Starship Asterisk*

neufer wrote:

Ann wrote:
When all is said and done, maybe the closest analog to the blue bridge between the central elliptical galaxies of SDSS J1531+3414 might be the well-known star forming shock front caused by the collision between galaxies NGC 7318 A and B in Stephan's Quintet. According to my software Guide, NGC 7318A is an elliptical while NGC 7318B is a spiral galaxy. The blue shock front in the picture you can see in my post is glowing from invisible X-rays, mapped as blue light. However, there is real star formation producing optical and ultraviolet light there too, as can be seen in this picture.

Except for the fact that the Stephan's Quintet case is supposed to represent a shock between merging galaxies
whereas today's APOD is supposed to represent a gravitational condensation in the wake of two already merged galaxies.

Ann wrote:
When all is said and done, maybe the closest analog to the blue bridge between the central elliptical galaxies of SDSS J1531+3414 might be the well-known star forming shock front caused by the collision between galaxies NGC 7318 A and B in Stephan's Quintet. According to my software Guide, NGC 7318A is an elliptical while NGC 7318B is a spiral galaxy. The blue shock front in the picture you can see in my post is glowing from invisible X-rays, mapped as blue light. However, there is real star formation producing optical and ultraviolet light there too, as can be seen in this picture.

http://en.wikipedia.org/wiki/Stephan%27s_Quintet wrote:

[c][size=150][b]Hickson Compact Group 92: [color=#40FF00]H-alpha = green,[/color] [color=#FF0000]8-micrometre infrared light = red,[/color] [color=#0000FF]visible red light = blue[/color][/b][/size][/c]

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<<Four of the five galaxies in Stephan's Quintet form a physical association, Hickson Compact Group 92, and are involved in a cosmic dance that most likely will end with the galaxies merging. Radio observations in the early 1970s revealed a mysterious filament of emission which lies in inter-galactic space between the galaxies in the group. This same region is also detected in the faint glow of ionized atomic hydrogen seen in the visible part of the spectrum. Two space telescopes have recently provided new insight into the nature of the strange filament, which is now believed to be a giant intergalactic shock-wave (similar to a sonic boom but traveling in intergalactic gas rather than air) caused by one galaxy (NGC 7318B) falling into the center of the group at several millions of miles per hour.

As NGC 7318B collides with gas in the group, a huge shock wave bigger than the Milky Way spreads throughout the medium between the galaxies, heating some of the gas to temperatures of millions of degrees where they emit X-rays detectable with the NASA Chandra X-ray Observatory.

Perhaps even more unexpected is the discovery of very powerful molecular hydrogen signals from the shock wave, seen by the NASA Spitzer Space Telescope which detects infrared radiation. The molecular hydrogen emission, which is seen through infrared spectral analysis using the Spitzer Space Telescope is one of the most turbulent formations of molecular hydrogen ever seen, and the strongest emission originates near the center of the green area in the visible light picture discussed earlier. This phenomenon was discovered by an international team led by scientists at the California Institute of Technology and includes scientists from Australia, Germany and China. The detection of molecular hydrogen from the collision was initially unexpected because the hydrogen molecule is very fragile and is easily destroyed in shock waves of the kind expected in Stephan's Quintet. However, one solution is that when a shock front moves through a cloudy medium like the center of the group, millions of smaller shocks are produced in a turbulent layer, and this can allow molecular hydrogen to survive. Most notable is the fact that this collision can help provide a view into what happened in the postulated beginning of the universe some 14 billion years ago, since shocked molecular hydrogen is likely to be present in the early universe.>>

MarkBour wrote:My first question is about the central part of the image. Are there two galaxies that are almost in line from our viewpoint, are they not just in line, but merging, or, what seems much more likely at first glance, is this just a lens-doubled image of a single galaxy?

4.1. Origin of the ultraviolet emission

We consider three scenarios for the physical nature and origin of the clumpy NUV continuum emission.

1. It is a gravitationally lensed image (or a set of images) from a higher redshift background galaxy (or multiple galaxies).
2. It is a chance superposition along the line of sight, arising instead from a projection effect due to unrelated foreground sources.
3. It arises from ongoing or very recent star formation taking place within the stellar envelope of the interacting elliptical galaxies.

Scenarios (1) and (2) are entirely ruled out by spectroscopic evidence. [Hereafter it gets quite technical. Check the paper for details.]

ddonnelly wrote:Those large lensed circles around the central galaxy are BLUE. If they are from 'way more distant galaxies they should be RED, eh?

starsurfer wrote:There's a few connected galaxy systems in the nearby universe. One of the most well known is Keenan's System, an image by Stephen Leshin, another is Arp 295. One galaxy cluster that contains tidal bridge systems is the Hercules Galaxy Cluster, they can be seen in this image by Tony Hallas.

MarkBour wrote:My second question is about the edge-on galaxy a little above those (spiral, or elliptical, I can't say). Why doesn't it look distorted, or show multiple images? Is it between us and the lens?

Boomer12k wrote:I wonder what WE look like from over there.... do they see a similar effect from us?

Beyond wrote:Massive=Dense?

Ann wrote:If those blue squiggles are young stars at the same distance as the two central ellipticals, then that is a tremendous amount of star formation. All those lensed background galaxies suggest that the yellow ellipticals are really massive and presumably large in size.

metamorphmuses wrote:As to the phenomenon itself, on a gut level I feel like it might have something special to say about Dark Matter, too. I can't help but try to picture how the Dark Matter halos of the galaxies are merging and molding the "bridge" of stars. Or maybe not, but when I look at the image and the lensing, I feel like the invisible mass there is beckoning at us.