APOD: N11: Star Clouds of the LMC (2022 Apr 12)

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VictorBorun
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Re: APOD: N11: Star Clouds of the LMC (2022 Apr 12)

Post by VictorBorun » Mon Apr 18, 2022 10:52 pm

Ann wrote: Sun Apr 17, 2022 5:54 pm Take a look at the CFHT image of NGC 4569 (M90) and its satellite galaxy again:
Image[1].jpg
Now I see.
In a large or medium-size galaxy cluster (like Virgo cluster of this comment) a galaxy (like M90 of this comment) is sometimes experiencing ram pressure, and then there is a tail of ionized hydrogen observable in Hα.
But it's not universal.
A small galaxy cluster like our Local Cluster with shallow gravity well has low velocities of galaxies and low density of intergalactic media.
As for Magellanic galaxies they are dwarfs and their ram pressure tails would have small cross-sections and their Hα tails would be even harder to see.
There can be some co-movement of dwarf galaxies and media around Milky Way near the plane of Milky Way, too; then the headwind is much slower than the orbit velocity.

All said a young stellar cluster in a galaxy (like N11 of the Large Magellanic Cloud posted here) has by all means much, much brighter Hα glowing bubble than any ram pressure tail of the LMC.

There is a dichotomy:

either a galaxy is gas-rich galaxy (in the field or in a small galaxy cluster) and has red glowing Hα bubbles around young stellar clusters

or

a galaxy is gas-stripped by a headwind (both fast and dense, in a large or medium-size galaxy cluster) and has a red glowing Hα tail

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