The Energy Sources of Ultraluminous Galaxies

Nov 27, 2009
The ultraluminous galaxy IRAS 19297-0406 as seen by the Hubble Space Telescope. An infrared study finds that in about one-third of such galaxies there is a supermassive black hole in the nucleus dominating the energy production. Credit: NASA, the NICMOS Group (STScI, ESA), and the NICMOS Science Team (University of Arizona)

(PhysOrg.com) -- Ultraluminous infrared galaxies ((ULIRGs) are galaxies whose luminosity exceeds that of a trillion suns; for comparison, the Milky Way galaxy has a typical (and much more modest) luminosity of only about ten billion suns. ULIRGs were discovered by an all-sky infrared survey satellite in the 1980's, and since then the origin(s) of their huge infrared emission has been widely debated. Extreme infrared activity is known to be associated with interacting galaxies, and optical imaging indeed shows that many ULIRGs are in collision, but this fact does not answer the question of what physical mechanism powers the luminosity. Might the same process be underway at a low level in our galaxy?

The two primary known sources of global energy production in are star formation and accretion activity around a massive black hole in the nucleus (a so-called active ). Both of them produce radiation that heats up the dust -- the origin of the intense infrared emission.

The dust obscures optical light and makes conventional diagnostics difficult, but the dust emission itself has specific color characteristics that can distinguish between the two cases. SAO astronomer Guido Risaliti and seven of his colleagues have used the to study the infrared emission from seventy-one ULIRGs in an attempt to quantify the relative role each process plays in the energetics of ULIRGs.

The scientists find that approximately 70% of the sources have the characteristic signature of an active nucleus, a significant conclusion made possible by the use of their dust emission diagnostic technique. Furthermore, they find that, with regard to energy production, predominates in approximately two-thirds of the sources; in the other one-third of ULIRGs the nucleus plays the dominant role in powering the galaxy, and this fraction increases among the most luminous ULIRGs.

Our does have a massive black hole at its nucleus, but now activity around it is very quiescent. Perhaps when the Milky Way collides with the Andromeda galaxy in a few billion years, an event many astronomers suspect will occur, the interaction will trigger the nucleus to become more active, and our galaxy to become, if not ultraluminous, then at least more luminous than it is today.

Provided by Harvard-Smithsonian Center for Astrophysics (news : web)

Explore further: Young binary star system may form planets with weird and wild orbits

add to favorites email to friend print save as pdf

Related Stories

Galaxies cluster near dark matter, study finds

Apr 20, 2006

Try mixing caramel into vanilla ice cream -- you will always end up with globs and swirls of caramel. Scientists are finding that galaxies may distribute themselves in similar ways throughout the universe and ...

Hubble Eyes Star Birth in the Extreme

Jun 13, 2006

Staring into the crowded, dusty core of two merging galaxies, NASA's Hubble Space Telescope has uncovered a region where star formation has gone wild.

Recommended for you

Evidence of a local hot bubble carved by a supernova

15 hours ago

I spent this past weekend backpacking in Rocky Mountain National Park, where although the snow-swept peaks and the dangerously close wildlife were staggering, the night sky stood in triumph. Without a fire, ...

Astronomers measure weight of galaxies, expansion of universe

23 hours ago

Astronomers at the University of British Columbia have collaborated with international researchers to calculate the precise mass of the Milky Way and Andromeda galaxies, dispelling the notion that the two galaxies have similar ...

Mysterious molecules in space

Jul 29, 2014

Over the vast, empty reaches of interstellar space, countless small molecules tumble quietly though the cold vacuum. Forged in the fusion furnaces of ancient stars and ejected into space when those stars ...

Comet Jacques makes a 'questionable' appearance

Jul 28, 2014

What an awesome photo! Italian amateur astronomer Rolando Ligustri nailed it earlier today using a remote telescope in New Mexico and wide-field 4-inch (106 mm) refractor. Currently the brightest comet in ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
Nov 27, 2009
This comment has been removed by a moderator.
omatumr
1 / 5 (3) Nov 30, 2009
Does anyone doubt that the energy source is repulsive interactions between neutrons?

With kind regards,
Oliver K. Manuel
Former NASA PI for Apollo
Alexa
1 / 5 (1) Dec 03, 2009
Does anyone doubt that the energy source is repulsive interactions between neutrons?
Of course, because these repulsive interactions are like strings - they must be charged by something. Which force has made neutrons so close?
omatumr
2 / 5 (2) Dec 03, 2009
Like particles oppose each other, and they also pair up in atomic and nuclear structures.

a.) Electrons
b.) Protons
c.) Neutrons

Why do you think that they "must be charged by something"?

With kind regards,
Oliver K. Manuel