Feeding galaxy caught in distant searchlight by international research team

July 04, 2013

(Santa Barbara, Calif.) -- An international group of astronomers that includes UC Santa Barbara astrophysicist Crystal Martin and former UCSB postdoctoral researcher Nicolas Bouché has spotted a distant galaxy hungrily snacking on nearby gas. The gas is seen to fall inward toward the galaxy, creating a flow that both fuels star formation and drives the galaxy's rotation. This is the best direct observational evidence so far supporting the theory that galaxies pull in and devour nearby material in order to grow and form stars. The results will appear in the July 5 issue of the journal Science.

Spiral galaxies like our own Milky Way formed billions of years ago in the dark matter concentrations that began to grow shortly after the Big Bang. As gas cooled and condensed, stars formed, which, over time, synthesized heavy elements and polluted the galaxy with this enriched material upon their death.

But what that model has not been able to explain is the continuous formation of stars in some galaxies, despite the constant rate at which galaxies turn molecular gas into stars. The simplest model calls for a closed system and predicts star formation should have ceased long ago due to the limited gas supply.

"It's been a problem," said Martin. Galaxies should use up their gas on a time scale that's much shorter than what has been observed, she explained. In fact our own galaxy should have already run out of gas, but stars continue to form in it. "Galaxies must have a mechanism for acquiring more gas," she continued, adding that, historically, no means has existed to directly detect the inflow of the cold fuel.

Now, however, thanks to the background light from the quasar HE 2243-60, Martin and her colleagues have been able to observe distinct signatures near a typical star-forming galaxy that indicate the inflow of gas feeding the galaxy. In this scenario, gas is drawn into a galaxy and then circles around it, rotating with it before falling in. Although some evidence of such accretion had been observed in galaxies before, the motion of the gas and its other properties had not been fully explored until now.

The background quasar is, by chance, perfectly well positioned for this study. "This kind of alignment is very rare, but was critical for this study," explained first author Bouché, who is now with the Research Institute in Astrophysics and Planetology in Toulouse, France.

The astronomers used two instruments known as SINFONI (Spectrograph for INtegral Field Observations in the Near Infrared) and UVES (Ultraviolet and Visual Echelle Spectrograph), both of which are mounted on European Southern Observatory's Very Large Telescope at the Paranal Observatory in northern Chile. The new observations showed both how the galaxy itself was rotating and revealed the composition and motion of the gas outside the galaxy.

The result is the discovery of how an active star-forming galaxy feeds its prodigious growth, according to co-author Michael Murphy, from the Swinburne University of Technology in Australia. "[We've] observed, as directly as possible, the feeding process for forming huge numbers of stars very quickly 11 billion years ago," he said. The observation also strengthens the argument that low-mass galaxies are formed through these cold streams, which also allow galaxies to prolong their star formation process.

"It is impressive to see in the data the telltale signatures of this infalling gas matching those expected in numerical simulations," said Bouché.
-end-
Other members of the research team include Glenn G. Kacprzak, also of Swinburne University and an Australian Research Council Super Science Fellow; Céline Péroux of Aix Marseille University, France; Thierry Contini of University Paul Sabatier of Toulouse, France; and Miroslava Dessauges-Zavadsky of the Observatory of Geneva, Switzerland.

University of California - Santa Barbara

Related Astrophysics Articles from Brightsurf:

Astrophysics: A direct view of star/disk interactions
'Nature' publication: The GRAVITY instrument developed for the Very Large Telescope in Chile probes deep into the TW Hydrae system to shape our view of accretion processes in young stars similar to the young Sun

Explosive nuclear astrophysics
An international team has made a key discovery related to 'presolar grains' found in some meteorites.

Using techniques from astrophysics, researchers can forecast drought up to ten weeks ahead
Researchers at the University of Sussex have developed a system which can accurately predict a period of drought in East Africa up to ten weeks ahead.

Astrophysics and AI may offer key to early dementia diagnosis
Crucial early diagnosis of dementia in general practice could improve thanks to a computer model designed in a collaboration between Brighton and Sussex Medical School (BSMS) and astrophysicists at the University of Sussex.

Hubble studies gamma-ray burst with highest energy ever seen
NASA's Hubble Space Telescope has given astronomers a peek at the location of the most energetic outburst ever seen in the universe -- a blast of gamma-rays a trillion times more powerful than visible light.

NASA's TESS presents panorama of southern sky
The glow of the Milky Way -- our galaxy seen edgewise -- arcs across a sea of stars in a new mosaic of the southern sky produced from a year of observations by NASA's Transiting Exoplanet Survey Satellite (TESS).

Giant exoplanet around tiny star challenges understanding of how planets form
An international team of researchers with participation from the University of Göttingen has discovered the first large gas giant orbiting a small star.

'Ringing' black hole validates Einstein's general relativity 10 years ahead of schedule
For the first time, astrophysicists have heard a black hole ringing like a bell.

A family of comets reopens the debate about the origin of Earth's water
Where did the Earth's water come from? Although comets, with their icy nuclei, seem like ideal candidates, analyses have so far shown that their water differs from that in our oceans.

Astronomers discover 2,000-year-old remnant of a nova
For the first time, a European research team involving the University of Göttingen has discovered the remains of a nova in a galactic globular cluster.

Read More: Astrophysics News and Astrophysics Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.