Dear Nereid and Phobos (seat belt on) can we talk about redshifts?

[Nereid]

continued (2) ...

Do you have some examples we can review?

he is talking about the Arp objects: http://members.aol.com/arpgalaxy/

there are 388 catalogued http://members.aol.com/arpgalaxy/arpord.html

they are all galaxies/quasars that are clearly close enough to touch/interact- but a doppler redshift would indicate that they are very far away from one another-

I think there is probably some weird gravity effects going on here to cause the discrepancy without the need to attack the doppler-from-expansion or the BB- but unfortunatley mainstream cosmologists and even some astronomers ignore this data because it is often used to discredit the Big Bang- so we are all still waiting for a hypothesis from mainstream science- and waiting- and waiting-

Dear Phobos:

Rather than quote, re-quote, etc (kind of messy) I’ll address your quotes one by one.

#1 For some examples, let’s pick just two examples, to keep things manageable:

Here is a link to some information about NGC7603 with two high-redshift knots embedded in the arm connecting the galaxy to its apparently-ejected neighbor. Accidental alignments like this should boggle the mind. If anyone would like to calculate the chances of this alignment, please chime in.

http://quasars.org/ngc7603.htm

Here is a Hubble image of NGC4319 and Markarian 205. Click on the photo and then download the high-resolution version. Open it in Photoshop and manipulate the contrast and brightness settings. The bridge between the two will jump out at you. The Hubble Space Telescope took this picture – there is no sleight-of-hand here. The official version of the image is pretty mundane. Even minor enhancement brings out the bridge, though.

http://hubblesite.org/newscenter/ne...leases/2002/23/

#2 Yes, of course astronomers acknowledge that there are various means by which light can be redshifted. The problem is that the astronomical community has determined that the observed high redshifts of quasars are primarily (read “entirely”) cosmological. If there is even ONE convincing example of a physical relationship between a high-redshift object and a low-redshift object, this rule-of-thumb is automatically void and needs to be re-validated.

#3 I have no access to Hubble’s original papers either. Halton Arp has been privileged to work with some of the finest observational astronomers, however; well before their work was entombed by the assumptions of others. His first position after attaining his doctorate was as Edwin Hubble’s assistant, and I expect that he has a deeper appreciation for Hubble’s thought-processes than most contemporary astronomers. The quote is from a fairly long letter Dr. Arp wrote to me in response to another letter I had written to an astronomy magazine in regard to the apparent bridge between Q2203 +292 and a nearby spiral in a recently published photo. He wanted to convey to me that even Edwin Hubble was uncomfortable with the current fad of using redshifts to establish the distance to every observable object. There is an old saying - “to a man with a hammer in his hand, every problem looks like a nail”. It might now be appropriate to ask if the Hubble Constant has been plastered onto quasars and other high-redshift objects even before the natures of such “quasi-stellar” objects have been adequately explored.

#4 Being outside the mainstream does not invalidate Arp’s work. Copernicus and Galileo were outside the mainstream. Einstein was outside the mainstream. People who make paradigm-altering observations are always outside the mainstream until their observations are accepted. That does not make them wrong, nor should it lay them open to ridicule. I wonder how Galileo would have survived under “peer review” if he had not already used his telescopes to demonstrate to other inquisitive individuals that he was onto something. He probably would have died very early in the inquiry, like the other heretics.

#5 Not a pun (although I love them). Halton Arp is a real gentleman. 50 years from now, the people who have done their very best to bury him in these past few decades will be discredited and many will be reviled for their efforts to discredit him. He is a decent man, and he comports himself with dignity.

 

[Nereid]

Last one (can't resist) ...

ditto...hang on, Turbo1

Oy - fasten your seat-belt, turbo1. You don't know what you just got yourself into...

I must say that I really have no idea what Russ could have meant! :surprise: :shy:

 

[Chronos]

Now for the high redshift objects. Let's agree that there is a 100% possibility of finding a very bright high-redshift object in an area the size of the close up (1 square arc-minute = 3600 square arc-seconds). Assuming the luminous filament to be 5 arc-seconds across and 60 arc-seconds long, the filament occupies 1/12 the area of the closeup. There is therefore one chance in twelve that the object can appear projected on any part of the filament. Add a second such object and there is one chance in 144 that both can be touching the filament. What are the chances that both of them will be located in the center of the filament, width-wise? How about 1/60 x 1/60 or 1 chance in 3600? And that's if we believe that there is a 100% probability of finding two bright objects of redshift >0.24 in such a small area.

