Blue Shifting Galaxies Question.

[BigDon]

Well a lot of folks here like to talk about the astronomical red shift due to universal expansion, which is a fascinating subject I'll grant you. But it's been done to death of late. With a lot of repeat and some downright fanciful questions.

And I'm going to resist temptation to play stupid and ask, "Now if we were on the other side of the universe, would we see the galaxies blue shifting towards us?" just to see if I could get Astromark to pull more of his hair out.

But I won't as:

A: I like Astromark.

B: Astromark seems to be at a tolerance nadir at the moment and I'm worried about his remaining hair.

My real question is can somebody give me the names of any large scale objects seemly blue shifting towards our galaxy in spite of what should be a considerable red shift due to distance?

Thank you.

[Nereid]

Well a lot of folks here like to talk about the astronomical red shift due to universal expansion, which is a fascinating subject I'll grant you. But it's been done to death of late. With a lot of repeat and some downright fanciful questions.

And I'm going to resist temptation to play stupid and ask, "Now if we were on the other side of the universe, would we see the galaxies blue shifting towards us?" just to see if I could get Astromark to pull more of his hair out.

But I won't as:

A: I like Astromark.

B: Astromark seems to be at a tolerance nadir at the moment and I'm worried about his remaining hair.

My real question is can somebody give me the names of any large scale objects seemly blue shifting towards our galaxy in spite of what should be a considerable red shift due to distance?

Thank you.

(bold added)

That's a good question!

I can't give you any such names ... and I look forward to answers from other BAUTians (BAUTers?), esp those who can provide any such names!

Perhaps there's a nearby AGN one of whose jets points towards us (more or less)? Not what you had in mind for "any large scale objects" though, right?

[George]

Would the 5 or 6 galaxies in the relatively close Virgo Cluster count? The cluster is receeding from us at about 1100 km/s, yet IC 3258 (highest blueshift) has a radial approach to us of 517 km/s. [It won't zoom by us, however. ]

[Ari Jokimaki]

We'll use NED's master list of galaxy distances. We'll select the "NED-1D" database, and sort it by "Vgsr" column (velocity with respect to galactic standard of rest). Then we'll calculate equivalent velocity from distance ("D" column) using Hubble law and value H0 = 71 km/s /Mpc. Results for few worst cases are presented in table below. Values in parenthesis are alternative values (for galaxies having many alternative distance determinations).

Difference in the velocities for rest of the blueshifted object was quite small, so these are only ones (found in NED) worth mentioning in this context. As you can see, there's only few objects, and only two are "large scale objects" (NGC 4419 and M68) as seen from Earth.

NAME         Vgsr      Vdist

VCC 0846     -782      1290
VCC 0815     -752      1410
VCC 0810     -392      1010 (1210)
VCC 0928     -310      1360
NGC 4419     -306      960 (1260)
M68          -302      820 (1250)

Links to NED pages of above objects:

VCC 0846
VCC 0815
VCC 0810
VCC 0928
NGC 4419
MESSIER 68

[Ari Jokimaki]

In addition to the objects above, there are some objects that have clearly smaller Vgsr than their distance based velocity, so they are blueshifted with reference to their distance based redshift. Following objects have difference (Vdiff = Vgsr - Vdist) smaller than -3000 km/s:

NAME                      Vgsr    Vdist   Vdiff

1ES 2037+521              15470   48422   -32952
1ES 2200+420              19862   30530   -10668
[MH93] 014355.4-562057    25108   33512    -8404
FCCB 0602                 18171   25560    -7389
[P94a] 081751.35+155320.5 25397   32660    -7263
[HM92] 230149-3736.8      28757   35926    -7169
[M96b] J152109.75+275508  36555   43452    -6897
IC 1601                    3642    8733    -5091
ESO 514- G 001            12534   17253    -4719
CGCG 044-035               7137   11786    -4649
[HM93] 132819-3257.6      15043   19667    -4624
[MH93a] 103235.1-341103   19760   24282    -4522
IC 0277                     272    4587    -4315
LSBG F119-024             12998   17253    -4255
1ES 2344+514              12900   17111    -4211
CGCG 307-023              14436   18602    -4166
UGC 00607                 11753   15904    -4151
2dFGRS S839Z607           17665   21513    -3848
UGC 05691                 15968   19738    -3770
ESO 156- G 008            16924   20661    -3737
NGC 7200                   2850    6553    -3703
1ES 1959+650              14050   17750    -3700
MCG +08-25-047             8087   11786    -3699
SGC 1955.1-5624           11693   15052    -3359
LCSB S1315O               14998   18318    -3320
WOOTS J110136.37-060631.6 11601   14910    -3309
[WM92] 212426.8-614612    21565   24708    -3143
[TB93] 2131.14-6257.7     14618   17679    -3061
ESO 576- G 001             2756    5801    -3045
CGCG 016-058              10324   13348    -3024

[parejkoj]

There are plenty of galaxies in clusters that are blueshifted relative to the mean cluster velocity. I'd guess that is what the majority of the objects on Ari's second list are.

The base of quasar 3c273's jet almost certainly is blueshifted compared with its nominal redshift of 0.158. The velocity of the base of the jet is very close to the speed of light (based on VLBI studies of the motion of jet clumps), but it would be very hard to measure that spectroscopically as there aren't really any line features to speak of. The jets of some blazars (being pointed nearly directly at us) might have substantial blueshfits, but they have basically featureless spectra, so there is no good way to measure it.

[Sam5]

My real question is can somebody give me the names of any large scale objects seemly blue shifting towards our galaxy in spite of what should be a considerable red shift due to distance?

Thank you.

The most famous blue-shifted galaxy is M-31, the Andromeda galaxy. It's nearby, and our galaxy and it are moving toward each other.

[speedfreek]

The most famous blue-shifted galaxy is M-31, the Andromeda galaxy. It's nearby, and our galaxy and it are moving toward each other.

Yes but it is nearby as you say and therefore should not have any cosmological redshift anyway. Don is asking for examples of galaxies in regions that should have cosmological redshift due to the expansion of the universe.

[Sam5]

Yes but it is nearby as you say and therefore should not have any cosmological redshift anyway. Don is asking for examples of galaxies in regions that should have cosmological redshift due to the expansion of the universe.

Don't we judge their distances by their redshifts?

If we find a galaxy that has a small image size and that has a blueshift, what would make us think it is at redshift distances, if it doesn't have a redshift? Wouldn't we just think it is a small galaxy nearby?

[George]

If we find a galaxy that has a small image size and that has a blueshift, what would make us think it is at redshift distances, if it doesn't have a redshift? Wouldn't we just think it is a small galaxy nearby?

Another way to say that is to ask, "At what radial velocity must a galaxy have if it is at a cosmological distance to exhibit a blueshift?". Answer that one and you will see why Nereid did a double smiley.

[Celestial Mechanic]

Don't we judge their distances by their redshifts?

If we find a galaxy that has a small image size and that has a blueshift, what would make us think it is at redshift distances, if it doesn't have a redshift? Wouldn't we just think it is a small galaxy nearby?

A good question. Based on the overwhelming mass of observations to date, a galaxy with a small image size and a blueshift will be presumed to be a small nearby galaxy. It would require something anomalous, such as lack of cepheid variables or other distance markers found in nearby galaxies, or grossly underluminous type IA supernovae to raise questions about its distance.