Making stars in early galaxies

Dec 10, 2012
An image of the active star-forming galaxy M82 at three wavelengths: UV (blue), near-infrared (green) and far-infrared (red). New research indicates that even in the early universe galaxies actively forming stars do so in the same general way, modulated by the amount of gas and dust they contain. Credit: CfA and L. Lanz

(Phys.org)—Ten billion years ago or so, at least according to the current picture, the youthful universe began to produce an abundance of new stars. The very first ones appeared in the young cosmos after only a few hundred million years, but they were unlike stars of today. The universe back then contained almost no elements other than hydrogen (and some helium), and so these first stars contained mostly hydrogen and were very massive. By the time a few billion years had passed, however, this first generation of stars had manufactured many other elements that enriched the natal gas. These elements could help the gas cool as it compressed, and so they aided gravity as it collapsed material to form a wide range of new stars, many of them similar to the Sun. After a few billion years, galaxies acquired their mature forms and were populated by nearly normal stars. Then, for reasons that are not understood, they began making stars at unprecedentedly high rates.

Astronomers gazing at distant galaxies find that those whose light has been traveling towards us for between nine and eleven billion years show dramatic increases in , about ten times more active than what we see today. The evidence comes from these galaxies' luminosities and copious , both earmarks of . This general story has been known for about ten years, but there have always been questions about it because distant galaxies are faint and therefore hard to see. Perhaps only the most unusual bright galaxies in this epoch are undergoing such starbursts?

SAO Ho Seong Hwang, together with a team of 13 colleagues, wanted to answer this question. First, they had to have a clear understanding of what drives star formation in galaxies in the first place. They argued in their prior research (consistent with other research programs) that the presence of abundant, molecular gas in was the key to regulating star formation in normal galaxies. But measuring the molecular gas content is not always so easy, especially in more distant galaxies, because light from the gas – sampled by the millimeter emission of carbon monoxide – can be faint. However, the scientists found that infrared emission by dust, as seen with the Herschel Space Observatory, is bright - and also a good tracer of molecular gas.

In a new paper in the Astrophysical Journal, the scientists extend their analysis to galaxies so far away that their light has been traveling for over ten billion years. Analysis of the infrared observations of these galaxies shows that in nearly all cases their emission has the same general spectral character—the only correction needed is for the amount of dust, and not (for example) in the way stars are made. The scientists demonstrate for the first time that the infrared dust emission can predict the gas, and hence estimate the star-forming activity. The reason, then, that distant galaxies are so luminous is because they lack many elements and their gas and dust are thereby deficient. That deficiency results in brighter star formation emission.

Explore further: A star's early chemistry shapes life-friendly atmospheres

add to favorites email to friend print save as pdf

Related Stories

A universal law for star formation

Jan 09, 2012

(PhysOrg.com) -- Star formation is studied by astronomers not only because it produces new stars and planetary systems. It also generates copious amounts of ultraviolet light that heats dust which in turn ...

Herschel paints new story of galaxy evolution

Sep 13, 2011

(PhysOrg.com) -- ESA's Herschel infrared space observatory has discovered that galaxies do not need to collide with each other to drive vigorous star birth. The finding overturns this long-held assumption ...

Galaxies in the young cosmos

May 21, 2012

(Phys.org) -- The universe was born about 13.7 billion years ago in the big bang. The Sun and its system of planets formed about five billion years ago. What happened, then, during that long, intervening stretch ...

Recommended for you

A star's early chemistry shapes life-friendly atmospheres

21 hours ago

Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless ...

Image: X-raying the cosmos

Apr 22, 2014

When we gaze up at the night sky, we are only seeing part of the story. Unfortunately, some of the most powerful and energetic events in the Universe are invisible to our eyes – and to even the best optical ...

Mysteries of nearby planetary system's dynamics solved

Apr 22, 2014

Mysteries of one of the most fascinating nearby planetary systems now have been solved, report authors of a scientific paper to be published by the journal Monthly Notices of the Royal Astronomical Society in its ...

User comments : 0

More news stories

How many moons does Venus have?

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, ...

First-of-its-kind NASA space-weather project

A NASA scientist is launching a one-to-two-year pilot project this summer that takes advantage of U.S. high-voltage power transmission lines to measure a phenomenon that has caused widespread power outages ...

Phase transiting to a new quantum universe

(Phys.org) —Recent insight and discovery of a new class of quantum transition opens the way for a whole new subfield of materials physics and quantum technologies.

Imaging turns a corner

(Phys.org) —Scientists have developed a new microscope which enables a dramatically improved view of biological cells.