I know that in an infinite universe, there is a nearly 100% probablility of finding any combination of such objects, but we are not in an infinite "observable" universe. Our observable universe is bounded by cosmological horizons and by the ability of our sensors to detect the things we study.

I think it is reasonable to predict, given the number of galaxies we can observe, that it is highly improbable such coincidences would not be found. The article Nereid referred to regarding HST findings related to the Hubble constant is much more convincing than Arp's portrait gallery of freaks of nature.

I also think Arp, while well intended, is statistically challenged and has a history of using dubious math to arrive at equally dubious conclusions: which is why he does not have much mainstream support. A good example is the Newman-Terzian paper http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995ApJ...441..505N&db_key=AST&high=3325b47acc06425

The book of nature lies continuously open before our eyes (I speak of the Universe) but it can't be understood without first learning to understand the language and characters in which it is written. It is written in mathematical language, and its characters are geometrical figures. - Galileo Galilei

 

[Nereid]

This recent study of a very massive, mid-distance cluster (z~=0.5) combines observations from Chandra, Keck, Subaru, and Gemini-N. It is part of a set of programs aimed at discovering the evolution of LSS (large scale structure), in particular how galaxy clusters came to have the size and structure that we see today. The role of 'filaments' is important in this.

Interestingly, the astronomers found indications that "significant dynamical activity at scales greater than 5 Mpc from the cluster, well beyond the virial radius. The observations imply an in-fall of matter along this preferred axis direction. The funneling will persist for roughly the next 4 Gyr, assuming an in-fall speed of ~1000 km/s.[/color]"

 

[Nereid]

GOODS result

Hubble, Galaxies Across Time and Space is an IMAX film based on the GOODS survey.

As there are ~30,000 galaxy images in GOODS, of which ~11,000 have measured redshifts, this might be a good test of the Arp hypothesis - how many 'discordant redshifts' appear in the GOODS data? AFAIK, all results are in the public domain, so anyone can check the selection methods used, for determining what constitutes a 'galaxy', and for interpreting spectra in terms of redshift.

In some ways it's a pity this is already 'finished'; otherwise we could ask Arp (or supporters) what they would expect to find in such a survey, and compare their predictions with the observations.

 

[Nereid]

How big are the public GOODS* data files? Seat belts on please (just the HST BViz observations) ... " The files for each section, both the science and the weight map images, are ~268.4 MB in size each (8192 x 8192 pixels, each with a 32 depth), and there are images in each of the four GOODS passbands. Thus, the CDF-S data set requires 2x268.4x18x4 = 38.655 GB, the HDF-N requires 2x268.4x17x4 = 36.507 GB. The full data set requires 38.655 + 36.507 = 75.162 GB.[/color]"

*"GOODS will survey approximately 300 square arcmin divided into two fields: the Hubble Deep Field North and the Chandra Deep Field South. These are among the most data-rich portions of the sky, and are the sites of the deepest observations from Hubble, Chandra, ESA's XMM-Newton, and from many ground-based facilities. Dividing our survey area provides insurance against cosmic variance due to galaxy clustering, and guarantees that astronomers in both hemispheres can carry out related observations.[/color]" ... and Spitzer too.

 

[big-egg]

Questions?

Are the disparate red shifts associated only with quasars and galaxies?

Are there coupling galaxies with disparate red shifts?

Are there supernovas in the proximity of the quasars?

What about the quantum red shifts? They will also create a hard problem to the BBT.

Are there statistical steadies on disparate red shifts?

Thank you for your time to consider these thought provoking questions.

 

[turbo]

Thank you Chronos

I also think Arp, while well intended, is statistically challenged and has a history of using dubious math to arrive at equally dubious conclusions: which is why he does not have much mainstream support. A good example is the Newman-Terzian paper http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995ApJ...441..505N&db_key=AST&high=3325b47acc06425

I am very surprised that you cited that statistically flawed paper, but I am very happy that you did so. The authors misstated Arp's premise and then applied statistics in a very creative way to downplay the improbability of something truly implausible.

