Author Topic: Wednesday, 16th March, 2011: a controversial galaxy  (Read 25255 times)

NGC3314

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #45 on: September 10, 2012, 01:59:27 pm »
A redshift difference that small within a galaxy cluster can arise completely from the Doppler component of redshift, in this case amounting to less than 300 km/s relative motion along the line of sight. The velocity dispersion in the Virgo cluster from internal motions is about 800 km/s, so within this range the redshifts don't tell us about location within the cluster; the observed redshift comes from the product of (1+z) values for separate contributions - in this case cosmological (from here to the Virgo cluster) and Doppler (motion within the cluster) contributions. For such cases, we need additional data to judge whether two galaxies are close enough to be interacting - hence the interest in whether these galaxies show morphological distortions that would indicate that they are actually interacting.

(I would also like to be sure which one is in front, to know how to interpret that lack of dust absorption from the spiral on the side toward the elliptical).

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #46 on: September 10, 2012, 06:40:50 pm »
Another puzzling case.:


http://cas.sdss.org/dr7/en/tools/explore/obj.asp?id=588017604696408195
http://cas.sdss.org/dr7/en/tools/explore/obj.asp?id=588017604696408114

I copied below post from another thread.:
I read today the blog "The Finale of Merger Zoo; 27 March 2012 by John" and I've taken a look at the 54 thumbnails.
I don't understand if it is only a "zooites" sample or the base of more detailed study by the team.

I have some doubts on few pairs which can't be interacting at hundreds of megaparsecs apart, and i suggest to carefully estimate the distance between the two (or three) nuclei of the pair in interaction.
example
Pair
objid_in_pair                ra          dec                  z            neighbor_in _pair          n_ra              n_dec     n_z      sep (arcmin)  dist Mpc
588017604696408195 221.32866 38.805889 0.059753 588017604696408114 221.34691 38.781006 0.032244 1.72 203.2  ???

(...)

588017604696408195 is NGC 5753 (and the other one is NGC 5755)!
You missed, that in NED there is given a different redshift than in SDSS and an essential note: "SDSS has z = 0.059750 +- 0.000167" !
NED cites z=0.032099.  (It has nearly same redshift as the other galaxy and thus they might interact.)
So the redshift or spectrum in SDSS (DR7/DR8) seems to be wrong! (I have no clue, why the redshift in SDSS is different than in NED!) 
On the other hand, I wonder, if the disturbance of NGC 5755 is really caused by NGC 5753 or if NGC 5755 is actually itsself a GPair (at the spectrum target in SDSS there seems to be another galaxy: 588017604696408114).
Simbad says:
NGC 5753 -- Galaxy in Pair of Galaxies
NGC 5755 -- Interacting Galaxies

 :-\ ???
« Last Edit: September 10, 2012, 06:47:29 pm by zutopian »

NGC3314

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #47 on: September 10, 2012, 07:58:24 pm »
This is an exciting field - zooming out shows NGC 5752/4, a clearly interacting pair at the lower redshift z=0.0152. The whole area showed up on the original atlas photo for Arp 297, and it wasn't clear for lack of data for many years that the two pairs are at different distances.



Everything looks in order with the DR7 spectrum of NGC 5753; no idea what the redshift issue is, the absorption lines are in the right places for the listed z=0.0598. NED cites a 1992 redshift survey of IRAS galaxies for their value. If the DR7 value is correct , that would suggest that NGC 5755 would be the remnant of an interaction which might have already merged both galaxies (since in that case we would see no other culprit for causing the distortion). The redshift of NGC 5755 has a bit more pedigree in NED, with a vintage-2000 reprocessing of earlier data through both emission and absorption template correlation.

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #48 on: September 10, 2012, 10:12:31 pm »
This is an exciting field - zooming out shows NGC 5752/4, a clearly interacting pair at the lower redshift z=0.0152. The whole area showed up on the original atlas photo for Arp 297, and it wasn't clear for lack of data for many years that the two pairs are at different distances.

Everything looks in order with the DR7 spectrum of NGC 5753; no idea what the redshift issue is, the absorption lines are in the right places for the listed z=0.0598. NED cites a 1992 redshift survey of IRAS galaxies for their value. If the DR7 value is correct , that would suggest that NGC 5755 would be the remnant of an interaction which might have already merged both galaxies (since in that case we would see no other culprit for causing the distortion). The redshift of NGC 5755 has a bit more pedigree in NED, with a vintage-2000 reprocessing of earlier data through both emission and absorption template correlation.

