Introduction
Galaxy interaction and merging is seen throughout the universe, and it is believed to be an important mechanism in galaxy formation and evolution; large elliptical galaxies may be the remnants of past mergers. The effect of interaction and merging can be seen in distorted and asymmetric galaxy morphologies and in the presence of tidal tails. Accompanying these morphological effects is also increased star formation and starburst activity, fostered by the shocks driven into the interstellar medium by the galaxy collision.
Antennae Galaxy – Prototypical Galaxy Merger
The prototypical galaxy merger is the Antennae galaxy, a merger of the two galaxies NGC4038 and NGC4039, which was observed several times with Chandra for a total exposure of nearly a week over a two-year period. These Chandra observations revealed a population of 120 X-ray sources, of which 14 are variable ULXs. The Antennae are filled with hot interstellar medium, which has a variety of temperatures in different parts of the galaxies and is enriched in metals (Ne, Mg, Si, Fe); the abundances in certain regions are much larger than in our own Solar neighborhood, and the relative amounts of these elements are consistent with production in the SNII explosions typical of a young stellar population rich in massive stars. Two galaxy-size loops of hot gas are also seen in the Antennae, embedded in a more tenuous diffuse hot halo. While the geometry of these features is yet to be explained, their presence suggest outflows that may disperse the metals in the inter-galactic space.
Chandra image of the Antennae (top), including point sources and extended emission. Bottom left: zooming in the hot interstellar medium. Bottom right: elements detected in the hot interstellar medium (red: Fe, O and Ne blend; green: Mg; Blue: Si). (Source: NASA/CXC/SAO/G. Fabbiano et al.)
This montage of Chandra images (Left) shows a pair of interacting galaxies known as The Antennae. Rich deposits of neon, magnesium, and silicon were discovered in the interstellar gas of this system.
"3-Color, Full Field" – The top image, a wide field X-ray view, reveals spectacular loops of hot gas spreading out from the southern part of The Antenna into intergalactic space. Also shown are huge clouds of multimillion degree gas and bright point like sources due to neutron stars and black holes. The image is color coded so that low, medium and high energy X-rays appear as red, green and blue, respectively. Direct hits between stars are extremely rare when galaxies collide, but huge gas clouds can crash into each other at high speeds, creating shock waves that heat the clouds and the surrounding gas to millions of degrees.
"Diffuse Emmision" – In the closeup view on the lower left, also color coded by X-ray energies, the point sources have been taken out to emphasize the hot gas clouds in the central regions of The Antennae.
Collisions between the gas clouds may trigger a stellar baby boom. The most massive of these young stars race through their evolution in a few million years and explode as supernovas. Heavy elements manufactured inside these stars are blown away by the explosions that further heat the gas clouds and enrich them with heavy elements such as neon, magnesium, silicon and iron.
"Element Map" – The image at the lower right is processed and color-coded to show regions rich in iron (red), magnesium (green) and silicon (blue). These are the types of elements that form the ultimate building blocks for habitable planets.
Enrichment from supernovas occurs in all galaxies, but usually the new elements are observed in a highly diluted form as they are mixed up with the rest of the interstellar gas. This Chandra image is remarkable in that it shows clouds in which magnesium and silicon are 16 and 24 times as abundant as in the Sun.
As the enriched gas cools, a new generation of stars will form, and with them new planets. A number of studies indicate that clouds enriched in heavy elements are more likely to form stars with planetary systems. Several hundred million years from now, an unusually high number of planets may form in The Antennae.
| Fast Facts for Antennae |
| Credit |
NASA/CXC/SAO/G.Fabbiano et al. |
| Scale |
Image is 4.8 arcmin across. |
| Category |
Normal Galaxies & Starburst Galaxies |
| Coordinates (J2000) |
RA 12h 01m 53.70s | Dec -18° 52' 35.5'' |
| Constellation |
Corvus |
| Observation Dates |
December 1, 1999; December 29, 2001;
November 22, 2002; May 31, 2002;
April 18, 2002; July 10, 2002; July 13, 2002 |
| Observation Time |
117 hours |
| Obs. IDs |
315, 3040-44, 3718 |
| Color Code |
Energy (Red: 0.3-0.65 keV, Green: 0.65-1.5 keV, Blue: 1.5-6.0 keV) |
| Instrument |
ACIS |
| Also Known As |
NGC 4038, NGC 4039 |
| Distance Estimate |
60 million light years |
| Release Date |
January 07, 2004 |
Images of Interacting Galaxies
Interacting Galaxies.
"Interacting Galaxies" Astronomy textbooks typically present galaxies as staid, solitary, and majestic island worlds of glittering stars. But galaxies have a dynamical side. They have close encounters that sometimes end in grand mergers and overflowing sites of new star birth as the colliding galaxies morph into wondrous new shapes. View the (Source/Credit: NASA, ESA, A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration.)
References
External Links
Preview Image
"Antennae Galaxies’ Fertile Marriage" The Universe is an all-action arena for some of the largest, most slowly evolving and surprising processes known to mankind. A new picture taken by the Advanced Camera for Surveys (ACS), onboard the NASA/ESA Hubble Space Telescope, shows the best ever view of the Antennae galaxies - seemingly a violent clash between a pair of once isolated galaxies, but in reality a fertile marriage. (Source: NASA/ESA.)
Citation
Fabbiano, Pepi, Ph.D. (Contributing Author); Bernard Haisch (Topic Editor). 2008. "Interacting Galaxies and Mergers." In: Encyclopedia of the Cosmos. Eds. Bernard Haisch and Joakim F. Lindblom (Redwood City, CA: Digital Universe Foundation). [First published November 24, 2007].