Let's say you have a large galaxy and eleven associated smaller galaxies, clusters, whatever. If the smaller objects are physically associated with (and effected by) the more massive object, we would reasonably expect about half the smaller objects moving around that massive galaxy would be moving toward us relative to the host, and would therefore be blueshifted in relation to the host. If the host has one object it around it, there is one chance in two (1/2) that the object would be redshifted with respect to the host. If there are two objects, there is one chance in four (1/4) that both objects would be redshifted relative to the host. To save time, we will extrapolate: if there are eleven objects around the host, there is only one chance in 4096 that all eleven objects will be found to be redshifted relative to the host.

In the paper cited above, the authors de-coupled the massive host galaxy from any effects on the associated small objects, and then restated the problem as a simple matter of ordination, saying in effect "there is one in twelve chances for the host galaxy to have the smallest redshift so that's a 1/12 chance for the observation that all the smaller objects will be redshifted relative to the large massive galaxy." That has to be one of the most cynical applications of "statistics" I have seen.

The problem that Arp was illustrating is that lower-mass companions of large galaxies are preferentially redshifted with respect to their hosts (like M51 and NGC 5195). It is easy to statistically refute the significance of this trend with one or two objects, but when smaller objects are overwhelmingly found to be redshifted relative to their host galaxies, there can be only two explanations - either we are at most privileged position in the whole universe, where all smaller objects are preferentially running away from us heedless of the gravitational effects of their host galaxies OR these smaller objects have an additional intrinsic redshift that we don't yet understand. I prefer the latter.

 

[meteor]

"A catalogue of southern peculiar galaxies and associations" (Arp, 1987)
http://nedwww.ipac.caltech.edu/level5/SPGA_Atlas/frames.html

This catalogue includes galaxies that are apparently connected. Can be an useful source of information

Also, in post 119 of this thread
https://www.physicsforums.com/showthread.php?t=3593&page=3&pp=40
I give my explanation of the fact that two objects with different redshift seems to be connected

 

[Chronos]

How can you not give an 8% chance that anyone of 12 objects in a group is the least red shifted among the group? The main point of the Newman-Terzian paper was point out the flawed initial assumption Arp used. Intrinsic red shift is a very unsatisfactory explanation. Why would less massive bodies have more intrinsic red shift than the most massive body in a group? The preponderance of evidence supports the conclusion that z=distance. Arp's 388 potential 'exceptions' should not be given more credence than the overwhelming number of confirmations in support of expansion and the BB model. Exceptions, however, are interesting, and point the way to more refined explanations. That only means the current model is incomplete, not fundamentally wrong. Give credit where credit is due. We already know the current model has problems. Quantum physics and GR just don't mix without a quantum theory of gravity. I don't like the idea of appealing to higher orders of reality to explain the problem. Adding strings and branes, imo, only creates more difficulties than they resolve... 'mommy, where did strings come from?'. I think it is a mistake to stray from the observable universe into the unobservable to find answers. It flys into the face of science as I know it.

 

[turbo]

How can you not give an 8% chance that anyone of 12 objects in a group is the least red shifted among the group? The main point of the Newman-Terzian paper was point out the flawed initial assumption Arp used.

The problem with the "statistical treatment" of the example is that the authors of the paper stripped out causality with regard to the gravitational influence of the largest body - it was ignored completely. If you were to make some observations relating to the movements of bodies in our solar system, surely you would not use a method that disregards the gravitational influence of the sun! This is exactly what the authors of that paper did.

To restate:

There are eleven relatively small objects in the domain of one very large massive object.

The motions of the small objects orbiting the massive host object have a 50:50 chance of being toward us or away from us relative to the host.

If the host has one object it around it, there is one chance in two (1/2) that the object would be redshifted with respect to the host. If there are two objects, there is one chance in four (1/4) that both objects would be redshifted relative to the host. To save time, we will extrapolate: if there are eleven objects around the host, there is only one chance in 4096 that all eleven objects will be found to be redshifted relative to the host.

This is very basic statement of probability. If there is 1/x probabilty of an object being in a particular state, the probability of a set of objects with y members all being in that state at one time is 1/(x to the y power). It's hard for me to understand how the Newman-Terzian paper was published with such a very glaring basic statistical error.

