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enter image description here
(source)

When they saw in neutral hydrogen wavelength they saw a neutral hydrogen bridge, while the Hubble Space Telescope concluded that the light from the quasar was redshifted. So if it's redshifted, how can a quasar be so near to earth? When the distances were measured the quasar was 1 billion light years away and NGC 4319 was 77 million times near so Mk205 is 14 times away from NGC 4319. Then how can there be a neutral hydrogen bridge between those two galaxies?

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    $\begingroup$ Do you have any references for this? (It’s hard to know how to answer your question when you don’t tell us who “they” were or where the distance measurements come from.) $\endgroup$ May 16, 2023 at 11:22
  • $\begingroup$ this case was handled by haltop arp and bubble measured the distances in the recent past $\endgroup$ Jun 13, 2023 at 16:45

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Some details about the image you have shown can be found here.

The gist of this is that the image shows a nearby galaxy, NGC 4319 (estimated to be about 77 million light years away) in the centre and a more distant quasar, MKN 205 (estimated from its redshift to be about a billion light years away) towards the top-right.

This is almost certainly a line of sight coincidence- the two objects are at completely different distances and cannot be interacting.

What I think you are asking about is earlier work by Halton Arp who claimed that many quasars had some association or had been ejected from nearby galaxies. The pair NGC 4319 and MKN 205 was a prime example and part of the cited evidnce was an apparent "bridge" of material extending between the two. There seems no doubt that there is some luminous feature, though it is hardly apparent in the HST image. Cecil & Stockton (1985) demonstrated the reality of the feature but argued that it was most likely a tidal tail formed by the interaction of MKN 205 with the compact galaxy seen just to the bottom-left of it and which has a similar redshift to MKN 205, though that interpretation continued to be disputed by Sulentic & Arp (1987).

I think that the subsequent observations of absorption lines in the spectrum of MKN 205 seen at the redshift of NGC 4319 conclusively demonstrate that MKN 205 is further away than NGC 4319 (Bowen & Blades 1993), but that still does not eliminate the possible association. As far as I can tell, that is where we are.

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  • $\begingroup$ thank you for explaining it $\endgroup$ Jun 16, 2023 at 17:35

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