Runaway Galaxy

[orin stepanek]

http://hubblesite.org/newscenter/archiv ... s/2014/14/
The best resolution available can be found here.
ABOUT THIS IMAGE:
The spiral galaxy ESO 137-001 looks like a dandelion caught in a breeze in this new Hubble Space Telescope image.

The galaxy is zooming toward the upper right of this image, in between other galaxies in the Norma cluster located over 200 million light-years away. The road is harsh: intergalactic gas in the Norma cluster is sparse, but so hot at 180 million degrees Fahrenheit that it glows in X-rays.

The spiral plows through the seething intra-cluster gas so rapidly — at nearly 4.5 million miles per hour — much of its own gas is caught and torn away. Astronomers call this "ram pressure stripping." The galaxy's stars remain intact due to the binding force of their gravity.

Tattered threads of gas, the blue jellyfish-tendrils sported by ESO 137-001 in the image, illustrate the process. Ram pressure has strung this gas away from its home in the spiral galaxy and out over intergalactic space. Once there, these strips of gas have erupted with young, massive stars, which are pumping out light in vivid blues and ultraviolet.

The brown, smoky region near the center of the spiral is being pushed in a similar manner, although in this case it is small dust particles, and not gas, that are being dragged backwards by the intra-cluster medium.

From a star-forming perspective, ESO 137-001 really is spreading its seeds into space like a dandelion in the wind. The stripped gas is now forming stars. However, the galaxy, drained of its own star-forming fuel, will have trouble making stars in the future. Through studying this runaway spiral, and other galaxies like it, astronomers hope to gain a better understanding of how galaxies form stars and evolve over time.

The image, obtained through Hubble's Wide Field Camera 3, is also decorated with hundreds of stars from within the Milky Way. Though not connected in the slightest to ESO 137-001, these stars and the two reddish elliptical galaxies contribute to a vibrant celestial vista.

Object Name: ESO 137-001

Image Type: Astronomical


Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Acknowledgment: M. Sun (University of Alabama, Huntsville

Click to view full size image

[MargaritaMc]

There's a Hubblecast video about this galaxy here:

http://www.spacetelescope.org/videos/heic1404a/

I found the description of ram-pressure stripping that Dr Liske shoes to be very helpful.

It doesn't yet seem to be on YouTube, but probably will be eventually.


http://www.spacetelescope.org/news/heic1404/ is the ESA press release, with images that include this composite of the Hubble image and one from Chandra which shows a gas stream only visible in the X-ray part of the electromagnetic spectrum.

Click to view full size image

[geckzilla]

I'm glad they did a press release for this galaxy. It's so very interesting!

[rstevenson]

The spiral plows through the seething intra-cluster gas so rapidly — at nearly 4.5 million miles per hour — much of its own gas is caught and torn away.

That's a very dramatic statement, but we need to compare it to known speeds of other galaxies like, for example, the Milky Way, to make any sense of it. According to a variety of sources, the Milky Way is moving at about 550 km/s, or about 1.23 million miles per hour, releative to the cosmic background radiation. So this "runaway" galaxy is moving at about 3.6 times the speed of the Milky Way.

Rob

[Chris Peterson]

The spiral plows through the seething intra-cluster gas so rapidly — at nearly 4.5 million miles per hour — much of its own gas is caught and torn away.

That's a very dramatic statement, but we need to compare it to known speeds of other galaxies like, for example, the Milky Way, to make any sense of it. According to a variety of sources, the Milky Way is moving at about 550 km/s, or about 1.23 million miles per hour, releative to the cosmic background radiation. So this "runaway" galaxy is moving at about 3.6 times the speed of the Milky Way.

I don't think that's the proper reference frame for comparison.

Most galaxies have some peculiar motion with respect to the CMB, but the intergalactic material around them is moving with them. It seems like what's special here is that the galaxy is moving very fast with respect to its local medium. So what we should be comparing is the velocity of various galaxies with respect to their local intergalactic medium, not with respect to the CMB, Hubble flow, or any other cosmological scale reference frame.

[rstevenson]

Good point Chris. One reference I read suggested the Milky Way was itself moving contrary to the motion of its local group, so perhaps it too is experienceing ram pressure stripping. I wonder if we could tell from within the Milky Way?

Rob

[BDanielMayfield]

Good point Chris. One reference I read suggested the Milky Way was itself moving contrary to the motion of its local group, so perhaps it too is experienceing ram pressure stripping. I wonder if we could tell from within the Milky Way?

Rob

If the Milky Way is experienceing such stripping, it couldn't be much, or we wouldn't have so many active star forming areas here.

What I wonder is, what in thunder is ESO 137-001 running away from, and how come it's in such a hurry?

Bruce

[geckzilla]

I have a hard time understanding how a galaxy could get moving in a direction perpendicular to its disk plane. It makes me wonder if the intergalactic medium is moving through it instead of the other way around. I guess it's impossible to tell the difference.

[Chris Peterson]

I have a hard time understanding how a galaxy could get moving in a direction perpendicular to its disk plane. It makes me wonder if the intergalactic medium is moving through it instead of the other way around. I guess it's impossible to tell the difference.

I suppose a galaxy could be launched in any direction at all by an interaction with another galaxy. Why would there be a preferred direction? But it seems more likely to me that the galaxy didn't get set in motion, but has always had this velocity, retained from that of the material from which it formed.

[geckzilla]

Just from watching collision simulations it looks to me like galaxies get thrown around kind of like frisbees. It's not like a more solid body which can retain its shape after a gravitational interaction, is it? It is fluid. Well, like I said, I am having a hard time imagining it. I have never seen a galaxy pass by another in such a way. Forming that way seems like a good alternative.

[BDanielMayfield]

Are there any other wider shots or views back in the direction this galaxy is moving from? Is it moving outward from a close, gravitational slingshot type interaction with a larger galaxy or galaxy grouping? That would provide a simple explanation, but by just looking at the images presented in this discussion I wouldn’t think that would have been the case, since apart from the gas and dust being stripped from it the Runaway Galaxy looks normal. If it had been accelerated gravitationally wouldn’t the galaxy’s shape have been effected?

Could this galaxy be an outer member of one of two galactic clusters that are swinging past one another?

Bruce

[geckzilla]

It's behind a very dense screen of stars from our galaxy so it's pretty hard to tell one way or another what's going on but there isn't anything obvious in the broader view. ESO 137-001 is in the center of this image.