier than around one billion years after the Big Bang, so we’re confident that this is when the first massive galaxies must have formed,” concludes Henry Joy McCracken, a co-author on the paper [4].

In addition, the astronomers found that massive galaxies were more plentiful than had been thought. Galaxies that were previously hidden make up half of the total number of massive galaxies present when the Universe was between 1.1 and 1.5 billion years old [5]. These new results, however, contradict current models of how galaxies evolved in the early Universe, which do not predict any monster galaxies at these early times.

To complicate things further, if massive galaxies are unexpectedly dustier in the early Universe than astronomers predict then even UltraVISTA wouldn’t be able to detect them. If this is indeed the case, the currently-held picture of how galaxies formed in the early Universe may also require a complete overhaul.

The Atacama Large Millimeter/submillimeter Array (ALMA) will also search for these game-changing dusty galaxies. If they are found they will also serve as targets for ESO’s 39-metre European Extremely Large Telescope (E-ELT - http://eso.​org/​e-elt), which will enable detailed observations of some of the first ever galaxies.