Order of Kilopi
Yes - and there are examples that may pop up from older papers as new data is collected. For example in the first of my 2 long posts I noted this quote from Bergvall (1981):Originally Posted by antoniseb
But Bergvall did not have a redshift for the object. SDSS measured the redshift and it is 24243 km s-1 while NGC 4441 has a redshift of just under 3000 km s-1. I would love to see higher resolution optical and radio imaging of this system.
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Would you like to see the association in HI overlaid on an R-band image (Fig. 2 in the paper below)? It's hard to call this a "merger" though, when the main galaxy exhibits a counter-tail in HI. We would have to suspend some physical laws if we were to believe that a large galaxy can sprout a counter-tail in "anticipation" of an impending merger with a small companion. That's more than a bit strained.
http://pos.sissa.it/archive/conferen...MH2004_040.pdf
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This looks like a pretty good shot of NGC 4441. I'm not sure which "companion" he's talking about, but I see no reason to doubt that any of the smaller galaxies are in the background as their redshifts indicate.
Everyone is entitled to his own opinion, but not his own facts.
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The companion is just out of the frame, to the north (assuming the people publishing the photo followed that convention).
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Wow ... thanks for finding that paper. Nice image!
Agreed. I think as we move toward talking about whether the velocity differentials are caused by gravitationally induced peculiar motions or by an unknown intrinsic redshift mechanism we will find that it is very difficult to hold up peculiar motions as the explanation.It's hard to call this a "merger" though, when the main galaxy exhibits a counter-tail in HI. We would have to suspend some physical laws if we were to believe that a large galaxy can sprout a counter-tail in "anticipation" of an impending merger with a small companion. That's more than a bit strained.
http://pos.sissa.it/archive/conferen...MH2004_040.pdf
For example, the masses required to explain these motions (if the velocity differences are hypothesized to be peculiar motions) are huge. In the B2 1637+29 system, the required masses were ~3x10^13 solar masses.
For NGC 7603 we can use the velocity difference of 7898 km s-1 to calculate the total mass required for the system assuming an elliptical orbit:
Mtot = V^2/G[2/r-1/a] where r is the separation in kpc, a is the semimajor axis in kpc and G has a value of 4.31x10^-6 kpc x Km^2/M(sun) x sec^2.
Assuming NGC 7603 is at its Hubble distance of 120.6 Mpc with H0=70, the angular separation from NGC 7603B is 0.9 arc min or a projected separation of 31.6 kpc. Adopting a semimajor axis of 500 kpc (the actual value has little effect on the final result) gives a total mass of:
2.4 x 10^14 solar masses
To put that in perspective a typical large spiral galaxy has a mass of ~ 10^11 solar masses, so NGC 7603 would need to be ~1000x more massive than a typical spiral. Even one of the most rapidly rotating galaxies discovered ugc 12591 only has a mass on the order of 10^12 solar masses. Since NGC 7603 is in a region devoid of any massive companions it is difficult to reconcile this mass discrepancy.
Order of Kilopi
According to Bergvall the companion was ~14 kpc to the SE. Using their redshift and Hubble constant value that indicates that they were referring to the two objects at about 7-8 O'clock on the image. The northernmost of those two objects was the one reported in HyperLeda to have an SDSS redshift of ~24000 km s-1.
Clearly NGC 4441 shows signs of interaction and the high z galaxy is in the location indicated by Bergvall as being connected by a clearly seen bridge. This is another system worth further scrutiny.
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This reminds me of one of Arp's complaints where follow-up studies of objects he singled out as important examples, were most times cropped (deliberate or accidental) to leave out the most interesting features. Add this to the problem of the very incomplete redshift measurements of the AM catalogue.
Cheers.
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I've looked at Bergvall's Fig. 2 (talk about cropping), which used a film emulsion, and compared it to the image graciously provided by David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration (which I cropped from their original), and I'm having a bit of a problem reconciling the two images, and not just because the Bergvall image is an isodensity contour map. Well, take a look....