Intrinsic red shift is a very unsatisfactory explanation.

The explanation may be unsatisfactory, but that does not invalidate the observations. The scientific method requires that if we cannot disprove the observations, we must come up with a model that explains them, and use the model to make testable predictions that can be used to verify, disprove, or refine the model.

 

[Chronos]

Turbo: Objections noted. Not all apparent redshift anomalies have been satisfactoriy explained using the standard model. Progress is, however, being made. So far as Newman-Terzian is concerned, I am not aware of any published studies refuting their position. I would be interested if you know of any references.

 

[Chronos]

Hubble, Galaxies Across Time and Space is an IMAX film based on the GOODS survey.

As there are ~30,000 galaxy images in GOODS, of which ~11,000 have measured redshifts, this might be a good test of the Arp hypothesis - how many 'discordant redshifts' appear in the GOODS data? AFAIK, all results are in the public domain, so anyone can check the selection methods used, for determining what constitutes a 'galaxy', and for interpreting spectra in terms of redshift.

In some ways it's a pity this is already 'finished'; otherwise we could ask Arp (or supporters) what they would expect to find in such a survey, and compare their predictions with the observations.

You may find this interesting: http://arxiv.org/PS_cache/astro-ph/pdf/0208/0208117.pdf

 

[turbo]

Thanks for posting that paper. Similar to your discomfort with intrinsic redshifts, I have a problem getting comfortable with the concept of quantized redshifts. My gut feeling is that there is a very simple understandable reason for discrepant redshifts, and that once we figure out the mechanics, the cause will be something that causes a smooth continuum of redshift, not a stepwise progression.

 

[Nereid]

To restate:

There are eleven relatively small objects in the domain of one very large massive object.

The motions of the small objects orbiting the massive host object have a 50:50 chance of being toward us or away from us relative to the host.

If the host has one object it around it, there is one chance in two (1/2) that the object would be redshifted with respect to the host. If there are two objects, there is one chance in four (1/4) that both objects would be redshifted relative to the host. To save time, we will extrapolate: if there are eleven objects around the host, there is only one chance in 4096 that all eleven objects will be found to be redshifted relative to the host.

This is very basic statement of probability. If there is 1/x probabilty of an object being in a particular state, the probability of a set of objects with y members all being in that state at one time is 1/(x to the y power). It's hard for me to understand how the Newman-Terzian paper was published with such a very glaring basic statistical error.

I'll get back to this in more detail when I've read more, but just quickly ... the tidal locking of Io, Europa, and Ganymede means that the probabilities of 'N moving towards' vs 'M moving away' is not random, so the probabilities turbo-1 describes would not apply (actually, *could* not apply). There's also measurement error - how many 'small' objects would show essentially zero redshift (wrt something), within the measurement error?

 

[turbo]

Nereid, I'll willingly play the devil's advocate on this one. What if you have a cloud of smaller objects that are essentially captivated and falling directly into the larger object without significant orbital motion? Some objects will be redshifted, a smaller number will be blueshifted (because we will miss a portion of those objects due to obscuration by the host galaxy) and those objects that are dropping into the host galaxy on a plane perpendicular to our line of sight will exhibit the same redshift as the host.

Assuming NO orbital motion (direct infall only), and an obsuration of blueshifted objects of 10%, and non-discrepant redshift due to perpendicular orientation of infall paths of some objects (maybe another 10%), we still have a probability of less than one in 512 that all the small objects that surround the massive host will exhibit an excess redshift relative to the host. This is a far cry from 8% (1/12) cited in Nemnam-Terzian.

I believe that these are very fair, conservative estimates. I don't want to paint you into a corner and try to make you defend the Newman-Terzian paper, but what do you think of their paper?

 

[Chronos]

respect

Thanks for posting that paper. Similar to your discomfort with intrinsic redshifts, I have a problem getting comfortable with the concept of quantized redshifts. My gut feeling is that there is a very simple understandable reason for discrepant redshifts, and that once we figure out the mechanics, the cause will be something that causes a smooth continuum of redshift, not a stepwise progression.

we are in agreement. i respect your objections and agree that current models are lacking. we need better predictive models to sort it out. something is still missing. the universe is a maddening puzzle. it taunts and teases us, but, resists yielding its secrets. i do believe, however, current models are more correct than incorrect. the evidence appears, at least to me, to be overwhelming. the piece still missing, imo, is quantum gravity.

are there observations that contradict expansion as the 'big picture' of the universe? of course. information theory [shannon and godel] insist this will always be the case. will someone find a paradigm shift to further advance our understanding of how the universe works? i hope so. i object to being trapped within a place as small as our solar system. that is what current theory condemns us to and i am not comfortable with that either. if we can see it, we should be able to explore it.