I have never thought of the possibility, "that NGC 5755 would be the remnant of an interaction which might have already merged both galaxies"! :o Interesting suggestion!
Concerning NGC 5752/4, I found out, that the GPair is quite familiar to you!
Image: Hubble Interacting Galaxy NGC 5754: http://hubblesite.org/newscenter/archive/releases/2008/16/image/bw/
Image Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama, Tuscaloosa)
BTW, on wikipedia there is shown another image of that 2 GPairs, on which an incredibly long tidal tail of NGC 5752 is visible.   
« Last Edit: September 10, 2012, 11:38:32 pm by zutopian »

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #49 on: October 25, 2012, 07:28:10 pm »
Here is another case:
Is it a merger of 2 galaxies and a QSO (z>1) overlap?
Or the QSO might be also involved in the interaction. It is at the center of a galaxy. So it might be ejected by the galaxy!
Sorry, I couldn't resist to do that comment on the forum. ;D


http://talk.galaxyzoo.org/objects/AGZ00033vr/discussions/DGZ10068rs

One of the NED Refs is:
"A Test for the Origin of Quasar Redshifts"
Piotr Popowski (MPA), Wolfgang Weinzierl (MPA)
(Submitted on 18 Sep 2003 (v1), last revised 30 Oct 2003 (this version, v2))
http://arxiv.org/abs/astro-ph/0309511

EDIT:
DR7 says z=0.033, but DR8 says z=1.347 (specclass=QSO).
http://cas.sdss.org/dr7/en/tools/explore/obj.asp?id=587742191528116273
http://skyserver.sdss3.org/dr8/en/tools/explore/obj.asp?id=1237667912753020966
« Last Edit: November 17, 2013, 10:47:23 pm by zutopian »

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #50 on: May 11, 2013, 11:34:45 am »
Warning: this topic has not been posted in for at least 120 days.


http://talk.galaxyzoo.org/objects/AGZ00016sp

It looks like a merger, doesn't it?, but the galaxies have different redshifts in NED! (no spectra in SDSS)
I used #overlap and mentioned the different redshifts, but three other zooites used #merger. (once before my comment and twice after my comment.)
I had posted it in the overlap topic on the forum before.
LY had posted it in the "Galaxy Systems" topic and there is shown a further galaxy 588848899888972392, which has a similiar redshift (NED) as 588848899888972120.:



A 2- (not 3-) galaxy system, bottom to top:
2MASX J08233628-0011549  588848899888972392 z=0.055
CGCG 004-010 NED02  588848899888972120 z=0.054
CGCG 004-010 NED01  588848899888972121 z=0.035
« Last Edit: May 11, 2013, 12:48:27 pm by zutopian »

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #51 on: September 20, 2013, 06:01:31 am »
Warning: this topic has not been posted in for at least 120 days.

Here is a GPair, which resembles the "contoversial GPair".: The big galaxy has also an AGN, but in this case both galaxies have similiar redshifts!:


http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id=1237657189836390539 z=0.107
http://skyserver.sdss3.org/dr9/en/tools/explore/obj.asp?id=1237657189836390540  z=0.105

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #52 on: June 08, 2014, 03:44:07 pm »
Warning: this topic has not been posted in for at least 120 days.

Here is a different case.: Copy from GZ blog post:

Quote
So a galaxy with z=0.049 is moving away at  14,700 km/s, and is located about 650 million light years away, while a galaxy with z=0.26 is moving at about 89,000 km/s and is 3 billion light years away.
How, then, could two such galaxies each be a source of radio emission which appear to be connected with a thin radio filament? 
(...)
Radio Galaxy Zoo participants have looked at approximately 40,000 systems so far, so in such a large collection, this unusual object is likely just a coincidence, rather than some failure in our understanding of cosmic expansion.(...)
http://blog.galaxyzoo.org/2014/06/08/remarkable-discoveries-underway-citizen-scientists-fire-up-radio-galaxy-zoo/

« Last Edit: June 08, 2014, 04:11:01 pm by zutopian »

zutopian

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Re: Wednesday, 16th March, 2011: a controversial galaxy
« Reply #53 on: July 01, 2014, 05:17:17 am »
HST image of NGC 7603 and companion:


https://archive.stsci.edu/missions/hst/previews/U2E6/U2E62R01T.jpg

Release Date: 1995-07-04
Proposal ID  : 5479