Another Galaxy Smashed Through Andromeda 200 Million Years Ago

[Fraser]

Astronomers have gathered evidence that the Andromeda Galaxy collided with dwarf galaxy M32 about 200 million years ago. The evidence was seen by NASA's Spitzer Space Telescope, which measured the distribution of gas rings in the galaxy's disk. These dust rings allowed astronomers to calculate when M32 smashed through Andromeda's galactic plane, like tracing ripples in a pond.

Read the full blog entry

[antoniseb]

Here's the paper

[Reader]

If Andromeda and M31 were involved in a collison then, following the example of most interacting galaxies, we should see evidence of a burst of star formation in both galaxies. I am not aware of any such evidence.

[John Mendenhall]

? Isn't there star formation in dust rings? The paper says star formation is included in the simulation.

[Duane]

If Andromeda and M31 were involved in a collison then, following the example of most interacting galaxies, we should see evidence of a burst of star formation in both galaxies. I am not aware of any such evidence.

Um, Andromedae IS M31.

But to the point. I suggest 200,000,000 years is enough time for the starburst to have pertered out, given the lack of continmuing interaction.

[RUF]

A previous article on UT stated that M31 has more stars than the Milky Way, but the Milky Way is much more massive. It was suggested that M31 underwent a period of massive star formation in the past, and that the Milky Way is undergoing such a starforming period now. Maybe this period of starforming in M31 occurred after the collision with M32 210 mya.

[Hamilcar]

Um, Andromedae IS M31.

But to the point. I suggest 200,000,000 years is enough time for the starburst to have pertered out, given the lack of continmuing interaction.

A 200 Myr population is pretty easy to detect.

[transreality]

This paper finds two populations of star formation in M32, one at 10GYr and 1 at 2 Gyr, and says that "...the younger population cannot be any younger than 2 GYr or it would produce a strong signature..."

http://arxiv.org/abs/astro-ph/0411118

[ArgoNavis]

the Spitzer image makes M31 looks somewhat like a ring galaxy