 

[Nereid]

Mesolensing is in between microlensing (point-like mass) and macrolensing (galactic-like mass) and has been proposed as a means by which to indirectly observe CDM. The means proposed is to observe multipli-imaged quasars and to record any phasing anomalies, and from those infer the mass and/or extent of the CDM doing the lensing.

King objects aren't a class or type of object, if I understand correctly, they are objects that conform to a particular model of mass distribution, and they have been invoked in the form of galactic halos to explain away the statistical preference in some studies for quasars to appear in closer (angular) proximity to galaxies than can be accounted for by chance.

Am working my way slowly through the posts in this thread, and have got up to here.

Several questions, and possible lines of investigation, occur to me:
- examine the Arp hypothesis (-ses?), that AGN galaxies (inc Seyferts) eject quasars (yes, that's an oversimplification); that the preponderance of galaxy/quasar discordant redshifts also involve ULX. I'm not sure yet what to do about his galaxy/galaxy discordant redshift observations.
- take a closer look at gravitational lensing - micro, meso, and 'traditional'
- GOODS, 2dF, and SDSS as tests of Arp's ideas. e.g. if there are ~300 'Arp' objects among the ~23k de Vaucouleur catalogue (RC3), then there should be ~300 among the 30k GOODS galaxies, and ~3k among the ~250k 2dF ones, and ~10k among the ~1m Subaru/XMM-Newton ones (many assumptions behind these statements!); are there?
- both 2dF and SDSS should permit a far more rigorous testing of any quasar/(active) galaxy association than finding interesting objects by eye and taking a deeper look; medium-deep surveys should also provide good tests
- among objects whose distance has been established by means independent of redshift, there will likely be some from Arp's catalogue, and surely some Seyferts (etc). What about associated discordant redshift objects? E.g. an SN in both objects of such a pair? We can look for ourselves, because there's a pretty complete list of all SN available on the internet.

Finally, some clarifications on King objects, meso-lensing, CDM cosmology, etc.

One of the challenges for the concordance model ('\Lambda CDM') is that it predicts far more 'small(ish) galaxies' than are actually observed, IIRC between 1 and 2 OOM too many. Now the model doesn't say what sort of things these objects should be, just (approx) what their mass function should be (how many of mass M₁, how many of mass M₂, etc), and (approx) the distribution of mass within them (hence 'King objects'; OK some oversimplification here too). Most importantly, it doesn't distiguish between baryonic matter and dark matter! Enter theories of galaxy evolution, and where it starts to get messy; enter observations, and where it starts to get interesting! Even within the Local Group - the ~20 (30?) galaxies dominated by the Milky Way and M31 - we keep finding more and more things, such as dwarf galaxies like Andromeda 9, dwarf galaxies being shredded by the MW, and inter-galactic clouds of gas. But the critical thing is the DM, which, because it's dark, can't be 'seen' in X-rays, the optical, radio, etc. However, DM objects can be detected through gravitational lensing; the question is, what sort of gravitational lens signature would a DM object leave on the light (radio, X-rays, etc) from a distant quasar? Or, within an Arp hypothesis, what should the results of observations designed to find 'meso-lensing by King objects' be?

 

[turbo]

I wish I had more time... Suggestions, anyone?

There is such a ton of research material available...

Nereid, your suggestions re: SN in Arp objects led me to this great SN list

http://web.pd.astro.it/supern/snear.txt

and I started comparing it to the Arp catalog, which is a pain in the butt. Differences in nomenclature make it very likely that I would miss Arp objects in the SN catalog.

http://members.aol.com/arpgalaxy/arplist.html

I decided to cut to the chase and Googled supernova and Arp and found this article about multiple SN in Arp 299:

http://www.space.com/scienceastronomy/aas202_supernova_030527.html

Which led me to explore Arp 299 in more detail. There is wealth of material in NED, of course, and there is a nice Arp 299 page here:

http://www.cv.nrao.edu/~jhibbard/a299/a299.html

It seems that Arp 299 might be a little "too" complex for the SN data to be really useful, as evidenced by this really busy paper:

http://www.journals.uchicago.edu/ApJ/journal/issues/ApJ/v532n2/50399/50399.text.html

I will try to locate a more "normal" Arp pair with SN data available. Can anyone suggest a more productive approach to locating SN data in apparently-interacting objects with discordant redshifts?

