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BigDon
2009-Jan-20, 02:07 AM
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
2009-Jan-20, 02:45 AM
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
2009-Jan-20, 03:03 AM
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
2009-Jan-20, 06:49 AM
We'll use NED's master list of galaxy distances (http://nedwww.ipac.caltech.edu/level5/NED1D/intro.html). 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 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=vcc+846&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)
VCC 0815 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=vcc+815&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)
VCC 0810 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=vcc+810&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)
VCC 0928 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=vcc+928&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)
NGC 4419 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=ngc+4419&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)
MESSIER 68 (http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=m68&extend=no&hconst=73&omegam=0.27&omegav=0.73&corr_z=1&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES)

Ari Jokimaki
2009-Jan-20, 07:06 AM
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
2009-Jan-21, 03:09 AM
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
2009-Jan-21, 06:40 PM
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
2009-Jan-21, 06:49 PM
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
2009-Jan-21, 07:52 PM
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
2009-Jan-21, 08:26 PM
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
2009-Jan-21, 08:31 PM
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.