The "bridge" in the Bergvall image (right) does not really seem to be there in the Hogg digital image. [Edit to add: I mean, there may be a smidgin of flux there, but there's flux all the way around NGC 4441, not just between it and the small galaxy that Bergvall thinks is "clearly" connected by a bridge.]
And the two wispy "arms" at 4:00 and 5:00 o'clock of the Hogg image that are rather key features of this galaxy have completely lost their continuity in the Bergvall image.
Besides, Bergvall tells us that VII Zw 454 is fairly nearby to the northwest (upper right out of frame), and it has nearly the same apparent magnitude as NGC 4441, which certainly makes it a candidate for the interacting companion that apparently disrupted the morphology of 4441.
Depending on its redshift, of course.
Everyone is entitled to his own opinion, but not his own facts.
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It is perhaps for the mainstream astronomers who, apart from yourself, have conspicuously stopped contributing to this thread to show in what way this work might be without meaning and lacking in rigour.That's the question: Does it have any meaning? Is it really rigorous?
I thought it had been made clear that the findings strongly suggested a trend. No-one has claimed to be at the stage of reaching conclusions.
Why and how would it be biased?
You state, in your signature, that "Everyone is entitled to his own opinion but not his own facts". Is your "Not in the slightest" offering meant to be an opinion or a fact? And do you know whether your fellow mainstreamers endorse it and if so, why?Not in the slightest.
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There are at least 3 things that have to be accounted for when you compare these two images:I've looked at Bergvall's Fig. 2 (talk about cropping), which used a film emulsion, and compared it to the image graciously provided by David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration (which I cropped from their original), and I'm having a bit of a problem reconciling the two images, and not just because the Bergvall image is an isodensity contour map. Well, take a look....
The "bridge" in the Bergvall image (right) does not really seem to be there in the Hogg digital image. [Edit to add: I mean, there may be a smidgin of flux there, but there's flux all the way around NGC 4441, not just between it and the small galaxy that Bergvall thinks is "clearly" connected by a bridge.]
And the two wispy "arms" at 4:00 and 5:00 o'clock of the Hogg image that are rather key features of this galaxy have completely lost their continuity in the Bergvall image.
(1) The Bergvall image is in the V-band and I'm not sure what band(s) are compiled to make that SDSS image. In the paper linked to by Turbo-1 the image was in the R-band. The strength of features in any given image will be affected by the band selection and the age of the features. Recent bursts of star formation will be readily detectable in B and V-band images because of the younger O and B class stars that dominate the light output of the young starbursts.
(2) Even with your cropping, the SDSS image is still covering a larger angular extent than the Bergvall image. Note that the bigger of the two companions is in the lower left corner of the Bergvall image.
(3) The Bergvall image is rotated such that up not North. See the arrows in the upper left of the image.
When you combine #'s 2 and 3 it is not correct to imply that the two "wispy arms" were not in the Bergvall image because the have "lost continuity". In fact the smaller angular extent and rotation of the Bergvall image relative to the SDSS image is the reason the wispy arms are not seen in the Bergvall frame. The concentration of contours in the lower right corner of the Bergvall frame should be the start of the closer of the wispy arms.
VII Zw 454 is NGC 4391. It has a redshift of 1474 km s-1 whereas NGC 4441 has a redshift of 2768 km s-1. The angular separation of the two objects is 14 arc min. At the NGC 4441 redshift distance this would indicate an projected separation of ~ 160 kpc.Besides, Bergvall tells us that VII Zw 454 is fairly nearby to the northwest (upper right out of frame), and it has nearly the same apparent magnitude as NGC 4441, which certainly makes it a candidate for the interacting companion that apparently disrupted the morphology of 4441.
Depending on its redshift, of course.
Interestingly enough this provides an excellent example of the need to check sources. It just so happens that NGC 4441 has a Surface Brightness Fluctuation method distance of 19 Mpc (Tonry et al 2000). But Tonry et al list a redshift of 1553 km s-1 not 2768 km s-1. So I checked the list of redshift measurements in LEDA. The only raw data that indicates a redshift of ~ 1500 km s-1 was a 1977 measurement. All of the more recent measurements - including the SDSS measurement are at ~2700 km s-1. Now if you go to NED you will find redshifts around 1400 km s-1 listed several times - but those redshifts are from the RC3 catalog which was based upon older redshift measurements and probably used that 1977 measurement.