 

[Nereid]

The list of SN that you found seems similar to the 'official' one, associated with the IAU circulars (CBAT - Central Bureau of Astronomical Telegrams - is currently administered by the Smithsonian Astrophysical Observatory?); http://cfa-www.harvard.edu/iau/lists/RecentSupernovae.html is their list of SN since the start of 2003 (there's also a link to all SN).

You may find the best way to find a match is to put the list into a database or spreadsheet, sort by RA (or dec), filter by close matches to Arp objects (I assume you have a list of their RAs and decs), and examine each such in detail.

Be aware that even the IAU list has errors in it! They seem to be mostly typos (e.g. transposed digits).

 

[Chronos]

well, i hoped to blow the whole arp thing out of the equation. the preponderance of evidence says arp is wrong. i referenced two papers that explain why i am persuaded to think how i do. if you wish to change my mind, offer me papers that refute them. i have great respect for terzian as a scientist. his credentials are impeccable. he has published many papers and is highly respected in the scientific community. no one, to my knowledge, has ever refuted his papers. you don't achieve the honorary chair of cornell university by being a quack. apologies. if mr terzian cared to speak here, we should listen.

 

[turbo]

well, i hoped to blow the whole arp thing out of the equation. the preponderance of evidence says arp is wrong. i referenced two papers that explain why i am persuaded to think how i do. if you wish to change my mind, offer me papers that refute them. i have great respect for terzian as a scientist. his credentials are impeccable. he has published many papers and is highly respected in the scientific community. no one, to my knowledge, has ever refuted his papers. you don't achieve the honorary chair of cornell university by being a quack. apologies. if mr terzian cared to speak here, we should listen.

You don't need someone with a Phd to refute the Newman-Terzian paper for you. Trust your own abilities. Read the paper and you will see that the authors (with lots of hand-waving and misdirection) ignored the central point of Arp's argument - that the smaller bodies are under the gravitational influence of the large body and therefore must exhibit some predictable behavior in their motions relative to the host. After butchering the model by ignoring gravity, they then treated the redshift relationships as a matter of simple ordination, saying that the bodies are all essentially equivalent, and that there is a 1 in 12 chance (8%) that the largest galaxy will have the smallest redshift. Those methods are so basically wrong, the paper should never have gotten past the referees.

Just sketch out the model on a piece of paper (large galaxy surrounded by 11 smaller bodies), assign some orbits to the small bodies and then imagine the coincidence (one in 4096) that would have to occur for ALL the smaller bodies to be moving away from us relative to the host. Here's a wrinkle: When you sketch out the model, assign one of the bodies an orbit that is about perpendicular to our line of sight. Now, try to arrange for that object to have a redshift relative to the host without invoking an intrinsic redshift of some kind.

Once you have sketched out the model and done some thought-experiments with it, re-read the Newman-Terzian paper. The flaws in their analysis will become immediately apparent. It's not rocket science.

Added 2:40pm... Let's do a really simplified example, with all objects in about the same plane around a central body - just like our own solar system. To an observer outside our "solar system" each "planet" would have measurable redshift relative to the sun less than 50% of the time. There would be no measurable redshift near transit or occultation and there would be blueshift on the other side of the orbit. If the outside observer noted ALL NINE "planets" being redshifted relative to the sun he would surmise (and rightly so) that he was observing a very special and rare alignment, with less than one chance in 1024 of ocurring at the particular time of his observation. He would not say "well, there are 10 objects in that system, so there is one chance in ten that the central object would have the least amount of redshift." At least he wouldn't say that if he had any sense. The Newman-Terzian paper uses exactly that approach to "refute" Arp. You don't need a Phd to invalidate the Newman-Terzian paper, just grade-school math and some common sense.