<http://www.cosmosportal.org/articles/view/135735/>
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Introduction
Galaxy interaction and merging is seen throughout the universe, and it is believed to be an important mechanism in galaxy formation and evolution; large elliptical galaxies may be the remnants of past mergers. The effect of interaction and merging can be seen in distorted and asymmetric galaxy morphologies and in the presence of tidal tails. Accompanying these morphological effects is also increased star formation and starburst activity, fostered by the shocks driven into the interstellar medium by the galaxy collision.
Antennae Galaxy – Prototypical Galaxy Merger
The prototypical galaxy merger is the Antennae galaxy, a merger of the two galaxies NGC4038 and NGC4039, which was observed several times with Chandra for a total exposure of nearly a week over a two-year period. These Chandra observations revealed a population of 120 X-ray sources, of which 14 are variable ULXs. The Antennae are filled with hot interstellar medium, which has a variety of temperatures in different parts of the galaxies and is enriched in metals (Ne, Mg, Si, Fe); the abundances in certain regions are much larger than in our own Solar neighborhood, and the relative amounts of these elements are consistent with production in the SNII explosions typical of a young stellar population rich in massive stars. Two galaxy-size loops of hot gas are also seen in the Antennae, embedded in a more tenuous diffuse hot halo. While the geometry of these features is yet to be explained, their presence suggest outflows that may disperse the metals in the inter-galactic space.
Chandra image of the Antennae (top), including point sources and extended emission. Bottom left: zooming in the hot interstellar medium. Bottom right: elements detected in the hot interstellar medium (red: Fe, O and Ne blend; green: Mg; Blue: Si). (Source: NASA/CXC/SAO/G. Fabbiano et al.)
This montage of Chandra images (Left) shows a pair of interacting galaxies known as The Antennae. Rich deposits of neon, magnesium, and silicon were discovered in the interstellar gas of this system.
"3-Color, Full Field" – The top image, a wide field X-ray view, reveals spectacular loops of hot gas spreading out from the southern part of The Antenna into intergalactic space. Also shown are huge clouds of multimillion degree gas and bright point like sources due to neutron stars and black holes. The image is color coded so that low, medium and high energy X-rays appear as red, green and blue, respectively. Direct hits between stars are extremely rare when galaxies collide, but huge gas clouds can crash into each other at high speeds, creating shock waves that heat the clouds and the surrounding gas to millions of degrees.
"Diffuse Emmision" – In the closeup view on the lower left, also color coded by X-ray energies, the point sources have been taken out to emphasize the hot gas clouds in the central regions of The Antennae.
Collisions between the gas clouds may trigger a stellar baby boom. The most massive of these young stars race through their evolution in a few million years and explode as supernovas. Heavy elements manufactured inside these stars are blown away by the explosions that further heat the gas clouds and enrich them with heavy elements such as neon, magnesium, silicon and iron.
"Element Map" – The image at the lower right is processed and color-coded to show regions rich in iron (red), magnesium (green) and silicon (blue). These are the types of elements that form the ultimate building blocks for habitable planets.
Enrichment from supernovas occurs in all galaxies, but usually the new elements are observed in a highly diluted form as they are mixed up with the rest of the interstellar gas. This Chandra image is remarkable in that it shows clouds in which magnesium and silicon are 16 and 24 times as abundant as in the Sun.
As the enriched gas cools, a new generation of stars will form, and with them new planets. A number of studies indicate that clouds enriched in heavy elements are more likely to form stars with planetary systems. Several hundred million years from now, an unusually high number of planets may form in The Antennae.
| Fast Facts for Antennae |
| Credit |
NASA/CXC/SAO/G.Fabbiano et al. |
| Scale |
Image is 4.8 arcmin across. |
| Category |
Normal Galaxies & Starburst Galaxies |
| Coordinates (J2000) |
RA 12h 01m 53.70s | Dec -18° 52' 35.5'' |
| Constellation |
Corvus |
| Observation Dates |
December 1, 1999; December 29, 2001;
November 22, 2002; May 31, 2002;
April 18, 2002; July 10, 2002; July 13, 2002 |
| Observation Time |
117 hours |
| Obs. IDs |
315, 3040-44, 3718 |
| Color Code |
Energy (Red: 0.3-0.65 keV, Green: 0.65-1.5 keV, Blue: 1.5-6.0 keV) |
| Instrument |
ACIS |
| Also Known As |
NGC 4038, NGC 4039 |
| Distance Estimate |
60 million light years |
| Release Date |
January 07, 2004 |
Images of Interacting Galaxies
Interacting Galaxies.
"Interacting Galaxies" Astronomy textbooks typically present galaxies as staid, solitary, and majestic island worlds of glittering stars. But galaxies have a dynamical side. They have close encounters that sometimes end in grand mergers and overflowing sites of new star birth as the colliding galaxies morph into wondrous new shapes. View the (Source/Credit: NASA, ESA, A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration.)
References
External Links
Preview Image
"Antennae Galaxies’ Fertile Marriage" The Universe is an all-action arena for some of the largest, most slowly evolving and surprising processes known to mankind. A new picture taken by the Advanced Camera for Surveys (ACS), onboard the NASA/ESA Hubble Space Telescope, shows the best ever view of the Antennae galaxies - seemingly a violent clash between a pair of once isolated galaxies, but in reality a fertile marriage. (Source: NASA/ESA.)
Citation
Fabbiano, Pepi, Ph.D. (Contributing Author); Bernard Haisch (Topic Editor). 2008. "Interacting Galaxies and Mergers." In: Encyclopedia of the Cosmos. Eds. Bernard Haisch and Joakim F. Lindblom (Redwood City, CA: Digital Universe Foundation). [First published November 24, 2007].
<http://www.cosmosportal.org/articles/view/135735/>
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