NGC 4391 also has a SBF method distance in Tonry et al - 24 Mpc. But the uncertainty of the two distances overlap. So you might be right Cougar - they could be at the same distance. At the SBF distances the projected separation of the two galaxies is only about 80 kpc - so interaction is very reasonable if we assume that they are in fact at the same distance despite the modest ~0.50 mag differences in the SBF distance moduli.
But now we run into the redshift problem. If we want to claim that NGC 4391 is responsible for the disturbed morphology of NGC 4441 then how do we explain the difference in redshift? First it should be noted that at a distance of 21.5 Mpc, NGC 4441 should have a redshift of 1505 km s-1 - so its observed to have an excess redshift of ~1260 km s-1.
A look in Simbad reveals that there are a number of other galaxies within 2 degrees of NGC 4441 with redshifts of ~ 2600 -3100 km s-1:
N4210 (2839 km s-1)
N4221 (1421)
N4256 (2637)
N4332 (2997)
N4510 (2848)
N4512 (3086)
N4521 (2649)
One of those galaxies NGC 4210 has a TFR distances of 41.1 Mpc (B-band) and 46.3 Mpc (K-band). The TFR distance of NGC 4210 provides a much better fit to the Hubble relation than the SBF distance to NGC 4441. If we assume a significant error in the SBF distance and that NGC 4210 is a good estimator of the average for the group, then we could account for NGC 4391 if we assume it's SBF distance is also incorrect and its interaction with NGC 4441 has caused a peculiar motion of ~1300 km s-1 toward us.
Order of Kilopi
Right. But O and B class stars are not detectable in (what I assume is) visible light?
Yes, of course. I wanted to include the whole picture.
Yes, I saw those. Up is not north, but it's only tweaked a bit. Major "mile markers" are pretty easy to correlate.
In the Hogg visible light image, the flux of those wisps is fairly continuous from the central bulge out to the brighter area near (what I guess is) that reddish star. In the V-band, we only get the bulge and that brighter area, which is really emphasized using that filter. Not much in between.
Well, if the bigger of the two "companion" galaxies is in the lower left corner of the Bergvall image, the arms should be starting back by the bulge. That concentration of contours in the lower right corner is the brighter arm area down by that reddish star.
Thanks for your ensuing analysis. But as far as the "speckled bridge" in Bergvall's image that sort of goes over to that high redshift galaxy, I don't know what to make of it. Does the "bridge" stop there? Hard to tell since Bergvall cut the frame there. If it continues past, I should think that would rule out the "bridge" label. Of course, as I said, there's not much there at all in visible light.
Oh, good. I try to guard against jumping to conclusions when the evidence is insufficient.
Well, the fact that the population I believe that is being drawn from are specifically peculiar objects mostly compiled by Arp makes it just a little suspect.Why and how would it be biased?
Not in the slightest.It is a fact. Mainstreamers and nonmainstreamers alike should recognize that absence of evidence is not evidence of absence.
Everyone is entitled to his own opinion, but not his own facts.
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Why and how would it be biased?Ad-hom attacks, now? Are you going to disparage the Russian team when Ari presents findings from the VV catalog? And how about Barry Madore? Isn't he on your enemies list, too, since he worked with Arp?
As I have pointed out to you several times, these people sought out interesting associations of galaxies and they selected them on the basis of their visual appearance, NOT their redshifts. The fact that the members of some of the associations were later found to exhibit discordant redshifts has no bearing on the manner in which the associations were selected and cataloged.
