Entire galaxies feel the heat from newborn stars: Bursts of star birth can curtail future galaxy growth

Apr 25, 2013
This illustration shows a messy, chaotic galaxy undergoing bursts of star formation. This star formation is intense; it was known that it affects its host galaxy, but this new research shows it has an even greater effect than first thought. The winds created by these star formation processes stream out of the galaxy, ionising gas at distances of up to 650 000 light-years from the galactic center. Credit: ESA, NASA

(Phys.org) —Astronomers using the NASA/ESA Hubble Space Telescope have shown for the first time that bursts of star formation have a major impact far beyond the boundaries of their host galaxy. These energetic events can affect galactic gas at distances of up to twenty times greater than the visible size of the galaxy—altering how the galaxy evolves, and how matter and energy is spread throughout the Universe.

When galaxies form , they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the , but are rarer in nearby galaxies.

During these bursts, hundreds of millions of stars are born, and their combined effect can drive a powerful wind that travels out of the galaxy. These winds were known to affect their host galaxy—but this new research now shows that they have a significantly greater effect than previously thought.

An international team of astronomers observed 20 , some of which were known to be undergoing a starburst. They found that the winds accompanying these star formation processes were capable of ionising gas up to 650 000 light-years from the —around twenty times further out than the visible size of the galaxy. This is the first direct observational evidence of local starbursts impacting the bulk of the gas around their , and has important consequences for how that galaxy continues to evolve and form stars.

"The extended material around galaxies is hard to study, as it's so faint," says team member Vivienne Wild of the University of St. Andrews. "But it's important—these envelopes of cool gas hold vital clues about how galaxies grow, process mass and energy, and finally die. We're exploring a new frontier in !"

The team used the Spectrograph (COS) instrument on the /ESA to analyse light from a mixed sample of starburst and control galaxies. They were able to probe these faint envelopes by exploiting even more distant objects—quasars, the intensely luminous centres of distant galaxies powered by huge black holes. By analysing the light from these quasars after it passed through the foreground galaxies, the team could probe the galaxies themselves.

"Hubble is the only observatory that can carry out the observations necessary for a study like this," says lead author Sanchayeeta Borthakur, of Johns Hopkins University. "We needed a space-based telescope to probe the hot gas, and the only instrument capable of measuring the extended envelopes of galaxies is COS."

The starburst galaxies within the sample were seen to have large amounts of highly ionised gas in their halos—but the galaxies that were not undergoing a starburst did not. The team found that this ionisation was caused by the energetic winds created alongside newly forming stars.

This has consequences for the future of the galaxies hosting the starbursts. Galaxies grow by accreting gas from the space surrounding them, and converting this gas into stars. As these winds ionise the future fuel reservoir of gas in the galaxy's envelope, the availability of cool gas falls—regulating any future star formation.

"Starbursts are important phenomena—they not only dictate the future evolution of a single galaxy, but also influence the cycle of matter and energy in the Universe as a whole," says team member Timothy Heckman, of Johns Hopkins University. "The envelopes of galaxies are the interface between galaxies and the rest of the Universe—and we're just beginning to fully explore the processes at work within them."

Explore further: Millisecond pulsars clearly demonstrate that pulsars are neutron stars

More information: The team's results will appear in the 1 May 2013 issue of The Astrophysical Journal. iopscience.iop.org/0004-637X/768/1/18/

Related Stories

The wild early lives of today's most massive galaxies

Jan 25, 2012

(PhysOrg.com) -- Using the APEX telescope, a team of astronomers has found the strongest link so far between the most powerful bursts of star formation in the early Universe, and the most massive galaxies ...

Hubble sees light and dust in a nearby starburst galaxy

Apr 08, 2013

(Phys.org) —Visible as a small, sparkling hook in the dark sky, this beautiful object is known as J082354.96+280621.6, or J082354.96 for short. It is a starburst galaxy, so named because of the incredibly ...

Hubble catches the moment the lights went out

Feb 06, 2013

(Phys.org)—The further away you look, the further back in time you see. Astronomers use this fact to study the evolution of the Universe by looking at nearby and more distant galaxies and comparing their ...

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 ...

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 : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1 / 5 (5) Apr 25, 2013
Blah, blah, blah, hot gas....
Tuxford
1 / 5 (3) May 13, 2013
"Galaxies grow by accreting gas from the space surrounding them, and converting this gas into stars."

A likely faulty assumption that has astronomers in a pickle. One day they will have to reconsider this, and include other mechanisms for galactic growth. What mechanism, you ask? Growth from the inside out. Time for a rethink.

http://phys.org/n...ace.html