 

[Chronos]

Orientation could matter. If the axis of rotation is pointed at the observer, all bodies in the associated group would have indistinguishable redshifts. The lack of relative blue shifts is more puzzling than explanatory

 

[turbo]

Orientation could matter. If the axis of rotation is pointed at the observer, all bodies in the associated group would have indistinguishable redshifts. The lack of relative blue shifts is more puzzling than explanatory

Exactly! When orbit inclination is taken into account, we should expect the smaller objects to have significant redshifts with respect to the host less than half the time. Finding 11 out of 11 small objects around a large galaxy to be redshifted relative to the host is actually much more implausible than Arp calculated. He used a simple 50:50 (redshift-blueshift) calculation, which is generously conservative.

 

[shrumeo]

why were they assuming that the smaller bodies are orbiting the larger galaxy?
what was the indication that they were gravitationally associated?
I forgot, sorry.

 

[shrumeo]

Apologies for my ignorance!

Sorry for mixing threads but I hope someone could clear this up.

This came from "Seeing Red" thread:

In this page comes the formula for the calculation of gravitational redshift for a photon emitted from a star
http://en.wikipedia.org/wiki/Gravitational_redshift

<br /> z= \frac {G}{c^2}* \frac{M}{R}<br />

M is the mass of the star and R its radius

I guess I never thought to try something as simple as pluggin into this eq. so I tried it for a typical quasar (or at least how it's typically described). So I replied with:

so a quasar is supposed to have a mass comparable to a galaxy
i will say a typical galaxy holds 10b stars,
let's just say our hypothetical quasar has 10b solar masses
IIRC, a typical quasar has a radius comparable to the solar system
I will just say 30 AU

mass of sun = 2.3 x 10^33 g (from the Wikepedia page)
10b x this = 2.3 x 10^43 g
radius of 30 AU ~ 4.5 x 10^14 cm

plugging these into the equation above, I get a gravitational redshift from a typical quasar to be z=3.78 !

Please tell me if my assumptions are wrong.
Thanks

 

[shrumeo]

Oh, wait, they are wrong. I was using the approximation for a small star.
When you use the real eq. you realize there is a limit to M/R, otherwise you are a black hole. Sorry for blemishing this thread.
:)

 

[turbo]

NGC 450 and UGC 806 - interacting galaxies.GC 4

Here is a very compelling example of interacting galaxies that appear (if redshift=distance) to be simply a chance projection. The authors evaluate the pair in light of morphology, redshift, rotational speed, etc, and conclude that the galaxies must be interacting despite their widely disparate redshifts. Go to the page below and get the scanned refereed PDF article.

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994ApJ...432..135M

There are a number of very good photographs of this pair on the 'net. Here is a page containing some interesting pictures of interacting galaxy pairs, including this one.

http://www.astr.ua.edu/pairs2.html

 

[Nereid]

Here is a very compelling example of interacting galaxies that appear (if redshift=distance) to be simply a chance projection. The authors evaluate the pair in light of morphology, redshift, rotational speed, etc, and conclude that the galaxies must be interacting despite their widely disparate redshifts. Go to the page below and get the scanned refereed PDF article.

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994ApJ...432..135M

There are a number of very good photographs of this pair on the 'net. Here is a page containing some interesting pictures of interacting galaxy pairs, including this one.

http://www.astr.ua.edu/pairs2.html

Don't you mean UGC 807?

I note that the Arp et al paper which you cite was published in 1994; I also note that NGC 450 and UGC 807 were the subject of several Hubble observations - images and spectra - how do Arp et al's claims stack up in the light of the much higher resolution HST observations?

If anyone's intetested, http://archive.stsci.edu/cgi-bin/genlinks_search.cgi?target=NGC450&resolver=SIMBAD is a place you can start your search for raw data, to perform your own analyses ...

 

[turbo]

You're right of course. I slipped a number key (l-r) when typing - I'm an acceptable touch-typist most times, but have trouble with numbers, and didn't catch it in proofreading.

At any rate, UGC 807 (with the higher redshift) appears more likely to be in front of NGC 450 than in back of it, and there are morphological problems between the pair that point to interaction - these are not a chance projection.

http://nedwww.ipac.caltech.edu/level5/index.html

There are some really wonderful atlases here, where lots more of these conundrums can be found.