As far as bias is concerned, I was asked (by antoniseb, IIR) if smaller companions routinely showed excess redshift (an Arpian idea, for certain), and I decided to look specifically at the M51-types, in part because the A-M catalog had an entire chapter dedicated to the type and because the M51-types are an identifiable sub-set of bridged associations, which pertained to the current topic. I did my best to avoid biasing the sample, taking every M51-type association that I could find, and was quite surprised by the strength of the redshift trends in the data set. Ari and dgruss23 have since whittled away at that data set, tightening up the standards (visual appearance) by which the samples are selected to be in the group. They have looked at the images (the Arp and A-M catalogs are available on-line) and have consulted with one another, then recommended to me which associations should be in the data set and which should not. I then refined the data set and re-ran the stats. We may have to make some more cuts if we tighten the criteria for group membership.
If you would like to review the Arp, A-M, and VV catalogs you can do the same type of work that we are doing - then you will get a feel for the reality of the redshift trends. You may want to choose associations of a different type or associations made up of a different class of galaxies (ellipticals or irregulars, for instance) and see if there are any redshift trends there. There may or may not be similar trends in non-M51-type associations - we don't know yet, and you can help us find out, if you want. The catalogs (and NED and HyperLeda) are on-line for all of us to use.
Order of Kilopi
Ok, I'm going to try making a table to show why the significance of the band selection is important. In this paper the SDSS u,g,r,i, and z bands are defined:
Now the V-band is at 5397A. For the g-band we find the limit of its range by adding half the width to the peak. That gives 4800 + 700 = 5500 angstroms. For the r band we substract 6250 - 700 = 5550 angstroms.Code:Band Peak wavelength width (angstroms) (angstroms) u' 3500 600 g' 4800 1400 r' 6250 1400 i' 7700 1500 z' 9100 1200
The image you linked to uses the SDSS g,r, and i filters. Notice that the v-band filter peaks in the valley between the SDSS g and r bands. Now that does not mean that the feature should not have been detected by SDSS -but it provides a plausible explanation. If the feature has a stellar population that peaks in the V-band it would not be as distinct in the SDSS image. Obviously a V-band image with modern equipment would be nice.
But then you indicated that the Bervall image failed to detect features that we don't know that it did not detect because those features were outside the Bergvall frame. That was my point about the cut. Nothing wrong with looking at the larger frame.Yes, of course. I wanted to include the whole picture.
If you look at the NW ends of those wisps, there is a sizeable gap between the end of the dense portion of the wisp and the sphere of NGC 4441. Because of the rotation of the Bergvall image, the lower right corner cuts through this gap.Yes, I saw those. Up is not north, but it's only tweaked a bit. Major "mile markers" are pretty easy to correlate.
In the Hogg visible light image, the flux of those wisps is fairly continuous from the central bulge out to the brighter area near (what I guess is) that reddish star. In the V-band, we only get the bulge and that brighter area, which is really emphasized using that filter. Not much in between.
That's my take.Well, if the bigger of the two "companion" galaxies is in the lower left corner of the Bergvall image, the arms should be starting back by the bulge. That concentration of contours in the lower right corner is the brighter arm area down by that reddish star.
Good question. We can speculate that since the point of figure 2 in the Bergvall paper was to show the bridge, Bergvall cut the frame down to the size that highlighted the feature.Thanks for your ensuing analysis. But as far as the "speckled bridge" in Bergvall's image that sort of goes over to that high redshift galaxy, I don't know what to make of it. Does the "bridge" stop there? Hard to tell since Bergvall cut the frame there. If it continues past, I should think that would rule out the "bridge" label. Of course, as I said, there's not much there at all in visible light.
The first Arp catalog was created before he ever thought that there were large redshift deviations. The second AM catalog was compiled optically. It is hard to claim there is a redshift bias in his catalog when at over half of the objects lack any redshift data even now.Well, the fact that the population I believe that is being drawn from are specifically peculiar objects mostly compiled by Arp makes it just a little suspect.
Order of Kilopi
Oh, please. My criticism is valid and yours is not.
I recall a question being asked before, and I don't know if it was satisfactorily resolved: Objects that are farther away generally appear smaller. Objects that are farther away generally have larger redshifts. Unless we can establish that a smaller object is actually a companion at the same distance as the host and not a background object in a chance alignment, we would expect smaller objects to routinely show higher redshifts than the larger objects.
