Apr. 25, 2013 ? When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, 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 nearby galaxies, some of which were known to be undergoing a starburst. They found that the winds accompanying these star formation processes were capable of ionising [1] gas up to 650 000 light-years from the galactic centre -- 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 host galaxy, 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 galaxy evolution!"
The team used the Cosmic Origins Spectrograph (COS) instrument [2] on the NASA/ESA Hubble Space Telescope 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."
The team's results will appear in the 1 May 2013 issue of The Astrophysical Journal.
Notes
[1] A gas is said to be ionised when its atoms have lost one or more electrons -- in this case by energetic winds exciting galactic gas and knocking electrons out of the atoms within.
[2] Spectrographs are instruments that break light into its constituent colours and measure the intensity of each colour, revealing information about the object emitting the light -- such as its chemical composition, temperature, density, or velocity.
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The above story is reprinted from materials provided by ESA/Hubble Information Centre.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Sanchayeeta Borthakur, Timothy Heckman, David Strickland, Vivienne Wild, David Schiminovich. THE IMPACT OF STARBURSTS ON THE CIRCUMGALACTIC MEDIUM. The Astrophysical Journal, 2013; 768 (1): 18 DOI: 10.1088/0004-637X/768/1/18
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
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Public release date: 24-Apr-2013
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The U.S. real estate market is seeing a bit of a rebound right now and, with it, real estate-related online services like Zillow, Redfin?and?Trulia and newcomers like Houzz are also getting back in the groove of launching regular updates. Trulia today launched its redesigned iPad app, which now features new listing pages with large photos, a new navigation menu and an improved map view. The Trulia redesign comes a week after?Zillow launched its revamped iPhone app. Previously, Trulia’s property pages looked a bit cluttered compared to some of the competing services, but in this redesign, they are being overhauled. Images are now significantly larger, and the sidebar now features a map view, as well as pricing history and additional information, without trying to cramp all of the details about the home into it. The sidebar now also features a bit more local info, including the median home price in the neighborhood and school ratings. Trulia previously only showed this information in its property results map. Users can also use the usual iOS gestures to zoom in and out of the new images. The rest of the app now follows the same design style as the property pages, including the new navigation menu, which has also been streamlined and simplified compared to the previous version. Just like before, though, the app still puts a map at the center of the search experience. In this new version, however, the company has added colored markers to make it easier to see which houses you’ve already looked at and which ones have just come on the market. Trulia has been slowly ramping up its development over the last few months, recently launching its Trulia Suggests feature, which learns from your browsing habits on the site and provides users with personalized recommendations. As we reported last month, Trulia is also currently looking to raise about $150 million in follow-on funding to strengthen its cash reserves and for potential acquisitions and mergers.
