Hubble Provides Evidence That Galaxies Do Not Confine Starbursts
Lee Rannals for redOrbit.com — Your Universe Online
Astronomers writing in The Astrophysical Journal say they’ve observed how bursts of star formation have a major impact beyond the boundaries of their host galaxy.
When galaxies form new stars, they can create frantic episodes of activity known as starbursts. Scientists using the Hubble Space Telescope say these events can affect galactic gas at distances of up to 20 times greater than the visible size of the galaxy.
The team of astronomers observed 20 nearby galaxies, some of which were known to be undergoing a starburst. They found that the winds from these starbursts were capable of ionizing gas up to 650,000 light years from the galactic center. This was the first direct observational evidence of local starbursts impacting the bulk of the gas around their host galaxy.
“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 on the Hubble Space Telescope to probe this sample of starburst and control galaxies.
“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 (JHU). “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 seen by the team have large amounts of highly ionized gas in their halos. The team saw that this ionization was caused by the energetic winds created alongside newly forming stars.
“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 JHU. “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.”
In January this year, astronomers reported a series of starbursts that had taken place in the central region of our own galaxy, Milky Way. This team used the Stratospheric Observatory for Infrared Astronomy (SOFIA) to document the starbursts.