I appreciate your analysis. I'm just not sure what it means.
Everyone is entitled to his own opinion, but not his own facts.
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Specifically the claim was that the bone fide dwarf companions of nearby galaxies have a tendency to have slightly higher redshifts than their giant companion. In this case we were looking only at those smaller galaxies with less that a few hundred kps difference in apparent velocity from the central galaxy.
A second line discussed similar looks at what appeared to be interacting galaxies with small velocity differences.
The point, as I understood it was that a small sample seemed to indicate that there was a bias of 50 to 100 kps of extra red shift for the smaller companions. The pro-Arp side was saying this was evidence for some kind of intrinsic redshift for smaller (newer in the Arp cosmology) galaxies. I personally have no explanation, except to say I'd like more data, which they've been working to provide.
Forming opinions as we speak
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I'm not sure that pithy little aphorisms such as this one can replace actual reasoning sufficiently to convince anyone, particularly when it doesn't even fit the case...It is a fact. Mainstreamers and nonmainstreamers alike should recognize that absence of evidence is not evidence of absence.
Shades of Harry Wormwood in "Matilda" (1996): "I'm big, you're little. I'm smart, you're dumb. I'm right, you're wrong. And there's nothing you can do about it."Oh, please. My criticism is valid and yours is not.
Really? Why precisely?
Order of Kilopi
Oh, yes, that would be a different question. I was responding more to Turbo's post #1624 that contained the following list....Specifically the claim was that the bone fide dwarf companions of nearby galaxies have a tendency to have slightly higher redshifts than their giant companion. In this case we were looking only at those smaller galaxies with less that a few hundred kps difference in apparent velocity from the central galaxy.
A-M #...........V..km/s
0324-524........-260
0523-400........-156
73.................-108
86..................-96
85.....................5
1108-300---------18
82....................39
1304-333...........81
58....................92
0327-285..........128
0639-582..........145
88...................165
2256-254..........324
1353-272..........354
2105-332..........361
0500-620..........780
2100-381.........1555
2256-304.........2352
0037-305.........2627
92..................7898
0058-402.........9642
67................11230
2052-221.......36526
Everyone is entitled to his own opinion, but not his own facts.
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Just to contribute by info New paper from Arp et al.
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Several weeks ago I mentioned a straight line tidal disruption of a galaxy interacting with the milky way. Finally, I am reminded of links about this.
http://www.bautforum.com/showthread.php?t=39353
Forming opinions as we speak
Order of Kilopi
New paper, small sample, same methods, same result. It's interesting that they casually discount microlensing, yet the rather definitive paper on the topic by Scranton, Menard, et al. is not so much as mentioned.
Everyone is entitled to his own opinion, but not his own facts.
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The authors did not "casually discount microlensing" as you claim, but gave a well-reasoned explanation why microlensing is not a viable player.
The fact that they cited a 2005 paper based on data from the very large SDSS survey data is a sign of scientific integrity. The fact that they did not cite your favorite paper in the world means nothing - the field is fast-moving, and the Scranton-Menard interpretation is not written in stone. The Arpians could reasonably cite some of the work by Strauss, Fan, et al, who are regularly serving up anomalies for BB cosmology to chew on.
Order of Kilopi
I chose that word carefully and for good reason. Whatever their explanation, their bottom-line statement was "apparently this excess cannot be accounted for by microlensing." Apparently? Why do they add this word to this sentence? If they conclusively hold this position, why don't they say "clearly" or "we conclude"? In the context, I take this usage to mean "appearing as such but not necessarily so; seeming." That's why I say they casually discount the microlensing explanation. Surely these authors are well aware of Scranton et al's paper on this subject. And as I said, It's interesting that they casually discount microlensing, yet the rather definitive paper on the topic by Scranton, Menard, et al. is not so much as mentioned. Do they have a problem with Scranton's paper? Do they disagree with Scranton's finding? Or, I hate to say it, but it seems like they're just cherry-picking a paper that is friendly to their ATM position while not mentioning a word of the fact that there is published work out there saying exactly the opposite.
I do not call sweeping contradictory evidence under the rug "scientific integrity."
