New KIPAC tool gives scientists a closer look at merging galaxies

Apr 12, 2012 by David Reffkin
Hubble Space Telescope image of two galaxies merging. This system is known as the “Antennae Galaxies” (NGC 4038-4039). (Image courtesy Hubble Space Telescope)

(Phys.org) -- Scientists at SLAC’s Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) have created sophisticated computer simulations that show galaxy mergers in much more detail than ever before.

On large cosmic scales, galaxies are the fundamental “molecular” units that occupy much of space. Understanding how they gravitationally interact is an important part of astrophysical research, since they can help explain star formation and other phenomena. Central black holes in some galaxies, for example, create huge jets of energy, a mysterious activity that intrigues researchers.

Mergers between galaxies are rare. Based on its relatively undisturbed structure, we can estimate that our own Milky Way galaxy has not been part of any major mergers within the last 10 billion years. When they do happen, they can produce some of the most awe-inspiring images from space. Such events may completely change the size and shape of galaxies, disrupting spiral arms and funneling stars into central bulges. Individual stars are so far apart from each other, however, that an actual collision between two of them is extremely unlikely.

It is difficult to completely resolve the details of two interacting galaxies simply by observing them. So scientists devise computer simulations of millions of galaxies evolving through the history of the universe, hoping to see mergers in process. Impossible to manage by hand, the immense amount of detail involved in these simulations requires special tools for tracking clusters of galactic matter over time. However, current analysis tools can’t differentiate the uniquely individual parts of galaxies during a merger, so the most interesting fine details are lost as the two galaxies become one.

To solve this problem, KIPAC graduate student Peter Behroozi, along with Professor Risa Wechsler and recent KIPAC alumna Heidi Wu, developed a new computational algorithm that uses both position and velocity information to distinguish in simulations. The algorithm’s formal name is Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement (ROCKSTAR). In essence, the program accounts for the speed, location and direction of the galactic elements. The result is a highly detailed picture of galaxy formation and disruption.

By extension, the algorithm’s measurement of galactic motions will also contribute to the larger study of the mass and energy content of the universe.

This work is based in part on a paper submitted to The Astrophysical Journal, online now on arXiv, and on an article by Peter Behroozi and Jack Singal for the KIPAC “Tidbits” newsletter.

Explore further: Astronomers find 'cousin' planets around twin stars

add to favorites email to friend print save as pdf

Related Stories

3D galaxies -- coming straight on for you

Jun 29, 2011

As we've recently learned, the ATLAS3D project was able to study 260 individual galaxies and do some very amazing things. By imaging in both red and blue shift, astronomers were able to take stellar measurements and give ...

Transforming galaxies

Feb 13, 2012

(PhysOrg.com) -- Many of the Universe's galaxies are like our own, displaying beautiful spiral arms wrapping around a bright nucleus. Examples in this stunning image, taken with the Wide Field Camera 3 on ...

A spiral galaxy in Hydra

Apr 09, 2012

(Phys.org) -- This image from the NASA/ESA Hubble Space Telescope shows NGC 4980, a spiral galaxy in the southern constellation of Hydra. The shape of NGC 4980 appears slightly deformed, something which is ...

Exposing the Nature of Cosmic Liaisons

Oct 16, 2007

Risa Wechsler of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) and her collaborators have devised a powerful technique to study how interactions between galaxies affect star formation. ...

How can growing galaxies stay silent?

Dec 19, 2011

Beginning around 2005, astronomers began discovering the presence of very large galaxies at a distance of around 10 billion lightyears. But while these galaxies were large, they didn’t appear to have ...

'Cosmic fruit machine' matches collisions

Nov 24, 2009

(PhysOrg.com) -- A new website will give everyone the chance to contribute to science by playing a 'cosmic fruit machine' and compare images of colliding galaxies with millions of simulated images of galactic ...

Recommended for you

How small can galaxies be?

Sep 29, 2014

Yesterday I talked about just how small a star can be, so today let's explore just how small a galaxy can be. Our Milky Way galaxy is about 100,000 light years across, and contains about 200 billion stars. Th ...

The coolest stars

Sep 29, 2014

One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are ...

Simulations reveal an unusual death for ancient stars

Sep 29, 2014

(Phys.org) —Certain primordial stars—those 55,000 and 56,000 times the mass of our Sun, or solar masses—may have died unusually. In death, these objects—among the Universe's first-generation of stars—would ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Lurker2358
not rated yet Apr 12, 2012
Individual stars are so far apart from each other, however, that an actual collision between two of them is extremely unlikely.


Yeah, here we go again with this "line".

http://www.youtub...cBlvfjow

I guess there must have been "only" a couple hundred billion "unlikely collisions" in that simulation.

It damn near collapses to a single object.