by Ann » Tue Sep 07, 2021 10:14 am
This is what
Wikipedia wrote about NGC 520:
1)
It is as bright in the infrared and radio bands as the Antennae Galaxies.
2)
Simulations indicate this object consists of two galactic disks that began interacting about 300 million years ago.
3)
In the X-ray band, the interacting galaxies appear around half as luminous as expected.
4)
Analysis of the gas and molecular features suggests the secondary merger component is gas poor.
5)
A large galactic wind is evident, being driven by the starburst activity.
A comparison between NGC 520 and NGC4038/NGC 4039 (the Antennae Galaxies) makes it immediately obvious that the Antennae galaxies are chock full of "clumps" of star clusters and nebulas, whereas such clumps are all but absent in NGC 520. In other words, the Antennae Galaxies are presently undergoing a starburst, whereas no signs of a starburst can easily be seen in NGC 520.
An aside here: By far most of the starburst of the Antennae Galaxies is taking place in just one of the colliding galaxies, NGC 4038 (the galaxy at top in the image). The other galaxy, NGC 4039, contributes little to the starburst.
As for NGC 520, much of its star formation ability may already be spent. Wikipedia said that one of the colliding components of NGC 520 was gas-poor, and presumably much of the gas in the other component has been used up. What we see is a rich population of bluish but moderate stars of spectral classes A and F, and only a few small clusters of hotter and more massive stars.
Yes, but Wikipedia spoke of a starburst in NGC 520! Where is that starburst located? There is only one answer: In one of the two nuclei.
The best-known example of a nuclear starburst is in nearby galaxy M82. Much like NGC 520, M82 displays virtually no signs at all of star formation in its disk. But its nucleus is a raging furnace of star formation and a furious galactic wind blowing from its nucleus.
There is apparently a nuclear starburst in one of the nuclei of NGC 520, too.
Ann
This is what [url=https://en.wikipedia.org/wiki/NGC_520]Wikipedia[/url] wrote about NGC 520:
1) [b][color=#FF0000]It is as bright in the infrared and radio bands as the Antennae Galaxies[/color][/b].
2) [b][color=#0040FF]Simulations indicate this object consists of two galactic disks that began interacting about 300 million years ago[/color][/b].
3) [b][color=#FF00FF]In the X-ray band, the interacting galaxies appear around half as luminous as expected[/color][/b].
4) [b][color=#FF8000]Analysis of the gas and molecular features suggests the secondary merger component is gas poor[/color][/b].
5) [b][color=#FF00FF]A large galactic wind is evident, being driven by the starburst activity[/color][/b].
[float=left][img3="NGC 520: Colliding Galaxies from Hubble. Image Credit: NASA, ESA, Hubble; Processing & Copyright: William Ostling (The Astronomy Enthusiast)"]https://apod.nasa.gov/apod/image/2109/NGC520_HubbleOstling_960.jpg[/img3][/float][float=right][img3="The Antennae Galaxies. Photo: ESA/Hubble."]https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Antennae_Galaxies_reloaded.jpg/1024px-Antennae_Galaxies_reloaded.jpg[/img3][/float]
[clear][/clear]
A comparison between NGC 520 and NGC4038/NGC 4039 (the Antennae Galaxies) makes it immediately obvious that the Antennae galaxies are chock full of "clumps" of star clusters and nebulas, whereas such clumps are all but absent in NGC 520. In other words, the Antennae Galaxies are presently undergoing a starburst, whereas no signs of a starburst can easily be seen in NGC 520.
An aside here: By far most of the starburst of the Antennae Galaxies is taking place in just one of the colliding galaxies, NGC 4038 (the galaxy at top in the image). The other galaxy, NGC 4039, contributes little to the starburst.
As for NGC 520, much of its star formation ability may already be spent. Wikipedia said that one of the colliding components of NGC 520 was gas-poor, and presumably much of the gas in the other component has been used up. What we see is a rich population of bluish but moderate stars of spectral classes A and F, and only a few small clusters of hotter and more massive stars.
Yes, but Wikipedia spoke of a starburst in NGC 520! Where is that starburst located? There is only one answer: In one of the two nuclei.
[float=left][img3="Smallish elliptical galaxy NGC 3077, with an active and starforming nucleus. Credit:
NASA, ESA, J. Dalcanton and B. Williams (University of Washington)"]https://cdn.spacetelescope.org/archives/images/screen/heic0819d.jpg[/img3][/float][float=right][img3="Starburst galaxy M82. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)"]https://upload.wikimedia.org/wikipedia/commons/thumb/c/ce/M82_HST_ACS_2006-14-a-large_web.jpg/1280px-M82_HST_ACS_2006-14-a-large_web.jpg[/img3][/float]
[clear][/clear]
The best-known example of a nuclear starburst is in nearby galaxy M82. Much like NGC 520, M82 displays virtually no signs at all of star formation in its disk. But its nucleus is a raging furnace of star formation and a furious galactic wind blowing from its nucleus.
There is apparently a nuclear starburst in one of the nuclei of NGC 520, too.
Ann