Exposing the Nature of Cosmic Liaisons

Oct 16, 2007
Exposing the Nature of Cosmic Liaisons
Risa Wechsler has developed a new tool for measuring how galaxy interactions, such as that which drew out the trail of stars in the Tadpole Galaxy (pictured here), affect the rate of star formation.

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. Their results shed light on the fundamental processes that drive galactic evolution.

In the early universe, the rate of star formation was higher than it is today. Galaxies frequently collided and coalesced with one another, spawning a profusion of new stars with each encounter. Although such prolific events are now relatively infrequent, less spectacular galactic interactions continue to forge stars and shape galaxies. Observational studies suggest that even these interactions increase the rate of star formation, but there is little consensus on the frequency and magnitude of such events.

"To study this, you need to observe pairs of galaxies, which have either just interacted or are about to interact, and determine whether their star formation rate is higher or lower than similar galaxies that haven't interacted," said Wechsler, who collaborated with researchers from the Center for Cosmology at the University of California in Irvine and the University of Chicago. Although the idea is straightforward, its execution is problematic. Galaxy interactions are highly complex and dynamic, and observation yields a mere snapshot of the unfolding events.

One complication is that the majority of galaxies exist in groups, where frequent interactions may have exhausted a galaxy's star-forming resources. In such crowded environments, it is difficult to discern the immediate effects of an isolated interaction. According to Wechsler, "it's very hard from observations alone to figure out how to control for this."

To overcome this technical hurdle, Wechsler used a cosmological simulation of dark matter and galaxies. “The simulation allowed us to see statistically how galaxies are connected to their environment. This enabled us to estimate the bias of pairs [toward group environments], and then to try to define selection criteria that would give us isolated pairs and appropriate controls." The criteria also controlled for galaxy age and brightness, thus optimizing their comparability.

Elizabeth Barton, Wechsler's collaborator from UCI, then used these criteria to analyze a subset of the 2dF astronomical survey. The analysis revealed that 14% of the galaxies in close pairs exhibited star formation rates boosted by at least a factor of 5, and on average a factor of 30. "This is the first clean estimate of triggered star formation from a large galaxy sample," Wechsler noted. "Our selection criteria allow us to constrain how the star formation rate changes in interactions, and will help us figure out how star formation contributes to galaxy evolution."

Source: by Elizabeth Buchen, SLAC

Explore further: Precise ages of largest number of stars hosting planets ever measured

Related Stories

Can pollution help trees fight infection?

6 hours ago

Trees that can tolerate soil pollution are also better at defending themselves against pests and pathogens. "It looks like the very act of tolerating chemical pollution may give trees an advantage from biological ...

Most internet anonymity software leaks users' details

6 hours ago

Virtual Private Networks (VPNs) are legal and increasingly popular for individuals wanting to circumvent censorship, avoid mass surveillance or access geographically limited services like Netflix and BBC ...

Improving rice flour to aid food poverty

6 hours ago

A new, high-quality rice flour could help towards aiding global food poverty. "This rice flour serves not only as an alternative to wheat flour for those with wheat intolerance, but could also help to overcome ...

In the UK, bPay offers fob, band or sticker options

7 hours ago

Method of payment: "Cash or credit?" The two options sound so yesterday. In the UK, technology support in banking offers a new type of menu—band on the wrist, fob or sticker. The three new devices from ...

WikiLeaks says NSA spied on French business

8 hours ago

WikiLeaks has released documents that it says show that the U.S. National Security Agency eavesdropped on France's top finance officials and high-stakes French export bids over a decade in what the group called targeted economic ...

Recommended for you

The discovery of the molecule Si-C-Si in space

17 hours ago

The space between stars is not empty—it contains a vast reservoir of diffuse material with about 5-10% of the total mass of our Milky Way galaxy. Most of the material is gas, but about 1% of this mass (quite ...

Hubble view of a nitrogen-rich nebula

18 hours ago

This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4,000 light-years away in the southern constellation of Scorpius (The Scorpion).

Is the universe ringing like a crystal glass?

Jun 26, 2015

Many know the phrase "the big bang theory." There's even a top television comedy series with that as its title. According to scientists, the universe began with the "big bang" and expanded to the size it ...

Improved sensors help navigate gravity waves

Jun 26, 2015

Efforts to detect gravitational waves—which were first predicted by Albert Einstein nearly 100 years ago—are advancing with international researchers including UWA researchers boosting the sensitivity ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.