You can lose the attitude anytime.
The fact that they did not mention a well-argued finding that microlensing yields the observed excess is significant, it seems to me. Is this a "political advertisement" or a scientific paper?
Certainly not. It's science. But I was unaware that anyone had challenged this finding or pointed out errors in their methods. Do you have a cite?
Except they didn't. What relevance would Strauss & Fan's work have to Arp's new paper anyway?
Everyone is entitled to his own opinion, but not his own facts.
Established Member
They used the word "apparently" in the abstract. In the body of the paper, they gave a detailed explanation of the effects that Myers et al found in the SDSS survey. The use of qualifying words like "evidently", "apparently", in an abstract is a sign that the authors are careful and will present evidence to back up their statement.
They cited a recent paper that used data from a very large survey that is still in the data-collection stage.
There are lots of other papers out there describing quasar/galaxy correlations, too. Why don't we make a big list of them and blast Arp et al for each one they failed to cite? By the way, based on the data set, various authors have found both positive correlations and anti-correlations between quasars and galaxies. We have gone over this before.
The fact that they did not cite your favorite paper is not equivalent to dishonesty. If you want to critique the paper, dive in and show us where Arp et al are in error.
As I have pointed out several times, Fan, Strauss et al examined 161 quasars at z>4 and not a single one of them was lensed, despite the assumed large column densities. If lensing plays such a huge role in determining the apparent distribution of quasars on the sky, why were not even one of the most redshifted quasars in the SDSS set lensed?
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I agree the various band characteristics are important. And with large redshifts, the bands are all offset into other band regions. I need to know more about all the different bands, where they are located along the spectrum, what letter they're assigned, and what characteristics each emphasizes, but I couldn't readily find a site on this. Anyone know of one?
Everyone is entitled to his own opinion, but not his own facts.
Established Member
Cougar, I don't know of any comprehensive listing of spectral bands, although Wikipedia has what looks like a good list covering the IR bands. If you don't get a response from dgruss23 in the next few days, please understand that he is dealing with a family emergency and may be occupied for a time.
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Sorry to hear that.
Thanks. I'll keep looking.
Everyone is entitled to his own opinion, but not his own facts.
Established Member
Go to this sdss webpage for details on the sdss filters, including ascii files describing the filter pass Q.E. vs. wavelength.
Order of Kilopi
Since the bridges discussion seems to have died down, it might be worthwhile to move on and discuss whether or not the evidence for interaction in the discordant redshift bridged associations demands an intrinsic redshift explanation (with as yet uncertain mechanism) or can be explained by a more mundane process. For example, I put forward one argument here .
Order of Kilopi
Yes, there you spoke of peculiar velocities, or more generally relative velocities. This is one form of "intrinsic redshift." And of course gravitational redshift is another form of "intrinsic redshift." We think we know most everything there is to know about how these forms affect redshift. And of course the cosmological redshift has a great effect on an object's redshift, though we don't consider that "intrinsic." I see no reason to rule out the possibility of a discovered modification to our understandings or even another form of "intrinsic or otherwise redshift" that our current understanding doesn't recognize. (But once it was recognized, it would probably appear mundane.)
At this point I don't think the evidence is solid enough to "demand" the necessity to modify our current understandings. I want to see a DNA match in the sky. As the compilers in this thread have lamented, a lot of the evidence is missing. I haven't seen any Lyman-type absorption comparisons that might exonerate the guilty-looking interlopers.
This is a key component of your proclamation. If an explanation is needed (assuming there is evidence), then it could be any explanation, or combination of them....
....even a mundane one.
Everyone is entitled to his own opinion, but not his own facts.
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You do not miss the point. You understand the point, but actively support the avoidance of the point. The evidence is not just missing, it is actively avoided. It is not politically correct to do spectoscopy on Arp or A-M associations, lest Arp be proven right. If the mainstream wants to prove Arp to be a crackpot, it would only take a short run on today's big telescopes with multiple-optical-fiber spectrographs to do so. The sceptic in me believes that such refutations have been attemped, and have failed.
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